Mobile Communications Chapter 7: Wireless LANs

Transcription

1 Mobile Communications Chapter 7: Wireless LANs Characteristics IEEE PHY MAC Roaming.11a, b, g, h, i HIPERLAN (Não é dado) Bluetooth / IEEE x IEEE /.20/.21/.22 RFID Comparison Prof. Dr.-Ing. Jochen Schiller, MC SS05 7.1

2 Mobile Communication Technology according to IEEE Local wireless networks WLAN WiFi a b h i/e/ /w g ZigBee Personal wireless nw. WPAN a/b a/b Bluetooth Wireless distribution networks WMAN (Broadband Wireless Access) WiMAX + Mobility (Mobile Broadband Wireless Access) Prof. Dr.-Ing. Jochen Schiller, MC SS05 7.2

3 Characteristics of wireless LANs Advantages very flexible within the reception area Ad-hoc networks without previous planning possible (almost) no wiring difficulties (e.g. historic buildings, firewalls) more robust against disasters like, e.g., earthquakes, fire - or users pulling a plug... Disadvantages typically very low bandwidth compared to wired networks (1-10 Mbit/s) due to shared medium many proprietary solutions, especially for higher bit-rates, standards take their time (e.g. IEEE ) products have to follow many national restrictions if working wireless, it takes a vary long time to establish global solutions like, e.g., IMT-2000 Prof. Dr.-Ing. Jochen Schiller, MC SS05 7.3

4 Design goals for wireless LANs global, seamless operation low power for battery use no special permissions or licenses needed to use the LAN robust transmission technology simplified spontaneous cooperation at meetings easy to use for everyone, simple management protection of investment in wired networks security (no one should be able to read my data), privacy (no one should be able to collect user profiles), safety (low radiation) transparency concerning applications and higher layer protocols, but also location awareness if necessary Prof. Dr.-Ing. Jochen Schiller, MC SS05 7.4

5 Comparison: infrared vs. radio transmission Infrared uses IR diodes, diffuse light, multiple reflections (walls, furniture etc.) Radio Advantages Advantages experience from wireless WAN and mobile phones can be used coverage of larger areas possible (radio can penetrate walls, furniture etc.) simple, cheap, available in many mobile devices no licenses needed simple shielding possible Disadvantages Disadvantages very limited license free frequency bands shielding more difficult, interference with other electrical devices interference by sunlight, heat sources etc. many things shield or absorb IR light low bandwidth Example typically using the license free ISM band at 2.4 GHz Example IrDA (Infrared Data Association) interface available everywhere Prof. Dr.-Ing. Jochen Schiller, Many different products MC SS05 7.5

6 Comparison: infrastructure vs. ad-hoc networks infrastructure network AP AP wired network AP: Access Point AP ad-hoc network Prof. Dr.-Ing. Jochen Schiller, MC SS05 7.6

7 Architecture of an infrastructure network Station (STA) LAN STA1 802.x LAN Basic Service Set (BSS) BSS1 Portal Access Point Access Point ESS group of stations using the same radio frequency Access Point Distribution System station integrated into the wireless LAN and the distribution system Portal BSS2 bridge to other (wired) networks Distribution System STA2 terminal with access mechanisms to the wireless medium and radio contact to the access point LAN STA3 Prof. Dr.-Ing. Jochen Schiller, interconnection network to form one logical network (EES: Extended Service Set) based on several BSS MC SS05 7.7

8 Architecture of an ad-hoc network Direct communication within a limited range LAN Station (STA): terminal with access mechanisms to the wireless medium Independent Basic Service Set (IBSS): group of stations using the same radio frequency STA1 STA3 IBSS1 STA2 IBSS2 STA5 STA LAN Prof. Dr.-Ing. Jochen Schiller, MC SS05 7.8

9 IEEE standard fixed terminal mobile terminal infrastructure network access point application application TCP TCP IP IP LLC LLC LLC MAC MAC MAC MAC PHY PHY PHY PHY Prof. Dr.-Ing. Jochen Schiller, MC SS05 7.9

10 Layers and functions PLCP Physical Layer Convergence Protocol MAC access mechanisms, fragmentation, encryption clear channel assessment signal (carrier sense) PMD Physical Medium Dependent MAC Management synchronization, roaming, MIB, power management modulation, coding PHY Management channel selection, MIB Station Management LLC MAC MAC Management PLCP PHY Management PMD coordination of all management functions Station Management PHY DLC Prof. Dr.-Ing. Jochen Schiller, MC SS

11 Physical layer (classical) 3 versions: 2 radio (typ. 2.4 GHz), 1 IR data rates 1 or 2 Mbit/s FHSS (Frequency Hopping Spread Spectrum) spreading, despreading, signal strength, typ. 1 Mbit/s min. 2.5 frequency hops/s (USA), two-level GFSK modulation DSSS (Direct Sequence Spread Spectrum) DBPSK modulation for 1 Mbit/s (Differential Binary Phase Shift Keying), DQPSK for 2 Mbit/s (Differential Quadrature PSK) preamble and header of a frame is always transmitted with 1 Mbit/s, rest of transmission 1 or 2 Mbit/s chip sequence (11 symbols) : +1, -1, +1, +1, -1, +1, +1, +1, -1, -1, -1 (Barker code) max. radiated power 1 W (USA), 100 mw (EU), min. 1mW Infrared nm, diffuse light, typ. 10 m range carrier detection, energy detection, synchronization Prof. Dr.-Ing. Jochen Schiller, MC SS

12 FHSS PHY packet format (Não) Synchronization synch with pattern SFD (Start Frame Delimiter) start pattern PLW (PLCP_PDU Length Word) length of payload incl. 32 bit CRC of payload, PLW < 4096 PSF (PLCP Signaling Field) data of payload (1 or 2 Mbit/s) HEC (Header Error Check) CRC with x16+x12+x synchronization variable SFD PLW PSF HEC payload PLCP preamble bits PLCP header Prof. Dr.-Ing. Jochen Schiller, MC SS

13 DSSS PHY packet format Synchronization synch., gain setting, energy detection, frequency offset compensation SFD (Start Frame Delimiter) Signal data rate of the payload (0A: 1 Mbit/s DBPSK; 14: 2 Mbit/s DQPSK) Service Length future use, 00: compliant length of the payload HEC (Header Error Check) protection of signal, service and length, x16+x12+x synchronization 16 SFD PLCP preamble signal service length HEC variable bits payload PLCP header = 192 bit a 1 Mbps -> 192 us (em b a partir de signal pode ser a 2 Mbps) Prof. Dr.-Ing. Jochen Schiller, MC SS

14 MAC layer I - DFWMAC Traffic services Asynchronous Data Service (mandatory) exchange of data packets based on best-effort support of broadcast and multicast Time-Bounded Service (optional) implemented using PCF (Point Coordination Function) Access methods DFWMAC-DCF CSMA/CA (mandatory) collision avoidance via randomized back-off mechanism minimum distance between consecutive packets ACK packet for acknowledgements (not for broadcasts) DFWMAC-DCF w/ RTS/CTS (optional) Distributed Foundation Wireless MAC avoids hidden terminal problem DFWMAC- PCF (optional) access point polls terminals according to a list Prof. Dr.-Ing. Jochen Schiller, MC SS

15 MAC layer II Priorities defined through different inter frame spaces no guaranteed, hard priorities SIFS (Short Inter Frame Spacing) PIFS (PCF IFS) highest priority, for ACK, CTS, polling response medium priority, for time-bounded service using PCF DIFS (DCF, Distributed Coordination Function IFS) lowest priority, for asynchronous data service Tslot = 9; SIFS = 16; PIFS = 25; DIFS = 34 us DIFS DIFS medium busy PIFS SIFS contention next frame t direct access if medium is free DIFS Prof. Dr.-Ing. Jochen Schiller, MC SS

16 CSMA/CA access method I DIFS contention window (CW) (randomized back-off mechanism) DIFS medium busy direct access if medium is free DIFS next frame t slot time station ready to send starts sensing the medium (Carrier Sense based on CCA, Clear Channel Assessment) if the medium is free for the duration of an Inter-Frame Space (IFS), the station can start sending (IFS depends on service type) if the medium is busy, the station has to wait for a free IFS, then the station must additionally wait a random back-off time (collision avoidance, multiple of slot-time) CW = 7, 15, 31, 63, 127 if another station occupies the medium during the back-off time of the station, the back-off timer stops (fairness) Prof. Dr.-Ing. Jochen Schiller, MC SS

17 Binary Exponential Backoff Stations choose their backoff time randomly from contention Window Ideal contention window size is trade-off between acceptable load and experienced delay Initial contention window size (CWmin) is 7 slots (backoff time between 0 and 7) After collision (no ack), contention window is doubled until CWmax = 255 is reached: 7 -> 15 -> 31 -> 63 -> 127 -> 255 Prof. Dr.-Ing. Jochen Schiller, MC SS

18 competing stations - simple version (no RTS/CTS) DIFS DIFS station1 station2 DIFS boe bor boe busy DIFS boe bor boe busy boe busy boe bor boe boe busy station3 station4 boe bor station5 busy bor t busy medium not idle (frame, ack etc.) boe elapsed backoff time packet arrival at MAC bor residual backoff time Prof. Dr.-Ing. Jochen Schiller, MC SS

19 CSMA/CA access method II Sending unicast packets station has to wait for DIFS before sending data receivers acknowledge at once (after waiting for SIFS) if the packet was received correctly (CRC) automatic retransmission of data packets in case of transmission errors DIFS sender data SIFS receiver ACK DIFS other stations waiting time Prof. Dr.-Ing. Jochen Schiller, data t contention MC SS

20 DFWMAC (Distributed Foundation Wireless MAC) Sending unicast packets station can send RTS with reservation parameter after waiting for DIFS (reservation determines amount of time the data packet needs the medium) acknowledgement via CTS after SIFS by receiver (if ready to receive) sender can now send data at once, acknowledgement via ACK other stations store medium reservations distributed via RTS and CTS DIFS sender RTS data SIFS receiver other stations CTS SIFS SIFS NAV (RTS) NAV (CTS) defer access NAV Network Allocation Vector Prof. Dr.-Ing. Jochen Schiller, ACK DIFS data t contention MC SS

21 Timing diagram of collision and successful transmission. (a) RTS/CTS collision, (b) RTS/CTS successful transmission, (c) Basic frame collision (d) Basic frame successful transmission ( note: in (a) and (c), crossed block represents collision). Prof. Dr.-Ing. Jochen Schiller, MC SS

22 Fragmentation DIFS sender RTS frag1 SIFS receiver CTS SIFS frag2 SIFS ACK1 SIFS SIFS ACK2 NAV (RTS) NAV (CTS) other stations DIFS NAV (frag1) NAV (ACK1) contention Prof. Dr.-Ing. Jochen Schiller, MC SS data t

23 DFWMAC-PCF t0 t1 medium busy PIFS point coordinator wireless stations stations NAV SuperFrame SIFS D1 SIFS D2 SIFS SIFS U1 U2 NAV contention free period Prof. Dr.-Ing. Jochen Schiller, MC SS

24 DFWMAC-PCF II (cont.) t2 point coordinator wireless stations stations NAV D3 PIFS SIFS D4 t3 t4 CFend SIFS U4 NAV contention free period contention period t CFend - contention free period end Prof. Dr.-Ing. Jochen Schiller, MC SS

25 Frame format Types control frames, management frames, data frames Sequence numbers important against duplicated frames due to lost ACKs Addresses receiver, transmitter (physical), BSS identifier, sender (logical) Miscellaneous sending time, checksum, frame control, data bytes Frame Duration/ Address Address Address Sequence Address Control ID Control 4 bits Data CRC 1 Protocol To From More Power More Type Subtype Retry WEP Order version DS DS Frag Mgmt Data MAC header + trailer = 34 octets Prof. Dr.-Ing. Jochen Schiller, MC SS

26 MAC address format scenario ad-hoc network infrastructure network, from AP infrastructure network, to AP infrastructure network, within DS to DS from DS address 1 address 2 address 3 address 4 DA DA SA BSSID BSSID SA BSSID SA DA RA TA DA SA DS: Distribution System AP: Access Point DA: Destination Address SA: Source Address BSSID: Basic Service Set Identifier RA: Receiver Address (AP) TA: Transmitter Address (AP) Prof. Dr.-Ing. Jochen Schiller, MC SS

27 Endereços MAC adhoc DA, SA, BSSID 01 wired to wireless DA, BSSID, SA 10 wireless to wired (BSSID) SA DA BSSID DA SA DA,SA BSSID SA DA BSSID, SA, DA 11 via wireless (bridge) RA, TA, DA, SA DA,SA RA TA SA DA DA,SA Prof. Dr.-Ing. Jochen Schiller, DA,SA MC SS

28 Special Frames: ACK, RTS, CTS Acknowledgement bytes ACK Frame Receiver Duration Control Address 4 CRC Request To Send bytes RTS Frame Receiver Transmitter Duration Control Address Address Clear To Send bytes CTS Frame Receiver Duration Control Address Prof. Dr.-Ing. Jochen Schiller, MC SS05 4 CRC CRC

29 MAC management Synchronization try to find a WLAN, try to stay within a WLAN timer etc. Power management sleep-mode without missing a message periodic sleep, frame buffering, traffic measurements Association/Reassociation integration into a LAN roaming, i.e. change networks by changing access points scanning, i.e. active search for a network MIB - Management Information Base managing, read, write (SNMP) Prof. Dr.-Ing. Jochen Schiller, MC SS

30 Synchronization using a Beacon (infrastructure) beacon interval access point medium B B busy busy B busy B busy t value of the timestamp B Prof. Dr.-Ing. Jochen Schiller, beacon frame (BSSID, Timestamp) MC SS

31 Synchronization using a Beacon (ad-hoc) beacon interval station1 B1 B1 B2 station2 medium busy busy B2 busy busy t value of the timestamp B beacon frame Prof. Dr.-Ing. Jochen Schiller, MC SS05 random delay 7.31

32 Power management Idea: switch the transceiver off if not needed States of a station: sleep and awake Timing Synchronization Function (TSF) stations wake up at the same time Infrastructure Traffic Indication Map (TIM) list of unicast receivers transmitted by AP Delivery Traffic Indication Map (DTIM) list of broadcast/multicast receivers transmitted by AP Ad-hoc Ad-hoc Traffic Indication Map (ATIM) announcement of receivers by stations buffering frames more complicated - no central AP collision of ATIMs possible (scalability?) Prof. Dr.-Ing. Jochen Schiller, MC SS

33 Power saving with wake-up patterns (infrastructure) TIM interval access point DTIM interval D B T busy medium busy T d D B busy busy p station d t T TIM D B broadcast/multicast DTIM awake p PS poll d data transmission to/from the station PS Power Saving Prof. Dr.-Ing. Jochen Schiller, MC SS

34 Power saving with wake-up patterns (ad-hoc) ATIM window station1 beacon interval B1 station2 A B2 B2 D a B1 d t B beacon frame awake random delay a acknowledge ATIM Prof. Dr.-Ing. Jochen Schiller, A transmit ATIM D transmit data d acknowledge data MC SS

35 Scanning Scanning involves the active search for a BSS. IEEE differentiates between passive and active scanning. Passive scanning - listening into the medium to find other networks, i.e., receiving the beacon of another network issued by access point. Active scanning - sending a probe on each channel and waiting for a response. Beacon and probe responses contain the information necessary to join the new BSS. Prof. Dr.-Ing. Jochen Schiller, MC SS

36 Active Scanning Prof. Dr.-Ing. Jochen Schiller, MC SS

37 Roaming No or bad connection? Then perform: Scanning scan the environment, i.e., listen into the medium for beacon signals or send probes into the medium and wait for an answer Reassociation Request station sends a request to one or several AP(s) Reassociation Response success: AP has answered, station can now participate failure: continue scanning AP accepts Reassociation Request signal the new station to the distribution system the distribution system updates its data base (i.e., location information) typically, the distribution system now informs the old AP so it can release resources Prof. Dr.-Ing. Jochen Schiller, MC SS

38 Roaming: Active Scanning / Authentication/ Reassociation Prof. Dr.-Ing. Jochen Schiller, MC SS

39 Handoff with IAPP (Inter Access Point Protocol), IEEE f Prof. Dr.-Ing. Jochen Schiller, MC SS

40 WLAN: IEEE b Data rate 1, 2, 5.5, 11 Mbit/s, depending on SNR User data rate max. approx. 6 Mbit/s Connection set-up time Transmission range 300m outdoor, 30m indoor Max. data rate ~10m indoor Frequency Quality of Service Limited (no automated key distribution, sym. Encryption) Special Advantages/Disadvantages Free 2.4 GHz ISM-band Limited, WEP insecure, SSID Availability Typ. Best effort, no guarantees (unless polling is used, limited support in products) Manageability Security Connectionless/always on Many products, many vendors Prof. Dr.-Ing. Jochen Schiller, Advantage: many installed systems, lot of experience, available worldwide, free ISM-band, many vendors, integrated in laptops, simple system Disadvantage: heavy interference on ISM-band, no service guarantees, slow relative speed only MC SS

41 IEEE b PHY frame formats Long PLCP PPDU format synchronization SFD signal service length HEC PLCP preamble bits variable payload PLCP header 192 µs at 1 Mbit/s DBPSK 1, 2, 5.5 or 11 Mbit/s Short PLCP PPDU format (optional) 56 short synch. 16 SFD signal service length HEC PLCP preamble (1 Mbit/s, DBPSK) bits variable payload PLCP header (2 Mbit/s, DQPSK) 96 µs Prof. Dr.-Ing. Jochen Schiller, 2, 5.5 or 11 Mbit/s MC SS

42 Channel selection (non-overlapping) Europe (ETSI) channel channel 7 channel MHz [MHz] US (FCC) / Canada (IC) channel channel 6 channel MHz Prof. Dr.-Ing. Jochen Schiller, MC SS [MHz] 7.42

43 WLAN: IEEE a Data rate Connection set-up time 6, 9, 12, 18, 24, 36, 48, 54 Mbit/s, depending on SNR User throughput (1500 byte packets): 5.3 (6), 18 (24), 24 (36), 32 (54) 6, 12, 24 Mbit/s mandatory Transmission range Quality of Service E.g., 54 Mbit/s up to 5 m, 48 up to 12 m, 36 up to 25 m, 24 up to 30m, 18 up to 40 m, 12 up to 60 m Free , , GHz ISM-band Security Limited (no automated key distribution, sym. Encryption) Special Advantages/Disadvantages Frequency Typ. best effort, no guarantees (same as all products) Manageability 100m outdoor, 10m indoor Connectionless/always on Limited, WEP insecure, SSID Advantage: fits into 802.x standards, free ISM-band, available, simple system, uses less crowded 5 GHz band Disadvantage: stronger shading due to higher frequency, no QoS Availability Some products, some vendors Prof. Dr.-Ing. Jochen Schiller, MC SS

44 IEEE a PHY frame format rate reserved length parity 6 16 tail service variable 6 variable payload tail pad bits PLCP header PLCP preamble 12 signal data 1 6 Mbit/s variable symbols 6, 9, 12, 18, 24, 36, 48, 54 Mbit/s 250 Ksymbol/s -> Tsymbol = 4 ms -> PLCP+signal = 13x4 = 52 ms Prof. Dr.-Ing. Jochen Schiller, MC SS

45 Operating channels for a / US U-NII channel 5350 [MHz] 16.6 MHz channel center frequency = *channel number [MHz] [MHz] 16.6 MHz Prof. Dr.-Ing. Jochen Schiller, MC SS

46 OFDM in IEEE a (and HiperLAN2) OFDM with 52 used subcarriers (64 in total) 48 data + 4 pilot (plus 12 virtual subcarriers) khz spacing khz pilot channel center frequency Prof. Dr.-Ing. Jochen Schiller, MC SS05 subcarrier number 7.46

47 WLAN: IEEE developments (03/2005) c: Bridge Support Definition of MAC procedures to support bridges as extension to 802.1D d: Regulatory Domain Update Support of additional regulations related to channel selection, hopping sequences e: MAC Enhancements QoS Enhance the current MAC to expand support for applications with Quality of Service requirements, and in the capabilities and efficiency of the protocol Definition of a data flow ( connection ) with parameters like rate, burst, period Additional energy saving mechanisms and more efficient retransmission f: Inter-Access Point Protocol Establish an Inter-Access Point Protocol for data exchange via the distribution system g: Data Rates > 20 Mbit/s at 2.4 GHz; 54 Mbit/s, OFDM Successful successor of b, performance loss during mixed operation with 11b h: Spectrum Managed a Extension for operation of a in Europe by mechanisms like channel measurement for dynamic channel selection (DFS, Dynamic Frequency Selection) and power control (TPC, Transmit Power Control) Prof. Dr.-Ing. Jochen Schiller, MC SS

48 WLAN: IEEE developments (03/2005) i: Enhanced Security Mechanisms Enhance the current MAC to provide improvements in security. TKIP enhances the insecure WEP, but remains compatible to older WEP systems AES provides a secure encryption method and is based on new hardware j: Extensions for operations in Japan Changes of a for operation at 5GHz in Japan using only half the channel width at larger range k: Methods for channel measurements Devices and access points should be able to estimate channel quality in order to be able to choose a better access point of channel m: Updates of the standards n: Higher data rates above 100Mbit/s Changes of PHY and MAC with the goal of 100Mbit/s at MAC SAP MIMO antennas (Multiple Input Multiple Output), up to 600Mbit/s are currently feasible However, still a large overhead due to protocol headers and inefficient mechanisms p: Inter car communications Communication between cars/road side and cars/cars Planned for relative speeds of min. 200km/h and ranges over 1000m Usage of GHz band in North America Prof. Dr.-Ing. Jochen Schiller, MC SS

49 WLAN: IEEE future developments (03/2005) r: Faster Handover between BSS Secure, fast handover of a station from one AP to another within an ESS Current mechanisms (even newer standards like i) plus incompatible devices from different vendors are massive problems for the use of, e.g., VoIP in WLANs Handover should be feasible within 50ms in order to support multimedia applications efficiently s: Mesh Networking Design of a self-configuring Wireless Distribution System (WDS) based on Support of point-to-point and broadcast communication across several hops t: Performance evaluation of networks Standardization of performance measurement schemes u: Interworking with additional external networks v: Network management Extensions of current management functions, channel measurements Definition of a unified interface w: Securing of network control Classical standards like , but also i protect only data frames, not the control frames. Thus, this standard should extend i in a way that, e.g., no control frames can be forged. Note: Not all standards will end in products, many ideas get stuck at working group level Info: 802wirelessworld.com, standards.ieee.org/getieee802/ Prof. Dr.-Ing. Jochen Schiller, MC SS

50 ETSI HIPERLAN (historical) (não é dado) ETSI standard European standard, cf. GSM, DECT,... Enhancement of local Networks and interworking with fixed networks integration of time-sensitive services from the early beginning HIPERLAN family one standard cannot satisfy all requirements range, bandwidth, QoS support commercial constraints HIPERLAN 1 standardized since 1996 no products! higher layers medium access control layer channel access control layer physical layer HIPERLAN layers logical link control layer medium access control layer network layer data link layer physical layer OSI layers Prof. Dr.-Ing. Jochen Schiller, physical layer IEEE 802.x layers MC SS

51 Overview: original HIPERLAN protocol family Application Frequency Topology Antenna Range QoS Mobility Interface Data rate Power conservation HIPERLAN 1 wireless LAN HIPERLAN 2 access to ATM fixed networks HIPERLAN 3 wireless local loop HIPERLAN 4 point-to-point wireless ATM connections GHz point-to-point GHz decentralized adcellular, point-tohoc/infrastructure centralized multipoint omni-directional directional 50 m m 5000 m 150 m statistical ATM traffic classes (VBR, CBR, ABR, UBR) <10m/s stationary conventional LAN ATM networks 23.5 Mbit/s >20 Mbit/s yes 155 Mbit/s not necessary HIPERLAN 1 never reached product status, the other standards have been renamed/modfied! Prof. Dr.-Ing. Jochen Schiller, MC SS

52 HIPERLAN 1 - Characteristics Data transmission point-to-point, point-to-multipoint, connectionless 23.5 Mbit/s, 1 W power, 2383 byte max. packet size Services asynchronous and time-bounded services with hierarchical priorities compatible with ISO MAC Topology infrastructure or ad-hoc networks transmission range can be larger then coverage of a single node ( forwarding integrated in mobile terminals) Further mechanisms power saving, encryption, checksums Prof. Dr.-Ing. Jochen Schiller, MC SS

53 HIPERLAN 1 - Physical layer Scope modulation, demodulation, bit and frame synchronization forward error correction mechanisms measurements of signal strength channel sensing Channels 3 mandatory and 2 optional channels (with their carrier frequencies) mandatory channel 0: GHz channel 1: GHz channel 2: GHz optional channel 3: GHz channel 4: GHz Prof. Dr.-Ing. Jochen Schiller, MC SS

54 HIPERLAN 1 - Physical layer frames Maintaining a high data-rate (23.5 Mbit/s) is power consuming problematic for mobile terminals packet header with low bit-rate comprising receiver information only receiver(s) address by a packet continue receiving Frame structure LBR (Low Bit-Rate) header with 1.4 Mbit/s 450 bit synchronization minimum 1, maximum 47 frames with 496 bit each for higher velocities of the mobile terminal (> 1.4 m/s) the maximum number of frames has to be reduced HBR LBR synchronization data0 data1... datam-1 Modulation GMSK for high bit-rate, FSK for LBR header Prof. Dr.-Ing. Jochen Schiller, MC SS

55 HIPERLAN 1 - CAC sublayer Channel Access Control (CAC) assure that terminal does not access forbidden channels priority scheme, access with EY-NPMA Priorities 5 priority levels for QoS support QoS is mapped onto a priority level with the help of the packet lifetime (set by an application) if packet lifetime = 0 it makes no sense to forward the packet to the receiver any longer standard start value 500ms, maximum 16000ms if a terminal cannot send the packet due to its current priority, waiting time is permanently subtracted from lifetime based on packet lifetime, waiting time in a sender and number of hops to the receiver, the packet is assigned to one out of five priorities the priority of waiting packets, therefore, rises automatically Prof. Dr.-Ing. Jochen Schiller, MC SS

56 HIPERLAN 1 - EY-NPMA I EY-NPMA (Elimination Yield Non-preemptive Priority Multiple Access) 3 phases: priority resolution, contention resolution, transmission finding the highest priority every priority corresponds to a time-slot to send in the first phase, the higher the priority the earlier the time-slot to send higher priorities can not be preempted if an earlier time-slot for a higher priority remains empty, stations with the next lower priority might send after this first phase the highest current priority has been determined IPS IPA IES IESV IYS transmission prioritization contention Prof. Dr.-Ing. Jochen Schiller, user data yield listening elimination survival verification elimination burst priority assertion priority detection synchronization transmission MC SS05 t 7.56

57 HIPERLAN 1 - EY-NPMA II Several terminals can now have the same priority and wish to send contention phase Elimination Burst: all remaining terminals send a burst to eliminate contenders ( , high bit- rate) Elimination Survival Verification: contenders now sense the channel, if the channel is free they can continue, otherwise they have been eliminated Yield Listening: contenders again listen in slots with a nonzero probability, if the terminal senses its slot idle it is free to transmit at the end of the contention phase the important part is now to set the parameters for burst duration and channel sensing (slot-based, exponentially distributed) data transmission the winner can now send its data (however, a small chance of collision remains) if the channel was idle for a longer time (min. for a duration of 1700 bit) a terminal can send at once without using EY-NPMA synchronization using the last data transmission Prof. Dr.-Ing. Jochen Schiller, MC SS

58 HIPERLAN 1 - DT-HCPDU/AK-HCPDU LBR LBR bit HI HDA HDA HDACS BLIR = n BLIRCS 1 AID HBR TI BLI = n PLI = m HID byte DA SA UD 19 - (52n-m-4) PAD CS (52n-m-3) - (52n-4) (52n-3) - 52n Data HCPDU bit AIDCS Acknowledgement HCPDU bit HI AID HI: HBR-part Indicator HDA: Hashed Destination HCSAP Address HDACS: HDA CheckSum BLIR: Block Length Indicator BLIRCS: BLIR CheckSum TI: Type Indicator BLI: Block Length Indicator HID: HIPERLAN IDentifier DA: Destination Address SA: Source Address UD: User Data ( byte) PAD: PADding CS: CheckSum AID: Acknowledgement IDentifier AIDS: AID CheckSum Prof. Dr.-Ing. Jochen Schiller, MC SS

59 HIPERLAN 1 - MAC layer Compatible to ISO MAC Supports time-bounded services via a priority scheme Packet forwarding support of directed (point-to-point) forwarding and broadcast forwarding (if no path information is available) support of QoS while forwarding Encryption mechanisms mechanisms integrated, but without key management Power conservation mechanisms mobile terminals can agree upon awake patterns (e.g., periodic wake-ups to receive data) additionally, some nodes in the networks must be able to buffer data for sleeping terminals and to forward them at the right time (so called stores) Prof. Dr.-Ing. Jochen Schiller, MC SS

60 HIPERLAN 1 - DT-HMPDU bit UP KID LI = n TI = 1 byte RL PSN DA SA ADA ASA ML ML IV IV UD (n-2) SC Data HMPDU (n-1) - n n= LI: Length Indicator TI: Type Indicator RL: Residual Lifetime PSN: Sequence Number DA: Destination Address SA: Source Address ADA: Alias Destination Address ASA: Alias Source Address UP: User Priority ML: MSDU Lifetime KID: Key Identifier IV: Initialization Vector UD: User Data, byte SC: Sanity Check (for the unencrypted PDU) Prof. Dr.-Ing. Jochen Schiller, MC SS

61 Information bases Route Information Base (RIB) - how to reach a destination [destination, next hop, distance] Neighbor Information Base (NIB) - status of direct neighbors [neighbor, status] Hello Information Base (HIB) - status of destination (via next hop) [destination, status, next hop] Alias Information Base (AIB) - address of nodes outside the net [original MSAP address, alias MSAP address] Source Multipoint Relay Information Base (SMRIB) - current MP status [local multipoint forwarder, multipoint relay set] Topology Information Base (TIB) - current HIPERLAN topology [destination, forwarder, sequence] Duplicate Detection Information Base (DDIB) - remove duplicates [source, sequence] Prof. Dr.-Ing. Jochen Schiller, MC SS

62 Ad-hoc networks using HIPERLAN 1 1 RIB NIB HIB AIB SMRIB TIB DDIB RIB NIB HIB AIB DDIB 2 Forwarder 4 Information Bases (IB): RIB: Route NIB: Neighbor HIB: Hello AIB: Alias SMRIB: Source Multipoint Relay TIB: Topology DDIB: Duplicate Detection 3 Forwarder RIB NIB HIB AIB DDIB 5 RIB NIB HIB AIB DDIB RIB NIB HIB AIB SMRIB TIB DDIB neighborhood (i.e., within radio range) Prof. Dr.-Ing. Jochen Schiller, RIB NIB HIB AIB SMRIB TIB DDIB MC SS05 6 Forwarder 7.62

63 Some history: Why wireless ATM? seamless connection to wired ATM, a integrated services highperformance network supporting different types a traffic streams ATM networks scale well: private and corporate LANs, WAN B-ISDN uses ATM as backbone infrastructure and integrates several different services in one universal system mobile phones and mobile communications have an ever increasing importance in everyday life current wireless LANs do not offer adequate support for multimedia data streams merging mobile communication and ATM leads to wireless ATM from a telecommunication provider point of view goal: seamless integration of mobility into B-ISDN Problem: very high complexity of the system never reached products Prof. Dr.-Ing. Jochen Schiller, MC SS

64 ATM - basic principle favored by the telecommunication industry for advanced high-performance networks, e.g., B-ISDN, as transport mechanism statistical (asynchronous, on demand) TDM (ATDM, STDM) cell header determines the connection the user data belongs to mixing of different cell-rates is possible different bit-rates, constant or variable, feasible interesting for data sources with varying bit-rate: e.g., guaranteed minimum bit-rate additionally bursty traffic if allowed by the network ATM cell: 5 48 [byte] cell header user data connection identifier, checksum etc. Prof. Dr.-Ing. Jochen Schiller, MC SS

65 Cell-based transmission asynchronous, cell-based transmission as basis for ATM continuous cell-stream additional cells necessary for operation and maintenance of the network (OAM cells; Operation and Maintenance) OAM cells can be inserted after fixed intervals to create a logical frame structure if a station has no data to send it automatically inserts idle cells that can be discarded at every intermediate system without further notice if no synchronous frame is available for the transport of cells (e.g., SDH or Sonet) cell boundaries have to be detected separately (e.g., via the checksum in the cell header) Prof. Dr.-Ing. Jochen Schiller, MC SS

66 B-ISDN protocol reference model 3 dimensional reference model three vertical planes (columns) user plane control plane management plane three hierarchical layers Out-of-Band-Signaling: user data is transmitted separately from control information control user plane plane higher higher layers layers layer management physical layer ATM layer ATM adaptation layer ATM adaptation layer ATM layer layers physical layer planes Prof. Dr.-Ing. Jochen Schiller, MC SS plane management management plane

67 ATM layers Physical layer, consisting of two sub-layers physical medium dependent sub-layer coding bit timing transmission transmission convergence sub-layer HEC (Header Error Correction) sequence generation and verification transmission frame adaptation, generation, and recovery cell delineation, cell rate decoupling ATM layer cell multiplexing/demultiplexing VPI/VCI translation cell header generation and verification GFC (Generic Flow Control) ATM adaptation layer (AAL) Prof. Dr.-Ing. Jochen Schiller, MC SS

68 ATM adaptation layer (AAL) Provides different service classes on top of ATM based on: bit rate: constant bit rate: e.g. traditional telephone line variable bit rate: e.g. data communication, compressed video time constraints between sender and receiver: with time constraints: e.g. real-time applications, interactive voice and video without time constraints: e.g. mail, file transfer mode of connection: connection oriented or connectionless AAL consists of two sub-layers: Convergence Sublayer (CS): service dependent adaptation Common Part Convergence Sublayer (CPCS) Service Specific Convergence Sublayer (SSCS) Segmentation and Reassembly Sublayer (SAR) sub-layers can be empty Prof. Dr.-Ing. Jochen Schiller, MC SS

69 ATM and AAL connections end-system A AAL ATM end-system B service dependent AAL connections service independent ATM connections AAL ATM physical layer ATM layer: physical layer ATM network service independent transport of ATM cells multiplex and demultiplex functionality application AAL layer: support of different services Prof. Dr.-Ing. Jochen Schiller, MC SS

70 ATM Forum Wireless ATM Working Group ATM Forum founded the Wireless ATM Working Group June 1996 Task: development of specifications to enable the use of ATM technology also for wireless networks with a large coverage of current network scenarios (private and public, local and global) compatibility to existing ATM Forum standards important it should be possible to easily upgrade existing ATM networks with mobility functions and radio access two sub-groups of work items Radio Access Layer (RAL) Protocols radio access layer wireless media access control wireless data link control radio resource control handover issues Prof. Dr.-Ing. Jochen Schiller, Mobile ATM Protocol Extensions handover signaling location management mobile routing traffic and QoS Control network management MC SS

71 WATM services Office environment multimedia conferencing, online multimedia database access Universities, schools, training centers distance learning, teaching Industry database connection, surveillance, real-time factory management Hospitals reliable, high-bandwidth network, medical images, remote monitoring Home high-bandwidth interconnect of devices (TV, CD, PC,...) Networked vehicles trucks, aircraft etc. interconnect, platooning, intelligent roads Prof. Dr.-Ing. Jochen Schiller, MC SS

72 WATM components WMT (Wireless Mobile ATM Terminal) RAS (Radio Access System) EMAS-E (End-user Mobility-supporting ATM Switch - Edge) EMAS-N (End-user Mobility-supporting ATM Switch - Network) M-NNI (Network-to-Network Interface with Mobility support) LS (Location Server) AUS (Authentication Server) Prof. Dr.-Ing. Jochen Schiller, MC SS

73 Reference model EMAS-N WMT RAS EMAS-E M-NNI WMT RAS EMAS-N LS AUS Prof. Dr.-Ing. Jochen Schiller, MC SS

74 User plane protocol layers fixed network segment radio segment MATM terminal WATM terminal adapter RAS EMAS -E EMAS -N fixed end system ATMSwitch user process user process AAL AAL ATM ATMCL ATMCL RAL RAL ATM ATM ATM ATM ATM PHY PHY PHY PHY PHY PHY PHY PHY Prof. Dr.-Ing. Jochen Schiller, MC SS

75 Control plane protocol layers fixed network segment radio segment MATM terminal WATM terminal adapter EMAS -E EMAS -N ATMSwitch fixed end system SIG, M-UNI SIG, M-UNI, M-PNNI SIG, M-PNNI SIG, PNNI, UNI SIG, UNI SAAL SAAL SAAL SAAL SAAL ATM ATM ATM ATM PHY PHY PHY RAS M-ATM ATMCL ATMCL RAL RAL ATM PHY PHY PHY PHY PHY Prof. Dr.-Ing. Jochen Schiller, MC SS

76 Reference model with further access scenarios I 1: wireless ad-hoc ATM network 2: wireless mobile ATM terminals 3: mobile ATM terminals 4: mobile ATM switches 5: fixed ATM terminals 6: fixed wireless ATM terminals WMT: wireless mobile terminal WT: wireless terminal MT: mobile terminal T: terminal AP: access point EMAS: end-user mobility supporting ATM switch (-E: edge, -N: network) NMAS: network mobility supporting ATM switch MS: mobile ATM switch Prof. Dr.-Ing. Jochen Schiller, MC SS

77 Reference model with further access scenarios II WMT 1 RAS 2 WMT EMAS -E RAS ACT WMT EMAS -N EMAS -E MT 5 T 6 RAS 3 WT NMAS MS RAS RAS T 4 Prof. Dr.-Ing. Jochen Schiller, MC SS

78 BRAN Broadband Radio Access Networks Motivation deregulation, privatization, new companies, new services How to reach the customer? alternatives: xdsl, cable, satellite, radio Radio access flexible (supports traffic mix, multiplexing for higher efficiency, can be asymmetrical) quick installation economic (incremental growth possible) Market private customers (Internet access, tele-xy...) small and medium sized business (Internet, MM conferencing, VPN) Scope of standardization access networks, indoor/campus mobility, Mbit/s, 50 m-5 km coordination with ATM Forum, IETF, ETSI, IEEE,... Prof. Dr.-Ing. Jochen Schiller, MC SS

79 Broadband network types Common characteristics ATM QoS (CBR, VBR, UBR, ABR) HIPERLAN/2 short range (< 200 m), indoor/campus, 25 Mbit/s user data rate access to telecommunication systems, multimedia applications, mobility (<10 m/s) HIPERACCESS wider range (< 5 km), outdoor, 25 Mbit/s user data rate fixed radio links to customers ( last mile ), alternative to xdsl or cable modem, quick installation Several (proprietary) products exist with 155 Mbit/s plus QoS HIPERLINK currently no activities intermediate link, 155 Mbit/s connection of HIPERLAN access points or connection between HIPERACCESS nodes Prof. Dr.-Ing. Jochen Schiller, MC SS

80 BRAN and legacy networks Independence BRAN as access network independent from the fixed network Interworking of TCP/IP and ATM under study Layered model Network Convergence Sub-layer as superset of all requirements for IP and ATM Coordination core network ATM core network IP network convergence sublayer BRAN data link control BRAN PHY-1 BRAN PHY-2 IETF (TCP/IP) ATM forum (ATM) ETSI (UMTS) CEPT, ITU-R,... (radio frequencies)... Prof. Dr.-Ing. Jochen Schiller, MC SS

81 HiperLAN2 (historical) Official name: BRAN HIPERLAN Type 2 H/2, HIPERLAN/2 also used High data rates for users More efficient than a Connection oriented QoS support Dynamic frequency selection Security support Strong encryption/authentication Mobility support Network and application independent convergence layers for Ethernet, IEEE 1394, ATM, 3G Power save modes Plug and Play No products but several mechanisms have been Adopted by other standards (e.g a) Prof. Dr.-Ing. Jochen Schiller, MC SS

82 HiperLAN2 architecture and handover scenarios AP MT1 1 APT APC MT2 3 MT3 APT APC 2 MT4 AP Core Network (Ethernet, Firewire, ATM, UMTS) APT Prof. Dr.-Ing. Jochen Schiller, MC SS

83 Centralized vs. direct mode AP AP/CC control control control data MT1 MT2 MT1 data Centralized Prof. Dr.-Ing. Jochen Schiller, MT2 MT1 data control Direct MC SS MT2 +CC

84 HiperLAN2 protocol stack Higher layers DLC control SAP Radio link control sublayer Radio resource control DLC user SAP Convergence layer DLC conn. control Assoc. control Data link control basic data transport function Error control Radio link control Scope of HiperLAN2 standards Medium access control Physical layer Prof. Dr.-Ing. Jochen Schiller, MC SS

85 Physical layer reference configuration PDU train from DLC (PSDU) mapping scrambling FEC coding interleaving OFDM PHY bursts (PPDU) radio transmitter Prof. Dr.-Ing. Jochen Schiller, MC SS

86 Operating channels of HiperLAN2 in Europe channel [MHz] 16.6 MHz 140 channel [MHz] MHz center frequency = *channel number [MHz] Prof. Dr.-Ing. Jochen Schiller, MC SS

87 Basic structure of HiperLAN2 MAC frames 2 ms 2 ms MAC frame 2 ms MAC frame broadcast phase MAC frame downlink phase variable 2 ms MAC frame random access phase uplink phase variable... TDD, 500 OFDM symbols per frame variable LCH PDU type payload CRC LCH PDU type sequence number payload CRC bit LCH transfer syntax bit UDCH transfer syntax (long PDU) 54 byte Prof. Dr.-Ing. Jochen Schiller, MC SS

88 Valid configurations of HiperLAN2 MAC frames 2 ms 2 ms MAC frame MAC frame broadcast 2 ms MAC frame downlink 2 ms MAC frame uplink random access BCH FCH ACH DL phase DiL phase UL phase RCHs BCH FCH ACH DiL phase UL phase RCHs BCH FCH ACH UL phase RCHs BCH FCH ACH UL phase RCHs BCH FCH ACH DL phase DiL phase RCHs BCH FCH ACH DiL phase RCHs BCH FCH ACH BCH FCH ACH DL phase DL phase Prof. Dr.-Ing. Jochen Schiller, Valid combinations of MAC frames for a single sector AP RCHs RCHs MC SS

89 Mapping of logical and transport channels BCCH FCCH RFCH LCCH RBCH DCCH UDCH UBCH UMCH downlink BCH FCH ACH UDCH DCCH LCCH LCH SCH RCH SCH ASCH UDCH LCH UBCH uplink Prof. Dr.-Ing. Jochen Schiller, UMCH DCCH RBCH LCH SCH direct link MC SS LCCH

90 Bluetooth Idea Universal radio interface for ad-hoc wireless connectivity Interconnecting computer and peripherals, handheld devices, PDAs, cell phones replacement of IrDA Embedded in other devices, goal: 5 /device (2005: 40 /USB bluetooth) Short range (10 m), low power consumption, license-free 2.45 GHz ISM Voice and data transmission, approx. 1 Mbit/s gross data rate One of the first modules (Ericsson). Prof. Dr.-Ing. Jochen Schiller, MC SS

91 Bluetooth History 1994: Ericsson (Mattison/Haartsen), MC-link project Renaming of the project: Bluetooth according to Harald Blåtand Gormsen [son of Gorm], King of Denmark in the 10th century (was: ) 1998: foundation of Bluetooth SIG, : erection of a rune stone at Ercisson/Lund ;-) 2001: first consumer products for mass market, spec. version 1.1 released 2005: 5 million chips/week Special Interest Group Original founding members: Ericsson, Intel, IBM, Nokia, Toshiba Added promoters: 3Com, Agere (was: Lucent), Microsoft, Motorola > 2500 members Common specification and certification of products Prof. Dr.-Ing. Jochen Schiller, MC SS

92 History and hi-tech 1999: Ericsson mobile communications AB reste denna sten till minne av Harald Blåtand, som fick ge sitt namn åt en ny teknologi för trådlös, mobil kommunikation. Prof. Dr.-Ing. Jochen Schiller, MC SS

93 and the real rune stone Located in Jelling, Denmark, erected by King Harald Blåtand in memory of his parents. The stone has three sides one side showing a picture of Christ. Inscription: "Harald king executes these sepulchral monuments after Gorm, his father and Thyra, his mother. The Harald who won the whole of Denmark and Norway and turned the Danes to Christianity." Btw: Blåtand means of dark complexion (not having a blue tooth ) This could be the original colors of the stone. Inscription: auk tani karthi kristna (and made the Danes Christians) Prof. Dr.-Ing. Jochen Schiller, MC SS

94 Characteristics 2.4 GHz ISM band, 79 (23) RF channels, 1 MHz carrier spacing Channel 0: 2402 MHz channel 78: 2480 MHz G-FSK modulation, mw transmit power FHSS and TDD Frequency hopping with 1600 hops/s Hopping sequence in a pseudo random fashion, determined by a master Time division duplex for send/receive separation Voice link SCO (Synchronous Connection Oriented) FEC (forward error correction), no retransmission, 64 kbit/s duplex, pointto-point, circuit switched Data link ACL (Asynchronous ConnectionLess) Asynchronous, fast acknowledge, point-to-multipoint, up to kbit/s symmetric or 723.2/57.6 kbit/s asymmetric, packet switched Topology Overlapping piconets (stars) forming a scatternet Prof. Dr.-Ing. Jochen Schiller, MC SS

95 Piconet Collection of devices connected in an ad hoc fashion P One unit acts as master and the others as slaves for the lifetime of the piconet S S M Master determines hopping pattern, slaves have to synchronize SB S P Each piconet has a unique hopping pattern Participation in a piconet = synchronization to hopping sequence P M=Master S=Slave SB P=Parked SB=Standby Each piconet has one master and up to 7 simultaneous slaves (> 200 could be parked) Prof. Dr.-Ing. Jochen Schiller, MC SS

96 Forming a piconet All devices in a piconet hop together Master gives slaves its clock and device ID Hopping pattern: determined by device ID (48 bit, unique worldwide) Phase in hopping pattern determined by clock Addressing Active Member Address (AMA, 3 bit) Parked Member Address (PMA, 8 bit) SB SB SB SB SB SB SB S SB SB SB Prof. Dr.-Ing. Jochen Schiller, MC SS05 P S M P S P SB 7.96

97 Scatternet Linking of multiple co-located piconets through the sharing of common master or slave devices Devices can be slave in one piconet and master of another Communication between piconets Devices jumping back and forth between the piconets P S S S P P M Piconets (each with a capacity of 720 kbit/s) M SB M=Master S=Slave P=Parked SB=Standby S P SB Prof. Dr.-Ing. Jochen Schiller, SB S MC SS

98 Bluetooth protocol stack audio apps. NW apps. vcal/vcard TCP/UDP OBEX telephony apps. AT modem commands IP mgmnt. apps. TCS BIN SDP BNEP PPP Control RFCOMM (serial line interface) Audio Logical Link Control and Adaptation Protocol (L2CAP) Link Manager Baseband Radio AT: attention sequence OBEX: object exchange TCS BIN: telephony control protocol specification binary BNEP: Bluetooth network encapsulation protocol Prof. Dr.-Ing. Jochen Schiller, SDP: service discovery protocol RFCOMM: radio frequency comm. MC SS Host Controller Interface

99 Frequency selection during data transmission 625 µs fk M fk+1 fk+2 fk+3 fk+4 fk+5 fk+6 S M S M S M t fk fk+3 fk+4 fk+5 fk+6 M S M S M t fk fk+1 M S fk+6 M t Prof. Dr.-Ing. Jochen Schiller, MC SS

100 Baseband Piconet/channel definition Low-level packet definition Access code Channel, device access, e.g., derived from master address (48-bit) Packet header 1/3-FEC, active member address (broadcast + 7 slaves), link type, alternating bit ARQ/SEQ, checksum 68(72) access code packet header 4 preamble 64 sync. (4) 3 (trailer) AM address bits payload type flow ARQN SEQN HEC Prof. Dr.-Ing. Jochen Schiller, MC SS bits

101 SCO payload types payload (30) HV1 audio (10) HV2 audio (20) HV3 DV FEC (20) FEC (10) audio (30) audio (10) header (1) payload (0-9) 2/3 FEC CRC (2) (bytes) Prof. Dr.-Ing. Jochen Schiller, MC SS

102 ACL Payload types payload (0-343) header (1/2) DM1 header (1) DH1 header (1) DM3 header (2) DH3 header (2) DM5 header (2) DH5 header (2) AUX1 header (1) payload (0-339) payload (0-17) 2/3 FEC payload (0-27) payload (0-121) CRC (2) CRC (2) (bytes) CRC (2) 2/3 FEC CRC (2) payload (0-183) CRC (2) payload (0-224) 2/3 FEC payload (0-339) CRC (2) CRC (2) payload (0-29) Prof. Dr.-Ing. Jochen Schiller, MC SS

103 Baseband data rates ACL 1 slot 3 slot 5 slot SCO Type Payload User Header Payload [byte] [byte] FEC CRC Symmetric Asymmetric max. Rate max. Rate [kbit/s] [kbit/s] Forward Reverse DM /3 yes DH no yes DM /3 yes DH no yes DM /3 yes DH no yes AUX no no HV1 na 10 1/3 no 64.0 HV2 na 20 2/3 no 64.0 HV3 na 30 no no 64.0 DV 1D 10+(0-9) D 2/3 D yes D D Data Medium/High rate, High-quality Voice, Data and Voice Prof. Dr.-Ing. Jochen Schiller, MC SS

104 Baseband link types Polling-based TDD packet transmission 625µs slots, master polls slaves SCO (Synchronous Connection Oriented) Voice Periodic single slot packet assignment, 64 kbit/s full-duplex, point-to-point ACL (Asynchronous ConnectionLess) Data MASTER SLAVE 1 SLAVE 2 Variable packet size (1,3,5 slots), asymmetric bandwidth, point-to-multipoint SCO f0 ACL f4 SCO f6 f1 SCO f12 ACL f8 f7 f9 f13 ACL f20 f19 f17 f5 Prof. Dr.-Ing. Jochen Schiller, SCO f18 ACL f14 MC SS05 f

105 Robustness Slow frequency hopping with hopping patterns determined by a master Protection from interference on certain frequencies Separation from other piconets (FH-CDMA) Retransmission Error in payload (not header!) ACL only, very fast Forward Error Correction MASTER SLAVE 1 NAK SCO and ACL A C B C D F ACK H E SLAVE 2 Prof. Dr.-Ing. Jochen Schiller, G MC SS05 G 7.105

106 Baseband states of a Bluetooth device unconnected standby detach inquiry transmit AMA park PMA page connected AMA hold AMA Standby: do nothing Inquire: search for other devices Page: connect to a specific device Connected: participate in a piconet sniff AMA connecting active low power Park: release AMA, get PMA Sniff: listen periodically, not each slot Hold: stop ACL, SCO still possible, possibly participate in another piconet Prof. Dr.-Ing. Jochen Schiller, MC SS

107 Example: Power consumption/csr BlueCore2 Typical Average Current Consumption (1) VDD=1.8V Temperature = 20 C Mode SCO connection HV3 (1s interval Sniff Mode) (Slave) SCO connection HV3 (1s interval Sniff Mode) (Master) SCO connection HV1 (Slave) SCO connection HV1 (Master) ACL data transfer 115.2kbps UART (Master) ACL data transfer 720kbps USB (Slave) ACL data transfer 720kbps USB (Master) ACL connection, Sniff Mode 40ms interval, 38.4kbps UART ACL connection, Sniff Mode 1.28s interval, 38.4kbps UART Parked Slave, 1.28s beacon interval, 38.4kbps UART Standby Mode (Connected to host, no RF activity) Deep Sleep Mode(2) Notes: (1) Current consumption is the sum of both BC212015A and the flash. (2) Current consumption is for the BC212015A device only. (More: ) Prof. Dr.-Ing. Jochen Schiller, MC SS ma 26.0 ma 53.0 ma 53.0 ma 15.5 ma 53.0 ma 53.0 ma 4.0 ma 0.5 ma 0.6 ma 47.0 µa 20.0 µa 7.107

108 Example: Bluetooth/USB adapter (2002: 50 ) Prof. Dr.-Ing. Jochen Schiller, MC SS

109 L2CAP - Logical Link Control and Adaptation Protocol Simple data link protocol on top of baseband Connection oriented, connectionless, and signalling channels Protocol multiplexing RFCOMM, SDP, telephony control Segmentation & reassembly Up to 64kbyte user data, 16 bit CRC used from baseband QoS flow specification per channel Follows RFC 1363, specifies delay, jitter, bursts, bandwidth Group abstraction Create/close group, add/remove member Prof. Dr.-Ing. Jochen Schiller, MC SS

110 L2CAP logical channels Master Slave L2CAP Slave L2CAP 2 d 1 1 d d d d 1 baseband signalling L2CAP 1 baseband ACL baseband connectionless Prof. Dr.-Ing. Jochen Schiller, connection-oriented MC SS d d 2

111 L2CAP packet formats Connectionless PDU length CID=2 PSM payload bytes Connection-oriented PDU length CID payload bytes Signalling command PDU 2 2 length CID=1 bytes One or more commands code ID length data Prof. Dr.-Ing. Jochen Schiller, MC SS

112 Security User input (initialization) PIN (1-16 byte) Pairing PIN (1-16 byte) E2 Authentication key generation (possibly permanent storage) E2 link key (128 bit) Authentication link key (128 bit) E3 Encryption key generation (temporary storage) E3 encryption key (128 bit) Encryption encryption key (128 bit) Keystream generator Keystream generator payload key Ciphering payload key Cipher data Data Data Prof. Dr.-Ing. Jochen Schiller, MC SS

113 SDP Service Discovery Protocol Inquiry/response protocol for discovering services Searching for and browsing services in radio proximity Adapted to the highly dynamic environment Can be complemented by others like SLP, Jini, Salutation, Defines discovery only, not the usage of services Caching of discovered services Gradual discovery Service record format Information about services provided by attributes Attributes are composed of an 16 bit ID (name) and a value values may be derived from 128 bit Universally Unique Identifiers (UUID) Prof. Dr.-Ing. Jochen Schiller, MC SS

114 Additional protocols to support legacy protocols/apps. RFCOMM Emulation of a serial port (supports a large base of legacy applications) Allows multiple ports over a single physical channel Telephony Control Protocol Specification (TCS) Call control (setup, release) Group management OBEX Exchange of objects, IrDA replacement WAP Interacting with applications on cellular phones Prof. Dr.-Ing. Jochen Schiller, MC SS

115 Profiles Represent default solutions for a certain usage model Vertical slice through the protocol stack Basis for interoperability Applications Protocols Generic Access Profile Service Discovery Application Profile Cordless Telephony Profile Intercom Profile Serial Port Profile Additional Profiles Headset Profile Advanced Audio Distribution Dial-up Networking Profile PAN Fax Profile Audio Video Remote Control LAN Access Profile Basic Printing Generic Object Exchange Profile Basic Imaging Object Push Profile Extended Service Discovery File Transfer Profile Generic Audio Video Distribution Synchronization Profile Hands Free Hardcopy Cable Replacement Prof. Dr.-Ing. Jochen Schiller, MC SS Profiles

116 WPAN: IEEE Bluetooth Data rate Connection set-up time Synchronous, connection-oriented: 64 kbit/s Asynchronous, connectionless kbit/s symmetric / 57.6 kbit/s asymmetric Transmission range POS (Personal Operating Space) up to 10 m with special transceivers up to 100 m Quality of Service Free 2.4 GHz ISM-band Security Challenge/response (SAFER+), hopping sequence Availability Public/private keys needed, key management not specified, simple system integration Special Advantages/Disadvantages Frequency Guarantees, ARQ/FEC Manageability Depends on power-mode Max. 2.56s, avg. 0.64s Integrated into many products, several vendors Prof. Dr.-Ing. Jochen Schiller, Advantage: already integrated into several products, available worldwide, free ISM-band, several vendors, simple system, simple ad-hoc networking, peer to peer, scatternets Disadvantage: interference on ISM-band, limited range, max. 8 devices/network&master, high set-up latency MC SS

117 WPAN: IEEE : Coexistance Coexistence of Wireless Personal Area Networks (802.15) and Wireless Local Area Networks (802.11), quantify the mutual interference : High-Rate Standard for high-rate (20Mbit/s or greater) WPANs, while still lowpower/low-cost Data Rates: 11, 22, 33, 44, 55 Mbit/s Quality of Service isochronous protocol Ad hoc peer-to-peer networking Security Low power consumption Low cost Designed to meet the demanding requirements of portable consumer imaging and multimedia applications Prof. Dr.-Ing. Jochen Schiller, MC SS

118 WPAN: IEEE future developments 2 Several working groups extend the standard a: Alternative PHY with higher data rate as extension to Applications: multimedia, picture transmission b: Enhanced interoperability of MAC Correction of errors and ambiguities in the standard c: Alternative PHY at GHz Goal: data rates above 2 Gbit/s Not all these working groups really create a standard, not all standards will be found in products later Prof. Dr.-Ing. Jochen Schiller, MC SS

119 WPAN: IEEE future developments : Low-Rate, Very Low-Power Low data rate solution with multi-month to multi-year battery life and very low complexity Potential applications are sensors, interactive toys, smart badges, remote controls, and home automation Data rates of kbit/s, latency down to 15 ms Master-Slave or Peer-to-Peer operation Up to 254 devices or simpler nodes Support for critical latency devices, such as joysticks CSMA/CA channel access (data centric), slotted (beacon) or unslotted Automatic network establishment by the PAN coordinator Dynamic device addressing, flexible addressing format Fully handshaked protocol for transfer reliability Power management to ensure low power consumption 16 channels in the 2.4 GHz ISM band, 10 channels in the 915 MHz US ISM band and one channel in the European 868 MHz band Basis of the ZigBee technology Prof. Dr.-Ing. Jochen Schiller, MC SS

120 ZigBee Relation to similar to Bluetooth / Pushed by Chipcon, ember, freescale (Motorola), Honeywell, Mitsubishi, Motorola, Philips, Samsung More than 150 members Promoter (40000$/Jahr), Participant (9500$/Jahr), Adopter (3500$/Jahr) No free access to the specifications (only promoters and participants) ZigBee platforms comprise IEEE for layers 1 and 2 ZigBee protocol stack up to the applications Prof. Dr.-Ing. Jochen Schiller, MC SS

121 WPAN: IEEE future developments 4 Several working groups extend the standard a: Alternative PHY with lower data rate as extension to Properties: precise localization (< 1m precision), extremely low power consumption, longer range Two PHY alternatives UWB (Ultra Wideband): ultra short pulses, communication and localization CSS (Chirp Spread Spectrum): communication only b: Extensions, corrections, and clarifications regarding Usage of new bands, more flexible security mechanisms : Mesh Networking Partial meshes, full meshes Range extension, more robustness, longer battery live Not all these working groups really create a standard, not all standards will be found in products later Prof. Dr.-Ing. Jochen Schiller, MC SS

122 Some more IEEE standards for mobile communications IEEE : Broadband Wireless Access / WirelessMAN / WiMax Wireless distribution system, e.g., for the last mile, alternative to DSL 75 Mbit/s up to 50 km LOS, up to 10 km NLOS; 2-66 GHz band Initial standards without roaming or mobility support e adds mobility support, allows for roaming at 150 km/h Unclear relation to , started as fixed system IEEE : Mobile Broadband Wireless Access (MBWA) Licensed bands < 3.5 GHz, optimized for IP traffic Peak rate > 1 Mbit/s per user Different mobility classes up to 250 km/h and ranges up to 15 km IEEE : Media Independent Handover Interoperability Standardize handover between different 802.x and/or non 802 networks IEEE : Wireless Regional Area Networks (WRAN) Radio-based PHY/MAC for use by license-exempt devices on a noninterfering basis in spectrum that is allocated to the TV Broadcast Service Prof. Dr.-Ing. Jochen Schiller, MC SS

123 WLAN: Home RF yet another standard, no success Data rate 0.8, 1.6, 5, 10 Mbit/s Transmission range Connection set-up time Quality of Service 300m outdoor, 30m indoor Frequency 2.4 GHz ISM Strong encryption, no open access Advantage: extended QoS support, host/client and peer/peer, power saving, security Disadvantage: future uncertain due to DECT-only devices plus a/b for data Adapter 130, base station 230 Availability Like DECT & 802-LANs Special Advantages/Disadvantages Cost Up to 8 streams A/V, up to 8 voice streams, priorities, best-effort Manageability Security 10 ms bounded latency Several products from different vendors, no more support Prof. Dr.-Ing. Jochen Schiller, MC SS

124 RF Controllers ISM bands Data rate Typ. up to 115 kbit/s (serial interface) Transmission range m, depending on power (typ mw) Connection set-up time Quality of Service Typ. 27 (EU, US), 315 (US), 418 (EU), 426 (Japan), 433 (EU), 868 (EU), 915 (US) MHz (depending on regulations) Some products with added processors Cost Cheap: Availability Very simple, same as serial interface Special Advantages/Disadvantages Security none Manageability Frequency N/A Advantage: very low cost, large experience, high volume available Disadvantage: no QoS, crowded ISM bands (particularly 27 and 433 MHz), typ. no Medium Access Control, 418 MHz experiences interference with TETRA Many products, many vendors Prof. Dr.-Ing. Jochen Schiller, MC SS

125 RFID Radio Frequency Identification (1) Data rate Transmission of ID only (e.g., 48 bit, 64kbit, 1 Mbit) kbit/s Transmission range Passive: up to 3 m Active: up to m Simultaneous detection of up to, e.g., 256 tags, scanning of, e.g., 40 tags/s Connection set-up time Quality of Service 125 khz, MHz, 433 MHz, 2.4 GHz, 5.8 GHz and many others Application dependent, typ. no crypt. on RFID device Cost Very simple, same as serial interface Special Advantages/Disadvantages Security none Manageability Frequency Depends on product/medium access scheme (typ. 2 ms per device) Very cheap tags, down to 1 (passive) Advantage: extremely low cost, large experience, high volume available, no power for passive RFIDs needed, large variety of products, relative speeds up to 300 km/h, broad temp. range Disadvantage: no QoS, simple denial of service, crowded ISM bands, typ. oneway (activation/ transmission of ID) Availability Many products, many vendors Prof. Dr.-Ing. Jochen Schiller, MC SS

126 RFID Radio Frequency Identification (2) Function Standard: In response to a radio interrogation signal from a reader (base station) the RFID tags transmit their ID Enhanced: additionally data can be sent to the tags, different media access schemes (collision avoidance) Features No line-of sight required (compared to, e.g., laser scanners) RFID tags withstand difficult environmental conditions (sunlight, cold, frost, dirt etc.) Products available with read/write memory, smart-card capabilities Categories Passive RFID: operating power comes from the reader over the air which is feasible up to distances of 3 m, low price (1 ) Active RFID: battery powered, distances up to 100 m Prof. Dr.-Ing. Jochen Schiller, MC SS

127 RFID Radio Frequency Identification (3) Applications Total asset visibility: tracking of goods during manufacturing, localization of pallets, goods etc. Loyalty cards: customers use RFID tags for payment at, e.g., gas stations, collection of buying patterns Automated toll collection: RFIDs mounted in windshields allow commuters to drive through toll plazas without stopping Others: access control, animal identification, tracking of hazardous material, inventory control, warehouse management,... Local Positioning Systems GPS useless indoors or underground, problematic in cities with high buildings RFID tags transmit signals, receivers estimate the tag location by measuring the signal s time of flight Prof. Dr.-Ing. Jochen Schiller, MC SS

128 RFID Radio Frequency Identification (4) Security Denial-of-Service attacks are always possible Interference of the wireless transmission, shielding of transceivers IDs via manufacturing or one time programming Key exchange via, e.g., RSA possible, encryption via, e.g., AES Future Trends RTLS: Real-Time Locating System big efforts to make total asset visibility come true Integration of RFID technology into the manufacturing, distribution and logistics chain Creation of electronic manifests at item or package level (embedded inexpensive passive RFID tags) 3D tracking of children, patients Prof. Dr.-Ing. Jochen Schiller, MC SS

129 RFID Radio Frequency Identification (5) Devices and Companies AXCESS Inc., Checkpoint Systems Group, GEMPLUS, Intermec/Intellitag, I-Ray Technologies, RF Code, Texas Instruments, WhereNet, Wireless Mountain, XCI, Only a very small selection Prof. Dr.-Ing. Jochen Schiller, MC SS

130 RFID Radio Frequency Identification (6) Example Product: Intermec RFID UHF OEM Reader Read range up to 7m Anticollision algorithm allows for scanning of 40 tags per second regardless of the number of tags within the reading zone US: unlicensed 915 MHz, Frequency Hopping Read: 8 byte < 32 ms Write: 1 byte < 100ms Example Product: Wireless Mountain Spider Proprietary sparse code anti-collision algorithm Detection range 15 m indoor, 100 m line-of-sight > 1 billion distinct codes Read rate > 75 tags/s Operates at 308 MHz Prof. Dr.-Ing. Jochen Schiller, MC SS

131 RFID Radio Frequency Identification (7) Relevant Standards American National Standards Institute Automatic Identification and Data Capture Techniques ISO TC 104 / SC 4, Road Transport and Traffic Telematics JTC 1/SC 17, Identification and communication ETSI, Identification Cards and related devices ERO, European Telecommunications Standards Institute JTC 1/SC 31, European Radiocommunications Office ANSI, CEN TC 278, Transport Information and Control Systems ISO/TC204, Prof. Dr.-Ing. Jochen Schiller, MC SS

132 RFID Radio Frequency Identification (8) ISO Standards ISO MH Data Identifiers EAN.UCC Application Identifiers ISO Syntax for High Capacity ADC Media ISO Transfer Syntax ISO Part 2, khz Part 3, MHz Part 4, 2.45 GHz Part 5, 5.8 GHz Part 6, UHF ( MHz, 433 MHz) ISO RFID Device Conformance Test Methods ISO RF Tag and Interrogator Performance Test Methods Prof. Dr.-Ing. Jochen Schiller, MC SS

133 ISM band interference Many sources of interference OLD Microwave ovens, microwave lightning , b, g, , Home RF Even analog TV transmission, surveillance Unlicensed metropolitan area networks NEW Levels of interference Physical layer: interference acts like noise Spread spectrum tries to minimize this FEC/interleaving tries to correct MAC layer: algorithms not harmonized Fusion Lighting, Inc. E.g., Bluetooth might confuse Prof. Dr.-Ing. Jochen Schiller, MC SS

134 vs.(?) /Bluetooth Bluetooth may act like a rogue member of the network DIFS 500 byte 100 byte channels SIFS ACK SIFS ACK 100 byte (separated by installation) DIFS SIFS ACK DIFS SIFS ACK DIFS 100 byte SIFS ACK SIFS ACK SIFS ACK DIFS 100 byte 500 byte DIFS byte SIFS ACK DIFS 500 byte DIFS DIFS DIFS f [MHz] Does not know anything about gaps, inter frame spacing etc b channels 1000 byte (separated by hopping pattern) t IEEE discusses these problems Proposal: Adaptive Frequency Hopping a non-collaborative Coexistence Mechanism Real effects? Many different opinions, publications, tests, formulae, Results from complete breakdown to almost no effect Bluetooth (FHSS) seems more robust than b (DSSS) Prof. Dr.-Ing. Jochen Schiller, MC SS

135 Wireless & Mobile Communications Chapter 6: Network Protocols/Mobile IP Motivation Data transfer Encapsulation Security IPv6 Problems DHCP Ad-hoc networks Routing protocols

136 Why Mobile IP? What do cellular networks and wireless LANs provide? Wireless connectivity Mobility at the data link layer What is Dynamic Host Configuration Protocol (DHCP)? It provides local IP addresses for mobile hosts Is not secure Does not maintain network connectivity when moving around What they do not provide: Transparent connectivity at the network layer Mobility with local access The difference between mobility and nomadicity! ICS 243E - Ch 6 Net. Protocols Winter

137 What is Mobile IP? Mobile IP provides network layer mobility Provides seamless roaming Extends the home network over the entire Internet ICS 243E - Ch 6 Net. Protocols Winter

138 IP Overview 1/3 IP Addressing : Dotted Decimal Notation: 32 bits (4x8) used to represent IPv4 addresses Network Prefix and Host Portions: p - prefix, h - host, p + h = 32. If p = 24 then h = = 8. Using above address the network prefix will be and host will be 18. For those of you familiar with subnet masks, p represents the number of 1 s in the subnet mask. If p = 24, subnet mask is , if p = 26, subnet mask is ICS 243E - Ch 6 Net. Protocols Winter

139 IP Overview 2/3 IP Routing: Network prefix is used for routing. Routing tables are used to look up next hop and the interface on the router that is to be used. In the routing tables we use the following notation: target/prefix length, e.g., /24, or /26. If two subnet masks/prefixes fit the address, the one with the largest prefix is chosen for routing. E.g., a router with the following 3 entries in its table: /32 (p=32 host specific) and /24 (0<p<32 network prefix) and /0 (p=0 default) will use entry 2 for an IP packet with destination and entry 3 for destination ICS 243E - Ch 6 Net. Protocols Winter

140 IP Overview 3/3 Domain Name System (DNS): used to translate a host name to an IP address. A host sends a query to a server to obtain the IP address of a destination of which it only has the host name. Link Layer Addresses - Address Resolution Protocol (ARP): Once a host has the IP address of a destination it then needs to finds its layer 2 address or the layer 2 address of the next hop on the path. A broadcast message is sent and the targeted host responds with its layer 2 address. A proxy ARP is a response by a node for another node that cannot respond at the time the request is made (e.g. the node is a mobiel node and not on its host net at the time, its home agent will respond in its stead). A gratuitous ARP, is a reply to no ARP request, used by a node that just joins the network and wants to make its address known. Can be used by a mobile node upon its return to its home net. ICS 243E - Ch 6 Net. Protocols Winter

141 Motivation for Mobile IP IP Routing based on IP destination address, network prefix (e.g ) determines physical subnet change of physical subnet implies change of IP address to have a topologically correct address (standard IP) or needs special entries in the routing tables Specific routes to end-systems? requires changing all routing table entries to forward packets to the right destination does not scale with the number of mobile hosts and frequent changes in the location, security problems Changing the IP-address? adjust the host IP address depending on the current location almost impossible to find a mobile system, DNS updates take long time TCP connections break, security problems ICS 243E - Ch 6 Net. Protocols Winter

142 What Mobile IP does: Mobile IP solves the following problems: if a node moves without changing its IP address it will be unable to receive its packets, if a node changes its IP address it will have to terminate and restart its ongoing connections everytime it moves to a new network area (new network prefix). Mobile IP is a routing protocol with a very specific purpose. Mobile IP is a network layer solution to node mobility in the Internet. Mobile IP is not a complete solution to mobility, changes to the transport protocols need to be made for a better solution (i.e., the transport layers are unaware of the mobile node s point of attachment and it might be useful if, e.g., TCP knew that a wireless link was being used!). ICS 243E - Ch 6 Net. Protocols Winter

143 Requirements to Mobile IP (RFC 2002) Transparency mobile end-systems keep their IP address continuation of communication after interruption of link possible point of connection to the fixed network can be changed Compatibility Security support of the same layer 2 protocols as IP no changes to current end-systems and routers required mobile end-systems can communicate with fixed systems authentication of all registration messages Efficiency and scalability only little additional messages to the mobile system required (connection typically via a low bandwidth radio link) world-wide support of a large number of mobile systems in the whole Internet ICS 243E - Ch 6 Net. Protocols Winter

144 Mobile IP Terminology Mobile Node (MN) system (node) that can change the point of connection to the network without changing its IP address Home Agent (HA) system in the home network of the MN, typically a router registers the location of the MN, tunnels IP datagrams to the COA Foreign Agent (FA) system in the current foreign network of the MN, typically a router forwards the tunneled datagrams to the MN, typically also the default router for the MN Care-of Address (COA) address of the current tunnel end-point for the MN (at FA or MN) actual location of the MN from an IP point of view can be chosen, e.g., via DHCP Correspondent Node (CN) communication partner ICS 243E - Ch 6 Net. Protocols Winter

145 Mobile IP Operation: Summary Consists of 3 steps: Agent discovery, Registration, and Routing/Tunneling ICS 243E - Ch 6 Net. Protocols Winter

146 Operation Summary 1/3 Agent Advertisement/Discovery: consists of broadcast messages used by mobiles to detect that they have moved and are required to register with a new FA. FAs send agent advertisements MNs can solicit for agents if they have not heard an agent advertisement in awhile or use some other mechanism to obtain a COA or temp. IP address (e.g. DHCP). MNs know they are home when they recognize their HA. ICS 243E - Ch 6 Net. Protocols Winter

147 Operation Summary 2/3 Registration: used by a MN to inform the FA that it is visiting. The new care of address of the MN is sent to the HA. Registration expires, duration is negotiated during registration Mobile must re-register before it expires All registrations are authenticated The MN sends a regristration request in to the FA which passes it along to the home agent. The HA responds to the FA which then informs the MN that all is in order and registration is complete. ICS 243E - Ch 6 Net. Protocols Winter

148 Operation Summary 3/3 Routing/Encapsulation/Tunneling: consists of the delivery of the packets to the mobile node at its current care of address. Sender does not need to know that the destination is a MN. HA intercepts all packets for the MN and passes them along to MN using a tunnel. MN communicates directly with the CN. Referred to as Triangle Routing ICS 243E - Ch 6 Net. Protocols Winter

149 Example network HA MN router home network mobile end-system Internet (physical home network for the MN) FA foreign network router (current physical network for the MN) CN end-system ICS 243E - Ch 6 Net. Protocols router Winter

150 Data transfer to the mobile system HA 2 MN home network receiver 3 Internet FA 1 CN sender ICS 243E - Ch 6 Net. Protocols foreign network 1. Sender sends to the IP address of MN, HA intercepts packet (proxy ARP) 2. HA tunnels packet to COA, here FA, by encapsulation 3. FA forwards the packet to the MN Winter

151 Data transfer from the mobile system HA 1 home network MN sender Internet FA foreign network 1. Sender sends to the IP address of the receiver as usual, FA works as default router CN receiver ICS 243E - Ch 6 Net. Protocols Winter

152 Overview COA home network router FA router HA MN foreign network Internet CN router home network router HA router FA MN 4. Internet foreign network 1. CN router ICS 243E - Ch 6 Net. Protocols Winter

153 Network integration Agent Advertisement Discovery HA and FA periodically send advertisement messages into their physical subnets MN listens to these messages and detects, if it is in the home or a foreign network (standard case for home network) MN reads a COA from the FA advertisement messages Registration (always limited lifetime!) MN signals COA to the HA via the FA, HA acknowledges via FA to MN these actions have to be secured by authentication Routing/Encapsulation/Tunneling HA advertises the IP address of the MN (as for fixed systems), i.e. standard routing information packets to the MN are sent to the HA, independent of changes in COA/FA ICS 243E - Ch 6 Net. Protocols Winter

154 Agent advertisement type #addresses checksum lifetime 31 code addr. size router address 1 preference level 1 router address 2 preference level 2... type length registration lifetime sequence number R B H F M G V reserved COA 1 COA 2... ICS 243E - Ch 6 Net. Protocols Winter

155 Registration MN FA HA MN HA t t ICS 243E - Ch 6 Net. Protocols Winter

156 Mobile IP registration request type S B DMG V rsv home address home agent COA lifetime 31 identification extensions... ICS 243E - Ch 6 Net. Protocols Winter

157 Processing Registration Messages 1/3 A MN, depending on which registration scenario it is in, will figure what addresses to use in the various fields of the Registration request message. Link layer addresses are tricky: A MN may not use ARP if it is using a FA COA. It needs to use the address of the FA as the destination address. If it is using a collocated COA, then it uses ARP to locate the default router using its COA as source. Note that if the R bit is set is uses the FA address as the destination address. For de-registration is uses ARP to locate the HA link address and it uses its own home address for the ARP message. For network layer addresses (i.e., IP addresses): It uses the FA address as destination address when using the FA COA and its own home address as the source address. If using a collocated COA it uses its COA as source address and the HA address as destination address. Note that if the R bit is set then is must use the same addresses as for the FA COA scenario. For de-registration it uses its own home address as source and the HA address as destination. ICS 243E - Ch 6 Net. Protocols Winter

158 Processing Registration Messages 2/3 For the FA: A FA may refuse a Registration request for a number of reasons: lifetime too long, authentication failed, requested tunneling not supported, cannot handle another MN (current load too high). If an FA does not refuse the request it relays it to the HA. Relaying is different from forwading as the FA is required to process the packet and create new headers. Some important fields of the request message are recorded for use later on: MN link layer address, MN IP address, UDP source port, HA IP address, identification number and requested lifetime. Regarding a Registration reply message, the FA can refuse it and send a decline to the MN is it finds the reply from the HA to be invalid. Otherwise it updates its list of visiting MNs and begins acting on behalf of the MN. ICS 243E - Ch 6 Net. Protocols Winter

159 Processing Registration Messages 3/3 For a HA The HA will determine, as the FA did, whether it will accept the request. If it does not it returns a code in the reply message indicating the cause of the failed request. If the request is accepted, the reply is sent back by reversing all the IP addresses and UDP port numbers. The HA updates the binding table corresponding to that MN dependent upon the nature of the request. ICS 243E - Ch 6 Net. Protocols Winter

160 Routing/Tunneling 1/5 Routing a packet to a MN involves the following: A router on the home link, possibly the HA, advertises reachability to the network prefix of the MN s home address. All packets are therefore routed to the MN s home link. A HA intercepts the packets for the MN and tunnels a copy to each COA in the binding table. At the foreign link either the MN extracts the packet (collocated COA) or the FA extracts the packet and forwards it to the MN. ICS 243E - Ch 6 Net. Protocols Winter

161 Routing/Tunneling 2/5 A HA can use one of two methods to intercept a MN s packets: The HA is a router with multiple network interfaces. In that case it advertises reachability to the MN s home network prefix. The HA is not a router with multiple intefaces. It must use ARP to receive the MN s packets. It either responds to ARP requests on behalf of the MN (proxy ARP) or uses gratuitous ARPs to inform the home network that it is receiving the MN s IP packets. This is to update any ARP caches that hosts and other devices might have. ICS 243E - Ch 6 Net. Protocols Winter

162 Routing/Tunneling 3/5 How to fool the routing table into handling tunneled packets at the HA? A virtual interface is used to do the encapsulation. A packet destined for the MN is handled by the routing routine as all received IP packets are. The routing table has a host specific entry for the MN. This host specific entry is used to route the packet to a virtual interface that basically consists of a process that does encapsulation. Once encapsulation has been performed the packet is sent to be processed by the routing routine again. This time the destination address is the COA and it is routed normally. ICS 243E - Ch 6 Net. Protocols Winter

163 Routing/Tunneling 4/5 How to fool the routing table into handling tunneled packets at the FA? The same procedure is used as above. A packet coming in with a COA that is one of the FA addresses is handled by the routing routine. A host specific address (its own address) in the routing table points to the higher layers and the packet is passed on to a virtual interface. The virtual interface consists of a process that decapsulates the packet and re-routes it to the routing routine. The routing routine routes the packet normally based upon a host specific entry that is the MN s home address (for which it has the link layer address!). ICS 243E - Ch 6 Net. Protocols Winter

164 Routing/Tunneling 5/5 How does a MN route its packets? It needs to find a router to send all its packets to. It can select a router in one of a number of ways dependent upon whether it has a FA COA or a collocated COA. Having a FA COA does not imply that the MN needs to use it as its default router for sending packets. It can use any router that sends advertisements or that is advertised in the Agent Advertisement message. If the MN is using a collocated COA it needs to listen for router advertisements or is it hears none, use DHCP to find the default router. Determining the link layer address is another issue. Collocated COA MNs can use ARP. FA COA must note the link layer address when they receive router advertisements or agent advertisements. ICS 243E - Ch 6 Net. Protocols Winter

165 Encapsulation Process original IP header new IP header outer header ICS 243E - Ch 6 Net. Protocols original data new data inner header Winter 2001 original data 6.31

166 Types of Encapsulation Three types of encapsulation protocols are specified for Mobile IP: IP-in-IP encapsulation: required to be supported. Full IP header added to the original IP packet. The new header contains HA address as source and Care of Address as destination. Minimal encapsulation: optional. Requires less overhead but requires changes to the original header. Destination address is changed to Care of Address and Source IP address is maintained as is. Generic Routing Encapsulation (GRE): optional. Allows packets of a different protocol suite to be encapsulated by another protocol suite. Type of tunneling/encapsulation supported is indicated in registration. ICS 243E - Ch 6 Net. Protocols Winter

167 IP in IP Encapsulation IP in IP encapsulation (mandatory in RFC 2003) tunnel between HA and COA ver. IHL TOS length IP identification flags fragment offset TTL IP-in-IP IP checksum IP address of HA Care-of address COA ver. IHL TOS length IP identification flags fragment offset TTL lay. 4 prot. IP checksum IP address of CN IP address of MN TCP/UDP/... payload ICS 243E - Ch 6 Net. Protocols Winter

168 Minimum Encapsulation Minimal encapsulation (optional) avoids repetition of identical fields e.g. TTL, IHL, version, TOS only applicable for unfragmented packets, no space left for fragment identification ver. IHL TOS length IP identification flags fragment offset TTL min. encap. IP checksum IP address of HA care-of address COA lay. 4 protoc. S reserved IP checksum IP address of MN original sender IP address (if S=1) TCP/UDP/... payload ICS 243E - Ch 6 Net. Protocols Winter

169 Generic Routing Encapsulation outer header new header GRE header original header original data original header original data new data ver. IHL TOS length IP identification flags fragment offset TTL GRE IP checksum IP address of HA Care-of address COA C R K S s rec. rsv. ver. protocol checksum (optional) offset (optional) key (optional) sequence number (optional) routing (optional) ver. IHL TOS length IP identification flags fragment offset TTL lay. 4 prot. IP checksum IP address of CN IP address of MN TCP/UDP/... payload ICS 243E - Ch 6 Net. Protocols Winter

170 Routing techniques Triangle Routing: tunneling in its simplest form has all packets go to home network (HA) and then sent to MN via a tunnel. This involves two IP routes that need to be set-up, one original and the second the tunnel route. Causes unnecessary network overhead and adds to the latency. Route optimization: allows the correstpondent node to learn the current location of the MN and tunnel its own packets directly. Problems arise with mobility: correspondent node has to update/maintain its cache. authentication: HA has to communicate with the correspondent node to do authentication, i.e., security association is with HA not with MN. ICS 243E - Ch 6 Net. Protocols Winter

171 Optimization of packet forwarding Change of FA packets on-the-fly during the change can be lost new FA informs old FA to avoid packet loss, old FA now forwards remaining packets to new FA this information also enables the old FA to release resources for the MN ICS 243E - Ch 6 Net. Protocols Winter

172 Change of foreign agent CN HA FAold FAnew MN request update ACK data data MN changes location registration registration update ACK data data warning data update ACK data data t ICS 243E - Ch 6 Net. Protocols Winter

173 Problems with Triangle Routing Triangle routing has the MN correspond directly with the CN using its home address as the SA Firewalls at the foreign network may not allow that Multicasting: if a MN is to participate in a multicast group, it needs to use a reverse tunnel to maintain its association with the home network. TTL: a MN might have a TTL that is suitable for communication when it is in its HM. This TTL may not be sufficient when moving around (longer routes possibly). When using a reverse tunnel, it only counts as a single hop. A MN does not want to change the TTL everytime it moves. Solution: reverse tunneling ICS 243E - Ch 6 Net. Protocols Winter

174 Reverse tunneling (RFC 2344) HA 2 MN home network sender 1 Internet FA 3 CN receiver ICS 243E - Ch 6 Net. Protocols foreign network 1. MN sends to FA 2. FA tunnels packets to HA by encapsulation 3. HA forwards the packet to the receiver (standard case) Winter

175 Mobile IP with reverse tunneling Routers accept often only topologically correct addresses (firewall!) a packet from the MN encapsulated by the FA is now topologically correct Multicast and TTL problems solved Reverse tunneling does not solve all problems with firewalls, the reverse tunnel can be abused to circumvent security mechanisms (tunnel hijacking) optimization of data paths, i.e. packets will be forwarded through the tunnel via the HA to a sender (longer routes) The new standard is backwards compatible the extensions can be implemented easily ICS 243E - Ch 6 Net. Protocols Winter

176 Mobile IP and IPv6 Mobile IP was developed for IPv4, but IPv6 simplifies the protocols security is integrated and not an add-on, authentication of registration is included COA can be assigned via auto-configuration (DHCPv6 is one candidate), every node has address autoconfiguration no need for a separate FA, all routers perform router advertisement which can be used instead of the special agent advertisement MN can signal a sender directly the COA, sending via HA not needed in this case (automatic path optimization) soft hand-over, i.e. without packet loss, between two subnets is supported MN sends the new COA to its old router the old router encapsulates all incoming packets for the MN and forwards them to the new COA authentication is always granted ICS 243E - Ch 6 Net. Protocols Winter

177 Problems with Mobile IP Security authentication with FA problematic, for the FA typically belongs to another organization no protocol for key management and key distribution has been standardized in the Internet patent and export restrictions Firewalls typically mobile IP cannot be used together with firewalls, special set-ups are needed (such as reverse tunneling) QoS many new reservations in case of RSVP tunneling makes it hard to give a flow of packets a special treatment needed for the QoS Security, firewalls, QoS etc. are topics of current research and discussions! ICS 243E - Ch 6 Net. Protocols Winter

178 Security in Mobile IP Security requirements (Security Architecture for the Internet Protocol, RFC 1825) Integrity any changes to data between sender and receiver can be detected by the receiver Authentication sender address is really the address of the sender and all data received is really data sent by this sender Confidentiality only sender and receiver can read the data Non-Repudiation sender cannot deny sending of data Traffic Analysis creation of traffic and user profiles should not be possible Replay Protection receivers can detect replay of messages ICS 243E - Ch 6 Net. Protocols Winter

179 IP security architecture 1/2 Two or more partners have to negotiate security mechanisms to setup a security association typically, all partners choose the same parameters and mechanisms Two headers have been defined for securing IP packets: Authentication-Header guarantees integrity and authenticity of IP packets if asymmetric encryption schemes are used, non-repudiation can also be guaranteed IP-Header IP header Authentification-Header authentication header UDP/TCP-Paket UDP/TCP data Encapsulation Security Payload protects confidentiality between communication partners not encrypted IP header ICS 243E - Ch 6 Net. Protocols encrypted ESP header Winter 2001 encrypted data 6.45

180 IP security architecture 2/2 Mobile Security Association for registrations parameters for the mobile host (MH), home agent (HA), and foreign agent (FA) Extensions of the IP security architecture extended authentication of registration MH-FA authentication FA-HA authentication MH-HA authentication registration request MH registration reply registration request FA registration reply HA prevention of replays of registrations time stamps: 32 bit time stamps + 32 bit random number responses: 32 bit random number (MH) + 32 bit random number (HA) ICS 243E - Ch 6 Net. Protocols Winter

181 Key distribution Home agent distributes session keys FA HA MH response: EHA-FA {session key} EHA-MH {session key} foreign agent has a security association with the home agent mobile host registers a new binding at the home agent home agent answers with a new session key for foreign agent and mobile node ICS 243E - Ch 6 Net. Protocols Winter

182 DHCP: Dynamic Host Configuration Protocol Application simplification of installation and maintenance of networked computers supplies systems with all necessary information, such as IP address, DNS server address, domain name, subnet mask, default router etc. enables automatic integration of systems into an Intranet or the Internet, can be used to acquire a COA for Mobile IP Client/Server-Model the client sends via a MAC broadcast a request to the DHCP server (might be via a DHCP relay) DHCPDISCOVER DHCPDISCOVER server client ICS 243E - Ch 6 Net. Protocols client relay Winter

183 DHCP - protocol mechanisms client initialization server (not selected) determine the configuration DHCPDISCOVER DHCPDISCOVER DHCPOFFER DHCPOFFER server (selected) determine the configuration collection of replies selection of configuration DHCPREQUEST (reject) DHCPREQUEST (options) confirmation of configuration DHCPACK initialization completed release DHCPRELEASE ICS 243E - Ch 6 Net. Protocols Winter 2001 delete context 6.49

184 DHCP characteristics Server Renewal of configurations IP addresses have to be requested periodically, simplified protocol Options several servers can be configured for DHCP, coordination not yet standardized (i.e., manual configuration) available for routers, subnet mask, NTP (network time protocol) timeserver, SLP (service location protocol) directory, DNS (domain name system) Big security problems! no authentication of DHCP information specified ICS 243E - Ch 6 Net. Protocols Winter

185 Ad hoc networks Standard Mobile IP needs an infrastructure Home Agent/Foreign Agent in the fixed network DNS, routing etc. are not designed for mobility Sometimes there is no infrastructure! remote areas, ad-hoc meetings, disaster areas cost can also be an argument against an infrastructure! Main topic: routing no default router available every node should be able to forward A ICS 243E - Ch 6 Net. Protocols B Winter 2001 C 6.51

186 Routing examples for an ad-hoc network N1 N1 N2 N3 N4 N4 N5 time = t1 ICS 243E - Ch 6 Net. Protocols N3 N2 good link weak link Winter 2001 N5 time = t2 6.52

187 Traditional routing algorithms Distance Vector periodic exchange of messages with all physical neighbors that contain information about who can be reached at what distance selection of the shortest path if several paths available Link State periodic notification of all routers about the current state of all physical links router get a complete picture of the network Example ARPA packet radio network (1973), DV-Routing every 7.5s exchange of routing tables including link quality updating of tables also by reception of packets routing problems solved with limited flooding ICS 243E - Ch 6 Net. Protocols Winter

188 Problems of traditional routing algorithms Dynamics of the topology frequent changes of connections, connection quality, participants Limited performance of mobile systems periodic updates of routing tables need energy without contributing to the transmission of user data, sleep modes difficult to realize limited bandwidth of the system is reduced even more due to the exchange of routing information links can be asymmetric, i.e., they can have a direction dependent transmission quality Problem protocols have been designed for fixed networks with infrequent changes and typically assume symmetric links ICS 243E - Ch 6 Net. Protocols Winter

189 DSDV (Destination Sequenced Distance Vector) Expansion of distance vector routing Sequence numbers for all routing updates assures in-order execution of all updates avoids loops and inconsistencies Decrease of update frequency store time between first and best announcement of a path inhibit update if it seems to be unstable (based on the stored time values) ICS 243E - Ch 6 Net. Protocols Winter

190 Dynamic source routing I Split routing into discovering a path and maintainig a path Discover a path Maintaining a path only if a path for sending packets to a certain destination is needed and no path is currently available only while the path is in use one has to make sure that it can be used continuously No periodic updates needed! ICS 243E - Ch 6 Net. Protocols Winter

191 Dynamic source routing II Path discovery broadcast a packet with destination address and unique ID if a station receives a broadcast packet if the station is the receiver (i.e., has the correct destination address) then return the packet to the sender (path was collected in the packet) if the packet has already been received earlier (identified via ID) then discard the packet otherwise, append own address and broadcast packet sender receives packet with the current path (address list) Optimizations limit broadcasting if maximum diameter of the network is known caching of address lists (i.e. paths) with help of passing packets stations can use the cached information for path discovery (own paths or paths for other hosts) ICS 243E - Ch 6 Net. Protocols Winter

192 Dynamic Source Routing III Maintaining paths after sending a packet wait for a layer 2 acknowledgement (if applicable) listen into the medium to detect if other stations forward the packet (if possible) request an explicit acknowledgement if a station encounters problems it can inform the sender of a packet or look-up a new path locally ICS 243E - Ch 6 Net. Protocols Winter

193 Clustering of ad-hoc networks Internet cluster super cluster ICS 243E - Ch 6 Net. Protocols Winter

194 Interference-based routing Routing based on assumptions about interference between signals N1 N2 R1 S1 N3 N4 N5 N6 R2 S2 neighbors (i.e. within radio range) N7 ICS 243E - Ch 6 Net. Protocols N8 Winter 2001 N9 6.60

195 Examples for interference based routing Least Interference Routing (LIR) Max-Min Residual Capacity Routing (MMRCR) calculate the cost of a path based on a probability function of successful transmissions and interference Least Resistance Routing (LRR) calculate the cost of a path based on the number of stations that can receive a transmission calculate the cost of a path based on interference, jamming and other transmissions LIR is very simple to implement, only information from direct neighbors is necessary ICS 243E - Ch 6 Net. Protocols Winter

196 Wireless &Mobile Communications Chapter 7: Mobile Transport Layer Motivation TCP-mechanisms Indirect TCP Snooping TCP Mobile TCP Fast retransmit/recovery Transmission freezing Selective retransmission Transaction oriented TCP

197 Motivation I Transport protocols typically designed for Fixed end-systems Fixed, wired networks Research activities Performance Congestion control Efficient retransmissions TCP congestion control packet loss in fixed networks typically due to (temporary) overload situations routers have to discard packets as soon as the buffers are full TCP recognizes congestion only indirectly via missing (I.e., timed out) acknowledgements Immediate retransmissions unwise, they would only contribute to the congestion and make it even worse slow-start algorithm is used as a reactive action to reduce the network load ICS 243E - Ch7 Transport Protocols Winter

198 Motivation II TCP slow-start algorithm sender calculates/negotiates a congestion window threshold for a receiver start with a congestion window size equal to one segment exponential increase of the congestion window up to the congestion threshold, then linear increase missing acknowledgement causes the reduction of the congestion threshold to one half of the current congestion window congestion window starts again with one segment TCP fast retransmit/fast recovery TCP sends an acknowledgement only after receiving a packet if a sender receives several acknowledgements for the same packet, this is due to a gap in received packets at the receiver It indicates that the receiver got all packets up to the gap and is actually receiving packets, but some are missing (hence gap) Sender concludes that packet loss is not due to congestion, continue with current congestion window (do not use slow-start), just retransmit all packets from beginning of reported gap (go back N). ICS 243E - Ch7 Transport Protocols Winter

199 Influences of mobility on TCP-mechanisms TCP assumes congestion if packets are dropped typically wrong in wireless networks, here we often have packet loss due to transmission errors furthermore, mobility itself can cause packet loss, if e.g. a mobile node roams from one access point (e.g. foreign agent in Mobile IP) to another while there are still packets in transit to the old access point and forwarding from old to new access point is not possible for some reason The performance of an unmodified (I.e., as is) TCP degrades severely note that TCP cannot be changed fundamentally due to the large base of installation in the fixed network, TCP for mobility has to remain compatible the basic TCP mechanisms keep the whole Internet together ICS 243E - Ch7 Transport Protocols Winter

200 Proposals to modify TCP to work in mobile environments Approach Indirect TCP Snooping TCP M-TCP Fast retransmit/ fast recovery Transmission/ time-out freezing Selective retransmission Transaction oriented TCP ICS 243E - Ch7 Transport Protocols Winter

201 1. Indirect TCP I Indirect TCP or I-TCP segments the connection no changes to the basic TCP protocol for hosts connected to the wired Internet, millions of computers use this protocol (or slight variants of it) optimized TCP protocol for mobile hosts splitting of the TCP connection at, e.g., the foreign agent into 2 TCP connections, no real end-to-end connection any longer hosts in the fixed part of the net do not notice the characteristics of the wireless part mobile host access point (foreign agent) standard TCP wireless TCP ICS 243E - Ch7 Transport Protocols wired Internet Winter

202 I-TCP socket and state migration access point1 socket migration and state transfer Internet access point2 mobile host ICS 243E - Ch7 Transport Protocols Winter

203 Indirect TCP II Advantages no changes in the fixed network necessary, no changes for the hosts (TCP protocol) necessary, all current optimizations to TCP (Reno, Vegas, etc.) still work transmission errors on the wireless link do not propagate into the fixed network simple to control, mobile TCP is used only for one hop between, e.g., a foreign agent and mobile host therefore, very fast retransmission of packets is possible, the short delay on the mobile hop is known Disadvantages loss of end-to-end semantics, an acknowledgement to a sender does now not any longer mean that a receiver really got a packet, foreign agents might crash higher latency possible due to buffering of data within the foreign agent and forwarding to a new foreign agent ICS 243E - Ch7 Transport Protocols Winter

204 2. Snooping TCP I Transparent extension of TCP within the foreign agent buffering of packets sent to the mobile host lost packets on the wireless link (both directions!) will be retransmitted immediately by the mobile host or foreign agent, respectively (so called local retransmission) the foreign agent therefore snoops the packet flow and recognizes acknowledgements in both directions, it also filters ACKs changes to the basic TCP only within the foreign agent local retransmission correspondent host foreign agent wired Internet mobile host snooping of ACKs ICS 243E - Ch7 Transport Protocols buffering of data end-to-end TCP connection Winter

205 Snooping TCP II Data transfer to the mobile host FA buffers data until it receives ACK of the MH, FA detects packet loss via duplicated ACKs or time-out fast retransmission possible, transparent for the fixed network Data transfer from the mobile host FA detects packet loss on the wireless link via sequence numbers, FA answers directly with a NACK to the MH MH can now retransmit data with only a very short delay Integration of the MAC layer MAC layer often has similar mechanisms to those of TCP thus, the MAC layer can already detect duplicated packets due to retransmissions and discard them Problems snooping TCP does not isolate the wireless link as good as ITCP snooping might be useless depending on encryption schemes ICS 243E - Ch7 Transport Protocols Winter

206 3. Mobile TCP Special handling of lengthy and/or frequent disconnections M-TCP splits as I-TCP does unmodified TCP fixed network to supervisory host (SH) optimized TCP SH to MH Supervisory host no caching, no retransmission monitors all packets, if disconnection detected set sender window size to 0 sender automatically goes into persistent mode Advantages old or new SH reopen the window maintains semantics, supports disconnection, no buffer forwarding Disadvantages loss on wireless link propagated into fixed network adapted TCP on wireless link ICS 243E - Ch7 Transport Protocols Winter

207 4. Fast retransmit/fast recovery Change of foreign agent often results in packet loss TCP reacts with slow-start although there is no congestion Forced fast retransmit as soon as the mobile host has registered with a new foreign agent, the MH sends duplicated acknowledgements on purpose this forces the fast retransmit mode at the communication partners additionally, the TCP on the MH is forced to continue sending with the actual window size and not to go into slow-start after registration Advantage simple changes result in significant higher performance Disadvantage further mix of IP and TCP, no transparent approach ICS 243E - Ch7 Transport Protocols Winter

208 5. Transmission/time-out freezing Mobile hosts can be disconnected for a longer time no packet exchange possible, e.g., in a tunnel, disconnection due to overloaded cells or mux. with higher priority traffic TCP disconnects after time-out completely TCP freezing MAC layer is often able to detect interruption in advance MAC can inform TCP layer of upcoming loss of connection TCP stops sending, but does now not assume a congested link MAC layer signals again if reconnected Advantage scheme is independent of data Disadvantage TCP on mobile host has to be changed, mechanism depends on MAC layer ICS 243E - Ch7 Transport Protocols Winter

209 6. Selective retransmission TCP acknowledgements are often cumulative ACK n acknowledges correct and in-sequence receipt of packets up to n if single packets are missing quite often a whole packet sequence beginning at the gap has to be retransmitted (goback-n), thus wasting bandwidth Selective retransmission as one solution RFC2018 allows for acknowledgements of single packets, not only acknowledgements of in-sequence packet streams without gaps sender can now retransmit only the missing packets Advantage much higher efficiency Disadvantage more complex software in a receiver, more buffer needed at the receiver ICS 243E - Ch7 Transport Protocols Winter

210 7. Transaction oriented TCP TCP phases connection setup, data transmission, connection release using 3-way-handshake needs 3 packets for setup and release, respectively thus, even short messages need a minimum of 7 packets! Transaction oriented TCP Advantage RFC1644, T-TCP, describes a TCP version to avoid this overhead connection setup, data transfer and connection release can be combined thus, only 2 or 3 packets are needed efficiency Disadvantage requires changed TCP mobility not longer transparent ICS 243E - Ch7 Transport Protocols Winter

211 Comparison of different approaches for mobile TCP Approach Indirect TCP Mechanism splits TCP connection into two connections Disadvantages loss of TCP semantics, higher latency at handover Snooping TCP snoops data and transparent for end-to- problematic with acknowledgements, local end connection, MAC encryption, bad isolation retransmission integration possible of wireless link M-TCP splits TCP connection, Maintains end-to-end Bad isolation of wireless chokes sender via semantics, handles link, processing window size long term and frequent overhead due to disconnections bandwidth management Fast retransmit/ avoids slow-start after simple and efficient mixed layers, not fast recovery roaming transparent Transmission/ freezes TCP state at independent of content changes in TCP time-out freezing disconnect, resumes or encryption, works for required, MAC after reconnection longer interrupts dependant Selective retransmit only lost data very efficient slightly more complex retransmission receiver software, more buffer needed Transaction combine connection Efficient for certain changes in TCP oriented TCP setup/release and data applications required, not transparent transmission ICS 243E - Ch7 Transport Protocols Advantages isolation of wireless link, simple Winter

212 Digital Modulation Techniques in Mobile Communications Fahredd'n Sadikoglu 1

213 Digital Modulation Technique Sender Destination Message Modulation Message Channel Fahredd'n Sadikoglu Demodulation 2

214 Modulation Techniques Modulation is the process of encoding information from a message source in a manner suitable for transmition. The ultimate goal of a modulation technique is to transport the message signal through a radio channel with the best possible quality while occupying the least amount of radio spectrum. Sender Message Modulation Channel D(t) C(t)=A COS (wt+φ) Fahredd'n Sadikoglu 3

215 Modulation may be done by varying the amplitude,phase, or frequency of a high frequency carrier in accordance with the amplitude of the message signal. C(t)=A COS (wt+φ) ASK FSK PSK

216 Amplitude Shift Keying (ASK) - Pulse shaping can be employed to remove spectral spreading. - ASK demonstrates poor performance, as it is heavily affected by noise and interference.

217 Frequency Shift Keying (FSK) - Bandwidth occupancy of FSK is dependant on the spacing of the two symbols. A frequency spacing of 0.5 times the symbol period is typically used. - FSK can be expanded to a M-ary scheme, employing multiple frequencies as different states. -

218 Phase Shift Keying (PSK) - Binary Phase Shift Keying (BPSK) demonstrates better performance than ASK and FSK. - PSK can be expanded to a M-ary scheme, employing multiple phases and amplitudes as different states. - Filtering can be employed to avoid spectral spreading.

219 PSK & DPSK Fahredd'n Sadikoglu 8

220 Multi-Phase Binary Phase Shift Keying (BPSK) Im 1: f1(t)= p(t) cos(wct) 0: f0(t)= p(t)cos(wct+p) M-ary PSK 2p pk t ) p t ) cos wct + M k x Re x x x Im x x Re x x Fahredd'n Sadikoglu x x 9

221 QPSK * Quadrature Phase Shift Keying is effectively two independent BPSK systems (I and Q), and therefore exhibits the same performance but twice the bandwidth efficiency. * Quadrature Phase Shift Keying can be filtered using raised cosine filters to achieve excellent out of band suppression. * Large envelope variations occur during phase transitions, thus requiring linear amplification.

222 Quadrature Phase-Shift Keying (QPSK) Constellation diagram for QPSK with Gray coding. Each adjacent symbol only differs by one bit. QPSK can encode two bits per symbol, shown in the diagram with Gray coding to minimize the BER twice the rate of BPSK. QPSK may be used either to double the data rate compared to a BPSK system while maintaining the bandwidth of the signal or to maintain the data-rate of BPSK but halve the Fahredd'n Sadikoglu bandwidth needed. 11

223 Constellation diagram for QPSK with Gray coding. Each adjacent symbol only differs by one bit. QPSK can encode two bits per symbol, shown in the diagram with Gray coding to minimize the BER twice the rate of BPSK. QPSK may be used either to double the data rate compared to a BPSK system while maintaining the bandwidth of the signal or to maintain the datarate of BPSK but halve the bandwidth needed.

224 QPSK Modeled as two BPSK systems in parallel Ts=2 Tb 0101 Im x x Re x x Rb Rb/2 Serial to Parallel Converter x cos wct BPF - x Rb/2 Fahredd'n Sadikoglu 13

225 The binary data that is conveyed by this waveform is: The odd bits, highlighted here, contribute to the in-phase component: The even bits, highlighted here, contribute to the quadrature-phase component: In the timing diagram for QPSK. The binary data stream is shown beneath the time axis. The two signal components with their bit assignments are shown the top and the total, combined signal at the bottom. Note the abrupt changes in phase at some of the bit-period boundaries which are not satisfied.

226 QPSK TYPES Fahredd'n Sadikoglu 15

227 QPSK Fahredd'n Sadikoglu 16

228 Fahredd'n Sadikoglu 17

229 Offset QPSK (OQPSK) Ideally amplitude of QPSK signal is constant If pulses are shaped, then constant envelope is lost and phase shift of p radians causes waveform to go to zero briefly Can only use less efficient linear amplifiers OQPSK or Staggered QPSK Waveforms are shifted by ½ bit Fahredd'n Sadikoglu 18

230 OQPSK Bit transitions occur every Tb sec Limited to changes of +/- p/2 Smaller envelope variations -T T 3T 5T 7T 9T 0 2T 4T 6T Fahredd'n Sadikoglu 19

231 Offset Quadrature Phase-Shift Keying (OQPSK) Offset quadrature phase-shift keying OQPSK is a variant of Phase Shift Keying modulation using 4 different values of the phase to transmit. It is sometimes called Staggered quadrature phase shift keying SQPSK. OQPSK limits the phase-jumps that occur at symbol boundaries to no more than 90 and reduces the effects on the amplitude of the signal due to any low-pass filtering.

232 OPSK Fahredd'n Sadikoglu 21

233 QPSK vs. OQPSK Fahredd'n Sadikoglu 22

234 QPSK & OQPSK (-1, 1) (aq, ai) (1, 1) cos ωt sinωt (-1, -1) (1, -1) Fahredd'n Sadikoglu 23

235 Disadvantages of OQPSK (1) OQPSK introduces a delay of half a symbol into the demodulation process. In other words, using OQPSK increases the temporal efficiency of normal QPSK. The reason is that the in phase and quadrature phase components of the OQPSK cannot be simultaneously zero. Hence, the range of the fluctuations in the signal is smaller. (2) An additional disadvantage is that the quiescient power is nonzero, which may be a design issue in devices targeted for low power applications.

236 QPSKp/4Dual constellation diagram for π/4-qpsk. This shows the two separate constellations with identical Gray coding but rotated by 45 with respect to each other. This final variant of QPSK uses two identical constellations which are rotated by 45 (π / 4 radians, hence the name) with respect to one another. Usually, either the even or odd data bits are used to select points from one of the constellations and the other bits select points from the other constellation. This also reduces the phase-shifts from a maximum of 180, but only to a maximum of 135 and so the amplitude fluctuations of π / 4 QPSK are between OQPSK and non-offset QPSK. Fahredd'n Sadikoglu 25

237 QPSK OQPSK p/4-qpsk Fahredd'n Sadikoglu 26

238 Minimum Shift Keying (MSK) It is a special type of continuous phasefrequency shift keying (CPFSK). The peak frequency deviation is equal to 1/4 the bit rate. MSK has a modulation index of 0.5. KMSK=2 F / Rb Fahredd'n Sadikoglu 27

239 The name Minimum Shift Keying (MSK) implies the minimum frequency separation that allows orthogonal detection as two FSK signals VH(t) & VL(t). T VH(t)VL(t)dt =0 0 MSK is a spectrally efficient modulation scheme and is particularly attractive for use in mobile communication systems because of its possesses properties such as : constant envelope. Spectral efficiency. Good BER performance. Self-synchronizing capability.

240 MSK MSK uses changes in phase to represent 0's and 1's, but unlike most other keying, the pulse sent to represent a 0 or a 1, not only depends on what information is being sent, but what was previously sent. The pulse used in MSK is the following: Fahredd'n Sadikoglu 29

241 Right from the equation we can see that θ(t) depends not only from the symbol being sent (from the change in the sign), but it can be seen that is also depends on θ(0) which means that the pulse also depends on what was previously sent. To see how this works let's work through an example. Assume the data being sent is , then the phase of the signal would fluctuate as seen in the figure below.

242 If it assumed that h = 1/2, then the figure simplifies. The phase can now go up or down by increments of pi/2, and the values at which the phase can be (at integer intervals of Tb) are {-pi/2, 0, pi/2, pi}. The above example now changes to the graph below. The figure illustrates one feature of MSK that may not be obvious, when a large number of the same symbol is transmitted, the phase does not go to infinity, but rotates around 0 phase.

243 An MSK signal can be thought of as a special form of OQPSK where the baseband rectangular pulses are replaced with half-sinusoidal pulses. N-1 N-1 SMSK(t)= mii(t)p(t-2itb)cos2 ח fct+ mqi(t)p(t-2itb-tb)sin2 ח fct. i=0 i=0 where cos( ח t/2tb) 0<t<2Tb P(t) = 0 elsewhere

244 MSK better than QPSK Even though the derivation of MSK was produced by analyzing the changes in phase, MSK is actually a form of frequency-shift-keying (FSK) with (where f1 and f2 are the frequencies used for the pulses). MSK produces an FSK with the minimum difference between the frequencies of the two FSK signals such that the signals do not interfere with each other. MSK produces a power spectrum density that falls off much faster compared to the spectrum of QPSK. While QPSK falls off at the inverse square of the frequency, MSK falls off at the inverse fourth power of the frequency. Thus MSK can operate in a smaller bandwidth compared to QPSK. Fahredd'n Sadikoglu 33

245 Generating minimum-shift keying Fahredd'n Sadikoglu 34

246 MSK Fahredd'n Sadikoglu 35

247 Gaussian Minimum Shift Keying GMSK Even though MSK's power spectrum density falls quite fast, it does not fall fast enough so that interference between adjacent signals in the frequency band can be avoided. To take care of the problem, the original binary signal is passed through a Gaussian shaped filter before it is modulated with MSK. Frequency Response: The principle parameter in designing an appropriate Gaussian filter is the timebandwidth product WTb. Please see the following figure for the frequency response of different Gaussian filters. Note that MSK has a time-bandwidth product of infinity. Fahredd'n Sadikoglu 36

248 As can be seen from above, GMSKs power spectrum drops much quicker than MSK's. Furthermore, as WTb is decreased, the roll-off is much quicker.

249 Time-Domain Response: Since lower time-bandwidth products produce a faster power-spectrum roll-off, why not have a very small time-bandwidth product. It happens that with lower time-bandwidth products the pulse is spread over a longer time, which can cause intersymbol interference. Therefore as a compromise between spectral efficiency and time-domain performance, an intermediate time-bandwidth product must be chosen.

250 Fahredd'n Sadikoglu 39

251 Fahredd'n Sadikoglu 40

252 Fahredd'n Sadikoglu 41

253 Fahredd'n Sadikoglu 42

254 The figure shows the 16-bit NRZ (Non-Return-to-Zero) sequence (-1,-1,-1,+1,+1,-1,+1,+1,+1,+1,-1,+1,-1,+1,-1,-1) and the corresponding phase trajectory of MSK (left) and GMSK (right) signals. The phase increment per symbol is for the MSK signal.

255 The figure shows the in phase I (real) and quadrature Q (imaginary) components of the MSK (left) and GMSK (right) corresponding base band equivalent signals.

256 The figure shows the MSK and GMSK modulated signals for two different symbols. Notice the slight difference of frequency between the modulated signal of symbol (-1) and symbol (1). This shows the FM nature of MSK and GMSK signals.

257 The reliability of a data message produced by a GMSK system is highly dependent on the following: (1) Receiver thermal noise: this is produced partly by the receive antenna and mostly by the radio receiver. (2) Channel fading: this is caused by the multipath propagation nature of the radio channel. (3) Band limiting: This is mostly associated with the receiver If frequency and phase characteristics (4) DC drifts: may be caused by a number of factors such as temperature variations, asymmetry of the frequency response of the receiver, frequency drifts of the receiver local oscillator.

258 (5)Frequency offset: * This refers to the receiver carrier frequency drift relative to the frequency transmitted caused by the finite stability of all the frequency sources in the receiver. The shift is also caused partly by Doppler shifts, which result due to the relative transmitter/receiver motion. * The frequency offset causes the received IF signal to be off-center with respect to the IF filter response, and this cause more signal distortion. * The frequency offset also results in a proportional DC component at the discriminator output.

259 (6)Timing errors: - The timing reference causes the sampling instants to be offset from the center of the transmit eye. - As GMSK is a filtered version of MSK, this introduces another variable that can be used to describe the exact nature of the GMSK modulation. - This variable is referred to as the BT, where B is the 3dB point of the Gaussian filter, and T is the bit duration. Therefore a BT of infinity would relate to MSK. - The smaller the BT the smaller the spectral density however this comes at a trade off of increased inter-symbol interference. - This is because by smoothing the edges of the bit pulses they begin to overlap each other. The greater the smoothing, the greater the overlapping, until eventually individual bits may be undetectable.

260 How to implement a GMSK modulator? Fahredd'n Sadikoglu 49

261 How to implement a GMSK demodulator? Fahredd'n Sadikoglu 50

262 GSM Modulation Specifications In the GSM standard, Gaussian Minimum Shift Keying with a time-bandwidth product of 0.3 was chosen as a compromise between spectral efficiency and intersymbol interference. With this value of WTb, 99% of the power spectrum is within a bandwidth of 250 khz, and since GSM spectrum is divided into 200 khz channels for multiple access, there is very little interference between the channels. The speed at which GSM can transmit at, with WTb=0.3, is 271 kb/s. (It cannot go faster, since that would cause intersymbol interference). Fahredd'n Sadikoglu 51

263 References [5] S. Haykin, Communication Systems, 4th Edition, New York: John Wiley & Sons, Inc., 2001, pp [6] J.G. Sempere, "An overview of the GSM system by Javier Gozalvez Sempere," [Online document], April 1998, Available Fahredd'n Sadikoglu 52

264 UNIT 5 4G NETWORKS SYLLABUS Introduction 4G vision 4G features and challenges - Applications of 4G 4G Technologies: Multicarrier Modulation, Smart antenna techniques, OFDM-MIMO systems, Adaptive Modulation and coding with time slot scheduler, Cognitive Radio INTRODUCTION The First generation wireless mobile communication systems were introduced in early eighties and second generations systems in the late 1980s were intended primarily for transmission of voice. The initial systems used analog frequency modulation where as the second as well as the subsequent mobile systems use digital communication techniques with time division multiplexing (TDM), frequency division multiplexing (FDM) or the code division multiple access (CDMA). The third generation wireless systems which are just getting introduced in the world markets offer considerably higher data rates, and allow significant improvements over the 2G systems. The 3G Wireless systems were proposed to provide voice and paging services to provide interactive multimedia including teleconferencing and internet access and variety of other services. However, these systems offer wide area network (WAN) coverage of 384 kbps peak rate and limited coverage for 2 Mbps. Hence providing broadband services would be one of the major goals of the 4G Wireless systems. 4G is the next generation of wireless networks that will totally replace 3G networks. It is supposed to provide its customers with better speed and all IP based multimedia services. 4G is all about an integrated, global network that will be able

265 Wireless Networks 5.2 to provide a comprehensive IP solution where voice, data and streamed multimedia can be given to users on an "Anytime, Anywhere" basis. At present we have many technologies each capable of performing functions like supporting voice traffic using voice over IP (VoIP), broadband data access in mobile environment etc., but there is a great need of deploying such technologies that can integrate all these systems into a single unified system. 4G presents a solution of this problem as it is all about seamlessly integrating the terminals, networks and applications. 4G mobile systems focus on seamless integration of existing wireless technologies including WWAN, WLAN, and Bluetooth (See following figure). This is in contrast with 3G, which merely focuses on developing new standards and hardware. Fig Seamless connections of networks

266 4G Networks 5.3 In addition to wide area cellular systems, diverse wireless transmission technologies are being deployed, including digital audio broadcast (DAB) and digital video broadcast (DVB) for wide-area broadcasting, local multipoint distribution service (LMDS), and multichannel multipoint distribution service (MMDS) for fixed wireless access. The 4G systems will encompass all systems from various networks, public to private, operator-driven broadband networks to personal areas, and ad hoc networks. The 4G systems will be interoperable with 2G and 3G systems, as well as with digital (broadband) broadcasting systems. The 4G intends to integrate from satellite broadband to high altitude platform to cellular 2G and 3G systems to wireless local loop (WLL) and broadband wireless access (BWA) to WLAN, and wireless personal area networks (WPANs), all with IP as the integrating mechanism EVOLUTION OF MOBILE TECHNOLOGY The history and evolution of mobile service from the 1G (First generation) to fourth generation is discussed in this section. (i) First generation The process began with the designs in the 1970s that have become known as 1G. Almost all of the systems from this generation were analog systems where voice was considered to be the main traffic. The first generation wireless standards used plain TDMA and FDMA. These systems could often be listened to by third parties. Some of the standards are NMT, AMPS, Hicap, CDPD, Mobitex, DataTac, TACS and ETACS. (ii) Second generation (2G) The 2G (second generation) systems designed in the 1980s were still used mainly for voice applications but were based on digital technology, including digital signal processing techniques. These 2G systems provided circuit switched

267 5.4 Wireless Networks data communication services at a low speed. All the standards belonging to this generation were commercial centric and they were digital in form. The second generation standards are GSM, iden, D-AMPS, IS-95, PDC, CSD, PHS, GPRS, HSCSD, and WiDEN. 2.5 G 2.5G is the intermediate generation between 2G and 3G cellular wireless technologies. This term is used to describe 2G-systems that have implemented a packet switched domain in addition to the circuit switched domain. 2.5G is not an officially defined term rather it was invented for marketing purpose. 2.5G provides some of the benefits of 3G (e.g. it is packet-switched) and can use some of the existing 2G infrastructure in GSM and CDMA networks EDGE (Enhanced Data rates for GSM Evolution) EDGE (EGPRS) is an abbreviation for Enhanced Data rates for GSM Evolution, is a digital mobile phone technology, invented by AT&T. EDGE technology is an extended version of GSM & works in GSM networks. EDGE is add-on to GPRS and can function on any network with GPRS deployed on it, provided the carrier implements the necessary upgrades. It allows the clear and fast transmission of data. One need not install any additional hardware and software in order to make use of EDGE Technology. Also, there are no additional charges for utilizing this technology. (iii) Third generation (3G) To meet the growing demands in network capacity, rates required for high speed data transfer and multimedia applications, 3G standards started evolving. The systems in this standard are essentially a linear enhancement of 2G systems. They are based on two parallel backbone infrastructures, one consisting of circuit switched nodes, and one of packet oriented nodes. There are many 3G technologies as W-CDMA, CDMA2000.UMTS, DECT, WiMAX

268 4G Networks 5.5 3G has the following enhancements over 2.5G and previous networks: Enhanced audio and video streaming; Several Times higher data speed; Video-conferencing support; Web and WAP browsing at higher speeds; IPTV (TV through the Internet) support. Global Roaming 3.5G - HSDPA (High-Speed Downlink Packet Access): High-Speed Downlink Packet Access (HSDPA) is a mobile telephony protocol, also called 3.5G. It is an enhanced version and the next intermediate generation of 3G UMTS allowing for higher data transfer speeds. HSDPA is a packet-based data service in W-CDMA downlink with data transmission up to 8-10 Mbps (and 20 Mbps for MIMO systems) over a 5 MHz bandwidth in WCDMA downlink. This high data rate is enabled by use of adaptive modulation can coding (AMC), hybrid automatic repeat-request (HARQ), and fast packet scheduling at the access point. 3.75G -HSUPA (High-Speed Uplink Packet Access): High Speed Uplink Packet Access (HSUPA) is a UMTS /WCDMA uplink evolution technology. The HSUPA mobile telecommunications technology is directly related to HSDPA and the two are complimentary to one another. HSUPA will enhance advanced person-to-person data applications with higher and symmetric data rates, like mobile and real-time person- to person gaming. 4G 3G may not be sufficient to meet needs of future high-performance applications like multi-media, full-motion video, wireless teleconferencing. Multiple standards for 3G make it difficult to roam and interoperate across networks. Requirement of a

269 Wireless Networks 5.6 single broadband network with high data rates which integrates wireless LANs, Bluetooth, cellular networks, etc (iv) Fourth generation (4G) Also known as "Beyond 3G", 4G refers to the fourth generation of wireless communications. The deployment of 4G networks should be in the timeframe and will enable another leap in wireless data-rate and spectral efficiency. ITU has specified IMT-A (IMT-Advanced) for 4G standards. 4G is all about convergence; convergence of wired and wireless networks, wireless technologies including GSM, wireless LAN, and Bluetooth as well as computers, consumer electronics, communication technology and several others. 4G is a Mobile multimedia, anytime anywhere, Global mobility support, integrated wireless solution, and customized personal service network system. Technology 1G 2G 2.5G 3G 4G Design Began Implementation ? Services Analog voice Digital voice Higher Higher Completely Standards NMT, GSM, AMPS, iden, Hicap, D-MPS CDPD, TACS, ETACS capacity, capacity packetized broadband data data upto 2 mbps GPRS, EDGE, etc. WCDMA, CDMA 2000 IP based, speed upto hundreds of MBs Single standard

270 4G Networks 5.7 Technology 1G 2G 2.5G 3G 4G Data kbps 2 Mbps 200 Mbps Bandwidth kbps kbps Multiplexing FDMA TDMA, TDMA, CDMA CDMA? CDMA CDMA PSTN PSTN, packet Packet network Internet Core Network PSTN network Fig Series of mobile generations and features Table 5.1. Comparison of key parameters of 4G with 3G Details 3G including 2.5 G (EDGE) 4G Major requirement driving architecture Predominantly voice driven, data was always add on Converge data and voice over IP Network architecture Wide area cell-based Hybrid-integration of WLAN (WiFi, Bluetooth) and wireless wide-area networks Speeds 384 kbps to 2 Mbps 20 to 100 Mbps in mobile mode Frequency band Dependent on country or Higher frequency bands continent (1.8 to 2.4 GHz) (2 to 8 GHz) Bandwidth 5 to 20 MHz 100 MHz or more Switching design basis Circuit and packet All digital with packetized voice Access technologies WCDMA, cdma2000 OFDM and multicarrier (MC)-CDMA Forward error correction 1 1 Convolutional codes rate 2, 3 Concatenated coding schemes

271 Wireless Networks 5.8 Details Component design 3G including 2.5 G (EDGE) Optimized antenna design, multiband adapters 4G Smart antenna, softwaredefined multiband and wideband radios Internet protocol Number of airlink protocol (IP) including IPv5.0 Mobile top speed 200 km/h All IP (IPv6.0) 200 km/h Fig Evolution of 4G technology G VISION The 4G systems are projected to solve the still-remaining problems of 3G systems. They are designed to provide a wide variety of new services, from highquality voice to high-definition video to high-data-rate wireless channels.

272 4G Networks 5.9 The term 4G is used broadly to include several types of broadband wireless access communication systems, not only cellular systems. 4G is described as MAGIC Mobile multimedia, Anytime anywhere, Global mobility support, Integrated wireless solution, and Customized personal service. The 4G systems will not only support the next generation mobile services, but also will support the fixed wireless networks. The 4G systems are about seamlessly integrating terminals, networks, and applications to satisfy increasing user demands. This new generation of wireless is intended to complement and replace the 3G systems, perhaps in 5 to 10 years. Accessing information anywhere, anytime, with a seamless connection to a wide range of information and services, and receiving a large volume of information, data, pictures, video, and so on, are the keys of the 4G infrastructures. The future 4G infrastructures will consist of a set of various networks using IP (Internet protocol) as a common protocol so that users are in control because they will be able to choose every application and environment. Based on the developing trends of mobile communication, 4G will have broader bandwidth, higher data rate, and smoother and quicker handoff and will focus on ensuring seamless service across a multitude of wireless systems and networks. The key concept is integrating the 4G capabilities with all of the existing mobile technologies through advanced technologies. Application adaptability and being highly dynamic are the main features of 4G services of interest to users. These features mean services can be delivered and be available to the personal preference

273 Wireless Networks 5.10 of different users and support the users traffic, air interfaces, radio environment, and quality of service. Connection with the network applications can be transferred into various forms and levels correctly and efficiently. The dominant methods of access to this pool of information will be the mobile telephone, PDA, and laptop to seamlessly access the voice communication, high-speed information services, and entertainment broadcast services. BLOCK DIAGRAM Fig G visions G FEATURES AND CHALLENGES There are several reasons which are sufficient to answer a simple question- why do we need to adopt 4G technology? Below are some of the features of 4G which make it an above all technology. High usability: anytime, anywhere, and with any technology Support for multimedia services at low transmission cost Personalization Integrated services

274 4G Networks 5.11 Fig G features 4G networks will be all-ip-based heterogeneous networks that will allow users to use any system at anytime and anywhere. Users carrying an integrated terminal can use a wide range of applications provided by multiple wireless networks. 4G systems will provide not only telecommunications services, but also data and multimedia services. To support multimedia services, high-data-rate services with system reliability will be provided. At the same time, a low per-bit transmission cost will be maintained by an improved spectral efficiency of the system. Personalized service will be provided by 4G networks. It is expected that when 4G services are launched, users in widely different locations, occupations, and economic classes will use the services. 4G systems will also provide facilities for integrated services. Users can use multiple services from any service provider at the same time. High performance Industry experts say that users will not be able to take advantages of rich multimedia content across wireless networks with 3G. In contrast to this 4G will feature extremely high quality video of quality comparable to HD (high definition) TV. Wireless downloads at speeds reaching 100 Mbps, i.e. 50 times of 3G, are possible with 4G.

275 5.12 Wireless Networks Interoperability and easy roaming Multiple standards of 3G make it difficult to roam and interoperate across various networks, whereas 4G provides a global standard that provides global mobility. Various heterogeneous wireless access networks typically differ in terms of coverage, data rate, latency, and loss rate. Therefore, each of them is practically designed to support a different set of specific services and devices, 4G will encompass various types of terminals, which may have to provide common services independently of their capabilities. This concept is referred to as service personalization. Fully converged services If a user want to be able to access the network from lots of different platforms: cell phones, laptops, PDAs he is free to do so in 4G which delivers connectivity intelligent and flexible enough to support streaming video, VoIP telephony, still or moving images, , Web browsing, e-commerce, and location-based services through a wide variety of devices. That means Freedom for consumers. Low cost 4G systems will prove far cheaper than 3G, since they can be built a top existing networks and won't require operators to completely retool and won't require carriers to purchase costly extra spectrum. 4G is spectrally efficient, so carriers can do more with less. Scalability It is most challenging aspect of the mobile networks. It refers to ability to handle ever increasing number of users and services. Since an all IP core layer of 4G is easily scalable, it is ideally suited to meet this challenge.

276 4G Networks 5.13 CHALLENGES: To migrate current systems to 4G with the above mentioned features, we have to face a number of challenges. That can be classified into based on three things such as Based on mobile station (i) Multimode user terminals (ii) Wireless system discovery (iii) Wireless system selection Based on system (i) Terminal mobility (ii) Network infrastructure and QoS support (iii) Security (iv) Fault tolerance and survivability Based on service (i) Multioperators and billing system (ii) Personal mobility (a) Mobile Station challenges 1. Multimode User Terminals Challenge: For reducing operational costs, devices that operate on 4G networks should have the capability to operate in several networks. This will not solely reduce the operating cost but also will simplify style problems and will reduce power consumption. To accessing completely different mobile and wireless networks simultaneously is one among the major issues 4G networks have been addressing.

277 Wireless Networks 5.14 Proposed solutions: One of the mechanisms that has been proposed to handle this problem is termed as multi-mode devices. This mechanism can be achieved through a software system radio that allows the end-user device to adapt itself to various wireless interfaces of the networks. 2. Discovery of wireless system Challenge: Due to the heterogeneity of 4G networks, wireless devices need to process signals sent from totally different systems, discover available services, and connect to applicable service providers. Varied service providers have their own protocols which can be incompatible with each other yet as with the user s device. This issue might complicate the process of selecting the most applicable technology based on the time, places and services provided, and thus, may affect the quality of service provided to the end user. Proposed solutions: System initiated discoveries. This mechanism allows automatic download of software system modules based on the wireless system the user is connected to. Another approach to handle this problem relies overlay networks. In this case, the end-user device is connected to different networks through an overlay network. 3. Selection of wireless System Challenge: With the support of 4G user terminals, we have a tendency to select any accessible wireless network for each specific communication session. As each network has distinctive selection, pattern applicable network for a particular service might optimize system performance and resource usage.

278 4G Networks 5.15 Moreover, the right network different will confirm the QoS required by every session. However, it's difficult to choose an appropriate network for every communication session since network accessibility changes from time to time. Proposed solutions: The wireless system can be selected according to the best possible fit of user QoS requirements, available network resources, or user preferences. (b) System Challenges 1. Terminal Mobility Challenge: To produce wireless services at anytime and anywhere, terminal mobility may be Present in 4G infrastructure. Terminal mobility allows mobile clients to roam across geographic boundaries of wireless networks. There are two main issues in terminal mobility: (i) location management and (ii) handoff management. Location management involves handling all the information regarding the roaming terminals, such as original and current situated cells, authentication information, and QoS capabilities. On the other hand, handoff management maintains communications when the terminal roams. Proposed solutions: Signaling schemes and fast handoff mechanisms are proposed. ongoing

279 Wireless Networks QoS Support and Network Infrastructure Challenge: Existing wireless systems can be classified into 2 types: non-ip-based and IP-based. Several non-ip-based systems are highly optimized for voice delivery (e.g., GSM, cdma2000, and UMTS). On the other hand, IP-based systems are usually optimized for data services (e.g., wireless fidelity and Hiper LAN). In 4G wireless environments, the problem in integrating these 2 systems becomes apparent. research challenges such as QoS guarantee for end-to-end services need to be addressed, though they are by no suggests that easy to tackle, especially when time-sensitive or multimedia applications are considered. Proposed solutions: Current QoS styles are usually made with a particular wireless system in mind. For example, the 3G Partnership Project (3GPP) has proposed a comprehensive QoS design for UMTS. Providing QoS only in UMTS cannot guarantee end-to-end QoS as a result of systems that are non-umts are involved. to deal with this drawback, internetworking with most common QoS architectures is studied in 3GPP.We believe that internet working mechanisms involving layer three (or above) operations is also needed. 3. Security Issue Challenge: In the development of 4G Networks, security measures must be established that modify data transmission to be as safe as possible. Specifically, The 4G core addresses quality, security, and QoS through reuse of existing mechanisms while still attempting to work on some quality and relinquishing issues.

280 4G Networks 5.17 Therefore, it is necessary for the organization to develop an effective series of tools that support most 4G security measures as a method of protecting data that is transmitted across the network from hackers and other security violations. Multiple levels of security, including increased requirements for authentication, will be necessary to protect data and data that is transmitted across the network. The heterogeneity of these wireless networks exchanging different types of data complicates the security issues. The encryption and cryptography methods being used for 3G networks are not appropriate for 4G networks as new devices and services are introduced for the first time in 4G networks Proposed solutions: To overcome these security issues, 2approaches can be followed. The first is to modify the existing security and privacy methods so they will be applicable to heterogeneous 4G networks. Another approach is to develop new dynamic reconfigurable, adaptive, and lightweight mechanisms whenever the currently utilized strategies cannot be adapted to 4Gnetworks. 4. Fault tolerance and survivability Challenge: To minimize the failures and their potential impacts in any level of treelike topology in wireless networks. Proposed solutions: Fault-tolerant architectures for heterogeneous networks and failure recovery protocols are proposed.

281 Wireless Networks 5.18 (c) Service challenges: 1. Multioperators and billing system Challenge: To collect, manage, and store the customers accounting information from multiple service providers. Also, to bill the customers with simple but detailed information has become much more complicated with 4G networks. This can be mainly due to 4G networks are heterogeneous and the frequent interaction of service providers. Proposed solutions: Various billing and accounting frameworks are being proposed toachieve this goal 2. Personal Mobility Challenge: Personal mobility concentrates on the movement of users instead of users terminals, and involves the availability of personal communications and customized operating environments to provide seamless personal mobility to users without modifying the existing servers in heterogeneous systems Proposed solutions: Mobile-agent-based infrastructure is one wide solution during this infrastructure, every user is typically allotted a singular symbol and served by some personal mobile agents (or specialized pc programs running on some servers). The seagents act as intermediaries between the user and therefore the net. Following figure shows the carriers migration from 3.5G to 4G systems.

282 4G Networks 5.19 Fig Carrier migration from 3.5G to 4G 5.5. APPLICATIONS OF 4G Some applications area of 4G system has follows: Virtual Presence: This means that 4G provides user services at all times, even if the user is off-site. Virtual Navigation: 4G provides users with virtual navigation through which a user can access a database of the streets, buildings etc. Tele-Geoprocessing Applications: This is a combination of GIS (Geographical Information System) and GPS (Global Positioning System) in which a user can get the location by querying.

283 Wireless Networks 5.20 Tele-Medicine And Education: 4G will support remote health monitoring of patients. For people who are interested in life long education, 4G provides a good opportunity. Crisis Management: Natural disasters can cause break down in communication systems. In today s world it might take days or 7 weeks to restore the system. But in 4G it is expected to restore such crisis issues in a few hours. Multimedia Video Services 4G wireless systems are expected to deliver efficient multimedia services at very high data rates. Basically there are two types of video services: bursting and streaming video services. Streaming is performed when a user requires real-time video services, in which the server delivers data continuously at a playback rate. Bursting is basically file downloading using a buffer and this is done at the highest data rate taking advantage of the whole available bandwidth G TECHNOLOGIES The various technologies used in 4G system has follows: Multicarrier modulation (MCM) Smart antenna techniques OFDM-MIMO Adaptive modulation and coding with time slot scheduler Cognitive Radio

284 4G Networks MULTICARRIER MODULATION (MCM) To achieve a 4G standard, a new approach is needed to avoid the divisiveness we have seen in the 3G realm. One promising underlying technology to accomplish this is multicarrier modulation (MCM). Multicarrier modulation (MCM) is a derivative of frequency-division multiplexing. It is not a new technology. Forms of multicarrier systems are currently used in DSL modems and digital audio/video broadcast (DAB/DVB). MCM is a baseband process that uses parallel equal bandwidth subchannels to transmit information. Normally implemented with Fast Fourier Transform (FFT) techniques. Advantages: MCM s advantages include Better performance in the inter-symbol-interference (ISI) environment, Avoidance of single-frequency interferers. Disadvantages: MCM increases the peak to-average ratio (PAVR) of the signal To overcome ISI a cyclic extension or guard band must be added to the data. Difference (D) The difference, D, of the peak-to-average ratio between MCM and a single carrier system is a function of the number of subcarriers, N, as: D (db) = 10 log N Cyclic extension works as follows: If N is the original length of a block, and the channel s response is of length M, the cyclically extended symbol has a new length of N + M I. The Image presented by this sequence, to the convolution with the channel, looks as if it was convolved with a periodic sequence consisting of a

285 Wireless Networks 5.22 repetition of the original block of N. Therefore, the new symbol of length N + M 1 sampling periods has no ISI. The cost is an increase in energy and encoded bits added to the data. At the MCM receiver, only N samples are processed, and M 1 samples are discarded, resulting in a loss in signal-to-noise ratio (SNR) as shown in Equation 1. N+M 1 SNRloss = 10 log db N (1) Two different types of MCM are likely candidates for 4G. These include Multicarrier code division multiple access (MC-CDMA) and orthogonal frequency division multiplexing (OFDM) using time division multiple access (TDMA) MC-CDMA is actually OFDM with a CDMA overlay. Similar to single-carrier CDMA systems, the users are multiplexed with orthogonal codes to distinguish users in MC-CDMA. However, in MC-CDMA, each user can be allocated several codes, where the data is spread in time or frequency. Either way, multiple users access the system simultaneously. In OFDM with TDMA, the users are assigned time slots to transmit and receive data. Typically MC-CDMA uses quadrature phase shift keying (QPSK) for modulation, while OFDM with TDMA could use more high-level modulations, such as multilevel quadrature amplitude modulation (M-QAM) (where M = 4 to 256). Why OFDM? OFDM overcomes most of the problems with both FDMA and TDMA (i.e., ICI and ISI). OFDM splits the available bandwidth into many narrow band channels. The carriers for each channel are orthogonal to one another allowing them to be spaced very close together, with no overhead as in the FDMA. Because of this

286 4G Networks 5.23 there is no great need for users to be time multiplexed as in TDMA, thus there is no overhead associated with switching between the users. Each carrier in an OFDM signal has a very narrow bandwidth (i.e., 1 KHz), thus the resulting symbol rate is low. This results in signal having a high tolerance to multipath delay spread, as a delay spread must be very long to cause ISI (i.e., > 500 sec). OFDM- subchannels: The OFDM divides a broadband channel into many parallel subchannels. The subchannel pulse shape is a square wave which is shown in following figure. Fig A broadband channel divided into many parallel narrowband channels The OFDM receiver senses the channel and corrects distortion on each subchannel before the transmitted data can be extracted. In OFDM, each of the frequencies is an integer multiple of a fundamental frequency. This ensures that even though subchannels, overlap, they do not interfere with each other which is shown in following figure.

287 Wireless Networks 5.24 Fig Overlapping subchannels SMART ANTENNA TECHNIQUES The main purpose of the radio communication depends on the advancements of the antennas which refer to smart or intelligent antennas. In early 90s, in order to meet growing data rate needs of the data communication, many transmission techniques were proposed such as spatial multiplexing which increases the bandwidth conservation and power efficiency. Spatial multiplexing provides the multiple deployment of antennas at the transmitting and receiving end and then independent streams of data can be transmitted as requested by the user can be transmitted simultaneously from the all transmitting antennas. Thus increasing the throughput into multiple folds with minimum number of the transmitting and receiving antennas. There are two types of smart antennas which are switched beam smart antennas and adaptive array smart antennas. Switched beam systems have several available fixed beam patterns which help in making decisions as to which beam to access at any given point of time based on

288 4G Networks 5.25 the requirements of the system. While adaptive arrays allow the antenna to steer the beam to any direction of interest while simultaneously nulling interfering signals. Fig Transmit or Receive Diversity The reliability in transmitting high speed data in the fading channel can be improved by using more antennas at the transmitter or at the receiver. This is called transmit or receive diversity. Both transmit/receive diversity and transmit spatial multiplexing are categorized into the space-time coding techniques, which does not necessarily require the channel knowledge at the time of transmitting the signals. The other category is closed-loop multiple antenna technologies which use the channel knowledge at the transmitter. A smart antenna system consists of multiple antenna elements with signal processing to automatically optimize the antennas radiation (transmitter) and/or reception (receiver) patterns in response to the signal environment. One smartantenna variation in particular, MIMO, shows promise in 4G systems. MIMO (Multi-Input Multi-Output) is a smart antenna system where smartness is considered at both transmitter and the receiver. MIMO represents space-division multiplexing (SDM) information signals are multiplexed on spatially separated N

289 Wireless Networks 5.26 multiple antennas and received on M antennas. Figure shows a general block diagram of a MIMO system. Smart antenna techniques, such as multiple-input multiple-output (MIMO) systems, can extend the capabilities of the 3G and 4G systems to provide customers with increased data throughput for mobile high-speed data applications. MIMO systems use multiple antennas at both the transmitter and receiver to increase the capacity of the wireless channel which is shown in following figure. With MIMO systems, it may be possible to provide in excess of 1 Mbps for 2.5G wireless TDMA EDGE and as high as20 Mbps for 4G systems. BLOCK DIAGRAM: Fig MIMO system There are four antennas available for both transmitter and receiver this is used to provide four times the data rate of a single antenna system without an increased in transmit power or bandwidth. MIMO system can transmit different signals from each antenna simultaneously in the same bandwidth and separated at the receiver.