Wireless LANs & PANs Case Study: Bluetooth & IEEE802.15 W.lan.4 Dr.M.Y.Wu@CSE Shanghai Jiaotong University Shanghai, China Dr.W.Shu@ECE University of New Mexico Albuquerque, NM, USA
W.wan.4-2 PANs: Bluetooth & 802.15 Bluetooth Overview Piconets & Scatternets PHY layer MAC layer Logical Link Control Management 802.15 & others End
W.wan.4-3 PANs: Personal area networks PAN = Networks that connect devices within a small range Typically 10-100 meters Applications Realtime data and voice transmissions Cable replacement, get rid off net of wires Hook laptop, PDA, headphones,printer, camera Ad hoc networking Sensor networks RFIDs
W.wan.4-4 Bluetooth overview Overview Universal radio interface for ad-hoc wireless connectivity Short range (10 m), low power consumption, licensefree 2.45 GHz ISM Interconnecting laptop, PDA, headphones,printer, camera, replacement of IrDA Specifies the physical, link, and MAC layers Applications built on top of Bluebooth using HCI (Host Control Interface)
W.wan.4-5 Bluetooth history History 1994: Ericsson MC-link project 1998: foundation of Bluetooth SIG, at www.bluetooth.org 2001: spec. version 1.1 released 2005: 5 million chips/week Sponsors Initial: Ericsson, Nokia, IBM, Intel, Toshiba Expended in 1999: 3Com, Microsoft, Motorola, Agere (was: Lucent), More than 2500 members in SIG as adopters Common specification and certification of products
W.wan.4-6 Bluetooth history History and Hi-tech The name "Bluetooth" is taken from the 10th century Danish King Harald Blatand - or Harold Bluetooth in English.
W.wan.4-7 Bluetooth design Design goals Global operation on voice & data No fixed infrastructure required for network setup Small, low-power, low-cost radio, embedded in devices, goal: $5-10/node; in 2005: $50/USB bluetooth Topology Overlapping piconets (stars) forming a scatternet Master-slave connection One of the first modules (Ericsson).
W.wan.4-8 Bluetooth architecture: piconet Components Master node One per piconet Slave node Up to 7 per piconet Parked node Connected, but not actively participating, up to 256 per piconet, limited listening Standby node Not connected, only native clock is running S SB P M=Master S=Slave P M SB S S P P=Parked SB=Standby
W.wan.4-9 Bluetooth architecture: piconet Collection of devices connected in an ad hoc fashion One unit acts as master and the others (max 7) as slaves Each piconet has a unique hopping pattern Master announce its clock & ID Master determines hopping pattern (by its 48-bit device address) Slaves have to synchronize (Participation in) S SB P M=Master S=Slave P M SB S S P P=Parked SB=Standby
W.wan.4-10 Bluetooth architecture: scatternets M=Master S=Slave P=Parked SB=Standby S SB P M S S P S M P Piconets (each with a capacity of 720 kbit/s) P SB SB S Scatternets: Linking of multiple co-located piconets through the sharing of common master or slave devices Communication between piconets Devices jumping back and forth between the piconets
W.wan.4-11 Bluetooth architecture: scatternets Within a piconet Every active members (master/slaves) share 1 MHz bandwidth Among co-located piconets They can co-exist by hopping independently Aggregately share 79 MHz bandwidth Interconnect of co-located piconets scatternets Nodes can belong to multiple piconets by TDM Can be a slave in two different piconets Can be a master in one piconet and a slave in another piconet Cannot be a master in two different piconets, since master defines a piconet No standard for synchronize between piconets Inefficient use of resources, cause drop of connection
W.wan.4-12 Bluetooth protocol stack App Transport Network Link PHY Audio Apps Audio Internet Apps TCP/UDP IP PPP Telephony Apps AT Modem interface RFCOMM (Serial Line Interface) Logical Link Control & Adaptation Protocol (L2CAP) Baseband RAdio vcard Apps Management Apps Service Discov Protocol (SDP) Link Manager Host Control Interface (HCI)
W.wan.4-13 Bluetooth: protocol stack Radio Baseband Frequency hopping selection Connection creation & management MAC Link management Power management Security management LLC & adaptation protocol
W.wan.4-14 Bluetooth PHY: radio 2.4 GHz ISM band (2402-2480) 79 RF hopping channels 1 MHz carrier spacing GFSK modulation Devices within 10m can share up to 865 kbps (<1 mbps) Peak Tx power 20 dbm FHSS/TDD/TDMA Frequency hopping, good protection against interference Hopping sequence with 1600 hops/s in a pseudo random fashion, determined by a master, Time division duplex for send/receive separation Low cost, low power implementation
W.wan.4-15 Bluetooth PHY: radio All devices in a piconet hop together Master gives slaves its clock and device ID Hopping pattern: determined by device ID Phase in hopping pattern determined by clock Channels 79 1 MHz channels, each divided into 625 μs slots 1600 hops/s, hop occurs after each packet transmitted Packets can be 1, 3, or 5 slots in length Clocks Native clock, 28-bit, ticks 3,200 times/s 312.5 μs, ½ length of hopping slot
W.wan.4-16 Bluetooth PHY: radio Transmitting packets in multiple slots Hop freq used for 1 st slot will remain for others Freq used with the following slots are catching back to the regular sequence 625 µs f k f k+1 f k+2 f k+3 f k+4 f k+5 M S M S M S M f k+6 t f k f k+3 f k+4 f k+5 f k+6 M S M S M t f k M f k+1 f k+6 S M t
W.wan.4-17 Bluetooth PHY: radio TDD (Time Division Duplex) Transmit and receive in alternate time slots Master-slave architecture Master transmits in an even-numbered slot Slave transmits in following odd-numbered slot Traffic scheduling Master polls slaves explicitly or implicitly Sending a master-to-slave data/control packet Master can adjust scheduling algorithm dynamically Scheduling algorithms are not specified in Bluetooth standard
W.wan.4-18 Bluetooth PHY: radio Low power design Transmission 1 mw to reach 10m, to reach 100m, amplify signal to 100mW Class 1: greatest distance Max 100mW (+20dBm), min 1mW, power control required Class 2: Max 2.4mW (+4dBm), min.25mw, power control optional Class 3: lowest power, 1mW Active 50-100mW active power Voice mode, 8-30 ma, 75 hours Data mode, average 5 ma at 20 kbps, 120 hours Standby Standby current < 0.3 ma, 3 months
W.wan.4-19 Bluetooth MAC: link types Voice link SCO (Synchronous Connection Oriented) FEC (forward error correction), no retransmission, 64 kbit/s duplex, point-to-point, circuit switched Periodic single slot packet assignment Master can support up to 3 SCO links at the same time Data link ACL (Asynchronous ConnectionLess) Asynchronous, fast acknowledge, point-to-multipoint, packet switched Variable packet size (1,3,5 slots), asymmetric bandwidth up to 433.9 kbps symm or 723.2/57.6 kbps asymmetric Forward error detection (2/3 FEC) and retransmission
W.wan.4-20 Bluetooth MAC: link types Achievable data rate on the ACL link DMx = x-slot 2/3 FEC protected; DHx = x-slot unproteted Type Symmetric (kbps) Asymmetric (kbps) DM1 108.8 108.0 108.8 DH1 172.8 172.8 172.8 DM3 256.0 384.0 54.4 DH3 384.0 576.0 86.4 DM5 286.7 477.8 36.3 DH5 432.6 721.0 57.6
W.wan.4-21 Baseband MAC: link types Polling-based TDD packet transmission 625µs slots, master polls slaves SCO & ACL can co-exist MASTER SCO ACL SCO ACL SCO ACL SCO ACL f 0 f 6 f 8 f 12 f 4 f 20 f 14 f 18 SLAVE 1 f 1 f 7 f 9 f 13 f 19 SLAVE 2 f 5 f 21 f 17
W.wan.4-22 Bluetooth: baseband Standby: do nothing Inquire: search for other devices Page: connect to a specific device Connected: participate in a piconet detach standby inquiry page unconnected connecting Park: release AMA, get PMA Sniff: listen periodically, not each slot Hold: stop ACL, SCO still possible, possibly participate in another piconet transmit AMA park PMA hold AMA connected AMA sniff AMA active low power
W.wan.4-23 Bluetooth: baseband Addressing Logical address Active Member Address (AM_ADDR, 3 bit) Max 2 3 = 8 active members Parked Member Address (PM_ADDR, 8 bit) Max 2 8 = 256 parked members Device address, 48-bit, unique worldwide, is partitioned into 3 parts the lower address part (LAP) is used in piconet ID, error checking, security check, etc. the remaining two parts are proprietary address of the manufacture organizations
W.wan.4-24 Bluetooth: connection management Initially, all the nodes in standby mode. Someone begins Inquiry/Page to form a new piconet Inquiry, to collect information about nearby devices Potential master: Inquiry: follow a known frequency hopping sequence (only 32 frequencies used with the fixed IAC (Inquiry Access Code)) to announce the master ID Upon receipt of DAC, goto Page state Potential slaves: Inquiry Scan: hopping at very slow speed for the same 32 frequencies Inquiry Response: upon receiving IAC, wait for a random time, then send DAC (Device Access Code) to request to join to the new piconet, goto Page Scan state
W.wan.4-25 Bluetooth: connection management Page, to establish connection Master to be: Page: adjust frequency and send a paging message to the slave to be to allow it join, with slave s FHS known Responded back in previous Inquiry In an existing piconet, the master helped two slaves to form a new piconet Page Response: Upon receipt of a slave s DAC, send page response message including CAC (Channel Access Code); Connection established Slave to be Page scan: upon receipt of Paging message, respond back its DAC (Device Access Code) Waiting for CAC and then adjust clock to join piconet
W.wan.4-26 Bluetooth: baseband Access code derived from the master Three types CAC (Channel Access Code): Used to identify a piconet DAC (Device Access Code) Used for paging & its subsequent response IAC (Inquiry Access Code) Used for inquiry phase
W.wan.4-27 Bluetooth: baseband Low-level packet definition Access code derived from the master Packet header, 18-bit, with 1/3 FEC to have 54-bit 3-bit AM_ADDR (broadcast + 7 slaves), 4-bit packet type, 1-bit flow control, alternating bit ARQ/SEQ, 8-bit header-error-control 68(72) 54 0-2745 bits access code packet header payload 4 64 (4) preamble sync. (trailer) 3 4 1 1 1 8 bits AM address type flow ARQN SEQN HEC
W.wan.4-28 Bluetooth MAC: packets Packet formats Access Code, 48-bit, 2/3 FEC 72-bit Packet Header, 18-bit, 1/3 FEC 54-bit Payload, max 2745 Signaling (control) packets ID, Null, Poll, FHS, DM1, Data/voice packets SCO: Voice HV1, HV2, HV3, DV, ACL: Data DM1, DM2, DM3,
W.wan.4-29 Bluetooth MAC: LMP LMP (Link Management Protocol) Power management Security management Authentication on device Challenge-response mechanism Based on a commonly shared secret key Generated by PIN (personal identification number) Encryption on link
W.wan.4-30 Bluetooth MAC: low power Power saving in an active state Receiver can determine quickly if continued reception needed or not by correlating incoming packet with piconet access code If not (takes 100μs), return to sleep for this receiving slot, as well as the following sending slot unless it s master If yes, detect the destination slave address If matched, continue receiving Otherwise, go back to sleep for this receiving slot, as well as the following sending slot Low power states Park, Hold, Sniff
W.wan.4-31 Bluetooth MAC: low power HOLD mode Low power state Devices connected but not participating If no communication needed for some time, master can put slave in HOLD mode to allow a slave to Goto sleep Switch to another piconet Perform scanning, inquiry or paging After Hold expires, slave returns to channel SCO: Synchronization remains during HOLD period, no ACL SNIFF mode, similar to HOLD mode Slave can skip some receive slots to save power Master and slave agree on which slots slave will listen to channel
W.wan.4-32 Bluetooth MAC: low power PARK mode -- Low power state Motivation Low duty-cycle mode low power Help master to handle more than 7 slaves Give up its AM_ADDR, obtain a 8-bit PM_ADDR Slave wakes up occasionally to resynchronize with master & check for broadcasting Master establishes beacon channel Enable parked slaves to remain synchronized to piconet Allow master to broadcast (dest addr: all 0s) Slave cannot communication until unpacked
W.wan.4-33 Bluetooth: low power example Power consumption in BlueCore 2: typical Average Current Consumption, with VDD=1.8V Temperature = 20 C Active Mode SCO connection HV3 (1s interval Sniff Mode) (Slave) 26.0 ma SCO connection HV3 (1s interval Sniff Mode) (Master) 26.0 ma SCO connection HV1 (Slave) 53.0 ma SCO connection HV1 (Master) 53.0 ma ACL data transfer 115.2kbps UART (Master) 15.5 ma ACL data transfer 720kbps USB (Slave) 53.0 ma ACL data transfer 720kbps USB (Master) 53.0 ma ACL connection, Sniff Mode 40ms interval, 38.4kbps UART 4.0 ma ACL connection, Sniff Mode 1.28s interval, 38.4kbps UART 0.5 ma Low power mode Parked Slave, 1.28s beacon interval, 38.4kbps UART 0.6 ma Standby Mode (Connected to host, no RF activity) 47.0 µa Deep Sleep Mode(2) 20.0 µa Source: www.csr.com
W.wan.4-34 PANs: Bluetooth & 802.15 Bluetooth Overview Piconets & Scatternets PHY layer MAC layer Logical Link Control Management 802.15 & others End
W.wan.4-35 Bluetooth: L2CAP L2CAP (Logical Link Control and Adaptation Protocol) Simple data link protocol on top of baseband Connection oriented Connectionless, and Signaling 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
W.wan.4-36 Bluetooth: L2CAP Establish logical channels over baseband Slave Master Slave L2CAP baseband L2CAP L2CAP 2 d 1 1 d d d d 1 1 d d 2 baseband baseband signalling ACL connectionless connection-oriented
W.wan.4-37 L2CAP packet formats L2CAP packet formats CID=1, signal CID=2, ACL CID, SCO Connectionless PDU 2 2 2 0-65533 bytes length CID=2 PSM payload Connection-oriented PDU 2 2 0-65535 bytes length CID payload Signaling command PDU 2 2 bytes length CID=1 One or more commands 1 1 2 0 code ID length data
W.wan.4-38 PANs: Bluetooth & 802.15 Bluetooth Overview Piconets & Scatternets PHY layer MAC layer Logical Link Control Management 802.15 & others End
W.wan.4-39 Bluetooth: SDP 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)
W.wan.4-40 Bluetooth: apps support 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
W.wan.4-41 Bluetooth: profiles Represent default solutions for a certain usage model Vertical slice through the protocol stack Basis for interoperability 13 profiles group into 4 categories: Generic profiles: Generic Access SDP Telephony profiles Cordless, Intercom Headset Profile Networking profiles LAN, FAX, dialup Serial profiles Serial port, USB Protocols Applications Profiles
W.wan.4-42 PANs: Bluetooth & 802.15 Bluetooth Overview Piconets & Scatternets PHY layer MAC layer Logical Link Control Management 802.15 & others End
W.wan.4-43 WPAN: IEEE 802.15 802.15-2: Coexistance Coexistence of Wireless Personal Area Networks (802.15) and Wireless Local Area Networks (802.11), quantify the mutual interference 802.15-3: High-Rate Standard for high-rate (20Mbit/s or greater) WPANs, while still low-power/low-cost Data Rates: 11, 22, 33, 44, 55 Mbit/s QoS isochronous protocol Ad hoc peer-to-peer networking Security Designed to meet the demanding requirements of portable consumer imaging and multimedia applications
W.wan.4-44 WPAN: IEEE 802.15 Several working groups extend the 802.15.3 standard 802.15.3a: Alternative PHY with higher data rate as extension to 802.15.3 Applications: multimedia, picture transmission 802.15.3b: Enhanced interoperability of MAC Correction of errors and ambiguities in the standard 802.15.3c: Alternative PHY at 57-64 GHz Goal: data rates above 2 Gbps
W.wan.4-45 WPAN: IEEE 802.15 & ZigBee 802.15-4: 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 20-250 kbit/s, latency down to 15 ms Master-Slave or Peer-to-Peer operation Up to 254 devices or 64516 simpler nodes Support for critical latency devices, such as joysticks 16 channels in the 2.4 GHz ISM band, 10 channels in the 915 MHz US ISM band
W.wan.4-46 ZigBee Relation to 802.15.4 similar to Bluetooth / 802.15.1 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 802.15.4 for layers 1 and 2 ZigBee protocol stack up to the applications
W.wan.4-47 WPAN: IEEE 802.15.4 802.15.4a: Alternative PHY with lower data rate as extension to 802.15.4 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 802.15.4b: Extensions, corrections, and clarifications regarding 802.15.4 Usage of new bands, more flexible security mechanisms 802.15.5: Mesh Networking Partial meshes, full meshes Range extension, more robustness, longer battery live
W.wan.4-48 Other IEEE802.xx IEEE 802.16: 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 802.16e adds mobility support, allows for roaming at 150 km/h Unclear relation to 802.20, 802.16 started as fixed system IEEE 802.20: 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 802.22: 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
W.wan.4-49 802.11 vs. 802.15/Bluetooth f [MHz] 2402 Bluetooth may act like a rogue member of the 802.11 network Does not know anything about gaps, inter frame spacing etc. IEEE 802.15-2 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 802.11b (DSSS) 2480 802.11b DIFS DIFS 500 byte DIFS 100 byte SIFS ACK SIFS ACK DIFS DIFS 100 byte 1000 byte SIFS ACK 500 byte DIFS 100 byte SIFS ACK SIFS ACK DIFS SIFS ACK DIFS 100 byte DIFS SIFS ACK 500 byte DIFS 100 byte SIFS ACK t 3 channels (separated by installation) 802.15.1 79 channels (separated by hopping pattern)
W.wan.4-50 Readings Textbooks C. S. Ram Murthy & B. S. Manoj, Ad Hoc Wireless Networks, Chapter 2.5, Bluetooth, pages 88-98. W. Stallings, Wireless Communications & Networks, Chapter 15, Bluetooth and IEEE 802.15, pages 463-510.
W.wan.4-51 PANs: Bluetooth & 802.15 Bluetooth Overview Piconets & Scatternets PHY layer MAC layer Logical Link Control Management 802.15 & others End