Broadband Wireless Access Technologies

Transcription

1 Broadband Wireless Access Technologies Qian Li Ph.D. student of UiO Research interests: Computer networks and protocols Current project: Less than Best Effort TCP Passt project: A geographic routing protocol for mobile adhoc Cognitive Radio Networks March 23rd, UiO 1 / 40

2 Presented papers IEEE Tutorial J. Zyren and A. Petrick IEEE Wireless Local Area Networks B.P. Crow, I. Widjaja, L.G. Kim, and P.T. Sakai IEEE Communications Magazine 1997 A Survey on Emerging Broadband Wireless Access Technologies M. Kuran and T. Tugcu Computer Networks / 40

3 Agenda , HiperLAN WM AN WiMax, WiBro, HAP, WL AN , NGSN N A W W 3 / 40

4 Wireless Local Area Networks (WLAN) 4 / 40

5 IEEE Standards Standards Release Frequency (GHz) Stream Date Rate (Mbps) Modulation , 2 DSSS, FHSS / 5 <= 54 DSSS, OFDM / 5 <= 150 DSSS, OFDM , 5, 60 <= / <= 6757 DSSS, OFDM Source: 5 / 40

6 PHY Amendments Amendments Release Frequency (GHz) Bandwidth (MHz) Stream Date Rate (Mbps) Modulation a / , 9, 12, 18, 24, 36, 48, 54 OFDM b , 2, 5.5, 11 DSSS g , 9, 12, 18, 24, 36, 48, 54 OFDM n / 5 20 <= MIMO-OFDM 40 <= <= <= <= <= <= <= 6757 OFDM, SC, LPSC <= 347 MIMO-OFDM ac ad ah Source: MIMO-OFDM 6 / 40

7 Miscellaneous Amendments IEEE c: Bridge operation procedures; included in the IEEE 802.1D standard (2001) IEEE d: International (country-to-country) roaming extensions (2001) IEEE e: Enhancements: QoS, including packet bursting (2005) IEEE F: Inter-Access Point Protocol (2003) Withdrawn February 2006 IEEE h: Spectrum Managed a (5 GHz) for European compatibility (2004) IEEE i: Enhanced security (2004) IEEE j: Extensions for Japan (2004) IEEE k: Radio resource measurement enhancements (2008) IEEE p: WAVE Wireless Access for the Vehicular Environment (such as ambulances and passenger cars) (July 2010) IEEE r: Fast BSS transition (FT) (2008) IEEE s: Mesh Networking, Extended Service Set (ESS) (July 2011) Source: 7 / 40

8 Miscellaneous Amendments Cont. IEEE T: Wireless Performance Prediction (WPP) test methods and metrics Recommendation cancelled IEEE u: Improvements related to HotSpots and 3rd-party authorization of clients, e.g., cellular network offload (February 2011) IEEE v: Wireless network management (February 2011) IEEE w: Protected Management Frames (September 2009) IEEE y: MHz Operation in the U.S. (2008) IEEE z: Extensions to Direct Link Setup (DLS) (September 2010) IEEE aa: Robust streaming of Audio Video Transport Streams (June 2012) IEEE ae: Prioritization of Management Frames (March 2012) IEEE af: TV Whitespace (February 2014) IEEE ai: Fast Initial Link Setup (December 2016) Source: 8 / 40

9 GHz Band Source: 9 / 40

10 GHz Band Non-overlapping channels Source: Fanny Mlinarsky, / 40

11 Modulation Techniques Spread Spectrum Frequency Hopping Spread Spectrum (FHSS) Direct Sequence Spread Spectrum (DSSS) Advantages Resistance to narrow band interference Resistance to jamming Resistance to eavesdropping Resistance to fading Multiple access capabilities Orthogonal Frequency Division Multiplexing (OFDM) High spectrum efficiency Resistance to narrow band interference Resistance to frequency selective fading Elimination of inter symbol interference by introducing guard intervals between symbols Improved signal to noise ratio by utilizing echo and time spreading 11 / 40

12 Frequency Hopping Spread Spectrum (FHSS) Frequency f8 Energy f f6 f5 f4 f3 f2 f1 f1 f2 f3 f4 f5 f6 f7 f8 (a) Channel assignment Frequency Time (b) Channel use Source: Fraida Fund, / 40

13 FHSS PN Sequence Generators A linear feedback shift register as a psudeo noise sequence generator Source: Fraida Fund, / 40

14 Direct Sequence Spread Spectrum (DSSS) Resultant high rate data (*) Bandwidth thereom: (Width in frequency domain) * (Width in time domain) 2π (#) Sources: (*) (#) 14 / 40

15 DSSS Transmitter & Receiver Source: Ajal A.J., / 40

16 DSSS Correlator / 40

17 Orthogonal Frequency Division Multiplexing (OFDM) Source: 17 / 40

18 OFDM Transmitter & Receiver OFDM Transmitter Block Diagram OFDM Receiver Block Diagram Source: 18 / 40

19 IEEE MAC Frame Format Bytes /2 6 0/2 0/4 var 4 (#) Bits (*) 19 / 40 Source: (*) (#)

20 MAC Distributed Coordination Function (DCF) Carrier Sensing Multiple Access with Collision Avoidance (CSMA/CA) Part of the Wi-Fi Alliance's interoperability standard, widely supported Contention Window (CW) = 2 ^ (2+i), i = 1, 2,, in number of time slots Backoff time = floor(cw * ranf()), 0 <ranf() < 1 20 / 40

21 MAC Hidden Node 21 / 40

22 MAC Point Coordination Function (PCF) Not part of the Wi-Fi Alliance's interoperability standard, not widely implemented CFP Repetition Interval: an integral number of beacon frames Time used to successfully transmit 2 max-size MPDUs + overhead + B + CF_END <= CFP <= CFP Repetition Interval time used to successfully transmit 1 max-size MPDU (+ ACK + handshake) in CP period Polling mechanism: Round robin, polling position is memorized to the next CFP. Paper 2 proposal: a station is dropped from the polling list after K consecutive times of no data to transmit. Optimal setting K = 1 End of CFP: Paper 2 proposal: When the polling list becomes empty CFEnd CFEnd 22 / 40

23 MAC PCF Cont. PC to station transmission Station to station transmission 23 / 40

24 MAC Simulation Results DCF Suggested RTS_Threshold: octets Optimal Fragmentation_threshold: octets Suggested MSDU for a low BER (10 ^ -5) channel: the larger the better PCF Optimal voice payload length: CFP = 4 becons: octets CFP = 5 becons: octets Suggested polling parameter K: 1 Maximum number of voice stations can be supported: 16 (CFP = 4 becons) 24 / 40

25 Miscellaneous Security Authentication: Open system, shared key, 802.1X authentication Encryption: WEP, WPA, WPA2 QoS e Hybrid Coordination Function: priority based round robin scheduler Enhanced Distributed Coordination Function: packets are queued in different Access Categories Block acknowledgments Direct Link Protocol: frames are sent from one WSTA to another directly in an infrastructure QBSS, without using the DS. High throughput: n Mobility: r, p (WAVE) Mesh: s 25 / 40

26 ETSI HiperLAN High Performance Radio Local Area Network Discontinued because could not achieve market success Standards Release Frequency (GHz) Bandwidth (MHz) Data Rate (Mbps) Modulation HiperLAN <= 20 OFDM HiperLAN <= 54 OFDM 26 / 40

27 HiperLAN DLC Controlled by Central Controller (CC) or AP (a) Centralized Mode (b) Direct mode Source: 27 / 40

28 Wireless Metropolitan Area Networks (WMAN) Point to Multipoint Mesh 28 / 40

29 WiMax Source: T. Gyorgy, / 40

30 WiMax Deployment 2004: First launch 2010: 11 million subscribers worldwide, 2% of all fix broadband subscribers 2011: Usage declined 2015: Sprint Cooperation began closing its WiMax networks 30 / 40 Source:

31 IEEE Standards Release Frequency (GHz) Topology/Feature (LOS) PMP a (NLOS) Mesh , LOS PMP, Mesh, Mobility 2-11, NLOS 2-6, Mobility 31 / 40

32 PHY 32 / 40

33 MAC Converting network layer packets into MAC Segment Data Units, Payload Header Suppression, etc. Packing/fragmenting MSDUs into MPDUs, system access, bandwidth allocation Authentication and encryption 33 / 40

34 Mesh Centralized scheduling for Internet traffic Distributed scheduling for intranet traffic Make decision based on two-hop neighborhood information Coordinated: collision free Uncoordinated: collisions are possible MBS: Parent of MSS-B MSS-b: Parent of MSS-a <= 64 connections / link MSS-a Scheduling Tree Centralized scheduling Source: 34 / 40

35 QoS Connections: established over physical wireless links Service Flows: associated with a connection, comprising QoS parameters Scheduling services allocating resources for each connection based on QoS requirements 35 / 40

36 Other WMAN Standards Standards Release Connection Frequency (GHz) Bandwidth (MHz) Modulation Aggregate Data rate (Mbps) Topology/F eatures ETSI HiperAccess 2002 LOS OFDM PMP ETSI HiperMan 2003 NLOS < 11 varies OFDM 25 per Sec PMP, Mesh TTA WiBro 2004, P1 2005, P2 NLOS OFDMA 18/50 per Sec, down 6 per Sec, up Static, mobile NLOS (TV white space) 6 OFDMA <= / 40

37 High Altitude Platform (HAP) 17-22KM HAPs data network, LOS: 47 48GHz (ITU) HALO system architecture, Using multiple transmitters to form cells, coverage area: 7200 KM^2, 10Gbps data rate 37 / 40

38 Wireless Wide Area Networks (WWAN) IEEE Supports high velocity: speed up to 250kmph NLOS (f < 3.5GHz) Connectionless Channel bandwidth: 1.25 or 5 MHz 38 / 40

39 Next Generation Satellite Networks (NGSN) Better mobility support Better coverage 4 GEOs or 11 MEOs give global coverage Longer delay Example NGEO satellite systems 39 / 40 Picture source:

40 Thank you 40 / 40