Sideseadmed IRT 0040 Cognitive Radio Communications. Avo 08. märts 2011

Transcription

1 Sideseadmed IRT 0040 Cognitive Radio Communications Avo 08. märts 2011

2 Increasing Demand Rapid growth in the wireless communications sector, requiring more spectral bandwidth Increasing number of users Increasing number of new wireless services being offered

3 Increasing Demand Some applications are bandwidth-intensived Rapid growth in the wireless communications sector, requiring more spectral bandwidth Increasing number of users Increasing number of new wireless services being offere

4 Too Much Growth? Spectrum scarcity due to command-andcontrol structure of frequency allocation Fixed amount of spectrum versus growing number of wireless applications/users License holders maintain exclusive rights to their allocated spectrum Purchased during a spectrum auction Allocated via government decree, e.g., military, television

5 Spectrum Scarcity devices not permitted to transmit in licensed bands Allocated unlicensed bands (with transmit constraints) Industrial, Scientific, Medical (ISM) bands» 900 MHz, 1.8 GHz, 2.4 GHz, 5.8 GHz Unlicensed National Information Infrastructure (UNII) band» 5.15 GHz GHz

6 Needs Public safety sector especially affected by these issues Need for reliable communications across platforms employing different communication standards different wireless standards for a wide range of applications Tower of Babel syndrome Interoperability issues

7 Software Defined Radio

8 8 Classical multi-user channels

9 Defineerimine Cognitive radio is an intelligent wireless communication system that is aware of its surrounding environment (i.e., outside world), and uses the methodology of understanding-by-building to learn from the environment and adapt its internal states to statistical variations in the incoming RF stimuli by making corresponding changes in certain operating parameters (e.g., transmit-power, carrier-frequency, and modulation strategy) in real-time, with two primary objectives in mind: highly reliable communications whenever and wherever needed; efficient utilization of the radio spectrum. S. Haykin, Cognitive Radio: Brain-Empowered Wireless Communications, IEEE J-SAC, Feb

10 Esmane ja teisene kasutus Primary users Secondary/cognitive users 10

11 Spektrikasutus Measurement studies have shown that in both the time and frequency domains that spectrum is underutilized Spectrum Holes

12 Dynamic Spectrum Access Fill with secondary users Spectrum measurement across the 900 khz 1 GHz band (Lawrence, KS, USA)

13 Kasutus ajas

14 Kasutusnäited Measured Spectrum Occupancy in Chicago and New York City PLM, Amateur, others: MHz TV 2-6, RC: MHz Air traffic Control, Aero Nav: MHz Fixed Mobile, Amateur, others: MHz TV 7-13: MHz Maritime Mobile, Amateur, others: MHz Fixed Mobile, Aero, others: MHz Amateur, Fixed, Mobile, Radiolocation, MHz TV 14-20: MHz TV 21-36: MHz TV 37-51: MHz TV 52-69: MHz Cell phone and SMR: MHz Unlicensed: MHz Paging, SMS, Fixed, BX Aux, and FMS: MHz IFF, TACAN, GPS, others: MHz Amateur: MHz Aero Radar, Military: MHz Space/Satellite, Fixed Mobile, Telemetry: MHz Mobile Satellite, GPS, Meteorologicial: MHz Fixed, Fixed Mobile: MHz PCS, Asyn, Iso: MHz TV Aux: MHz Common Carriers, Private, MDS: MHz Space Operation, Fixed: MHz Amateur, WCS, DARS: MHz Telemetry: MHz U-PCS, ISM (Unlicensed): MHz ITFS, MMDS: MHz Surveillance Radar: MHz Chicago New York City 0.0% 25.0% 50.0% 75.0% 100.0% Spectrum Occupancy

15 Mõõteauto (ca 1927)

16 USRP Universal Software Radio Peripheral 2 (USRP2) Unit Motherboard FPGA DAC / ADC Daughterboards RF front-end Interchangeable

17 Multicarrier Transmitter Receiver

18 Spectrum Opportunity A channel is an opportunity for A B if the transmission from A to B can succeed the interference power to primary is below a prescribed level 18

19 Spectrum Sharing

20 Secondary Spectrum Access (SSA) SSA is a vertical (licensed) spectrum sharing License holder of the band operates as the primary system Secondary users are allowed to access the licensed band of primary, complying with certain requirements Cognitive Radio (CR) is an enabling technology to implement SSA A recent example is FCC s decision to allow secondary access to TV white spaces Overlay SSA Only access the band IF the primary is absent Underlay SSA Secondary users can access the band when the primary is transmitting, BUT the received interference by primary receivers should be below a threshold 20

21 Saatjate kavandamine

22 Underlay vs overlay

23 Non-contiguous OFDM (NC-OFDM) NC-OFDM transmitter 23

24 Non-contiguous OFDM (NC-OFDM) NC-OFDM receiver 24

25 Parameter Relationships Minimize BER Transmit Power Symbol Rate TDD Modulation Index Minimize Spectral Interference Maximize Throughput Frame Size Bandwidth Minimize Spectral Efficiency Minimize Power Modulation Type Coding Rate 25

26 BER M-QAM QAM 8QAM 16QAM 32QAM 64QAM 128QAM 256QAM 512QAM 1024QAM 2048QAM SNR(dB)

27 Goodput (normalized to Rc) Goodput Goodput versus frame size for varying bit error rates x x MTU (bytes)

28 Packet networks

29 Depicting the history of cognitive radio 29

30 IEEE SCC41

31 Defineerimised

32 TV White Spaces (USA) IEEE WG starts working on a CR based PHY/MAC spec Notice of Inquiry Notice of Proposed Rule Making Public Notice 2003 Report on Sensing, Interference to DTVs & Other Radios 2004 Report on Interference Rej. Cap. of DTV Rx s 2005 Sep Initial R & O and Further NPRM Sensing Proto Testing Mar July 2007 Mar IEEE first official LB June 2008 Aug Nov Dec Feb Mar June 2009 Field Tests Final Rule and Order Final rules in Federal Registry IEEE starts 2 nd LB 32

33 IEEE Fixed point-to-multipoint wireless regional area networks (WRAN) Reuse of TV broadcast bands on a non-interfering basis Specify Cognitive Radio based PHY/MAC layers Cognitive Radio Entity for spectrum management Master-Slave architecture: Base Stations (BS) Cusumer Premise Equipments (CPEs) 33

34 The PHY overview Parameters Frequency range Bandwidth Data rate Spectral Efficiency Payload modulation Transmit EIRP Specification 54~862 MHz 6 and/or 7, and/or 8 MHz 1.51~22.69 Mb/s 0.25~3.78 b/s/hz QPSK, 16-QAM, 64-QAM Default 4W for CPEs Multiple Access OFDMA FFT Mode 2048 Cyclic Prefix Modes ¼, 1/8, 1/16, 1/32 Duplex TDD 34

35 Sensing architecture and strategy Begin Sensing Coarse Sensing (Analog, RSSI, MRSS, FFT ) Fine Sensing Spectrum Usage Database (BS) MAC (Select single channel) FFT Spectral Correlation CSFD AAC Field Sync ATSC Segment Sync Optimum Radiometer Multi-cycle Detector Y occupied? End Sensing N

36 Sensing

37 Coexistence Beacon Protocol (CBP) CBP packets carry the schedule of the QPs and self-coexistence information Other cases also possible depending on location of the CPEs Case 1: Case 2: 37

38 Security Spectrum sensing data falsification (SSDF) attacks

39 Public Safety and Cognitive Radio Modern public safety networks are designed around some important ideas: Cellular frequency reuse Trunking Digital modulation Frequency duplexing Time division multiple access

40 GNU Radio Components Hardware Frontend Host Computer RF Frontend ( Daugtherboard ) ADC/DAC and Digital Frontend ( USRP ) GNU Radio Software

41 Lingid