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John Ankcorn Networks and Mobile Systems Group MIT LCS

Software Technologies for Wireless Communication and Multimedia. John Ankcorn Networks and Mobile Systems Group MIT LCS. Better communication (not just better networks). Different applications have different requirements Bandwidth, latency, error rate, security

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John Ankcorn Networks and Mobile Systems Group MIT LCS

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  1. Software Technologies for Wireless Communication and Multimedia John Ankcorn Networks and Mobile Systems Group MIT LCS

  2. Better communication (not just better networks) • Different applications have different requirements • Bandwidth, latency, error rate, security • In a wireless network channel conditions • Vary significantly over time • Hard to predict • Customize network on-the-fly • Application-specific and condition-specific • Design for the actual case • Not the worst (or even average) case • Integrate applications and communications • Adapt to user needs and conditions John Ankcorn

  3. Digital Communication Many-one One-one • Only the channel is out of our control Source Source Encoder Channel Encoder Channel One-many One-one Many-one Sink Source Decoder Channel Decoder John Ankcorn

  4. OSI Layers Virtual Radio Layers bytes LinkFraming bits Data link Channel Coding bits Line Coding symbols Modulation Discrete signal Multiple Access Discrete signal A/D Conversion Physical Continuous signal Freq. Conv. Continuous signal An Adaptive Wireless Network Interface John Ankcorn

  5. From Physical Radios to Virtual Radios SpectrumWare Radio Edison’s Radio pages = (BlockSize/4096) +1; if((guppi_open("guppi0",pages)) < 0 ) exit(0); guppi_start_rec(); for ( i=0 ; i< NumBlocks ; i++){ pdata = (char *)guppi_rec_buf(); for ( j=0 ; j< IntsPerBlock ; j++){ RealTap_ptr=RealTap; ImagTap_ptr=ImagTap; OutputDataReal = 0.0; OutputDataImag = 0.0; a=cos(TwoPi * CenterFreq / (float)SampleFreqIn * index); b=sin(TwoPi * CenterFreq / (float)SampleFreqIn * index); index += DecFactor; for ( k=0; k< FilterLength ; k++, pdata++){ OutputDataReal += ((float)*pdata * RealTap[k]); OutputDataImag += ((float)*pdata * ImagTap[k]); ... John Ankcorn

  6. Ideal Software Radio Wideband Antenna Wideband ADC Processor and Memory A/D D/A RF Power Amp John Ankcorn

  7. A Short Demonstration John Ankcorn

  8. SpectrumWare Virtual Radio PC AMPS TV Patch Panel PSpectra Environment Wideband IF (33MSPS) Linux Multiband Frontend A/D,D/A GuPPI John Ankcorn

  9. Modulation: 8-PSK with high SNR John Ankcorn

  10. Modulation: 8-PSK with low SNR John Ankcorn

  11. Modulation: QPSK with low SNR John Ankcorn

  12. Footprint Processing Model Synchronization: Determine which samples have information about ak Start of footprint for ak Detection: Compute an estimate for symbol akfrom samples ak John Ankcorn

  13. Duration of Input Filter Fundamental sample relationships • Time duration of input  ability to resolve frequencies • Number of samples used  reduce effect of noise John Ankcorn

  14. Sum >  decide “1” Sum < - decide “0” 0 N = 10 20 30 Symbol detection: matched filter • To decide whether transmitted bit was “1” or “0” • 1) Compute filter output • 2) Apply Threshold Test John Ankcorn

  15. 2 2 Adaptive symbol detection Receiver uses: Quality of channel Desired error rate To control: Accuracy Power consumption Bit rate (with protocol) 10 0 -10 Threshold N = 10 20 30 Terms in sum 10 0 Software optimization Sort samples! -10 N = 10 20 30 John Ankcorn

  16. Av 30 20 • Average number of steps • Lowest after 6th step 10 n 1 2 3 4 5 6 7 8 9 10 How many terms to compute? • Calibrate • For n = 1..N • Plot bit-error rate vs.  • To achieve a given BER • Pick n,  BER n = 3 10-1 10-3 n = 4 10-5 n = 10  10-7 • Test after n steps • If |sum| < , test again • after N steps John Ankcorn

  17. Research Directions: Low power communications • Sensors • Battery operated • Simple function • Probe • Analog-to-digital conversion • Transmitter • Low data rate • Gateway • Connect devices to wired LAN • Add timestamp to data John Ankcorn

  18. Operating Room To Hospital Network Firewall Display Gateway Sensor Local Area Network Low power communications: Application • First application: Hospital Operating Rooms John Ankcorn

  19. Current Research Directions: Universal Availability • Multimedia data communications • Dynamic resource allocation by application • Energy • Spectrum • Explore uses of communication between layers • Adapt protocol based on transmission channel • Adapt transmission to needs of protocol • Flexible physical networks • Some access everywhere • Download physical layer processing • Local communication standards John Ankcorn

  20. Summary • Flexible processing yields: • Better communications availability • Better resource utilization • Application-optimized communications performance John Ankcorn

  21. More Information • Project home page: • http://nms.lcs.mit.edu/spectrumware • Contact: • John Ankcorn jca@lcs.mit.edu John Ankcorn

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