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

January 2001John AnkcornSlide 1 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

January 2001John AnkcornSlide 2 Digital Communication Only the channel is out of our control Source Encoder Channel Encoder Sink Source Decoder Channel Decoder Channel One-many Many-one One-one Many-one

January 2001John AnkcornSlide 3 An Adaptive Wireless Network Interface Physical Data link LinkFraming bytes bits symbols Discrete signal Continuous signal Channel Coding Line Coding Modulation Multiple Access A/D Conversion Freq. Conv. OSI LayersVirtual Radio Layers

January 2001John AnkcornSlide 4 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]);... From Physical Radios to Virtual Radios Edison’s Radio SpectrumWare Radio

January 2001John AnkcornSlide 5 Ideal Software Radio Processor and Memory A/D D/A RF Power Amp Wideband Antenna Wideband ADC

January 2001John AnkcornSlide 6 A Short Demonstration

January 2001John AnkcornSlide 7 PC Linux Wideband IF (33MSPS) PSpectra Environment AMPSTV Patch Panel SpectrumWare Virtual Radio Multiband Frontend A/D,D/A GuPPI

January 2001John AnkcornSlide 8 Modulation: 8-PSK with high SNR

January 2001John AnkcornSlide 9 Modulation: 8-PSK with low SNR

January 2001John AnkcornSlide 10 Modulation: QPSK with low SNR

January 2001John AnkcornSlide 11 Footprint Processing Model Start of footprint for a k akak Detection: Compute an estimate for symbol a k from samples Synchronization: Determine which samples have information about a k

January 2001John AnkcornSlide 12 Fundamental sample relationships Filter Duration of Input Time duration of input  ability to resolve frequencies Number of samples used  reduce effect of noise

January 2001John AnkcornSlide 13 To decide whether transmitted bit was “1” or “0” 1) Compute filter output 2) Apply Threshold Test Symbol detection: matched filter N = Sum >  decide “1” Sum < -  decide “0”

January 2001John AnkcornSlide 14 Adaptive symbol detection Terms in sum N = Receiver uses: Quality of channel Desired error rate To control: Accuracy Power consumption Bit rate (with protocol) 22 Threshold N = Software optimization Sort samples! 22

January 2001John AnkcornSlide 15 How many terms to compute? Calibrate For n = 1..N Plot bit-error rate vs.  To achieve a given BER Pick n,   n = 3 n = 4 n = 10 BER Test after n steps If |sum| < , test again after N steps n Av Average number of steps Lowest after 6th step

January 2001John AnkcornSlide 16 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

January 2001John AnkcornSlide 17 Low power communications: Application First application: Hospital Operating Rooms Gateway Display Firewall To Hospital Network Operating Room Sensor Local Area Network

January 2001John AnkcornSlide 18 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

January 2001John AnkcornSlide 19 Summary Flexible processing yields: Better communications availability Better resource utilization Application-optimized communications performance

January 2001John AnkcornSlide 20 More Information Project home page: Contact: John