i think that this is nearly the beginning of task 1
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ti_mo
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function result = calc_doppler_freq(rrv, carrier_freq)
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result = rrv * carrier_freq / physconst('LightSpeed');
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end
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function [cfgEHT, simParameters, channel, chInfo, maxChDelay, satelliteDopplerShift, chanBW] = create_baseline_configuration(profile, ...
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bandwidth_mhz, ...
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include_free_space_pathloss, ...
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delay_model, ...
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carrier_frequency, ...
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elevation_angle, ...
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mobile_speed, ...
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mobile_altitude, ...
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satellite_altitude, ...
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random_stream, ...
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seed, ...
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tx_antenna_count, ...
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rx_antenna_count, ...
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apep, ...
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mcs)
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switch bandwidth_mhz
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case 20
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chanBW = 'CBW20';
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case 40
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chanBW = 'CBW40';
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case 80
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chanBW = 'CBW80';
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case 160
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chanBW = 'CBW160';
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case 320
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chanBW = 'CBW320';
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otherwise
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error("Not supported bandwidth!");
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end
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cfgEHT = wlanEHTMUConfig(chanBW);
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cfgEHT.User{1}.APEPLength = apep;
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cfgEHT.NumTransmitAntennas = tx_antenna_count;
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cfgEHT.User{1}.NumSpaceTimeStreams = 1;
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cfgEHT.User{1}.MCS = mcs;
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fs = wlanSampleRate(chanBW);
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simParameters.IncludeFreeSpacePathLoss = include_free_space_pathloss;
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simParameters.DelayModel = delay_model;
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simParameters.CarrierFrequency = carrier_frequency;
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simParameters.ElevationAngle = elevation_angle;
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simParameters.MobileSpeed = mobile_speed;
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simParameters.MobileAltitude = mobile_altitude;
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simParameters.SatelliteAltitude = satellite_altitude;
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simParameters.SampleRate = fs;
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simParameters.RandomStream = random_stream;
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simParameters.Seed = seed;
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simParameters.NumTransmitAntennas = tx_antenna_count;
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simParameters.NumReceiveAntennas = rx_antenna_count;
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simParameters.NTNChannelType = "TDL";
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simParameters.DelayProfile = "NTN-TDL-" + profile;
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simParameters.DelaySpread = 30e-9;
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c = physconst("lightspeed");
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satelliteDopplerShift = dopplerShiftCircularOrbit( ...
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simParameters.ElevationAngle,simParameters.SatelliteAltitude, ...
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simParameters.MobileAltitude,simParameters.CarrierFrequency);
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channel = nrTDLChannel;
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channel.DelayProfile = simParameters.DelayProfile;
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channel.DelaySpread = simParameters.DelaySpread;
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channel.SatelliteDopplerShift = satelliteDopplerShift;
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channel.MaximumDopplerShift = simParameters.MobileSpeed*simParameters.CarrierFrequency/c;
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channel.NumTransmitAntennas = simParameters.NumTransmitAntennas;
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channel.NumReceiveAntennas = simParameters.NumReceiveAntennas;
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channel.SampleRate = simParameters.SampleRate;
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channel.RandomStream = simParameters.RandomStream;
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channel.Seed = simParameters.Seed;
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chInfo = info(channel);
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maxChDelay = ceil(max(chInfo.PathDelays*channel.SampleRate)) + chInfo.ChannelFilterDelay;
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end
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@@ -0,0 +1,43 @@
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carrier_frequency = 2.4e9;
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wifi_be_subcarrier_spacing = 78.125e3;
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leo_altitude = 600e3;
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bandwidth = 20;
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mcs = 2;
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apep = 1000;
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tx_antenna_count = 1;
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rx_antenna_count = 1;
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elevation_angle = 50;
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random_stream = "mt19937ar with seed";
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seed = 666;
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ntn_tdl_delay_profiles = ["A" "B" "C" "D"];
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[cfgEHT, simParameters, channel, chInfo, maxChDelay, satelliteDopplerShift, chanBW] = ...
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create_baseline_configuration(ntn_tdl_delay_profiles(3), bandwidth, false, "None", ...
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carrier_frequency, elevation_angle, 0, ...
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0, leo_altitude, random_stream, ...
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seed, tx_antenna_count, ...
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rx_antenna_count, apep, mcs);
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normalized_cfo = satelliteDopplerShift / wifi_be_subcarrier_spacing;
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disp("Channel Info: ")
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disp(chInfo)
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disp("Satellite Doppler Shift: " + satelliteDopplerShift)
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disp("Normalized CFO: " + normalized_cfo)
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snrs = (0:1:40);
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packets_per_snr = 250;
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maxNumErrors = 10;
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errorCounts = zeros(size(snrs));
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for snrIndex = 1:length(snrs)
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errorCounts(snrIndex) = simulateTransmission(cfgEHT, channel, snrs(snrIndex), packets_per_snr, maxNumErrors, simParameters, chanBW, snrIndex);
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end
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errorRate = errorCounts / packets_per_snr;
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disp("ErrorRatePerSNR: " + errorRate);
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@@ -0,0 +1,4 @@
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> This PDF will be a bit more 'well defined'
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## Task1
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For the baseline configuration with f_c = 2.4GHz, LEO altitude 600km, elevation angle 50° (like example), and static receiver, the computed satellite Doppler shift is approximately 35.56kHz. With the IEEE 802.11be subcarrier spacing of 78.125kHz, this corresponds to a normalized CFO of \epsilon \approx 0.455. Therefore, the Doppler shift is below one subcarrier spacing but still represents a significant fraction of the OFDM subcarrier spacing.
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@@ -0,0 +1,3 @@
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function result = normalized_carrier_frequency_offset(freq_doppler, delta_freq_subcarrier)
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result = freq_doppler / delta_freq_subcarrier;
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end
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@@ -0,0 +1,72 @@
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function numPacketErrors = simulateTransmission(cfgEHT, channel, snr, packets, maxNumErrors, simParameters, chanBW, substreamIndex)
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numPacketErrors = 0;
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ofdmInfo = wlanEHTOFDMInfo('EHT-Data', cfgEHT);
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ind = wlanFieldIndices(cfgEHT);
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if nargin < 8
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substreamIndex = 1;
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end
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stream = RandStream('combRecursive', Seed=simParameters.Seed);
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stream.Substream = substreamIndex;
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RandStream.setGlobalStream(stream);
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snrVal = convertSNR(snr, "snrsc", "snr", FFTLength=ofdmInfo.FFTLength, NumActiveSubcarriers=ofdmInfo.NumTones);
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for packetIdx = 1:packets
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if numPacketErrors >= maxNumErrors
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break;
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end
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txPSDU = randi([0 1], psduLength(cfgEHT) * 8, 1);
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tx = wlanWaveformGenerator(txPSDU, cfgEHT);
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txPad = [tx; zeros(50, cfgEHT.NumTransmitAntennas)];
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reset(channel);
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rx = awgn(channel(txPad), snrVal);
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coarsePacketOffset = wlanPacketDetect(rx, chanBW);
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if isempty(coarsePacketOffset)
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numPacketErrors = numPacketErrors + 1;
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continue;
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end
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lstf = rx(coarsePacketOffset + (ind.LSTF(1) : ind.LSTF(2)), :);
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coarseFrequencyOffset = wlanCoarseCFOEstimate(lstf, chanBW);
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rx = frequencyOffset(rx, simParameters.SampleRate, -coarseFrequencyOffset);
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nonhtfields = rx(coarsePacketOffset + (ind.LSTF(1) : ind.LSTF(2)), :);
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finePacketOffset = wlanSymbolTimingEstimate(nonhtfields, chanBW);
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packetOffset = coarsePacketOffset + finePacketOffset;
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if packetOffset > 50
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numPacketErrors = numPacketErrors + 1;
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continue;
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end
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rxLLTF = rx(packetOffset + (ind.LLTF(1) : ind.LLTF(2)), :);
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fineFrequencyOffset = wlanFineCFOEstimate(rxLLTF, chanBW);
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rx = frequencyOffset(rx, simParameters.SampleRate, -fineFrequencyOffset);
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rxHELTF = rx(packetOffset + (ind.EHTLTF(1) : ind.EHTLTF(2)), :);
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heltfDemod = wlanEHTDemodulate(rxHELTF, "EHT-LTF", cfgEHT);
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[chanEstimate, pilotEstimate] = wlanEHTLTFChannelEstimate(heltfDemod, cfgEHT);
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rxData = rx(packetOffset + (ind.EHTData(1) : ind.EHTData(2)), :);
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demodSym = wlanEHTDemodulate(rxData, "EHT-Data", cfgEHT);
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nVarEst = wlanEHTDataNoiseEstimate(demodSym(ofdmInfo.PilotIndices, :, :),pilotEstimate, cfgEHT);
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demodDataSym = demodSym(ofdmInfo.DataIndices, :, :);
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chanEstimateData = chanEstimate(ofdmInfo.DataIndices, :, :);
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[eqSym, csi] = wlanEHTEqualize(demodDataSym, chanEstimateData, nVarEst, cfgEHT, 'EHT-Data');
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rxPSDU = wlanEHTDataBitRecover(eqSym, nVarEst, csi, cfgEHT);
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numPacketErrors = numPacketErrors + any(biterr(txPSDU, rxPSDU));
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end
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end
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