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224 lines
6.6 KiB
Matlab
224 lines
6.6 KiB
Matlab
%% LTE Downlink Channel Estimation and Equalization
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%% Cell-Wide Settings
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clear
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plot_noise_estimation_only=true;
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SNR_values_db=linspace(0,30,8);
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Nrealizations=1 ;
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preEVM = zeros(length(SNR_values_db),Nrealizations);
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postEVM_mmse = zeros(length(SNR_values_db),Nrealizations);
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postEVM_mmse_lin = zeros(length(SNR_values_db),Nrealizations);
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postEVM_srslte = zeros(length(SNR_values_db),Nrealizations);
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enb.NDLRB = 6; % Number of resource blocks
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enb.CellRefP = 1; % One transmit antenna port
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enb.NCellID = 0; % Cell ID
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enb.CyclicPrefix = 'Normal'; % Normal cyclic prefix
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enb.DuplexMode = 'FDD'; % FDD
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%% Channel Model Configuration
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rng(1); % Configure random number generators
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cfg.Seed = 2; % Random channel seed
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cfg.NRxAnts = 2; % 1 receive antenna
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cfg.DelayProfile = 'EVA'; % EVA delay spread
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cfg.DopplerFreq = 120; % 120Hz Doppler frequency
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cfg.MIMOCorrelation = 'Low'; % Low (no) MIMO correlation
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cfg.InitTime = 0; % Initialize at time zero
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cfg.NTerms = 16; % Oscillators used in fading model
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cfg.ModelType = 'GMEDS'; % Rayleigh fading model type
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cfg.InitPhase = 'Random'; % Random initial phases
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cfg.NormalizePathGains = 'On'; % Normalize delay profile power
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cfg.NormalizeTxAnts = 'On'; % Normalize for transmit antennas
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%% Channel Estimator Configuration
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cec = struct; % Channel estimation config structure
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cec.PilotAverage = 'UserDefined'; % Type of pilot symbol averaging
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cec.FreqWindow = 9; % Frequency window size
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cec.TimeWindow = 9; % Time window size
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cec.InterpType = 'Linear'; % 2D interpolation type
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cec.InterpWindow = 'Centered'; % Interpolation window type
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cec.InterpWinSize = 1; % Interpolation window size
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%% Subframe Resource Grid Size
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gridsize = lteDLResourceGridSize(enb);
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K = gridsize(1); % Number of subcarriers
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L = gridsize(2); % Number of OFDM symbols in one subframe
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P = gridsize(3); % Number of transmit antenna ports
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for nreal=1:Nrealizations
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%% Transmit Resource Grid
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txGrid = [];
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RSRP = [];
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%% Payload Data Generation
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% Number of bits needed is size of resource grid (K*L*P) * number of bits
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% per symbol (2 for QPSK)
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numberOfBits = K*L*P*2;
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% Create random bit stream
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inputBits = randi([0 1], numberOfBits, 1);
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% Modulate input bits
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inputSym = lteSymbolModulate(inputBits,'QPSK');
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%% Frame Generation
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% For all subframes within the frame
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for sf = 0:10
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% Set subframe number
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enb.NSubframe = mod(sf,10);
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% Generate empty subframe
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subframe = lteDLResourceGrid(enb);
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% Map input symbols to grid
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%subframe(:) = inputSym;
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% Generate synchronizing signals
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pssSym = ltePSS(enb);
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sssSym = lteSSS(enb);
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pssInd = ltePSSIndices(enb);
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sssInd = lteSSSIndices(enb);
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% Map synchronizing signals to the grid
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subframe(pssInd) = pssSym;
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subframe(sssInd) = sssSym;
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% Generate cell specific reference signal symbols and indices
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cellRsSym = lteCellRS(enb);
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cellRsInd = lteCellRSIndices(enb);
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% Map cell specific reference signal to grid
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subframe(cellRsInd) = cellRsSym;
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% Append subframe to grid to be transmitted
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txGrid = [txGrid subframe]; %#ok
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end
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txGrid([1:5 68:72],6:7) = zeros(10,2);
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%% OFDM Modulation
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[txWaveform,info] = lteOFDMModulate(enb,txGrid);
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txGrid = txGrid(:,1:140);
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%% SNR Configuration
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for snr_idx=1:length(SNR_values_db)
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SNRdB = SNR_values_db(snr_idx); % Desired SNR in dB
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SNR = 10^(SNRdB/20); % Linear SNR
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%% Fading Channel
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cfg.SamplingRate = info.SamplingRate;
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% Pass data through the fading channel model
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%rxWaveform = lteFadingChannel(cfg,txWaveform);
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rxWaveform = txWaveform;
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%% Additive Noise
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% Calculate noise gain
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N0 = 1/(sqrt(2.0*enb.CellRefP*double(info.Nfft))*SNR);
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% Create additive white Gaussian noise
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noise = N0*complex(randn(size(rxWaveform)),randn(size(rxWaveform)));
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noiseTx(snr_idx) = N0;
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% Add noise to the received time domain waveform
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rxWaveform = rxWaveform + noise;
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%% Synchronization
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offset = lteDLFrameOffset(enb,rxWaveform);
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rxWaveform = rxWaveform(1+offset:end,:);
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%% OFDM Demodulation
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rxGrid = lteOFDMDemodulate(enb,rxWaveform);
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rxGrid = rxGrid(:,1:140);
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addpath('../../debug/lte/phy/lib/ch_estimation/test')
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%% Channel Estimation
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[estChannel, noiseEst(snr_idx)] = lteDLChannelEstimate(enb,cec,rxGrid);
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output=[];
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snrest_srslte = zeros(10,1);
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noise_srslte = zeros(10,1);
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rsrp = zeros(1,10);
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for i=0:9
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[d, a, out, snrest_srslte(i+1), noise_srslte(i+1), rsrp(i+1)] = srslte_chest(enb.NCellID,enb.CellRefP,rxGrid(:,i*14+1:(i+1)*14),[0.1 0.8 0.1],[0.1 0.9],i);
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output = [output out];
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end
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RSRP = [RSRP rsrp];
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meanRSRP(snr_idx)=mean(rsrp);
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SNR_srslte(snr_idx)=mean(snrest_srslte);
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noiseEst_srslte(snr_idx)=mean(noise_srslte);
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if ~plot_noise_estimation_only
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%% MMSE Equalization
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eqGrid_mmse = lteEqualizeMMSE(rxGrid, estChannel, noiseEst(snr_idx));
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eqGrid_srslte = reshape(output,size(eqGrid_mmse));
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% Analysis
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%Compute EVM across all input values EVM of pre-equalized receive signal
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preEqualisedEVM = lteEVM(txGrid,rxGrid);
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fprintf('%d-%d: Pre-EQ: %0.3f%%\n', ...
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snr_idx,nreal,preEqualisedEVM.RMS*100);
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%EVM of post-equalized receive signal
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postEqualisedEVM_mmse = lteEVM(txGrid,reshape(eqGrid_mmse,size(txGrid)));
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fprintf('%d-%d: MMSE: %0.3f%%\n', ...
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snr_idx,nreal,postEqualisedEVM_mmse.RMS*100);
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postEqualisedEVM_srslte = lteEVM(txGrid,reshape(eqGrid_srslte,size(txGrid)));
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fprintf('%d-%d: srslte: %0.3f%%\n', ...
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snr_idx,nreal,postEqualisedEVM_srslte.RMS*100);
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preEVM(snr_idx,nreal) = preEqualisedEVM.RMS;
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postEVM_mmse(snr_idx,nreal) = mean([postEqualisedEVM_mmse.RMS]);
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postEVM_srslte(snr_idx,nreal) = mean([postEqualisedEVM_srslte.RMS]);
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end
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end
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end
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% subplot(1,2,1)
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if ~plot_noise_estimation_only
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plot(SNR_values_db, mean(preEVM,2), ...
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SNR_values_db, mean(postEVM_mmse,2), ...
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SNR_values_db, mean(postEVM_srslte,2))
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legend('No Eq','MMSE-lin','MMSE-srslte')
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grid on
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end
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% subplot(1,2,2)
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if plot_noise_estimation_only
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SNR_matlab = 1./(noiseEst*sqrt(2.0)*enb.CellRefP);
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subplot(1,3,1)
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plot(SNR_values_db, SNR_values_db, SNR_values_db, 10*log10(SNR_srslte),SNR_values_db, 10*log10(SNR_matlab))
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legend('Theory','srsLTE','Matlab')
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subplot(1,3,2)
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plot(SNR_values_db, 10*log10(noiseTx), SNR_values_db, 10*log10(noiseEst_srslte),SNR_values_db, 10*log10(noiseEst))
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legend('Theory','srsLTE','Matlab')
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subplot(1,3,3)
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plot(1:10*length(SNR_values_db),RSRP,10*(1:length(SNR_values_db)),meanRSRP)
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end
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