mirror of https://github.com/PentHertz/srsLTE.git
273 lines
7.0 KiB
Matlab
273 lines
7.0 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=false;
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SNR_values_db=100;%linspace(20,35,8);
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Nrealizations=1;
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w1=0.1;
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w2=0.3;
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enb.NDLRB = 25; % 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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K=enb.NDLRB*12;
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P=K/6;
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%% Channel Model Configuration
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cfg.Seed = 0; % Random channel seed
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cfg.InitTime = 0;
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cfg.NRxAnts = 1; % 1 receive antenna
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cfg.DelayProfile = 'EPA';
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% doppler 5, 70 300
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cfg.DopplerFreq = 5; % 120Hz Doppler frequency
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cfg.MIMOCorrelation = 'Low'; % Low (no) MIMO correlation
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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 = 'Causal'; % 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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Ks = gridsize(1); % Number of subcarriers
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L = gridsize(2); % Number of OFDM symbols in one subframe
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Ports = gridsize(3); % Number of transmit antenna ports
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%% Allocate memory
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Ntests=4;
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hest=cell(1,Ntests);
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for i=1:Ntests
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hest{i}=zeros(K,140);
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end
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hls=zeros(4,4*P*10);
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MSE=zeros(Ntests,Nrealizations,length(SNR_values_db));
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noiseEst=zeros(Ntests,Nrealizations,length(SNR_values_db));
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legends={'matlab','ls',num2str(w1),num2str(w2)};
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colors={'bo-','rx-','m*-','k+-','c+-'};
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colors2={'b-','r-','m-','k-','c-'};
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addpath('../../build/srslte/lib/ch_estimation/test')
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offset=-1;
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for nreal=1:Nrealizations
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%% Transmit Resource Grid
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txGrid = [];
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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 = Ks*L*Ports*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) = ones(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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fprintf('SNR=%.1f dB\n',SNRdB)
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%% Fading Channel
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cfg.SamplingRate = info.SamplingRate;
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[rxWaveform, chinfo] = lteFadingChannel(cfg,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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% Add noise to the received time domain waveform
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rxWaveform_nonoise = rxWaveform;
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rxWaveform = rxWaveform + noise;
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%% Synchronization
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if (offset==-1)
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offset = lteDLFrameOffset(enb,rxWaveform);
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end
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rxWaveform = rxWaveform(1+offset:end,:);
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rxWaveform_nonoise = rxWaveform_nonoise(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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rxGrid_nonoise = lteOFDMDemodulate(enb,rxWaveform_nonoise);
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rxGrid_nonoise = rxGrid_nonoise(:,1:140);
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% True channel
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h=rxGrid_nonoise./(txGrid);
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%% Channel Estimation with Matlab
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tmpnoise=zeros(10,1);
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for i=1:10
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enb.NSubframe=i-1;
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[hest{1}(:,(1:14)+(i-1)*14), tmpnoise(i), hls(:,(1:4*P)+(i-1)*4*P)] = ...
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lteDLChannelEstimate2(enb,cec,rxGrid(:,(i-1)*14+1:i*14));
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end
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noiseEst(1,nreal,snr_idx)=mean(tmpnoise)*sqrt(2)*enb.CellRefP;
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%% LS-Linear estimation with srsLTE
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[tmp, ~, ~, noiseEst(2,nreal,snr_idx)] = srslte_chest(enb.NCellID,enb.CellRefP,rxGrid);
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hest{2}=reshape(tmp, size(hest{1}));
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%% LS-Linear + averaging with srsLTE
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[tmp, ~, ~, noiseEst(3,nreal,snr_idx)] = srslte_chest(enb.NCellID,enb.CellRefP,rxGrid,w1);
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hest{3}=reshape(tmp, size(hest{1}));
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%% LS-Linear + more averaging with srsLTE
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[tmp, ~, ~, noiseEst(4,nreal,snr_idx)] = srslte_chest(enb.NCellID,enb.CellRefP,rxGrid,w2);
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hest{4}=reshape(tmp, size(hest{1}));
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%% Compute MSE
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for i=1:Ntests
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MSE(i,nreal,snr_idx)=mean(mean(abs(h-hest{i}).^2));
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fprintf('MSE test %d: %f\n',i, 10*log10(MSE(i,nreal,snr_idx)));
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end
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%% Plot a single realization
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if (length(SNR_values_db) == 1)
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sym=1;
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ref_idx=1:P;
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ref_idx_x=[1:6:K];% (292:6:360)-216];% 577:6:648];
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n=1:(K*length(sym));
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for i=1:Ntests
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plot(n,abs(reshape(hest{i}(:,sym),1,[])),colors2{i});
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hold on;
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end
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plot(n, abs(h(:,sym)),'g-')
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% plot(ref_idx_x,real(hls(3,ref_idx)),'ro');
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hold off;
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tmp=cell(Ntests+1,1);
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for i=1:Ntests
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tmp{i}=legends{i};
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end
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tmp{Ntests+1}='Real';
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legend(tmp)
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xlabel('SNR (dB)')
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ylabel('Channel Gain')
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grid on;
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fprintf('Mean MMSE Robust %.2f dB\n', 10*log10(MSE(4,nreal,snr_idx)))
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fprintf('Mean MMSE matlab %.2f dB\n', 10*log10(MSE(1,nreal,snr_idx)))
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end
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end
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end
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%% Compute average MSE and noise estimation
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mean_mse=mean(MSE,2);
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mean_snr=10*log10(1./mean(noiseEst,2));
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%% Plot average over all SNR values
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if (length(SNR_values_db) > 1)
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subplot(1,2,1)
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for i=1:Ntests
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plot(SNR_values_db, 10*log10(mean_mse(i,:)),colors{i})
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hold on;
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end
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hold off;
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legend(legends);
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grid on
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xlabel('SNR (dB)')
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ylabel('MSE (dB)')
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subplot(1,2,2)
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plot(SNR_values_db, SNR_values_db,'k:')
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hold on;
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for i=1:Ntests
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plot(SNR_values_db, mean_snr(i,:), colors{i})
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end
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hold off
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tmp=cell(Ntests+1,1);
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tmp{1}='Theory';
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for i=2:Ntests+1
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tmp{i}=legends{i-1};
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end
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legend(tmp)
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grid on
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xlabel('SNR (dB)')
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ylabel('Estimated SNR (dB)')
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end
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