Документация

simParameters = [];             % Clear simParameters variable
simParameters.NFrames = 2;      % Number of 10ms frames
simParameters.SNRIn = [-5 0 5]; % SNR range

% Set waveform type and PDSCH numerology (SCS and CP type)
simParameters.NRB = 51;                  % Bandwidth in number of resource blocks (51RBs at 30kHz SCS for 20MHz BW)
simParameters.SubcarrierSpacing = 30;    % 15, 30, 60, 120, 240 (kHz)
simParameters.CyclicPrefix = 'Normal';   % 'Normal' or 'Extended'
simParameters.NCellID = 1;               % Cell identity

% DL-SCH/PDSCH parameters
simParameters.PDSCH.PRBSet = 0:simParameters.NRB-1; % PDSCH PRB allocation
simParameters.PDSCH.SymbolSet = 0:13;           % PDSCH symbol allocation in each slot
simParameters.PDSCH.EnableHARQ = true;          % Enable/disable HARQ, if disabled, single transmission with RV=0, i.e. no retransmissions

simParameters.PDSCH.NLayers = 2;                % Number of PDSCH layers
simParameters.NTxAnts = 8;                      % Number of PDSCH transmission antennas
if simParameters.PDSCH.NLayers > 4              % Multicodeword transmission
    simParameters.NumCW = 2;                        % Number of codewords
    simParameters.PDSCH.TargetCodeRate = [490 490]./1024; % Code rate used to calculate transport block sizes
    simParameters.PDSCH.Modulation = {'16QAM','16QAM'};   % 'QPSK', '16QAM', '64QAM', '256QAM'
    simParameters.NRxAnts = 8;                            % Number of UE receive antennas
else
    simParameters.NumCW = 1;                        % Number of codewords
    simParameters.PDSCH.TargetCodeRate = 490/1024;  % Code rate used to calculate transport block sizes
    simParameters.PDSCH.Modulation = '16QAM';       % 'QPSK', '16QAM', '64QAM', '256QAM'
    simParameters.NRxAnts = 2;                      % Number of UE receive antennas
end

% DM-RS and antenna port configuration (TS 38.211 section 7.4.1.1)
simParameters.PDSCH.PortSet = 0:simParameters.PDSCH.NLayers-1; % DM-RS ports to use for the layers
simParameters.PDSCH.PDSCHMappingType = 'A';     % PDSCH mapping type ('A'(slot-wise),'B'(non slot-wise))
simParameters.PDSCH.DMRSTypeAPosition = 2;      % Mapping type A only. First DM-RS symbol position (2,3)
simParameters.PDSCH.DMRSLength = 1;             % Number of front-loaded DM-RS symbols (1(single symbol),2(double symbol))
simParameters.PDSCH.DMRSAdditionalPosition = 0; % Additional DM-RS symbol positions (max range 0...3)
simParameters.PDSCH.DMRSConfigurationType = 2;  % DM-RS configuration type (1,2)
simParameters.PDSCH.NumCDMGroupsWithoutData = 0;% CDM groups without data
simParameters.PDSCH.NIDNSCID = 1;               % Scrambling identity (0...65535)
simParameters.PDSCH.NSCID = 0;                  % Scrambling initialization (0,1)
% Reserved PRB patterns (for CORESETs, forward compatibility etc)
simParameters.PDSCH.Reserved.Symbols = [];      % Reserved PDSCH symbols
simParameters.PDSCH.Reserved.PRB = [];          % Reserved PDSCH PRBs
simParameters.PDSCH.Reserved.Period = [];       % Periodicity of reserved resources

% Define the propagation channel type
simParameters.ChannelType = 'CDL'; % 'CDL' or 'TDL'

% SS burst configuration
simParameters.SSBurst.BlockPattern = 'Case B';    % 30kHz subcarrier spacing
simParameters.SSBurst.SSBTransmitted = [0 1 0 1]; % Bitmap indicating blocks transmitted in the burst
simParameters.SSBurst.SSBPeriodicity = 20;        % SS burst set periodicity in ms (5, 10, 20, 40, 80, 160)

validateNLayers(simParameters);

gnb = simParameters;
pdsch = simParameters.PDSCH;

% Specify additional required fields for PDSCH
pdsch.RNTI = 1;

Xoh_PDSCH = 0;     % The Xoh-PDSCH overhead value is taken to be 0 here

nTxAnts = simParameters.NTxAnts;
nRxAnts = simParameters.NRxAnts;

if strcmpi(simParameters.ChannelType,'CDL')
    channel = nrCDLChannel; % CDL channel object

    % Use CDL-C model (Urban macrocell model)
    channel.DelayProfile = 'CDL-C';
    channel.DelaySpread = 300e-9;

    % Turn the overall number of antennas into a specific antenna panel
    % array geometry
    [channel.TransmitAntennaArray.Size, channel.ReceiveAntennaArray.Size] = ...
        hArrayGeometry(nTxAnts,nRxAnts);

elseif strcmpi(simParameters.ChannelType,'TDL')
    channel = nrTDLChannel; % TDL channel object
    % Set the channel geometry
    channel.DelayProfile = 'TDL-C';
    channel.DelaySpread = 300e-9;
    channel.NumTransmitAntennas = nTxAnts;
    channel.NumReceiveAntennas = nRxAnts;
else
    error('ChannelType parameter field must be either CDL or TDL.');
end

waveformInfo = hOFDMInfo(gnb);
channel.SampleRate = waveformInfo.SamplingRate;

chInfo = info(channel);
maxChDelay = ceil(max(chInfo.PathDelays*channel.SampleRate)) + chInfo.ChannelFilterDelay;

% Create SS burst information structure
ssburst = simParameters.SSBurst;
ssburst.NCellID = gnb.NCellID;
ssburst.SampleRate = waveformInfo.SamplingRate;

ssbInfo = hSSBurstInfo(ssburst);

% Map the occupied subcarriers and transmitted symbols of the SS burst
% (defined in the SS burst numerology) to PDSCH PRBs and symbols in the
% data numerology
[mappedPRB,mappedSymbols] = mapNumerology(ssbInfo.OccupiedSubcarriers,ssbInfo.OccupiedSymbols,ssbInfo.NRB,gnb.NRB,ssbInfo.SubcarrierSpacing,gnb.SubcarrierSpacing);

% Configure the PDSCH to reserve these resources so that the PDSCH
% transmission does not overlap the SS burst
reservation.Symbols = mappedSymbols;
reservation.PRB = mappedPRB;
reservation.Period = ssburst.SSBPeriodicity * (gnb.SubcarrierSpacing/15); % Period in slots
pdsch.Reserved(end+1) = reservation;

% Array to store the maximum throughput for all SNR points
maxThroughput = zeros(length(simParameters.SNRIn),1);
% Array to store the simulation throughput for all SNR points
simThroughput = zeros(length(simParameters.SNRIn),1);

% Set up Redundancy Version (RV) sequence, number of HARQ processes and
% the sequence in which the HARQ processes are used
if pdsch.EnableHARQ
    % In the final report of RAN WG1 meeting #91 (R1-1719301), it was
    % observed in R1-1717405 that if performance is the priority, [0 2 3 1]
    % should be used. If self-decodability is the priority, it should be
    % taken into account that the upper limit of the code rate at which
    % each RV is self-decodable is in the following order: 0>3>>2>1
    rvSeq = [0 2 3 1];
else
    % HARQ disabled - single transmission with RV=0, no retransmissions
    rvSeq = 0;
end
% Specify the order in which we cycle through the HARQ processes
NHARQProcesses = 16;
harqSequence = 1:NHARQProcesses;

% Create DLSCH encoder system object
encodeDLSCH = nrDLSCH;
encodeDLSCH.MultipleHARQProcesses = true;
encodeDLSCH.TargetCodeRate = pdsch.TargetCodeRate;

% Create DLSCH decoder system object
decodeDLSCH = nrDLSCHDecoder;
decodeDLSCH.MultipleHARQProcesses = true;
decodeDLSCH.TargetCodeRate = pdsch.TargetCodeRate;

for snrIdx = 1:numel(simParameters.SNRIn)

    % Set the random number generator settings to default values
    rng('default');
    reset(decodeDLSCH);

    SNRdB = simParameters.SNRIn(snrIdx);
    fprintf('\nSimulating transmission scheme 1 (%dx%d) and SCS=%dkHz with %s channel at %gdB SNR for %d 10ms frame(s)\n',...
        nTxAnts,nRxAnts,gnb.SubcarrierSpacing, ...
        simParameters.ChannelType,SNRdB,gnb.NFrames);

    % Initialize variables used in the simulation and analysis
    bitTput = [];           % Number of successfully received bits per transmission
    txedTrBlkSizes = [];    % Number of transmitted info bits per transmission

    % Initialize the state of all HARQ processes
    harqProcesses = hNewHARQProcesses(NHARQProcesses,rvSeq,gnb.NumCW);
    harqProcCntr = 0; % HARQ process counter

    % Reset the channel so that each SNR point will experience the same
    % channel realization
    reset(channel);

    % Total number of OFDM symbols in the simulation period
    NSymbols = gnb.NFrames * 10 * waveformInfo.SymbolsPerSubframe;

    % OFDM symbol number associated with start of each PDSCH transmission
    gnb.NSymbol = 0;

    % Running counter of the number of PDSCH transmission instances
    % The simulation will use this counter as the slot number for each
    % PDSCH
    pdsch.NSlot = 0;

    % Index to the start of the current set of SS burst samples to be
    % transmitted
    ssbSampleIndex = 1;

    % Obtain a precoding matrix (wtx) to be used in the transmission of the
    % first transport block
    estChannelGrid = getInitialChannelEstimate(gnb,nTxAnts,channel);
    newWtx = getPrecodingMatrix(pdsch.PRBSet,pdsch.NLayers,estChannelGrid);

    while gnb.NSymbol < NSymbols  % Move to next slot, gnb.NSymbol increased in steps of one slot

        % Generate a new SS burst when necessary
        if (ssbSampleIndex==1)
            nSubframe = gnb.NSymbol / waveformInfo.SymbolsPerSubframe;
            ssburst.NFrame = floor(nSubframe / 10);
            ssburst.NHalfFrame = mod(nSubframe / 5,2);
            [ssbWaveform,~,ssbInfo] = hSSBurst(ssburst);
        end

        % Get HARQ process index for the current PDSCH from HARQ index table
        harqProcIdx = harqSequence(mod(harqProcCntr,length(harqSequence))+1);

        % Update current HARQ process information (this updates the RV
        % depending on CRC pass or fail in the previous transmission for
        % this HARQ process)
        harqProcesses(harqProcIdx) = hUpdateHARQProcess(harqProcesses(harqProcIdx),gnb.NumCW);

        % Calculate the transport block sizes for the codewords in the slot
        [pdschIndices,dmrsIndices,dmrsSymbols,pdschIndicesInfo] = hPDSCHResources(gnb,pdsch);
        trBlkSizes = hPDSCHTBS(pdsch,pdschIndicesInfo.NREPerPRB-Xoh_PDSCH);

        % HARQ: check CRC from previous transmission per codeword, i.e. is
        % a retransmission required?
        for cwIdx = 1:gnb.NumCW
            NDI = false;
            if harqProcesses(harqProcIdx).blkerr(cwIdx) % Errored
                if (harqProcesses(harqProcIdx).RVIdx(cwIdx)==1) % end of rvSeq
                    resetSoftBuffer(decodeDLSCH,cwIdx-1,harqProcIdx-1);
                    NDI = true;
                end
            else    % No error
                NDI = true;
            end
            if NDI
                trBlk = randi([0 1],trBlkSizes(cwIdx),1);
                setTransportBlock(encodeDLSCH,trBlk,cwIdx-1,harqProcIdx-1);
            end
        end

        % Encode the DL-SCH transport blocks
        codedTrBlock = encodeDLSCH(pdsch.Modulation,pdsch.NLayers,...
            pdschIndicesInfo.G,harqProcesses(harqProcIdx).RV,harqProcIdx-1);

        % Get wtx (precoding matrix) calculated in previous slot
        wtx = newWtx;

        % PDSCH modulation and precoding
        pdschSymbols = nrPDSCH(codedTrBlock,pdsch.Modulation,pdsch.NLayers,gnb.NCellID,pdsch.RNTI);
        pdschSymbols = pdschSymbols*wtx;

        % PDSCH mapping in grid associated with PDSCH transmission period
        pdschGrid = zeros(waveformInfo.NSubcarriers,waveformInfo.SymbolsPerSlot,nTxAnts);
        [~,pdschAntIndices] = nrExtractResources(pdschIndices,pdschGrid);
        pdschGrid(pdschAntIndices) = pdschSymbols;

        % PDSCH DM-RS precoding and mapping
        for p = 1:size(dmrsSymbols,2)
            [~,dmrsAntIndices] = nrExtractResources(dmrsIndices(:,p),pdschGrid);
            pdschGrid(dmrsAntIndices) = pdschGrid(dmrsAntIndices) + dmrsSymbols(:,p)*wtx(p,:);
        end

        % OFDM modulation of associated resource elements
        txWaveform = hOFDMModulate(gnb, pdschGrid);

        % Add the appropriate portion of SS burst waveform to the
        % transmitted waveform
        Nt = size(txWaveform,1);
        txWaveform = txWaveform + ssbWaveform(ssbSampleIndex + (0:Nt-1),:);
        ssbSampleIndex = mod(ssbSampleIndex + Nt,size(ssbWaveform,1));

        % Pass data through channel model. Append zeros at the end of the
        % transmitted waveform to flush channel content. These zeros take
        % into account any delay introduced in the channel. This is a mix
        % of multipath delay and implementation delay. This value may
        % change depending on the sampling rate, delay profile and delay
        % spread
        txWaveform = [txWaveform; zeros(maxChDelay, size(txWaveform,2))];
        [rxWaveform,pathGains,sampleTimes] = channel(txWaveform);

        % Add AWGN to the received time domain waveform
        % Normalize noise power to take account of sampling rate, which is
        % a function of the IFFT size used in OFDM modulation. The SNR
        % is defined per RE for each receive antenna (TS 38.101-4).
        SNR = 10^(SNRdB/20);    % Calculate linear noise gain
        N0 = 1/(sqrt(2.0*nRxAnts*double(waveformInfo.Nfft))*SNR);
        noise = N0*complex(randn(size(rxWaveform)),randn(size(rxWaveform)));
        rxWaveform = rxWaveform + noise;

        % Perfect synchronization. Use information provided by the channel
        % to find the strongest multipath component
        pathFilters = getPathFilters(channel); % get path filters for perfect channel estimation
        [offset,mag] = nrPerfectTimingEstimate(pathGains,pathFilters);
        rxWaveform = rxWaveform(1+offset:end, :);

        % Perform OFDM demodulation on the received data to recreate the
        % resource grid
        rxGrid = hOFDMDemodulate(gnb, rxWaveform);

        % Perfect channel estimation, use the value of the path gains
        % provided by the channel
        estChannelGrid = nrPerfectChannelEstimate(pathGains,pathFilters,gnb.NRB,gnb.SubcarrierSpacing,pdsch.NSlot,offset,sampleTimes,gnb.CyclicPrefix);

        % Get perfect noise estimate (from the noise realization)
        noiseGrid = hOFDMDemodulate(gnb,noise(1+offset:end ,:));
        noiseEst = var(noiseGrid(:));

        % Get precoding matrix for next slot
        newWtx = getPrecodingMatrix(pdsch.PRBSet,pdsch.NLayers,estChannelGrid);

        % Apply precoding to Hest
        % Linearize 4D matrix and reshape after multiplication
        K = size(estChannelGrid,1);
        estChannelGrid = reshape(estChannelGrid,K*waveformInfo.SymbolsPerSlot*nRxAnts,nTxAnts);
        estChannelGrid = estChannelGrid*wtx.';
        estChannelGrid = reshape(estChannelGrid,K,waveformInfo.SymbolsPerSlot,nRxAnts,pdsch.NLayers);

        % Get PDSCH resource elements from the received grid
        [pdschRx,pdschHest] = nrExtractResources(pdschIndices,rxGrid,estChannelGrid);

        % Equalization
        [pdschEq,csi] = nrEqualizeMMSE(pdschRx,pdschHest,noiseEst);

        % Decode PDSCH physical channel
        [dlschLLRs,rxSymbols] = nrPDSCHDecode(pdschEq,pdsch.Modulation,gnb.NCellID,pdsch.RNTI,noiseEst);

        % Scale LLRs by CSI
        csi = nrLayerDemap(csi); % CSI layer demapping
        for cwIdx = 1:gnb.NumCW
            Qm = length(dlschLLRs{cwIdx})/length(rxSymbols{cwIdx}); % bits per symbol
            csi{cwIdx} = repmat(csi{cwIdx}.',Qm,1);   % expand by each bit per symbol
            dlschLLRs{cwIdx} = dlschLLRs{cwIdx} .* csi{cwIdx}(:);   % scale
        end

        % Decode the DL-SCH transport channel
        decodeDLSCH.TransportBlockLength = trBlkSizes;
        [decbits,harqProcesses(harqProcIdx).blkerr] = decodeDLSCH(dlschLLRs,pdsch.Modulation,pdsch.NLayers,harqProcesses(harqProcIdx).RV,harqProcIdx-1);

        % Store values to calculate throughput (only for active PDSCH instances)
        if(any(trBlkSizes) ~= 0)
            bitTput = [bitTput trBlkSizes.*(1-harqProcesses(harqProcIdx).blkerr)];
            txedTrBlkSizes = [txedTrBlkSizes trBlkSizes];
        end

        % Update starting symbol number of next PDSCH transmission
        gnb.NSymbol = gnb.NSymbol + size(pdschGrid,2);
        % Update count of overall number of PDSCH transmissions
        pdsch.NSlot = pdsch.NSlot + 1;
        % Update HARQ process counter
        harqProcCntr = harqProcCntr + 1;

        % Display transport block error information per codeword managed by current HARQ process
        fprintf('\n(%3.2f%%) HARQ Proc %d: ',100*gnb.NSymbol/NSymbols,harqProcIdx);
        estrings = {'passed','failed'};
        rvi = harqProcesses(harqProcIdx).RVIdx;
        for cw=1:length(rvi)
            cwrvi = rvi(cw);
            % Create a report on the RV state given position in RV sequence and decoding error
            if cwrvi == 1
                ts = sprintf('Initial transmission (RV=%d)',rvSeq(cwrvi));
            else
                ts = sprintf('Retransmission #%d (RV=%d)',cwrvi-1,rvSeq(cwrvi));
            end
            fprintf('CW%d:%s %s. ',cw-1,ts,estrings{1+harqProcesses(harqProcIdx).blkerr(cw)});
        end

     end

    % Calculate maximum and simulated throughput
    maxThroughput(snrIdx) = sum(txedTrBlkSizes); % Max possible throughput
    simThroughput(snrIdx) = sum(bitTput,2);      % Simulated throughput

    % Display the results dynamically in the command window
    fprintf([['\n\nThroughput(Mbps) for ', num2str(gnb.NFrames) ' frame(s) '],...
        '= %.4f\n'], 1e-6*simThroughput(snrIdx)/(gnb.NFrames*10e-3));
    fprintf(['Throughput(%%) for ', num2str(gnb.NFrames) ' frame(s) = %.4f\n'],...
        simThroughput(snrIdx)*100/maxThroughput(snrIdx));

end

figure;
plot(simParameters.SNRIn,simThroughput*100./maxThroughput,'o-.')
xlabel('SNR (dB)'); ylabel('Throughput (%)'); grid on;
title(sprintf('(%dx%d) / NRB=%d / SCS=%dkHz',...
              nTxAnts,nRxAnts,gnb.NRB,gnb.SubcarrierSpacing));

% Bundle key parameters and results into a combined structure for recording
simResults.simParameters = simParameters;
simResults.simThroughput = simThroughput;

function validateNLayers(simParameters)
% Validate the number of layers
    if length(simParameters.PDSCH.PortSet)~= simParameters.PDSCH.NLayers
        error('The number of elements of PortSet (%d) must be the same as the number of layers (%d)',...
            length(simParameters.PDSCH.PortSet), simParameters.PDSCH.NLayers);
    end

    if simParameters.PDSCH.NLayers > min(simParameters.NTxAnts,simParameters.NRxAnts)
        error('The number of layers (%d) must satisfy NLayers <= min(NTxAnts,NRxAnts) = min(%d,%d) = (%d)',...
            simParameters.PDSCH.NLayers,simParameters.NTxAnts,simParameters.NRxAnts,min(simParameters.NTxAnts,simParameters.NRxAnts));
    end
end

function estChannelGrid = getInitialChannelEstimate(gnb,nTxAnts,channel)
% Obtain channel estimate before first transmission. This can be used to
% obtain a precoding matrix for the first slot.

    ofdmInfo = hOFDMInfo(gnb);

    chInfo = info(channel);
    maxChDelay = ceil(max(chInfo.PathDelays*channel.SampleRate)) + chInfo.ChannelFilterDelay;

    % Temporary waveform (only needed for the sizes)
    tmpWaveform = zeros((ofdmInfo.SamplesPerSubframe/ofdmInfo.SlotsPerSubframe)+maxChDelay,nTxAnts);

    % Filter through channel
    [~,pathGains,sampleTimes] = channel(tmpWaveform);

    % Perfect timing synch
    pathFilters = getPathFilters(channel);
    offset = nrPerfectTimingEstimate(pathGains,pathFilters);

    nslot = gnb.NSymbol/ofdmInfo.SymbolsPerSlot;

    % Perfect channel estimate
    estChannelGrid = nrPerfectChannelEstimate(pathGains,pathFilters,gnb.NRB,gnb.SubcarrierSpacing,nslot,offset,sampleTimes);

end

function wtx = getPrecodingMatrix(PRBSet,NLayers,hestGrid)
% Calculate precoding matrix given an allocation and a channel estimate

    % Allocated subcarrier indices
    allocSc = (1:12)' + 12*PRBSet(:).';
    allocSc = allocSc(:);

    % Average channel estimate
    [~,~,R,P] = size(hestGrid);
    estAllocGrid = hestGrid(allocSc,:,:,:);
    Hest = permute(mean(reshape(estAllocGrid,[],R,P)),[2 3 1]);

    % SVD decomposition
    [~,~,V] = svd(Hest);
    wtx = V(:,1:NLayers).';

end

function [mappedPRB,mappedSymbols] = mapNumerology(subcarriers,symbols,nrbs,nrbt,fs,ft)
% Map the SSBurst numerology to PDSCH numerology. The outputs are:
%   - mappedPRB: 0-based PRB indices for carrier resource grid (arranged in a column)
%   - mappedSymbols: 0-based OFDM symbol indices in a slot for carrier resource grid (arranged in a row)
%     carrier resource grid is sized using gnb.NRB, gnb.CyclicPrefix, spanning 1 slot
% The input parameters are:
%   - subcarriers: 1-based row subscripts for SSB resource grid (arranged in a column)
%   - symbols: 1-based column subscripts for SSB resource grid (arranged in an N-by-4 matrix, 4 symbols for each transmitted burst in a row, N transmitted bursts)
%     SSB resource grid is sized using ssbInfo.NRB, normal CP, spanning 5 subframes
%   - nrbs: source (SSB) NRB
%   - nrbt: target (carrier) NRB
%   - fs: source (SSB) SCS
%   - ft: target (carrier) SCS

    mappedPRB = unique(fix((subcarriers-(nrbs*6) - 1)*fs/(ft*12) + nrbt/2),'stable');

    symbols = symbols.';
    symbols = symbols(:).' - 1;

    if (ft < fs)
        % If ft/fs < 1, reduction
        mappedSymbols = unique(fix(symbols*ft/fs),'stable');
    else
        % Else, repetition by ft/fs
        mappedSymbols = reshape((0:(ft/fs-1))' + symbols(:)'*ft/fs,1,[]);
    end

end