Block error rate

numTrBlks = 4;        % Number of simulated transport blocks
SNRdB = -32:4:0;      % SNR range in dB
ireps = [0 5 9];      % Range of reps simulated

• The variable NPDSCHDataType indicates whether the NPDSCH is carrying the SystemInformationBlockType1-NB (SIB1-NB) or not, and whether the NPDSCH is carrying the broadcast control channel (BCCH) or not. The allowed values of NPDSCHDataType are 'SIB1NB', 'BCCHNotSIB1NB' and 'NotBCCH'. Note that SIB1-NB belongs to the BCCH.

• The number of NPDSCH repetitions and the transport block size (TBS) are affected by whether NPDSCH is carrying SIB1-NB or not (see 3GPP TS 36.213 16.4.1.3 and 16.4.1.5 [ 2 ]). NPDSCHDataType set to 'SIB1NB' indicates that the NPDSCH is carrying SIB1-NB; NPDSCHDataType set to either 'BCCHNotSIB1NB' or 'NotBCCH' indicates that the NPDSCH is not carrying SIB1-NB.

• The NPDSCH repetition pattern and the scrambling sequence generation is affected by whether NPDSCH is carrying BCCH or not (see 3GPP TS 36.211 10.2.3 [ 1 ]). NPDSCHDataType set to either 'SIB1NB' or 'BCCHNotSIB1NB' indicates that the NPDSCH is carrying BCCH; NPDSCHDataType set to 'NotBCCH' indicates that the NPDSCH is not carrying BCCH.

NPDSCHDataType = 'NotBCCH';  % The allowed values are 'SIB1NB', 'BCCHNotSIB1NB' or 'NotBCCH'

• The variable ISF configures the number of subframes for a NPDSCH according to 3GPP TS 36.213 Table 16.4.1.3-1 [ 2 ]. Valid values for ISF are 0…7.

• The variable SchedulingInfoSIB1 configures the number of NPDSCH repetitions according to 3GPP TS 36.213 Table 16.4.1.3-3 and the TBS according to Table 16.4.1.5.2-1 [ 2 ]. Valid values for SchedulingInfoSIB1 are 0…11.

• The variable IRep configures the number of NPDSCH repetitions according to 3GPP TS 36.213 Table 16.4.1.3-2 [ 2 ]. Valid values for IRep are 0…15.

• The variable IMCS together with IRep configure the TBS according to 3GPP TS 36.213 Table 16.4.1.5.1-1 [ 2 ]. Valid values for IMCS are 0…13.

ISF = 0;                % Resource assignment field in DCI (DCI format N1 or N2)
SchedulingInfoSIB1 = 0; % Scheduling information field in MasterInformationBlock-NB (MIB-NB)
IMCS = 4;               % Modulation and coding scheme field in DCI (DCI format N1 or N2)

• 'Standalone': NB-IoT carrier deployed outside the LTE spectrum, e.g. the spectrum used for GSM or satellite communications

• 'Guardband': NB-IoT carrier deployed in the guardband between two LTE carriers

• 'Inband-SamePCI': NB-IoT carrier deployed in resource blocks of a LTE carrier, with enb.NBRefP the same as the number of CRS ports enb.CellRefP

• 'Inband-DifferentPCI': NB-IoT carrier deployed in resource blocks of a LTE carrier, with enb.NBRefP different as enb.CellRefP

• NPDSCHDataType is either 'BCCHNotSIB1NB' or 'NotBCCH'

• enb.OperationMode is either 'Inband-SamePCI' or 'Inband-DifferentPCI'

enb.NFrame = 0;     % Simulation starting frame number
enb.NSubframe = 0;  % Simulation starting subframe number
enb.NNCellID = 0;   % NB-IoT physical cell ID
enb.NBRefP = 2;     % Number of NRS antenna ports, should be either 1 or 2
enb.OperationMode = 'Inband-DifferentPCI';  % The allowed values are 'Inband-SamePCI', 'Inband-DifferentPCI', 'Guardband' or 'Standalone'
if strcmpi(enb.OperationMode,'Inband-SamePCI')
    enb.CellRefP = enb.NBRefP;     % The allowed values are NBRefP or 4
    enb.NCellID = enb.NNCellID;
elseif strcmpi(enb.OperationMode,'Inband-DifferentPCI')
    enb.CellRefP = 4; % Number of Cell RS antenna ports (Must be equal to NBRefP or 4)
    enb.NCellID = 1;
end
if (strcmpi(NPDSCHDataType,'BCCHNotSIB1NB') || strcmpi(NPDSCHDataType,'NotBCCH')) && ...
        (strcmpi(enb.OperationMode,'Inband-SamePCI') || strcmpi(enb.OperationMode,'Inband-DifferentPCI'))
    enb.ControlRegionSize = 3;     % The allowed values are 0...13
end

channel = struct;                    % Initialize channel config structure
channel.Seed = 6;                    % Channel seed
channel.NRxAnts = 1;                 % 1 receive antenna
channel.DelayProfile ='EPA';         % Delay profile
channel.DopplerFreq = 5;             % Doppler frequency in Hz
channel.MIMOCorrelation = 'Low';     % Multi-antenna correlation
channel.NTerms = 16;                 % Oscillators used in fading model
channel.ModelType = 'GMEDS';         % Rayleigh fading model type
channel.InitPhase = 'Random';        % Random initial phases
channel.NormalizePathGains = 'On';   % Normalize delay profile power
channel.NormalizeTxAnts = 'On';      % Normalize for transmit antennas

% Channel estimator behavior
perfectChannelEstimator = true;

% Configure channel estimator
cec.PilotAverage = 'UserDefined';   % Type of pilot symbol averaging
cec.TimeWindow = 1;                 % Time window size in REs
cec.FreqWindow = 25;                % Frequency window size in REs
cec.InterpType = 'Cubic';           % 2D interpolation type
cec.InterpWindow = 'Centered';      % Interpolation window type
cec.InterpWinSize = 3;              % Interpolation window size
cec.Reference = 'NRS';              % Channel estimator reference signal

• The number of repetitions (NRep)

• The number of subframes used for a NPDSCH when there is no repetition (NSF)

• The transport block size (TBS)

for repIdx = 1:numel(ireps)

    npdschInfo = hNPDSCHInfo;
    npdschInfo.NPDSCHDataType = NPDSCHDataType;
    npdschInfo.ISF = ISF;
    if strcmpi(NPDSCHDataType,'SIB1NB')  % NPDSCH carrying SIB1-NB
        npdschInfo.SchedulingInfoSIB1 = SchedulingInfoSIB1;
    else % NPDSCH not carrying SIB1-NB
        npdschInfo.IRep = ireps(repIdx); % Repetition number field in DCI (DCI format N1 or N2)
        npdschInfo.IMCS = IMCS;          % Modulation and coding scheme field in DCI (DCI format N1 or N2)
        % Verify the inputs of IRep and IMCS
        if isempty(npdschInfo.TBS)
            npdschInfo.TBSTable
            error(['Invalid [ITBS,ISF] (where ITBS=IMCS=' num2str(IMCS)...
                ', ISF=' num2str(ISF)  ') pair, empty TBS is returned, check valid pairs in the above table or 3GPP TS 36.213 table 16.4.1.5.1-1']);
        end
    end

    npdsch.NSF = npdschInfo.NSF;
    npdsch.NRep = npdschInfo.NRep;
    npdsch.NPDSCHDataType = NPDSCHDataType;
    npdsch.RNTI = 1;

    [~,info] = lteNPDSCHIndices(enb,npdsch);
    rmoutlen = info.G;           % Bit length after rate matching, i.e. codeword length
    trblklen = npdschInfo.TBS;   % Transport block size
    R = (trblklen+24)/rmoutlen;  % DL-SCH channel coding rate, 24 denotes the number of CRC bits
    if R >= 1
        error(['DL-SCH coding rate (' num2str(R) ') larger than or equal to 1 for the configured parameters.']);
    end

    %  The NPDSCH repetition pattern for the current configuration is
    %  displayed below
    displayPattern = false;
    % Display NPDSCH repetition pattern
    if displayPattern == true
        npdschInfo.displaySubframePattern;
    end

    % Absolute subframe number at the starting point of the simulation
    NSubframe = enb.NFrame*10+enb.NSubframe;

    % Initialize BLER and throughput result
    maxThroughput = zeros(length(SNRdB),1);
    simThroughput = zeros(length(SNRdB),1);
    bler = zeros(1,numel(SNRdB));

    % The temporary variables 'enb_init' and 'channel_init' are used to create
    % the temporary variable 'enb' and 'channel' within the SNR loop to create
    % independent simulation loops for the 'parfor' loop
    enb_init = enb;
    channel_init = channel;

    for snrIdx = 1:numel(SNRdB)
    % parfor snrIdx = 1:numel(SNRdB)
    % To enable the use of parallel computing for increased speed comment out
    % the 'for' statement above and uncomment the 'parfor' statement below.
    % This needs the Parallel Computing Toolbox. If this is not installed
    % 'parfor' will default to the normal 'for' statement.

        % Set the random number generator seed depending to the loop variable
        % to ensure independent random streams
        rng(snrIdx,'combRecursive');

        fprintf('nSimulating %d transport blocks at %gdB SNRn',numTrBlks,SNRdB(snrIdx));

        enb = enb_init;         % Initialize eNodeB configuration
        channel = channel_init; % Initialize fading channel configuration
        txcw = [];              % Initialize the transmitted codeword
        numBlkErrors = 0;       % Number of transport blocks with errors
        estate = [];            % Initialize NPDSCH encoder state
        dstate = [];            % Initialize NPDSCH decoder state
        lastOffset = 0;         % Initialize overall frame timing offset
        offset = 0;             % Initialize frame timing offset
        subframeGrid = lteNBResourceGrid(enb); % Initialize the subframe grid

        subframeIdx = NSubframe;
        numRxTrBlks = 0;
        while (numRxTrBlks < numTrBlks)

            % Set current subframe and frame numbers
            enb.NSubframe = mod(subframeIdx,10);
            enb.NFrame = floor((subframeIdx)/10);

            % Generate the NPSS symbols and indices
            npssSymbols = lteNPSS(enb);
            npssIndices = lteNPSSIndices(enb);
            % Map the symbols to the subframe grid
            subframeGrid(npssIndices) = npssSymbols;

            % Generate the NSSS symbols and indices
            nsssSymbols = lteNSSS(enb);
            nsssIndices = lteNSSSIndices(enb);
            % Map the symbols to the subframe grid
            subframeGrid(nsssIndices) = nsssSymbols;

            % Establish if either NPSS or NSSS is transmitted and if so,
            % do not transmit NPDSCH in this subframe
            isDataSubframe = isempty(npssSymbols) && isempty(nsssSymbols);

            % Create a new transport block and encode it when the
            % transmitted codeword is empty. The receiver sets the codeword
            % to empty to signal that all subframes in a bundle have been
            % received (it is also empty before the first transmission)
            if isempty(txcw)
                txTrBlk = randi([0 1],trblklen,1);
                txcw = lteNDLSCH(rmoutlen,txTrBlk);
            end

            if (isDataSubframe)
                % Generate NPDSCH symbols and indices for a subframe
                [txNpdschSymbols,estate] = lteNPDSCH(enb,npdsch,txcw,estate);
                npdschIndices = lteNPDSCHIndices(enb,npdsch);
                % Map the symbols to the subframe grid
                subframeGrid(npdschIndices) = txNpdschSymbols;
                % Generate the NRS symbols and indices
                nrsSymbols = lteNRS(enb);
                nrsIndices = lteNRSIndices(enb);
                % Map the symbols to the subframe grid
                subframeGrid(nrsIndices) = nrsSymbols;
            end

            % Perform OFDM modulation to generate the time domain waveform
            [txWaveform,ofdmInfo] = nbOFDMModulate(enb,subframeGrid);

            % Add 25 sample padding. This is to cover the range of delays
            % expected from channel modeling (a combination of
            % implementation delay and channel delay spread)
            txWaveform =  [txWaveform; zeros(25, enb.NBRefP)]; %#ok<AGROW>

            % Initialize channel time for each subframe
            channel.InitTime = subframeIdx/1000;

            % Pass data through channel model
            channel.SamplingRate = ofdmInfo.SamplingRate;
            [rxWaveform,fadingInfo] = lteFadingChannel(channel, txWaveform);

            % Calculate noise gain including compensation for downlink power
            % allocation
            SNR = 10^(SNRdB(snrIdx)/10);

            % Normalize noise power to take account of sampling rate, which
            % is a function of the IFFT size used in OFDM modulation, and
            % the number of antennas
            N0 = 1/sqrt(2.0*enb.NBRefP*double(ofdmInfo.Nfft)*SNR);

            % Create additive white Gaussian noise
            noise = N0*complex(randn(size(rxWaveform)), ...
                                randn(size(rxWaveform)));

            % Add AWGN to the received time domain waveform
            rxWaveform = rxWaveform + noise;

            %------------------------------------------------------------------
            %            Receiver
            %------------------------------------------------------------------

            % Perform timing synchronization, extract the appropriate
            % subframe of the received waveform, and perform OFDM
            % demodulation
            if(perfectChannelEstimator)
                offset = hPerfectTimingEstimate(fadingInfo);
            else
                % In this example, the subframe offset calculation relies
                % on NPSS present in subframe 5, so we need to pad the
                % subframes before it so that the frame offset returned by
                % lteNBDLFrameOffset is the offset for subframe 5
                sfTsamples = ofdmInfo.SamplingRate*1e-3;
                if (enb.NSubframe==5)
                    padding = zeros([sfTsamples*5,size(rxWaveform,2)]);
                    offset = lteNBDLFrameOffset(enb, [padding; rxWaveform]);
                    if (offset > 25) || (offset < 0)
                        offset = lastOffset;
                    end
                    lastOffset = offset;
                end
            end

            % Synchronize the received waveform
            rxWaveform = rxWaveform(1+offset:end, :);

            % Perform OFDM demodulation on the received data to recreate the
            % resource grid
            rxSubframe = nbOFDMDemodulate(enb,rxWaveform);

            % Channel estimation
            if(perfectChannelEstimator)
                % Perfect channel estimation
                estChannelGrid = nbDLPerfectChannelEstimate(enb, channel, offset);
                noiseGrid = nbOFDMDemodulate(enb, noise(1+offset:end ,:));
                noiseEst = var(noiseGrid(:));
            else

                [estChannelGrid, noiseEst] = lteDLChannelEstimate( ...
                enb, cec, rxSubframe);
            end

            if (isDataSubframe)
                % Get NPDSCH indices
                npdschIndices = lteNPDSCHIndices(enb, npdsch);

                % Get PDSCH resource elements from the received subframe. Scale the
                % received subframe by the PDSCH power factor Rho. The PDSCH is
                % scaled by this amount, while the cell reference symbols used for
                % channel estimation (used in the PDSCH decoding stage) are not.
                [rxNpdschSymbols, npdschHest] = lteExtractResources(npdschIndices, ...
                    rxSubframe, estChannelGrid);

                % Decode NPDSCH
                [rxcw,dstate,symbols] = lteNPDSCHDecode(...
                                     enb, npdsch, rxNpdschSymbols, npdschHest, noiseEst,dstate);

                % Decode the transport block when all the subframes in a bundle
                % have been received
                if dstate.EndOfTx
                   [trblkout,blkerr] = lteNDLSCHDecode(trblklen,rxcw);
                   numBlkErrors = numBlkErrors + blkerr;
                   numRxTrBlks = numRxTrBlks + 1;
                   % Re-initialize to enable the transmission of a new transport block
                   txcw = [];
                end
            end

            subframeIdx = subframeIdx + 1;

        end

        % Calculate the block error rate
        bler(snrIdx) = numBlkErrors/numTrBlks;
        fprintf('NPDSCH BLER = %.4f n',bler(snrIdx));
        % Calculate the maximum and simulated throughput
        maxThroughput(snrIdx) = trblklen*numTrBlks; % Max possible throughput
        simThroughput(snrIdx) = trblklen*(numTrBlks-numBlkErrors);  % Simulated throughput
        fprintf('NPDSCH Throughput(%%) = %.4f %%n',simThroughput(snrIdx)*100/maxThroughput(snrIdx));

    end

Simulating 4 transport blocks at -32dB SNR

Simulating 4 transport blocks at -32dB SNR
NPDSCH BLER = 1.0000 
NPDSCH Throughput(%) = 0.0000 %

Simulating 4 transport blocks at -28dB SNR
NPDSCH BLER = 1.0000 
NPDSCH Throughput(%) = 0.0000 %

Simulating 4 transport blocks at -24dB SNR
NPDSCH BLER = 1.0000 
NPDSCH Throughput(%) = 0.0000 %

Simulating 4 transport blocks at -20dB SNR
NPDSCH BLER = 1.0000 
NPDSCH Throughput(%) = 0.0000 %

Simulating 4 transport blocks at -16dB SNR
NPDSCH BLER = 1.0000 
NPDSCH Throughput(%) = 0.0000 %

Simulating 4 transport blocks at -12dB SNR
NPDSCH BLER = 0.2500 
NPDSCH Throughput(%) = 75.0000 %

Simulating 4 transport blocks at -8dB SNR
NPDSCH BLER = 0.0000 
NPDSCH Throughput(%) = 100.0000 %

Simulating 4 transport blocks at -4dB SNR
NPDSCH BLER = 0.0000 
NPDSCH Throughput(%) = 100.0000 %

Simulating 4 transport blocks at 0dB SNR
NPDSCH BLER = 0.0000 
NPDSCH Throughput(%) = 100.0000 %

Simulating 4 transport blocks at -32dB SNR
NPDSCH BLER = 1.0000 
NPDSCH Throughput(%) = 0.0000 %

Simulating 4 transport blocks at -28dB SNR
NPDSCH BLER = 1.0000 
NPDSCH Throughput(%) = 0.0000 %

Simulating 4 transport blocks at -24dB SNR
NPDSCH BLER = 0.2500 
NPDSCH Throughput(%) = 75.0000 %

Simulating 4 transport blocks at -20dB SNR
NPDSCH BLER = 0.0000 
NPDSCH Throughput(%) = 100.0000 %

Simulating 4 transport blocks at -16dB SNR
NPDSCH BLER = 0.0000 
NPDSCH Throughput(%) = 100.0000 %

Simulating 4 transport blocks at -12dB SNR
NPDSCH BLER = 0.0000 
NPDSCH Throughput(%) = 100.0000 %

Simulating 4 transport blocks at -8dB SNR
NPDSCH BLER = 0.0000 
NPDSCH Throughput(%) = 100.0000 %

Simulating 4 transport blocks at -4dB SNR
NPDSCH BLER = 0.0000 
NPDSCH Throughput(%) = 100.0000 %

Simulating 4 transport blocks at 0dB SNR
NPDSCH BLER = 0.0000 
NPDSCH Throughput(%) = 100.0000 %

    if repIdx == 1
        fh = figure;
        grid on;
        hold on;
        xlabel('SNR (dB)');
        ylabel('BLER');
        legendstr = {['NRep = ' num2str(npdsch.NRep)]};
    else
        legendstr = [legendstr ['NRep = ' num2str(npdsch.NRep)]]; %#ok<AGROW>
    end
    figure(fh);
    plot(SNRdB, bler, '-o');

end
% Set figure title
if strcmpi(NPDSCHDataType,'SIB1NB')
    npdsch.NSF = 8;
end
title([' ' char(npdsch.NPDSCHDataType) ': TBS=' num2str(trblklen)...
    '; NSF=' num2str(npdsch.NSF) '; ' num2str(enb_init.NBRefP) ' NRS port(s)' ]);
legend(legendstr);

• hPerfectTimingEstimate.m

• hNPDSCHInfo.m

1. 3GPP TS 36.211 «Physical channels and modulation»

2. 3GPP TS 36.213 «Physical layer procedures»

3. 3GPP TS 36.321 «Medium Access Control (MAC) protocol specification»

4. 3GPP TS 36.101 «User Equipment (UE) radio transmission and reception»

% NB-IoT DL OFDM Modulator
function [waveform,info] = nbOFDMModulate(enb,grid)
    % Apply default window size according to TS 36.104 Table E.5.1-1a
    if(~isfield(enb,'Windowing'))
        enb.Windowing = 6;
    end
    % Use NB-IoT SC-FDMA to get the 1/2 subcarrier shift on the OFDM modulation
    enb.NBULSubcarrierSpacing = '15kHz';
    [waveform,info] = lteSCFDMAModulate(enb,grid);
end

% NB-IoT DL OFDM Demodulator
function grid = nbOFDMDemodulate(enb,rxWaveform)
    % Use NB-IoT SC-FDMA to get the 1/2 subcarrier shift on the OFDM modulation
    enb.NBULSubcarrierSpacing = '15kHz';
    grid = lteSCFDMADemodulate(enb,rxWaveform,0.55); % CP fraction of 0.55
end

% NB-IoT DL Perfect Channel Estimator
function H = nbDLPerfectChannelEstimate(enb,channel,timefreqoffset)
    % Reconfigure NB-IoT UL perfect channel estimator to perform DL perfect
    % channel estimation
    enb.NBULSubcarrierSpacing = '15kHz';
    enb.NTxAnts = enb.NBRefP;
    enb.TotSlots = 2;
    H = lteULPerfectChannelEstimate(enb, channel,timefreqoffset);
end

NPDSCH BLER = 1.0000 
NPDSCH Throughput(%) = 0.0000 %

Simulating 4 transport blocks at -28dB SNR
NPDSCH BLER = 1.0000 
NPDSCH Throughput(%) = 0.0000 %

Simulating 4 transport blocks at -24dB SNR
NPDSCH BLER = 1.0000 
NPDSCH Throughput(%) = 0.0000 %

Simulating 4 transport blocks at -20dB SNR
NPDSCH BLER = 1.0000 
NPDSCH Throughput(%) = 0.0000 %

Simulating 4 transport blocks at -16dB SNR
NPDSCH BLER = 1.0000 
NPDSCH Throughput(%) = 0.0000 %

Simulating 4 transport blocks at -12dB SNR
NPDSCH BLER = 1.0000 
NPDSCH Throughput(%) = 0.0000 %

Simulating 4 transport blocks at -8dB SNR
NPDSCH BLER = 1.0000 
NPDSCH Throughput(%) = 0.0000 %

Simulating 4 transport blocks at -4dB SNR
NPDSCH BLER = 1.0000 
NPDSCH Throughput(%) = 0.0000 %

Simulating 4 transport blocks at 0dB SNR
NPDSCH BLER = 0.0000 
NPDSCH Throughput(%) = 100.0000 %