This is my ofdm code , which simulates ofdm reciever and transmitter , over a rayleigh channel , using 16Qam modulation, with doppler.
function [BitsRx] = OfdmDopplerBer(~)
Rs = 54.64e5;
% Symbol Duration, [s]
Ts = 1/Rs;
% Carrier Frequency, [Hz]
f = 1.5e9;
% Modulation Order of QPSK by definition
M = 16;
% Number of Bits in QPSK Symbol
k = log2(M);
% QPSK Signal Bandwidth, [Hz]
F = 1/Ts;
% Number of Subcarriers (equal to Number of FFT points)
numSC = 1024;
%NumSymbols=3;
% Guard Bands Subcarriers
GuardBandSC = [10; 10];
% Central Null Subcarrier
DCNull = true;
DCNullSC = numSC/2 + 1;
% Number of Pilot Subcarriers
numPilotSC = 10;
PilotSC =[15 125 236 346 456 567 677 787 898 1008]';
% Length of Cyclic Prefix
lenCP = numSC/4;
% OFDM Modulator Object
OFDMModulator = comm.OFDMModulator( ...
'FFTLength', numSC, ...
'NumGuardBandCarriers', GuardBandSC, ...
'Windowing',true,...
'InsertDCNull', DCNull, ...
'PilotInputPort', true, ...
'PilotCarrierIndices', PilotSC, ...
'CyclicPrefixLength', lenCP);
OFDMDemodulator = comm.OFDMDemodulator(OFDMModulator);
% Mapping of Subcarriers in Time-Frequency Space
%showResourceMapping(OFDMModulator)
% Number of Data Subcarriers
numDataSC = info(OFDMModulator).DataInputSize(1);
% Size of Data Frame
szDataFrame = [numDataSC 1];
% Size of Pilot Frame
szPilotFrame = info(OFDMModulator).PilotInputSize;
% OFDM Symbol Duration with Cyclic Prefix, [s]
Ts_OFDM = (numSC + lenCP)*Ts;
% OFDM Symbol Rate with Cyclic Prefix, [1/s]
Rs_OFDM = 1/Ts_OFDM;
% Decreasing of Symbol Rate by using OFDM
Rs/Rs_OFDM;
% Subcarrier Bandwidth, [Hz]
F_SC = F/numSC;
clear ans
% Discrete Paths Relative Delays, [s]
PathDelays = [0 3 5 6 11]*Ts ;
% Discrete Paths Max Delay, [s]
Tm = max(PathDelays);
% Channel Coherence Bandwidth [2, p. 960; 3, p. 399], [Hz]
Fc = 1/Tm;
% Discrete Paths Average Gains, [dB]
PathAvGains = [0 -8 -17 -21 -25];
% Discrete Paths K Factors
K = [0.1 0.1 0.1 0.1 0.1];
% Approximate Speed of Ionospheric Irregularities, [m/s]
v=170.14;
% Light Speed, [m/s]
c = 3e8;
% Max Doppler Frequency Shift for all Discrete Paths, [Hz]
fD = v*f/c;
% Channel Coherence Time [3, p. 400], [s]
Tc = 1/fD;
spsSync = 1;
norms = [1 sqrt(2) 0 sqrt(10) 0 sqrt(42)];
doppler1 = comm.PhaseFrequencyOffset( ...
FrequencyOffset=fD, ...
PhaseOffset=0, ...
SampleRate=Rs);
varDelay = dsp.VariableFractionalDelay;
%% Rician Channel Object
RicianFadingChannel = comm.RicianChannel( ...
'SampleRate', Rs, ...
'PathDelays', PathDelays, ...
'AveragePathGains', PathAvGains, ...
'NormalizePathGains', true, ...
'KFactor', K, ...
'MaximumDopplerShift', fD, ...
'DirectPathDopplerShift', zeros(size(K)), ...
'DirectPathInitialPhase', zeros(size(K)), ...
'DopplerSpectrum', doppler('Jakes') ...
);
% Delay in Channel Object, [sample]
ChanDelay = info(RicianFadingChannel).ChannelFilterDelay;
%% AWGN Channel Object
AWGNChannel = comm.AWGNChannel( ...
'NoiseMethod', 'Signal to noise ratio (SNR)', ...
'SNR', 0 ...
);
% table(F, F_SC, Fc, fD, 'VariableNames', {'F, [Hz]', 'F_SC, [Hz]', 'Fc, [Hz]', 'fD, [Hz]'})
% table(Ts, Ts_OFDM, Tm, Tc, 'VariableNames', {'Ts, [s]', 'Ts_OFDM, [s]', 'Tm, [s]', 'Tc, [s]'})
% Range of Eb/N0
EbNo = 0:60;
% Number of Transmitted Frames
numFrames = 500;
% BER Calculators Object
BERCalculater = comm.ErrorRate;
% BER Variable for Imitation Modeling Result
BER = zeros(3,length(EbNo));
% Loop for the Range of Eb/N0
for n = 1:length(EbNo)
% Setting the Eb/No in AWGN Channel Object
AWGNChannel.SNR = EbNo(n) + 10*log10(k) + 10*log10(numDataSC/numSC);
% BER Calculation
reset(BERCalculater);
BERn = zeros(3,1);
% Loop for the Number of Transmitted Frames
for fr = 1:numFrames
% >>> Transmitter >>>
% Generation of Data Bits
BitsTx = randi([0 M-1], [szDataFrame,1]);
constellation = qammod(0:M-1, M, 'gray');
% Normalize the constellation
constellation = constellation / norms(k);
% Apply phase offset
% constellation = constellation * exp(1i * phaseOffset);
% Define General QAM Modulator with custom constellation
QAMModulator = comm.GeneralQAMModulator('Constellation', constellation);
SignalTx1 = zeros(szDataFrame);
% Modulate the data symbols
SignalTx1 = QAMModulator(BitsTx);
% Generation of Pilot Signals
PilotSignalTx = complex(ones(szPilotFrame), zeros(szPilotFrame));
% OFDM Modulation
SignalTx2 = OFDMModulator(SignalTx1, PilotSignalTx);
% Power of Transmitted Signal
% Compute the power of the transmitted signal
SignalTxPower = sum(abs(SignalTx2).^2) / length(SignalTx2);
% Adding zero samples to the end of Transmitted Signal
% to not lose shifted samples caused by delay after Rician Channel
SignalTx2 = [SignalTx2; zeros(ChanDelay, 1)];
%SignalTx2_with_pfo = pfo(SignalTx2);
%%
% Rician Channel
SignalChan1 = RicianFadingChannel(SignalTx2);
% Removing first ChanDelay samples and
% selection of Channel's Signal related to Transmitted Signal
SignalChan1 = SignalChan1(ChanDelay + 1 : end);
%% introducing the delay in frequency and symbol time due to doppler
txDoppler = doppler1(SignalChan1);
txDelay = varDelay(txDoppler, fr/numFrames);
SignalChan3=txDelay;
%%
% AWGN Channel
AWGNChannel.SignalPower = SignalTxPower;
SignalChan2 = AWGNChannel(SignalChan3);
% >>> Receiver >>>
% OFDM Demodulation
[SignalRx1, PilotSignalRx] = OFDMDemodulator(SignalChan2);
%%
% LS Channel Estimation
% Obtaining discrete points of Channel Frequency Response
% based on dividing the Received Pilot Signals by the known ones
ChanFR_dp = PilotSignalRx ./ PilotSignalTx;
% Interpolation of Channel Frequency Response
% ChanFR_int = zeros(numSC, 1); % Preallocate the result array
ChanFR_int = fixed.interp1( ...
PilotSC, ...
ChanFR_dp, ...
GuardBandSC(1) + 1 : numSC - GuardBandSC(2), ...
'linear' ...
);
% Selection of Data Subcarriers components of Frequency Response
% by cutting out components of Pilot and DC Subcarriers
% Remove components of Pilot and DC Subcarriers
ChanFR_int([PilotSC; DCNullSC] - GuardBandSC(1)) = [];
% LS Solution
SignalRx2 = SignalRx1./ ChanFR_int.';
% 2. Denormalize the signal
SignalRx2 = SignalRx2* norms(k);
QAMDemodulator = comm.GeneralQAMDemodulator('Constellation',...
qammod(0:M-1, M, 'gray'));
% Demodulate the received signal
BitsRx = QAMDemodulator(SignalRx2);
%BitsRx = qamdemod(SignalRx2*sqrt(10),M,"gray");
% BER Calculation
BERn = BERCalculater(BitsTx, BitsRx);
end
% BER Results
BER(:,n) = BERn;
end
clear n fr BERn
disp(BitsRx);
end
I am trying to convert this code to hdl, but am facing this error in the fixed point conversion part
Expected input 1 to have fixed dimensions for System object comm.OFDMModulator.
refering to this line
SignalTx2 = OFDMModulator(SignalTx1, PilotSignalTx);
Can someone help with this ?
