I am getting some errors of a script that I try to run

When I run below script

% Parameters

M = 16; % Modulation order

k = log2(M); % Bits per symbol

numBits = k * 2.5e5; % Total bits to process

sps = 4; % Samples per symbol (oversampling factor)

filtlen = 10; % Filter length in symbols

rolloff = 0.25; % Filter rolloff factor

% Generate random binary data

dataIn = randi([0 1], numBits, 1);

% Apply convolutional encoding

constrlen = [5 4]; % Code constraint length

genpoly = [23 35 0; 0 5 13]; % Generator polynomials

tPoly = poly2trellis(constrlen, genpoly);

dataEnc = convenc(dataIn, tPoly);

% Modulate using 16-QAM

dataSymbolsIn = bit2int(dataEnc, k);

dataMod = qammod(dataSymbolsIn, M);

% Apply raised cosine filtering

rrcFilter = rcosdesign(rolloff, filtlen, sps);

txSignal = upfirdn(dataMod, rrcFilter, sps, 1);

% Add AWGN (simulate noisy channel)

SNR_dB = 10; % Signal-to-noise ratio in dB

rxSignal = awgn(txSignal, SNR_dB, 'measured');

% Demodulate 16-QAM

dataSymbolsOut = qamdemod(rxSignal, M, 'OutputType', 'bit');

% Viterbi decoding

decodedData = vitdec(dataSymbolsOut, tPoly, 100, 'trunc', 'hard');

% Calculate bit error rate

bitErrors = biterr(dataIn, decodedData);

bitErrorRate = bitErrors / numBits;

fprintf('Bit Error Rate: %.4f\n', bitErrorRate);

I am getting below errors,

Error using vitdec (line 271)

Length of the input code vector must be a multiple of the number of bits in an

input symbol.

Error in test3 (line 34)

decodedData = vitdec(dataSymbolsOut, tPoly, 100, 'trunc', 'hard');

can someone help me to correct them

Answer 1

[Alberto Alvarez Polegre]

You forgot to include the filter at the receiver. Try this:

% Parameters
M = 16;                 % Modulation order
k = log2(M);            % Bits per symbol
numBits = k * 2.5e5;    % Total bits to process
sps = 4;                % Samples per symbol (oversampling factor)
filtlen = 10;           % Filter length in symbols
rolloff = 0.25;         % Filter rolloff factor

% Generate random binary data
dataIn = randi([0 1], numBits, 1);

% Apply convolutional encoding
constrlen = [5 4];      % Code constraint length
genpoly = [23 35 0; 0 5 13]; % Generator polynomials
tPoly = poly2trellis(constrlen, genpoly);
dataEnc = convenc(dataIn, tPoly);

% Modulate using 16-QAM
dataMod = qammod(dataEnc,M,InputType='bit');

% Transmit filter
rrcFilter = rcosdesign(rolloff,filtlen,sps);
txSignal = upfirdn(dataMod,rrcFilter,sps);

% Add AWGN (simulate noisy channel)
SNR_dB = 10; % Signal-to-noise ratio in dB
rxSignal = awgn(txSignal, SNR_dB, 'measured');

% Receive filter
rxSignalFilt = upfirdn(rxSignal,rrcFilter,1,sps); % Apply receive filter
rxSignalFilt = rxSignalFilt(filtlen+1:end-filtlen); % Account for filter delay

% Demodulate 16-QAM
dataSymbolsOut = qamdemod(rxSignalFilt, M, 'OutputType', 'bit');

% Viterbi decoding
decodedData = vitdec(dataSymbolsOut, tPoly, 100, 'trunc', 'hard');

% Calculate bit error rate
bitErrors = biterr(dataIn, decodedData);
bitErrorRate = bitErrors / numBits;
fprintf('Bit Error Rate: %.4f\n', bitErrorRate);

You might want to take a look at the Wireless Communications Onramp course.