Pulse shaping on BER

Question

Rory Gilmor 2022-10-4

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1817430-pulse-shaping-on-ber

回答： vidyesh 2024-9-15

I build a pam-2 modulation, then I make a pulse shaping with half sine (matched filter). Then I send it through the AWGN channel. At the end I do down sampling and demodulation. But i have problem with plotting BER. I don't understand what I'm doing wrong:

clc;

clear;

N=1e4;

N2 = 1e2;

M = 2;

range = 0:10;

error = zeros(1,length(range)); %BER

%

% half sine

Rc = 1e3; % Chip rate

T = 1/Rc; % inverse of chip rate

Tc = 0.5* T;

Fs = 2e3; % sampling frequency

dt = 1/Fs;

over = Fs/Rc; % sampling factor

sps = 10;

time = 0:dt/sps:2*T;

half_Sine = sin(pi*time/(2*T)).^3;

%% BER

for i = 1:length(range)

for n = 1:N2

% Modulation

x=randi([0 M-1],N,1);

h_mod = pammod(x,M);

over_data=upsample(h_mod,over);

txSig = conv(over_data,half_Sine, 'same');

% AWGN

Ps = mean(((txSig)).^2);

Sigma = sqrt(Ps * 10^(-range(i)/10) / 2);

Noise = randn(length(txSig), 1) * Sigma;

rx_SIG = Noise + txSig;

% Downsample

down = rx_SIG(1:over:end);

% Demodulation

hDemod = pamdemod(down,M);

% Errors

error(i) = error(i)+...

sum(hDemod~=x) / length(hDemod);

end

BER = error/n;

end

figure(1);

grid on

semilogy(range,BER);

title('BER');

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

vidyesh 2024-9-15

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1817430-pulse-shaping-on-ber#answer_1516830

在 MATLAB Online 中打开

Hi Rory,

The issue lies in the below line of code:

txSig = conv(over_data,half_Sine, 'same');

Are you trying to simulate the channel or trying to modulate to a higher frequency by using convolution?

In either scenario, you will have to perform deconvolution at the receiever side. But the 'deconv' function is very sensitive to noise, so it may not give the desired results either.

For simulating the channel/modulation, refer the below examples and functions:

1) Rayleigh Channel fading: https://www.mathworks.com/matlabcentral/fileexchange/62779-bpsk-over-rayleigh-fading-channel?s_tid=srchtitle_support_results_3_Rayleigh%2520channel

2) 'comm.Rayleigh' function: https://www.mathworks.com/help/comm/ref/comm.rayleighchannel-system-object.html?searchHighlight=rayleigh&s_tid=srchtitle_support_results_3_rayleigh

3) 'modulate' function: https://www.mathworks.com/help/signal/ref/modulate.html?searchHighlight=modulate&s_tid=srchtitle_support_results_1_modulate

Utilizing the above functions or following the process used in the example will be a better option over using 'conv'