Changing traceback gmsk viterbi demodulator object
3 Ansichten (letzte 30 Tage)
Ältere Kommentare anzeigen
Hi,
I want to see how changing the traceback (Tb) of a gmsk demodulator affects the BER curve in GMSK (pulse length=3), but there is no variation in the BER curve when Tb change, except when Tb=1. I tried Tb values from 2 to 100, does anybody have an idea why it occurs?
Thanks in advance.
%%
close all
clear all
clc
%% Modulation parameters
oversamp = 30;
L = 3;
h = 0.5;
BT = 0.5;
fast_sim=0;
%% Bit generation and diff encoding
Nbits=10e4; % 12 bits for fixed input
%Nbits=5000;
bits = randi([0 1],1,Nbits-2);
bits = [[0 1] , bits];
encoded_bits = xor(bits(1:end-1),bits(2:end));
encoded_bits = not(encoded_bits);
encoded_bits = (encoded_bits*2 - 1)';
%encoded_bits =[-1 1 -1 -1 1 1 1 1 -1 1 1 -1]';
%% Objects
hMod = comm.GMSKModulator(...
'SamplesPerSymbol',oversamp,...
'BitInput', false,'InitialPhaseOffset' ,0, 'PulseLength',L);
hDeMod = comm.GMSKDemodulator(...
'BitOutput',false,...
'SamplesPerSymbol',oversamp, 'InitialPhaseOffset' ,0, 'PulseLength',L,...
'TracebackDepth',2);
%% Modulation
object_gfsk= step(hMod,encoded_bits);
%% BER calculation for Matlab object
EbNodB = 0:1:10;
%EbNodB =100;
BER = zeros(1,numel(EbNodB));
for index = 1: numel(EbNodB)
EbNodB(index),
errors = 0;
count = 0;
while(1)
%% Channel
hAWGN = comm.AWGNChannel('NoiseMethod','Signal to noise ratio (Eb/No)','EbNo', (EbNodB(index)),'SamplesPerSymbol',oversamp);
received = step(hAWGN, (object_gfsk));
reset(hAWGN)
%% Demodulator
estimatedBits=step(hDeMod, received);
reset (hDeMod);%OJO NO BORRAR
%% Error estimation
hError = comm.ErrorRate('ReceiveDelay', hDeMod.TracebackDepth);
errorStats = step(hError, (encoded_bits(1:end)) , (estimatedBits));
errorsN = errorStats(2);
errors = errors + errorsN;
count = count + 1;
if(fast_sim == 1)
if(errors>300 || count > 500)
BER(index) = errors / (count*numel(encoded_bits));
break;
end
else
if(errors>700 || count > 1200)
BER(index) = errors / (count*numel(encoded_bits));
break;
end
end
end
end
%% Plotting
semilogy(EbNodB,BER,'k','LineWidth',1.5);
grid on
1 Kommentar
gidon schwartz
am 15 Nov. 2020
Bearbeitet: gidon schwartz
am 16 Nov. 2020
hi,
Is it possibble that in GMSK a traceback of 2 is sufficient for decoding ( and therefore no improvement is shown for higher values of TB)?
do you have any new conclusions regarding this question?
Antworten (0)
Siehe auch
Kategorien
Mehr zu Modulation finden Sie in Help Center und File Exchange
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!