OQPSK or MSK delay problems

Started by dpas...@gmail.com January 12, 2010
Hi all!

Basically my project is a bit generator+spreader+modulator --> demodulator+despreader.

A 4 bit sequence is converted to a 32 chip sequence by the spreader.

If I use a QPSK and without AWGN channel, I get 0 BER before and after the despreader.

However when I use the MSK (or OQPSK) and I add the delay beacuse of the modulation (2 bits for OQPSK and the traceback length for the MSK), I get 0 BER after the demodulation but not after the despreader.

I tried to simulate the model from matlab in a loop for different delays in the bit symbol error rate calculation block but I haven't good results.

Anyone can help me on this?

thanks in advance!