Why can't i achieve 0BER for inf SNR ?

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Nauka Fernando
Nauka Fernando on 13 Feb 2011
A communication link with a tranmitter, channel and reciever is implemmented using a,
-bernouli binary generator with 2 samples per sencons at a 0.1 sampling rate then, spread using a PN sequence with a 0.02 sampling rate and then it is fed to a QPSK modulation block and sent through a AWGN channel with inf SNR.
Signal is then received to a QPSK demodulator and de-spread using the same PN code. But the system doesn't result 0BER for inf SNR. Is this cause because of the generator polynomial patern of PN code ?? Need to achieve 0BER.. Plz help..

Answers (1)

Walter Roberson
Walter Roberson on 13 Feb 2011
I am not very familiar with those functions, but I am wondering if the difficulty is in the fact that 0.1 cannot be exactly represented in binary floating point? And 0.1 is an odd multiple of 0.02 so the two numbers could potentially have different round offs on the occasional sample.
I imagine that the infinite SNR AWGN channel might not be synchronized on the two side, so there could occasionally be slop about exactly which receiving bucket sampled which transmitting bucket. I would be wary about that unless the system was configured for a common clock. Or is an AWGN channel self-synchronizing on the clock signal?

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