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From: Andy Luotto on 17 May 2010 06:35
hello
i have an issue due to my unproper understanding of sample and frame
based stuff in simulink
i ahave a bit stream which i want to drive N-PSK mappers: for BPSK i
have 1 bit/symbol, for QPSK 2 bits / symbol, for 8-PSK 3 bit/symbol. i
want the same signal drive all of them, then selecting the proper
complex number depending on which modulation scheme i want to use

as soon as the bits are generated, the symbols rate is
- same as the bit rate dor BPSK
- half of the bit rate for QPSK
- 1/3 of the bit rate for 8-PSK
in order to make simulink handling this i put a buffer block upfront
QPSK and 8-PSK
- BPSK => no buffering
- QPSK: buffering with 'output buffer size=2 (keep 2 consecutive bits
to create a symbol)
- QPSK: buffering with 'output buffer size=3 (keep 3 bits consecutive
bits to create a symbol)

i.e.

BPSK => sj=bk, j= k
QPSK => sj={b(k),(bk-1) j=2*k
8PSK => sjsj={b(k),(bk-1),b(k-2)} j=3*k

doing this in HW is pretty straightforward to me, still this frame-vs.
sample-based stuff is a bit confusing

thanks to whoever will help

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