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CCK demodulation

Started by bizoo December 18, 2007
Hi fellas,
I am doing CCK demodulation by 802.11 standard. I have a signal which is a
real WLAN packet but i am doing the decoding off line. My original goal is
to do this online with a DSP  but intially i am saving the packet and
doing decoding offline. I know where the CCK modulation starts in a WLAN
packet so i starts decoding from that very instant. My operation steps are
listed below:

1. I downsample my data from 200Mbps to 11 Mbps
2. At 11Mbps, i add I and Q component and divide the whole packets into
octets.
3. I take the first octet, multiply it with the whole RAKE matrix and find
out which bit combinations were used for d2.....d7.
4. I do this operation for all octets and fin out d2....d7 for all
octets.
5. To calculate d0 and d1, i go back at the product out put of RAKE matrix
and choose the maximum product(which is a complex number). I do this for
all incoming octets.
6. I take alll these results of rake multiplication, pass it through a
DQPSK demodulator
and for every single input , i found d0 and d1. i attach this to d0 and d1
to d2...d7 and complete all my octets this way.
7. I passed them finally through a descrambler to find original bits.



The problem is very simple that my result doesnot match with the original
input which i know what is. But the reason of teh problem, i cant figure
out. Can some one find out any mistake in the above proceure, am i missing
some thing.?

br