Viterbi--OFDM


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Hallo,

I guess I explained to less. I’m using hard symbol coding. As I read in
the documentation, I can use the trellis modulated Symbols how ever I
want to. So on the transmitter side, I do not forward the trellis
modulated symbols to a QAM modulator or something. I convert the
generated fsm symbols let’s say with 2 Bits per Byte with a
unpacked_to_packed block back into a byte with all symbols use. So I
have 4 trellis coded symbols in each byte. And the so coded bytes I
forward to the ofdm_mod to transmit it.

On the receiver side, I take the packet handed over by the
ofdm_demodulator “complete usual ofdm demodulation”. So if no error
occured i should get back bytes with 4 fsm hard symbols each. I take
these bytes and make a pack_to_unpack and get back the 4 bytes with one
2bit fsm symbol each. this steam of chunks is than decoded by a
hard_symbol viterbi. The principle is the same like in one of the
trellis examples with an outer coding.

it should in an error free case be the same as taking the symbols
generated by a tcm into a viterbi. the scheme is:

input(packet with leading and ending zeros to force defined
states)—pack_to_unpack–tcm(hard_symbol)–unpack_to_pack–ofdm_mod–CHANNEL–ofdm_demod–pack_to_unpack–combined_viterbi(hard_symbol)–unpack_to_pack—

And I don’t know why I doesn’t work all the time.
Is there an error in my idea?

Cheers,

Tobias

Am 09.09.2010 21:57, schrieb Veljko P.:

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