OFDM simulation

[M.Nasiriyan]

Hi.
What do you know about parallel implementing of OFDM? Can it be in
software or it is in hardware field only? By the other words, if we
want to increase the efficiency by using parraleling, do we save time
or memory or both?

 

[red rover]

I'm having some problems seeing posts lately.
Is that this NG or my ISP? I cannot see the
original post anymore.

Parallel implementing of OFDM? Some steps have to
be sequential so they could be pipelined, not done
in parallel. Depending on what you call parallel,
it is not uncommon to break up FFT/IFFTs to gain
processing efficiencies. Do a google search on
something like "butterfly fft" and you should find
something on rad 4 butterflys. You can break
a large FFT into smaller FFTs that could be done
faster. But unless you can spread those to other
processors or hardware you'll still end up doing
them sequentially (but faster).

Naturally you can do it in hardware or software, it
just depends on the speed required and the type of
processor available. DSP processors are obviously
designed for these type of operations. For really heavy
duty processing there is also dedicated FFT/IFFT processors.

Can you give any more information on what your requirements
are? Data rates, bandwidth, etc.

The NG comp.dsp would have some expertise too.

Steve

 

[Georg Acher]

|> something on rad 4 butterflys. You can break
|> a large FFT into smaller FFTs that could be done
|> faster. But unless you can spread those to other
|> processors or hardware you'll still end up doing
|> them sequentially (but faster).

By using smaller FFTs you can gain a major speedup, since the data addressing
scheme is not very cache-friendly. Eg. when using a sequential "radix-32" FFT as
the basic block for a 32K-FFT you can direct more than 60% of the data traffic to
a very small and fast memory. When using prefetching during the calculation of
the smaller FFT, you can hide the latency of the larger memory.

The only drawback of that solution is the slightly confusing address generator
;-)