On Fri, Jul 25, 2008 at 9:57 PM, Johnathan Corgan <
address@hidden> wrote:
On Fri, Jul 25, 2008 at 6:12 PM, Nikhil <address@hidden> wrote:
> I'm curious -- in a channel sounder application what benefit, if any is
> there to performing the cross-correlation on the FPGA? This is assuming
> you are continuously transmitting the PRBS and computing the impulse
> response at the receive end at a rate that is consistent with variations
in
> the channel (i.e. not continuously).
The channel sounder transmitter is sending the PRNG modulated BPSK at
32 Mchips/sec. You need to do the correlation at this speed; it's not
possible to send that much data over the USB to the host.
I was thinking that since you don't need to probe the channel at the Rx
continuously as it does not change that fast, one solution would be to
buffer a sequence length (~2kB for a 511 bit m-seq) and then transfer it
over the USB link at a slower rate.
A channel sounder in software would work for chip rates less than 4
Mchip/sec. But that limits the resolution of your impulse response to
about 250 ns per bin, or 75 meters per bin in the spatial domain.
--
Johnathan Corgan
Corgan Enterprises LLC
http://corganenterprises.com/