That is not always true, actually it depends on when and where you are
going to measure a channel, For example in a office during a day,
channel could change several times in a second. So for indoor
applications a channel sounder should be as fast as possible.
I can refer you to these papers to study more channe behavior:
K.Pahlavan, et.al. Indoor Geolocation Science and Technology
N.Patwari, et.al. Robust Location Distinction using Temporal Link Signatures
you can also see our website for more information and papers:
http://span.ece.utah.edu/pmwiki/pmwiki.php?n=Main.PHY-basedDistinction
regards,
hamed
Quoting Nikhil <[EMAIL PROTECTED]>:
On Fri, Jul 25, 2008 at 9:57 PM, Johnathan Corgan <
[EMAIL PROTECTED]> wrote:
On Fri, Jul 25, 2008 at 6:12 PM, Nikhil <[EMAIL PROTECTED]> 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/
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