Re: [Discuss-gnuradio] Channel measurements?

[Mohammad Hamed Firooz]

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 <address@hidden>:

> 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/