On Mon, Jul 28, 2008 at 6:14 PM, Mohammad Hamed Firooz <[EMAIL PROTECTED]>wrote:
> > 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. > That's correct Hamed. I don't disagree with what you just wrote. By "consistent with variations in the channel" in the message prior to the last one, I was implying at a meaningful rate. So probing an indoor channel 1000 times a second at peak people-traffic times is more than adequate. And between successive "probes" you have enough time to transfer the captured sequence over the USB at a slower rate than the max. sampling rate of 64 MSamples per second in the Rx. But this assumes you can store about 2kB of data on the FPGA. Nikhil > 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/ >>> >>> >> > > _______________________________________________ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > http://lists.gnu.org/mailman/listinfo/discuss-gnuradio >
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