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From: | Mohammad Hamed Firooz |
Subject: | Re: [Discuss-gnuradio] Channel measurements? |
Date: | Sat, 26 Jul 2008 14:02:17 -0600 |
User-agent: | Internet Messaging Program (IMP) H3 (4.0.4) |
HiJohnathan is right, If you fulfill the channel measurement in software your temporal resolution is not sufficient and you may not be able to resolve lots of paths specially for indoor applications. For more information I can refer you to Rappaport's book "Wireless Communications: Principles and Practice (2nd Edition)". If you want to have a channel sounder you have to implement the correlation part inside the FPGA. Actually we are working on that. I have implement a channel sounder which works using 802.11b packets. As you may know 802.11b use DSSS in its physical layer. We implement the de-spreading part inside the FPGA. (you can find the 802.11b receiver here: http://span.ece.utah.edu/pmwiki/pmwiki.php?n=Main.80211bReceiver)
Thanks to that now we have a channel sounder with the resolution of 30ns which is fine for indoor measurements. We plan to published it on the web in the next two weeks after doing the last testing and debuging. But if anyone is interested s/he can contact me to send her/him the code.
regards, hamed http://span.ece.utah.edu/pmwiki/pmwiki.php Quoting Johnathan Corgan <address@hidden>:
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. 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 address@hidden http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
-- Mohammad Hamed Firooz ECE Department, U of Utah Salt Lake City UT, 48112
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