Re: [Discuss-gnuradio] High bandwidth channel estimation using the USRP
On Mon, Dec 15, 2008 at 8:28 AM, Emanuel Birge wrote: > I'm interested in calculating an estimate of the impulse response of a > speaker cable, using pseudo-white noise and bypassing all forms of > interpolation/decimation/modulation/demodulation-blocks, for as wide a > bandwidth as possible. However, and please correct me if I'm wrong, the > USB-interface on the USRP is too slow (8 MHz) to, so to speak, do this > "online". Say I want to use 10,000 pseudo-white samples with at least 8bit > resolution. Is this possible without rewriting very much of the > Verilog-code? The BasicRX and TX do not pass DC; they are transformer coupled and have a ~100 KHz highpass response at the low end. The alternative is the LFRX and LFTX cards, which do pass DC, but have lowpass filtering at ~30 MHz. So you will only be able to calculate the impulse response convolved with that of one of these filters. There is a GNU Radio component called gr-sounder, which implements a custom FPGA build for the USRP. The transmitter will generate an m-sequence PN code of a configurable length and chipping rate for channel sounding purposes; this is likely suitable for what you need. The receiver will correlate the received signal at all possible PN code phases and produce a complex vector of the correlation results. Also, your results will be affected by the coupling of the USRP daughterboards to the speaker cable. They are designed for a broadband match of 50 ohms across their frequency range. Speaker cable is not typically designed with this in mind and the mismatch will like cause a frequency-dependent amplitude response. Maybe that is what you trying to measure, however. -Johnathan ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] High bandwidth channel estimation using the USRP
On Monday 15 December 2008 17:28:31 Emanuel Birge wrote: > Hi! > > My name is Emanuel and I'm doing my master thesis project for a small > company called Actiwave (http://www.actiwave.se). We recently bought a > USRP-board together with an assortment of daughterboards. The dboards I'll > be using for my thesis are the BasicTX & -RX. After that short introduction > I'll move right to the topic: > > Question A: > I'm interested in calculating an estimate of the impulse response of a > speaker cable, using pseudo-white noise and bypassing all forms of > interpolation/decimation/modulation/demodulation-blocks, for as wide a > bandwidth as possible. However, and please correct me if I'm wrong, the > USB-interface on the USRP is too slow (8 MHz) to, so to speak, do this > "online". Say I want to use 10,000 pseudo-white samples with at least 8bit > resolution. Is this possible without rewriting very much of the > Verilog-code? As long as you stick to humans as your intended audience, and not bats, 100kHz should be more then enough. As the frequency response of the DDC filters is flat for ~0.5 of the sampling bandwidth (you can find the FR in the USRP FAQ), a sampling rate of 200kHz is more than satisfactory for your work. Everything else is esoteric ... Stefan -- Stefan Brüns / Bergstraße 21 / 52062 Aachen mailto:lurch at gmx.li http://www.kawo1.rwth-aachen.de/~lurchi/ phone: +49 241 53809034 mobile: +49 151 50412019 ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] High bandwidth channel estimation using the USRP
Hi, I you want to do sampling @ 8 bit, USRP bandwidth can be extended to 16MHz. See usrp_fft.py with option (-8). Regards, firas ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
[Discuss-gnuradio] High bandwidth channel estimation using the USRP
Hi! My name is Emanuel and I'm doing my master thesis project for a small company called Actiwave (http://www.actiwave.se). We recently bought a USRP-board together with an assortment of daughterboards. The dboards I'll be using for my thesis are the BasicTX & -RX. After that short introduction I'll move right to the topic: Question A: I'm interested in calculating an estimate of the impulse response of a speaker cable, using pseudo-white noise and bypassing all forms of interpolation/decimation/modulation/demodulation-blocks, for as wide a bandwidth as possible. However, and please correct me if I'm wrong, the USB-interface on the USRP is too slow (8 MHz) to, so to speak, do this "online". Say I want to use 10,000 pseudo-white samples with at least 8bit resolution. Is this possible without rewriting very much of the Verilog-code? Question B: Is it possible if rewriting very much of the Verilog-code? Below is an illustration of what I want to do. - -- -- | gen. wh. noise | => | store on ursp | => | transmit & receive @ full speed | => | store received on usrp | => | trans. to host | - -- -- Thank you in advance, Emanuel Birge ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
