On Wed, Jul 23, 2008 at 10:43 PM, Jason Uher <
address@hidden> wrote:
Hey all,
What is the best way to measure the channel for use in space-time
coding schemes using an RFX2400 board?
As far as I know you can only get the I and Q streams out of the USRP,
and I'm not sure how you would get a set of channel coefficients.
Are you trying to measure the impulse response of the channel? If so, then one technique would be to transmit a known pseudo-random bit sequence (an m-sequence) using BPSK modulation at the carrier frequency of interest. The chip rate of the sequence determines the measurement system bandwidth, while the sequence length determines the 'dynamic range' of the measurement.
At the receiver set the LO to the same carrier frequency as that at the transmitter. Here you need to cross-correlate the equivalent low-pass received signal with the known m-sequence to give the (complex) impulse response of the channel. Any 'peaks' that exceed your definition of a threshold noise level would be your channel coefficients in the time domain.
Nikhil
I am planning on using the conjugate of the measured channel to
'reverse' the damage done by transmission.
Sorry if I am missing something fundamental here, I've only done
channel coding in theory and am trying to get a practical
implementation going on.
Jason
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