Re: [Discuss-gnuradio] Channel Response in OFDM with MIMO USRP

[Paul Fuxjaeger]

On 13.01.13 22:00, Jack M wrote:
> Well, I'm running the regular OFDM rx-chain which includes preamble
> detection->sampler->fft->so on. On the transmitter, each frame
> (preamble[1 OFDM symbol] + data[multiple OFDM symbols]) acts as a burst
> which includes the required timestamps and the burst tags.

Nice, I'd be interested in how your chain looks like in GNURadio. I'm in 
the middle of building a good 802.11n RX chain, but it's only offline so 
far, a simple looped sequential recipe in matlab that needs synced 
baseband blocks as input and tries to decode all frames it finds in it.

> I was just somehow hoping to get a flat channel for some analysis which
> otherwise is a pain, since I have to do it without channel equalization.
> This phase change results in symbols rotating in the I/Q domain. :)

Your channel is super flat and good-natured. But I don't think that 
there is a way to avoid post-fft multiplication with a complex vector 
that has the appropriate linear phase progression over subcarriers. I 
guess one could call it manual fine-timing compensation, or some sort of 
"static channel phase equalization" ;)


-paul