Re: [Discuss-gnuradio] OFDM Updates

[Tom Rondeau]

CHIN-YA HUANG wrote:
> Hello Tom,
>
> Based on your information below I know the problem will be receiver. However, 
> if I want to solve the receiver's problem. Where is the starting point you 
> suggestion? From the gnu-radio core part?
>
>
> Chin-Ya
>   

This problem will be fixed once I get time to merge my current branch, 
which will be in a few days, hopefully.

Tom


> From:   Tom Rondeau
> Subject:        [Discuss-gnuradio] OFDM Updates
> Date:   Thu, 07 Feb 2008 14:09:58 +0000
> User-agent:     Thunderbird 2.0.0.9 (Windows/20071031)
> For anyone working with the OFDM code, my latest check-in to the trunk fixes 
> some of the main issues of transmitting over the air. Using benchmark_ofdm_rx 
> and benchmark_ofdm_tx on different machines, I am now able to successfully 
> capture most packets with any modulation at the appropriate signal level.
>
> I say most packets because there is still an issue involved in the receiver 
> where the regenerator signal pops up before the peak detector signal resets it 
> and causes a problem in the packet sampler. To see what I mean, run
> "benchmark_ofdm.py --log"
>
> And look at the output of the regen and peak detector blocks:
> gr_plot_char.py ofdm_sync_pn-regen_b.dat ofdm_sync_pn-peaks_b.dat
>
>
> This will plot a series of 0's with a few 1's, where the peaks occur. The peak 
> detector sends it out once, and then the regenerator takes over. For every 
> packet, there is one output of the peak detector. If you look, sometimes the 
> peak detector will hit just after a regenerated signal. By this point, it's too 
> late and the ofdm_sampler has already triggered off of the regen signal and 
> ignores the peak.
>
> It's a bit of a hassle, but I'll look into it soon. Any help is appreciated, 
> though :)
>
> Tom
>
>