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Re: [Discuss-gnuradio] OFDM serial to parallel mappping

From: Tom Rondeau
Subject: Re: [Discuss-gnuradio] OFDM serial to parallel mappping
Date: Thu, 24 Apr 2008 11:00:53 +0100
User-agent: Thunderbird (Windows/20080213)


Does anyone have clear idea about how gunradio implements serial to parallel 
mapping since 802.11 has 52 channels?
I check the gr_ofdm_mapper_bcv.cc , but still have no idea about it. In further, I want to apply an array mapping to implement that different channels use different constellation. Does anyone have another comments if I apply an array in the gr_ofdm_mapper_bcv.cc file?


The OFDM system uses fft_length number of subcarriers and occupied_tones number of used subcarriers. The used subcarriers are mapped to the middle of the fft_length subcarriers leaving the same number of guardband subcarriers on either side. The middle two subcarriers are also nulled to avoid DC affects.

The mapping is done in gr_ofdm_mapper_bcv.cc. If you want to play with this, I'd make a copy of this one as a different version of the mapping.


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