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From: | Marcus Müller |
Subject: | Re: [Discuss-gnuradio] problem with ofdm bandwidth and sampling rate |
Date: | Fri, 05 Jun 2015 11:02:04 +0200 |
User-agent: | Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0 |
Hi Alphonso, well, your OFDM mod block uses the whole nyquist bandwidth of your sampled signal, ie. at the output of the OFDM mod block, all frequencies in [-pi;pi] (relative frequencies, as sampling rate doesn't really exist in this world) are used. After the resampler, only frequencies in [-(11/48)pi;(11/48)pi] are occupied. You feed that signal directly into the OFDM demod block. How is that block supposed to know to only look into that sub band? You will have to resample exactly inversely to your TX resampler, before trying to demodulate that. You still have to move the upsampled signal from 0 Hz to your desired center frequency, and then you'll have to convert to a real signal, before being able to feed things to a sound card. On the receive side, you'd need to do the inverse. Best regards, Marcus On 06/05/2015 10:15 AM, address@hidden
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