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Re: [Discuss-gnuradio] Re: [Openbts-discuss] how openbts set channel ban

From: Marcus D. Leech
Subject: Re: [Discuss-gnuradio] Re: [Openbts-discuss] how openbts set channel bandwidth?
Date: Tue, 28 Dec 2010 20:22:31 -0500
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On 12/28/2010 08:05 PM, James Jordan wrote:
Hi Alexander, where the filter perform? In gnuradio?
Since there is a filter, openbts must set it, how openbts set the filter?


The OpenBTS software likely sets the incoming decimation rate to match as closely as possible the desired receive bandwidth,
  then it likely applies an FIR bandpass filter on the software side.

This is, after all, Software Defined Radio, so it should be no surprise to anyone that applications (OpenBTS, or whatever) use filters implemented in software to condition the signals before further processing. None of that requires the analog filtering to work in anything other than an anti-alias mode. Filtering and bandwidth reduction is performed first in the FPGA, in the digital domain, and then on the host, with software, again in the digital domain. Either Gnu Radio, or OpenBTS, or whatever.

Marcus Leech
Principal Investigator
Shirleys Bay Radio Astronomy Consortium

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