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

[James Jordan]

Hi Marcus, Thanks for reply. If set the decimation rate exactly the  receive bandwidth then gnuradio will automaticly 
filter the signal at the  receive bandwidth?

On Wed, Dec 29, 2010 at 9:22 AM, Marcus D. Leech <address@hidden> wrote:

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?

Regards.

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
http://www.sbrac.org



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