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

[Marcus D. Leech]

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