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Re: [Discuss-gnuradio] [GSoC] gr-inspector update / ask for feedback

From: Sebastian Müller
Subject: Re: [Discuss-gnuradio] [GSoC] gr-inspector update / ask for feedback
Date: Sat, 28 May 2016 05:55:45 -0700

Hi Jan,

thanks for the feedback!
PFBs are a topic I discussed with my mentors and we decided to not use them because of the following reasons. When using PFBs, there is a trade-off between band resolution and calculation effort (few filters lead to low number of possible frequency bands, many filters may have a high cpu usage). Since the band separation is not dependend on the input siganls, I think I can have a more efficient solution with „customized“ FIR filters for each signal. The second reason is the implementation effort that needs to be done (not only for the PFB but also for recombining the bands again to reconstruct the signals) is quite higher than for using FIR filters. We were afraid that time would be too short for implementing this (since all this should work until the midterms in four weeks).
We assume to have a moderate number of signals in the input spectrum (let’s say less than 5) and I think the FIR filter approach is more attractive here. But of course cpu usage is a topic which I have to deal with. Therefore I plan to use a lookup-table with precalculated taps for different bandwidths and steepnesses. Also, steepness (or something similiar) should be a parameter of the block, so the user can can somehow control the cpu usage with that.

I hope that answers your question!


Am 28. Mai 2016 um 12:45:49, Jan Krämer (address@hidden) schrieb:

Hey Sebastian,

great work in your first week. Looking pretty good.
One question though. At the end you propose to seperate the signals with a filterbank of xlating FIRs. Is there a use case or a way to do that with a polyphase filterbank? Cause multiple FIRs are going to become a major burden for the CPU if their number rises, especially if the filterorder gets pretty high e.g. for narrowband signals.

Anyway keep up the good work.


2016-05-27 14:51 GMT+02:00 Sebastian Müller <address@hidden>:
Hi all,

there is a new blog post concerning the gr-inspector toolbox:

There I describe what I have done in my first week of GSoC. Mainly I have prototyped a signal detection block and started planning the signal separator block (which is used to pass the detected signals serialized).

As always, comments are very welcome :)


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