Re: [Discuss-gnuradio] To implement WiMAX with GnuRadio or not?

[Alexander Chemeris]

On Sat, May 28, 2011 at 18:23, Marcus D. Leech <address@hidden> wrote:
>> Cool! It would be truly great to see a simplified example of this in
>> the GnuRadio repository, and at least somehow mentioned on the wiki.
> Yes, I suppose it would.  I'll put it on my list, but so many other
> things to do :-(
>
>>> The other "trick" that I use is to use the XMLRPC server stuff that Josh put
>>> in GRC--it allows you to set flowgraph variables from an
>>>  outside program, which is really great!
>>>
>> Hum. Any examples?
>>
>> I also wonder - have you quantified overhead of those methods - in
>> latency, jitter, memory, etc?
>>
>>
> Well, in terms of the FIFO I/O, they're pretty-darned efficient in
> Linux, at least as efficient as disk I/O,
>  although since FIFOs (named pipes) are implemented in kernel memory,
> they're typically a lot
>  faster.

Problem here is that FIFO's are not very well suited for real-time
operation, IIRC. Have you tried a shared memory and shared signals
across applications?

> I've never needed the XMLRPC stuff to "go real fast", since I typically
> use it to modify flow-graph
>  parameters that change infrequently.  One of the things I use it for
> in one of my applications that I
>  did for a customer is for active RFI excision for a science
> application.  The flow-graph produces
>  a spectral estimate which is sent over a FIFO to an external program
> that analyses the spectrum, and
>  then, if necessary, sends back parameters for a multi-notch filter
> into the flow-graph.

Good idea. With only one problem - XML is a bit of overhead for
real-time application messaging :)

I wonder - have anyone considered using Google's Protocol Buffers or a
similar messaging scheme with fast serialization/deserialization?
http://code.google.com/apis/protocolbuffers/docs/overview.html


-- 
Regards,
Alexander Chemeris.