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List:       gnuradio-discuss
Subject:    Re: [Discuss-gnuradio] Half-Duplex Relay
From:       Martin Braun <martin.braun () ettus ! com>
Date:       2014-01-30 15:56:06
Message-ID: 52EA7616.2070403 () ettus ! com
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On 30.01.2014 16:49, David Halls wrote:
> Thanks Martin,
>
> So your recommendation would be not to spend too much time poking around
> with USRP latency stuff:
>
> http://code.ettus.com/redmine/ettus/projects/uhd/wiki/latency

This is an excellent guide, and a good read. In this case, I doubt UHD 
is the limiting factor.

> Is there an obvious way to benchmark the latency in GNU Radio? I have
> basically stuck your decoder and encoders back to back in the relay
> code, so it is pretty intensive. I suppose that implementing some of it
> in the FPGA may help? I have no experience in that field at all though...

It would certainly help, but you'd be looking at an absurd amount of 
work. I can't think of a good pure GNU Radio way to measure latency, though.

> The current implementation is enough to show proof of concept but is
> very inefficient.

That's true, but given that it's clicked together, 10 ms latency is not 
all that bad.

> Is there an obvious way to increase the payload length without getting
> buffer issues in the code - have you ever tried increasing it
> significantly in your implementation?

See Aditya's question. Tagged stream blocks operate on one packet at a 
time, so it's limited.

MB



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