Re: [Discuss-gnuradio] Programming USRP as a relay node

[Martin DvH]

On Sat, 2009-07-04 at 14:15 +0300, Tasos Kyrillidis wrote:
> Hello everyone,
> 
> I am a postgraduate student at Technical University of Crete, Chania
> and i am currently working on a project with USRPs. Part of our
> project is to communicate with a relay node. But this relay node is a
> little bit slow, because there is data transfer from USRP to PC and
> then from PC to USRP. So, there is an idea to program the FPGA of USRP
> as a relay without any communication between PC and USRP - the relay
> node just detects packets and retransmit them without any further
> processing. 
> 
> 1. One idea is to program the FPGA to include a packet detector and a
> raised cosine filter. But I read somewhere that the default FPGA has
> only 5% available resources and i am wondering if these resources are
> enough for a packet detector and a raised cosine filter?
You can free up resources by reducing the number of channels.
In your case, only one RX and one TX channel in stead of two.
You can also replace the halfband filter with a raised cosine filter.
(Note, you can only use a limited number of taps, depending on the
decimation factor)

A simple signal level detector should be doable.
For a packet detector and best S/N ratio you should completely
demodulate the packets and remodulate them (regenerate the signal)
This will be quite complicated though and possibly not fit in the FPGA.

When you use a USRP2 you have much more room in the FPGA. Implementing a
complete receiver, packet detector and transmitter will certainly fit,
but it will still be a complicated design.

Greetings,
Martin 


> 
> 2. In case there are enough resources (in some way), could anyone
> estimate how difficult would be to implement it? Has the current
> configuration to be changed a lot or including the appropriate modules
> is enough?
> 
> I know that my questions are kind of abstract but i couldnt express
> them differently
> 
> Thanks anyway
> 
> Tasos Kyrillidis
> 
> 
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