Re: [Discuss-gnuradio] MAC layer development and USRP2

[Veljko Pejovic]

Two independent PC+USRP nodes. All the ACK related logic was
implemented at the Python layer.

Another thing that I tried was to connect the two nodes via Ethernet
(I have two Ethernet NICs in each of the PCs) and then use USRPs for
data and Ethernet for ACKs. I still couldn't get good results,
although I had some issues with the OFDM decoding latency, so I can't
really say where the bottleneck was.


Veljko


2010/4/6 Jeff Brower <address@hidden>:
> Veljko-
>
>> I tried with a stop-and-wait ARQ and two USRP2s with XCVR2450s, but
>> the delay was too long and inconsistent. I can't remember the exact
>> figures, but definitely up to milliseconds.
>
> Do you mean two USRP2s back-to-back?  Or both connected to motherboard ports?
>
> -Jeff
>
>> 2010/4/6 George Nychis <address@hidden>:
>>>
>>>
>>> On Tue, Apr 6, 2010 at 10:07 AM, Charles Irick <address@hidden> wrote:
>>>>
>>>> Thanks for the reply George. I'm still looking for a little more
>>>> information on this topic.
>>>>
>>>> - What is PMT
>>>
>>> http://gnuradio.org/redmine/wiki/1/TypePMT
>>>
>>>>
>>>> - Why was m-block removed
>>>
>>> http://osdir.com/ml/discuss-gnuradio-gnu/2010-01/msg00066.html
>>>
>>>>
>>>> - Has anyone measured latency with the USRP2 and GigE
>>>
>>> I'm not sure.
>>>
>>>>
>>>> - Is GigE alone not capable of handling MAC turnaround times or is
>>>> software to blame for this
>>>
>>> I think the latency is on hundreds of microseconds, which is greater than,
>>> say, an 802.11 ACK turnaround time (24us).
>>>
>>>>
>>>> - Is the scheduler the main issue in the way it handles i/o between blocks
>>>
>>>  There are some details of this in the second link I gave.
>>>
>>> - George
>>>
>>>
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>>>
>>
>>
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>
>