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

[Jeff Brower]

Marcus-

> On 04/06/2010 09:44 PM, John Gilmore wrote:
>>> Which part of the Linux issue... sustained throughput or latency?  I 
>>> wouldn't be surprised to find that latency
>>> hasn't
>>> improved substantially because it's not a priority for server software.  
>>> Even VoIP applications are not concerned
>>> about a 1 msec improvement... whereas that makes or breaks a wireless MAC.
>>>
>>
> Simple test.  Core 2 Duo system, 2.33GHz, Fedora 11.
>
> A 1500 byte ping test to localhost yields an average RTT of about
> 33usecs.  That tests most of
>   the network stack except for hardware interfaces, and gives you some
> notion of "best case"
>   for latency/turn-around time.
>
> If MACs have requirements that are more aggressive than 20-50usec
> turnaround time, then relying
>   purely on software in a running general-purpose operating system, even
> on relatively-good hardware
>   may be optimistic.

I think there is no way to avoid that MAC-related processing has to be done 
prior to the server motherboard.

-Jeff