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

[George Nychis]

On Wed, Apr 7, 2010 at 4:54 PM, Per Zetterberg <address@hidden> wrote:

Dear All,

Regarding MAC layer development I would like to empasize on the importance of time-stamps. With time-stamps we can at least do slotted schemes. Maybe non-slotted schemes can be approximated by slotted ones ?

Hi Per,

I'm not sure what you're attempting to do, and if you're tried the USRP1 inband timestamps, but I do have a slotted scheme I am looking for someone to test:

http://www.mail-archive.com/address@hidden/msg23432.html

While I say "anyone interested in build?"  I have one ready for someone to help test:
https://www.cgran.org/browser/projects/cmu_macs/trunk/src/lib/tmac.cc#L109

Imagine a basestation and a client in the network.  Therefore you have 2 slots per round.  With the MAC, you specify the slot time and the guard time, and then when you run it, the client uses the timestamp when the basestation's beacon was received to determine how to align its own slots.  It uses a TX timestamp to align its transmissions very tightly.  I was able to achieve microsecond level guard bands.

- George