[Openbts-discuss] RACH messages

[Timur A. <tim...@um...>]

Hi there,

I'm working on a project to try to see how often phones request
resources, as well as the reference numbers used, collisions, etc. I
was going to take some pieces of the OpenBTS codebase and adapt it,
since I was just going to try to look at the occurrence of RACH
channel request messages.

So far, I separated all the code that I think is required and modified
the USRPDevice class (because I'm using DBSRX, rather than a
transceiver board). I'm also trying to do this with the standard
firmware (maybe that's a problem?). The problem I ran into is that I
seem to be recording the bursts correctly, but the detectRACH()
function identifies it as a RACH burst. I was checking the bit vectors
after the unUSRPify() step and demodulation to see if the ext tail
bits and synch bits would line up and they didn't seem to be correct.
I modified the RACHDetector::writeLowSide() method to ensure it
doesn't reject the message based on the BSIC. It seems to be rejecting
the message when checking the tail bits to be all 0s.

I assume no one else is working in this direction, but if someone
could suggest possible issues to check out, that would be awesome :)

Thank you.

-- 
Cheers,
Timur