gsm850 and host/layer23/src/mobile

Joshua Lackey jl at
Thu Jun 2 20:11:48 UTC 2011

I'm having issues getting the mobile application to work and I'm
wondering if this is a gsm850 problem.  I have a couple of debugging
ideas but I thought I would post here just in case the answer is obvious
to someone else.

I'm testing on both a c118 and a c139.

I'm using the remotes/origin/sylvain/testing branch and this does have
quadband support.  I've edited target/firmware/Makefile and defined

I have a valid SIM in my phone that works with both phones using the
default Motorola firmware.  The 'sim reader 1' command is able to gather
(most of) the necessary information.  (The access class is not correctly
read from the SIM but I haven't bothered tracking down why yet -- I just
hardcoded an access class of 0xffff.)

The mobile program correctly scans the frequency ranges and finds a good
tower and then attempts to do a location update.  It generates a RACH
channel request and then (appears to) send it.

The problem is that the phone never receives an immediate assignment
response.  The log shows multiple immediate assignments received, but
none match the request reference (RA and FN the burst was sent in.)

So it appears that the tower never receives the channel request I send.

The only test I have done so far is to monitor the uplink frequency with
a USRP ( during the location update procedure.  It looks like
the phone is actually transmitting at the correct times, but I am not
positive.  (I'd have to write some custom code before I can definitively
say one way or the other.)

The only other idea I have right now is that perhaps the timing advance
calculation is incorrect.  There are a couple of constants used without
any explanation and I guess it is possible that these constants don't
work for my configuration.  I'm going to start going through these
constants to determine if I can find a value that works.

Any other ideas to try here?  Anyone else gotten this to work in the US?

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