CCCH

[Dieter Spaar]

Hello Eric,

On Fri, 17 Jul 2009 17:52:17 +0200, "Eric Cathelinaud" <e.cathelinaud at googlemail.com> wrote:
> 
> If nothing possible I will try to deal with the 470ms period.
> Can you tell me if the mobile will RACH at each paging request or if it can
> miss some?

If the MS receives a paging request for itself and is allowed to access
the network, than it will start the immediate assign procedure (The details
are in GSM 04.08, a good overview with reference to the specification is at
http://en.wikipedia.org/wiki/Um_Interface, many thanks to David Burgess for
writing it down). The MS will not react on further paging request as long as
the immediate assign procedure is running.

> I already saw in OpenBSC that the paging request is sometimes send more than
> once for a call so I am not sure. May be it could be something to fixe in
> the code? Or the phone sometimes doesn't react as it should?

The BSC can't be sure that a single paging request is received by the
MS so it (optionally) has to repeat it (there can be distortions, weak
signal and so on).

> Normally the RACH is sent 3 time slots after the paging request right?

I don't think so, the RACH is always on TS0 of the uplink (at least this
is how I understand it) and the PCH is not necessarily on TS0 (depending
on the configuration). The reaction of the MS surley depends on the
firmware/hardware of the phone and how fast it works, so you don't
have a fixed delay. The MS usually has enough time to react, the
T3113 timer defines how long to wait for a PAGING RESPONSE and than
optionally repeat the paging request (if and how often the paging
request is repeated, is not defined in the specification). I don't
have exact numbers for the T3113 timer because its up to network,
but common values seems to be around 5 seconds.

Best regards,
  Dieter
-- 
Dieter Spaar, Germany                           spaar at mirider.augusta.de