Eric Cathelinaud e.cathelinaud at
Tue Jul 28 14:30:13 CEST 2009

Hello Dieter,

Sorry I am answering quite late on this subject.

> 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
>, 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.
> 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.

Thanks for the explanations. I can't test it since I have no communication
analyzer to see the communication between the MS & BTS but at least with
wireshark I can see it's more than 500 ms in one of my tests.
For the RACH I found in GSM 05.02 that it can be on TS0,2,4,6 like the PCH.
(Clause 7 Table 3 of 9: Mapping of logical channels onto physical channels)
The RACH is always randomly sent, even at the beginning without any

Now I am trying to find the window of time during which this random time can
be found.

>  <spaar at>

Eric Cathelinaud
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