Hello Eric,
On Fri, 17 Jul 2009 17:52:17 +0200, "Eric Cathelinaud" e.cathelinaud@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
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 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.
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 collision.
Now I am trying to find the window of time during which this random time can be found.
Eric Cathelinaud
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Dieter Spaar -
Eric Cathelinaud