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i observed onething while doing a drive test….the mobile camped on the cell of another network and still it was in idle mode (not in limited service mode). roaming with other network was allowed. but the mobile when entered in its own network coverage area….it didnt camp on its own cell. it remained camped on the cell of the other network. kindly tell me how to look into this problem.
after camping on an “external” cell, the MS will select a cell from its own network only if it totally looses the “external” coverage, or after IMSI DETACH/ATTACH or after manual reselection.
Maybe some MS’s can automatically check if their own their primary network, but I don’t think that’s in the standards.
Pix
There are two cases:
1. A Visited network belongs to the Home network country, then MS shall periodically attempt to obtain service on its Home network. For this purpose, a value T minutes may be stored in the SIM (from range 6 minutes to 8 hours in 6 minute steps) OR IT INDICATES THAT NO PERIODIC ATTEMPTS SHALL BE MADE.
2. A Visited network belongs to the other country, then MS will act, as Pix saidthanks for the details, Pan.
The value “T” minutes, do you know where/how it is defined ?Thanks,
PixPIX
It is defined by SIM issuers and probably it is may be changed by home operator (e.g., by means of SIM Application Toolkit)
Ok, thanks !
Do you happen to know how long is this value, in average ? More like 5 minutes or 120 minutes ?PIX, I don’t know exactly. a default value of 30 minutes is used, if no value is stored in the SIM (you may see about in 03.22). If this value is increased, then battery power consumption is decreased (it is well), but if T-value is very large, the MS will stay in visited network during this time, thou it is in home network coverage (it is bad).
thanks to you all for your valuable comments. In my case, the external network was the network of another country.
I have seen example similar to this with MS in idle mode. The MS re-scanned and camped on cells of V/fone and O2 at different times while MS in idle mode when the home network was T-Mobile. The answer was that the T-Mobile coverage RxLv was very poor (dropped below -114dbm) in the area of testing (rural) and performed re-scan. The MS wouldn’t make call on V/fone or O2 as there no T-Mobile roaming agreement with these operators.
To AD
Additionally: this problem (Network selection in border areas) is recognized in Rel-7. Moreover, IMSI DETACH/ATTACH can’t to resolve this problem,because the mobile will look for the Registered network.
It is indicated:
“The performance of PLMN selection in border areas should be improved, as it has been noted that network operators are advising their customers to manually select the HPLMN to avoid accidental roaming.”
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