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Reply To: Country Border Roaming Issue


Hi Pix, OK I have no problem with yours or Pan observations on certain types scenarios.. And thanks to all of you willing to discuss this, I do respect it.

What happens where:

Case 1
MS camping on hPLMN :
a belongs to hPLMN
b belongs to vPLMN
MS receives RXLEV(a) = -98dBm and RXLEV(b) = -98dBm.

MS camping on vPLMN :
a belongs to hPLMN
b belongs to vPLMN
MS receives RXLEV(a) = -87dBm and RXLEV(b) = -87dBm

Additionally, PAN mentioned GSM03.22

Ok well looking at GSM0322 R99 it says

4.4.3 PLMN selection
A PLMN shall be understood to be received with high quality signal if the signal level is above -85 dBm (see 23.122).

If the HPLMN is not found, the MS shall remain on the VPLMN…

OK, so as discussion, Jean’s subs MSs are not detecting HPLMN just sometimes, not all the time, and when that happens subs use VPLMN or get barred from use.

So put GSM 0322 4.4.3 in context with Jean’s subs and the words “If the HPLMN is not found” become important, because at times the MSs are finding HPLMN.

The question comes what circumstances can there exist, which are set out under GSM 03.22 3.0 Requirement and technical solutions.

Because this a coast/border issue I do not see same hard principles applying when sub with MS is not home country as opposed to say 400Km away from home (out of radio reach of HPLMN).

Pix I see the switch ON point you make, but if MS is in-building or at side of building and goes behind buildng at switch ON so NLOS with VPLMN the MS can be getting a mix of signals including HPLMN cells. So at switch ON whilst MS looks to EFLOCI and any LAI in it, the speed of processing may mean the MS may consider VPLMN cells for seconds but with HPLMN cells being detected then it as likely to look to HPLMN. Remember I am discussing coast/border area, not every scenario…

If you not satisfied with the above then there is of course GSM0322 In VPLMN of home country
The MS shall periodically attempt to obtain service on its HPLMN. For this purpose, a value T minutes may be stored in the SIM, T is either in the range 6 minutes to 8 hours in 6 minute steps or it indicates that no periodic attempts shall be made. If no value is stored in the SIM, a default value of 30 minutes is used.

The attempts to access the HPLMN shall be as specified below:

a) The periodic attempts shall only be performed in automatic mode when the MS is roaming in its home country;

b) After switch on, a period of at least 2 minutes and at most T minutes shall elapse before the first attempt is made;

c) The MS shall make an attempt if the MS is on the VPLMN at time T after the last attempt;

d) Periodic attempts shall only be performed by the MS while in idle mode;

e) If the HPLMN is not found, the MS shall remain on the VPLMN.

I do not think manual selection as permenant solution is good, as it suggests network cannot fix problem. If barring is not put in place of Loc-Upd etc then -110dBm as backstop is one element of a number of things that could be done.

This is just discussion, I not try to change the world 🙂