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Inbound Roamer

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  • #65605

    Hi, it may not be a pure RF question but it is still related in some part as the solution would need RF optimization. My question is how do mobile select a network when roaming for the first time? Does it scan GSM then DCS then UMTS and from lowest to the highest channel?

    Thank you.


    hi ako,

    I can’t answer to you directly, because I never dived into all those details. But I can tell you where you will find the answer:

    3GPP 23.122 chapter 4.4.3 PLMN SELECTION

    It starts with this :

    “The ME shall utilise all the information stored in the SIM related to the PLMN selection; e.g. “HPLMN Selector with Access Technology”, “Operator controlled PLMN Selector with Access Technology”, “User Controlled PLMN Selector with Access Technology”, “Forbidden PLMNs”, “Equivalent HPLMN”, see 3GPP TS 31.102 [40].”

    So I guess you’ll find answers in 31.102 as well.

    Have a good read and please let us know your findings.



    Hi Pix,

    Thanks for the reply and reference. I will check on it and post my findings.

    I did some tests and SIM do remember (or technically, phone wrote into the SIM the last used network details) and used this in the next registration. I am more interested to know how the MS scans the frequency when last used network is not available. Maybe i can find it in the reference you gave.


    Pix, I always get benifit from your comments, thnx lot.

    But a Q? How can we improve our our roaming capture compared to our compititor, any advice are their any parameters or frequency need to be defined ?



    well, I’m no expert, but I would recommend you check the related 3GPP docs (called “non access stratum, 23.122”)

    With my little knowledge about this topic, I know that you just need to get the strongest RXLEV, and you should not restrict the selection (in other words, use the RXLEV ACCESS MIN at the lowest value -110dBm, and a MS TX PWR MAX CCH @33dBm, not more !!)

    Also, try to place your PLMN as a “friendly” PLMN in the SIM cards of the roamers. To do that, AFAIK, you must ask the “roaming” operator to build SIM in this way. It’s a kind of roaming agreement I assume ? It’s definitely not something that will bring more revenues right away, but it can pay in the long term.

    Also, you can advertise in the airports by telling the roamers to select the network manually.


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