According to 3gpp, if the network selection mode is automatic then the order of selection at start /recovery from a lack of coverage is as follows:
- Last registered PLMN; this is stored in SIM.
- PLMN from user controlled PLMN selector in order of priority.
- PLMN from operator controlled PLMN selector in order of priority.
- Other PLMN with sufficient signal strength in random order.
- Other PLMN in decreasing signal quality.
Issuing the command AT+COPS=0, forces a complete scan of all the available PLMNs and these are added to the PLMN list and sorted in the decreasing order of Rx level. Then it selects the PLMN in the order defined by 3GPP and not directly to the last stored PLMN. So by issuing this command WCPU® will be able to register to the best available network instead of registering to the last registered network.
User controlled PLMN selection can be achieved using the AT commands AT+CPLS (used to select one of the PLMN) and AT+CPOL (Used to edit SIM preferred list of networks).