Method of performing automatic PLMN selection in IOPS-capable wireless communication system
A wireless communication system includes an LOPS-capable user equipment, an LOPS-mode eNB and a normal-mode eNB. When the user equipment is under the coverage of both the LOPS-mode eNB and the normal-mode eNB, the user equipment is configured to perform automatic PLMN by registering on both the IOPS-mode eNB and the normal-mode eNB so as to maintain both normal-mode communications and IOPS mode communications.
1. A method of performing an automatic public land mobile network (PLMN) selection in an IOPS (isolated evolved universal terrestrial radio access network operations for public safety) capable wireless communication system, comprising:
a user equipment selecting a first PLMN as a primary PLMN and registering on the primary PLMN;
the user equipment performing a PLMN search when registering on the primary PLMN;
the user equipment determining whether a second PLMN can be detected in the PLMN search and is currently unable to provide connectivity to the first PLMN;
the user equipment selecting the second PLMN as a secondary PLMN if the second PLMN is detected in the PLMN search and is currently unable to provide connectivity to the first PLMN; and
the user equipment registering on both the primary PLMN and the secondary PLMN after selecting the secondary PLMN, wherein:
the first PLMN is a normal PLMN connected to a macro evolved packet core (EPC) which serves the user equipment in a normal mode of operation, and the second PLMN is an IOPS PLMN connected to a local EPC which provides a local connectivity and public safety services to the user equipment in an IOPS mode of operation when a backhaul from the IOPS PLMN to the macro EPC is lost or not available to the user equipment.
2. The method of claim 1 , further comprising:
assigning a normal PLMN identity to the first PLMN or the second PLMN for use in the normal mode of operation; and
assigning an IOPS-dedicated PLMN identity to the first PLMN or the second PLMN for use in the IOPS mode of operation.
3. The method of claim 1 , further comprising:
storing an IOPS-dedicated PLMN identity associated with the first PLMN or the second PLMN for use in the IOPS mode of operation in a smartcard of the user equipment.
4. The method of claim 1 , wherein the user equipment performing the PLMN search includes:
access stratum (AS) layers of the user equipment reporting information associated with all available PLMNs to a non-access stratum (NAS) layer of the user equipment; and
the NAS layer determining if the available PLMNs include the second PLMN.
5. The method of claim 1 , further comprising:
determining if the user equipment needs to detach from the primary PLMN or the secondary PLMN based on a signal quality of the primary PLMN or a signal quality the secondary PLMN.
6. The method of claim 1 , further comprising:
the user equipment remaining registering on the primary PLMN if the second PLMN cannot be detected in the PLMN search.
7. The method of claim 1 , wherein the user equipment registering on both the primary PLMN and the secondary PLMN includes:
the user equipment listening to a first cell in the primary PLMN at a first time slot using a smartcard; and
the user equipment listening to a second cell in the secondary PLMN at a second time slot using the smartcard, wherein the first time slot and the second time slot are not overlapped.
8. The method of claim 1 , wherein the user equipment registering on both the primary PLMN and the secondary PLMN includes:
the user equipment listening to a first cell in the primary PLMN at a first time slot using a first smartcard; and
the user equipment listening to a second cell in the secondary PLMN at a second time slot using a second smartcard, wherein the first time slot and the second time slot are not overlapped.
9. The method of claim 1 , wherein the user equipment registering on both the primary PLMN and the secondary PLMN includes:
the user equipment listening to a first cell in the primary PLMN using a first smartcard and listening to a second cell in the secondary PLMN using a second smartcard simultaneously.