Implementing the idle mode while out of a RAN coverage area
A method for a user equipment (UE) connected to a serving Radio Access Network (RAN) through a serving cell is provided. The serving RAN may include a Non-Terrestrial Network (NTN). The method receives, from the serving cell, satellite information regarding a coverage area of the serving RAN. After receiving the satellite information, the method determines, based on the satellite information, that the UE will be disconnected from the serving RAN by moving out of the coverage area of the serving RAN after a specific period of time. The method maintains an Access Stratum (AS) layer configuration of the UE without performing any task associated with an Idle mode of the UE while the UE is staying out of the coverage area of the serving RAN.
1 . A method for a user equipment (UE) connected to a serving Radio Access Network (RAN) through a first serving cell, the serving RAN comprising a Non-Terrestrial Network (NTN), the method comprising:
receiving, from the first serving cell, satellite information regarding a coverage area of the serving RAN;
determining, based on the satellite information, that the UE will be disconnected from the serving RAN by moving out of the coverage area of the serving RAN after a specific period of time; and
maintaining an Access Stratum (AS) layer configuration of the UE, wherein the UE forgoes performing tasks associated with an Idle mode of the UE while the UE is staying out of the coverage area of the serving RAN and is disconnected from the serving RAN, the tasks associated with the Idle mode of the UE comprising at least a RAN notification area update procedure.
2 . The method of claim 1 , wherein the satellite information is associated with a satellite that configures the first serving cell of the UE and indicates at least one of:
a RAN or Radio Access Technology (RAT) or cell service available period, and
a RAN or RAT or cell service unavailable period.
3 . The method of claim 1 , further comprising receiving, from the first serving cell, the AS layer configuration via UE-specific control signaling before the UE moves out of the coverage area of the serving RAN.
4 . The method of claim 3 , wherein:
the AS layer configuration comprises one or more cell selection priorities associated with one or more frequency carriers,
the UE-specific control signaling comprises a radio resource control (RRC) Release message, and
the RRC Release message instructs the UE to move to the Idle mode.
5 . The method of claim 4 , wherein:
the AS layer configuration further comprises UE inactive AS layer context, and
the UE inactive AS layer context is stored at the UE after receiving the RRC Release message.
6 . The method of claim 4 , wherein:
maintaining the AS layer configuration comprises maintaining an Inactive state context for the AS layer that is stored at the UE,
the one or more cell selection priorities comprise priority information for selecting, while the UE is in the Idle mode, a second serving cell to connect to the NTN,
the first serving cell is associated with a first satellite of the NTN, and
the second serving cell is associated with a second satellite of the NTN, which is different from the first satellite of the NTN.
7 . The method of claim 1 , further comprising:
receiving the AS layer configuration via UE-specific control signaling; and
storing the AS layer configuration, which comprises at least one of a log measurement configuration or log measurement results, before moving out of the coverage area of the serving RAN.
8 . The method of claim 1 , further comprising determining how to implement one or more timers associated with the Idle mode of the UE while the UE is staying out of the coverage area of the serving RAN.
9 . The method of claim 1 , further comprising:
performing at least one idle mode task associated with the Idle mode of the UE after moving to another coverage area of the serving RAN and connecting back with the serving RAN, wherein the Idle mode task of the UE further comprises a cell selection or reselection procedure.
10 . The method of claim 1 , wherein:
the Idle mode comprises one of (i) an Evolved-Universal Terrestrial Radio Access (E-UTRA) or New Radio (NR) Radio Resource Control (RRC) Inactive state and (ii) an E-UTRA or NR RRC Idle state, and
a task associated with the Idle mode of the UE further comprises a task associated with an E-UTRA Radio Access Technology (RAT) or a task associated with an NR RAT.
11 . A user equipment (UE) connected to a satellite through a non-terrestrial network (NTN), the UE comprising:
one or more non-transitory computer-readable media storing one or more computer-executable instructions; and
at least one processor coupled to the one or more non-transitory computer-readable media, and configured to execute the one or more computer-executable instructions to cause the UE to:
receive, from a first serving cell, satellite information regarding a coverage area of a serving Radio Access Network (RAN) comprising the NTN;
determine, based on the satellite information, that the UE will be disconnected from the serving RAN by moving out of the coverage area of the serving RAN after a specific period of time; and
maintain an Access Stratum (AS) layer configuration of the UE, wherein the UE forgoes performing tasks associated with an Idle mode of the UE while the UE is staying out of the coverage area of the serving RAN and is disconnected from the serving RAN, the tasks associated with the Idle mode of the UE comprising at least a RAN notification area update procedure.
12 . The UE of claim 11 , wherein the satellite information is associated with a satellite that configures the first serving cell of the UE and indicates at least one of:
a RAN or Radio Access Technology (RAT) or cell service available period, and
a RAN or RAT or cell service unavailable period.
13 . The UE of claim 11 , wherein the at least one processor is further configured to execute the one or more computer-executable instructions to cause the UE to receive, from the first serving cell, the AS layer configuration via UE-specific control signaling before the UE moves out of the coverage area of the serving RAN.
14 . The UE of claim 13 , wherein:
The AS layer configuration comprises one or more cell selection priorities associated with one or more frequency carriers,
the UE-specific control signaling comprises a radio resource control (RRC) Release message, and
the RRC Release message instructs the UE to move to the Idle mode.
15 . The UE of claim 14 , wherein:
the AS layer configuration further comprises UE inactive AS context, and
the UE inactive AS context is stored at the UE after receiving the RRC Release message.
16 . The UE of claim 14 , wherein:
maintaining the AS layer configuration comprises maintaining an Inactive state context for the AS layer that is stored at the UE,
the one or more cell selection priorities comprise priority information for selecting, while the UE is in the Idle mode, a second serving cell to connect to the NTN,
the first serving cell is associated with a second satellite of the NTN, and
the second serving cell is associated with a second satellite of the NTN, which is different from the first satellite of the NTN.
17 . The UE of claim 11 , wherein the at least one processor is further configured to execute the one or more computer-executable instructions to cause the UE to:
receive the AS layer configuration via UE-specific control signaling; and
store the AS layer configuration, which comprises at least one of a log measurement configuration or log measurement results, before moving out of the coverage area of the serving RAN.
18 . The UE of claim 11 , wherein the at least one processor is further configured to execute the one or more computer-executable instructions to cause the UE to determine how to implement one or more timers associated with the Idle mode of the UE while the UE is staying out of the coverage area of the serving RAN.
19 . The UE of claim 11 , wherein the at least one processor is further configured to execute the one or more computer-executable instructions to cause the UE to perform at least one task associated with the Idle mode of the UE after moving to another coverage area of the serving RAN and connecting back with the serving RAN, wherein the Idle mode task of the UE further comprises a cell selection or reselection procedure.
20 . The UE of claim 11 , wherein:
the Idle mode comprises one of (i) an Evolved-Universal Terrestrial Radio Access (E-UTRA) or New Radio (NR) Radio Resource Control (RRC) Inactive state and (ii) an E-UTRA or NR RRC Idle state, and
a task associated with the Idle mode of the UE further comprises a task associated with an E-UTRA Radio Access Technology (RAT) or a task associated with an NR RAT.