Inter-RAT transitioning utilizing system information messaging
Methods, systems, and devices are described for transitioning between different radio access technologies (RATs) utilizing system information messages to trigger the transition. Some embodiments may involve utilizing a system information message (e.g., SIB19, SI2quater) that may be received from a serving cell over a first radio RAT (e.g., 2G, 3G, 4G) while in a connected mode with the serving cell. A transition may be initiated from the connected mode with the serving cell to an idle mode with the serving cell in response to the received system information message. A reselection may be performed from the idle mode with the serving cell to a target cell utilizing a second RAT (e.g., 3G, 4G, or 5G) in response to the received system information message.
1. A method of reselection in a wireless communications system comprising:
receiving, at a user equipment (UE), a system information message from a serving cell over a first radio access technology (RAT) while in a connected mode with the serving cell, wherein the system information message comprises a neighbor list, information indicating coverage by a second RAT, carrier frequency information regarding the second RAT, or information directing the UE to an allowed public land mobile network (PLMN);
initiating, at the UE, a transition from the connected mode with the serving cell to an idle mode with the serving cell in response to the received system information message; and
performing a reselection from the idle mode with the serving cell to a target cell utilizing the second RAT in response to the received system information message.
2. The method of claim 1 , wherein the system information message comprises a system information block (SIB).
3. The method of claim 2 , wherein the SIB comprises a SIB 19 or an SI2quater.
4. The method of claim 1 , wherein the receiving the system information message occurs during an RRC connected state.
5. The method of claim 1 , wherein the initiating the transition comprises initiating a connection release in response to the received system information message.
6. The method of claim 1 , wherein the initiating the transition comprises: indicating a radio link failure (RLF) of a radio link with the serving cell.
7. The method of claim 5 , further comprising:
transmitting a signaling connection release indication in order to initiate the connection release.
8. The method of claim 1 , wherein the first RAT comprises a 2G RAT, a 3G RAT, or a 4G RAT.
9. The method of claim 1 , wherein the second RAT comprises a 4G RAT.
10. The method of claim 1 , wherein the wireless communications system is configured without network support for an inter-RAT handover from the first RAT to the second RAT.
11. The method of claim 1 , wherein the wireless communications system is configured without support for autonomous handover of the UE from the first RAT to the second RAT.
12. The method of claim 1 , further comprising: preserving a current packet data protocol (PDP) context from prior to receiving the system information message at least until after performing the reselection.
13. The method of claim 1 , wherein the initiating the transition to the idle mode occurs while the UE is scheduled to receive data from the serving cell.
14. The method of claim 1 , wherein the reselection comprises a non-blind attempt.
15. The method of claim 1 , wherein the performing the reselection commences promptly after transitioning to the idle mode.
16. A device for wireless communication in a wireless communication system, comprising:
at least one processor; and
memory in electronic communication with the at least one processor, the memory storing instructions that, when executed by the at least one processor, cause the device to:
receive, at a user equipment (UE), a system information message from a serving cell over a first radio access technology (RAT) while in a connected mode with the serving cell, wherein the system information message comprises a neighbor list, information indicating coverage by a second RAT, carrier frequency information regarding the second RAT, or information directing the UE to an allowed public land mobile network (PLMN);
initiate, at the UE, a transition from the connected mode with the serving cell to an idle mode with the serving cell in response to the received system information message; and
perform a reselection from the idle mode with the serving cell to a target cell utilizing the second RAT in response to the received system information message.
17. The communications device of claim 16 , wherein the system information message comprises a system information block (SIB).
18. The communications device of claim 16 , wherein the instructions are executable to cause the device to:
initiate a connection release in response to the received system information message.
19. The communications device of claim 16 , wherein the instructions are executable to cause the device to:
indicate a radio link failure (RLF) of a radio link with the serving cell.
20. The communications device of claim 18 , wherein the instructions are executable to cause the device to:
transmit a signaling connection release indication in order to initiate the connection release.
21. The communications device of claim 16 , wherein the first RAT comprises a 2G RAT, a 3G RAT, or a 4G RAT.
22. The communications device of claim 16 , wherein the second RAT comprises a 4G RAT.
23. The communications device of claim 16 , wherein the wireless communications system is configured without support for an inter-RAT handover from the first RAT to the second RAT.
24. The communications device of claim 16 , wherein the wireless communications system is configured without support for autonomous handover of the UE from the first RAT to the second RAT.
25. The communications device of claim 16 , wherein the reselection comprises a non-blind attempt.
26. The communications device of claim 16 , wherein the instructions are executable to cause the device to:
commence the reselection promptly after transitioning to the idle mode.
27. A wireless communications system comprising:
means for receiving, at a user equipment (UE), a system information message from a serving cell over a first radio access technology (RAT) while in a connected mode with the serving cell, wherein the system information message comprises a neighbor list, information indicating coverage by a second RAT, carrier frequency information regarding the second RAT, or information directing the UE to an allowed public land mobile network (PLMN);
means for initiating, at the UE, a transition from the connected mode with the serving cell to an idle mode with the serving cell in response to the received system information message; and
means for performing a reselection from the idle mode with the serving cell to a target cell utilizing the second RAT in response to the received system information message.
28. A non-transitory computer-readable medium storing code for wireless communication, the code comprising instructions executable for:
receiving, at a user equipment (UE), a system information message from a serving cell over a first radio access technology (RAT) while in a connected mode with the serving cell, wherein the system information message comprises a neighbor list, information indicating coverage by a second RAT, carrier frequency information regarding the second RAT, or information directing the UE to an allowed public land mobile network (PLMN);
initiating, at the UE, a transition from the connected mode with the serving cell to an idle mode with the serving cell in response to the received system information message; and
performing a reselection from the idle mode with the serving cell to a target cell utilizing the second RAT in response to the received system information message.