System and method for returning to 5G after fallback

1. A method, comprising:

receiving, by a wireless station, a fallback connection, for a Fifth Generation (5G) New Radio (NR) standalone-capable end device, from a second network to a first network to support a voice call on the end device, wherein the fallback connection supports a voice-over-Long Term Evolution (VoLTE) call;

detecting, by the wireless station, an end of the VoLTE call; and

initiating, by the wireless station and based on the detecting, a handover of the end device back to the second network, wherein the initiating occurs while the end device is in a radio resource control (RRC) connected mode, and wherein the initiating includes:

identifying whether the end device has dual connectivity capability,

sending, after the detecting and based on the identifying, instructions to initiate a non-standalone connection with the second network via the wireless station when the end device has the dual connectivity capability, and

sending, to the end device and within an RRC Connection Reconfiguration message, radio measurement configurations for NR frequency bands when the end device does not have the dual connectivity capability.

2. The method of claim 1 , wherein wireless station includes an evolved Node B for an Evolved Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (E-UTRAN),

wherein the first network includes the E-UTRAN for an LTE network, and

wherein the second network device includes a 5G network.

3. The method of claim 1 , further comprising:

sending, in response to the receiving, a B1 measurement configuration to the end device during the VoLTE call.

4. The method of claim 3 , wherein the B1 measurement configuration instructs the end device to provide a measurement report when the end device detects leaving a coverage area of the second network.

5. The method of claim 4 , wherein the initiating further comprises:

directing, based on a failure to receive the measurement report, the handover of the end device back to the second network.

6. The method of claim 1 , wherein the initiating includes:

sending, to the end device and without relying on a signal measurement from the end device, a RRC Release message with redirection instructions to the second network.

7. A network device comprising:

an interface to wirelessly communicate with end devices via a first network; and

a processor configured to:

receive a fallback connection, for a Fifth Generation (5G) New Radio (NR) standalone-capable end device, from a second network to the first network to support a voice call on the end device, wherein the fallback connection supports a voice-over-Long Term Evolution (VoLTE) call,

detect an end of the VoLTE call, and

initiate, based on the detecting, a handover of the end device back to the second network, wherein the initiating occurs while the end device is in a radio resource control (RRC) connected mode, and wherein the initiating includes:

identifying whether the end device has dual connectivity capability,

sending, after the detecting and based on the identifying, instructions to initiate a non-standalone connection with the second network via the network device when the end device has the dual connectivity capability, and

sending, to the end device and within an RRC Connection Reconfiguration message, radio measurement configurations for NR frequency bands when the end device does not have the dual connectivity capability.

8. The network device of claim 7 , wherein the network device includes an evolved Node B for an E-UTRAN.

9. The network device of claim 7 , wherein, when the processor detects the end of the VoLTE call, the processor is further configured to:

detect a data session on the first network that continues after the end of the VoLTE call.

10. The network device of claim 7 , wherein the first network includes a LTE network, and wherein the second network device includes a 5G network.

11. The network device of claim 7 , wherein the processor is further configured to:

send, in response to receiving the fallback connection, a B1 measurement configuration to the end device during the VoLTE call, wherein the B1 measurement configuration instructs the end device to provide a measurement report when the end device detects leaving a coverage area of the second network.

12. The network device of claim 7 , wherein, the processor is further configured to:

send, to the end device, a release message for the first network with redirection instructions to the second network.

13. The network device of claim 7 , wherein, when identifying whether the end device has dual connectivity capability, the processor is further configured to:

identify an Evolved Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (E-UTRAN)-NR Dual Connectivity (EN-DC) capability of the end device.

14. A non-transitory computer-readable medium containing instructions executable by at least one processor, the non-transitory computer-readable medium comprising one or more instructions to cause the at least one processor to:

receive, by a wireless station for a first network, a fallback connection, for a Fifth Generation (5G) New Radio (NR) standalone-capable end device, from a second network to the first network to support a voice call on the end device, wherein the fallback connection supports a voice-over-Long Term Evolution (VoLTE) call;

detect, by the wireless station, an end of the VoLTE call; and

initiate, by the wireless station and based on the detecting, a handover of the end device back to the second network, wherein the initiating occurs while the end device is in a radio resource control (RRC) connected mode, and wherein the instructions to initiate the handover further include instructions to:

identify whether the end device has dual connectivity capability;

send, after the detecting and based on the identifying, instructions to initiate a non-standalone connection with the second network via the wireless station when the end device has the dual connectivity capability; and

send, to the end device and within an RRC Connection Reconfiguration message, radio measurement configurations for NR frequency bands when the end device does not have the dual connectivity capability.

15. The non-transitory computer-readable medium of claim 14 , further comprising instructions to cause the at least one processor to:

send, to the end device, a RRC Release message with redirection instructions to the second network and without relying on a signal measurement from the end device.

16. The network device of claim 7 , wherein the processor is further configured to:

store an inter-radio access technology (RAT) neighbor list, and

wherein the initiating further comprises providing direction to another wireless station based on the inter-RAT neighbor list.

17. The network device of claim 7 , wherein the processor is further configured to:

send, to the end device, a RRC Release message with redirection instructions to the second network, wherein sending the RRC Release message is triggered without relying on a signal measurement from the end device.

18. The network device of claim 7 , wherein the processor is further configured to:

send, in response to receiving the fallback connection, a B1 measurement configuration to the end device during the VoLTE call.

19. The method of claim 1 , wherein identifying whether the end device has dual connectivity capability includes identifying whether the end device has an E-UTRAN-NR Dual Connectivity (EN-DC) capability.

20. The non-transitory computer-readable medium of claim 14 , wherein the dual connectivity capability includes an E-UTRAN-NR Dual Connectivity (EN-DC) capability.