Random access procedure for handover

• US 9,936,524 B2
• Filed: 12/24/2014
• Issued: 04/03/2018
• Est. Priority Date: 12/24/2014
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Intel Corporation
• Inventors: Zhu, Jing, Gai, Yi
• Primary Examiner(s): PASIA, REDENTOR M
• Application Number:
  US14/582,364
• Publication Number:
  US 20160192399A1
• Time in Patent Office: 1,196 Days
• CPC Class Codes: H04W 36/0022 for transferring data sessions between adjacent core network technologies
• CPC Class Codes: H04W 74/0833 Random access procedures, e.g. with 4-step access

Abstract

Technology for switching from a wireless local area network (WLAN) to a wireless wide area network (WWAN) is disclosed. A multi-radio access technology (multi-RAT) user equipment (UE) can receive WLAN-specific dedicated physical random access channel (PRACH) allocation information from an evolved node B (eNB) to enable the multi-RAT UE to perform an inter-RAT WLAN-to-WWAN handover. The multi-RAT UE can initiate the inter-RAT WLAN-to-WWAN handover at the multi-RAT UE by performing random access with the eNB using the WLAN-specific dedicated PRACH allocation information.

Claims

1. A multi-radio access technology (multi-RAT) user equipment (UE) operable to switch from a wireless local area network (WLAN) to a wireless wide area network (WWAN), the UE having one or more processors configured to:

receive WLAN-specific dedicated physical random access channel (PRACH) allocation information from an evolved node B (eNB) to enable the multi-RAT UE to perform an inter-RAT WLAN-to-WWAN handover;

initiate the inter-RAT WLAN-to-WWAN handover at the multi-RAT UE by performing random access with the eNB using the WLAN-specific dedicated PRACH allocation information; and

wherein the WLAN-specific dedicated PRACH allocation information includes a time division multiplexing (TDM)-based dedicated PRACH allocation to enable a plurality of multi-RAT UEs to each initiate an inter-RAT WLAN-to-WWAN handover using a same PRACH preamble, a subframe index, and a frame index per cycle, wherein the PRACH preamble is a preamble shared among a group of UEs.

2. The multi-RAT UE of claim 1, wherein the one or more processors are further configured to perform non-contention based random access or contention-based random access with the eNB using the WLAN-specific dedicated PRACH allocation information.

3. The multi-RAT UE of claim 1, wherein the WWAN network includes a Third Generation Partnership Project (3GPP) Long Term Evolution (LTE) Release 8, 9, 10, 11 or 12 network.

4. The multi-RAT UE of claim 1, wherein the one or more processors are further configured to initiate the inter-RAT WLAN-to-WWAN handover by performing at least one of time division multiplexing (TDM) or code division multiplexing (CDM) random access using the WLAN-specific dedicated PRACH allocation information.

5. The multi-RAT UE of claim 1, wherein the one or more processors are further configured to receive WLAN-specific PRACH configuration information that is broadcast from the eNB via a system information block type 2 (SIB2) message, the WLAN-specific PRACH configuration information to be used for performing the inter-RAT WLAN-to-WWAN handover for the multi-RAT UE using the same PRACH preamble.

6. The multi-RAT UE of claim 5, wherein the WLAN-specific PRACH configuration information includes a root sequence number for the WLAN-to-LTE handover, a PRACH configuration index for the WLAN-to-LTE handover, a high speed flag for the WLAN-to-LTE handover, a zero correlation zone configuration for the WLAN-to-LTE handover, and a PRACH frequency offset for the WLAN-to-LTE handover.

7. The multi-RAT UE of claim 1, wherein the one or more processors are further configured to receive the WLAN-specific dedicated PRACH allocation information from the eNB in response to sending a handover request message to the eNB, the handover request message for switching the multi-RAT UE using the same PRACH preamble from operating over the WWAN to operating over the WLAN.

8. The multi-RAT UE of claim 1, wherein the one or more processors are further configured to receive the WLAN-specific dedicated PRACH allocation information in a handover response message, the multi-RAT UE being configured to switch to operating over the WLAN upon receiving the handover response message from the eNB.

9. The multi-RAT UE of claim 1, wherein the one or more processors are further configured to initiate the WLAN-to-WWAN handover at the multi-RAT UE by performing at least one of time division multiplexing (TDM) or code division multiplexing (CDM) random access using a PRACH preamble included in the WLAN-specific dedicated PRACH allocation information, a subframe index included in the WLAN-specific dedicated PRACH allocation information, and a frame index per cycle included in the WLAN-specific dedicated PRACH allocation information.

10. The multi-RAT UE of claim 9, wherein the PRACH preamble is a unique preamble for the UE.

11. The multi-RAT UE of claim 1, wherein the WLAN-to-WWAN handover at the UE occurs in an integrated WLAN and WWAN network.

12. A method for facilitating wireless local area network (WLAN) to wireless wide area network (WWAN) handover, the method comprising:

sending WLAN-specific physical random access channel (PRACH) configuration information from an evolved node B (eNB) to a user equipment (UE), the WLAN-specific PRACH configuration information for WLAN-to-WWAN handover at the UE;

receiving, at the eNB from the UE, a handover request message to switch the UE from operating over the WWAN to operating over the WLAN;

sending a handover response message from the eNB to the UE, the handover response including WLAN-specific dedicated PRACH allocation information, the UE transitioning into operating over the WLAN upon receiving the handover response message from the eNB; and

facilitating the WLAN-to-WWAN handover for the UE, the UE initiating the WLAN-to-WWAN handover by performing at least one of time division multiplexing (TDM) or code division multiplexing (CDM) based random access using the WLAN-specific dedicated PRACH allocation information wherein the WLAN-specific dedicated PRACH allocation information includes the time division multiplexing (TDM)-based dedicated PRACH allocation to enable a plurality of multi-RAT UEs to each initiate an inter-RAT WLAN-to-WWAN handover using a same PRACH preamble, a subframe index, and a frame index per cycle, wherein the PRACH preamble is a preamble shared among a group of UEs.

13. The method of claim 12, further comprising sending the WLAN-specific PRACH configuration information via a system information block 2 (SIB2) message that is broadcast to the UE.

14. The method of claim 12, wherein the WLAN-to-WWAN handover is triggered at the UE in response to WLAN interference that exceeds a defined threshold.

15. The method of claim 12, wherein the WLAN-specific PRACH configuration information includes a root sequence number for the WLAN-to-LTE handover, a PRACH configuration index for the WLAN-to-LTE handover, a high speed flag for the WLAN-to-LTE handover, a zero correlation zone configuration for the WLAN-to-LTE handover, and a PRACH frequency offset for the WLAN-to-LTE handover.

16. The method of claim 12, wherein the handover request message received from the UE to switch from WWAN to WLAN includes a number of data resource blocks (DRBs) offloaded to a WLAN link and associated DRB identifiers (IDs).

17. The method of claim 12, further comprising receiving an additional handover request message from the UE to switch from WLAN to WWAN, the additional handover request message including a number of data resource blocks (DRBs) offloaded to a WWAN link and associated DRB identifiers (IDs).

18. A user equipment (UE) operable to switch from a wireless local area network (WLAN) to a wireless wide area network (WWAN), the UE comprising:

a communication module configured to receive time division multiplexing (TDM)-based WLAN-specific dedicated physical random access channel (PRACH) allocation information from an evolved node B (eNB) to enable the UE to perform the WLAN-to-WWAN handover, wherein the communication module is stored in a digital memory device or is implemented in a hardware circuit; and

a handover module configured to initiate the WLAN-to-WWAN handover at the UE by performing TDM-based non-contention based random access with the eNB using the WLAN-specific dedicated PRACH allocation information, wherein the WLAN-specific dedicated PRACH allocation information includes the time division multiplexing (TDM)-based dedicated PRACH allocation to enable a plurality of multi-RAT UEs to each initiate an inter-RAT WLAN-to-WWAN handover using a same PRACH preamble, a subframe index, and a frame index per cycle, wherein the PRACH preamble is a preamble shared among a group of UEs, and the handover module is stored in a digital memory device or is implemented in a hardware circuit.

19. The UE of claim 18, wherein the WWAN network includes a Third Generation Partnership Project (3GPP) Long Term Evolution (LTE) Release 8, 9, 10, 11 or 12 network.

20. The UE of claim 18, wherein the communication module is further configured to receive WLAN-specific PRACH configuration information that is broadcast from the eNB via a system information block type 2 (SIB2) message, the WLAN-specific PRACH configuration information to be used for performing the WLAN-to-WWAN handover at the UE.

21. The UE of claim 18, wherein the communication module is further configured to receive the TDM-based WLAN-specific dedicated PRACH allocation information from the eNB in response to sending a handover request message to the eNB, the handover request message for switching the UE from operating over the WWAN to operating over the WLAN.

22. The UE of claim 18, wherein the handover module is further configured to initiate the WLAN-to-WWAN handover at the UE by performing time division multiplexing (TDM) non-contention based random access using a PRACH preamble included in the WLAN-specific dedicated PRACH allocation information, a subframe index included in the WLAN-specific dedicated PRACH allocation information, and a frame index per cycle included in the WLAN-specific dedicated PRACH allocation information.