US-12621725-B2 - Coordinated handover

US12621725B2US 12621725 B2US12621725 B2US 12621725B2US-12621725-B2

Abstract

A method for coordinated handover in a system comprising a first UE ( 101 ) communicating with a second UE ( 102 ) using a sidelink channel, wherein both the first UE and the second UE are being served by a source cell ( 104 ). The method includes the first UE detecting (s 402 ) a handover event indicating that the first UE should trigger the source cell to initiate a handover of the first UE from the source cell to a neighbor cell. The method further includes, as a result of the first UE detecting the handover event, the first UE transmitting (s 404 ) to the second UE a handover event message indicating that the first UE has detected the handover event.

Inventors

Peter Ökvist
Tommy Arngren

Assignees

TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

Dates

Publication Date: 20260505
Application Date: 20201001

Claims (13)

1 . A method for coordinated handover in a system comprising a first user equipment (UE) communicating with a second UE using a sidelink channel, wherein both the first UE and the second UE are being served by a source cell, the method comprising: the first UE detecting a handover event indicating that the first UE should trigger the source cell to initiate a handover of the first UE from the source cell to a neighbor cell; and as a result of the first UE detecting the handover event indicating that the first UE should trigger the source cell to initiate the handover of the first UE from the source cell to the neighbor cell, the first UE transmitting to the second UE a handover event message indicating that the first UE has detected the handover event; and the first UE transmitting a measurement report to the source cell, wherein the measurement report comprises measurement information, and the handover event message transmitted to the second UE comprises the measurement information.
2 . The method of claim 1 , wherein the handover event message triggers the second UE to trigger the source cell to initiate a handover of the second UE from the source cell to the neighbor cell.
3 . The method of claim 1 , wherein the first UE detecting the handover event comprises the first UE determining that the first UE should transmit to the source cell the measurement report.
4 . The method of claim 3 , further comprising: the first UE transmitting the measurement report to the source cell; and after transmitting the measurement report, the first UE receiving from the source cell a configuration message comprising configuration information, wherein the handover event message transmitted to the second UE comprises the configuration information.
5 . The method of claim 1 , wherein the first UE detecting a handover event comprises: the first UE obtaining a first measurement result associated with the source cell and the first UE obtaining a second measurement result associated with the neighbor cell, and the handover event message transmitted to the second UE comprises the first measurement result and the second measurement result.
6 . The method of claim 1 , wherein the handover event message comprises configuration information that was contained in a configuration message that was transmitted by the source cell to the first UE.
7 . The method of claim 1 , wherein the handover event message comprises a first measurement result obtained by the first UE and associated with the source cell and a second measurement result obtained by the first UE and associated with the neighbor cell.
8 . The method of claim 1 , wherein the first UE is a first fence-pole device (FPD) of a fence-pole group (FPG), and the second UE is a second FPD of the FPG.
9 . A method for coordinated handover in a system comprising a first user equipment, UE, communicating with a second UE using a sidelink channel, wherein both the first UE and the second UE are being served by a source cell, the method comprising: the second UE receiving a handover event message transmitted by the first UE as a result of the first UE detecting a handover event indicating that the first UE should trigger the source cell to initiate a handover of the first UE from the source cell to a neighbor cell; and after receiving the handover event message, the second UE triggering the source cell to initiate a handover of the second UE from the source cell to the neighbor cell, wherein the first UE transmitted a measurement report to the source cell, the measurement report comprises measurement information, and the handover event message transmitted to the second UE comprises the measurement information.
10 . A first user equipment (UE), the first UE comprising: processing circuitry; and a memory, the memory containing instructions executable by the processing circuitry, wherein the first UE is configured to perform a method comprising: detecting a handover event indicating that the first UE should trigger a source cell to initiate a handover of the first UE from the source cell to a neighbor cell, wherein the source cell serves the first UE and a second UE; as a result of the first UE detecting the handover event, transmitting to the second UE a handover event message indicating that the first UE has detected the handover event; and transmitting a measurement report to the source cell, wherein the measurement report comprises measurement information, and the handover event message transmitted to the second UE comprises the measurement information.
11 . A second user equipment (UE), the second UE comprising: processing circuitry; and a memory, the memory containing instructions executable by the processing circuitry, wherein the second UE is configured to perform a method comprising: receiving a handover event message transmitted by a first UE as a result of the first UE detecting a handover event, wherein both the first UE and the second UE are served by a source cell; and after receiving the handover event message, triggering the source cell to initiate a handover of the second UE from the source cell to a neighbor cell, wherein the first UE transmitted a measurement report to the source cell, the measurement report comprises measurement information, and the handover event message transmitted to the second UE comprises the measurement information.
12 . A non-transitory computer readable storage medium storing a computer program comprising instructions which when executed by processing circuitry of a user equipment (UE) causes the UE to perform the method of claim 1 .
13 . A non-transitory computer readable storage medium storing a computer program comprising instructions which when executed by processing circuitry of a user equipment (UE) causes the UE to perform the method of claim 9 .

Description

CROSS REFERENCE TO RELATED APPLICATIONS This application is a 35 U.S.C. § 371 National Stage of International Patent Application No. PCT/EP2020/077476, filed 2020 Oct. 1. TECHNICAL FIELD Disclosed are embodiments related to coordinated handover in a system comprising a first user equipment (UE) communicating with a second UE using a sidelink channel. BACKGROUND There are situations in which a first UE communicates with a second UE using a device-to-device (D2D) sidelink (SL) channel. As one example, the two UEs may be part of a group of UEs, where each UE is functioning as fence pole device (FPD) in a geo-fencing system, thereby forming a fence pole group (FPG). The relative motion among the UEs in the FPG may be static, but the FPG as whole may move in some direction, for example, as being moved in context of being packets/pallets/wagons carried by a transport truck, train, ship, or other (e.g. container carrying vehicle or vessel). As some point, the FPG may approach the boarder of the cell that is currently serving the FPG. Accordingly, the signal strength from the serving cell may decrease while at the same time the signal strength of a neighboring cell increases. When this situation occurs, a legacy procedure for handover may be triggered. SUMMARY Certain challenges presently exist. For instance, if the first UE and the second UE are far enough apart, then it is possible that the handover procedure is first triggered for the first UE, and then, at a later time, it is triggered for the second UE. The result of this is that the sidelink channel may be lost between the time when the first UE is handed over to the neighbor cell and the time when the second UE is handed over to the neighbor cell because the SL resources are assigned to the UEs by their respective serving cell. With a scenario of an elongated transport object, such loss of the SL channel between the first and second UEs may extend over quite some time. This could cause problems for an application (e.g., a geo-fencing application) running on the UEs that rely on the SL channel. Accordingly, this disclosure in one aspect provides a method for coordinated handover in a system comprising a first UE communicating with a second UE using a sidelink channel, wherein both the first UE and the second UE are being served by a source cell. In one embodiments, the method includes the first UE detecting a handover event indicating that the first UE should trigger the source cell to initiate a handover of the first UE from the source cell to a neighbor cell. The method also includes, as a result of the first UE detecting the handover event, the first UE transmitting to the second UE a handover event message indicating that the first UE has detected the handover event. In one embodiment, the handover event message triggers the second UE to trigger the source cell to initiate a handover of the second UE from the source cell to the neighbor cell. In another embodiment, the method includes the second UE receiving a handover event message transmitted by the first UE as a result of the first UE detecting a handover event. The method further includes, after receiving the handover event message, the second UE triggering the source cell to initiate a handover of the second UE from the source cell to a neighbor cell. In another aspect there is provided a computer program comprising instructions which when executed by processing circuitry causes the processing circuitry to perform any of the methods disclosed herein. In another aspect there is provided a carrier containing the computer program, wherein the carrier is one of an electronic signal, an optical signal, a radio signal, and a computer readable storage medium. A significant advantage of the embodiments disclosed herein is that the embodiments reduce the time between when the first UE is handed over to the neighbor cell and when the second UE is handed over to the neighbor cell. More generally, the embodiments enable all UEs within a particular group (e.g., a FPG) to be handed over to the neighboring cell at essentially the same time. Thus, to the extent the SL channel is lost during the handover from the source cell to the neighbor cell, a new SL channel can be rapidly established. Another advantage is that the process is transparent to the network (e.g., the base station serving the source cell). BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated herein and form part of the specification, illustrate various embodiments. FIG. 1 illustrates a simplified architecture for ProSe. FIG. 2 illustrates an example message flow. FIG. 3 illustrates a geofencing system according to an embodiment. FIG. 4 is a flowchart illustrating a process according to some embodiments. FIG. 5 is a flowchart illustrating a process according to some embodiments. FIG. 6 illustrates a UE according to some embodiments. FIG. 7 is a functional block diagram of a user equipment according to some embodiments. D