US-12628053-B2 - Method and apparatus for conditional handover

US12628053B2US 12628053 B2US12628053 B2US 12628053B2US-12628053-B2

Abstract

An apparatus comprising means for receiving requests from a plurality of master nodes to be included added as a secondary node into as part of a conditional handover process for a user equipment; means for obtaining, from each of said requests, an identification of the user equipment involved in the conditional handover process; and means for determining, based on said identifications of the user equipment, that a plurality of said requests concern the same user equipment.

Inventors

Krzysztof Kordybach
Srinivasan Selvaganapathy
Ahmad Awada
Subramanya CHANDRASHEKAR

Assignees

NOKIA TECHNOLOGIES OY

Dates

Publication Date: 20260512
Application Date: 20220317
Priority Date: 20210506

Claims (18)

1 . An apparatus comprising at least one processor and at least one memory, said at least one memory stored with computer program code thereon, the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to perform: receive requests from a plurality of master nodes to be added as a secondary node as part of a conditional handover process for a user equipment; obtain, from each of said requests, an identification of the user equipment involved in the conditional handover process, wherein the identification of the user equipment is unique among said master nodes sending requests to be added as a secondary node; and determine, based on said identifications of the user equipment, that a plurality of said requests concern the same user equipment.
2 . The apparatus according to claim 1 , wherein the identification of the user equipment is temporary such that its validity is dependent on a preparation time for the conditional handover process.
3 . The apparatus according to claim 1 , comprising computer program code configured to cause the apparatus to perform: obtain the identification of the user equipment from an Addition Request received from a master node.
4 . The apparatus according to claim 3 , wherein the identification of the user equipment comprises an identification of a secondary node to a current serving node of the user equipment included in the Addition Request.
5 . The apparatus according to claim 4 , wherein the identification of the user equipment further comprises an identification of the current serving node of the user equipment included in the Addition Request.
6 . The apparatus according to claim 4 , wherein the identification of the user equipment comprises a random number, generated by the current serving node of the user equipment or the secondary node to a current serving node of the user equipment, included in the Addition Request.
7 . The apparatus according to claim 4 , wherein the identification of the user equipment comprises an identification of the current serving node of the user equipment and the identification of the user equipment in the current serving node of the user equipment, both included in the Addition Request.
8 . The apparatus according to claim 4 , comprising computer program code configured to cause the apparatus to perform: obtain, from at least one of said master nodes, a request to release radio resources reserved for the user equipment by the apparatus in response to the master node receiving a conditional handover cancel request from the current serving node of the user equipment.
9 . The apparatus according to claim 8 , wherein the conditional handover cancel request comprises the temporary identification for the Secondary Cell Group configuration.
10 . The apparatus according to claim 1 , comprising computer program code configured to cause the apparatus to perform: generate a temporary identification for a Secondary Cell Group configuration; and include the temporary identification for the Secondary Cell Group configuration in acknowledgement messages to be sent to one or more of said plurality of master nodes.
11 . A method comprising: receiving, by an access node, requests from a plurality of master nodes to be added as a secondary node as part of a conditional handover process for a user equipment; obtaining, from each of said requests, an identification of the user equipment involved in the conditional handover process, wherein the identification of the user equipment is unique among said master nodes; and determining, based on said identifications of the user equipment, that a plurality of said requests concern the same user equipment.
12 . The method according to claim 11 , wherein the identification of the user equipment is temporary such that its validity is dependent on a preparation time for the conditional handover process.
13 . The method according to claim 11 , wherein the identification of the user equipment is obtained from an Addition Request received from a master node.
14 . The method according to claim 13 , wherein the identification of the user equipment comprises an identification of a secondary node to a current serving node of the user equipment included in the Addition Request.
15 . The method according to claim 14 , wherein the identification of the user equipment comprises an identification of the current serving node of the user equipment and the identification of the user equipment in the current serving node of the user equipment, both included in the Addition Request.
16 . The method according to claim 14 , wherein the identification of the user equipment comprises a random number, generated by the current serving node of the user equipment or the secondary node to a current serving node of the user equipment, included in the Addition Request.
17 . The method according to claim 14 , comprising obtaining, from at least one of said master nodes, a request to release radio resources reserved for the user equipment by the access node in response to the master node receiving a conditional handover cancel request from the current serving node of the user equipment.
18 . The method according to claim 11 , comprising generating, by the access node, a temporary identification for a Secondary Cell Group configuration; and including the temporary identification for the Secondary Cell Group configuration in acknowledgement messages to be sent to one or more of said plurality of master nodes.

Description

RELATED APPLICATION This application was originally filed as a Patent Cooperation Treaty Application No. PCT/EP2022/056981, filed on Mar. 17, 2022, which claims priority from Indian provisional application No. 202141020659 filed on May 6, 2021, both of which are hereby incorporated by reference in their entirety. TECHNICAL FIELD The present invention relates to handover methods. BACKGROUND A conditional handover (CHO) is a feature supported in LTE and in 5G NR. The CHO resembles in many aspects the previously known “ordinary” handover (HO), i.e. the legacy HO. As a main difference to the legacy HO, in the CHO the user equipment (UE) starts the preparations for handover to the target node only when an additional CHO execution condition is met. Another difference between the legacy HO and the CHO is the preparation of multiple target cells in the CHO. Thus, the CHO reserves more resources at target cells than a legacy HO while waiting for the execution. In case of multiple preparations, each of the target Master Nodes (MNs) may prepare its own target Secondary Node (SN). Each target SN will therefore have to reserve the needed resources, too. The CHO has also been specified for UEs configured with use of Dual Connectivity. Therein, the source MN node sends a handover request to a plurality of target MNs, which in turn select a target SN and prepares it as part of the CHO preparation. The handover request may concern a single UE; i.e. a handover request concerning one UE is sent to a plurality of target MNs, which in turn may select a common target SN for the CHO preparation. However, while the target MNs are aware of each preparation that concerns the same UE and may therefore optimize the radio resource reservation accordingly, the target SN has no means identify the handover request concerning the same UE, and therefore the target SN has to carry out the radio resource reservation as if each of the handover requests were concerning a different UE. SUMMARY Now, an improved method and technical equipment implementing the method has been invented, by which the above problems are alleviated. Various aspects include a method, an apparatus and a non-transitory computer readable medium comprising a computer program, or a signal stored therein, which are characterized by what is stated in the independent claims. Various details of the embodiments are disclosed in the dependent claims and in the corresponding images and description. The scope of protection sought for various embodiments of the invention is set out by the independent claims. The embodiments and features, if any, described in this specification that do not fall under the scope of the independent claims are to be interpreted as examples useful for understanding various embodiments of the invention. According to a first aspect, there is provided an apparatus comprising means for receiving requests from a plurality of master nodes to be added as a secondary node as part of a conditional handover process for a user equipment; means for obtaining, from each of said requests, an identification of the user equipment involved in the conditional handover process; and means for determining, based on said identifications of the user equipment, that a plurality of said requests concern the same user equipment. An apparatus according to a second aspect comprises at least one processor and at least one memory, said at least one memory stored with computer program code thereon, the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to perform: receive requests from a plurality of master nodes to be added as a secondary node as part of a conditional handover process for a user equipment; obtain, from each of said requests, an identification of the user equipment involved in the conditional handover process; and determine, based on said identifications of the user equipment, that a plurality of said requests concern the same user equipment. According to an embodiment, the identification of the user equipment is unique among said master nodes. According to an embodiment, the identification of the user equipment is temporary such that its validity is dependent on a preparation time for the conditional handover process. According to an embodiment, the apparatus comprises computer program code configured to cause the apparatus to perform: obtain the identification of the user equipment from an Addition Request received from a master node. According to an embodiment, the identification of the user equipment comprises an identification of a secondary node to a current serving node of the user equipment included in the Addition Request. According to an embodiment, the identification of the user equipment further comprises an identification of the current serving node of the user equipment included in the Addition Request. According to an embodiment, the identification of the user equipment comprises