US-12621730-B2 - Target cell prioritization for layer 1/layer 2 triggered mobility

US12621730B2US 12621730 B2US12621730 B2US 12621730B2US-12621730-B2

Abstract

In general, the current subject matter relates to target cell prioritization for layer 1/layer 2 triggered mobility (LTM). In some implementations, target cell prioritization for LTM can include receiving, at a serving distributed unit (DU) of a base station from a centralized unit control plane (CU-CP) of the base station, information indicating a handover priority ranking of a plurality of Layer 1/Layer 2 triggered mobility (LTM) target cells of a second DU of the base station, and selecting, at the serving DU and based on the received information, one of the plurality of LTM target cells for handover of service for a user equipment (UE) from the serving DU, and triggering the handover of the service for the UE from the serving DU to the selected target cell. Each of the plurality of LTM target cells from which the serving DU selects satisfies handover criteria.

Inventors

Subramanya CHANDRASHEKAR
Awn MUHAMMAD

Assignees

Rakuten Mobile, Inc.
RAKUTEN SYMPHONY, INC.

Dates

Publication Date: 20260505
Application Date: 20230124

Claims (16)

1 . An apparatus, comprising: at least one processor, and at least one non-transitory storage media storing instructions that, when executed by the at least one processor, cause the at least one processor to perform operations comprising: receiving, at a serving distributed unit (DU) of a base station from a centralized unit control plane (CU-CP) of the base station, information indicating a handover priority ranking of a plurality of Layer 1/Layer 2 triggered mobility (LTM) target cells of a second DU of the base station, and selecting, at the serving DU and based on the received information, one of the plurality of LTM target cells for handover of service for a user equipment (UE) from the serving DU, and triggering the handover of the service for the UE from the serving DU to the selected target cell, wherein each of the plurality of LTM target cells from which the serving DU selects satisfies handover criteria, the handover being a Layer 1/Layer 2 handover triggered by a Layer 1/Layer 2 measurement with respect to the selected target cell of the second DU that is different from the serving DU, wherein the handover priority ranking is based on respective similarities between a serving cell configuration of a serving cell and a target cell configuration of each of the plurality of LTM target cells.
2 . The apparatus of claim 1 , wherein the target cell configuration of each of the plurality of LTM target cells includes at least one of: a configuration regarding guaranteed bit rate (GBR) allocation for GBR data radio bearers (DRBs), a configuration regarding packet data unit (PDU) session to DRB mapping, a configuration regarding a carrier configuration for carrier aggregation, a configuration regarding slice mapping for UE services, and a configuration regarding the UE's accepted DRBs.
3 . The apparatus of claim 2 , wherein at least one target DU including the plurality of LTM target cells provides the target cell configuration for each of the plurality of LTM target cells to the CU-CP in an F1 message.
4 . The apparatus of claim 3 , wherein the at least one target DU also provides a list of changes for the plurality of LTM target cells compared to a serving cell configuration.
5 . The apparatus of claim 1 , wherein the handover priority ranking is based on the configuration of each of the plurality of LTM target cells compared to a configuration of the serving cell.
6 . The apparatus of claim 5 , where the handover priority ranking is re-computed whenever an LTM target cell is added, reconfigured, or removed for the UE.
7 . The apparatus of claim 1 , wherein the handover criteria includes a predetermined threshold radio quality; the operations further comprise determining, at the serving DU, which one or more of the plurality of target cells has a radio quality above the predetermined threshold radio quality; and the selection is among only the one or more determined target cells.
8 . The apparatus of claim 1 , wherein the triggering includes transmitting, from the serving DU to the UE, a Medium Access Control (MAC) control element (CE) message.
9 . The apparatus of claim 1 , wherein the base station has a disaggregated architecture.
10 . The apparatus of claim 1 , wherein the base station includes a Next Generation Radio Access network (NG-RAN) node.
11 . The apparatus of claim 10 , wherein the NG-RAN node includes a gNodeB or an ng-eNodeB.
12 . The apparatus of claim 1 , wherein the base station includes the at least one processor and the at least one non-transitory storage media.
13 . At least one non-transitory storage media storing instructions that, when executed by at least one processor, cause the at least one processor to perform operations comprising: receiving, at a serving distributed unit (DU) of a base station from a centralized unit control plane (CU-CP) of the base station, information indicating a handover priority ranking of a plurality of Layer 1/Layer 2 triggered mobility (LTM) target cells of a second DU of the base station; and selecting, at the serving DU and based on the received information, one of the plurality of LTM target cells for handover of service for the UE from the serving DU, and triggering the handover of the service for a user equipment (UE) from the serving DU to the selected target cell, wherein each of the plurality of LTM target cells from which the serving DU selects satisfies handover criteria, the handover being a Layer 1/Layer 2 handover triggered by a Layer 1/Layer 2 measurement with respect to the selected target cell of the second DU that is different from the serving DU, wherein the handover priority ranking is based on respective similarities between a serving cell configuration of a serving cell and a target cell configuration of each of the plurality of LTM target cells.
14 . The storage media of claim 13 , wherein the target cell configuration of each of the plurality of LTM target cells includes at least one of: a configuration regarding guaranteed bit rate (GBR) allocation for GBR data radio bearers (DRBs), a configuration regarding packet data unit (PDU) session to DRB mapping, a configuration regarding a carrier configuration for carrier aggregation, a configuration regarding slice mapping for UE services, and a configuration regarding the UE's accepted DRBs.
15 . A computer-implemented method, comprising: receiving, at a serving distributed unit (DU) of a base station from a centralized unit control plane (CU-CP) of the base station, information indicating a handover priority ranking of a plurality of Layer 1/Layer 2 triggered mobility (LTM) target cells of a second DU of the base station; and selecting, at the serving DU and based on the received information, one of the plurality of LTM target cells for handover of service for a user equipment (UE) from the serving DU, and triggering the handover of the service for the UE from the serving DU to the selected target cell, wherein each of the plurality of LTM target cells from which the serving DU selects satisfies handover criteria, the handover being a Layer 1/Layer 2 handover triggered by a Layer 1/Layer 2 measurement with respect to the selected target cell of the second DU that is different from the serving DU, wherein the handover priority ranking is based on respective similarities between a serving cell configuration of a serving cell and a target cell configuration of each of the plurality of LTM target cells.
16 . The method of claim 15 , wherein the target cell configuration of each of the plurality of LTM target cells includes at least one of: a configuration regarding guaranteed bit rate (GBR) allocation for GBR data radio bearers (DRBs), a configuration regarding packet data unit (PDU) session to DRB mapping, a configuration regarding a carrier configuration for carrier aggregation, a configuration regarding slice mapping for UE services, and a configuration regarding the UE's accepted DRBs.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS The present application claims priority to and is the 35 U.S.C. 371 United States National Phase application based on International Patent Application No. PCT/US23/61177, filed on Jan. 24, 2023, entitled “TARGET CELL PRIORITIZATION FOR LAYER 1/LAYER 2 TRIGGERED MOBILITY,” which is hereby incorporated by reference in its entirety. TECHNICAL FIELD In some implementations, the current subject matter relates to telecommunications systems, and in particular, to target cell prioritization for layer 1/layer 2 triggered mobility (LTM). BACKGROUND In today's world, cellular networks provide on-demand communications capabilities to individuals and business entities. Typically, a cellular network is a wireless network that can be distributed over land areas, which are called cells. Each such cell is served by at least one fixed-location transceiver, which is referred to as a cell site or a base station. Each cell can use a different set of frequencies than its neighbor cells in order to avoid interference and provide improved service within each cell. When cells are joined together, they provide radio coverage over a wide geographic area, which enables a large number of mobile telephones, and/or other wireless devices or portable transceivers to communicate with each other and with fixed transceivers and telephones anywhere in the network. Such communications are performed through base stations and are accomplished even if the mobile transceivers are moving through more than one cell during transmission. Major wireless communications providers have deployed such cell sites throughout the world, thereby allowing communications mobile phones and mobile computing devices to be connected to the public switched telephone network and public Internet. A mobile telephone is a portable telephone that is capable of receiving and/or making telephone and/or data calls through a cell site or a transmitting tower by using radio waves to transfer signals to and from the mobile telephone. In view of a large number of mobile telephone users, current mobile telephone networks provide a limited and shared resource. In that regard, cell sites and handsets can change frequency and use low power transmitters to allow simultaneous usage of the networks by many callers with less interference. Coverage by a cell site can depend on a particular geographical location and/or a number of users that can potentially use the network. For example, in a city, a cell site can have a range of up to approximately ½ mile; in rural areas, the range can be as much as 5 miles; and in some areas, a user can receive signals from a cell site 25 miles away. The following are examples of some of the digital cellular technologies that are in use by the communications providers: Global System for Mobile Communications (“GSM”), General Packet Radio Service (“GPRS”), cdmaOne, CDMA2000, Evolution-Data Optimized (“EV-DO”), Enhanced Data Rates for GSM Evolution (“EDGE”), Universal Mobile Telecommunications System (“UMTS”), Digital Enhanced Cordless Telecommunications (“DECT”), Digital AMPS (“IS-136/TDMA”), and Integrated Digital Enhanced Network (“iDEN”). The Long Term Evolution, or 4G LTE, which was developed by the Third Generation Partnership Project (“3GPP”) standards body, is a standard for a wireless communication of high-speed data for mobile phones and data terminals. A 5G standard is currently being developed and deployed. 3GPP cellular technologies like LTE and 5G NR are evolutions of earlier generation 3GPP technologies like the GSM/EDGE and UMTS/HSPA digital cellular technologies and allows for increasing capacity and speed by using a different radio interface together with core network improvements. Cellular networks can be divided into radio access networks and core networks. The radio access network (RAN) can include network functions that can handle radio layer communications processing. The core network can include network functions that can handle higher layer communications, e.g., internet protocol (IP), transport layer and applications layer. In some cases, the RAN functions can be split into baseband unit functions and the radio unit functions, where a radio unit connected to a baseband unit via a fronthaul network, for example, can be responsible for lower layer processing of a radio physical layer while a baseband unit can be responsible for the higher layer radio protocols, e.g., MAC, RLC, etc. A base station for a 5G cellular network can include a centralized unit (CU), one or more distributed units (DUs) communicatively coupled to the CU, and one or more radio units (RUs) each communicatively coupled to at least one of the one or more DUs and each configured to be communicatively coupled to one or more mobile phones and/or other user equipments (UEs). The CU can be logically split into a control plane portion CU-CP and one or more user plane portions (CU-UP). During the course of a UE's communicative coup