COMMUNICATIONS DEVICES, INFRASTRUCTURE EQUIPMENT, AND METHODS

Abstract

A method for operating infrastructure equipment of a source wireless communication network in a conditional handover is provided. The method configures one or more conditions for triggering a handover of a communication device from a source cell provided by the source infrastructure equipment to a target cell provided by target infrastructure equipment of the wireless communication network. The method transmits to the communication device an indication of the one or more conditions for triggering the handover of the communication device from the source cell to the target cell. The method determines that a change has occurred or is expected to occur in a Network Energy Saving (NES) mode of at least one of the source cell and the target cell. In response, the method transmits the evaluation trigger signal to the communication device. The evaluation trigger signal instructs the communication device to evaluate one or more of the conditions for triggering the handover of the communication device from the source cell to the target cell.

Description

[Technical Field]

[0001] The present disclosure relates to communication devices, infrastructure equipment of a wireless communication network, and methods of operating communication devices and infrastructure equipment of a wireless communication network in a conditional handover.

[0002] This application claims Paris Agreement priority from European Patent Application No. EP22216609.2, the entire contents of which are incorporated herein by reference.

[0003] The "Background" discussion provided herein is intended to generally provide a context for the present disclosure. The work of the currently named inventor(s) (to the extent described in the Background section) and aspects of the description that may not be admitted as prior art at the time of filing this application are not admitted, expressly or impliedly, as prior art to the present invention.

[0004] Third- and fourth-generation mobile communication systems, such as those based on the UMTS and LTE (Long Term Evolution) architectures defined by 3GPP®, can support more sophisticated services than the simple voice and messaging services offered by previous generations of mobile communication systems. For example, thanks to the improved air interface and increased data rates offered by LTE systems, users can enjoy high-data-rate applications, such as mobile video streaming and mobile video conferencing, that were previously only available over fixed-line data connections. Therefore, there is a strong demand for deploying such networks, and their coverage areas, i.e., the geographic locations where they can be connected, are expected to increase at an ever-increasing rate.

[0005] Future wireless communication networks are expected to routinely and efficiently support communication with a wider range of devices involving more diverse data traffic profiles and types than current systems are optimized to support. For example, it is envisioned that future wireless communication networks will be expected to efficiently support communication with devices including reduced complexity devices, MTC (Machine Type Communication) devices, high-resolution video displays, VR headsets, etc. Some of these various devices, e.g., low-complexity devices to support the "Internet of Things," will be deployed in large numbers and may typically engage in the transmission of relatively small amounts of data with relatively high latency tolerances.

[0006] In light of this, future wireless communication networks, such as those sometimes referred to as 5G or New Radio (NR) systems / New Radio Access Technology (RAT) systems [1], as well as future iterations / releases of existing systems, will need to efficiently support connectivity for a wide range of devices associated with various applications and various characteristic data traffic profiles. Traditionally, connectivity for each device is maintained through a so-called "handover" procedure, in which a communication device switches its access point to a wireless communication network in response to instructions from the wireless communication network or when one or more conditions are met. Given the increasing diversity of device types and capabilities in future wireless communication networks, improvements to handover procedures are needed. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] US Patent Application Publication No. 2019 / 223073 [Patent Document 2] International Publication No. 2022 / 151297 [Patent Document 3] International Publication No. 2022 / 091037 [Non-patent literature]

[0008] [Non-Patent Document 1] JUHA KORHONEN ET AL, "[PRE120]

[0304] [NES] Summary of Connected Mode Mobility - 8.3.5 (Nokia)", Vol. {0} 3GPP RAN 2, No. {0} Toulouse, FR; 20221114 - 20221118, 16 November 2022 (2022-11-16), 3GPP DRAFT; R2-2213703; TYPE DISCUSSION; FS_NETW_ENERGY_NR, 3RD GENERATION PARTNERSHIP PROJECT (3GPP), MOBILE COMPETENCE CENTRE; 650, ROUTE DES LUCIOLES; FRANCE Summary of the Invention [Problem to be solved by the invention]

[0009] The present disclosure helps to address or alleviate at least some of the above-mentioned problems. [Means for solving the problem]

[0010] According to an example embodiment, a method for operating infrastructure equipment of a source wireless communication network in a conditional handover can be provided. The method configures one or more conditions for triggering a handover of a communication device from a source cell provided by the source infrastructure equipment to a target cell provided by target infrastructure equipment of the wireless communication network. The method transmits to the communication device an indication of the one or more conditions for triggering the handover of the communication device from the source cell to the target cell. The method determines that a change has occurred or is expected in a Network Energy Saving (NES) mode of at least one of the source cell and the target cell. In response, the method transmits the evaluation trigger signal to the communication device. The evaluation trigger signal instructs the communication device to evaluate one or more of the conditions for triggering the handover of the communication device from the source cell to the target cell.

[0011] Exemplary embodiments also provide a method for operating a communication device in a conditional handover. The method includes receiving, from infrastructure equipment of a source wireless communication network, an indication of one or more conditions for triggering a handover of the communication device from a source cell provided by the source infrastructure equipment to a target cell provided by target infrastructure equipment of the wireless communication network. The method also includes receiving, from the source infrastructure equipment, an evaluation trigger signal instructing the communication device to evaluate one or more of the conditions for triggering the handover of the communication device from the source cell to the target cell. The evaluation trigger signal is received by the communication device from the source infrastructure equipment in response to a change or an expected change in a Network Energy Saving (NES) mode of at least one of the source cell and the target cell. In response, the method evaluates one or more of the conditions for triggering the handover of the communication device from the source cell to the target cell. The method determines that one or more of the evaluated conditions are satisfied. In response, the method initiates the handover of the communication device from the source cell to the target cell.

[0012] According to embodiments, an energy-efficient conditional handover can be provided in a wireless communication network by transmitting an evaluation trigger signal to a communication device in response to determining that an NES mode change has occurred or is expected to occur in at least one of a source cell and a target cell. The transmission of the evaluation trigger signal enables the wireless communication network to control when the communication device evaluates one or more conditions for handover based on the change or expected change in the NES mode of the source cell and / or the target cell. Because the communication device evaluates one or more of the conditions in response to receiving the evaluation trigger signal (instead of the periodic or continuous evaluation characteristic of conventional conditional handover), fewer condition evaluations are expected to be performed before reaching a positive evaluation result (i.e., a determination that one or more of the conditions are satisfied), thereby reducing energy consumption of the wireless communication network. Furthermore, as will be appreciated from the detailed description below, the transmission of the evaluation trigger signal in response to determining that an NES mode change has occurred or is expected in at least one of a source cell and a target cell means that the communication device can switch cells (or remain in a cell) in response to the change or expected change in the NES mode. For example, the wireless communication network may efficiently control which communication devices are placed into which cells in response to changes in NES mode, for example, according to a network planning strategy.

[0013] Aspects and features of the present disclosure are defined by the following claims.

[0014] It is to be understood that both the foregoing general description and the following detailed description are exemplary of the present technology and are not restrictive thereof. The described embodiments, together with further advantages, will be best understood by reference to the following detailed description taken in conjunction with the accompanying drawings, in which:

[0015] The present disclosure and many of the attendant advantages thereof will be readily appreciated as the same becomes better understood by reference to and consideration of the following detailed description in conjunction with the accompanying drawings, in which like reference characters refer to the same or corresponding parts throughout the several views. [Brief explanation of the drawings]

[0016] [Figure 1] 1 illustrates generally certain aspects of an LTE-type wireless communication system that may be configured to operate in accordance with certain embodiments of the present disclosure; [Figure 2] 1 illustrates generally certain aspects of a New Radio Access Technology (RAT) wireless communication system that may be configured to operate in accordance with certain embodiments of the present disclosure. [Figure 3] 1 is a schematic block diagram of an example of a source infrastructure equipment controlling a handover of a communication device to a target infrastructure equipment. [Figure 4] 1 illustrates a schematic diagram of a conventional conditional handover procedure. [Figure 5] 1 is a flow diagram illustrating a method for operating infrastructure equipment of a source wireless communication network in a conditional handover according to example embodiments. [Figure 6] FIG. 1 is a flow diagram illustrating a method of operating a communications device in a conditional handover according to example embodiments. DETAILED DESCRIPTION OF THE INVENTION

[0017] [LTE+ (Long Term Evolution Advanced) radio access technology (4G)] 1 is a schematic diagram illustrating some basic features of a mobile communications network / system 100 that generally operates according to LTE principles, but may support other radio access technologies, and may be adapted to implement embodiments of the present disclosure described herein. Certain aspects of the various elements of FIG. 1 and their modes of operation are known and defined in the relevant standards administered by the 3GPP (RTM) organization and described in numerous publications, e.g., Holma H. ​​and Toskala A. [2]. It will be understood that aspects of the operation of the communications network described herein that are not described in detail (e.g., regarding specific communication protocols and physical channels for communicating between different elements) may be implemented in accordance with any known technology, e.g., the relevant standards and known proposed amendments and additions to those standards.

[0018] The network 100 includes multiple base stations 101 connected to a core network portion 102. Each base station provides a support area 103 (e.g., a cell) over which data can be communicated with each communication device 104. Data is transmitted from the base station 101 to each communication device 104 within its respective support area 103 via a wireless downlink. Data is also transmitted from each communication device 104 to the base station 101 via a wireless uplink. The core network portion 102 routes data to each communication device 104 via each base station 101 and provides functions such as authentication, mobility management, and charging. Each communication device may also be referred to as a mobile station, user equipment (UE), user terminal, portable radio, terminal device, etc. A base station, which is an example of network infrastructure equipment / network access node, may also be referred to as a transceiver station / Node B / e-Node B, g-Node B (gNB), etc. In this regard, various terminology may often be associated with different generations of wireless communication systems for elements providing generally equivalent functionality. However, the exemplary embodiments of the present disclosure may equally be implemented in different generations of wireless communication systems, such as 5G or New Radio (NR), as described below, and for simplicity, specific terminology may be used regardless of the underlying network architecture. That is, the use of specific terminology in connection with some exemplary implementations is not intended to indicate that these implementations are limited to the particular generation of networks that may be most relevant to such specific terminology.

[0019] [New Radio Access Technology (RAT) (5G)] FIG. 2 is a schematic diagram illustrating a network architecture for a new RAT wireless communication network / system 200 based on a previously proposed approach that may also be adapted to provide functionality according to embodiments of the present disclosure described herein. The new RAT network 200 shown in FIG. 2 includes a first communication cell 201 and a second communication cell 202. Each communication cell 201, 202 includes a control node (centralized unit) 221, 222 that communicates with a core network component 210 via wired or wireless links 251, 252. Each control node 221, 222 also communicates with multiple distributed units (radio access nodes / remote transmission and reception points (TRPs)) 211, 212, respectively, within their respective cells. Again, these communications may be via wired or wireless links. The distributed units 211, 212 are responsible for providing a radio access interface for each communication device connected to the network. Each distributed unit 211, 212 has a support area (radio access footprint) 241, 242, where the sum of the support areas of the distributed units defines the support area of ​​each communication cell 201, 202 under control of a control node. Each distributed unit 211, 212 has transceiver circuitry for transmitting and receiving radio signals and processing circuitry configured to control each distributed unit 211, 212.

[0020] From a broad high-level functional perspective, the core network component 210 of the new RAT communication network shown in Figure 2 can be considered to correspond broadly to the core network 102 shown in Figure 1, and each control node 221, 222 and their associated distributed units / TRPs 211, 212 can be considered to provide functionality broadly corresponding to the base station 101 of Figure 1. The term network infrastructure equipment / access node can be used to include these elements as well as more traditional base station-type elements in wireless communication systems. Depending on the application, scheduling responsibility for planned transmissions over the air interface between each distributed unit and each communication device can reside with the control node / centralized unit and / or the distributed unit / TRP.

[0021] A communication device or user equipment 260 is shown in Figure 2 within the support area of ​​a first communication cell 201. This communication device 260 may therefore exchange signaling with a first control node 221 in the first communication cell via one of the distributed units 211 associated with the first communication cell 201. It will be appreciated that in some cases, communications for a given communication device are routed through only one of the distributed units, although in some other embodiments, communications associated with a given communication device may be routed through two or more distributed units, for example, in soft handover or other scenarios.

[0022] For simplicity, the example of Figure 2 shows two communication cells 201, 202 and one communication device 260, but of course in reality the system may include multiple communication cells (each supported by a control node and multiple distributed units) serving multiple communication devices.

[0023] It will be further understood that FIG. 2 is merely one example of a proposed architecture for a new RAT communication system that may employ techniques consistent with the principles described herein, and that the functionality disclosed herein may also be applicable to wireless communication systems having different architectures.

[0024] Accordingly, exemplary embodiments of the present disclosure described herein may be implemented on wireless communication systems / networks according to a wide variety of architectures, such as the exemplary architectures shown in FIG. 1 and FIG. 2 . Accordingly, it will be understood that the particular wireless communication architecture in any given implementation is not particularly important to the principles described herein. In this regard, exemplary embodiments of the present disclosure are generally described in the context of communications between network infrastructure equipment / access nodes and communication devices, but the specific nature of the network infrastructure equipment / access nodes and communication devices will depend on the network infrastructure for the implementation. For example, in some scenarios, the network infrastructure equipment / access nodes may include base stations, such as the LTE-type base station 101 shown in FIG. 1 , adapted to provide functionality according to the principles described herein. In other examples, the network infrastructure equipment / access nodes may include control units / control nodes 221, 222 and / or TRPs 211, 212 of the type shown in FIG. 2 , adapted to provide functionality according to the principles described herein.

[0025] A wireless communication network in which a handover can be performed is shown in detail in Figure 3. As can be seen in Figure 3, a communication device 502 is handed over from a source cell provided by source infrastructure equipment 504 to a target cell provided by target infrastructure equipment 506. The source and target cells are not shown in Figure 3 for clarity, but it will be understood that the source and target cells may broadly correspond to cells 3 and 12, as described above in conjunction with Figures 1 and 2. The source and target infrastructure equipment 504 and the target infrastructure equipment 506 form part of a radio access network for a core network 508. As can be seen, the communication device 502 is an example of a communication device, such as communication device 260 of Figure 2. The communication device 502 may, in one example, be user equipment.

[0026] Prior to the handover, the communications device 502 transmits signals on the uplink UL and receives signals on the downlink DL from the source infrastructure equipment 504. The source infrastructure equipment 504 and the target infrastructure equipment 506 can each be thought of as a combination of the gNB 101 or control node 221 and the TRP 211. Before the handover, the communications device 502 is shown transmitting uplink data to the source infrastructure equipment 504 over uplink resources UL of the radio access interface, as indicated generally by the dashed arrow 274b directed towards the source infrastructure equipment 504. The communications device 502 can similarly be configured to receive downlink data transmitted from the source infrastructure equipment 504 over downlink resources DL, as indicated generally by the dashed arrow 288b from the source infrastructure equipment 504 towards the communications device 502. After the handover, the communications device 502 is shown transmitting uplink data to the target infrastructure equipment 506 over uplink resources UL of the radio access interface, as indicated generally by the solid arrow 288a directed towards the target infrastructure equipment 506. The communication device 502 may similarly be configured to receive downlink data transmitted from the target infrastructure equipment 506 via downlink resources DL, as indicated by the solid arrow 274a from the target infrastructure equipment 506 toward the communication device 502.

[0027] 3, the source and target infrastructure equipment 504, 506 are connected to a core network 508 via interfaces 278, 279 to controllers 504c, 506c of each infrastructure equipment 504. The source and target infrastructure equipment 504, 506 have receivers 504b, 506b connected to antennas 504d, 506d, respectively, and transmitters 504a, 506a connected to antennas 504d, 506d, respectively. Correspondingly, the communication device 502 has a controller 502c connected to a receiver 502b that receives signals from antenna 502d, and a transmitter 502a also connected to antenna 502d.

[0028] The controllers 504c and 506c are configured to control the source and target infrastructure devices 504 and 506, respectively. The controllers 504c and 506c may include processing circuitry, which in turn may include various subunits / subcircuits to provide functionality as described further herein. These subunits may be implemented as separate hardware elements or as functions of appropriately configured processing circuitry. Thus, the controllers 504c and 506c may include circuitry appropriately configured / programmed to provide the desired functionality using conventional programming / configuration techniques for devices used in wireless communication systems. The transmitters 504a and 506a and receivers 504b and 506b may include signal processing and radio frequency filters, amplifiers, and circuitry according to conventional configurations. The transmitters 504a and 506a, receivers 504b and 506b, and controllers 504c and 506c are shown in FIG. 3 schematically as separate elements for simplicity. However, it will be appreciated that the functionality of these elements may be provided in a variety of ways, such as by using one or more appropriately programmed programmable computers, or by using one or more appropriately configured application specific integrated circuits (ASICs) / circuitry / chips / chipsets. As will be appreciated, infrastructure equipment 504 typically includes various other elements associated with its operational functions.

[0029] Correspondingly, the controller 502c of the communication device 502 may include processing circuitry configured to control the transmitter 502a and receiver 502b and may include various subunits / subcircuits to provide functionality as described further herein. These subunits may be implemented as separate hardware elements or as functions of appropriately configured processing circuitry. Thus, the controller 502c may include circuitry appropriately configured / programmed to provide the desired functionality using conventional programming / configuration techniques for wireless communication system equipment. Similarly, the transmitter 502a and receiver 502b may include signal processing and radio frequency filters, amplifiers, and circuitry according to conventional configurations. The transmitter 502a, receiver 502b, and controller 502c are shown schematically in FIG. 3 as separate elements for simplicity. However, it will be appreciated that the functionality of these elements may be provided in a variety of ways, such as using one or more appropriately programmed programmable computers or one or more appropriately configured application-specific integrated circuits (ASICs), circuitry, chips, or chipsets. As will be appreciated, communications device 502 typically includes various other elements associated with its operational functionality, such as a power source, a user interface, etc., although these are not shown in FIG. 3 for simplicity.

[0030] The controllers 504c and 502c may be configured to execute instructions stored in a computer-readable medium, such as a non-volatile memory. The process steps described herein may be performed, for example, by a combination of a microprocessor and random access memory operating according to instructions stored in a computer-readable medium.

[0031] [Conventional conditional handover] Aspects of NR are concerned with improving mobility, particularly mobility robustness for new services that require low latency and high reliability performance (e.g., URLLC). Situations may arise where the cell currently serving a user equipment becomes unsuitable or the radio link between the user equipment and the source gNB providing support within the cell deteriorates. In such situations, it is generally desirable for the user equipment to switch to being served by a cell of a target gNB. One way of structuring a handover of a user equipment from a source gNB to a target gNB is called a "conditional handover."

[0032] An example of a conditional handover is shown in Figure 4, which is reproduced from [3], the entire contents of which are incorporated by reference. Figure 4 schematically illustrates communications over a wireless communication network between a communication device 502, a source infrastructure equipment 504, a target infrastructure equipment 506, other possible target infrastructure equipment 511, an Access Mobility and Mobility Management Function (AMF) 512, and a User Plane Function (UPF) 514. In Figure 4, the source infrastructure equipment 504, the target infrastructure equipment 506, and other possible target infrastructure equipment 511 are depicted as "gNBs," although it will be understood that infrastructure equipment of other wireless communication networks (e.g., eNBs, etc.) may be used. The AMF 512 and the UPF 514 are functions in a core network (e.g., core network 508) of the wireless communication network.

[0033] As shown in FIG. 4, before performing handover, the communication device 502 transmits and receives user plane data to the AMF 512 and the UPF 514 via the source infrastructure equipment 504. In step 0, the AMF 512 provides mobility control information to the source infrastructure equipment 504. In step 1, the communication device 502 reports measurements to the source infrastructure equipment 504. Such measurements may include measurements performed by the communication device 502, such as reference signal received power (RSRP), reference signal received quality (RSRQ), and / or signal-to-interference ratio (SINR) of reference signals from the source infrastructure equipment 504, the target infrastructure equipment 506, and / or other possible target infrastructure equipment 511. In step 2, the source infrastructure equipment 504 decides to configure the communication device 502 for conditional handover (CHO). In step 3, the source infrastructure equipment 504 sends a handover request to the target infrastructure equipment 506 and other possible target infrastructure equipment 511. In response, in step 4, the target infrastructure equipment 506 and other possible target infrastructure equipment 511 perform access control. Then, in step 5, the target infrastructure equipment 506 and other possible target infrastructure equipment 511 send a handover request response to the source infrastructure equipment 504. In response to receiving the handover request response, the source infrastructure equipment 504 sends a conditional handover configuration message to the communication device 502 in step 6. The conditional handover configuration message may be a radio resource control (RRC) configuration message. The conditional handover configuration message includes one or more conditions for triggering a handover of the communication device 502 from a source cell served by the source infrastructure equipment 504.For example, the one or more conditions in the conditional handover configuration message may include one or more conditions to be satisfied to trigger a handover to a target cell provided by the target infrastructure equipment 506 and one or more other conditions to be satisfied to trigger a handover to other target cells provided by other possible target infrastructure equipment 511. The conditions included in the conditional handover configuration message are described in more detail below. After receiving the conditional handover configuration message, the communication device 502 sends an RRC Reconfiguration Complete message to the source infrastructure equipment 504. After receiving the conditional handover configuration message, the communication device 502 may continuously or periodically evaluate the conditions included in the handover configuration message for triggering a handover to determine whether the conditions for triggering a handover are met. If the communication device 502 determines that the conditions for triggering a handover are met, it initiates the handover. For example, the communication device 502 disconnects from a source cell provided by source infrastructure equipment 504 and connects to a target cell provided by target infrastructure equipment 506. In the example shown in Figure 4, the communication device 502 determines that a condition is met to trigger a handover to the target infrastructure equipment 506. While the communication device 502 evaluates the condition, the source infrastructure equipment 604 sends an early status transfer to the other possible target infrastructure equipment in step 7a, and subsequent user data from the UPF 514 is routed via the source infrastructure equipment 504 to the other possible target infrastructure equipment 511.In step 8, the target infrastructure equipment 506 determines that the handover of the communication device 502 from the source cell served by the source infrastructure equipment 504 to the target cell served by the target infrastructure equipment 506 has been successful. In response, the target infrastructure equipment 506 sends a handover success message to the source infrastructure equipment 504 in step 8a. In step 8b, the source infrastructure equipment 504 sends an SN status transfer message to the target infrastructure equipment 506. Subsequent user data from the UPF 514 to the source infrastructure equipment is routed to the target infrastructure equipment 506. In step 8c, a handover cancel message is sent from the source infrastructure equipment 504 to the target infrastructure equipment and other possible target infrastructure equipment 511.

[0034] As described above in step 6 of FIG. 4, the source infrastructure equipment 504 may send a conditional handover configuration message to the communication device 502 that includes one or more conditions for triggering a handover.

[0035] An example of a condition that must be met to trigger a handover of the communication device 502 is "Event A3." The condition defined by Event A3 is met when the signal quality of a cell served by a neighboring infrastructure equipment (e.g., target infrastructure equipment 506 or other possible target infrastructure equipment 511) becomes higher than the signal quality of a cell served by the source infrastructure equipment 504 by a predefined offset.

[0036] Another example of a condition that must be met to trigger a handover of the communication device 502 is "Event A4." The condition defined by Event A4 is met if the cell served by the neighboring infrastructure equipment exceeds an absolute threshold.

[0037] Another example of a condition that must be met to trigger a handover of the communication device 502 is "Event A5." If the signal quality of the cell being served by the source infrastructure equipment 504 is below an absolute threshold and the signal quality of a neighboring infrastructure equipment exceeds an absolute threshold, the condition defined by Event A5 is met.

[0038] The "signal quality" described above with respect to the definition of each of events A3, A4, and A5 may be measured by the communications device 502 using one or more signal quality parameters, such as RSRP, RSRQ, and SINR. For example, the communications device 502 may determine that the condition outlined in event A3 is met if the measured RSRP of a cell served by a neighboring infrastructure equipment is higher than the measured RSRP for the cell served by the source infrastructure equipment 504 by a predefined offset. In another example, the communications device 502 may determine that the condition outlined in event A3 is met if the measured RSRP and RSRQ of a cell served by a neighboring infrastructure equipment are higher than the measured RSRP and RSRQ of the cell served by the source infrastructure equipment 504 by a predefined offset, respectively. The 3GPP Group Release 16 standards support measurements of only one reference signal type and up to two signal quality parameters when determining whether events A3, A4, and / or A5 are met.

[0039] Thus, each of the events A3, A4, and A5 indicates a condition for triggering a handover of the communication device 502 from the source infrastructure equipment 504. To trigger this handover, only one of the conditions included in the conditional handover configuration message may need to be met, or two or more or all of the conditions may need to be met. In one example, only the event A3 is included as a condition, and if the event A3 is met, the handover is triggered. In another example, both the events A3 and A4 are included as conditions, and if either the event A3 or A4 is met, the handover is triggered. In another example, both the events A3 and A4 are included as conditions, and if either the event A3 or A4 is met, the handover is triggered.

[0040] Further details of each of the events A3, A4 and A5 are provided in TS 36.331, the entire contents of which are incorporated by reference.

[0041] [Network Energy Saving (NES)] With release 18 of the 3PP standard, a new research item has been started on NES ([4]). The objectives of this research item are to: (i) Define a base station energy consumption model Objective (i) is expected to include adapting the framework for power consumption modeling and evaluation methodology for NR user equipment power saving (described in [5]) to the base station side. This is expected to include adaptation of the relative DL and UL energy consumption (e.g., power amplifier (PA) efficiency, number of TXRU interfaces, base station load), sleep states and associated transition times, and one or more reference parameters / configurations. (ii) Define evaluation methods and key performance indicators (KPIs). Objective (ii) is expected to include the development of an evaluation methodology to assess system-level network energy consumption and energy-saving effects, and the evaluation / balancing of the impact on network and user performance (e.g., KPIs related to spectral efficiency, capacity, user perceived throughput (UPT), latency, handover performance, call drop rate, initial access performance, and Service Level Agreement (SLA) guarantees), energy efficiency, user equipment power consumption, and complexity. The evaluation methodology is expected to emphasize reusing existing KPIs where applicable, rather than focusing on a single KPI. If existing KPIs are insufficient, new KPIs can be developed as appropriate. It is yet to be determined which KPIs to evaluate and how. (iii) Identify technologies on the gNB and UE side to improve network energy efficiency from both the base station transmission and reception sides. Objective (iii) is expected to include dynamic and / or quasi-static efficient operation and finer granularity adaptation of transmission and / or reception in one or more of network energy saving techniques in the time, frequency, space and power domains with potential support / feedback from and potential assistance information of the user equipment. Objective (iii) is also expected to include information exchange / coordination over the network interface.

[0042] The study item is expected to prioritize idle / empty and low / medium load scenarios, where different loads are allowed between carriers and between adjacent cells. The exact definition of such loads is expected to be determined as part of the study item.

[0043] The research topic is expected to prioritize the following single-carrier and multi-carrier deployment examples: Includes urban micro, time division duplex (TDD) and massive multiple-input multiple-output (MIMO) in FR1, allowing small cells to be modeled. FR2 beam-based scenario (Note: this scenario can also model small cells) Urban / rural macro in FR1 with or without Dynamic Spectrum Sharing (DSS). In the case of DSS, there is no expected impact on LTE. Evolved-Universal Terrestrial Radio Access-New Radio Dual Connectivity (EN-DC) / New Radio Dual Connectivity (NR-DC) macros using Frequency Division Duplex (FDD) primary cells (Pcells) and TDD / Massive MIMO at high FR1 / FR2 frequencies

[0044] Existing user equipment is intended to continue to be able to access networks implementing Release 18 network energy saving technologies, with the exception of technologies specifically developed for greenfield deployments.

[0045] Network Energy Saving (NES) Mode It is proposed that each cell provided by infrastructure equipment of a wireless communication network be configured to operate according to the NES mode. Table 1 (reproduced from [6]) shows examples of the proposed NES modes.

[0046] [Table 1]

[0047] In Table 1, the transition time T of the NES mode is the time it takes for a cell to enter or exit the NES mode. The additional transition energy E of the NES mode is the energy required for a cell to enter or exit the NES mode with respect to the reference energy. The relative power P of the NES mode is the power consumed when a cell enters or exits the NES mode with respect to the reference power.

[0048] As will be understood by those skilled in the art, the relative power of the deep sleep NES mode is lower than the relative power of the light sleep NES mode, which is lower than the relative power of the micro sleep NES mode. In other words, P1 < P2 < P3. Also, as will be understood by those skilled in the art, the relative power of the NES mode of the active UL is lower than that of the NES mode of the active DL. In other words, P5 < P4.

[0049] Table 2 (reproduced from [6]) shows examples of the values of the relative power P for the NES mode shown in Table 1 for different base station categories and reference configuration sets. Further details regarding these base station categories and reference configuration sets are described in [6].

[0050]

Table 2

[0051] In addition to the NES modes suggested in Table 1, other NES modes are contemplated. For example, a cell may be configured to operate according to an NES mode in which the relative power is lower and requires a longer transition time than the deep sleep NES mode. This may be referred to as hibernation sleep, semi-off, or NES mode. Another example of an NES mode is the "OFF" NES mode, in which the cell is turned off for uplink and downlink data transmissions. As will be appreciated by those skilled in the art, communication devices in a cell in the OFF NES mode may still receive reference signals or transmit wake-up signals to wake up the cell.

[0052] Configuring network cells to operate according to an NES mode is expected to improve network energy conservation. For example, different cells in a wireless communication network can operate according to different NES modes according to a network planning strategy. For example, if uplink / downlink traffic is expected to occur in a cell soon, the cell can be configured for a micro-sleep NES mode. On the other hand, if uplink / downlink traffic is not expected to occur in another cell for a significant period of time, the cell can be configured for a deep-sleep NES mode.

[0053] Improvements to conditional handover for NES are described in [6] and [7], the entire contents of which are incorporated by reference. In particular, it has been proposed to improve conditional handover by making the evaluation of conditional handover conditions independent of the NES mode of the source / target cell. However, in existing conditional handover procedures, each communication device periodically or continuously evaluates handover conditions, which can result in energy waste. Furthermore, each communication device may not be aware of changes or expected changes in the NES mode of cells in a wireless communication network. Therefore, each communication device may remain unnecessarily in a cell with an NES mode that is inappropriate for that communication device for an extended period of time, resulting in further energy waste. For example, a communication device may be in a cell that has just entered NES mode, but cannot offload to another cell until it evaluates the conditions for handover. Therefore, improving the energy efficiency of conditional handovers remains a technical challenge.

[0054] Therefore, there is a need for communication devices, infrastructure equipment and methods for improving the energy efficiency of conditional handovers over wireless communication networks.

[0055] A method for operating infrastructure equipment of a source wireless communication network in a conditional handover according to exemplary embodiments is shown in Figure 5. The method begins in step S1.

[0056] After step S1, in step S2, the method configures one or more conditions for triggering a handover of a communication device from a source cell provided by a source infrastructure equipment to a target cell provided by a target infrastructure equipment of the wireless communication network.

[0057] The one or more conditions may be explicitly or implicitly based on the NES mode of at least one of the source cell and the target cell. An example of an explicit condition based on the NES mode of the target cell is that the communication device hands over to the target cell if the target cell is configured to operate according to a light sleep or micro sleep NES mode. An example of an implicit condition based on the NES mode of the target cell is that the communication device hands over to the target cell if the Reference Signal Received Power (RSRP) of the target cell detected by the communication device exceeds a predefined threshold. In this example, the target cell may be configured to operate according to a deep sleep NES mode, and the source infrastructure equipment configures the RSRP threshold relatively high because the target cell is in the deep sleep NES mode. Similarly, if the target cell is configured to operate according to a light sleep NES mode, the source infrastructure equipment may configure the RSRP threshold relatively low (i.e., lower than if the target cell were configured to operate according to the deep sleep NES mode). Further examples of conditions for triggering a handover are described in the "Example Conditions for Handover" section below.

[0058] After step S2, in step S3, the method includes transmitting to the communication device an indication of one or more conditions for triggering a handover of the communication device from the source cell to the target cell. For example, the source infrastructure equipment may transmit a conditional handover configuration message (such as that described in step 6 of FIG. 4) including one or more conditions for triggering the handover. The conditional handover message may be transmitted, for example, as an RRC signal.

[0059] After step S3, in step S4, the method determines that a change to the NES mode of at least one of the source cell and the target cell is necessary or expected.

[0060] It will be understood that a "change in NES mode" of a cell refers to a change of the cell from one NES mode to another NES mode (such as the NES modes shown in Table 1), or a change from a state in which the cell is not operating in an NES mode (the "NES mode OFF" state) to a state in which the cell is operating in an NES mode (the "NES mode ON" state), or a change from a state in which the cell is operating in an NES mode (the "NES mode ON" state) to a state in which the cell is not operating in an NES mode (the "NES mode OFF" state). An example of an "NES mode OFF" state is when the cell is "ON" and not operating in an NES mode. An example of an "NES mode ON" state is when the cell is in an NES mode that is turned off for uplink and downlink data transmission. Another example of an "NES mode ON" state is when the cell is operating in one of the NES modes shown in Table 1.

[0061] The source infrastructure equipment may determine that there has been or is expected to be a change in the NES mode of the source cell, or that there has been or is expected to be a change in the NES mode of the target cell, or that there has been or is expected to be a change in the NES mode of both the source cell and the target cell.

[0062] In some embodiments, the source infrastructure equipment may determine that the NES mode of at least one of the source cell and the target cell has changed (i.e., has already changed). For example, the source infrastructure equipment may determine that the NES mode of the source cell has changed. In some embodiments, the source infrastructure equipment may determine that the NES mode of the target cell has changed based on an indication received from the target infrastructure equipment (e.g., via the Xn interface) that the NES mode of the target cell has changed. In some embodiments, the source infrastructure equipment may determine that the NES mode of the target cell has changed based on receiving an indication from the target infrastructure equipment that the target cell has changed from operating in accordance with an NES mode OFF state to operating in accordance with an NES mode ON state.

[0063] In some embodiments, the source infrastructure equipment may determine that a change in the NES mode of at least one of the source cell and the target cell is expected (i.e., will be changed at some point in the future). For example, the source infrastructure equipment may decide to change the NES mode of the source cell, and in response to this decision, the source infrastructure equipment may transmit an evaluation trigger signal. In another example, the source infrastructure equipment may determine that a change in the NES mode of the target cell is expected based on an indication received from the target infrastructure equipment that a change in the NES mode of the target cell is expected. For example, the target infrastructure equipment may decide to change the NES mode of the target cell and transmit an indication to the source infrastructure equipment that the NES mode of the target cell is to be changed. In one example, the source infrastructure equipment may determine that a change in the NES mode of the target cell is expected based on receiving an indication from the target infrastructure equipment that the target cell is to change from operating according to an NES mode OFF state to operating according to an NES mode ON state.

[0064] After step S4, in response, in step S5, the method transmits an evaluation trigger signal to the communications device, the evaluation trigger signal instructing the communications device to evaluate one or more of the conditions for triggering a handover of the communications device from the source cell to the target cell.

[0065] In some embodiments, the evaluation trigger signal specifically indicates one or more of these conditions to be evaluated by the communications device. For example, the evaluation trigger signal may instruct the communications device to evaluate a subset of the conditions indicated to the communications device by the source infrastructure equipment in step S3. For example, in step S3, the indication of one or more conditions received from the source infrastructure equipment may indicate multiple conditions with "index 1" and "index 2," respectively. Then, in step S5, the evaluation trigger signal may indicate that the condition identified by index 1 should be evaluated by the communications device. In other examples, the evaluation trigger signal instructs the communications device to evaluate all of the conditions indicated to the communications device by the source infrastructure equipment in step S3.

[0066] In some embodiments, the evaluation trigger signal may include an indication of the NES mode of at least one of the source cell and the target cell. For example, one of the conditions may be that if the target cell is in a light sleep NES mode, the communications device should hand over to the target cell. In this example, the evaluation trigger signal instructing the communications device to evaluate the condition also instructs the communications device that the NES mode of the target cell has changed or will be changed to a light sleep NES mode.

[0067] In some embodiments, the target infrastructure equipment determines that the NES mode of the target cell has changed or will change and transmits an instruction to the source infrastructure equipment to transmit an evaluation trigger signal to the communication device. Thus, the source infrastructure equipment determines that a change in the NES mode of the target cell is expected based on an instruction to transmit the evaluation trigger signal received from the target infrastructure equipment. In this case, the determination is an implicit determination based on the instruction to transmit the evaluation trigger signal not including an explicit indication that a change has occurred or is expected in the target cell. In some embodiments, the instruction to transmit the evaluation trigger signal to the communication device is transmitted over an Xn interface between the source infrastructure equipment and the target infrastructure equipment. In such embodiments, the target infrastructure equipment effectively triggers the evaluation of one or more conditions by the communication device. In one example, the target infrastructure equipment can determine that the NES mode of the target cell has changed based on the target cell changing from an NES mode ON state to an NES mode OFF state. For example, the target cell may be activated by a communication device in the target cell transmitting an activation signal to the target infrastructure equipment. Therefore, the target infrastructure equipment can effectively prompt the handover of the communication device to the target cell when the target cell is changed to the NES mode OFF state.

[0068] In some embodiments, the source infrastructure equipment may transmit handover assist information to the target infrastructure equipment. Based on the change or expected change in the NES mode of the target cell and the handover assist information, the target infrastructure equipment may decide to transmit an instruction to the source infrastructure equipment to transmit an evaluation trigger signal. In response, the target infrastructure equipment may transmit the evaluation trigger signal to the source infrastructure equipment. The handover assist information may include one or more of a number of communication devices in the source cell as candidates for handover to the target cell, a quality of service required for each communication device, a service required for each communication device, and a traffic volume required for each communication device.

[0069] In some embodiments, the evaluation trigger signal is a communication device-specific RRC signal. In some embodiments, the evaluation trigger signal is a groupcast RRC signal received by multiple communication devices in the source cell. In this case, the groupcast RRC signal includes a group-common Radio Network Temporary Identifier (RNTI) for identifying the multiple communication devices in the source cell.

[0070] In some embodiments, the evaluation trigger signal is a communication device-specific Medium Access Control (MAC) signal. In some embodiments, the evaluation trigger signal is a groupcast MAC signal received by multiple communication devices in the source cell. In this case, the groupcast MAC signal includes a group-common RNTI for identifying the multiple communication devices in the source cell.

[0071] In some embodiments, the evaluation trigger signal is a MAC Control Element (CE) signal.

[0072] In some embodiments, the evaluation trigger signal is a broadcast signal that is received by multiple communication devices in the source cell.

[0073] In some embodiments, the evaluation trigger signal is included in group-common downlink control information (DCI) received by a plurality of communication devices in the source cell, the group-common DCI including a group-common RNTI for identifying the plurality of communication devices in the source cell.

[0074] The method ends in step S6.

[0075] A method for operating a communications device in conditional handover according to example embodiments is shown in Figure 6. The method begins in step S11.

[0076] After step S11, in step S12, the method receives, from infrastructure equipment of the source wireless communication network, one or more conditions for triggering a handover of the communication device from a source cell provided by the source infrastructure equipment to a target cell provided by a target infrastructure of the wireless communication network.

[0077] After step S12, in step S13, the method receives an evaluation trigger signal from the source infrastructure equipment instructing the communications device to evaluate one or more conditions for triggering a handover of the communications device from the source cell to the target cell, the evaluation trigger signal being received by the communications device from the source infrastructure equipment in response to a change or expected change in the NES mode of at least one of the source cell and the target cell.

[0078] After step S13, in step S14, the method evaluates one or more of the conditions for triggering a handover of the communication device from the source cell to the target cell in response.

[0079] After step S14, in step S15 the method determines that one or more of the evaluated conditions are satisfied.

[0080] After step S15, in response, in step S16, the method initiates a handover of the communication device from the source cell to the target cell.

[0081] Initiating the handover may include disconnecting a radio access interface or radio link provided by the source infrastructure equipment and connecting to a radio access interface or radio link provided by the target infrastructure equipment. Initiating the handover may include establishing a radio connection with the target relay infrastructure equipment. For example, the communication device may initiate an access procedure with the target infrastructure equipment. In one example, the communication device may initiate a Random Access Channel (RACH) procedure with the target infrastructure equipment.

[0082] The method ends in step S17.

[0083] As described above with reference to Figures 5 and 6, the source infrastructure equipment responsively transmits an evaluation trigger signal to the communication device, which evaluates one or more of the above conditions. The communication device determines that the conditions are met and initiates handover. Thus, embodiments enable the wireless communication network to recognize a change or expected change in NES mode and to control when the communication device evaluates the above conditions. Because the communication device evaluates one or more of the conditions in response to receiving the evaluation trigger signal (instead of the periodic or continuous evaluation characteristic of conventional conditional handovers), fewer condition evaluations are expected to be performed before reaching a positive evaluation result (i.e., a determination that one or more of the conditions are met), thereby reducing energy consumption of the wireless communication network. Furthermore, transmitting an evaluation trigger signal in response to determining that the NES mode of at least one of the source and target cells has changed or is expected means that the communication device can switch cells (or remain in a cell) in response to the change or expected change in NES mode. The wireless communication network can, for example, efficiently control which communication devices are placed into which cells in response to changes in NES mode according to a network planning strategy.

[0084] [Evaluation Stop Signal] In some embodiments, an evaluation trigger signal is transmitted by the source infrastructure equipment to the communications device to instruct the communications device to evaluate one or more conditions, and a second subsequent signal (referred to herein as an "evaluation stop signal") is transmitted by the source infrastructure equipment to the communications device to instruct the communications device to stop evaluating the one or more conditions.

[0085] In some embodiments, the source infrastructure equipment may transmit the evaluation stop signal to the communication device in response to another change in the NES mode of at least one of the source cell and the target cell. For example, the source infrastructure equipment may transmit the evaluation trigger signal to the communication device in response to determining that the target cell has changed from an "NES mode ON" state to an "NES mode OFF" state. Then, subsequently, the source infrastructure equipment may transmit the evaluation stop signal to the communication device in response to determining that the target cell has changed from an "NES mode OFF" state to an "NES mode ON" state.

[0086] The evaluation stop signal is sent in response to "another change of the NES mode of at least one of the source cell and the target cell" if: An evaluation trigger signal is sent in response to a change or an expected change in the NES mode of the source cell, and an evaluation stop signal is sent in response to a change or an expected change in the NES mode of the source cell. An evaluation trigger signal is sent in response to a change or expected change of the NES mode of the target cell, and an evaluation stop signal is sent in response to a change or expected change of the NES mode of the target cell. An evaluation trigger signal is sent in response to a change or expected change of the NES mode of the source cell, and an evaluation stop signal is sent in response to a change or expected change of the NES mode of the target cell. An evaluation trigger signal is sent in response to a change or expected change of the NES mode of the target cell, and an evaluation stop signal is sent in response to a change or expected change of the NES mode of the source cell.

[0087] In some embodiments, the evaluation stop signal may be sent based on the expiration of a pre-configured timer.

[0088] Thus, the evaluation trigger signal and the evaluation stop signal may be used to enable and disable evaluation of one or more conditions, respectively. In some embodiments, one or both of the evaluation trigger signal and the evaluation stop signal may be transmitted as a MAC CE. Because the MAC layer is closer to the physical layer than higher layers such as the RRC layer, the use of a MAC CE allows for rapid transmission of the evaluation trigger signal and the evaluation stop signal, and therefore rapid enabling and disabling of evaluation of one or more conditions.

[0089] [Evaluation resume signal] In some embodiments, another signal subsequent to the stop evaluation signal (referred to herein as a "resume evaluation signal") is sent by the source infrastructure equipment to the communications device to instruct the communications device to resume evaluation of one or more conditions.

[0090] In some embodiments, the source infrastructure equipment may transmit the resume evaluation signal to the communications device in response to yet another change in the NES mode of at least one of the source cell and the target cell. For example, the source infrastructure equipment may transmit the stop evaluation signal to the communications device in response to determining that the target cell has changed from an "NES mode OFF" state to an "NES mode ON" state. Then, subsequently, the source infrastructure equipment may transmit the resume evaluation signal to the communications device in response to determining that the target cell has changed from an "NES mode ON" state to an "NES mode OFF" state.

[0091] The evaluation stop signal is sent in response to "further change of the NES mode of at least one of the source cell and the target cell" if: An evaluation stop signal is sent in response to a change or expected change of the NES mode of the source cell, and an evaluation resume signal is sent in response to a change or expected change of the NES mode of the source cell. The evaluation stop signal is sent in response to a change or expected change of the NES mode of the target cell, and the evaluation resume signal is sent in response to a change or expected change of the NES mode of the target cell. An evaluation stop signal is sent in response to a change or expected change of the NES mode of the source cell, and an evaluation resume signal is sent in response to a change or expected change of the NES mode of the target cell. The evaluation stop signal is sent in response to a change or expected change of the NES mode of the target cell, and the evaluation resume signal is sent in response to a change or expected change of the NES mode of the source cell.

[0092] In some embodiments, the resume evaluation signal may be sent based on the expiration of a pre-configured timer.

[0093] Therefore, the resume evaluation signal can be used to re-enable the evaluation of one or more conditions. In some embodiments, the resume evaluation signal can be transmitted as a MAC CE. Because the MAC layer is closer to the physical layer than higher layers such as the RRC layer, using a MAC CE allows for rapid transmission, and the resume evaluation signal can allow for rapid re-enablement of the evaluation of one or more conditions.

[0094] In one example, a wireless communication network may include multiple target cell candidates (e.g., three target cell candidates). The target cell candidates may be provided by the same or different target infrastructure equipment. The source infrastructure equipment may configure a communication device in a source cell provided by the source infrastructure equipment to have configuration for each of the multiple target cell candidates. For example, the communication device may be configured with configuration, such as measurements and / or conditions, for handover to each of the multiple target cell candidates.

[0095] In a conventional conditional handover, a communication device may evaluate handover conditions for each of a number of candidate target cells and will handover to a candidate target cell for which the handover conditions are met (e.g., due to a threshold being met for a certain event).

[0096] However, depending on the exemplary embodiments, the communication device may or may not evaluate handover conditions for target cell candidates based on the NES mode of the target cell candidate. For example, a first and a second candidate among the plurality of target cell candidates may not be in NES mode, and a third candidate among the plurality of target cell candidates may be in NES mode (e.g., the third target cell may be turned off). According to the exemplary embodiments, the communication device may evaluate the conditions for handing over to the first target cell and the second target cell. However, the communication device may determine that the conditions for handing over to the first target cell and the second target cell are not met. In some examples, the communication device continuously evaluates the handover conditions for the first target cell and the second target cell. This evaluation may continue for a certain period of time if the handover conditions are not met. At a later stage, the NES mode of the third target cell may be changed. For example, the third target cell may be turned on. According to example embodiments, the source infrastructure equipment may determine that the NES mode of the third target cell has changed and, in response, transmit a signal to the communication device to instruct it to evaluate conditions for handing over to the third target cell. The communication device may then evaluate conditions for handing over to the first target cell, conditions for handing over to the second target cell, and conditions for handing over to the third target cell. The communication device will first handover to the target cell for which the handover conditions are met. Thus, in some examples, the communication device may handover to the second target cell, in other examples, the communication device may handover to the first target cell, and in other examples, the communication device may handover to the third target cell.In some examples, the communications device then evaluates conditions for handing over to the third target cell instead of conditions for handing over to the first target cell and the second target cell based on the instruction to evaluate conditions for the third target cell being received.

[0097] [Example Conditions for Handover] As mentioned above, the source infrastructure equipment configures one or more conditions for the communication device that, if met, lead to a handover of the communication device from the source cell to the target cell. Further examples of such conditions are as follows: If there has been or is expected to be a change in the source cell to NES mode ON (e.g., to deep sleep NES mode or the cell is turned OFF), the communication device will handover from the source cell to the target cell. In one example, the source infrastructure equipment may send an evaluation trigger signal to the communication device after determining that the NES mode of the source cell has changed. In this way, the source infrastructure equipment can facilitate network energy saving by going to NES mode ON, and thus offload its respective communication device to the target cell. If the target cell has changed or is expected to change to an NES mode OFF state or a low-power NES mode (e.g., to a relatively high-power NES mode such as a light sleep NES mode), the communication device will handover from the source cell to the target cell. In one example, the source infrastructure equipment may send an evaluation trigger signal to the communication device after determining that the NES mode of the target cell has changed. In this way, the target infrastructure equipment can accept the new communication device when it switches to an NES mode OFF state or a low-power NES mode. If the source cell has undergone or is expected to undergo a change to an NES mode OFF state (or to a low-power NES mode (e.g., to a relatively high-power NES mode such as light sleep NES mode)), the communications device will handover from the source cell to the target cell. In one example, the source infrastructure equipment may send an evaluation trigger signal to the communications device after determining that the NES mode of the source cell has changed. In this example, communications devices that wish to operate in NES mode ON may be offloaded to the target cell, facilitating energy conservation. If the target cell has undergone or is expected to undergo a change to an NES mode ON state (e.g., to a deep sleep NES mode), the communication device will handover from the source cell to the target cell. In one example, the source infrastructure equipment may transmit an evaluation trigger signal to the communication device after determining that the NES mode of the target cell has changed. In this way, the target infrastructure equipment can accommodate new communication devices that wish to operate in an NES mode ON state, which promotes energy saving.

[0098] While this disclosure focuses in part on implementations in LTE-based and / or 5G networks to provide specific examples, it will be understood that the same principles are applicable to other wireless communication systems. Thus, while the terminology used herein is generally the same as or similar to that of the LTE and 5G standards, the teachings are not limited to current versions of LTE and 5G, but are equally applicable to any suitable configurations that are not based on LTE or 5G and / or that comply with future versions of LTE, 5G, or other standards.

[0099] It should be noted that various example techniques described herein may rely on predetermined / defined information, in the sense that it is known in advance by both the base station and the communication devices. Such predetermined / defined information may be generally established, for example, by definition in an operating standard for the wireless communication system, or by previously exchanged signaling between the base station and each communication device, such as system information signaling, or in connection with radio resource control configuration signaling, or by information stored in a SIM application. In other words, the specific manner in which relevant predefined information is established and shared between elements of the wireless communication system is not particularly important to the operating principles described herein. Furthermore, it should be noted that various example techniques described herein rely on information exchanged / communicated between various elements of the wireless communication system. Furthermore, unless the context dictates otherwise, such communication is generally performed in accordance with conventional techniques, for example, with respect to a particular signaling protocol and type of communication channel used. In other words, the specific manner in which relevant information is exchanged between various elements of the wireless telecommunication system is not particularly important to the operating principles described herein.

[0100] It will be appreciated that the principles described herein are not limited to any particular type of communications device, but are more generally applicable to any type of communications device, e.g., these techniques are not limited to URLLC / IIoT devices or other low latency communications devices, but are applicable, for example, to any type of communications device that operates using a wireless link to a communications network.

[0101] It will be further appreciated that the principles described herein are applicable to any type of wireless communication system that supports dynamic scheduling of shared communications resources, not just LTE-based or 5G / NR-based wireless communication systems.

[0102] Further particular and preferred aspects of the invention are set out in the accompanying independent and dependent claims. It will be appreciated that features of the independent claims may be combined with features of the dependent claims in combinations other than those explicitly set out in the claims.

[0103] Accordingly, the foregoing discussion discloses and describes merely exemplary embodiments of the present invention. As will be understood by those skilled in the art, the present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The disclosure of the present invention, as well as the remaining claims, is hereby intended to be illustrative and not limiting of the scope of the disclosure. This disclosure defines in part the scope of the preceding claim terms, including readily discernible variations of the teachings herein, so that the inventive subject matter is not dedicated to the public.

[0104] Each feature of the present disclosure is defined by the following numbered paragraphs. Paragraph (1) A method of operating infrastructure equipment of a source wireless communication network in a conditional handover, comprising: configuring one or more conditions for triggering a handover of a communication device from a source cell served by the source infrastructure equipment to a target cell served by a target infrastructure equipment of the wireless communication network; sending an indication of the one or more conditions to the communication device for triggering the handover of the communication device from the source cell to the target cell; determining that a change has occurred or is expected to occur in a Network Energy Saving (NES) mode of at least one of the source cell and the target cell; and in response, transmitting the evaluation trigger signal to the communication device instructing the communication device to evaluate one or more of the conditions for triggering the handover of the communication device from the source cell to the target cell; method. Paragraph (2) The method of Paragraph (1), further comprising: transmitting an evaluation stop signal instructing the communication device to stop evaluating the one or more conditions for triggering the handover of the communication device from the source cell to the target cell; method. Paragraph (3) The method of paragraph 2, further comprising: transmit an evaluation resume signal instructing the communication device to resume evaluation of the one or more conditions for triggering the handover of the communication device from the source cell to the target cell. method. Paragraph (4) The method of paragraph 3, comprising: One or more of the evaluation trigger signal, the evaluation stop signal, and the evaluation resume signal are transmitted in a Medium Access Control (MAC) control element. method. Paragraph (5) The method according to any one of paragraphs 1 to 4, The evaluation trigger signal includes an indication of the NES mode of at least one of the source cell and the target cell. method. Paragraph (6) The method according to any one of paragraphs 1 to 4, The evaluation trigger signal is a radio resource control (RRC) signal dedicated to the communication device. method. Paragraph (7) The method according to any one of paragraphs 1 to 4, The evaluation trigger signal is a groupcast RRC (Radio Resource Control) signal received by a plurality of communication devices in the source cell, the groupcast RRC signal including a group-common RNTI (Radio Network Temporary Identifier) ​​for identifying the plurality of communication devices in the source cell. method. Paragraph (8) The method according to any one of paragraphs 1 to 4, The evaluation trigger signal is a Medium Access Control (MAC) signal dedicated to the communication device. method. Paragraph (9) The method according to any one of paragraphs 1 to 4, The evaluation trigger signal is a groupcast medium access control (MAC) signal received by a plurality of communication devices in the source cell, the groupcast MAC signal including a group-common Radio Network Temporary Identifier (RNTI) for identifying the plurality of communication devices in the source cell. method. Paragraph (10) The method according to any one of paragraphs 1 to 4, The evaluation trigger signal is a broadcast signal received by a plurality of communication devices in the source cell. method. Paragraph (11) The method according to any one of paragraphs 1 to 4, The evaluation trigger signal is included in group-common downlink control information (DCI) received by a plurality of communication devices in the source cell, the DCI including a group-common Radio Network Temporary Identifier (RNTI) for identifying the plurality of communication devices in the source cell. method. Paragraph (12) The method according to any one of paragraphs 1 to 11, Determining that there has been or is expected to be a change in the NES mode of at least one of the source cell and the target cell includes: receiving an indication from the target infrastructure equipment that there has been or is expected to be a change in the NES mode of the target cell. method. Paragraph (13) The method according to paragraph 12, The indication that the NES mode of the target infrastructure device has changed is transmitted over an Xn interface between the source infrastructure device and the target infrastructure device. method. Paragraph (14) The method according to any one of paragraphs 1 to 11, Determining that there has been or is expected to be a change in the NES mode of at least one of the source cell and the target cell includes: receiving an indication from the target infrastructure equipment to transmit the evaluation trigger signal to the communication device in response to a change or anticipated change in the NES mode of the target cell. method. Paragraph (15) The method of Paragraph 14, further comprising: sending handover assist information to the target infrastructure equipment, the handover assist information including one or more of a number of communication devices in the source cell as candidates for handover to the target cell, a quality of service required for the communication devices, a service required for the communication devices, and an amount of traffic required for the communication devices; method. Paragraph (16) A method of operating a communications device in a conditional handover, comprising: receiving, from infrastructure equipment of a source wireless communication network, an indication of one or more conditions for triggering a handover of a communication device from a source cell provided by the source infrastructure equipment to a target cell provided by target infrastructure equipment of the wireless communication network; receiving an evaluation trigger signal from the source infrastructure equipment instructing the communications device to evaluate one or more of the conditions for triggering the handover of the communications device from the source cell to the target cell, the evaluation trigger signal received by the communications device from the source infrastructure equipment in response to a change or expected change in a Network Energy Saving (NES) mode of at least one of the source cell and the target cell; and evaluating one or more of the conditions for triggering the handover of the communication device from the source cell to the target cell; determining that one or more of the evaluated conditions are satisfied, and in response: Initiating the handover of the communication device from the source cell to the target cell method. Paragraph (17) The method of paragraph 16, further comprising: receiving a stop evaluation signal instructing the communication device to stop evaluating the one or more conditions for triggering the handover of the communication device from the source cell to the target cell; method. Paragraph (18) The method of paragraph 16, further comprising: receiving a resume evaluation signal instructing the communication device to resume evaluation of the one or more conditions for triggering the handover of the communication device from the source cell to the target cell; method. Paragraph (19) The method according to paragraph 18, One or more of the evaluation trigger signal, the evaluation stop signal, and the evaluation resume signal are received by a Medium Access Control (MAC) control element. method. Paragraph (20) The method according to any one of paragraphs 16 to 19, The evaluation trigger signal includes an indication of the NES mode of at least one of the source cell and the target cell. method. Paragraph (21) The method according to any one of paragraphs 16 to 20, The evaluation trigger signal is a radio resource control (RRC) signal dedicated to the communication device. method. Paragraph (22) The method according to any one of paragraphs 16 to 20, The evaluation trigger signal is a groupcast RRC (Radio Resource Control) signal received by a plurality of communication devices in the source cell, the groupcast RRC signal including a group-common RNTI (Radio Network Temporary Identifier) ​​for identifying the plurality of communication devices in the source cell. method. Paragraph (23) The method according to any one of paragraphs 16 to 20, The evaluation trigger signal is a Medium Access Control (MAC) signal dedicated to the communication device. method. Paragraph (24) The method according to any one of paragraphs 16 to 20, The evaluation trigger signal is a groupcast medium access control (MAC) signal received by a plurality of communication devices in the source cell, the groupcast MAC signal including a group-common Radio Network Temporary Identifier (RNTI) for identifying the plurality of communication devices in the source cell. method. Paragraph (25) The method according to any one of paragraphs 16 to 20, The evaluation trigger signal is a broadcast signal received by a plurality of communication devices in the source cell. method. Paragraph (26) The method according to any one of paragraphs 16 to 20, The evaluation trigger signal is included in group-common downlink control information (DCI) received by a plurality of communication devices in the source cell, the DCI including a group-common Radio Network Temporary Identifier (RNTI) for identifying the plurality of communication devices in the source cell. method. Paragraph (27) Infrastructure equipment of a source wireless communication network used for conditional handover, comprising: a transmitter configured to transmit a signal; a receiver configured to receive a signal; configuring one or more conditions for triggering a handover of a communication device from a source cell served by the source infrastructure equipment to a target cell served by a target infrastructure equipment of the wireless communication network; sending an indication of the one or more conditions to the communication device for triggering the handover of the communication device from the source cell to the target cell; determining that a change has occurred or is expected to occur in a Network Energy Saving (NES) mode of at least one of the source cell and the target cell; and in response, transmitting the evaluation trigger signal to the communication device instructing the communication device to evaluate one or more of the conditions for triggering the handover of the communication device from the source cell to the target cell; a control unit configured in combination with the transmitting unit and the receiving unit as described above; Equipped with Infrastructure equipment. Paragraph (28) A communication device for use in a conditional handover, comprising: a transmitter configured to transmit a signal; a receiver configured to receive a signal; receiving, from infrastructure equipment of a source wireless communication network, an indication of one or more conditions for triggering a handover of a communication device from a source cell provided by the source infrastructure equipment to a target cell provided by target infrastructure equipment of the wireless communication network; receiving an evaluation trigger signal from the source infrastructure equipment instructing the communications device to evaluate one or more of the conditions for triggering the handover of the communications device from the source cell to the target cell, the evaluation trigger signal received by the communications device from the source infrastructure equipment in response to a change or expected change in a Network Energy Saving (NES) mode of at least one of the source cell and the target cell; and evaluating one or more of the conditions for triggering the handover of the communication device from the source cell to the target cell; determining that one or more of the evaluated conditions are satisfied, and in response: Initiating the handover of the communication device from the source cell to the target cell a control unit configured in combination with the transmitting unit and the receiving unit as described above; Equipped with Communication devices. Paragraph (29) Circuitry for infrastructure equipment of a source wireless communication network for use in a conditional handover, comprising: transmit circuitry configured to transmit a signal; receiving circuitry configured to receive a signal; configuring one or more conditions for triggering a handover of a communication device from a source cell served by the source infrastructure equipment to a target cell served by a target infrastructure equipment of the wireless communication network; sending an indication of the one or more conditions to the communication device for triggering the handover of the communication device from the source cell to the target cell; determining that a change has occurred or is expected to occur in a Network Energy Saving (NES) mode of at least one of the source cell and the target cell; and in response, transmitting the evaluation trigger signal to the communication device instructing the communication device to evaluate one or more of the conditions for triggering the handover of the communication device from the source cell to the target cell; a control circuit section configured by combining the transmission circuit section and the reception circuit section as described above; Equipped with Circuit section. Paragraph (30) A circuit for a communications device used in a conditional handover, comprising: transmit circuitry configured to transmit a signal; receiving circuitry configured to receive a signal; receiving, from infrastructure equipment of a source wireless communication network, an indication of one or more conditions for triggering a handover of a communication device from a source cell provided by the source infrastructure equipment to a target cell provided by target infrastructure equipment of the wireless communication network; receiving an evaluation trigger signal from the source infrastructure equipment instructing the communications device to evaluate one or more of the conditions for triggering the handover of the communications device from the source cell to the target cell, the evaluation trigger signal received by the communications device from the source infrastructure equipment in response to a change or expected change in a Network Energy Saving (NES) mode of at least one of the source cell and the target cell; and evaluating one or more of the conditions for triggering the handover of the communication device from the source cell to the target cell; determining that one or more of the evaluated conditions are satisfied, and in response: Initiating the handover of the communication device from the source cell to the target cell a control circuit section configured by combining the transmission circuit section and the reception circuit section as described above; Equipped with Circuit section. Paragraph (31) A wireless communication network comprising a source infrastructure equipment according to paragraph 27 and a communication device according to paragraph 28. Paragraph (32) A computer program comprising instructions which, when loaded into a computer, cause the computer to carry out a method according to any one of paragraphs 1 to 26. Paragraph (33) A non-transitory computer-readable storage medium storing the computer program of paragraph 32. [Reference] [1] RP-182090, "Revised SID: Study on NR Industrial Internet of Things (IoT)," 3GPP RAN#81. [2] Holma H. and Toskala A, "LTE for UMTS OFDMA and SC-FDMA based radio access", John Wiley and Sons, 2009. [3] TS38.300 V16.5.0, "NG and NR-RAN Overall Description", Release 16. [4] RP-213554, "Study on network energy savings for NR". [5] TR38.840, "Study on User Equipment (UE) power saving in NR", Release 16. [6] TR38.864, "Study on network energy savings for NR", Release 18. [7] R2-2213040, "Post RAN2#120 TP for TR 38.864", Release 18.

Claims

1. 1. A method of operating infrastructure equipment of a source wireless communication network in a conditional handover, comprising: configuring one or more conditions for triggering a handover of a communication device from a source cell served by the source infrastructure equipment to a target cell served by a target infrastructure equipment of the wireless communication network; sending to the communication device an indication of the one or more conditions for triggering the handover of the communication device from the source cell to the target cell; determining that a change has occurred or is expected to occur in a Network Energy Saving (NES) mode of at least one of the source cell and the target cell; and in response, transmitting an evaluation trigger signal to the communication device instructing the communication device to evaluate one or more of the conditions for triggering the handover of the communication device from the source cell to the target cell; method.

2. 10. The method of claim 1 further comprising: transmitting an evaluation stop signal instructing the communication device to stop evaluating the one or more conditions for triggering the handover of the communication device from the source cell to the target cell; method.

3. 3. The method of claim 2, further comprising: transmit an evaluation resume signal instructing the communication device to resume evaluation of the one or more conditions for triggering the handover of the communication device from the source cell to the target cell. method.

4. 4. The method of claim 3, One or more of the evaluation trigger signal, the evaluation stop signal, and the evaluation resume signal are transmitted in a Medium Access Control (MAC) control element. method.

5. 10. The method of claim 1, The evaluation trigger signal includes an indication of the NES mode of at least one of the source cell and the target cell. method.

6. 10. The method of claim 1, The evaluation trigger signal is a radio resource control (RRC) signal dedicated to the communication device. method.

7. 10. The method of claim 1, The evaluation trigger signal is a groupcast RRC (Radio Resource Control) signal received by a plurality of communication devices in the source cell, the groupcast RRC signal including a group-common RNTI (Radio Network Temporary Identifier) ​​for identifying the plurality of communication devices in the source cell. method.

8. 10. The method of claim 1, The evaluation trigger signal is a Medium Access Control (MAC) signal dedicated to the communication device. method.

9. 10. The method of claim 1, The evaluation trigger signal is a groupcast medium access control (MAC) signal received by a plurality of communication devices in the source cell, the groupcast MAC signal including a group-common Radio Network Temporary Identifier (RNTI) for identifying the plurality of communication devices in the source cell. method.

10. 10. The method of claim 1, The evaluation trigger signal is a broadcast signal received by a plurality of communication devices in the source cell. method.

11. 10. The method of claim 1, The evaluation trigger signal is included in group-common downlink control information (DCI) received by a plurality of communication devices in the source cell, the DCI including a group-common Radio Network Temporary Identifier (RNTI) for identifying the plurality of communication devices in the source cell. method.

12. 10. The method of claim 1, Determining that there has been or is expected to be a change in NES mode of at least one of the source cell and the target cell includes: receiving an indication from the target infrastructure equipment that there has been or is expected to be a change in the NES mode of the target cell. method.

13. 13. The method of claim 12, The indication that the NES mode of the target infrastructure device has changed is transmitted over an Xn interface between the source infrastructure device and the target infrastructure device. method.

14. 10. The method of claim 1, Determining that there has been or is expected to be a change in the NES mode of at least one of the source cell and the target cell includes: receiving an indication from the target infrastructure equipment to transmit the evaluation trigger signal to the communications device in response to a change or anticipated change in the NES mode of the target cell. method.

15. 15. The method of claim 14, further comprising: sending handover assist information to the target infrastructure equipment, the handover assist information including one or more of a number of communication devices in the source cell as candidates for handover to the target cell, a quality of service required for the communication devices, a service required for the communication devices, and a traffic volume required for the communication devices; method.

16. 1. A method of operating a communications device in conditional handover, comprising: receiving, from infrastructure equipment of a source wireless communication network, an indication of one or more conditions for triggering a handover of a communication device from a source cell provided by the source infrastructure equipment to a target cell provided by target infrastructure equipment of the wireless communication network; receiving an evaluation trigger signal from the source infrastructure equipment instructing the communications device to evaluate one or more of the conditions for triggering the handover of the communications device from the source cell to the target cell, the evaluation trigger signal received by the communications device from the source infrastructure equipment in response to a change or expected change in a Network Energy Saving (NES) mode of at least one of the source cell and the target cell; and evaluating one or more of the conditions for triggering the handover of the communication device from the source cell to the target cell; determining that one or more of the evaluated conditions are satisfied, and in response: Initiating the handover of the communication device from the source cell to the target cell method.

17. 17. The method of claim 16, further comprising: receiving an evaluation stop signal instructing the communication device to stop evaluating the one or more conditions for triggering the handover of the communication device from the source cell to the target cell; method.

18. 17. The method of claim 16, further comprising: receiving a resume evaluation signal instructing the communication device to resume evaluation of the one or more conditions for triggering the handover of the communication device from the source cell to the target cell; method.

19. 20. The method of claim 18, One or more of the evaluation trigger signal, the evaluation stop signal, and the evaluation resume signal are received by a Medium Access Control (MAC) control element. method.

20. 17. The method of claim 16, The evaluation trigger signal includes an indication of the NES mode of at least one of the source cell and the target cell. method.

21. 17. The method of claim 16, The evaluation trigger signal is a radio resource control (RRC) signal dedicated to the communication device. method.

22. 17. The method of claim 16, The evaluation trigger signal is a groupcast RRC (Radio Resource Control) signal received by a plurality of communication devices in the source cell, the groupcast RRC signal including a group-common RNTI (Radio Network Temporary Identifier) ​​for identifying the plurality of communication devices in the source cell. method.

23. 17. The method of claim 16, The evaluation trigger signal is a Medium Access Control (MAC) signal dedicated to the communication device. method.

24. 17. The method of claim 16, The evaluation trigger signal is a groupcast medium access control (MAC) signal received by a plurality of communication devices in the source cell, the groupcast MAC signal including a group-common Radio Network Temporary Identifier (RNTI) for identifying the plurality of communication devices in the source cell. method.

25. 17. The method of claim 16, The evaluation trigger signal is a broadcast signal received by a plurality of communication devices in the source cell. method.

26. 17. The method of claim 16, The evaluation trigger signal is included in group-common downlink control information (DCI) received by a plurality of communication devices in the source cell, the DCI including a group-common Radio Network Temporary Identifier (RNTI) for identifying the plurality of communication devices in the source cell. method.

27. 1. An infrastructure device of a source wireless communication network for use in a conditional handover, comprising: a transmitter configured to transmit a signal; a receiver configured to receive a signal; configuring one or more conditions for triggering a handover of a communication device from a source cell served by the source infrastructure equipment to a target cell served by a target infrastructure equipment of the wireless communication network; sending to the communication device an indication of the one or more conditions for triggering the handover of the communication device from the source cell to the target cell; determining that a change has occurred or is expected to occur in a Network Energy Saving (NES) mode of at least one of the source cell and the target cell; and in response, transmitting an evaluation trigger signal to the communication device instructing the communication device to evaluate one or more of the conditions for triggering the handover of the communication device from the source cell to the target cell; a control unit configured in combination with the transmitting unit and the receiving unit as described above; Equipped with Infrastructure equipment.

28. 1. A communication device for use in conditional handover, comprising: a transmitter configured to transmit a signal; a receiver configured to receive a signal; receiving, from infrastructure equipment of a source wireless communication network, an indication of one or more conditions for triggering a handover of a communication device from a source cell provided by the source infrastructure equipment to a target cell provided by target infrastructure equipment of the wireless communication network; receiving an evaluation trigger signal from the source infrastructure equipment instructing the communications device to evaluate one or more of the conditions for triggering the handover of the communications device from the source cell to the target cell, the evaluation trigger signal received by the communications device from the source infrastructure equipment in response to a change or expected change in a Network Energy Saving (NES) mode of at least one of the source cell and the target cell; and evaluating one or more of the conditions for triggering the handover of the communication device from the source cell to the target cell; determining that one or more of the evaluated conditions are satisfied, and in response: Initiating the handover of the communication device from the source cell to the target cell a control unit configured in combination with the transmitting unit and the receiving unit as described above; Equipped with Communication devices.

29. 1. A circuit for infrastructure equipment of a source wireless communication network for use in a conditional handover, comprising: transmit circuitry configured to transmit a signal; receiving circuitry configured to receive a signal; configuring one or more conditions for triggering a handover of a communication device from a source cell served by the source infrastructure equipment to a target cell served by a target infrastructure equipment of the wireless communication network; sending to the communication device an indication of the one or more conditions for triggering the handover of the communication device from the source cell to the target cell; determining that a change has occurred or is expected to occur in a Network Energy Saving (NES) mode of at least one of the source cell and the target cell; and in response, transmitting an evaluation trigger signal to the communication device instructing the communication device to evaluate one or more of the conditions for triggering the handover of the communication device from the source cell to the target cell; a control circuit section configured by combining the transmission circuit section and the reception circuit section as described above; Equipped with Circuit section.

30. 1. A circuit for a communication device for use in conditional handover, comprising: transmit circuitry configured to transmit a signal; receiving circuitry configured to receive a signal; receiving, from infrastructure equipment of a source wireless communication network, an indication of one or more conditions for triggering a handover of a communication device from a source cell provided by the source infrastructure equipment to a target cell provided by target infrastructure equipment of the wireless communication network; receiving an evaluation trigger signal from the source infrastructure equipment instructing the communications device to evaluate one or more of the conditions for triggering the handover of the communications device from the source cell to the target cell, the evaluation trigger signal received by the communications device from the source infrastructure equipment in response to a change or expected change in a Network Energy Saving (NES) mode of at least one of the source cell and the target cell; and evaluating one or more of the conditions for triggering the handover of the communication device from the source cell to the target cell; determining that one or more of the evaluated conditions are satisfied, and in response: Initiating the handover of the communication device from the source cell to the target cell a control circuit section configured by combining the transmission circuit section and the reception circuit section as described above; Equipped with Circuit section.

31. 29. A wireless communication network comprising a source infrastructure equipment according to claim 27 and a communication device according to claim 28.

32. A computer program comprising instructions which, when loaded into a computer, cause said computer to carry out the method of claim 1 or claim 16.

33. 33. A non-transitory computer-readable storage medium storing the computer program of claim 32.

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