CHO configuration for fast offload during cell shutdown

Abstract

A system, method, apparatus, and non-transitory computer-readable medium are provided for conditional handover configuration that enables energy savings and fast offload during cell shutdown. The method includes receiving, with a user equipment, one or more handover configurations from a serving cell, the one or more handover configurations including an energy saving conditional handover configuration, at least one of which includes an indication of candidate target cells or information for target cell selection. The method also includes receiving, from the serving cell, an indication of activation of an energy saving mode at the serving cell, and selecting a target cell from the one or more candidate target cells based at least in part on the handover configuration and the received indication of activation of the energy saving mode at the serving cell.

Description

[Technical Field]

[0001] The exemplary and non-limiting embodiments relate generally to network communications, and more particularly to handover procedures. [Background technology]

[0002] In network communications, it is known to perform cell shutdowns to allow energy savings. Summary of the Invention

[0003] The following summary is intended to be illustrative only and is not intended to limit the scope of the claims.

[0004] According to an aspect, an apparatus comprising at least one processor and at least one memory including computer program code, wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to at least: receive one or more handover configurations from a serving cell, the one or more handover configurations including an energy saving conditional handover configuration, and at least one of the one or more handover configurations including at least one of an indication of one or more candidate target cells or information for target cell selection; receive from the serving cell an indication of activation of an energy saving mode at the serving cell; and select a target cell from the one or more candidate target cells based at least in part on the one or more handover configurations and the received indication of activation of the energy saving mode at the serving cell.

[0005] According to one aspect, a method includes receiving, with a user equipment, one or more handover configurations from a serving cell, the one or more handover configurations including an energy saving conditional handover configuration, and at least one of the one or more handover configurations including at least one of an indication of one or more candidate target cells or information for target cell selection; receiving, from the serving cell, an indication of activation of an energy saving mode at the serving cell; and selecting a target cell from the one or more candidate target cells based at least in part on the one or more handover configurations and the received indication of activation of the energy saving mode at the serving cell.

[0006] According to an aspect, an apparatus includes means for receiving one or more handover configurations from a serving cell, the one or more handover configurations including an energy saving conditional handover configuration, at least one of the one or more handover configurations including at least one of an indication of one or more candidate target cells or information for target cell selection; receiving an indication of activation of an energy saving mode at the serving cell from the serving cell; and selecting a target cell from the one or more candidate target cells based at least in part on the one or more handover configurations and the received indication of activation of the energy saving mode at the serving cell.

[0007] According to one aspect, a non-transitory computer-readable medium having stored thereon program instructions that, when executed on at least one processor, cause the at least one processor to: cause reception of one or more handover configurations from a serving cell, the one or more handover configurations including an energy saving conditional handover configuration, and at least one of the one or more handover configurations including at least one of an indication of one or more candidate target cells or information for target cell selection; cause reception from the serving cell of an indication of activation of an energy saving mode at the serving cell; and select a target cell from the one or more candidate target cells based at least in part on the one or more handover configurations and the received indication of activation of the energy saving mode at the serving cell.

[0008] According to an aspect, an apparatus comprising at least one processor and at least one memory including computer program code, wherein the at least one memory and the computer program code are configured to cause, with the at least one processor, the apparatus to at least: determine to activate an energy saving mode; generate one or more handover configurations, wherein the one or more handover configurations include an energy saving conditional handover configuration, and at least one of the one or more handover configurations includes at least one of an indication of one or more candidate target cells or information for target cell selection; transmit the one or more handover configurations to a user equipment; initiate activation of the energy saving mode; and transmit an indication of the activation of the energy saving mode to the user equipment.

[0009] According to one aspect, a method includes: determining to activate an energy saving mode; generating one or more handover configurations, the one or more handover configurations including an energy saving conditional handover configuration, and at least one of the one or more handover configurations including at least one of an indication of one or more candidate target cells or information for target cell selection; transmitting the one or more handover configurations to a user equipment; initiating activation of an energy saving mode; and transmitting an indication of the activation of the energy saving mode to the user equipment.

[0010] According to an aspect, an apparatus includes means for determining to activate an energy saving mode; generating one or more handover configurations, where the one or more handover configurations include an energy saving conditional handover configuration, and at least one of the one or more handover configurations includes at least one of an indication of one or more candidate target cells or information for target cell selection; transmitting the one or more handover configurations to a user equipment; initiating activation of an energy saving mode; and transmitting an indication of the activation of the energy saving mode to the user equipment.

[0011] According to one aspect, a non-transitory computer-readable medium having stored thereon program instructions that, when executed on at least one processor, cause the at least one processor to: determine to activate an energy saving mode; generate one or more handover configurations, the one or more handover configurations including an energy saving conditional handover configuration, at least one of the one or more handover configurations including at least one of an indication of one or more candidate target cells or information for target cell selection; cause transmission of the one or more handover configurations to user equipment; initiate activation of an energy saving mode; and cause transmission of an indication of activation of the energy saving mode to the user equipment.

[0012] According to an aspect, a computer program product storing instructions for at least performing the following: receiving one or more handover configurations from a serving cell, the one or more handover configurations including an energy saving conditional handover configuration, and at least one of the one or more handover configurations including at least one of an indication of one or more candidate target cells or information for target cell selection; receiving an indication of activation of an energy saving mode at the serving cell from the serving cell; and selecting a target cell from the one or more candidate target cells based at least in part on the one or more handover configurations and the received indication of activation of the energy saving mode at the serving cell.

[0013] According to an aspect, a computer program storing instructions for at least performing the following: determining to activate an energy saving mode; generating one or more handover configurations, the one or more handover configurations including an energy saving conditional handover configuration, at least one of the one or more handover configurations including at least one of an indication of one or more candidate target cells or information for target cell selection; transmitting the one or more handover configurations to a user equipment; initiating activation of an energy saving mode; and transmitting an indication of the activation of the energy saving mode to the user equipment.

[0014] The foregoing aspects and other features are explained in the following description taken in conjunction with the accompanying drawings. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a block diagram of one possible, non-limiting example system in which example embodiments may be implemented. [Figure 2] FIG. 1 illustrates features described herein. [Figure 3A] 1 is a flow chart illustrating the steps described herein. [Figure 3B] 1 is a flow chart illustrating the steps described herein. [Figure 4] FIG. 1 illustrates features described herein. [Figure 5] 1 is a flow chart illustrating the steps described herein. [Figure 6] 1 is a flow chart illustrating the steps described herein. [Figure 7] 1 is a flow chart illustrating the steps described herein. [Figure 8] 1 is a flow chart illustrating the steps described herein. DETAILED DESCRIPTION OF THE INVENTION

[0016] The following abbreviations that may appear in the specification and / or drawings are defined as follows: 3GPP Third Generation Partnership Project 5G fifth generation 5GC 5G Core Network AI artificial intelligence AMF Access and Mobility Management Functions BB Baseband CE Control Elements CHO Conditional Handover CN Core Network CPC Conditional PS Cell Change CSI-RS Channel State Information Reference Signal CU Central Unit DCI Downlink Control Information DL Downlink DRX Discontinuous Reception DTX Discontinuous Transmission DU Distributed Unit eDRX Enhanced Discontinuous Reception eMBB Enhanced Mobile Broadband eMTC Enhanced Machine Type Communication eNB (or eNodeB) Evolved Node B (e.g., LTE base station) EN-DC E-UTRA-NR dual connectivity A node that provides NR user plane and control plane protocol termination towards en-gNB or En-gNB UE and acts as a secondary node in the EN-DC ES Energy Savings ES-CHO Energy Saving Conditional Handover E-UTRA Evolved Universal Terrestrial Radio Access, i.e., LTE radio access technology gNB (or gNodeB) A base station for 5G / NR, i.e., a node that provides NR user plane and control plane protocol termination towards UEs and is connected to 5GC via the NG interface. HFN Hyperframe Number HO Handover IE Information Elements I / F interface L1 Layer 1 LTE Long Term Evolution MAC Media Access Control (m)MIMO (Massive) Multi-in Multi-out ML Machine Learning MME Mobility Management Entity ng or NG New Generation ng-eNB or NG-eNB New Generation eNB NR new radio N / W or NW Network O&M Operation and Maintenance OFDM Orthogonal Frequency Division Multiplexing OPEX Operating costs PBCH Physical Broadcast Channel PDCP Packet Data Convergence Protocol PHY physical layer PoC Push-to-talk over cellular PSG Power Saving Group PSW Power Saving Window RA Registration Area RAN Radio Access Network RAT Radio Access Technology RedCap Reduced Capability RF radio frequency RLC Radio Link Control RNA RAN-based notification area RRC Radio Resource Control RRH Remote Radio Head RRM Radio Resource Management RS reference signal RSRP reference signal received power RSRQ Reference Signal Received Quality RU Wireless Unit Rx Receiver SDAP Service Data Adaptation Protocol SFN System Frame Number SGW Serving Gateway SI System Information SIB System Information Block SINR Signal to Interference Plus Noise Ratio SMF Session Management Facility SS Sync Signal SSB sync signal block TA Tracking Area TCI Transmit Configuration Indicator TRX Transceiver Tx transmitter UE User Equipment (e.g., wireless, typically mobile device) UPF User Plane Function

[0017] FIG. 1 illustrates a block diagram of one possible, non-limiting example in which an example may be implemented. Shown are a user equipment (UE) 110, a radio access network (RAN) node 170, and network element(s) 190. In the example of FIG. 1, the user equipment (UE) 110 wirelessly communicates with a radio network 100. The UE is a wireless device that can access the radio network 100. The UE 110 includes one or more processors 120, one or more memories 125, and one or more transceivers 130, which are interconnected via one or more buses 127. Each of the one or more transceivers 130 includes a receiver (Rx) 132 and a transmitter (Tx) 133. The one or more buses 127 may be an address bus, a data bus, or a control bus, and may include any interconnection mechanism, such as a series of lines on a motherboard or integrated circuit, optical fiber or other optical communication facilities, etc. The one or more transceivers 130 are connected to one or more antennas 128. The one or more memories 125 include computer program code 123. The UE 110 includes a module 140, which is comprised of one or both of portions 140-1 and / or 140-2, which may be implemented in numerous ways. The module 140 may be implemented in hardware as module 140-1, such as as part of one or more processors 120. The module 140-1 may also be implemented as an integrated circuit or via other hardware, such as a programmable gate array. In another example, the module 140 may be implemented as module 140-2, which is implemented as computer program code 123 and executed by the one or more processors 120. For example, the one or more memories 125 and the computer program code 123 may be configured to cause the user equipment 110, using the one or more processors 120, to perform one or more of the operations described herein. The UE 110 communicates with the RAN node 170 via a wireless link 111.

[0018] The RAN node 170 in this example is a base station that provides access to the radio network 100 by wireless devices such as the UE 110. The RAN node 170 may be, for example, a base station for 5G, also known as New Radio (NR). In 5G, the RAN node 170 may be an NG-RAN node, defined as either a gNB or an ng-eNB. A gNB is a node that provides NR user plane and control plane protocol terminations toward the UE and connects to the 5GC (e.g., network element(s) 190) via an NG interface. An ng-eNB is a node that provides E-UTRA user plane and control plane protocol terminations toward the UE and connects to the 5GC via an NG interface. An NG-RAN node may include multiple gNBs, which may also include a central unit (CU) (gNB-CU) 196 and distributed unit(s) (DU) (gNB-DU), of which DU 195 is shown. Note that a DU may include a radio unit (RU) or may be coupled to and control the RU. The gNB-CU is a logical node that hosts the RRC, SDAP, and PDCP protocols of the gNB or the RRC and PDCP protocols of the en-gNB, and controls the operation of one or more gNB-DUs. The gNB-CU terminates the F1 interface connected to the gNB-DU. The F1 interface is indicated by reference numeral 198, which also indicates a link between a remote element of the RAN node 170 and a centralized element of the RAN node 170, such as between the gNB-CU 196 and the gNB-DU 195. The gNB-DU is a logical node that hosts the RLC layer, MAC layer, and PHY layer of the gNB or en-gNB, and its operation is partially controlled by the gNB-CU. One gNB-CU supports one or more cells. One cell is supported by only one gNB-DU. The gNB-DU terminates the F1 interface 198 connected to the gNB-CU.It should be noted that although the DU 195 is considered to include the transceiver 160, e.g., as part of an RU, in some instances it may have the transceiver 160 as part of a separate RU, e.g., under the control of the DU 195, connected to the DU 195. The RAN node 170 may also be an eNB (Evolved Node B) base station for LTE (Long Term Evolution), or any other suitable base station or node.

[0019] The RAN node 170 includes one or more processors 152, one or more memories 155, one or more network interfaces (N / WI / F(s)) 161, and one or more transceivers 160, which are interconnected via one or more buses 157. Each of the one or more transceivers 160 includes a receiver Rx 162 and a transmitter Tx 163. The one or more transceivers 160 are connected to one or more antennas 158. The one or more memories 155 include computer program code 153. The CU 196 may include the processor(s) 152, the memory 155, and the network interface 161. Note that the DU 195 may also include its own memory(s) and processor(s), and / or other hardware, which are not shown.

[0020] The RAN node 170 comprises a module 150 including one or both of portions 150-1 and / or 150-2, which may be implemented in numerous ways. The module 150 may be implemented in hardware as module 150-1, such as implemented as part of one or more processors 152. The module 150-1 may also be implemented as an integrated circuit or via other hardware, such as a programmable gate array. In another example, the module 150 may be implemented as module 150-2, which is implemented as computer program code 153 and executed by one or more processors 152. For example, the one or more memories 155 and the computer program code 153 are configured to cause the RAN node 170, using the one or more processors 152, to perform one or more of the operations described herein. It should be noted that the functionality of the module 150 may be distributed, such as distributed between the DU 195 and the CU 196, or may be implemented solely within the DU 195.

[0021] One or more network interfaces 161 communicate over a network, such as via links 176 and 131. Two or more gNBs 170 may communicate, for example, using link 176. Link 176 may be wired or wireless, or both, and may implement, for example, an Xn interface for 5G, an X2 interface for LTE, or other suitable interface for other standards.

[0022] The one or more buses 157 may be an address bus, a data bus, or a control bus and may include any interconnection mechanism, such as a series of lines on a motherboard or integrated circuit, optical fiber or other optical communication facilities, radio channels, etc. For example, one or more transceivers 160 may be implemented as a remote radio head (RRH) 195 for LTE, or a distributed unit (DU) 195 for a gNB implementation for 5G, and other elements of the RAN node 170 may be in a different physical location from the RRH / DU, and the one or more buses 157 may, in part, be implemented as part of, for example, an optical fiber cable or other appropriate network connection to connect other elements of the RAN node 170 (e.g., a central unit (CU), gNB-CU) to the RRH / DU 195. Reference numeral 198 also indicates those appropriate network link(s).

[0023] It should be noted that while the description herein refers to a "cell" performing a function, it is clear that the equipment forming the cell performs the function. A cell constitutes part of a base station; that is, there may be multiple cells per base station. For example, there may be three cells for a single carrier frequency and associated bandwidth, each covering one-third of a 360-degree area, so that the coverage area of ​​a single base station covers an approximately oval or circular shape. Furthermore, each cell may correspond to a single carrier, and the base station may use multiple carriers. Thus, if there are three 120-degree cells per carrier and two carriers, the base station has a total of six cells.

[0024] The wireless network 100 may comprise network element(s) 190, which may comprise core network functions and provide connectivity via link(s) 181 to further networks, such as telephone networks and / or data communication networks (e.g., the Internet). Such core network functions for 5G may include access and mobility management function(s) (AMF(s)) and / or user plane functions (UPF(s)) and / or session management function(s) (SMF(s)). Such core network functions for LTE may include MME (Mobility Management Entity) / SGW (Serving Gateway) functions. It should be noted that these are merely example functions that may be supported by the network element(s) 190, and that both 5G and LTE functions may be supported. The RAN node 170 is coupled to the network element 190 via link 131. Link 131 may be implemented, for example, as a 5G NG interface, an LTE S1 interface, or other interface suitable for other standards. Network element 190 includes one or more processors 175, one or more memories 171, and one or more network interfaces (N / WI / F(s)) 180, interconnected via one or more buses 185. One or more memories 171 include computer program code 173. One or more memories 171 and computer program code 173 are configured, using one or more processors 175, to cause network element 190 to perform one or more operations.

[0025] The wireless network 100 may implement network virtualization. Network virtualization is the process of combining hardware and software network resources and functions to create a single software-based management entity: a virtual network. Network virtualization involves platform virtualization, which is often combined with resource virtualization. Network virtualization is categorized as either external network virtualization, which combines multiple networks or portions of networks to create a virtual unit, or internal network virtualization, which provides network-like functionality to software containers on a single system. It should be noted that the virtualized entities resulting from network virtualization are further implemented at some level using hardware, such as the processor 152 or 175 and memory 155 and 171, and that such virtualized entities produce technical effects.

[0026] The computer-readable memories 125, 155, and 171 may be of any type suitable for the local technology environment and may be implemented using any suitable data storage technology, such as semiconductor-based memory devices, flash memory, magnetic memory devices and systems, optical memory devices and systems, fixed memory, and removable memory. The computer-readable memories 125, 155, and 171 may be means for performing storage functions. The processors 120, 152, and 175 may be of any type suitable for the local technology environment, including, by way of non-limiting example, one or more of a general-purpose computer, a special-purpose computer, a microprocessor, a digital signal processor (DSP), and a processor based on a multi-core processor architecture. The processors 120, 152, and 175 may be means for performing functions, such as control of the UE 110, the RAN node 170, and other functions described herein.

[0027] In general, various embodiments of user equipment 110 may include, but are not limited to, cellular telephones such as smartphones, tablets, personal digital assistants (PDAs) with wireless communication capabilities, portable computers with wireless communication capabilities, image capture devices such as digital cameras with wireless communication capabilities, gaming devices with wireless communication capabilities, music storage and playback devices with wireless communication capabilities, internet appliances that allow wireless internet access and browsing, tablets with wireless communication capabilities, and portable units or terminals incorporating combinations of such functionality.

[0028] The features described herein generally relate to enhancements for network energy conservation in 5G NR and in future technologies, such as 6G. More specifically, the features described herein may generally relate to conditional handover features in 5G NR, which may be used during cell shutdown for network energy conservation.

[0029] Reducing energy consumption in mobile networks, especially in the RAN, which consumes the largest portion of the total energy consumption in a network, has received significant attention. Research on network energy savings will be conducted in 3GPP Rel. 18 and may aim to identify network energy saving techniques in the time domain, frequency domain, spatial domain, and / or power domain, for both transmission and reception. Potential support / feedback from the UE, potential UE assistance information, and information exchange / coordination over the network interface may also be within the scope of the research (RP-213554).

[0030] In Rel.18, there is also an NG-RAN work item, Artificial Intelligence (AI) / Machine Learning (ML) (RP-213602), based on the Rel.17 study and has the study description "Study on enhancement for data collection for NR and EN-DC" contained in RP-201620. This work item aims to specify support for data collection enhancement and signaling within existing NG-RAN interfaces and architectures for several AI / ML-based use cases. One of those use cases is energy savings.

[0031] Energy-saving features have been introduced to minimize network energy consumption and energy-related operational costs. Energy-saving deployments consider capacity booster cells deployed in addition to coverage cells to boost E-UTRA or NR capacity in single or dual connectivity. These cells can be optimized by switching them off when capacity is not needed and reactivating them on demand. Switching off cells can be performed by OAM and by the NG-RAN node that owns the capacity cell. The NG-RAN node can autonomously switch off cells, for example, using cell load information. Shutting down cells during low-load periods is one of the most effective means to achieve network energy savings. This is because it can turn off all of the cell's power-hungry hardware components, thereby achieving a significant reduction in energy consumption. In a cell shutdown scenario, power consumption can be reduced by 10 to 15% when the cell is shut down compared to when the cell is not shut down. Referring now to Figure 2, an example of the cell shutdown feature is shown. A power saving group (PSG) is a set of cells (i.e., frequency layer) that cover the same area. In the example of Figure 2, PSG-1 includes two cells 210a and 210b that cover the same area at different frequencies, PSG-2 includes two cells 220a and 220b that cover the same area at different frequencies, and PSG-3 includes two cells 230a and 230b that cover the same area at different frequencies. In the example of Figure 2, each PSG is composed of two frequency layers, but this example is not limiting and more or fewer frequency layers may be included in more or fewer PSGs.

[0032] Cells can be switched off to save energy. Energy savings can translate into operational cost (OPEX) savings. For each PSG, the load may be compared to one or more thresholds. If the load is less than a threshold, the cell may be switched off. If the load is greater than another threshold, the cell may be switched on again. The thresholds may be predetermined. The comparison of the load of the PSG may be compared against the thresholds. Under low traffic conditions, a layer(s) of the PSG can be switched off without unduly degrading network performance, while still saving energy.

[0033] The cell switch-off procedure, as described above, can offer potential energy savings. Additionally, other measures can be employed to conserve energy while the cell is still active. For example, micro-cutting of the radio frequency (RF) path (e.g., micro-discontinuous transmission (DTX)) can result in a 10-20% reduction in electrical consumption (e.g., over 40% in no-load situations). This entails that RF power consumption can be reduced as part of the RF path micro-cutting when no transmissions are taking place. As a further example, (massive) multiple-in multiple-out ((m)MIMO) muting can reduce power consumption by 10-30%. In the first case, the switching-off can occur horizontally, for example, for half the transceivers. In the second case, the switching-off can occur vertically, for example, for half the transceivers. If baseband components can also be switched off, power consumption may be further reduced.

[0034] The features described herein generally relate to the Conditional Handover (CHO) defined in 5G NR Release 16. This new handover procedure may enable a UE to perform a handover if certain handover conditions are met. In other words, CHO is a handover that is performed by a UE when configured execution conditions are met, without requiring a handover command by / from the network. This procedure may have the technical effect of avoiding delays associated with network control procedures and reducing handover failures.

[0035] When a decision to shut down a cell is made (e.g., by the cell or autonomously by the operation and management function (O&M)), UEs currently connected to the cell need to be offloaded from the cell before the shutdown is complete. This may be done by handing over each connected UE to a neighboring cell. Neighboring cells may have overlapping coverage, and it may be possible to accommodate the additional load using regular handover. Neighboring cells may belong to the coverage layer or to another frequency layer (e.g., if the shutdown is performed in a PSG of a given frequency layer). If the offloading is not completed before the cell is shut down, handover (HO) failure(s) may occur. Faster offloading may have the technical effect of improving power consumption reduction.

[0036] However, offloading traffic from a cell using a normal handover can be quite time-consuming. This process may involve initiating a gradual reduction in transmit power (e.g., of synchronization signal blocks (SSBs)) in multiple successive steps, which in turn may reduce the received signal strength (reference signal received power / reference signal received quality (RSRP / RSRQ)) observed by the UE. UE(s) in RRC connected mode can perform radio resource management (RRM) measurements (RSRP / RSRQ) of the serving cell and neighboring cells and report these measurements to the network. This can assist the network in identifying relevant neighboring cells that can be used for UE handover given the UE's radio conditions. For example, when the target cell's RSRP is within a defined offset better than the serving cell's RSRP, the UE may trigger an A3 event (triggered when a neighboring cell improves by an offset over the serving cell) and send a measurement report (indicating the best candidate cell) to the serving cell. After determining the target cell for a given UE based on the UE's RRM measurement reports, the serving cell can finally prepare the selected cell via Xn and trigger a handover by sending a handover command to the UE. However, the handover procedure may be affected by handover failures. After each handover failure, the UE needs to perform cell selection, followed by re-establishment. As a result, the UE may have to perform re-establishment on the source cell and repeat the handover procedure (i.e., to the target cell) (e.g., if the conditions for handover persist).

[0037] Exemplary embodiments of the present disclosure may have the technical effect of enabling faster cell offloading (e.g., avoiding HO failures) before shutting down the cell to improve power consumption reduction.

[0038] According to TS38.331 section 5.3.5.13 "Conditional Reconfiguration," the CHO configuration (ConditionalReconfiguration-r16 of RRCReconfig) provided by the source gNB to the UE may include the following information elements (IEs): candidate target Sp cell(s) prepared for conditional handover (generated by candidate gNB(s)), execution criteria (e.g., criteria to be used by the UE for conditional reconfiguration execution generated by the source gNB (i.e., controlling when CHO should be triggered)), and / or RS type (SSB or Channel State Information Reference Signal (CSI-RS) based) (e.g., RS to be used by the UE to obtain beam and cell measurements used to evaluate the conditional reconfiguration execution condition). Note that only a single reference signal type is supported for CHO, and a maximum of two different trigger quantities (e.g., RSRP and RSRQ, RSRP and SINR, etc.) can be simultaneously configured for evaluation of the CHO execution condition for a single candidate cell.

[0039] Note that TS38.331 specifies that when a UE is configured with a CHO configuration, it may receive an HO command from a gNB before the CHO execution conditions are met. The UE can trigger a handover based on the received HO command without waiting for any of the CHO conditions to be met. This means that the legacy HO command can take precedence over the CHO configuration (if configured).

[0040] Up to eight CHO configurations may be configured for one UE (depending on the UE capabilities), where each CHO configuration may consist of a CHO ID, one to two MeasIDs (e.g., one with RSRP and one with RSRQ), and / or an (intra-RAT) HO command.

[0041] When triggered, CHO may be performed as a normal handover.

[0042] In contrast to the exemplary embodiments of the present disclosure, in legacy CHO, the UE may start evaluating the CHO execution condition(s) when it receives the CHO configuration and may stop evaluating the execution condition(s) when a handover is performed.

[0043] Referring now to FIG. 3, a basic intra-access and mobility management function / user plane function (AMF / UPF) conditional handover scenario is shown, as described in TS 338.300. At 302, user data may be transmitted between the UE and the source gNB. At 304, user data may be transmitted between the source gNB and the UPF. At 306, mobility control information may be provided to the source gNB by the AMF. At 308, measurement and control report(s) may be transmitted between the UE and the source gNB. At 310, the source gNB may make a CHO decision, for example, based on information in the measurement and control report(s). At 312, the gNB may send one or more handover requests to the target gNB. At 314, the source gNB may send one or more handover requests to other potential target gNB(s). This step may be optional. At 316, the target gNB may perform admission control. At 318, the other potential target gNB(s) may optionally perform admission control. At 320, the target gNB may send one or more handover request acknowledgments to the source gNB. At 322, the other potential target gNB(s) may send one or more handover request acknowledgments to the source gNB. At 324, the source gNB may send an RRC reconfiguration message to the UE. At 326, the UE may send an RRC reconfiguration complete message to the source gNB. Steps 302-326 may be considered part of handover preparation 350.

[0044] At 328, the UE may evaluate the CHO condition(s). At 330, the UE may disconnect from the old cell (source gNB) and synchronize to the new cell (target gNB or other potential target gNB(s)). At 332, the source gNB may optionally send an early status transmission to the other potential target gNB(s). At 334, the UPF may send user data to the source gNB, and the source gNB may optionally forward the user data to the other potential target gNB(s). At 336, the UE, source gNB, and target gNB may complete the CHO handover. Steps 328-336 may be considered part of handover execution 360.

[0045] At 338, the target gNB may send a handover success message to the source gNB. At 340, the source gNB may perform an SN status transfer to the target gNB. At 342, the UPF may send user data to the source gNB, and the source gNB may forward the user data to the target gNB. At 344, the source gNB may send a handover cancel message to the target gNB, and optionally to other potential target gNB(s). Steps 338-344 may be considered part of handover completion 370.

[0046] Referring now to Figure 4, an example of the ConditionalReconfiguration IE (410) is shown, which may be used to add, modify, and / or remove configurations for conditional reconfiguration (TS38.423). As described in the ConditionalReconfiguration field description (420), the attemptCondReconfig field may be used to cause the UE to perform a conditional reconfiguration if the selected cell is a target candidate cell and is the first cell selection after a failure. The condReconfigToAddModList field may be used to provide a list of configurations of candidate Sp cells to be added or modified for the CHO or CPC. The condReconfigToRemoveList field may be used to provide a list of configurations of candidate Sp cells to be removed.

[0047] The portion of the handover request from the source NG-RAN node to the target NG-RAN node requesting the preparation of resources for the handover is shown in Table 1. [Table 1]

[0048] "Estimated Arrival Probability" may allow the target node to apply some statistical resource optimization based on the estimated arrival probability (where 100% may be interpreted as the UE arriving for sure, as in "classical HO").

[0049] A technical effect of the exemplary embodiments of the present disclosure may be to enable enhanced conditional handover for energy conservation.

[0050] In an exemplary embodiment, the network may configure an RRC-connected UE with one or more energy-saving specific conditional handover (ES-CHO) configurations, which may include parameters optimized for energy saving. The technical effect of the ES-CHO configurations may be to enable fast offloading of the UE to a different cell. In an exemplary embodiment, the UE may use the ES-CHO configurations when the serving cell (e.g., a capacity cell) enters one or more corresponding "energy saving modes" (e.g., "cell shutdown," "network transmit power reduction," "mMIMO transmit antenna element muting," etc.).

[0051] The use of such ES-CHO configuration(s) can have the technical effect of enabling faster offloading of UEs to a different cell (compared to classical HO), which is required before the cell enters a new mode, and may allow the cell to achieve greater energy savings potential. This benefit may be particularly important if more dynamic time adaptation of power saving modes is expected as part of the evolution of 3GPP energy efficient schemes (e.g., Rel. 18 Study on Energy Saving (RP-213554)).

[0052] In an exemplary embodiment, the ES-CHO configuration may include one or more candidate target cells. The one or more candidate target cells may include at least one of cells of a coverage tier associated with the serving cell or cells of a frequency tier (e.g., a frequency tier lower than the serving tier) that has a lower priority for entering a given energy saving mode (e.g., cell switching off) than the frequency tier of the serving cell. For example, the assignment of the target cell(s) may be based on a network shutdown policy and / or network deployment (e.g., depending on which frequency tiers are shut down and, in what order, which (lower) frequency tier(s) provide coverage when a given (higher) frequency tier is shut down). A dedicated ES-CHO configuration may be associated with each “energy saving” mode.

[0053] In an exemplary embodiment, a network indication may be used to trigger the UE application of the ES-CHO configuration. In other words, the serving cell may indicate when an ES-CHO "command" may be executed by the UE (i.e., when the ES-CHO configuration should be applied) using any combination of the following options: Implicit Indication: The UE may execute the ES-CHO command whenever the serving cell indicates that the UE is in / applying the "energy saving" mode associated with the CHO configuration received. In an exemplary embodiment, the network indication of the current "energy saving" mode may be provided via system information. Explicit Indication: The serving cell may explicitly indicate activation of the ES-CHO configuration, or similarly may explicitly indicate network offload (e.g., decision to shut down). In an exemplary embodiment, these indications may be provided by Downlink Control Information (DCI) / MAC CE. Time-based indication: The ES-CHO configuration may include the (predicted) time when it should be implemented. This may have the technical effect of giving a cell an opportunity to serve traffic when it is already planning a shutdown in the near future. In an exemplary embodiment, the time may be provided using a system frame number (SFN) or hyperframe number (HFN). Additionally or alternatively, the time may be provided using a (predicted) number of time units in the future (e.g., after receiving the ES-CHO configuration), depending on when the ES-CHO configuration should be applied.

[0054] In an exemplary embodiment, the UE can select a target cell for ES-CHO. If the serving cell indicates that an ES-CHO command associated with a particular energy saving mode must be executed, the UE can determine the target cell based on one of the following options, which can be selected based on a capacity / frequency tier determination: Option #1 / Default (the target cell may be selected by the UE from the configured cells based on radio measurements (e.g., RRM measurements). The UE may collect RRM measurements for target cells included in the corresponding ES-CHO configuration and may select a target cell for ES-CHO from the configured target cells based on the collected RRM measurements. In an example embodiment, the ES-CHO configuration may include radio conditions to be evaluated. Option #2 (Target cell may be selected by UE based on predetermined / pre-provided information(s) and / or network configuration(s)). The UE can select a target cell for ES-CHO without performing RRM measurements based on the UE's predetermined / stored information of (suitable) target cells among potential target cells provided in the ES-CHO configuration and / or the network's predetermined / stored information and the network configuration of the target cell, as well as selection criteria. (In an exemplary embodiment, the ES-CHO configuration may comprise a list of target cells, and each target cell may be associated with a given Transmission Configuration Indicator (TCI) state / downlink (DL) beam (SSB / CSI-RS based) of the serving cell and / or a serving cell RSRP value. The UE can then select a target cell corresponding to that serving beam (TCI state) / RSRP level.) Additionally or alternatively, the target cell selection may be performed based on the TCI state associated with the serving cell.

[0055] In an exemplary embodiment, the target cell selection may be optimized using AI / ML. According to the above exemplary embodiment, AI / ML may be used to train the capacity / frequency tiers so that the UE can perform the target cell selection for the UE-CHO.

[0056] Machine learning tools such as neural networks, as noted above, are being utilized in an increasing number of applications in many different types of devices, such as mobile phones. Neural networks and other machine learning tools may be capable of learning characteristics from input data in either a supervised or unsupervised manner. Such learning may be the result of a training algorithm or may be the result of a meta-level neural network providing a training signal.

[0057] A training algorithm may consist of modifying some characteristics of a neural network so that its output is as close as possible to the desired output. Training may involve modifying the characteristics of the neural network to minimize or reduce the error in the output, also known as loss. Examples of losses include mean squared error (MSE), cross entropy, etc. In modern deep learning methods, training is an iterative process, and in each iteration, the algorithm modifies the weights of the neural network so that the network's output gradually improves, i.e., the loss gradually decreases.

[0058] Although training a neural network may involve an optimization process, the final goal of machine learning differs from the general goal of optimization. In optimization, the goal is to minimize loss. In machine learning, in addition to the optimization goal, a common goal is to have a model learn the characteristics of data distributions from a limited training data set. In other words, an additional training process is used to ensure that the neural network learns to use a limited training data set in order to learn to generalize to previously unseen data, i.e., data that was not used to train the model. This additional goal is usually called generalization. In practice, data may be divided into at least two sets: a training set and a validation set. The training set may be used to train the network, i.e., to modify its learnable parameters to minimize loss. The validation set may be used to check the performance of the neural network using data that was not used to minimize loss (i.e., data that was not part of the training set), and the performance of the neural network using the validation set may indicate the final performance of the model. The errors on the training set and the validation set may be monitored during the training process to understand whether the neural network is learning at all and whether it is learning to generalize. If the network is learning at all, the training set error should decrease. If the network is not learning, the model may be underfitting. If the network is learning to generalize, the validation set error should decrease and not be much larger than the training set error. If the training set error is low but the validation set error is much larger than the training set error, or if the validation set error does not decrease or even increases, the model may be overfitting. Overfitting may mean that the model has memorized the characteristics of the training set and performs well only on that set, but performs poorly on sets not used to tune its parameters. In other words, the model is not learning to generalize.

[0059] In an exemplary embodiment, the capacity / frequency layer can build a confidence (probability) regarding how well it knows the overlapping radio environment provided by the coverage / frequency layer and the target cell of the coverage / frequency layer that is suitable for offloading a given UE in case of handover. In an exemplary embodiment, the UE's RSRP / RSRQ measurements of the strongest neighboring cell, along with the UE's location (exact coordinates, beam information, etc.), can be used to map the best target cell of the coverage / frequency layer(s) to which the UE can be offloaded in the next cell change to the location / area / beam of the energy saving (ES) cell. As another option, the capacity cell can use the UE trajectory prediction information calculated / predicted by the capacity cell alone or together with the UE measurements (e.g., the UE's RSRP / RSRQ measurements of the strongest neighboring cell, UE location information, etc.) to determine the best coverage cell to which UE traffic should be offloaded in case the cell is switched off. For example, if a predicted UE trajectory in a capacity cell can determine the next (coverage) cell with high probability, this may enable the capacity cell to build a high confidence in a suitable target cell within its coverage / frequency layer to offload a particular UE in case of handover. In an exemplary embodiment, the confidence (probability) value may be updated based on feedback regarding different UE locations and selected options corresponding to handover performance, e.g., regarding UE performance of the handed over UE in terms of bit rate, packet loss rate, latency, etc. In an exemplary embodiment, if the confidence (probability) is higher than a threshold, the UE may select a target cell based on predetermined information and / or network configuration. In an exemplary embodiment, if the confidence (probability) is equal to or lower than a threshold, the UE may select a target cell based on RRM measurements. The threshold may be selected to be a high value, e.g., 90% confidence.

[0060] In an exemplary embodiment, the target cell may prepare / be prepared for ES-CHO. In an exemplary embodiment, the preparation of the target cell may be performed according to legacy procedures, with the addition of a power saving trigger / cause and, if available, a (predicted) time for the power saving mode to be applied. The target gNB may optimize RRM resource reservations based on the received information. Additionally or alternatively, information regarding CHO handover preparation may be added to a cell deactivation indication sent towards a neighboring gNB via the Xn / X2 interface. The information regarding CHO handover preparation may include a list of currently active UEs offloaded to that gNB (i.e., UEs for which a neighboring gNB is configured as a target cell for offload-based CHO).

[0061] 5, an example signaling flowchart is shown, in accordance with an example embodiment of the present disclosure. The signaling flowchart includes interactions between UEs that may be in an RRC_Connected state with a serving gNB.

[0062] At 510, the serving gNB may decide / determine to use ES-CHO during cell shutdown. At 512, the serving gNB may send a handover request to the target gNB. The handover request may include an ES-CHO information request including a cell shutdown trigger. This may consider an example where target cell preparation may be performed as per legacy procedures, with the addition of a power saving trigger / cause and, if available, a (predicted) time for the power saving mode to be applied. At 514, the target gNB may perform admission control. At 516, the target gNB may send a handover request acknowledgement to the serving gNB. At 520, the serving gNB may generate an ES-CHO configuration. The ES-CHO configuration may include information for target cell selection. At 522, the serving gNB may send an RRCReconfig message to the UE. The RRCReconfig message may include an ES-CHO configuration, which may include target gNB(s) for offload, target cell(s) for offload, and / or information for target cell selection. In an example embodiment, the information for target cell selection may be based at least in part on the handover request acknowledgment. At 524, the UE may send an RRCReconfigComplete message to the serving gNB. At 526, the UE may store the ES-CHO configuration without applying it. For example, a condition for applying the ES-CHO configuration may not occur.

[0063] At 530, the serving gNB may receive / detect an energy saving mode trigger. For example, the energy saving mode trigger may be a cell shutdown trigger. Other types of energy saving mode triggers may be possible and would occur to one skilled in the art (e.g., a "cell shutdown" trigger, a "network transmit power reduction" trigger, a "mMIMO transmit antenna element muting" trigger, etc.). At 532, the serving gNB may send a deactivation indication to the target gNB. The deactivation indication may include an ES-CHO information request. This may be an example of information related to CHO handover preparation that is added to the cell deactivation indication sent to neighboring gNBs via the Xn / X2 interface. At 534, the target gNB may perform admission control. At 536, the target gNB may send a handover request acknowledgement to the serving gNB. At 540, the serving gNB may send a cell shutdown indication to the UE. For example, the indication may be part of system information. In an example embodiment, the indication may be based at least in part on the handover request acknowledgment. At 542, the UE may evaluate the ES-CHO configuration and select a target cell according to the received information. The UE may disconnect from the serving cell and synchronize with the (selected) target cell. At 550, ES-CHO may be completed. At 560, the target gNB may send feedback regarding ES-CHO to the serving gNB.

[0064] Referring now to FIG. 6, a flowchart of an exemplary network algorithm for updating the confidence level for target cell selection for UE offloading during energy-saving operation of a source node is shown. The source node may have an initial confidence level regarding the best candidate target cell for a given UE or for a set of UEs at a given location (610). This may be available through network configuration or through some initial guesses made by the source cell, for example, by utilizing ML models available at the source. At the start, this guess / confidence level may not always be accurate enough; therefore, the source node may update / improve the guess / confidence level, for example, through UE measurements (620) that may enable the determination of the strongest candidate target cell for different UEs and UE locations, as well as through feedback information from the target node regarding actual UE performance after handover has been performed (620). This information may help the source node train the ML models it has available (630). When the source cell has sufficiently good reliability regarding the best target node for a given UE / set of UEs at a particular location, the source cell may reduce or switch off RRM measurements for this UE / set of UEs (i.e., configure the UE(s) to operate in option #2 of embodiment #3) (650). In other words, if the new reliability is greater than a threshold (640), the source cell may cause the UE to reduce / stop using RRM measurements and instead let the UE select a target cell / enable target cell selection for the UE based on predetermined information and / or network configuration (650). If the UE was not previously performing RRM measurements, the UE may be instructed to continue omitting to perform RRM measurements.

[0065] Even without RRM measurements, the source cell may determine that its confidence in the best target has decreased, for example, through feedback information regarding the UE's performance after a handover has been performed. A decrease in performance (640) can trigger the source node to turn RRM measurements back on for a given UE (or a set of UEs at a given location) by having them operate under option #1 of embodiment #3 (660). The RRM measurements can also provide input to the source cell to retrain an ML model that determines the best candidate target cell for a given UE or a set of UEs at a particular location. In other words, if the confidence is determined to be below a threshold (640), the source cell may determine that the initial confidence in the target is equal to the new confidence in the target and can trigger / enable target cell selection for the UE based on the RRM measurements.

[0066] 7 illustrates potential steps of an example method 700. The example method 700 may include receiving one or more handover configurations from a serving cell, the one or more handover configurations including an energy saving conditional handover configuration, where at least one of the one or more handover configurations includes at least one of an indication of one or more candidate target cells or information for target cell selection (710), receiving from the serving cell an indication of activation of an energy saving mode at the serving cell (720), and selecting a target cell from the one or more candidate target cells based at least in part on the one or more handover configurations and the received indication of activation of the energy saving mode at the serving cell (730).

[0067] 8 illustrates potential steps of an example method 800. The example method 800 may include determining to activate an energy saving mode (810), generating one or more handover configurations, where the one or more handover configurations include an energy saving conditional handover configuration, and where at least one of the one or more handover configurations includes at least one of an indication of one or more candidate target cells or information for target cell selection (820), transmitting the one or more handover configurations to the user equipment (830), initiating activation of the energy saving mode (840), and transmitting an indication of the activation of the energy saving mode to the user equipment (850).

[0068] According to one exemplary embodiment, an apparatus comprises at least one processor and at least one memory including computer program code, wherein the at least one memory and the computer program code are configured, using the at least one processor, to cause the apparatus to at least: receive one or more handover configurations from a serving cell, where the one or more handover configurations may include an energy saving conditional handover configuration, and at least one of the one or more handover configurations may include at least one of an indication of one or more candidate target cells or information for target cell selection; receive from the serving cell an indication of activation of an energy saving mode at the serving cell; and select a target cell from the one or more candidate target cells based at least in part on the one or more handover configurations and the received indication of activation of the energy saving mode at the serving cell.

[0069] An indication of the activation of the energy saving mode may be included in the broadcast message.

[0070] The exemplary apparatus may further be configured to disconnect from the serving cell and synchronize with the selected target cell.

[0071] At least one of the one or more handover configurations may further include an indication of one or more measurements to perform.

[0072] The example apparatus may be further configured to perform at least one of the one or more measurements and select a target cell based at least in part on a result of the at least one performed measurement.

[0073] Selecting the target cell may include the exemplary device being further configured to select the target cell based at least in part on one of predetermined information in the device associated with the target cell or information for target cell selection, where the information for target cell selection may include at least one of a transmission configuration indicator state associated with the serving cell or the target cell, a reference signal received power value associated with the serving cell or the target cell, a downlink beam of the serving cell or the target cell, or selection criteria.

[0074] The exemplary device may be in a radio resource control connected state.

[0075] The indication of activation of the energy saving mode in the serving cell may include an indication of at least one of shutting down the cell, reducing network transmit power, or muting multiple-in multiple-out transmit antenna elements.

[0076] The indication of the one or more candidate target cells may be based at least in part on one or more network shutdown policies of the serving cell, one or more frequency layers of the serving cell to be shut down, the order of shutdown of the one or more frequency layers of the serving cell to be shut down, or at least one of the frequency layers in the same power saving group as at least one of the one or more frequency layers of the serving cell to be shut down.

[0077] The example apparatus may be further configured to select an energy saving conditional handover configuration of the one or more handover configurations based at least in part on an indication of activation of an energy saving mode in the serving cell, and selecting a target cell may be further based on the selected energy saving conditional handover configuration.

[0078] The exemplary apparatus may be further configured to receive an indication of when the one or more handover configurations are applied, where the indication may include at least one of an indication of activation of an energy saving mode in the serving cell, a network offload indication, an indication of activation of the one or more handover configurations, or an indication of a time for implementation of the one or more handover configurations, where the indication of time may include a system frame number, a hyperframe number, or a number of time units.

[0079] The network offload indication or the indication of activation of one or more handover configurations may include one of downlink control information or a medium access control control element.

[0080] According to one aspect, an exemplary method may be provided that includes receiving, with user equipment, one or more handover configurations from a serving cell, where the one or more handover configurations may include an energy saving conditional handover configuration, and at least one of the one or more handover configurations may include at least one of an indication of one or more candidate target cells or information for target cell selection; receiving, from the serving cell, an indication of activation of an energy saving mode at the serving cell; and selecting a target cell from the one or more candidate target cells based at least in part on the one or more handover configurations and the received indication of activation of the energy saving mode at the serving cell.

[0081] An indication of the activation of the energy saving mode may be included in the broadcast message.

[0082] The example method may further include disconnecting the user equipment from the serving cell and synchronizing the user equipment with the selected target cell.

[0083] At least one of the one or more handover configurations may further include an indication of one or more measurements to perform.

[0084] The example method may further include performing at least one of the one or more measurements and selecting a target cell based at least in part on a result of the at least one performed measurement.

[0085] Selecting the target cell may include selecting the target cell based at least in part on one of predetermined information in the user equipment associated with the target cell or information for target cell selection, where the information for target cell selection may include at least one of a transmission configuration indicator state associated with the serving cell or the target cell, a reference signal received power value associated with the serving cell or the target cell, a downlink beam of the serving cell or the target cell, or selection criteria.

[0086] The user equipment may be in a radio resource control connected state.

[0087] The indication of activation of the energy saving mode in the serving cell may include an indication of at least one of shutting down the cell, reducing network transmit power, or muting multiple-in multiple-out transmit antenna elements.

[0088] The indication of the one or more candidate target cells may be based at least in part on one or more network shutdown policies of the serving cell, one or more frequency layers of the serving cell to be shut down, the order of shutdown of the one or more frequency layers of the serving cell to be shut down, or at least one of the frequency layers in the same power saving group as at least one of the one or more frequency layers of the serving cell to be shut down.

[0089] The example method may further include selecting an energy saving conditional handover configuration from among the one or more handover configurations based at least in part on an indication of activation of an energy saving mode in the serving cell, and the selection of the target cell may be further based on the selected energy saving conditional handover configuration.

[0090] The example method may further include receiving an indication of when the one or more handover configurations are applied, where the indication may include at least one of an indication of activation of an energy saving mode in the serving cell, a network offload indication, an indication of activation of the one or more handover configurations, or an indication of a time for implementation of the one or more handover configurations, where the indication of time may include at least one of a system frame number, a hyperframe number, or a number of time units.

[0091] The network offload indication or the indication of activation of one or more handover configurations may include one of downlink control information or a medium access control control element.

[0092] According to one example embodiment, the apparatus may comprise circuitry configured to: receive one or more handover configurations from a serving cell, where the one or more handover configurations may include an energy saving conditional handover configuration, and at least one of the one or more handover configurations may include at least one of an indication of one or more candidate target cells or information for target cell selection; receive an indication of activation of an energy saving mode at the serving cell from the serving cell; and select a target cell from the one or more candidate target cells based at least in part on the one or more handover configurations and the received indication of activation of the energy saving mode at the serving cell.

[0093] According to one exemplary embodiment, an apparatus comprises a processing circuit and a memory circuit including computer program code, the memory circuit and the computer program code configured, using the processing circuit, to enable the apparatus to: receive one or more handover configurations from a serving cell, where the one or more handover configurations may include an energy saving conditional handover configuration, and at least one of the one or more handover configurations may include at least one of an indication of one or more candidate target cells or information for target cell selection; receive from the serving cell an indication of activation of an energy saving mode at the serving cell; and select a target cell from the one or more candidate target cells based at least in part on the one or more handover configurations and the received indication of activation of the energy saving mode at the serving cell.

[0094] As used in this application, the term "circuitry" may refer to one or more or all of the following: (a) hardware-only circuit implementations (e.g., implementations with only analog and / or digital circuitry), and (b) combinations of hardware circuitry and software, such as (where applicable): (i) a combination of analog and / or digital hardware circuitry(s) with software / firmware, and (ii) any portion of a hardware processor(s) with software (including digital signal processor(s)), software, and memory(s) that cooperate to cause a device such as a cell phone or server to perform various functions; and (c) hardware circuit(s) and / or processor(s), such as a microprocessor(s) or portion of a microprocessor(s), that requires software (e.g., firmware) to operate, but the software may be absent when not necessary for operation. This definition of circuitry applies to all uses of the term in this application, including any claims. As a further example, as used in this application, the term circuit also encompasses merely a hardware circuit or processor(s) implementation, or a portion of a hardware circuit or processor and its (or their) accompanying software and / or firmware implementation. The term circuit also encompasses, for example, a baseband or processor integrated circuit for a mobile device, or a similar integrated circuit in a server, cellular network device, other computing device, or other network device, if applicable to certain claim elements.

[0095] According to one example embodiment, the apparatus may comprise means for receiving one or more handover configurations from a serving cell, where the one or more handover configurations may include an energy saving conditional handover configuration, and at least one of the one or more handover configurations may include at least one of an indication of one or more candidate target cells or information for target cell selection; receiving an indication of activation of an energy saving mode at the serving cell from the serving cell; and selecting a target cell from the one or more candidate target cells based at least in part on the one or more handover configurations and the received indication of activation of the energy saving mode at the serving cell.

[0096] An indication of the activation of the energy saving mode may be included in the broadcast message.

[0097] The means may be further configured to perform a disconnection from the serving cell and a synchronization with the selected target cell.

[0098] At least one of the one or more handover configurations may further include an indication of one or more measurements to perform.

[0099] The means may be further configured to perform at least one of the one or more measurements and select a target cell based at least in part on a result of the at least one performed measurement.

[0100] The means configured to select a target cell may comprise means configured to select a target cell based at least in part on one of predetermined information in the device associated with the target cell or information for target cell selection, where the information for target cell selection may include at least one of a transmission configuration indicator state associated with the serving cell or the target cell, a reference signal received power value associated with the serving cell or the target cell, a downlink beam of the serving cell or the target cell, or selection criteria.

[0101] The exemplary device may be in a radio resource control connected state.

[0102] The indication of activation of the energy saving mode in the serving cell may include an indication of at least one of shutting down the cell, reducing network transmit power, or muting multiple-in multiple-out transmit antenna elements.

[0103] The indication of the one or more candidate target cells may be based at least in part on one or more network shutdown policies of the serving cell, one or more frequency layers of the serving cell to be shut down, the order of shutdown of the one or more frequency layers of the serving cell to be shut down, or at least one of the frequency layers in the same power saving group as at least one of the one or more frequency layers of the serving cell to be shut down.

[0104] The means may be further configured to perform selecting an energy saving conditional handover configuration of the one or more handover configurations based at least in part on an indication of activation of the energy saving mode in the serving cell, and selecting the target cell may be further based on the selected energy saving conditional handover configuration.

[0105] The means may be further configured to execute receiving an indication of when the one or more handover configurations are applied, and the indication may include at least one of an indication of activation of an energy saving mode in the serving cell, a network offload indication, an indication of activation of the one or more handover configurations, or an indication of a time for implementation of the one or more handover configurations, and the indication of time may include at least one of a system frame number, a hyperframe number, or a number of time units.

[0106] The network offload indication or the indication of activation of one or more handover configurations may include one of downlink control information or a medium access control control element.

[0107] According to one exemplary embodiment, a non-transitory computer-readable medium having program instructions stored thereon, when executed with at least one processor, causes the at least one processor to: cause reception of one or more handover configurations from a serving cell, where the one or more handover configurations may include an energy saving conditional handover configuration, and at least one of the one or more handover configurations may include at least one of an indication of one or more candidate target cells or information for target cell selection; cause reception from the serving cell of an indication of activation of an energy saving mode at the serving cell; and select a target cell from the one or more candidate target cells based at least in part on the one or more handover configurations and the received indication of activation of the energy saving mode at the serving cell.

[0108] An indication of the activation of the energy saving mode may be included in the broadcast message.

[0109] The exemplary non-transitory computer-readable medium may be further configured to cause a disconnection from the serving cell and synchronize with the selected target cell.

[0110] At least one of the one or more handover configurations may further include an indication of one or more measurements to perform.

[0111] The exemplary non-transitory computer-readable medium may be further configured to cause at least one of the one or more measurements to be performed and to select a target cell based at least in part on a result of the at least one performed measurement.

[0112] Selecting the target cell may include the exemplary non-transitory computer-readable medium being further configured to select the target cell based at least in part on at least one of predetermined information in the non-transitory computer-readable medium associated with the target cell or information for target cell selection, where the information for target cell selection may include at least one of a transmission configuration indicator state associated with the serving cell or the target cell, a reference signal received power value associated with the serving cell or the target cell, a downlink beam of the serving cell or the target cell, or selection criteria.

[0113] The indication of activation of the energy saving mode in the serving cell may include an indication of at least one of shutting down the cell, reducing network transmit power, or muting multiple-in multiple-out transmit antenna elements.

[0114] The indication of the one or more candidate target cells may be based at least in part on one or more network shutdown policies of the serving cell, one or more frequency layers of the serving cell to be shut down, the order of shutdown of the one or more frequency layers of the serving cell to be shut down, or at least one of the frequency layers in the same power saving group as at least one of the one or more frequency layers of the serving cell to be shut down.

[0115] The exemplary non-transitory computer-readable medium may be further configured to select an energy saving conditional handover configuration among the one or more handover configurations based at least in part on an indication of activation of an energy saving mode in the serving cell, and selecting the target cell may be further based on the selected energy saving conditional handover configuration.

[0116] The exemplary non-transitory computer-readable medium may be further configured to cause reception of an indication of when one or more handover configurations are applied, where the indication may include at least one of an indication of activation of an energy saving mode in a serving cell, a network offload indication, an indication of activation of one or more handover configurations, or an indication of a time for implementation of the one or more handover configurations, where the indication of time may include at least one of a system frame number, a hyperframe number, or a number of time units.

[0117] The network offload indication or the indication of activation of one or more handover configurations may include one of downlink control information or a medium access control control element.

[0118] According to one exemplary embodiment, a machine-readable non-transitory program storage device may be provided, the non-transitory program storage device tangibly embodying a program of instructions executable by the machine to perform operations, the operations may include causing reception of one or more handover configurations from a serving cell, the one or more handover configurations may include an energy saving conditional handover configuration, and at least one of the one or more handover configurations may include at least one of an indication of one or more candidate target cells or information for target cell selection; causing reception from the serving cell of an indication of activation of an energy saving mode at the serving cell; and selecting a target cell from the one or more candidate target cells based at least in part on the one or more handover configurations and the received indication of activation of the energy saving mode at the serving cell.

[0119] According to one exemplary embodiment, the apparatus may include at least one processor and at least one memory including computer program code, wherein the at least one memory and the computer program code are configured, using the at least one processor, to cause the apparatus to at least: determine to activate an energy saving mode; generate one or more handover configurations, wherein the one or more handover configurations may include an energy saving conditional handover configuration, and at least one of the one or more handover configurations may include at least one of an indication of one or more candidate target cells or information for target cell selection; send the one or more handover configurations to the user equipment; initiate activation of the energy saving mode; and send an indication of the activation of the energy saving mode to the user equipment.

[0120] An indication of the activation of the energy saving mode may be included in the broadcast message.

[0121] The example apparatus may be further configured to: send a respective energy saving conditional handover information request to at least one of the one or more candidate target cells, where each energy saving conditional handover information request may include an energy saving mode trigger; and receive a handover request acknowledgement from the at least one candidate target cell.

[0122] The example apparatus may be further configured to: send a respective cell deactivation indication to at least one of the one or more candidate target cells, where each cell deactivation indication may include at least one of an energy saving conditional handover information request, information regarding handover preparation for the conditional handover, or a list of currently active user equipment to be offloaded to each of the one or more candidate target cells; and receive a handover request acknowledgement from the one or more candidate target cells.

[0123] At least one of the one or more handover configurations may further include an indication of one or more measurements to perform.

[0124] The example apparatus may be further configured to: receive, from the user equipment, an indication of a result of at least one of the one or more measurements; determine, based at least in part on the indication of the result of the at least one of the one or more measurements, a confidence that a target cell of the one or more candidate target cells will be selected by the user equipment for synchronization; compare the determined confidence to a threshold; and, based on a determination that the determined confidence is greater than the threshold, instruct the user equipment to omit performing the one or more measurements; perform target cell selection based on at least one of predetermined information related to the target cell or information for target cell selection; and, based on a determination that the determined confidence is less than or equal to the threshold, instruct the user equipment to perform target cell selection based on performing the one or more measurements.

[0125] The information for target cell selection may include at least one of a state of a transmission configuration indicator associated with the device or target cell, a received power value of a reference signal associated with the device or target cell, a downlink beam of the device or target cell, or a selection criterion.

[0126] The energy saving mode may include at least one of shutting down the cell, reducing network transmit power, or muting multiple-in multiple-out transmit antenna elements.

[0127] The indication of the one or more candidate target cells may be based at least in part on one or more network shutdown policies, one or more frequency layers to be shut down, an order of shutdown of the one or more frequency layers to be shut down, or at least one of a frequency layer in the same power saving group as at least one of the one or more frequency layers to be shut down.

[0128] The exemplary apparatus may be further configured to transmit an indication to the user equipment as to when the one or more handover configurations are applied, where the indication may include at least one of an indication of activation of an energy saving mode, a network offload indication, an indication of activation of the one or more handover configurations, or an indication of a time for implementation of the one or more handover configurations, where the indication of time may include a system frame number, a hyperframe number, or a number of time units.

[0129] The network offload indication or the indication of activation of one or more handover configurations may include one of downlink control information or a medium access control control element.

[0130] According to one aspect, an exemplary method may be provided, the method including: determining to activate an energy saving mode; generating one or more handover configurations, where the one or more handover configurations may include an energy saving conditional handover configuration, and at least one of the one or more handover configurations may include at least one of an indication of one or more candidate target cells or information for target cell selection; transmitting the one or more handover configurations to a user equipment; initiating activation of an energy saving mode; and transmitting an indication of the activation of the energy saving mode to the user equipment.

[0131] An indication of the activation of the energy saving mode may be included in the broadcast message.

[0132] The example method may further include transmitting a respective energy saving conditional handover information request to at least one of the one or more candidate target cells, where each energy saving conditional handover information request may include an energy saving mode trigger, and receiving a handover request acknowledgement from the at least one candidate target cell.

[0133] An example method may further include transmitting a respective cell deactivation indication to at least one of the one or more candidate target cells, where each cell deactivation indication may include at least one of an energy saving conditional handover information request, information regarding handover preparation for a conditional handover, or a list of currently active user equipment to be offloaded to each of the one or more candidate target cells; and receiving a handover request acknowledgement from the one or more candidate target cells.

[0134] At least one of the one or more handover configurations may further include an indication of one or more measurements to perform.

[0135] The example method may further include receiving, from the user equipment, an indication of a result of at least one of the one or more measurements; determining a confidence level that a target cell of the one or more candidate target cells will be selected by the user equipment for synchronization based at least in part on the indication of the result of the at least one of the one or more measurements; comparing the determined confidence level with a threshold; and, based on a determination that the determined confidence level is greater than the threshold, instructing the user equipment to omit performing the one or more measurements and perform target cell selection based on at least one of predetermined information related to the target cell or information for target cell selection; and, based on a determination that the determined confidence level is less than or equal to the threshold, instructing the user equipment to perform target cell selection based on performing the one or more measurements.

[0136] The information for target cell selection may include at least one of a state of a transmission configuration indicator associated with the base station or target cell, a reference signal received power value associated with the base station or target cell, a downlink beam of the base station or target cell, or a selection criterion.

[0137] The energy saving mode may include at least one of shutting down the cell, reducing network transmit power, or muting multiple-in multiple-out transmit antenna elements.

[0138] The indication of the one or more candidate target cells may be based at least in part on one or more network shutdown policies, one or more frequency layers to be shut down, an order of shutdown of the one or more frequency layers to be shut down, or at least one of a frequency layer in the same power saving group as at least one of the one or more frequency layers to be shut down.

[0139] The example method may further include transmitting an indication to the user equipment as to when the one or more handover configurations are applied, where the indication may include at least one of an indication of activation of an energy saving mode, a network offload indication, an indication of activation of the one or more handover configurations, or an indication of a time for implementation of the one or more handover configurations, where the indication of time may include a system frame number, a hyperframe number, or a number of time units.

[0140] The network offload indication or the indication of activation of one or more handover configurations may include one of downlink control information or a medium access control control element.

[0141] According to one exemplary embodiment, the apparatus may comprise circuitry configured to: determine to activate an energy saving mode; generate one or more handover configurations, where the one or more handover configurations may include an energy saving conditional handover configuration, and at least one of the one or more handover configurations may include at least one of an indication of one or more candidate target cells or information for target cell selection; generate the one or more handover configurations to the user equipment; initiate activation of the energy saving mode; and send an indication of the activation of the energy saving mode to the user equipment.

[0142] According to one exemplary embodiment, an apparatus may include a processing circuit and a memory circuit including computer program code, the memory circuit and the computer program code configured to enable, using the processing circuit, the apparatus to: determine to activate an energy saving mode; generate one or more handover configurations, where the one or more handover configurations may include an energy saving conditional handover configuration, and at least one of the one or more handover configurations may include at least one of an indication of one or more candidate target cells or information for target cell selection; generate the one or more handover configurations to a user equipment; initiate activation of the energy saving mode; and send an indication of the activation of the energy saving mode to the user equipment.

[0143] According to one exemplary embodiment, the apparatus may comprise means for determining to activate an energy saving mode; generating one or more handover configurations, where the one or more handover configurations may include an energy saving conditional handover configuration, and at least one of the one or more handover configurations may include at least one of an indication of one or more candidate target cells or information for target cell selection; transmitting the one or more handover configurations to the user equipment; initiating activation of the energy saving mode; and transmitting an indication of the activation of the energy saving mode to the user equipment.

[0144] An indication of the activation of the energy saving mode may be included in the broadcast message.

[0145] The means may be further configured to: send a respective energy saving conditional handover information request to at least one of the one or more candidate target cells, where each energy saving conditional handover information request may include an energy saving mode trigger; and receive a handover request acknowledgement from the at least one candidate target cell.

[0146] The means may be configured to: send a respective cell deactivation indication to at least one of the one or more candidate target cells, where each cell deactivation indication may include at least one of an energy saving conditional handover information request, information regarding handover preparation for a conditional handover, or a list of currently active user equipment to be offloaded to each of the one or more candidate target cells; and receive a handover request acknowledgement from the one or more candidate target cells.

[0147] At least one of the one or more handover configurations may further include an indication of one or more measurements to perform.

[0148] The means may be further configured to: receive from the user equipment an indication of a result of at least one of the one or more measurements; determine a confidence level that a target cell of the one or more candidate target cells will be selected by the user equipment for synchronization based at least in part on the indication of a result of the at least one of the one or more measurements; compare the determined confidence level with a threshold; and, based on a determination that the determined confidence level is greater than the threshold, instruct the user equipment to omit performing the one or more measurements and perform target cell selection based on at least one of predetermined information related to the target cell or information for target cell selection; and, based on a determination that the determined confidence level is less than or equal to the threshold, instruct the user equipment to perform target cell selection based on performing the one or more measurements.

[0149] The information for target cell selection may include at least one of a state of a transmission configuration indicator associated with the device or target cell, a received power value of a reference signal associated with the device or target cell, a downlink beam of the device or target cell, or a selection criterion.

[0150] The energy saving mode may include at least one of shutting down the cell, reducing network transmit power, or muting multiple-in multiple-out transmit antenna elements.

[0151] The indication of the one or more candidate target cells may be based at least in part on one or more network shutdown policies, one or more frequency layers to be shut down, an order of shutdown of the one or more frequency layers to be shut down, or at least one of a frequency layer in the same power saving group as at least one of the one or more frequency layers to be shut down.

[0152] The means may be further configured to execute transmitting an indication to the user equipment as to when the one or more handover configurations are applied, and the indication may include at least one of an indication of activation of an energy saving mode, a network offload indication, an indication of activation of the one or more handover configurations, or an indication of a time for implementation of the one or more handover configurations, and the indication of time may include a system frame number, a hyperframe number, or a number of time units.

[0153] The network offload indication or the indication of activation of one or more handover configurations may include one of downlink control information or a medium access control control element.

[0154] According to one exemplary embodiment, a non-transitory computer-readable medium having program instructions stored thereon, when executed with at least one processor, causes the at least one processor to: determine to activate an energy saving mode; generate one or more handover configurations, where the one or more handover configurations may include an energy saving conditional handover configuration, and at least one of the one or more handover configurations may include at least one of an indication of one or more candidate target cells or information for target cell selection; generate the one or more handover configurations to a user equipment; initiate activation of an energy saving mode; and cause transmission of an indication of activation of the energy saving mode to the user equipment.

[0155] An indication of the activation of the energy saving mode may be included in the broadcast message.

[0156] The exemplary non-transitory computer-readable medium may be further configured to cause transmission of each energy saving conditional handover information request to at least one of the one or more candidate target cells, where each energy saving conditional handover information request may include an energy saving mode trigger, and cause reception of a handover request acknowledgment from the at least one candidate target cell.

[0157] The exemplary non-transitory computer-readable medium may be further configured to: cause transmission of a respective cell deactivation indication to at least one of the one or more candidate target cells, where each cell deactivation indication may include at least one of an energy saving conditional handover information request, information regarding handover preparation for a conditional handover, or a list of currently active user equipment to be offloaded to each of the one or more candidate target cells; and cause receipt of a handover request acknowledgment from the one or more candidate target cells.

[0158] At least one of the one or more handover configurations may further include an indication of one or more measurements to perform.

[0159] The exemplary non-transitory computer-readable medium may be further configured to: cause receipt, from the user equipment, of an indication of a result of at least one of the one or more measurements; determine a confidence level that a target cell of the one or more candidate target cells will be selected by the user equipment for synchronization based at least in part on the indication of the result of the at least one of the one or more measurements; compare the determined confidence level with a threshold; and, based on a determination that the determined confidence level is greater than the threshold, instruct the user equipment to omit performing the one or more measurements and perform target cell selection based on at least one of predetermined information related to the target cell or information for target cell selection; and, based on a determination that the determined confidence level is less than or equal to the threshold, instruct the user equipment to perform target cell selection based on performing the one or more measurements.

[0160] The information for target cell selection may include at least one of a state of a transmission configuration indicator associated with the base station or target cell, a reference signal received power value associated with the base station or target cell, a downlink beam of the base station or target cell, or a selection criterion.

[0161] The energy saving mode may include at least one of shutting down the cell, reducing network transmit power, or muting multiple-in multiple-out transmit antenna elements.

[0162] The indication of the one or more candidate target cells may be based at least in part on one or more network shutdown policies, one or more frequency layers to be shut down, an order of shutdown of the one or more frequency layers to be shut down, or at least one of a frequency layer in the same power saving group as at least one of the one or more frequency layers to be shut down.

[0163] The exemplary non-transitory computer-readable medium may be further configured to cause transmission to user equipment of an indication of when one or more handover configurations are applied, where the indication may include at least one of an indication of activation of an energy saving mode, a network offload indication, an indication of activation of one or more handover configurations, or an indication of a time for implementation of the one or more handover configurations, where the indication of time may include at least one of a system frame number, a hyperframe number, or a number of time units.

[0164] The network offload indication or the indication of activation of one or more handover configurations may include one of downlink control information or a medium access control control element.

[0165] According to another example embodiment, a machine-readable non-transitory program storage device may be provided, the non-transitory program storage device tangibly embodying a program of instructions executable by the machine to perform operations, the operations including determining to activate an energy saving mode; generating one or more handover configurations, where the one or more handover configurations may include an energy saving conditional handover configuration, and at least one of the one or more handover configurations may include at least one of an indication of one or more candidate target cells or information for target cell selection; generating the one or more handover configurations to the user equipment; initiating activation of the energy saving mode; and causing transmission of an indication of activation of the energy saving mode to the user equipment.

[0166] According to another example embodiment, a computer program may include instructions stored thereon for at least performing the following: receiving one or more handover configurations from a serving cell, where the one or more handover configurations may include an energy saving conditional handover configuration, and at least one of the one or more handover configurations may include at least one of an indication of one or more candidate target cells or information for target cell selection; receiving an indication of activation of an energy saving mode at the serving cell from the serving cell; and selecting a target cell from the one or more candidate target cells based at least in part on the one or more handover configurations and the received indication of activation of the energy saving mode at the serving cell.

[0167] According to another example embodiment, a computer program may include instructions stored thereon to at least perform the following: determining to activate an energy saving mode; generating one or more handover configurations, where the one or more handover configurations may include an energy saving conditional handover configuration, and at least one of the one or more handover configurations may include at least one of an indication of one or more candidate target cells or information for target cell selection; generating the one or more handover configurations to a user equipment; initiating activation of an energy saving mode; and transmitting an indication of the activation of the energy saving mode to the user equipment.

[0168] It should be understood that the foregoing description is illustrative only. Various alternatives and modifications may be devised by those skilled in the art. For example, features recited in the various dependent claims may be combined with each other in any suitable combination(s). Furthermore, features from different embodiments described above may be selectively combined into new embodiments. Accordingly, the description is intended to embrace all such alternatives, modifications, and variations that fall within the scope of the appended claims.

Claims

1. It is a device, At least one processor, At least one memory containing computer program code and Equipped with, The at least one memory and the computer program code are used by the at least one processor to provide the device with at least one Receiving a conditional handover configuration from a serving cell, wherein the conditional handover configuration is associated with an energy saving mode, Receiving the conditional handover configuration, which includes the indication of one or more candidate target cells, Perform radio resource management (RRM) measurements on the serving cell and adjacent cells, and report these measurements to the serving cell. After receiving the conditional handover configuration, the serving cell receives an indication from the serving cell to activate the energy saving mode in the serving cell, Subject to receiving the indication of activation of the energy saving mode in the serving cell, a target cell for handover is selected from the one or more candidate target cells based on the RRM measurement. The apparatus configured to perform the following action.

2. The conditional handover configuration further includes information for target cell selection, and the at least one memory and the computer program code are used by the at least one processor to send the device, Based on the information for selecting the target cell, the target cell is selected from the one or more candidate target cells for handover. The apparatus according to claim 1, configured to perform the following.

3. The information for selecting the target cell includes one or more execution conditions, and the at least one memory and the computer program code are used by the at least one processor to send the device, Evaluate one or more of the execution conditions, and select the target cell from the one or more candidate target cells based on the evaluation of the one or more execution conditions. The apparatus according to claim 2, configured to perform the following.

4. The apparatus according to claim 2, wherein the information for selecting the target cell includes one or more wireless conditions to be evaluated.

5. The apparatus according to claim 1, wherein the indication for activating the energy saving mode is included in a broadcast message.

6. The at least one memory and the computer program code are used by the at least one processor to provide the device. Being disconnected from the serving cell, To synchronize with the selected target cell It is configured to perform the following: The apparatus according to claim 1.

7. The apparatus according to claim 1, wherein the conditional handover configuration further includes indication of one or more measurements of the RRM measurement, and the selection of a target cell for handover is performed based on the one or more measurements.

8. The apparatus according to claim 1, wherein the apparatus is in a wireless resource control connection state.

9. The indication for activating the energy saving mode in the serving cell is Cell shutdown, Reduce network transmission power, or Muting of multi-in / multi-out transmitting antenna elements Including at least one of the following indications, The apparatus according to claim 1.

10. The at least one memory and the computer program code are used by the at least one processor to provide the device. The conditional handover configuration is configured to receive an indication of when it should be applied, and the indication is: The indication for activating the energy saving mode in the serving cell, Network offload indication, Indication of activation of the aforementioned conditional handover configuration, or Indication of time for implementing the aforementioned conditional handover configuration The indication of the time includes at least one of the following: System frame number, Hyperframe number, or Time units Including at least one of the following: The apparatus according to claim 1.

11. The network offload indication, or the indication for activating the conditional handover configuration, Downlink control information, or Media access control control element The apparatus according to claim 10, comprising one of the following.

12. It is a method, Receiving a conditional handover configuration from a serving cell using user equipment, wherein the conditional handover configuration is associated with an energy saving mode, Receiving the conditional handover configuration, which includes the indication of one or more candidate target cells, Performing radio resource management (RRM) measurements on the serving cell and adjacent cells, and reporting these measurements to the serving cell / network, After receiving the conditional handover configuration, the serving cell receives an indication from the serving cell to activate the energy saving mode in the serving cell, Subject to receiving the indication of activation of the energy saving mode in the serving cell, a target cell for handover is selected from the one or more candidate target cells based on the RRM measurement. The method, including the method described above.

13. A non-temporary computer-readable medium containing stored instructions, wherein, when the instructions are executed by at least one processor, the at least one processor is configured to: Receiving a conditional handover configuration from a serving cell, wherein the conditional handover configuration is associated with an energy saving mode, Receiving the conditional handover configuration, which includes the indication of one or more candidate target cells, Performing radio resource management (RRM) measurements on the serving cell and adjacent cells, and reporting these measurements to the serving cell / network, After receiving the conditional handover configuration, the serving cell receives an indication from the serving cell to activate the energy saving mode in the serving cell, Subject to receiving the indication of activation of the energy saving mode in the serving cell, a target cell for handover is selected from the one or more candidate target cells based on the RRM measurement. The non-temporary computer-readable medium that enables at least the execution of the following.

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