Baseline handover

Abstract

Baseline Handover Example embodiments relate to baseline handover (BHO). In some examples, a method of a first apparatus may comprise receiving, from a second apparatus, and as part of a layer 3, L3, baseline handover, BHO, procedure, downlink synchronization information associated with at least one candidate target cell, and commencing downlink synchronization for the at least one candidate target cell based on the downlink synchronization information, wherein the downlink synchronization is commenced prior to receiving a first instruction from the second apparatus to perform BHO to a particular cell from the at least one candidate target cell.

Description

[0001] Baseline Handover

[0002] Technical Field

[0003] Example embodiments relate to baseline handover (BHO).

[0004] Background

[0005] In cellular networks, handover refers to a process in which a user device is caused to disconnect from a current cell, which may be referred to as a serving or source cell, and is then caused to connect to a different cell, which may be referred to as a target cell. The purpose may be to ensure that the user device is connected to a cell with, for example, better signal quality, although other considerations may apply. The handover is usually controlled, at least in part, by a network node associated with the current serving cell. Baseline handover (BHO) is a handover process that uses higher-layer signalling, for example layer 3 (L3) signalling for handover decisions. L3 refers to the network layer in the context of fifth generation (5G) radio networks or alternatively the Radio Resource Control (RRC) layer.

[0006] Summary

[0007] According to some aspects, there is provided the subject matter of the independent claims. Some further aspects are defined in the dependent claims. The embodiments that do not fall under the scope of the claims are to be interpreted as examples useful for understanding the disclosure.

[0008] According to a first aspect of the invention, there is provided a first apparatus comprising at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the first apparatus to: receive, from a second apparatus, and as part of a layer 3, L3, baseline handover, BHO, procedure, downlink synchronization information associated with at least one candidate target cell; and commence downlink synchronization for the at least one candidate target cell based on the downlink synchronization information, wherein the downlink synchronization is commenced prior to receiving a first instruction from the second apparatus to perform BHO to a particular cell from the at least one candidate target cell.

[0009] In some examples, the at least one processor and the at least one memory store instructions that, when executed by the at least one processor, cause the first apparatus to: transmit, to the second apparatus, and prior to receiving the first instruction from the second apparatus, an indication that downlink synchronization for the at least one candidate target cell has at least commenced.In some examples, the at least one processor and the at least one memory store instructions that, when executed by the at least one processor, further cause the first apparatus to: receive the first instruction; and commence, in response to receiving the first instruction, a random-access, RACH, procedure with the particular cell.

[0010] In some examples, the first instruction is received with a radio resource control, RRC, reconfiguration message.

[0011] In some examples, the at least one processor and the at least one memory store instructions that, when executed by the at least one processor, further cause the first apparatus to: detect a reporting event; and transmit, to the second apparatus, and in response to detecting the reporting event, a first measurement report as part of the BHO procedure, wherein the downlink synchronization information is received from the second apparatus in response to the transmitting of the first measurement report. In some examples, the first measurement report includes at least L3 measurements. In some examples, the first measurement report further includes layer 1, LI, measurements.

[0012] In some examples, the at least one processor and the at least one memory store instructions that, when executed by the at least one processor, further cause the first apparatus to: receive, from the second apparatus, and in response to transmitting the first measurement report including the at least L3 measurements, a second instruction to perform LI measurements; perform LI measurements in accordance with the second instruction; and transmit, to the second apparatus, the LI measurements in a second measurement report.

[0013] In some examples, the downlink synchronization is performed for the at least one candidate target cell until the earliest of: receipt of the first instruction; or expiry of a, or a respective, time period, associated with the downlink synchronization information for the at least one candidate target cell; or receipt of a third instruction to suspend downlink synchronization for the at least one candidate target cell. In some examples, activation of the, or the respective, time period is commenced upon the receiving of the downlink synchronization information for the at least one candidate target cell.

[0014] In some examples, the at least one processor and the at least one memory store instructions that, when executed by the at least one processor, further cause the first apparatus to: obtain the, or the respective, time period, from the second apparatus.In some examples, the at least one processor and the at least one memory store instructions that, when executed by the at least one processor, further cause the first apparatus to: obtain assistance information from the second apparatus, wherein the, or the respective, time period is determined by the first apparatus based at least in part on the assistance information. In some examples, the assistance information indicates at least one of: a maximum latency period associated with an application running at the first apparatus; a periodicity associated with at least one reference signal transmitted by the at least one candidate target cell.

[0015] In some examples, the at least one processor and the at least one memory store instructions that, when executed by the at least one processor, cause the first apparatus to: transmit, to the second apparatus, at least an indication of the determined time period or the respective time periods. In some examples, the indication of the determined time period or the respective time periods is transmitted until the downlink synchronization is at least commenced.

[0016] In some examples, the downlink synchronization information for the at least one candidate target cell indicates at least one Transmission Control Indicator, TCI, state to be activated for the at least one candidate target cell.

[0017] In some examples, the at least one processor and the at least one memory store instructions that, when executed by the at least one processor, cause the first apparatus to: activate the indicated at least one TCI state for the at least one candidate target cell; and perform downlink synchronization for the at least one candidate target cell based on a configuration associated with the at least one activated TCI state for the at least one candidate target cell.

[0018] In some examples, the at least one processor and the at least one memory store instructions that, when executed by the at least one processor, cause the first apparatus to: deactivate the at least one activated TCI state for the at least one candidate target cell in response to at least one of: receipt of the first instruction; expiry of the, or the respective, time period, associated with the at least one activated TCI state for the at least one candidate cell; or receipt of the third instruction to suspend downlink synchronization for the at least one candidate target cell.

[0019] In some examples, the indication that downlink synchronization for the at least one candidate target cell has at least commenced is comprised in a third measurement report as part of the BHO procedure.According to a second aspect of the invention, there is provided a method of a first apparatus, comprising: receiving, from a second apparatus, and as part of a layer 3, L3, baseline handover, BHO, procedure, downlink synchronization information associated with at least one candidate target cell; and commencing downlink synchronization for the at least one candidate target cell based on the downlink synchronization information, wherein the downlink synchronization is commenced prior to receiving a first instruction from the second apparatus to perform BHO to a particular cell from the at least one candidate target cell.

[0020] In some embodiments, the second aspect may comprise any feature described in relation to the first aspect.

[0021] According to a third aspect of the invention, there is provided a computer program product comprising program instructions which, when the program instructions are executed by a first apparatus, cause the first apparatus to carry out a method of: receiving, from a second apparatus, and as part of a layer 3, L3, baseline handover, BHO, procedure, downlink synchronization information associated with at least one candidate target cell; and commencing downlink synchronization for the at least one candidate target cell based on the downlink synchronization information, wherein the downlink synchronization is commenced prior to receiving a first instruction from the second apparatus to perform BHO to a particular cell from the at least one candidate target cell.

[0022] In some embodiments, the third aspect may comprise any feature described in relation to the first aspect.

[0023] According to a fourth aspect of the invention, there is provided a computer program product embodied on a non-transitory distribution medium readable by a computer and comprising program instructions which, when the program instructions are executed by a first apparatus, cause the first apparatus to: receive, from a second apparatus, and as part of a layer 3, L3, baseline handover, BHO, procedure, downlink synchronization information associated with at least one candidate target cell; and commence downlink synchronization for the at least one candidate target cell based on the downlink synchronization information, wherein the downlink synchronization is commenced prior to receiving a first instruction from the second apparatus to perform BHO to a particular cell from the at least one candidate target cell.In some embodiments, the fourth aspect may comprise any feature described in relation to the first aspect.

[0024] According to a fifth aspect of the invention, there is provided a first apparatus, comprising: means for receiving, from a second apparatus, and as part of a layer 3, L3, baseline handover, BHO, procedure, downlink synchronization information associated with at least one candidate target cell; and means for commencing downlink synchronization for the at least one candidate target cell based on the downlink synchronization information, wherein the downlink synchronization is commenced prior to receiving a first instruction from the second apparatus to perform BHO to a particular cell from the at least one candidate target cell.

[0025] In some embodiments, the fifth aspect may comprise any feature described in relation to the first aspect.

[0026] In some embodiments, the first apparatus is comprised by a user terminal.

[0027] According to a sixth aspect of the invention, there is provided a second apparatus comprising at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the second apparatus to: receive, from a first apparatus, a first measurement report as part of a Layer 3, L3, baseline handover, BHO, procedure; transmit, to the first apparatus, and in response to receiving the first measurement report, downlink synchronization information associated with at least one candidate target cell; and transmit to the first apparatus, and subsequent to the transmitting of the downlink synchronization information, a first instruction to perform BHO to a particular cell from the at least one candidate target cell, wherein the particular cell is determined based at least in part on the measurement report.

[0028] In some examples, the at least one processor and the at least one memory store instructions that, when executed by the at least one processor, cause the second apparatus to: receive, from the first apparatus, an indication that downlink synchronization for the at least one candidate target cell has at least commenced, wherein the first instruction is transmitted in response to the receiving of the indication.

[0029] In some examples, the first instruction is transmitted with a radio resource control, RRC, reconfiguration message.In some examples, the first measurement report includes at least L3 measurements. In some examples, the first measurement report further includes layer 1, LI, measurements.

[0030] In some examples, the at least one processor and the at least one memory store instructions that, when executed by the at least one processor, cause the second apparatus to: transmit, to the first apparatus, and in response to receiving the first measurement report including the at least L3 measurements, a second instruction to perform LI measurements; and receive, from the first apparatus, LI measurements in a second measurement report.

[0031] In some examples, the at least one processor and the at least one memory store instructions that, when executed by the at least one processor, cause the second apparatus to: transmit, to the first apparatus, a, or a respective, time period associated with the downlink synchronization information for the at least one candidate target cell, wherein the, or the respective time period, indicates a time period for which downlink synchronization is to be performed by the first apparatus.

[0032] In some examples, the at least one processor and the at least one memory store instructions that, when executed by the at least one processor, cause the second apparatus to: transmit, to the first apparatus, assistance information for enabling the first apparatus to determine a, or a respective, time period associated with the downlink synchronization information for the at least one candidate target cell, wherein the, or the respective time period, indicates a time period for which downlink synchronization is to be performed by the first apparatus.

[0033] In some examples, the assistance information indicates at least one of: a maximum latency period associated with an application running at the first apparatus; a periodicity associated with at least one reference signal transmitted by the at least one candidate target cell.

[0034] In some examples, the at least one processor and the at least one memory store instructions that, when executed by the at least one processor, cause the second apparatus to: receive, from the first apparatus, at least an indication of the determined time period or respective time periods.

[0035] In some examples, the at least the indication of the determined time period or the respective time periods is received until downlink synchronization is at least commenced at the first apparatus.In some examples, the at least one processor and the at least one memory store instructions that, when executed by the at least one processor, cause the second apparatus to: transmit, to the first apparatus, a third instruction to suspend downlink synchronization for the at least one candidate target cell.

[0036] In some examples, the downlink synchronization information for the at least one candidate target cell indicates at least one Transmission Control Indicator, TCI, state to be activated for the at least one candidate target cell.

[0037] In some examples, the indication that downlink synchronization for the at least one candidate target cell has at least commenced is comprised in a third measurement report as part of the BHO procedure.

[0038] According to a seventh aspect of the invention, there is provided a method of a second apparatus, comprising: receiving, from a first apparatus, a first measurement report as part of a Layer 3, L3, baseline handover, BHO, procedure; transmitting, to the first apparatus, and in response to receiving the first measurement report, downlink synchronization information associated with at least one candidate target cell; and transmitting to the first apparatus, and subsequent to the transmitting of the downlink synchronization information, a first instruction to perform BHO to a particular cell from the at least one candidate target cell, wherein the particular cell is determined based at least in part on the measurement report.

[0039] In some embodiments, the seventh aspect may comprise any feature described in relation to the sixth aspect.

[0040] According to an eighth aspect of the invention, there is provided a computer program product comprising program instructions which, when the program instructions are executed by a second apparatus, cause the second apparatus to carry out a method of: receiving, from a first apparatus, a first measurement report as part of a Layer 3, L3, baseline handover, BHO, procedure; transmitting, to the first apparatus, and in response to receiving the first measurement report, downlink synchronization information associated with at least one candidate target cell; and transmitting to the first apparatus, and subsequent to the transmitting of the downlink synchronization information, a first instruction to perform BHO to a particular cell from the at least one candidate target cell, wherein the particular cell is determined based at least in part on the measurement report.In some embodiments, the eighth aspect may comprise any feature described in relation to the sixth aspect.

[0041] According to a ninth aspect of the invention, there is provided a computer program product embodied on a non-transitory distribution medium readable by a computer and comprising program instructions which, when the program instructions are executed by a second apparatus, cause the second apparatus to: receive, from a first apparatus, a first measurement report as part of a Layer 3, L3, baseline handover, BHO, procedure; transmit, to the first apparatus, and in response to receiving the first measurement report, downlink synchronization information associated with at least one candidate target cell; and transmit to the first apparatus, and subsequent to the transmitting of the downlink synchronization information, a first instruction to perform BHO to a particular cell from the at least one candidate target cell, wherein the particular cell is determined based at least in part on the measurement report.

[0042] In some embodiments, the ninth aspect may comprise any feature described in relation to the sixth aspect.

[0043] According to a tenth aspect of the invention, there is provided a second apparatus, comprising: means for receiving, from a first apparatus, a first measurement report as part of a Layer 3, L3, baseline handover, BHO, procedure; means for transmitting, to the first apparatus, and in response to receiving the first measurement report, downlink synchronization information associated with at least one candidate target cell; and means for transmitting to the first apparatus, and subsequent to the transmitting of the downlink synchronization information, a first instruction to perform BHO to a particular cell from the at least one candidate target cell, wherein the particular cell is determined based at least in part on the measurement report..

[0044] In some embodiments, the tenth aspect may comprise any feature described in relation to the sixth aspect.

[0045] In some embodiments, the second apparatus is comprised by a network node.

[0046] Drawings

[0047] In the following, example embodiments will be described in greater detail with reference to the embodiments and the accompanying drawings, in which:

[0048] Figure 1 illustrates an example communication network;Figure 2 is a signalling diagram illustrating an example of a BHO procedure;

[0049] Figure 3 is a flow diagram according to some example embodiments;

[0050] Figure 4 is a signalling diagram illustrating an example of a BHO procedure according to some example embodiments;

[0051] Figure 5 is a flow diagram of operations according to some example embodiments;

[0052] Figure 6 is a flow diagram of operations according to some example embodiments;

[0053] Figure 7 illustrates an example of an apparatus; and

[0054] Figure 8 illustrates a non-transitory medium.

[0055] Detailed Description

[0056] Example embodiments relate generally to mobility in communication networks and baseline handover (BHO) processes.

[0057] In cellular communication networks, handover refers to a process in which a user device, or user equipment (UE), is caused to disconnect from a current cell, which may be referred to as a serving or source cell (hereafter serving cell) and is then caused to connect to a different cell, which may be referred to as a target cell which may be selected from one or more candidate (or potential) target cells. The purpose may, for example, be to ensure that the user device is connected to a target cell with better signal quality, although other considerations may apply. The handover is usually controlled, at least in part, by a network node associated with the current serving cell.

[0058] BHO is a handover process that uses higher-layer signalling, for example layer 3 (L3) signalling for the handover decisions. L3 refers to the network layer in the context of fifth generation (5G) radio networks, or alternatively the Radio Resource Control (RRC) layer. BHO is to be distinguished from lower-layer handover processes such as lower-layer triggered mobility (LTM) processes that mainly considers layer 1 (LI) signalling for the handover decisions.

[0059] The following embodiments are exemplary. Although the specification may refer to "an", "one", or "some" embodiment(s) in several locations of the text, this does not necessarily mean that each reference is made to the same embodiment(s), or that a particular feature only applies to a single embodiment. Single features of different embodiments may also be combined to provide other embodiments. Further, when a particular feature, structure, or characteristic is described in connection of an embodiment, it is within the knowledge of one skilled in the art to apply such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described. It shall be understood that although the terms "first," "second" and the like may be used herein to describe variouselements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another.

[0060] For the purposes of the present disclosure, the phrases "at least one of A or B", "at least one of A and B", and "A and / or B" means (A), (B), or (A and B). For the purposes of the present disclosure, the phrase "A, B, and / or C" means (A), (B), (C), (A and B), (A and C), (B and C), or (A, B, and C).

[0061] Embodiments described may be implemented in a communication network, such as any of the following radio access technologies (RATs): Worldwide Interoperability for Micro-wave Access (WiMAX), Global System for Mobile communications (GSM, 2G), GSM EDGE radio access Network (GERAN), General Packet Radio Service (GRPS), Universal Mobile Telecommunication System (UMTS, 3G) based on basic wideband-code division multiple access (W-CDMA), high-speed packet access (HSPA), Long Term Evolution (LTE), LTE-Advanced, and enhanced LTE (eLTE), 5G (also called NR), or any future RAT such as 6G. Moreover, communication within the communication network may utilize any proper wireless communication technology, comprising but not limited to: Code Division Multiple Access (CDMA), Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), Frequency Division Duplex (FDD), Time Division Duplex (TDD), Multiple-Input Multiple-Output (MIMO), Orthogonal Frequency Division Multiple (OFDM), and / or Discrete Fourier Transform spread OFDM (DFT-s-OFDM).

[0062] As used herein, the term "network node" (alternatively "network device") refers to a node in a communication network via which user equipment may access the network and / or which is capable of controlling radio communication and managing radio resources within a cell. The network node may be referred to as a base station (BS), an access point (AP) or an access node. The network node may be, depending on the applied technology, for example, a node B (NodeB or NB), an evolved NodeB (eNodeB or eNB), an NR NB (also referred to as a gNB), a Remote Radio Unit (RRU), a radio head (RH), a remote radio head (RRH), a relay, an Integrated Access and Backhaul (IAB) node, a low power node, a nonterrestrial network (NTN) or non-ground network node such as a satellite network device, a low earth orbit (LEO) satellite and a geosynchronous earth orbit (GEO) satellite, or an aircraft network device.

[0063] Moreover, in connection of split radio access network (RAN), the network node may refer to a centralised unit (CU) of a base station and / or a distributed unit (DU) of a base station. An interface between CU and DU may be referred to as an Fl interface in NR. In the split RAN architecture, node operations may be carried out, at least partly, in thecentral / centralized unit, CU, (e.g. server, host or node) operationally coupled to the DU, (e.g. a radio head / node). One CU may control one or more DUs, acting at least as transmit / receive (Tx / Rx) nodes. In some embodiments, the DUs may comprise e.g. a radio link control (RLC), medium access control (MAC) layer and a physical (PHY) layer, whereas the CU may comprise the layers above RLC layer, such as a packet data convergence protocol (PDCP) layer, a radio resource control (RRC) and an internet protocol (IP) layer. Other functional splits are possible too. In practice, any processing task may be performed in either the CU or the DU and the boundary where the responsibility is shifted between the CU and the DU may depend on the applied implementation.

[0064] The term "terminal device" or alternatively "user terminal" refers to any end device that may be capable of wireless communication. By way of example, a terminal device may be referred to as a communication device, user equipment (UE), user device, a Subscriber Station (SS), or a Mobile Station (MS). The terminal device may include a mobile phone, a cellular phone, a smart phone, voice over IP (VoIP) phones, wireless local loop phones a tablet, a wearable terminal device, a personal digital assistant (PDA), portable computers, desktop computer, image capture terminal devices such as digital cameras, gaming terminal devices, music storage and playback appliances, vehicle-mounted wireless terminal devices, USB dongles, an Internet of Things (loT) device, a watch or other wearable, a head-mounted display (HMD), a vehicle, a drone, a medical device and applications (e.g., remote surgery), an industrial device and applications (e.g., a robot and / or other wireless devices operating in an industrial and / or an automated processing chain contexts), a consumer electronics device, a device operating on commercial and / or industrial wireless networks, and the like. For ease of explanation, the term UE will be used hereinafter but any of the above alternatives may be used.

[0065] A term "resource", as used herein, may refer to radio resources in time domain, in frequency domain, in space domain, and / or in code domain. Some examples of resources include e.g. a physical resource block (PRB), a radio frame, a subframe, a time slot, a subband, a frequency region, a sub-carrier, a beam, etc. The term "transmission" and / or "reception" may refer to wirelessly transmitting and / or receiving via a wireless propagation channel on radio resources.

[0066] FIG. 1 illustrates an example of a communication network to which examples disclosed herein may be applied. The communication network or a cellular communication network may comprise a first network node 110 providing one or more cells, such as cell 100, and a second network node 112 providing one or more other cells, such as cell 102. In some examples, there may be greater than two network nodes each providing one or more cells.Each cell may be, e.g., a macro cell, a micro cell, femto, or a pico cell, for example. The cell may define a coverage area or a service area of the corresponding network node.

[0067] The first network node 110 may provide a UE 120 (one or more UEs) with wireless access to the communication network. The wireless access may comprise downlink (DL) communication from the first network node to the UE 120 and / or uplink (UL) communication from the UE 120 to the first network node. Examples of uplink channels comprise physical uplink control channel (PUCCH) for transmitting control information and physical uplink shared channel (PUSCH) for transmitting data towards the network. Examples of downlink channels comprise physical downlink control channel (PDCCH) for transmitting control information and physical downlink shared channel (PDSCH) for transmitting data towards the user equipment.

[0068] There may be a plurality of UEs 120, 122 in the system. Each of them may be served by the same or by different ones of the first and second network nodes 110, 112. UEs 120, 122 may be configured with dual connectivity (DC), wherein the UE, e.g. UE 120, may be connected to multiple network nodes, for example the first and second network nodes, 110, 112. The UEs 120, 122 may communicate with each other, in case a device-to-device (D2D) communication interface is established between them via a so-called sidelink (SL). Such D2D communications may be referred to as machine-to-machine, peer-to-peer (P2P) communications, or vehicle-to-vehicle (V2V), for example.

[0069] In the case of multiple network nodes in the communication network, the first and second network nodes 120, 122 may be connected to each other via an interface. LTE specifications call such an interface as X2 interface. An interface between an LTE node and a 5G node, or between two 5G nodes may be called Xn interface.

[0070] The first and second network nodes 110 and 112 may be further connected via another interface to a core network 116 of the communication network. The LTE specifications specify the core network as an evolved packet core (EPC), and the core network may comprise e.g. a mobility management entity (MME) and a gateway node. The MME may handle mobility of terminal devices in a tracking area encompassing a plurality of cells and handle signalling connections between the terminal devices and the core network. The gateway node may handle data routing in the core network and to / from the terminal devices. The 5G specifications specify the core network as a 5G core (5GC). The 5G core may comprise e.g. an access and mobility management function (AMF) and a user plane function / gateway (UPF) and other functions. The AMF may handle termination of non-access stratum (NAS) signalling, NAS ciphering & integrity protection, registrationmanagement, connection management, mobility management, access authentication and authorization, security context management. The UPF node may support packet routing and forwarding, packet inspection and quality of service (QoS) handling, for example.

[0071] FIG. 2 is a signal flow diagram of a BHO process.

[0072] The BHO process may be the same, or similar to, that described in, for example, 3GPP Release 15. FIG. 2 illustrates interaction and messaging between the UE 120, the first network node 110, assumed to be associated with a current serving cell of the UE, and a second network node 112, assumed to be associated with a candidate target cell of the UE.

[0073] In an operation 2.1, the UE 120 may transmit a measurement report to the first network node 110. The UE 120 may transmit the measurement report in response to detecting a trigger event. For example, the UE 120 may be configured with a measurement and reporting configuration, or separate measurement and reporting configurations, which for example indicate resources for performing one or more L3 measurements on reference signals transmitted by a plurality of cells, such as the serving cell and one or more candidate target cells, an indication of one or more conditions (based upon which a measurement report is triggered) and resources for reporting at least some of the one or more L3 measurements in a measurement report to the current serving cell. The one or more conditions may be associated with one or more events, such as (but not limited to) so-called A3 events wherein the L3 measurements indicate that at least one candidate target cell becomes better than the current serving cell. Upon detection of such an event, the measurement report may include at least L3 measurements of the at least one candidate target cell, wherein the measurements may include metrics such as at least one of reference signal received power (RSRP), reference signal received quality (RSRQ) or signal to interference noise ratio (SINR). The L3 measurements may include the L3 cell quality derivation and L3 beam measurements for individual beams of the at least one candidate target cell, for example as per 3GPP TS 38.331.

[0074] In an operation 2.2, the first network node 110 may identify the need to trigger BHO to the second network node 112 (assumed to be associated with a best or preferred candidate target cell or cells).

[0075] In an operation 2.3, the first network node 110 responsively transmits a BHO request to the second network node 112, requesting a handover configuration for said candidate target cell or cells. It will be appreciated that the handover configuration may comprise aradio protocol configuration for the candidate target cell or cells that the UE 120 will apply upon performing BHO to the candidate target cell or cells of the second network node 112.

[0076] In an operation 2.4, the second network node 112 may responsively perform an admission control process and generate the above-mentioned handover configuration for the candidate target cell or cells indicated in the BHO request.

[0077] In an operation 2.5, the second network node 112 may transmit to the first network node 110 an instruction or message, for example a handover request acknowledgment, including the above-mentioned handover configuration for the candidate target cell or cells and which may be part of a handover command.

[0078] In an operation 2.6, the first network node 110 may responsively transmit to the UE 120 an instruction or message, for example a handover command (alternatively BHO command) which may be the same, or is based upon, the handover command received from the second network node 112 and which includes the handover configuration for the candidate target cell or cells. The instruction may be received by the UE 120 in an RRC reconfiguration message.

[0079] In an operation 2.7, the UE 120 may responsively initiate a so-called random-access procedure using a random-access channel (RACH) towards the candidate target cell or cells based on the handover configuration. As will be appreciated, the RACH procedure involves the UE establishing using downlink (and uplink) synchronization (time and / or frequency synchronization) with the candidate target cell or cells for subsequent communications over PDCCH and PDSCH (and PUCCH and PUSCH) channels. The RACH procedure may be considered a fine-tuning process for initial access with the candidate target cell or cells. For example, the UE 120 may receive, using the RACH, one or more transmission configuration indicator (TCI) states, or indications thereof, per candidate target cell or cells, that are to be used or activated by the UE. For example, the TCI state may define a set of transmission parameters, such as spatial properties, e.g., transmission and reception angles, that the UE 120 may utilize for downlink reception and uplink transmission. For example, the TCI state may define one or more reference signals and / or quasi co-location (QCL) information of the one or more reference signals. The reference signals may for example comprise at least one of synchronization signal blocks (SSB), tracking reference signals (TRS) or channel state information-reference signals (CSI-RS). The QCL information may include at least one of doppler spread, doppler shift, average delay, delay spread and spatial reception parameters. The UE 120 may for example derive such parameter(s) for fine-tuned synchronization by measuring the one or more referencesignals and applies these parameters for receiving and transmitting data with the candidate target cell or cells associated with said TCI state(s).

[0080] There is a time period during which the UE 120 exchanges no data with the serving cell nor the candidate target cell or cells, which may be referred to as the BHO interruption time. The RACH procedure in BHO requires the UE 120 to perform the above-described synchronization with the candidate target cell, to ensure that the UE can correctly receive and decode downlink transmissions using, for example, PDCCH and PDSCH channels. The TCI states, for example, are only indicated in the RACH procedure and activating a TCI state means that the UE 120 initiates and continues to keep track of the fine downlink time and / or frequency synchronization for said TCI state; hence there is a time interval from the time instance when the UE receives the TCI state activation command as part of the operation 2.7 and the time that TCI state becomes active; this may be referred to as the TCI state activation delay and this contributes to the BHO interruption time. BHO has a relatively large interruption time compared to, for example, LTM, given that downlink synchronization occurs quite late (when the UE 120 commences the RACH process) which may be unsuitable for certain UEs or applications that require a shorter interruption time.

[0081] Example embodiments may avoid or mitigate such disadvantages, for example by decreasing the BHO interruption time.

[0082] Figure 3 is a flow diagram showing operations 300 that may be performed by one or more example embodiments. The operations 300 may be performed by hardware, software, firmware or a combination thereof. The operations 300 may be performed by one, or respective, means, a means being any suitable means such as one or more processors or controllers in combination with computer-readable instructions provided on one or more memories.

[0083] The operations 300 may, for example, be performed by a first apparatus, for example the UE 120 of Figure 1. The order of operations 300 is not necessarily indicative of their order of processing or performance.

[0084] A first operation 310 may comprise receiving, from a second apparatus, and as part of a layer 3, L3, baseline handover, BHO, procedure, downlink synchronization information associated with at least one candidate target cell.

[0085] A second operation 320 may comprise commencing downlink synchronization for the at least one candidate target cell based on the downlink synchronization information, whereinthe downlink synchronization is commenced prior to receiving a first instruction from the second apparatus to perform BHO to a particular cell from the at least one candidate target cell.

[0086] The second apparatus may comprise a network node associated with the current serving cell.

[0087] The operations 300 thus provide early downlink synchronization for at least one candidate target cell, whereby said downlink synchronization is commenced prior to receiving the first instruction which may be equated with receiving the BHO command in operation 2.6. Thus, when the BHO command is received, the first apparatus, or UE 120, has at least commenced (and possibly completed) downlink synchronization with the candidate target cell and BHO interruption time is reduced.

[0088] In some examples, a further (optional) operation 330 may comprise transmitting, to the second apparatus, and (also) prior to receiving the first instruction from the second apparatus, an indication that downlink synchronization for the at least one candidate target cell has at least commenced (or has completed). Thus, the second apparatus knows that it is appropriate to initiate the BHO procedure and transmit the handover request message as part of BHO as in operation 2.3 of Figure 2.

[0089] In some examples, further operations may comprise receiving the first instruction, for example the BHO command, and responsively commencing a RACH procedure with the particular cell. The first instruction may be received with a RRC message, for example.

[0090] In some examples, the downlink synchronization information may be received in response to the first apparatus earlier transmitting, to the second apparatus, a first measurement report. Accordingly, in some examples, further operations may comprise detecting a reporting event, for example (but not limited to) an A3 event, and transmitting, to the second apparatus, and in response to detecting the reporting event, a first measurement report as part of the BHO procedure, wherein the downlink synchronization information is received from the second apparatus in response to the transmitting of the first measurement report. In some examples, the first measurement report includes at least L3 measurements. In some examples, the first measurement report further includes layer 1, LI, measurements which are lower layer measurements at the physical layer. In some examples, in response to transmitting the first measurement report including the at least L3 measurements, another operation may comprise receiving, from the second apparatus, a second instruction to perform LI measurements, performing the LI measurements andtransmitting, to the second apparatus, the LI measurements in a second measurement report. LI measurements may provide more specific cell measurements, and the downlink synchronization information may be based, at least in part, on at least some of the LI measurements. As described below, the downlink synchronization information for the at least one candidate target cell may indicate at least one TCI state to be activated for the at least one candidate target cell; LI measurements may be used to fine-tune the TCI state activation.

[0091] In some examples, the downlink synchronization may be performed for a limited time and then suspended or ceased. For example, the downlink synchronization may be performed until receipt of the first instruction. For example, the downlink synchronization may be performed until expiry of a, or a respective, time period associated with the downlink synchronization information for the at least one candidate target cell, if expiry occurs earlier than receiving the first instruction. In some examples, the second apparatus may optionally transmit a third instruction to suspend downlink synchronization for the at least one candidate target cell, in which case the first apparatus responsively suspends said downlink synchronization for the at least one candidate target cell, for example if the third instruction is received earlier than receiving the first instruction or expiry of the, or the respective, time period associated with the downlink synchronization information.

[0092] In some examples, activation (starting of) the, or the respective, time period is commenced upon the receiving of the downlink synchronization information for the at least one candidate target cell.

[0093] In some examples, the, or the respective, time period is obtained from (e.g., received or configured by) the second apparatus.

[0094] In some examples, the, or the respective, time period is determined by the first apparatus based at least in part on assistance information. Another operation may therefore comprise obtaining (e.g., receiving) assistance information from the second apparatus and determining the, or the respective, time period based at least in part on the assistance information. For example, the assistance information may indicate at least one of a maximum latency period associated with an application running at the first apparatus or a periodicity associated with at least one reference signal transmitted by the at least one candidate target cell.

[0095] In some examples, another operation may comprise transmitting, to the second apparatus, at least an indication of the determined time period or the respective time periods. Insome examples, the indication of the determined time period or the respective time periods is or are transmitted until the downlink synchronization is at least commenced (or completed).

[0096] In some examples, the downlink synchronization information for the at least one candidate target cell indicates at least one TCI state to be activated for the at least one candidate target cell. In some examples, therefore, other operations may comprise activating the indicated at least one TCI state for the at least one candidate target cell, and performing downlink synchronization for the at least one candidate target cell based on a configuration associated with the at least one activated TCI state for the at least one candidate target cell. In some examples, other operations may comprise deactivating the at least one activated TCI state for the at least one candidate target cell in response to at least one of receipt of the first instruction, expiry of the, or the respective, time period, associated with the at least one activated TCI state for the at least one candidate cell, or, if provided, receipt of the third instruction to suspend downlink synchronization for the at least one candidate target cell.

[0097] In some examples, the indication that downlink synchronization for the at least one candidate target cell has at least commenced is comprised in a third measurement report as part of the BHO procedure.

[0098] Example embodiments will be described in more detail with reference to FIG. 4. For example, it will be assumed that the downlink synchronization information comprises a configuration or indication of one or more TCI states of a candidate target cell, although other example embodiments may involve other forms of downlink synchronization information usable by the UE to perform the operations as described above.

[0099] FIG. 4 illustrates interaction and messaging between a UE 420, a first network node 410 which is assumed to be associated with a current serving cell of the UE and a second network node 412 which is assumed to be associated with a candidate target cell of the UE. A third network node 414 is also shown to indicate the availability of at least one other candidate target cell of the UE.

[0100] In an operation 4.1, the UE 420 may transmit a measurement report to the first network node 410. The UE 420 may transmit the measurement report in response to detecting a trigger event. For example, the UE 420 may be configured with a measurement and reporting configuration, or separate measurement and reporting configurations, which for example indicates resources for performing one or more L3 (or L3 and LI) measurementson reference signals transmitted by a plurality of cells, such as the serving cell and one or more candidate target cells, an indication of one or more conditions (based upon which a measurement report is triggered) and resources for reporting at least some of the one or more measurements in a measurement report to the current serving cell. The one or more conditions may be associated with one or more events, such as (but not limited to) so-called A3 events wherein the measurements indicate that at least one candidate target cell becomes better than the current serving cell. Upon detection of such an event, the measurement report may include measurements of the at least one candidate target cell, wherein the measurements may include metrics such as at least one of reference signal received power (RSRP), reference signal received quality (RSRQ) or signal to interference noise ratio (SINR). The L3 measurements may include the L3 cell quality derivation and L3 beam measurements for individual beams of the at least one candidate target cell, for example as per 3GPP TS 38.331. As described above, in some examples, the measurement report may also include LI measurements and / or the UE 420 may be instructed by the first network node 410 to perform LI measurements and report them in a second measurement report.

[0101] In an operation 4.2, the first network node 410 evaluates the measurements in the measurement report and identifies a requirement to trigger BHO to one or more candidate target cells. The first network node 410 may further determine one or more TCI states per target candidate cell(s) and prepares to instruct the UE 420 to activate the determined one or more TCI states.

[0102] In an operation 4.3, the first network node 410 may transmit to the UE 420 a RRC reconfiguration message, or similar, including a configuration or instruction to activate the determined one or more TCI states of the one or more candidate target cells. This instruction is equivalent to transmitting the downlink synchronization information referred to above. The instruction may also include a configuration of the one or more TCI states of the one or more candidate target cells. This is notably performed prior to transmitting any BHO command or instruction and so also prior to the RACH procedure.

[0103] In an operation 4.4, the UE 420 activates the determined one or more TCI states of the one or more candidate target cells. As explained above, this commences the downlink synchronization process to obtain and track time and / or frequency synchronization parameters (e.g., by tracking reference signals and acquiring and maintaining QCL information) for the one or more TCI states to enable data exchange in due course.In an operation 4.5, the UE 420 may start a timer upon receipt of the RRC reconfiguration message. The activated one or more TCI states may be associated with a time period, or respective time periods, during which downlink synchronization is performed for the activated one or more TCI states and which is suspended if the timer reaches the time period or respective time period, provided a BHO command or instruction is not received beforehand. Alternatively, instead of starting a timer, the time period, or respective time periods, may count down and the downlink synchronization for the activated one or more TCI states is suspended upon the time period(s) reaches zero.

[0104] As described above, the time period, or the respective time periods, may be earlier obtained from the first network node 410, or may be determined by the UE 420 based on assistance information received from the first network node 410. For example, the assistance information may be cell-specific assistance information, in other words assistance information specific to the particular candidate target cell. For example, the assistance information may indicate a maximum (tolerable) latency associated with an application running on the UE 420 or similar. For example, the assistance information may indicate directly or indirectly a periodicity. For example, the assistance information may indicate SSB-related information, such as SSB periodicity.

[0105] Optionally, another operation (not shown) may comprise the UE 420 transmitting, to the first network node 410, at least an indication of the determined time period or the respective time periods.

[0106] In an operation 4.6, the UE 420 transmits to the first network node 410 an optional signal or message, for example (but not limited to) a second measurement report, which may include a feedback indication that the one or more TCI states associated with the one or more candidate target cells have been activated. Instead of including the feedback in a measurement report, a dedicated signal or message may be used for this purpose, e.g., a media access control-control element (MAC-CE) or RRC message configured as a UE assistance information (UAI) message for example. An advantage of providing the feedback indication is that the first network node 410 is made aware that downlink synchronization has at least commenced (or possibly completed) which prevents the subsequent BHO instruction or command from being issued prematurely.

[0107] The feedback indication may optionally be a condition of the first network node subsequently commencing subsequent operations of the BHO process.In an operation 4.7, the first network node 410 is responsively triggered to transmit a handover request to a particular one of the candidate target cells. This may be based, at least in part, on the earlier L3 (and possibly LI) measurements. In this example, the first network node 410 determines that the particular candidate target cell is associated with the second network node 412.

[0108] In an operation 4.8, the first network node 410 transmits the handover request to the second network node 412 in a manner similar to that described with reference to FIG. 2, operation 2.3.

[0109] In an operation 4.9, the second network node 412 performs admission control in a manner similar to that described with reference to FIG. 2, operation 2.4.

[0110] In an operation 4.10, the second network node 412 transmits to the first network node 410 a message, for example a handover request acknowledgment, including the above-mentioned handover configuration for the candidate target cell which may be part of a handover command. This operation is similar to that described with reference to FIG. 2, operation 2.5.

[0111] In an operation 4.11, the first network node 410 may responsively transmit to the UE 420 a BHO command or instruction which may be the same, or may be based upon, the handover command received from the second network node 412 and which includes the handover configuration for the candidate target cell. The instruction may comprise an indication of which TCI state(s) are to be applied or used as part of a subsequent RACH procedure, i.e., which of the activated TCI state(s) is or are to be used for PDCCH and or PDSCH reception. The instruction may be comprised in an RRC reconfiguration message. This operation is similar to that described with reference to FIG. 2, operation 2.6.

[0112] In an operation 4.12, the UE 420 may responsively initiate the RACH process towards the candidate target cell based on the received handover configuration.

[0113] FIG. 5 is a flow diagram which may be useful for understanding operation 4.5 according to a particular example.

[0114] A first operation 501 comprises the UE 420 receiving a TCI state activation for a candidate (i.e., potential) candidate cell, as per operation 4.3. A second operation 503 comprises the UE activating said TCI state as per operation 4.4 and starting a timer for said activated TCI state as per operation 4.5; in this example, the timer counts down from a time periodassociated with the activated TCI state. A third operation 503 comprises determining if the timer has expired. If so, a fourth operation comprises deactivating the activated TCI state associated with the timer thereby to suspend synchronization. If not, a fifth operation 505 comprises determining if a BHO command has been received. If so, the RACH procedure is initiated in an operation 506. If not, the process returns to the third operation 503.

[0115] Figure 6 is a flow diagram showing operations 600 that may be performed by one or more example embodiments. The operations 600 may be performed by hardware, software, firmware or a combination thereof. The operations 600 may be performed by one, or respective, means, a means being any suitable means such as one or more processors or controllers in combination with computer-readable instructions provided on one or more memories.

[0116] The operations 600 may, for example, be performed by a second apparatus, for example the first network node 110, 410 of Figures 1, 2 or 4. The order of operations 600 is not necessarily indicative of their order of processing or performance.

[0117] A first operation 610 may comprise receiving, from a first apparatus, a first measurement report as part of a Layer 3, L3, baseline handover, BHO, procedure.

[0118] A second operation 620 may comprise transmitting, to the first apparatus, and in response to receiving the first measurement report, downlink synchronization information associated with at least one candidate target cell.

[0119] A third operation 630 may comprise transmitting, to the first apparatus, and subsequent to the transmitting of the downlink synchronization information, a first instruction to perform BHO to a particular cell from the at least one candidate target cell, wherein the particular cell is determined based at least in part on the measurement report.

[0120] In some examples, another operation may comprise receiving, from the first apparatus, an indication that downlink synchronization for the at least one candidate target cell has at least commenced, wherein the first instruction is transmitted in response to the receiving of the indication.

[0121] In some examples, the first instruction is transmitted with a radio resource control, RRC, reconfiguration message.In some examples, the first measurement report includes at least L3 measurements. In some examples, the first measurement report further includes layer 1, LI, measurements. In some examples, other operations may comprise transmitting, to the first apparatus, and in response to receiving the first measurement report including the at least L3 measurements, a second instruction to perform LI measurements, and receiving, from the first apparatus, LI measurements in a second measurement report.

[0122] In some examples, other operations may comprise transmitting, to the first apparatus, a, or a respective, time period associated with the downlink synchronization information for the at least one candidate target cell, wherein the, or the respective time period, indicates a time period for which downlink synchronization is to be performed by the first apparatus.

[0123] In some examples, other operations may comprise transmitting, to the first apparatus, assistance information for enabling the first apparatus to determine a, or a respective, time period associated with the downlink synchronization information for the at least one candidate target cell, wherein the, or the respective time period, indicates a time period for which downlink synchronization is to be performed by the first apparatus. The assistance information may indicate at least one of a maximum latency period associated with an application running at the first apparatus, or a periodicity associated with at least one reference signal transmitted by the at least one candidate target cell.

[0124] In some examples, another operation may comprise receiving, from the first apparatus, at least an indication of the determined time period or respective time periods. The at least the indication of the determined time period or the respective time periods may be received until downlink synchronization is at least commenced at the first apparatus.

[0125] In some examples, another operation may comprise transmitting, to the first apparatus, a third instruction to suspend downlink synchronization for the at least one candidate target cell.

[0126] In some examples, the downlink synchronization information for the at least one candidate target cell indicates at least one Transmission Control Indicator, TCI, state to be activated for the at least one candidate target cell.

[0127] In some examples, the indication that downlink synchronization for the at least one candidate target cell has at least commenced is comprised in a third measurement report as part of the BHO procedure.Advantages associated with example embodiments include, but are not limited to, the ability of a first apparatus, e.g., UE, to establish early downlink synchronization with a candidate target cell which may significantly reduce BHO interruption time. This may be particularly useful for latency-critical or latency-sensitive applications in, for example 5G and / or future communications networks (e.g., 6G) that may use BHO as the underlying handover mechanism. Indeed, it may allow BHO to be used as the underlying handover technology from the start of a future communication network technology. Example embodiments may also be advantageous for frequency range 2 (FR2) deployments, wherein cell deployment may be relatively dense and so there may be many handovers and therefore interruption times to be catered for.

[0128] Example Apparatus

[0129] Fig. 7 shows, by way of example, a block diagram of an apparatus 10. The apparatus 10 comprises, for example, at least one processor 12 and at least one memory 14 storing instructions 15 that, when executed by the at least one processor, cause the apparatus 10 at least to perform the method or methods as disclosed herein, and any of the embodiments thereof. In an example, the at least one memory and the instructions (e.g. a computer program code, software), are configured, with the at least one processor, to cause the apparatus 10 to perform the method or methods as disclosed herein, and any of the embodiments thereof.

[0130] A processor 12 may comprise circuitry, or be constituted as circuitry or circuitries, the circuitry or circuitries being configured to perform phases of methods in accordance with example embodiments described herein. As used in this application, the term "circuitry" may refer to one or more or all of the following : (a) hardware-only circuit implementations, such as implementations in only analog and / or digital circuitry, and (b) combinations of hardware circuits and software, such as, as applicable: (i) a combination of analog and / or digital hardware circuit(s) with software / firmware and (ii) any portions of hardware processor(s) with software (including digital signal processor(s)), software, and memory(ies) that work together to cause an apparatus, such as a user equipment, to perform various functions) and (c) hardware circuit(s) and or processor(s), such as a microprocessor(s) or a portion of a microprocessor(s), that requires software (e.g., firmware) for operation, but the software may not be present when it is not needed for operation. This definition of circuitry applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term circuitry also covers an implementation of merely a hardware circuit or processor (or multiple processors) or portion of a hardware circuit or processor and its (or their) accompanyingsoftware and / or firmware. The term circuitry also covers, for example and if applicable to the particular claim element, a baseband integrated circuit or processor integrated circuit for a mobile device or a similar integrated circuit in server, a cellular network device, or other computing or network device.

[0131] The memory 14 may be implemented using any suitable data storage technology. The memory may comprise a database for storing data. The memory 14 may be at least in part external to apparatus 10 but accessible to apparatus 10.

[0132] The instructions 15 may be comprised in a computer readable medium or a non-transitory computer readable medium. A term non-transitory, as used herein, is a limitation of the medium itself (i.e. tangible, not a signal) as opposed to a limitation on data storage persistency (e.g. random access memory, RAM, vs. read only memory, ROM).

[0133] For example, the apparatus 10 is a terminal device, such as the UE of Figures 1, 2 or 4. As another example, the apparatus is comprised in such a terminal device, e.g. as a chipset configured to control the terminal device. The apparatus 10 may be caused or configured to perform at least the method of Figure 3 and / or any one or more of the embodiments described.

[0134] As another example, the apparatus 10 is a network node, such as the network node of Figure 1, 2 or 4. The apparatus 10 may be caused or configured to perform at least the method of Figure 6 and / or any one or more of the embodiments described.

[0135] The apparatus may comprise one or more entities of any of protocol layers, such as a MAC entity, an RRC entity, an RLC entity, a PDCP entity or a PHY entity. In some embodiments, the entity is configured to perform at least the method of Fig. 5 and / or any one or more of the embodiments described.

[0136] The apparatus 10 comprises a radio interface 16. The radio interface 16 may provide the apparatus 10 with communication capabilities. The radio interface 16 may comprise a receiver configured to receive information in accordance with at least one cellular or non-cellular standard. The radio interface 16 may comprise a transmitter configured to transmit information in accordance with at least one cellular or non-cellular standard. The receiver may comprise more than one receiver. The transmitter may comprise more than one transmitter. The radio interface 16 may comprise a transceiver configured to receive and transmit information in accordance with at least one cellular or non-cellular standard. The transceiver may comprise more than one transceiver.The apparatus 10 may comprise a user interface 18 comprising, for example, at least one of a keypad, a microphone, a touch display, a display, a speaker, etc. The user interface 18 may be used to control the apparatus by the user. The user interface 18 may be external to the apparatus 10. For example, the apparatus 10 may be connected to another device, such as a computer, either via wireless or wired connection, and the apparatus 10 is controlled by the user via the computer.

[0137] Figure 8 shows a non-transitory media 800 according to some embodiments. The non-transitory media 800 is a computer readable storage medium. It may be e.g. a CD, a DVD, a USB stick, a blue ray disk, etc. The non-transitory media 800 stores computer program code, causing an apparatus to perform the method of any preceding process for example as disclosed in relation to the flow diagrams and related features thereof.

[0138] Names of network elements, protocols, and methods are based on current standards. In other versions or other technologies, the names of these network elements and / or protocols and / or methods may be different, as long as they provide a corresponding functionality. For example, embodiments may be deployed in 2G / 3G / 4G / 5G networks and further generations of 3GPP but also in non-3GPP radio networks such as WiFi.

[0139] In an embodiment, at least some of the processes described herein may be carried out by an apparatus comprising means for carrying out at least some of the described processes. Means for performing method steps as disclosed herein may include software and / or hardware components of the apparatus 10. For example, the at least one processor 12, the memory 14, and the computer program code form means for carrying out the method or methods as disclosed herein, and any of the embodiments thereof. As used herein the term "means" is to be construed in singular form, i.e. referring to a single element, or in plural form, i.e. referring to a combination of single elements. Therefore, terminology "means for [performing A, B, C]", is to be interpreted to cover an apparatus in which there is only one means for performing A, B and C, or where there are separate means for performing A, B and C, or partially or fully overlapping means for performing A, B, C. Further, terminology "means for performing A, means for performing B, means for performing C" is to be interpreted to cover an apparatus in which there is only one means for performing A, B and C, or where there are separate means for performing A, B and C, or partially or fully overlapping means for performing A, B, C.

[0140] Even though the invention has been described above with reference to an example according to the accompanying drawings, it is clear that the invention is not restrictedthereto but can be modified in several ways within the scope of the appended claims. Therefore, all words and expressions should be interpreted broadly and they are intended to illustrate, not to restrict, the embodiment. It will be obvious to a person skilled in the art that, as technology advances, the inventive concept can be implemented in various ways. Further, it is clear to a person skilled in the art that the described embodiments may, but are not required to, be combined with other embodiments in various ways.

[0141] 1

Claims

Claims1. A first apparatus, comprising:at least one processor; andat least one memory storing instructions that, when executed by the at least one processor, cause the first apparatus at least to:receive, from a second apparatus, and as part of a layer 3, L3, baseline handover, BHO, procedure, downlink synchronization information associated with at least one candidate target cell; andcommence downlink synchronization for the at least one candidate target cell based on the downlink synchronization information, wherein the downlink synchronization is commenced prior to receiving a first instruction from the second apparatus to perform BHO to a particular cell from the at least one candidate target cell.

2. The first apparatus of claim 1, whereinthe at least one processor and the at least one memory store instructions that, when executed by the at least one processor, cause the first apparatus to:transmit, to the second apparatus, and prior to receiving the first instruction from the second apparatus, an indication that downlink synchronization for the at least one candidate target cell has at least commenced.

3. The first apparatus of claim 1 or claim 2, whereinthe at least one processor and the at least one memory store instructions that, when executed by the at least one processor, further cause the first apparatus to:receive the first instruction; andcommence, in response to receiving the first instruction, a random-access, RACH, procedure with the particular cell.

4. The first apparatus of claim 3, whereinthe first instruction is received with a radio resource control, RRC, reconfiguration message.

5. The first apparatus of any preceding claim, whereinthe at least one processor and the at least one memory store instructions that, when executed by the at least one processor, further cause the first apparatus to:detect a reporting event; andtransmit, to the second apparatus, and in response to detecting the reporting event, a first measurement report as part of the BHO procedure,28wherein the downlink synchronization information is received from the second apparatus in response to the transmitting of the first measurement report.

6. The first apparatus of claim 5, whereinthe first measurement report includes at least L3 measurements.

7. The first apparatus of claim 6, whereinthe first measurement report further includes layer 1, LI, measurements.

8. The first apparatus of claim 6, whereinthe at least one processor and the at least one memory store instructions that, when executed by the at least one processor, further cause the first apparatus to:receive, from the second apparatus, and in response to transmitting the first measurement report including the at least L3 measurements, a second instruction to perform LI measurements;perform LI measurements in accordance with the second instruction; and transmit, to the second apparatus, the LI measurements in a second measurement report.

9. The first apparatus of any preceding claim, whereinthe downlink synchronization is performed for the at least one candidate target cell until the earliest of:receipt of the first instruction; orexpiry of a, or a respective, time period, associated with the downlink synchronization information for the at least one candidate target cell; or receipt of a third instruction to suspend downlink synchronization for the at least one candidate target cell.

10. The first apparatus of claim 9, whereinactivation of the, or the respective, time period is commenced upon the receiving of the downlink synchronization information for the at least one candidate target cell.

11. The first apparatus of claim 9 or claim 10, whereinthe at least one processor and the at least one memory store instructions that, when executed by the at least one processor, further cause the first apparatus to:obtain the, or the respective, time period, from the second apparatus.

12. The first apparatus of claim 9 or claim 10, whereinthe at least one processor and the at least one memory store instructions that, when executed by the at least one processor, further cause the first apparatus to:obtain assistance information from the second apparatus,wherein the, or the respective, time period is determined by the first apparatus based at least in part on the assistance information.

13. The first apparatus of claim 12, whereinthe assistance information indicates at least one of:a maximum latency period associated with an application running at the first apparatus;a periodicity associated with at least one reference signal transmitted by the at least one candidate target cell.

14. The first apparatus of any of claim 12 or claim 13, whereinthe at least one processor and the at least one memory store instructions that, when executed by the at least one processor, cause the first apparatus to:transmit, to the second apparatus, at least an indication of the determined time period or the respective time periods.

15. The first apparatus of claim 14, whereinthe indication of the determined time period or the respective time periods is transmitted until the downlink synchronization is at least commenced.

16. The first apparatus of any preceding claim, whereinthe downlink synchronization information for the at least one candidate target cell indicates at least one Transmission Control Indicator, TCI, state to be activated for the at least one candidate target cell.

17. The first apparatus of claim 16, whereinthe at least one processor and the at least one memory store instructions that, when executed by the at least one processor, cause the first apparatus to:activate the indicated at least one TCI state for the at least one candidate target cell; andperform downlink synchronization for the at least one candidate target cell based on a configuration associated with the at least one activated TCI state for the at least one candidate target cell.

18. The first apparatus of claim 17, when dependent on any of claims 9 to 15, whereinthe at least one processor and the at least one memory store instructions that, when executed by the at least one processor, cause the first apparatus to:deactivate the at least one activated TCI state for the at least one candidate target cell in response to at least one of:receipt of the first instruction;expiry of the, or the respective, time period, associated with the at least one activated TCI state for the at least one candidate cell; orreceipt of the third instruction to suspend downlink synchronization for the at least one candidate target cell.

19. The first apparatus of claim 2, or any claim dependent thereon, wherein the indication that downlink synchronization for the at least one candidate target cell has at least commenced is comprised in a third measurement report as part of the BHO procedure.

20. A second apparatus, comprising:at least one processor; andat least one memory storing instructions that, when executed by the at least one processor, cause the second apparatus at least to:receive, from a first apparatus, a first measurement report as part of a Layer 3, L3, baseline handover, BHO, procedure;transmit, to the first apparatus, and in response to receiving the first measurement report, downlink synchronization information associated with at least one candidate target cell; andtransmit to the first apparatus, and subsequent to the transmitting of the downlink synchronization information, a first instruction to perform BHO to a particular cell from the at least one candidate target cell, wherein the particular cell is determined based at least in part on the measurement report.

21. The second apparatus of claim 20, whereinthe at least one processor and the at least one memory store instructions that, when executed by the at least one processor, cause the second apparatus to:receive, from the first apparatus, an indication that downlink synchronization for the at least one candidate target cell has at least commenced, wherein the first instruction is transmitted in response to the receiving of the indication.

22. The second apparatus of claim 20 or claim 21, whereinthe first instruction is transmitted with a radio resource control, RRC, reconfiguration message.

23. The second apparatus of any of claims 20 to 22, whereinthe first measurement report includes at least L3 measurements.

24. The second apparatus of claim 23, whereinthe first measurement report further includes layer 1, LI, measurements.

25. The second apparatus of claim 23, whereinthe at least one processor and the at least one memory store instructions that, when executed by the at least one processor, cause the second apparatus to:transmit, to the first apparatus, and in response to receiving the first measurement report including the at least L3 measurements, a second instruction to perform LI measurements; andreceive, from the first apparatus, LI measurements in a second measurement report.

26. The second apparatus of any of claims 20 to 25, whereinthe at least one processor and the at least one memory store instructions that, when executed by the at least one processor, cause the second apparatus to:transmit, to the first apparatus, a, or a respective, time period associated with the downlink synchronization information for the at least one candidate target cell, wherein the, or the respective time period, indicates a time period for which downlink synchronization is to be performed by the first apparatus.

27. The second apparatus of any of claims 20 to 25, whereinthe at least one processor and the at least one memory store instructions that, when executed by the at least one processor, cause the second apparatus to:transmit, to the first apparatus, assistance information for enabling the first apparatus to determine a, or a respective, time period associated with the downlink synchronization information for the at least one candidate target cell, wherein the, or the respective time period, indicates a time period for which downlink synchronization is to be performed by the first apparatus.

28. The second apparatus of claim 27, whereinthe assistance information indicates at least one of:a maximum latency period associated with an application running at the first apparatus;a periodicity associated with at least one reference signal transmitted by the at least one candidate target cell.

29. The second apparatus of claim 27 or claim 28, whereinthe at least one processor and the at least one memory store instructions that, when executed by the at least one processor, cause the second apparatus to:receive, from the first apparatus, at least an indication of the determined time period or respective time periods.

30. The second apparatus of claim 29, whereinthe at least the indication of the determined time period or the respective time periods is received until downlink synchronization is at least commenced at the first apparatus.

31. The second apparatus of any of claims 20 to 30, whereinthe at least one processor and the at least one memory store instructions that, when executed by the at least one processor, cause the second apparatus to:transmit, to the first apparatus, a third instruction to suspend downlink synchronization for the at least one candidate target cell.

32. The second apparatus of any of claims 20 to 31, whereinthe downlink synchronization information for the at least one candidate target cell indicates at least one Transmission Control Indicator, TCI, state to be activated for the at least one candidate target cell.

33. The second apparatus of claim 21, or any claim dependent thereon, wherein the indication that downlink synchronization for the at least one candidate target cell has at least commenced is comprised in a third measurement report as part of the BHO procedure.

34. A method of a first apparatus, comprising:receiving, from a second apparatus, and as part of a layer 3, L3, baseline handover, BHO, procedure, downlink synchronization information associated with at least one candidate target cell; andcommencing downlink synchronization for the at least one candidate target cell based on the downlink synchronization information, wherein the downlink synchronizationis commenced prior to receiving a first instruction from the second apparatus to perform BHO to a particular cell from the at least one candidate target cell.

35. A method of a second apparatus, comprising:receiving, from a first apparatus, a first measurement report as part of a Layer 3, L3, baseline handover, BHO, procedure,transmitting, to the first apparatus, and in response to receiving the first measurement report, downlink synchronization information associated with at least one candidate target cell; andtransmitting to the first apparatus, and subsequent to the transmitting of the downlink synchronization information, a first instruction to perform BHO to a particular cell from the at least one candidate target cell, wherein the particular cell is determined based at least in part on the measurement report.

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