Triggering random access

Abstract

Example embodiments of the disclosure relate to apparatuses, methods and a computer readable medium for triggering random access In a method, a first apparatus receives a configuration indicating at least one candidate cell. The first apparatus receives a command triggering cell switch towards a target cell of the at least one candidate cell. Based on the command, the first apparatus determines whether random access is to be triggered for the cell switch. The first apparatus performs the cell switch based on the determining.

Description

TRIGGERING RANDOM ACCESSFIELDS

[0001] Various example embodiments of the present disclosure generally relate to the field of telecommunication and in particular, to methods, devices, apparatuses and a computer readable storage medium for triggering random access (RA).BACKGROUND

[0002] In a Layer 1(L1) / Layer 2 (L2)-Triggered Mobility (LTM) procedure, a gNB receives LI measurement report(s) from user equipment (UE), and on their basis the gNB changes UE serving cell by a cell switch command (CSC) signaled via a medium access control (MAC) control element (CE). The cell switch command indicates an LTM candidate configuration that the gNB previously prepared and provided to the UE through Radio Resource Control (RRC) signaling. Then, the UE switches to a target cell according to the cell switch command. The LTM procedure may be used to reduce the mobility latency. In the LTM cell switch, the UE may perform a contention based random access (CBRA), contention free random access (CFRA) or random access channel (RACH)-less procedure.SUMMARY

[0003] In a first aspect of the present disclosure, there is provided a first apparatus. The first apparatus includes at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the first apparatus at least to: receive a configuration indicating at least one candidate cell; receive a command triggering cell switch towards a target cell of the at least one candidate cell; determine, based on the command, whether random access is to be triggered for the cell switch; and perform the cell switch based on the determining.

[0004] In a second aspect of the present disclosure, there is provided a second apparatus. The second apparatus includes at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the second apparatus at least to: transmit, to a first apparatus, a configuration indicating at least one candidatecell; transmit, to the first apparatus, a command triggering cell switch towards a target cell of the at least one candidate cell, where the command indicates whether random access is to be triggered for the cell switch.

[0005] In a third aspect of the present disclosure, there is provided a method. The method includes: receiving a configuration indicating at least one candidate cell; receiving a command triggering cell switch towards a target cell of the at least one candidate cell; determining, based on the command, whether random access is to be triggered for the cell switch; and performing the cell switch based on the determining.

[0006] In a fourth aspect of the present disclosure, there is provided a method. The method includes: transmitting, to a first apparatus, a configuration indicating at least one candidate cell; transmitting, to the first apparatus, a command triggering cell switch towards a target cell of the at least one candidate cell, where the command indicates whether random access is to be triggered for the cell switch.

[0007] In a fifth aspect of the present disclosure, there is provided a first apparatus. The first apparatus includes means for receiving a configuration indicating at least one candidate cell; means for receiving a command triggering cell switch towards a target cell of the at least one candidate cell; means for determining, based on the command, whether random access is to be triggered for the cell switch; and means for performing the cell switch based on the determining.

[0008] In a sixth aspect of the present disclosure, there is provided a second apparatus. The second apparatus includes means for transmitting, to a first apparatus, a configuration indicating at least one candidate cell; means for transmitting, to the first apparatus, a command triggering cell switch towards a target cell of the at least one candidate cell, where the command indicates whether random access is to be triggered for the cell switch.

[0009] In a seventh aspect of the present disclosure, there is provided a computer readable medium. The computer readable medium includes instructions stored thereon for causing an apparatus to perform at least the method according to the third aspect.

[0010] In an eighth aspect of the present disclosure, there is provided a computer readable medium. The computer readable medium includes instructions stored thereon for causing an apparatus to perform at least the method according to the fourth aspect.

[0011] It is to be understood that the Summary section is not intended to identify keyor essential features of embodiments of the present disclosure, nor is it intended to be used to limit the scope of the present disclosure. Other features of the present disclosure may become easily comprehensible through the following description.BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Some example embodiments may now be described with reference to the accompanying drawings, where:

[0013] FIG. 1 illustrates an example LTM cell switch command MAC CE;

[0014] FIG. 2 illustrates an example communication environment in which example embodiments of the present disclosure may be implemented;

[0015] FIG. 3 illustrates a signaling flow for communications between first and second apparatuses according to some example embodiments of the present disclosure;

[0016] FIG. 4 illustrates an example LTM cell switch command MAC CE with random access triggered according to some example embodiments of the present disclosure;

[0017] FIG. 5 illustrates another example LTM cell switch command MAC CE without random access triggered according to some other example embodiments of the present disclosure;

[0018] FIG. 6 illustrates a flowchart of a method implemented at a first apparatus according to some example embodiments of the present disclosure;

[0019] FIG. 7 illustrates a flowchart of a method implemented at a second apparatus according to some example embodiments of the present disclosure;

[0020] FIG. 8 illustrates a simplified block diagram of a device that is suitable for implementing example embodiments of the present disclosure; and

[0021] FIG. 9 illustrates a block diagram of an example computer readable medium in accordance with some example embodiments of the present disclosure.

[0022] Throughout the drawings, the same or similar reference numerals represent the same or similar element.DETAILED DESCRIPTION

[0023] Principle of the present disclosure may now be described with reference to someexample embodiments. It is to be understood that these embodiments are described only for the purpose of illustration and help those skilled in the art to understand and implement the present disclosure, without suggesting any limitation as to the scope of the disclosure. Embodiments described herein may be implemented in various manners other than the ones described below.

[0024] In the following description and claims, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skills in the art to which this disclosure belongs.

[0025] References in the present disclosure to “one embodiment,” “an embodiment,” “an example embodiment,” and the like indicate that the embodiment described may include a particular feature, structure, or characteristic, but it is not necessary that every embodiment includes the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

[0026] It may be understood that although the terms “first,” “second,”... , etc. in front of noun(s) and the like may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another and they do not limit the order of the noun(s). For example, a first element could be termed a second element, and similarly, a second element could be termed a first element, without departing from the scope of example embodiments. As used herein, the term “and / or” includes any and all combinations of one or more of the listed terms.

[0027] As used herein, “at least one of the following: ” and “at least one of ” and similar wording, where the list of two or more elements are joined by “and” or “or”, mean at least any one of the elements, or at least any two or more of the elements, or at least all the elements.

[0028] As used herein, unless stated explicitly, performing a step “in response to A” does not indicate that the step is performed immediately after “A” occurs and one or more intervening steps may be included.

[0029] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It may be further understood that the terms “comprises”, “comprising”, “has”, “having”, “includes” and / or “including”, when used herein, specify the presence of stated features, elements, and / or components etc., but do not preclude the presence or addition of one or more other features, elements, components and / or combinations thereof.

[0030] 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 mobile phone or server, 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.

[0031] 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) accompanying software 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.

[0032] As used herein, the term “communication network” refers to a network following any suitable communication standards, such as New Radio (NR), Long Term Evolution (LTE), LTE-Advanced (LTE-A), Wideband Code Division Multiple Access (WCDMA), High-Speed Packet Access (HSPA), Narrow Band Internet of Things (NB-IoT) and so on. Furthermore, the communications between a terminal device and a network device in the communication network may be performed according to any suitable generation communication protocols, including, but not limited to, the first generation (1G), the second generation (2G), 2.5G, 2.75G, the third generation (3G), the fourth generation (4G), 4.5G, the fifth generation (5G), the sixth generation (6G) communication protocols, and / or any other protocols either currently known or to be developed in the future. Embodiments of the present disclosure may be applied in various communication systems. Given the rapid development in communications, there may of course also be future type communication technologies and systems with which the present disclosure may be embodied. It should not be seen as limiting the scope of the present disclosure to only the aforementioned system.

[0033] As used herein, the term “network device” refers to a node in a communication network via which a terminal device accesses the network and receives services therefrom. The network device may refer to a base station (BS) or an access point (AP), 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 header (RH), a remote radio head (RRH), a relay, an Integrated Access and Backhaul (IAB) node, a low power node such as a femto, a pico, a non-terrestrial network (NTN) or non-ground network device such as a satellite network device, a low earth orbit (LEO) satellite and a geosynchronous earth orbit (GEO) satellite, an aircraft network device, and so forth, depending on the applied terminology and technology. In some example embodiments, radio access network (RAN) split architecture includes a Centralized Unit (CU) and a Distributed Unit (DU) at an IAB donor node. An IAB node includes a Mobile Terminal (IAB-MT) part that behaves like a UE toward the parent node, and a DU part of an IAB node behaves like a base station toward the next-hop IAB node.

[0034] The term “terminal device” refers to any end device that may be capable of wireless communication. By way of example rather than limitation, a terminal device may also be referred to as a communication device, user equipment (UE), a Subscriber Station (SS), a Portable Subscriber Station, a Mobile Station (MS), or an Access Terminal(AT). The terminal device may include, but not limited to, 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, wireless endpoints, mobile stations, laptop-embedded equipment (LEE), laptop-mounted equipment (LME), USB dongles, smart devices, wireless customerpremises equipment (CPE), 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. The terminal device may also correspond to a Mobile Termination (MT) part of an IAB node (e.g., a relay node). In the following description, the terms “terminal device”, “communication device”, “terminal”, “user equipment” and “UE” may be used interchangeably.

[0035] As used herein, the term “resource,” “transmission resource,” “resource block,” “physical resource block” (PRB), “uplink resource,” or “downlink resource” may refer to any resource for performing a communication, for example, a communication between a terminal device and a network device, such as a resource in time domain, a resource in frequency domain, a resource in space domain, a resource in code domain, or any other combination of the time, frequency, space and / or code domain resource enabling a communication, and the like. In the following, unless explicitly stated, a resource in both frequency domain and time domain may be used as an example of a transmission resource for describing some example embodiments of the present disclosure. It is noted that example embodiments of the present disclosure are equally applicable to other resources in other domains.

[0036] When the LTM procedure is configured by a network, it is possible to activate Transmission Configuration Indicator (TCI) states of one or multiple cells that are different from a current serving cell. For instance, the TCI states of the LTM candidate cells may be activated in advance before any of those cells become a serving cell. This allows the UE to be downlink (DL) synchronized with those cells, thereby facilitating a faster cell switch to one of those cells when cell switch is triggered.

[0037] When the LTM procedure is configured by the network, it is possible to initiate uplink (UL) timing advance (TA) acquisition (also referred to as early TA) procedure of one or multiple cells that are different from the current serving cells. If the cell has the same NTA as the current serving cells or NTA=0, the early TA acquisition procedure is not required. The network may request the UE to perform early TA acquisition of a candidate cell before a cell switch. The early TA acquisition procedure is triggered by Physical Downlink Control Channel (PDCCH) order or realized through UE -based TA measurement as configured by radio resource control (RRC) signaling. In the former case, the gNB to which the candidate cell belongs calculates the TA value and sends it to the gNB to which the serving cell belongs. The serving cell sends the TA value in the LTM cell switch command MAC CE when triggering LTM cell switch. In the latter case, the UE performs TA measurement for the candidate cells after being configured by RRC signaling but the exact time the UE performs TA measurement is up to UE implementation. The UE applies the TA value measured by itself and performs random access channel (RACH)-less LTM upon receiving the cell switch command. The network may also send a TA value in the LTM cell switch command MAC CE without early TA acquisition.

[0038] Depending on the availability of a valid TA value, the UE performs either a RACH-less LTM or RACH-based LTM cell switch. If the TA value is provided in the cell switch command, the UE applies the TA value as instructed by the network. In the case where UE-based TA measurement is configured, but no TA value is provided in the cell switch command, the UE applies the TA value by itself if available. Meanwhile, the UE performs RACH-less LTM cell switch upon receiving the cell switch command. If no valid TA value is available, the UE performs RACH-based LTM cell switch.

[0039] Regardless of whether the UE is configured for UE-based TA measurement for a certain candidate cell, it may still follow the PDCCH order, which includes requesting a random access procedure towards the candidate cells. This also applies to the candidate cells for which the UE is capable of deriving TA values by itself. Additionally, regardless of whether the UE has already performed a random access procedure towards the candidate cells, it may still follow the UE-based measurement configuration if configured by the network.

[0040] For RACH-less LTM, the UE accesses the target cell using either a configured grant or a dynamic grant. The configured grant is provided in the LTM candidateconfiguration, and the UE selects the configured grant occasion associated with the beam indicated in the cell switch command. Upon initiation of LTM cell switch to the target cell, the UE starts to monitor PDCCH on the target cell for dynamic scheduling. Before RACH-less LTM procedure completion, the UE may not trigger random access procedure if it does not have a valid Physical Uplink Control Channel (PUCCH) resource for triggered Scheduling Requests (SRs). There are some principles that may be applied to LTM. One of the principles is that a security key is maintained upon an LTM cell switch. The other one of the principles is that subsequent LTM is supported.

[0041] LTM supports both intra-gNB-DU and intra-gNB-CU inter-gNB-DU mobility. LTM may further support mobility for DUs (cells) hosted by different CUs (i.e. inter- gNB-CU mobility). LTM supports both intra-frequency and inter-frequency mobility, including mobility to inter-frequency cell that is not a current serving cell. LTM is supported only for licensed spectrum. A non-carrier aggregation (CA) scenario and a nonDC scenario where a primary cell (PCell) changes may be supported. A CA scenario where PCell and secondary cell (SCell)(s) change may be supported. A dual connectivity scenario where PCell and master cell group (MCG) SCell(s) change and intra-SN PSCell and secondary cell group (SCG) SCell(s) change without a master node (MN) involvement may be supported. However, LTM for simultaneous PCell and PSCell change may not be supported. While the UE has stored LTM candidate configurations the UE may also execute any Layer 3 (L3) handover command sent by the network.

[0042] In control plane (C-Plane) handling, a cell switch command is conveyed in a MAC CE, which contains necessary information to perform the LTM cell switch. The overall procedure for LTM is described below. At step 1, the UE sends a MeasurementReport message to the gNB. At step 2, the gNB decides to configure LTM and initiates LTM preparation. At step 3, the gNB transmits an RRCReconfiguration message to the UE including the LTM candidate configurations. The UE stores the LTM candidate configurations and transmits an RRCReconfigurationComplete message to the gNB. At step 4a, The UE performs DL synchronization with the candidate cell(s) before receiving the cell switch command. At step 4b, when UE-based TA measurement is configured, the UE acquires the TA value(s) of the candidate cell(s) by measurement. The UE performs early TA acquisition with the candidate cell(s) as requested by the network before receiving the cell switch command. This is done via CFRA triggered by a PDCCH order from the source cell, following which the UE sends a preamble towards the indicatedcandidate cell. In order to minimize the data interruption of the source cell due to CFRA towards the candidate cell(s), the UE doesn’t receive a random access response from the network for the purpose of TA value acquisition and the TA value of the candidate cell is indicated in the cell switch command. The UE doesn’t maintain the TA timer for the candidate cell and relies on network implementation to guarantee the TA validity.

[0043] At step 5, the UE performs LI measurements on the configured candidate cell(s) and transmits LI measurement reports to the gNB. LI measurement is performed as long as the RRC reconfiguration (step 2) is applicable. At step 6, the gNB decides to execute cell switch to a target cell and transmits a MAC CE triggering cell switch by including the candidate configuration index of the target cell. The UE switches to the target cell and applies the configuration indicated by candidate configuration index. At step 7, the UE performs the random access procedure towards the target cell, if UE does not have valid TA of the target cell. At step 8, the UE completes the LTM cell switch procedure by sending a RRCReconfigurationComplete message to target cell. If the UE has performed a RA procedure in step 7 the UE considers that LTM cell switch execution is successfully completed when the random access procedure is successfully completed. For RACH-less LTM, the UE considers that LTM cell switch execution is successfully completed when the UE determines that the network has successfully received its first UL data.

[0044] The steps 4-8 can be performed multiple times for subsequent LTM using the LTM candidate configuration(s) provided in step 2. Thus, subsequent LTM is done by repeating the early synchronization, LTM cell switch execution, and LTM cell switch completion steps without releasing other LTM candidate configurations after each LTM cell switch completion. The general procedure over the air interface is applicable to SCG LTM.

[0045] the LTM cell switch command MAC CE structure and field descriptions as follows. The LTM Cell Switch Command MAC CE may be identified by MAC subheader with extended logical channel identifier (eLCID). FIG. 1 illustrates an example LTM cell switch command MAC CE. As shown in FIG. 1, the LTM Cell Switch Command MAC CE has a variable size with following fields:- R 102: Reserved bit, set to 0;- Target Configuration identifier (ID) 106: This field indicates the index of candidatetarget configuration to apply for LTM cell switch, corresponding to Itm-Candidateld minus 1 as specified in the current communication specification. The length of the field is 3 bits;- Timing Advance Command 108: This field indicates whether the TA is valid for the LTM target cell (i.e. the SpCell corresponding to the target configuration indicated by Target Configuration ID field). If the value of this field is set to FFF, this field indicates that no valid timing adjustment is available for the PTAG of the LTM target cell; Otherwise, this field indicates the index value TA used to control the amount of timing adjustment that the MAC entity has to apply in the current communication specification, and that the UE may skip the Random Access procedure for this LTM cell switch. The length of the field is 12 bits;- TCI state ID 110: This field indicates and activates the TCI state for the LTM target cell (i.e. the SpCell of the target configuration indicated by the Target Configuration ID field). The TCI state is identified by TCI-Stateldm Itm-DL-OrJointTCI- StateToAddModList as specified in the current communication specification. If the value of unifiedTCI-StateType in the configuration indicated by Target Configuration ID field is joint, this field is for joint TCI state, otherwise, this field is for downlink TCI state. The length of the field is 7 bits;- UL TCI state ID 112: This field indicates and activates the uplink TCI state for the LTM target cell (i.e. the SpCell of the target configuration indicated by the Target Configuration ID field). The most significant bits of UL TCI state ID are considered as reserved bits and the remainder 6 bits indicate the TCI-UL-Stateldm Itm-UL-TCI- StatesToAddModList as specified in the current communication specification. This field is included if the value of unifiedTCI-StateType in the configuration indicated by Target Configuration ID field is separate. The length of the field is 8 bits;- C 114: This field indicates the presence of the contention-free Random Access Resources fields. If the value of this field is set to 1, the following fields are present, including Random Access Preamble index field, S / U field, SS / PBCH index field and PRACH Mask index field. If the value of this field is set to 0, Random Access Preamble index field, SS / PBCH index field and PRACH Mask index field are absent, and S / U field is considered as Reserved field.- S / U 116: This field indicates which UL carrier to transmit the PRACH of the contention-free Random Access Resources. If the value of this field is set to 1, SUL is used; otherwise, NUL is used. The length of the field is 1 bit;- Random Access Preamble index 118: This field indicates the Random Access Preamble index of the contention-free Random Access Resources. The length of the field is 6 bits;- synchronization signal (SS) / physical broadcast channel (PBCH) index 120: This field indicates the SS / PBCH that may be used to determine the RACH occasion for the PRACH transmission of the contention-free Random Access Resources. The length of the field is 6 bits;- PRACH Mask index 122: This field indicates the RACH occasion(s) associated with the SS / PBCH indicated by "SS / PBCH index" for the PRACH transmission of the contention-free Random Access Resources, referring to the rach-ConfigDedicated (if not provided otherwise to the rach-ConfigCommon) in the UL BWP configuration of firstActiveUplinkBWP-Id as specified in the current communication specification. The length of the field is 4 bits.

[0046] After the network instructs the UE to perform LTM cell switch procedure by sending the LTM Cell Switch Command MAC CE, the UE may take the following behaviour for LTM upon receiving the LTM CSC MAC CE. If the MAC entity receives an LTM Cell Switch Command MAC CE on a Serving Cell, the MAC entity may indicate to upper layers that the LTM cell switch procedure is triggered and the Target Configuration ID included in the MAC CE. In the case that the MAC reset operation is performed, as requested by upper layers, if Timing Advance Command value (hexadecimal) is not set as FFF, the MAC entity may process the received Timing Advance Command; the MAC entity may consider the RACH-less LTM cell switch to be ongoing; if the MAC entity is associated with SCG, the MAC entity may indicate to upper layers to skip the Random Access procedure for this LTM cell switch.

[0047] If the Timing Advance measurement is configured as specified in the current communication specification and the UE has successfully measured the Timing Advance for the indicated LTM target, the MAC entity may process the measured Timing Advance and consider the RACH-less LTM cell switch to be ongoing. If the MAC entity is associated with SCG, the MAC entity may indicate to upper layers to skip the Random Access procedure for this LTM cell switch. If TCI state information is included, the MAC entity may consider the DLRS (e.g. SSB or channels state information-reference signals / tracking reference signals (CSI-RS / TRS)) corresponding to the indicated TCI state as the one used for configured uplink grant selection for the initial uplink transmissiontowards the candidate cell for RACH-less LTM cell switch; and the MAC entity may indicate to lower layers the information regarding the TCI state information included in the LTM Cell Switch Command MAC CE.

[0048] Currently, there is an issue in LTM cell switch where a network (NW) cannot trigger a Random Access procedure for the LTM at all in case the UE is configured with a UE based TA measurement. The UE based TA measurement may not be very reliable since the exact time the UE performs TA measurement is left up to UE implementation, and therefore, there is a need to enable such NW behavior (enforcing RA based LTM) in 3 GPP as well.

[0049] This limits the network options for triggering cell switch since the current option is to trigger CFRA based cell switch or RACH-less cell switch but the NW cannot enforce CFRA based cell switch if UE based TA measurement is configured. Furthermore, the CFRA based cell switch with the CFRA resource as configured in the LTM CSC MAC CE is limited to a synchronization signal block (SSB) as indicated in the MAC CE, not allowing fallback to other beams and CBRA in case that the SSB is not good enough anymore. Hence, in some cases, the network may desire to use contention based random access, e.g., in case that CFRA resources may not be available or cannot be provided to the UE, or the NW may desire to use the CFRA resource(s) configured via RRC for the target candidate cell, allowing the CBRA fallback at the same time.

[0050] Example embodiments of the present disclosure provides a solution to trigger a certain type of random access in the cell switch command. In this solution, a first apparatus (for example, a terminal device) receives, from a second apparatus (for example, a network device), a configuration indicating at least one candidate cell and a command triggering cell switch towards a target cell of the at least one candidate cell. This command will also be referred to as a cell switch command or a CSC. Based on the command, the first apparatus determines whether random access is to be triggered for the cell switch, and performs the cell switch based on the determining. For example, the command may trigger the first apparatus may initiate CFRA based, CBRA based or RACH-less cell switch.

[0051] In this way, the network may enforce a certain type of RA for cell switch using the cell switch command, which provides more flexible options for the network to trigger cell switch. Thus, the cell switch may be performed more efficiently, and resourceefficiency and network capacity may be improved.

[0052] It is to be noted that although the issue is originating from the LTM cell switch, the proposed solution herein may be applied in general for different types of cell switch. In the following, some example embodiments will be described using the LTM cell switch as an example while the example embodiments herein can be applied in general for other types of cell switch.

[0053] FIG. 2 illustrates an example communication environment 200 in which example embodiments of the present disclosure may be implemented.

[0054] As shown in FIG. 2, the communication environment 200 includes a first apparatus 210 which may operate as a terminal device, and a second apparatus 220 which may operate as a network device. The second apparatus 220 provides at least one cell, for example, including a cell 222 and a cell 224, which may serve the first apparatus 210.

[0055] In the following, for the purpose of illustration, some example embodiments may be described with the first apparatus 210 operating as a terminal device (for example, a UE) and the second apparatus 220 operating as a network device (for example, a gNB). However, in some example embodiments, operations described in connection with a terminal device may be implemented at a network device or other device, and operations described in connection with a network device may be implemented at a terminal device or other device.

[0056] In some example embodiments, if the first apparatus 210 is a terminal device and the second apparatus 220 is a network device, a link from the second apparatus 220 to the first apparatus 210 is referred to as a downlink (DL), and a link from the first apparatus 210 to the second apparatus 220 is referred to as an uplink (UL). In DL, the second apparatus 220 is a transmitting (TX) device (or a transmitter) and the first apparatus 210 is a receiving (RX) device (or a receiver). In UL, the first apparatus 210 is a TX device (or a transmitter) and the second apparatus 220 is a RX device (or a receiver).

[0057] Communications in the communication environment 200 may be implemented according to any proper communication protocol(s), including, but not limited to, cellular communication protocols of the first generation (1G), the second generation (2G), the third generation (3G), the fourth generation (4G), the fifth generation (5G), the sixth generation (6G), and the like, wireless local network communication protocols such asInstitute for Electrical and Electronics Engineers (IEEE) 802.11 and the like, and / or any other protocols currently known or to be developed in the future. Moreover, the communication may utilize any proper wireless communication technology, including 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), Discrete Fourier Transform spread OFDM (DFT-s-OFDM) and / or any other technologies currently known or to be developed in the future.

[0058] It is to be understood that the number and types of apparatuses are shown in FIG. 1 for the purpose of illustration without suggesting any limitation. For example, the communication environment 200 may include any suitable number of terminal devices and network devices. One of the network devices may provide any number of cells.

[0059] In the communication environment 200, when the first apparatus 210 is moving, cell switch may be performed for the first apparatus 210. For example, the first apparatus 210 may move towards the cell 224. In this case, the cell 224 may be referred to as a target cell 224. The cell switch may be triggered by a command from the second apparatus 220. After the cell switch is completed, the target cell 224 may become a new serving cell for the first apparatus 210.

[0060] In various example embodiments, the command triggering the cell switch indicates whether random access is to be trigger for the cell switch. Based on the command, the first apparatus 210 may determine a certain type of random access procedure such as a CFRA, CBRA or RACH-less procedure is to be initiated for the cell switch.

[0061] Some example implementations of the present disclosure will be described in detail below with reference to FIGS. 3 to 5.

[0062] FIG. 3 illustrates a signaling flow 300 for communication between the first apparatus 210 and the second apparatus 220 according to some example embodiments of the present disclosure.

[0063] As shown in FIG. 3, the second apparatus 220 transmits (310), to the first apparatus 210, a configuration indicating at least one candidate cell (for example, the cells222 and 224). Correspondingly, the first apparatus 210 receives (320) this configuration from the second apparatus 220. This configuration may be transmitted via higher signaling such as RRC signaling.

[0064] The second apparatus 220 transmits (330), to the first apparatus 210, a command (for example, an LTM cell switch command) triggering cell switch towards a target cell (for example, the cell 224). Correspondingly, the first apparatus 210 receives (340) this command from the second apparatus 220. The command may be transmitted (330) in a MAC CE (for example, an LTM cell switch command MAC CE).

[0065] The command indicates whether random access is to be triggered for the cell switch. Based on the command, the first apparatus 210 determines (350) whether random access is to be triggered for the cell switch. Based on the determining (350), the first apparatus 210 performs (360) the cell switch towards the target cell 224. For example, if it is determined (350) that the random access is to be triggered, the first apparatus 210 may perform (360) the cell switch by initiating a CFRA or CBRA procedure. If it is determined (350) that the random access is not to be triggered, the first apparatus 210 may perform (360) the cell switch by initiating a RACH-less procedure.

[0066] In some example embodiments, the command may contain an indication (referred to as a first indication) whether random access is to be triggered. In the example embodiments where the command is transmitted in the MAC CE, the first indication may be carried via a field (referred to as a first field) in the MAC CE. Some example embodiments in this regard will be described with reference to FIGS. 4 and 5 which illustrate example LTM cell switch command MAC CEs according to some example embodiments of the present disclosure.

[0067] In some example embodiments, the first field may include an existing field (for example, an S / U field in a bit position 402 and a C field 404 in FIG. 4, and an S / U field 502 and a C field 504 in FIG. 5) or a specific field (for example, a CB field in the bit position 402 and a CB field 506) in the MAC CE. In some example embodiments, the C field 404 or 504 may include a bit, also referred to a C bit.

[0068] In one example, a field (for example, the CB field in the bit position 402 or the CB field 506) in the MAC CE may be defined to indicate whether the first apparatus 210 is to initiate an RA procedure for the LTM cell switch or not. In some examples, the field indicating the first apparatus 210 to trigger an RA procedure may indicate the firstapparatus 210 to trigger a CBRA procedure (for the cell switch). For example, a specific value (e.g., index ‘0’ or ‘ 1 ’) may indicate that an RA procedure is not to be initiated.. In this case, the first apparatus 210 may rely on RACH-less LTM based on the NW indicated TAC or UE based TA measurement. Another specific value (e.g., index ‘ 1’ or ‘0’) may indicate that the RA procedure is to be initiated.

[0069] In some example embodiments, the command may contain an indication (referred to as a second indication) whether the existing field or the specific field in the MAC CE carries the first indication to trigger the random access. In some example embodiments, the second indication may be carried in the MAC CE via a field or a bit (for example, the C fields 404 and 504) that indicates presence of CFRA resource information (for example, random access preamble index fields 406 and 508) in the command.

[0070] In an example, if the C field 404 or 504 in the LTM CSC MAC CE is set to a specific value, an existing field (for example, the S / U field in the bit position 402 or the S / U field 502) may be reused to indicate whether RA is to be triggered. In one example, if the C bit 404 or 504 indicating presence of CFRA resource fields 406 and 508 is set to a specific value (e.g. 0), the S / U field in the bit position 402 or the S / U field 502 may be interpreted as a RA trigger indication. If the S / U field in the bit position 402 or the S / U field 502 is set to a specific value, it may indicate that cell switch is performed using RA. If the S / U field in the bit position 402 or the S / U field 502 is set to another specific value, it may indicate that RA is not triggered, and the first apparatus 210 may be configured to perform RACH-less LTM cell switch.

[0071] In another example, if the C field 404 or 504 is set to a specific value, a specific field (for example, the CB field in the bit position 402 or the CB field 506) may be used to indicate whether RA is to be triggered. In one example, if the C field 404 or 504 indicating presence of CFRA resource fields is set to a specific value (e.g. 0), one field (e.g. the CB field in the bit position 402 or the CB field 506) in the Cell switch command may be interpreted as an RA trigger indication. If the CB field in the bit position 402 or the CB field 506 is set to a specific value, it may indicate that cell switch is performed using RA. If the CB field in the bit position 402 or the CB field 506 is set to another specific value, it may indicate that RA is not triggered, and the first apparatus 210 may be configured to perform RACH-less LTM cell switch. In some examples, the RA trigger indication may indicate specifically to trigger a CBRA procedure.

[0072] In some example embodiments, the existing field and the specific field may be encoded in a same bit position (for example, the bit position 402) of the MAC CE. In one embodiment, the field (for example, the C field 404) in the LTM cell switch command (CSC) MAC CE, which is used to indicate the presence of CFRA resource information (for example, the random access preamble index field 406) in the LTM CSC MAC CE, may be further used to indicate existence of different specific fields in the same bit position (for example, the bit position 402) in the LTM CSC MAC CE, depending on the set index value of the field (for example, the C field 404). In other words, depending on whether the C field 404 is set to index ‘0’ or ‘ 1 ’, a different field may be encoded for a specific bit position (for example, the bit position 402) in the LTM CSC MAC CE.

[0073] In some example embodiments, if the field or the bit (for example, the C field 404) indicates that the CFRA resource information (for example, the random access preamble index field 406) is available in the command, the first indication may carried via the existing field (for example, S / U field in the bit position 402) that indicates an uplink carrier to initiate a random access procedure using CFRA resources. Accordingly, the first apparatus 210 may determine that the first indication to trigger the random access is carried via the existing field that indicates an uplink carrier to initiate a random access procedure using CFRA resources.

[0074] In some example embodiments, if the field or the bit (for example, the C field 404) indicates that the CFRA resource information (for example, the random access preamble index field 406) is available in the command, the first indication may be carried via the existing field (for example, C field in the bit position 404) that indicates to initiate a random access procedure using CFRA resource(s). Accordingly, the first apparatus 210 may determine that the first indication to trigger the random access is carried via the existing field that indicates to initiate a random access procedure using CFRA resource(s).

[0075] In some example embodiments, if the field or the bit (for example, the C field 404) indicates that the CFRA resource information is absent in the command, the first indication may be carried via the specific field (for example, the CB field in the bit position 402) encoded in a same bit position (402) as the existing field (for example, the S / U field in the bit position 402 that indicates an uplink carrier to initiate a random access procedure using CFRA resources). Accordingly, the first apparatus 210 may determine that the first indication is carried via the specific field encoded in the same bit position asthe existing field that indicates an uplink carrier to initiate a random access procedure using CFRA resources.

[0076] In one example, if the C field 404 in the LTM CSC MAC CE is set to a specific value (e.g. index ‘ 1’ or ‘0’) indicating availability of CFRA resource information in the LTM CSC MAC CE, the S / U field (for example, the S / U field in the bit position 402) may be present. If the C field 404 in the LTM CSC MAC CE is set to another specific value (e.g. index ‘0’ or ‘ 1’) indicating that CFRA resource information is not present in the LTM CSC MAC CE, another field (for example, the CB field in the bit position 402) may be present instead. In this way, in the case that the S / U field is not present, the same bit position may be used to indicate whether the RA is to be triggered or not. No specific bit position(s) needs to be reserved for this purpose, and other bits may be saved for further use.

[0077] In some example embodiments, a field or a bit (for example, the C fields 404 and 504) that indicates presence of CFRA resource information (for example, for example, random access preamble index fields 406 and 508) in the command may serve as the first field carrying the first indication whether the RA is to be triggered.

[0078] In some example embodiments, in the case that the field or the bit (for example, the C fields 404 and 504) is set as a value indicating that the CFRA resource information is available in the command, the CFRA resource information may be excluded in the command to indicate that the random access is to be triggered. Accordingly, if the first apparatus 210 determines that the field or the bit (for example, the C fields 404 and 504) indicates that the CFRA resource information is available and the CFRA resource information is absent in the command, the first apparatus 210 may determine (350) that the random access is to be triggered. In this way, for example, the C field 404 or 504 set to a specific value (e.g., '1') indicating the availability of CFRA resource information in the LTM CSC MAC CE is further used to trigger a Random Access procedure by not signaling the CFRA resource information.

[0079] In some example embodiments, in the case that the cell switch command is transmitted (310) in the MAC CE, a size of the MAC CE may be used to indicate whether to trigger the RA for the cell switch. In an example, the first apparatus 210 may determine that CFRA resource information is available in the MAC CE, for example, based on the C field 404 or 504. Then, the first apparatus 210 may determine (350), based on a size ofthe MAC CE, whether the random access is to be triggered. For example, if the size of the MAC CE is equal to or less than a threshold, the first apparatus 210 may determine (350) that the random access is to be triggered.

[0080] In one embodiment, the first apparatus 210 may determine (350) the triggering of Random Access for LTM cell switch based on the C field 404 or 504 and the size of the MAC CE. In one example, if the C field 404 or 504 indicates the availability of the CFRA resource information, but the size of the MAC CE cannot fit a required size (for example, a threshold), then the first apparatus 210 may determine (350) that Random Access is triggered for the LTM cell switch.

[0081] In some example embodiments, if it is determined (350) that the random access is to be triggered, the first apparatus 210 may perform (360) the cell switch using the random access. In one embodiment where a field (e.g. the CB field 506) in the LTM CSC MAC CE indicates whether the Random Access is triggered for the cell switch, a specific value of this field may indicate that the random access is triggered or not triggered. In one example, if the field indicates triggering of random access, the cell switch may be performed (360) using random access.

[0082] In some example embodiments, the command may indicate a type of the random access to be triggered for the cell switch. Accordingly, based on the command, the first apparatus 210 may determine the type of the random access to be triggered.

[0083] In some example embodiments, if the random access is triggered, the CFRA resource fields (for example, random access preamble index fields 406 and 508) may not present in the LTM cell switch command. In this case, after the first apparatus 210 determines that the CFRA resource information is absent in the command, the first apparatus 210 may perform (360) the cell switch without using CFRA resources, for example, by initiating a CBRA procedure for the cell switch. As such, by not signaling the CFRA resource fields, the cell switch command may indicate CBRA to be triggered for the cell switch.

[0084] In some example embodiments, after the first apparatus 210 determines (350) RA is to be triggered, the first apparatus 210 may perform (360) the cell switch by initiating a CBRA procedure. For example, if the first apparatus 210 determines (350) that RA is triggered based on one or more embodiments herein, the first apparatus 210 may perform (360) only a CBRA procedure.

[0085] In some example embodiments, after the first apparatus 210 determines (350) RA is to be triggered, if the first apparatus 210 determines that CFRA resources are configured, the first apparatus 210 may perform (360) the cell switch by initiating a random access procedure using the CFRA resources. For example, if the first apparatus 210 determines (350) that RA is triggered based on one or more example embodiments herein, the first apparatus 210 may first determine whether a serving cell configuration (for example, decoded upon receiving the cell switch command) associated with an LTM candidate configuration provisions CFRA resources (for example, RRC configured CFRA resources). If the CFRA resources are present, the first apparatus 210 may use the CFRA resources in the Random Access procedure.

[0086] In some example embodiments, if the first apparatus 210 determines (350) that the RA is to be triggered, the first apparatus 210 may determine that transmission configuration indicator (TCI) state information (for example, a TCI state ID field 408 or 510 and a UL TCI state ID field 410 or 512) is absent or ignored in the command. The TCI state information may include at least one octet (for example, octet 4 412 and octet 414 in FIG. 4 and octet 4 514 and octet 516 in FIG. 5) containing at least one TCI state identifier (ID) field (for example, the TCI state ID fields 408 and 410 in FIG. 4 and the TCI state ID fields 510 or 512 in FIG. 5).

[0087] In one embodiment, if the first apparatus 210 determines (350) that random access is triggered, octets (for example, octet 4 412 and octet 414 in FIG. 4 and octet 4 514 and octet 516 in FIG. 5) containing TCI State fields (for example, the TCI state ID fields 408 and 410 in FIG. 4 and the TCI state ID fields 510 or 512 in FIG. 5) may be not present in the LTM CSC MAC CE. Alternatively, the TCI state ID fields 408 and 410 in FIG. 4 and the TCI state ID fields 510 or 512 in FIG. 5 may be ignored by the first apparatus 210.

[0088] The TCI state IDs may indicate a beam, for example, including a downlink beam and an uplink beam in the target cell, which is to be used by the first apparatus 210 for the cell switch. If the first apparatus 210 performs a random access procedure, it may indicate a beam to the network. For example, if CBRA is used for the cell switch, the first apparatus 210 may select a synchronization signal (SS) block and then transmit a random access preamble associated with that SS block and the beam. In this case, these TCI state ID fields 408, 410, 510 and 512 may not be needed since the first apparatus 210 selectsthe beam in the random access procedure. In some cases, for example, there may be no measurement report from the first apparatus 210 for any of the beams for the target cell. In these cases, the network may want the first apparatus 210 to perform random access based cell switch and then to indicate a best beam to the network using the random access procedure. Thus, the TCI state ID fields 408, 410, 510 and 512 may be either not present or ignored. As such, the network may enforce the first apparatus 210 to perform random access and report a suitable beam for the target cell.

[0089] In some example embodiments, the cell switch command may contain an indication (referred to as a third indication) whether TCI state information is absent or ignored in the command. For example, in the case that the command is transmitted (310) in a MAC CE, and the third indication is carried via a field (referred to as a second field) in the MAC CE. In an example, a reserved field (for example, R fields 416 and 518) may serve as the second field. If this field is set to a specific value, then these TCI state ID fields (for example, the TCI state ID fields 408, 410, 510 and 512) maybe either not present or ignored.

[0090] In one embodiment, a field (i.e., the second field) in the LTM cell switch command MAC CE may indicate the presence of the TCI state IDs (for example, the TCI state ID fields 408, 410, 510 and 512) or octets (for example, octet 4 412 and octet 414 in FIG. 4 and octet 4 514 and octet 516 in FIG. 5) containing the TCI State IDs. If this field is set to specific value (e.g. 0), the octets containing TCI state ID fields may be not present (e.g. not encoded into the MAC CE). If this field (i.e. indicating the presence of the TCI state ID fields) is set to a specific value (e.g. 0), the octets containing TCI state ID fields may be ignored / not read (by the first apparatus 210) in the MAC CE.

[0091] In some example embodiments, if the second field is set as a value indicating that the TCI state information is absent or ignored in the command, this value may further indicate that the random access is to be triggered. Accordingly, the first apparatus 210 may determine that the random access is to be triggered. In this case, the second field may be further used to indicate that the random access is to be triggered. That is, the second field may serve as the first field to trigger the random access.

[0092] In some examples, the field indicating presence of TCI State ID fields may apply for a case where the random access procedure is triggered for the cell switch. As an example, the MAC CE may indicate the first apparatus 210 to trigger random access andapply the TCI State IDs in the TCI ID fields for the target cells after cell switch.

[0093] In some examples, the field indicating presence of TCI State ID fields may apply for a case where the random access procedure is not triggered (i.e. by the specific field) for the cell switch. As an example, the MAC CE may indicate the first apparatus 210 that CFRA information is present (e.g. the C field indicates it) and another field indicates whether the TCI State IDs in the TCI ID fields are present in the MAC CE.

[0094] For example, if the second field is set to specific value (e.g. 0), then the octets (for example, octet 4 412 and octet 414 in FIG. 4 and octet 4 514 and octet 516 in FIG. 5) containing TCI state ID fields (for example, the TCI state ID fields 408, 410, 510 and 512) may be not present in the MAC CE, or the octets in the MAC CE may be ignored or are not present. In this example, the MAC CE where a field may indicate whether the TCI state ID field(s) are present (i.e. TCI state ID fields are not encoded / included or are ignored) may further indicate triggering of cell switch using random access. As an example, the field may indicate that TCI State ID fields are not present (or are ignored), it may further indicate triggering of cell switch using random access.

[0095] If the second field is set to specific value (e.g. 1), the octets (for example, octet 4 412 and octet 414 in FIG. 4 and octet 4 514 and octet 516 in FIG. 5) containing TCI state ID fields (for example, the TCI state ID fields 408, 410, 510 and 512) may be present in the MAC CE.

[0096] In some example embodiments, if based on the cell switch command, the first apparatus 210 determines the TCI state information is present or not ignored and the random access is to be triggered, then the first apparatus 210 may perform (360) the cell switch by applying the TCI state information. For example, in the case that the second field is set to specific value (e.g. 1), the octets (for example, octet 4 412 and octet 414 in FIG. 4 and octet 4 514 and octet 516 in FIG. 5) containing the TCI state ID fields (for example, the TCI state ID fields 408, 410, 510 and 512) are present (and not to be ignored) in the MAC CE. In this case, if the MAC CE indicates triggering of cell switch using random access (for example, by the first field such as the S / U field or the CB field in the bit position 402 or the C field 404 in FIG. 4, and the S / U field 502, the C field 504 and the CB field 506 in FIG. 5), the first apparatus 210 may apply the TCI state ID(s) as indicated TCI state.

[0097] In some example embodiments, in the case that the CFRA resource informationis available in the command, a random access preamble index (for example, the random access preamble index field 406 or 508) may be set as a predefined value to indicate that at least one of a synchronization signal and physical broadcast channel block index (for example, SS / PBCH index fields 418, 420, 520 and 522) or a physical random access channel (PRACH) mask index (for example, PRACH Mask index fields 422 and 524) is absent in the command. Accordingly, in the case that the first apparatus 210 determines that CFRA resource information is available in the command, for example, by the C field 404 or 504, if a random access preamble index is set as a predefined value, the first apparatus 210 may determine that at least one of a synchronization signal and physical broadcast channel block index or a PRACH mask index is absent in the command.

[0098] In one embodiment, the C field 404 or 504 in the LTM CSC MAC CE may indicate the availability of CFRA resource information in the LTM CSC MAC CE, and the RA preamble index (for example, the RA preamble index field 406 or 508) may be set to 000000. In this case, the first apparatus 210 may initiate a CFRA procedure for the cell switch. In this embodiment, the SSB / PBCH index (for example, the SS / PBCH index field 418, 420, 520 or 522) and the PRACH Mask index (for example, the PRACH Mask index field 422 or 524) may not be signaled. In other words, based on the RA preamble index set to 000000, the first apparatus 210 may determine that a random access procedure is to be initiated (without a CFRA preamble index) and that the SSB / PBCH and PRACH Mask indices are NOT encoded in the MAC CE. With this option, bits (for example, one byte) in the LTM CSC MAC CE may be saved. Thus, the size of the command may be reduced, thereby further reducing signaling overhead and improving the resource efficiency and network capacity.

[0099] Some example structures of the LTM Cell Switch Command MAC CE will be discussed below with reference to FIGS. 4 and 5. Based on a structure 400 as shown in FIG. 4, in some example embodiments, the C field 404 is used to indicate either the S / U field or the CB field is present in the bit position 402. Example definitions of the C field, the S / U field and the CB field are as below.C: This field indicates the presence of the contention-free Random Access Resources fields. If the value of this field is set to 1, the following fields are present, including Random Access Preamble index field, SS / PBCH index field and PRACH Mask index field. If the value of this field is set to 0, Random Access Preamble index field,SS / PBCH index field and PRACH Mask index field are absent. If this field is set to 1, S / U field is present; otherwise, CB field is present instead.- S / U: This field indicates which UL carrier to transmit the PRACH of the contention-free Random Access Resources. If the value of this field is set to 1, SUL is used; otherwise, NUL is used. The length of the field is 1 bit;- CB: This field indicates whether Random Access procedure shall be initiated for the current LTM cell switch. If this field is set to 1, Random Access procedure is triggered. If the value is set to 0, the Rach-less cell switch is triggered.

[0100] Based on a structure 500 as shown in FIG. 5, In some example embodiments, the C field 504 set to a specific value (for example, 0) enables the S / U field 502 or the CB field 506 to trigger the random access. Example definitions of the C field, the S / U field and the CB field are as below.- C: This field indicates the presence of the contention-free Random Access Resources fields. If the value of this field is set to 1, the following fields are present, including Random Access Preamble index field, S / U field, SS / PBCH index field and PRACH Mask index field. If the value of this field is set to 0, Random Access Preamble index field, SS / PBCH index field and PRACH Mask index field are absent, S / U field or CB field indicates (whether) the cell switch is performed using random access procedure.- S / U: This field indicates which UL carrier to transmit the PRACH of the contention-free Random Access Resources. If the value of this field is set to 1, SUL is used; otherwise, NUL is used. The length of the field is 1 bit; if the C bit is set to 0, and this value is set to 1, it indicates the cell switch using random access. If the C bit is set to 0, and this value is set to 0, the cell switch command indicates rach-less cell switch.- CB: if the C bit is set to 0, and this value is set to 1, it indicates the cell switch using random access. If the C bit is set to 0, and this value is set to 0, the cell switch command indicates rach-less cell switch.

[0101] In some other example embodiments, a specific field such as the CB field 506 is defined to trigger the random access as below.- CB: if this value is set to 1, it indicates the LTM cell switch using random access. If the value of this field is set to 1, Random Access Preamble index field, SS / PBCH index field and PRACH Mask index field are absent. If the value is set to 0, the C field in cellswitch command indicates the presence of the contention-free Random Access Resources fields.

[0102] FIG. 6 shows a flowchart of an example method 600 implemented at a first apparatus in accordance with some example embodiments of the present disclosure. For the purpose of discussion, the method 600 may be described from the perspective of the first apparatus 210 in FIG. 2.

[0103] At block 610, the first apparatus 210 receives a configuration indicating at least one candidate cell. At block 620, the first apparatus 210 receives a command triggering cell switch towards a target cell of the at least one candidate cell. At block 630, the first apparatus 210 determines, based on the command, whether random access is to be triggered for the cell switch. At block 640, the first apparatus 210 performs the cell switch based on the determining.

[0104] In some example embodiments, based on determining that the random access is to be triggered, the first apparatus 210 may determine a type of the random access to be triggered for the cell switch, based on the command.

[0105] In some example embodiments, the command may contain a first indication whether the random access is to be triggered.

[0106] In some example embodiments, the command may be received in a MAC CE, and the first indication is carried via a first field in the MAC CE.

[0107] In some example embodiments, the first field may include an existing field or a specific field in the MAC CE.

[0108] In some example embodiments, the command may contain a second indication whether the existing field or the specific field in the MAC CE carries the first indication.

[0109] In some example embodiments, the second indication may be carried in the MAC CE via a field or a bit that indicates presence of CFRA resource information in the command.

[0110] In some example embodiments, based on the field or the bit indicating that the CFRA resource information is available in the command, the first apparatus 210 may determine that the first indication is carried via the existing field that indicates an uplink carrier to initiate a random access procedure using CFRA resources.

[0111] In some example embodiments, based on the field or the bit indicating that the CFRA resource information is absent in the command, the first apparatus 210 may determine that the first indication is carried via the specific field encoded in a same bit position as the existing field that indicates an uplink carrier to initiate a random access procedure using CFRA resources.

[0112] In some example embodiments, based on determining that the field or the bit indicates that the CFRA resource information is available and the CFRA resource information is absent in the command, the first apparatus 210 may determine that the random access is to be triggered.

[0113] In some example embodiments, the first apparatus 210 may determine that CFRA resource information is available in the MAC CE. The first apparatus 210 may determine, based on a size of the MAC CE, whether the random access is to be triggered.

[0114] In some example embodiments, based on the size of the MAC CE being equal to or less than a threshold, the first apparatus 210 may determine that the random access is to be triggered.

[0115] In some example embodiments, based on determining that the random access is to be triggered, the first apparatus 210 may perform the cell switch using the random access.

[0116] In some example embodiments, based on determining that CFRA resource information is absent in the command, the first apparatus 210 may perform the cell switch without using CFRA resources.

[0117] In some example embodiments, based on determining that CFRA resources are configured, the first apparatus 210 may perform the cell switch by initiating a random access procedure using CFRA resources, based on determining that the CFRA resources are configured.

[0118] In some example embodiments, the first apparatus 210 may perform the cell switch by initiating a CBRA procedure.

[0119] In some example embodiments, the first apparatus 210 may determine that TCI state information is absent or ignored in the command.

[0120] In some example embodiments, the command may contain a third indicationwhether TCI state information is absent or ignored in the command.

[0121] In some example embodiments, the command may be received in a MAC CE, and the third indication may be carried via a second field in the MAC CE.

[0122] In some example embodiments, the second field may be set as a value indicating that the TCI state information is absent or ignored in the command. The value may further indicate that the random access is to be triggered.

[0123] In some example embodiments, the TCI state information may include at least one octet containing at least one TCI state identifier (ID) field.

[0124] In some example embodiments, the first apparatus 210 may determine, based on the command, that the TCI state information is present or not ignored. The first apparatus 210 may determine, based on the command, that the random access is to be triggered. In these example embodiments, the first apparatus 210 may perform the cell switch by applying the TCI state information.

[0125] In some example embodiments, the first apparatus 210 may determine that CFRA resource information is available in the command. Based on a random access preamble index being set as a predefined value, the first apparatus 210 may determine that at least one of a synchronization signal and physical broadcast channel block index or a physical random access channel mask index may be absent in the command.

[0126] FIG. 7 shows a flowchart of an example method 700 implemented at a second apparatus in accordance with some example embodiments of the present disclosure. For the purpose of discussion, the method 700 may be described from the perspective of the second apparatus 220 in FIG. 2.

[0127] At block 710, the second apparatus 220 transmits, to the first apparatus 210, a configuration indicating at least one candidate cell.

[0128] At block 720, the second apparatus 220 transmits, to the first apparatus 210, a command triggering cell switch towards a target cell of the at least one candidate cell. The command indicates whether random access is to be triggered for the cell switch.

[0129] In some example embodiments, the command may indicate that the random access is to be triggered, and the command may further indicate a type of the random access to be triggered for the cell switch.

[0130] In some example embodiments, the command may contain a first indication whether the random access is to be triggered.

[0131] In some example embodiments, the command may be transmitted in a MAC CE. The first indication may be carried via a first field in the MAC CE.

[0132] In some example embodiments, the first field may include an existing field or a specific field in the MAC CE.

[0133] In some example embodiments, the command may contain a second indication whether the existing field or the specific field in the MAC CE carries the first indication.

[0134] In some example embodiments, the second indication may be carried in the MAC CE via a field or a bit that indicates presence of CFRA resource information in the command.

[0135] In some example embodiments, the field or the bit may indicate that the CFRA resource information is available in the command, and the first indication may be carried via the existing field that indicates an uplink carrier to initiate a random access procedure using CFRA resources.

[0136] In some example embodiments, the field or the bit may indicate that the CFRA resource information is absent in the command, and the first indication may be carried via the specific field encoded in a same bit position as the existing field that indicates an uplink carrier to initiate a random access procedure using CFRA resources.

[0137] In some example embodiments, the first field may include a field or a bit that indicates presence of CFRA resource information in the command.

[0138] In some example embodiments, the field or the bit may be set as a value indicating that the CFRA resource information is available in the command. The CFRA resource information may be excluded in the command to indicate that the random access is to be triggered.

[0139] In some example embodiments, the command may be transmitted in a MAC CE, and the MAC CE may contain CFRA resource information. In these example embodiments, a size of the MAC CE may indicate whether the random access is to be triggered.

[0140] In some example embodiments, the size of the MAC CE may be equal to or lessthan a threshold to indicate that the random access is to be triggered.

[0141] In some example embodiments, the command may contain a third indication whether TCI state information is absent or ignored in the command.

[0142] In some example embodiments, the command may be transmitted in a MAC CE, and the third indication may be carried via a second field in the MAC CE.

[0143] In some example embodiments, the second field may be set as a value indicating that the TCI state information is absent or ignored in the command, and the value may further indicate that the random access is to be triggered.

[0144] In some example embodiments, the TCI state information may include at least one octet containing at least one TCI state identifier (ID) field.

[0145] In some example embodiments, CFRA resource information may be available in the command, and a random access preamble index may be set as a predefined value to indicate that at least one of a synchronization signal and physical broadcast channel block index or a physical random access channel mask index is absent in the command.

[0146] All operations and features related to the first apparatus 210 and the second apparatus 220 as described above with reference to FIGS. 2 to 5 are likewise applicable to the methods 600 and 700 and have similar effects. For the purpose of simplification, the details will be omitted.

[0147] FIG. 8 is a simplified block diagram of a device 800 that is suitable for implementing example embodiments of the present disclosure. The device 800 may be provided to implement a communication device, for example, the first apparatus 210 or the second apparatus 220 as shown in FIG. 2. As shown, the device 800 includes one or more processors 810, one or more memories 820 coupled to the processor 810, and one or more communication modules 840 coupled to the processor 810.

[0148] The communication module 840 is for bidirectional communications. The communication module 840 has one or more communication interfaces to facilitate communication with one or more other modules or devices. The communication interfaces may represent any interface that is necessary for communication with other network elements. In some example embodiments, the communication module 840 may include at least one antenna.

[0149] The processor 810 may be of any type suitable to the local technical network and may include one or more of the following: general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on multicore processor architecture, as non-limiting examples. The device 800 may have multiple processors, such as an application specific integrated circuit chip that is slaved in time to a clock which synchronizes the main processor.

[0150] The memory 820 may include one or more non-volatile memories and one or more volatile memories. Examples of the non-volatile memories include, but are not limited to, a Read Only Memory (ROM) 824, an electrically programmable read only memory (EPROM), a flash memory, a hard disk, a compact disc (CD), a digital video disk (DVD), an optical disk, a laser disk, and other magnetic storage and / or optical storage. Examples of the volatile memories include, but are not limited to, a random access memory (RAM) 822 and other volatile memories that may not last in the power-down duration.

[0151] A computer program 830 includes computer executable instructions that are executed by the associated processor 810. The instructions of the program 830 may include instructions for performing operations / acts of some example embodiments of the present disclosure. The program 830 may be stored in the memory, e.g., the ROM 824. The processor 810 may perform any suitable actions and processing by loading the program 830 into the RAM 822.

[0152] The example embodiments of the present disclosure may be implemented by means of the program 830 so that the device 800 may perform any process of the disclosure as discussed with reference to FIG. 2 to FIG. 7. The example embodiments of the present disclosure may also be implemented by hardware or by a combination of software and hardware.

[0153] In some example embodiments, the program 830 may be tangibly contained in a computer readable medium which may be included in the device 800 (such as in the memory 820) or other storage devices that are accessible by the device 800. The device 800 may load the program 830 from the computer readable medium to the RAM 822 for execution. In some example embodiments, the computer readable medium may include any types of non-transitory storage medium, such as ROM, EPROM, a flash memory, a hard disk, CD, DVD, and the like. The term “non-transitory,” as used herein, is alimitation of the medium itself (i.e., tangible, not a signal) as opposed to a limitation on data storage persistency (e.g., RAM vs. ROM).

[0154] FIG. 9 shows an example of the computer readable medium 900 which may be in form of CD, DVD or other optical storage disk. The computer readable medium 900 has the program 830 stored thereon.

[0155] Generally, various embodiments of the present disclosure may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. Some aspects may be implemented in hardware, and other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device. Although various aspects of embodiments of the present disclosure are illustrated and described as block diagrams, flowcharts, or using some other pictorial representations, it is to be understood that the block, apparatus, system, technique or method described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.

[0156] Some example embodiments of the present disclosure also provide at least one computer program product tangibly stored on a computer readable medium, such as a non- transitory computer readable medium. The computer program product includes computerexecutable instructions, such as those included in program modules, being executed in a device on a target physical or virtual processor, to carry out any of the methods as described above. Generally, program modules include routines, programs, libraries, objects, classes, components, data structures, or the like that perform particular tasks or implement particular abstract data types. The functionality of the program modules may be combined or split between program modules as desired in various embodiments. Machine-executable instructions for program modules may be executed within a local or distributed device. In a distributed device, program modules may be located in both local and remote storage media.

[0157] Program code for carrying out methods of the present disclosure may be written in any combination of one or more programming languages. The program code may be provided to a processor or controller of a general purpose computer, special purpose computer, or other programmable data processing apparatus, such that the program code, when executed by the processor or controller, cause the functions / operations specified inthe flowcharts and / or block diagrams to be implemented. The program code may execute entirely on a machine, partly on the machine, as a stand-alone software package, partly on the machine and partly on a remote machine or entirely on the remote machine or server.

[0158] In the context of the present disclosure, the computer program code or related data may be carried by any suitable carrier to enable the device, apparatus or processor to perform various processes and operations as described above. Examples of the carrier include a signal, computer readable medium, and the like.

[0159] The computer readable medium may be a computer readable signal medium or a computer readable storage medium. A computer readable medium may include but not limited to an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples of the computer readable storage medium would include an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

[0160] Further, although operations are depicted in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In certain circumstances, multitasking and parallel processing may be advantageous. Likewise, although several specific implementation details are contained in the above discussions, these should not be construed as limitations on the scope of the present disclosure, but rather as descriptions of features that may be specific to particular embodiments. Unless explicitly stated, certain features that are described in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, unless explicitly stated, various features that are described in the context of a single embodiment may also be implemented in a plurality of embodiments separately or in any suitable sub-combination.

[0161] Although the present disclosure has been described in languages specific to structural features and / or methodological acts, it is to be understood that the present disclosure defined in the appended claims is not necessarily limited to the specific featuresor acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.

[0162] Various example embodiments of the techniques have been described. In addition to or as an alternative to the above, the following examples are described. The features described in any of the following examples may be utilized with any of the other examples described herein.

[0163] In an aspect, a first apparatus (210) includes: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the first apparatus (210) at least to: receive (320, 610) a configuration indicating at least one candidate cell (222, 224); receive (340, 620) a command triggering cell switch towards a target cell (224) of the at least one candidate cell (222, 224); determine (350, 630), based on the command, whether random access is to be triggered for the cell switch; and perform (360, 640) the cell switch based on the determining (350, 630).

[0164] In some example embodiments, the first apparatus (210) is further caused to: based on determining (350, 630) that the random access is to be triggered, determine a type of the random access to be triggered for the cell switch, based on the command.

[0165] In some example embodiments, at least one of the following is utilized by the first apparatus (210): the command contains a first indication whether the random access is to be triggered; the command is received (340, 620) in a medium access control (MAC) control element (CE), and the first indication is carried via a first field in the MAC CE; or the first field includes an existing field or a specific field in the MAC CE.

[0166] In some example embodiments, at least one of the following is utilized by the first apparatus (210): the command contains a second indication whether the existing field or the specific field in the MAC CE carries the first indication; or the second indication is carried in the MAC CE via a field or a bit (404) that indicates presence of contention free random access (CFRA) resource information in the command.

[0167] In some example embodiments, the at least one memory and the at least one processor cause the first apparatus (210) to perform at least one of: based on the field or the bit (404) indicating that the CFRA resource information is available in the command, determining that the first indication is carried via the existing field that indicates an uplink carrier to initiate a random access procedure using CFRA resources; or based on the fieldor the bit (404) indicating that the CFRA resource information is absent in the command, determining that the first indication is carried via the specific field encoded in a same bit position (402) as the existing field that indicates an uplink carrier to initiate a random access procedure using CFRA resources.

[0168] In some example embodiments, the first field includes a field or a bit (404, 504) that indicates presence of contention free random access (CFRA) resource information in the command; and / or the at least one memory and the at least one processor cause the first apparatus (210) to: based on determining that the field or the bit (404, 504) indicates that the CFRA resource information is available and the CFRA resource information is absent in the command, determine (350, 630) that the random access is to be triggered.

[0169] In some example embodiments, the command is received (340, 620) in a medium access control (MAC) control element (CE); and the at least one memory and the at least one processor cause the first apparatus (210) to perform at least one of determining that contention free random access (CFRA) resource information is available in the MAC CE, and determining (350, 630), based on a size of the MAC CE, whether the random access is to be triggered; or based on the size of the MAC CE being equal to or less than a threshold, determining (350, 630) that the random access is to be triggered.

[0170] In some example embodiments, the at least one memory and the at least one processor cause the first apparatus (210) to: based on determining (350, 630) that the random access is to be triggered, perform (360, 640) the cell switch using the random access.

[0171] In some example embodiments, the at least one memory and the at least one processor further cause the first apparatus (210) to perform at least one of: based on determining that contention free random access (CFRA) resource information is absent in the command, performing the cell switch without using CFRA resources; performing (360, 640) the cell switch by initiating a random access procedure using CFRA resources, based on determining that the CFRA resources are configured; or performing (360, 640) the cell switch by initiating a contention based random access (CBRA) procedure.

[0172] In some example embodiments, the at least one memory and the at least one processor further cause the first apparatus (210) to: determine that transmission configuration indicator (TCI) state information is absent or ignored in the command.

[0173] In some example embodiments, at least one of the following is utilized by the first apparatus (210): the command contains a third indication whether transmission configuration indicator (TCI) state information is absent or ignored in the command; or the command is received (340, 620) in a medium access control (MAC) control element (CE), and the third indication is carried via a second field in the MAC CE.

[0174] In some example embodiments, at least one of the following is utilized by the first apparatus (210): the second field is set as a value indicating that the TCI state information is absent or ignored in the command, and the value further indicates that the random access is to be triggered; or the TCI state information includes at least one octet (412, 414, 514, 516) containing at least one TCI state identifier (ID) field (408, 410, 510, 512).

[0175] In some example embodiments, the at least one memory and the at least one processor cause the first apparatus (210) to: determine, based on the command, that the TCI state information is present or not ignored; determine (350, 630), based on the command, that the random access is to be triggered; and perform (360, 640) the cell switch by applying the TCI state information.

[0176] In some example embodiments, the at least one memory and the at least one processor cause the first apparatus (210) to: determine that contention free random access (CFRA) resource information is available in the command; and based on a random access preamble index being set as a predefined value, determine that at least one of a synchronization signal and physical broadcast channel block index or a physical random access channel mask index is absent in the command.

[0177] In an aspect, a second apparatus (220) includes: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the second apparatus (220) at least to: transmit (310, 710), to a first apparatus (210), a configuration indicating at least one candidate cell (222, 224); transmit (320, 720), to the first apparatus (210), a command triggering cell switch towards a target cell (224) of the at least one candidate cell (222, 224), where the command indicates whether random access is to be triggered for the cell switch.

[0178] In some example embodiments, the command indicates that the random access is to be triggered, and the command further indicating a type of the random access to be triggered for the cell switch.

[0179] In some example embodiments, at least one of the following is utilized by the second apparatus (220): the command contains a first indication whether the random access is to be triggered; the command is transmitted (310, 710) in a medium access control (MAC) control element (CE), and the first indication is carried via a first field in the MAC CE; or the first field includes an existing field or a specific field in the MAC CE.

[0180] In some example embodiments, at least one of the following is utilized by the second apparatus (220): the command contains a second indication whether the existing field or the specific field in the MAC CE carries the first indication; or the second indication is carried in the MAC CE via a field or a bit (404) that indicates presence of contention free random access (CFRA) resource information in the command.

[0181] In some example embodiments, at least one of the following is utilized by the second apparatus (220): the field or the bit (404) indicates that the CFRA resource information is available in the command, and the first indication is carried via the existing field that indicates an uplink carrier to initiate a random access procedure using CFRA resources; or the field or the bit (404) indicates that the CFRA resource information is absent in the command, and the first indication is carried via the specific field encoded in a same bit position (402) as the existing field that indicates an uplink carrier to initiate a random access procedure using CFRA resources.

[0182] In some example embodiments, at least one of the following is utilized by the second apparatus (220): the first field includes a field or a bit (404, 504) that indicates presence of contention free random access (CFRA) resource information in the command; or the field or the bit (404, 504) is set as a value indicating that the CFRA resource information is available in the command, and the CFRA resource information is excluded in the command to indicate that the random access is to be triggered.

[0183] In some example embodiments, at least one of the following is utilized by the second apparatus (220): the command is transmitted (320, 720) in a medium access control (MAC) control element (CE), and the MAC CE contains contention free random access (CFRA) resource information; a size of the MAC CE indicates whether the random access is to be triggered; or the size of the MAC CE is equal to or less than a threshold to indicate that the random access is to be triggered.

[0184] In some example embodiments, at least one of the following is utilized by thesecond apparatus (220): the command contains a third indication whether transmission configuration indicator (TCI) state information is absent or ignored in the command; or the command is transmitted (320, 720) in a medium access control (MAC) control element (CE), and the third indication is carried via a second field in the MAC CE.

[0185] In some example embodiments, at least one of the following is utilized by the second apparatus (220): the second field is set as a value indicating that the TCI state information is absent or ignored in the command, and the value further indicates that the random access is to be triggered; or the TCI state information includes at least one octet (412, 414, 514, 516) containing at least one TCI state identifier (ID) field (408, 410, 510, 512).

[0186] In some example embodiments, contention free random access (CFRA) resource information is available in the command, and a random access preamble index is set as a predefined value to indicate that at least one of a synchronization signal and physical broadcast channel block index or a physical random access channel mask index is absent in the command.

[0187] In an aspect, the first apparatus (210) includes means for receiving (320, 610) a configuration indicating at least one candidate cell (222, 224); means for receiving (340, 620) a command triggering cell switch towards a target cell (224) of the at least one candidate cell (222, 224); means for determining (350, 630), based on the command, whether random access is to be triggered for the cell switch; and means for performing (360, 640) the cell switch based on the determining (350, 630).

[0188] In some example embodiments, the first apparatus (210) further includes: means for based on determining (350, 630) that the random access is to be triggered, determining a type of the random access to be triggered for the cell switch, based on the command.

[0189] In some example embodiments, at least one of the following is utilized by the first apparatus (210): the command contains a first indication whether the random access is to be triggered; the command is received (340, 620) in a medium access control (MAC) control element (CE), and the first indication is carried via a first field in the MAC CE; or the first field includes an existing field or a specific field in the MAC CE.

[0190] In some example embodiments, at least one of the following is utilized by the first apparatus (210): the command contains a second indication whether the existing fieldor the specific field in the MAC CE carries the first indication; or the second indication is carried in the MAC CE via a field or a bit (404) that indicates presence of contention free random access (CFRA) resource information in the command.

[0191] In some example embodiments, the first apparatus (210) further includes: means for based on the field or the bit (404) indicating that the CFRA resource information is available in the command, determining that the first indication is carried via the existing field that indicates an uplink carrier to initiate a random access procedure using CFRA resources; or means for based on the field or the bit (404) indicating that the CFRA resource information is absent in the command, determining that the first indication is carried via the specific field encoded in a same bit position (402) as the existing field that indicates an uplink carrier to initiate a random access procedure using CFRA resources.

[0192] In some example embodiments, the means for determining (350, 630) includes determining (350, 630) that the random access is to be triggered, based on determining that the field or the bit (404, 504) indicates that the CFRA resource information is available and the CFRA resource information is absent in the command.

[0193] In some example embodiments, the means for determining (350, 630) includes configuring the first apparatus (210) to at least one of determining that contention free random access (CFRA) resource information is available in the MAC CE, determining (350, 630), based on a size of the MAC CE, whether the random access is to be triggered; or based on the size of the MAC CE being equal to or less than a threshold, determining (350, 630) that the random access is to be triggered.

[0194] In some example embodiments, the means for performing (360, 640) includes: performing (360, 640) the cell switch using the random access based on determining (350, 630) that the random access is to be triggered.

[0195] In some example embodiments, the means for performing (360, 640) includes configuring the first apparatus (210) to at least one of: performing (360, 640) the cell switch without using CFRA resources, based on determining that contention free random access (CFRA) resource information is absent in the command; performing (360, 640) the cell switch by initiating a random access procedure using CFRA resources, based on determining that the CFRA resources are configured; or performing (360, 640) the cell switch by initiating a contention based random access (CBRA) procedure.

[0196] In some example embodiments, the first apparatus (210) further includes: means for determining that transmission configuration indicator (TCI) state information is absent or ignored in the command.

[0197] In some example embodiments, at least one of the following is utilized by the first apparatus (210): the command contains a third indication whether transmission configuration indicator (TCI) state information is absent or ignored in the command; or the command is received (340, 620) in a medium access control (MAC) control element (CE), and the third indication is carried via a second field in the MAC CE.

[0198] In some example embodiments, at least one of the following is utilized by the first apparatus (210): the second field is set as a value indicating that the TCI state information is absent or ignored in the command, and the value further indicates that the random access is to be triggered; or the TCI state information includes at least one octet (412, 414, 514, 516) containing at least one TCI state identifier (ID) field (408, 410, 510, 512).

[0199] In some example embodiments, the first apparatus (210) is further configured to perform at least one of: determining, based on the command, that the TCI state information is present or not ignored; determining (350, 630) includes means for determining (350, 630), based on the command, that the random access is to be triggered; and performing (360, 640) includes means for performing (360, 640) the cell switch by applying the TCI state information.

[0200] In some example embodiments, the first apparatus (210) includes: means for determining that contention free random access (CFRA) resource information is available in the command; and means for based on a random access preamble index being set as a predefined value, determining that at least one of a synchronization signal and physical broadcast channel block index or a physical random access channel mask index is absent in the command.

[0201] In an aspect, a second apparatus includes means for transmitting (310, 710), to a first apparatus (210), a configuration indicating at least one candidate cell (222, 224); means for transmitting (320, 720), to the first apparatus (210), a command triggering cell switch towards a target cell (224) of the at least one candidate cell (222, 224), where the command indicates whether random access is to be triggered for the cell switch.

[0202] In some example embodiments, the command indicates that the random access is to be triggered, and the command further indicating a type of the random access to be triggered for the cell switch.

[0203] In some example embodiments, at least one of the following is utilized by the second apparatus (220): the command contains a first indication whether the random access is to be triggered; the command is transmitted (310, 710) in a medium access control (MAC) control element (CE), and the first indication is carried via a first field in the MAC CE; or the first field includes an existing field or a specific field in the MAC CE.

[0204] In some example embodiments, at least one of the following is utilized by the second apparatus (220): the command contains a second indication whether the existing field or the specific field in the MAC CE carries the first indication; or the second indication is carried in the MAC CE via a field or a bit (404) that indicates presence of contention free random access (CFRA) resource information in the command.

[0205] In some example embodiments, at least one of the following is utilized by the second apparatus (220): the field or the bit (404) indicates that the CFRA resource information is available in the command, and the first indication is carried via the existing field that indicates an uplink carrier to initiate a random access procedure using CFRA resources; or the field or the bit (404) indicates that the CFRA resource information is absent in the command, and the first indication is carried via the specific field encoded in a same bit position (402) as the existing field that indicates an uplink carrier to initiate a random access procedure using CFRA resources.

[0206] In some example embodiments, at least one of the following is utilized by the second apparatus (220): the first field includes a field or a bit (404, 504) that indicates presence of contention free random access (CFRA) resource information in the command; or the field or the bit (404, 504) is set as a value indicating that the CFRA resource information is available in the command, and the CFRA resource information is excluded in the command to indicate that the random access is to be triggered.

[0207] In some example embodiments, at least one of the following is utilized by the second apparatus (220): the command is transmitted (320, 720) in a medium access control (MAC) control element (CE), and the MAC CE contains contention free random access (CFRA) resource information; a size of the MAC CE indicates whether the random accessis to be triggered; or the size of the MAC CE is equal to or less than a threshold to indicate that the random access is to be triggered.

[0208] In some example embodiments, at least one of the following is utilized by the second apparatus (220): the command contains a third indication whether transmission configuration indicator (TCI) state information is absent or ignored in the command; or the command is transmitted (320, 720) in a medium access control (MAC) control element (CE), and the third indication is carried via a second field in the MAC CE.

[0209] In some example embodiments, at least one of the following is utilized by the second apparatus (220): the second field is set as a value indicating that the TCI state information is absent or ignored in the command, and the value further indicates that the random access is to be triggered; or the TCI state information includes at least one octet (412, 414, 514, 516) containing at least one TCI state identifier (ID) field (408, 410, 510, 512).

[0210] In some example embodiments, contention free random access (CFRA) resource information is available in the command, and a random access preamble index is set as a predefined value to indicate that at least one of a synchronization signal and physical broadcast channel block index or a physical random access channel mask index is absent in the command.

[0211] In an aspect, a method (600) includes: receiving (320, 610) a configuration indicating at least one candidate cell (222, 224); receiving (340, 620) a command triggering cell switch towards a target cell (224) of the at least one candidate cell (222, 224); determining (350, 630), based on the command, whether random access is to be triggered for the cell switch; and performing (360, 640) the cell switch based on the determining (350, 630).

[0212] In an aspect, a method (700) includes: transmitting (310, 710), to a first apparatus (210), a configuration indicating at least one candidate cell (222, 224); transmitting (320, 720), to the first apparatus (210), a command triggering cell switch towards a target cell (224) of the at least one candidate cell (222, 224), where the command indicates whether random access is to be triggered for the cell switch.

[0213] In an aspect, a computer readable medium includes instructions stored thereon for causing an apparatus at least to perform the steps or operations as described above.

Claims

WHAT IS CLAIMED IS:

1. 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 at least to: receive a configuration indicating at least one candidate cell; receive a command triggering cell switch towards a target cell of the at least one candidate cell; determine, based on the command, whether random access is to be triggered for the cell switch; and perform the cell switch based on the determining.

2. The first apparatus of claim 1, wherein the first apparatus is further caused to: based on determining that the random access is to be triggered, determine a type of the random access to be triggered for the cell switch, based on the command.

3. The first apparatus of claim 1 or 2, wherein at least one of the following is utilized by the first apparatus: the command contains a first indication whether the random access is to be triggered; the command is received in a medium access control (MAC) control element (CE), and the first indication is carried via a first field in the MAC CE; or the first field comprises an existing field or a specific field in the MAC CE.

4. The first apparatus of claim 3, wherein at least one of the following is utilized by the first apparatus: the command contains a second indication whether the existing field or the specific field in the MAC CE carries the first indication; orthe second indication is carried in the MAC CE via a field or a bit (404) that indicates presence of contention free random access (CFRA) resource information in the command.

5. The first apparatus of claim 4, wherein the at least one memory and the at least one processor cause the first apparatus to perform at least one of based on the field or the bit indicating that the CFRA resource information is available in the command, determining that the first indication is carried via the existing field that indicates an uplink carrier to initiate a random access procedure using CFRA resources; or based on the field or the bit indicating that the CFRA resource information is absent in the command, determining that the first indication is carried via the specific field encoded in a same bit position as the existing field that indicates an uplink carrier to initiate a random access procedure using CFRA resources.

6. The first apparatus of claim 3, wherein the first field comprises a field or a bit that indicates presence of contention free random access (CFRA) resource information in the command; and / or wherein the at least one memory and the at least one processor cause the first apparatus to: based on determining that the field or the bit indicates that the CFRA resource information is available and the CFRA resource information is absent in the command, determine that the random access is to be triggered.

7. The first apparatus of claim 1, wherein the command is received in a medium access control (MAC) control element (CE); and wherein the at least one memory and the at least one processor cause the first apparatus to perform at least one of determining that contention free random access (CFRA) resource information isavailable in the MAC CE, determining (350, 630), based on a size of the MAC CE, whether the random access is to be triggered; or based on the size of the MAC CE being equal to or less than a threshold, determining that the random access is to be triggered.

8. The first apparatus of any of claims 1 to 7, wherein the at least one memory and the at least one processor cause the first apparatus to: based on determining that the random access is to be triggered, perform the cell switch using the random access.

9. The first apparatus of claim 8, wherein the at least one memory and the at least one processor further cause the first apparatus to perform at least one of based on determining that contention free random access (CFRA) resource information is absent in the command, performing the cell switch without using CFRA resources; performing the cell switch by initiating a random access procedure using CFRA resources, based on determining that the CFRA resources are configured; or performing the cell switch by initiating a contention based random access (CBRA) procedure.

10. The first apparatus of any of claims 8 to 9, wherein the at least one memory and the at least one processor further cause the first apparatus to: determine that transmission configuration indicator (TCI) state information is absent or ignored in the command.

11. The first apparatus of claim 1, wherein at least one of the following is utilized by the first apparatus: the command contains a third indication whether transmission configurationindicator (TCI) state information is absent or ignored in the command; or the command is received in a medium access control (MAC) control element (CE), and the third indication is carried via a second field in the MAC CE.

12. The first apparatus of claim 11, wherein at least one of the following is utilized by the first apparatus: the second field is set as a value indicating that the TCI state information is absent or ignored in the command, and the value further indicates that the random access is to be triggered; or the TCI state information comprises at least one octet containing at least one TCI state identifier (ID) field.

13. The first apparatus of any of claims 11 to 12, wherein the at least one memory and the at least one processor cause the first apparatus to: determine, based on the command, that the TCI state information is present or not ignored; determine, based on the command, that the random access is to be triggered; and perform the cell switch by applying the TCI state information.

14. The first apparatus of any of claims 1 to 13, wherein the at least one memory and the at least one processor cause the first apparatus to: determine that contention free random access (CFRA) resource information is available in the command; and based on a random access preamble index being set as a predefined value, determine that at least one of a synchronization signal and physical broadcast channel block index or a physical random access channel mask index is absent in the command.

15. 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: transmit, to a first apparatus, a configuration indicating at least one candidate cell; transmit, to the first apparatus, a command triggering cell switch towards a target cell of the at least one candidate cell, wherein the command indicates whether random access is to be triggered for the cell switch.

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