Discarding random access resources

Abstract

Example embodiments of the disclosure relate to apparatuses, methods and a computer readable medium for discarding random access resources In a method, a first apparatus receives a configuration indicating contention free random access resources for at least one cell. The first apparatus receives a command triggering cell switch towards a target cell of the at least one cell. The first apparatus determines whether the CFRA resources are to be discarded or retained. The first apparatus performs the cell switch based on the determining.

Description

DISCARDING RANDOM ACCESS RESOURCESFIELDS

[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 discarding random access resources.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 the target cell according to the cell switch command. The LTM procedure may be used to reduce the mobility latency. If the UE is provided with a Contention-free random access (CFRA) resource in the cell switch command, the UE applies the CFRA resource and performs CFRA using the indicated preamble and synchronization signal block (SSB) until a random access (RA) procedure succeeds or fails.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 contention free random access (CFRA) resources for at least one cell; receive a command triggering cell switch towards a target cell of the at least one cell; determine whether the CFRA resources are to be discarded or retained; 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 storinginstructions that, when executed by the at least one processor, cause the second apparatus at least to: transmit, to a first apparatus, a configuration indicating CFRA resources for at least one cell; transmit, to the first apparatus, a command triggering cell switch towards a target cell of the at least one cell; and transmit, to the first apparatus, an indication whether the CFRA resources are to be discarded or retained.

[0005] In a third aspect of the present disclosure, there is provided a method. The method includes: receiving a configuration indicating CFRA resources for at least one cell; receiving a command triggering cell switch towards a target cell of at least one cell; determining whether the CFRA resources are to be discarded or retained; 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 CFRA resources for at least one cell; transmitting, to the first apparatus, a command triggering cell switch towards a target cell of at least one cell; and transmitting, to the first apparatus, an indication whether the CFRA resources are to be discarded or retained.

[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 CFRA resources for at least one cell; means for receiving a command triggering cell switch towards a target cell of at least one cell; means for determining whether the CFRA resources are to be discarded or retained; 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 CFRA resources for at least one cell; means for transmitting, to the first apparatus, a command triggering cell switch towards a target cell of at least one cell; and means for transmitting, to the first apparatus, an indication whether the CFRA resources are to be discarded or retained.

[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 thereonfor 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 key or 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 communication between a first apparatus and a second apparatus according to some example embodiments of the present disclosure;

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

[0017] FIG. 5 illustrates an example flowchart of discarding random access resources according to some 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 some example 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 andif 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 activateTransmission 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, regardlessof 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 candidate configuration, 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 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 non-DC 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 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] Regarding LTM cell switch command, the network may instruct the UE to perform LTM cell switch procedure by sending the LTM Cell Switch Command 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 (hexa-decimal) is not set as FFF, the MAC entity may process the received Timing Advance Command; the MAC entity may consider the RACH-less LTMcell 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.

[0043] 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 SSB corresponding to the indicated TCI state as the one used for configured uplink grant selection for the initial uplink transmission towards 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.

[0044] 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 candidate target 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 IDfield). 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. Thelength of the field is 4 bits.

[0045] Regarding random access resource selection, in the case that the selected RA TYPE is set to 4-stepRA, if the Random Access procedure was initiated for SpCell beam failure recovery, and if the beamFailureRecoveryTimer is either running or not configured, and if the contention-free Random Access Resources for beam failure recovery request associated with any of the SSBs and / or CSI-RSs have been explicitly provided by RRC, and if at least one of the SSBs with SS-RSRP above rsrp-ThresholdSSB amongst the SSBs in candidateBeamRSList or the CSI-RSs with CSI-RSRP above rsrp- ThresholdCSI-RS amongst the CSI-RSs in candidateBeamRSList is available, the MAC entity may select an SSB with SS-RSRP above rsrp-ThresholdSSB amongst the SSBs in candidateBeamRSList or a CSI-RS with CSI-RSRP above rsrp-ThresholdCSI-RS amongst the CSI-RSs in candidateBeamRSList. If CSI-RS is selected, and there is no ra- Preamblelndex associated with the selected CSI-RS, the MAC entity may set the PREAMBLE INDEX to a ra-Preamblelndex corresponding to the SSB in candidateBeamRSList which is quasi-colocated with the selected CSI-RS as specified in the current communication specification. Otherwise, the MAC entity may set the PREAMBLE INDEX to a ra-Preamblelndex corresponding to the selected SSB or CSI-RS from the set of Random Access Preambles for beam failure recovery request.

[0046] If the ra-Preamblelndex has been explicitly provided by PDCCH, and if the ra- Preamblelndex is not ObOOOOOO, the MAC entity may set the PREAMBLE INDEX to the signalled ra-Preamblelndex and the MAC entity may select the SSB signalled by PDCCH. If the ra-Preamblelndex has been explicitly provided by an LTM Cell Switch Command MAC CE, the MAC entity may set the PREAMBLE INDEX to the indicated ra- Preamblehidex: and the MAC entity may select the SSB signalled by the LTM Cell Switch Command MAC CE. If the contention-free Random Access Resources associated with SSBs have been explicitly provided in rach-ConfigDedicated and at least one SSB with SS-RSRP above rsrp-ThresholdSSB amongst the associated SSBs is available, the MAC entity may select an SSB with SS-RSRP above rsrp-ThresholdSSB amongst the associated SSBs; and the MAC entity may set the PREAMBLE INDEX to a ra-Preamblelndex corresponding to the selected SSB. If the contention-free Random Access Resources associated with CSI-RSs have been explicitly provided in rach-ConfigDedicated and at least one CSI-RS with CSI-RSRP above rsrp-ThresholdCSI-RS amongst the associatedCSI-RSs is available, the MAC entity may select a CSI-RS with CSI-RSRP above rsrp- ThresholdCSI-RS amongst the associated CSI-RSs; and the MAC entity may set the PREAMBLE INDEX to a ra-Preamblelndex corresponding to the selected CSI-RS. If the Random Access procedure was initiated for SI request (as specified in the current communication specification), and if the Random Access Resources for SI request have been explicitly provided by RRC: if at least one of the SSBs with SS-RSRP above rsrp- ThresholdSSB is available, the MAC entity may select an SSB with SS-RSRP above rsrp- Thre sholdS SB and otherwise the MAC entity may select any SSB. The MAC entity may select a Random Access Preamble corresponding to the selected SSB, from the Random Access Preamble(s) determined according to ra-PreambleStartlndex as specified in the current communication specification. The MAC entity may set the PREAMBLE INDEX to selected Random Access Preamble. For the contention-based Random Access preamble selection, if at least one of the SSBs with SS-RSRP above rsrp-ThresholdSSB is available: the MAC entity may select an SSB with SS-RSRP above rsrp-ThresholdSSB otherwise, the MAC entity may select any SSB.

[0047] As discussed above, if the UE is provided with a CFRA resource in the LTM CSC MAC CE, the UE applies the CFRA resource and performs CFRA using the indicated preamble and SSB until the RA procedure succeeds or fails. Further, if no CFRA resource is provided in the LTM CSC MAC CE, the UE checks if a CFRA resource is configured in the LTM candidate configuration via RRC signaling. Furthermore, the UE applies contention-based random access (CBRA) if a CFRA resource cannot be selected (for example, the CFRA resource is not configured or is invalid).

[0048] When the LTM cell switch is triggered, and the network intends to initiate a random access procedure, there are no means for the network to enforce a CBRA-only procedure. On the other hand, since the CFRA resources are preconfigured by the network for the UE, the CFRA resources may be pre-assigned by a target node for a limited time only, which may depend entirely on the implementation of the network. If CFRA resources need to be removed from the UE configuration, RRC reconfiguration is required, which hinders the benefits of the LTM feature such as reducing the mobility latency.

[0049] According to some example embodiments of the present disclosure, there is provided a solution for discarding random access resources. In the solution, a first apparatus (for example, a terminal device) receives, from a second apparatus (for example,a network device), a configuration indicating CFRA resources for at least one cell and a command triggering cell switch towards a target cell of the at least one cell. The first apparatus determines whether the CFRA resources are to be discarded or retained, and performs the cell switch based on the determining.

[0050] In this way, (pre-configured) CFRA resources may be discarded upon the cell switch if needed, for example, if the network determines the CFRA resources are not to be usable anymore or if the network intends to use at least part of the CFRA resources for another UE(s). Thus, the resource efficiency may be improved, and network capacity may be enhanced.

[0051] 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.

[0052] FIG. 2 illustrates an example communication environment 200 in which example embodiments of the present disclosure may be implemented.

[0053] 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.

[0054] 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.

[0055] 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, thesecond 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).

[0056] Communications in the communication environment 200 may be implemented according to any proper communication protocol(s), comprising, 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 as Institute 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, comprising but not limited to: Code Division Multiple Access (CDMA), Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), Frequency Division Duplex (FDD), Time Division Duplex (TDD), Multiple-Input Multiple-Output (MIMO), Orthogonal Frequency Division Multiple (OFDM), Discrete Fourier Transform spread OFDM (DFT-s-OFDM) and / or any other technologies currently known or to be developed in the future.

[0057] 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.

[0058] 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 also 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.

[0059] Some example implementations of the present disclosure will be described in detail below with reference to FIGS. 3 to 5.

[0060] FIG. 3 illustrates a signaling flow 300 for communication between the first apparatus 210 and the second apparatus 220 according to some example embodiments ofthe present disclosure.

[0061] As shown in FIG. 3, the second apparatus 220 transmits (310), to the first apparatus 210, a configuration indicating CFRA resources for at least one cell (for example, the cells 222 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.

[0062] 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) of at least one cell. Correspondingly, the first apparatus 210 receives (340) this command from the second apparatus 220. The command may be transmitted in a MAC CE (for example, an LTM cell switch command MAC CE).

[0063] The first apparatus 210 determines (350) whether the CFRA resources are to be discarded or retained. Based on the determining (350), the first apparatus 210 performs (360) the cell switch (for example, LTM cell switch). For example, if the first apparatus 210 determines (350) that the CFRA resources are to be discarded, the first apparatus 210 may discard any explicitly signaled CFRA resources before initiating a Random Access procedure for the cell switch. If the first apparatus 210 determines (350) that the CFRA resources are to be retained, the CFRA resources may be retained. In this case, the first apparatus 210 may or may not use CFRA resources for the cell switch. For example, if CBRA is to be performed by the first apparatus 210 in the cell switch, the CFRA resources may not be used. In another example, if the first apparatus 210 determines that the CFRA resources are retained for the cell switch, the first apparatus 210 may not use the CFRA resources for the cell switch, consequently, using CBRA resources for the cell switch.

[0064] In this way, the second apparatus 220 may enforce the first apparatus 210 to discard all (or a subset) of the CFRA resources upon the LTM cell switch, thereby enforcing the CBRA for LTM cell switch.

[0065] In some example embodiments, the determining (350) may be implemented by the first apparatus 210 based on an indication (which may be either an explicit indication or an implicit indication) from the second apparatus 220. For example, the second apparatus transmits, to the first apparatus 210, an indication whether the CFRA resources are to be discarded or retained. Accordingly, based on the indication, the first apparatus210 may determine (350) whether the CFRA resources are to be discarded or retained.

[0066] In some example embodiments, the indication may comprise an explicit indication (referred to as a first indication) whether the CFRA resources are to be discarded or retained. In some example embodiments, in the case that the command is transmitted (330) in a MAC CE, the first indication may be carried in the MAC CE. Some example embodiments in this regard will be described with reference to FIG. 4 which illustrates an example LTM cell switch command MAC CE according to some example embodiments of the present disclosure.

[0067] In some example embodiments, the first indication may be carried via at least one field (for example, R fields 402 and 404 or S / U or DR field 416) and / or at least one bit (for example, one bit for the R fields 402 and 404) in the MAC CE. For example, a reserved bit (e.g., a bit for R fields 402 and 404) in the MAC CE may be reused or allocated to carry the first indication.

[0068] In some example embodiments, a random access preamble index (for example, a random access preamble index field 418) in the MAC CE may be used to indicate whether the CFRA resources are to be discarded or retained. In some example embodiments, the random access preamble index may be set as a predefined value to indicate that the CFRA resources are to be discarded. In an example, a value “000000” of the random access preamble index field 418 may be used as the indication. For instance, if the value of the random access preamble index field 418 is set to “000000”, the first apparatus 210 may determine (350) that the CFRA resources are to be discarded. It should be noted that if the random access preamble index field 418 is of a different size than 6 bits, the predefined value may be set to any number of zeros, e.g., 7 zeros (“0000000”) to indicate what the random access preamble index field 418 size is.

[0069] For example, the random access preamble index may be set to “000000”, and C bit may be set (for example, as “ 1”) to indicate that CFRA resource fields (for example, a random access preamble index field 418, an SS / PBCH index filed 420, and a PRACH mask index 422) are existing in the MAC CE. In this case, the first apparatus may determine (350) that the CFRA resources are to be discarded. As another example, if the random access preamble index field is set to ObOOOOOO, the first apparatus 210 may discard any explicitly signaled CFRA resources before initiating the Random Access procedure.It should be noted that the value “000000” may be illustrated and may have an equal meaning with ObOOOOOO.

[0070] In some example embodiments, if the random access preamble index (for example, the random access preamble index field 418) in the MAC CE is set as a predefined value to indicate that the CFRA resources are to be discarded to indicate whether the CFRA resources are to be discarded or retained, at least one of an indication of a synchronization signal (SS) and physical broadcast channel (PBCH) block (for example, an SS / PBCH index filed 420) or an indication of a physical random access channel (PRACH) mask index (for example, a PRACH mask index 422) may be excluded in the MAC CE. In an example, if the random access preamble index field 418 is set to “000000”, the SSB / PBCH Index field 420 or the PRACH mask index 422 are not encoded for the LTM CSC MAC CE to further reduce the overhead of the MAC CE.

[0071] In some example embodiments, a new field (for example, R fields 402 and 404 or the S / U or DR field 416) in the MAC CE may indicate whether the CFRA resources are to be discarded or retained. For example, a field in the MAC CE with 1 bit using one for the reserved (R) bits (for example, R fields 402 and 404) in the MAC CE may be used to indicate whether the CFRA resources are to be discarded or retained.

[0072] In some example embodiments, the discarding of the CFRA resources may be implemented for not only the target cell but also one or more other candidate cells. For example, the second apparatus 220 may transmit, to the first apparatus 210, an indication (referred to as a second indication) whether the CFRA resources are to be discarded for the target cell (for example, the cell 224) or the at least one cell (for example, the cells 222 and 224). Correspondingly, the first apparatus 210 may receive the second indication and then determine whether the CFRA resources are to be discarded for the target cell or the at least one cell. In some examples, the first indication may serve as the second indication.

[0073] In an example, the second indication may be carried in the LTM CSC MAC CE which is used to indicate to the first apparatus 110 to discard the CFRA resources configured for the LTM target cell as indicated by a target configuration identity (also represented as Target Config ID such as a target configuration ID (target config ID) field 406) of a target cell in the LTM CSC MAC CE. Alternatively, or in addition, the secondindication may be used to indicate to the first apparatus 110 to discard the CFRA resources configured for any LTM candidate cell. For example, if the RA preamble index field 418 is set to “000000”, the second indication may be encoded in the same bit position as the S / U field 416 indicating whether CFRA resources configured for any LTM candidate cell may be discarded (for example, all the LTM candidate cells configured by upper layers) or only for the LTM target cell as indicated by the Target Config ID 406 may be discarded.

[0074] In some example embodiments, the second apparatus 220 may transmit, to the first apparatus 210, an indication (referred to as a third indication) whether a random access procedure is to be initiated for the cell switch. Correspondingly, the first apparatus 210 may receive the third indication. In some example embodiments, in the case that the command triggering cell switch towards the target cell is received in the MAC CE, the third indication may be contained in the MAC CE. For example, if a C field 414 indicates that no random access information fields (for example, the random access preamble index field 418) are presented in the LTM CSC MAC CE, the third indication may be encoded in the same bit position as the S / U field 416 indicating whether the random access procedure may be initiated for the LTM cell switch.

[0075] In another example, the random access preamble index field 418 may serve as the third indication. For example, if the random access preamble index field 418 is set to ObOOOOOO, the first apparatus 210 may initiate the random access procedure.

[0076] In some example embodiments, the third indication may further indicate whether the CFRA resources are to be discarded or retained. That is, the third indication may further indicate whether the CFRA resources are to be discarded or retained. In this case, the third indication may serve as the first indication. For instance, if the random access procedure is initiated by the third indication, the first apparatus 210 may discard the CFRA resources.

[0077] In some example embodiments, in the case that the random access preamble index (for example, the random access preamble index field 418) is set as a predefined value, and an indication of presence of a CFRA resource field (for example, the C field 414) may be encoded in the MAC CE to trigger the random access procedure with the CFRA resources retained for the random access procedure. In one example, the random access preamble index (for example, the random access preamble index field 418) may beset to “000000”, and the C field 414 may be set to indicate the availability of the CFRA resource fields, which may be used to trigger the random access procedure with RRC configured CFRA resources retained for the random access procedure.

[0078] In some example embodiments, the second apparatus 220 may transmit an implicit indication to indicate whether the CFRA resources are to be discarded or retained. Such an indication may include a configuration of CFRA beam failure recovery (BFR) resources for the target cell 224 to indicate that the CFRA resources are to be retained. After the first apparatus 210 receives this configuration, the first apparatus 210 may determine (350) that the CFRA resources are to be retained. For instance, if CFRA BFR resources are configured for the LTM target cell as indicated by the Target Config ID, the CFRA BFR resources are not to be released by the indication.

[0079] In some example embodiments, a timer may be applied for the determining (350). In response to a timer for discarding the CFRA resources being inactive, the first apparatus 210 may determine (350) that the CFRA resources are to be discarded. For example, a timer (also represented as discardTimerCFRA) may be configured for the RRC configured CFRA resources for the first apparatus 210 to determine (350) if the CFRA resources may be used for the random access. In an example, upon expiry of the timer or if the timer is not running upon receiving the LTM CSC MAC CE, the first apparatus 210 may discard the CFRA resources configured for the at least one cell.

[0080] FIG. 5 shows an example process 500 of discarding the random access resources at the first apparatus according to some example embodiments of the present disclosure. In this example, the cell switch is implemented as LTM cell switch.

[0081] As shown in FIG. 5, At block 510, the first apparatus 210 receives one or more LTM configurations for at least one cell including CFRA resources for at least one of the at least one cell.

[0082] At block 520, the first apparatus 210 receives a command triggering an LTM cell switch event towards a target cell of the at least one cell. The command for triggering the LTM cell switch event may be received in an MAC CE.

[0083] At block 530, the first apparatus 210 determines if contention free resources (for example, CFRA resources) are to be discarded. For example, the first apparatus 210 may receive an indication (either explicit or implicit), and determine whether to discard thecontention free resources based on the indication. For example, the first apparatus 210 may determine whether to discard the contention free resources based on a random access preamble index in the MAC CE. For instance, the first apparatus 210 may determine whether to discard the contention free resources based on a new filed in the MAC CE. As another example, the first apparatus 210 may determine whether to discard the contention free resources based on a condition of a timer, for example, the timer for discarding the resources becoming inactive.

[0084] At block 540, the first apparatus 210 performs the LTM cell switch based on the determining. For example, upon or after the determination of whether the CFRA resources are to be discarded, the first apparatus 210 discard or retain the CFRA resources for the LTM cell switch towards the target cell.

[0085] Some example implementations of the present disclosure associated with the LTM cell switch command and the LTM cell switch command MAC CE may be described in detail below.

[0086] An example implementation of the LTM Cell Switch Command will be discussed below by taking the third generation partnership project (3GPP) TS 38.321 V18.0.0 as an example.

[0087] An example implementation of the LTM Cell Switch Command MAC CE will be discussed below by taking 3GPP TS 38.321 v!8.0.0 as an example.Example Methods, Device and Medium

[0088] FIG. 6 shows a flowchart of an example method 600 implemented at the first apparatus 210 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.

[0089] At block 610, the first apparatus 210 receives a configuration indicating contention free random access (CFRA) resources for at least one cell.

[0090] At block 620, the first apparatus 210 receives a command triggering cell switch towards a target cell of the at least one cell.

[0091] At block 630, the first apparatus 210 determines whether the CFRA resources are to be discarded or retained.

[0092] At block 640, the first apparatus 210 performs the cell switch based on thedetermining.

[0093] In some example embodiments, the first apparatus 210 may receive a first indication whether the CFRA resources are to be discarded or retained. The first apparatus 210 may determine, based on the first indication, whether the CFRA resources are to be discarded or retained.

[0094] In some example embodiments, the command may be received in a medium access control (MAC) control element (CE). The first indication may be carried in the MAC CE.

[0095] In some example embodiments, the first indication may be carried via at least one field and / or at least one bit in the MAC CE.

[0096] In some example embodiments, a random access preamble index in the MAC CE may be set as a predefined value to indicate that the CFRA resources are to be discarded.

[0097] In some example embodiments, at least one of an indication of a synchronization signal and physical broadcast channel block or an indication of a physical random access channel mask index may be excluded in the MAC CE.

[0098] In some example embodiments, a new field in the MAC CE may indicate whether the CFRA resources are to be discarded or retained.

[0099] In some example embodiments, the first apparatus 210 may receive a second indication whether the CFRA resources are to be discarded for the target cell or the at least one cell.

[0100] In some example embodiments, the first apparatus 210 may receive a third indication whether a random access procedure is to be initiated for the cell switch.

[0101] In some example embodiments, the third indication may further indicate whether the CFRA resources are to be discarded or retained.

[0102] In some example embodiments, the command may be received in a medium access control (MAC) control element (CE). The third indication may be carried in the MAC CE.

[0103] In some example embodiments, the random access preamble index may be set as a predefined value. An indication of presence of a CFRA resource field may be encodedin the MAC CE to trigger the random access procedure with the CFRA resources retained for the random access procedure.

[0104] In some example embodiments, the first apparatus 210 may receive a configuration of CFRA beam failure recovery (BFR) resources for the target cell. Based on receiving the configuration, the first apparatus 210 may determine that the CFRA resources are to be retained.

[0105] In some example embodiments, in response to a timer for discarding the CFRA resources being inactive, the first apparatus 210 may determine that the CFRA resources are to be discarded.

[0106] FIG. 7 shows a flowchart of an example method 700 implemented at the second apparatus 220 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.

[0107] At block 710, the second apparatus 220 transmits, to the first apparatus 210, a configuration indicating contention free random access (CFRA) resources for at least one cell.

[0108] 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 cell.

[0109] At block 730, the second apparatus 220 transmits, to the first apparatus 210, an indication whether the CFRA resources are to be discarded or retained.

[0110] In some example embodiments, the command may be transmitted in a medium access control (MAC) control element (CE). The indication may include a first indication carried in the MAC CE.

[0111] In some example embodiments, the first indication may be carried via at least one field and / or at least one bit in the MAC CE.

[0112] In some example embodiments, a random access preamble index in the MAC CE may be set as a predefined value to indicate that the CFRA resources are to be discarded.

[0113] In some example embodiments, at least one of an indication of a synchronization signal and physical broadcast channel block or an indication of a physical random accesschannel mask index may be excluded in the MAC CE.

[0114] In some example embodiments, a new field in the MAC CE may indicate whether the CFRA resources are to be discarded or retained.

[0115] In some example embodiments, the second apparatus 220 may transmit, to the first apparatus 210, a second indication whether the CFRA resources are to be discarded for the target cell or the at least one cell.

[0116] In some example embodiments, the second apparatus 220 may transmit, to the first apparatus 210, a third indication whether a random access procedure is to be initiated for the cell switch.

[0117] In some example embodiments, the third indication may further indicate whether the CFRA resources are to be discarded or retained.

[0118] In some example embodiments, the command may be received in a medium access control (MAC) control element (CE). The third indication may be carried in the MAC CE.

[0119] In some example embodiments, the random access preamble index may be set as a predefined value. An indication of presence of a CFRA resource field may be encoded in the MAC CE to trigger the random access procedure with the CFRA resources retained for the random access procedure.

[0120] In some example embodiments, the indication may include a configuration of CFRA beam failure recovery (BFR) resources for the target cell to indicate that the CFRA resources are to be retained.

[0121] 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.

[0122] 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 communicationinterfaces 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.

[0123] 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.

[0124] 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.

[0125] 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.

[0126] 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.

[0127] 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 device800 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 a limitation of the medium itself (i.e., tangible, not a signal) as opposed to a limitation on data storage persistency (e.g., RAM vs. ROM).

[0128] 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.

[0129] 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.

[0130] 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.

[0131] 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 in the 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.

[0132] 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.

[0133] 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.

[0134] 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 ofa single embodiment may also be implemented in a plurality of embodiments separately or in any suitable sub-combination.

[0135] 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 features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.

[0136] 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.

[0137] In an aspect, a 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 (210) at least to: receive (320, 510, 610) a configuration indicating contention free random access (CFRA) resources for at least one cell (222, 224); receive (340, 520, 620) a command triggering cell switch towards a target cell (224) of the at least one cell (222, 224); determine (350, 530, 630) whether the CFRA resources are to be discarded or retained; and perform (360, 540, 640) the cell switch based on the determining (350, 530, 630).

[0138] In some example embodiments, the at least one memory and the at least one processor cause the first apparatus (210) to: receive a first indication whether the CFRA resources are to be discarded or retained; and determine (350, 530, 630), based on the first indication, whether the CFRA resources are to be discarded or retained.

[0139] In some example embodiments, the command is received (340, 520, 620) in a medium access control (MAC) control element (CE), and the first indication is carried in the MAC CE.

[0140] In some example embodiments, the first indication is carried via at least one field and / or at least one bit in the MAC CE.

[0141] In some example embodiments, a random access preamble index in the MAC CE is set as a predefined value to indicate that the CFRA resources are to be discarded.

[0142] In some example embodiments, at least one of an indication of a synchronization signal and physical broadcast channel block or an indication of a physical random access channel mask index is excluded in the MAC CE.

[0143] In some example embodiments, a new field in the MAC CE indicates whether the CFRA resources are to be discarded or retained.

[0144] In some example embodiments, the at least one memory and the at least one processor further cause the first apparatus (210) to: receive a second indication whether the CFRA resources are to be discarded for the target cell (224) or the at least one cell (222, 224).

[0145] In some example embodiments, the at least one memory and the at least one processor further cause the first apparatus (210) to: receive a third indication whether a random access procedure is to be initiated for the cell switch.

[0146] In some example embodiments, the third indication further indicates whether the CFRA resources are to be discarded or retained.

[0147] In some example embodiments, the command is received in a medium access control (MAC) control element (CE), and the third indication is carried in the MAC CE.

[0148] In some example embodiments, the random access preamble index is set as a predefined value, and an indication of presence of a CFRA resource field is encoded in the MAC CE to trigger the random access procedure with the CFRA resources retained for the random access procedure.

[0149] In some example embodiments, the at least one memory and the at least one processor cause the first apparatus (210) to: receive a configuration of CFRA beam failure recovery (BFR) resources for the target cell (224); and based on receiving the configuration, determine (350, 530, 630) that the CFRA resources are to be retained.

[0150] In some example embodiments, the at least one memory and the at least one processor cause the first apparatus (210) to: in response to a timer for discarding the CFRA resources being inactive, determine (350, 530, 630) that the CFRA resources are to be discarded.

[0151] In an aspect, a second apparatus includes at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause thesecond apparatus (220) at least to: transmit (310, 710), to a first apparatus (210), a configuration indicating contention free random access (CFRA) resources for at least one cell (222, 224); transmit (330, 720), to the first apparatus (210), a command triggering cell switch towards a target cell (224) of the at least one cell (222, 224); and transmit (730), to the first apparatus (210), an indication whether the CFRA resources are to be discarded or retained.

[0152] In some example embodiments, the command is transmitted (230) in a medium access control (MAC) control element (CE), and the indication comprises a first indication carried in the MAC CE.

[0153] In some example embodiments, the first indication is carried via at least one field and / or at least one bit in the MAC CE.

[0154] In some example embodiments, a random access preamble index in the MAC CE is set as a predefined value to indicate that the CFRA resources are to be discarded.

[0155] In some example embodiments, at least one of an indication of a synchronization signal and physical broadcast channel block or an indication of a physical random access channel mask index is excluded in the MAC CE.

[0156] In some example embodiments, a new field in the MAC CE indicates whether the CFRA resources are to be discarded or retained.

[0157] In some example embodiments, the at least one memory and the at least one processor further cause the second apparatus (220) to: transmit, to the first apparatus (210), a second indication whether the CFRA resources are to be discarded for the target cell (224) or the at least one cell (222, 224).

[0158] In some example embodiments, the at least one memory and the at least one processor further cause the second apparatus (220) to: transmit, to the first apparatus (210), a third indication whether a random access procedure is to be initiated for the cell switch.

[0159] In some example embodiments, the third indication further indicates whether the CFRA resources are to be discarded or retained.

[0160] In some example embodiments, the command is received in a medium access control (MAC) control element (CE), and the third indication is carried in the MAC CE.

[0161] In some example embodiments, the random access preamble index is set as a predefined value, and an indication of presence of a CFRA resource field is encoded in the MAC CE to trigger the random access procedure with the CFRA resources retained for the random access procedure.

[0162] In some example embodiments, the indication comprises a configuration of CFRA beam failure recovery (BFR) resources for the target cell (224) to indicate that the CFRA resources are to be retained.

[0163] In an aspect, a first apparatus includes means for receiving (320, 510, 610) a configuration indicating contention free random access (CFRA) resources for at least one cell (222, 224); means for receiving (340, 520, 620) a command triggering cell switch towards a target cell (224) of the at least one cell (222, 224); means for determining (350, 530, 630) whether the CFRA resources are to be discarded or retained; and means for performing (360, 540, 640) the cell switch based on the determining (350, 530, 630).

[0164] In some example embodiments, the first apparatus further includes: means for receiving a first indication whether the CFRA resources are to be discarded or retained. The means for determining (350, 530, 630) includes means for determining (350, 530, 630), based on the first indication, whether the CFRA resources are to be discarded or retained.

[0165] In some example embodiments, the command is received (340, 520, 620) in a medium access control (MAC) control element (CE), and the first indication is carried in the MAC CE.

[0166] In some example embodiments, the first indication is carried via at least one field and / or at least one bit in the MAC CE.

[0167] In some example embodiments, a random access preamble index in the MAC CE is set as a predefined value to indicate that the CFRA resources are to be discarded.

[0168] In some example embodiments, at least one of an indication of a synchronization signal and physical broadcast channel block or an indication of a physical random access channel mask index is excluded in the MAC CE.

[0169] In some example embodiments, a new field in the MAC CE indicates whether the CFRA resources are to be discarded or retained.

[0170] In some example embodiments, the first apparatus further comprises: means for receiving a second indication whether the CFRA resources are to be discarded for the target cell (224) or the at least one cell (222, 224).

[0171] In some example embodiments, the first apparatus further comprises: means for receiving a third indication whether a random access procedure is to be initiated for the cell switch.

[0172] In some example embodiments, the third indication further indicates whether the CFRA resources are to be discarded or retained.

[0173] In some example embodiments, the command is received in a medium access control (MAC) control element (CE), and the third indication is carried in the MAC CE.

[0174] In some example embodiments, the random access preamble index is set as a predefined value, and an indication of presence of a CFRA resource field is encoded in the MAC CE to trigger the random access procedure with the CFRA resources retained for the random access procedure.

[0175] In some example embodiments, the first apparatus further includes: means for receiving a configuration of CFRA beam failure recovery (BFR) resources for the target cell (224). The means for determining (350, 530, 630) includes means for based on receiving the configuration, determining (350, 530, 630) that the CFRA resources are to be retained.

[0176] In some example embodiments, the means for determining (350, 530, 630) includes means for in response to a timer for discarding the CFRA resources being inactive, determining (350, 530, 630) that the CFRA resources are to be discarded.

[0177] In an aspect, a second apparatus includes means for transmitting (310, 710), to a first apparatus (210), a configuration indicating contention free random access (CFRA) resources for at least one cell (222, 224); means for transmitting (330, 720), to the first apparatus (210), a command triggering cell switch towards a target cell (224) of the at least one cell (222, 224); and means for transmitting (730), to the first apparatus (210), an indication whether the CFRA resources are to be discarded or retained.

[0178] In some example embodiments, the command is transmitted (230) in a medium access control (MAC) control element (CE), and the indication comprises a first indicationcarried in the MAC CE.

[0179] In some example embodiments, the first indication is carried via at least one field and / or at least one bit in the MAC CE.

[0180] In some example embodiments, a random access preamble index in the MAC CE is set as a predefined value to indicate that the CFRA resources are to be discarded.

[0181] In some example embodiments, at least one of an indication of a synchronization signal and physical broadcast channel block or an indication of a physical random access channel mask index is excluded in the MAC CE.

[0182] In some example embodiments, a new field in the MAC CE indicates whether the CFRA resources are to be discarded or retained.

[0183] In some example embodiments, the second apparatus further comprises: means for transmitting, to the first apparatus (210), a second indication whether the CFRA resources are to be discarded for the target cell (224) or the at least one cell (222, 224).

[0184] In some example embodiments, the second apparatus further comprises: means for transmitting, to the first apparatus (210), a third indication whether a random access procedure is to be initiated for the cell switch.

[0185] In some example embodiments, the third indication further indicates whether the CFRA resources are to be discarded or retained.

[0186] In some example embodiments, the command is received in a medium access control (MAC) control element (CE), and the third indication is carried in the MAC CE.

[0187] In some example embodiments, the random access preamble index is set as a predefined value, and an indication of presence of a CFRA resource field is encoded in the MAC CE to trigger the random access procedure with the CFRA resources retained for the random access procedure.

[0188] In some example embodiments, the indication comprises a configuration of CFRA beam failure recovery (BFR) resources for the target cell (224) to indicate that the CFRA resources are to be retained.

[0189] In an aspect, a method includes receiving (320, 510, 610) a configuration indicating contention free random access (CFRA) resources for at least one cell (222, 224);receiving (340, 520, 620) a command triggering cell switch towards a target cell (224) of the at least one cell (222, 224); determining (350, 530, 630) whether the CFRA resources are to be discarded or retained; and performing (360, 540, 640) the cell switch based on the determining (350, 530, 630).

[0190] In an aspect, a method includes transmitting (310, 710), to a first apparatus (210), a configuration indicating contention free random access (CFRA) resources for at least one cell (222, 224); transmitting (330, 720), to the first apparatus (210), a command triggering cell switch towards a target cell (224) of the at least one cell (222, 224); and transmitting (730), to the first apparatus (210), an indication whether the CFRA resources are to be discarded or retained.

[0191] 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 contention free random access (CFRA) resources for at least one cell; receive a command triggering cell switch towards a target cell of the at least one cell; determine whether the CFRA resources are to be discarded or retained; and perform the cell switch based on the determining.

2. The first apparatus of claim 1, wherein the at least one memory and the at least one processor cause the first apparatus to: receive a first indication whether the CFRA resources are to be discarded or retained; and determine, based on the first indication, whether the CFRA resources are to be discarded or retained.

3. The first apparatus of claim 2, wherein the command is received in a medium access control (MAC) control element (CE), and the first indication is carried in the MAC CE.

4. The first apparatus of claim 3, wherein the first indication is carried via at least one field and / or at least one bit in the MAC CE.

5. The first apparatus of claim 3 or 4, wherein a random access preamble index in the MAC CE is set as a predefined value toindicate that the CFRA resources are to be discarded.

6. The first apparatus of claim 5, wherein at least one of an indication of a synchronization signal and physical broadcast channel block or an indication of a physical random access channel mask index is excluded in the MAC CE.

7. The first apparatus of claim 3 or 4, wherein a new field in the MAC CE indicates whether the CFRA resources are to be discarded or retained.

8. The first apparatus of any of claims 1 to 7, wherein the at least one memory and the at least one processor further cause the first apparatus to: receive a second indication whether the CFRA resources are to be discarded for the target cell or the at least one cell.

9. The first apparatus of claim 2, wherein the at least one memory and the at least one processor further cause the first apparatus to: receive a third indication whether a random access procedure is to be initiated for the cell switch.

10. The first apparatus of claim 9, wherein the third indication further indicates whether the CFRA resources are to be discarded or retained.

11. The first apparatus of claim 9 or 10, wherein the command is received in a medium access control (MAC) control element (CE), and the third indication is carried in the MAC CE.

12. The first apparatus of claim 11, wherein the random access preamble index is set as a predefined value, and an indication ofpresence of a CFRA resource field is encoded in the MAC CE to trigger the random access procedure with the CFRA resources retained for the random access procedure.

13. The first apparatus of claim 1, wherein the at least one memory and the at least one processor cause the first apparatus to: receive a configuration of CFRA beam failure recovery (BFR) resources for the target cell; and based on receiving the configuration, determine that the CFRA resources are to be retained.

14. The first apparatus of claim 1, wherein the at least one memory and the at least one processor cause the first apparatus to: in response to a timer for discarding the CFRA resources being inactive, determine that the CFRA resources are to be discarded.

15. A second apparatus comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the second apparatus at least to: transmit, to a first apparatus, a configuration indicating contention free random access (CFRA) resources for at least one cell; transmit, to the first apparatus, a command triggering cell switch towards a target cell of the at least one cell; and transmit, to the first apparatus, an indication whether the CFRA resources are to be discarded or retained.

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