Reusing uplink resources without obligatory reconfiguration when a time alignment timer expires, and related devices, methods and computer programs

Abstract

Devices, methods and computer programs for reusing uplink resources without obligatory reconfiguration when a time alignment timer expires are disclosed. At least some example embodiments may allow explicitly signalling the purpose of a random access procedure to a network node (210) via using a disclosed timing advance radio network temporary identifier.

Description

[0001] REUSING UPLINK RESOURCES WITHOUT OBLIGATORY RECONFIGURATION WHEN A TIME ALIGNMENT TIMER EXPIRES , AND RELATED DEVICES , METHODS AND COMPUTER PROGRAMS

[0002] TECHNICAL FIELD

[0003] The disclosure relates generally to communications and, more particularly but not exclusively, to reusing uplink resources without obligatory reconfiguration when a time alignment timer expires , as well as related devices , methods and computer programs .

[0004] BACKGROUND

[0005] When a user device loses uplink (UL) synchroni zation due to a time alignment timer expiring at the user device side , this eventually leads to a medium access control (MAC ) -initiated random access (RA) procedure as follows :

[0006] - the user device releases physical UL control channel ( PUCCH) / semi-persistent scheduling ( SRS ) resources ( including a scheduling request indication ( SRI ) ) , releases active grants and flushes UL hybrid automatic retransmission query (HARQ) buf fers ;

[0007] - radio resource control (RRC ) of the user device RRC is informed; and

[0008] - the MAC-initiated RA procedure is started when the SRI is triggered .

[0009] However, at least in some situations there may be a need to speed up this procedure and to shorten the interruption of UL traf fic .

[0010] BRIEF SUMMARY

[0011] The scope of protection sought for various example embodiments of the invention is set out by the independent claims . The example embodiments and features , i f any, described in this speci fication that do not fall under the scope o f the independent claims are to be interpreted as examples useful for understanding various example embodiments of the invention .

[0012] An example embodiment of a user device comprises at least one proces sor , and at least one memory storing instructions that , when executed by the at least one processor, cause the user device at least to establish a connection towards a source network node of a radio access network via a source cell supported by the source network node . The instructions that , when executed by the at least one proces sor, further cause the user device at least to receive , from the radio access network, a timing advance , TA, parameter, including a TA - radio network temporary identifier, RNTI , associated with the source cell . The instructions that , when executed by the at least one processor, further cause the user device at least to use the TA parameter in case of a related TA procedure being triggered .

[0013] In an example embodiment , alternatively or in addition to the above-described example embodiments , the user device is further caused to : receive , from the radio access network, a Medium Access Control , MAC, configuration including the TA-RNTI .

[0014] In an example embodiment , alternatively or in addition to the above-described example embodiments , the user device is further caused to : monitor a time alignment timer, TAT , and in case of expiry of the TAT trigger the related TA procedure .

[0015] In an example embodiment , alternatively or in addition to the above-described example embodiments , the related TA procedure is a random access procedure .

[0016] In an example embodiment , alternatively or in addition to the above-described example embodiments , the user device is further caused to : in case of a triggered related TA procedure , transmit a random access request message towards the source cell , including using Contention Based Random Access , CBRA, receive , from the source cell , a random access response message , and subsequently transmit a message including the TA-RNTI associated with the source cell towards the source cell .

[0017] In an example embodiment , alternatively or in addition to the above-described example embodiments , the TA-RNTI indicates a cause of the related TA Procedure , including indicating at least one of : expiry of related time alignment timer, TAT , detection of out of sync, assigned uplink resource for data transmission currently not in use , assigned uplink resource for data transmission not released, data transmission on assigned uplink resources to be continued once TA i s re-acquired, data waiting in buf fer to be transmitted .

[0018] In an example embodiment , alternatively or in addition to the above-described example embodiments , the user device is further caused to : receive , from the radio access network, a configuration indicating at least one candidate cell the user device may connect to ; and receive , from the radio access network, a timing advance , TA parameter, including a TA - radio network temporary identi fier, RNTI , associated with a configured candidate cell , and the TA-RNT I associated with the source cell and the TA-RNTI associated with the configured candidate cell being the same or di f ferent .

[0019] In an example embodiment , alternatively or in addition to the above-described example embodiments , the source network node supports at least one of distributed unit , DU, functionality or a layer 2 protocol of the radio access network and / or at least one of central unit , CU, functionality or a layer 3 protocol of the radio access network .

[0020] In an example embodiment , alternatively or in addition to the above-described example embodiments , the configuration is related to Layer 1 / Layer 2 triggered mobility, LTM .

[0021] In an example embodiment , alternatively or in addition to the above-described example embodiments , the user device is further caused to : receive , from the radio access network, an RRCReconf iguration message including the TA-RNTI associated with the configured candidate cell and / or the source cell , and reconfigure the user device with the LTM .

[0022] In an example embodiment , alternatively or in addition to the above-described example embodiments , the user device is further caused to : receive , from the source network node , a message including a TA acquisition trigger to trigger the related TA procedure for the source cell with associated TA-RNTI .

[0023] In an example embodiment , alternatively or in addition to the above-described example embodiments , the user device is further caused to : transmit a random access request message towards the source cell , receive , from the source cell , a random access response message , and subsequently transmit a message including the TA- RNTI associated with the source cell towards the source cell .

[0024] In an example embodiment , alternatively or in addition to the above-described example embodiments , the user device is further caused to : transmit a random access request message towards the triggered candidate cell , receive , from the candidate cell , a random access response message , and subsequently transmit a message including the TA-RNTI associated with the triggered cell towards the triggered candidate cell .

[0025] In an example embodiment , alternatively or in addition to the above-described example embodiments , the user device is further caused to : after receiving, from the triggered candidate cell , the random access response message , subsequently transmit a message including the TA-RNTI associated with the triggered cell towards the source cell .

[0026] In an example embodiment , alternatively or in addition to the above-described example embodiments , the user device is further caused to : after receiving, from the triggered candidate cell , the random access response message , subsequently refraining from at least one of : starting a related contention resolution procedure , starting a related contention resolution timer, or considering the TA acquisition invalid when a related contention resolution timer expires .

[0027] In an example embodiment , alternatively or in addition to the above-described example embodiments , the related TA procedure relates to at least one of : a TA acquisition procedure , an early TA acquisition procedure , a TA acquis ition with a random acces s procedure , or a TA re-acquisition procedure .

[0028] In an example embodiment , alternatively or in addition to the above-described example embodiments , the at least one candidate cell for the user device to connect to include at least one of : a target cel l for the user device to switch to , or a target cell for the user device to add as a second radio link connection .

[0029] In an example embodiment , alternatively or in addition to the above-described example embodiments , the TA parameter is a user device specific parameter assigned by the source cell .

[0030] In an example embodiment , alternatively or in addition to the above-described example embodiments , together with the TA parameter an associated timer is as signed indicating a time period for the TA parameter to be considered valid by the user device .

[0031] In an example embodiment , alternatively or in addition to the above-described example embodiments , the TA parameter associated with the configured candidate cell is a user device speci fic parameter assigned by the associated configured candidate cell or the source cell .

[0032] In an example embodiment , alternatively or in addition to the above-described example embodiments , together with the TA parameter an associated timer is as signed indicating a time period for the TA parameter associated with the configured candidate cell to be considered valid by the user device .

[0033] An example embodiment of a source network node comprises at least one proces sor, and at least one memory storing instructions that , when executed by the at least one processor, cause the source network node at least to establish a connection towards a user device via a source cell of a radio access network supported by the source network node . The instructions , when executed by the at least one processor, further cause the source network node at least to transmit , to the user device via the radio acces s network, a timing advance , TA, parameter, including a TA - radio network temporary identi fier, RNTI , associated with the source cell .

[0034] In an example embodiment , alternatively or in addition to the above-described example embodiments , the source network node i s further caused to : transmit , to the user device via the radio access network, a Medium Access Control , MAC, configuration including the TA- RNTI .

[0035] In an example embodiment , alternatively or in addition to the above-described example embodiments , the related TA procedure is a random access procedure .

[0036] In an example embodiment , alternatively or in addition to the above-described example embodiments , the source network node is further caused to : in case o f a triggered related TA procedure, receive a random access request message from the user device via the source cell , including using Contention Based Random Access , CBRA, transmit , to the user device via the source cell , a random access response message , and subsequently receive a message including the TA-RNTI associated with the source cell from the user device via the source cell .

[0037] In an example embodiment , alternatively or in addition to the above-described example embodiments , the TA-RNTI indicates a cause of the related TA Procedure , including indicating at least one of : expiry of related time alignment timer, TAT , detection of out of sync, assigned uplink resource for data transmission currently not in use , assigned uplink resource for data transmission not released, data transmission on assigned uplink resources to be continued once TA i s re-acquired, data waiting in buf fer to be transmitted .

[0038] In an example embodiment , alternatively or in addition to the above-described example embodiments , the source network node i s further caused to : transmit , to the user device via the radio access network, a configuration indicating at least one candidate cell the user device may connect to ; and transmit , to the user device via the radio access network, a timing advance , TA, parameter, including a TA - radio network temporary identi fier, RNTI , associated with a configured candidate cell , and the TA-RNTI associated with the source cell and the TA-RNTI associated with the configured candidate cell being the same or di f ferent .

[0039] In an example embodiment , alternatively or in addition to the above-described example embodiments , the source network node supports at least one of distributed unit , DU, functionality or a layer 2 protocol of the radio access network and / or at least one of central unit , CU, functionality or a layer 3 protocol of the radio access network .

[0040] In an example embodiment , alternatively or in addition to the above-described example embodiments , the configuration is related to Layer 1 / Layer 2 triggered mobility, LTM .

[0041] In an example embodiment , alternatively or in addition to the above-described example embodiments , the source network node is further caused to : transmit , to the user device via the radio access network, an RRCRe- conf iguration message including the TA-RNTI associated with the configured candidate cel l and / or the source cell . In an example embodiment , alternatively or in addition to the above-described example embodiments , the source network node is further caused to : transmit , to the user device , a message including a TA acquisition trigger to trigger the related TA procedure for the source cell with associated TA-RNTI .

[0042] In an example embodiment , alternatively or in addition to the above-described example embodiments , the source network node is further caused to : receive a random access request message from the user device via the source cell , transmit , to the user device via the source cell , a random access response message , and subsequently receive a message including the TA-RNTI associated with the source cell from the user device via the source cell .

[0043] In an example embodiment , alternatively or in addition to the above-described example embodiments , the source network node is further caused to : receive a random access request message from the user device via the triggered candidate cell , transmit , to the user device via the candidate cell , a random access response message , and subsequently receive a message including the TA-RNTI associated with the triggered cell from the user device via the triggered candidate cell .

[0044] In an example embodiment , alternatively or in addition to the above-described example embodiments , the source network node i s further caused to : after transmitting, to the user device via the triggered candidate cell , the random access response message , subsequently receive a message including the TA-RNTI associated with the triggered cel l from the user device via the source cell .

[0045] In an example embodiment , alternatively or in addition to the above-described example embodiments , the related TA procedure relates to at least one of : a TA acquisition procedure , an early TA acquisition procedure , a TA acquis ition with a random acces s procedure , or a TA re-acquisition procedure .

[0046] In an example embodiment , alternatively or in addition to the above-described example embodiments , the at least one candidate cell for the user device to connect to include at least one of : a target cel l for the user device to switch to , or a target cell for the user device to add as a second radio link connection .

[0047] In an example embodiment , alternatively or in addition to the above-described example embodiments , the TA parameter is a user device specific parameter assigned by the source cell .

[0048] In an example embodiment , alternatively or in addition to the above-described example embodiments , together with the TA parameter an associated timer is as signed indicating a time period for the TA parameter to be considered valid by the user device .

[0049] In an example embodiment , alternatively or in addition to the above-described example embodiments , the TA parameter associated with the configured candidate cell is a user device speci fic parameter assigned by the associated configured candidate cell or the source cell .

[0050] In an example embodiment , alternatively or in addition to the above-described example embodiments , together with the TA parameter an associated timer is as signed indicating a time period for the TA parameter associated with the configured candidate cell to be considered valid by the user device .

[0051] An example embodiment of a method comprises establishing, by a user device , a connection towards a source network node of a radio access network via a source cell supported by the source network node . The method further comprises receiving, at the user device from the radio access network, a timing advance , TA, parameter, including a TA - radio network temporary identi fier, RNTI , associated with the source cell . The method further comprises using, by the user device , the TA parameter in case of a related TA procedure being triggered .

[0052] An example embodiment of a method comprises establishing, by a source network node , a connection towards a user device via a source cell of a radio access network supported by the source network node . The method further comprises transmitting, from the source network node to the user device via the radio access network, a timing advance , TA, parameter, including a TA - radio network temporary identi fier, RNTI , associated with the source cell .

[0053] An example embodiment of an apparatus comprises means for carrying out a method according to any of the above-described example embodiments .

[0054] An example embodiment of a computer program product comprises program code configured to perform a method according to any of the above-described example embodiments when the computer program product is executed on a computer .

[0055] DESCRIPTION OF THE DRAWINGS

[0056] The accompanying drawings , which are included to provide a further understanding of the embodiments and constitute a part of this specification, illustrate embodiments and together with the description help to explain the principles of the embodiments . In the drawings :

[0057] FIG . 1 shows an example embodiment of the subj ect matter described herein illustrating an example system, where various embodiments of the present disclosure may be implemented;

[0058] FIG . 2A shows an example embodiment of the subj ect matter described herein illustrating a user device ;

[0059] FIG . 2B shows an example embodiment of the subj ect matter described herein illustrating a source network node ; FIG. 3 shows an example embodiment of the subject matter described herein illustrating a method in re-acquiring uplink synchronization with a primary time alignment group;

[0060] FIG. 4 shows an example embodiment of the subject matter described herein illustrating a method for a user device; and

[0061] FIG. 5 shows an example embodiment of the subject matter described herein illustrating a method for a source network node.

[0062] Like reference numerals are used to designate like parts in the accompanying drawings.

[0063] DETAILED DESCRIPTION

[0064] Reference will now be made in detail to embodiments, examples of which are illustrated in the accompanying drawings. The detailed description provided below in connection with the appended drawings is intended as a description of the present examples and is not intended to represent the only forms in which the present example may be constructed or utilized. The description sets forth the functions of the example and the sequence of steps for constructing and operating the example. However, the same or equivalent functions and sequences may be accomplished by different examples.

[0065] Fig. 1 illustrates example system 100, where various embodiments of the present disclosure may be implemented. System 100 may comprise a radio access network 110 of a fifth generation (5G) new radio (NR) network or a network beyond 5G wireless networks, 110. An example representation of system 100 is shown depicting user device 200 and source network node 210.

[0066] At least in some embodiments, radio access network 110 may be comprised in one or more massive machine- to-machine (M2M) network (s) , massive machine type communications (mMTC) network(s) , internet of things (ToT) network(s) , industrial internet-of-things (IIoT) network^) , enhanced mobile broadband (eMBB) network(s) , ultra-reliable low-latency communication (URLLC) network^) , and / or the like. In other words, radio access network 110 may be configured to serve diverse service types and / or use cases, and it may logically be seen as comprising one or more networks.

[0067] User device 200 may include, e.g., a mobile phone, a smartphone, a tablet computer, a smart watch, or any hand-held, portable and / or wearable device. User device 200 may also be referred to as a user equipment (UE) . Source network node 210 may comprise, e.g., a base station. The base station may include, e.g., any device suitable for providing an air interface for client devices to connect to a wireless network via wireless transmissions .

[0068] At least in some embodiments, source network node 210 may be logically split into nodes called centralized units (CUs) and distributed units (DUs) . For example, the CUs may host higher layer protocols, such as radio resource control (RRC) , service data adaptation protocol (SDAP) , and / or packet data convergence protocol (PDCP) . The DUs may host, e.g., radio link control (RLC) , medium access control (MAC) , and / or higher physical (PHY) layers.

[0069] The following description provides further details of examples of network nodes. In a 5G NR network, a gNodeB (also known as gNB) may include, e.g., a node that provides NR user plane and control plane protocol terminations towards the UE and that is connected via a NG interface to the 5G core (5GC) , e.g., according to 3GPP TS 38.300 V16.6.0 (2021-06) section 3.2, which is hereby incorporated by reference herein.

[0070] A gNB supports various protocol layers, e.g., Layer 1 (LI) - physical layer, Layer 2 (L2) , and Layer 3 (L3) . The layer 2 (L2) of NR is split into the following sublayers: Medium Access Control (MAC) , Radio Link Control (RLC) , Packet Data Convergence Protocol (PDCP) and Service Data Adaptation Protocol (SDAP) , where, e . g . :

[0071] The physical layer offers to the MAC sublayer transport channels;

[0072] The MAC sublayer offers to the RLC sublayer logical channels;

[0073] The RLC sublayer offers to the PDCP sublayer RLC channels;

[0074] The PDCP sublayer offers to the SDAP sublayer radio bearers;

[0075] The SDAP sublayer offers to 5GC quality of service (QoS) flows;

[0076] "Comp." refers to header compression and "Segm." refers to segmentation;

[0077] Control channels include broadcast control channel (BCCH) and physical control channel (PCCH) .

[0078] Layer 3 (L3) includes e.g., radio resource control (RRC) , e.g., according to 3GPP TS 38.300 V16.6.0 (2021-06) section 6, which is hereby incorporated by reference herein.

[0079] A gNB central unit (gNB-CU) includes, e.g., a logical node hosting, e.g., radio resource control (RRC) , service data adaptation protocol (SDAP) , and packet data convergence protocol (PDCP) protocols of the gNB or RRC and PDCP protocols of the en-gNB, that controls the operation of one or more gNB distributed units (gNB-DUs) . The gNB-CU terminates the Fl interface connected with the gNB-DU. A gNB-CU may also be referred to herein as a CU, a central unit, a centralized unit, or a control unit.

[0080] A gNB Distributed Unit (gNB-DU) includes, e.g., a logical node hosting, e.g., radio link control (RLC) , media access control (MAC) , and physical (PHY) layers of the gNB or en-gNB, and its operation is partly controlled by the gNB-CU. One gNB-DU supports one or multiple cells. One cell is supported by only one gNB-DU. The gNB-DU terminates the Fl interface connected with the gNB-CU. A gNB-DU may also be referred to herein as DU or a distributed unit.

[0081] A gNB-CU-Control Plane (gNB-CU-CP) includes, e.g., a logical node hosting, e.g., the RRC and the control plane part of the PDCP protocol of the gNB-CU for an en-gNB or a gNB. The gNB-CU-CP terminates the El interface connected with the gNB-CU-User Plane (gNB-CU- UP) and the Fl-C interface connected with the gNB-DU.

[0082] A gNB-CU-User Plane (gNB-CU-UP) includes, e.g., a logical node hosting, e.g., the user plane part of the PDCP protocol of the gNB-CU for an en-gNB, and the user plane part of the PDCP protocol and the SDAP protocol of the gNB-CU for a gNB. The gNB-CU-UP terminates the El interface connected with the gNB-CU-CP and the Fl-U interface connected with the gNB-DU, e.g., according to 3GPP TS 38.401 V16.6.0 (2021-07) section 3.1, which is hereby incorporated by reference herein.

[0083] Different functional splits between the central and distributed unit are possible, e.g., called options :

[0084] Option 1 (lA-like split) :

[0085] The function split in this option is similar to the 1A architecture in dual connectivity (DC) . RRC is in the central unit. PDCP, RLC, MAC, physical layer, and RE are in the distributed unit.

[0086] Option 2 (3C-like split) :

[0087] The function split in this option is similar to the 3C architecture in DC. RRC and PDCP are in the central unit. RLC, MAC, physical layer, and RE are in the distributed unit.

[0088] Option 3 (intra RLC split) :

[0089] Low RLC (partial function of RLC) , MAC, physical layer, and RE are in the distributed unit. PDCP and high RLC (the other partial function of RLC) are in the central unit.

[0090] Option 4 (RLC-MAC split) :

[0091] MAC, physical layer, and RF are in the distributed unit. PDCP and RLC are in the central unit.

[0092] Or else, e.g., according to 3GPP TR 38.801 V14.0.0 (2017-03) section 11, which is incorporated by reference herein.

[0093] As used herein, the term "network node" may refer to any of a gNB, a gNB-CU, a gNB-DU, a gNB-CU-CP, or a gNB-CU-UP, or any combination of them.

[0094] A RAN (radio access network) node or network node such as, e.g. a gNB, base station, gNB-CU, or gNB- DU, or parts thereof, may be implemented using, e.g., an apparatus with at least one processor and / or at least one memory with processor-readable instructions ("program") configured to support and / or provision and / or process CU and / or DU related functionality and / or features, and / or at least one protocol (sub-) layer of a RAN (radio access network) , e.g. layer 2 and / or layer 3.

[0095] The gNB-CU and gNB-DU parts may, e.g., be colocated or physically separated. The gNB-DU may even be split further, e.g., into two parts, e.g., one including processing equipment and one including an antenna. A central unit (CU) may also be called BBU / REC / RCC / C- RAN / V-RAN, O-RAN, or part thereof. A distributed unit (DU) may also be called RRH / RRU / RE / RU, or part thereof. Hereinafter, in various example embodiments of the present disclosure, a network node, which supports at least one of central unit control plane functionality or a layer 3 protocol of a radio access network, may be, e.g., a gNB-CU-CP. Similarly, a network node, which supports at least one of distributed unit functionality or a layer 2 protocol of the radio access network, may be, e.g., a gNB-DU .

[0096] A gNB-CU may support one or multiple gNB-DUs . A gNB-DU may support one or multiple cells and, thus, could support a serving cell for a user equipment apparatus (UE) or support a candidate cell for handover, dual connectivity, and / or carrier aggregation, among other procedures.

[0097] The user equipment apparatus (UE) may be or include a wireless or mobile device, an apparatus with a radio interface to interact with a RAN (radio access network) , a smartphone, an in-vehicle apparatus, an loT device, or a M2M device, among other types of user equipment. Such a UE may include: at least one processor; and at least one memory including program code; where the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus at least to perform certain operations, such as, e.g., RRC connection to the RAN. In embodiments, the UE may be configured to generate a message (e.g., including a cell ID) to be transmitted via radio towards a RAN (e.g., to reach and communicate with a serving cell) . In embodiments, the UE may generate and transmit and receive RRC messages containing one or more RRC PDUs (packet data units) . Persons skilled in the art will understand RRC protocol as well as other procedures a UE may perform.

[0098] In the following, various example embodiments will be discussed. At least some of these example embodiments described herein may allow reusing uplink resources without obligatory reconfiguration when a time alignment timer expires.

[0099] Furthermore, at least some of the example embodiments described herein may allow explicitly signalling the purpose of a random access (RA) procedure to source network node 210 via using a disclosed timing advance radio network temporary identifier (TA-RNTI) .

[0100] Furthermore, at least some of the example embodiments described herein may allow a shorter traffic interruption time, since user device 200 starts the RA procedure immediately after the time alignment timer expires and does not wait for a scheduling request indication (SRI) trigger.

[0101] Furthermore, at least some of the example embodiments described herein may allow minimizing the traffic interruption time and reducing RRC messaging, because it is optional for source network node 210 to reconfigure UL resources after a successful completion of the RA procedure since user device 200 does not release these UL resources in the first place.

[0102] Fig. 2A is a block diagram of user device 200, in accordance with an example embodiment.

[0103] User device 200 comprises one or more processors 202 and one or more memories 204 that comprise computer program code. User device 200 may also include other elements, such as transceiver 206 configured to enable user device 200 to transmit and / or receive information to / from other devices, as well as other elements not shown in Fig. 2A. In one example, user device 200 may use transceiver 206 to transmit or receive signalling information and data in accordance with at least one cellular communication protocol. Transceiver 206 may be configured to provide at least one wireless radio connection, such as for example a 3GPP mobile broadband connection (e.g., 5G or 6G) . Transceiver 206 may comprise, or be configured to be coupled to, at least one antenna to transmit and / or receive radio frequency signals .

[0104] Although user device 200 is depicted to include only one processor 202, user device 200 may include more processors. In an embodiment, memory 204 is capable of storing instructions, such as an operating system and / or various applications. Furthermore, memory 204 may include a storage that may be used to store, e.g., at least some of the information and data used in the disclosed embodiments. Furthermore , processor 202 is capable of executing the stored instructions . In an embodiment , processor 202 may be embodied as a multi-core processor, a single core processor, or a combination of one or more multi-core processors and one or more s ingle core processors . For example , processor 202 may be embodied as one or more of various processing devices , such as a coprocessor, a microprocessor, a controller, a digital signal processor ( DSP ) , a processing circuitry with or without an accompanying DSP, or various other processing devices including integrated circuits such as , for example , an application specific integrated circuit (AS IC ) , a field programmable gate array ( FPGA) , a microcontroller unit (MCU) , a hardware accelerator, a special-purpose computer chip, a neural network (NN) chip, an arti ficial intelligence (Al ) accelerator, a tensor processing unit ( TPU) , a neural processing unit (NPU) , or the like . In an embodiment , processor 202 may be configured to execute hard-coded functionality . In an embodiment , processor 202 is embodied as an executor of software instructions , wherein the instructions may speci fically configure processor 202 to perform the algorithms and / or operations described herein when the instructions are executed .

[0105] Memory 204 may be embodied as one or more volatile memory devices , one or more non-volatile memory devices , and / or a combination of one or more volatile memory devices and non-volatile memory devices . For example , memory 204 may be embodied as semiconductor memories ( such as mask ROM, PROM (programmable ROM) , EPROM ( erasable PROM) , flash ROM, RAM ( random access memory) , etc . ) .

[0106] User device 200 may comprise any of various types of devices used directly by an end user entity and capable of communication in a wireless network, such as a user equipment (UE ) . Such devices include but are not limited to smartphones , tablet computers , smart watches , lap top computers, internet-of-things (loT) devices, massive machine-to-machine (M2M) devices, massive machine type communications (mMTC) devices, industrial internet-of-things (IIoT) devices, enhanced mobile broadband (eMBB) devices, ultra-reliable low-latency communication (URLLC) devices, and / or devices mounted in vehicles, etc.

[0107] When executed by at least one processor 202, instructions stored in at least one memory 204 cause user device 200 at least to establish a connection towards source network node 210 of radio access network 110 via a source cell supported by source network node 210.

[0108] The instructions that, when executed by at least one processor 202, further cause user device 200 at least to receive, from radio access network 110, a timing advance (TA) parameter, including a TA - radio network temporary identifier (RNTI) associated with the source cell. For example, the TA parameter may be user device 200 specific parameter assigned by the source cell .

[0109] The instructions that, when executed by at least one processor 202, further cause user device 200 at least to use the TA parameter in case of a related TA procedure being triggered. For example, the related TA procedure may be a random access procedure. At least in some embodiments, the related TA procedure may relate to at least one of: a TA acquisition procedure, an early TA acquisition procedure, a TA acquisition with a random access procedure, or a TA re-acquisition procedure.

[0110] At least in some embodiments, user device 200 may be further caused to: receive, from radio access network 110, a Medium Access Control (MAC) configuration including the TA-RNTI.

[0111] At least in some embodiments, user device 200 may be further caused to: monitor a time alignment timer ( TAT ) , and in case of expiry of the TAT trigger the related TA procedure .

[0112] At least in some embodiments , user device 200 may be further caused to : in case of a triggered related TA procedure , transmit a random access request message towards the source cell , including using Contention Based Random Access ( CBRA) , receive , from the source cell , a random access response message , and subsequently transmit a message including the TA-RNTI associated with the source cell towards the source cell .

[0113] At least in some embodiments , the TA-RNTI may indicate a cause of the related TA Procedure, including indicating at least one of : expiry of related time alignment timer TAT , detection of out of sync, assigned uplink resource for data transmission currently not in use, assigned uplink resource for data transmission not released, data transmission on assigned uplink resources to be continued once TA is re-acquired, data waiting in buf fer to be transmitted .

[0114] At least in some embodiments , user device 200 may be further caused to : receive , from radio access network 110 , a configuration indicating at least one candidate cell user device 200 may connect to ; and receive , from radio acces s network 110 , a timing advance TA parameter, including a TA - radio network temporary identi fier RNTI associated with a configured candidate cell , and the TA-RNTI associated with the source cell and the TA-RNTI associated with the configured candidate cell being the same or dif ferent . For example, the configuration may be related to Layer 1 / Layer 2 triggered mobility ( LTM) .

[0115] At least in some embodiments , user device 200 may be further caused to : receive , from radio access network 110 , an RRCReconf iguration message including the TA-RNTI associated with the configured candidate cell and / or the source cell , and reconfigure user device 200 with the LTM . At least in some embodiments , user device 200 may be further caused to : receive , from source network node 210 , a message including a TA acquisition trigger to trigger the related TA procedure for the source cell with associated TA-RNTI .

[0116] At least in some embodiments , user device 200 may be further caused to : transmit a random access request message towards the source cell , receive , from the source cell , a random access response message , and subsequently transmit a message including the TA-RNTI associated with the source cell towards the source cell .

[0117] At least in some embodiments , user device 200 may be further caused to : transmit a random access request message towards the triggered candidate cell , receive , from the candidate cell , a random access response message , and subsequently transmit a message including the TA-RNTI associated with the triggered cell towards the triggered candidate cell .

[0118] At least in some embodiments , user device 200 may be further caused to : after receiving, from the triggered candidate cell , the random access response message , subsequently transmit a message including the TA-RNTI associated with the triggered cell towards the source cell .

[0119] At least in some embodiments , user device 200 may be further caused to : after receiving, from the triggered candidate cell , the random access response message , subsequently refraining from at least one of : starting a related contention resolution procedure , starting a related contention resolution timer, or considering the TA acquisition invalid when a related contention resolution timer expires .

[0120] At least in some embodiments , the at least one candidate cell for user device 200 to connect to may include at least one of : a target cell for user device 200 to switch to , or a target cell for user device 200 to add as a second radio link connection . At least in some embodiments, together with the TA parameter an associated timer may be assigned indicating a time period for the TA parameter to be considered valid by user device 200.

[0121] At least in some embodiments, the TA parameter associated with the configured candidate cell may be user device 200 specific parameter assigned by the associated configured candidate cell or the source cell.

[0122] At least in some embodiments, together with the TA parameter an associated timer may be assigned indicating a time period for the TA parameter associated with the configured candidate cell to be considered valid by user device 200.

[0123] When executed by the at least one processor 202, instructions stored in at least one memory 204 may further cause user device 200 at least to perform: in response to a TA timer expiring, pausing use of a set of uplink (UL) resources without releasing the set of UL resources. For example, the TA timer may expire for a primary time alignment Group (PTAG) , e.g., when user device 200 has not received a timing advance command (TAG) for a longer period than that defined by the TA timer .

[0124] At least in some embodiments, the set of the UL resources may comprise resources related to a physical UL control channel (PUCCH) , a sounding reference signal (SRS) , a semi-persistent scheduling (SPS) , and / or a physical UL shared channel (PUSCH) .

[0125] The instructions, when executed by the at least one processor 202, may further cause the user device 200 at least to perform transmitting an indication of initiating a random access (RA) procedure to a source network node 210.

[0126] At least in some embodiments, the transmitting of the indication of initiating the RA procedure to the source network node 210 may be performed without waiting for a scheduling request indication (SRI) trigger. At least in some embodiments, the instructions, when executed by the at least one processor 202, may further cause the user device 200 to perform receiving a random access response (RAR) UL grant from the source network node 210 in response to the transmitting of the indication of initiating the RA procedure.

[0127] The instructions, when executed by the at least one processor 202, may further cause the user device 200 at least to perform transmitting a TA radio network temporary identifier (TA-RNTI) medium access control control element (MCE) to the source network node 210. The TA-RNTI MCE comprises a TA-RNTI previously assigned to the user device 200 by the source network node 210.

[0128] For example, the TA-RNTI may be assigned from a common pool of RNTIs. At least in some embodiments, the TA-RNTI may not be used for any transmission in either direction (e.g., not used as a scrambling sequence by any physical channel) .

[0129] At least in some embodiments, the TA-RNTI MCE may be transmitted in a transmission scheduled by the received RAR UL grant.

[0130] For example, the TA-RNTI MCE may include a fixed size UL MCE with a dedicated logical channel identification (LCID) or a dedicated enhanced LCID (eLCID) . At least in some embodiments, the TA-RNTI MCE may be used as an Msg3 of an CBRA to carry the TA-RNTI (e.g., using a RAR grant and scrambled with a Temp C-RNTI) .

[0131] At least in some embodiments, a standard MAC subheader for a fixed size medium access control (MAC) packet data unit (PDU) may be used (R / R / LCID / (eLCID) ) . For example, either two reserved bits and a 6-bit LCID may be used when an LCID is decided to be used for the TA-RNTI MCE. Alternatively, two reserved bits and a 6- bit LCID (set to 34) may be used in a first octet and an 8-bit eLCID may be used in a second octet when a one- octet eLCID is decided to be used for the TA-RNTI MCE. At least in some embodiments , the assignment of the TA-RNTI to the user device 200 by the serving source network node 210 may be performed as part of a medium access control (MAC ) configuration, and the initiated RA procedure may comprise a MAC-initiated RA procedure .

[0132] The instructions , when executed by the at least one processor 202 , may further cause the user device 200 at least to perform restarting the use of the set of the UL resources in response to a succes s ful completion of the initiated RA procedure .

[0133] Fig . 2B is a block diagram of source network node 210 , in accordance with an example embodiment . At least in some embodiments , source network node 210 may be associated with a serving cell for user device 200 . At least in some embodiments , source network node 210 may support at least one of distributed unit ( DU) functionality or a layer 2 protocol of radio access network 110 and / or at least one of central unit ( CU) functionality or a layer 3 protocol of radio access network 110 .

[0134] Source network node 210 comprises one or more processors 212 and one or more memories 214 that comprise computer program code . Source network node 210 may also include other elements , such as transceiver 216 configured to enable source network node 210 to transmit and / or receive information to / from other devices , as well as other elements not shown in Fig . 2B . In one example , source network node 210 may use transceiver 216 to transmit or receive signalling information and data in accordance with at least one cellular communication protocol . Transceiver 216 may be configured to provide at least one wireless radio connection, such as for example a 3GPP mobile broadband connection ( e . g . , 5G or 6G ) . Transceiver 216 may comprise , or be conf igured to be coupled to , at least one antenna to transmit and / or receive radio frequency signals . Although source network node 210 is depicted to include only one processor 212, source network node 210 may include more processors. In an embodiment, memory 214 is capable of storing instructions, such as an operating system and / or various applications. Furthermore, memory 214 may include a storage that may be used to store, e.g., at least some of the information and data used in the disclosed embodiments.

[0135] Furthermore, processor 212 is capable of executing the stored instructions. In an embodiment, processor 212 may be embodied as a multi-core processor, a single core processor, or a combination of one or more multi-core processors and one or more single core processors. For example, processor 212 may be embodied as one or more of various processing devices, such as a coprocessor, a microprocessor, a controller, a digital signal processor (DSP) , a processing circuitry with or without an accompanying DSP, or various other processing devices including integrated circuits such as, for example, an application specific integrated circuit (ASIC) , a field programmable gate array (FPGA) , a microcontroller unit (MCU) , a hardware accelerator, a special-purpose computer chip, a neural network (NN) chip, an artificial intelligence (Al) accelerator, a tensor processing unit (TPU) , a neural processing unit (NPU) , or the like. In an embodiment, processor 212 may be configured to execute hard-coded functionality. In an embodiment, processor 212 is embodied as an executor of software instructions, wherein the instructions may specifically configure processor 212 to perform the algorithms and / or operations described herein when the instructions are executed.

[0136] Memory 214 may be embodied as one or more volatile memory devices, one or more non-volatile memory devices, and / or a combination of one or more volatile memory devices and non-volatile memory devices. For ex- ample, memory 214 may be embodied as semiconductor memories (such as mask ROM, PROM (programmable ROM) , EPROM (erasable PROM) , flash ROM, RAM (random access memory) , etc . ) .

[0137] Source network node 210 may comprise a base station. The base station may include, e.g., a 5G or 6G base station (gNB) or any such device providing an air interface for user devices to connect to a wireless network via wireless transmissions. At least in some embodiments, source network node 210 may be logically split into a centralized unit (CU) and a distributed unit (DU) .

[0138] When executed by at least one processor 212, instructions stored in at least one memory 214 cause source network node 210 at least to establish a connection towards user device 200 via the source cell of radio access network 110 supported by source network node 210.

[0139] The instructions, when executed by at least one processor 212, further cause source network node 210 at least to transmit, to user device 200 via radio access network 110, the TA parameter including the TA-RNTI associated with the source cell.

[0140] At least in some embodiments, source network node 210 may be further caused to: transmit, to user device 200 via radio access network 110, the MAC configuration including the TA-RNTI.

[0141] At least in some embodiments, source network node 210 may be further caused to: in case of the triggered related TA procedure, receive the random access request message from user device 200 via the source cell, including using the CBRA, transmit, to user device 200 via the source cell, the random access response message, and subsequently receive the message including the TA-RNTI associated with the source cell from user device 200 via the source cell. At least in some embodiments , source network node 210 may be further caused to transmit , to user device 200 via radio access network 110 , a configuration indicating at least one candidate cell user device 200 may connect to ; and transmit , to user device 200 via radio access network 110 , the TA parameter including the TA-RNTI associated with the configured candidate cell , and the TA-RNTI associated with the source cell and the TA-RNTI associated with the configured candidate cell being the same or di f ferent .

[0142] At least in some embodiments , source network node 210 may be further caused to : transmit , to user device 200 via radio access network 110 , an RRCRecon- figuration message including the TA-RNTI associated with the configured candidate cell and / or the source cell .

[0143] At least in some embodiments , source network node 210 may be further caused to : transmit , to user device 200 , the message including the TA acquisition trigger to trigger the related TA procedure for the source cell with associated TA-RNTI .

[0144] At least in some embodiments , source network node 210 may be further caused to : receive the random access request message from user device 200 via the source cell , transmit , to user device 200 via the source cell , the random access response message , and subsequently receive the message including the TA-RNTI associated with the source cell from user device 200 via the source cell .

[0145] At least in some embodiments , source network node 210 may be further caused to : receive the random access request message from user device 200 via the triggered candidate cell , transmit , to user device 200 via the candidate cell , the random access response message , and subsequently receive the message including the TA-RNTI associated with the triggered cell from user device 200 via the triggered candidate cell . At least in some embodiments , source network node 210 may be further caused to : after transmitting, to user device 200 via the triggered candidate cell , the random access response message , subsequently receive the message including the TA-RNTI associated with the triggered cell from user device 200 via the source cell .

[0146] When executed by the at least one processor 212 , instructions stored in at least one memory 214 may further cause the source network node 210 at least to perform receiving from the user device 200 the indication of initiating the RA procedure .

[0147] At least in some embodiments , the instructions , when executed by the at least one processor 202 , may further cause the source network node 210 to perform transmitting the RAR UL grant to the user device 200 in response to the receiving of the indication of initiating the RA procedure .

[0148] The instructions , when executed by the at least one processor 212 , may further cause the source network node 210 at least to perform receiving from the user device 200 the TA-RNTI MCE . As discus sed above in more detail , the TA-RNTI MCE comprises the TA-RNTI previously assigned to the user device 200 by the source network node 210 .

[0149] At least in some embodiments , the TA-RNTI MCE may be received in a transmi ssion scheduled by the transmitted RAR UL grant .

[0150] At least in some embodiments , the assignment of the TA-RNTI to the user device 200 by the serving source network node 210 may be performed as part of the MAC configuration, and the initiated RA procedure may comprise a MAC-initiated RA procedure .

[0151] The instructions , when executed by the at least one processor 212 , may further cause the source network node 210 at least to perform identi fying a purpose of the initiated RA procedure based on the received TA- RNTI MCE . The instructions, when executed by the at least one processor 212, may further cause the source network node 210 at least to perform: in response the TA timer expiring being the identified purpose of the initiated RA procedure, determining that reconfiguring UL resources for the user device 200 is optional after a successful completion of the initiated RA procedure.

[0152] Further features of source network node 210 directly result from the functionalities and parameters of user device 200 and thus are not repeated here.

[0153] Fig. 3 illustrates an example signalling diagram 300 of a method of using the disclosed TA-RNTI MCE in a contention based RA (CBRA) performed to re-acquire uplink synchronization with a primary time alignment group (PTAG) in accordance with an example embodiment.

[0154] At operation 301, user device 200 may be configured with the TA-RNTI by the serving cell. It may be configured as a part of a basic MAC configuration (e.g., similarly to TPC-x-RNTIs) .

[0155] Source network node 210 may recognize from the context what is the purpose of an RA using the TA-RNTI MCE. If source network node 210 is associated with the serving cell for user device 200, it means that source network node 210 deals with a re-synchronization with the PTAG.

[0156] At operation 302, the time alignment timer expires for the PTAG.

[0157] At operation 303, user device 200 stops using UL resources (PUCCH, SRS, SPS, PUSCH) but they are not released .

[0158] At operation 304, user device 200 RRC is informed about operation 303 (UL resources are put on hold but they are not be released) .

[0159] At operation 305, user device 200 immediately starts a MAC-initiated RA procedure by sending a Msgl (a physical RA channel (PRACH) transmission) . It is to noted that the disclosed CBRA variant may be followed also in the case when source network node 210 initiates it by itself.

[0160] At operation 306, the serving cell sends the RAR to user device 200, and user device 200 applies the TAG.

[0161] At operation 307, user device 200 sends a Msg3 using the RAR grant and scrambled with a temporary cell RNTI (Temp C-RNTI) . The TA-RNTI MCE is sent.

[0162] At operation 308, when the serving cell decodes the TA-RNTI MCE, it may recognize user device 200 and the purpose of the RA procedure. Thus, source network node 210 knows that the RA procedure is performed due to the time alignment timer expiration, and that the UL resources have not been released by user device 200.

[0163] At operations 309 and 310, source network node 210 and user device 200 proceed with CBRA completion (contention resolution may performed, e.g., in the same way as for a legacy CBRA) .

[0164] At operation 311, once the RA procedure is completed successfully, user device 200 may start to use all UL resources again. There is no need to reconfigure them.

[0165] At operations 312-313, source network node 210 may still decide to reconfigure user device 200, e.g., in a suitable legacy way. However, this reconfiguration is optional.

[0166] The following relates to exemplary implementations with respect to TA-RNTI:

[0167] Regarding the configuration of a TA-RNTI: A configuration of a TA-RNTI (and its related TA-RNTI value) may be performed using a Radio resource control information element (RRC IE) . An RRC IE like CellGroup- Config and / or MAC-CellGroupConf ig may be used to set TA- RNTI value through RRCSetup / RRCResume / RRCReconf igura- tion' s masterCellGroup . This may be performed by appropriate modifications of, e.g., future releases of 3GPP TS38.331 V17.6.0 (2023-09) , in particular section 6.3.2., or other specif ication ( s ) .

[0168] Regarding the modified RA procedure with TA- RNTI (e.g., sending TA-RNTI MAC CE after receiving RAR) appropriate modifications may be added to, e.g., future releases of 3GPP TS38.321 V17.6.0 (2023-09) , in particular sections 5.1.1 and / or 5.1.1a, or other specification (s) . Similarly, at least one of the following sections of TS38.321 may be modified to cover the respective TA-RNTI procedural amendments, e.g., 5.1.4 (new option for sending TA-RNTI MAC CE) , 5.1.5 (new option to cover TA-RNTI MAC CE) , 5.2 (in case of time alignment timer expiration for PTAG add new option for putting UL resources on hold instead of releasing them) , 6.1.3 (new MAC CE definition including new TA-RNTI) , 6.2.1 (new LCID / eLCID for new UL MAC CE : TA-RNTI MCE) , 7.1 (new RNTI values for new TA-RNTI) .

[0169] Fig. 4 illustrates an example flow chart of method 400 for user device 200, in accordance with an example embodiment.

[0170] At operation 401, user device 200 establishes the connection towards source network node 210 of radio access network 110 via the source cell supported by the source network node 210.

[0171] At operation 402, user device 200 receives from radio access network 110 the TA parameter including the TA-RNTI associated with the source cell.

[0172] At operation 403, user device 200 uses the TA parameter in case of the related TA procedure being triggered .

[0173] Embodiments and examples with regard to Fig. 4 may be carried out by user device 200 of Fig. 2A. Operations 401-403 may, for example, be carried out by at least one processor 202 and at least one memory 204. Further features of method 400 directly resulting from the functionalities and parameters of user device 200 are not repeated here . Method 400 can be carried out by computer programs or portions thereof .

[0174] Another example of an apparatus suitable for carrying out the embodiments and examples with regard to Fig . 4 comprises means for : establishing, at operation 401 , the connection towards source network node 210 of radio access network 110 via the source cel l supported by source network node 210 ; receiving, at operation 402 , from radio access network 110 , the TA parameter including the TA-RNTI associated with the source cell ; and using, at operation 403 , the TA parameter in case of the related TA procedure being triggered .

[0175] Fig . 5 illustrates an example flow chart of method 500 for source network node 210 , in accordance with an example embodiment .

[0176] At operation 501 , source network node 210 establishes the connection towards user device 200 via the source cell of radio access network 110 supported by the source network node 210 .

[0177] At operation 502 , source network node 210 transmits to user device 200 via radio access network 110 , the TA parameter including the TA-RNTI associated with the source cell .

[0178] Embodiments and examples with regard to Fig . 5 may be carried out by source network node 210 of Fig . 2B . Operations 501-502 may, for example , be carried out by at least one processor 212 and at least one memory 214 . Further features of method 500 directly resulting from the functionalities and parameters of source network node 210 are not repeated here . Method 500 can be carried out by computer programs or portions thereof .

[0179] Another example of an apparatus suitable for carrying out the embodiments and examples with regard to Fig . 5 comprises means for : establishing, at operation 501, the connection towards user device 200 via the source cell of radio access network 110 supported by source network node 210; and transmitting, at operation 502, to user device 200 via radio access network 110, the TA parameter including the TA-RNTI associated with the source cell.

[0180] User device 200 may comprise means for performing at least one method described herein. In one example, the means may comprise at least one processor 202, and at least one memory 204 storing instructions that, when executed by at least one processor 202, cause user device 200 to perform the method.

[0181] Source network node 210 may comprise means for performing at least one method described herein. In one example, the means may comprise at least one processor 212, and at least one memory 214 storing instructions that, when executed by at least one processor 212, cause source network node 210 to perform the method.

[0182] The functionality described herein can be performed, at least in part, by one or more computer program product components such as software components. According to an embodiment, user device 200 and / or source network node 210 may comprise a processor or processor circuitry, such as for example a microcontroller, configured by the program code when executed to execute the embodiments of the operations and functionality described. Alternatively, or in addition, the functionality described herein can be performed, at least in part, by one or more hardware logic components. For example, and without limitation, illustrative types of hardware logic components that can be used include Field-programmable Gate Arrays (FPGAs) , Application-specific Integrated Circuits (ASICs) , Application-specific Standard Products (ASSPs) , System-on-a-chip systems (SOCs) , Complex Programmable Logic Devices ( CPLDs ) , Tensor Processing Units ( TPUs ) , and Graphics Processing Units ( GPUs ) .

[0183] Any range or device value given herein may be extended or altered without losing the ef fect sought . Also , any embodiment may be combined with another embodiment unless explicitly disallowed .

[0184] Although the subj ect matter has been described in language speci fic to structural features and / or acts , it is to be understood that the subj ect matter defined in the appended claims is not necessarily limited to the speci fic features or acts described above . Rather, the speci fic features and acts described above are disclosed as examples of implementing the claims and other equivalent features and acts are intended to be within the scope of the claims .

[0185] It will be understood that the benefits and advantages described above may relate to one embodiment or may relate to several embodiments . The embodiments are not limited to those that solve any or all of the stated problems or those that have any or all of the stated benef its and advantages . It wi ll further be understood that reference to ' an ' item may refer to one or more of those items .

[0186] The steps of the methods described herein may be carried out in any suitable order, or simultaneously where appropriate . Additionally, individual blocks may be deleted from any of the methods without departing from the spirit and scope of the subj ect matter described herein . Aspects of any of the embodiments described above may be combined with aspects of any of the other embodiments described to form further embodiments without losing the ef fect sought .

[0187] The term ' comprising ' is used herein to mean including the method, blocks or elements identi fied, but that such blocks or elements do not comprise an exclusive list and a method or apparatus may contain additional blocks or elements .

[0188] It will be understood that the above descrip- tion is given by way of example only and that various modi f ications may be made by those s kil led in the art . The above speci fication, examples and data provide a complete description of the structure and use of exemplary embodiments . Although various embodiments have been described above with a certain degree of particularity, or with reference to one or more individual embodiments , those skilled in the art could make numerous alterations to the disclosed embodiments without departing from the spirit or scope of this speci fica- tion .

Claims

CLAIMS :

1. A user device (200) , comprising: at least one processor (202) ; and at least one memory (204) storing instructions that, when executed by the at least one processor (202) , cause the user device (200) at least to: establish a connection towards a source network node (210) of a radio access network (110) via a source cell supported by the source network node (210) ; receive, from the radio access network (110) , a timing advance, TA, parameter, including a TA - radio network temporary identifier, RNTI, associated with the source cell; and use the TA parameter in case of a related TA procedure being triggered.

2. The user device (200) according to claim 1, wherein the user device (200) is further caused to: receive, from the radio access network (110) , a Medium Access Control, MAC, configuration including the TA- RNTI .

3. The user device (200) according to claim 1, wherein the user device (200) is further caused to: monitor a time alignment timer, TAT, and in case of expiry of the TAT trigger the related TA procedure.4 . The user device (200) according to claim 1, wherein the related TA procedure is a random access procedure .

5. The user device (200) according to claim 4, wherein the user device (200) is further caused to: in case of a triggered related TA procedure, transmit a random access request message towards the source cell, including using Contention Based Random Access, CBRA, receive, from the source cell, a random access responsemessage, and subsequently transmit a message including the TA-RNTI associated with the source cell towards the source cell.

6. The user device (200) according to claim 1, wherein the TA-RNTI indicates a cause of the related TA Procedure, including indicating at least one of: expiry of related time alignment timer, TAT, detection of out of sync, assigned uplink resource for data transmission currently not in use, assigned uplink resource for data transmission not released, data transmission on assigned uplink resources to be continued once TA is re-acquired, data waiting in buffer to be transmitted.

7. The user device (200) according to claim 1, wherein the user device (200) is further caused to: receive, from the radio access network (110) , a configuration indicating at least one candidate cell the user device (200) may connect to; and receive, from the radio access network (110) , a timing advance, TA, parameter, including a TA - radio network temporary identifier, RNTI, associated with a configured candidate cell, and the TA-RNTI associated with the source cell and the TA-RNTI associated with the configured candidate cell being the same or different.

8. The user device (200) according to claim 1, wherein the source network node (210) supports at least one of distributed unit, DU, functionality or a layer 2 protocol of the radio access network (110) and / or at least one of central unit, CU, functionality or a layer 3 protocol of the radio access network (110) .

9. The user device (200) according to claim 7, wherein the configuration is related to Layer 1 / Layer 2 triggered mobility, LTM.

10. The user device (200) according to claim 9, wherein the user device (200) is further caused to: receive, from the radio access network (110) , an RRCRe- conf iguration message including the TA-RNTI associated with the configured candidate cell and / or the source cell, and reconfigure the user device (200) with the LTM.

11. The user device (200) according to claim 1, wherein the user device (200) is further caused to: receive, from the source network node (210) , a message including a TA acquisition trigger to trigger the related TA procedure for the source cell with associated TA-RNTI .

12. The user device (200) according to claim 1, wherein the user device (200) is further caused to: transmit a random access request message towards the source cell, receive, from the source cell, a random access response message, and subsequently transmit a message including the TA-RNTI associated with the source cell towards the source cell.

13. The user device (200) according to claim 7, wherein the user device (200) is further caused to: transmit a random access request message towards the triggered candidate cell, receive, from the candidate cell, a random access response message, and subsequently transmit a message including the TA-RNTI associated with the triggered cell towards the triggered candidate cell.

14. The user device (200) according to claim 13, wherein the user device (200) is further caused to: after receiving, from the triggered candidate cell, the random access response message, subsequently transmit a message including the TA-RNTI associated with the triggered cell towards the source cell.

15. The user device (200) according to claim 13, wherein the user device (200) is further caused to: after receiving, from the triggered candidate cell, the random access response message, subsequently refraining from at least one of: starting a related contention resolution procedure, starting a related contention resolution timer, or considering the TA acquisition invalid when a related contention resolution timer expires.

16. The user device (200) according to claim 1, wherein the related TA procedure relates to at least one of: a TA acquisition procedure, an early TA acquisition procedure, a TA acquisition with a random access procedure, or a TA re-acquisition procedure.

17. The user device (200) according to claim 7, wherein the at least one candidate cell for the user device (200) to connect to include at least one of: a target cell for the user device (200) to switch to, or a target cell for the user device (200) to add as a second radio link connection.

18. The user device (200) according to claim 1, wherein the TA parameter is a user device (200) specific parameter assigned by the source cell.

19. The user device (200) according to claim 18, wherein together with the TA parameter an associated timer is assigned indicating a time period for the TA parameter to be considered valid by the user device (200) .

20. The user device (200) according to claim 7, wherein the TA parameter associated with the configured candidate cell is a user device (200) specificparameter assigned by the associated configured candidate cell or the source cell .21 . The user device ( 200 ) according to claim 20 , wherein together with the TA parameter an associated timer is assigned indicating a time period for the TA parameter associated with the configured candidate cell to be considered valid by the user device ( 200 ) .

Images