Side-link security configuration process

Abstract

A user equipment (UE) for performing unicast sidelink communication with a second user equipment and a method thereof are disclosed. A method for a first user equipment to perform direct sidelink communication with a second user equipment includes the following steps: receiving a first indication including sidelink signaling; in response to receiving the first indication, performing at least one of the following: updating a configuration for performing a transmission / reception process of the first user equipment so as to update a key based on the updated configuration for performing the transmission / reception process; pausing at least one data transmission / reception process; and resuming at least one data transmission / reception process.

Description

[0001] This invention is a divisional application of the patent application for invention with the application number 202080009930.7 and the invention name "Sidelink Security Configuration Process" filed on November 17, 2020. Technical Field

[0002] The present invention generally relates to the field of sidelink communication, and more specifically, to a key update process used by user equipment performing unicast sidelink communication. Still more specifically, the present invention is directed to a UE performing unicast sidelink communication with a second UE and a method therefor. Background Art

[0003] With the emergence of the Internet-of-things (IoT) and modern and next-generation communication standards and systems, more and more devices are starting to connect to generate and report, convey, share, and / or process data. Regarding the communication systems and paradigms involved, there is an obvious trend towards decentralized, local, and independent communication. While most established communication systems are based on a more or less hierarchical architecture, where - for example - mobile devices communicate with upper-level base stations in the hierarchy, the trend is towards a flat hierarchical configuration. In such configurations, mobile devices (e.g., mobile phones, devices, sensors, or what is commonly referred to as user equipment (UE)) are also allowed to communicate directly with each other without the need to involve entities that are somewhat higher in the hierarchy, such as base stations, access points, (e)Node Bs, and the like.

[0004] One area where devices are increasingly connected to each other relates to the field of so-called Vehicle-to-Everything (V2X) communication, which includes transferring information from a vehicle to any entity that can affect the vehicle and vice versa. V2X is a vehicle communication system that includes more specific types of communication, such as Vehicle-to-Infrastructure (V2I), Vehicle-to-vehicle (V2V), Vehicle-to-Pedestrian (V2P), Vehicle-to-device (V2D), or Vehicle-to-grid (V2G). Thus, the latest V2X communication uses cellular networks and was initially defined in Long Term Evolution (LTE) in 3GPP Release 14. It is designed to operate in several modes, such as Device-to-device (D2D). In 3GPP Release 15, the V2X functionality has been extended to support 5G (eV2X), where eV2X refers to the enhancement of V2X that has been facilitated by providing 5G (5th generation) technology. The use cases of eV2X include vehicle platooning, autonomous driving, extended sensors, remote driving, and the like.

[0005] V2X communication combined with cellular networks offers the advantages of supporting both direct communication (V2V / D2D) between vehicles and communication based on traditional cellular networks, and provides a migration path to 5G-based systems and services.

[0006] In conventional cellular traffic, an Evolved Node B (eNB) communicates with a UE via the Uplink (UL) and Downlink (DL) for both control signaling and conveying (payload) data. This concept has been extended in D2D communication by introducing sidelink (SL) transmission, and in particular, unicast transmission between two UEs in NR Release 16 (3GPP TR 38.885 V16.0.0 "Study on NR Vehicle-to-Everything (V2X)"). SUMMARY OF THE INVENTION

[0007] [Technical Problem]

[0008] In the case of such SL transmission, Proximity-based Services (ProSe) have been developed to allow direct discovery between two nearby UEs and direct communication between the two UEs via the SL channel. In LTE Release 15, the security aspects of the ProSe feature are defined, including, for example, the introduction of a key update process in 3GPP TS 24.334 V15.2.0, "Proximity-services (ProSe) User Equipment (UE) to ProSe function protocol aspects; Stage 3 (Release 15)". Generally speaking, key update refers to the process by which one or more keys (e.g., encryption keys) used for communication are updated. In this case, the key update process is used to refresh the security context on an established direct link (i.e., the security algorithms and keys used for integrity protection and encryption of messages transmitted between the two UEs).

[0009] Figure 1 FIG. is a schematic illustration outlining a known process by which key update can be achieved, as defined in 3GPP TS 24.334 V15.2.0.

[0010] In Figure 1 process step S11 of, the first UE 10 starts the direct link key update process to refresh the security context by sending a DIRECT_REKEYING_REQUEST message to the second UE 20 (target UE) and starting a timer T4112.

[0011] In Figure 1 process step S12 of, if the active timer T4112 is not running, then the second UE 20 processes the received DIRECT_REKEYING_REQUEST message and starts a direct security mode control process acting as the commanding UE.

[0012] The direct security mode control process establishes a security association for the direct link between two ProSe-enabled UEs through the exchange of message contents related to direct security mode establishment, and can be performed during the direct link key update process or during the direct link establishment process. After the successful completion of the direct security mode control process, the selected security algorithms and keys are used for integrity protection and encryption of messages exchanged between the UEs.

[0013] In process step S13, the second UE 20, which acts as the commanding UE, sends an unencrypted DIRECT_SECURITY_MODE_COMMAND message to the first UE 10, but uses the new security context integrity protection message. After sending the DIRECT_SECURITY_MODE_COMMAND message, the second UE 20 starts timer T4111.

[0014] In process step S14, after receiving the DIRECT_SECURITY_MODE_COMMAND message, the first UE 10, which acts as the peer UE, checks whether the security mode command is acceptable. This is done by performing the integrity check of the message and by checking that the received UE security capabilities have not changed compared to the latest value sent by the first UE 10 to the second UE 20 in the DIRECT_REKEYING_REQUEST message.

[0015] In process step S15, if the DIRECT_SECURITY_MODE_COMMAND message is acceptable, then the first UE 10 sends an encrypted DIRECT_SECURITY_MODE_COMPLETE message protected with the new security context. From this time on, the first UE 10 uses the new security context to protect all signaling messages and user data.

[0016] In process step S16, after receiving the DIRECT_SECURITY_MODE_COMPLETE message, the second UE 20 stops timer T4111. From this time on, the second UE 20 uses the new security context to protect all signaling messages and user data.

[0017] In process step S19, after completing the direct security mode control process, i.e., after receiving the DIRECT_SECURITY_MODE_COMPLETE message, the second UE 20 sends a DIRECT_REKEYING_RESPONSE message to notify the first UE 10 of the completion of this direct link key update process.

[0018] In process step S20, after receiving the DIRECT_REKEYING_RESPONSE message, the first UE 10 stops timer T4112.

[0019] Alternatively, if the DIRECT_SECURITY_MODE_COMMAND message is not acceptable in process step S14, then the first UE 10 sends a DIRECT_SECURITY_MODE_REJECT message in process step S17. After receiving the DIRECT_SECURITY_MODE_REJECT message, in process step S18, the second UE 20 stops timer T4111 and may abort an ongoing process that triggered the initiation of the direct security mode control process.

[0020] The inventors have recognized that Figure 1 the key update process does not define how to implement the key update process such that the same key or multiple keys will be used for all bearers between two UEs at any given time. Specifically, in the case of successful key update, it is still necessary to establish how to change the key simultaneously between two UEs for both transmission and reception. Similarly, in the case of unsuccessful key update, it is still necessary to establish how to keep the original key unchanged, i.e., to avoid misalignment of keys between two UEs for both transmission and reception.

[0021] Therefore, problems may occur due to misalignment of keys between two UEs for transmission and reception, where the first UE 10 transmits a message using a first key and the second UE 20 attempts to receive the message using a different key. This may result in incorrect message reception and subsequent reduced throughput in unicast SL communication.

[0022] [Overview of the solution]

[0023] The present invention is intended to solve one or more of the above technical problems using known key update and security configuration processes.

[0024] Specifically, in view of the limitations discussed above, according to a first example aspect herein, the inventors have designed a method for a first user equipment UE to perform direct sidelink communication with a second UE. The method includes the steps of: receiving a first indication including sidelink signaling; in response to receiving the first indication, performing at least one of the following: updating a configuration for performing a transmission / reception process of the first UE to update a key based on the updated configuration for performing the transmission / reception process; pausing at least one data transmission / reception process; and resuming at least one data transmission / reception process.

[0025] According to a second example aspect herein, the inventors have further designed a computer program including instructions that, when executed by a processor of a UE, cause the UE to perform the method according to the first example aspect.

[0026] According to a third example aspect herein, the inventors have further designed a non-transitory computer-readable storage medium storing a computer program according to the second example aspect.

[0027] According to a fourth example aspect herein, the inventors have further designed a signal carrying a computer program according to the second example aspect.

[0028] According to a fourth example aspect herein, the inventors have further designed a UE configured to perform direct sidelink communication with a second UE, wherein the UE is configured to perform a method according to the first example aspect.

[0029] Thus, the above example aspects can be used to reduce or avoid the inability to correctly receive messages sent via SL due to the key update process, thus reducing or avoiding throughput degradation in unicast SL communication. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Embodiments of the present invention will now be described in detail with reference to the following drawings by way of non-limiting examples only. Unless otherwise indicated, the same reference numerals presented in different figures may refer to the same or functionally similar elements.

[0031] Figure 1 A schematic illustration for outlining known processes by which key updates can be achieved.

[0032] Figure 2 A schematic illustration of a radio communication system according to an example aspect herein.

[0033] Figure 3A A flowchart showing a process by which a UE can perform direct sidelink communication according to a first example aspect herein.

[0034] Figure 3B A flowchart showing a process by which a UE can perform direct sidelink communication according to a second example aspect herein.

[0035] Figure 3C A flowchart showing a process by which a UE can perform direct sidelink communication according to a third example aspect herein.

[0036] Figure 4 A schematic sequence diagram showing a process by which a first UE and a second UE can update a security configuration for direct sidelink communication according to a first example aspect herein.

[0037] Figure 5 A schematic sequence diagram showing a process by which a first UE and a second UE can update a security configuration for direct sidelink communication according to a second example aspect herein.

[0038] Figure 6 A flowchart showing a process by which a first UE performing direct side - link communication with a second user equipment can re - establish a PDCP entity.

[0039] Figure 7 Showing according to example aspects herein Figure 2 A block diagram of an example signal - processing hardware configuration in any one of the UEs.

[0040] Figure 8 Showing according to example aspects herein Figure 2 A block diagram of an example signal - processing hardware configuration of a radio base station.

[0041] Explanation of reference numerals

[0042] 1: Radio communication system;

[0043] 10: First UE;

[0044] 20: Second UE;

[0045] 30: Radio base station;

[0046] 40: Cell;

[0047] 50, 60: Reference symbols;

[0048] 110, 210: Control parts;

[0049] 120, 220, 710, 810: Transmission / reception parts;

[0050] 130, 230: Memories;

[0051] 300, 320, 330, 400, 500, 600: Processes;

[0052] 700, 800: Signal - processing hardware;

[0053] 705, 805: Antennas;

[0054] 720, 820: Control parts;

[0055] 730, 830: Working memories;

[0056] 740, 840: Instruction storages;

[0057] 750, 850: Computer - readable storage media;

[0058] 760, 860: Computer - readable signals;

[0059] 815: Network communication interface;

[0060] S11, S12, S13, S14, S15, S16, S17, S18, S19, S20, S40, S41, S42, S43, S44, S45, S46, S47, S48, S49, S50, S51, S52, S53, S54, S55, S301, S302, S303, S304, S321, S322, S323, S331, S332, S333, S601, S602, S603, S604, S605, S606: Process steps;

[0061] T4111, T4112: Timers. Detailed implementation

[0062] The example embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0063] In the case where a technical feature in the drawings, the detailed description, or any claim is followed by a reference numeral, the reference numeral has been included solely for the purpose of increasing the intelligibility of the drawings, the detailed description, and the claims. Accordingly, the reference numeral or the absence of a reference numeral has no limiting effect on the scope of any claim element.

[0064] Figure 2 It is a schematic illustration of a radio communication system 1 according to an example aspect herein. The radio communication system 1 includes a first UE 10, a second UE 20, and a radio base station 30. Both the first UE 10 and the second UE 20 can perform radio communication with the radio base station 30. As in this example, the radio base station 30 can be a 5G gNB (next-generation Node B). Alternatively, the radio base station can be, for example, an LTE-A or an LTE eNodeB.

[0065] UE 10, UE 20 can include processing functions and communication functions so as to operate according to one or more of the conventional telecommunication standards, which include - but are not limited to - GSM, PCS, 3GPP, LTE, LTE-A, UMTS, 3G, 4G, 5G. By way of example, as in this example, UE 10 can include a control section 110, a transmission / reception section 120, and a memory 130. Similarly, as in this example, UE 20 can include a control section 210, a transmission / reception section 220, and a memory 230.

[0066] The radio base station 30 is configured to provide access to the radio communication network for the UEs 10, 20 in the cell 40, for example, via beamforming. In Figure 2 the example illustrated, the radio base station 30 serves only two UEs 10, 20. However, in an alternative example, the radio base station 30 can serve three or more than three UEs.

[0067] In this example, UEs 10 and 20 can be configured to transmit data and / or uplink control information (UCI) to radio base station 30 via the UL, and receive data and / or downlink control information via the DL. The UL and DL between each of UEs 10 and 20 and radio base station 30 are indicated by Figure 2 reference symbol 50 in. By way of example, either of UEs 10 and 20 can transmit data and / or UCI on an uplink shared channel (e.g., PUSCH), and / or transmit UCI to radio base station 30 on an uplink control channel (e.g., PUCCH), and / or receive information transmitted by radio base station 30 on a downlink channel (e.g., PDSCH, PDCCH, PBCH, etc.).

[0068] In addition, the first UE 10 and the second UE 20 can perform direct communication using unicast SL communication, i.e., perform direct sidelink communication. The sidelink between the first UE 10 and the second UE 20 is indicated by Figure 2 reference symbol 60 in.

[0069] The air interface between the first UE 10 and the second UE 20 can be referred to as the PC5 interface, and in this example, UEs 10 and 20 can be configured to communicate via the PC5 interface using ProSe direct communication features, as described in 3GPP TS24.334 V15.2.0.

[0070] The SL between UEs 10 and 20 can be established by any suitable method. By way of example, the SL between UEs 10 and 20 can be established using ProSe direct discovery features, as described in 3GPP TS24.334 V15.2.0.

[0071] In this example, UEs 10 and 20 can be configured to transmit and receive data and / or control information on a sidelink shared channel (e.g., PSSCH), and / or transmit and receive control information on a sidelink control channel (e.g., PSCCH). Additionally or alternatively, UEs 10 and 20 can be configured to communicate via sidelink using any other sidelink channel (e.g., PSBCH). The resources allocated to the SL can be obtained, for example, from the UL, i.e., from subframes on the UL frequency in Frequency Division Duplex (FDD) or Time Division Duplex (TDD).

[0072] Figure 3AFIG. 300 is a flow chart showing a process 300 by which a UE may perform direct side link communication according to a first example aspect herein. Optional process steps are indicated by Figure 3A the dashed lines in

[0073] Process 300 is described herein as being performed by a UE 10 of Figure 2 . Additionally or alternatively, Figure 2 a UE 20 of Figure 3A may be configured to perform process 300 of

[0074] In Figure 3A process step S301, UE 10 receives a first indication including side link signaling. The first indication may include any suitable message, signaling, notification, whether internal or received from an external entity via wired or wireless communication.

[0075] By way of example, the first indication may include an internal indication from an upper layer. In this case, receiving the first indication by UE 10 includes receiving from another higher layer in the protocol stack via a layer in the protocol stack.

[0076] The internal indication from the upper layer may be in the form of a request or any other suitable signaling.

[0077] The first indication may include side link signaling as the first indication is configured to enable or initiate side link communication of a lower layer. For example, the first indication may include an internal indication configured to enable or initiate the transmission of PC5-S signaling, e.g., DIRECT_REKEYING_REQUEST, direct security mode command. That is, the first indication may include an upper layer internal indication configured to enable or initiate the transmission of PC5-S signaling of a lower layer.

[0078] By way of an alternative, receiving the first indication may include a transmit / receive portion 120 of UE 10 receiving the first indication via direct side link communication from a second UE (e.g., Figure 2 UE 20 of

[0079] In this case, the side link signaling may include signaling transmitted via the side link. For example, the first indication may include at least one of the following:

[0080] ● PC5-S signaling, e.g., DIRECT_REKEYING_REQUEST, direct security mode command, DIRECT_SECURITY_MODE_COMPLETE DIRECT_REKEYING_RESPONSE;

[0081] ● PC5-RRC signaling, for example, RRC Reconfiguration Sidelink, RRC Reconfiguration Complete Sidelink;

[0082] ● User plane indication, for example, control protocol data units (PDUs) of the Service Data Adaptation Protocol (SDAP), packet data convergence protocol (PDCP), or radio link control (RLC), or medium access control (MAC) control element (CE).

[0083] By way of example, the PDCP user plane indication may include a PDCP entity re - establishment request.

[0084] In Figure 3A In process step S302, in response to receiving the first indication, UE 10 updates the configuration for performing the transmission / reception process of UE 10 so as to update the key based on the updated configuration for performing the transmission / reception process.

[0085] UE 10 may update the configuration for performing the transmission / reception process of UE 10 in response to receiving the first indication, since the update step is after and depends on the reception of the first indication. The control part 110 of UE 10 may be configured to perform process step S302.

[0086] The data transmission / reception process may include, for example, any process, procedure, or mechanism performed by UE 10 at any layer of the protocol stack that allows UE 10 to perform unicast sidelink communication with another UE (e.g., Figure 2 UE 20). Specifically, the data transmission / reception process may, for example, allow UE 10 to transmit and / or receive data using direct sidelink communication.

[0087] By way of example, as in this example, updating the configuration for performing the transmission / reception process of UE 10 by the control unit 110 of UE 10 may include at least one of the following:

[0088] ● Performing at least one action at the packet data convergence protocol (PDCP) layer, including at least one of re - establishment, use of a new key, compression protocol reset, and variable reset;

[0089] ● Any one of radio link control (RLC), re - establishment, release, and addition;

[0090] ● Change of logical channel identifier (LCID);

[0091] ● Full configuration;

[0092] ● Release and / or addition of bearers; and

[0093] ● Media access control (MAC) reset.

[0094] More generally, updating the configuration for performing the transmission / reception process of UE 10 so as to update the key based on the updated configuration for performing the transmission / reception process may include receiving a new key (e.g., encryption key) from an upper layer and / or using a new key.

[0095] Additionally or alternatively, updating the configuration for performing the transmission / reception process of UE 10 so as to update the key based on the updated configuration for performing the transmission / reception process may include the UE actively determining an updated key in response to the configuration for performing the updated transmission / reception process. Alternatively, the key may be automatically updated and / or updated by an upper layer in response to an update of the configuration for performing the transmission / reception process of UE 10.

[0096] For example, as in this example, updating the configuration for performing the transmission / reception process of UE 10 by the control unit 110 may include updating at least one aspect (e.g., parameter) of the configuration of UE 10 that affects how UE 10 performs sidelink communication. This may subsequently cause an update of one or more parameters on which the key (e.g., encryption key) for sidelink communication is generated, thereby causing an update of the key for sidelink communication.

[0097] By way of example, as in this embodiment, the key may be a key for encrypting data for unicast sidelink communication. As in this example, UE 10 may be configured to use one or more key derivation functions at least once to generate a key. For example, one or more key derivation functions may include, for example, any suitable cryptographic hash function, such as SHA - 2 or SHA - 3 or a message authentication code (MAC) algorithm (e.g., HMAC - SHA256 or HMAC - SHA3 - 256).

[0098] As in this example, each key derivation function may include one or more input parameters. The one or more input parameters may be based on the configuration used to perform the transmission / reception process of the UE 10. By way of example, the one or more input parameters may include at least one value, such as, for example, a logical channel identifier (LCID) that identifies a PDCP instance, a PDCP internal counter (PDCP-SN), etc. In this case, updating the configuration used to perform the transmission / reception process of the UE 10 by the control unit 110 may include directly updating at least one value or performing a reconfiguration that causes at least one value to change (e.g., PDCP or RLC re-establishment, MAC reset, or any of the examples discussed above).

[0099] By updating at least one value, one or more input parameters of one or more key derivation functions can be updated.

[0100] As in this example, updating the key based on the updated configuration used to perform the transmission / reception process of the UE 10 includes generating a key at least once using one or more key derivation functions based on the updated one or more input parameters.

[0101] By way of another example, the UE 10 may update the configuration used to perform the transmission / reception process of the UE 10 by performing a PDCP re-establishment of the PDCP entity (i.e., PDCP re-establishment) in order to update the key based on the updated configuration used to perform the transmission / reception process. For example, the UE 10 may perform a PDCP re-establishment of the PDCP entity of the SL via which it receives the first indication from the second UE 20 (i.e., the PDCP entity of the PC5 interface). In this case, the second indication may include, for example, a PDCP user plane indication (e.g., a PDCP entity re-establishment request).

[0102] By way of example, performing a PDCP re-establishment of the PDCP entity may include using a new key, receiving a new key from an upper layer, resetting a compression protocol (e.g., a Robust Header Compression (ROHC) protocol), and resetting at least one of one or more variable values.

[0103] Figure 3A The process 300 may further include a process step S303 as needed. In process step S303, the UE 10 transmits a second indication to the second UE (e.g., Figure 2 the UE 20). As in this example, the transmission / reception part 120 of the UE 10 may be configured to transmit the second indication to the second UE.

[0104] For example, in this embodiment, the optional process step S303 may be executed before the process step S302, and the second indication may include information indicating that the configuration and / or key for performing the transmission / reception process of the UE 10 is being updated or to be updated. Alternatively, the optional process step S303 may be subsequently executed in response to the process step S302, and the second indication may include information indicating that the configuration and / or key for performing the transmission / reception process of the UE 10 has been updated.

[0105] By way of example, the second indication may include at least one of the following:

[0106] ● PC5-S signaling, for example, DIRECT_REKEYING_REQUEST, direct security mode command, DIRECT_SECURITY_MODE_COMPLETE, DIRECT_REKEYING_RESPONSE;

[0107] ● PC5-RRC signaling, for example, RRC reconfiguration sidelink, RRC reconfiguration complete sidelink;

[0108] ● User plane indication, for example, control PDU of SDAP, PDCP, or RLC or MAC CE.

[0109] In the case where the process step S303 is executed before the process step S302 and the second indication includes information indicating that the configuration and / or key for performing the transmission / reception process of the UE 10 is being updated or to be updated, the second UE may update the key at its end or perform any other activity related to the key update process in response to receiving the second indication. This may include, for example, transmitting a third indication to the second UE of the UE 10. By way of example, the third indication may include information indicating that the key has been updated by the second UE. In this case, the process step S302 may be subsequently executed in response to receiving such a third indication from the second UE.

[0110] Additionally or alternatively, Figure 3A the process 300 may optionally further include a process step S304. In the process step S304, in the case where the key is successfully updated, the UE 10 may perform transmission and / or reception with the second UE using the updated key.

[0111] Alternatively, in the process step S304, in the case where the key is not successfully updated, the UE 10 may perform transmission and / or reception with the second UE using the previously configured key.

[0112] As described above, when using a conventional key update process, problems may occur due to misalignment between two UEs with keys for transmission and reception, where a first UE 10 transmits a message using a first key and a second UE 20 attempts to receive the message using a different key. This may result in the message not being received correctly and subsequently a reduction in throughput in unicast SL communication.

[0113] By updating the configuration for performing the transmission / reception process of UE 10 such that, in response to receiving a first indication including sidelink signaling, the key is updated based on the updated configuration for performing the transmission / reception process, it is possible to ensure that the update of the key is synchronized with the transmission or reception via the sidelink by UE 10. That is, when receiving a first indication including sidelink signaling, the key can be appropriately updated such that any transmission or reception performed via the sidelink in response to the reception of the first indication can be performed using the appropriately updated key.

[0114] Thus, Figure 3A process 300 may help ensure that transmissions and receptions via the sidelink use appropriate keys.

[0115] Figure 3B FIG. is a flowchart showing a process 320 by which a UE may perform direct sidelink communication according to a second example aspect herein. Optional process steps are indicated by Figure 3B dashed lines in.

[0116] Process 320 is described herein as being performed by Figure 2 UE 10. Additionally or alternatively, Figure 2 UE 20 may be configured to perform Figure 3B process 320.

[0117] In Figure 3B process step S321 of, UE 10 receives a first indication including sidelink signaling. Figure 3B Process step S321 of corresponds to Figure 3A process step S301 of, and thus Figure 3A the above description of process step S301 of also applies to Figure 3B process step S321 of.

[0118] In Figure 3B process step S322 of, UE 10 suspends at least one data transmission / reception process in response to receiving the first indication. For example, the control unit 110 of UE 10 may be configured to suspend at least one data transmission / reception process.

[0119] UE 10 may suspend at least one data transmission / reception process in response to receiving a first indication, since the suspension step is after the reception of the first indication and depends on the reception of the first indication.

[0120] The at least one data transmission / reception process may include, for example, any process, procedure, or mechanism performed by UE 10 at any layer of the protocol stack that allows UE 10 to perform unicast sidelink communication with another UE (e.g., Figure 2 UE 20). Specifically, the at least one data transmission / reception process may, for example, allow UE 10 to transmit and / or receive data using direct sidelink communication.

[0121] In this case, by suspending the at least one data transmission / reception process, UE 10 can be prevented from transmitting and / or receiving data using direct sidelink communication. Thus, suspending the at least one data transmission / reception process may alternatively be referred to as suspending data.

[0122] By way of example, as in this example, suspending the at least one data transmission / reception process may include at least one of the following:

[0123] ● Suspending a bearer, a Packet Data Convergence Protocol (PDCP) entity, and / or a Radio Link Control (RLC) entity; and

[0124] ● Suspending transmission and / or reception.

[0125] Figure 3B Process 320 may optionally further include process step S323. In process step S323, UE 10 transmits a second indication to a second UE (e.g., Figure 2 UE 20). As in this example, the transmission / reception part 120 of UE 10 may be configured to transmit the second indication to the second UE.

[0126] As in this example, optional process step S323 may be performed before process step S322 and the second indication may include, for example, information indicating that the at least one data transmission / reception process is in or to be suspended, information configured to initiate a key update process, and / or information related to the key update process. Alternatively, optional process step S323 may be performed subsequently and in response to process step S322, and the second indication may include, for example, information indicating that the at least one data transmission / reception process has been suspended, information configured to initiate a key update process, and / or information related to the key update process.

[0127] By way of example, the second indication may include at least one of the following:

[0128] ● PC5-S signaling, for example, DIRECT_REKEYING_REQUEST, direct security mode command, DIRECT_SECURITY_MODE_COMPLETE, DIRECT_REKEYING_RESPONSE;

[0129] ● PC5-RRC signaling, for example, RRC reconfiguration for sidelink, RRC reconfiguration complete for sidelink;

[0130] ● User plane indication, for example, control PDU of SDAP, PDCP, or RLC or MAC CE.

[0131] As described above, when using a conventional key update process, problems may occur due to misalignment between the keys used by two UEs for transmission and reception, where the first UE 10 transmits a message using a first key and the second UE 20 attempts to receive the message using a different key. This may result in incorrect reception of the message and subsequently reduced throughput in unicast SL communication.

[0132] It is possible to ensure that the UE 10 does not perform transmission or reception on the sidelink by pausing at least one data transmission / reception process in response to receiving a first indication including sidelink signaling. This can be advantageous in cases where the UE is unsure whether a second UE (e.g., UE 20) with which it performs unicast sidelink communication has properly updated the key. Thus, a situation where the first UE 10 transmits a message using a first key and the second UE attempts to receive the message using a different key can be avoided.

[0133] Therefore, Figure 3B process 320 can help reduce incorrect reception of messages in direct sidelink communication.

[0134] Figure 3C FIG. 330 is a flowchart showing a process by which a UE can perform direct sidelink communication according to a third example aspect herein. Optional process steps are indicated by Figure 3B dashed lines in FIG.

[0135] Process 330 is described herein as being performed by Figure 2 UE 10. Additionally or alternatively, Figure 2 UE 20 can be configured to perform Figure 3C process 330.

[0136] In Figure 3C process step S331, UE 10 receives a first indication including sidelink signaling. Figure 3C Process step S331 corresponds to Figure 3A process step S301 and Figure 3Bprocess step S321, and thus Figure 3A the above description of process step S301 also applies to Figure 3C process step S331.

[0137] In Figure 3C process step S332, UE 10 resumes at least one data transmission / reception process in response to receiving a first indication.

[0138] UE 10 may resume at least one data transmission / reception process in response to receiving a first indication because the resume step is after and depends on the reception of the first indication. For example, the control unit 110 of UE 10 may be configured to resume at least one data transmission / reception process.

[0139] As in this example, at least one data transmission / reception process may include any process, procedure, or mechanism performed by UE 10 at any layer of the protocol stack that allows UE 10 to perform unicast sidelink communication with another UE (e.g., Figure 2 UE 20) and that has been pre-suspended. Specifically, at least one data transmission / reception process may, for example, allow UE 10 to transmit and / or receive data using direct sidelink communication.

[0140] In this case, by resuming at least one data transmission / reception process, UE 10 can be enabled to resume transmitting and / or receiving data using direct sidelink communication. Thus, resuming at least one data transmission / reception process may alternatively be referred to as resuming data.

[0141] By way of example, as in this example, resuming at least one data transmission / reception process may include at least one of the following:

[0142] ● Resuming a bearer, a Packet Data Convergence Protocol (PDCP) entity, and / or a Radio Link Control (RLC) entity; and

[0143] ● Performing at least one PDCP layer action, including at least one of the following: re-establishing, changing keys, compression protocol reset, and retransmission of unacknowledged data.

[0144] Figure 3C Process 330 may optionally further include process step S333. In process step S333, UE 10 transmits a second indication to a second UE (e.g., Figure 2 UE 20). As in this example, the transmission / reception part 120 of UE 10 may be configured to transmit the second indication to the second UE.

[0145] As in this example, the optional process step S333 may be performed before process step S332 and the second indication may include, for example, information indicating that at least one data transmission / reception process is resuming or to be resumed, information configured to initiate a key update process, and / or information related to the key update process. Alternatively, the optional process step S333 may be performed subsequently and in response to process step S332, and the second indication may include, for example, information indicating that at least one data transmission / reception process has resumed, information configured to initiate a key update process, and / or information related to the key update process.

[0146] By way of example, the second indication may include at least one of the following:

[0147] ● PC5-S signaling, for example, DIRECT_REKEYING_REQUEST, direct security mode command, DIRECT_SECURITY_MODE_COMPLETE, DIRECT_REKEYING_RESPONSE;

[0148] ● PC5-RRC signaling, for example, RRC reconfiguration sidelink, RRC reconfiguration complete sidelink;

[0149] ● User plane indication, for example, control PDU of SDAP, PDCP, or RLC or MAC CE.

[0150] In the case where process step S333 is performed before process step S332, the second UE may update the key at its end or perform any other activity related to the key update process in response to receiving the second indication. This may include, for example, transmitting a third indication to the second UE of UE 10. By way of example, the third indication may include information indicating that the key has been updated by the second UE. In this case, process step S332 may be performed subsequently and in response to receiving such a third indication from the second UE.

[0151] As described above, when using a conventional key update process, problems may occur due to misalignment between the two UEs for the keys used for transmission and reception, where the first UE 10 transmits a message using a first key and the second UE 20 attempts to receive the message using a different key. This may result in incorrect reception of the message and subsequently reduced throughput in unicast SL communication.

[0152] By resuming at least one data transmission / reception process in response to receiving a first indication including sidelink signaling, UE 10 may selectively perform transmission or reception on the sidelink. This may be advantageous in the case where the UE has previously suspended at least one data transmission / reception process and determines that a second UE (e.g., UE 20) with which it performs unicast sidelink communication has properly updated the key.

[0153] Thus, the UE 10 can control the resumption of transmission or reception on the sidelink such that, for example, the resumption of transmission or reception on the sidelink is only performed when the key is properly updated, thereby avoiding a situation where the first UE 10 transmits a message using the first key and the second UE attempts to receive the message using a different key.

[0154] Thus, Figure 3C the process 330 of

[0155] Additionally, the steps of any one of the process 300 of Figure 3A the process 320 of Figure 3B and the process 330 of Figure 3C can be combined to achieve further advantages.

[0156] By way of example, Figure 3A the process 300 of Figure 3B can be modified to further include pausing at least one data transmission / reception process by the UE 10 in response to receiving a first indication as described in the process step S322 of

[0157] The pausing step can be performed Figure 3A before the process step S302 of

[0158] In this way, it can be advantageously ensured that at least one data transmission / reception process is paused when the key is updated. In this way, misalignment between the two UEs for the keys used for transmission and reception can be reduced or avoided, where the first UE 10 transmits a message using the first key and the second UE 20 attempts to receive the message using a different key. Figure 3A Alternatively, in the case where the optional process step S303 of the process 300 of Figure 2 is performed before the process step S302 of the process 300, the pausing step can be performed before the process step S303. In this case, it can be advantageously ensured that at least one data transmission / reception process is paused before notifying the second UE (e.g.,

[0159] the UE 20 of Figure 3Ais performed after process step S302 of. In this way, it can be advantageously ensured that once the key is updated, at least one data transmission / reception process is suspended until the corresponding update of the key is generated in the second UE. In this way, misalignment between the two UEs for the keys used for transmission and reception can be reduced or avoided, where the first UE 10 transmits a message using a first key and the second UE 20 attempts to receive the message using a different key.

[0160] Additionally or alternatively, Figure 3A process 300 of can be modified to include the recovery by UE 10 of at least one data transmission / reception process as described for Figure 3C process step S332 of.

[0161] The recovery step can be performed after Figure 3A process step S302 of. In this way, it can be advantageously ensured that at least one data transmission / reception process is recovered only after the key has been successfully updated.

[0162] By way of alternative, in the case where Figure 3A optional process step S303 of process 300 is performed after process step S302 of process 300 and in response to receiving a third indication from the second UE, the recovery step can then be performed to receive the third indication. In this case, it can be advantageously ensured that at least one data transmission / reception process is recovered only after the corresponding successful update of the key has been performed by the second UE (e.g., Figure 2 UE 20 of). In this way, misalignment between the two UEs for the keys used for transmission and reception can be reduced or avoided, where the first UE 10 transmits a message using a first key and the second UE 20 attempts to receive the message using a different key.

[0163] Similarly, in the case where Figure 3A optional process step S303 of process 300 is performed before process step S302 of process 300 and in response to receiving a third indication from the second UE, the recovery step can then be performed to receive the third indication and process step S302. In this case, it can be advantageously ensured that at least one data transmission / reception process is recovered only after the successful update of the key has been first performed by the second UE (e.g., Figure 2 UE 20 of). In this way, misalignment between the two UEs for the keys used for transmission and reception can be reduced or avoided, where the first UE 10 transmits a message using a first key and the second UE 20 attempts to receive the message using a different key.

[0164] Regarding Figure 4 、 Figure 5 and Figure 6 describe how Figure 3A 、Figure 3B and Figure 3C specific examples of the process steps of

[0165] Figure 4 is a schematic sequence diagram of process 400 by which a first UE and a second UE according to a first example aspect in this document can update the security configuration for direct sidelink communication Figure 4 Process 400 is triggered or initiated by an internal indication at the first UE

[0166] The process 400 described in this document enables Figure 2 UE 10 of Figure 2 to act as the first UE and

[0167] In Figure 4 process step S40 of

[0168] the first UE 10 receives a first indication including sidelink signaling. The first indication includes an internal indication from an upper layer. That is, the reception of the first indication by the first UE 10 may include receiving from another higher layer in the protocol stack through a layer in the protocol stack

[0169] In Figure 4 process step S41 of Figure 4 process step S41 corresponds to Figure 3B process step S322 of Figure 3B and thus Figure 4 the above description of process step S322 also applies to

[0170] In Figure 4 process step S42 of

[0171] By way of example, the second indication may include information indicating that the configuration and / or key for performing the transmission / reception procedure of the first UE 10 is being updated or to be updated, information configured to initiate the key update procedure, and / or other information related to the key update procedure. For example, the second indication may include at least one of the following:

[0172] ● PC5-S signaling, such as DIRECT_REKEYING_REQUEST, direct security mode command;

[0173] ● PC5-RRC signaling, such as RRC reconfiguration for sidelink;

[0174] ● User plane indication, such as control PDU of SDAP, PDCP, or RLC or MAC CE.

[0175] In Figure 4 process step S43 of Figure 4 in response to receiving the second indication from the first UE 10, the second UE 20 updates the configuration for performing the transmission / reception procedure of the second UE 20 so as to update the key based on the updated configuration for performing the transmission / reception procedure. Figure 3A process step S43 of Figure 3A corresponds to process step S302 of Figure 4 and thus

[0176] In Figure 4 process step S44 of Figure 4 process step S44 of Figure 3B corresponds to process step S322 of Figure 3B and thus Figure 4 the above description of process step S322 of

[0177] In Figure 4 process step S45 of

[0178] By way of example, the second indication may include information indicating that the configuration and / or key for performing the transmission / reception procedure of the second UE 20 has been updated, and / or other information related to the key update procedure. For example, the second indication may include at least one of the following:

[0179] ● PC5-S signaling, for example, DIRECT_SECURITY_MODE_COMMAND, DIRECT_SECURITY_MODE_COMPLETE, DIRECT_REKEYING_RESPONSE;

[0180] ● PC5-RRC signaling, for example, RRC Reconfiguration for Sidelink, RRC Reconfiguration Complete for Sidelink;

[0181] ● User plane indication, for example, control PDU of SDAP, PDCP, or RLC, or MAC CE.

[0182] In Figure 4 process step S46 of Figure 4 in response to receiving a third indication, the first UE 10 updates the configuration for performing the transmission / reception process of the UE 10, so as to update the key based on the updated configuration for performing the transmission / reception process. Figure 3A process step S46 of Figure 3A corresponds to process step S302 of Figure 4 and thus the above description of process step S302 of

[0183] In Figure 4 process step S47 of Figure 4 the first UE 10 resumes at least one data transmission / reception process. Figure 3C process step S47 of Figure 3C corresponds to process step S332 of Figure 4 and thus the above description of process step S332 of

[0184] In Figure 4 process step S48 of

[0185] By way of example, the fourth indication may include information indicating that at least one data transmission / reception process has been resumed, and / or other information related to the key update process. For example, the second indication may include at least one of the following:

[0186] ● PC5-S signaling, for example, DIRECT_SECURITY_MODE_COMPLETE, DIRECT_REKEYING_RESPONSE;

[0187] ● PC5-RRC signaling, for example, RRC Reconfiguration for Sidelink, RRC Reconfiguration Complete for Sidelink;

[0188] ● User plane indication, e.g., control PDU of SDAP, PDCP, or RLC or MAC CE.

[0189] In Figure 4 process step S49 of Figure 4 in response to receiving a fourth indication from the first UE 10, the second UE 20 resumes at least one data transmission / reception process. Figure 3C process step S49 corresponds to Figure 3C process step S332 of Figure 4 and thus the above description of process step S332 of

[0190] According to Figure 4 process 400 of

[0191] before transmitting a second indication to the second UE 20 and before updating its own key, the first UE 10 pauses at least one data transmission / reception process. In this way, it can be advantageously ensured that at least one data transmission / reception process is paused when the first UE updates its key, and data transmission to the second UE or reception of data from the second UE is avoided when the second UE updates its key at the end or performs any other activity related to the key update process in response to receiving the second indication. In this way, misalignment between the keys used for transmission and reception of the two UEs can be reduced or avoided, where the first UE 10 transmits a message using a first key and the second UE 20 attempts to receive the message using a different key. Figure 4 In addition, according to

[0192] process 400 of Figure 4 the second UE 20 updates its own key and then pauses at least one data transmission / reception process. In this way, it can be advantageously ensured that once the key is updated, at least one data transmission / reception process is paused until a corresponding update of the key occurs in the first UE 10. In this way, misalignment between the keys used for transmission and reception of the two UEs can be reduced or avoided, where the first UE 10 transmits a message using a first key and the second UE 20 attempts to receive the message using a different key.

[0193] In addition, according to Figure 4In process 400, the first UE 10 updates its key and then resumes at least one data transmission / reception process. In this way, it can be advantageously ensured that at least one data transmission / reception process is resumed only after the key has been successfully updated.

[0194] Furthermore, according to Figure 4 In process 400, the second UE 20 resumes at least one data transmission / reception process in response to receiving a fourth indication. Thus, it can be advantageously ensured that at least one data transmission / reception process is resumed only after confirming that the first UE 10 has successfully updated its key. In this way, misalignment between the keys used for transmission and reception by the two UEs can be reduced or avoided, where the first UE 10 transmits a message using a first key and the second UE 20 attempts to receive the message using a different key.

[0195] Therefore, Figure 4 Process 400 can be used to avoid incorrect message reception, thus reducing or avoiding throughput degradation in unicast SL communication.

[0196] Figure 5 FIG. is a schematic sequence diagram of process 500 by which a first UE and a second UE according to a second example aspect herein can update a security configuration for direct sidelink communication. Figure 5 Process 500 is triggered or initiated by receiving signaling at the first UE. Figure 5 Process 500 can be triggered or initiated by an internal indication at the second UE or by any other suitable method.

[0197] Process 500 described herein enables Figure 2 UE 10 to act as the first UE and Figure 2 UE 20 to act as the second UE. Alternatively, UE 20 can act as the first UE and UE 10 can act as the second UE.

[0198] In Figure 5 In process step S50, the second UE 20 updates the configuration for performing the transmission / reception process of the second UE 20 in order to update the key based on the updated configuration for performing the transmission / reception process. Figure 5 Process step S50 corresponds to Figure 3A Process step S302, and thus Figure 3A The above description of process step S302 also applies to Figure 5 Process step S50.

[0199] In Figure 5 In process step S51, the second UE 20 pauses at least one data transmission / reception process. Figure 5 Process step S51 corresponds to Figure 3Bprocess step S322, and thus Figure 3B the above description of process step S322 of also applies to Figure 5 process step S51.

[0200] In Figure 5 process step S52, the second UE 20 transmits a first indication to the first UE 10. As in this example, the transmission / reception part 220 of the second UE 20 can be configured to transmit the first indication to the first UE 10.

[0201] By way of example, the first indication may include information indicating that the configuration and / or key for performing the transmission / reception process of the second UE 20 has been updated, information configured to initiate a key update process, and / or other information related to the key update process. For example, the second indication may include at least one of the following:

[0202] ● PC5-S signaling, for example, DIRECT_REKEYING_REQUEST, direct security mode command;

[0203] ● PC5-RRC signaling, for example, RRC reconfiguration sidelink;

[0204] ● User plane indication, for example, control PDU of SDAP, PDCP or RLC or MAC CE.

[0205] In Figure 5 process step S53, in response to receiving the first indication, the first UE 10 updates the configuration for performing the transmission / reception process of the UE 10 in order to update the key based on the updated configuration for performing the transmission / reception process. Figure 5 process step S53 corresponds to Figure 3A process step S302, and thus Figure 3A the above description of process step S302 of also applies to Figure 5 process step S53.

[0206] In Figure 5 process step S54, the first UE 10 transmits a second indication to the second UE 20. As in this example, the transmission / reception part 120 of the first UE 10 can be configured to transmit the second indication to the second UE 20.

[0207] By way of example, the second indication may include information indicating that the configuration and / or key for performing the transmission / reception process of the first UE 10 has been updated, and / or other information related to the key update process. For example, the second indication may include at least one of the following:

[0208] ● PC5-S signaling, e.g., DIRECT_SECURITY_MODE_COMMAND, DIRECT_SECURITY_MODE_COMPLETE, DIRECT_REKEYING_RESPONSE;

[0209] ● PC5-RRC signaling, e.g., RRC Reconfiguration for Sidelink, RRC Reconfiguration Complete for Sidelink;

[0210] ● User plane indication, e.g., control PDU of SDAP, PDCP or RLC or MAC CE.

[0211] In Figure 5 process step S55, in response to receiving a second indication from the first UE 10, the second UE 20 resumes at least one data transmission / reception process. Figure 5 Process step S55 of Figure 3C corresponds to Figure 3C process step S332 of Figure 5 and thus

[0212] The above description of Figure 5 process step S332 also applies to

[0213] process step S55 of Figure 5 According to

[0214] process 500, the second UE 20 updates its own key and then pauses at least one data transmission / reception process. In this way, it can be advantageously ensured that once the key is updated, at least one data transmission / reception process is paused until the corresponding update of the key is generated in the first UE 10. In this way, misalignment between the keys used for transmission and reception in the two UEs can be reduced or avoided, where the first UE 10 transmits a message using a first key and the second UE 20 attempts to receive the message using a different key. Figure 5In process 500, the second UE 20 resumes at least one data transmission / reception process in response to receiving the second indication. Thus, it can be advantageously ensured that at least one data transmission / reception process is resumed only after confirming that the first UE 10 has successfully updated its key. In this way, misalignment between the keys used for transmission and reception by the two UEs can be reduced or avoided, where the first UE 10 transmits a message using the first key and the second UE 20 attempts to receive the message using a different key.

[0215] Therefore, Figure 5 Process 500 can be used to avoid incorrect message reception, thus reducing or avoiding throughput degradation in unicast SL communication.

[0216] Figure 6 A flowchart showing a process 600 by which a first UE 10 performing direct side-link communication with a second user equipment 20 can re-establish a PDCP entity.

[0217] The process 600 described herein enables Figure 2 the UE 10 to act as the first UE and Figure 2 the UE 20 to act as the second UE. Alternatively, the UE 20 can act as the first UE and the UE 10 can act as the second UE.

[0218] In Figure 6 process step S601, the first UE 10 receives a first indication including signaling from the second UE 20, and the first indication is a PDCP user plane indication in the form of a PDCP entity re-establishment request.

[0219] By way of example, the transmission / reception part 120 of the first UE 10 can be configured to receive a PDCP entity re-establishment request from the second UE 20.

[0220] In Figure 6 process step S602, the first UE 10 performs PDCP re-establishment of the PDCP entity (i.e., PDCP re-establishment).

[0221] For example, the UE 10 can perform PDCP re-establishment of the PDCP entity via the SL through which it receives the first indication from the second UE 20 (i.e., the PDCP entity of the PC5 interface). Additionally or alternatively, by way of example, performing PDCP re-establishment of the PDCP entity can include using a new key, receiving a new key from an upper layer, resetting a compression protocol (e.g., the Robust Header Compression (ROHC) protocol), and resetting at least one of one or more variable values.

[0222] Figure 6The process 600 may optionally further include process step S603. In process step S603, UE 10 receives a first direct security mode command after performing PDCP re - establishment of the PDCP entity.

[0223] By way of example, the first direct security mode command is of a first type (first - type direct security mode command). Additionally or alternatively, the transmit / receive part 120 of the first UE 10 may be configured to receive the first direct security mode command.

[0224] Additionally or alternatively, Figure 6 The process 600 may optionally further include process step S604. In process step S604, UE 10 transmits and / or receives user plane and signaling after receiving the first direct security mode command.

[0225] Additionally or alternatively, Figure 6 The process 600 may optionally further include process step S605. In process step S605, UE 10 transmits a second direct security mode command after receiving the first direct security mode command.

[0226] By way of example, the second direct security mode command may belong to a second type (second - type direct security mode command) different from the first type of the first direct security mode command. For example, the second direct security mode command may be a direct security mode completion command.

[0227] Additionally or alternatively, Figure 6 The process 600 may optionally further include process step S606. In process step S606, UE 10 is configured to complete PDCP entity re - establishment upon receiving a direct security mode command.

[0228] Figure 7 Shown is a block diagram of an example signal - processing hardware configuration 700 for either UE 10 or UE 20 according to an example embodiment herein. As in this example embodiment, Figure 2 The programmable signal - processing hardware 700 is configured to act as Figure 7 either UE 10 or UE 20. Figure 2 either UE 10 or UE 20.

[0229] However, it should be noted that Figure 2One or both of the UEs 10, 20 may alternatively be implemented in non-programmable hardware such as, for example, an application-specific integrated circuit (ASIC) or in any other suitable manner using any suitable combination of hardware components and software components such that the UE 100 includes the processing and communication functions necessary to operate in accordance with one or more conventional telecommunications standards, including - but not limited to - LTE, LTE-A, UMTS, 3G, 4G, 5G.

[0230] The programmable signal processing hardware 700 includes a transmit / receive section 710 and one or more antennas 705. The signal processing device 700 also includes a control section 720 (by way of example, a processor such as a Central Processing Unit (CPU) or a Graphics Processing Unit (GPU)), a working memory 730 (e.g., a random access memory), and an instruction store 740 that stores computer-readable instructions that, when executed by the control section 720, cause the control section 720 to perform Figure 2 the functions of either of the UEs 10, 20.

[0231] The instruction store 740 may include a ROM preloaded with computer-readable instructions (e.g., in the form of an electrically-erasable programmable read-only memory (EEPROM) or flash memory). Alternatively, the instruction store 740 may include a RAM or a similar type of memory, and the computer-readable instructions of a computer program may be input thereto from a computer program product (e.g., a non-transitory computer-readable storage medium 750 in the form of a CD-ROM, DVD-ROM, etc. or a computer-readable signal 760 carrying computer-readable instructions).

[0232] Figure 8 FIG. showing an example signal processing hardware configuration 800 of a radio base station 30 according to an example embodiment herein. As in this example embodiment, Figure 2 the programmable signal processing hardware 800 may be configured to act as Figure 2 Figure 2 ​radio base station 30. However, it should be noted that the radio base station 30 may alternatively be implemented in non-programmable hardware such as, for example, an application specific integrated circuit (ASIC) or in any other suitable manner using any suitable combination of hardware components and software components such that the radio base station 30 includes the processing and communication functions necessary to operate in accordance with one or more conventional telecommunication standards, which include - but are not limited to - LTE, LTE-A, UMTS, 3G, 4G, 5G.

[0233] The programmable signal processing hardware 800 includes a transmit / receive section 810 and one or more antennas 805. The signal processing device 800 also includes a network communication interface 815, a control section 820 (by way of example, a processor such as a central processing unit (CPU) or a graphics processing unit (GPU)), a working memory 830 (e.g., random access memory), and an instruction store 840 that stores computer-readable instructions which, when executed by the control section 820, cause the processor 820 to perform Figure 2 the functions of the radio base station 30.

[0234] The instruction store 840 may include a ROM pre-loaded with computer-readable instructions (e.g., in the form of an electrically erasable programmable read-only memory (EEPROM) or flash memory). Alternatively, the instruction store 840 may include a RAM or a similar type of memory, and the computer-readable instructions of the computer program may be input thereto from a computer program product (e.g., a non-transitory computer-readable storage medium 850 in the form of a CD-ROM, DVD-ROM, etc. or a computer-readable signal 860 carrying computer-readable instructions).

[0235] Although detailed embodiments have been described, they are provided only to give a better understanding of the invention as defined by the independent claims and are not to be considered limiting.

Claims

1. A method for a first user equipment to perform direct side - link communication with a second user equipment, the method comprising: Receiving, via a PC5 interface, a first indication including side - link signaling from the second user equipment; In response to receiving the first indication, pausing at least one data transmission / reception process; Before updating a configuration for performing the transmission / reception process, transmitting a second indication to the second user equipment; Receiving a third indication from the second user equipment; In response to receiving the third indication, updating the configuration for performing the transmission / reception process and updating a key based on the updated configuration for performing the transmission / reception process; In response to updating the configuration, resuming the at least one data transmission / reception process; And In response to resuming the at least one data transmission / reception process, transmitting a fourth indication to the second user equipment.

2. The method for a first user equipment to perform direct side - link communication with a second user equipment according to claim 1, wherein the first indication is an internal indication from an upper layer.

3. The method for a first user equipment to perform direct side - link communication with a second user equipment according to claim 1, wherein the second indication includes at least one of the following: DIRECT_REKEYING_REQUEST, DIRECT SECURITY MODE COMMAND, DIRECT_SECURITY_MODE_COMPLETE.

4. A first user equipment configured to perform direct side - link communication with a second user equipment, the first user equipment comprising: A control part; A transmission / reception part; And A memory, Wherein: The first user equipment is configured to: Receive, via a PC5 interface, a first indication including side - link signaling from the second user equipment; In response to receiving the first indication, pause at least one data transmission / reception process; Before updating a configuration for performing the transmission / reception process, transmit a second indication to the second user equipment; Receive a third indication from the second user equipment; In response to receiving the third indication, update the configuration for performing the transmission / reception process and update a key based on the updated configuration for performing the transmission / reception process; In response to updating the configuration, resume the at least one data transmission / reception process; and In response to resuming the at least one data transmission / reception process, transmit a fourth indication to the second user equipment.

5. The first user equipment according to claim 4, wherein the first indication is an internal indication from an upper layer.

6. The first user equipment according to claim 4, wherein the second indication includes at least one of the following: DIRECT_REKEYING_REQUEST, DIRECT SECURITY MODE COMMAND, DIRECT_SECURITY_MODE_COMPLETE.

7. A method for a second user equipment to perform direct side - link communication with a first user equipment, the method comprising: Update the configuration for performing the transmission / reception process, and update the key based on the updated configuration for performing the transmission / reception process; Suspend at least one data transmission / reception process; Send a first indication including sidelink signaling to the first user equipment via the PC5 interface, where the first indication controls the first user equipment to update the configuration for performing the transmission / reception process and update the key based on the updated configuration for performing the transmission / reception process; Receive a second indication from the first user equipment; In response to receiving the second indication, resume the at least one data transmission / reception process.

8. The method for a second user equipment and a first user equipment to perform direct sidelink communication according to claim 7, wherein the second indication includes at least one of the following: DIRECT_REKEYING_REQUEST, DIRECT SECURITY MODE COMMAND, DIRECT_SECURITY_MODE_COMPLETE.

9. A second user equipment configured to perform direct sidelink communication with a first user equipment, the second user equipment comprising: A control part; A transmission / reception part; And A memory, Wherein: The second user equipment is configured to: Update the configuration for performing the transmission / reception process, and update the key based on the updated configuration for performing the transmission / reception process; Suspend at least one data transmission / reception process; Send a first indication including sidelink signaling to the first user equipment via the PC5 interface, where the first indication controls the first user equipment to update the configuration for performing the transmission / reception process and update the key based on the updated configuration for performing the transmission / reception process; Receive a second indication from the first user equipment; In response to receiving the second indication, resume the at least one data transmission / reception process.

10. The second user equipment according to claim 9, wherein the second indication includes at least one of the following: DIRECT_REKEYING_REQUEST, DIRECT SECURITY MODE COMMAND, DIRECT_SECURITY_MODE_COMPLETE.

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