CN115996445A

CN115996445A - System information acquisition method and user equipment

Info

Publication number: CN115996445A
Application number: CN202211156283.XA
Authority: CN
Inventors: 王学龙
Original assignee: MediaTek Singapore Pte Ltd
Current assignee: MediaTek Singapore Pte Ltd
Priority date: 2021-10-19
Filing date: 2022-09-22
Publication date: 2023-04-21
Also published as: WO2023065107A1

Abstract

The embodiment of the invention provides a system information acquisition method and user equipment. The method comprises the following steps: establishing a side link connection with a remote user equipment in a wireless network by a relay user equipment, wherein the relay user equipment is served by an access link of a base station in the wireless network; acquiring a System Information Block (SIB) type list which is interested by the remote user equipment; receiving a short message from the wireless network through the access link; acquiring one or more SIBs from the wireless network based on the received short message; and forwarding one or more selected SIBs to the remote user equipment, wherein each selected SIB is an acquired SIB in a list of SIB types of interest to the remote user equipment. By utilizing the invention, the updated SI can be effectively transmitted to the remote UE.

Description

System information acquisition method and user equipment

Technical Field

The present invention relates to wireless communications, and more particularly to system information (system information, SI) acquisition for Side Link (SL) relay operations.

Background

The 5G radio access technology will become a key component of modern access networks. It will address the high traffic growth and the increasing high bandwidth connection demands. Wireless relay in a cellular network provides extended coverage and improved transmission reliability. Long term evolution (long term evolution, LTE) networks introduced 3GPP SL, which is a direct communication between two User Equipments (UEs) without signal relay by a base station. In 3GPP New Radio (NR), SL continues to evolve. With new functionality supported successively, SL provides low latency, high reliability and high throughput for communication between devices. The use of SL for wireless relay may provide a reliable and efficient way for traffic forwarding. Various applications between the remote UE and the network may rely on communications over a relay channel provided by the relay UE, such as vehicle-to-evaluation (V2X) communications, public Safety (PS) communications, and the like. During sidelink relay operation, the network may update the SI, and the relay UE and the remote UE may need to acquire the updated SI.

Improvements and enhancements are needed to efficiently transmit updated SI for remote UEs.

Disclosure of Invention

The embodiment of the invention provides a system information acquisition method, which is used for relay user equipment and comprises the following steps: establishing a side link connection with a remote user equipment in a wireless network by the relay user equipment, wherein the relay user equipment is served by an access link of a base station in the wireless network; acquiring a System Information Block (SIB) type list which is interested by the remote user equipment; receiving a short message from the wireless network through the access link; acquiring one or more SIBs from the wireless network based on the received short message; and forwarding one or more selected SIBs to the remote user equipment, wherein each selected SIB is an acquired SIB in a list of SIB types of interest to the remote user equipment.

Another embodiment of the present invention provides a user equipment, including: a transceiver for receiving and transmitting radio frequency signals in a wireless network; a side link connection manager for establishing a side link connection in the wireless network with a remote user equipment, wherein the user equipment is served by an access link of a base station in the wireless network; an interest list processor, configured to obtain a SIB type list of a system information block of interest to the user equipment; a short message processor for receiving a short message from the wireless network via the access link; an acquisition processor configured to acquire one or more SIBs from the wireless network based on the received short message; and a SIB processor for forwarding one or more selected SIBs to the remote user equipment, wherein each selected SIB is an acquired SIB in a SIB type list of interest to the remote user equipment.

The present invention further provides a storage medium storing a program that, when executed, causes a user equipment to execute the steps of the system information acquisition method in the present application.

By utilizing the invention, the updated SI can be effectively transmitted to the remote UE.

Drawings

The drawings illustrate embodiments of the invention, wherein like numerals indicate like components.

Fig. 1 is a system diagram of an exemplary wireless network for system information acquisition for side link relay operation in accordance with an embodiment of the present invention.

Fig. 2 is a schematic diagram of an exemplary NR wireless system with a centralized upper layer of NR radio interface stacks according to an embodiment of the present invention.

Fig. 3A is an exemplary schematic diagram of an NR wireless network integrating two UEs according to an embodiment of the present invention.

Fig. 3B is an exemplary diagram of an NR wireless network with SI acquisition by a plurality of remote UEs through side link relay according to an embodiment of the present invention.

Fig. 4 is an exemplary flow diagram of a relay UE transmitting an updated SIB of interest to a remote UE over a side link to the remote UE in accordance with an embodiment of the present invention.

Fig. 5 is an exemplary diagram of a detailed procedure in which a relay UE acquires SI through a side chain according to an embodiment of the present invention.

Fig. 6 is an exemplary flowchart of acquiring SI through a side link relay operation according to an embodiment of the present invention.

Detailed Description

Reference will now be made in detail to some embodiments of the present invention, examples of which are illustrated in the accompanying drawings.

Several aspects of the telecommunications system will now be described with reference to various apparatus and methods, which are described in the following detailed description, and which are illustrated in the accompanying drawings by various blocks, components, circuits, processes, algorithms, etc., collectively referred to as "elements". These elements may be implemented using electronic hardware, computer software, or any combination thereof. Whether such elements are implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system.

Fig. 1 is a system diagram of an exemplary wireless network for system information acquisition for side link relay operation in accordance with an embodiment of the present invention. The wireless network may be an NR network or employ other radio access technologies. The wireless network supports various wireless communication services. These services may have different quality of service (quality of service, qoS) requirements, such as latency and reliability requirements. The wireless network 100 includes one or more fixed infrastructure elements that form a network that is distributed over a geographic area. The base unit may also be referred to as an access point, an access terminal, a base station, a node B, an evolved node B (eNode-B), a next generation node B (gNB), or other terminology used in the art. The network may be a homogeneous network or a heterogeneous network, and may be deployed using the same or different frequencies. The gNB101 and the gNB102 are base stations in the NR network, and service areas thereof may or may not overlap with each other. A backhaul connection (backhaul connection) such as 141 connects non-co-located receiving base stations such as the

gnbs

101, 102. These backhaul connections may or may not be ideal. gNB101 is connected to gNB102 through an Xn interface.

The wireless network 100 also includes a plurality of communication devices or mobile stations, such as UEs 111, 112, 113 and 114. The UE may also be referred to as a mobile terminal, mobile phone, smart phone, wearable device, ioT device, tablet, notebook, or other terminology used in the art. An exemplary mobile device in wireless network 100 has SL functionality. The mobile device may establish one or more connections with one or more base stations (e.g., gNB101, 102). It is also possible for a mobile device to disconnect from a base station on its access link, but to send and receive data packets with another mobile station or stations or one or more base stations over the SL connection. The disconnected UE may be an in-coverage UE or an out-of-coverage UE. An out-of-coverage UE may also obtain SI updates through a side link connection.

UE111, acting as a relay UE, is served by access link 131 of gNB 101. UE111 also establishes a sidelink 121 with remote UE 112, a sidelink 122 with remote UE 113, and a sidelink 123 with remote UE 114. In an embodiment, the remote UE obtains SI and/or SI updates through a side link PC5 interface. The SI may be one or more system information blocks (system information block, SIBs). In one scenario, there is no active access link/Uu interface link between the remote UE 112 and the wireless network 100 within coverage, such as when the remote UE 112 is in an RRC idle or RRC inactive state. Remote UE 112 receives SI updates and other system information on side link 121 through relay UE 111. In other scenarios, an in-coverage UE 113 has an Uplink (UL) and Downlink (DL) connection with the gNB102 via an access link connection/Uu interface 132 and a sidelink connection 122 with the UE 111. UE 113 may obtain any necessary SI through Uu interface connection 132 or through a side link/PC 5 interface connection 122 with relay UE 111. In yet another scenario, the out-of-coverage UE 114 has no access link/Uu interface link with the wireless network 100. Out-of-coverage UE 114 receives SI updates and other system information over sidelink 123 through relay UE 111.

Fig. 1 further shows a simplified block schematic diagram of a base station and a mobile device/UE for system information acquisition. The gNB102 has an antenna 156 that transmits and receives radio signals. RF transceiver circuitry 153 coupled to the antenna receives RF signals from antenna 156, converts the RF signals to baseband signals, and sends the baseband signals to processor 152. The RF transceiver 153 also converts baseband signals received from the processor 152 into RF signals and sends to the antenna 156. The processor 152 processes the received baseband signals and invokes different functional modules to perform the functional features in the gNB 102. Memory 151 stores program instructions and data 154 to control the operation of gNB 102. The gNB102 also includes a set of control modules 155 for performing the functional tasks to communicate with the mobile station.

UE111 has an antenna 165 for transmitting and receiving radio signals. An RF transceiver circuit 163 coupled to the antenna receives RF signals from the antenna 165, converts the RF signals to baseband signals, and sends the baseband signals to the processor 162. In one embodiment, the RF transceiver may include two RF modules (not shown). The first RF module is used for High Frequency (HF) transmission and reception; another RF module is different from the HF transceiver for transmission and reception of different frequency bands. The RF transceiver 163 also converts the baseband signal received from the processor 162 into an RF signal and transmits to the antenna 165. The processor 162 processes the received baseband signal and invokes different functional modules to perform functional features in the UE 111. Memory 161 stores program instructions and data 164 to control the operation of UE 111. Antenna 165 sends uplink transmissions to antenna 156 of gNB101 and receives downlink transmissions from antenna 156 of gNB 101.

UE111 also includes a set of control modules for performing functional tasks. These control modules may be implemented in circuitry, software, firmware, or a combination of the above. The side link connection manager 191 establishes SL connections in the wireless network where the UE is served by the access link of the base station in the wireless network. The interest list processor 192 obtains a list of SIB types of interest to the remote UE. The short message processor 193 receives a short message from a wireless network through an access link. The acquisition processor 194 acquires one or more SIBs from the wireless network based on the received short message. The SIB processor 195 forwards one or more selected SIBs to the remote UE, wherein each selected SIB is an acquired SIB on a SIB type list of interest for the remote UE. The storage manager 196 stores a list of SIB types of interest to the remote UE in the remote UE context of the remote UE during the lifetime of the remote UE.

Fig. 2 is a schematic diagram of an exemplary NR wireless system with a centralized upper layer of NR radio interface stacks according to an embodiment of the present invention. Different protocol split options are possible between Central Units (CUs) and Distributed Units (DUs) of the gNB node. The functional partitioning between CUs and DUs of the gNB node may depend on the transport layer. The low performance transmission between the CUs and DUs of the gNB node may enable the higher protocol layers of the NR radio stack to be supported in the CUs, since the higher protocol layers have lower performance requirements on the transport layers in terms of bandwidth, delay, synchronization and jitter. In one embodiment, the service data adaptation protocol (service data adaptation protocol, SDAP) and packet data convergence protocol (packet data convergence protocol, PDCP) layers are located at the CU, while the radio link control (radio link control, RLC), medium access control (media access control, MAC) and Physical (PHY) layers are located at the DU. The core unit (core unit) 201 is connected to a central unit 211 having a gNB upper layer 252. In an embodiment 250, the gNB upper layer 252 includes a PDCP layer and an optional SDAP layer. The central unit 211 is connected to distributed

units

221, 222, and 223, wherein the distributed

units

221, 222, and 223 correspond to

cells

231, 232, and 233, respectively. Distributed

units

221, 222, and 223 include a gNB lower layer 251. In an embodiment, the gNB lower layer 251 includes PHY, MAC, and RLC layers. In another embodiment 260, each gNB has a protocol stack 261 including SDAP, PDCP, RLC, MAC and a PHY layer.

In an embodiment, the SI/SIB update is communicated by the relay UE to the remote UE through a sidelink connection between the remote UE and the relay UE. The side link relay may be configured as a one-hop relay or a multi-hop relay. Further, the relay UE may be configured to forward SI/SIB updates to multiple remote UEs.

Fig. 3A is an exemplary schematic diagram of an NR wireless network integrating two UEs according to an embodiment of the present invention. Remote UE 301 establishes a relay path with gNB 302 through relay UE 303. Relay UE303 communicates with gNB 302 via access link 311. Relay UE303 communicates with remote UE 301 over side link 312. The gNB 302 transmits data packets destined for the remote UE 301 to the relay UE303 through DL and receives data packets from the remote UE 301 from the relay UE303 through UL. In an NR network, gNB 302 is connected to network entity 304 through S1 link 313. Relay UE303 relays traffic between the gNB 302 and the remote UE 301. Relay UE303 may operate as a layer 2 relay or a layer 3 relay. In an embodiment, relay UE303 relays SI requests to gNB 302 for remote UE 301 when remote UE 301 is in an RRC idle state. In another embodiment, when remote UE 301 is in an RRC connected state, remote UE 301 has an access link including UL and DL with gNB 302 and a side link 312 established with relay UE 303. In an NR system, remote UE 301 may obtain SI updates through its access link/Uu interface link directly connected with gNB 302. The remote UE 301 in RRC connected state may also obtain SI updates from the side link connection/PC 5 interface connection 312 through the relay UE 303.

In an example, in step 331, relay UE303 obtains and maintains a list of SIB types of interest to remote UE 301. Relay UE303 receives the short message from the gNB 302, acquires the updated SI/SIB, and forwards the updated SIB of interest to remote UE 301.

In the NR network, a short message in paging downlink control information (downlink control information, DCI) is used to send SI modification and public warning system (public warning system, PWS) notifications to the UE. In step 321, relay UE303 receives the short message from the gNB 302. A paging radio network temporary identifier (paging radio network temporary identifier, P-RNTI) may be used to send a short message over a physical downlink control channel (physical downlink control channel, PDCCH) via the short message field of DCI format 1_0, with or without associated paging messages. In an example, the relay UE303 obtains the updated SI/PWS based on the short message in step 332 and forwards the SI/PWS to the remote UE 301 via a side link connection through a PC5RRC message in step 322. In another option, the relay UE303 forwards the short message to the remote UE 301.

Fig. 3B is an exemplary diagram of an NR wireless network with SI acquisition by a plurality of remote UEs through side link relay according to an embodiment of the present invention. Relay UE 353 establishes access link 361 with gNB 352. Remote UE 351 in coverage establishes a side link 362 with relay UE 353. An out-of-coverage remote UE355 establishes a side link 363 with relay UE 353. In an embodiment, relay UE 353 forwards SI/PWS to in-coverage UE 351 and out-of-coverage UE 355. In step 381, relay UE 353 obtains a list of SIB types of interest for each remote UE (including in-coverage UE 351 and out-of-coverage UE 355). In an embodiment, the list of SIB types of interest for each UE is stored in a remote UE context of the remote UE for the lifecycle of the respective remote UE. For example, a list of SIB types of interest to the remote UE 351 is stored in the remote UE context of the UE 351; the list of SIB types of interest to the remote UE355 is stored in the remote UE context of the UE 355. In step 371, relay UE 353 receives a short message indicating SI modification and/or PWS notification. In step 382, relay UE 353 acquires the updated SI/SIB indicated in the short message. In an example, relay UE 353 maintains a list of SIB types of interest for each remote UE and forwards updated SIBs on the list of SIB types of interest to the respective remote UE using side chains. For example, in step 372, relay UE 353 forwards the updated SIBs of interest to remote UE 351 via a PC5RRC message. In step 373, relay UE 353 forwards the updated SIBs of interest to remote UE355 via a PC5RRC message.

In one example, the relay UE receives a short message from the gNB, acquires the SI/PWS and sends it to the remote UE. The potential signaling between the remote UE in RRC connected state and the gNB through Uu can be avoided by only sending the modified SI to the remote UE (in RRC connected state or RRC idle/RRC inactive state), since the remote UE does not need to request SI in on-demand (on-demand) manner over the Uu interface. Potential signaling on the PC5 interface of the side link between the remote UE and the relay UE in RRC idle/RRC inactive state can also be avoided, since the remote UE does not need to request SI from the relay UE in an on-demand manner over the PC5 interface.

Fig. 4 is an exemplary flow diagram of a relay UE transmitting an updated SIB of interest to a remote UE over a side link to the remote UE in accordance with an embodiment of the present invention. Relay UE 401 has an access link connection 411 with the gNB 403. Relay UE 401 is also connected to remote UE 402 by a side link 412. In step 431, relay UE 401 obtains a list of SIB types of interest from remote UE 402. Remote UE 402 may send the list of SIB types of interest to relay UE 401 during or after PC5 connection establishment. In other embodiments, relay UE 401 obtains and/or updates the list of SIB types of interest for remote UE 402 by maintaining a list of all SIB requests from remote UE 402. In step 432, relay UE 401 receives the short message from gNB403 over the Uu interface. In step 421, relay UE 401 acquires the updated SIB from the network after receiving the short message. In step 433, relay UE 401 forwards only those SIBs of interest to remote UE 402. From the perspective of PC5-RRC, the above example specifies a "SIB subscription" type of signaling exchange between the relay UE and the remote UE. Remote UE 402 sends the SIB list of interest to relay UE 401 via an existing PC5-RRC message or a new PC5-RRC message. In an embodiment, the PC5-RRC message is a new PC5-RRC message used during PC5RRC connection setup. Upon receiving the list, relay UE 401 maintains the list in the remote UE context for the life of the remote UE (i.e., as long as the remote UE, such as remote UE 402, is still connected to the relay UE through PC 5). As such, when relay UE 401 acquires the updated SIBs from the network, relay UE 401 transmits only SIBs of interest to remote UE 402 through PC5 RRC. In an embodiment, relay UE 401 records all SIBs requested by remote UE 402 (e.g., via a PC5RRC message) during the lifecycle of establishing a PC5RRC connection between relay UE 401 and remote UE 402. Based on the SIB request from the remote UE, relay UE 401 maintains a list of SIBs of interest to the remote UE. When relay UE 401 receives a short message from the network, relay UE 401 first acquires the SIB. In an embodiment, when relay UE 401 is in an RRC connected state, relay UE 401 may acquire one or more SIBs through an on-demand SIB acquisition procedure, such as through its own dedicated SIB request (dedicatedSIBRequest). Subsequently, relay UE 401 transmits only SIBs of interest to remote UE 402 through PC5 RRC.

In another example (not shown in the figure), when the remote UE 402 establishes an RRC connection with the base station/gNB 403, the remote UE 402 may perform an on-demand procedure, such as requesting a SIB from the network through a dedicatedSIBRequest signaling via the Uu interface. The gNB403 may record the above request from the remote UE 402 in its UE context. Subsequently, the gNB403 informs the relay UE 401 of the SIB interest (e.g., SIB type list) of the remote UE through an RRC message such as an RRC reconfiguration message. This may occur when relay UE 401 starts its relay service or during a relay operation. After relay UE 401 receives the SIB interest (e.g., SIB list) of the remote UE, relay UE 401 maintains the list in the remote UE context for the lifetime of the remote UE (i.e., as long as remote UE 402 remains connected to relay UE 401 through PC 5). As such, when relay UE 401 acquires updated SI from the network, relay UE 401 transmits only SIBs of interest to remote UE 402 through PC5 RRC. In another example, when relay UE 401 receives a short message from the network, relay UE 401 first acquires SI (e.g., through its own dedicatedSIBRequest when relay UE 401 is in RRC connected state). Subsequently, relay UE 401 transmits the modified SIB type list to remote UE 402. When the remote UE 402 receives the modified SIB type list, if the remote UE 402 needs a modified SIB, it may request the modified SIB on the PC5 by an on-demand request. As such, relay UE 401 sends only SIBs of interest to remote UE 402 through PC5 RRC.

Fig. 5 is an exemplary diagram of a detailed procedure in which a relay UE acquires SI through a side chain according to an embodiment of the present invention. The relay UE establishes an access link with a gNB in the wireless network. The relay UE acquires a SIB type list of interest to the remote UE in step 501. The SIB type list of interest to the remote UE may be obtained by PC5RRC message during or after the sidelink establishment. The PC5RRC message may be an existing PC5RRC message or a new PC5RRC message. When a side link is established between the relay UE and the remote UE, the remote UE may inform/update the SIB type list of interest in any UE state (including RRC connected, RRC idle, and RRC inactive state). The remote UE may be in coverage or out of coverage.

In step 502, the relay UE maintains or stores a list of SIB types of interest for each remote UE. The relay UE obtains and/or updates the SIB type list of interest to the respective remote UE during the lifetime of the remote UE (during the time the PC5 connection is active). The relay UE may maintain a plurality of SIB type lists of interest for a plurality of respective remote UEs. The list of SIB types of interest is maintained in the UE context of the corresponding remote UE.

When the relay UE receives a short message in step 503, the relay UE considers all remote UEs having a side link connection to operate on the short message. The short message received from the network indicates an SI update and/or a PWS notification. The SI update indication may be SIB1 with the update. In an embodiment, the PWS SIB is forwarded to the remote UE when the remote UE is in an RRC idle or RRC inactive state. In another embodiment, SIB1 is forwarded to the remote UE when SIB1 is updated.

In step 504, the relay UE acquires the SIB. In an embodiment, the relay UE obtains an updated SIB based on the received short message. The relay UE may employ an on-demand SI/SIB acquisition procedure, e.g., acquired through a dedicatedSIBRequest when the relay UE is in an RRC connected state. The relay UE receives SI/SIB updates over an access link with the gNB.

In step 505, the relay UE forwards one or more SIBs/SIs to the remote UE. Since the relay UE maintains a list of SIB types of interest for each remote UE, only SIBs of interest for each UE are forwarded to each respective UE. In an embodiment, the SIB1 update is forwarded to the remote UE. In another embodiment, the PWS SIB is forwarded to the remote UE.

Fig. 6 is an exemplary flowchart of acquiring SI through a side link relay operation according to an embodiment of the present invention. In step 601, the UE establishes a sidelink connection with a remote UE in the wireless network, wherein the relay UE is served by an access link of a base station in the wireless network. In step 602, the UE obtains a list of system information block types of interest to the remote UE. In step 603, the ue receives a short message from the wireless network over the access link. In step 604, the ue obtains one or more SIBs from the wireless network based on the received short message. In step 605, the UE forwards one or more selected SIBs to the remote UE, wherein each selected SIB is an acquired SIB on a SIB type list of interest to the remote UE.

In one embodiment, a storage medium (e.g., a computer-readable storage medium) stores a program that, when executed, causes a UE to perform embodiments of the present invention.

Although the invention has been described in connection with specific embodiments for purposes of illustration, the invention is not limited thereto. Accordingly, various modifications, adaptations, and combinations of the various features of the described embodiments can be practiced without departing from the scope of the invention as set forth in the claims.

Claims

1. A method for acquiring system information is used for relay user equipment and comprises the following steps:

establishing a side link connection with a remote user equipment in a wireless network by the relay user equipment, wherein the relay user equipment is served by an access link of a base station in the wireless network;

acquiring a System Information Block (SIB) type list which is interested by the remote user equipment;

receiving a short message from the wireless network through the access link;

acquiring one or more SIBs from the wireless network based on the received short message; and

one or more selected SIBs are forwarded to the remote user equipment, wherein each selected SIB is an acquired SIB in a list of SIB types of interest to the remote user equipment.

2. The method of system information acquisition according to claim 1, wherein the relay user equipment obtains the SIB type list of interest to the remote user equipment via a side link connection with the remote user equipment through a PC5 radio resource control RRC message.

3. The system information acquisition method of claim 2, wherein the PC5RRC message is an existing PC5RRC message.

4. The system information acquisition method of claim 2, wherein the PC5RRC message is a new PC5RRC message used during PC5RRC connection establishment.

5. The system information acquisition method according to claim 1, wherein the short message indicates a system information modification or a public warning system notification.

6. The method of claim 5, wherein a common alert system SIB is forwarded to the remote user equipment.

7. The method of acquiring system information according to claim 5, wherein the short message indicating system information modification is SIB1.

8. The method of system information acquisition of claim 7, wherein the updated SIB1 is forwarded to the remote user equipment.

9. The system information acquisition method of claim 1, wherein the relay user equipment obtains a list of SIB types of interest to the remote user equipment by recording all SIB requests sent by the remote user equipment.

10. The method of system information acquisition of claim 1, wherein the relay user equipment acquires the one or more SIBs through an on-demand SIB acquisition procedure.

11. The method of claim 1, wherein a list of SIB types of interest to the remote user device is stored in a remote user device context of the remote user device during a lifecycle of the remote user device.

12. A user equipment, comprising:

a transceiver for receiving and transmitting radio frequency signals in a wireless network;

a side link connection manager for establishing a side link connection in the wireless network with a remote user equipment, wherein the user equipment is served by an access link of a base station in the wireless network;

an interest list processor, configured to obtain a SIB type list of a system information block of interest to the user equipment;

a short message processor for receiving a short message from the wireless network via the access link;

an acquisition processor configured to acquire one or more SIBs from the wireless network based on the received short message; and

a SIB processor for forwarding one or more selected SIBs to the remote user equipment, wherein each selected SIB is an acquired SIB in a list of SIB types of interest to the remote user equipment.

13. The user device of claim 12, wherein the user device obtains a list of SIB types of interest to the remote user device via a side-chain connection with the remote user device through a PC5 radio resource control, RRC, message.

14. The user device of claim 13, wherein the PC5RRC message is an existing PC5RRC message.

15. The user device of claim 13, wherein the PC5RRC message is a new PC5RRC message used during PC5RRC connection establishment.

16. The user device of claim 12, wherein the short message indicates a system information modification or a public warning system notification.

17. The user device of claim 16, wherein the short message indicating system information modification is SIB1, wherein an updated SIB1 is forwarded to the remote user device.

18. The user device of claim 12, wherein the user device obtains a list of SIB types of interest to the remote user device by recording all SIB requests sent by the remote user device.

19. The user device of claim 12, wherein the user device acquires the one or more SIBs through an on-demand SIB acquisition procedure.

20. The user device of claim 12, further comprising:

a storage manager to store a list of SIB types of interest to the remote user device in a remote user device context of the remote user device during a lifecycle of the remote user device.

21. A storage medium storing a program which, when executed, causes a user equipment to perform the steps of the system information acquisition method of any one of claims 1 to 11.