Absolute time distribution over sidelink communications

Abstract

Methods, systems, and devices for wireless communication are described. A wireless communication system may establish a sidelink message and an information element (IE) that may be used to distribute absolute time information from a first user equipment (UE) to a second UE. A participating UE (e.g., the first UE or the second UE) may be mobile or stationary (e.g., a roadside unit (RSU)). The first UE may provide an absolute time with a ten nanosecond resolution to the second UE, and the absolute time may refer to an international standard (e.g., world time coordination (UTC) time or global positioning system (GPS) time). In some embodiments, time messages (e.g., between the first UE and the second UE) may be exchanged using PC5 Radio Resource Control (RRC) signaling or Medium Access Control (MAC) Control Elements (MAC-CEs). The time distribution may be provided unilaterally based on request-response signaling or by participating UEs (e.g., the first UE).

Description

Technical Field

[0001] The following relates to wireless communications, including absolute time distribution on sidelink communications. Background Art

[0002] Wireless communication systems are widely deployed to provide various types of communication content, such as voice, video, packet data, messaging, broadcast, etc. These systems may be able to support communication with multiple users by sharing available system resources (e.g., time, frequency, and power). Examples of such multiple access systems include fourth generation (4G) systems (such as long term evolution (LTE) systems, advanced LTE (LTE-A) systems, or LTE-A Pro systems) and fifth generation (5G) systems (which may be referred to as new radio (NR) systems). These systems may employ techniques such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal FDMA (OFDMA), or discrete Fourier transform spread orthogonal frequency division multiplexing (DFT-S-OFDM).

[0003] A wireless multiple access communication system may include one or more network entities, each of which supports wireless communication of communication devices, which may be referred to as user equipment (UE). Some wireless communication systems may support sidelink communication between UEs. In such systems, it may be appropriate for a UE to identify absolute time for use in various applications or for communication with other UEs or network entities. Improved techniques for distributing absolute time information in a wireless communication system supporting sidelink communication may be desirable. Summary of the invention

[0004] The described technology relates to improved methods, systems, devices and apparatuses for supporting absolute time distribution on sidelink communications. A wireless communication system may establish a sidelink message and information element (IE) that can be used to distribute absolute time information from a first user equipment (UE) to at least a second UE (e.g., a second UE and zero or more other UEs). The participating UE (e.g., the first UE or the second UE) may be mobile or stationary (e.g., a roadside unit (RSU)). The first UE may provide absolute time to the second UE, and the absolute time may be referenced to an international standard (e.g., Universal Time Coordinated (UTC) time or Global Positioning System (GPS) time). PC5 radio resource control (RRC) signaling or medium access control (MAC) control element (MAC-CE) may be used to exchange time messages (e.g., between the first UE and the second UE). Time distribution may be based on request-response signaling or provided unilaterally by a participating UE (e.g., the first UE).

[0005] A method for wireless communication at a first UE is described. The method may include: receiving a sidelink message including time information indicating an absolute time value of a reference calendar date from a second UE, wherein the sidelink message is received based on a set of multiple time intervals established for communication between the first UE and the second UE; setting an absolute time clock at a boundary of a reference time interval in the set of multiple time intervals based on the absolute time value; and communicating based on the absolute time clock.

[0006] An apparatus for wireless communication at a first UE is described. The apparatus may include a processor, a memory coupled to the processor, and instructions stored in the memory. The instructions may be executable by the processor to cause the apparatus to: receive a sidelink message including time information indicating an absolute time value of a reference calendar date from a second UE, wherein the sidelink message is received based on a set of multiple time intervals established for communication between the first UE and the second UE; set an absolute time clock at a boundary of a reference time interval in the set of multiple time intervals based on the absolute time value; and communicate based on the absolute time clock.

[0007] Another apparatus for wireless communication at a first UE is described. The apparatus may include: means for receiving a sidelink message including time information indicating an absolute time value of a reference calendar date from a second UE, wherein the sidelink message is received based on a set of multiple time intervals established for communication between the first UE and the second UE; means for setting an absolute time clock at a boundary of a reference time interval in the set of multiple time intervals based on the absolute time value; and means for communicating based on the absolute time clock.

[0008] A non-transitory computer-readable medium storing code for wireless communication at a first UE is described. The code may include instructions that can be executed by a processor to: receive a sidelink message including time information indicating an absolute time value of a reference calendar date from a second UE, wherein the sidelink message is received based on a set of multiple time intervals established for communication between the first UE and the second UE; based on the absolute time value, set an absolute time clock at a boundary of a reference time interval in the set of multiple time intervals; and communicate based on the absolute time clock.

[0009] Some examples of the methods, apparatus, and non-transitory computer-readable media described herein may also include operations, features, components, or instructions for sending a request for the time information to the second UE, wherein in response to sending the request, the side link message including the time information may be received from the second UE.

[0010] In some examples of the methods, apparatus, and non-transitory computer-readable media described herein, the boundary of the reference time interval may be located at the beginning of the reference time interval, and the reference time interval is immediately after the time interval in which the side link message can be received.

[0011] Some examples of the methods, apparatus, and non-transitory computer-readable media described herein may also include operations, features, components, or instructions for receiving an indicator of the reference time interval in the time information of the sidelink message.

[0012] In some examples of the methods, apparatus, and non-transitory computer-readable media described herein, the indicator of the reference time interval includes a distributed frame number.

[0013] In some examples of the methods, apparatus, and non-transitory computer-readable media described herein, the side link message includes a first field and a second field, the first field including the absolute time value, the second field including the indicator of the reference time interval, and the second field including a third field indicating additional reference time information.

[0014] In some examples of the methods, apparatus, and non-transitory computer-readable media described herein, the side link message includes a first field including the absolute time value and the indicator of the reference time interval, and the side link message includes a second field indicating additional reference time information.

[0015] In some examples of the methods, apparatus, and non-transitory computer-readable media described herein, the time information indicates a type of the absolute time value, the type of the absolute time value corresponding to Universal Coordinated Time, Global Positioning System time, or local clock time.

[0016] In some examples of the methods, apparatus, and non-transitory computer-readable media described herein, receiving the side link message including the time information may include operations, features, components, or instructions for: receiving a medium access control (MAC) control element (MAC-CE) including the time information from the second UE in a broadcast or multicast transmission.

[0017] Some examples of the methods, apparatus, and non-transitory computer-readable media described herein may also include operations, features, components, or instructions for communicating with the second UE or the third UE for timing synchronization, wherein the reference time interval includes a frame having boundaries determined based on communicating with the second UE or the third UE for timing synchronization.

[0018] In some examples of the methods, apparatus, and non-transitory computer-readable media described herein, the first UE may be outside of a coverage area of ​​any network entity and the second UE may be within a coverage area of ​​at least one network entity.

[0019] A method for wireless communication at a first UE is described. The method may include: receiving a message including first time information indicating a first absolute time value, wherein the first absolute time value refers to a calendar date; setting an absolute time clock at a first boundary of a first reference time interval based on the first absolute time value; determining a second absolute time value at a second boundary of a second reference time interval based on the absolute time clock, wherein the second reference time interval is one of a set of multiple time intervals established for communication between the first UE and a second UE; and sending a sidelink message including second time information indicating the second absolute time value to the second UE.

[0020] An apparatus for wireless communication at a first UE is described. The apparatus may include a processor, a memory coupled to the processor, and instructions stored in the memory. The instructions may be executable by the processor to cause the apparatus to: receive a message including first time information indicating a first absolute time value, wherein the first absolute time value refers to a calendar date; set an absolute time clock at a first boundary of a first reference time interval based on the first absolute time value; determine a second absolute time value at a second boundary of a second reference time interval based on the absolute time clock, wherein the second reference time interval is one of a set of multiple time intervals established for communication between the first UE and a second UE; and send a sidelink message including second time information indicating the second absolute time value to the second UE.

[0021] Another apparatus for wireless communication at a first UE is described. The apparatus may include: means for receiving a message including first time information indicating a first absolute time value, wherein the first absolute time value refers to a calendar date; means for setting an absolute time clock at a first boundary of a first reference time interval based on the first absolute time value; means for determining a second absolute time value at a second boundary of a second reference time interval based on the absolute time clock, wherein the second reference time interval is one of a set of multiple time intervals established for communication between the first UE and a second UE; and means for sending a sidelink message including second time information indicating the second absolute time value to the second UE.

[0022] A non-transitory computer-readable medium storing code for wireless communication at a first UE is described. The code may include instructions that can be executed by a processor to: receive a message including first time information indicating a first absolute time value, wherein the first absolute time value refers to a calendar date; set an absolute time clock at a first boundary of a first reference time interval based on the first absolute time value; determine a second absolute time value at a second boundary of a second reference time interval based on the absolute time clock, wherein the second reference time interval is one of a set of multiple time intervals established for communication between the first UE and a second UE; and send a sidelink message including second time information indicating the second absolute time value to the second UE.

[0023] Some examples of the methods, apparatus, and non-transitory computer-readable media described herein may also include operations, features, components, or instructions for: receiving a request for the second time information from the second UE, wherein in response to receiving the request, the side link message including the second time information may be sent to the second UE.

[0024] In some examples of the methods, apparatus, and non-transitory computer-readable media described herein, receiving the message including the first time information may include operations, features, components, or instructions for: receiving a downlink message including the first time information indicating the first absolute time value from a network entity.

[0025] In some examples of the methods, apparatuses, and non-transitory computer-readable media described herein, the first reference time interval may be indicated by a system frame number in the first time information.

[0026] In some examples of the methods, apparatus, and non-transitory computer-readable media described herein, receiving the message including the first time information may include operations, features, components, or instructions for: receiving a second side link message including the first time information indicating the first absolute time value from a third UE.

[0027] In some examples of the methods, apparatus, and non-transitory computer-readable media described herein, the first reference time interval may be indicated by a distributed frame number in the first time information.

[0028] In some examples of the methods, apparatus, and non-transitory computer-readable media described herein, the second boundary of the second reference time interval may be located at the beginning of the second reference time interval, and the second reference time interval is immediately after the time interval in which the side link message can be sent.

[0029] Some examples of the methods, apparatus, and non-transitory computer-readable media described herein may also include operations, features, components, or instructions for: sending an indicator of the second reference time interval in the second time information of the sidelink message.

[0030] In some examples of the methods, apparatus, and non-transitory computer-readable media described herein, the indicator of the second reference time interval includes a distributed frame number.

[0031] In some examples of the methods, apparatus, and non-transitory computer-readable media described herein, the side link message includes a first field and a second field, the first field including the second absolute time value, the second field including the indicator of the second reference time interval, and the second field including a third field indicating additional reference time information.

[0032] In some examples of the methods, apparatus, and non-transitory computer-readable media described herein, the first side link message includes a first field including the second absolute time value and the indicator of the second reference time interval, and the side link message includes a second field indicating additional reference time information.

[0033] In some examples of the methods, apparatus, and non-transitory computer-readable media described herein, the second time information indicates a type of the second absolute time value, the type of the second absolute time value corresponding to Universal Coordinated Time, Global Positioning System time, or local clock time.

[0034] In some examples of the methods, apparatus, and non-transitory computer-readable media described herein, sending the side link message including the second time information may include operations, features, components, or instructions for: sending a medium access control (MAC) control element (MAC-CE) including the second time information in a broadcast or multicast transmission.

[0035] Some examples of the methods, apparatus, and non-transitory computer-readable media described herein may also include operations, features, components, or instructions for communicating with a third UE or a network entity for timing synchronization, wherein the boundary of the first reference time interval and the second reference time interval may be determined based on communicating with the third UE or the network entity for timing synchronization.

[0036] In some examples of the methods, apparatus, and non-transitory computer-readable media described herein, the first UE may be within a coverage area of ​​at least one network entity and the second UE may be outside of a coverage area of ​​any network entity. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1An example of a wireless communication system supporting absolute time distribution on sidelink communications in accordance with one or more aspects of the present disclosure is illustrated.

[0038] Figure 2 An example of a wireless communication system supporting absolute time distribution on sidelink communications in accordance with one or more aspects of the present disclosure is illustrated.

[0039] Figure 3 An example of absolute time distribution on sidelink communications according to one or more aspects of the present disclosure is illustrated.

[0040] Figure 4 An example of a medium access control (MAC) control element (MAC-CE) for distributing time information on sidelink communications in accordance with one or more aspects of the present disclosure is illustrated.

[0041] Figure 5 An example of a process flow to support absolute time distribution over sidelink communications in accordance with one or more aspects of the present disclosure is illustrated.

[0042] Figure 6 and Figure 7 A block diagram of a device supporting absolute time distribution over sidelink communications is shown in accordance with one or more aspects of the present disclosure.

[0043] Figure 8 A block diagram of a communications manager supporting absolute time distribution over sidelink communications is shown in accordance with one or more aspects of the present disclosure.

[0044] Fig. 9 A diagram of a system including a device supporting absolute time distribution over sidelink communications is shown in accordance with one or more aspects of the present disclosure.

[0045] Fig.10 and Fig.11 A flow chart illustrating a method of supporting absolute time distribution on sidelink communications according to one or more aspects of the present disclosure is shown. DETAILED DESCRIPTION

[0046] Some wireless communication systems may support sidelink communications between user equipment (UE). In such systems, it may be appropriate for the UE to identify absolute time for use in various applications or for communicating with other UEs or network entities. For example, having accurate time information (e.g., nanosecond or ten nanosecond resolution) may be useful for many aspects of UE operation such as coordinating actions or communications. Some mechanisms may be defined for the network to notify the UE of absolute time (e.g., Universal Time Coordinated (UTC) time or Global Positioning System (GPS) time) via a Uu connection using public system information signaling or dedicated signaling. However, in some cases, such signaling of absolute time may not be defined for UEs that support sidelink communications outside the coverage area of ​​the network. That is, the technology for signaling absolute time to the UE without a Uu connection may be undefined, and the functionality of the UE may be limited.

[0047] The described technology provides efficient distribution of absolute time information in a wireless communication system supporting sidelink communication. The wireless communication system can establish a sidelink message and IE that can be used to distribute absolute time information from a first UE to a second UE. The participating UE (e.g., the first UE or the second UE) can be mobile or stationary (e.g., a roadside unit (RSU)). The first UE can provide absolute time to the second UE, and the absolute time can refer to an international standard (e.g., UTC time or GPS time). The absolute time can have a nanosecond or ten nanosecond resolution. PC5 radio resource control (RRC) signaling or medium access control (MAC) control element (MAC-CE) can be used to exchange time messages (e.g., between the first UE and the second UE). Time distribution can be based on request-response signaling or provided unilaterally by a participating UE (e.g., the first UE).

[0048] Various aspects of the present disclosure are first described in the context of a wireless communication system. Further, various aspects of the present disclosure are exemplified by and described with reference to apparatus diagrams, system diagrams, and flow diagrams related to absolute time distribution on sidelink communications.

[0049] Figure 1 An example of a wireless communication system 100 supporting absolute time distribution on sidelink communications according to one or more aspects of the present disclosure is illustrated. The wireless communication system 100 may include one or more network entities 105, one or more UEs 115, and a core network 130. In some examples, the wireless communication system 100 may be a Long Term Evolution (LTE) network, an Advanced LTE (LTE-A) network, an LTE-A Pro network, a New Radio (NR) network, or a network operating according to other systems and radio technologies, including future systems and radio technologies not explicitly mentioned herein.

[0050] The network entities 105 may be dispersed throughout a geographic area to form the wireless communication system 100, and may include devices in different forms or with different capabilities. In various examples, the network entities 105 may be referred to as network elements, mobility elements, radio access network (RAN) nodes, or network equipment, among other nomenclature. In some examples, the network entities 105 and the UE 115 may communicate wirelessly via one or more communication links 125 (e.g., radio frequency (RF) access links). For example, the network entity 105 may support a coverage area 110 (e.g., a geographic coverage area) within which the UE 115 and the network entity 105 may establish one or more communication links 125. The coverage area 110 may be an example of a geographic area within which the network entity 105 and the UE 115 may support signal communications according to one or more radio access technologies (RATs).

[0051] The UEs 115 may be dispersed throughout the coverage area 110 of the wireless communication system 100, and each UE 115 may be stationary or mobile, or stationary and mobile at different times. The UEs 115 may be devices in different forms or with different capabilities. Figure 1 Some example UEs 115 are illustrated in FIG. 1 . The UEs 115 described herein may be capable of supporting communications with various types of devices, such as Figure 1 Other UEs 115 or network entities 105 are shown.

[0052] As described herein, a node of the wireless communication system 100 (which may be referred to as a network node or a wireless node) may be a network entity 105 (e.g., any network entity described herein), a UE 115 (e.g., any UE described herein), a network controller, an apparatus, a device, a computing system, one or more components, or another suitable processing entity configured to perform any of the techniques described herein. For example, the node may be a UE 115. As another example, the node may be a network entity 105. As another example, a first node may be configured to communicate with a second node or a third node. In one aspect of this example, the first node may be a UE 115, the second node may be a network entity 105, and the third node may be a UE 115. In another aspect of this example, the first node may be a UE 115, the second node may be a network entity 105, and the third node may be a network entity 105. In other aspects of this example, the first node, the second node, and the third node may be different relative to these examples. Similarly, references to UE 115, network entity 105, apparatus, device, computing system, etc. may include disclosure of UE 115, network entity 105, apparatus, device, computing system, etc. as nodes. For example, a disclosure that UE 115 is configured to receive information from network entity 105 also discloses that the first node is configured to receive information from a second node.

[0053] In some examples, the network entities 105 may communicate with the core network 130, or communicate with each other, or both. For example, the network entities 105 may communicate with the core network 130 via one or more backhaul communication links 120 (e.g., according to S1, N2, N3 or other interface protocols). In some examples, the network entities 105 may communicate with each other via the backhaul communication link 120 (e.g., according to X2, Xn or other interface protocols) directly (e.g., directly between the network entities 105) or indirectly (e.g., via the core network 130). In some examples, the network entities 105 may communicate with each other via the midhaul communication link 162 (e.g., according to the midhaul interface protocol) or the fronthaul communication link 168 (e.g., according to the fronthaul interface protocol) or any combination thereof. The backhaul communication link 120, the midhaul communication link 162, or the fronthaul communication link 168 may be or include one or more wired links (e.g., electrical links, optical fiber links), one or more wireless links (e.g., radio links, wireless optical links), etc. or various combinations thereof. UE 115 may communicate with core network 130 via communication link 155 .

[0054] One or more of the network entities 105 described herein may include or may be referred to as a base station 140 (e.g., a transceiver base station, a radio base station, an NR base station, an access point, a radio transceiver, a NodeB, an eNodeB (eNB), a next generation NodeB or a gigabit NodeB (any of which may be referred to as a gNB), a 5G NB, a next generation eNB (ng-eNB), a home NodeB, a home eNodeB, or other suitable terms). In some examples, the network entity 105 (e.g., a base station 140) may be implemented in an aggregated (e.g., monolithic, stand-alone) base station architecture, which may be configured to utilize a protocol stack physically or logically integrated within a single network entity 105 (e.g., a single RAN node, such as a base station 140).

[0055] In some examples, the network entity 105 may be implemented in a disaggregated architecture (e.g., a disaggregated base station architecture, a disaggregated RAN architecture) that may be configured to utilize a protocol stack that is physically or logically distributed between two or more network entities 105, such as an integrated access backhaul (IAB) network, an open RAN (O-RAN) (e.g., a network configuration sponsored by the O-RAN Alliance), or a virtualized RAN (vRAN) (e.g., a cloud RAN (C-RAN)). For example, the network entity 105 may include one or more of the following: a central unit (CU) 160, a distributed unit (DU) 165, a radio unit (RU) 170, a RAN intelligent controller (RIC) 175 (e.g., a near real-time RIC (near RT RIC), a non-real-time RIC (non-RT RIC)), a service management and orchestration (SMO) 180 system, or any combination thereof. The RU 170 may also be referred to as a radio head, a smart radio head, a remote radio head (RRH), a remote radio unit (RRU), or a transmit receive point (TRP). One or more components of the network entity 105 in the decomposed RAN architecture may be co-located, or one or more components of the network entity 105 may be located in distributed locations (e.g., separate physical locations). In some examples, one or more network entities 105 of the decomposed RAN architecture may be implemented as virtual units (e.g., virtual CU (VCU), virtual DU (VDU), virtual RU (VRU)).

[0056] The functional split between CU 160, DU 165, and RU 170 is flexible and may support different functionalities, depending on which functions (e.g., network layer functions, protocol layer functions, baseband functions, RF functions, and any combination thereof) are performed at CU 160, DU 165, or RU 170. For example, a functional split of a protocol stack may be employed between CU 160 and DU 165 such that CU 160 may support one or more layers of a protocol stack and DU 165 may support one or more different layers of a protocol stack. In some examples, CU 160 may host higher protocol layer (e.g., layer 3 (L3), layer 2 (L2)) functionality and signaling (e.g., radio resource control (RRC), service data adaptation protocol (SDAP), packet data convergence protocol (PDCP)). The CU 160 may be connected to one or more DUs 165 or RUs 170, and the one or more DUs 165 or RUs 170 may host lower protocol layers, such as layer 1 (L1) (e.g., physical (PHY) layer) or L2 (e.g., radio link control (RLC) layer, medium access control (MAC) layer) functionality and signaling, and may each be at least partially controlled by the CU 160. Additionally or alternatively, a functional split of the protocol stack may be employed between the DU 165 and the RU 170, such that the DU 165 may support one or more layers of the protocol stack, and the RU 170 may support one or more different layers of the protocol stack. The DU 165 may support one or more different cells (e.g., via one or more RUs 170). In some cases, the functional split between CU 160 and DU 165 or between DU 165 and RU 170 can be within the protocol layer (e.g., some functions of the protocol layer can be performed by one of CU 160, DU 165, or RU 170, while other functions of the protocol layer are performed by different ones of CU 160, DU 165, or RU 170). CU 160 can be further functionally split into CU control plane (CU-CP) and CU user plane (CU-UP) functions. CU 160 can be connected to one or more DUs 165 via midhaul communication links 162 (e.g., F1, F1-c, F1-u), and DU 165 can be connected to one or more RUs 170 via fronthaul communication links 168 (e.g., open fronthaul (FH) interface). In some examples, midhaul communication link 162 or fronthaul communication link 168 may be implemented based on an interface (e.g., a channel) between layers of a protocol stack supported by respective network entities 105 that communicate via such communication links.

[0057] In some wireless communication systems (e.g., wireless communication system 100), infrastructure and spectrum resources for radio access may support wireless backhaul link capabilities to supplement wired backhaul connections, thereby providing an IAB network architecture (e.g., to core network 130). In some cases, in an IAB network, one or more network entities 105 (e.g., IAB nodes 104) may be partially controlled by each other. One or more IAB nodes 104 may be referred to as donor entities or IAB donors. One or more DUs 165 or one or more RUs 170 may be controlled in part by one or more CUs 160 associated with a donor network entity 105 (e.g., donor base station 140). One or more donor network entities 105 (e.g., IAB donors) may communicate with one or more additional network entities 105 (e.g., IAB nodes 104) via supported access and backhaul links (e.g., backhaul communication links 120). The IAB node 104 may include an IAB mobile terminal (IAB-MT) controlled (e.g., scheduled) by a coupled IAB donor's DU 165. The IAB-MT may include an independent set of antennas for relaying communications with the UE 115, or may share the same antennas of the IAB node 104 (e.g., of the RU 170) for access via the DU 165 of the IAB node 104 (e.g., referred to as a virtual IAB-MT (vIAB-MT)). In some examples, the IAB node 104 may include a DU 165 that supports communication links with additional entities (e.g., IAB node 104, UE 115) within a relay chain or configuration (e.g., downstream) of the access network. In such cases, one or more components of the decomposed RAN architecture (e.g., one or more IAB nodes 104 or components of the IAB node 104) may be configured to operate according to the techniques described herein.

[0058] Where the techniques described herein are applied to the context of a disaggregated RAN architecture, one or more components of the disaggregated RAN architecture may be configured to support absolute time distribution on sidelink communications as described herein. For example, some operations described as being performed by a UE 115 or a network entity 105 (e.g., a base station 140) may additionally or alternatively be performed by one or more components of the disaggregated RAN architecture (e.g., an IAB node 104, a DU 165, a CU 160, a RU 170, a RIC 175, a SMO 180).

[0059] UE 115 may include or may be referred to as a mobile device, a wireless device, a remote device, a handheld device, or a subscriber device, or some other suitable term, where a "device" may also be referred to as a unit, a station, a terminal, or a client, etc. UE 115 may also include or may be referred to as a personal electronic device, such as a cellular phone, a personal digital assistant (PDA), a tablet computer, a laptop computer, or a personal computer. In some examples, UE 115 may include or may be referred to as a wireless local loop (WLL) station, an Internet of Things (IoT) device, an Internet of Everything (IoE) device, or a machine type communication (MTC) device, etc., which may be implemented in various objects such as appliances or vehicles, meters, etc.

[0060] The UE 115 described herein may be capable of communicating with various types of devices such as other UEs 115 which may sometimes act as relays, as well as network entities 105 and network equipment including macro eNBs or gNBs, small cell eNBs or gNBs, or relay base stations, etc. Figure 1 shown.

[0061] The UE 115 and the network entity 105 may wirelessly communicate with each other via one or more communication links 125 (e.g., access links) using resources associated with one or more carriers. The term "carrier" may refer to a collection of RF spectrum resources having a physical layer structure defined for supporting the communication link 125. For example, a carrier for the communication link 125 may include a portion of an RF spectrum band (e.g., a bandwidth portion (BWP)) that operates according to one or more physical layer channels for a given radio access technology (e.g., LTE, LTE-A, LTE-A Pro, NR). Each physical layer channel may carry acquisition signaling (e.g., synchronization signals, system information), control signaling for coordinating carrier operations, user data, or other signaling. The wireless communication system 100 may support communications with the UE 115 using carrier aggregation or multi-carrier operation. Depending on the carrier aggregation configuration, the UE 115 may be configured to have multiple downlink component carriers and one or more uplink component carriers. Carrier aggregation may be used for both frequency division duplex (FDD) and time division duplex (TDD) component carriers. Communication between the network entity 105 and other devices may refer to communication between these devices and any portion (e.g., entity, sub-entity) of the network entity 105. For example, the terms "send," "receive," or "communicate" when referring to the network entity 105 may refer to any portion of a network entity 105 (e.g., base station 140, CU 160, DU 165, RU 170) of a RAN communicating with another device (e.g., directly or via one or more other network entities 105).

[0062] In some examples, such as in a carrier aggregation configuration, a carrier may also have acquisition signaling or control signaling that coordinates the operation of other carriers. A carrier may be associated with a frequency channel (e.g., an Evolved Universal Mobile Telecommunications System Terrestrial Radio Access (E-UTRA) Absolute RF Channel Number (EARFCN)) and may be identified based on a channel raster used for discovery by UE 115. A carrier may operate in a standalone mode, in which case initial acquisition and connection may be made by UE 115 via the carrier, or a carrier may operate in a non-standalone mode, in which case a different carrier (e.g., of the same or different radio access technology) is used to anchor the connection.

[0063] The communication link 125 shown in the wireless communication system 100 may include downlink transmissions (e.g., forward link transmissions) from the network entity 105 to the UE 115, uplink transmissions (e.g., return link transmissions) from the UE 115 to the network entity 105, or both, as well as other transmission configurations. A carrier may carry downlink communications or uplink communications (e.g., in FDD mode), or may be configured to carry downlink communications and uplink communications (e.g., in TDD mode).

[0064] A carrier may be associated with a particular bandwidth of the RF spectrum, and in some examples, the carrier bandwidth may be referred to as the "system bandwidth" of the carrier or wireless communication system 100. For example, the carrier bandwidth may be one of a set of bandwidths of carriers for a particular radio access technology (e.g., 1.4 megahertz (MHz), 3 MHz, 5 MHz, 10 MHz, 15 MHz, 20 MHz, 40 MHz, or 80 MHz). A device of the wireless communication system 100 (e.g., a network entity 105, a UE 115, or both) may have a hardware configuration that supports communications using a particular carrier bandwidth, or may be capable of being configured to support communications using one of the carrier bandwidths in the set of carrier bandwidths. In some examples, the wireless communication system 100 may include a network entity 105 or a UE 115 that supports concurrent communications using carriers associated with multiple carrier bandwidths. In some examples, each served UE 115 may be configured to operate using a portion (e.g., a subband, a BWP) or all of the carrier bandwidth.

[0065] The signal waveform transmitted via the carrier may include multiple subcarriers (e.g., using multi-carrier modulation (MCM) techniques, such as orthogonal frequency division multiplexing (OFDM) or discrete Fourier transform spread OFDM (DFT-S-OFDM)). In a system using MCM technology, a resource element may refer to a symbol period (e.g., the duration of a modulation symbol) and a resource of a subcarrier, in which case the symbol period and the subcarrier spacing may be inversely related. The number of bits carried by each resource element may depend on the modulation scheme (e.g., the order of the modulation scheme, the coding rate of the modulation scheme, or both), so that a relatively high number of resource elements (e.g., in the transmission duration) and a relatively high order modulation scheme may correspond to a relatively high rate of communication. Wireless communication resources may refer to a combination of RF spectrum resources, time resources, and spatial resources (e.g., spatial layers or beams), and the use of multiple spatial resources may increase the data rate or data integrity used for communication with UE 115.

[0066] One or more parameter sets for a carrier may be supported, and the parameter sets may include subcarrier spacing (Δf) and cyclic prefixes. A carrier may be divided into one or more BWPs with the same or different parameter sets. In some examples, a UE 115 may be configured with multiple BWPs. In some examples, a single BWP for a carrier may be active at a given time, and communications of a UE 115 may be constrained to one or more active BWPs.

[0067] The time interval for the network entity 105 or the UE 115 may be expressed as a multiple of a basic time unit, which may be, for example, a sampling period T s =1 / (Δf max ·N f ) seconds, for which Δf max It can represent the supported subcarrier spacing, and N f The supported discrete Fourier transform (DFT) size may be indicated. The time intervals of the communication resources may be organized according to radio frames each having a specified duration (e.g., 10 milliseconds (ms)). Each radio frame may be identified by a system frame number (SFN) (e.g., ranging from 0 to 1023).

[0068] Each frame may include multiple consecutively numbered subframes or time slots, and each subframe or time slot may have the same duration. In some examples, the frame may be divided into subframes (e.g., in the time domain), and each subframe may be further divided into a certain number of time slots. Alternatively, each frame may include a variable number of time slots, and the number of time slots may depend on the subcarrier spacing. Each time slot may include a certain number of symbol periods (e.g., depending on the length of the cyclic prefix appended in front of each symbol period). In some wireless communication systems 100, the time slot may be further divided into a plurality of micro time slots associated with one or more symbols. Excluding the cyclic prefix, each symbol period may be associated with one or more (e.g., N f The duration of a symbol period may depend on the subcarrier spacing or the operating frequency band.

[0069] A subframe, a time slot, a mini-time slot, or a symbol may be the smallest scheduling unit (e.g., in the time domain) of the wireless communication system 100 and may be referred to as a transmission time interval (TTI). In some examples, the TTI duration (e.g., the number of symbol periods in a TTI) may be variable. Additionally or alternatively, the smallest scheduling unit of the wireless communication system 100 may be dynamically selected (e.g., in a burst of a shortened TTI (sTTI)).

[0070] According to various techniques, physical channels may be multiplexed using carriers for communication. Physical control channels and physical data channels may be multiplexed for signaling via downlink carriers, for example, using one or more of a time division multiplexing (TDM) technique, a frequency division multiplexing (FDM) technique, or a hybrid TDM-FDM technique. A control region (e.g., a control resource set (CORESET)) of a physical control channel may be defined by a set of symbol periods and may extend across a system bandwidth of a carrier or a subset of that system bandwidth. One or more control regions (e.g., CORESETs) may be configured for a set of UEs 115. For example, one or more UEs in UE 115 may monitor or search a control region to obtain control information according to one or more search space sets, and each search space set may include one or more control channel candidates in one or more aggregation levels arranged in a cascaded manner. The aggregation level of a control channel candidate may refer to the amount of control channel resources (e.g., control channel elements (CCEs)) associated with coded information for a control information format having a given payload size. The search space sets may include a common search space set configured for transmitting control information to multiple UEs 115 , and a UE-specific search space set for transmitting control information to a specific UE 115 .

[0071] The network entity 105 may provide communication coverage via one or more cells (e.g., macro cells, small cells, hot spots, or other types of cells, or any combination thereof). The term "cell" may refer to a logical communication entity used to communicate with the network entity 105 (e.g., using a carrier), and may be associated with an identifier (e.g., a physical cell identifier (PCID), a virtual cell identifier (VCID), or other cell identifier) ​​used to distinguish adjacent cells. In some examples, a cell may also refer to a coverage area 110 or a portion of a coverage area 110 (e.g., a sector) on which a logical communication entity operates. Depending on various factors such as the capabilities of the network entity 105, such cells may range from smaller areas (e.g., structures, subsets of structures) to larger areas. For example, a cell may be or may include a building, a subset of a building, or an external space between or overlapping coverage areas 110, and the like.

[0072] A macro cell generally covers a relatively large geographic area (e.g., several kilometers in radius) and may allow unrestricted access to a UE 115 that has a service subscription with a network provider that supports the macro cell. A small cell may be associated with a lower power network entity 105 (e.g., a lower power base station 140) than a macro cell, and the small cell may operate using the same or different (e.g., licensed, unlicensed) frequency band as the macro cell. A small cell may provide unrestricted access to a UE 115 that has a service subscription with a network provider, or may provide restricted access to a UE 115 associated with a small cell (e.g., a UE 115 in a closed subscriber group (CSG), a UE 115 associated with a user in a home or office). A network entity 105 may support one or more cells, and may also use one or more component carriers to support communications via one or more cells.

[0073] In some examples, a carrier may support multiple cells, and different cells may be configured according to different protocol types (e.g., MTC, narrowband IoT (NB-IoT), enhanced mobile broadband (eMBB)) that may provide access to different types of devices.

[0074] In some examples, the network entities 105 (e.g., base stations 140, RUs 170) may be mobile and thus provide communication coverage for mobile coverage areas 110. In some examples, different coverage areas 110 associated with different technologies may overlap, but the different coverage areas 110 may be supported by the same network entity 105. In some other examples, overlapping coverage areas 110 associated with different technologies may be supported by different network entities 105. The wireless communication system 100 may include, for example, a heterogeneous network in which different types of network entities 105 provide coverage for various coverage areas 110 using the same or different radio access technologies.

[0075] Some UEs 115, such as MTC or IoT devices, may be low-cost or low-complexity devices and may allow automated communication between machines (e.g., via machine-to-machine (M2M) communication). M2M communication or MTC may refer to data communication technology that allows devices to communicate with each other or with a network entity 105 (e.g., base station 140) without human intervention. In some examples, M2M communication or MTC may include communication from devices that integrate sensors or meters to measure or capture information and relay such information to a central server or application that uses the information or presents the information to a person interacting with the application. Some UEs 115 may be designed to collect information or implement automated behavior of machines or other devices. Examples of applications for MTC devices include: smart metering, inventory monitoring, water level monitoring, equipment monitoring, health care monitoring, field survival monitoring, weather and geographic event monitoring, fleet management and tracking, remote security sensing, physical access control, and transaction-based commercial charging.

[0076] Some UEs 115 may be configured to employ an operating mode that reduces power consumption, such as half-duplex communication (e.g., a mode that supports unidirectional communication via transmission or reception but does not transmit and receive concurrently). In some examples, half-duplex communication may be performed with a reduced peak rate. Other energy-saving techniques for UEs 115 include entering a power-saving deep sleep mode when not engaged in active communications, operating using limited bandwidth (e.g., according to narrowband communications), or a combination of these techniques. For example, some UEs 115 may be configured to operate using a narrowband protocol type that is associated with a defined portion or range (e.g., a set of subcarriers or resource blocks (RBs)) within a carrier, within a guard band of a carrier, or outside a carrier.

[0077] The wireless communication system 100 may be configured to support ultra-reliable communication or low-latency communication or various combinations thereof. For example, the wireless communication system 100 may be configured to support ultra-reliable low-latency communication (URLLC). UE 115 may be designed to support ultra-reliable or low-latency or critical functions. Ultra-reliable communication may include private communication or group communication, and may be supported by one or more services (such as push-to-talk, video, or data). Support for ultra-reliable, low-latency functions may include prioritization of services, and such services may be used for public safety or general commercial applications. The terms ultra-reliable, low-latency, and ultra-reliable low-latency may be used interchangeably herein.

[0078] In some examples, the UE 115 may be configured to support communication directly with other UEs 115 via a device-to-device (D2D) communication link 135 (e.g., according to a peer-to-peer (P2P), D2D, or sidelink protocol). In some examples, one or more UEs 115 in a group that are performing D2D communication may be within a coverage area 110 of a network entity 105 (e.g., a base station 140, a RU 170), which may support aspects of such D2D communication configured (e.g., scheduled) by the network entity 105. In some examples, one or more UEs 115 in such a group may be outside the coverage area 110 of the network entity 105, or may otherwise be unable or not configured to receive transmissions from the network entity 105. In some examples, a group of UEs 115 communicating via D2D communication may support a one-to-many (1:M) system, in which each UE 115 transmits to each of the other UEs 115 in the group. In some examples, the network entity 105 may facilitate scheduling of resources for D2D communication. In some other examples, D2D communications may be performed between UEs 115 without involving network entity 105 .

[0079] In some systems, the D2D communication link 135 can be an example of a communication channel (such as a sidelink communication channel) between vehicles (e.g., UE 115). In some examples, the vehicles can communicate using vehicle-to-everything (V2X) communications, vehicle-to-vehicle (V2V) communications, or some combination of these. The vehicles can signal information related to traffic conditions, signal scheduling, weather, safety, emergency situations, or any other information related to the V2X system. In some examples, vehicles in the V2X system can communicate with roadside infrastructure (such as roadside units) using vehicle-to-network (V2N) communications, or communicate with the network via one or more network nodes (e.g., network entity 105, base station 140, RU 170), or both.

[0080] The core network 130 may provide user authentication, access authorization, tracking, Internet Protocol (IP) connectivity, and other access, routing, or mobility functions. The core network 130 may be an evolved packet core (EPC) or a 5G core (5GC), which may include at least one control plane entity (e.g., a mobility management entity (MME), an access and mobility management function (AMF)) for managing access and mobility and at least one user plane entity (e.g., a serving gateway (S-GW), a packet data network (PDN) gateway (P-GW), or a user plane function (UPF)) for routing packets or interconnecting to an external network. The control plane entity may manage non-access stratum (NAS) functions, such as mobility, authentication, and bearer management of UE 115 served by a network entity 105 (e.g., a base station 140) associated with the core network 130. User IP packets may be delivered through the user plane entity, which may provide IP address allocation and other functions. The user plane entity may be connected to the IP service 150 of one or more network operators. IP services 150 may include access to the Internet, an intranet, an IP Multimedia Subsystem (IMS), or packet-switched streaming services.

[0081] The wireless communication system 100 may operate using one or more frequency bands that may be in the range of 300 megahertz (MHz) to 300 gigahertz (GHz). Generally speaking, the region from 300 MHz to 3 GHz is referred to as the ultra-high frequency (UHF) region or decimeter band because the wavelength ranges from about one decimeter to one meter in length. UHF waves may be blocked or redirected by buildings and environmental features (which may be referred to as clusters), but these waves may be sufficient to penetrate structures so that macro cells provide services to UEs 115 located indoors. Communications using UHF waves may be associated with smaller antennas and shorter ranges (e.g., less than 100 kilometers) compared to communications using lower frequencies and longer waves in the high frequency (HF) or very high frequency (VHF) portions of the spectrum below 300 MHz.

[0082] The wireless communication system 100 may utilize licensed and unlicensed RF spectrum bands. For example, the wireless communication system 100 may use unlicensed bands (such as the 5 GHz Industrial, Scientific, and Medical (ISM) band) to employ license assisted access (LAA), LTE unlicensed (LTE-U) radio access technology, or NR technology. When operating using unlicensed RF spectrum bands, devices such as network entity 105 and UE 115 may employ carrier sensing for conflict detection and avoidance. In some examples, operations using unlicensed bands may be based on carrier aggregation configuration (e.g., LAA) in conjunction with component carriers operating using licensed bands. Operations using unlicensed spectrum may include downlink transmissions, uplink transmissions, P2P transmissions, or D2D transmissions, and the like.

[0083] The network entity 105 (e.g., base station 140, RU 170) or UE 115 may be equipped with multiple antennas that can be used to employ technologies such as transmit diversity, receive diversity, multiple-input multiple-output (MIMO) communication, or beamforming. The antennas of the network entity 105 or UE 115 may be located in one or more antenna arrays or antenna panels, which may support MIMO operations or transmit or receive beamforming. For example, one or more base station antennas or antenna arrays may be co-located at an antenna assembly, such as an antenna tower. In some examples, antennas or antenna arrays associated with the network entity 105 may be located at different geographical locations. The network entity 105 may include an antenna array having a collection of multiple rows and columns of antenna ports that the network entity 105 can use to support beamforming for communications with the UE 115. Similarly, the UE 115 may include one or more antenna arrays that may support various MIMO or beamforming operations. Additionally or alternatively, the antenna panel may support RF beamforming for signals sent via the antenna ports.

[0084] Beamforming (which may also be referred to as spatial filtering, directional transmission, or directional reception) is a signal processing technique that may be used at a transmitting device or a receiving device (e.g., a network entity 105, a UE 115) to shape or direct an antenna beam (e.g., a transmit beam, a receive beam) along a spatial path between the transmitting device and the receiving device. Beamforming may be achieved by combining signals conveyed via antenna elements of an antenna array so that some signals propagating along a particular direction relative to the antenna array experience constructive interference, while other signals experience destructive interference. Adjustments to signals conveyed via antenna elements may include the transmitting device or the receiving device applying an amplitude offset, a phase offset, or both to signals carried via antenna elements associated with the device. Adjustments associated with each of these antenna elements may be defined by a set of beamforming weights associated with a particular direction (e.g., relative to the antenna array of the transmitting device or the receiving device or relative to some other direction).

[0085] The wireless communication system 100 may be a packet-based network that operates according to a layered protocol stack. In the user plane, communications at the bearer or PDCP layer may be IP-based. The RLC layer may perform packet segmentation and reassembly to communicate via logical channels. The MAC layer may perform priority processing and multiplexing of logical channels into transport channels. The MAC layer may also implement error detection techniques, error correction techniques, or both to support retransmission to improve link efficiency. In the control plane, the RRC layer may provide the establishment, configuration, and maintenance of an RRC connection that supports a radio bearer for user plane data between the UE 115 and the network entity 105 or the core network 130. The PHY layer may map a transport channel to a physical channel.

[0086] As mentioned above, UE 115 can communicate with each other via D2D communication link 135. D2D communication link 135 can be referred to as side link. In some cases, side link communication may include communication on one or more side link channels. For example, side link data transmission may be performed on physical side link shared channel (PSSCH), side link discovery expression transmission may be performed on physical side link discovery channel (PSDCH) (e.g., to allow neighboring devices to discover each other's presence), side link control information transmission may be performed on physical side link control channel (PSCCH), side link feedback transmission may be performed on physical side link feedback channel (PSFCH), and side link broadcast transmission may be performed on physical side link broadcast channel (PSBCH). Side link communication may also include sending a reference signal from one UE 115 to another UE 115.

[0087] Sidelink communication may occur in a transmit or receive resource pool. The minimum resource allocation unit for sidelink communication may be a subchannel in the frequency domain, and the resource allocation for sidelink communication in the time domain may be a time slot. Some time slots may not be available for sidelink, and some time slots may contain feedback resources. In some cases, a sidelink transmission from one UE 115 to another UE 115 may be a transmission on a sidelink resource on which another UE 115 can monitor the sidelink transmission. In some aspects, the RRC configuration for sidelink communication may be preconfigured (e.g., preloaded on UE 115) or signaled to UE 115 (e.g., from base station 105). In some examples, network entity 105 facilitates scheduling of resources for sidelink communication (e.g., in resource allocation mode 1). In other cases, sidelink communication is performed between UE 115 without the participation of network entity 105 (e.g., in resource allocation mode 2).

[0088] In the wireless communication system 100, it may be appropriate for the UE 115 to identify absolute time for use in various applications or for communication with other UEs 115 or network entities 105. For example, having accurate time information may be useful for many aspects of UE sidelink operation. Some mechanisms may be defined for the network (e.g., in LTE or NR) to notify the UE 115 of absolute time (e.g., UTC time or GPS time) through a Uu connection using public system information signaling (e.g., system information block (SIB) 9 (SIB9)) or dedicated signaling (e.g., in DLInformationTransfer IE). However, in some cases, such signaling of absolute time may not be defined for UEs 115 that support sidelink communication outside the coverage area of ​​the network (e.g., V2X or Industrial IoT (IiOT) devices). That is, the technology for signaling absolute time to the UE 115 without a Uu connection may be undefined, and the functionality of the UE 115 may be limited.

[0089] The wireless communication system 100 may support efficient techniques for distributing absolute time information to UE 115 supporting sidelink communication. The wireless communication system 100 may establish sidelink messages and IEs that can be used to distribute absolute time information from a first UE 115 to a second UE 115 (e.g., messages and IEs used to propagate absolute time information in an over-the-air (OTA) sidelink communication). The participating UE 115 (e.g., the first UE 115 or the second UE 115) may be mobile or stationary (e.g., a roadside unit (RSU)). The first UE 115 may provide absolute time to the second UE 115, and the absolute time may be referenced to an international standard (e.g., UTC time or GPS time). PC5-RRC signaling or MAC-CE may be used to exchange time messages (e.g., between the first UE 115 and the second UE 115). Time distribution may be based on request-response signaling or provided unilaterally by the participating UE 115 (e.g., the first UE 115).

[0090] Figure 2 An example of a wireless communication system 200 that supports absolute time distribution on sidelink communications according to one or more aspects of the present disclosure is illustrated. The wireless communication system 200 includes UE 115-a and UE 115-b, which may be reference Figure 1 The wireless communication system 200 also includes a network entity 205, which may be a reference Figure 1An example of a UE 115 or a network entity 105 is depicted. The wireless communication system 200 may implement aspects of the wireless communication system 100. For example, the wireless communication system 200 may support efficient techniques for distributing absolute time information to a UE 115 supporting sidelink communications.

[0091] UE 115-b may receive first time information 215 from wireless device 205, the first time information indicating a first absolute time value of a reference calendar date. UE 115-b may then set an absolute time clock at a boundary of a first reference time interval based on the first absolute time value. The boundary of the first reference time interval may correspond to the end of the time interval in which the first time information 215 is received or the beginning of a time interval after the time interval in which the first time information 215 is received. The first reference time interval may be one of a plurality of time intervals established for communication at UE 115-b. For example, if wireless device 205 is a network entity, the first reference time interval may be one of a plurality of system frames established for communication with network entity 105. Alternatively, if wireless device 205 is UE 115, the first reference time interval may be one of a plurality of distributed frames established for communication with UE 115. In any case, UE 115-b may identify the first absolute time value at the boundary of the first reference time interval and may keep track of the absolute time.

[0092] Because UE 115-b can keep track of absolute time, UE 115-b can share or distribute absolute time to other UEs 115. For example, UE 115-b can send second time information indicating a second absolute time value (e.g., a time value referenced to universal time), and UE 115-a can receive the second time information. UE 115-a can then set an absolute time clock at a boundary of a second reference time interval based on the second absolute time value. The second reference time interval can be one of a plurality of time intervals 220 established for communication at UE 115-a. For example, UE 115-a can communicate with UE 115-b to establish a time interval 220 for communicating with UE 115-b, or UE 115-a can identify the time interval 220 in other ways. Therefore, UE 115-b can identify the second absolute time value at the boundary of the second reference time interval and can keep track of the absolute time. That is, UE 115-b may distribute absolute time information (eg, second time information including a second absolute time value) to UE 115-a via a side link.

[0093] Figure 3An example of absolute time distribution 300 over sidelink communications in accordance with one or more aspects of the present disclosure is illustrated.

[0094] In a first example 300-a, UE 115-c may be within a coverage area of ​​network entity 105-a, and UE 115-d and UE 115-e may be outside of the coverage area of ​​any network entity 105. Network entity 105-a may send a SIB9 message indicating absolute time information (e.g., absolute time to UE 115-c via SIB9), and UE 115-c may receive the SIB9 message. The absolute time information may indicate a first absolute time value at a boundary of a first reference time interval, where the first reference time interval is one of a plurality of first time intervals established for communication between network entity 105-a and UE 115-c. UE 115-c may send a master information block side link (MIBSL) to UE 115-d, the MIBSL indicating or identifying a plurality of second time intervals for communication between UE 115-c and UE 115-d (e.g., for synchronization with UE 115-d via MIBSL). UE 115-c may then send a sidelink message indicating a second absolute time value at a boundary of a second reference time interval (e.g., an absolute (UTC, GPS) time sent to UE 115-d via a sidelink), and UE 115-d may receive the sidelink message, wherein the second reference time interval is one of a plurality of second time intervals established for communication between UE 115-c and UE 115-d. Similarly, UE 115-d may send a MIBSL to UE 115-e indicating or identifying a plurality of third time intervals for communication between UE 115-d and UE 115-e (e.g., for synchronization with UE 115-e via the MIBSL). UE 115-d may then send, and UE 115-e may receive, a sidelink message indicating a third absolute time value (e.g., an absolute (UTC, GPS) time sent to UE 115-e via a sidelink) at a boundary of a third reference time interval, wherein the third reference time interval is one of multiple third time intervals established for communication between UE 115-d and UE 115-e.

[0095] In a second example 300-b, UE 115-f, UE 115-g, and UE 115-h may each be outside of a coverage area of ​​any network entity 105. A global navigation satellite system (GNSS) 305 may send a message indicating absolute time information (e.g., GNSS time), and UE 115-f may receive the message. The absolute time information may indicate a first absolute time value and ephemeris data of one or more of the GNSS transmitters. UE 115-f may use the absolute time information and the ephemeris data to calculate an absolute time at UE 115-f. UE 115-f may send a MIBSL to UE 115-g, the MIBSL indicating or identifying a plurality of first time intervals for communication between UE 115-f and UE 115-g (e.g., for synchronization with UE 115-g via the MIBSL). UE 115-f may then send, and UE 115-g may receive, a sidelink message indicating a second absolute time value at a boundary of a first reference time interval (e.g., an absolute (UTC, GPS) time sent to UE 115-g via a sidelink), wherein the first reference time interval is one of a plurality of first time intervals established for communication between UE 115-f and UE 115-g. Similarly, UE 115-g may send, to UE 115-h, a MIBSL indicating or identifying a plurality of second time intervals for communication between UE 115-g and UE 115-h (e.g., for synchronization with UE 115-h via the MIBSL). UE 115-g may then send, and UE 115-h may receive, a sidelink message indicating a third absolute time value at a boundary of a second reference time interval (e.g., an absolute (UTC, GPS) time sent to UE 115-h via a sidelink), where the second reference time interval is one of multiple second time intervals established for communication between UE 115-g and UE 115-h.

[0096] The described technology may support various messages or IEs for distributing absolute time information (e.g., second time information 210) on a side link. In one aspect, the absolute time information may be distributed in a PC5-RRC message. In some examples, the PC5-RRC message may include an indication of an absolute time with reference to a distributed frame number (DFN), and the PC5-RRC message may be similar to a SIB9 message (e.g., including a field similar to a SIB9 message). If the PC5-RRC message is similar to the SIB9 message, there may be minimal changes at UE115-a to receive the PC5-RRC message. In other examples, the PC5-RRC message may be simplified (e.g., having less nesting than the SIB9 message) and may include a single IE to indicate the absolute time with reference to the DFN (e.g., UTC time or GPS time). If the PC5-RRC message is simplified, the overhead of the PC5-RRC message and the complexity of parsing the PC5-RRC message may be minimized. On the other hand, the absolute time information may be distributed in the MAC-CE (e.g., multicast or broadcast to multiple UEs 115).

[0097] A PC5-RRC message similar to a SIB9 message may include a first field and a second field, the first field including an absolute time value, the second field including an indicator of a reference time interval, and the second field may include a third field indicating additional reference time information. For example, the PC5-RRC message may include a SL-TimeInformation IE, and the SL-TimeInformation IE may include an sl-timeInfo IE (e.g., a first field) and an sl-referenceTimeInfo IE (e.g., a second field). The sl-timeInfo IE (e.g., a first field) may include a SidelinkTimeInfoUTC IE, which indicates a UTC time corresponding to a DFN boundary at or immediately after the DFN at which the SL-TimeInformation IE is sent (or received). The SidelinkTimeInfoUTC IE or field may calculate the number of UTC seconds since 00:00:00 on the Gregorian calendar date January 1, 1900 (e.g., midnight between Sunday, December 31, 1899 and Monday, January 1, 1900) in units of 10 ms. The sl-referenceTimeInfo IE (e.g., the second field) may include an sl-referenceDFN IE indicating a reference DFN corresponding to the reference time information. The sl-referenceTimeInfo IE may also include a time field including additional reference time information. For example, the time field may refer to an SL-ReferenceTime IE (e.g., the third field) indicating a time reference with a granularity of 10ns. If the sl-referenceTimeInfo field is received in the SL-TimeInfoUTC, the time field may indicate the time at the end boundary of the DFN that sends (or receives) the SL-TimeInfoUTC or at the DFN boundary immediately after the end boundary. If the sl-referenceTimeInfo field is received in the SL-TimeInfoUTC, the sl-referenceTimeInfo field may be excluded when determining a change in system information (e.g., a change in time may not result in a system information change notification nor in a modification of the valueTag in SIB1). The SL-ReferenceTime IE may also include a refSource field indicating a time source for the reference time.

[0098] A simplified PC5-RRC message (e.g., having less nesting than a SIB9 message) may include a first field and a second field, the first field including an absolute time value and an indicator of a reference time interval, and the second field indicating additional reference time information. For example, the PC5-RRC message may include an SL-ReferenceTimeInformation IE (e.g., the first field), and the SL-ReferenceTimeInformation IE may include a time field and an sl-referenceDFN field. The time field may refer to an SL-ReferenceTime IE (e.g., the second field) indicating a time reference with a granularity of 10ns, and the sl-referenceDFN field may indicate a reference DFN corresponding to the reference time information. If the sl-referenceTimeInfo field is received in the SL-TimeInfoUTC, the time field may indicate a time at an end boundary of a DFN that sends (or receives) the SL-TimeInfoUTC or at a DFN boundary immediately after the end boundary. If the sl-referenceTimeInfo field is received in SL-TimeInfoUTC, the sl-referenceTimeInfo field may be excluded when determining changes in system information (e.g., a change in time may result in neither a system information change notification nor a modification of the valueTag in SIB1). The SL-ReferenceTimeInformation IE may also include a TimeInfoType IE, which may indicate whether the absolute time provided is GPS time, UTC time, or unspecified (e.g., a local clock). The SL-ReferenceTime IE, which is referenced by the time field and indicates a time reference with a granularity of 10ns, may include a refDays field, a refSeconds field, a refMilliSeconds field, a refTenNanoSeconds field, a dayLightSavingTime field, a leapSeconds field, and a localTimeOffset field.

[0099] In some cases, the described techniques may also support a PC5-RRC time distribution request message that the UE 115 may use to request absolute time information. For example, the UE 115-a may explicitly request absolute time information from the UE 115-b. In one example, the request may be based on the SL-ReferenceTimeInfo IE. In this example, the UE 115-a may send a SL-ReferenceTimeRequest IE including an sl-timeInfo field requesting the SL-TimeInfo IE, and the UE 115-a may receive a message with the SL-TimeInfo IE in response to sending the SL-ReferenceTimeRequest IE. In another example, the request may be based on the SL-ReferenceTimeInformation IE. In this example, the UE 115-a may send a SL-ReferenceTimeRequest IE including an sl-ReferenceTimeInformation field requesting the SL-ReferenceTimeInformation IE, and the UE 115-a may receive a message with the SL-ReferenceTimeInformation IE in response to sending the SL-ReferenceTimeRequest IE.

[0100] Figure 4 An example of a MAC-CE 400 for distributing time information on sidelink communications according to one or more aspects of the present disclosure is illustrated. The UE 115 may multicast or broadcast the MAC-CE 400 to multiple UEs 115 and may include absolute time information for each of the multiple UEs. The MAC-CE 400 may include a SidelinkTimeInfoUTC IE 405 that indicates a UTC time corresponding to a DFN boundary at or immediately after the DFN at which the MAC-CE 400 is sent (or received). The SidelinkTimeInfoUTC IE or field may calculate the number of UTC seconds since 00:00:00 on the Gregorian calendar date January 1, 1900 (e.g., midnight between Sunday, December 31, 1899 and Monday, January 1, 1900) in units of 10 ms. The MAC-CE 400 may also include a leapSeconds field, a localTimeOffset field, a refDays field, a refSeconds field, a refMilliSeconds field, and another refSeconds field or a refTenNanoSeconds field.

[0101] Figure 5An example of a process flow 500 for supporting absolute time distribution on sidelink communications in accordance with one or more aspects of the present disclosure is illustrated. The process flow 500 includes UE 115-i and UE 115-j, which may be reference Figures 1 to 4 The process flow 500 also includes a wireless device 505, which may be a reference Figures 1 to 4 The process flow 500 may implement aspects of the wireless communication system 100 or the wireless communication system 200. For example, the process flow 500 may support efficient techniques for distributing absolute time information to the UE 115 supporting sidelink communications.

[0102] In the following description of process flow 500, signaling exchanged between UE 115-i, UE 115-j, and wireless device 505 may be exchanged in an order different from the example order shown, or operations performed by UE 115-i, UE 115-j, and wireless device 505 may be performed in a different order or at a different time. Some operations may also be omitted from process flow 500, and other operations may be added to process flow 500.

[0103] At 510, the wireless device 505 may send a message including first time information indicating a first absolute time value, and the UE 115-j may receive the message. The first absolute time value may reference a calendar date, an international standard, or both.

[0104] At 515, UE 115-j may set an absolute time clock at a first boundary of a first reference time interval based on the first absolute time value. If the wireless device 505 is the network entity 105, the message including the time information may be a downlink message, the first reference time interval may be a system frame, and the first reference time interval may be indicated by the SFN in the first time information. If the wireless device 505 is the UE 115, the message including the time information may be a sidelink message, the first reference time interval may be a distributed frame, and the first reference time interval may be indicated by the DFN in the first time information.

[0105] At 520, UE 115-i and UE 115-j may communicate with each other for timing synchronization. For example, UE 115-i and UE 115-j may communicate to establish time intervals for communication between UE 115-i and UE 115-j (e.g., the start time of the time interval, the index of the time interval, and the duration of each time interval). In some examples, UE 115-i may communicate with another UE 115 for timing synchronization (e.g., to establish a time interval for communication at UE 115-i). In some examples, timing synchronization information (e.g., to establish a time interval for communication) may be broadcast or multicast to multiple UEs including UE 115-i.

[0106] UE 115-j may determine a second absolute time value at a second boundary of a second reference time interval based on an absolute time clock at UE 115-j. The second absolute time value may reference a calendar date, an international standard, or both. The second reference time interval may be one of the time intervals established for communications between UE 115-i and UE 115-j or for communications at UE 115-i.

[0107] At 525, UE 115-j may send a sidelink message (e.g., a PC5-RRC message or a MAC-CE) including second time information indicating a second absolute time value, and UE 115-i may receive the sidelink message. In some examples, UE 115-i may send a request for the second time information, and UE 115-j may receive the request, and in response to the request, UE 115-i may receive a sidelink message including the second time information, and UE 115-j may send the sidelink message. In some examples, the sidelink message includes a first field and a second field, the first field including the second absolute time value, the second field including an indicator of a second reference time interval, and the second field including a third field indicating additional reference time information. In some examples, the sidelink message includes a first field, the first field including the second absolute time value and an indicator of the second reference time interval, and the sidelink message includes a second field indicating the additional reference time information. The second time information may indicate a type of the second absolute time value, the type of the second absolute time value corresponding to UTC time, GPS time, or local clock time.

[0108] At 530, UE 115-i may set an absolute time clock at a boundary of a second reference time interval based on the absolute time value. In some examples, the boundary of the second reference time interval may be located at the beginning of the second reference time interval, and the second reference time interval may be immediately after (e.g., after and adjacent to) a time interval in which a second sidelink message is received or sent. In some examples, in the second time information of the sidelink message, UE 115-j may send an indicator of the second reference time interval, and UE 115-i may receive the indicator. The reference time interval may be a distributed frame, and the indicator of the reference time interval may be a DFN.

[0109] At 535, UE 115-i may communicate (e.g., exchange data) with UE 115-j or other UEs 115 based on the absolute time clock. For example, accurate absolute time may be useful for IoT applications or automotive V2X communications.

[0110] Figure 6 A block diagram 600 of a device 605 supporting absolute time distribution on sidelink communications according to one or more aspects of the present disclosure is shown. The device 605 may be an example of aspects of the UE 115 as described herein. The device 605 may include a receiver 610, a transmitter 615, and a communication manager 620. The device 605 may also include a processor. Each of these components may communicate with each other (e.g., via one or more buses).

[0111] The receiver 610 may provide means for receiving information such as packets associated with various information channels (e.g., control channels, data channels, information channels related to absolute time distribution on sidelink communications), user data, control information, or any combination thereof. The information may be communicated to other components of the device 605. The receiver 610 may utilize a single antenna or a collection of multiple antennas.

[0112] The transmitter 615 may provide means for transmitting signals generated by other components of the device 605. For example, the transmitter 615 may transmit information such as packets associated with various information channels (e.g., control channels, data channels, information channels related to absolute time distribution on sidelink communications), user data, control information, or any combination thereof. In some examples, the transmitter 615 may be co-located with the receiver 610 in a transceiver module. The transmitter 615 may utilize a single antenna or a collection of multiple antennas.

[0113] The communication manager 620, the receiver 610, the transmitter 615, or various combinations thereof, or various components thereof, may be examples of means for performing various aspects of absolute time distribution on sidelink communications as described herein. For example, the communication manager 620, the receiver 610, the transmitter 615, or various combinations thereof, or components thereof, may support methods for performing one or more of the functions described herein.

[0114] In some examples, the communication manager 620, the receiver 610, the transmitter 615, or various combinations or components thereof may be implemented in hardware (e.g., in a communication management circuit). The hardware may include a processor, a digital signal processor (DSP), a central processing unit (CPU), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, a microcontroller, discrete gate or transistor logic, discrete hardware components, or any combination thereof that is configured to or otherwise supports components for performing the functions described in the present disclosure. In some examples, the processor and a memory coupled to the processor may be configured to perform one or more of the functions described herein (e.g., by executing instructions stored in the memory by the processor).

[0115] Additionally or alternatively, in some examples, the communication manager 620, the receiver 610, the transmitter 615, or various combinations or components thereof may be implemented in code executed by a processor (e.g., as communication management software or firmware). If implemented in code executed by a processor, the functionality of the communication manager 620, the receiver 610, the transmitter 615, or various combinations or components thereof may be performed by a general purpose processor (e.g., configured as or otherwise supporting components for performing the functions described in the present disclosure), a DSP, a CPU, an ASIC, an FPGA, a microcontroller, or any combination of these or other programmable logic devices.

[0116] In some examples, communication manager 620 may be configured to perform various operations (e.g., receive, obtain, monitor, output, transmit) using or otherwise cooperating with receiver 610, transmitter 615, or both. For example, communication manager 620 may receive information from receiver 610, transmit information to transmitter 615, or be integrated in conjunction with receiver 610, transmitter 615, or both to obtain information, output information, or perform various other operations as described herein.

[0117] According to examples as disclosed herein, the communication manager 620 may support wireless communications at the first UE. For example, the communication manager 620 may be configured to or otherwise support components for receiving a sidelink message including time information indicating an absolute time value of a reference calendar date from a second UE, wherein the sidelink message is received based on a set of multiple time intervals established for communications between the first UE and the second UE. The communication manager 620 may be configured to or otherwise support components for setting an absolute time clock at a boundary of a reference time interval in the set of multiple time intervals based on the absolute time value. The communication manager 620 may be configured to or otherwise support components for communicating based on the absolute time clock.

[0118] Additionally or alternatively, according to examples as disclosed herein, the communication manager 620 may support wireless communications at the first UE. For example, the communication manager 620 may be configured to or otherwise support components for receiving a message including first time information indicating a first absolute time value, wherein the first absolute time value refers to a calendar date. The communication manager 620 may be configured to or otherwise support components for setting an absolute time clock at a boundary of a first reference time interval based on the first absolute time value. The communication manager 620 may be configured to or otherwise support components for determining a second absolute time value at a second boundary of a second reference time interval based on the absolute time clock, wherein the second reference time interval is one of a set of multiple time intervals established for communication between the first UE and the second UE. The communication manager 620 may be configured to or otherwise support components for sending a sidelink message including second time information indicating a second absolute time value to the second UE.

[0119] By including or configuring a communication manager 620 according to the examples described herein, the device 605 (e.g., a processor that controls or otherwise couples with the receiver 610, the transmitter 615, the communication manager 620, or a combination thereof) may support techniques for reducing processing, reducing power consumption, or more efficiently utilizing communication resources. Since the described techniques may provide for distributing absolute time information on sidelink communications, the device 605 may be able to identify absolute time and use the absolute time in various applications (e.g., IoT applications) or sidelink communications (e.g., V2X communications). Therefore, the efficiency of these applications or sidelink communications may be improved, resulting in reduced processing, reduced power consumption, or more efficient utilization of communication resources.

[0120] Figure 7A block diagram 700 of a device 705 supporting absolute time distribution on sidelink communications according to one or more aspects of the present disclosure is shown. The device 705 may be an example of aspects of the device 605 or UE 115 as described herein. The device 705 may include a receiver 710, a transmitter 715, and a communication manager 720. The device 705 may also include a processor. Each of these components may communicate with each other (e.g., via one or more buses).

[0121] The receiver 710 may provide means for receiving information such as packets associated with various information channels (e.g., control channels, data channels, information channels related to absolute time distribution on sidelink communications), user data, control information, or any combination thereof. The information may be communicated to other components of the device 705. The receiver 710 may utilize a single antenna or a collection of multiple antennas.

[0122] The transmitter 715 may provide means for transmitting signals generated by other components of the device 705. For example, the transmitter 715 may transmit information such as packets associated with various information channels (e.g., control channels, data channels, information channels related to absolute time distribution on sidelink communications), user data, control information, or any combination thereof. In some examples, the transmitter 715 may be co-located with the receiver 710 in a transceiver module. The transmitter 715 may utilize a single antenna or a collection of multiple antennas.

[0123] The device 705 or its various components may be examples of components for performing various aspects of absolute time distribution on side link communications as described herein. For example, the communication manager 720 may include a time information manager 725, a clock manager 730, a timing manager 735, or any combination thereof. The communication manager 720 may be an example of various aspects of the communication manager 620 as described herein. In some examples, the communication manager 720 or its various components may be configured to perform various operations (e.g., receive, obtain, monitor, output, send) using or otherwise cooperating with the receiver 710, the transmitter 715, or both. For example, the communication manager 720 may receive information from the receiver 710, transmit information to the transmitter 715, or be integrated with the receiver 710, the transmitter 715, or both to obtain information, output information, or perform various other operations as described herein.

[0124] According to examples as disclosed herein, the communication manager 720 may support wireless communications at the first UE. The time information manager 725 may be configured to or otherwise support components for receiving a sidelink message including time information indicating an absolute time value of a reference calendar date from a second UE, wherein the sidelink message is received based on a set of multiple time intervals established for communications between the first UE and the second UE. The clock manager 730 may be configured to or otherwise support components for setting an absolute time clock at a boundary of a reference time interval in the set of multiple time intervals based on the absolute time value. The timing manager 735 may be configured to or otherwise support components for communicating based on the absolute time clock.

[0125] Additionally or alternatively, according to examples as disclosed herein, the communication manager 720 may support wireless communications at the first UE. The time information manager 725 may be configured to or otherwise support components for receiving a message including first time information indicating a first absolute time value, wherein the first absolute time value refers to a calendar date. The clock manager 730 may be configured to or otherwise support components for setting an absolute time clock at a boundary of a first reference time interval based on the first absolute time value. The time information manager 725 may be configured to or otherwise support components for determining a second absolute time value at a second boundary of a second reference time interval based on the absolute time clock, wherein the second reference time interval is one of a set of multiple time intervals established for communication between the first UE and the second UE. The time information manager 725 may be configured to or otherwise support components for sending a sidelink message including second time information indicating a second absolute time value to the second UE.

[0126] Figure 8 A block diagram 800 of a communication manager 820 supporting absolute time distribution on sidelink communications in accordance with one or more aspects of the present disclosure is shown. The communication manager 820 may be an example of aspects of the communication manager 620, the communication manager 720, or both as described herein. The communication manager 820 or its various components may be examples of components for performing various aspects of absolute time distribution on sidelink communications as described herein. For example, the communication manager 820 may include a time information manager 825, a clock manager 830, a timing manager 835, a synchronization manager 840, or any combination thereof. Each of these components may communicate with each other directly or indirectly (e.g., via one or more buses).

[0127] According to examples as disclosed herein, the communication manager 820 may support wireless communications at the first UE. The time information manager 825 may be configured to or otherwise support components for receiving a side link message including time information indicating an absolute time value of a reference calendar date from a second UE, wherein the side link message is received based on a set of multiple time intervals established for communications between the first UE and the second UE. The clock manager 830 may be configured to or otherwise support components for setting an absolute time clock at a boundary of a reference time interval in the set of multiple time intervals based on the absolute time value. The timing manager 835 may be configured to or otherwise support components for communicating based on the absolute time clock.

[0128] In some examples, the time information manager 825 may be configured or otherwise support components for sending a request for time information to a second UE, wherein in response to sending the request, a sidelink message including the time information is received from the second UE.

[0129] In some examples, the second boundary of the reference time interval is located at the beginning of the reference time interval, and the reference time interval is immediately after the time interval in which the side link message is received.

[0130] In some examples, time information manager 825 may be configured or otherwise support components for receiving an indicator of a reference time interval in the time information of a sidelink message.

[0131] In some examples, the indicator of the reference time interval includes a distributed frame number.

[0132] In some examples, the sidelink message includes a first field including an absolute time value and a second field including an indicator of a reference time interval, and the second field includes a third field indicating additional reference time information.

[0133] In some examples, the sidelink message includes a first field that includes an absolute time value and an indicator of a reference time interval, and the sidelink message includes a second field that indicates additional reference time information.

[0134] In some examples, the time information indicates a type of absolute time value, the type of the absolute time value corresponding to Coordinated Universal Time, Global Positioning System time, or local clock time.

[0135] In some examples, to support receiving side link messages including time information, the time information manager 825 may be configured as or otherwise support components for receiving a medium access control (MAC) control element (MAC-CE) including time information from a second UE in a broadcast or multicast transmission.

[0136] In some examples, synchronization manager 840 may be configured or otherwise support components for communicating with a second UE or a third UE for timing synchronization, wherein the reference time interval includes frames having boundaries determined based on communicating with the second UE or the third UE for timing synchronization.

[0137] In some examples, the first UE is outside the coverage area of ​​any network entity and the second UE is within the coverage area of ​​at least one network entity.

[0138] Additionally or alternatively, according to examples as disclosed herein, the communication manager 820 may support wireless communication at the first UE. In some examples, the time information manager 825 may be configured to or otherwise support a component for receiving a message including first time information indicating a first absolute time value, wherein the first absolute time value refers to a calendar date. In some examples, the clock manager 830 may be configured to or otherwise support a component for setting an absolute time clock at a first boundary of a first reference time interval based on the first absolute time value. In some examples, the time information manager 825 may be configured to or otherwise support a component for determining a second absolute time value at a second boundary of a second reference time interval based on the absolute time clock, wherein the second reference time interval is a time interval in a set of multiple time intervals established for communication between the first UE and the second UE. In some examples, the time information manager 825 may be configured to or otherwise support a component for sending a side link message including second time information indicating a second absolute time value to the second UE.

[0139] In some examples, the time information manager 825 may be configured or otherwise support components for receiving a request for second time information from a second UE, wherein in response to receiving the request, a sidelink message including the second time information is sent to the second UE.

[0140] In some examples, to support receiving a message including first time information, time information manager 825 may be configured or otherwise support components for receiving a downlink message including first time information indicating a first absolute time value from a network entity.

[0141] In some examples, the first reference time interval is indicated by a system frame number in the first time information.

[0142] In some examples, to support receiving a message including the first time information, the time information manager 825 may be configured or otherwise support components for receiving a second sidelink message including the first time information indicating a first absolute time value from a third UE.

[0143] In some examples, the first reference time interval is indicated by a distributed frame number in the first time information.

[0144] In some examples, the second boundary of the second reference time interval is located at the beginning of the second reference time interval, and the second reference time interval is immediately after the time interval for sending the side link message.

[0145] In some examples, the time information manager 825 may be configured or otherwise support components for sending an indicator of the second reference time interval in the second time information of the side link message.

[0146] In some examples, the indicator of the second reference time interval includes a distributed frame number.

[0147] In some examples, the sidelink message includes a first field including a second absolute time value and a second field including an indicator of a second reference time interval, and the second field includes a third field indicating additional reference time information.

[0148] In some examples, the first sidelink message includes a first field including a second absolute time value and an indicator of a second reference time interval, and the sidelink message includes a second field indicating additional reference time information.

[0149] In some examples, the second time information indicates a type of the second absolute time value, the type of the second absolute time value corresponding to Universal Coordinated Time, Global Positioning System time, or local clock time.

[0150] In some examples, to support sending a side link message including second time information, the time information manager 825 may be configured as or otherwise support components for sending a medium access control (MAC) control element (MAC-CE) including the second time information in a broadcast or multicast transmission.

[0151] In some examples, the synchronization manager 840 may be configured as or otherwise support components for communicating with a third UE or network entity for timing synchronization, wherein boundaries of the first reference time interval and the second reference time interval are determined based on communicating with the third UE or network entity for timing synchronization.

[0152] In some examples, the first UE is within the coverage area of ​​at least one network entity and the second UE is outside the coverage area of ​​any network entity.

[0153] Fig. 9A diagram of a system 900 including a device 905 supporting absolute time distribution on sidelink communications according to one or more aspects of the present disclosure is shown. The device 905 may be an example of a device 605, a device 705, or a UE 115 as described herein, or include components thereof. The device 905 may communicate (e.g., wirelessly) with one or more network entities 105, one or more UEs 115, or any combination thereof. The device 905 may include components for two-way voice and data communications, including components for sending and receiving communications, such as a communication manager 920, an input / output (I / O) controller 910, a transceiver 915, an antenna 925, a memory 930, a code 935, and a processor 940. These components may be electronically communicated or otherwise coupled (e.g., operatively, communicatively, functionally, electronically, electrically) via one or more buses (e.g., a bus 945).

[0154] I / O controller 910 may manage input and output signals for device 905. I / O controller 910 may also manage peripheral devices that are not integrated into device 905. In some cases, I / O controller 910 may represent a physical connection or port to an external peripheral device. In some cases, I / O controller 910 may utilize an operating system, such as MS- MS- OS / or another known operating system. Additionally or alternatively, I / O controller 910 may represent or interact with a modem, keyboard, mouse, touch screen, or similar device. In some cases, I / O controller 910 may be implemented as part of a processor (such as processor 940). In some cases, a user may interact with device 905 via I / O controller 910 or via hardware components controlled by I / O controller 910.

[0155] In some cases, the device 905 may include a single antenna 925. However, in some other cases, the device 905 may have more than one antenna 925, which may be capable of concurrently transmitting or receiving multiple wireless transmissions. The transceiver 915 may communicate bidirectionally via one or more antennas 925, a wired or wireless link, as described herein. For example, the transceiver 915 may represent a wireless transceiver and may communicate bidirectionally with another wireless transceiver. The transceiver 915 may also include a modem for: modulating packets; providing the modulated packets to one or more antennas 925 for transmission; and demodulating packets received from one or more antennas 925. The transceiver 915 or the transceiver 915 and one or more antennas 925 may be examples of transmitters 615, transmitters 715, receivers 610, receivers 710, or any combination thereof or components thereof as described herein.

[0156] The memory 930 may include random access memory (RAM) and read-only memory (ROM). The memory 930 may store computer-readable, computer-executable code 935 including instructions that, when executed by the processor 940, cause the device 905 to perform various functions described herein. The code 935 may be stored in a non-transitory computer-readable medium, such as a system memory or another type of memory. In some cases, the code 935 may not be directly executable by the processor 940, but may (e.g., when compiled and executed) cause the computer to perform the functions described herein. In some cases, the memory 930 may also contain, among other things, a basic I / O system (BIOS) that may control basic hardware or software operations, such as interaction with peripheral components or devices.

[0157] The processor 940 may include an intelligent hardware device (e.g., a general-purpose processor, a DSP, a CPU, a microcontroller, an ASIC, an FPGA, a programmable logic device, a discrete gate or transistor logic component, a discrete hardware component, or any combination thereof). In some cases, the processor 940 may be configured to operate a memory array using a memory controller. In some other cases, the memory controller may be integrated into the processor 940. The processor 940 may be configured to execute computer-readable instructions stored in a memory (e.g., a memory 930) to enable the device 905 to perform various functions (e.g., functions or tasks that support absolute time distribution on side link communications). For example, the device 905 or a component of the device 905 may include a processor 940 and a memory 930 coupled to or coupled to the processor 940, and the processor 940 and the memory 930 are configured to perform the various functions described herein.

[0158] According to examples as disclosed herein, the communication manager 920 may support wireless communications at the first UE. For example, the communication manager 920 may be configured to or otherwise support components for receiving a sidelink message including time information indicating an absolute time value of a reference calendar date from a second UE, wherein the sidelink message is received based on a set of multiple time intervals established for communications between the first UE and the second UE. The communication manager 920 may be configured to or otherwise support components for setting an absolute time clock at a boundary of a reference time interval in the set of multiple time intervals based on the absolute time value. The communication manager 920 may be configured to or otherwise support components for communicating based on the absolute time clock.

[0159] Additionally or alternatively, according to examples as disclosed herein, the communication manager 920 may support wireless communications at the first UE. For example, the communication manager 920 may be configured to or otherwise support components for receiving a message including first time information indicating a first absolute time value, wherein the first absolute time value refers to a calendar date. The communication manager 920 may be configured to or otherwise support components for setting an absolute time clock at a boundary of a first reference time interval based on the first absolute time value. The communication manager 920 may be configured to or otherwise support components for determining a second absolute time value at a second boundary of a second reference time interval based on the absolute time clock, wherein the second reference time interval is one of a set of multiple time intervals established for communication between the first UE and the second UE. The communication manager 920 may be configured to or otherwise support components for sending a sidelink message including second time information indicating a second absolute time value to the second UE.

[0160] By including or configuring a communication manager 920 according to the examples described herein, the device 905 may support techniques for reducing processing, reducing power consumption, or more efficiently utilizing communication resources. Since the described techniques may provide for distributing absolute time information on sidelink communications, the device 905 may be able to identify absolute time and use the absolute time in various applications (e.g., IoT applications) or sidelink communications (e.g., V2X communications). Therefore, the efficiency of these applications or sidelink communications may be improved, resulting in reduced processing, reduced power consumption, or more efficient utilization of communication resources.

[0161] In some examples, the communication manager 920 may be configured to perform various operations (e.g., receive, monitor, transmit) using or otherwise cooperating with the transceiver 915, one or more antennas 925, or any combination thereof. Although the communication manager 920 is illustrated as a separate component, in some examples, one or more functions described with reference to the communication manager 920 may be supported or performed by the processor 940, the memory 930, the code 935, or any combination thereof. For example, the code 935 may include instructions that are executable by the processor 940 to cause the device 905 to perform various aspects of absolute time distribution on sidelink communications as described herein, or the processor 940 and the memory 930 may be otherwise configured to perform or support such operations.

[0162] Fig.10 A flow chart illustrating a method 1000 for supporting absolute time distribution on sidelink communications according to one or more aspects of the present disclosure is shown. The operations of the method 1000 may be implemented by a UE or a component thereof as described herein. For example, the operations of the method 1000 may be implemented by a UE or a component thereof as described in reference to Figures 1 to 9 The UE 115 described herein may be executed. In some examples, the UE may execute an instruction set to control the functional elements of the UE to perform the described functions. Additionally or alternatively, the UE may use dedicated hardware to perform various aspects of the described functions.

[0163] At 1005, the method may include receiving a sidelink message including time information indicating an absolute time value of a reference calendar date from a second UE, wherein the sidelink message is received according to a set of multiple time intervals established for communication between the first UE and the second UE. The operations of 1005 may be performed according to examples as disclosed herein. In some examples, aspects of the operations of 1005 may be performed by Figure 8 The described time information manager 825 is executed.

[0164] At 1010, the method may include setting an absolute time clock at a boundary of a reference time interval in the set of multiple time intervals based on the absolute time value. The operations of 1010 may be performed according to examples disclosed herein. In some examples, aspects of the operations of 1010 may be performed by reference to Figure 8 The clock manager 830 is used to execute.

[0165] At 1015, the method may include communicating according to an absolute time clock. The operations of 1015 may be performed according to examples disclosed herein. In some examples, aspects of the operations of 1015 may be described by reference to Figure 8 The described timing manager 835 is executed.

[0166] Fig.11A flow chart illustrating a method 1100 for supporting absolute time distribution on sidelink communications according to one or more aspects of the present disclosure is shown. The operations of the method 1100 may be implemented by a UE or a component thereof as described herein. For example, the operations of the method 1100 may be implemented by a UE or a component thereof as described in reference to Figures 1 to 9 The UE 115 described herein may be executed. In some examples, the UE may execute an instruction set to control the functional elements of the UE to perform the described functions. Additionally or alternatively, the UE may use dedicated hardware to perform various aspects of the described functions.

[0167] At 1105, the method may include receiving a message including first time information indicating a first absolute time value, wherein the first absolute time value refers to a calendar date. The operations of 1105 may be performed according to examples as disclosed herein. In some examples, aspects of the operations of 1105 may be performed by referring to Figure 8 The described time information manager 825 is executed.

[0168] At 1110, the method may include setting an absolute time clock at a first boundary of a first reference time interval based on the first absolute time value. The operations of 1110 may be performed according to examples disclosed herein. In some examples, aspects of the operations of 1110 may be performed by reference to Figure 8 The clock manager 830 is used to execute.

[0169] At 1115, the method may include determining a second absolute time value at a second boundary of a second reference time interval based on the absolute time clock, wherein the second reference time interval is one of a set of multiple time intervals established for communication between the first UE and the second UE. The operations of 1115 may be performed according to examples as disclosed herein. In some examples, aspects of the operations of 1115 may be performed by Figure 8 The described time information manager 825 is executed.

[0170] At 1120, the method may include sending a sidelink message including second time information indicating a second absolute time value to the second UE. The operations of 1120 may be performed according to examples as disclosed herein. In some examples, aspects of the operations of 1120 may be performed as described in reference to Figure 8 The described time information manager 825 is executed.

[0171] The following provides an overview of various aspects of the disclosure:

[0172] Aspect 1: A method for performing wireless communications at a first UE, the method comprising: receiving a side link message including time information of an absolute time value indicating a reference calendar date from a second UE, wherein the side link message is received based on a plurality of time intervals established for communications between the first UE and the second UE; setting an absolute time clock at a boundary of a reference time interval in the plurality of time intervals based at least in part on the absolute time value; and communicating based on the absolute time clock.

[0173] Aspect 2: According to the method according to Aspect 1, the method also includes: sending a request for the time information to the second UE, wherein in response to sending the request, the sidelink message including the time information is received from the second UE.

[0174] Aspect 3: A method according to any one of Aspects 1 to 2, wherein the boundary of the reference time interval is located at the beginning of the reference time interval, and the reference time interval is immediately after the time interval in which the side link message is received.

[0175] Aspect 4: According to the method according to any one of Aspects 1 to 3, the method also includes: receiving an indicator of the reference time interval in the time information of the sidelink message.

[0176] Aspect 5: The method according to aspect 4, wherein the indicator of the reference time interval comprises a distributed frame number.

[0177] Aspect 6: A method according to any one of Aspects 4 to 5, wherein the side link message includes a first field and a second field, the first field includes the absolute time value, the second field includes the indicator of the reference time interval, and the second field includes a third field indicating additional reference time information.

[0178] Aspect 7: A method according to any one of Aspects 4 to 6, wherein the side link message includes a first field, the first field includes the absolute time value and the indicator of the reference time interval, and the side link message includes a second field indicating additional reference time information.

[0179] Aspect 8: The method according to any one of aspects 1 to 7, wherein the time information indicates a type of the absolute time value, the type of the absolute time value corresponding to Coordinated Universal Time, Global Positioning System time, or local clock time.

[0180] Aspect 9: A method according to any one of Aspects 1 to 8, wherein receiving the sidelink message including the time information includes: receiving a medium access control (MAC) control element (MAC-CE) including the time information from the second UE in a broadcast or multicast transmission.

[0181] Aspect 10: According to any one of Aspects 1 to 9, the method also includes: communicating with the second UE or the third UE for timing synchronization, wherein the reference time interval includes a frame having boundaries determined at least in part based on communicating with the second UE or the third UE for timing synchronization.

[0182] Aspect 11: The method according to any one of aspects 1 to 10, wherein the first UE is outside the coverage area of ​​any network entity and the second UE is within the coverage area of ​​at least one network entity.

[0183] Aspect 12: A method for performing wireless communications at a first UE, the method comprising: receiving a message including first time information indicating a first absolute time value, wherein the first absolute time value refers to a calendar date; setting an absolute time clock at a first boundary of a first reference time interval based at least in part on the first absolute time value; determining a second absolute time value at a second boundary of a second reference time interval based at least in part on the absolute time clock, wherein the second reference time interval is one of multiple time intervals established for communication between the first UE and a second UE; and sending a sidelink message including second time information indicating the second absolute time value to the second UE.

[0184] Aspect 13: According to the method according to Aspect 12, the method also includes: receiving a request for the second time information from the second UE, wherein in response to receiving the request, the sidelink message including the second time information is sent to the second UE.

[0185] Aspect 14: The method according to any one of aspects 12 to 13, wherein receiving the message including the first time information comprises: receiving a downlink message including the first time information indicating the first absolute time value from a network entity.

[0186] Aspect 15: The method according to Aspect 14, wherein the first reference time interval is indicated by a system frame number in the first time information.

[0187] Aspect 16: A method according to any one of aspects 12 to 15, wherein receiving the message including the first time information includes: receiving a second sidelink message including the first time information indicating the first absolute time value from a third UE.

[0188] Aspect 17: The method according to Aspect 16, wherein the first reference time interval is indicated by a distributed frame number in the first time information.

[0189] Aspect 18: A method according to any one of Aspects 12 to 17, wherein the second boundary of the second reference time interval is located at the beginning of the second reference time interval, and the second reference time interval is immediately after the time interval for sending the side link message.

[0190] Aspect 19: According to the method of any one of Aspects 12 to 18, the method further includes: sending an indicator of the second reference time interval in the second time information of the sidelink message.

[0191] Aspect 20: The method according to aspect 19, wherein the indicator of the second reference time interval comprises a distributed frame number.

[0192] Aspect 21: A method according to any one of Aspects 19 to 20, wherein the side link message includes a first field and a second field, the first field includes the second absolute time value, the second field includes the indicator of the second reference time interval, and the second field includes a third field indicating additional reference time information.

[0193] Aspect 22: A method according to any one of Aspects 19 to 21, wherein the first side link message includes a first field, the first field includes the second absolute time value and the indicator of the second reference time interval, and the side link message includes a second field indicating additional reference time information.

[0194] Aspect 23: A method according to any one of Aspects 12 to 22, wherein the second time information indicates a type of the second absolute time value, and the type of the second absolute time value corresponds to Coordinated Universal Time, Global Positioning System time, or local clock time.

[0195] Aspect 24: A method according to any one of Aspects 12 to 23, wherein sending the side link message including the second time information includes: sending a medium access control (MAC) control element (MAC-CE) including the second time information in a broadcast or multicast transmission.

[0196] Aspect 25: According to the method described in any one of Aspects 12 to 24, the method further includes: communicating with a third UE or a network entity for timing synchronization, wherein the boundary of the first reference time interval and the second reference time interval is determined based on communicating with the third UE or the network entity for timing synchronization.

[0197] Aspect 26: The method according to any one of aspects 12 to 25, wherein the first UE is within the coverage area of ​​at least one network entity and the second UE is outside the coverage area of ​​any network entity.

[0198] Aspect 27: An apparatus for performing wireless communications at a first UE, the apparatus comprising: a processor; a memory coupled to the processor; and instructions stored in the memory and executable by the processor to cause the apparatus to perform a method according to any one of Aspects 1 to 11.

[0199] Aspect 28: An apparatus for wireless communication at a first UE, the apparatus comprising: at least one component for performing the method according to any one of aspects 1 to 11.

[0200] Aspect 29: A non-transitory computer-readable medium storing a code for wireless communication at a first UE, the code comprising instructions executable by a processor to perform a method according to any one of aspects 1 to 11.

[0201] Aspect 30: An apparatus for performing wireless communications at a first UE, the apparatus comprising: a processor; a memory coupled to the processor; and instructions stored in the memory and executable by the processor to cause the apparatus to perform a method according to any one of Aspects 12 to 26.

[0202] Aspect 31: An apparatus for wireless communication at a first UE, the apparatus comprising: at least one component for performing a method according to any one of aspects 12 to 26.

[0203] Aspect 32: A non-transitory computer-readable medium storing code for wireless communication at a first UE, the code comprising instructions executable by a processor to perform the method according to any one of aspects 12 to 26.

[0204] It should be noted that the methods described herein describe possible implementations, and that the various operations and steps may be rearranged or otherwise modified and that other implementations are possible. Furthermore, aspects from two or more methods may be combined.

[0205] Although aspects of LTE, LTE-A, LTE-A Pro, or NR systems may be described for example purposes, and LTE, LTE-A, LTE-A Pro, or NR terminology may be used in much of the description, the techniques described herein may also be applicable to networks other than LTE, LTE-A, LTE-A Pro, or NR networks. For example, the described techniques may be applicable to various other wireless communication systems, such as Ultra Mobile Broadband (UMB), Institute of Electrical and Electronics Engineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Flash-OFDM, and other systems and radio technologies not explicitly mentioned herein.

[0206] The information and signals described herein may be represented using any of a variety of different techniques and methods. For example, data, instructions, commands, information, signals, bits, symbols, and chips mentioned throughout the specification may be represented by voltage, current, electromagnetic waves, magnetic fields or magnetic particles, optical fields or optical particles, or any combination thereof.

[0207] The various illustrative blocks and components described in conjunction with the disclosure herein may be implemented or performed using a general purpose processor, DSP, ASIC, CPU, FPGA or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general purpose processor may be a microprocessor, but in an alternative, the processor may be any processor, controller, microcontroller, or state machine. The processor may also be implemented as a combination of computing devices (e.g., a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration).

[0208] The functions described herein may be implemented using hardware, software executed by a processor, firmware, or any combination thereof. When implemented using software executed by a processor, the functions may be stored as one or more instructions or codes of a computer-readable medium, or sent using one or more instructions or codes of a computer-readable medium. Other examples and specific implementations are within the scope of the present disclosure and the appended claims. For example, due to the nature of software, the functions described herein may be implemented using software executed by a processor, hardware, firmware, hard wiring, or a combination of any of these items. Features that implement the functions may also be physically located at different locations, including being distributed so that the various parts of the functions are implemented at different physical locations.

[0209] Computer-readable medium includes both non-transient computer storage medium and communication medium, and it includes any medium that facilitates computer program to be transmitted from one position to another position.Non-transient storage medium can be any available medium that can be accessed by general or special-purpose computer.By way of example and not limitation, non-transient computer-readable medium can include RAM, ROM, electrically erasable programmable ROM (EEPROM), flash memory, compact disc (CD) ROM or other optical disc storage device, disk storage device or other magnetic storage device, or can be used for carrying or storing desired program code parts and any other non-transient medium that can be accessed by general or special-purpose computer or general or special-purpose processor in the form of instruction or data structure.Moreover, any connection is appropriately referred to as computer-readable medium.For example, if software is sent from website, server or other remote source using coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL) or wireless technology such as infrared, radio and microwave, then coaxial cable, fiber optic cable, twisted pair, DSL or wireless technology such as infrared, radio and microwave are included in the definition of computer-readable medium. Disks and optical disks used herein include CDs, laser optical disks, optical optical disks, digital versatile disks (DVDs), floppy disks, and Blu-ray disks. Disks can reproduce data magnetically, while optical disks can reproduce data optically using lasers. Combinations of the above are also included within the scope of computer-readable media.

[0210] As used herein (including in the claims), "or" used in a list of items (e.g., a list of items followed by a phrase such as "at least one of" or "one or more of") indicates an inclusive list, so that, for example, a list of at least one of A, B, or C means A or B or C or AB or AC or BC or ABC (i.e., A and B and C). In addition, as used herein, the phrase "based on" should not be interpreted as a reference to a closed set of conditions. For example, an example step described as "based on condition A" can be based on both condition A and condition B without departing from the scope of the present disclosure. In other words, as used herein, the phrase "based on" should be interpreted in the same manner as the phrase "based at least in part on."

[0211] The term "determining" encompasses a variety of actions, and thus, "determining" may include calculating, computing, processing, deriving, investigating, looking up (such as via looking up in a table, database or other data structure), ascertaining, and the like. Furthermore, "determining" may include receiving (e.g., receiving information), accessing (e.g., accessing data stored in a memory), etc. Additionally, "determining" may include parsing, obtaining, selecting, choosing, establishing, and other such similar actions.

[0212] In the drawings, similar components or features may have the same reference label. In addition, various components of the same type may be distinguished by following the reference label with a dash and a second label to distinguish between similar components. If only the first reference label is used in the specification, the description may apply to any of the similar components having the same first reference label, regardless of the second or other subsequent reference labels.

[0213] The descriptions set forth herein in conjunction with the accompanying drawings describe example configurations and do not represent all examples that may be implemented or within the scope of the claims. The term "example" as used herein means "used as an example, instance, or illustration," rather than "preferred" or "advantageous over other examples." The specific implementation includes specific details to provide an understanding of the described techniques. However, these techniques may be practiced without these specific details. In some cases, known structures and devices are shown in block diagram form to avoid obscuring the concepts of the described examples.

[0214] The description herein is provided to enable one of ordinary skill in the art to implement or use the present disclosure. Various modifications to the present disclosure will be apparent to one of ordinary skill in the art, and the general principles defined herein may be applied to other variations without departing from the scope of the present disclosure. Thus, the present disclosure is not limited to the examples and designs described herein, but should be granted the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An apparatus for wireless communication at a first user equipment (UE), the apparatus comprising: processor; a memory coupled to the processor; and instructions stored in the memory and executable by the processor to cause the apparatus to: receiving, from a second UE, a sidelink message including time information indicating an absolute time value of a reference calendar date, wherein the sidelink message is received according to a plurality of time intervals established for communications between the first UE and the second UE; setting an absolute time clock at a boundary of a reference time interval in the plurality of time intervals based at least in part on the absolute time value; and Communications are performed according to the absolute time clock.

2. The apparatus of claim 1 , wherein the instructions are further executable by the processor to cause the apparatus to: A request for the time information is sent to the second UE, wherein the sidelink message including the time information is received from the second UE in response to sending the request.

3. The apparatus according to claim 1, wherein the boundary of the reference time interval is located at the beginning of the reference time interval, and the reference time interval is immediately after the time interval in which the side link message is received.

4. The apparatus of claim 1, wherein the instructions are further executable by the processor to cause the apparatus to: An indicator of the reference time interval is received in the time information of the sidelink message. The apparatus of claim 4 , wherein the indicator of the reference time interval comprises a distributed frame number.

6. The apparatus of claim 4, wherein the sidelink message comprises a first field and a second field, the first field comprising the absolute time value, the second field comprising the indicator of the reference time interval, and the second field comprising a third field indicating additional reference time information.

7. The apparatus of claim 4, wherein the sidelink message comprises a first field including the absolute time value and the indicator of the reference time interval, and the sidelink message comprises a second field indicating additional reference time information. 8 . The apparatus of claim 1 , wherein the time information indicates a type of the absolute time value, the type of the absolute time value corresponding to Coordinated Universal Time, Global Positioning System time, or local clock time.

9. The apparatus of claim 1 , wherein the instructions for receiving the sidelink message including the time information are executable by the processor to cause the apparatus to: A medium access control (MAC) control element (MAC-CE) including the time information is received from the second UE in a broadcast or multicast transmission.

10. The apparatus of claim 1, wherein the instructions are further executable by the processor to cause the apparatus to: communicating with the second UE or the third UE for timing synchronization, wherein the reference time interval comprises a frame having boundaries determined at least in part based on communicating with the second UE or the third UE for timing synchronization.

11. The apparatus of claim 1, wherein the first UE is outside the coverage area of ​​any network entity and the second UE is within the coverage area of ​​at least one network entity.

12. An apparatus for wireless communication at a first user equipment (UE), the apparatus comprising: processor; a memory coupled to the processor; and instructions stored in the memory and executable by the processor to cause the apparatus to: receiving a message including first time information indicating a first absolute time value, wherein the first absolute time value references a calendar date; setting an absolute time clock at a first boundary of a first reference time interval based at least in part on the first absolute time value; determining, based at least in part on the absolute time clock, a second absolute time value at a second boundary of a second reference time interval, wherein the second reference time interval is one of a plurality of time intervals established for communications between the first UE and a second UE; as well as A sidelink message including second time information indicating the second absolute time value is sent to the second UE.

13. The apparatus of claim 12, wherein the instructions are further executable by the processor to cause the apparatus to: A request for the second time information is received from the second UE, wherein in response to receiving the request, the sidelink message including the second time information is sent to the second UE.

14. The apparatus of claim 12, wherein the instructions for receiving the message including the first time information are executable by the processor to cause the apparatus to: A downlink message including the first time information indicating the first absolute time value is received from a network entity.

15. The apparatus according to claim 14, wherein the first reference time interval is indicated by a system frame number in the first time information.

16. The apparatus of claim 12, wherein the instructions for receiving the message including the first time information are executable by the processor to cause the apparatus to: A second sidelink message including the first time information indicating the first absolute time value is received from a third UE.

17. The apparatus according to claim 16, wherein the first reference time interval is indicated by a distributed frame number in the first time information.

18. The apparatus of claim 12, wherein the second boundary of the second reference time interval is located at the beginning of the second reference time interval, and the second reference time interval is immediately after a time interval in which the sidelink message is sent.

19. The apparatus of claim 12, wherein the instructions are further executable by the processor to cause the apparatus to: An indicator of the second reference time interval is sent in the second time information of the sidelink message.

20. The apparatus of claim 19, wherein the indicator of the second reference time interval comprises a distributed frame number.

21. The apparatus of claim 19, wherein the sidelink message comprises a first field and a second field, the first field comprising the second absolute time value, the second field comprising the indicator of the second reference time interval, and the second field comprising a third field indicating additional reference time information.

22. The apparatus of claim 19, wherein the first sidelink message comprises a first field including the second absolute time value and the indicator of the second reference time interval, and the sidelink message comprises a second field indicating additional reference time information.

23. The apparatus of claim 12, wherein the second time information indicates a type of the second absolute time value, the type of the second absolute time value corresponding to Coordinated Universal Time, Global Positioning System time, or local clock time.

24. The apparatus of claim 12, wherein the instructions for sending the sidelink message including the second time information are executable by the processor to cause the apparatus to: A medium access control (MAC) control element (MAC-CE) including the second time information is transmitted in a broadcast or multicast transmission.

25. The apparatus of claim 12, wherein the instructions are further executable by the processor to cause the apparatus to: Communicate with a third UE or a network entity for timing synchronization, wherein boundaries of the first reference time interval and the second reference time interval are determined based on communicating with the third UE or the network entity for timing synchronization.

26. The apparatus of claim 12, wherein the first UE is within a coverage area of ​​at least one network entity and the second UE is outside a coverage area of ​​any network entity.

27. A method for wireless communication at a first user equipment (UE), the method comprising: receiving, from a second UE, a sidelink message including time information indicating an absolute time value of a reference calendar date, wherein the sidelink message is received according to a plurality of time intervals established for communications between the first UE and the second UE; setting an absolute time clock at a boundary of a reference time interval in the plurality of time intervals based at least in part on the absolute time value; and Communications are performed according to the absolute time clock.

28. The method according to claim 27, further comprising: A request for the time information is sent to the second UE, wherein the sidelink message including the time information is received from the second UE in response to sending the request.

29. A method for wireless communication at a first user equipment (UE), the method comprising: receiving a message including first time information indicating a first absolute time value, wherein the first absolute time value references a calendar date; setting an absolute time clock at a first boundary of a first reference time interval based at least in part on the first absolute time value; determining, based at least in part on the absolute time clock, a second absolute time value at a second boundary of a second reference time interval, wherein the second reference time interval is one of a plurality of time intervals established for communications between the first UE and a second UE; as well as A sidelink message including second time information indicating the second absolute time value is sent to the second UE.

30. The method according to claim 29, further comprising: A request for the second time information is received from the second UE, wherein in response to receiving the request, the sidelink message including the second time information is sent to the second UE.

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