Enhanced Frequency Range 2 (FR2) Side Link Rediscovery

Abstract

Specific aspects of this disclosure relate to techniques for sidelink rediscovery in millimeter-wave (e.g., frequency range 2) bands without repetitive beamforming. For example, a Tx UE can perform a first beam training with an Rx UE. The Tx UE can generate a discovery message including at least one of the following: an indication of an index to the beam training reference signal (BT-RS) sequence of the first beam training; an indication of a timer for changing the BT-RS sequence; or an indication of a second BT-RS sequence to be used by the Tx UE before the timer expires. The second BT-RS sequence can be indicated as an index to a set of BT-RS sequences including the BT-RS sequence associated with the first beam training. The Tx UE can send the generated discovery message to the Rx UE.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority to U.S. Application No. 17 / 116,608, filed on December 9, 2020, which has been assigned to its assignee and whose entire contents are incorporated herein by reference. Technical Field

[0003] This disclosure relates to various aspects of wireless communication, and more specifically to techniques for side link communication and beam management. Background Technology

[0004] Wireless communication systems are widely deployed to provide a variety of telecommunications services such as telephone, video, data, messaging, and broadcasting. Typical wireless communication systems employ multiple access technologies that enable communication with multiple users by sharing available system resources (e.g., bandwidth, transmit power). Examples of such multiple access systems include 3GPP Long Term Evolution (LTE) systems, LTE-A systems, Code Division Multiple Access (CDMA) systems, Time Division Multiple Access (TDMA) systems, Frequency Division Multiple Access (FDMA) systems, Orthogonal Frequency Division Multiple Access (OFDMA) systems, Single Carrier Frequency Division Multiple Access (SC-FDMA) systems, and Time Division Synchronous Code Division Multiple Access (TD-SCDMA) systems, among others.

[0005] These multiple access technologies have been adopted in various telecommunications standards to provide a common protocol that enables different wireless devices to communicate at the city, country, region, and even global levels. New radios (e.g., 5G NR) are examples of emerging telecommunications standards. NR is a set of enhancements to the LTE mobile standard released by 3GPP. NR is designed to better integrate with other open standards by improving spectrum efficiency, reducing costs, improving service, utilizing new spectrum, and using OFDM with a cyclic prefix (CP) on both the downlink (DL) and uplink (UL), thereby better supporting mobile broadband internet access. For these purposes, NR supports beamforming, multiple-input multiple-output (MIMO) antenna technology, and carrier aggregation.

[0006] However, with the continued growth in demand for mobile broadband access, there is a need for further improvements to LTE and NR technologies. Preferably, these improvements should be applicable to other multiple access technologies and telecommunications standards that employ these technologies. Summary of the Invention

[0007] The systems, methods, and apparatuses disclosed herein have several aspects, none of which is solely responsible for their desired properties. Without limiting the scope of this disclosure as set forth in the claims below, some features will now be briefly discussed. After considering this discussion, and particularly after reading the section entitled "Detailed Description," one will understand how the features of this disclosure provide advantages including improved feedback signaling.

[0008] A particular aspect provides a method for wireless communication by a first user equipment (UE). The method typically includes: completing a first beam training with a receiver (Rx) UE; generating a discovery message including at least one of the following: an indication of an index to a beam training reference signal (BT-RS) sequence of the first beam training; an indication of a timer for changing the BT-RS sequence; or an indication of a second BT-RS sequence to be used by the Rx UE before the timer expires. The second BT-RS sequence is indicated as an index to a set of BT-RS sequences including the BT-RS sequence associated with the first beam training. The method further includes: sending the discovery message to the Rx UE.

[0009] A particular aspect provides a method for wireless communication by a first UE. This method typically includes: performing first beam training with a Tx UE based on a first set of beam training reference signals (BT-RS) sequences for potential wireless communication on a sidelink; determining that wireless communication on the sidelink is of no interest; starting a timer; receiving from the Tx UE, before the timer expires, a discovery message indicating a change associated with the first set of BT-RS sequences; and decoding the discovery message to maintain the sidelink.

[0010] A specific aspect provides a first UE. The first UE typically includes: a processing system configured to: complete a first beam training with a second UE; and generate a discovery message including at least one of the following: an indication of a beam training reference signal (BT-RS) sequence index for the first beam training; an indication of a timer for changing the BT-RS sequence; or an indication of a second BT-RS sequence to be used by the first UE before the timer expires, wherein the second BT-RS sequence is indicated as an index for a set of BT-RS sequences including the BT-RS sequence associated with the first beam training; and a transmitter configured to send the discovery message to the second UE.

[0011] A specific aspect provides a first UE. The first UE typically includes: a processing system configured to: perform first beam training with a second UE based on a first set of beam training reference signals (BT-RS) sequences for potential wireless communication on a side link; determine that wireless communication on the side link is of no interest, and initiate a timer based on the determination; and a receiver configured to receive from the second UE a discovery message indicating a change associated with the first set of BT-RS sequences before the timer expires, wherein the processing system is further configured to maintain the side link based on the change.

[0012] Various aspects of this disclosure provide UEs, units, devices, processors, and computer-readable media for performing the methods described herein.

[0013] To achieve the foregoing and related objectives, one or more aspects include the features fully described and specifically pointed out in the following claims. The following description and drawings set forth certain illustrative features of one or more aspects in detail. However, these features indicate only a few of the various ways in which the principles of each aspect can be employed. Attached Figure Description

[0014] To gain a full understanding of the foregoing features of this disclosure, a more specific description of the invention, briefly summarized above, can be obtained by referring to various aspects, some of which are illustrated in the accompanying drawings. However, it should be noted that the drawings illustrate only specific, typical aspects of this disclosure and are therefore not intended to limit the scope of the disclosure, as the description may be adapted to other equally effective aspects.

[0015] Figure 1 This is a conceptual illustrated block diagram of a telecommunications system based on a specific aspect of this disclosure.

[0016] Figure 2 This is a conceptual illustration of a block diagram illustrating the design of an example base station (BS) and user equipment (UE) based on specific aspects of this disclosure.

[0017] Figure 3A and 3B An illustration of an example vehicle-to-everything (V2X) system is shown, representing some aspects of this disclosure.

[0018] Figure 4A and 4B The message used for the discovery in the side link is shown.

[0019] Figure 5 An example beam training period between two UEs in side-link communication is shown, according to a specific aspect of this disclosure.

[0020] Figure 6 An example rediscovery process using sidelink communication between two UEs is shown, based on a specific aspect of this disclosure.

[0021] Figure 7 This is a flowchart illustrating an example operation for wireless communication according to a specific aspect of this disclosure.

[0022] Figure 8 This is a flowchart illustrating an example operation for wireless communication according to a specific aspect of this disclosure.

[0023] Figure 9 An example protocol for sidelink rediscovery is shown, based on specific aspects of this disclosure.

[0024] Figure 10 Two example variations are shown for providing beam training timing within a beam training period, based on specific aspects of this disclosure.

[0025] Figure 11 An example sequence of beam training reference signal (BT-RS) with cyclic variation according to a specific aspect of this disclosure is shown.

[0026] Figure 12 An example sequence of BT-RS with variations within a beam training cycle is shown, according to a specific aspect of this disclosure.

[0027] Figure 13 A communication device is shown, which may include various components configured to perform operations of the techniques disclosed herein.

[0028] Figure 14 A communication device is shown, which may include various components configured to perform operations of the techniques disclosed herein.

[0029] For ease of understanding, the same reference numerals are used to denote the same elements in the figures where possible. It is conceivable that elements disclosed in one aspect may be beneficially used in other aspects without specific description. Detailed Implementation

[0030] This disclosure provides apparatus, methods, processing systems, and computer-readable media for sidelink rediscovery, for example, when an established beamp-pair link (BPL) is not in use and maintaining the BPL is more efficient than performing new beam training. For example, when two user equipments (UEs) have completed beam training and before device discovery, a transmitter (Tx) UE can generate a discovery message including an indication of an index to the beam training reference signal (BT-RS) sequence of the completed beam training, an indication of a timer, and an indication of a second BT-RS sequence to be used by the Tx UE before the timer expires. The second BT-RS sequence can be indicated as an index to a set of BT-RS sequences including those associated with the completed beam training. The Tx UE sends the discovery message to a receiver (Rx) UE. If the Rx UE receives the discovery message before the timer expires, the Rx UE subsequently decodes the discovery message to maintain the sidelink for discovery.

[0031] The following description provides examples of configurations for SL communication in a communication system and does not limit the scope, applicability, or examples described in the claims. Changes may be made to the function and arrangement of the elements discussed without departing from the scope of this disclosure. Various examples may be appropriately omitted, substituted, or added to various processes or components. For example, the described methods may be performed in a different order than described, and individual steps may be added, omitted, or combined. Furthermore, features described with respect to some examples may be combined in some other examples. For example, any number of aspects described herein may be used to implement an apparatus or practice. Moreover, the scope of this disclosure is intended to cover such apparatus or methods practiced using structures, functions, or structures and functions other than those described herein. It should be understood that any aspect disclosed herein may be implemented by one or more elements of the claims. In this document, the word “exemplary” is used to mean “serving as an example, instance, or illustration.” Any aspect described herein as “exemplary” is not necessarily to be construed as superior to or more advantageous than other aspects.

[0032] Typically, any number of wireless networks can be deployed within a given geographic area. Each wireless network can support a specific Radio Access Technology (RAT) and can operate on one or more frequencies. A RAT can also be referred to as a radio technology, air interface, etc. A frequency can also be referred to as a carrier, subcarrier, frequency channel, tone, subband, etc. Each frequency can support a single RAT within a given geographic area to avoid interference between wireless networks using different RATs. In some cases, 5G NR RAT networks can be deployed.

[0033] Figure 1An example wireless communication network 100 in which various aspects of this disclosure may be implemented is shown. For example, the wireless communication network 100 may be an NR system (e.g., a 5G NR network).

[0034] like Figure 1 As shown, the wireless communication network 100 may include multiple base stations (BSs) 110a-z (also referred to individually or collectively as BS 110 herein) and other network entities. BS 110 may provide communication coverage for a specific geographic area (sometimes referred to as a “cell”), which may be stationary or mobile depending on the location of the mobile BS 110. In some examples, BS 110 may use any suitable transport network to interconnect with each other and / or connect to one or more other BSs or network nodes (not shown) in the wireless communication network 100 via various types of backhaul interfaces (e.g., direct physical connections, wireless connections, virtual networks, etc.).

[0035] exist Figure 1 In the examples shown, BS 110a, 110b, and 110c can be macro BSs for macro cells 102a, 102b, and 102c, respectively. For pico cell 102x, BS 110x can be a pico BS. For femtocells 102y and 102z, BS 110y and 110z can be femtocell BSs, respectively. A BS can support one or more cells. BS 110 communicates with user equipment UEs 120a-y (each UE is also individually referred to as UE 120 or collectively as UE 120) in the wireless communication network 100. UEs 120 (e.g., 120x, 120y, etc.) can be distributed throughout the wireless communication network 100, and each UE 120 can be stationary or mobile. In some cases, UE 120a can establish sidelink communication with UE 120t, which may or may not be covered by another cell or base station such as macro cell 102a or base station 110a. As discussed further in the various examples below, UEs 120a and 120t can establish side-link communication using millimeter waves without relying on base station 110a.

[0036] Depending on specific aspects, UE 120 can be configured to perform discovery operations. For example... Figure 1 As shown, UE 120a includes a discovery manager 122. Discovery manager 122 can be configured to perform discovery operations for reselecting a relay UE, as described in more detail herein. BS 110 may also include a discovery manager 112. Discovery manager 112 can use discovery messages to configure resources for relay selection, as described in more detail herein.

[0037] The wireless communication network 100 may also include a relay station (e.g., relay station 110r), also referred to as a relay, which receives data and / or other information transmissions from an upstream station (e.g., BS 110a or UE 120r) and sends data and / or other information transmissions to a downstream station (e.g., UE 120 or BS 110), or relays transmissions between UEs 120 to facilitate communication between devices.

[0038] Network controller 130 can be coupled to a group of BSs 110 and provide coordination and control for these BSs 110. Network controller 130 can communicate with BSs 110 via backhaul. BSs 110 can also communicate with each other via wireless or wired backhaul (e.g., directly or indirectly).

[0039] Figure 2 It is shown (for example, in) Figure 1 Example components of BS 110a and UE 120a in wireless communication networks can be used to implement various aspects of this disclosure.

[0040] In BS 110a, transmit processor 220 can receive data from data source 212 and control information from controller / processor 240. The control information can be used for the Physical Broadcast Channel (PBCH), Physical Control Format Indicator Channel (PCFICH), Physical Hybrid ARQ Indicator Channel (PHICH), Physical Downlink Control Channel (PDCCH), Group Common PDCCH (GC-PDCCH), etc. Data can be used for the Physical Downlink Shared Channel (PDSCH), etc. Processor 220 can process (e.g., encode and symbol map) the data and control information to acquire data symbols and control symbols respectively. Transmit processor 220 can also generate reference symbols, such as those for the Primary Synchronization Signal (PSS), Secondary Synchronization Signal (SSS), and Cell-Specific Reference Signal (CRS). Transmit (TX) Multiple-Input Multiple-Output (MIMO) processor 230 can perform spatial processing (e.g., precoding) on ​​data symbols, control symbols, and / or reference symbols (where applicable) and can provide an output symbol stream to the modulators (MODs) in 232a-232t. Each modulator 232 can process its own output symbol stream (e.g., for OFDM, etc.) to obtain an output sample stream. Each modulator can further process (e.g., convert to analog, amplify, filter, and upconvert) the output sample stream to obtain a downlink signal. The downlink signals from the modulators 232a-232t can be transmitted via antennas 234a-234t, respectively.

[0041] In UE 120a, antennas 252a-252r can receive downlink signals from BS 110a and can provide the received signals to demodulators (DEMODs) in transceivers 254a-254r respectively. Each demodulator 254 can adjust (e.g., filter, amplify, downconvert, and digitize) the corresponding received signal to obtain an input sample. Each demodulator can further process the input sample (e.g., for OFDM, etc.) to obtain the received symbols. MIMO detector 256 can obtain the received symbols from all demodulators in 254a-254r, perform MIMO detection on the received symbols if applicable, and provide the detected symbols. Receiver processor 258 can process (e.g., demodulate, deinterleave, and decode) the detected symbols, provide the decoded data for UE 120a to data sink 260, and provide the decoded control information to controller / processor 280.

[0042] On the uplink, at UE 120a, transmit processor 264 can receive and process data from data source 262 (e.g., for the Physical Uplink Shared Channel (PUSCH)) and control information from controller / processor 280 (e.g., for the Physical Uplink Control Channel (PUCCH)). Transmit processor 264 can also generate reference symbols for reference signals (e.g., for sounding reference signals (SRS)). Symbols from transmit processor 264 can be pre-encoded by TX MIMO processor 266 (if applicable), further processed by demodulators in transceivers 254a-254r (e.g., for SC-FDM, etc.), and transmitted to BS 110a. At BS 110a, uplink signals from UE 120a can be received by antenna 234, processed by modulator 232, detected by MIMO detector 236 (if applicable), and further processed by receive processor 238 to obtain decoded data and control information transmitted by UE 120a. The receiver processor 238 can provide the decoded data to the data sink 239 and the decoded control information to the controller / processor 240.

[0043] Memory 242 and 282 can store data and program code for BS 110a and UE 120a, respectively. Scheduler 244 can schedule the UE for data transmission on the downlink and / or uplink.

[0044] The controller / processor 280 and / or other processors and modules at UE 120a can perform or direct the performance of processes targeting the techniques described herein. Figure 2As shown, the controller / processor 280 of UE 120a has a discovery manager 122, and the controller / processor 280 of BS 110 has a discovery manager 112. Although shown at the controller / processor, the operations described herein can be performed using other components of UE 120a.

[0045] Figure 3A and 3B Illustrations of example vehicle-to-everything (V2X) systems according to some aspects of this disclosure are shown. For example, in Figure 3A and 3B The UE shown can communicate via the sidelink channel and can perform sidelink CSI reporting as described herein.

[0046] exist Figure 3A and 3B The V2X system provided in China offers two complementary transmission modes. Figure 3A The first transmission mode, illustrated by example, involves direct communication (e.g., also known as sidelink communication) between participants that are close to each other in a local area. Figure 3B The second transmission mode, illustrated by way of example, involves network communication over a network, which can be implemented on a Uu interface (e.g., a wireless communication interface between the radio access network (RAN) and the UE). As shown, UEs 352 and 354 can communicate with each other using a side link (SL) 398.

[0047] Reference Figure 3A A V2X system 300 (e.g., including vehicle-to-vehicle (V2V) communication) is shown with two UEs 302 and 304 (e.g., vehicles). A first transmission mode allows direct communication between different participants in a given geographic location. As shown, the vehicle may have a wireless communication link 306 with a person (V2P) (e.g., via a UE) through a PC5 interface. Communication between UEs 302 and 304 can also occur through PC5 interface 308. Similarly, communication can occur from UE 302 to other highway components (e.g., highway component 310) such as traffic signals or signs (V2I) via PC5 interface 312. Figure 3AIn each communication link shown, bidirectional communication can occur between components, thus each component can be both a transmitter and a receiver of information. The V2X system 300 can be a self-managing system implemented without assistance from network entities. Because no network service interruption occurs during handover operations of mobile vehicles, the self-managing system can achieve improved spectral efficiency, reduced costs, and increased reliability. The V2X system can be configured to operate in licensed or unlicensed spectrum, allowing any vehicle equipped with the system to access public frequencies and share information. This cooperative / universal spectrum operation allows for secure and reliable operation.

[0048] Figure 3B A V2X system 350 is illustrated for communication between UE 352 (e.g., a vehicle) and UE 354 (e.g., a vehicle) via network entity 356. These network communications can occur via discrete nodes such as base stations (e.g., eNBs or gNBs), where discrete nodes send and receive information to and from UEs 352 and 354 (e.g., relaying information between UEs 352 and 354). Network communication via vehicle-to-network (V2N) links (e.g., Uu links 358 and 310) can be used for long-distance communication, such as transmitting the presence of a car accident some distance ahead along a road or highway. Nodes can send other types of communication to vehicles, such as traffic flow conditions, road hazard warnings, environmental / weather reports, and service station availability. Such data can be obtained from cloud-based shared services.

[0049] In some cases, two or more secondary entities (e.g., UEs) can communicate with each other using sidelink signaling. As mentioned above, V2V and V2X communications are examples of communications that can be transmitted via sidelinks. Other applications of sidelink communication can include public safety or service announcement communications, communications for proximity services, communications for UE-to-network relay, device-to-device (D2D) communications, Internet of Things (IoE) communications, Internet of Things (IoT) communications, mission-critical mesh communications, and other suitable applications. Typically, a sidelink can refer to a direct link between one subordinate entity (e.g., UE1) and another subordinate entity (e.g., UE2). This allows communication (also referred to herein as “sidelink signaling”) to be sent and received using a sidelink, even if the scheduling entity can be used for scheduling or control purposes, without relaying the communication through the scheduling entity (e.g., BS). In some examples, licensed spectrum (unlike wireless LANs, which typically use unlicensed spectrum) can be used to transmit sidelink signals.

[0050] Various sidelink channels can be used for sidelink communication, including the Physical Sidelink Discovery Channel (PSDCH), Physical Sidelink Control Channel (PSCCH), Physical Sidelink Shared Channel (PSSCH), and Physical Sidelink Feedback Channel (PSFCH). The PSDCH can carry discovery expressions that enable nearby devices to discover each other. The PSCCH can carry control signaling, such as sidelink resource configurations and other parameters used for data transmission, and the PSSCH can carry data transmission. The PSFCH can carry feedback such as Channel State Information (CSI) related to sidelink channel quality.

[0051] Example discovery techniques for sidelink beam training

[0052] For Long Term Evolution (LTE), the discovery pool and communication pool can be configured separately in Radio Resource Control (RRC) reconfiguration messages and System Information Blocks (SIBs), or they can be pre-configured (e.g., in the standard). For example, for a UE in idle operating mode, a common communication pool can be provided in LTE SIB18, and a common discovery pool can be provided in LTE SIB19. A common resource pool typically refers to resources available to multiple UEs for a specific purpose (e.g., data communication or discovery). The common communication pool and discovery pool can be provided separately in pre-configurations for out-of-coverage (OOC) UEs. Dedicated communication pools and discovery pools can be provided separately for UEs in connected operating mode in RRC reconfiguration messages. A dedicated resource pool typically refers to resources dedicated to a specific UE for communication or discovery.

[0053] In some cases, transmit (TX) and receive (RX) pools can be configured. For example, a public TX pool can be configured or pre-configured in the SIB. The public TX pool can be rewritten by dedicated configuration via RRC reconfiguration messages. The RX pool can always be public among LTE UEs and can be provided (e.g., configured) only via RRC messages during handover (HO) from one cell to another. The RX pool may be independent of the UE's RRC state. In some implementations, dedicated resource allocation can be configured only for the TX pool.

[0054] There are various differences between the discovery pool and the communication pool. For example, sidelink control information (SCI) may not be used in the discovery message. Both the communication pool and the discovery pool can be defined by periodic subframe pools of resources in the time domain and periodic pools of resource blocks (RBs) in the frequency domain. In LTE, the communication pool and the discovery pool can share the same RB pool definition. For example, the bandwidth used for the discovery pool and the communication pool can be from 2 RBs to 200 RBs, and the starting position of the resource pool can be configurable. For the communication pool, separate frequency allocations can be defined for control and data transmission. The communication pool and the discovery pool can use different periodicity configurations. For example, the period for the communication pool can be from 40 ms to 320 ms, but the period for the discovery pool can be from 320 ms to 10.24 seconds. In other words, the communication pool can be denser than the discovery pool.

[0055] Figure 4A and 4B The message used for the discovery in the side link is shown. Figure 4A The discovery protocol, referred to as "Model A" discovery, is illustrated. As shown, UE 402 can use a resource pool configured for discovery to send announcement messages 412, 414, 416, and 418 (hereinafter also referred to as "discovery announcements"). These announcement messages can be received by other UEs 404, 406, 408, and 410 that are monitoring the announcement messages. The announcement messages can be sent in the PC5 communication channel, as per the information provided. Figure 3A and 3B As described. Once received, one or more notification messages can be used by UE 402 to connect with one or more of UEs 404, 406, 408, and 410.

[0056] Figure 4B The diagram illustrates a discovery protocol known as "Model B" discovery. As shown, UE 402 can be the discovering UE and may be sending appeal messages 452, 454, 456, and 458 (hereinafter also referred to as "discovery notifications"). These appeal messages can be received by one or more UEs 404, 406, 408, and 410. For example, as shown, UEs 404 and 406 can send response messages 460 and 462 back to UE 402 to facilitate a connection on the sidelink. For instance, UE 402 can perform channel measurements to select the UE 404 or 406 with the highest link quality and establish a connection with the selected UE.

[0057] In some cases, for sidelink communication in frequency range 2 (FR2, for example, encompassing the band from 24.25 GHz to 52.6 GHz, also known as the millimeter-wave range) or similar directional frequency ranges subject to path loss (attenuation), beamforming is required to achieve communication over the practical range to mitigate the directional nature of high-frequency beams. Such beamforming requires exhaustive beam searching and periodic beam training for maintenance, which increases energy efficiency and overhead.

[0058] Furthermore, unlike beamforming with a base station (gNB) where each UE only needs to form a beam pair link (BPL) with one base station, sidelink FR2 communication can be more challenging in real-world scenarios where many UEs can form beam pairs links (BPLs) with each other. Due to this distributed nature of the network, system-wide resources need to be allocated for beam training. These resources are periodic. UEs can transmit beam training reference signals (BT-RS or BT-RS sequences) at the beam training time. Receiver (Rx) UEs can detect BT-RS and transmit feedback on the dominant beam (e.g., random access channel, "RACH"). Beam training is performed across the entire 360-degree angular space at the transmitter (Tx) UE and Rx UE (e.g., ...). N × N It is performed by exhaustive beam search and scanning of (each beam).

[0059] Once the Tx UE and Rx UE have established a possible BPL through beam scanning, the UE can perform device discovery to establish communication for various applications. Device discovery requires knowing the UE identifier (ID) (e.g., Layer 2 ID) used for sub-6 operations.

[0060] Figure 5 An example beam training period between two UEs in side-link communication is illustrated according to a specific aspect of this disclosure. As shown, the beam training period includes multiple training cycles T0, T1, ... T m Each training cycle T m This can include three events: (1) transmitting several beam pilots in multiple directions; (2) processing the beam pilots to identify the direction of the desired signal strength; and (3) transmitting a random access channel (RACH) sequence in the identified direction. Completing beam training will enable the Tx UE and Rx UE to know the beam direction.

[0061] For example, Figure 5 The Tx UE in the lower left corner can first transmit multiple pilot beams in various directions, such as exhaustively in 360 degrees. Figure 5The Rx UE in the lower right corner can perform beam scanning similarly. After beam scanning is complete, the Rx UE determines the dominant direction for each BT-RS sequence received from the Tx UE. Each Tx UE can have orthogonal BT-RS. The Rx UE then processes the beam pilots and sends the RACH sequence to the Tx UE in the dominant direction.

[0062] For Tx UEs and Rx UEs to discover each other, a UE must associate its BPL with another UE. This discovery allows the UE to identify devices and upper-layer services. Because FR2 links typically have high overhead for establishment and maintenance, it is beneficial for the UE to establish and / or maintain trained or paired links for the relevant services. This saves time that would otherwise be spent creating and dismantling unnecessary links.

[0063] This disclosure enables the sending of discovery messages at the device level and service level. Discovery messages may also include beamforming information for receiving and future beam association or directional communication. Due to the directional nature of millimeter waves, such as links at FR2, there are no system-wide resources available for discovery messages. No directional information is broadcast.

[0064] In some cases, the discovery message may include the UE's device ID. Current and potential future device locations may also be included in the discovery message. For example, location information may be collected by the UE based on its current area ID and its direction of movement and / or acceleration. The location or change of location of the Tx UE may be used by the Rx UE to determine the Tx UE's trajectory.

[0065] In some cases, a discovery message may include an application layer service ID or a list of application layer service IDs. The discovery message may also include metadata for one or more services listed by service ID. The discovery message may also include beam and directionality information. For example, the discovery message may indicate the beam training pilots used by the UE for the current beam training period and future beam training periods. In some cases, the discovery message will also contain the Tx beam training timings used by the UE in future beam training periods. The UE may also send a time-domain division (TDD) mode for the beam corresponding to a directional discovery message. The receiver uses the TDD mode to send a discovery response. The UE that receives the discovery message searches for PSSCH resources in the time slot indicated in the TDD mode to send a discovery response.

[0066] The UE can use device and service information to manage beamformed links. In one scenario, the service ID and metadata are used to accept or reject discovery notifications / advertisements. If the Rx UE does not support the service, it can reject the discovery message. The Rx UE can infer that service information from the Tx UE is irrelevant. For example, information from a vehicle behind the Tx UE in another lane (i.e., the Rx UE in a V2X sidelink scenario) may be irrelevant and not used by the Rx UE. In another scenario, the service ID, metadata, along with device location and trajectory, can be used to accept / reject discovery.

[0067] Given the device-specific discovery messages discussed above, in Figures 4A-4B The Model A discovery and Model B discovery discussed can each exhibit the following characteristics. In Model A discovery, the Rx UE can send one or more RACHs to the Tx UE during the beam training period. The Rx UE also sends a discovery notification in each direction on which it sends the RACH. The discovery notification can contain the BT-RS sequence ID used by the Tx UE for beam training. The discovery notification can also include one or more future beam training opportunities within the BT period. The discovery notification is sent via PSSCH (e.g., ...). Figure 6 (As discussed further below), and can be performed using a shared channel resource reservation procedure. The receiver of the discovery notification (e.g., the Tx UE) can send a discovery response. In some cases, even when the Tx UE receives a discovery notification and is not interested, it can still send a discovery response indicating rejection. In some cases, the Tx UE may not send any discovery response regarding the received discovery notification.

[0068] In Model B discovery, a Tx UE that has already sent a beam training pilot can send a discovery message in the direction from which the Rx UE receives the RACH. The Tx UE sends a discovery announcement to the Rx UE, and upon receiving the announcement, the Rx UE determines whether to discover the Tx UE at the device or service level based on the UE ID or service ID indicated in the announcement. If the Rx UE determines that it is interested in the device or service, it can send a discovery response based on the time-domain division (TDD) mode of the discovery announcement.

[0069] Example enhancement techniques for lateral link FR2 reselection discovery

[0070] Specific aspects of this disclosure relate to techniques for sidelink rediscovery in millimeter-wave (e.g., frequency range 2) bands without repetitive beamforming. For example, a Tx UE can complete a first beam training with an Rx UE. The Tx UE can generate a discovery message including at least one of the following: an indication of an index to the beam training reference signal (BT-RS) sequence of the first beam training; an indication of a timer for changing the BT-RS sequence; or an indication of a second BT-RS sequence to be used by the Tx UE before the timer expires. The second BT-RS sequence can be indicated as an index to a set of BT-RS sequences including the BT-RS sequence associated with the first beam training. The Tx UE can send the generated discovery message to the Rx UE. Before the timer expires, the Rx UE can receive the discovery message indicating the change associated with the first set of BT-RS sequences from the Rx UE; and decode the discovery message to maintain the sidelink (e.g., by completing the device discovery process using initial successful beam training).

[0071] As mentioned above, due to inherent path loss in high-frequency ranges (such as FR2), wireless links typically require beamforming and spatial filtering to achieve sufficient range. In relatively low-frequency ranges (such as FR1), links can be transmitted omnidirectionally or using wide beams, eliminating the need for beamforming. In cases involving multiple UEs, each sidelink UE can form multiple beam pairs (BPLs) with other sidelink UEs (or peer UEs). Therefore, the beam discovery process involved can have higher overhead than the beam discovery process between the UE and the base station (such as the gNB or eNB in ​​a Uu link).

[0072] Figure 6 An example rediscovery process using sidelink communication between two UEs according to a specific aspect of this disclosure is illustrated. As shown, discovery using PSSCH is performed after the beam training period. During the beam training period, system-wide resources can be used for beam discovery. The beam training process can use long beam training periods repeated over a large timescale. For example, a 100 ms beam training period can be repeated once per second, resulting in 10% overhead. In contrast, for beam training of the Uu link between the UE and the base station, a 5 ms beam training period can be used every 20 ms synchronization period.

[0073] An initial beam training phase (BPL) can be established after the initial beam training period. The Tx UE and Rx UE can then use the PSSCH to send and / or receive beam discovery messages for device and service discovery. As shown, various discovery events can occur in the PSSCH. By identifying device and service information, the Tx UE or Rx UE can respond to discovery messages when interested. For example, the Rx UE might want to discover the Tx UE when it is running an application that collects data useful to the Rx UE. For instance, in a V2X scenario, the Rx UE might want to discover the Tx UE that is collecting visual or navigational information collected at the Tx UE but not directly available to the Rx UE. On the other hand, even if beam training between the Tx UE and Rx UE is successful and the BPL can be established, the Tx UE or Rx UE may decide that it is not interested in or that the information or application provided by the other UE is irrelevant. For example, in a V2X scenario, when an Rx UE is associated with a vehicle in a different lane, some safety information provided by the Tx UE of the vehicle ahead may be useless. Similarly, sensor data from a front-facing camera may be useful to the Rx UE behind the Tx UE, but not to the Rx UE in front.

[0074] This disclosure provides techniques for effectively utilizing completed beam training and potential beamlines, even when the beamline is not currently being used for user plane data because, after beam training is completed, the Tx UE and Rx UE have learned the beam orientation to reach each other (after considerable effort). An Rx UE that has decoded the beamline pilot can continue to monitor the beamline corresponding to the decoded beamline pilot during periodic beam training. A Tx UE transmitting a beam training reference signal (BT-RS) sequence can indicate changes in the BT-RS sequence when new data becomes available (e.g., for which the Rx UE is of interest). Thus, since the beam is known before application layer data becomes available, the beam is maintained for future use, improving resource allocation and operational efficiency. This beneficial operation / configuration is referred to herein as rediscovery or reuse of discovery information.

[0075] For example, in some aspects, after beam training, the Tx UE can indicate the current BT-RS sequence index, timer, and another BT-RS sequence (e.g., to be used by the Tx UE to utilize a known or trained beam orientation) in a discovery message or response. Timer (e.g., T s The BT-RS sequence is the duration within which the BT-RS may or may not change, and after which the BT-RS will definitely change. Another BT-RS sequence can be found at the current time.t and timer in t + T s The BT-RS sequence changes between expiration dates. This new BT-RS sequence can be indicated as an index to a set of known BT-RS sequences. When the current BT-RS sequence changes to another BT-RS sequence, this change indicates that new information (e.g., sensor data, service data, or applications) has become available. During operation, after successful beamforming, the Rx UE can determine that the Tx UE is not interested in the BPL, and the Rx UE can start a timer Ts. If a change in the BT-RS sequence sent by the Tx UE is detected before the timer Ts expires, the Rx UE can notify the Tx UE or attempt to decode the received discovery message from the Tx UE. As a result, initial beamforming is not wasted simply because the initial BPL (based on the initial BT-RS sequence) is not used.

[0076] Figure 7 This is a flowchart illustrating an example operation 700 for wireless communication according to a specific aspect of this disclosure. Operation 700 can be performed, for example, by a transmitter UE (e.g., such as...). Figure 5 It is executed by Tx UE in the middle.

[0077] Operation 700 can be implemented in one or more processors (e.g., Figure 2 The software components that execute and run on the controller / processor 280. Furthermore, the relay UE's transmission and reception of signals in operation 700 can be achieved, for example, through one or more antennas (e.g., Figure 2 This can be achieved via antenna 252. In certain aspects, the relay UE can transmit and / or receive signals via a bus interface of one or more processors (e.g., controller / processor 280) that acquires and / or outputs signals.

[0078] In box 710, operation 700 can be initiated by the Tx UE: completing the first beam training with the second UE. In box 720, the Tx UE generates a discovery message that includes at least one of the following: an indication of an index to the beam training reference signal (BT-RS) sequence of the first beam training, an indication of a timer for changing the BT-RS sequence, or an indication of a second BT-RS sequence to be used by the first UE before the timer expires. The second BT-RS sequence is indicated as an index to a set of BT-RS sequences that include the BT-RS sequence associated with the first beam training. In box 730, the Tx UE sends the discovery message to the second UE.

[0079] Figure 8This is a flowchart illustrating an example operation 800 for wireless communication according to a specific aspect of this disclosure. Operation 800 can be, for example, provided by an Rx UE (e.g., such as...). Figure 5 Operation 800 can be performed when Tx UE and Rx UE discover each other in the side walkway using millimeter-wave beamforming. Figure 7 The operation is complementary to 700.

[0080] Operation 800 can be implemented in one or more processors (e.g., Figure 2 Software components that execute and run on the controller / processor 280. Furthermore, in operation 600, the remote UE can transmit and receive signals via, for example, one or more antennas (e.g., Figure 2 This can be achieved via antenna 252. In certain aspects, the transmission and / or reception of signals by the remote UE can be achieved via a bus interface of one or more processors (e.g., controller / processor 280) that acquires and / or outputs signals.

[0081] Operation 800 can begin at block 810: Based on the first set of Beam Training Reference Signals (BT-RS) sequences, complete the first beam training with the second UE for potential wireless communication on the sidelink. At 820, the Rx UE determines that it is not interested in wireless communication on the sidelink. For example, when the Rx UE receives and analyzes device or service information indicated in the first set of BT-RS sequences, the Rx UE can determine that the device or service available from the Tx UE is irrelevant to the current operation of the Rx UE. At 830, the Rx UE starts a timer. The timer sets a time limit within which, if the device or service information becomes of interest to the Rx UE, successful beamforming with the Tx UE can be reused or rediscovered.

[0082] At 840, before the timer expires, the Rx UE receives a discovery message from the Tx UE indicating a change associated with the first set of BT-RS sequences. For example, the Rx UE may receive an updated or replaced BT-RS sequence from the Tx UE. This change may indicate different device and service information provided by the Tx UE. When the Rx UE discovers that it is interested in the different device and service information provided by the Tx UE, at 850, the Rx UE decodes the discovery message to maintain the sidelink using the completed beamforming training with the Tx UE. Otherwise, when the timer expires, or if the updated BT-RS sequence in the discovery message does not indicate the device or service information of interest, the Rx UE abandons the sidelink.

[0083] Operations 700 and 800 can also be performed in Figure 9 Demonstration in China Figure 9An example protocol 900 for lateral link rediscovery according to a specific aspect of this disclosure is illustrated. In this specific aspect, at 906, Tx UE 902 and Rx UE 904 have completed beamtraining using a first set of BT-RS sequences. For example, both Tx UE 902 and Rx UE 904 can exhaustively transmit beam pilots in all available directions to identify the main beam direction of the other UE. Typically, device discovery based on device or service information indicated in the first set of BT-RS sequences can be performed subsequently after beamtraining is completed. However, in this disclosure, if there is no interest in the device or service information of the Tx UE, Rx UE 904 may not perform discovery at 908. In some cases, Rx UE 904 may start a timer. Ts And in the response, indicate the timer to Tx UE 902 Ts In some cases, Tx UE 902 can also start a timer and indicate the timer to Rx UE 904.

[0084] In version 910, Rx UE 904 can be used with a timer. Ts Before the timer expires, the updated BT-RS sequence is monitored; Tx UE 902 can monitor device discovery attempts. For example, in 912, Tx UE 902 can signal a set of changed, updated, or replaced BT-RS sequences indicating changes in device or service information. Before the timer expires, in 914, Rx UE 904 can attempt to decode or respond to a discovery message from Tx UE 902 based on the updated BT-RS sequence to complete device discovery based on the initial completed beamtrain and the updated BT-RS (e.g., based on new device or service information).

[0085] In some cases, the Tx UE can randomly select one or more beam training opportunities based on a second BT-RS sequence. Random selection of one or more beam training opportunities can include randomly selecting beam training instances within a range (e.g., regarding...). Figure 10 (As discussed in Solution 1). The Tx UE can notify the beam training instance in a discovery message. In some examples, the sending of the discovery message can be based on beam training at each beam training instance. The Tx UE can select a new beam training instance after the timer expires and adopt a new BT-RS sequence based on the new beam training instance.

[0086] In sidelink communication scenarios, Rx UEs can perform operations similar to those performed by Tx UEs. The designation of transmitter (Tx) and receiver (Rx) UEs can be specific to each device or service discovery. A UE that acts as a Tx UE in one application can be an Rx UE in another application.

[0087] In some cases, a Tx UE can select one or more beam training opportunities based on the usage status of each beam training opportunity within one or more beam training opportunities. Because beam training opportunities are system-wide resources and shared by all UEs in the network, when each UE selects a resource to use, the UE needs to determine whether the resource is available, i.e., whether another UE in the network has not yet used the resource.

[0088] In some cases, the Tx UE can notify one or more beam training opportunities before the timer expires.

[0089] In some cases, without any changes in data transmission requirements, the Tx UE can update its timer to reflect the actual time before a change occurred on the BT-RS. The updated timer can be used by the Tx UE during beampup link creation with another UE.

[0090] In some cases, the Tx UE may detect a change in communication requirements. The Tx UE can determine that the second BT-RS sequence has already been used by the Rx UE. In response, the Tx UE can update the second BT-RS sequence and timer, and notify the Rx UE of the updated second BT-RS sequence and timer.

[0091] Figure 10 Two example variations (i.e., solutions 1 and 2) for providing beam training opportunities within a beam training period, according to specific aspects of this disclosure, are illustrated. To reuse or rediscover devices based on previously successful beam training, the Rx UE also needs to know which beam training opportunity to use. Solutions 1 and 2 provide two different examples for determining the beam training opportunity. In some cases, the Tx UE may randomly select the training opportunity (e.g., solution 1) or based on competition for each beam training opportunity (e.g., solution 2). Since beam training opportunities are system-wide resources and shared by all UEs in the network, each UE may need to select the resource it can use based on whether the UE knows the resource is available (i.e., whether the resource has already been used by another UE).

[0092] In Solution 1, the Tx UE can randomly select a beam training instance between [0, 𝑚]. For example, the Tx UE can select training instance 3 and notify the selected training instance in a discovery message or response. For the next... Ts During the time period, Tx UE uses training instance 3 to send BT-RS. During the time period... Ts Afterwards, the Tx UE can select a new BT instance and use a different RS sequence.

[0093] In Solution 2, Tx UE can be time [ t , t + Ts [Notify different beam training times within the specified time period. For example, in the next time period.] Ts There are four beam training opportunities, for example [0, 3, 5, 2]. Tx UE will use these beam training opportunities [0, 3, 5, 2] in each training session within a consecutive training session.

[0094] Based on certain aspects of this disclosure, Figure 11 An example sequence 1100 with a beam training reference signal (BT-RS) that varies cyclically is shown, and Figure 12 An example sequence 1200 of BT-RS with variations within a single beam training cycle is shown. Figure 11 and 12 The examples provided illustrate techniques for continuous discovery. In continuous discovery messages, a discovery message (where BT-RS and...) is sent... Ts After all have been notified, when there are no changes in data transmission requirements, the Tx UE can notify the same set of BT-RS. For example, as Figure 11 As shown, in the time period Ts Within this time period, discovery message 1101, BT-RS sequence 1105, and discovery response 1103 (if any) were detected. Ts The internals are the same. However, Tx UE can change the timer. Ts This is to reflect the actual time until the BT-RS changes. Ts The timer update can also be used by any new UE that is capable of creating and sending BT-RS by a known UE's BPL. For example, sequence 1100 Ts It may include different numbers of detection responses 1103 to indicate changes in BT-RS, such as during the indicated time period. Ts The updated BT-RS 1107 at the end.

[0095] In some cases, such as Figure 12As shown, when the data requirement changes and the Tx UE uses an alternative BT-RS, the Tx UE can notify the new BT-RS with an alternative sequence, and the Tx UE can... Ts Notifications are given as the time of sequence change. For example, as shown in the figure, within a time period... Ts During this period, the initial BT-RS sequence 1105 was updated to BT-RS sequence 1107. The update to BT-RS sequence 1107 can also reset the time frame for the changed sequence. Ts This allows for the rediscovery of another cycle.

[0096] Figure 13 A communication device 1300 is shown, which may include various components (e.g., corresponding to functional module components) configured to perform operations of the techniques disclosed herein, such as in Figure 7 and 8 The operation is illustrated herein. Communication device 1300 includes a processing system 1302 coupled to transceiver 1308. Transceiver 1308 is configured to transmit and receive signals for communication device 1300 via antenna 1310, such as the various signals described herein. Processing system 1302 may be configured to perform processing functions for communication device 1300, including processing signals received and / or to be transmitted by communication device 1300.

[0097] Processing system 1302 includes processor 1304 coupled to computer-readable medium / memory 1312 via bus 1306. In a particular aspect, computer-readable medium / memory 1312 is configured to store instructions (e.g., computer-executable code) that, when executed by processor 1304, cause processor 1304 to perform... Figure 7 and 8The operation is illustrated in the figure. In a particular aspect, the computer-readable medium / memory 1312 stores: code 1314 for generating a discovery message, the discovery message including at least one of the following: an indication of an index to a beam training reference signal (BT-RS) sequence of the first beam training; an indication of a timer for changing the BT-RS sequence; or an indication of a second BT-RS sequence to be used by the second UE before the timer expires, wherein the second BT-RS sequence is indicated as an index to a set of BT-RS sequences including the BT-RS sequence associated with the first beam training; and code 1318 for outputting the discovery message to be sent to the second UE. In a particular aspect, the processor 1304 has circuitry configured to implement the code stored in the computer-readable medium / memory 1312. Processor 1304 includes: circuitry 1322 for performing first beam training with a second UE; circuitry 1324 for generating a discovery message, the discovery message including at least one of the following: an indication of an index to a beam training reference signal (BT-RS) sequence of the first beam training; an indication of a timer for changing a BT-RS sequence; or an indication of a second BT-RS sequence to be used by the second UE before the timer expires, wherein the second BT-RS sequence is indicated as an index to a set of BT-RS sequences including the BT-RS sequence associated with the first beam training; and circuitry 1326 for outputting the discovery message for transmission to the second UE.

[0098] Figure 14 A communication device 1400 is shown, which may include operations configured to perform the techniques disclosed herein (such as in...). Figure 7 and 8 The communication device 1400 includes various components (e.g., corresponding to functional module components) shown in the diagram. The communication device 1400 includes a processing system 1402 coupled to a transceiver 1408. The transceiver 1408 is configured to transmit and receive signals for the communication device 1400 via an antenna 1410, such as the various signals described herein. The processing system 1402 can be configured to perform processing functions for the communication device 1400, including processing signals received and / or to be transmitted by the communication device 1400.

[0099] Processing system 1402 includes processor 1404 coupled to computer-readable medium / memory 1412 via bus 1406. In a particular aspect, computer-readable medium / memory 1412 is configured to store data that, when executed by processor 1404, causes processor 1404 to perform operations... Figure 7 and 8The instructions for operation shown are (e.g., computer-executable code). In a particular aspect, the computer-readable medium / memory 1412 stores: code 1414 for completing a first beam training with the second UE based on a first set of beam training reference signals (BT-RS) sequences for potential wireless communication on the side link; code 1416 for determining that there is no interest in wireless communication on the side link; code 1417 for starting a timer; code 1418 for obtaining a discovery message from the second UE indicating a change associated with the first set of BT-RS sequences before the timer expires; and code 1420 for decoding the discovery message to maintain the side link. In a particular aspect, the processor 1404 has circuitry configured to implement the code stored in the computer-readable medium / memory 1412. The processor 1404 includes: circuitry 1422 for performing first beam training with a second UE based on a first set of beam training reference signals (BT-RS) sequences for potential wireless communication on a side link; circuitry 1424 for determining that wireless communication on the side link is of no interest; circuitry 1426 for starting a timer; circuitry 1428 for obtaining a discovery message from the second UE indicating a change associated with the first set of BT-RS sequences before the timer expires; and circuitry 1429 for decoding the discovery message to maintain the side link.

[0100] In addition to the aspects mentioned above, aspects of specific combinations are also within the scope of this disclosure, some of which are as follows:

[0101] Aspect 1: A method for wireless communication by a first user equipment (UE), comprising: completing a first beam training with a second UE; generating a discovery message, the discovery message including at least one of the following: an indication of a beam training reference signal (BT-RS) sequence index for the first beam training, an indication of a timer for changing a BT-RS sequence, or an indication of a second BT-RS sequence to be used by the first UE before the timer expires, wherein the second BT-RS sequence is indicated as an index for a set of BT-RS sequences including the BT-RS sequence associated with the first beam training; and sending the discovery message to the second UE.

[0102] Aspect 2: The method according to aspect 1 further includes: randomly selecting one or more beam training opportunities based on the second BT-RS sequence.

[0103] Aspect 3: According to the method of aspect 2, the random selection of the timing of the one or more beam training sessions includes randomly selecting at least one beam training instance within a range.

[0104] Aspect 4: The method according to aspect 3 further includes: notifying the beam training instance in the discovery message.

[0105] Aspect 5: According to the method of aspect 3, wherein the transmission of the discovery message is based on beam training at each of the at least one beam training instance.

[0106] Aspect 6: The method according to aspect 3 further includes: selecting a new beam training instance after the timer expires; and adopting a new BT-RS sequence based on the new beam training instance.

[0107] Aspect 7: The method according to any one of aspects 1-6 further includes: selecting the one or more beam training opportunities based on the usage status of each of the one or more beam training opportunities, wherein the usage status is based on system-wide resources.

[0108] Aspect 8: The method according to any one of aspects 1-7 further includes: notifying one or more beam training opportunities before the timer expires.

[0109] Aspect 9: The method according to any one of aspects 1-8 further includes: updating the timer to reflect the actual time up to the point where no change in data transmission requirements occurs.

[0110] Aspect 10: The method of Aspect 9 further includes: using the updated timer during the creation of a beam pair link with a third UE.

[0111] Aspect 11: The method according to any one of aspects 1-10 further includes: detecting a change in communication requirements; determining that a second BT-RS sequence has been used by the second UE; updating the second BT-RS sequence and the timer based on at least one of the detection or the determination; and notifying the updated second BT-RS sequence and the updated timer.

[0112] Aspect 12: A method for wireless communication by a first user equipment (UE), comprising: performing a first beam training with a second UE based on a first set of beam training reference signals (BT-RS) sequences for potential wireless communication on a side link; determining that wireless communication on the side link is of no interest; starting a timer based on the determination; receiving from the second UE, before the timer expires, a discovery message indicating a change associated with the first set of BT-RS sequences; and maintaining the side link based on the change.

[0113] Aspect 13: The method according to aspect 12 further includes: randomly selecting one or more beam training opportunities based on the changes associated with the first set of BT-RS sequences, the changes including an indication of a second BT-RS sequence.

[0114] Aspect 14: According to the method of aspect 13, wherein the random selection of the one or more beam training opportunities includes randomly selecting at least one beam training instance within a range.

[0115] Aspect 15: The method according to aspect 14 further includes: notifying the second UE of the at least one beam training instance.

[0116] Aspect 16: The method according to aspect 14 further includes: using the beam training instance to transmit the second BT-RS sequence.

[0117] Aspect 17: The method according to aspect 14 further includes: selecting a new beam training instance after the timer expires; and adopting a new BT-RS sequence based on the new beam training instance.

[0118] Aspect 18: The method according to any one of aspects 12-17 further includes: selecting the one or more beam training opportunities based on the usage status of each beam training opportunity in the one or more beam training opportunities, wherein the usage status is based on system-wide resources.

[0119] Aspect 19: The method according to any one of aspects 12-18 further includes: notifying one or more beam training opportunities before the timer expires.

[0120] Aspect 20: The method according to any one of aspects 12-19 further includes: updating the timer to reflect the actual time up to the point where no change in data transmission requirements occurs.

[0121] Aspect 21: The method according to aspect 20 further includes: using the updated timer during the creation of a beam pair link with a third UE.

[0122] Aspect 22: The method according to any one of aspects 12-21 further includes: detecting a change in communication requirements; determining that the second BT-RS sequence has been used by the second UE; updating the second BT-RS sequence and the timer based on at least one of the detection or the determination; and notifying the updated second BT-RS sequence and the updated timer.

[0123] Aspect 23: A first user equipment (UE) comprising: a processing system configured to complete a first beam training with a second UE and generate a discovery message, the discovery message including at least one of an indication of a beam training reference signal (BT-RS) sequence index of the first beam training, an indication of a timer for changing a BT-RS sequence, or an indication of a second BT-RS sequence to be used by the first UE before the timer expires, wherein the second BT-RS sequence is indicated as an index for a set of BT-RS sequences including the BT-RS sequence associated with the first beam training; and a transmitter configured to send the discovery message to the second UE.

[0124] Aspect 24: A first user equipment (UE) comprising: a processing system configured to perform first beam training with a second UE based on a first set of beam training reference signals (BT-RS) sequences for potential wireless communication on a side link, determine that wireless communication on the side link is of no interest, and initiate a timer based on the determination; and a receiver configured to receive from the second UE, the receiver being configured to receive a discovery message from the second UE before the timer expires, indicating a change associated with the first set of BT-RS sequences, wherein the processing system is further configured to maintain the side link based on the change.

[0125] Aspect 25: A first user equipment, comprising: a unit for performing a first beam training with a second UE; a unit for generating a discovery message, the discovery message including at least one of the following: an indication of a beam training reference signal (BT-RS) sequence index for the first beam training, an indication of a timer for changing a BT-RS sequence, or an indication of a second BT-RS sequence to be used by the first UE before the timer expires, wherein the second BT-RS sequence is indicated as an index for a set of BT-RS sequences including the BT-RS sequence associated with the first beam training; and a unit for sending the discovery message to the second UE.

[0126] Aspect 26: A first user equipment (UE) comprising: a unit for performing first beam training with a second UE based on a first set of beam training reference signals (BT-RS) sequences for potential wireless communication on a side link; a unit for determining that the wireless communication on the side link is of no interest; a unit for starting a timer based on the determination; a unit for receiving from the second UE a discovery message indicating a change associated with the first set of BT-RS sequences before the timer expires; and a unit for maintaining the side link based on the change.

[0127] Aspect 27: An apparatus for wireless communication by a first user equipment (UE), comprising a processing system configured to perform a first beam training with a second UE, generate a discovery message, the discovery message including at least one of the following: an indication of a beam training reference signal (BT-RS) sequence index for the first beam training, an indication of a timer for changing a BT-RS sequence, or an indication of a second BT-RS sequence to be used by the first UE before the timer expires, wherein the second BT-RS sequence is indicated as an index for a set of BT-RS sequences including the BT-RS sequence associated with the first beam training; and an interface configured to output the discovery message for transmission to the second UE.

[0128] Aspect 28: An apparatus for wireless communication by a first user equipment (UE), comprising a processing system configured to: perform first beam training with a second UE based on a first set of beam training reference signals (BT-RS) sequences for potential wireless communication on a side link; determine that the wireless communication on the side link is of no interest; and initiate a timer based on the determination; and an interface configured to obtain from the second UE, prior to the expiration of the timer, a discovery message indicating a change associated with the first set of BT-RS sequences, wherein the processing system is further configured to maintain the side link based on the change.

[0129] Aspect 29: A computer-readable medium for wireless communication by a first user equipment (UE), comprising code executable to: complete a first beam training with a second UE; generate a discovery message including at least one of an indication of an index of a beam training reference signal (BT-RS) sequence of the first beam training, an indication of a timer for changing a BT-RS sequence, or an indication of a second BT-RS sequence to be used by the first UE before the timer expires, wherein the second BT-RS sequence is indicated as an index for a set of BT-RS sequences including the BT-RS sequence associated with the first beam training; and output the discovery message for transmission to the second UE.

[0130] Aspect 30: A computer-readable medium for wireless communication by a first user equipment (UE), comprising code executable to: perform first beam training with a second UE based on a first set of beam training reference signals (BT-RS) sequences for potential wireless communication on a side link; determine that the wireless communication on the side link is of no interest; start a timer based on the determination; obtain from the second UE a discovery message indicating a change associated with the first set of BT-RS sequences before the timer expires; and maintain the side link based on the change.

[0131] The techniques described in this article can be used in various wireless communication technologies, such as NR (e.g., 5G NR), 3GPP Long Term Evolution (LTE), LTE Advanced (LTE-A), Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), Orthogonal Frequency Division Multiple Access (OFDMA), Single Carrier Frequency Division Multiple Access (SC-FDMA), Time Division Synchronous Code Division Multiple Access (TD-SCDMA), and other networks. The terms "network" and "system" are often used interchangeably. CDMA networks can implement radio technologies such as Universal Terrestrial Radio Access (UTRA), cdma2000, etc. UTRA includes Wideband CDMA (WCDMA) and other variants of CDMA. cdma2000 includes the IS-2000, IS-95, and IS-856 standards. TDMA networks can implement radio technologies such as Global System for Mobile Communications (GSM). OFDMA networks can implement radio technologies such as NR (e.g., 5G RA), evolved UTRA (E-UTRA), Ultra Mobile Broadband (UMB), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Flash OFDMA, etc. UTRA and E-UTRA are part of the Universal Mobile Telecommunications System (UMTS). LTE and LTE-A are versions of UMTS that use E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A, and GSM are described in documents from an organization called the 3rd Generation Partnership Project (3GPP). cdma2000 and UMB are described in documents from an organization called the 3rd Generation Partnership Project 2 (3GPP2). NR is an emerging wireless communication technology under development.

[0132] The techniques described herein can be used in the aforementioned wireless network and radio technologies, as well as other wireless network and radio technologies. For clarity, although terms commonly associated with 3G, 4G, and / or 5G wireless technologies may be used to describe aspects herein, aspects of this disclosure can be applied to other generation-based communication systems.

[0133] In 3GPP, the term "cell" can refer to a Node B (NB) and / or NB subsystem serving the coverage area, depending on the context in which the term is used. In NR systems, the term "cell" is used interchangeably with BS, Next Generation Node B (gNB or gNode B), Access Point (AP), Distributed Cell (DU), and Carrier or Transmit / Receive Point (TRP). A BS can provide communication coverage for macrocells, picocells, femtocells, and / or other types of cells. A macrocell can cover a relatively large geographic area (e.g., a radius of several kilometers) and allows UEs unrestricted access via a service subscription. A picocell can cover a relatively small geographic area and allows UEs with a service subscription to unrestricted access. A femtocell can cover a relatively small geographic area (e.g., a home) and allows restricted access for UEs associated with the femtocell (e.g., UEs in a Closed Subscriber Group (CSG), UEs of users in a home, etc.). A BS used for a macrocell can be called a macro BS. A BS used for a picocell can be called a pico BS. A BS used for a femtocell can be called a femto BS or a home BS.

[0134] A UE can also be referred to as a mobile station, terminal, access terminal, subscriber unit, station, customer premises equipment (CPE), cellular phone, smartphone, personal digital assistant (PDA), wireless modem, wireless communication device, handheld device, laptop computer, cordless phone, wireless local loop (WLL) station, tablet computer, camera, gaming device, netbook, smartbook, ultrabook, instrument, medical device or medical apparatus, biometric sensor / device, wearable device (such as smartwatch, smart clothing, smart glasses, smart wristband, smart jewelry (e.g., smart ring, smart bracelet, etc.)), entertainment device (e.g., music device, video device, satellite radio unit, etc.), vehicle component or sensor, smart meter / sensor, industrial manufacturing equipment, GPS device, or any other suitable device configured to communicate via wireless or wired media. Some UEs can be considered machine-type communication (MTC) devices or evolved MTC (eMTC) devices. MTC and eMTC UEs include, for example, robots, drones, remote devices, sensors, meters, monitors, location tags, etc., that can communicate with a BS, another device (e.g., a remote device), or some other entity. Wireless nodes can provide connectivity to or from the network, for example, via wired or wireless communication links (e.g., wide area networks, such as the Internet or cellular networks). Some UEs can be considered Internet of Things (IoT) devices, which can be narrowband IoT (NB-IoT) devices.

[0135] Certain wireless networks (e.g., LTE) use Orthogonal Frequency Division Multiplexing (OFDM) on the downlink and Single-Carrier Frequency Division Multiplexing (SC-FDM) on the uplink. OFDM and SC-FDM divide the system bandwidth into multiple (K) orthogonal subcarriers, often referred to as tones, frequency points, etc. Each subcarrier can be modulated with data. Typically, modulation symbols are transmitted using OFDM in the frequency domain and SC-FDM in the time domain. The spacing between adjacent subcarriers can be fixed, and the total number of subcarriers (K) can depend on the system bandwidth. For example, the subcarrier spacing can be 15 kHz, and the minimum resource allocation (called a "resource block" (RB)) can be 12 subcarriers (or 180 kHz). Therefore, for system bandwidths of 1.25, 2.5, 5, 10, or 20 MHz, the nominal Fast Fourier Transform (FFT) size can be equal to 128, 256, 512, 1024, or 2048, respectively. The system bandwidth can also be divided into multiple subbands. For example, a subband can cover 1.8 MHz (e.g., 6 RBs), and for system bandwidths of 1.25, 2.5, 5, 10, or 20 MHz, there can be 1, 2, 4, 8, or 16 subbands, respectively. In LTE, the basic transmission time interval (TTI) or packet duration is a 1ms subframe.

[0136] NR can utilize OFDM with CP on both uplink and downlink, and includes support for half-duplex operation using TDD. In NR, subframes are still 1ms, but the basic TTI is called a slot. A subframe contains a variable number of slots depending on the subcarrier spacing (e.g., 1, 2, 4, 8, 16, ... slots). NR RBs are 12 consecutive frequency subcarriers. NR can support a basic subcarrier spacing of 15 kHz, and other subcarrier spacings can be defined relative to the basic subcarrier spacing, such as 30 kHz, 60 kHz, 120 kHz, 240 kHz, etc. Symbol and slot lengths scale with the subcarrier spacing. The CP length also depends on the subcarrier spacing. Beamforming can be supported, and beam direction can be dynamically configured. MIMO transmission with precoding can also be supported. In some examples, MIMO configurations in DL can support up to 8 transmit antennas, multilayer DL transmission with up to 8 streams, and up to 2 streams per UE. In some examples, multilayer transmission with up to 2 streams per UE can be supported. Up to eight serving cells can be used to support the aggregation of multiple cells.

[0137] In some examples, access to the air interface can be scheduled. A scheduling entity (e.g., a BS) allocates resources for communication between some or all devices and apparatuses within its service area or cell. The scheduling entity can be responsible for scheduling, allocating, reconfiguring, and releasing resources for one or more subordinate entities. That is, for scheduled communication, the subordinate entity utilizes the resources allocated by the scheduling entity. The base station is not the only entity that can act as a scheduling entity. In some examples, a UE can act as a scheduling entity and can schedule resources for one or more subordinate entities (e.g., one or more other UEs), and the other UEs can use the resources scheduled by the UE for wireless communication. In some examples, a UE can act as a scheduling entity in a peer-to-peer (P2P) network and / or in a mesh network. In the mesh network example, in addition to communicating with a scheduling entity, UEs can also communicate directly with each other.

[0138] In some examples, two or more secondary entities (e.g., UEs) can communicate with each other using sidelink signals. Real-world applications of such sidelink communication can include public safety, proximity services, UE-to-network relay, vehicle-to-vehicle (V2V) communication, Internet of Things (IoE) communication, IoT communication, mission-critical mesh, and / or various other suitable applications. Typically, a sidelink signal can refer to a signal used for communication from one secondary entity (e.g., UE1) to another secondary entity (e.g., UE2), where the communication is not relayed by a scheduling entity (e.g., UE or BS), even if the scheduling entity could be used for scheduling and / or control purposes. In some examples, licensed spectrum (unlike wireless LANs, which typically use unlicensed spectrum) can be used to transmit sidelink signals.

[0139] The methods disclosed herein include one or more steps or actions for implementing the described methods. The steps and / or actions of the methods may be interchanged without departing from the scope of the claims. In other words, unless a specific order of steps or actions is specified, the order and / or use of specific steps and / or actions may be modified without departing from the scope of the claims.

[0140] As used herein, the phrase “at least one” in a list of items refers to any combination of these items, including a single member. For example, “at least one of a, b, or c” is intended to cover a, b, c, ab, ac, bc, and abc, as well as any combination with multiple identical elements (e.g., aa, aaa, aab, aac, abb, acc, bb, bbb, bbb, cc, and ccc, or any other ordering of a, b, and c).

[0141] As used herein, the term "determine" encompasses a wide variety of actions. For example, "determine" can include calculation, estimation, processing, derivation, investigation, searching (e.g., searching in a table, data pool, or other data structure), verification, etc. Furthermore, "determine" can include receiving (e.g., receiving information), accessing (e.g., accessing data in memory), etc. Moreover, "determine" can include parsing, selecting, choosing, building, etc.

[0142] The preceding description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be apparent to those skilled in the art, and the general principles defined herein may be applied to other aspects. Therefore, the claims are not intended to be limited to the aspects shown herein, but are to be given the full scope consistent with the language of the claims, wherein reference to an element in the singular, unless expressly stated, is not intended to mean “one and only one,” but rather “one or more.” Unless otherwise specified, the term “some” means one or more. All structural and functional equivalents of the elements throughout the various aspects described in this disclosure are known or will subsequently be known to a person skilled in the art, and are expressly incorporated herein by reference and intended to be covered by the claims. Moreover, nothing disclosed herein is intended to be offered to the public, whether or not such disclosure is expressly recited in the claims. Elements without claims are to be interpreted in accordance with 35 USC §112, Chapter 6, unless the element is expressly recited using the phrase “unit for…” or, in the case of a method claim, using the phrase “step for…”.

[0143] The various operations described above can be performed by any suitable unit capable of performing the corresponding function. This unit may include various hardware and / or software components and / or modules, including but not limited to circuits, application-specific integrated circuits (ASICs), or processors. Typically, in the case of operations as shown in the figures, these operations may have corresponding functional module components with similar numbering. For example, Figure 2 The processors 258, 264, and 266 of the UE 120 and / or the controller / processor 280 and / or the processors 220, 230, and 238 of the BS 110 and / or the controller / processor 240 shown can be configured to perform Figure 7 Operation 700 and / or Figure 8 Operation 800.

[0144] The unit for receiving may include Figure 2 The transceiver, receiver, or at least one antenna and at least one receiver processor shown are included. The unit for transmitting, the unit for sending, or the unit for outputting may include... Figure 2 The transceiver, transmitter, or at least one antenna and at least one transmission processor shown are included. Units for completion, generation, selection, random selection, notification, adoption, updating, use, detection, determination, initiation, maintenance, and completion may include a processing system that may include one or more processors, such as... Figure 2 The processors 258, 264 and 266 of the UE 120 and / or the controller / processor 280 shown, and / or the processors 220, 230, 238 and / or the controller / processor 240 of the BS 110.

[0145] In some cases, a device may have an interface (output unit) for outputting frames for transmission, rather than actually sending frames. For example, a processor may output frames to a radio frequency (RF) front end for transmission via a bus interface. Similarly, a device may have an interface (acquisition unit) for acquiring frames received from another device, rather than actually receiving frames. For example, a processor may acquire (or receive) frames from an RF front end for receiving via a bus interface.

[0146] The various illustrative logic blocks, modules, and circuits described in connection with this disclosure may be implemented or executed using a general-purpose processor, digital signal processor (DSP), application-specific integrated circuit (ASIC), field-programmable gate array (FPGA) or other programmable logic device (PLD), discrete gate or transistor logic, discrete hardware components, or any combination thereof, designed to perform the functions described herein. The general-purpose processor may be a microprocessor, but alternatively, the processor may be any commercially available processor, controller, microcontroller, or state machine. The processor may also be implemented as a combination of computing devices, such as a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors combined with a DSP core, or any other such configuration.

[0147] If implemented in hardware, the example hardware configuration could include a processing system in a wireless node. The processing system could be implemented using a bus architecture. The bus could include any number of interconnect buses and bridges, depending on the specific application and overall design constraints of the processing system. The bus could link together various circuits, including a processor, machine-readable media, and a bus interface. The bus interface could also be used to connect network adapters, etc., to the processing system via the bus. The network adapter could be used to implement signal processing functions at the PHY layer. In user terminal 120 (see...) Figure 1In this case, the user interface (e.g., keyboard, display, mouse, joystick, etc.) can also be connected to the bus. The bus can also link various other circuits, such as timing sources, peripherals, voltage regulators, power management circuits, etc., which are well known in the art and will not be described further. The processor can be implemented using one or more general-purpose and / or special-purpose processors. Examples include microprocessors, microcontrollers, DSP processors, and other circuits capable of executing software. Those skilled in the art will recognize that how best to implement the functions described for the processing system depends on the specific application and the overall design constraints imposed on the system as a whole.

[0148] If implemented in software, these functions can be stored or transmitted as one or more instructions or code on a computer-readable medium. Software should be broadly interpreted as instructions, data, or any combination thereof, regardless of whether it is referred to as software, firmware, middleware, microcode, hardware description language, or otherwise. Computer-readable media includes both computer storage media and communication media, with communication media encompassing any medium that facilitates the transfer of computer programs from one location to another. The processor may be responsible for managing the bus and general processing, including executing software modules stored on the machine-readable storage medium. The computer-readable storage medium may be coupled to the processor, allowing the processor to read information from and write information to the storage medium. Alternatively, the storage medium may be integrated into the processor. As an example, machine-readable media may include transmission lines, carrier waves modulated by data, and / or computer-readable storage media containing instructions separate from the wireless node, all accessible to the processor via a bus interface. Alternatively or additionally, the machine-readable medium, or any portion thereof, may be integrated into the processor, such as in cases where there may be caches and / or general-purpose register files. Examples of machine-readable storage media may include, for example, RAM (random access memory), flash memory, ROM (read-only memory), PROM (programmable read-only memory), EPROM (erasable programmable read-only memory), EEPROM (electrically erasable programmable read-only memory), registers, disks, optical disks, hard disks, or any other suitable storage media, or any combination thereof. Machine-readable media may be implemented in computer program products.

[0149] Software modules can comprise a single instruction or a number of instructions, and can be distributed across several different code segments, different programs, and multiple storage media. Computer-readable media can include multiple software modules. Software modules include instructions that, when executed by a device such as a processor, cause the processing system to perform various functions. Software modules can include send modules and receive modules. Each software module can reside in a single storage device or can be distributed across multiple storage devices. For example, when a trigger event occurs, a software module can be loaded from a hard disk into RAM. During the execution of a software module, the processor can load some instructions into a cache to improve access speed. One or more cache lines can then be loaded into a general-purpose register file for processor execution. When the functionality of a software module is mentioned below, it will be understood that such functionality is implemented by the processor when instructions from that software module are executed.

[0150] Furthermore, any connection is appropriately referred to as a computer-readable medium. For example, if software is transmitted from a website, server, or other remote source using coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared (IR), radio, and microwave, then the definition of medium includes coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave. Disks and platters, as used herein, include compressed optical discs (CDs), laser discs, optical discs, digital multifunction discs (DVDs), floppy disks, and Blu-ray® discs, wherein the disk typically magnetically copies data, while the disc reproduces data using lasers. Therefore, in some aspects, a computer-readable medium may include non-transitory computer-readable media (e.g., tangible media). Additionally, in other aspects, a computer-readable medium may include transient computer-readable media (e.g., signals). Combinations of the above should also be included within the scope of computer-readable media.

[0151] Therefore, specific aspects may include computer program products for performing the operations presented herein. For example, such computer program products may include computer-readable media having instructions stored thereon that are executable by one or more processors to perform the operations described herein. For example, instructions for performing the operations described herein.

[0152] Furthermore, it should be understood that modules and / or other suitable units for performing the methods and techniques described herein can be appropriately downloaded and / or otherwise obtained by the user terminal and / or base station. For example, such a device can be coupled to a server to facilitate the transmission of units for performing the methods described herein. Alternatively, the various methods described herein can be provided via storage units (e.g., RAM, ROM, physical storage media such as CDs or floppy disks, etc.) so that the user terminal and / or base station can obtain the various methods when the storage units are coupled or provided to the device. Furthermore, any other suitable techniques for providing the methods and techniques described herein to the device can be used.

[0153] It should be understood that the claims are not limited to the precise configuration and components shown above. Various modifications, alterations, and variations may be made to the arrangement, operation, and details of the methods and apparatus described above without departing from the scope of the claims.

Claims

1. A method for wireless communication by a first user equipment (UE), comprising: Complete the first beam training with the second UE; Send a first discovery message to the second UE, the first discovery message including at least one of the following: The indication of the first BT-RS sequence index of the current beam training reference signal (BT-RS) sequence associated with the first beam training; Indications for timers that change the BT-RS sequence, or An indication of the second BT-RS sequence index of the second BT-RS sequence to be used by the first UE before the timer for changing the BT-RS sequence expires; as well as Randomly select one or more beam training opportunities for the second UE to monitor the second BT-RS sequence, wherein the random selection of the one or more beam training opportunities for the second UE to monitor the second BT-RS sequence includes: randomly selecting at least one beam training instance of the second BT-RS sequence for the second UE to monitor in each of a plurality of beam training periods before the timer for changing the BT-RS sequence expires.

2. The method according to claim 1, further comprising: The first discovery message notifies the at least one beam training instance.

3. The method according to claim 1, wherein, The transmission of the first discovery message is based on beam training at each of the at least one beam training instance.

4. The method according to claim 1, further comprising: Select a new beam training instance after the timer expires; as well as The new BT-RS sequence is adopted based on the new beam training instance.

5. The method according to claim 1, further comprising: The one or more beam training opportunities are selected based on the usage status of each beam training opportunity, wherein the usage status is based on system-wide resources.

6. The method according to claim 1, further comprising: Notify one or more beam training opportunities before the timer expires.

7. The method according to claim 1, further comprising: After sending the first discovery message, a second discovery message is sent to the second UE, wherein the second discovery message includes the following when the first UE has not used the second BT-RS sequence before the timer expires: The updated timer, wherein the updated timer is the difference between the length of the timer and the time between sending the first discovery message and sending the second discovery message; The current BT-RS sequence index; and The second BT-RS sequence index.

8. The method according to claim 7, further comprising: The updated timer is used during the creation of the beam pair link with the third UE.

9. The method according to claim 1, further comprising: After sending the first discovery message, a second discovery message is sent to the second UE, wherein the second discovery message includes the following when the first UE uses the second BT-RS sequence before the timer expires: As the index of the second BT-RS sequence of the current BT-RS sequence; An updated timer, wherein the updated timer reflects the time between sending the first discovery message and using the second BT-RS sequence; and The third BT-RS sequence index of the third BT-RS sequence to be used by the first UE before the updated timer expires.

10. The method according to claim 1, wherein, Completing the first beam training with the second UE includes: Send one or more BT-RSs using the current BT-RS sequence to the second UE to discover beampup link with the second UE; and It was determined that there was no interest in wireless communication on the beam link.

11. The method of claim 10, further comprising: A notification message indicating the discovered beampair link is sent to the second UE, wherein the determination that wireless communication on the beampair link is of no interest is based on the fact that no response message to the notification message is received from the second UE.

12. The method of claim 10, further comprising: Receive an announcement message from the second UE indicating the discovered beam pair link; as well as Avoid sending a response to the notification message indicating that you are not interested in the discovered beam link.

13. The method according to claim 10, wherein, Sending the first discovery message includes: using the discovered beampup link to send the first discovery message.

14. The method of claim 10, wherein, Determining that wireless communication on the beampair link is of no interest includes: determining, for one or more service or application data, that wireless communication on the beampair link is of no interest.

15. The method of claim 14, further comprising: Based on the availability of data from the one or more services or applications, it is determined that the second BT-RS sequence will be used before the timer expires.

16. A first user equipment (UE), comprising: The processing system is configured as follows: Complete the first beam training with the second UE; and A transmitter configured to send a first discovery message to the second UE, the first discovery message including at least one of the following: The indication of the first BT-RS sequence index of the current beam training reference signal (BT-RS) sequence associated with the first beam training; Indications for timers that change the BT-RS sequence, or An indication of the second BT-RS sequence index of the second BT-RS sequence to be used by the first UE before the timer for changing the BT-RS sequence expires; and The processing system is further configured to: randomly select one or more beam training opportunities for the second UE to monitor the second BT-RS sequence, wherein the random selection of the one or more beam training opportunities for the second UE to monitor the second BT-RS sequence includes: randomly selecting at least one beam training instance of the second BT-RS sequence for the second UE to monitor in each of a plurality of beam training periods before the timer for changing the BT-RS sequence expires.

17. The first UE according to claim 16, wherein, The processing system is also configured to perform the method according to any one of claims 2 to 15.

18. A computer-readable medium for wireless communication by a first user equipment (UE), comprising code for performing the method according to any one of claims 1 to 15.

19. A first user equipment (UE), comprising: A unit for performing the method according to any one of claims 1 to 15.

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