Power efficient relay discovery procedure for sidelink

Abstract

Methods, systems, and devices for wireless communication are described. A user equipment (UE) can implement a power efficient discovery procedure to establish a relay. In some cases, the UE can monitor a resource pool for a relay beacon from a relay device and measure a received power of the relay beacon. If the received power satisfies a threshold, the UE can monitor for a relay announcement from the relay device and establish a sidelink connection with the relay device based on the relay announcement. The relay beacon can support a two-stage discovery procedure in which the UE determines that the relay device is available before processing the relay announcement to conserve power. Additional techniques for proximity-based discovery are described herein.

Description

[0001] Cross-referencing

[0002] This patent application claims priority to the following applications: U.S. Provisional Patent Application No. 63 / 108,784, filed November 2, 2020, entitled “POWER EFFICIENT RELAY DISCOVERY PROCEDURE FOR SIDELINK”, by HE et al.; and U.S. Patent Application No. 17 / 512,441, filed October 27, 2021, entitled “POWER EFFICIENT RELAY DISCOVERY PROCEDURE FOR SIDELINK”; each of the above applications is assigned to the assignee of this application. Technical Field

[0003] The following discussion relates to wireless communications, including a power-efficient relay discovery process for sidelinks. Background Technology

[0004] Wireless communication systems are widely deployed to provide various types of communication content, such as voice, video, packet data, messaging, and broadcasting. These systems may be able to support communication with multiple users by sharing available system resources (e.g., time, frequency, and power). Examples of such multiple access systems include fourth-generation (4G) systems (e.g., Long Term Evolution (LTE) systems, improved LTE (LTE-A) systems, or LTE-A Pro systems) and fifth-generation (5G) systems (which may be referred to as New Radio (NR) systems). These systems may employ technologies such as Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), Orthogonal Frequency Division Multiple Access (OFDMA), or Discrete Fourier Transform Extended Orthogonal Frequency Division Multiplexing (DFT-S-OFDM). A wireless multiple access communication system may include one or more base stations or one or more network access nodes, each base station or network access node simultaneously supporting communication with multiple communication devices (which may also be referred to as User Equipment (UE)). Summary of the Invention

[0005] The described techniques relate to improved methods, systems, devices, and apparatuses that support power efficient relay discovery procedures for sidelink. A user equipment (UE) can implement a two-stage discovery procedure that implements a relay beacon. For the two-stage discovery procedure, the UE can first detect a suitable relay device, and then the UE can perform processing to establish a relay connection. In a first stage, the UE can monitor for a relay beacon, which can be periodically broadcast by a relay device. If the relay beacon satisfies a relay selection criterion, the UE can perform a second stage of the discovery procedure. For example, if a measured power of the detected relay beacon exceeds a threshold, the UE can perform the second stage. In the second stage, the UE can monitor for a relay announcement from the relay device and attempt to establish a relay connection. In some examples, the relay device can include an indication of resources for the relay announcement in the relay beacon. The UE can then monitor the resources indicated by the relay beacon for the relay announcement. In some other examples, the UE can send a relay discovery request to the relay device, and the relay device can then send a relay announcement to the UE. Based on information in the relay announcement, the UE can determine whether to establish a sidelink connection with the relay device.

[0006] Some additional techniques for proximity-based discovery are described herein. For example, a UE can initiate a discovery procedure based on proximity to one or more nearby relay devices. The UE can maintain a database of relay devices and use positioning information for the relay devices and the UE to determine whether a relay device is nearby. In some cases, the UE can be configured with positioning information for candidate relay devices, and in some cases, the UE can determine and record positioning information for candidate relay devices. In some additional or alternative aspects, the UE can support both a passive discovery mode and an active discovery mode. In the passive mode, the UE can passively search for relay beacons, relay announcements, or both. In the active mode, the UE can periodically send a sidelink connection request to attempt to establish a sidelink connection. In some examples, a base station can configure the UE to use a certain discovery mode. In other examples, the UE can first operate in the passive mode and switch to the active mode under certain conditions. For example, the UE can switch to the active mode if the UE fails to find a relay after a period of passive discovery, or if the UE has delay-sensitive data or high-priority data to transmit or receive.

[0007] A method for wireless communication at a UE is described. The method can include monitoring a resource pool for a relay beacon from a relay device, detecting the relay beacon in the resource pool, receiving a relay announcement from the relay device based on the relay beacon satisfying a relay selection criterion, and establishing a sidelink connection with the relay device based on the relay announcement.

[0008] An apparatus for wireless communication at a UE is described. The apparatus can include a processor, memory coupled with the processor, and instructions stored in the memory. The instructions can be executable by the processor to cause the apparatus to monitor a resource pool for a relay beacon from a relay device, detect the relay beacon in the resource pool, receive a relay announcement from the relay device based on the relay beacon satisfying a relay selection criterion, and establish a sidelink connection with the relay device based on the relay announcement.

[0009] Another apparatus for wireless communication at a UE is described. The apparatus can include means for monitoring a resource pool for a relay beacon from a relay device, means for detecting the relay beacon in the resource pool, means for receiving a relay announcement from the relay device based on the relay beacon satisfying a relay selection criterion, and means for establishing a sidelink connection with the relay device based on the relay announcement.

[0010] A non-transitory computer-readable medium storing code for wireless communication at a UE is described. The code can include instructions executable by a processor to monitor a resource pool for a relay beacon from a relay device, detect the relay beacon in the resource pool, receive a relay announcement from the relay device based on the relay beacon satisfying a relay selection criterion, and establish a sidelink connection with the relay device based on the relay announcement.

[0011] Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein can further include operations, features, means, or instructions for transmitting a relay discovery request to the relay device based on the relay beacon satisfying the relay selection criterion, where receiving the relay announcement can be based on transmitting the relay discovery request.

[0012] Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein can further include operations, features, means, or instructions for identifying a set of resources associated with the relay announcement based on the relay beacon from the relay device, where receiving the relay announcement includes monitoring the set of resources associated with the relay announcement.

[0013] In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the set of resources can be preconfigured at the UE or dedicated to relay messages, or both.

[0014] In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the set of resources corresponds to a subset of resource blocks of a resource pool configured for the UE.

[0015] In some examples of the method, apparatuses, and non-transitory computer- readable medium described herein, the set of resources associated with the relay announcement can be in a different resource pool than a resource pool for the relay beacon, in a different time slot than the relay beacon, or both.

[0016] In some examples of the method, apparatuses, and non-transitory computer- readable medium described herein, the set of resources can be configured for a set of multiple UEs including at least the UE.

[0017] In some examples of the method, apparatuses, and non-transitory computer- readable medium described herein, the relay selection criteria can be based on a received power of the relay beacon satisfying a proximity threshold, a proximity of the relay device satisfying a proximity threshold (and the proximity of the relay device can be determined based on the relay beacon), or any combination thereof.

[0018] Some examples of the method, apparatuses, and non-transitory computer- readable medium described herein can further include operations, features, means, or instructions for decoding the relay beacon based on an identifier that can be common to a set of multiple relay devices including the relay device.

[0019] Some examples of the method, apparatuses, and non-transitory computer- readable medium described herein can further include operations, features, means, or instructions for receiving, from a base station, one or more sequences associated with a set of multiple relay devices, the one or more sequences including at least the sequence.

[0020] Some examples of the method, apparatuses, and non-transitory computer- readable medium described herein can further include operations, features, means, or instructions for decoding the relay beacon based on an identifier or a code associated with the relay discovery.

[0021] In some examples of the method, apparatuses, and non-transitory computer- readable medium described herein, the identifier can be an identifier of the relay device or an identifier associated with the relay discovery.

[0022] Some examples of the method, apparatuses, and non-transitory computer- readable medium described herein can further include operations, features, means, or instructions for identifying a payload of the relay beacon, where the payload includes an identifier of the relay device.

[0023] Some examples of the method, apparatuses, and non-transitory computer- readable medium described herein can further include operations, features, means, or instructions for identifying unified access control information associated with the relay device, where establishing the sidelink connection can be based on the unified access control information.

[0024] In some examples of the method, apparatuses, and non-transitory computer- readable medium described herein, the relay announcement includes unified access control information.

[0025] In some examples of the method, apparatuses, and non-transitory computer- readable medium described herein, the sidelink connection can be established based on the UE satisfying a criterion associated with the unified access control information.

[0026] A method for wireless communication at a relay device is described. The method can include transmitting a relay beacon using a resource pool, transmitting a relay announcement based on transmitting the relay beacon, and establishing a sidelink connection with a UE based on the relay announcement.

[0027] An apparatus for wireless communication at a relay device is described. The apparatus can include a processor, memory coupled with the processor, and instructions stored in the memory. The instructions can be executable by the processor to cause the apparatus to transmit a relay beacon using a resource pool, transmit a relay announcement based on transmitting the relay beacon, and establish a sidelink connection with a UE based on the relay announcement.

[0028] Another apparatus for wireless communication at a relay device is described. The apparatus can include means for transmitting a relay beacon using a resource pool, means for transmitting a relay announcement based on transmitting the relay beacon, and means for establishing a sidelink connection with a UE based on the relay announcement.

[0029] A non-transitory computer-readable medium storing code for wireless communication at a relay device is described. The code can include instructions executable by a processor to transmit a relay beacon using a resource pool, transmit a relay announcement based on transmitting the relay beacon, and establish a sidelink connection with a UE based on the relay announcement.

[0030] Some examples of the method, apparatuses, and non-transitory computer- readable medium described herein can further include operations, features, means, or instructions for receiving a relay discovery request from the UE, where transmitting the relay announcement can be based on receiving the relay discovery request.

[0031] Some examples of the method, apparatuses, and non-transitory computer- readable medium described herein can further include operations, features, means, or instructions for indicating a set of resources associated with the relay announcement based on the relay beacon, where transmitting the relay announcement includes transmitting the relay announcement using the set of resources.

[0032] In some examples of the method, apparatuses, and non-transitory computer- readable medium described herein, the set of resources can be preconfigured for the UE or dedicated for relay messages, or both.

[0033] In some examples of the method, apparatuses, and non-transitory computer- readable medium described herein, the set of resources corresponds to a subset of resource blocks of a resource pool configured for the UE.

[0034] In some examples of the method, apparatuses, and non-transitory computer- readable medium described herein, the set of resources associated with the relay announcement can be in a different resource pool than a resource pool used for the relay beacon, in a different time slot than the relay beacon, or both.

[0035] In some examples of the method, apparatuses, and non-transitory computer- readable medium described herein, the set of resources can be configured for a set of multiple UEs including at least the UE.

[0036] Some examples of the method, apparatuses, and non-transitory computer- readable medium described herein can further include operations, features, means, or instructions for encoding the relay beacon based on an identifier that can be common to a set of multiple relay devices including the relay device.

[0037] In some examples of the method, apparatuses, and non-transitory computer- readable medium described herein, the relay beacon can be scrambled with a sequence.

[0038] Some examples of the method, apparatuses, and non-transitory computer- readable medium described herein can further include operations, features, means, or instructions for scrambling the relay beacon based on an identifier of the relay device or an identifier associated with the relay discovery.

[0039] Some examples of the method, apparatuses, and non-transitory computer- readable medium described herein can further include operations, features, means, or instructions for including an identifier of the relay device in a payload of the relay beacon.

[0040] Some examples of the method, apparatuses, and non-transitory computer- readable medium described herein can further include operations, features, means, or instructions for indicating, to the UE, unified access control information associated with the relay device, where establishing the sidelink connection can be based on the unified access control information.

[0041] In some examples of the method, apparatuses, and non-transitory computer- readable medium described herein, the relay announcement includes unified access control information.

[0042] In some examples of the method, apparatuses, and non-transitory computer- readable medium described herein, the sidelink connection can be established based on the UE satisfying a criterion associated with the unified access control information.

[0043] A method for wireless communication at a UE is described. The method can include identifying a set of candidate relay devices to establish a sidelink connection with the UE, receiving a relay advertisement from a relay device based on first positioning information for the relay device and second positioning information for the UE, and establishing the sidelink connection with the relay device based on the relay advertisement.

[0044] An apparatus for wireless communication at a UE is described. The apparatus can include a processor, memory coupled with the processor, and instructions stored in the memory. The instructions can be executable by the processor to cause the apparatus to identify a set of candidate relay devices to establish a sidelink connection with the UE, receive a relay advertisement from a relay device based on first positioning information for the relay device and second positioning information for the UE, and establish the sidelink connection with the relay device based on the relay advertisement.

[0045] Another apparatus for wireless communication at a UE is described. The apparatus can include means for identifying a set of candidate relay devices to establish a sidelink connection with the UE, means for receiving a relay advertisement from a relay device based on first positioning information for the relay device and second positioning information for the UE, and means for establishing the sidelink connection with the relay device based on the relay advertisement.

[0046] A non-transitory computer-readable medium storing code for wireless communication at a UE is described. The code can include instructions executable by a processor to identify a set of candidate relay devices to establish a sidelink connection with the UE, receive a relay advertisement from a relay device based on first positioning information for the relay device and second positioning information for the UE, and establish the sidelink connection with the relay device based on the relay advertisement.

[0047] Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein can further include operations, features, means, or instructions for receiving a relay configuration indicating the set of candidate relay devices.

[0048] In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the relay configuration can be received from a base station or a previously connected relay device.

[0049] In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the relay configuration includes positioning information for the set of candidate relay devices, the positioning information including first positioning information for the relay device.

[0050] In some examples of the method, apparatuses, and non-transitory computer- readable medium described herein, the relay configuration includes scheduling information for the relay advertisement from the set of candidate relay devices, scheduling information for the relay beacon signal from the set of candidate relay devices, or both.

[0051] In some examples of the method, apparatuses, and non-transitory computer- readable medium described herein, the relay configuration indicates a set of resources associated with the relay advertisement, and monitoring for the relay advertisement includes monitoring the set of resources associated with the relay advertisement.

[0052] Some examples of the method, apparatuses, and non-transitory computer- readable medium described herein can further include operations, features, means, or instructions for receiving, from the set of candidate relay devices, one or more indications that a candidate relay device of the set of candidate relay devices can be stationary.

[0053] Some examples of the method, apparatuses, and non-transitory computer- readable medium described herein can further include operations, features, means, or instructions for determining positioning information for the set of candidate relay devices based on the one or more indications.

[0054] Some examples of the method, apparatuses, and non-transitory computer- readable medium described herein can further include operations, features, means, or instructions for transmitting a relay discovery request to a relay device based on the relay device being within a range of the UE, where receiving the relay advertisement can be based on transmitting the relay discovery request.

[0055] Some examples of the method, apparatuses, and non-transitory computer- readable medium described herein can further include operations, features, means, or instructions for receiving reference signals from the set of candidate relay devices, performing positioning measurements for the set of candidate relays based on receiving the reference signals, and determining positioning information for the set of candidate relay devices based on the positioning measurements.

[0056] Some examples of the method, apparatuses, and non-transitory computer- readable medium described herein can further include operations, features, means, or instructions for identifying a set of resources associated with the relay advertisement, where receiving the relay advertisement includes monitoring the set of resources associated with the relay advertisement.

[0057] In some examples of the method, apparatuses, and non-transitory computer- readable medium described herein, the set of resources can be preconfigured at the UE or dedicated to relay messages, or both.

[0058] In some examples of the method, apparatuses, and non-transitory computer- readable medium described herein, the set of resources corresponds to a subset of resource blocks of a resource pool configured for the UE.

[0059] A method for wireless communication at a relay device is described. The method can include indicating first positioning information of the relay device to establish a sidelink connection with a UE, transmitting a relay advertisement to the UE based on the first positioning information of the relay device, and establishing the sidelink connection with the UE based on the relay advertisement.

[0060] An apparatus for wireless communication at a relay device is described. The apparatus can include a processor, memory coupled with the processor, and instructions stored in the memory. The instructions can be executable by the processor to cause the apparatus to indicate first positioning information of the relay device to establish a sidelink connection with a UE, transmit a relay advertisement to the UE based on the first positioning information of the relay device, and establish the sidelink connection with the UE based on the relay advertisement.

[0061] Another apparatus for wireless communication at a relay device is described. The apparatus can include means for indicating first positioning information of the relay device to establish a sidelink connection with a UE, means for transmitting a relay advertisement to the UE based on the first positioning information of the relay device, and means for establishing the sidelink connection with the UE based on the relay advertisement.

[0062] A non-transitory computer-readable medium storing code for wireless communication at a relay device is described. The code can include instructions executable by a processor to indicate first positioning information of the relay device to establish a sidelink connection with a UE, transmit a relay advertisement to the UE based on the first positioning information of the relay device, and establish the sidelink connection with the UE based on the relay advertisement.

[0063] Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein can further include operations, features, means, or instructions for indicating scheduling information for the relay advertisement from the relay device, scheduling information for a relay beacon signal from the relay device, or both.

[0064] In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the first positioning information includes an indication that the relay device can be stationary.

[0065] Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein can further include operations, features, means, or instructions for receiving a relay discovery request from the UE based on the relay device being within range of the UE, where transmitting the relay advertisement can be based on receiving the relay discovery request.

[0066] Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein can further include operations, features, means, or instructions for identifying a set of resources associated with the relay announcement, where transmitting the relay announcement includes transmitting the relay announcement using the set of resources.

[0067] In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the set of resources can be preconfigured for the UE or dedicated for relay messages, or both.

[0068] In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the set of resources corresponds to a subset of resource blocks of a resource pool configured for the UE.

[0069] A method for wireless communication at a UE is described. The method can include monitoring a resource pool for relay broadcasts from relay devices according to a passive relay discovery mode, detecting a trigger to switch from the passive relay discovery mode to an active relay discovery mode, periodically transmitting a relay discovery request to the relay devices based on the active relay discovery mode, receiving a relay announcement from the relay devices based on transmitting the relay discovery request, and establishing a sidelink connection with the relay devices based on the relay announcement.

[0070] An apparatus for wireless communication at a UE is described. The apparatus can include a processor, memory coupled with the processor, and instructions stored in the memory. The instructions can be executable by the processor to cause the apparatus to monitor a resource pool for relay broadcasts from relay devices according to a passive relay discovery mode, detect a trigger to switch from the passive relay discovery mode to an active relay discovery mode, periodically transmit a relay discovery request to the relay devices based on the active relay discovery mode, receive a relay announcement from the relay devices based on transmitting the relay discovery request, and establish a sidelink connection with the relay devices based on the relay announcement.

[0071] Another apparatus for wireless communication at a UE is described. The apparatus can include means for monitoring a resource pool for relay broadcasts from relay devices according to a passive relay discovery mode, means for detecting a trigger to switch from the passive relay discovery mode to an active relay discovery mode, means for periodically transmitting a relay discovery request to the relay devices based on the active relay discovery mode, means for receiving a relay announcement from the relay devices based on transmitting the relay discovery request, and means for establishing a sidelink connection with the relay devices based on the relay announcement.

[0072] A non-transitory computer-readable medium storing code for wireless communication at a UE is described. The code can include instructions executable by a processor to monitor a resource pool for a relay broadcast from a relay device in accordance with a passive relay discovery mode, detect a trigger to switch from the passive relay discovery mode to an active relay discovery mode, transmit a relay discovery request to the relay device periodically based on the active relay discovery mode, receive a relay advertisement from the relay device based on transmitting the relay discovery request, and establish a sidelink connection with the relay device based on the relay advertisement.

[0073] In some examples of the method, apparatuses, and non-transitory computer- readable medium described herein, detecting the trigger can include operations, features, means, or instructions for identifying that a high priority message can be pending communication.

[0074] In some examples of the method, apparatuses, and non-transitory computer- readable medium described herein, detecting the trigger can include operations, features, means, or instructions for determining that a timer associated with the passive relay discovery mode can have expired.

[0075] Some examples of the method, apparatuses, and non-transitory computer- readable medium described herein can further include operations, features, means, or instructions for receiving an indication from a base station to use the passive relay discovery mode or the active relay discovery mode. BRIEF DESCRIPTION OF DRAWINGS

[0076] Figure 1 An example of a process flow that supports power efficient relay discovery procedures for sidelink is shown in accordance with aspects of the present disclosure.

[0077] Figure 2 An example of a process flow that supports power efficient relay discovery procedures for sidelink is shown in accordance with aspects of the present disclosure.

[0078] Figure 3 An example of a process flow that supports power efficient relay discovery procedures for sidelink is shown in accordance with aspects of the present disclosure.

[0079] Figure 4 An example of a process flow that supports power efficient relay discovery procedures for sidelink is shown in accordance with aspects of the present disclosure.

[0080] Figure 5 And Figure 6 A block diagram of a device that supports power efficient relay discovery procedures for sidelink is shown in accordance with aspects of the present disclosure.

[0081] Figure 7A block diagram illustrating a communications manager that supports power efficient relay discovery procedures for sidelink in accordance with aspects of the present disclosure is shown.

[0082] Figure 8 A diagram illustrating a system including a device that supports power efficient relay discovery procedures for sidelink in accordance with aspects of the present disclosure is shown.

[0083] Figures 9 to 13 A flow diagram illustrating a method that supports power efficient relay discovery procedures for sidelink in accordance with aspects of the present disclosure is shown. DETAILED DESCRIPTION

[0084] A user equipment (UE) can establish a sidelink connection with a relay device to facilitate transmission of information (e.g., user data) between the UE and a wireless network. The relay device can also communicate with a base station, e.g., to relay user data to or from the UE. To establish the sidelink connection, the UE (e.g., a remote UE) can first identify or discover the presence of at least one suitable relay device. In some systems, the remote UE can discover the relay device through a single message based discovery. In some examples of single message based discovery, the relay device can periodically transmit a sidelink discovery message. In other examples, the remote UE can transmit a sidelink discovery message, such as a relay discovery request, and nearby relay devices can transmit a response (e.g., a relay advertisement) back to the remote UE. Some single message based discovery procedures can use a large amount of power at the remote UE to establish a relay connection. Additionally, due to the high power usage, some devices (e.g., light or low power UEs) can not be able to support single message based discovery procedures. The techniques described herein provide power efficient discovery procedures.

[0085] In some cases, a remote UE can implement a two-stage discovery procedure. In some cases, the two-stage discovery procedure can be referred to as a passive mode for relay discovery. For the two-stage discovery procedure, a remote UE can first detect a suitable relay device, and then the remote UE can perform processing to establish a relay connection. In a first stage, a remote UE can monitor for a relay beacon, which can be periodically broadcast by a relay device. The relay beacon can include a sequence that is known to the remote UE. If the relay beacon satisfies relay selection criteria, the UE can perform a second stage of the discovery procedure. For example, the UE can determine whether a measured power of the detected relay beacon satisfies a threshold. In the second stage, the remote UE can monitor for a relay announcement from the relay device and attempt to establish a relay connection. In some examples, the relay device can include an indication of resources for the relay announcement in the relay beacon. The remote UE can then monitor the resources indicated by the relay beacon for the relay announcement. In some other examples, the remote UE can send a relay discovery request to the relay device, and the relay device can then send a relay announcement to the remote UE. Based on information in the relay announcement, the remote UE can determine whether to establish a sidelink connection with the relay device.

[0086] Some additional techniques for proximity-based discovery are described herein. For example, a remote UE can initiate a discovery procedure based on proximity to one or more nearby relay devices. In some examples, a remote UE can maintain a database of relay devices to determine whether a relay device is nearby. In some cases, a base station can configure a remote UE with positioning information for one or more candidate stationary relay devices. In some other cases, a relay device can indicate its positioning information to a remote UE (e.g., including that the relay device is stationary), and the remote UE can record the positioning information for the stationary relay device. In some cases, a remote UE can perform positioning measurements to identify nearby relay devices.

[0087] In some additional or alternative aspects, a remote UE can support both a passive discovery mode and an active discovery mode. In the passive mode, the remote UE can passively search for relay beacons, relay advertisements, or both. In the active mode, the remote UE can periodically transmit a sidelink connection request in an attempt to establish a sidelink connection. In some examples, a base station can configure a remote UE to use a certain discovery mode. In other examples, a remote UE can first operate in a passive mode and switch to an active mode under certain conditions. For example, a remote UE can switch to an active mode if the remote UE fails to find a relay after a period of passive discovery, or if the remote UE has delay-sensitive data or high-priority data to transmit or receive. According to examples of the present disclosure, a remote UE and a relay UE can utilize a power-efficient discovery procedure to establish a sidelink connection. These techniques can generally consume less power than single-message discovery techniques by reducing the amount of transmissions or monitoring at the remote UE and the relay device.

[0088] Aspects of the present disclosure are first described in the context of a wireless communications system. Aspects of the present disclosure are further illustrated by and described with reference to apparatus diagrams, system diagrams, and flowcharts that relate to power-efficient relay discovery procedures for sidelink, and with reference to methods that are described by the flowcharts.

[0089] Figure 1 An example of a wireless communications system 100 that supports power-efficient relay discovery procedures for sidelink is shown in accordance with aspects of the present disclosure. The wireless communications system 100 can include one or more base stations 105, one or more UEs 115, and a core network 130. In some examples, the wireless communications system 100 can be a Long Term Evolution (LTE) network, an LTE-Advanced (LTE-A) network, an LTE-A Pro network, or a New Radio (NR) network. In some examples, the wireless communications system 100 can support enhanced broadband communications, ultra-reliable (e.g., mission critical) communications, low-latency communications, or communications with low-cost and low-complexity devices, or any combination thereof.

[0090] The base stations 105 can be dispersed throughout the geographic area 100 and can be devices in different forms or having different capabilities. The base stations 105 and the UEs 115 can wirelessly communicate with one another via one or more communication links 125. Each base station 105 can provide a coverage area 110 over which

[0091] The UEs 115 can be dispersed throughout the coverage areas 110 of the wireless communications system 100, and each UE 115 can be stationary, or mobile, or both at different times. The UEs 115 can be devices in different forms or having different capabilities. Some example UEs 115 are illustrated in FIG. 1. The UEs 115 described herein can be able to communicate with various types of devices, such as other UEs 115, base stations 105, or network equipment (e.g., core network nodes, relay devices, integrated access and backhaul (IAB) nodes, or other network equipment), as shown in FIG. 1. Figure 1 Some example UEs 115 are illustrated in FIG. 1. The UEs 115 described herein can be able to communicate with various types of devices, such as other UEs 115, base stations 105, or network equipment (e.g., core network nodes, relay devices, integrated access and backhaul (IAB) nodes, or other network equipment), as shown in FIG. 1. Figure 1

[0092] The base stations 105 can communicate with the core network 130, or with one another, or both. For example, the base stations 105 can interface with the core network 130 through one or more backhaul links 120 (e.g., via an SI, N2, N3, or other interface). The base stations 105 can communicate with one another over the backhaul links 120 (e.g., via an X2, Xn, or other interface) either directly (e.g., direct

[0093] One or more of the base stations 105 described herein can include or can be referred to as a base transceiver station, a radio base station, an access point, a radio transceiver, a NodeB, an eNodeB (eNB), a next-generation NodeB or giga-NodeB (either of which can be referred to as a gNB), a Home NodeB, a Home eNodeB, or some other suitable terminology.

[0094] A UE 115 can include or can be referred to as a mobile device, a wireless device, a remote device, a handheld device, or a subscriber device, or some other suitable terminology, where the “device” can also be referred to as a unit, a station, a terminal, or a client, among other examples. A UE 115 can also include or can be referred to as a personal electronic device such as a cellular phone, a personal digital assistant (PDA), a tablet computer, a laptop computer, or a personal computer. In some examples, a UE 115 can include or be referred to as a wireless local loop (WLL) station, an Internet of Things (IoT) device, an Internet of Everything (IoE) device, or a machine type communications (MTC) device, among other examples, which can be implemented in various objects such as appliances, or vehicles, meters, or other items.

[0095] ​The UEs 115 described herein can be able to communicate with various types of devices, such as other UEs 115 that can sometimes act as relays or Figure 1 as shown.

[0096] The UEs 115 and the base stations 105 can wirelessly communicate with one another via one or more communication links 125 over one or more carriers. The term “carrier” can refer to a set of radio frequency spectrum resources (e.g., frequency channels) with a defined physical layer structure configured for supporting

[0097] communication links 125. For example, a carrier used for a communication link 125 can include a portion of a radio frequency spectrum band (e.g., a bandwidth part (BWP)) that is operated according to one or more physical layer channels for a given radio access technology (e.g., LTE, LTE-A, LTE-A Pro, NR). Each physical layer channel can carry acquisition signaling (e.g., synchronization signals, system information), control signaling (e.g., control channels), user data (e.g., data channels), or other signaling. The wireless communications system 100 can support communication with a UE 115 using carrier aggregation or multi-carrier operation. According to carrier aggregation, a UE 115 can be configured with multiple downlink component carriers and one or more uplink component carriers. Carrier aggregation can be used with both frequency division duplexing (FDD) and time division duplexing (TDD) component carriers.

[0098] The communication links 125 shown in wireless communications system 100 can include uplink transmissions from a UE 115 to a base station 105, or downlink transmissions from a base station 105 to a UE 115. Carriers can carry downlink or uplink communications (e.g., in an FDD mode) or can be configured to carry downlink and uplink communications (e.g., in a TDD mode).

[0099] A carrier can be associated with a specific bandwidth of the radio frequency spectrum, and in some examples, the carrier bandwidth can be referred to as the carrier or the “system bandwidth” of the wireless communication system 100. For example, the carrier bandwidth can be one of a number of defined bandwidths for a particular radio access technology (e.g., 1.4, 3, 5, 10, 15, 20, 40, or 80 MHz). Devices of the wireless communication system 100 (e.g., base station 105, UE 115, or both) can have a hardware configuration that supports communication on a specific carrier bandwidth, or can be configured to support communication on one carrier bandwidth in a set of carrier bandwidths. In some examples, the wireless communication system 100 may include a base station 105 or UE 115 that supports simultaneous communication via carriers associated with multiple carrier bandwidths. In some examples, each served UE 115 can be configured to operate on a portion (e.g., a subband, BWP) or all of the carrier bandwidth.

[0100] The signal waveform transmitted on a carrier can consist of multiple subcarriers (e.g., using multicarrier modulation (MCM) techniques such as Orthogonal Frequency Division Multiplexing (OFDM) or Discrete Fourier Transform Spread Spectrum OFDM (DFT-S-OFDM). In a system employing MCM, a resource element can include a symbol period (e.g., the duration of a modulation symbol) and a subcarrier, where the symbol period and subcarrier spacing are inversely related. The number of bits carried through each resource element can depend on the modulation scheme (e.g., the order of the modulation scheme, the decoding rate of the modulation scheme, or both). Therefore, the more resource elements UE 115 receives and the higher the order of the modulation scheme, the higher the data rate can be for UE 115. Wireless communication resources can refer to a combination of radio frequency spectrum resources, temporal resources, and spatial resources (e.g., spatial layers or beams), and the use of multiple spatial layers can further increase the data rate or data integrity used for communication with UE 115.

[0101] One or more digital schemes (numerologies) can be supported for a carrier, where the digital scheme may include a subcarrier spacing (Δf) and a cyclic prefix. A carrier can be divided into one or more BWPs with the same or different digital schemes. In some examples, UE 115 can be configured with multiple BWPs. In some examples, a single BWP for a carrier can be active at a given time, and communication for UE 115 can be restricted to one or more active BWPs.

[0102] It can be expressed in a basic unit of time (which can be, for example, T). s =1 / (Δf) max ·N f The sampling period is ) seconds, where Δf maxNscsmax f may represent a multiple of the maximum supported Discrete Fourier Transform (DFT) size) to represent time intervals for base stations 105 or UEs 115. Time intervals for the communications resources can be organized as radio frames, each

[0103] Each frame can include a plurality of sequentially-ordered subframes or slots, and each subframe or slot can have the same duration. In some examples, a frame can be partitioned (e.g., in the time domain) into subframes, and each subframe can be further partitioned into a number of slots. Alternatively, each frame can include a variable number of slots, and the number of slots can depend on the subcarrier spacing. Each slot can include a number of symbol periods (e.g., depending on the length of the cyclic prefix prepended to each symbol period). In some wireless communications systems 100, slots can be further partitioned into mini-slots, each mini-slot containing one or more symbols. Excluding the cyclic prefix, each symbol period can contain one or more (e.g., N f The duration of a symbol period can depend on the subcarrier spacing or the operating band.

[0104] A subframe, a slot, a mini-slot, or a symbol can be the smallest scheduling unit (e.g., in the time domain) of the wireless communications system 100 and can be referred to as a transmission time interval (TTI). In some examples, the TTI duration (e.g., the number of symbol periods in a TTI) can be variable. Additionally or alternatively, the smallest scheduling unit of the wireless communications system 100 can be dynamically selected (e.g., in bursts of shortened TTIs (sTTIs)).

[0105] Physical channels can be multiplexed on a carrier according to various techniques. A physical control channel and a physical data channel can be multiplexed on a downlink carrier, for example, using one or more of time division multiplexing (TDM) techniques, frequency division multiplexing (FDM) techniques, or hybrid TDM-FDM techniques. A control region (e.g., a control resource set (CORESET)) for a physical control channel can be defined by a quantity of symbol periods and can extend across the system bandwidth or a subset of the system bandwidth of the carrier. One or more control regions (e.g., CORESETs) can be configured for a set of UEs 115. For example, one or more of the UEs 115 can monitor or search control regions for control information according to one or more search space sets, and each search space set can include one or more control channel candidates arranged in a cascaded manner at one or more aggregation levels. An aggregation level for a control channel candidate can refer to a quantity of control channel resources (e.g., control channel elements (CCEs)) associated with encoded information for a control information format having a given payload size. Search space sets can include common search space sets configured for sending control information to multiple UEs 115 and UE-specific search space sets for sending control information to a specific UE 115.

[0106] Each base station 105 can provide communication coverage for one or more cells (e.g., macro cells, small cells, hot spots, or other types of cells, or any combination thereof). The term “cell” can refer to a logical communication entity used for communication with a base station 105 (e.g., on a carrier) and can be associated with a identifier, such as a physical cell identifier (PCID), virtual cell identifier (VCID), or other identifier, used to distinguish neighboring cells. In some examples, the cell can also refer to a geographical area 110 or a subset of a geographical area 110 (e.g., a sector) over which the logical communication entity operates. The range of such a cell can depend on a capacity of the base station 105 and can range from a small area (e.g., a structure, a subset of a structure, or a sub-area of a geographical area 110) to a large area. For example, a cell can be or include a building, a subset of a building, or an outdoor space between or overlapping with geographical areas 110, among other examples.

[0107] Macro cells typically cover a relatively large geographic area (e.g., a radius of several kilometers) and can allow unrestricted access by UE 115 with a service subscription to a network provider supporting the macro cell. In contrast, small cells can be associated with a lower-power base station 105 and can operate in the same or different (e.g., licensed, unlicensed) frequency bands as macro cells. Small cells can provide unrestricted access to UE 115 with a service subscription to a network provider, or restricted access to UE 115 associated with the small cell (e.g., UE 115 in a Closed Subscriber Group (CSG), or UE 115 associated with a user in a residence or office). Base station 105 can support one or more cells and can also support communication on one or more cells using one or more component carriers.

[0108] In some examples, a carrier can support multiple cells and can be configured with different cells based on different protocol types that can provide access for different types of devices (e.g., MTC, Narrowband IoT (NB-IoT), Enhanced Mobile Broadband (eMBB)).

[0109] In some examples, base station 105 may be mobile, and therefore provide communication coverage for mobile geographic coverage areas 110. In some examples, different geographic coverage areas 110 associated with different technologies may overlap, but the different geographic coverage areas 110 may be supported by the same base station 105. In other examples, overlapping geographic coverage areas 110 associated with different technologies may be supported by different base stations 105. Wireless communication system 100 may include, for example, a heterogeneous network, in which different types of base stations 105 use the same or different radio access technologies to provide coverage for various geographic coverage areas 110.

[0110] The wireless communication system 100 can support synchronous or asynchronous operation. For synchronous operation, base stations 105 can have similar frame timings, and transmissions from different base stations 105 can be approximately time-aligned. For asynchronous operation, base stations 105 can have different frame timings, and in some examples, transmissions from different base stations 105 may not be time-aligned. The techniques described herein can be used for both synchronous and asynchronous operation.

[0111] Some UEs 115, such as MTC or IoT devices, can be low cost or low complexity devices, and can provide for automated communication between machines (e.g., via Machine-to-Machine (M2M) communication). M2M communication or MTC can refer to data communication technologies that allow devices to communicate with one another or a base station 105 without human intervention. In some examples, M2M communication or MTC can include communications from devices that integrate sensors or meters to measure or capture information and relay such information to a central server or application program that makes use of the information or presents the information to humans in an intuitive manner. Some UEs 115 can be designed to collect information or enable automated behavior of machines or other devices. Examples of applications for MTC devices include smart metering, inventory monitoring, water level monitoring, equipment monitoring, healthcare monitoring, wildlife monitoring, climate and geological event monitoring, fleet management and tracking, remote security sensing, physical access control, and transaction-based business processes.

[0112] Some UEs 115 can be configured to employ operating modes that reduce power consumption, such as a half-duplex communications (e.g., a mode where a device transmits or receives in only one direction at a time). In some examples, half-duplex communications can be performed at a reduced peak rate. Other power conservation techniques for UEs 115 include entering a power saving deep sleep mode when not engaging in active communications, entering a power saving shallow sleep mode when not engaging in active communications, or entering a fractional duplex mode when not engaging in active communications. For example, some UEs 115 can be configured for operation using a narrowband protocol type that is associated with a defined portion or range (e.g., set of subcarriers or resource blocks (RBs)) within a carrier, within a guardband, or outside of a carrier.

[0113] The wireless communications system 100 can be configured to support ultra-reliable communications or low-latency communications, or various combinations thereof. For example, the wireless communications system 100 can be configured to support ultra-reliable low-latency communications (URLLC) or mission critical communications. UEs 115 can be designed to support ultra-reliable, low-latency, or critical functions (e.g., mission critical functions). Ultra-reliable communications can include private communication or group communication and can be supported by one or more mission critical services such as mission critical push-to-talk (MCPTT), mission critical video (MCVideo), or mission critical data (MCData). Support for mission critical functions can include prioritization of services, and mission critical services can be used for public safety or general commercial applications. The terms ultra-reliable, low-latency, mission critical, and ultra-reliable low- latency can be used interchangeably herein.

[0114] In some examples, UE 115 can also be able to communicate directly with other UEs 115 over a device-to-device (D2D) communication link 135 (e.g., using a peer-to-peer (P2P) or D2D protocol). One or more UEs 115 utilizing D2D communications can be within the geographic coverage area 110 of a base station 105. Other UEs 115 in such a group can be outside the geographic coverage area 110 of a base station 105 or be otherwise unable to receive transmissions from a base station 105. In some examples, groups of UEs 115 communicating via D2D communications can utilize a one-to-many (1 :M) system in which each UE 115 transmits to every other UE 115 in the group. In some examples, a base station 105 facilitates the scheduling of resources for D2D communications. In other cases, D2D communications are carried out between UEs 115 without the involvement of a base station 105.

[0115] In some systems, the D2D communication link 135 can be an example of a communication channel, such as a sidelink communication channel, between vehicles (e.g., UEs 115). In some examples, vehicles can communicate using vehicle-to-everything (V2X) communications, car-to-car (V2V) communications, or some combination of these. A vehicle can signal information related to traffic conditions, signal scheduling, weather, safety, emergencies, or any other information related to V2X systems. In some examples, vehicles in a V2X system can communicate with roadside infrastructure, such as roadside units, or with the network via one or more network nodes (e.g., base stations 105) using vehicle-to-network (V2N) communications, or both.

[0116] The core network 130 can provide user authentication, access authorization, tracking, Internet Protocol (IP) connectivity, and other access, routing, or mobility functions. The core network 130 can be an evolved packet core (EPC) or 5G core (5GC), which can include at least one control plane entity that manages access and mobility (e.g., a mobility management entity (MME), an access and mobility management function (AMF)) and at least one user plane entity that routes packets to and from user equipment (e.g., a serving gateway (S-GW), a packet data network (PDN) gateway (P-GW), or a user plane function (UPF)). The control plane entity can manage non-access stratum (NAS) functions, such as mobility, authentication, and bearer management for UEs 115 served by base stations 105 associated with the core network 130. User IP packets can be transferred through the user plane entity, which can provide IP address allocation as well as other functions. The user plane entity can be connected to the IP services 150 of the one or more network operators. The IP services 150 can include access to the Internet, Intranet(s), an IP multimedia subsystem (IMS), or a packet-switched streaming service.

[0117] Some of the network devices, such as a base station 105, can include subcomponents such as an access network entity 140, which can be an example of an access node controller (ANC). Each access network entity 140 can communicate with UEs 115 through one or more other access network transmission entities 145, which can be referred to as radio heads, smart radio heads, or transmission / reception points (TRPs). Each access network transmission entity 145 can include one or more antenna panels. In some configurations, various functions of each access network entity 140 or base station 105 can be distributed across various network devices (e.g., radio heads and ANCs) or consolidated into a single network device (e.g., a base station 105).

[0118] The wireless communications system 100 can operate using one or more frequency bands, typically in the range of 300 megahertz (MHz) to 300 gigahertz (GHz). Generally, the region from 300 MHz to 3 GHz is known as the ultra-high frequency (UHF) region or decimeter band, since the wavelengths range from approximately one decimeter to one meter in length. UHF waves can be blocked or redirected by buildings and environmental features, but the waves can penetrate structures sufficiently for a macro cell to provide service to UEs 115 located indoors. Transmission of UHF waves can be associated with smaller antennas and shorter ranges (e.g., less than 100 kilometers) compared to transmission using the smaller frequencies and longer waves of the high frequency (HF) or very high frequency (VHF) portion of the spectrum below 300 MHz.

[0119] The wireless communications system 100 can also operate in a super high frequency (SHF) region, also known as the centimeter band, from 3 GHz to 30 GHz, or in an extremely high frequency (EHF) region, also known as the millimeter band, from 30 GHz to 300 GHz, for example. In some examples, the wireless communications system 100 can support millimeter wave (mmW) communications between the UEs 115 and the base stations 105, and EHF antennas of the respective devices can be smaller and more closely spaced than UHF antennas. In some examples, this can facilitate using antenna arrays within a device. However, the propagation of EHF transmissions can be subject to even greater atmospheric attenuation than SHF or UHF transmissions, and EHF transmissions can therefore have a shorter range than SHF or UHF transmissions. Techniques disclosed herein can be employed across transmissions that use one or more different frequency regions, and designated use of bands across these frequency regions can differ by country or regulating body.

[0120] The wireless communications system 100 can utilize both licensed and unlicensed radio frequency spectrum bands. For example, the wireless communications system 100 can employ License Assisted Access (LAA), LTE-Unlicensed (LTE-U) radio access technology, or NR technology in an unlicensed frequency spectrum band, such as the 5 GHz industrial, scientific and medical (ISM) band. When operating in unlicensed frequency spectrum bands, devices such as the base stations 105 and the UEs 115 can employ carrier sensing for collision detection and avoidance. In some examples, operations in unlicensed frequency spectrum bands can be based on a carrier aggregation configuration in which a primary component carrier operates in a licensed frequency spectrum band and one or more secondary component carriers operate in an unlicensed frequency spectrum band. Operations in unlicensed spectrum can include downlink transmissions, uplink transmissions, P2P transmissions, or D2D transmissions, among other examples.

[0121] The base stations 105 or UEs 115 can be equipped with multiple antennas, which can be used to employ techniques such as transmit diversity, receive diversity, multiple-input multiple-output (MIMO) communications, or beamforming. The antennas of a base station 105 or a UE 115 can be co-located within one or more antenna arrays or antenna panels, which can support MIMO operations or transmit or receive beamforming. In some examples, one or more base station antennas or antenna arrays can be co-located with a antenna assembly, such as an antenna tower. In some examples, the antennas of a base station 105 can be located in diverse geographic locations, such as on different support structures or towers. The base stations 105 can have an antenna array with a number of rows and columns of antenna ports that the base station 105 can use to support beamforming of communications to UEs 115. Similarly, a UE 115 can have one or more antenna arrays that can support various MIMO or beamforming operations. Additionally or alternatively, antenna panels can support radio frequency beamforming of signals transmitted via the antenna ports.

[0122] The base stations 105 or the UEs 115 can use MIMO communications to exploit multipath signal propagation and increase the spectral efficiency. Such techniques can be referred to as spatial multiplexing. The multiple signals may, for example, be transmitted by the transmitting device via different antennas or different combinations of antennas. Similarly, the multiple signals can be received by the receiving device via different antennas or different combinations of antennas. Each of the multiple signals can be referred to as a spatial stream, and can carry bits associated with the same data stream (e.g., the same codeword) or different data streams (e.g., different codewords). Different spatial layers can be associated with different antenna ports used for channel measurement and reporting. MIMO techniques include single-user MIMO (SU-MIMO), where multiple spatial layers are transmitted to the same receiving device, and multiple-user MIMO (MU-MIMO), where multiple spatial layers are transmitted to multiple devices.

[0123] Beamforming, which can also be referred to as spatial filtering, directional transmission, or directional reception, is a signal processing technique that can be used at a transmitting device or a receiving device (e.g., a base station 105, a UE 115) to shape or steer a beam of energy in a specific direction. Beamforming can be achieved by combining the signals of multiple antennas, which effectively creates a spatial filter, where each antenna transmits or receives on a signal that has been weighted, i.e., shaped. For example, each antenna can transmit a signal that is adjusted in amplitude and / or phase, which allows the incoming or outgoing signals to be pushed in a particular direction. In some cases, beamforming can be achieved by adjusting the reflectivity or refractivity of various surfaces (e.g., through the use of Metasurfaces or Metamaterials). In general, beamforming can be used for directional transmission, i.e., where the energy is concentrated in one or more directions, or for directional reception, i.e., where the energy is received mostly from one or more directions.

[0124] As part of beamforming operations, the base stations 105 or UEs 115 can use beam sweeping techniques. For example, a base station 105 can use multiple antennas or antenna arrays (e.g., antenna panels) to conduct beamforming operations for directional communications with a UE 115. The base station 105 can send a signal (e.g., a synchronization signal, a reference signal, a beam selection signal, or other control signal) multiple times in different directions. For example, the base station 105 can send the signal according to different beamforming weight sets associated with different directions. Transmissions in different beam directions can be used to identify (e.g., by the transmitting device, such as a base station 105, or by the receiving device, such as a UE 115) a beam direction for subsequent transmits or receives by the base station 105.

[0125] Base stations 105 can transmit some signals (e.g., data signals associated with a particular receiving device, such as a UE 115) in a single beam direction (e.g., associated with a particular receiving device, such as a UE 115). In some examples, a beam direction associated with transmissions along a single beam direction can be determined based on a signal that is received by the UE 115 in one or more beam directions. For example, a UE 115 can receive one or more of the signals transmitted by the base station 105 in different directions and can report to the base station 105 an indication of the signal that the UE 115 received with a highest signal quality or an otherwise acceptable signal quality.

[0126] In some examples, transmissions by a device (e.g., by a base station 105 or a UE 115) can be performed using multiple beam directions, and the device can use a combination of digital precoding or radio frequency beamforming to generate a combined beam for transmissions (e.g., from a base station 105 to a UE 115). The UE 115 can report feedback indicating precoding weights for one or more beam directions, and the feedback can correspond to a configured number of beams across a system bandwidth or one or more sub-bands. The base station 105 can transmit reference signals that can be precoded or unprecoded (e.g., cell-specific reference signals (CRS), channel state information reference signals (CSI-RS)). The UE 115 can provide feedback for beam selection, which can be a precoding matrix indicator (PMI) or codebook-based feedback (e.g., a multi-panel type codebook, a linear combination type codebook, a port selection type codebook). Although these techniques are described with reference to signals transmitted in one or more directions by the base station 105, a UE 115 can employ similar techniques to

[0127] When receiving various signals from base stations 105, such as synchronization signals, reference signals, beam selection signals, or other control signals, a receiving device (e.g., a UE 115) can try multiple receive configurations (e.g., directional listening). For example, the receiving device can try multiple receive directions by receiving via different antenna subarrays, by processing received signals according to different antenna subarrays, by processing received signals according to different receive beamforming weight sets applied individually to signals received at multiple antenna elements of an antenna array, or by processing received signals according to different receive beamforming weight sets applied collectively to signals received at multiple antenna elements of an antenna array (any of which can be referred to as “listening” according to different receive configurations or receive directions). In some examples, the

[0128] Wireless communications system 100 can be a packet-based network that operates according to a layered protocol stack. In the user plane, communications at the bearer or Packet Data Convergence Protocol (PDCP) layer can be IP -based. A Radio Link Control (RLC) layer can perform packet segmentation and reassembly to communicate over logical channels. A Medium Access Control (MAC) layer can perform priority handling and multiplexing of logical channels into transport channels. The MAC layer can also use error detection techniques, error correction techniques, or both, to support retransmissions at the MAC layer, e.g., in case of successful decoding at the receiver. In the control plane, the Radio Resource Control (RRC) protocol layer can provide establishment, configuration, and maintenance of an RRC connection between a UE 115 and a base station 105 or a core network 130, which can support radio bearers for the user plane data. At the physical layer, transport channels can be mapped to physical channels.

[0129] The UEs 115 and the base stations 105 can support retransmissions of data to increase the likelihood that data is received successfully. Hybrid automatic repeat request (HARQ) feedback is one technique used to increase the likelihood that data is received correctly over a communication link 125. HARQ can include a combination of error detection (e.g., using a cyclic redundancy check (CRC)), forward error correction (FEC), and retransmission (e.g., automatic repeat request (ARQ)). HARQ can improve throughput at the MAC layer in poor radio conditions (e.g., low signal-to-noise conditions). In some examples, a device can support same-slot HARQ feedback, where the device can provide HARQ feedback in a specific time slot for data received in a previous time slot. In other cases, the device can provide HARQ feedback in a subsequent time slot or according to some other time interval.

[0130] Wireless communications systems are widely deployed to provide various types of communication content such as voice, video, packet data, messaging, broadcast, and so on. These systems can be multiple-access systems capable of supporting communication with multiple users by sharing the available system resources (e.g., time, frequency, and power). A wireless network, for example, a wireless local area network (WLAN), such as a Wi-Fi (i.e., Institute of Electrical and Electronics Engineers (IEEE) 802.11) network, can include access points (APs) that can communicate with one or more wireless or mobile devices. The APs can be coupled to a network, such as the Internet, and can enable mobile devices to communicate over the network (or communicate with other devices coupled to the access point). A wireless device can communicate with a network device bi-directionally. For example, in a WLAN, a device can communicate to an associated AP via downlink (e.g., communication links from the AP to the device) and uplink (e.g., communication links from the device to the AP). A wireless personal area network (PAN), which can include a Bluetooth connection, can provide short-range wireless connectivity between two or more paired wireless devices. For example, a wireless device, such as a cellular telephone, can exchange information, such as audio signals, with a wireless headset using wireless PAN communications.

[0131] The UEs 115 can implement a two-stage discovery procedure that implements relay beacons. For the two-stage discovery procedure, the UE 115 can first detect a suitable relay device, and then the UE 115 can perform processing to establish a relay connection. In a first stage, the UE 115 can monitor for a relay beacon, which can be periodically broadcast by a relay device. The relay device can be an example of a UE 115, a base station 105, a road side unit, or another wireless device. If a measured power of a detected relay beacon exceeds a threshold, the UE 115 can perform a second stage of the discovery procedure.

[0132] In a second stage, the UE 115 can monitor for a relay announcement from a relay device and attempt to establish a relay connection. In some examples, the relay device can include an indication of resources for the relay announcement in a relay beacon. The UE 115 can then monitor the resources indicated by the relay beacon for the relay announcement. In some other examples, the UE 115 can send a relay discovery request to the relay device and the relay device can then send a relay announcement to the UE 115. Based on information in the relay announcement, the UE 115 can determine whether to establish a sidelink connection with the relay device.

[0133] Some additional techniques for proximity-based discovery are described herein. For example, a UE 115 can initiate a discovery procedure based on proximity to one or more nearby relay devices. The UE 115 can maintain a database of relay devices and use positioning information for the relay devices and the UE 115 to determine whether a relay device is nearby. In some cases, the UE 115 can be configured with positioning information for candidate relay devices and in some cases, the UE 115 can determine and record positioning information for candidate relay devices.

[0134] In some additional or alternative aspects, a UE 115 can support both a passive discovery mode and an active discovery mode. In the passive mode, the UE 115 can passively search for relay beacons, relay announcements, or both. In the active mode, the UE 115 can periodically transmit a sidelink connection request to attempt to establish a sidelink connection. In some examples, a base station can configure the UE 115 to use a certain discovery mode. In other examples, the UE 115 can first operate in the passive mode and switch to the active mode under certain conditions. For example, the UE 115 can switch to the active mode if the UE 115 fails to find a relay after a period of passive discovery or if the UE 115 has delay-sensitive data or high-priority data to transmit or receive.

[0135] Figure 2 An example of a wireless communications system 200 that supports power efficient relay discovery procedures for sidelink in accordance with aspects of the present disclosure is shown. In some examples, wireless communications system 200 can implement aspects of wireless communications system 100.

[0136] Wireless communications system 200 can include UE 115-a, base station 105-a, and relay device 205. UE 115-a and base station 105-a can be respective examples of the UEs 115 and base stations 105 described with reference to FIG. 1. Relay device 205 can be an example of a UE 115, a base station 105, a transmission and reception point (TRP), a road-side unit, or any combination thereof. Figure 1 Wireless communications system 200 can include UE 115-a, base station 105-a, and relay device 205. UE 115-a and base station 105-a can be respective examples of the UEs 115 and base stations 105 described with reference to FIG. 1. Relay device 205 can be an example of a UE 115, a base station 105, a transmission and reception point (TRP), a road-side unit, or any combination thereof.

[0137] Wireless communication system 200 can support sidelink communication between devices. For example, wireless communication system 200 can implement aspects of vehicle-to-everything (V2X) wireless communication systems or other wireless communication systems that utilize sidelink communication. In some examples, devices can communicate on the PC5 interface used for sidelink channel 210.

[0138] UE 115-a may attempt to establish a relay connection with base station 105-a via relay device 205. To establish a sidelink connection, UE 115-a may first discover the presence of at least one suitable relay device. Relay device 205 may facilitate the transmission of information (e.g., user data) between UE 115-a and base station 105-a. In some examples, UE 115-a may be a remote UE, and relay device 205 may be a relay UE. Relay device 205 may communicate with base station 105-a via link 230.

[0139] In some systems, a remote UE 115 can discover relay devices via single-message discovery. In some examples of single-message discovery, the relay device may periodically send lateral walkway discovery messages. In other examples, the remote UE 115 may send lateral walkway discovery messages such as relay discovery requests, and a nearby relay device may send a response (e.g., a relay advertisement) back to the remote UE 115. Some single-message discovery procedures can consume significant power at the remote UE 115 to establish a relay connection. Furthermore, due to the high power consumption, some devices (e.g., lightweight or low-power UE 115) may not be able to support single-message discovery procedures. The techniques described herein provide a power-efficient discovery process.

[0140] For example, UE 115-a can implement a two-phase discovery process. In some cases, the two-phase discovery process can be referred to as a passive mode for relay discovery. For a two-phase discovery process, UE 115-a can first detect suitable relay devices, and then UE 115-a can perform processing to establish a relay connection.

[0141] In the first phase of the two-phase discovery process, UE 115-a can monitor relay beacon 215. Relay beacon 215 can be periodically broadcast by relay device 205. Relay beacon 215 may include or be a sequence known to UE 115-a.

[0142] In a first example, the relay beacon 215 can include a known sequence (e.g., include only a known sequence). In some examples, the relay beacon 215 can be scrambled by an identifier. In some cases, the identifier can be an identifier of the relay device 205. In some cases, the identifier can be a code that can assist the UE 115-a in identifying a relay in the vicinity of the UE 115-a. For example, the identifier can be a code that can be shorter than a relay device identifier but long enough to assist the UE 115-a in relay device identification. In some examples, the network (e.g., the relay device 205) can transmit a relay announcement 220. In some cases, the relay announcement can be transmitted according to an offset that is preconfigured in time relative to the relay beacon 215. The relay announcement 220 can be transmitted in the same resource pool as the relay beacon or a different resource pool.

[0143] In a second example, the relay beacon 215 can include a known sequence and a payload. In some examples, the relay beacon can be scrambled by an identifier. The identifier can be an identifier of the relay device 205, or the identifier can be a shorter code that is long enough to assist the UE 115-a in identifying a relay device in the vicinity of the UE 115-a. In some cases, if the relay beacon 215 includes a payload, the sequence can not be scrambled. In some examples, the payload can include an identifier that can be an identifier of the relay device 205. In some examples, the payload of the relay beacon 215 can include an indication of whether a relay announcement 220 is transmitted. For example, the relay beacon 215 can indicate that a relay announcement 220 is not (e.g., periodically) transmitted, and the relay device 205 can transmit a relay announcement 220 in response to a relay discovery request 225. In some cases, the relay beacon can include an indication that a relay announcement 220 is transmitted. The payload of the relay beacon 215 can include additional information about resource information (e.g., time resources, frequency resources, or both) for the relay announcement 220. For example, the relay beacon 215 can indicate a resource location in a discovery resource pool at which the relay device 205 transmits the relay announcement 220.

[0144] In some cases, the relay beacon 215 can be transmitted in a dedicated resource pool. For example, the wireless communications system 200 can support a dedicated resource pool for relay signaling, such as relay announcements, relay discovery requests, relay beacons, or any combination thereof. In some cases, the dedicated resource pool can be a segment of a resource pool configured by the network for discovery procedures. In some examples, the dedicated resource pool can be a narrow portion (e.g., in frequency) or subset of a resource pool or bandwidth configured for the UE 115-a. The dedicated resource pool can be used for transmission of relay beacons, discovery announcements, relay discovery requests, or any combination thereof. The discovery resource pool can include one or more global resource pools. In some cases, the discovery resource pool can be commonly known to relay devices, remote UEs 115, or both.

[0145] The UE 115-a can determine whether to perform a second stage of the discovery procedure based on the relay beacon satisfying a relay selection condition. In some cases, the UE 115-a can measure a power of the relay beacon 215, and if the measured power satisfies a threshold, the UE 115-a can perform the second stage of the discovery procedure. For example, the UE 115-a can measure a reference signal receive power of the relay beacon 215 and compare the reference signal receive power to a threshold. In some examples, the relay selection condition can be based on a proximity of the relay device 205 to the UE 115-a. For example, the UE 115-a can estimate whether the relay device 205 is in range based on the relay beacon 215, and the UE 115-a can perform the second stage of the discovery procedure based on the proximity of the relay device 205.

[0146] In the second stage, the UE 115-a can monitor for a relay announcement 220 from the relay device 205 and attempt to establish a relay connection. In some examples, the relay device 205 can include an indication of resources for the relay announcement 220 in the relay beacon 215. The UE 115-a can then monitor the resources indicated by the relay beacon 215 for the relay announcement. In some other examples, the UE 115-a can transmit a relay discovery request 225 to the relay device 205, and the relay device 205 can then transmit a relay announcement 220 to the remote UE. Based on information in the relay announcement 220, such as unified access control information, the UE 115-a can determine whether to establish a sidelink connection with the relay device 205. In some cases, the UE 115-a can establish a sidelink connection with the relay device 205 if the UE 115-a satisfies criteria of the unified access control information.

[0147] Some additional techniques for proximity-based discovery are described herein. For example, UE 115-a can initiate a discovery procedure based on proximity to one or more nearby relay devices. In some cases, UE 115-a can only trigger a discovery procedure if it knows that a relay device is nearby. UE 115-a can maintain a database of relay devices. In some cases, a base station can configure UE 115-a with positioning information for one or more candidate stationary relay devices. A stationary relay device can report the positioning information to the network (e.g., via base station 105). In some cases, the relay device can also report scheduling information for a relay beacon, a relay discovery announcement, or both. The network can then configure UE 115-a with a list of candidate stationary relays, which can include scheduling information, positioning information, or both. In some cases, UE 115-a can be configured with a set of candidate stationary relays via RRC signaling. For example, when UE 115-a disconnects from the wireless network (e.g., performs an RRC release), UE 115-a can receive an indication of a set of candidate relay devices and corresponding positioning and scheduling information for the candidate relay devices.

[0148] In some examples, UE 115-a can determine a database of relay devices. For example, a stationary relay device can announce (e.g., broadcast) to UEs 115 that the relay device is stationary. UE 115-a can receive the announcement and record the positioning information for the candidate relay device. In some cases, the stationary relay device can also announce the scheduling of a relay beacon, a relay announcement, or both.

[0149] In some cases, UE 115-a can perform positioning measurements to identify relay devices nearby. For example, UE 115-a can perform positioning measurements to identify its own positioning information, and then UE 115-a can use its own positioning information to check for relay devices nearby. If there is a candidate relay device nearby, UE 115-a can trigger a discovery procedure. In some cases, the discovery procedure can be a two-stage procedure as described herein. Additionally or alternatively, UE 115-a can implement a proactive discovery procedure (e.g., UE 115-a can periodically broadcast a discovery relay request signal, or can monitor for periodically broadcast discovery relay announcement signals). In some cases, the discovery procedure can be based on a ProSe discovery procedure. In some cases, the discovery procedure can use a dedicated resource pool as described herein.

[0150] In some additional or alternative aspects, UE 115-a can support both a passive discovery mode and an active discovery mode. In the passive mode, UE 115-a can passively search for relay beacons, relay announcements, or both. A relay device can broadcast a relay beacon or a relay announcement, or both. In the active mode, UE 115-a can periodically transmit a sidelink connection request in an attempt to establish a sidelink connection. In some examples, the network can configure UE 115-a to use a certain discovery mode. For example, when UE 115-a is connected to base station 105-a, base station 105-a can configure UE 115-a to use the passive discovery mode or the active discovery mode or at least start with the passive discovery mode or the active discovery mode. In some other examples, UE 115-a can switch between the passive mode and the active mode. For example, UE 115-a can first operate according to the passive mode and switch to the active mode if a condition is met or a triggering event occurs. For example, if UE 115-a fails to find a relay after a period of passive discovery, UE 115-a can switch to the active mode. Or, if UE 115-a has delay-sensitive data or high-priority data to transmit or receive, UE 115-a can switch to the active mode.

[0151] According to examples of the present disclosure, UEs 115 and relay devices can utilize power-efficient discovery procedures to establish sidelink connections. These techniques can generally consume less power than single message discovery techniques by reducing the amount of transmissions or monitoring at the remote UE and the relay device. For example, two-stage or passive discovery procedures can reduce energy consumption by passively monitoring beacon signals to identify a suitable relay device before performing more energy-consuming signaling or monitoring to establish a connection. Additionally, using positioning information prior to initiating a discovery procedure can reduce power consumption as the UE 115 can avoid expending power on discovery procedure signaling until it determines that a relay device is within range.

[0152] Figure 3 An example of a process flow 300 that supports power-efficient relay discovery procedures for sidelink in accordance with aspects of the present disclosure is shown. In some examples, process flow 300 can implement aspects of wireless communication system 100. Process flow 300 can be implemented by UE 115-b, relay device 305, or both. UE 115-b can be an example of a UE 115 as described with reference to Figure 1 and Figure 2 described with reference to Figure 1 and Figure 2 described with reference to Figure 2 described with reference to

[0153] UE 115-b can support a two-stage discovery procedure. The two-stage discovery procedure can include a detection stage and a processing stage. During the detection stage, UE 115-b can identify candidate relay devices (e.g., relay device 305) that can provide a relay or sidelink connection for UE 115-b. During the processing stage, UE 115-b can perform signaling to establish a sidelink connection.

[0154] At 310, relay device 305 can transmit a relay beacon using a resource pool. In some cases, relay device 305 can periodically transmit the relay beacon. The resource pool can be an example of a dedicated resource pool for discovery signaling. UE 115-b can monitor the resource pool for a relay beacon from relay device 305. In some cases, the relay beacon can include a known sequence and can be scrambled by an identifier (e.g., an identifier of relay device 305 or another known sequence). In some cases, the relay beacon can include a known sequence and a payload, where the payload can be used to indicate resource information or scheduling information for a relay announcement.

[0155] UE 115-b can detect a relay beacon in the resource pool. At 315, UE 115-b can determine whether the relay beacon satisfies a relay selection criterion. For example, UE 115-b can measure a received power of the relay beacon. In some cases, UE 115-b can measure a reference signal received power of the relay beacon. If the reference signal received power exceeds a threshold, it can be an indicator that relay device 305 has a strong enough signal to support a relay connection for UE 115-b. Additionally, receiving the relay beacon can be an indicator that relay device 305 can support a relay connection. If the measurement satisfies the threshold, UE 115-b can move to a second stage of the two-stage discovery procedure. For example, 310-315 can include a first stage or detection stage of the two-stage discovery procedure. If the relay beacon does not exceed the threshold, UE 115-b can perform the first stage of the two-stage discovery procedure again.

[0156] At 325, UE 115-b can receive a relay announcement from relay device 305 based on the relay beacon satisfying the relay selection criteria. In some cases, the relay beacon can include some scheduling or resource information for the transmission of the relay announcement. However, in some cases, the relay announcement can be sent “on-demand” or in response to a relay request signal. Thus, in some cases, UE 115-b can transmit a relay discovery request to relay device 305 at 320. The relay device can transmit the relay announcement in response to the relay discovery request. In some cases, processing the relay beacon and determining whether to monitor for the relay announcement, or whether to transmit a relay discovery request to receive the relay announcement, can be included in the second stage of a two-stage discovery procedure.

[0157] At 330, UE 115-b can identify unified access control information for relay device 305. UE 115-b can check the unified access control information and determine whether to establish a sidelink connection with relay device 305. In some cases, the relay announcement can include the unified access control information. In some cases, UE 115-b can establish the sidelink connection based on UE 115-b satisfying criteria of the unified access control information. In some other cases, UE 115-b can skip establishing the sidelink connection with relay device 305 based on the unified access control information, and UE 115-b can perform the discovery procedure again.

[0158] Figure 4 An example of a process flow 400 that supports power efficient relay discovery procedures for sidelink is shown in accordance with aspects of the present disclosure. In some examples, process flow 400 can implement aspects of wireless communication system 100. Process flow 400 can be implemented by UE 115-c, relay device 405, or both. UE 115-c can be an example of a UE 115 as described with reference to Figure 1 and Figure 2 Relay device 405 can be an example of a UE 115, base station 105, TRP, or road side unit as described with reference to Figure 1 and Figure 2 Relay device 405 can be an example of a UE 115, base station 105, TRP, or road side unit as described with reference to Figure 2

[0159] UE 115-c can support a positioning-based discovery procedure. For example, UE 115-c can trigger or perform a discovery procedure only when UE 115-c determines that there is a nearby relay device (e.g., relay device 405). The discovery procedure can be a two-stage discovery procedure or as described with reference to Figure 2 and Figure 3 ​The passive discovery procedure, the active discovery procedure, or both are described. For example, the UE 115-c can be configured to use the passive discovery procedure or the active discovery procedure. Additionally or alternatively, the UE 115-c can be configured with a set of triggers to switch between the active discovery procedure and the passive discovery procedure.

[0160] At 415, the UE 115-c can identify a set of candidate relay devices to establish a sidelink connection for the UE 115-c. The UE 115-c can maintain a database of relays. In some cases, the database can be configured for the UE 115-c via network assistance. The UE 115-c can receive a relay configuration from the network with a set of candidate stationary relay devices (e.g., when the UE 115-c is released from an RRC connection). In some cases, the relay configuration can include resources or scheduling information for relay beacons, relay advertisements, or both from the candidate relay devices. In some cases, the relay configuration can include an indication of a set of configured dedicated resources for discovery signaling.

[0161] In some cases, the UE 115-c can generate the database of relays. For example, at 410, the UE 115-c can receive one or more indications from the set of candidate relay devices that a candidate relay device in the set of candidate relay devices is stationary. The UE 115-c can record the location of the stationary relay, thereby generating the database. In some cases, the candidate relay devices can broadcast resources or scheduling information for relay beacons, relay advertisements, or both. In some cases, at 420, the UE 115-c can perform positioning measurements to determine positioning information for the set of candidate relay devices. For example, the UE 115-c can determine the positioning information based on reference signals transmitted by the set of candidate relay devices.

[0162] At 425, the UE 115-c can determine its positioning information. The UE 115-c can determine its location from the positioning measurements. The UE 115-c can use its location to check the database of relays to see if there are any candidate relays in the vicinity. If there are candidate relay devices in the vicinity, the UE 115-c can trigger a discovery procedure at 430. For example, the UE 115-c can perform a two-stage discovery procedure as described with reference to FIG. 3. Figure 3 The passive discovery procedure, the active discovery procedure, or both are described. For example, the UE 115-c can be configured to use the passive discovery procedure or the active discovery procedure. Additionally or alternatively, the UE 115-c can be configured with a set of triggers to switch between the active discovery procedure and the passive discovery procedure.

[0163] Figure 5A block diagram 500 of a device 505 that supports power efficient relay discovery procedures for sidelink in accordance with aspects of the present disclosure is shown. The device 505 can be an example of aspects of a UE 115 as described herein. The device 505 can include a receiver 510, a communications manager 515, and a transmitter 520. The device 505 can also include a processor. Each of these components can be in communication with one another (e.g., via one or more buses).

[0164] The receiver 510 can receive information such as packets, user data, or control information associated with various information channels (e.g., control channels, data channels, and information related to power efficient relay discovery procedures for sidelink, etc.). Information can be passed on to other components of the device 505. The receiver 510 can be an example of aspects of the transceiver 815 described with reference to FIG. 8. The receiver 510 can utilize a single antenna or a set of antennas. Figure 8 The transmitter 520 can transmit signals generated by other components of the device 505. In some examples, the transmitter 520 can be collocated with a receiver 510 in a transceiver 815. The

[0165] The communications manager 515 can monitor a resource pool for a relay beacon from a relay device, detect the relay beacon in the resource pool, receive a relay advertisement from the relay device based on the relay beacon satisfying a relay selection criterion, and establish a sidelink connection with the relay device based on the relay advertisement.

[0166] The communications manager 515 can also transmit a relay beacon using the resource pool, transmit a relay advertisement based on transmitting the relay beacon, and establish a sidelink connection with a UE based on the relay advertisement.

[0167] The communications manager 515 can also identify a set of candidate relay devices to establish a sidelink connection with a UE, receive a relay advertisement from a relay device based on first positioning information for the relay device and second positioning information for the UE, and establish a sidelink connection with the relay device based on the relay advertisement.

[0168] The communications manager 515 can also indicate first positioning information of a relay device to establish a sidelink connection with a UE, transmit a relay advertisement to the UE based on the first positioning information for the relay device, and establish a sidelink connection with the UE based on the relay advertisement.

[0169] The communications manager 515 can also monitor a resource pool for a relay broadcast from a relay device according to a passive relay discovery mode, detect a trigger to switch from the passive relay discovery mode to an active relay discovery mode, transmit a relay discovery request to the relay device periodically based on the active relay discovery mode, receive a relay advertisement from the relay device based on transmitting the relay discovery request, and establish a sidelink connection with the relay device based on the relay advertisement. The communications manager 515 can be an example of aspects of the communications manager 810 described herein.

[0170] The communications manager 515, or its sub-components, can be implemented in hardware, code (for example, software or firmware) executed by a processor, or any combination thereof. If implemented in code executed by a processor, the functions of the communications manager 515, or its sub-components can be executed by a general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field- programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described in the present disclosure.

[0171] The communications manager 515, or its sub-components, can be physically located at various positions, including being distributed so that functions of one or more components can be implemented at different physical locations by one or more physical components. In some examples, the communications manager 515, or its sub-components, can be a separate and distinct component in accordance with various aspects of the present disclosure. In some examples, the communications manager 515, or its sub-components, can be combined with one or more other hardware components, including but not limited to an input / output (I / O) component, a transceiver, a network server, another computing device, one or more other components described in the present disclosure, or a combination thereof in accordance with various aspects of the present disclosure.

[0172] Implementations as described herein, performed by communications manager 515, can enable one or more potential advantages. One implementation can allow a UE 115 to save power and increase battery life by performing less signaling or monitoring for a discovery procedure. Instead of blindly performing a discovery procedure, transmitting a discovery request signal, and monitoring for a discovery advertisement, the UE 115 can determine that a relay device is available (e.g., in the vicinity of the UE or with a strong signal strength) before attempting to establish a sidelink connection.

[0173] The transmitter 520 can transmit signals generated by other components of the device 505. In some examples, the transmitter 520 can be collocated with a receiver 510 in a transceiver module. For example, the transmitter 520 can be an example of aspects of the transceiver 815 described with reference to FIG. 8. The transmitter 520 can utilize a single antenna or a set of antennas. Figure 8 The transmitter 520 can transmit signals generated by other components of the device 505. In some examples, the transmitter 520 can be collocated with a receiver 510 in a transceiver module. For example, the transmitter 520 can be an example of aspects of the transceiver 815 described with reference to FIG. 8. The transmitter 520 can utilize a single antenna or a set of antennas. Figure 8 The transmitter 520 can transmit signals generated by other components of the device 505. In some examples, the transmitter 520 can be collocated with a receiver 510 in a transceiver module. For example, the transmitter 520 can be an example of aspects of the transceiver 815 described with reference to FIG. 8. The transmitter 520 can utilize a single antenna or a set of antennas. Figure 8

[0174] Figure 6 A block diagram 600 of a device 605 supporting a power-efficient relay discovery process for a sidelink, according to various aspects of this disclosure, is shown. Device 605 may be an example of aspects of device 505 or UE 115 as described herein. Device 605 may include a receiver 610, a communications manager 615, and a transmitter 670. Device 605 may also include a processor. Each of these components may communicate with each other (e.g., via one or more buses).

[0175] Receiver 610 can receive information such as packets, user data, or control information associated with various information channels (e.g., control channels, data channels, and information related to power-efficient relay discovery processes for sidelinks). This information can be passed to other components of device 605. Receiver 610 can be a reference... Figure 8 Examples of various aspects of the transceiver 815 are described. The receiver 610 can utilize a single antenna or a set of antennas.

[0176] Communication manager 615 may be an example of various aspects of communication manager 515 as described herein. Communication manager 615 may include a relay beacon receiving component 620, a relay beacon measurement component 625, a relay announcement receiving component 630, a sidelink establishment component 635, a relay beacon transmitting component 640, a relay announcement transmitting component 645, a candidate relay device configuration component 650, a passive discovery mode component 655, a discovery mode triggering component 660, and an active discovery mode component 665. Communication manager 615 may be an example of various aspects of communication manager 810 as described herein.

[0177] The relay beacon receiving component 620 can monitor the resource pool for relay beacons from the relay equipment. The relay beacon measurement component 625 can detect relay beacons in the resource pool. The relay announcement receiving component 630 can receive relay announcements from the relay equipment based on the relay beacons meeting the relay selection criteria. The side link establishment component 635 can establish a side link connection with the relay equipment based on the relay announcements.

[0178] The relay beacon sending component 640 can use a resource pool to send relay beacons. The relay advertisement sending component 645 can send relay advertisements based on the transmission of relay beacons. The sidelink establishment component 635 can establish a sidelink connection with the UE based on the relay advertisement.

[0179] The candidate relay device configuration component 650 can identify a set of candidate relay devices to establish a sidelink connection with a UE. The relay advertisement reception component 630 can receive a relay advertisement from a relay device based on first positioning information for the relay device and second positioning information for the UE. The sidelink establishment component 635 can establish a sidelink connection with the relay device based on the relay advertisement.

[0180] The candidate relay device configuration component 650 can indicate first positioning information for a relay device to establish a sidelink connection with a UE. The relay advertisement transmission component 645 can transmit a relay advertisement to the UE based on the first positioning information for the relay device. The sidelink establishment component 635 can establish a sidelink connection with the UE based on the relay advertisement.

[0181] The passive discovery mode component 655 can monitor a resource pool for a relay broadcast from a relay device according to a passive relay discovery mode. The discovery mode trigger component 660 can detect a trigger to switch from the passive relay discovery mode to an active relay discovery mode. The active discovery mode component 665 can periodically transmit a relay discovery request to the relay device based on the active relay discovery mode. The relay advertisement reception component 630 can receive a relay advertisement from the relay device based on transmitting the relay discovery request. The sidelink establishment component 635 can establish a sidelink connection with the relay device based on the relay advertisement.

[0182] The transmitter 670 can transmit signals generated by other components of the device 605. In some examples, the transmitter 670 can be collocated with a receiver 610 in a transceiver module. For example, the transmitter 670 can be an example of aspects of the transceiver 815 Figure 8 described with reference to FIG. 8. The transmitter 670 can utilize a single antenna or a set of antennas.

[0183] Figure 7 A block diagram 700 of a communications manager 705 that supports power efficient relay discovery procedures for sidelink in accordance with aspects of the present disclosure is shown. The communications manager 705 can be an example of aspects of the communications manager 515, the communications manager 615, or the communications manager 810 described herein. The communications manager 705 can include a relay beacon reception component 710, a relay beacon measurement component 715, a relay advertisement reception component 720, a sidelink establishment component 725, a relay request component 730, a discovery resource configuration component 735, a relay beacon transmission component 740, a relay advertisement transmission component 745, a candidate relay device configuration component 750, a positioning measurement component 755, a passive discovery mode component 760, a discovery mode trigger component 765, and an active discovery mode component 770. Each of these modules can communicate, directly or indirectly, with one another (e.g., via one or more buses).

[0184] The relay beacon receiving component 710 can monitor the resource pool for a relay beacon from a relay device. In some examples, the relay beacon receiving component 710 can decode the relay beacon based on an identifier that is common to a set of relay devices including the relay device. In some examples, the relay beacon receiving component 710 can decode the relay beacon based at least in part on an identifier or code associated with the relay discovery. In some examples, the relay beacon can be scrambled with the identifier or code associated with the relay discovery. In some cases, the identifier can be an identifier of the relay device or an identifier associated with the relay discovery.

[0185] In some examples, the relay beacon receiving component 710 can receive, from a base station, one or more sequences associated with a relay device, the one or more sequences including at least the sequence. In some examples, the relay beacon receiving component 710 can identify a payload of the relay beacon, where the payload includes an identifier of the relay device.

[0186] The relay beacon measuring component 715 can detect a relay beacon in the resource pool. In some cases, the relay beacon measuring component 715 can measure a received power of the relay beacon. The relay announcement receiving component 720 can receive a relay announcement from the relay device based on the relay beacon satisfying a relay selection criterion. In some cases, the relay announcement receiving component 720 can receive the relay announcement from the relay device based on the received power of the relay beacon satisfying a threshold.

[0187] In some examples, the relay announcement receiving component 720 can receive the relay announcement from the relay device based on first positioning information for the relay device and second positioning information for the UE. In some examples, the relay announcement receiving component 720 can receive the relay announcement from the relay device based on transmitting the relay discovery request.

[0188] The sidelink establishing component 725 can establish a sidelink connection with the relay device based on the relay announcement. In some examples, the sidelink establishing component 725 can establish the sidelink connection with the UE based on the relay announcement.

[0189] In some examples, the sidelink establishing component 725 can identify unified access control information associated with the relay device, where establishing the sidelink connection is based on the unified access control information. In some examples, the sidelink establishing component 725 can indicate the unified access control information associated with the relay device to the UE, where establishing the sidelink connection is based on the unified access control information. In some examples, the relay announcement can include the unified access control information. In some examples, the sidelink connection is established based on the UE satisfying a criterion associated with the unified access control information.

[0190] The relay beacon transmitting component 740 can transmit the relay beacon using the resource pool. In some examples, the relay beacon transmitting component 740 can encode the relay beacon based on a sequence that is common to a set of relay devices including the relay device.

[0191] In some examples, the relay beacon transmitting component 740 can include an identifier of the relay device in a payload of the relay beacon. The relay advertisement transmitting component 745 can transmit the relay advertisement based on transmitting the relay beacon.

[0192] In some examples, the relay advertisement transmitting component 745 can transmit the relay advertisement to the UE based on the first positioning information for the relay device. The candidate relay device configuring component 750 can identify a set of candidate relay devices to establish a sidelink connection with the UE.

[0193] In some examples, the candidate relay device configuring component 750 can indicate the first positioning information of the relay device to establish the sidelink connection with the UE. In some examples, the candidate relay device configuring component 750 can receive a relay configuration indicating the set of candidate relay devices.

[0194] In some examples, the candidate relay device configuring component 750 can receive, from the set of candidate relay devices, one or more indications that candidate relay devices in the set of candidate relay devices are stationary. In some examples, the candidate relay device configuring component 750 can determine positioning information for the set of candidate relay devices based on the one or more indications. In some cases, the relay configuration can be received from a base station or a previously connected relay device. In some cases, the relay configuration can include positioning information for the set of candidate relay devices including the first positioning information for the relay device. In some examples, the relay configuration includes scheduling information for the relay advertisement from the set of candidate relay devices, scheduling information for the relay beacon signal from the set of candidate relay devices, or both.

[0195] In some examples, the candidate relay device configuring component 750 can indicate scheduling information for the relay advertisement from the relay device, scheduling information for the relay beacon signal from the relay device, or both. In some cases, the relay configuration indicates a set of resources associated with the relay advertisement, where monitoring the relay advertisement includes monitoring the set of resources associated with the relay advertisement. In some examples, the first positioning information includes an indication that the relay device is stationary.

[0196] Passive discovery mode component 760 can monitor a resource pool for a relay broadcast from a relay device according to a passive relay discovery mode. Discovery mode trigger component 765 can detect a trigger to switch from the passive relay discovery mode to an active relay discovery mode. In some examples, discovery mode trigger component 765 can identify a high priority message is pending communication. In some examples, discovery mode trigger component 765 can determine a timer associated with the passive relay discovery mode has expired. In some examples, discovery mode trigger component 765 can receive an indication from a base station to use the passive relay discovery mode or the active relay discovery mode. Active discovery mode component 770 can periodically transmit a relay discovery request to the relay device based on the active relay discovery mode.

[0197] Relay request component 730 can transmit a relay discovery request to a relay device based on the relay beacon satisfying a relay selection criterion, where receiving the relay announcement is based on transmitting the relay discovery request. In some cases, relay request component 730 can transmit the relay discovery request to the relay device based on a received power of the relay beacon satisfying a threshold, where receiving the relay announcement is based on transmitting the relay discovery request. In some examples, relay request component 730 can receive a relay discovery request from a UE, where transmitting the relay announcement is based on receiving the relay discovery request. In some examples, the set of resources can be preconfigured at the UE or dedicated for relay messages, or both. In some examples, the set of resources can correspond to a subset of resource blocks of a resource pool or bandwidth configured for the UE. In some examples, the set of resources associated with the relay announcement is in a different resource pool than a resource pool used for the relay beacon, in a different time slot than the relay beacon, or both. In some examples, the set of resources is configured for a plurality of UEs including at least the UE.

[0198] In some examples, relay request component 730 can transmit the relay discovery request to the relay device based on the relay device being within a range of the UE, where receiving the relay announcement is based on transmitting the relay discovery request. In some examples, relay request component 730 can receive a relay discovery request from the UE based on the relay device being within a range of the UE, where transmitting the relay announcement is based on receiving the relay discovery request.

[0199] The discovery resource configuration component 735 can identify a set of resources associated with a relay announcement based on a relay beacon from a relay device, where receiving the relay announcement includes monitoring the set of resources associated with the relay announcement. In some examples, the discovery resource configuration component 735 can indicate the set of resources associated with the relay announcement based on the relay beacon, where transmitting the relay announcement includes transmitting the relay announcement using the set of resources. In some examples, the set of resources is preconfigured at the UE or dedicated for relay messages, or both. In some examples, the set of resources corresponds to a subset of resource blocks of a bandwidth configured for the UE. In some examples, the set of resources is preconfigured for the UE or dedicated for relay discovery messages, or both.

[0200] The positioning measurement component 755 can receive reference signals from the set of candidate relay devices. In some examples, the positioning measurement component 755 can perform positioning measurements for the set of candidate relay devices based on receiving the reference signals. In some examples, the positioning measurement component 755 can determine positioning information for the set of candidate relay devices based on the positioning measurements.

[0201] Figure 8 A diagram illustrating a system 800 including a device 805 that supports power efficient relay discovery procedures for sidelink in accordance with aspects of the present disclosure is shown. The device 805 can be an example of or include the components of device 505, device 605, or a UE 115 as described herein. The device 805 can include components for bi-directional voice and data communications including components for transmitting and receiving communications, including a communications manager 810, a transceiver 815, an antenna 820, memory 825, and a processor 835. These components can be in electronic communication via one or more buses (e.g., bus 840).

[0202] The communications manager 810 can monitor a resource pool for a relay beacon from a relay device, detect the relay beacon in the resource pool, receive a relay announcement from the relay device based on the relay beacon satisfying a relay selection criterion, and establish a sidelink connection with the relay device based on the relay announcement.

[0203] The communications manager 810 can also monitor a resource pool for a relay beacon from a relay device, detect the relay beacon in the resource pool, receive a relay announcement from the relay device based on the relay beacon satisfying a relay selection criterion, and establish a sidelink connection with the relay device based on the relay announcement.

[0204] The communications manager 810 can also identify a set of candidate relay devices to establish a sidelink connection with a UE, receive a relay announcement from a relay device based on first positioning information for the relay device and second positioning information for the UE, and establish the sidelink connection with the relay device based on the relay announcement.

[0205] The communications manager 810 can also indicate first positioning information of a relay device to establish a sidelink connection with a UE, transmit a relay advertisement to the UE based on the first positioning information of the relay device, and establish the sidelink connection with the UE based on the relay advertisement.

[0206] The communications manager 810 can also monitor a resource pool for a relay broadcast from a relay device in accordance with a passive relay discovery mode, detect a trigger to switch from the passive relay discovery mode to an active relay discovery mode, transmit a relay discovery request to the relay device periodically based on the active relay discovery mode, receive a relay advertisement from the relay device based on transmitting the relay discovery request, and establish a sidelink connection with the relay device based on the relay advertisement.

[0207] The transceiver 815 can communicate bi-directionally, via one or more antennas, wired, or wireless links as described above. For example, the transceiver 815 can represent a wireless transceiver and can communicate bi-directionally with another wireless transceiver. The transceiver 815 can also include a modem to modulate the packets and to provide the modulated packets to the antennas for transmission, and to demodulate packets received from the antennas.

[0208] In some cases, the wireless device can include a single antenna 820. However, in some cases the device can have more than one antenna 820, which can be capable of concurrently transmitting or receiving multiple wireless transmissions.

[0209] The memory 825 can include random access memory (RAM) and read-only memory (ROM). The memory 825 can store computer-readable, computer-executable code 830 including instructions that, when executed, cause the processor to perform various functions described herein. In some cases, the memory 825 can contain, among other things, a basic input / output system (BIOS), which can control basic hardware or software operation such as the interaction with peripheral components or devices.

[0210] The code 830 can include instructions to implement aspects of the present disclosure, including instructions to support wireless communications. The code 830 can be stored in a non-transitory computer-readable medium such as system memory or other type of memory. In some cases, the code 830 can not be directly executable by the processor 835 but can cause a computer (e.g., when compiled and executed) to perform functions described herein.

[0211] The processor 835 can include an intelligent hardware device, (e.g., a general- purpose processor, a DSP, a CPU, a microcontroller, an ASIC, an FPGA, a programmable logic device, a discrete gate or transistor logic component, a discrete hardware component, or any combination thereof). In some cases, the processor 835 can be configured to operate a memory array using a memory controller. In other cases, a memory controller can be integrated into the processor 835. The processor 835 can be configured to execute computer-readable instructions stored in a memory (e.g., the memory 825) to cause the device 805 to perform various functions (e.g., functions or tasks for supporting power efficient relay discovery procedures for sidelink).

[0212] Figure 9 A flow diagram illustrating a method 900 that supports power efficient relay discovery procedures for sidelink in accordance with aspects of the present disclosure is shown. The operations of method 900 can be implemented by a UE 115 or its components as described herein. For example, the operations of method 900 can be performed by a communications manager as described with reference to Figures 5 to 8 In some examples, a UE can execute a set of instructions to control the functional elements of the UE to perform the described functions. Additionally or alternatively, the UE can perform aspects of the described functions using special-purpose hardware.

[0213] At 905, the UE can monitor a resource pool for a relay beacon from a relay device. The operations of 905 can be performed according to the methods described herein. In some examples, aspects of the operations of 905 can be performed by a relay beacon receiving component as described with reference to Figures 5 to 8 FIG. 7.

[0214] At 910, the UE can detect a relay beacon in the resource pool. The operations of 910 can be performed according to the methods described herein. In some examples, aspects of the operations of 910 can be performed by a relay beacon measuring component as described with reference to Figures 5 to 8 FIG. 7.

[0215] At 915, the UE can receive a relay advertisement from the relay device based on the relay beacon satisfying a relay selection criterion. For example, the UE can measure a received power of the relay beacon and compare the received power of the relay beacon to a threshold. The operations of 915 can be performed according to the methods described herein. In some examples, aspects of the operations of 915 can be performed by a relay advertisement receiving component as described with reference to Figures 5 to 8 FIG. 7.

[0216] At 920, the UE can establish a sidelink connection with the relay device based on the relay advertisement. The operations of 920 can be performed according to the methods described herein. In some examples, aspects of the operations of 920 can be performed by a sidelink connection establishing component as described with reference to Figures 5 to 8The sidelink establishment component described to perform.

[0217] Figure 10 A flow chart illustrating a method 1000 that supports power efficient relay discovery procedures for sidelink in accordance with aspects of the present disclosure is shown. The operations of method 1000 can be implemented by a UE 115 or its components as described herein. For example, the operations of method 1000 can be performed by a communications manager as described with reference to Figures 5 to 8 The communications manager described to perform the operations of method 1000. In some examples, a UE can execute a set of instructions to control the functional elements of the UE to perform the described functions. Additionally or alternatively, the UE can perform aspects of the described functions using special-purpose hardware.

[0218] At 1005, the UE can transmit a relay beacon using the resource pool. The operations of 1005 can be performed according to the methods described herein. In some examples, aspects of the operations of 1005 can be performed by a relay beacon transmitting component as described with reference to Figures 5 to 8 The communications manager described to perform the operations of 1005. In some examples, a UE can execute a set of instructions to control the functional elements of the UE to perform the described functions. Additionally or alternatively, the UE can perform aspects of the described functions using special-purpose hardware.

[0219] At 1010, the UE can transmit a relay advertisement based on transmitting the relay beacon. The operations of 1010 can be performed according to the methods described herein. In some examples, aspects of the operations of 1010 can be performed by a relay advertisement transmitting component as described with reference to Figures 5 to 8 The communications manager described to perform the operations of 1010. In some examples, a UE can execute a set of instructions to control the functional elements of the UE to perform the described functions. Additionally or alternatively, the UE can perform aspects of the described functions using special-purpose hardware.

[0220] At 1015, the UE can establish a sidelink connection with the UE based on the relay advertisement. The operations of 1015 can be performed according to the methods described herein. In some examples, aspects of the operations of 1015 can be performed by a sidelink establishment component as described with reference to Figures 5 to 8 The communications manager described to perform the operations of 1015. In some examples, a UE can execute a set of instructions to control the functional elements of the UE to perform the described functions. Additionally or alternatively, the UE can perform aspects of the described functions using special-purpose hardware.

[0221] Figure 11 A flow chart illustrating a method 1100 that supports power efficient relay discovery procedures for sidelink in accordance with aspects of the present disclosure is shown. The operations of method 1100 can be implemented by a UE 115 or its components as described herein. For example, the operations of method 1100 can be performed by a communications manager as described with reference to Figures 5 to 8 The communications manager described to perform the operations of method 1100. In some examples, a UE can execute a set of instructions to control the functional elements of the UE to perform the described functions. Additionally or alternatively, the UE can perform aspects of the described functions using special-purpose hardware.

[0222] At 1105, the UE can identify a set of candidate relay devices to establish a sidelink connection with the UE. The operations of 1105 can be performed according to the methods described herein. In some examples, aspects of the operations of 1105 can be performed by a candidate relay device configuration component as described with reference to Figures 5 to 8 The communications manager described to perform the operations of 1105. In some examples, a UE can execute a set of instructions to control the functional elements of the UE to perform the described functions. Additionally or alternatively, the UE can perform aspects of the described functions using special-purpose hardware.

[0223] At 1110, the UE can receive a relay advertisement from the relay device based on the first positioning information for the relay device and the second positioning information for the UE. The operations of 1110 can be performed according to the methods described herein. In some examples, aspects of the operations of 1110 can be performed by a relay advertisement receiving component as described with reference to Figures 5 to 8 FIG. 15.

[0224] At 1115, the UE can establish a sidelink connection with the relay device based on the relay advertisement. The operations of 1115 can be performed according to the methods described herein. In some examples, aspects of the operations of 1115 can be performed by a sidelink establishing component as described with reference to Figures 5 to 8 FIG. 15.

[0225] Figure 12 A method 1200 that supports power efficient relay discovery procedure for sidelink in accordance with aspects of the present disclosure is shown. The operations of method 1200 can be implemented by a UE 115 or its components as described herein. For example, the operations of method 1200 can be performed by a communications manager as described with reference to Figures 5 to 8 FIG. 15. In some examples, a UE can execute a set of instructions to control the functional elements of the UE to perform the described functions. Additionally or alternatively, the UE can perform aspects of the described functions using special-purpose hardware.

[0226] At 1205, the UE can indicate first positioning information for a relay device to establish a sidelink connection with the UE. The operations of 1205 can be performed according to the methods described herein. In some examples, aspects of the operations of 1205 can be performed by a candidate relay device configuring component as described with reference to Figures 5 to 8 FIG. 15.

[0227] At 1210, the UE can transmit a relay advertisement to the UE based on the first positioning information for the relay device. The operations of 1210 can be performed according to the methods described herein. In some examples, aspects of the operations of 1210 can be performed by a relay advertisement transmitting component as described with reference to Figures 5 to 8 FIG. 15.

[0228] At 1215, the UE can establish a sidelink connection with the UE based on the relay advertisement. The operations of 1215 can be performed according to the methods described herein. In some examples, aspects of the operations of 1215 can be performed by a sidelink establishing component as described with reference to Figures 5 to 8 FIG. 15.

[0229] Figure 13A flowchart illustrating a method 1300 that supports power efficient relay discovery procedures for sidelink in accordance with aspects of the present disclosure is shown. The operations of method 1300 can be implemented by a UE 115 or its components as described herein. For example, the operations of method 1300 can be performed by a communications manager as described with reference to Figures 5 to 8 The described operations can be implemented as power efficient relay discovery procedures for sidelink by a UE 115 or its components as described herein. For example, the operations of methods 1300 can be performed by a communications manager as described with reference to

[0230] At 1305, the UE can monitor a resource pool for a relay broadcast from a relay device according to a passive relay discovery mode. The operations of 1305 can be performed according to the methods described herein. In some examples, aspects of the operations of 1305 can be performed by a passive discovery mode component as described with reference to Figures 5 to 8

[0231] At 1310, the UE can detect a trigger to switch from the passive relay discovery mode to an active relay discovery mode. The operations of 1310 can be performed according to the methods described herein. In some examples, aspects of the operations of 1310 can be performed by a discovery mode trigger component as described with reference to Figures 5 to 8

[0232] At 1315, the UE can periodically transmit a relay discovery request to the relay device based on the active relay discovery mode. The operations of 1315 can be performed according to the methods described herein. In some examples, aspects of the operations of 1315 can be performed by an active discovery mode component as described with reference to Figures 5 to 8

[0233] At 1320, the UE can receive a relay advertisement from the relay device based on transmitting the relay discovery request. The operations of 1320 can be performed according to the methods described herein. In some examples, aspects of the operations of 1320 can be performed by a relay advertisement reception component as described with reference to Figures 5 to 8

[0234] At 1325, the UE can establish a sidelink connection with the relay device based on the relay advertisement. The operations of 1325 can be performed according to the methods described herein. In some examples, aspects of the operations of 1325 can be performed by a sidelink establishment component as described with reference to Figures 5 to 8

[0235] The following provides an overview of aspects of the present disclosure:

[0236] ​​​​​Aspect 1: A method for wireless communication at a UE, comprising: monitoring a resource pool for a relay beacon from a relay device; detecting the relay beacon in the resource pool; receiving a relay announcement from the relay device based at least in part on the relay beacon satisfying a relay selection criterion; and establishing a sidelink connection with the relay device based at least in part on the relay announcement.

[0237] Aspect 2: The method of aspect 1, further comprising: transmitting a relay discovery request to the relay device based at least in part on the relay beacon satisfying the relay selection criterion, wherein receiving the relay announcement is based at least in part on transmitting the relay discovery request.

[0238] Aspect 3: The method of any of aspects 1-2, further comprising: identifying a set of resources associated with the relay announcement based at least in part on the relay beacon from the relay device, wherein receiving the relay announcement comprises monitoring the set of resources associated with the relay announcement.

[0239] Aspect 4: The method of aspect 3, wherein the set of resources is preconfigured at the UE or is specific to relay messages, or both.

[0240] Aspect 5: The method of any of aspects 3-4, wherein the set of resources corresponds to a subset of resource blocks of a resource pool configured for the UE.

[0241] Aspect 6: The method of any of aspects 3-5, wherein the set of resources associated with the relay announcement is in a different resource pool than the resource pool used for the relay beacon, in a different time slot than the relay beacon, or both.

[0242] Aspect 7: The method of any of aspects 3-6, wherein the set of resources is configured for a plurality of UEs including at least the UE.

[0243] Aspect 8: The method of any of aspects 1-7, wherein the relay selection criterion is based at least in part on: a received power of the relay beacon satisfying a proximity threshold, a proximity of the relay device satisfying a proximity threshold, or any combination thereof, the proximity of the relay device being determined based at least in part on the relay beacon.

[0244] Aspect 9: The method of any of aspects 1-8, further comprising: decoding the relay beacon based at least in part on an identifier that is common to a plurality of relay devices including the relay device.

[0245] Aspect 10: The method according to aspect 9 further includes: receiving from a base station one or more sequences associated with the plurality of relay devices, the one or more sequences including at least the sequence.

[0246] Aspect 11: The method according to any one of Aspects 1 to 10 further includes: decoding the relay beacon at least in part based on an identifier or code associated with relay discovery.

[0247] Aspect 12: According to the method of aspect 11, wherein the identifier is an identifier of the relay device or an identifier associated with relay discovery.

[0248] Aspect 13: The method according to any one of aspects 1 to 12 further includes: identifying the payload of the relay beacon, wherein the payload includes an identifier of the relay device.

[0249] Aspect 14: The method according to any one of Aspects 1 to 13 further includes: identifying unified access control information associated with the relay device, wherein the establishment of the side link connection is at least partially based on the unified access control information.

[0250] Aspect 15: According to the method of aspect 14, wherein the relay announcement includes the unified access control information.

[0251] Aspect 16: The method according to any one of Aspects 14 to 15, wherein the sidelink connection is established at least in part based on the UE satisfying a standard associated with the unified access control information.

[0252] Aspect 17: A method for wireless communication at a relay device, comprising: using a resource pool to transmit a relay beacon; transmitting a relay announcement at least in part based on transmitting the relay beacon; and establishing a sidelink connection with a UE at least in part based on the relay announcement.

[0253] Aspect 18: The method according to aspect 17 further includes: receiving a relay discovery request from the UE, wherein sending the relay announcement is at least in part based on receiving the relay discovery request.

[0254] Aspect 19: The method according to any one of Aspects 17 to 18 further includes: indicating a set of resources associated with the relay announcement based at least in part on the relay beacon, wherein sending the relay announcement includes using the set of resources to send the relay announcement.

[0255] Aspect 20: The method according to aspect 19, wherein the resource set is pre-configured for the UE or dedicated to relay messages, or both.

[0256] Aspect 21: The method of any one of aspects 19 through 20, wherein the set of resources corresponds to a subset of resource blocks of a resource pool configured for the UE.

[0257] Aspect 22: The method of any one of aspects 19 through 21, wherein the set of resources associated with the relay announcement is in a different resource pool than the resource pool for the relay beacon, in a different time slot than the relay beacon, or both.

[0258] Aspect 23: The method of any one of aspects 19 through 22, wherein the set of resources is configured for a plurality of UEs including at least the UE.

[0259] Aspect 24: The method of any one of aspects 17 through 23, further comprising encoding the relay beacon based at least in part on an identifier that is common to a plurality of relay devices including the relay device.

[0260] Aspect 25: The method of aspect 24, wherein the relay beacon is scrambled with a sequence.

[0261] Aspect 26: The method of any one of aspects 17 through 25, further comprising scrambling the relay beacon based at least in part on an identifier of the relay device or an identifier associated with relay discovery.

[0262] Aspect 27: The method of any one of aspects 17 through 26, further comprising including an identifier of the relay device in a payload of the relay beacon.

[0263] Aspect 28: The method of any one of aspects 17 through 27, further comprising indicating unified access control information associated with the relay device to the UE, wherein the establishing the sidelink connection is based at least in part on the unified access control information.

[0264] Aspect 29: The method of aspect 28, wherein the relay announcement includes the unified access control information.

[0265] Aspect 30: The method of any one of aspects 28 through 29, wherein the sidelink connection is established based at least in part on the UE satisfying a criterion associated with the unified access control information.

[0266] Aspect 31 : A method for wireless communication at a UE, comprising: identifying a set of candidate relay devices to establish a sidelink connection with the UE; receiving a relay advertisement from a relay device based at least in part on first positioning information for the relay device and second positioning information for the UE; and establishing the sidelink connection with the relay device based at least in part on the relay advertisement.

[0267] Aspect 32: The method of aspect 31, further comprising: receiving a relay configuration indicating the set of candidate relay devices.

[0268] Aspect 33: The method of aspect 32, wherein the relay configuration is received from a base station or a previously connected relay device.

[0269] Aspect 34: The method of any of aspects 32-33, wherein the relay configuration includes positioning information for the set of candidate relay devices, the positioning information including the first positioning information for the relay device.

[0270] Aspect 35: The method of any of aspects 32-34, wherein the relay configuration includes scheduling information for a relay advertisement from the set of candidate relay devices, scheduling information for a relay beacon signal from the set of candidate relay devices, or both.

[0271] Aspect 36: The method of any of aspects 32-35, wherein the relay configuration indicates a set of resources associated with the relay advertisement, the monitoring the relay advertisement comprising monitoring the set of resources associated with the relay advertisement.

[0272] Aspect 37: The method of any of aspects 31-36, further comprising: receiving one or more indications from the set of candidate relay devices that a candidate relay device in the set of candidate relay devices is stationary.

[0273] Aspect 38: The method of aspect 37, further comprising: determining positioning information for the set of candidate relay devices based at least in part on the one or more indications.

[0274] Aspect 39: The method of any of aspects 31-38, further comprising: transmitting a relay discovery request to the relay device based at least in part on the relay device being within a range of the UE, wherein receiving the relay advertisement is based at least in part on transmitting the relay discovery request.

[0275] Aspect 40: The method of any one of aspects 31-39, further comprising: receiving reference signals from the set of candidate relay devices; performing positioning measurements for the set of candidate relays based at least in part on receiving the reference signals; and determining positioning information for the set of candidate relay devices based at least in part on the positioning measurements.

[0276] Aspect 41: The method of any one of aspects 31-40, further comprising: identifying a set of resources associated with the relay announcement, wherein receiving the relay announcement comprises monitoring the set of resources associated with the relay announcement.

[0277] Aspect 42: The method of aspect 41, wherein the set of resources are preconfigured at the UE or dedicated for relay messages, or both.

[0278] Aspect 43: The method of any one of aspects 41-42, wherein the set of resources correspond to a subset of resource blocks of a resource pool configured for the UE.

[0279] Aspect 44: A method for wireless communications at a relay device, comprising: indicating first positioning information of the relay device to establish a sidelink connection with a UE; transmitting a relay announcement to the UE based at least in part on the first positioning information for the relay device; and establishing the sidelink connection with the UE based at least in part on the relay announcement.

[0280] Aspect 45: The method of aspect 44, further comprising: indicating scheduling information for a relay announcement from the relay device, scheduling information for a relay beacon signal from the relay device, or both.

[0281] Aspect 46: The method of any one of aspects 44-45, wherein the first positioning information comprises an indication that the relay device is stationary.

[0282] Aspect 47: The method of any one of aspects 44-46, further comprising: receiving a relay discovery request from the UE based at least in part on the relay device being within a range of the UE, wherein the transmitting the relay announcement is based at least in part on receiving the relay discovery request.

[0283] Aspect 48: The method of any one of aspects 44-47, further comprising: identifying a set of resources associated with the relay announcement, wherein transmitting the relay announcement comprises transmitting the relay announcement using the set of resources.

[0284] Aspect 49: The method of Aspect 48, wherein the set of resources is preconfigured for the UE or dedicated for relay messages, or both.

[0285] Aspect 50: The method of any one of Aspects 48-49, wherein the set of resources corresponds to a subset of resource blocks of a resource pool configured for the UE.

[0286] Aspect 51: A method for wireless communication at a UE, comprising: monitoring a resource pool for a relay broadcast from a relay device according to a passive relay discovery mode; detecting a trigger to switch from the passive relay discovery mode to an active relay discovery mode; periodically transmitting a relay discovery request to the relay device based at least in part on the active relay discovery mode; receiving a relay announcement from the relay device based at least in part on transmitting the relay discovery request; and establishing a sidelink connection with the relay device based at least in part on the relay announcement.

[0287] Aspect 52: The method of Aspect 51, wherein detecting the trigger comprises: identifying a high-priority message is pending communication.

[0288] Aspect 53: The method of any one of Aspects 51-52, wherein detecting the trigger comprises: determining a timer associated with the passive relay discovery mode has expired.

[0289] Aspect 54: The method of any one of Aspects 51-53, further comprising: receiving an indication from a base station to use the passive relay discovery mode or the active relay discovery mode.

[0290] Aspect 55: An apparatus for wireless communication at a UE, comprising a processor; memory coupled with the processor; and instructions stored in the memory and executable by the processor to cause the apparatus to perform the method of any of Aspects 1-16.

[0291] Aspect 56: An apparatus for wireless communication at a UE, comprising at least one means for performing the method of any of Aspects 1-16.

[0292] Aspect 57: A non-transitory computer-readable medium storing code for wireless communication at a UE, the code comprising instructions executable by a processor to perform the method of any of Aspects 1-16.

[0293] Aspect 58: An apparatus for wireless communication at a relay device, comprising a processor; memory coupled with the processor; and instructions stored in the memory and executable by the processor to cause the apparatus to perform the method of any of Aspects 17-30.

[0294] Aspect 59: An apparatus for wireless communication at a relay device, comprising at least one means for performing a method of any of aspects 17 through 30.

[0295] Aspect 60: A non-transitory computer-readable medium storing code for wireless communication at a relay device, the code comprising instructions executable by a processor to perform a method of any of aspects 17 through 30.

[0296] Aspect 61: An apparatus for wireless communication at a UE, comprising a processor; memory coupled with the processor; and instructions stored in the memory and executable by the processor to cause the apparatus to perform a method of any of aspects 31 through 43.

[0297] Aspect 62: An apparatus for wireless communication at a UE, comprising at least one means for performing a method of any of aspects 31 through 43.

[0298] Aspect 63: A non-transitory computer-readable medium storing code for wireless communication at a UE, the code comprising instructions executable by a processor to perform a method of any of aspects 31 through 43.

[0299] Aspect 64: An apparatus for wireless communication at a relay device, comprising a processor; memory coupled with the processor; and instructions stored in the memory and executable by the processor to cause the apparatus to perform a method of any of aspects 44 through 50.

[0300] Aspect 65: An apparatus for wireless communication at a relay device, comprising at least one means for performing a method of any of aspects 44 through 50.

[0301] Aspect 66: A non-transitory computer-readable medium storing code for wireless communication at a relay device, the code comprising instructions executable by a processor to perform a method of any of aspects 44 through 50.

[0302] Aspect 67: An apparatus for wireless communication at a UE, comprising a processor; memory coupled with the processor; and instructions stored in the memory and executable by the processor to cause the apparatus to perform a method of any of aspects 51 through 54.

[0303] Aspect 68: An apparatus for wireless communication at a UE, comprising at least one means for performing a method of any of aspects 51 through 54.

[0304] Aspect 69: A non-transitory computer-readable medium storing code for wireless communication at a UE, the code comprising instructions executable by a processor to perform a method of any of aspects 51 through 54.

[0305] It should be noted that the methods described herein describe possible implementations, and that the operations and the steps can be rearranged or otherwise modified and that other implementations are possible. Further, aspects from two or more of the methods can be combined.

[0306] Although aspects of an LTE, LTE-A, LTE-A Pro, or NR system can be described for purposes of example, and LTE, LTE-A, LTE-A Pro, or NR terminology can be used in much of the description, aspects of the described technology are applicable for use with any wireless communication system having code blocks, shared channels, and control channels. For example, the described techniques can be applied to UMB, Institute of Electrical and Electronics Engineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Flash-OFDM, and other systems and radio technologies not explicitly mentioned herein.

[0307] Information and signals described herein can be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that can be referenced throughout the description can be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

[0308] The various illustrative blocks and components described in connection with the disclosure herein can be implemented or performed with a general-purpose processor, a DSP, an ASIC, a CPU, a FPGA or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. The general-purpose processor can be a microprocessor, but in the alternative, the processor can be any processor, controller, or microcontroller. The processor can also be implemented as a combination of a

[0309] The functions described herein can be implemented in hardware, software executed by a processor, firmware, or any combination thereof. If implemented in software executed by a processor, the functions can be stored on or transmitted over as one or more instructions or code on a computer-readable medium. Other examples and implementations are within the scope of the disclosure and appended claims. For example, due to the nature of software, functions described herein can be implemented using software executed by a processor, hardware, firmware, hardwiring, or combinations of any of these. Features implementing functions can also be physically located at various positions, including being distributed as discrete components or

[0310] Computer-readable media includes both non-transitory computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. A non-transitory storage medium can be any available medium that can be accessed by a general purpose or special purpose computer. By way of example, and not limitation, non-transitory computer-readable media can comprise RAM, ROM, electrically erasable programmable ROM (EEPROM), flash memory, compact disk (CD) ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other non-transitory medium that can be used to carry or store desired program code means in the form of instructions or data structures and that can be accessed by a general-purpose or special-purpose computer, or a general-purpose or special-purpose processor. Also, any connection is properly termed a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of computer-readable medium. Disk and disc, as used herein, include CD, laser disc, optical disc, digital versatile disc (DVD), floppy disk and Blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above are also included within the scope of computer-readable media.

[0311] As used herein, including in the claims “or” as used in a list of items (for example, a list of items prefaced by a phrase such as “at least one of’ or “one or more of’) indicates an inclusive list such that, for example, a list of at least one of A, B, or C means A or B or C or AB or AC or BC or ABC (i.e., A and B and C). Also, as used herein, the phrase “based on” shall not be construed as a reference to a closed set of conditions. For example, an example step that is described as “based on condition A” can be based on both a condition A and a condition B without departing from the scope of the present disclosure. In other words, as used herein, the phrase “based on” shall be construed in the same manner as the phrase “based at least in part on.”

[0312] In the drawings, like reference numerals can be used to denote similar components throughout the several views. Further, various components of the same type can be distinguished by following the convention of placing the primary reference number in the hundreds column and a differentiation digit in the tens column (e.g., 102 vs. 102i). Common reference numerals can be used to denote like components throughout the specification and figures.

[0313] The description set forth herein, in connection with the appended drawings, describes example configurations and does not represent all the examples that can be implemented or that are within the scope of the claims. The term “example” as used herein means “serving as an example, instance, or illustration,” and not “preferred” over other examples. The detailed description includes specific details for the purpose of providing an understanding of the described techniques. These techniques, however, can be practiced without these specific details. In some instances, well-known structures and devices are shown in block diagram form in order to avoid obscuring the concepts of the described examples.

[0314] The description set forth herein describes example configurations and does not represent all the examples that can be implemented or that are within the scope of the claims. The term “example” as used herein means “serving as an example, instance, or illustration,” and not “preferred” over other examples. The detailed description includes specific details for the purpose of providing an understanding of the described techniques. These techniques, however, can be practiced without these specific details. In some instances, well-known structures and devices are shown in block diagram form in order to avoid obscuring the concepts of the described examples.

Claims

1. An apparatus for wireless communication at a user equipment (UE), comprising: processor; Memory coupled to the processor; as well as Instructions, which are stored in the memory and executable by the processor, cause the device to perform the following operations: Monitor the resource pool based on relay beacons from relay devices; Detect the relay beacon in the resource pool; A relay discovery request is sent to the relay device, at least in part, based on the relay beacon meeting the relay selection criteria. Receiving a relay announcement from the relay device at least in part based on the relay beacon satisfying the relay selection criteria and at least in part based on sending the relay discovery request; and A side link connection with the relay device is established at least in part based on the relay announcement.

2. The apparatus according to claim 1, wherein: The relay selection criteria are based at least in part on the following: the received power of the relay beacon meets a proximity threshold, the proximity of the relay device meets a proximity threshold, or any combination thereof, and the proximity of the relay device is determined at least in part based on the relay beacon.

3. The apparatus according to claim 1, wherein, The instructions are also executable by the processor to cause the device to perform the following operations: The relay beacon is decoded at least in part based on an identifier that is common to multiple relay devices, including the relay device.

4. The apparatus according to claim 3, wherein, The instructions are also executable by the processor to cause the device to perform the following operations: Receive one or more sequences associated with the plurality of relay devices from the network device.

5. The apparatus according to claim 1, wherein, The instructions are also executable by the processor to cause the device to perform the following operations: The relay beacon is decoded at least in part based on an identifier or code associated with relay discovery.

6. The apparatus according to claim 5, wherein, The identifier is the identifier of the relay device or an identifier associated with relay discovery.

7. The apparatus according to claim 1, wherein, The instructions are also executable by the processor to cause the device to perform the following operations: Identify the payload of the relay beacon, wherein the payload includes an identifier of the relay device.

8. An apparatus for wireless communication at a user equipment (UE), comprising: processor; Memory coupled to the processor; as well as Instructions, which are stored in the memory and executable by the processor, cause the device to perform the following operations: Monitor the resource pool based on relay beacons from relay devices; Detect the relay beacon in the resource pool; Relay announcements are received from the relay equipment based at least in part on the relay beacon meeting the relay selection criteria; Identifying a set of resources associated with the relay announcement based at least in part on the relay beacon from the relay device, wherein receiving the relay announcement includes monitoring the set of resources associated with the relay announcement; and A side link connection with the relay device is established at least in part based on the relay announcement.

9. The apparatus according to claim 8, wherein, The resource set is either pre-configured at the UE or dedicated to relay messages, or both.

10. The apparatus according to claim 8, wherein, The resource set corresponds to a subset of resource blocks configured for the resource pool of the UE.

11. The apparatus according to claim 8, wherein, The resource set associated with the relay announcement is in a different resource pool than the resource pool used for the relay beacon, in a different time slot than the relay beacon, or both.

12. The apparatus according to claim 8, wherein, The resource set is configured to include multiple UEs, including at least the UE.

13. An apparatus for wireless communication at a user equipment (UE), comprising: processor; Memory coupled to the processor; as well as Instructions, which are stored in the memory and executable by the processor, cause the device to perform the following operations: Monitor the resource pool based on relay beacons from relay devices; Detect the relay beacon in the resource pool; Relay announcements are received from the relay equipment based at least in part on the relay beacon meeting the relay selection criteria; Identify the unified access control information associated with the relay device; and The sidelink connection with the relay device is established at least in part based on the relay announcement and the unified access control information.

14. The apparatus according to claim 13, wherein, The relay announcement includes the unified access control information.

15. The apparatus according to claim 13, wherein, The sidelink connection is established, at least in part, based on the UE meeting the standards associated with the unified access control information.

16. An apparatus for wireless communication at a relay device, comprising: processor; Memory coupled to the processor; as well as Instructions, which are stored in the memory and executable by the processor, cause the device to perform the following operations: Use a resource pool to send relay beacons; The set of resources associated with the relay announcement is indicated at least in part based on the relay beacon; The relay announcement is transmitted at least in part based on transmitting the relay beacon, wherein transmitting the relay announcement includes using the resource set to transmit the relay announcement; and The sidelink connection with the user equipment (UE) is established at least in part based on the relay announcement.

17. The apparatus according to claim 16, wherein, The instructions are also executable by the processor to cause the device to perform the following operations: The relay discovery request is received from the UE, wherein sending the relay announcement is at least in part based on receiving the relay discovery request.

18. The apparatus according to claim 16, wherein, The resource set is pre-configured for the UE or dedicated to relay messages, or both.

19. The apparatus according to claim 16, wherein, The resource set corresponds to a subset of resource blocks configured for the resource pool of the UE.

20. The apparatus according to claim 16, wherein, The resource set associated with the relay announcement is in a different resource pool than the resource pool used for the relay beacon, in a different time slot than the relay beacon, or both.

21. The apparatus according to claim 16, wherein, The resource set is configured to include multiple UEs, including at least the UE.

22. The apparatus according to claim 16, wherein, The instructions are also executable by the processor to cause the device to perform the following operations: The relay beacon is encoded at least in part based on an identifier that is common to multiple relay devices, including the relay device.

23. The apparatus according to claim 16, wherein, The relay beacon is scrambled using a sequence associated with the relay device.

24. A method for wireless communication at a user equipment (UE), comprising: Monitor the resource pool based on relay beacons from relay devices; Detect the relay beacon in the resource pool; A relay discovery request is sent to the relay device, at least in part, based on the relay beacon meeting the relay selection criteria. Receiving a relay announcement from the relay device at least in part based on the relay beacon satisfying the relay selection criteria and at least in part based on sending the relay discovery request; and A side link connection with the relay device is established at least in part based on the relay announcement.

25. A method for wireless communication at a user equipment (UE), comprising: Monitor the resource pool based on relay beacons from relay devices; Detect the relay beacon in the resource pool; Relay announcements are received from the relay equipment based at least in part on the relay beacon meeting the relay selection criteria; Identifying a set of resources associated with the relay announcement based at least in part on the relay beacon from the relay device, wherein receiving the relay announcement includes monitoring the set of resources associated with the relay announcement; and A side link connection with the relay device is established at least in part based on the relay announcement.

26. The method of claim 25, wherein, The resource set is either pre-configured at the UE or dedicated to relay messages, or both.

27. A method for wireless communication at a relay device, comprising: Use a resource pool to send relay beacons; The set of resources associated with the relay announcement is indicated at least in part based on the relay beacon; The relay announcement is transmitted at least in part based on transmitting the relay beacon, wherein transmitting the relay announcement includes using the resource set to transmit the relay announcement; and The sidelink connection with the user equipment (UE) is established at least in part based on the relay announcement.

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