Patent Publication Number: US-2021195573-A1

Title: Methods and apparatuses for data retransmission using sidelink diversity

Description:
FIELD OF TECHNOLOGY 
     The present disclosure relates generally to wireless communications and more specifically to data retransmission using sidelink diversity. 
     BACKGROUND 
     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 may be capable of supporting communication with multiple users by sharing the available system resources (e.g., time, frequency, and power). Examples of such multiple-access systems include fourth generation (4G) systems such as Long Term Evolution (LTE) systems, LTE-Advanced (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 spread orthogonal frequency division multiplexing (DFT-S-OFDM). A wireless multiple-access communications system may include one or more base stations or one or more network access nodes, each simultaneously supporting communication for multiple communication devices, which may be otherwise known as user equipment (UE). 
     In some wireless communications systems, such as industrial interne of things (I-IoT) applications, various UEs may be configured to communicate with each other over sidelink channels. These sidelink communications may enhance the wireless systems via reduced latency, multi-path diversity, coverage extension, battery-life improvement, location enhancement, and infrastructure-less communication. In some cases, each of the UEs may use sidelink channel diversity to retransmit a received data transmission to a target UE. This is to help a base station transmit the data transmission intended for the target UE when the direct downlink connection between the base station and the target UE is broken or degraded beyond a predetermined point. 
     SUMMARY 
     The following presents a simplified summary of one or more aspects in order to provide a basic understanding of such aspects. This summary is not an extensive overview of all contemplated aspects, and is intended to neither identify key or critical elements of all aspects nor delineate the scope of any or all aspects. Its sole purpose is to present some concepts of one or more aspects in a simplified form as a prelude to the more detailed description that is presented later. 
     In some situations, a direct communication link between a target UE and a base station may not be optimal or usable for various reasons. A helper UE group may be formed to help forward the data from the base station to the target UE. In some cases, a helper UE may determine whether a received data transmission is intended for itself or a target UE and may use a sidelink channel diversity to retransmit the received data transmission to a target UE, when it determines that the data transmission is for the target UE. This is to help a base station transmit the data transmission intended for the target UE when the direct downlink connection between the base station and the target UE is broken or degraded beyond a predetermined point. 
     In an aspect of the disclosure, a method, a computer-readable medium, and an apparatus are provided. The apparatus is configured to determine whether a received data transmission is intended for itself or a target UE and to retransmit the received data transmission to a target UE using the sidelink channel diversity, when it determines that the data transmission is for the target UE. 
     In another aspect of the disclosure, a method, a computer-readable medium, and an apparatus are provided. The apparatus is configured to transmit a control message to a helper UE to allocate sideline resources for data retransmission by the helper UE, to transmit a data transmission to be forwarded to a target UE and to optionally trigger the data retransmission. 
     To the accomplishment of the foregoing and related ends, the one or more aspects comprise the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative features of the one or more aspects. These features are indicative, however, of but a few of the various ways in which the principles of various aspects may be employed, and this description is intended to include all such aspects and their equivalents. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates an example of a system for wireless communications in accordance with aspects of the present disclosure. 
         FIGS. 2A and 2B  illustrate examples of wireless communications systems in accordance with aspects of the present disclosure. 
         FIG. 3  illustrates an example of a wireless communications system in accordance with aspects of the present disclosure. 
         FIG. 4  illustrates an example of a flow diagram in accordance with aspects of the present disclosure. 
         FIGS. 5 a  through 5 d    illustrate example timelines of communications between a network node and a helper UE in accordance with aspects of the present disclosure. 
         FIGS. 6 and 7  show block diagrams of devices in accordance with aspects of the present disclosure. 
         FIG. 8  shows a block diagram of a communications manager in accordance with aspects of the present disclosure. 
         FIG. 9  shows a diagram of a system including a device in accordance with aspects of the present disclosure. 
         FIGS. 10 and 11  show block diagrams of devices in accordance with aspects of the present disclosure. 
         FIG. 12  shows a block diagram of a communications manager in accordance with aspects of the present disclosure. 
         FIG. 13  shows a diagram of a system including a device in accordance with aspects of the present disclosure. 
         FIGS. 14 through 15  show flowcharts illustrating methods performed by a UE or a like device in accordance with aspects of the present disclosure. 
         FIGS. 16 through 17  show flowcharts illustrating methods performed by a base station or a like device in accordance with aspects of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     In some wireless communications systems, such as industrial interne of things (I-Iot) applications and vehicle to everything (V2X) systems, various user equipments (UEs) may be configured to communicate with each other over sidelink channels. These sidelink communications may enhance the wireless systems via reduced latency, multi-path diversity, coverage extension, battery-life improvement, location enhancement, and infrastructure-less communication. A communication link may be established between a UE and a base station, but the link quality may be degraded due to fading or blockage. Another UE may be utilized to help the affected UE by communicating with the affected UE using a sidelink channel. In some cases, the UEs may perform various measurements to determine sidelink channel quality and diversity and other information such as UE state information to help the BS determine a helper UE group to help with the communications with the affected UE, which is also termed target UE in this disclosure. Once the helper UE group is determined, 
     In some cases, when a link between a base station fails or degrades due to fading, blocking, etc., then the base station may leverage one or more helper UEs from a helper UE groups to communicate data to and receive data from an affected UE (e.g., targeted UE) through the helper UE by leveraging a sidelink channel between the affected UE and the helper UE. From the perspective of a helper UE, the helper UE may determine whether a data transmission is intended for itself or a target UE, what sidelink resource to use for forwarding the data transmission to the target UE, and whether to decode at least part of the data transmission before retransmitting the data transmission to the target UE, etc. 
     Techniques are provided herein for a network node (a base station or programmable logic control (PLC) node) upon determine a helper UE group, to allocate sidelink resources to a helper UE, transmit a data transmission to the helper UE, and optionally send a trigger to the help UE to trigger the helper UE to forward the received data transmission to the target UE. 
     Particular aspects of the subject matter described herein may be implemented to realize one or more advantages. The described techniques may support improvements in the sidelink communication framework, decreasing signaling overhead, and improving reliability, among other advantages. As such, supported techniques may include improved network operations and, in some example aspects, may promote network efficiencies, among other benefits. 
     Aspects of the disclosure are initially described in the context of wireless communications systems. Aspects of the disclosure are further described with respect to wireless communications systems and a process flow diagram. Aspects of the disclosure are further illustrated by and described with reference to apparatus diagrams, system diagrams, and flowcharts that relate to determining a helper UE group. 
       FIG. 1  illustrates an example of a wireless communications system  100  in accordance with aspects of the present disclosure. The wireless communications system  100  may include one or more base stations  105 , one or more UEs  115 , and a core network  130 . In some example aspect, the wireless communications system  100  may 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 example aspects, the wireless communications system  100  may support enhanced broadband communications, ultra-reliable (e.g., mission critical) communications, low latency communications, communications with low-cost and low-complexity devices, or any combination thereof. 
     The base stations  105  may be dispersed throughout a geographic area to form the wireless communications system  100  and may be devices in different forms or having different capabilities. The base stations  105  and the UEs  115  may wirelessly communicate via one or more communication links  125 . Each base station  105  may provide a coverage area  110  over which the UEs  115  and the base station  105  may establish one or more communication links  125 . The coverage area  110  may be an example of a geographic area over which a base station  105  and a UE  115  may support the communication of signals according to one or more radio access technologies. 
     The UEs  115  may be dispersed throughout a coverage area  110  of the wireless communications system  100 , and each UE  115  may be stationary, or mobile, or both at different times. The UEs  115  may be devices in different forms or having different capabilities. Some example UEs  115  are illustrated in  FIG. 1 . The UEs  115  described herein may be able to communicate with various types of devices, such as other UEs  115 , the 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 . 
     The base stations  105  may communicate with the core network  130 , or with one another, or both. For example, the base stations  105  may interface with the core network  130  through one or more backhaul links  120  (e.g., via an S1, N2, N3, or other interface). The base stations  105  may communicate with one another over the backhaul links  120  (e.g., via an X2, Xn, or other interface) either directly (e.g., directly between base stations  105 ), or indirectly (e.g., via core network  130 ), or both. In some example aspects, the backhaul links  120  may be or include one or more wireless links. 
     One or more of the base stations  105  described herein may include or may be referred to by a person having ordinary skill in the art 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 a giga-NodeB (either of which may be referred to as a gNB), a Home NodeB, a Home eNodeB, or other suitable terminology. 
     A UE  115  may include or may be referred to as a mobile device, a wireless device, a remote device, a handheld device, or a subscriber device, or some other suitable terminology, where the “device” may also be referred to as a unit, a station, a terminal, or a client, among other examples. A UE  115  may also include or may be referred to as a personal electronic device such as a cellular phone, a personal digital assistant (PDA), a tablet computer, a laptop computer, or a personal computer. In some example aspects, a UE  115  may 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 may be implemented in various objects such as appliances, or vehicles, meters, among other examples. 
     The UEs  115  described herein may be able to communicate with various types of devices, such as other UEs  115  that may sometimes act as relays as well as the base stations  105  and the network equipment including macro eNBs or gNBs, small cell eNBs or gNBs, or relay base stations, among other examples, as shown in  FIG. 1 . 
     The UEs  115  and the base stations  105  may wirelessly communicate with one another via one or more communication links  125  over one or more carriers. The term “carrier” may refer to a set of radio frequency spectrum resources having a defined physical layer structure for supporting the communication links  125 . For example, a carrier used for a communication link  125  may 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 may carry acquisition signaling (e.g., synchronization signals, system information), control signaling that coordinates operation for the carrier, user data, or other signaling. The wireless communications system  100  may support communication with a UE  115  using carrier aggregation or multi-carrier operation. A UE  115  may be configured with multiple downlink component carriers and one or more uplink component carriers according to a carrier aggregation configuration. Carrier aggregation may be used with both frequency division duplexing (FDD) and time division duplexing (TDD) component carriers. 
     In some example aspects (e.g., in a carrier aggregation configuration), a carrier may also have acquisition signaling or control signaling that coordinates operations for other carriers. A carrier may be associated with a frequency channel (e.g., an evolved universal mobile telecommunication system terrestrial radio access (E-UTRA) absolute radio frequency channel number (EARFCN)) and may be positioned according to a channel raster for discovery by the UEs  115 . A carrier may be operated in a standalone mode where initial acquisition and connection may be conducted by the UEs  115  via the carrier, or the carrier may be operated in a non-standalone mode where a connection is anchored using a different carrier (e.g., of the same or a different radio access technology). 
     The communication links  125  shown in the wireless communications system  100  may 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 may carry downlink or uplink communications (e.g., in an FDD mode) or may be configured to carry downlink and uplink communications (e.g., in a TDD mode). 
     A carrier may be associated with a particular bandwidth of the radio frequency spectrum, and In some example aspects the carrier bandwidth may be referred to as a “system bandwidth” of the carrier or the wireless communications system  100 . For example, the carrier bandwidth may be one of a number of determined bandwidths for carriers of a particular radio access technology (e.g., 1.4, 3, 5, 10, 15, 20, 40, or 80 megahertz (MHz)). Devices of the wireless communications system  100  (e.g., the base stations  105 , the UEs  115 , or both) may have hardware configurations that support communications over a particular carrier bandwidth or may be configurable to support communications over one of a set of carrier bandwidths. In some example aspects, the wireless communications system  100  may include base stations  105  or UEs  115  that support simultaneous communications via carriers associated with multiple carrier bandwidths. In some example aspects, each served UE  115  may be configured for operating over portions (e.g., a sub-band, a BWP) or all of a carrier bandwidth. 
     Signal waveforms transmitted over a carrier may be made up of multiple subcarriers (e.g., using multi-carrier modulation (MCM) techniques such as orthogonal frequency division multiplexing (OFDM) or discrete Fourier transform spread OFDM (DFT-S-OFDM)). In a system employing MCM techniques, a resource element may consist of one symbol period (e.g., a duration of one modulation symbol) and one subcarrier, where the symbol period and subcarrier spacing are inversely related. The number of bits carried by each resource element may depend on the modulation scheme (e.g., the order of the modulation scheme, the coding rate of the modulation scheme, or both). Thus, the more resource elements that a UE  115  receives and the higher the order of the modulation scheme, the higher the data rate may be for the UE  115 . A wireless communications resource may refer to a combination of a radio frequency spectrum resource, a time resource, and a spatial resource (e.g., spatial layers or beams), and the use of multiple spatial layers may further increase the data rate or data integrity for communications with a UE  115 . 
     One or more numerologies for a carrier may be supported, where a numerology may include a subcarrier spacing (Δf) and a cyclic prefix. A carrier may be divided into one or more BWPs having the same or different numerologies. In some example aspects, a UE  115  may be configured with multiple BWPs. In some example aspects, a single BWP for a carrier may be active at a given time and communications for the UE  115  may be restricted to one or more active BWPs. 
     The time intervals for the base stations  105  or the UEs  115  may be expressed in multiples of a basic time unit which may, for example, refer to a sampling period of T s =1/(Δf max ·N f ) seconds, where Δf max  may represent the maximum supported subcarrier spacing, and N f  may represent the maximum supported discrete Fourier transform (DFT) size. Time intervals of a communications resource may be organized according to radio frames each having a specified duration (e.g., 10 milliseconds (ms)). Each radio frame may be identified by a system frame number (SFN) (e.g., ranging from 0 to 1023). 
     Each frame may include multiple consecutively numbered subframes or slots, and each subframe or slot may have the same duration. In some example aspects, a frame may be divided (e.g., in the time domain) into subframes, and each subframe may be further divided into a number of slots. Alternatively, each frame may include a variable number of slots, and the number of slots may depend on subcarrier spacing. Each slot may 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 , a slot may further be divided into multiple mini-slots containing one or more symbols. Excluding the cyclic prefix, each symbol period may contain one or more (e.g., N f ) sampling periods. The duration of a symbol period may depend on the subcarrier spacing or frequency band of operation. 
     A subframe, a slot, a mini-slot, or a symbol may be the smallest scheduling unit (e.g., in the time domain) of the wireless communications system  100  and may be referred to as a transmission time interval (TTI). In some example aspects, the TTI duration (e.g., the number of symbol periods in a TTI) may be variable. Additionally or alternatively, the smallest scheduling unit of the wireless communications system  100  may be dynamically selected (e.g., in bursts of shortened TTIs (sTTIs)). 
     Physical channels may be multiplexed on a carrier according to various techniques. A physical control channel and a physical data channel may 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 may be defined by a number of symbol periods and may extend across the system bandwidth or a subset of the system bandwidth of the carrier. One or more control regions (e.g., CORESETs) may be configured for a set of the UEs  115 . For example, one or more of the UEs  115  may monitor or search control regions for control information according to one or more search space sets, and each search space set may include one or multiple control channel candidates in one or more aggregation levels arranged in a cascaded manner. An aggregation level for a control channel candidate may refer to a number 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 may 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 . 
     Each base station  105  may provide communication coverage via one or more cells, for example a macro cell, a small cell, a hot spot, or other types of cells, or any combination thereof. The term “cell” may refer to a logical communication entity used for communication with a base station  105  (e.g., over a carrier) and may be associated with an identifier for distinguishing neighboring cells (e.g., a physical cell identifier (PCID), a virtual cell identifier (VCID), or others). In some example aspects, a cell may also refer to a geographic coverage area  110  or a portion of a geographic coverage area  110  (e.g., a sector) over which the logical communication entity operates. Such cells may range from smaller areas (e.g., a structure, a subset of structure) to larger areas depending on various factors such as the capabilities of the base station  105 . For example, a cell may be or include a building, a subset of a building, or exterior spaces between or overlapping with geographic coverage areas  110 , among other examples. 
     A macro cell generally covers a relatively large geographic area (e.g., several kilometers in radius) and may allow unrestricted access by the UEs  115  with service subscriptions with the network provider supporting the macro cell. A small cell may be associated with a lower-powered base station  105 , as compared with a macro cell, and a small cell may operate in the same or different (e.g., licensed, unlicensed) frequency bands as macro cells. Small cells may provide unrestricted access to the UEs  115  with service subscriptions with the network provider or may provide restricted access to the UEs  115  having an association with the small cell (e.g., the UEs  115  in a closed subscriber group (CSG), the UEs  115  associated with users in a home or office). A base station  105  may support one or multiple cells and may also support communications over the one or more cells using one or multiple component carriers. 
     In some example aspects, a carrier may support multiple cells, and different cells may be configured according to different protocol types (e.g., MTC, narrowband IoT (NB-IoT), enhanced mobile broadband (eMBB)) that may provide access for different types of devices. 
     In some example aspects, a base station  105  may be movable and therefore provide communication coverage for a moving geographic coverage area  110 . In some example aspects, 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, the overlapping geographic coverage areas  110  associated with different technologies may be supported by different base stations  105 . The wireless communications system  100  may include, for example, a heterogeneous network in which different types of the base stations  105  provide coverage for various geographic coverage areas  110  using the same or different radio access technologies. 
     The wireless communications system  100  may support synchronous or asynchronous operation. For synchronous operation, the base stations  105  may have similar frame timings, and transmissions from different base stations  105  may be approximately aligned in time. For asynchronous operation, the base stations  105  may have different frame timings, and transmissions from different base stations  105  may, In some example aspects, not be aligned in time. The techniques described herein may be used for either synchronous or asynchronous operations. 
     Some UEs  115 , such as MTC or IoT devices, may be low cost or low complexity devices and may provide for automated communication between machines (e.g., via Machine-to-Machine (M2M) communication). M2M communication or MTC may refer to data communication technologies that allow devices to communicate with one another or a base station  105  without human intervention. In some example aspects, M2M communication or MTC may 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 interacting with the application program. Some UEs  115  may 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, weather and geological event monitoring, fleet management and tracking, remote security sensing, physical access control, and transaction-based business charging. 
     Some UEs  115  may be configured to employ operating modes that reduce power consumption, such as half-duplex communications (e.g., a mode that supports one-way communication via transmission or reception, but not transmission and reception simultaneously). In some example aspects, half-duplex communications may be performed at a reduced peak rate. Other power conservation techniques for the UEs  115  include entering a power saving deep sleep mode when not engaging in active communications, operating over a limited bandwidth (e.g., according to narrowband communications), or a combination of these techniques. For example, some UEs  115  may 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 guard-band of a carrier, or outside of a carrier. 
     The wireless communications system  100  may be configured to support ultra-reliable communications or low-latency communications, or various combinations thereof. For example, the wireless communications system  100  may be configured to support ultra-reliable low-latency communications (URLLC) or mission critical communications. The UEs  115  may be designed to support ultra-reliable, low-latency, or critical functions (e.g., mission critical functions). Ultra-reliable communications may include private communication or group communication and may 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 may include prioritization of services, and mission critical services may be used for public safety or general commercial applications. The terms ultra-reliable, low-latency, mission critical, and ultra-reliable low-latency may be used interchangeably herein. 
     In some example aspects, a UE  115  may 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 may be within the geographic coverage area  110  of a base station  105 . Other UEs  115  in such a group may 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 example aspects, groups of the UEs  115  communicating via D2D communications may utilize a one-to-many ( 1 :M) system in which each UE  115  transmits to every other UE  115  in the group. In some example aspects, a base station  105  facilitates the scheduling of resources for D2D communications. In other cases, D2D communications are carried out between the UEs  115  without the involvement of a base station  105 . 
     In some systems, the D2D communication link  135  may be an example of a communication channel, such as a sidelink communication channel, between vehicles (e.g., UEs  115 ). In some example aspects, vehicles may communicate using vehicle-to-everything (V2X) communications, vehicle-to-vehicle (V2V) communications, or some combination of these. A vehicle may signal information related to traffic conditions, signal scheduling, weather, safety, emergencies, or any other information relevant to a V2X system. In some example aspects, vehicles in a V2X system may 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 with both. 
     The core network  130  may provide user authentication, access authorization, tracking, Internet Protocol (IP) connectivity, and other access, routing, or mobility functions. The core network  130  may be an evolved packet core (EPC) or 5G core (5GC), which may 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 or interconnects to external networks (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 may manage non-access stratum (NAS) functions such as mobility, authentication, and bearer management for the UEs  115  served by the base stations  105  associated with the core network  130 . User IP packets may be transferred through the user plane entity, which may provide IP address allocation as well as other functions. The user plane entity may be connected to the network operators IP services  150 . The operators IP services  150  may include access to the Internet, Intranet(s), an IP Multimedia Subsystem (IMS), or a Packet-Switched Streaming Service. 
     Some of the network devices, such as a base station  105 , may include subcomponents such as an access network entity  140 , which may be an example of an access node controller (ANC). Each access network entity  140  may communicate with the UEs  115  through one or more other access network transmission entities  145 , which may be referred to as radio heads, smart radio heads, or transmission/reception points (TRPs). Each access network transmission entity  145  may include one or more antenna panels. In some configurations, various functions of each access network entity  140  or base station  105  may 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 ). 
     The wireless communications system  100  may 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 because the wavelengths range from approximately one decimeter to one meter in length. The UHF waves may be blocked or redirected by buildings and environmental features, but the waves may penetrate structures sufficiently for a macro cell to provide service to the UEs  115  located indoors. The transmission of UHF waves may 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. 
     The wireless communications system  100  may also operate in a super high frequency (SHF) region using frequency bands from 3 GHz to 30 GHz, also known as the centimeter band, or in an extremely high frequency (EHF) region of the spectrum (e.g., from 30 GHz to 300 GHz), also known as the millimeter band. In some example aspects, the wireless communications system  100  may support millimeter wave (mmW) communications between the UEs  115  and the base stations  105 , and EHF antennas of the respective devices may be smaller and more closely spaced than UHF antennas. In some example aspects, this may facilitate use of antenna arrays within a device. The propagation of EHF transmissions, however, may be subject to even greater atmospheric attenuation and shorter range than SHF or UHF transmissions. The techniques disclosed herein may be employed across transmissions that use one or more different frequency regions, and designated use of bands across these frequency regions may differ by country or regulating body. 
     The wireless communications system  100  may utilize both licensed and unlicensed radio frequency spectrum bands. For example, the wireless communications system  100  may employ License Assisted Access (LAA), LTE-Unlicensed (LTE-U) radio access technology, or NR technology in an unlicensed band such as the 5 GHz industrial, scientific, and medical (ISM) band. When operating in unlicensed radio frequency spectrum bands, devices such as the base stations  105  and the UEs  115  may employ carrier sensing for collision detection and avoidance. In some example aspects, operations in unlicensed bands may be based on a carrier aggregation configuration in conjunction with component carriers operating in a licensed band (e.g., LAA). Operations in unlicensed spectrum may include downlink transmissions, uplink transmissions, P2P transmissions, or D2D transmissions, among other examples. 
     A base station  105  or a UE  115  may be equipped with multiple antennas, which may 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  may be located within one or more antenna arrays or antenna panels, which may support MIMO operations or transmit or receive beamforming. For example, one or more base station antennas or antenna arrays may be co-located at an antenna assembly, such as an antenna tower. In some example aspects, antennas or antenna arrays associated with a base station  105  may be located in diverse geographic locations. A base station  105  may have an antenna array with a number of rows and columns of antenna ports that the base station  105  may use to support beamforming of communications with a UE  115 . Likewise, a UE  115  may have one or more antenna arrays that may support various MIMO or beamforming operations. Additionally or alternatively, an antenna panel may support radio frequency beamforming for a signal transmitted via an antenna port. 
     The base stations  105  or the UEs  115  may use MIMO communications to exploit multipath signal propagation and increase the spectral efficiency by transmitting or receiving multiple signals via different spatial layers. Such techniques may 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. Likewise, the multiple signals may be received by the receiving device via different antennas or different combinations of antennas. Each of the multiple signals may be referred to as a separate spatial stream and may carry bits associated with the same data stream (e.g., the same codeword) or different data streams (e.g., different codewords). Different spatial layers may 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. 
     Beamforming, which may also be referred to as spatial filtering, directional transmission, or directional reception, is a signal processing technique that may be used at a transmitting device or a receiving device (e.g., a base station  105 , a UE  115 ) to shape or steer an antenna beam (e.g., a transmit beam, a receive beam) along a spatial path between the transmitting device and the receiving device. Beamforming may be achieved by combining the signals communicated via antenna elements of an antenna array such that some signals propagating at particular orientations with respect to an antenna array experience constructive interference while others experience destructive interference. The adjustment of signals communicated via the antenna elements may include a transmitting device or a receiving device applying amplitude offsets, phase offsets, or both to signals carried via the antenna elements associated with the device. The adjustments associated with each of the antenna elements may be defined by a beamforming weight set associated with a particular orientation (e.g., with respect to the antenna array of the transmitting device or receiving device, or with respect to some other orientation). 
     A base station  105  or a UE  115  may use beam sweeping techniques as part of beam forming operations. For example, a base station  105  may use multiple antennas or antenna arrays (e.g., antenna panels) to conduct beamforming operations for directional communications with a UE  115 . Some signals (e.g., synchronization signals, reference signals, beam selection signals, or other control signals) may be transmitted by a base station  105  multiple times in different directions. For example, the base station  105  may transmit a signal according to different beamforming weight sets associated with different directions of transmission. Transmissions in different beam directions may be used to identify (e.g., by a transmitting device, such as a base station  105 , or by a receiving device, such as a UE  115 ) a beam direction for later transmission or reception by the base station  105 . 
     Some signals, such as data signals associated with a particular receiving device, may be transmitted by a base station  105  in a single beam direction (e.g., a direction associated with the receiving device, such as a UE  115 ). In some example aspects, the beam direction associated with transmissions along a single beam direction may be determined based on a signal that was transmitted in one or more beam directions. For example, a UE  115  may receive one or more of the signals transmitted by the base station  105  in different directions and may 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. 
     In some example aspects, transmissions by a device (e.g., by a base station  105  or a UE  115 ) may be performed using multiple beam directions, and the device may use a combination of digital precoding or radio frequency beamforming to generate a combined beam for transmission (e.g., from a base station  105  to a UE  115 ). The UE  115  may report feedback that indicates precoding weights for one or more beam directions, and the feedback may correspond to a configured number of beams across a system bandwidth or one or more sub-bands. The base station  105  may transmit a reference signal (e.g., a cell-specific reference signal (CRS), a channel state information reference signal (CSI-RS)), which may be precoded or unprecoded. The UE  115  may provide feedback for beam selection, which may 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 a base station  105 , a UE  115  may employ similar techniques for transmitting signals multiple times in different directions (e.g., for identifying a beam direction for subsequent transmission or reception by the UE  115 ) or for transmitting a signal in a single direction (e.g., for transmitting data to a receiving device). 
     A receiving device (e.g., a UE  115 ) may try multiple receive configurations (e.g., directional listening) when receiving various signals from the base station  105 , such as synchronization signals, reference signals, beam selection signals, or other control signals. For example, a receiving device may try multiple receive directions by receiving via different antenna subarrays, by processing received signals according to different antenna subarrays, by receiving according to different receive beamforming weight sets (e.g., different directional listening weight sets) applied to signals received at multiple antenna elements of an antenna array, or by processing received signals according to different receive beamforming weight sets applied to signals received at multiple antenna elements of an antenna array, any of which may be referred to as “listening” according to different receive configurations or receive directions. In some example aspects, a receiving device may use a single receive configuration to receive along a single beam direction (e.g., when receiving a data signal). The single receive configuration may be aligned in a beam direction determined based on listening according to different receive configuration directions (e.g., a beam direction determined to have a highest signal strength, highest signal-to-noise ratio (SNR), or otherwise acceptable signal quality based on listening according to multiple beam directions). 
     The wireless communications system  100  may be a packet-based network that operates according to a layered protocol stack. In the user plane, communications at the bearer or Packet Data Convergence Protocol (PDCP) layer may be IP-based. A Radio Link Control (RLC) layer may perform packet segmentation and reassembly to communicate over logical channels. A Medium Access Control (MAC) layer may perform priority handling and multiplexing of logical channels into transport channels. The MAC layer may also use error detection techniques, error correction techniques, or both to support retransmissions at the MAC layer to improve link efficiency. In the control plane, the Radio Resource Control (RRC) protocol layer may provide establishment, configuration, and maintenance of an RRC connection between a UE  115  and a base station  105  or a core network  130  supporting radio bearers for user plane data. At the physical layer, transport channels may be mapped to physical channels. 
     The UEs  115  and the base stations  105  may support retransmissions of data to increase the likelihood that data is received successfully. Hybrid automatic repeat request (HARQ) feedback is one technique for increasing the likelihood that data is received correctly over a communication link  125 . HARQ may 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 may improve throughput at the MAC layer in poor radio conditions (e.g., low signal-to-noise conditions). In some example aspects, a device may support same-slot HARQ feedback, where the device may provide HARQ feedback in a specific slot for data received in a previous symbol in the slot. In other cases, the device may provide HARQ feedback in a subsequent slot, or according to some other time interval. 
     UEs  115  may be configured to communicate with each other over sidelink channels. These sidelink communications may enhance the wireless systems via reduced latency, multi-path diversity, coverage extension, battery-life improvement, location enhancement, and infrastructure-less communication. For example, a communication link may be established between a UE  115  and a base station  105 . However, the link quality may be degraded due to fading or blockage. Another UE  115  may be utilized to help the affected UE  115  by communicating with the affected UE  115  using a sidelink channel. In some cases, the UEs  115  may perform various measurements to determine sidelink channel quality, channel throughput, and other metrics to determine whether to utilize a sidelink channel. 
     Another UE may be utilized to help the affected UE by communicating with the affected UE using a sidelink channel. In some cases, the UEs may perform various measurements to determine sidelink channel correlation and diversity and other information such as UE state information to help the associated base station  105  determine a helper UE group. 
     In some cases, the UE  115  may determine whether a data transmission is intended for itself or a target UE, what sidelink resource to use for forwarding the data transmission to the target UE, and whether to decode at least part of the data transmission before retransmitting the data transmission to the target UE, etc. 
     In some cases, the base station  105 , upon determine a helper UE group, may transmit a control message to the helper UE to allocate sidelink resources to the helper UE, transmit data to the target UE, and optionally send a trigger to the help UE to trigger the helper UE to forward the received data to the target UE. 
       FIGS. 2A and 2B  illustrates illustrate examples of wireless communications systems  200  in accordance with aspects of the present disclosure. In some example aspects, wireless communications systems  200  may implement aspects of wireless communications system  100 . The wires communications systems  200  include base stations  105 - a  and  105 - b  and UEs  115 , which may be examples of the corresponding devices of  FIG. 1 . 
     As illustrated in  FIG. 2A , each of UE  115 - a,  UE  115 - b,  and UE  115 - c  may establish a respective communication link with base station  105 - a.  However, due to an issue such as fading or blocking, the communication link  125 - a  between UE  115 - a  and base station  105 - a  is degraded or is dropped. Thus, the base station  105 - a  may leverage sidelink channels (e.g., sidelink channel  205 - a ) to communicate with the UE  115 - a.  In  FIG. 2A , the UE  115 - c  is helping or assisting the UE  115 - a  by forwarding or retransmitting data received from the base station  105 - a  to the UE  115 - a  through the sidelink  205 - a.    
     To accomplish the goal of helping the UE  115 - a , the helper UEs  115  (e.g., UE  115 - b  and UE  115 - c ) may measure the sidelinks the target UE  115 - a.  The UEs  115 - b  and  115 - c  may send various reports to the base station  105 - a  for determination of a helper group and a sidelink within the helper UE group. Since the base station  105 - a  configures the reporting of the UE  115 - a , the base station  105 - a  may utilize various reports received from the helper UEs  115 - b  and  115 - c  to select the sidelink channel  205 - a  between the target UE  115 - a  and the help UE  115 - c  for communication with the UE  115 - a.  In some cases, the base station  105 - a  may transmit a control message to each of the UEs  115 - b  and  115 - c,  and the control message may request various reports on demand. The UEs  115 - b  and  115 - c  may report various sidelink measurements and diversity information, and UE state information, among others, to the base station  105 - a.  The base station  105 - a  may then transmit data and a relay instruction to one of the UEs  115 - b  and  105 - c  such that the UE  115 - b  or  115 - c  may retransmit the data to the UE  115 - a  using a sidelink channel. For example, the base station  105 - a  transmits the data to UE  115 - c  using link  125 - c,  and the UE  115 - c  relays/forwards/retransmits the data to UE  115 - a  using sidelink  205 - a.    
       FIG. 2B  includes base station  105 - b,  UE  115 - d,  UE  115 - e,  and UE  115 - f  as well as node  210 . The node  210  may be an example of a base station  105  or UE  115 , a mobile UE  115 , a power line communication UE  115 , a high powered UE  115 , a virtual base station, etc. In one example, the node  210  may be an example of a programmable logic controller (PLC) node that may have variety of physical configurations in various deployment scenario. For example, the PLC node may be a separate physical device deployed together with or separately from the base station  105 - b.  The node  210  communicates with base station  105 - b  over communication link  125 - g.  Further, the node  210  communicates with the UEs  115  over respective communication links  125 . However, due to an issue such as fading or blocking, the communication link  125 - d  between UE  115 - d  and the node  210  is degraded beyond a predetermined point or is dropped. Thus, the node  210  may leverage sidelink channels (e.g., sidelink channel  205 ) to communicate with the UE  115 - a.  In  FIG. 2B , the UE  115 - f  is helping or assisting the UE  115 - d  by forwarding or retransmitting data received from the node  210  to the UE  115 - d  through the sidelink  205 - b.    
     In some cases, the node  210  may transmit a control message to each of the UEs  115 - e  and  115 - f,  and the control message may allocate sidelink resources for the helper UE  115 - f  to use to forward the data transmission to the target UE  115 - d.  The node  210  may then transmit data and a relay instruction to one of the UEs  115 - e  and  105 - f  such that the UE  115 - e  or  115 - f  may retransmit the data to the UE  115 - d  using the allocate sidelink channel. For example, the node  210  transmits the data to UE  115 - d  using link  125 - f,  and the UE  115 - f  relays/forwards/retransmits the data to UE  115 - d  using the sidelink  205 - b.    
       FIG. 3  illustrates an example of a wireless communications system  300  in accordance with aspects of the present disclosure. In some example aspects, wireless communications system  300  may implement aspects of wireless communications system  100 . The wires communications systems  300  include base stations  105 - c  and UEs  115 , which may be examples of the corresponding devices of  FIGS. 1 and 2 . The base station  105 - c  may establish respective communication links  125  with the UEs  115 . 
     Due to an issue such as blocking or fading, the communication link  125 - g  between the base station  105 - c  and the UE  115 - g  may be degraded, fail, or be dropped. Accordingly, the base station  105 - c  may utilize techniques described herein to identify a sidelink for communication with the UE  115 - g.  The base station  105 - c  may transmit a control message to the UEs  115 - h  and  115 - i,  and the control message may indicate a sidelink resource allocation for the helper UEs  115 - h  and  115 - i  to retransmit / forward the received data to the target UE  115 - g.    
     In some example aspect, a UE  115  may determine sidelink quality with another UE  115  by measuring the signal transmission power on the sidelink associated with the other UE  115 . For example, the UE  115 - g  may transmit a sounding reference signal (SRS) using a power P 1 , and the UE  115 - h  and UE 115 - i  may receive the SRS. The base station  105 - c  and the UEs  115 - h  and  115 - i  may measure the received SRS power of the transmitted SRS. For example, UE  115 - i  may receive the SRS from UE  115 - g  at power P 1 *C 2 , where C 2  is the channel from the UE  115 - g  to the UE  115 - i.  UE  115 - i  is configured with a sidelink channel power of SP 2 . Thus, UE  115 - i  may calculate P 1 *C 2 *SP 2 , where C 2 *SP 2  is the received power of sidelink data sent from UE  115 - i  to UE  115 - g.  Similarly, the UE  115 - h  may receive the SRS from UE  115 - g  at power P 1 *C 1 , where C 1  is the channel from the UE  115 - g  to the UE  115 - h.  UE  115 - h  is configured with a sidelink channel power of SP 1 . Thus, UE  115 - h  may calculate P 1 *C 1 *SP 1 , where C 1 *SP 1  is the received power of sidelink data sent from UE  115 - h  to UE  115 - g.    
     In some example aspect, a base station  105  may determine downlink channel quality for resource allocation by measuring the signal transmission power on the downlink with the UE  115 . For example, the base station  105 - c  may be configured with a downlink power P and may calculate P 1 *C*P, where C is the downlink channel from the base station  105 - c  to the UE  115 - g.  Further, C*P may correspond to the received power of downlink data from the base station  105 - c  to UE  115 - g.  The base station  105 - c  may use or determine (e.g. set) a threshold T based on P 1 *C*P. For example, T may be 5 dB above P 1 *C*P. When other UEs  115  sidelink transmission power times its received SRS power (e.g., P 1 *C 1 *SP 1  or P 1 *C 2 *SP 2 ) satisfies (e.g., is greater than or equal to) the threshold, then that UE  115  may be a member of the helper UE group that may potentially assist the UE  115 - g  and hence may transmit a measurement report to base station  105 - c  indicating the that threshold T is satisfied. For example, if the UE  115 - i  determines that P 1 *C 2 *SP 2  is greater than the threshold T, then the base station  105 - c  may determine that the UE  115 - i  may be a member of the helper UE group that may assist the UE  115 - g  via sidelink communications. If a UE  115  determines that P 1 *C 2 *SP 2  does not satisfy the threshold, the UE  115  may not be a member of the helper UE group and thus may skip transmitting the measurement report. 
     In some cases, the base station  105 - c  may transmit the control message via radio resource control (RRC) messaging to the UEs  115 - i  and the UE  115 - h.  In some cases, the RRC message may also indicate the resources allocations for the UE  115 - i  and the UE  115 - h  to forward received data to the target UE  115 - g.    
       FIG. 4  illustrates an example of a process flow diagram  400  in accordance with aspects of the present disclosure. In some example aspects, process flow diagram  400  may implement aspects of wireless communications system  100 . Process flow diagram  400  includes UE  115 - j,  UE  115 - k,  and base station  105 - d,  which may be examples of the corresponding devices of  FIGS. 1 through 3 . The base station  105 - d  may establish a communication link with the UE  115 - j  and UE  115 - k.  In an alternative implementation, in place of the base station  105 - d  may be a PLC node as described in  FIGS. 1 through 3 . 
     At  402 , the base station  105 - d  transmits a control message to both the UE  115 - j  and UE  115 - k  while the UE  105 - j  may be the target UE and the UE  105 - k  may be a helper UE. In one example aspect, the control message may indicate whether the data transmission is for the UE or for the target UE via a downlink control information (DCI) included in a PDCCH message or via a map of a set of UEs, the map capable of uniquely identifies the target UE based in part on a data transmission. In one example aspect, the control message such a PDCCH message may also indicate a sidelink resource allocation for retransmission of the data transmission to the target UE. In one example aspect, the control message may also indicate whether the data transmission is to be at least partially decoded if the data transmission in intended for the target UE. 
     At  404 , the base station  105 - d  transmits a first data transmission to both target UE  115 - j  and the helper UE  115 - k,  and maybe some other UEs (not shown) as well. This may be termed first data transmission or initial data transmission, in reference to a later retransmission of the data transmission to the target UE by a helper UE. The first data transmission may optionally include some control information such as an indication of whether the helper UE  115 - k  should process the data transmission intended for the target UE  115 - j.    
     At  406 , the helper UE  115 - k  may send an uplink control message to indicate at least whether the first data transmission has been successfully received. In one example aspect, the helper UE  115 - k  sends the ACK/NAK after it has successfully processed at least part of the first/initial data transmission. 
     At  408 , in an optional step, the base station  105 - d  may transmit another control message to the helper UE  115 - k  to instruct the helper UE  115 - k  to commence retransmission/forwarding of the first data transmission to the target UE  115 - j.  This control message may be called a trigger message to trigger the helper UE  115 - j  to forward the first data transmission to the target UE  115 -j. In one example aspect, the base station  105 - d  sends the trigger message after receiving an ACK from the helper UE  115 - k  and after failing to receiving an ACK from the target UE  115 - j.    
     At  410 , the helper UE  115 - k,  in an alternative step, may send a control message to the target UE  115 - j  on a sidelink channel. The control message may indicate a resource allocation on the sidelink for the helper UE  115 - k  to forward the first data transmission and for the target UE  115 - j  to receive the forwarded first data transmission. 
     At  412 , the helper UE  115 - k  may forward the received first/initial data transmission to the target UE  115 - j  using the allocated sidelink resource. The data retransmission may be an exact copy of the first data transmission or may include some extra information, after the helper UE  115 - k  has successfully processed at least part of the first/initial data transmission. 
     At  414 , the target UE  115 - j  may transmit a sidelink (DL) control message to the helper UE  115 - k  to acknowledge a successful reception of the forwarded data or failure to receive the forwarded data transmission. In one example aspect, the control message may be carried on a sidelink channel that has been allocated in the control message transmitted from the helper UE  115 - k  to the target UE  115 - j  at  410 . 
     At  416 , the helper UE may forward the received ACK/NACK message to the base station  105 - d  in an uplink control message. In an alternative aspect, the helper UE may generate and send a new ACK/NACK to the base station  105 - d,  based on the received ACK/NACK from the target UE  115 - j.    
     The operations shown in  FIG. 4  are for illustration only. Note that the operation steps shown in  FIG. 4  may be merged, or removed and new steps may be added without deviating from the spirit of the present disclosure. 
       FIGS. 5 a  through 5 d    illustrate example timelines of communications between a network node and a helper UE in accordance with aspects of the present disclosure. In one example aspect, the network is one of a base station or a PLC node. Each of the timelines of  FIGS. 5 a    through  FIGS. 5 d    is divided into two parts,  1 s t  transmission and retransmission, referring to the initial data transmission from the base station to a helper UE and the retransmission/forwarding/relay of the initial data transmission from the helper UE to the target UE. 
       FIG. 5 a    shows an example timeline  500 - a  of operations by the base station, a helper UE and a target UE to accomplish data transmission from the base station to a target UE through a helper UE, using a sidelink between the helper UE and the target UE. Note that the operations shown in the timeline  500 - a  illustrate some example steps with an understanding that and some steps may be merged, or removed and the new steps may be added. 
     At  501 , a base station such as a 5G gNB transmits a control message such as PDCCH. The control message may include a resource allocation of a sidelink between the target UE and the helper UE. The control message may be sent to both the target UE and the helper UE. This may correspond to transmitting the control message at  402  of  FIG. 2 . 
     At  502 , the base station, upon transmitting the control messages, may transmit a data transmission to the helper UE and the target UE in a physical downlink shared channel (PDSCH) message. This may correspond to the first/initial data transmission at  404  of  FIG. 4 . 
     At  503 , G 1  is a guard interval to delineate the PDSCH at  502  and a physical uplink control channel (PUCCH) at  504 . In one example, the guard interval is for the time division duplex (TDD) transmission scheme. Similarly, the G 2 , G 3 , G 4 , and G 5  are subsequent guard intervals for  FIG. 5 a    and other guard intervals, G 1 , G 2 , G 3 , G 4 , G 5 , G 6 , or G 7 , are for  FIG. 5 b    through  FIG. 5   d.    
     At  504 , the base station may receive a PUCCH from either the helper UE, the target UE, or both in response to the data transmission of PDSCH at  502 . The PUCCH may include an ACK or NACK to the data transmission on PDSCH at  502 . This may correspond to the uplink control message at  406  of  FIG. 4 . 
     At  505 , the base station may transmit another control message PDCCH to initiate a retransmission /forwarding of the data transmission on PDSCH at  502 . The retransmission is to be performed by the helper UE. This may correspond to the trigger message transmitted at  408  of  FIG. 4 . 
     At  506 , the helper UE may transmit a control message to the target UE in a physical sidelink control channel (PSCCH) on a sidelink channel. The control message may indicate a resource allocation on the sidelink for the helper UE to forward the initial data transmission and for the target UE  115 - j  to know where to receive the forwarded initial data transmission. This may correspond to the DL control message sent at  410  of  FIG. 4 . 
     At  507 , after a guard interval G 3 , and upon receiving the PDCCH transmitted at  505 , the helper UE transmits a physical sidelink share channel (PSSCH) to the target UE to forward the data transmission received in PDSCH at  502 . This may correspond to the retransmission of the received first data transmission at  412  of  FIG. 4 . 
     At  508 , after a guard interval G 4 , the target UE sends a sidelink ACK to the helper UE using a sidelink channel between the helper UE and the target UE. This may correspond to the sidelink (SL) ACK transmitted at step  414  of  FIG. 4 . 
     At  509 , after a guard interval G 5 , the helper UE transmits an uplink control message PUCCH, to report to the base station what is received in the SL-ACK that is received at  508 . This may correspond to the uplink control message include ACK/NACK at step  416  of  FIG. 4 . 
     As indicated above, the operations shown in the timeline  500 - a  illustrate some example steps with an understanding that some steps may be merged, or removed and the new steps may be added. For example, an alternative to the trigger message in the PDCCH at  505  is not transmitting the trigger message at all. The helper UE may automatically forward the data transmission received at  502  to the target UE, once the helper UE determines that the data transmission is intended for the target UE, without waiting for a trigger message from the base station. 
       FIG. 5 b    shows an example timeline  500 - b  of operations by a base station, a PLC node, a helper UE, and a target UE to accomplish data transmission from the base station to a target UE through the PLC node and the helper UE, using a sidelink between the base station and the PLC node and a sideline between the helper UE and the target UE. One difference between the timeline  500 - a  and the timeline  500 - b  is that a PLC nod is involved in the process of transmitting data to a target UE through a helper UE and sidelink diversity. 
     At  511 , a base station such as a 5G gNB transmits a control message PDCCH. The control message may include a resource allocation of a sidelink between the target UE and the helper UE. The control message is sent to the PLC node instead the helper UE, as indicated at  501 . 
     At  512 , after a guard interval at G 1  and upon receiving the PDCC message transmitted at  511 , the PLC node may transmit a control message PSCCH to the helper UE using a sidelink channel. In one example aspect, the PSCCH may simply forward the received control message PDCCH. 
     At  513 , the PLC node may transmit an initial data transmission to the helper UE and the target UE in a physical shared sidelink channel (PSSCH). This may imply that the PLC is responsible for generating the initial data transmission. This may correspond to the first data transmission at  404  of  FIG. 4  or the transmission of PDSCH at  502  of  FIG. 5   a.    
     At  514 , the PLC node may receive an SL-ACK/NACK to the data transmission at  513  from the helper UE, the target UE or both on a sidelink (SL) channel. In one example aspect, the PLC node receives an ACK from the helper UE, a NACK or no response from the target UE. This means that the base station/PLC node needs to use the helper UE to retransmit/forward the initial data transmission to the target UE. 
     At  515 , the PLC may send an uplink control message in a PUCCH to the base station. In one example aspect, the control message in the PUCCH may simply copy the SL ACK received at  514 . 
     At  516 , the base station may transmit another control message PDCCH to initiate/trigger a retransmission /forwarding of the PSSCH transmitted at  513 . In one example aspect, the trigger message may be directly sent from the base station to the helper UE without going through the PLC node. This may correspond to the trigger message transmitted at  408  of  FIG. 4  and the PDCC transmitted to the help UE at  505  of  FIG. 5   a.    
     At  517 , the helper UE may transmit a control message to the target UE in a PSCCH (physical sidelink control channel) on a sidelink channel. The control message may indicate a resource allocation on the sidelink for the helper UE to forward the initial data transmission and for the target UE  115 - j  to receive the forwarded initial data transmission. This may correspond to the DL control message sent at  410  of  FIG. 4  and the initial data transmission sent in the PSSCH at  507  of  FIG. 5   a.    
     At  518 , upon receiving PDCCH transmitted at  516 , the helper UE transmits a physical sidelink share channel (PSSCH) to the target UE to forward the data transmission received in PDSCH at  513 , using the sidelink resource indicated at  517 . This may correspond to the retransmission of the received first data transmission at  412  of  FIG. 4  and forwarding of the initial data transmission at  507  of  FIG. 5   a.    
     At  519 , after a guard interval G 6 , the target UE sends a sidelink ACK to the helper UE using a sidelink channel between the helper UE and the target UE. This may correspond to the SL ACK transmitted at step  414  of  FIG. 4  and SL-ACK transmitted at  508  of  FIG. 5   a.    
     At  520 , after a guard interval G 7 , the helper UE transmits an uplink control message PUCCH, to report to the base station what is received in the SL-ACK received at  519 . This may correspond to the uplink ACK/NACK transmitted at step  416  of  FIG. 4  or the SL ACK at  508  of  FIG. 5 a      
     As indicated above, the operations shown in the timeline  500 - b  illustrate some example steps with an understanding that and some steps may be merged, or removed and the new steps may be added. For example, an alternative to the trigger message in the PDCCH at  516  is not transmitting the trigger message at all. The helper UE may automatically forward the data transmission received at  513  to the target UE, once the helper UE determines that the data transmission is intended for the target UE, without waiting for a trigger message from the base station. 
       FIG. 5 c    shows an example timeline  500 - c  of operations by the PLC note, a helper UE and a target UE to accomplish data transmission from a PLC node to a target UE through a helper UE, using a sidelink between the PLC node and the helper UE and a sidelink between the helper UE and the target UE. One difference between the timeline  500 - b  and the timeline  500 - c  is that in the timeline  500 - c,  the PLC node functions as a base station without involvement from any other base station. Another difference is that the PLC node does not transit a trigger message to the helper UE to trigger the retransmission/forwarding of the initial data transmission. Note that the operations shown in the timeline  500 - c  illustrate some example steps with an understanding that and some steps may be merged, or removed and the new steps may be added. 
     At  521 , a PLC node transmits a control message in a PSCCH. The control message may include a resource allocation of a sidelink between the target UE and the helper UE. The control message may be sent to both the target UE and the helper UE. This may correspond to transmitting the control message at  402  of  FIG. 2 , or transmitting the PDCCH at  501  of  FIG. 5 a    or  511  of  FIG. 5   b.    
     At  522 , the PLC node, upon transmitting the control message at  521 , may transmit the initial data to the helper UE and the target UE in a sidelink PSSCH channel. This may correspond to the first data transmission at  404  of  FIG. 4 , the PDSCH at  502  of  FIG. 5 a   , or at  513  of  FIG. 5   b.    
     At  523 , after a guard interval G 1 , the PLC node receives a sidelink ACK to the initial data transmission sent at  522  from the helper UE, the target UE or both, using a sidelink channel between the PLC node and the helper UE or the target UE. This may correspond to the SL ACK transmitted at step  414  of  FIG. 4 , the SL-ACK at  519  of  FIG. 5 b    or  508  of  FIG. 5   a.    
     At  524 , the PLC node may transmit a control message to the helper UE in a PSCCH (physical sidelink control channel) on a sidelink channel. The control message may indicate a resource allocation on the sidelink for the helper UE to forward the initial data transmission and for the target UE to receive the forwarded data transmission. This may correspond to the DL control message sent at  410  of  FIG. 4 . 
     At  525 , the helper UE may transmit a control message to the target UE in a PSCCH on a sidelink channel. The control message may forward to the target UE the control message the helper UE received at  524 , to indicate a resource allocation on the sidelink for the helper UE to forward the initial data transmission and for the target UE to receive the forwarded data transmission. 
     At  526 , the helper UE transmits a PSSCH to the target UE to forward the data transmission received in PDSCH at  522 , using the sidelink resource indicated at  524 . This may correspond to the retransmission of the received first data transmission at  412  of  FIG. 4  and forwarding of the initial data transmission at  507  of  FIG. 5   a.    
     At  527 , the target UE may send an ACK/NACK via a sidelink to the helper UE to indicate whether or not the forwarded data transmission has been successfully received. 
     As indicated above, the operations shown in the timeline  500 - c  illustrate some example steps with an understanding that and some steps may be merged, or removed and the new steps may be added, as shown in  FIG. 5   d.    
       FIG. 5 d    shows an example alternative timeline  500 - d  of operations by a PLC note, a helper UE and a target UE to accomplish data transmission from the PLC node to the target UE through the helper UE, using a sidelink between the PLC node and the helper UE and a sidelink between the helper UE and the target UE. In the timeline  500 - d,  the PLC node functions as a base station without involvement from any other base station. The operations of  500 - d  is similar to that of  500 - c,  except for elimination of some steps in favor of a fast data transmission via sidelink forwarding. 
     At  531 , the PLC node transmits a control message in a PSCCH. The control message may include a resource allocation of a sidelink between the target UE and the helper UE. The control message may be sent to both the target UE and the helper UE. This may correspond to transmitting the control message at  402  of  FIG. 2 , transmitting the PDCCH at  501  of  FIG. 5 a    or transmitting the PDCCH at  511  of  FIG. 5   b.    
     At  532 , the PLC node, upon transmitting the control messages, may transmit the initial data to the helper UE and the target UE in a sidelink PSSCH channel. This may correspond to the first data transmission at  404  of  FIG. 4 , or the PDSCH at  522  of  FIG. 5   c.    
     At  533 , upon receiving PSCCH transmitted at  531 , the helper UE transmits a physical sidelink control channel (PSCCH) to the target UE to forward the control message received at  531 . The control message includes sidelink resource allocation for the helper UE to forward the data transmission received at  532  and for the target UE to receive the forwarded data transmission. 
     At  534 , upon receiving PDCCH transmitted at  533 , the helper UE transmits a PSSCH to the target UE to retransmit/forward the data transmission received in PDSCH at  532 , using the sidelink resource indicated at  533 . This may correspond to the retransmission of the received first data transmission at  412  of  FIG. 4  and forwarding of the initial data transmission at  526  of  FIG. 5   c.    
     At  535 , the helper UE may send an ACK/NACK via a sidelink to the PLC node to indicate whether or not the forwarded data transmission has been successfully received, assuming that the helper UE itself receives an ACK message from the target UE. 
     As indicated above, the operations shown in the timeline  500 - d  illustrate some example steps with an understanding that and some steps may be merged, or removed. The  500 - d  is simplified version of  500 - c,  with operations at  523  and  524  eliminated. 
       FIG. 5  shows a block diagram  500  of a device  505  in accordance with aspects of the present disclosure. The device  505  may be an example of a UE  115  as described herein. The device  505  may include a receiver  510 , a communications manager  515 , and a transmitter  535 . The device  505  may also include a processor. Each of these components may be in communication with one another (e.g., via one or more buses). 
     The receiver  510  may 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 forwarding data transmission using sidelink communication, etc.). Information may be passed on to other components of the device  505 . The receiver  510  may be an example of aspects of the transceiver  920  described with reference to  FIG. 9 . The receiver  510  may utilize a single antenna or a set of antennas. 
     The communications manager  615  may be an example of aspects of the communications manager  715  as described herein. The communications manager  615  may be an example of aspects of the communications manager  910  described herein. 
     The transmitter  635  may transmit signals generated by other components of the device  505 . In some example aspects, the transmitter  535  may be collocated with a receiver  510  in a transceiver module. For example, the transmitter  535  may be an example of aspects of the transceiver  920  described with reference to  FIG. 9 . The transmitter  535  may utilize a single antenna or a set of antennas. 
       FIG. 7  shows a block diagram  700  of a device  705  in accordance with aspects of the present disclosure. The device Error! Reference source not found. 5  may be an example of aspects of a device  605 , or a UE  115 , as described herein. The device  705  may include a receiver  710 , a communications manager  715 , and a transmitter  735 . The device  705  may also include a processor. Each of these components may be in communication with one another (e.g., via one or more buses). 
     The communications manager  715  may include a data receiving component  715 , a target UE determination component  720 , and a data retransmission component  730 . The communications manager  715  may be an example of aspects of the communications manager  910  described herein. 
     The data receiving component  715  may receive an initial data transmission from a base station. The initial data transmission in either a unicast transmission to a UE or a multicast transmission to a group of UEs. If in a unicast transmission, the network node may send multiple transmissions to multiple UEs. If in a multicast transmission, the network node may use a Group-Radio Radio Network Temporary Identifier (G-RNTI) to identify a helper UE group and a target UE. 
     The target UE determination component  720  may determine whether the received data transmission is intended for the receiving UE or another UE such as a target UE. The target UE determination component  720  may determine whether the received data transmission is for the target UE based on a received control message. 
     The data retransmission component  730  may forward the received data transmission to a target UE. The data retransmission component  730  may know how to retransmit the initial data transmission based on a signaling message received from the network node. 
     The transmitter  735  may transmit signals generated by other components of the device  505 . In some example aspects, the transmitter  735  may be collocated with a receiver  510  in a transceiver module. For example, the transmitter  735  may be an example of aspects of the transceiver  920  described with reference to  FIG. 9 . The transmitter  735  may utilize a single antenna or a set of antennas. 
       FIG. 8  shows a block diagram  800  of a communications manager  805  in accordance with aspects of the present disclosure. The communications manager  805  may be an example of aspects of a communications manager  515 , a communications manager  715 , or a communications manager  910  described herein. The communications manager  805  may include a control component  810 , a data receiving component  815 , a target UE determination component  820 , a retransmission trigger component  825 , and a data retransmission component  830 . Each of these modules may communicate, directly or indirectly, with one another (e.g., via one or more buses). 
     The control component  810  may transmit an uplink control message to and receive a control message from a network node. The data receiving component  815  may receive an initial data transmission from the network node. 
     The target UE determination component  820  may determine whether the received data transmission is intended for the receiving UE or another UE such as a target UE. The target UE determination component  820  may determine whether the received data transmission is for the target UE based on a received control message. The control message may have a field indicating whether the data transmission is for a UE other than the receiving UE. 
     The retransmission trigger component  825  may receive a trigger message from the base station to initiate forwarding of the initial data transmission by the helper to the target UE. The trigger message may be included in a downlink control message received from the base station. The data retransmission component  730  may forward the received data transmission to the target UE, based on a signaling message received the network node. 
       FIG. 9  shows a diagram of a system  900  including a device  905  in accordance with aspects of the present disclosure. The device  905  may be an example of or include the components of device  605 , device  705 , or a UE  115  as described herein. The device  905  may include components for bi-directional voice and data communications including components for transmitting and receiving communications, including a communications manager  910 , an I/O controller  915 , a transceiver  920 , an antenna  925 , memory  930 , and a processor  940 . These components may be in electronic communication via one or more buses (e.g., bus  945 ). 
     The communications manager  910  may receive, from a base station, a control message that indicates whether the report of sidelink channel diversity information and UE state information is scheduled or on demand and a resource allocation for the report. The communication manager  910  may determine whether a received data transmission is intended for the receiving UE or a target UE. The communication manager  910  may also retransmit/forward the received data transmission to the target UE. 
     The I/O controller  915  may manage input and output signals for the device  905 . The I/O controller  915  may also manage peripherals not integrated into the device  905 . In some cases, the I/O controller  915  may represent a physical connection or port to an external peripheral. In some cases, the I/O controller  915  may utilize an operating system such as iOS®, ANDROID®, MS-DOS®, MS-WINDOWS®, OS/2®, UNIX®, LINUX®, or another known operating system. In other cases, the I/O controller  915  may represent or interact with a modem, a keyboard, a mouse, a touchscreen, or a similar device. In some cases, the I/O controller  915  may be implemented as part of a processor. In some cases, a user may interact with the device  905  via the I/O controller  915  or via hardware components controlled by the I/O controller  915 . 
     The transceiver  920  may communicate bi-directionally, via one or more antennas, wired, or wireless links as described above. For example, the transceiver  920  may represent a wireless transceiver and may communicate bi-directionally with another wireless transceiver. The transceiver  920  may also include a modem to modulate the packets and provide the modulated packets to the antennas for transmission, and to demodulate packets received from the antennas. 
     In some cases, the wireless device may include a single antenna  925 . However, in some cases the device may have more than one antenna  925 , which may be capable of concurrently transmitting or receiving multiple wireless transmissions. 
     The memory  930  may include RAM and ROM. The memory  930  may store computer-readable, computer-executable code  935  including instructions that, when executed, cause the processor to perform various functions described herein. In some cases, the memory  930  may contain, among other things, a basic input/output system (BIOS) which may control basic hardware or software operation such as the interaction with peripheral components or devices. 
     The processor  940  may include an intelligent hardware device, (e.g., a general-purpose processor, a digital signal processor (DSP), a CPU, a microcontroller, an ASIC, a field programmable gate array (FPGA), a programmable logic device, a discrete gate or transistor logic component, a discrete hardware component, or any combination thereof). In some cases, the processor  940  may be configured to operate a memory array using a memory controller. In other cases, a memory controller may be integrated into the processor  940 . The processor  940  may be configured to execute computer-readable instructions stored in a memory (e.g., the memory  930 ) to cause the device  905  to perform various functions (e.g., functions or tasks supporting determining UE sidelink diversity information and UE state information to facilitate communications with another UE via a sidelink channel). 
     The code  935  may include instructions to implement aspects of the present disclosure, including instructions to support wireless communications. The code  935  may be stored in a non-transitory computer-readable medium such as system memory or other type of memory. In some cases, the code  935  may not be directly executable by the processor  940  but may cause a computer (e.g., when compiled and executed) to perform functions described herein. 
       FIG. 10  shows a block diagram  1000  of a device  1005  in accordance with aspects of the present disclosure. The device  1005  may be an example of aspects of a base station  105  as described herein. The device  1005  may include a receiver  1010 , a communications manager  1015 , and a transmitter  1020 . The device  1005  may also include a processor. Each of these components may be in communication with one another (e.g., via one or more buses). 
     The receiver  1010  may 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 forwarding a data transmission to a target UE). Information may be passed on to other components of the device  1005 . The receiver  1010  may be an example of aspects of the transceiver  1320  described with reference to  FIG. 13 . The receiver  1010  may utilize a single antenna or a set of antennas. 
     The communications manager  1015  may transmit, to one or more helper UEs, a control message that indicates a sidelink resource allocation and whether a data transmission is intended for a target UE or the receiving UE. The communications manager  1015  may transmit a data transmission to a helper UE to be forwarded to the target UE. The communications manager  1015  may be an example of aspects of the communications manager  1310  described herein. 
     The communications manager  1015 , or its sub-components, may be implemented in hardware, code (e.g., 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  1015 , or its sub-components may be executed by a general-purpose processor, a DSP, an application-specific integrated circuit (ASIC), 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 in the present disclosure. 
     The communications manager  1015 , or its sub-components, may be physically located at various positions, including being distributed such that portions of functions are implemented at different physical locations by one or more physical components. In some example aspects, the communications manager  1015 , or its sub-components, may be a separate and distinct component in accordance with various aspects of the present disclosure. In some example aspects, the communications manager  1015 , or its sub-components, may 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. 
     The transmitter  1020  may transmit signals generated by other components of the device  1005 . In some example aspects, the transmitter  1020  may be collocated with a receiver  1010  in a transceiver module. For example, the transmitter  1020  may be an example of aspects of the transceiver  1320  described with reference to  FIG. 13 . The transmitter  1020  may utilize a single antenna or a set of antennas. 
       FIG. 11  shows a block diagram  1100  of a device  1105  in accordance with aspects of the present disclosure. The device Error! Reference source not found. 5  may be an example of aspects of a device  1005 , a base station  105 , or the PLC node  210  as described herein. The device  1105  may include a receiver  1110 , a communications manager  1115 , and a transmitter  1130 . The device  1105  may also include a processor. Each of these components may be in communication with one another (e.g., via one or more buses). 
     The receiver  1110  may 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 forwarding a data transmission to a target UE, etc.). Information may be passed on to other components of the device  1105 . The receiver  1110  may be an example of aspects of the transceiver  1320  described with reference to  FIG. 13 . The receiver  1110  may utilize a single antenna or a set of antennas. 
     The communications manager  1115  may be an example of aspects of the communications manager  1310  as described herein. The communications manager  1115  may include a control message transmit component  1120  and a data transmit component  1125 . The communications manager  1115  may be an example of aspects of the communications manager  1310  or the communications manager  1015 , described herein. 
     The control message transmit component  1120  may transmit a downlink control message to a PLC node, a helper UE, or a target UE. The downlink control message may include an indication of whether a downlink data transmission is for the receiving UE or a target UE, an indication of whether or not the receiving UE should process at least part of a data transmission, and a sidelink resource allocation for a helper UE to forward the data transmission to the target UE. 
     The data transmit component  1125  may transmit a data transmission to a set of helper UEs and the target UE. The data transmit component  1125  may send an initial data transmission in either a unicast transmission to a UE or a multicast transmission to a group of UEs. If in a unicast transmission, the network node may send multiple transmission to multiple UEs. If in a multicast transmission, the network node may use a Group-Radio Radio Network Temporary Identifier (G-RNTI) to identify a helper UE group and the target UE. 
     The transmitter  1130  may transmit signals generated by other components of the device  1105 . In some example aspects, the transmitter  1130  may be collocated with a receiver  1110  in a transceiver module. For example, the transmitter  1130  may be an example of aspects of the transceiver  1320  described with reference to  FIG. 13 . The transmitter  1130  may utilize a single antenna or a set of antennas. 
       FIG. 12  shows a block diagram  1200  of a communications manager  1205  in accordance with aspects of the present disclosure. The communications manager  1205  may be an example of aspects of a communications manager  1015 , a communications manager  1115 , or a communications manager  1310  described herein. The communications manager  1205  may include a control message transmit component  1210 , a data transmission component  1215 , a control message receiving component  1220 , and a trigger component  1225 . Each of these modules may communicate, directly or indirectly, with one another (e.g., via one or more buses). 
     The control message transmit component  1210  may transmit a downlink control message to a PLC node, a helper UE, or a target UE. The downlink control message may include an indication of whether a downlink data transmission is for the receiving UE or a target UE, an indication of whether or not the receiving UE should process at least part of a data transmission, and a sidelink resource allocation for a helper UE to forward the data transmission to the target UE. 
     The data transmit component  1215  may transmit a data transmission to a set of helper UEs and a target UE. The data transmit component  1125  may send an initial data transmission in either a unicast transmission to a UE or a multicast transmission to a group of UEs. If in a unicast transmission, the network node may send multiple transmission to multiple UEs. 
     The control message receiving component  1220  may receive and process an uplink control message. The uplink control message may include an ACK/NACK from a UE such as a helper UE or a target UE. 
     The trigger component  1225  may determine whether or not to send a trigger message to trigger a helper UE to initiate forwarding of a data transmission to a target UE. In one example aspect, the trigger message is included in a downlink control message. 
       FIG. 13  shows a diagram of a system  1300  including a device  1305  in accordance with aspects of the present disclosure. The device  1305  may be an example of or include the components of device  1005 , device  1105 , a base station  105 , ora PLC node  210  as described herein. The device  1305  may include components for bi-directional voice and data communications including components for transmitting and receiving communications, including a communications manager  1310 , a network communications manager  1315 , a transceiver  1320 , an antenna  1325 , memory  1330 , a processor  1340 , and an inter-station communications manager  1345 . These components may be in electronic communication via one or more buses (e.g., bus  1350 ). 
     The communications manager  1310  may transmit, to one or more helper UEs, a control message that indicates a sidelink resource allocation and whether a data transmission is intended for a target UE or the receiving UE. The communications manager  1015  may transmit a data transmission to a helper UE to be forwarded to the target UE. 
     The network communications manager  1315  may manage communications with the core network (e.g., via one or more wired backhaul links). For example, the network communications manager  1315  may manage the transfer of data communications for client devices, such as one or more UEs  115 . 
     The transceiver  1320  may communicate bi-directionally, via one or more antennas, wired, or wireless links as described above. For example, the transceiver  1320  may represent a wireless transceiver and may communicate bi-directionally with another wireless transceiver. The transceiver  1320  may also include a modem to modulate the packets and provide the modulated packets to the antennas for transmission, and to demodulate packets received from the antennas. In some cases, the wireless device may include a single antenna  1325 . However, in some cases the device may have more than one antenna  1325 , which may be capable of concurrently transmitting or receiving multiple wireless transmissions. 
     The memory  1330  may include RAM, ROM, or a combination thereof. The memory  1330  may store computer-readable code  1335  including instructions that, when executed by a processor (e.g., the processor  1340 ) cause the device to perform various functions described herein. In some cases, the memory  1330  may contain, among other things, a BIOS which may control basic hardware or software operation such as the interaction with peripheral components or devices. 
     The processor  1340  may include an intelligent hardware device, (e.g., a general-purpose processor, a DSP, a CPU, a microcontroller, an ASIC, an FPGA, a programmable logic device, a discrete gate or transistor logic component, a discrete hardware component, or any combination thereof). In some cases, the processor  1340  may be configured to operate a memory array using a memory controller. In some cases, a memory controller may be integrated into processor  1340 . The processor  1340  may be configured to execute computer-readable instructions stored in a memory (e.g., the memory  1330 ) to cause the device  1305  to perform various functions (e.g., functions or tasks supporting sounding reference signal channel measurement for sidelink communication). 
     The inter-station communications manager  1345  may manage communications with other base station  105 , and may include a controller or scheduler for controlling communications with UEs  115  in cooperation with other base stations  105 . For example, the inter-station communications manager  1345  may coordinate scheduling for transmissions to UEs  115  for various interference mitigation techniques such as beamforming or joint transmission. In some example aspects, the inter-station communications manager  1345  may provide an X2 interface within an LTE/LTE-A wireless communication network technology to provide communication between base stations  105 . 
     The code  1335  may include instructions to implement aspects of the present disclosure, including instructions to support wireless communications. The code  1335  may be stored in a non-transitory computer-readable medium such as system memory or other type of memory. In some cases, the code  1335  may not be directly executable by the processor  1340  but may cause a computer (e.g., when compiled and executed) to perform functions described herein. 
       FIG. 14  shows a flowchart illustrating a method  1400  in accordance with aspects of the present disclosure. The operations of method  1400  may be implemented by a UE  115  or its components as described herein. For example, the operations of method  1400  may be performed by a communications manager as described with reference to  FIGS. 6 through 9 . In some example aspects, a UE may execute a set of instructions to control the functional elements of the UE to perform the functions described below. Additionally or alternatively, a UE may perform aspects of the functions described below using special-purpose hardware. In one example aspect, the UE performing the method  1400  is a helper UE. 
     At  1404 , the UE receives a data transmission from a network node. The network node may be a base station, or a PLC node as described with reference to  FIG. 1  and  FIGS. 2 a   - 2   b.  The operations of  1404  may be performed according to the methods described herein. In some example aspects, aspects of the operations of  1404  may be performed by a data receiving component as described with reference to  FIGS. 6 through 9 . 
     At  1404 , the UE receives the data transmission in either a unicast transmission or a multicast transmission via a Group-Radio Radio Network Temporary Identifier (G-RNTI). In one example, the multicast transmission is to a UE group which comprises at least a helper UE group and a target UE. The helper UE group may include a group of UEs each of which may potentially help the network node forward /retransmit the data transmission to the target UE. In one example, the receiving UE is a member of the helper UE group. 
     At  1406 , the UE may determine whether the received data transmission is intended for a target UE or for the UE itself. The operations of  1406  may be performed according to the methods described herein. In some example aspects, aspects of the operations of  1406  may be performed by a target UE determination component as described with reference to  FIGS. 6 through 9 . 
     At  1406 , in one example aspect, the UE may determine whether the received data transmission is for the target UE based on a received control message. The control message may indicate whether the data transmission is for the receiving UE or for the target UE via a downlink control information (DCI) included in a PDCCH message. For example, the DCI field may have a one-bit field indicating whether or not the data transmission is for the receiving UE. 
     In another example aspect, the UE determines whether the received data transmission is for the target UE via a map of a set of UEs. The map is capable of uniquely identifies the target UE. For example, the map can be of a format {G_RNTI: targeted UE identity}. Hence when the UE uses the G RNTI to decode a received PDCCH, and then decode the corresponding data transmission in a PDSCH, the UE knows the data transmission is for a UE matching a targeted UE identity in the map. The map may be configured into the helper UE via in a semi-persistent manner using an RRC message from the base station. 
     At  14010 , the UE retransmit the received data transmission to the target UE upon determining that the data transmission is intended for the target UE. The operations of  1410  may be performed according to the methods described herein. In some example aspects, aspects of the operations of  1406  may be performed by a data retransmission component as described with reference to  FIGS. 6 through 9 . 
     In one example aspect, the retransmitting of the data transmission includes forwarding the data transmission to the target UE after decoding at least part of the receiving data transmission. In an alternative example aspect, the retransmitting of the data transmission includes forwarding the data transmission to the target UE without decoding any part of the received data transmission. The UE may know how to retransmit the received data transmission based on a signaling message received from the network node. The control message received prior to receiving the data transmission may include an indication of whether or not the receiving UE shall process the data transmission intended for another UE. 
     The method  1400  is for illustration purpose and shows one possible process for a UE or a helper UE to facilitate communications between the base station and a target UE using a sidelink channel. In practice, one or more steps shown in the illustrative flowchart for the method  1400  may be combined with other steps, performed in any suitable order, performed in parallel (e.g., simultaneously or substantially simultaneously), or removed. 
       FIG. 15  shows a flowchart illustrating a method  1500  in accordance with aspects of the present disclosure. The operations of method  1500  may be implemented by a UE  115  or its components as described herein. For example, the operations of method  1500  may be performed by a communications manager as described with reference to  FIGS. 6 through 9 . In some example aspects, a UE may execute a set of instructions to control the functional elements of the UE to perform the functions described below. Additionally or alternatively, a UE may perform aspects of the functions described below using special-purpose hardware. In one example aspect, the UE performing the method  1500  is a helper UE. 
     At  1502 , the UE receives a control message from a network node such as the base station  105  of  FIG. 1  or a PLC node such as  210  of  FIG. 2   b.  As described herein, the terms network node and base station may be used interchangeably, as made obvious by the context. The operations of  1502  may be performed according to the methods described herein. In some example aspects, aspects of the operations of  1502  may be performed by a control component as described with reference to  FIGS. 6 through 9 . 
     In one example aspect, the control message may include a downlink control information (DCI) field included in a PDCCH included in the received control message. The control message may include a sidelink resource allocation for retransmitting an initial data transmission if the data transmission is intended for a UE other than the receiving UE. The control message may also include an indication of whether to process at least part of the initial data transmission. Also included in the control message may be a target UE identifier. In one example aspect, the control message is received prior to receiving the initial data transmission. 
     At  1504 , the UE receives a data transmission from the network node. The network node may be a base station, or a PLC node as described with reference to  FIG. 2 b   . The operations of  1504  may be performed according to the methods described herein. In some example aspects, aspects of the operations of  1504  may be performed by a data receiving component as described with reference to  FIGS. 6 through 9 . 
     At  1504 , the UE receives the data transmission in either a unicast transmission or a multicast transmission via a Group-Radio Radio Network Temporary Identifier (G-RNTI). In one example, the multicast transmission is to a UE group which comprises at least a helper UE group and the target UE. The helper UE group may include a group of UEs each of which may potentially help the network node forward/retransmit the data transmission to the target UE. In one example, the receiving UE is a member of the helper UE group. 
     At  1506 , the UE may determine whether the received data transmission is intended for a target UE or for the receiving UE itself. The operations of  1506  may be performed according to the methods described herein. In some example aspects, aspects of the operations of  1506  may be performed by a target UE determination component as described with reference to  FIGS. 6 through 9 . 
     At  1506 , in one example aspect, the UE may determine whether the received data transmission is for the target UE based on a received control message. The control message may indicate whether the data transmission is for the receiving UE or for the target UE via a downlink control information (DCI) field included in a PDCCH message. For example, the DCI field may have a one-bit field indicating whether or not the data transmission is for the receiving UE. 
     In another example aspect, the UE may determine whether the received data transmission is for the target UE via a map of a set of UEs. The map is capable of uniquely identifies the target UE. In one example aspect, the map can be of a format {G RNTI: targeted UE identity}. Hence when the UE uses the G RNTI to decode a received PDCCH, and then decode the corresponding data transmission in a PDSCH, the UE knows the data transmission is for a UE matching a targeted UE identity in the map. The map may be configured into the helper UE via in a semi-persistent manner in an RRC message from the network node. 
     At  1508 , the UE receives a trigger message from the base station to initiate forwarding of the received data transmission by the helper to the target UE. The operations of  1508  may be performed according to the methods described herein. In some example, aspects of the operations of  1506  may be performed by a retransmission trigger component  825  as described with reference to  FIGS. 6 through 9 . 
     In one example aspect, the trigger message is included in a control message received from the base station. In one example aspect, the UE receives the trigger message upon successfully decoding at least part of the data transmission and upon the UE transmitting an indication to the base station that at least part of the data transmission has been successfully decoded. In one example aspect, the trigger message further comprises a modulation and coding scheme (MCS), a precoding matrix indicator (PMI), and a rank indicator (RI) for the UE to retransmit the data transmission to the target UE. 
     In one example aspect, the step of receiving trigger message is optional and may be eliminated all together. The UE may initiate forwarding of the received data transmission without waiting for any trigger message. This helper UE behavior may be configured by the base station via an RRC message in a semi-persistent manner. 
     At  1510 , the UE retransmit the received data transmission to the target UE upon determining that the data transmission is intended for the target UE. The operations of  1510  may be performed according to the methods described herein. In some example aspects, aspects of the operations of  1510  may be performed by a data retransmission component as described with reference to  FIGS. 6 through 9 . 
     In one example aspect, the retransmitting of the data transmission includes forwarding the data transmission to the target UE after decoding at least part of the data transmission. In an alternative example aspect, the retransmitting of the data transmission includes forwarding the data transmission to the target UE without decoding any part of the received data transmission. The UE may know how to retransmit the initial data transmission based on a signaling message received from the network node. The control message received prior to receiving the initial data transmission may include an indication of whether or not a receiving UE shall process the data transmission intended for another UE. 
     At  1512 , the UE transmits an uplink ACK/NACK to the base station/network node to indicate whether the retransmission of the data transmission is successful. The uplink control message may be transmitted in a PUCCH. The operations of  1512  may be performed according to the methods described herein. In some example aspects, aspects of the operations of  1512  may be performed by the control component as described with reference to  FIGS. 6 through 9 . 
     The helper UE may send the ACK/NACK message to the base station upon receiving an ACK/NACK from the target UE. The target UE may send an ACK upon its successfully decoding of the forwarded data transmission on a sidelink between the target UE and the helper UE. The resource for the helper UE to send the ACK/NACK can be allocated in the downlink control message that carries the trigger message if the trigger message is present. In an alternative example, the sidelink resource allocation for the ACK/NACK can be carried in the downlink control message received at  1502 . 
     The method  1500  is for illustration purpose and shows one possible process for a UE or a helper UE to facilitate communications between the base station and a target UE using a sidelink channel. In practice, one or more steps shown in the illustrative flowchart for the method  1500  may be combined with other steps, performed in any suitable order, performed in parallel (e.g., simultaneously or substantially simultaneously), or removed. 
       FIG. 16  shows a flowchart illustrating a method  1600  in accordance with aspects of the present disclosure. The operations of method  1600  may be implemented by a network node such as a base station  105  of  FIG. 1  or a PLC node  210  of  FIG. 2 b   , or by some components of the network node as described herein. For example, the operations of method  1600  may be performed by a communications manager as described with reference to  FIGS. 10 through 13 . In some example aspects, a base station may execute a set of instructions to control the functional elements of the base station to perform the functions described below. Additionally or alternatively, a base station may perform aspects of the functions described below using special-purpose hardware. As described herein, the terms network node and base station may be used interchangeably, as made obvious by the context. 
     At  1602 , the network node transmits a control message to at least one helper UE. The operations of  1602  may be performed according to the methods described herein. In some example aspects, aspects of the operations of  1602  may be performed by a control message transmit component as described with reference to  FIGS. 10 through 13 . 
     At  1602 , the network node sends a control message to one or more helper UEs. In one example aspect, the control message is a PDCCH that may include a downlink control information (DCI) field to indicate whether a receiving UE shall process at least part of a subsequent data transmission that is meant for a UE other than the receiving UE, such as a target UE. The control message may include a sidelink resource allocation for retransmitting the data transmission if the data transmission is intended for the target UE. Also included in the control message may be a target UE identifier. 
     At  1604 , the network node may send an initial data transmission in either a unicast transmission to a helper UE or a multicast transmission to a group of UEs. If in a unicast transmission, the network node may send multiple unicast transmissions to multiple UEs. If in a multicast transmission, the network node may use a Group-Radio Radio Network Temporary Identifier (G-RNTI) to include a helper UE group and the target UE. In one example aspect, the initial data transmission is sent to the target UE and a failure to receive a positive ACK from the target UE may trigger the network node to send a trigger message to a helper UE to trigger the forwarding of the initial data transmission to the target UE. 
     The method  1600  is for illustration purpose and shows one possible process for a helper UE to facilitate communications between the base station and a target UE using a sidelink channel. In practice, one or more steps shown in the illustrative flowchart for the method  1600  may be combined with other steps, performed in any suitable order, performed in parallel (e.g., simultaneously or substantially simultaneously), or removed. 
       FIG. 17  shows a flowchart illustrating a method  1700  in accordance with aspects of the present disclosure. The operations of method  1700  may be implemented by a network node such as a base station  105  of  FIG. 1  or a PLC node  210  of  FIG. 2 b   , or by some components of the network node as described herein. For example, the operations of method  1700  may be performed by a communications manager as described with reference to  FIGS. 10 through 13 . 
     In some example aspects, a base station may execute a set of instructions to control the functional elements of the base station to perform the functions described below. Additionally or alternatively, a base station may perform aspects of the functions described below using special-purpose hardware. In the context of  FIGS. 14-17 , the terms network node and base station/PLC node may be used exchangeably, as made obvious in the context. 
     At  1702 , the network node transmits a control message to at least one helper UE. The operations of  1702  may be performed according to the methods described herein. In some example aspects, aspects of the operations of  1702  may be performed by a control message transmit component as described with reference to  FIGS. 10 through 13 . 
     In one example aspect, the control message is a PDCCH that may include a downlink control information (DCI) field to indicate whether a receiving UE shall process at least part of a subsequent data transmission that is meant for a UE other than the receiving UE, such as a target UE. The control message may include a sidelink resource allocation for retransmitting the data transmission if the data transmission is intended for the target UE. Also included in the control message may be a target UE identifier. 
     At  1704 , the network node may send an initial data transmission to a group of UEs. The group of UEs may include a helper UE group and a target UE. The data transmission may be in either a unicast transmission or a multicast transmission. If in a unicast transmission, the network node may send multiple transmissions to multiple UEs. If in a multicast transmission, the network node may use a Group-Radio Radio Network Temporary Identifier (G-RNTI) to include the UE group. In one example aspect, the initial data transmission is also sent to the target UE and a failure to receive a positive ACK from the target UE triggers the network node to send a trigger message to a helper UE to trigger the forwarding of the initial data transmission to the target UE. 
     At  1706 , the network node may receive an uplink control message including an ACK/NAK to the initial data transmission sent to the target UE and one or more helper UEs. The operations of  1704  may be performed according to the methods described herein. In some example aspects, aspects of the operations of  1602  may be performed by a control message receiving component as described with reference to  FIGS. 10 through 13 . 
     In one example aspect, the network node/base station may receive a positive ACK from the target UE, despite the fact that the base station had detected previously that the downlink channel to the target UE was broken. This may avoid the situation where a previously broken downlink channel between the network node and the target UE comes back, but the network node still trigger a helper UE to forward the data transmission to the target UE that already received the data transmission. 
     At  1708 , the network node may send a trigger message to a helper UE to initiate the forwarding of the initial data transmission to the target UE. The operations of  1708  may be performed according to the methods described herein. In some example aspects, aspects of the operations of  1708  may be performed by a trigger component as described with reference to  FIGS. 10 through 13 . 
     In one example aspect, the trigger message is included in a downlink control message sent from the network/base station. In one example aspect, the network node may send the trigger message upon receiving an indication from the helper UE that it has successfully decoded at least part of the data transmission. In one example aspect, the trigger message further comprises a modulation and coding scheme (MCS), a precoding matrix indicator (PMI), and a rank indicator (RI) for the helper UE to retransmit the data transmission to the target UE. 
     In one example aspect, the step of sending a trigger message is optional and may be eliminated all together. The network node may configure the helper UE to initiate the forwarding of the received data transmission without waiting for any trigger message. The network node may accomplish this via an RRC message in a semi-persistent manner. 
     At  1710 , the network node may receive an uplink ACK/NACK from the helper UE to indicate whether the retransmission of the data transmission to the target UE is successful. The uplink control may be transmitted in a PUCCH. The operations of  1710  may be performed according to the methods described herein. In some example aspects, aspects of the operations of  1710  may be performed by a control message receiving component as described with reference to  FIGS. 10 through 13 . 
     The helper UE may send the ACK/NACK message to the base station upon receiving an ACK/NACK from the target UE. The target UE may send an ACK upon its successfully decoding the forwarded data transmission on a sidelink between the target UE and the helper UE. The network node may allocate the ACK/NACK resource for the helper UE to send the ACK/NACK in the downlink control message that carries the trigger message if the trigger message is present. In an alternative example aspect, the resource allocation for the ACK/NACK can be carried in the downlink control message transmitted at  1702 . 
     The method  1700  is for illustration purpose and shows one possible process for a network node to transmit a data transmission to a target UE through a helper UE using a sidelink channel. In practice, one or more steps shown in the illustrative flowchart for the method  1700  may be combined with other steps, performed in any suitable order, performed in parallel (e.g., simultaneously or substantially simultaneously), or removed. 
     It should be noted that the methods described herein describe possible implementations, and that the operations and the steps may be rearranged or otherwise modified and that other implementations are possible. Further, aspects from two or more of the methods may be combined. 
     Although aspects of an LTE, LTE-A, LTE-A Pro, or NR system may be described for purposes of example, and LTE, LTE-A, LTE-A Pro, or NR terminology may be used in much of the description, the techniques described herein are applicable beyond LTE, LTE-A, LTE-A Pro, or NR networks. For example, the described techniques may be applicable to various other wireless communications systems such as Ultra Mobile Broadband (UMB), Institute of Electrical and Electronics Engineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Flash-OFDM, as well as other systems and radio technologies not explicitly mentioned herein. 
     Information and signals described herein may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof. 
     The various illustrative blocks and components described in connection with the disclosure herein may be implemented or performed with a general-purpose processor, a DSP, an ASIC, a CPU, an FPGA or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor may be a microprocessor, but in the alternative, the processor may be any processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices (e.g., a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration). 
     The functions described herein may be implemented in hardware, software executed by a processor, firmware, or any combination thereof If implemented in software executed by a processor, the functions may 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 may be implemented using software executed by a processor, hardware, firmware, hardwiring, or combinations of any of these. Features implementing functions may also be physically located at various positions, including being distributed such that portions of functions are implemented at different physical locations. 
     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 may be any available medium that may be accessed by a general-purpose or special purpose computer. By way of example, and not limitation, non-transitory computer-readable media may include random-access memory (RAM), read-only memory (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 may be used to carry or store desired program code means in the form of instructions or data structures and that may 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. 
     As used herein, including in the claims, “or” as used in a list of items (e.g., 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” may 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.” 
     In the appended figures, similar components or features may have the same reference label. Further, various components of the same type may be distinguished by following the reference label by a dash and a second label that distinguishes among the similar components. If just the first reference label is used in the specification, the description is applicable to any one of the similar components having the same first reference label irrespective of the second reference label, or other subsequent reference label. 
     The description set forth herein, in connection with the appended drawings, describes example configurations and does not represent all the examples that may be implemented or that are within the scope of the claims. The term “example” used herein means “serving as an example, instance, or illustration,” and not “preferred” or “advantageous over other examples.” The detailed description includes specific details for the purpose of providing an understanding of the described techniques. These techniques, however, may be practiced without these specific details. In some instances, known structures and devices are shown in block diagram form in order to avoid obscuring the concepts of the described examples. 
     The description herein is provided to enable a person having ordinary skill in the art to make or use the disclosure. Various modifications to the disclosure will be apparent to a person having ordinary skill in the art, and the generic principles defined herein may be applied to other variations without departing from the scope of the disclosure. Thus, the disclosure is not limited to the examples and designs described herein, but is to be accorded the broadest scope consistent with the principles and novel features disclosed herein.