SRS based discovery for device to device communication

Systems and methods establishing and maintain a direct User Equipment to User Equipment communication link are disclosed. A User Equipment (UE) may receive a Sounding Reference Signal (SRS) from a neighboring UE. The UE may determine from the SRS that the UE is a good candidate for a direct link. The UE may also determine from the SRS an ID associated with the neighboring UE. The UE may send a direct link request to the UE serving gNB. The serving gNB may forward the request to a gNB serving the neighboring UE. The gNBs may negotiate a joint schedule for a beam a UE to UE beam search. The beam search may be conducted using SRS resources. The results of the beam search may be sent to the gNB and the gNB may determine a beam pair for a direct link.

BACKGROUND

The following relates generally to wireless communication, and more specifically to discovery of User Equipment (UE) using a Sounding Reference Signal (SRS).

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 support communication with multiple users by sharing the available system resources (e.g., time, frequency, and power). Examples of such multiple-access systems include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, and orthogonal frequency division multiple access (OFDMA) systems, (e.g., Long Term Evolution (LTE) system, or a New Radio (NR) system). A wireless multiple-access communications system may include base stations (e.g., a gNB or eNB) or other access network nodes, each simultaneously supporting communication for multiple communication devices, which may be otherwise known as user equipment (UE).

In some wireless systems, base stations and UEs may communicate using directional millimeter wave transmissions (e.g., beams), where beamforming techniques may be applied using one or more antenna arrays or panels to generate beams in different directions. Directional millimeter wave transmissions are expected to be utilized by many 5G compliant devices such as UEs. In many instances, it may be desirable for UEs to establish a direct device to device communication link. UEs must discover good link candidates and identify good directional beams for device to device communication link. Moreover, UEs may need resources for performing a directional beam search.

Accordingly, there is a need for systems and methods for UEs to discover other UEs that may be suitable for direct UE to UE communication links. Establishing a direct link may require a beam search to determine beam pairs for the direct UE to UE communication link. The beam search may require resources for performing the beam search. The following disclosure addresses these needs as well as other needs.

SUMMARY

In one exemplary aspect, a User Equipment (UE) receives a Sounding Reference Signal (SRS) from a neighboring UE. The UE may determine from the SRS that the UE is a good candidate for a direct link. The UE may also determine from the SRS an ID associated with the neighboring UE. The UE may send a direct link request with the ID to the UE serving gNB. The serving gNB may forward the request to a gNB serving the neighboring UE. The gNBs may then negotiate a joint schedule for a UE to UE beam search. The beam search may be accomplished using SRS resources. The results of the beam search may be sent to the gNB. The gNB may determine a beam pair for a direct link. The beam pair information may be sent to the UEs allowing the UE and the neighboring UE to establish a direct link.

In another exemplary aspect, a first User Equipment (UE) may receive a Sounding Reference Signal (SRS) from a second UE and measure a signal quality of the SRS; the first UE may determine whether the second UE is a candidate for a direct link based on the signal quality measurement and transmit a request to a first gNB to establish a direct link with the second UE.

In another exemplary aspect, a second User Equipment (UE) may receive from a second gNB a request to establish a direct link with a first UE and may receive a joint schedule for a beam search from the second gNB. The second UE may perform a beam search procedure according to the joint schedule.

In another exemplary aspect, a first gNB may receive a request for a direct link from a first User Equipment (UE) and may transmit the request for a direct link to a second gNB. The second gNB may negotiate a joint schedule with the second gNB for a beam search.

In another exemplary aspect a second gNB may receive a request for a direct link from a first User Equipment (UE); and negotiate a joint schedule for a beam search with a first gNB.

DETAILED DESCRIPTION

FIG.1illustrates an example of a wireless communications system100in accordance with various aspects of the present disclosure. The wireless communications system100includes base stations105, UEs110, and a core network115. In some examples, the wireless communications system100may be a Long-Term Evolution (LTE), LTE-Advanced (LTE-A) network, or a New Radio (NR) network. In some cases, wireless communications system100may support enhanced broadband communications, ultra-reliable (i.e., mission critical) communications, low latency communications, and communications with low-cost and low-complexity devices. Wireless communications system100may support the use of a difference in transmit and receive array gains for the calculation of an uplink transmit power.

Base stations105may wirelessly communicate with UEs110via one or more base station antennas. Each base station105may provide communication coverage for a respective geographic coverage area130. Communication links135shown in wireless communications system100may include uplink transmissions from a UE110to a base station105, or downlink transmissions, from a base station105to a UE110. Other communication links such as device to device communication link138may be a direct UE110to UE110link. Control information and data may be multiplexed on an uplink channel or downlink according to various techniques. Control information and data may be multiplexed on a downlink channel, for example, using time division multiplexing (TDM) techniques, frequency division multiplexing (FDM) techniques, or hybrid TDM-FDM techniques. In some examples, the control information transmitted during a transmission time interval (TTI) of a downlink channel may be distributed between different control regions in a cascaded manner (e.g., between a common control region and one or more UE-specific control regions).

In some cases, a UE110may also be able to communicate directly with other UEs (e.g., using a peer-to-peer (P2P) or device-to-device (D2D) protocol). One or more of a group of UEs110utilizing D2D communications may be within the coverage area130of a cell. Other UEs110in such a group may be outside the coverage area130of a cell, or otherwise unable to receive transmissions from a base station105. In some cases, groups of UEs110communicating via D2D communications may utilize a one-to-many (1:M) system in which each UE110transmits to every other UE110in the group. In some cases, a base station105facilitates the scheduling of resources for D2D communications. In other cases, D2D communications are carried out independent of a base station105. UE110may transmit SRS and receive SRS allowing for UE110to discover neighboring UEs.

In some cases, an MTC device may operate using half-duplex (one-way) communications at a reduced peak rate. MTC devices may also be configured to enter a power saving “deep sleep” mode when not engaging in active communications. In some cases, MTC or IoT devices may be designed to support mission critical functions and wireless communications system may be configured to provide ultra-reliable communications for these functions.

Base stations105may communicate with the core network115and with one another. For example, base stations105may interface with the core network115through backhaul links (e.g.,51, etc.). Base stations105may communicate with one another over backhaul links134(e.g., X2, etc.) either directly or indirectly (e.g., through core network115). Backhaul links may be wired or unwired. Base stations105may perform radio configuration and scheduling for communication with UEs110or may operate under the control of a base station controller (not shown). In some examples, base stations105may be macro cells, small cells, hot spots, or the like. Base stations105may also be referred to as gNBs.

The core network120may provide user authentication, access authorization, tracking, Internet Protocol (IP) connectivity, and other access, routing, or mobility functions. At least some of the network devices, such as base station105may include subcomponents such as an access network entity, which may be an example of an access node controller (ANC). Each access network entity may communicate with a number of UEs110through a number of other access network transmission entities, each of which may be an example of a smart radio head, or a transmission/reception point (TRP). In some configurations, various functions of each access network entity or base station105may be distributed across various network devices (e.g., radio heads and access network controllers) or consolidated into a single network device (e.g., a base station105).

Wireless communications system100may operate in an ultra-high frequency (UHF) frequency region using frequency bands from 700 MHz to 2600 MHz (2.6 GHz), although some networks (e.g., a wireless local area network (WLAN)) may use frequencies as high as 5 GHz. This region may also be known as the decimeter band, since the wavelengths range from approximately one decimeter to one meter in length. UHF waves may propagate mainly by line of sight, and may be blocked by buildings and environmental features. However, the waves may penetrate walls sufficiently to provide service to UEs110located indoors. Transmission of UHF waves is characterized by smaller antennas and shorter range (e.g., less than 100 km) compared to transmission using the smaller frequencies (and longer waves) of the high frequency (HF) or very high frequency (VHF) portion of the spectrum. In some cases, wireless communications system100may also utilize extremely high frequency (EHF) portions of the spectrum (e.g., from 30 GHz to 300 GHz). This region may also be known as the millimeter band, since the wavelengths range from approximately one millimeter to one centimeter in length. Thus, EHF antennas may be even smaller and more closely spaced than UHF antennas. In some cases, this may facilitate use of antenna arrays within a UE110(e.g., for directional beamforming). However, EHF transmissions may be subject to even greater atmospheric attenuation and shorter range than UHF transmissions.

Wireless communications system100may support mmW communications between UEs110and base stations105and in backhaul links. Devices operating in mmW or EHF bands may have multiple antennas to allow beamforming. That is, a base station105may use multiple antennas or antenna arrays to conduct beamforming operations for directional communications with a UE110. Beamforming (which may also be referred to as spatial filtering or directional transmission) is a signal processing technique that may be used at a transmitter (e.g., a base station105) to shape and/or steer an overall antenna beam in the direction of a target receiver (e.g., a UE110). This may be achieved by combining elements in an antenna array in such a way that transmitted signals at particular angles experience constructive interference while others experience destructive interference.

Multiple-input multiple-output (MIMO) wireless systems use a transmission scheme between a transmitter (e.g., a base station105) and a receiver (e.g., a UE110), where both transmitter and receiver are equipped with multiple antennas. Some portions of wireless communications system100may use beamforming. For example, base station105may have an antenna array with a number of rows and columns of antenna ports that the base station105may use for beamforming in its communication with UE110. Signals may be transmitted multiple times in different directions (e.g., each transmission may be beamformed differently). A mmW receiver (e.g., a UE110) may try multiple beams (e.g., antenna subarrays) while receiving the synchronization signals.

In some cases, the antennas of a base station105or UE110may be located within one or more antenna arrays, which may support beamforming or MIMO operation. One or more base station antennas or antenna arrays may be collocated at an antenna assembly, such as an antenna tower. In some cases, antennas or antenna arrays associated with a base station105may be located in diverse geographic locations. A base station105may multiple use antennas or antenna arrays to conduct beamforming operations for directional communications with a UE110.

In some cases, wireless communications system100may utilize enhanced component carriers (eCCs). An eCC may be characterized by one or more features including: wider bandwidth, shorter symbol duration, shorter TTIs, and modified control channel configuration. In some cases, an eCC may be associated with a carrier aggregation configuration or a dual connectivity configuration (e.g., when multiple serving cells have a suboptimal or non-ideal backhaul link). An eCC may also be configured for use in unlicensed spectrum or shared spectrum (where more than one operator is allowed to use the spectrum). An eCC characterized by wide bandwidth may include one or more segments that may be utilized by UEs110that are not capable of monitoring the whole bandwidth or prefer to use a limited bandwidth (e.g., to conserve power).

In some cases, an eCC may utilize a different symbol duration than other CCs, which may include use of a reduced symbol duration as compared with symbol durations of the other CCs. A shorter symbol duration is associated with increased subcarrier spacing. A device, such as a UE110or base station105, utilizing eCCs may transmit wideband signals (e.g., 20, 40, 60, 80 MHz, etc.) at reduced symbol durations (e.g., 16.67 microseconds). A TTI in eCC may consist of one or multiple symbols. In some cases, the TTI duration (that is, the number of symbols in a TTI) may be variable.

A shared radio frequency spectrum band may be utilized in an NR shared spectrum system. For example, an NR shared spectrum may utilize any combination of licensed, shared, and unlicensed spectrums, among others. The flexibility of eCC symbol duration and subcarrier spacing may allow for the use of eCC across multiple spectrums. In some examples, NR shared spectrum may increase spectrum utilization and spectral efficiency, specifically through dynamic vertical (e.g., across frequency) and horizontal (e.g., across time) sharing of resources.

A UE110attempting to access a wireless network may perform an initial cell search by detecting a primary synchronization signal (PSS) from a base station105. The PSS may enable synchronization of slot timing and may indicate a physical layer identity value. The UE110may then receive a secondary synchronization signal (SSS). The SSS may enable radio frame synchronization, and may provide a cell identity value, which may be combined with the physical layer identity value to identify the cell. The SSS may also enable detection of a duplexing mode and a cyclic prefix length. After receiving the PSS and SSS, the UE110may receive a master information block (MIB), which may be transmitted in a physical broadcast channel (PBCH) by the base station105. The MIB may contain system bandwidth information, a system frame number (SFN), and a physical HARQ indicator channel (PHICH) configuration.

After decoding the MIB, the UE110may receive one or more system information blocks (SIBs). For example, SIB1 may contain cell access parameters and scheduling information for other SIBs. For instance, SIB1 access information, including cell identity information, and it may indicate whether a UE110is allowed to camp on a coverage area130. SIB1 also includes cell selection information (or cell selection parameters) and scheduling information for other SIBs, such as SIB2. Decoding SDB1 may enable the UE110to receive SIB2, where SIB2 may contain radio resource control (RRC) configuration information related to random access channel (RACH) procedures, paging, physical uplink control channel (PUCCH), physical uplink shared channel (PUSCH), power control, sounding reference signal (SRS), and cell barring. Different SIBs may be defined according to the type of system information conveyed. In some cases, SIB2 may be scheduled dynamically according to information in SIB1, and includes access information and parameters related to common and shared channels.

After the UE110decodes SIB2, it may transmit a RACH preamble to a base station105. For example, the RACH preamble may be randomly selected from a set of 64 predetermined sequences. This may enable the base station105to distinguish between multiple UEs110trying to access the system simultaneously. The base station105may respond with a random access response that provides an uplink resource grant, a timing advance, and a temporary cell radio network temporary identifier (C-RNTI). The UE110may then transmit an RRC connection request along with a temporary mobile subscriber identity (TMSI) (e.g., if the UE110has previously been connected to the same wireless network) or a random identifier. The RRC connection request may also indicate the reason the UE110is connecting to the network (e.g., emergency, signaling, data exchange, etc.). The base station105may respond to the connection request with a contention resolution message addressed to the UE110, which may provide a new C-RNTI. If the UE110receives a contention resolution message with the correct identification, it may proceed with RRC setup. If the UE110does not receive a contention resolution message (e.g., if there is a conflict with another UE110), the UE110may repeat the RACH process by transmitting a new RACH preamble.

Wireless devices in wireless communications system100may send transmissions in accordance with a certain link budget. The link budget may account for allowed signal attenuation between a UE110and a base station105, as well as antenna gains at the UE110and base station105. Accordingly, the link budget may provide, for example, a maximum transmit power for the various wireless devices within wireless communications system100. In some cases, a UE110may coordinate transmit power with a serving base station105to mitigate interference, improve the uplink data rate, and prolong battery life.

Some of the communication devices in wireless communication system100may have modems that include a direct link component. For example, a base station105may have a base station modem160having a direct link component. The direct link component may have a transmit component762for transmitting directional beams. The direct link component may also have a receive component764for receiving directional beams. The receive component764may direct link requests allowing the base station to forward the link request to another base station. The direct link component may have a direct link processing component766that may support processing direct link request messages, negotiating a joint schedule, and determining beam pairs. During a beam search procedure, the transmit component may transmit on SRS resources.

A UE110may have a UE modem140featuring a direct link component. The direct link component may have a transmit component642for transmitting directional beams. The direct link component may also have a receive component644for receiving one or more directional beams. The direct link component may also have a beam search procedure component646for executing beam search procedures. The beam search procedure component646may be adapted to executing a beam search procedure in cooperation with another UE using SRS resources. The direct link processing component may be adapted to discover neighboring UEs via an SRS and to determine if a direct link should be established with a neighboring UE.

FIG.2illustrates an example of a second UE discovering a first UE206in accordance with aspects of the present disclosure. Shown in the illustration is a first cell202having a first UE206and a first gNB208in its coverage area. The first UE206and the first gNB208are in communication through a first link207. Also shown in the illustration is a second cell204having a second UE210and a second gNB208in its coverage area. The second UE210is in communication with the second gNB212through a second link211.

The first UE206in communication with the first gNB208through first link207may occasionally transmit an SRS214. The SRS214may be transmitted by the UE206to enable the first gNB208to estimate uplink channel quality, or may be used for uplink timing estimation for example. The SRS may also be used by the second UE210for discovery purposes. The second UE210may receive the SRS214from a neighboring UE allowing the second UE210to discover other UEs transmitting SRS like the first UE206. The SRS may also include a UE ID associated with the first UE206allowing the second UE210to positively identify the first UE206. The second UE210may evaluate the signal strength and/or quality of the received SRS to determine if a direct link may be established between the first UE206and the second UE210. If the received SRS214signal strength and/or quality is strong, then a direct link between the first UE206and second UE210may be a good option.

FIG.3illustrates an example of a direct link timeline300in accordance with aspects of the present disclosure. The UEs shown in the diagram may be the same UEs as shown inFIG.1andFIG.2. Shown in theFIG.3is a timeline for a first UE301, a first gNB302, a second gNB304and a second UE306.

During operation, the first UE301may send an SRS307to the first gNB302. The second UE306may receive the SRS307and determine that the received SRS has a signal strength and/or quality that would make the second UE306a good candidate for establishing a direct UE to UE link. The second UE306may also determine the ID of the first UE301from the SRS and send a request for a direct link308to the second gNB304. The second gNB304may be the serving gNB for second UE306. The second gNB306may then in turn forward the request for a direct link310the first gNB302. The first gNB302may be the serving gNB for the first UE301. The gNB302may in turn forward the request for a direct link312to the first UE301.

To facilitate a beam search procedure, the first gNB302and the second gNB304may negotiate a joint schedule314for performing a beam search. The first gNB302may send the joint schedule316to the first UE301. Similarly, the second gNB304may send the joint schedule318to the second UE306. The joint schedule may be used to determine how and when a direct link beam search procedure between the first UE301and the second UE306will be performed. The joint schedule may also call for the use of SRS resources during the direct link beam search.

Those skilled in the art will recognize there are many protocols for executing a beam search. In one exemplary aspect the first UE301may transmit in a first Transmit Search (TS) beam320in a first beam direction. Then the first UE301may transmit in a second TS beam322in a second beam direction. The first UE301may continue transmitting in different search beams in different directions until an Nth transmission in TS beam N324is sent. During this procedure the second UE306may try to receive the transmissions on a first receive beam in a first direction. Then, the first UE can retransmit the N TS beam324a second time while the second UE306attempts to receive the transmit beams on a second receive beam. This transmit sequence can be repeated M times326allowing the second UE306to attempt to receive the N transmissions on all M receive beams.

During the beam search the second UE306may prepare a beam search report. The beam search report may contain beam pair IDs, Reference Signal Receive Power (RSRP), Signal to Interference Noise Ratio (SINR), the Signal to Noise Ratio (SNR), Interference Measurement Resource (IMR) or other indicia of the radio link quality. The second UE306may then send the beam report326to the second gNB304. The second gNB304may in turn send the beam report328to the first gNB302. The first gNB302may in turn send the beam report330to the first UE301. The first UE301and the second UE306may then establish a direct link332. In various aspects, the beam pairs for the direct link may be chosen by the first UE301, the second UE306, the first gNB302or the second gNB306.

FIG.4illustrates an example of beam search400in accordance with aspects of the present disclosure. The beam search may be executed by the UEs shown inFIGS.1-3for example. Shown inFIG.4are a first UE401and second UE406executing an exemplary beam search procedure. The first UE401may transmit in a first Transmit Search (TS 1) beam410in a first direction while the second UE406receives on a first Receive Search (RS 1) beam420. The first UE401may then transmit on TS 2 beam412in a second direction while the second UE406continues to receive on RS 1 beam420. The first UE401may sweep through all N TS beams until UE401transmits on TS N beam414while the second UE continues to receive on RS 1 beam420.

The first UE401may repeat the N TS beam transmit sweep again with the second UE attempting to receive on RS 2 beam422. The first UE401may repeat the transmit sweep M times with the second UE406attempting to receive on each RS beam until the final sweep when the second UE receives on the RS M beam M424.

FIG.5illustrates an example of a direct link request500in accordance with aspects of the present disclosure. The base stations (gNBs) and UEs shown inFIG.5may be the base stations shown inFIGS.1-4. Shown inFIG.5are a first UE501and a second UE506. The first UE506is being served by a first gNB510. The second UE501is being served by a second gNB512. The second UE506may transmit an SRS507and the first UE501may receive the SRS507. The first UE501may determine that the SRS507is a strong signal and determine that the second UE506is a good candidate for a direct link. The first UE501may then transmit a direct link request503to the first gNB510. The first gNB510may forward the direct link request505to the second gNB512. The second gNB512may in turn forward the direct link request509to the first UE506.

FIG.6illustrates an example of a flow diagram for a first UE600in accordance with aspects of the present disclosure. The first UE executing the flow may be one of the UEs shown inFIG.1-5for example. The first UE executing the flow may receive an SRS602. The first UE may evaluate the received signal strength604and/or quality (e.g. RSRP, SINR, SNR IMR etc.) of the SRS. A strong SRS may be a good indicator that a second UE transmitting the SRS is a good direct link candidate606. The SRS may contain an ID allowing the first UE to positively identify the second UE. If the second UE is good direct link candidate, the first UE may send a direct link request to the gNB608serving the first UE. The gNB may then forward the direct link request to a gNB serving the second UE. If it is determined that a link may be established the gNBs may negotiate a joint schedule for a beam search.

The first UE may then receive the joint schedule610from its serving gNB. The joint schedule may specify resources for performing a beam search. The joint schedule in some aspects, will assign SRS resources for the beam search. The joint schedule may also include transmitter and receiver assignments for performing the beam search. If the first UE is a receiver during the beam search it may send beam search results614to its serving gNB. The serving gNB may determine transmitter and receiver beam pairs for a direct link or receive information about beam pairs from the other gNB. The serving gNB may then communicate the beam pair information allowing the first UE to establish a direct link616with the second UE.

FIG.7illustrates an example of a flow diagram for a second UE700in accordance with aspects of the present disclosure. The second UE executing the flow may be one of the UEs shown inFIG.1-5for example. The second UE may transmit an SRS702. The SRS may include the second UEs ID. The SRS signal may be received by a first UE located near the second UE. The first UE may send a direct link request to its serving gNB, that may forward the direct link request to the second UEs serving gNB, that may in turn forward it to the second UE, allowing the second UE to receive the direct link request704. The second UE may also receive a joint schedule706from its serving base station allowing the second UE to perform a beam search procedure708with the first UE. The joint schedule in some aspects, will assign SRS resources for the beam search. The joint schedule may also include transmitter and receiver assignments for performing the beam search.

The second UE may perform the beam search procedure708according to the joint schedule. If the second UE is a receiver during the beam search it may send beam search results710to its serving gNB. The serving gNB may determine transmitter and receiver beam pairs for a direct link or receive information about beam pairs from the other gNB. The serving gNB may then communicate the beam pair information allowing the second UE to establish a direct link712with the first UE.

FIG.8illustrates an example of a flow diagram for a first gNB800in accordance with aspects of the present disclosure. The first gNB executing the flow may be one of the base stations shown inFIG.1-5for example. The first gNB may receive a direct link request from a first UE being served802. The first gNB may transmit a direct link request to the gNB serving the second UE804. The first gNB may negotiate a joint schedule with the gNB serving the second UE806. The joint schedule in some aspects, will assign SRS resources for the beam search. The joint schedule may also include transmitter and receiver assignments for performing the beam search.

The first gNB may then transmit the joint schedule to the first UE808. Using the joint schedule, the first UE may perform a beam search. If the first UE is the receiver during the beam search the first UE will transmit a beam search report allowing the first base station to receive a beam search report from the first UE810. If the first UE is the transmitter the first base station may receive a beam search report or beam pair information from the other gNB811. The first gNB may then send beam pair information812to the first UE allowing the first UE to establish a direct link with the second UE.

FIG.9illustrates an example of a flow diagram for a second gNB900in accordance with aspects of the present disclosure. The second gNB may receive a direct link request from another gNB serving a first UE902. The first gNB may transmit a direct link request to the second UE904. The second gNB may negotiate a joint schedule with the gNB serving the first UE906. The joint schedule in some aspects, will assign SRS resources for the beam search. The joint schedule may also include transmitter and receiver assignments for performing the beam search.

The second gNB may then transmit the joint schedule to the second UE908. Using the joint schedule, the second UE may perform a beam search. If the second UE is the receiver during the beam search the second UE will transmit a beam search report allowing the second base station to receive a beam search report810from the second UE. If the second UE is the transmitter the first base station may receive a beam search report or beam pair information911from the other gNB. The second gNB may then send beam pair information912to the second UE allowing the second UE to establish a direct link with the first UE.

Referring toFIG.10, in accordance with various aspects of the present disclosure an example of an implementation of UE1010is shown1000. UE1010may be one of the UEs110depicted inFIG.1-5for example. UE1010may also be one of the UEs shown inFIG.3and may be functional to carry out the flows shown inFIGS.7and8. It may include a variety of components, some of which have already been described above, but including components such as one or more processors1012and memory1016and transceiver1002in communication via one or more buses1044, which may operate in conjunction with modem1040and the direct link component to enable one or more of the functions described herein related to discovering another UE via an SRS or sending an SRS allowing other UEs to discover it. In other aspects some of the functions of modem1040may be performed by other processors1012. The transmit component1044and receive component1062may be used to perform beam searches including beam searches that use SRS resources. Further, the one or more processors1012, modem1040, memory1016, transceiver1002, RF front end1088and one or more antennas1065, may be configured to support voice and/or data calls (simultaneously or non-simultaneously) in one or more radio access technologies as well as radar.

In an aspect, the one or more processors1012can include a modem1040that uses one or more modem processors. The various functions related to the direct link component may be included in modem1040and/or processors1012and, in an aspect, can be executed by a single processor, while in other aspects, different ones of the functions may be executed by a combination of two or more different processors. For example, in an aspect, the one or more processors1012may include any one or any combination of a modem processor, or a baseband processor, or a digital signal processor, or a transmit processor, or a receiver processor, or a transceiver processor associated with transceiver1002. In other aspects, some of the features of the one or more processors1012and/or modem1040associated with modem1040may performed by transceiver1002.

Also, memory1016may be configured to store data used herein and/or local versions of applications1075or the direct link component and/or one or more of its subcomponents being executed by at least one processor1012. Memory1016can include any type of computer-readable medium usable by a computer or at least one processor1012, such as random-access memory (RAM), read only memory (ROM), tapes, magnetic discs, optical discs, volatile memory, non-volatile memory, and any combination thereof. In an aspect, for example, memory1016may be a non-transitory computer-readable storage medium that stores one or more computer-executable codes defining radar component and/or one or more of its subcomponents, and/or data associated therewith, when UE1010is operating at least one processor1012.

Transceiver1002may include at least one receiver1006and at least one transmitter1008. Receiver1006may include hardware, firmware, and/or software code executable by a processor for receiving data, the code comprising instructions and being stored in a memory (e.g., computer-readable medium). Receiver1006may be, for example, a radio frequency (RF) receiver. In an aspect, receiver1006may receive signals transmitted by at least one base station. Additionally, receiver1006may process such received signals, including SRS, and also may obtain measurements of the signals, such as, but not limited to, Ec/Io, SNR, RSRP, RSSI, etc. Transmitter1008may include hardware, firmware, and/or software code executable by a processor for transmitting data, the code comprising instructions and being stored in a memory (e.g., computer-readable medium). A suitable example of transmitter1008may including, but is not limited to, an RF transmitter.

Moreover, in an aspect, UE1010may include RF front end1088, which may operate in communication with one or more antennas1065and transceiver1002for receiving and transmitting radio transmissions, for example, wireless communications transmitted by at least one base station or wireless transmissions transmitted by UE. RF front end1088may be connected to one or more antennas1065and can include one or more low-noise amplifiers (LNAs)1090, one or more switches1092, one or more power amplifiers (PAs)1098, and one or more filters1096for transmitting and receiving RF signals.

In an aspect, LNA1090can amplify a received signal at a desired output level. In an aspect, each LNA1090may have a specified minimum and maximum gain values. In an aspect, RF front end1088may use one or more switches1092to select a particular LNA1090and its specified gain value based on a desired gain value for a particular application.

Further, for example, one or more PA(s)1098may be used by RF front end1088to amplify a signal for an RF output at a desired output power level. In an aspect, each PA1098may have specified minimum and maximum gain values. In an aspect, RF front end1088may use one or more switches1092to select a particular PA1098and its specified gain value based on a desired gain value for a particular application.

Also, for example, one or more filters1096can be used by RF front end1088to filter a received signal to obtain an input RF signal. Similarly, in an aspect, for example, a respective filter1096can be used to filter an output from a respective PA1098to produce an output signal for transmission. In an aspect, each filter1096can be connected to a specific LNA1090and/or PA1098. In an aspect, RF front end1088can use one or more switches892to select a transmit or receive path using a specified filter1096, LNA1090, and/or PA1098, based on a configuration as specified by transceiver1002and/or processor1012.

As such, transceiver1002may be configured to transmit and receive wireless signals through one or more antennas1065via RF front end1088. In an aspect, transceiver may be tuned to operate at specified frequencies such that UE can communicate with, for example, one or more base stations or one or more cells associated with one or more base stations. In an aspect, for example, modem1040can configure transceiver1002to operate at a specified frequency and power level based on the UE configuration of the and the communication protocol used by modem1040.

In an aspect, modem1040can be a multiband-multimode modem, which can process digital data and communicate with transceiver1002such that the digital data is sent and received using transceiver1002. In an aspect, modem1040can be multiband and be configured to support multiple frequency bands for a specific communications protocol. In an aspect, modem1040can be multimode and be configured to support multiple operating networks and communications protocols. In an aspect, modem1040can control one or more components of UE (e.g., RF front end1088, transceiver1002) to enable transmission and/or reception of signals from the network based on a specified modem configuration. In an aspect, the modem configuration can be based on the mode of the modem and the frequency band in use. In another aspect, the modem configuration can be based on UE configuration information associated with as provided by the network during cell selection and/or cell reselection.

Referring toFIG.11, in accordance with various aspects of the present disclosure an example of an implementation of base station, such as one of the base stations (gNBs) shown inFIGS.1-3and5that may include a variety of components, some of which have already been described above, but including components such as one or more processors1112and memory1116and transceiver1102in communication via one or more buses1144, which may operate in conjunction with modem1160and direct link component o enable one or more of the functions described herein related to establishing a direct UE to EE link via an SRS discovery process. The base station shown inFIG.11may be also configured to execute the flows inFIGS.9-10.

The transceiver1102, receiver1106, transmitter1108, one or more processors1112, memory1116, applications1175, buses1144, RF front end1188, LNAs1190, switches1192, filters1196, PAs1198, and one or more antennas1165may be the same as or similar to the corresponding components of UE, as described above, but configured or otherwise programmed for base station operations as opposed to UE operations.