CN112314030A - Device-to-device (D2D) communication management techniques - Google Patents

Abstract

Methods and apparatus are provided that may be used in a base station and/or User Equipment (UE) to support or otherwise provide device-to-device (D2D) communication between candidate UEs in a shared radio spectrum. For example, the base station may determine that the first UE and the second UE are candidates for D2D communication and provide and indicate a grant-free uplink (GUL) resource allocation for D2D communication between the first UE and the second UE. The base station may further monitor D2D communications.

Description

Device-to-device (D2D) communication management techniques

This application claims priority and benefit of U.S. application serial No. 16/014,799 filed on 2018, 21/6 with the united states patent and trademark office, the entire contents of which are incorporated by reference as if fully set forth below and for all applicable purposes.

Technical Field

The following generally relates to wireless communications, and more particularly to techniques for supporting or otherwise managing device-to-device (D2D) communications, and more particularly to techniques for D2D communications potentially via unlicensed uplink (GUL) resources in a shared radio spectrum.

Background

Wireless communication 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., broadcast spectrum with respect to time, frequency, space, and/or power related aspects). Some examples of multiple access systems include fourth generation (4G) systems, such as Long Term Evolution (LTE) systems or LTE-Advanced (LTE-a) systems, and fifth generation (5G) systems, which may be referred to as New Radio (NR) systems. These systems may employ techniques such as Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), Orthogonal Frequency Division Multiple Access (OFDMA), or discrete fourier transform spread OFDM (DFT-S-OFDM). A wireless multiple-access communication system may include several base stations or network access nodes, each supporting communication for multiple communication devices, which may be otherwise referred to as User Equipment (UE).

These multiple access techniques have been employed in various telecommunications standards to provide a common protocol that enables different wireless devices to communicate on a municipal, national, regional, and even global level. For example, a fifth generation (5G) wireless communication technology, which may be referred to as a New Radio (NR), is contemplated to extend and support various usage scenarios and applications relative to current generations of mobile networks. In one aspect, the 5G communication technology may include: enhanced mobile broadband that addresses human-centric use cases to access multimedia content, services and data; ultra Low Latency (ULL) and/or Ultra Reliable Low Latency Communication (URLLC) with certain specifications for latency and reliability; and large-scale machine-type communications, which may allow for a very large number of connected devices and transmit relatively small amounts of non-delay sensitive information. However, as the demand for mobile broadband access continues to grow, further improvements in NR communication technology may be needed.

For example, a 5G NR may provide greater flexibility in wireless communications. This increased flexibility may be applied to different aspects of wireless communications, including various mechanisms and techniques for scheduling or communicating (e.g., signaling) information regarding assignments and/or feedback for transmissions. Therefore, new techniques for potential device-to-device (D2D) communication are needed, particularly D2D communication that uses, at least in part, unlicensed uplink (GUL) resources in a shared radio spectrum.

Disclosure of Invention

The described technology relates to improved methods, systems, devices or apparatus that may be used to support D2D communications that may be made at least in part using a gil resource in a shared radio spectrum.

According to certain example aspects of the present disclosure, a method for use at a first UE may be provided. The method may include receiving, at a first UE, an indication that a gil resource allocation has been or will be provided for D2D communications between the first UE and a second UE. The indication may be sent, for example, by the base station. The method may further comprise: at the first UE, D2D communication is supported at least in part by transmitting a first signal intended for the second UE via at least a first portion of a GUL resource allocation and receiving a second signal from the second UE via at least a second portion of the GUL resource allocation.

According to certain other example aspects of the present disclosure, there may be provided a first UE including a receiver, a transmitter, and a processing unit. The processing unit may be coupled to the receiver and the transmitter, and configured to obtain an indication that a GUL resource allocation has been or will be provided for D2D communication between the first UE and the second UE. The indication may be transmitted, for example, by the base station and received by the first UE via the receiver. The processing unit may be further configured to support D2D communication, for example, by initiating, via the transmitter, transmission of a first signal intended for a second UE via at least a first portion of a GUL resource allocation, and obtaining, via the receiver, a second signal from the second UE via at least a second portion of the GUL resource allocation.

According to still other example aspects of the present disclosure, a method for use at a base station may be provided. The method may include determining, at a base station, to provide a GUL resource allocation for D2D communication between a first UE and a second UE, and sending at least one indication to the first UE, the second UE, or both, wherein the at least one indication identifies at least a portion of the GUL resource allocation for use by the first UE, the second UE, or both, to support D2D communication therebetween.

According to some other example aspects of the present disclosure, there may be provided a base station including a receiver, a transmitter, and a processing unit. The processing unit may be coupled to the receiver and the transmitter and configured to determine to provide a GUL resource allocation for D2D communications between the first UE and the second UE, and initiate transmission of at least one indication to the first UE, the second UE, or both via the transmitter, wherein the at least one indication identifies at least a portion of the GUL resource allocation for use by the first UE, the second UE, or both to support D2D communications therebetween.

Drawings

Fig. 1 illustrates an example of a system for wireless communication that may support D2D channel measurements and/or D2D communications in accordance with certain aspects of the present disclosure.

Fig. 2A, 2B, 2C, and 2D are diagrams illustrating examples of downlink DL frame structures, DL channels within DL frame structures, uplink UL frame structures, and UL channels within UL frame structures, which may be measurable or otherwise potentially used to support D2D channel measurements and/or D2D communications, for example, as the system shown in fig. 1, in accordance with certain aspects of the present disclosure.

Fig. 3 is a schematic diagram illustrating an example of a base station and User Equipment (UE) that may support D2D channel measurements and/or D2D communications, e.g., as with the system shown in fig. 1, in accordance with certain aspects of the present disclosure.

Fig. 4 is a flow diagram illustrating an example method used by a base station to support D2D communication between two UEs in accordance with certain aspects of the present disclosure.

Fig. 5 is a flow diagram illustrating an example method for use by a UE to support D2D communication with another UE in accordance with certain aspects of the present disclosure.

Fig. 6 is a schematic diagram illustrating some example components that may be included within a base station in accordance with certain aspects of the present disclosure.

Fig. 7 is a schematic diagram illustrating some example components that may be included within a UE in accordance with certain aspects of the present disclosure.

Fig. 8 is a paging flow diagram illustrating some example message exchanges that may be used, at least in part, to implement a D2D communication technique in accordance with certain aspects of the present disclosure.

Detailed Description

Various aspects are now described with reference to the drawings. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of one or more aspects. It may be evident, however, that such aspect(s) may be practiced without these specific details.

In a cellular communication network, wireless devices may typically communicate with each other via one or more network entities such as base stations or scheduling entities. Some networks may additionally or alternatively support D2D communications that enable discovery and communication with nearby devices using direct links between devices (e.g., without having to communicate messages through base stations, relays, or other nodes). D2D communication may, for example, enable mesh network and device-to-network relay functionality. Some examples of D2D technology include Bluetooth pairing, Wi-Fi Direct (Direct), Miracast, and LTE-D. D2D communication may also be referred to as point-to-point (P2P) or sidelink communication.

D2D communication may be implemented using licensed or unlicensed frequency bands. D2D communication may avoid the overhead involved with routing to and from the base station. Thus, in some cases, D2D communication may provide better throughput, lower latency, and/or higher energy efficiency. MuLTEfire is a form of Long Term Evolution (LTE) network that may support D2D communications using unlicensed frequency bands. MuLTEfire may be used in any unlicensed spectrum where the use of spectrum is competing, although it was originally intended for deployment in 5GHz unlicensed bands in the united states and potentially also in 3.5GHz shared bands. MuLTEfire implements Listen Before Talk (LBT) policy for coexistence management. For example, when the UE is accessing a channel in the MuLTEfire communication system, the UE may perform a first LBT procedure (e.g., 25 μ β) if within the base station TxOP. If not within the base station TxOP, the UE may perform a second LBT procedure (e.g., cat.4LBT with random backoff). Further, the UE may be configured to start the LBT procedure at a different starting position/time to reduce collisions between one or more other UEs.

Aspects of the present disclosure provide methods and apparatus for supporting (e.g., initiating, managing, monitoring, ending, etc.) D2D communications, and in particular examples, utilizing, at least in part, unlicensed uplink (GUL) resources in a shared radio spectrum. When a UE transmits data without first requesting authorization of certain network resources from a base station or scheduling entity, such data transmission may be referred to as unlicensed or unlicensed traffic. In some wireless communication systems, base stations may coordinate with each other in allocating GUL resources for D2D connections or channels between UEs that are across cells. The base station may provide a GUL resource allocation (e.g., indication of activation/release, etc.) message to the UE. In some embodiments, such a GUL resource allocation message may be sent in a semi-persistent scheduling manner. For example, the UE may monitor for such messages as part of Downlink Control Information (DCI).

In a wireless communication system that may use a shared radio spectrum, a GUL transmission may be implemented in addition to a grant-based uplink transmission (e.g., DCI). A network entity (e.g., a base station) may allocate the GUL resources to one or more UEs, e.g., for D2D communication. For example, a first UE may allocate a GUL resource for D2D communications with a second UE in a shared radio spectrum. D2D communication in the shared radio spectrum may be implemented in a more centralized control mode, which may include more monitoring/assistance of the base station than is the case in a distributed control mode, where the UE may be configured to have more control over D2D communication.

A technique is described in which a shared radio spectrum is used for at least a portion of communications in a wireless communication system. In some examples, the shared radio spectrum may be used for Long Term Evolution (LTE) or LTE-Advanced (LTE-a) communications, Licensed Assisted Access (LAA) communications, enhanced LAA (elaa) communications, or MuLTEfire communications. The shared radio spectrum may be used in conjunction with or independent of the dedicated radio spectrum. The dedicated radio spectrum may include radio spectrum licensed for a particular user/device for a particular purpose. The shared radio spectrum may include spectrum available for Wi-Fi use, radio spectrum available for different radio access technologies, radio spectrum available for multiple Mobile Network Operators (MNOs) in an equally shared or prioritized manner, and so on.

In view of this background, as described in more detail herein, in certain example embodiments, a base station may be configured to determine to provide a GUL resource allocation for use in D2D communications between a first UE and a second UE. For example, a GUL resource allocation may be provided as part of a MultEfire framework or the like. The base station that has made such a determination may send one or more indications to the first UE and the second UE that identify all or an applicable portion of the GUL resource allocation for use by the first UE, the second UE, or both, to support D2D communication therebetween.

For example, the base station may identify the first UE and the second UE as D2D communication candidates based at least in part on one or more messages received from the first UE and/or the second UE, e.g., indicating an estimated location, range, etc. In another example, the base station may receive one or more requests for D2D communication from the first UE, the second UE, or both, and determine that D2D communication may be provided based at least in part on one or more such requests. In some cases, the base station may identify that such D2D communication may be provided based on other received information. For example, the base station may monitor/measure channel conditions, consider resource allocation, etc., which may inform D2D, at least in part, of the communication determination.

In some cases, once the D2D communication has been initiated, the base station is configured to monitor the D2D communication in some manner. For example, the base station may monitor the D2D communication by receiving a first signal via at least a first portion of the GUL resource allocation and/or a second signal via at least a second portion of the GUL resource allocation, wherein the first signal is transmitted from the first UE to the second UE and the second signal is transmitted by the second UE to the first UE as part of the D2D communication. Here, in some cases, the first portion of such a GUL resource allocation and the second portion of such a GUL resource allocation may comprise the same GUL resource allocation or different GUL resource allocations. In some embodiments, the first or second portion of the GUL resource allocation may comprise at least a portion of a previous GUL resource allocation provided to the first or second UE (respectively) to, for example, transmit certain (possibly non-D2D communications) signals intended primarily for the base station. In some embodiments, the base station may monitor D2D communications by monitoring traffic signals transmitted using the GUL resource allocations of D2D communications, ACK/NACK (HARQ, etc.), "keep-alive (keep-alive)" signals, etc.

The base station may, for example, be configured to end the D2D communication, e.g., by changing the gil resource allocation, notifying the UE, etc. For example, the base station may decide to end D2D communications based at least in part on one or more D2D channel measurement threshold parameters, one or more UE Sounding Reference Signal (SRS) threshold parameters, one or more D2D communication timeout threshold parameters, one or more D2D communication termination requests, a base station handover determination, a GUL resource reallocation determination, or some combination thereof, etc.

To support D2D communications, the first UE and the second UE may together or independently receive one or more indications that a GUL resource allocation has been or will be provided for D2D communications between the first UE and the second UE. In response to one or more such applicable indications, for example, the first UE may support D2D communication by transmitting a first signal intended for the second UE via at least a first portion of the GUL resource allocation and receiving a second signal from the second UE via at least a second portion of the GUL resource allocation. Similarly, for example, the second UE may support D2D communication by transmitting a second signal intended for the first UE via at least a second portion of the gil resource allocation and receiving a first signal from the first UE via at least a first portion of the gil resource allocation.

As mentioned, in certain embodiments, the first UE, the second UE, or both may be configured to send the request(s) for D2D communication to the base station. For example, the first UE may be configured to determine D2D channel measurements for SRS transmissions by the second UE and determine whether to transmit a request to the base station based at least in part on the D2D channel measurements. Further, in some embodiments, to support D2D communications, the first UE, the second UE, or both may be configured to transmit, for example, traffic, SRS, "continuously active" signals, etc., that may be used by the base station to monitor and maintain D2D communications.

The D2D communication may allow one of the UEs to communicate directly with another of the UEs, which may increase throughput, reduce latency, extend range (coverage area), improve energy efficiency, or some combination thereof, to name a few non-limiting examples. Thus, D2D communications may potentially be beneficial for various social applications, such as games, media sharing, location-based services, and the like. In another example, such D2D communications may potentially be beneficial with respect to wearable devices or other similar devices (e.g., smartphones, smartwatches, smart glasses, headsets, etc.) that may be collocated, particularly for data intensive communications (such as media streaming, augmented reality, virtual reality, etc.). In yet another potential example, such D2D communication may potentially be beneficial to internet of things (IoT) devices and the like, some or all of which may benefit by conserving battery power or other similar stored/available power.

Accordingly, those skilled in the art will recognize that the D2D channel measurement technique provided by way of example herein may be beneficial for a variety of different or same/similar types of UEs. Thus, for example, in certain embodiments, some UEs may include smart phones, tablets, laptops, positioning/tracking devices, wearable devices, display/glasses devices, vehicles, machines, electrical robots, drones, internet of things (IoT) devices, circuitry (e.g., controllers, sensors, actuators, data storage, etc.), and the like, or some combination thereof. Although an example is shown with two UEs, in some cases, the techniques provided herein may be implemented to support D2D communication between more than two UEs.

The present description includes some example D2D communication techniques, which are shown as may be implemented for an example framework (e.g., MuLTEfire 1.1) or other similarly configured device/network. It is to be appreciated, however, that unless specifically stated otherwise, the claimed subject matter is not intended to be so limited, as one of ordinary skill in the art will recognize, upon reading this specification and the accompanying drawings, that such exemplary techniques can be implemented in other types of frameworks/protocols, networks, signals, and the like.

Attention is now directed to fig. 1, which illustrates an example of a wireless communication system 100 that supports D2D communication, e.g., using, at least in part, a GUL resource in a shared radio spectrum, in accordance with various aspects of the present disclosure. The wireless communication system 100 may include, for example, base stations 105, UEs 115, and a core network 130. In some examples, the wireless communication system 100 may include a Long Term Evolution (LTE) network, an LTE-Advanced (LTE-a) network, or a New Radio (NR) network. In some cases, the wireless communication 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, and so forth.

In some examples, the wireless communication network 100 may include one or any combination of communication technologies including New Radio (NR) or 5G technologies, LTE-A, MuLTEfire technologies, Wi-Fi technologies, bluetooth technologies, or any other long or short range wireless communication technologies/frameworks. In an LTE/LTE-a/MuLTEfire network, the term evolved node b (enb) may be used generally to describe the base station 105, while the term UE may be used generally to describe the UE 115. The wireless communication network 100 may be a heterogeneous technology network in which different types of enbs provide coverage for various geographic areas. For example, an eNB or base station 105 may provide communication coverage for a macro cell, a small cell, or other type of cell. The term "cell" is a 3GPP term that can be used to describe a base station, a carrier or component carrier associated with a base station, or a coverage area (e.g., sector, etc.) of a carrier or base station, depending on the context.

The base station 105 may wirelessly communicate with the UE115 via one or more base station antennas. The base station 105 described herein may include or may be referred to by those skilled 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 Node B or a gigabit Node B (any of which may be referred to as a gNB), a home NodeB, a home eNodeB, or some other suitable terminology. The wireless communication system 100 may include different types of base stations 105 (e.g., macro cell base stations or small cell base stations). The UEs 115 described herein may be capable of communicating with various types of base stations 105 and network equipment, including macro enbs, small cell enbs, gnbs, relay base stations, and the like.

As shown in fig. 1, a base station 105 may be associated with a geographic coverage area 110, where communications with various UEs 115 are supported in the geographic coverage area 110. The base stations 105 may provide communication coverage for respective geographic coverage areas 110 via communication links 125, and the communication links 125 between the base stations 105 and the UEs 115 may utilize one or more carriers. The communication links 125 shown in the wireless communication system 100 may include uplink transmissions from the UEs 115 to the base stations 105 or downlink transmissions from the base stations 105 to the UEs 115. Downlink transmissions may also be referred to as forward link transmissions, and uplink transmissions may also be referred to as reverse link transmissions.

The geographic coverage area 110 of a base station 105 can be divided into sectors that form only a portion of the geographic coverage area 110, and each sector can be associated with a cell. For example, each base station 105 may provide communication coverage for a macro cell, a small cell, a hotspot, or other type of cell, or various combinations thereof. In some examples, the base stations 105 may be mobile and thus provide communication coverage for a moving geographic coverage area 110. In some examples, different geographic coverage areas 110 associated with different technologies may overlap, and the overlapping geographic coverage areas 110 associated with different technologies may be supported by the same base station or different base stations. The wireless communication system 100 may include, for example, a heterogeneous LTE/LTE-a or NR network in which different types of base stations provide coverage for various geographic coverage areas 110.

The term "cell" refers to a logical communication entity for communicating with the base station 105 (e.g., over a carrier) and may be associated with an identifier (e.g., Physical Cell Identifier (PCID), Virtual Cell Identifier (VCID)) for distinguishing neighboring cells operating via the same or different carrier. In some examples, one carrier may support multiple cells, and different cells may be configured according to different protocol types (e.g., Machine Type Communication (MTC), narrowband internet of things (NB-IoT), enhanced mobile broadband (eMBB), or others) that may provide access for different types of devices. In some cases, the term "cell" may refer to a portion (e.g., a sector) of geographic coverage area 110 over which a logical entity operates.

UEs 115 may be dispersed throughout the wireless communication system 100, and sometimes such UEs 115 may be fixed or mobile. UE115 may also be referred to as a mobile device, a wireless device, a remote device, a handset, or a subscriber device, or some other suitable terminology, where a "device" may also be referred to as a unit, station, terminal, or client. The UE115 may also be a personal electronic device, such as a cellular telephone, a Personal Digital Assistant (PDA), a tablet computer, a laptop computer, or a personal computer. In some examples, the UE115 may also refer to a Wireless Local Loop (WLL) station, an internet of things (IoT) device, an internet of everything (IoE) device, or an MTC device, among others, which may be implemented in various items such as appliances, vehicles, meters, and so forth.

Some UEs 115, such as MTC or IoT devices, may be low cost or low complexity devices and may provide automated communication between machines (e.g., via machine-to-machine (M2M) communication). M2M communication or MTC may refer to data communication techniques that allow devices to communicate with each other or with a base station 105 without human intervention. In some examples, M2M communications or MTC may include communications from devices that integrate sensors or meters to measure or capture information and relay the information to a central server or application that may use the information or present the information to a person interacting with the program or application. Some UEs 115 may be designed to collect information or implement automatic behavior of a machine. Examples of applications for MTC devices include smart metering, inventory monitoring, water level monitoring, device monitoring, healthcare monitoring, wildlife monitoring, weather and geological event monitoring, fleet management and tracking, remote security sensing, physical access control, and transaction-based business billing.

Some UEs 115 may be configured to employ a reduced power consumption mode of operation, such as half-duplex communications (e.g., a mode that supports unidirectional communications via transmission or reception but not both). In some examples, half-duplex communication may be performed at a reduced peak rate. Other power saving techniques for the UE115 include entering a power-saving "deep sleep" mode when not engaged in active communication, or operating on a limited bandwidth (e.g., according to narrowband communication). In some cases, the UE115 may be designed to support critical functions (e.g., mission critical functions), and the wireless communication system 100 may be configured to provide ultra-reliable communication for these functions.

In some cases, the UE115 may also be capable of other direct communications with other UEs 115 (e.g., using peer-to-peer (P2P), device-to-device (D2D) protocols, etc.). One or more UEs in the group of UEs 115 communicating with D2D may be within the geographic coverage area 110 of the base station 105. The other UEs 115 in the group may be outside the geographic coverage area 110 of the base station 105 or otherwise unable to receive transmissions from the base station 105. In some cases, a group of UEs 115 communicating via D2D communication may utilize a one-to-many (1: M) system in which each UE115 transmits to every other UE115 in the group. In some cases, the base station 105 may facilitate scheduling/allocation of resources for D2D communication. In other cases, some D2D communications may be performed between UEs 115 without the participation of base stations 105.

The base stations 105 may communicate with the core network 130 and may communicate with each other. For example, the base station 105 may interface with the core network 130 over a backhaul link 132 (e.g., via S1 or other interface). The base stations 105 may communicate with each other over backhaul links 134 (e.g., via X2 or other interface) either directly (e.g., directly between base stations 105) or indirectly (e.g., via core network 130).

The core network 130 may provide user authentication, access authorization, tracking, Internet Protocol (IP) connectivity, and other access, routing, or mobility functions. Core network 130 may be an Evolved Packet Core (EPC) that may include at least one Mobility Management Entity (MME), at least one serving gateway (S-GW), and at least one Packet Data Network (PDN) gateway (P-GW). The MME may manage non-access stratum (e.g., control plane) functions such as mobility, authentication, and bearer management for UEs 115 served by base stations 105 associated with the EPC. User IP packets may be communicated through the S-GW, which may itself be connected to the P-GW. The P-GW may provide IP address assignment as well as other functions. The P-GW may be connected to a network operator IP service. The operator IP services may include access to the internet, intranet(s), IP Multimedia Subsystem (IMS), or Packet Switched (PS) streaming services.

Some of the network devices, such as base stations 105, may include subcomponents, such as access network entities, which may be examples of Access Node Controllers (ANCs). Each access network entity may communicate with UE115 through a number of other access network transmitting entities, which may be referred to as radio heads, smart radio heads, or transmit/receive points (TRPs). In some configurations, the various functions of each access network entity or base station 105 may be distributed across various network devices (e.g., radio heads and access network controllers) or incorporated into a single network device (e.g., base station 105).

The wireless communication system 100 may operate using one or more frequency bands, typically in the range of 300MHz to 300 GHz. Generally, the region of 300MHz to 3GHz is referred to as the Ultra High Frequency (UHF) region or the decimeter band because the length of the wavelength ranges from about one decimeter to one meter. Building and environmental features may block or redirect UHF waves. However, the waves may penetrate the structure sufficiently to be served by the macro cell to the UE115 located indoors. UHF-wave transmission can be associated with smaller antennas and shorter distances (e.g., less than 100km) than longer-wave transmission using the smaller frequencies of the high-frequency (HF) or very-high-frequency (VHF) portions of the spectrum below 300 MHz.

The wireless communication system 100 may also operate in an ultra high frequency (SHF) region, also referred to as a centimeter frequency band, using a frequency band of 3GHz to 30 GHz. The SHF area includes frequency bands such as the 5GHz industrial, scientific, and medical (ISM) bands, which can be used opportunistically by devices that can tolerate interference from other users.

The wireless communication system 100 may also operate in the Extremely High Frequency (EHF) region of the spectrum, also referred to as the millimeter band (mm hz), e.g., from 30GHz to 300 GHz. In some examples, the wireless communication system 100 may support millimeter wave (mmW) communication between the UEs 115 and the base station 105, and the EHF antennas of the various devices may be even smaller and more closely spaced than UHF antennas. In some cases, this may facilitate the use of antenna arrays within the UE115 (e.g., for multiple-input multiple-output (MIMO) operations, such as spatial multiplexing, or for directional beamforming). However, the propagation of EHF transmissions may suffer from even greater atmospheric attenuation and shorter range than SHF or UHF transmissions. The techniques disclosed herein may be employed between transmissions using one or more different frequency regions, and the designated use of the frequency bands across these frequency regions may vary from country to country or regulatory agency to country.

In some cases, the wireless communication system 100 may utilize both a licensed radio frequency spectrum band and an unlicensed/shared radio frequency spectrum band. For example, the wireless communication system 100 may employ LTE licensed-assisted access (LTE-LAA) or unlicensed LTE (LTE-U) radio access technology or MuLTEfire radio access technology or NR technology in an unlicensed/shared radio band such as the 5GHz ISM band. When operating in the unlicensed/shared radio frequency spectrum band, wireless devices such as the base station 105 and the UE115 may employ a listen-before-talk (LBT) procedure to ensure that the frequency channel is clear before transmitting data. In some cases, operation in an unlicensed/shared radio band may be combined with CCs operating in a licensed band based on CA configuration. Operations in the unlicensed/shared radio spectrum may include downlink transmissions, uplink transmissions, peer-to-peer transmissions, or a combination of these transmissions. Duplexing in the unlicensed/shared radio spectrum may be based on Frequency Division Duplexing (FDD), Time Division Duplexing (TDD), or a combination of both.

In some cases, the antennas of a base station 105 or UE115 may be located within one or more antennas or antenna arrays, which may support MIMO operations, such as spatial multiplexing or transmit or receive beamforming. For example, one or more base station antennas or antenna arrays may be collocated in an antenna assembly such as an antenna tower. In some cases, the antennas or antenna arrays associated with the base station 105 may be located at different geographic locations. The base station 105 may have an antenna array with a plurality of rows and columns of antenna ports that the base station 105 may use to support beamforming for communications with the UEs 115. Likewise, the UE115 may have one or more antenna arrays that may support various MIMO or beamforming operations.

A MIMO wireless system uses a transmission scheme between a transmitting device (e.g., base station 105) and a receiving device (e.g., UE 115) in which both the transmitting device and the receiving device are equipped with multiple antennas. MIMO communications may employ multipath signal propagation to increase utilization of a radio frequency spectrum band by transmitting or receiving different signals via different spatial paths, which may be referred to as spatial multiplexing. Different signals may be transmitted, for example, by the transmitting device via different antennas or different combinations of antennas. Also, different signals may be received by the receiving device via different antennas or different combinations of antennas. Each of the different signals may be referred to as a separate spatial stream, and different antennas or different combinations of antennas at a given device (e.g., orthogonal resources of the device associated with spatial dimensions) may be referred to as spatial layers.

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., base station 105 or UE 115) to shape (shape) or steer (steer) an antenna beam (e.g., a transmit beam or a receive beam) along a direction between the transmitting device and the receiving device. Beamforming may be achieved by combining signals communicated via antenna elements in an antenna array such that signals propagating in a particular direction relative to the antenna array experience constructive interference while other signals experience destructive interference. The adjustment of the signals communicated via the antenna elements may include the transmitting device or the receiving device applying a certain phase offset, timing advance/delay or amplitude adjustment to the signals carried via each antenna element associated with the device. The adjustment associated with each antenna element may be defined by a set of beamforming weights associated with a particular direction (e.g., relative to an antenna array of a transmitting device or a receiving device, or relative to some other direction).

In one example, the base station 105 may use multiple antennas or antenna arrays for beamforming operations for directional communication with the UEs 115. For example, the signal may be transmitted multiple times in different directions, which may include transmitting the signal according to different sets of beamforming weights associated with different transmit directions. A receiving device (e.g., UE115, which may be an example of a mmW receiving device) may attempt multiple receive beams when receiving various signals such as synchronization signals or other control signals from the base station 105. For example, a receiving device may attempt multiple receive directions by: receiving via different antenna sub-arrays, processing received signals according to different antenna sub-arrays, receiving according to different sets of receive beamforming weights applied to signals received at multiple antenna elements of an antenna array, or processing received signals according to different sets of receive beamforming weights 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 beams or receive directions.

In some cases, the wireless communication system 100 may be a packet-based network operating 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. In some cases, the 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 processing and multiplex logical channels into transport channels. The MAC layer may also provide retransmissions at the MAC layer using hybrid automatic repeat request (HARQ) to improve link efficiency. In the control plane, a Radio Resource Control (RRC) protocol layer may provide establishment, configuration, and maintenance of RRC connections between the UE115 and the base station 105 or core network 130 that support radio bearers for user plane data. At the Physical (PHY) layer, transport channels may be mapped to physical channels.

In some cases, the UE115 and the base station 105 may support retransmission of data to increase the likelihood that the data is successfully received. HARQ feedback is a technique that increases the likelihood of correctly receiving data over the communication link 125. HARQ may include a combination of error detection (e.g., using Cyclic Redundancy Check (CRC)), Forward Error Correction (FEC), and retransmission (e.g., automatic repeat request (ARQ)). Under poor radio conditions (e.g., signal-to-noise ratio conditions), HARQ may improve throughput in the MAC layer. In some cases, a wireless device may support HARQ feedback for the same slot, where the device may provide HARQ feedback in a particular slot for data received in a previous symbol in the slot. In other cases, the device may provide HARQ feedback in a subsequent time slot or according to some other time interval.

The time interval in LTE or NR may be expressed in multiples of a basic time unit, e.g. may refer to T_sA sample period of 1/30,720,000 seconds. May be provided according to each having a thickness of 10 mmRadio frames of second (ms) duration to organize time intervals (T) of communication resources_f＝307200T_s). The radio frame may be identified by a System Frame Number (SFN) ranging from 0 to 1023. Each frame may include ten subframes numbered from 0 to 9, and each subframe may have a duration of 1 millisecond. The subframe may be further divided into two slots, each slot having a duration of 0.5 milliseconds, and each slot may contain 6 or 7 modulation symbol periods (e.g., depending on the length of the cyclic prefix before each symbol period). Each symbol period may contain 2048 sample periods in addition to a cyclic prefix. In some cases, a subframe may be the smallest scheduling unit of the wireless communication system 100 and may be referred to as a Transmission Time Interval (TTI). In other cases, the minimum scheduling unit of the wireless communication system 100 may be shorter than a subframe or may be dynamically selected (e.g., in a burst of shortened tti (sTTI) or in a selected component carrier using sTTI).

In some wireless communication systems, a slot may be further divided into a plurality of mini-slots (mini-slots) containing one or more symbols, and in some cases, a symbol or mini-slot of a mini-slot may be the smallest unit of scheduling. For example, the duration of each symbol may vary depending on the subcarrier spacing or operating frequency band. Some wireless communication systems may implement time slot aggregation, where multiple time slots or minislots may be aggregated together for communication between the UE115 and the base station 105.

A resource element may consist of one symbol period (e.g., the duration of one modulation symbol) and one subcarrier (e.g., 15kHz frequency range). A resource block may contain 12 consecutive subcarriers in the frequency domain (e.g., which together form one "carrier") and, for a conventional cyclic prefix in each Orthogonal Frequency Division Multiplexing (OFDM) symbol, 7 consecutive OFDM symbol periods (1 slot) in the time domain, or a total of 84 resource elements across the frequency and time domains. The number of bits carried by each resource element may depend on the modulation scheme (the configuration of the modulation symbols that may be applied in each symbol period). Thus, the more resource elements and the higher the modulation scheme (e.g., the greater the number of bits that may be represented by a modulation symbol according to a given modulation scheme), the higher the data rate may be for the UE 115. In a MIMO system, wireless communication resources may refer to a combination of radio frequency spectrum band resources, time resources, and spatial resources (e.g., spatial layers), and the use of multiple spatial layers may further increase the data rate for communicating with the UE 115.

The term "carrier" refers to a set of radio spectrum resources having a defined organization for supporting uplink or downlink communications over the communication link 125. For example, a carrier of the communication link 125 may include a portion of a radio frequency spectrum band, which may also be referred to as a frequency channel. In some examples, a carrier may be composed of multiple subcarriers (e.g., waveform signals having multiple different frequencies). A carrier may be organized to include multiple physical channels, where each physical channel may carry user data, control information, or other signaling.

The organization of the carriers may be different for different radio access technologies (e.g., LTE-A, NR, etc.). For example, communications over carriers may be organized according to TTIs or slots, each of which may include user data as well as control information or signaling to support decoding of the user data. The carriers may also include dedicated acquisition signaling (e.g., synchronization signals or system information, etc.) and control signaling that coordinates operation of the carriers. In some examples (e.g., in a carrier aggregation configuration), a carrier may also have acquisition signaling or control signaling that coordinates the operation of other carriers.

The physical channels may be multiplexed on the carriers according to various techniques. The physical control channels and physical data channels may be multiplexed on the downlink carrier using, for example, Time Division Multiplexing (TDM) techniques, Frequency Division Multiplexing (FDM) techniques, or hybrid TDM-FDM techniques. In some examples, the control information sent in the physical control channel may be distributed in a cascaded manner between different control regions (e.g., between a common control region or common search space and one or more UE-specific control regions or UE-specific search spaces).

The carrier may be associated with a particular bandwidth of the radio spectrum, and in some examples, the carrier bandwidth may be referred to as a carrier or "system bandwidth" of the wireless communication system 100. For example, the carrier bandwidth may be one of a plurality of predetermined bandwidths (e.g., 1.4, 3, 5, 10, 15, or 20MHz) of the carrier for a particular radio access technology. In some examples, system bandwidth may refer to the smallest bandwidth unit used to schedule communications between base stations 105 and UEs 115. In other examples, the base station 105 or UE115 may also support communication over a carrier having a smaller bandwidth than the system bandwidth. In such examples, the system bandwidth may be referred to as a "wideband" bandwidth, while the smaller bandwidth may be referred to as a "narrowband" bandwidth. In some examples of wireless communication system 100, wideband communication may be performed according to a carrier bandwidth of 20MHz and narrowband communication may be performed according to a carrier bandwidth of 1.4 MHz.

Devices (e.g., base stations or UEs 115) of the wireless communication system 100 may have a hardware configuration that supports communication over a particular carrier bandwidth or may be configured to support communication over one carrier bandwidth of a set of carrier bandwidths. For example, the base station 105 or the UE115 may perform some communications according to the system bandwidth (e.g., wideband communications) and may perform some communications according to a smaller bandwidth (e.g., narrowband communications). In some examples, the wireless communication system 100 may include base stations 105 and/or UEs that support simultaneous communication via carriers associated with more than one different bandwidth.

The wireless communication system 100 may support communication with UEs 115 over multiple cells or carriers, which may be referred to as Carrier Aggregation (CA) or multi-carrier operation. According to a carrier aggregation configuration, a UE115 may be configured with multiple downlink CCs and one or more uplink CCs. Carrier aggregation may be used with FDD and TDD component carriers.

In some cases, the wireless communication system 100 may utilize an enhanced component carrier (eCC). An eCC may be characterized by one or more features, including a wider carrier or frequency channel bandwidth, a shorter symbol duration, a shorter TTI duration, or a 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 suboptimal or non-ideal backhaul links). An eCC may also be configured for use in unlicensed/shared radio spectrum or shared radio spectrum (e.g., where more than one operator is allowed to use the spectrum). An eCC characterized by a wide carrier bandwidth may include one or more frequency bands that are unavailable to UEs 115, which UEs 115 are unable to monitor the entire carrier bandwidth, or are otherwise configured to use a limited carrier bandwidth (e.g., to save power).

In some cases, an eCC may utilize a different symbol duration than other CCs, which may include using a shortened symbol duration compared to the symbol durations of the other CCs. Shorter symbol durations may be associated with increased spacing between adjacent subcarriers. A device utilizing an eCC, such as a UE115 or a base station 105, may transmit a wideband signal (e.g., according to a frequency channel or carrier bandwidth of 20, 40, 60, 80MHz, etc.) within a shortened symbol duration (e.g., 16.67 microseconds). A TTI in an eCC may consist of one or more symbol periods. In some cases, the TTI duration (i.e., the number of symbol periods in a TTI) may be variable.

Wireless communication systems, such as NR systems, may use any combination of licensed, shared, and unlicensed/shared radio frequency spectrum bands or the like. Flexibility in eCC symbol duration and subcarrier spacing may allow eCC to be used across multiple spectra. In some examples, NR sharing spectrum may improve spectrum utilization and spectrum efficiency, particularly through dynamic vertical sharing (e.g., across frequency) and horizontal sharing (e.g., across time) of resources.

In various aspects, as further illustrated in fig. 1, a first UE 115-1 may be configured to support D2D communication with a second UE 115-2. Here, for example, D2D communication is represented by communication link 150. Base station 105-1 may request that UE 115-1 monitor SRS transmissions from UE115-2 represented by communication link 125-2 over communication link 125-1. For example, in some embodiments, base station 105-1 may determine that UE 115-1 and UE115-2 may be indicated as being within a threshold communication proximity of each other, e.g., based on serving node activity, location information, etc. In some cases, UE115-2 may be instructed (e.g., by base station 105-1) to transmit one or more specific SRSs, which may be monitored by UE 115-1. In a similar manner, UE115-2 may monitor one or more SRS transmissions from UE-115-1. In this manner, the UE may make D2D channel measurement(s) and send a corresponding report to base station 105-1. The base station 105-1, having identified the UE 115-1 and the UE115-2 as candidates for D2D communication, may establish D2D communication and monitor D2D communication between them using, at least in part, the example techniques provided herein.

Fig. 2A is a diagram 200 illustrating an example frame structure of one or more Downlink (DL) frames in accordance with various aspects of the present disclosure. Fig. 2B is a diagram 230 illustrating an example of channels within a frame structure of a DL frame in accordance with various aspects of the present disclosure. Fig. 2C is a diagram 250 illustrating an example frame structure of one or more Uplink (UL) frames in accordance with various aspects of the present disclosure. Fig. 2D is a diagram 280 illustrating an example of channels within a frame structure of a UL frame in accordance with various aspects of the present disclosure. Other wireless communication technologies may have different frame structures and/or different channels. A frame (10ms) may be divided into 10 equally sized sub-frames. Each subframe may include two consecutive slots. A resource grid may be used to represent two slots, each slot including one or more time-concurrent Resource Blocks (RBs) (also referred to as physical RBs (prbs)). The resource grid is divided into a plurality of Resource Elements (REs). For a conventional cyclic prefix, an RB contains 12 consecutive subcarriers in the frequency domain (e.g., for a subcarrier spacing of 15 kHz) and 7 consecutive symbols in the time domain (OFDM symbols for DL; SC-FDMA symbols for UL) for a total of 84 REs. For an extended cyclic prefix, an RB contains 12 consecutive subcarriers in the frequency domain and 6 consecutive symbols in the time domain for a total of 72 REs. The number of bits carried by each RE depends on the modulation scheme.

As shown in fig. 2A, some of the REs carry DL reference (pilot) signals (DL-RS) for channel estimation at the UE. The DL-RS may include cell-specific reference signals (CRSs) (e.g., also sometimes referred to as common RSs), UE-specific reference signals (UE-RSs), and channel state information reference signals (CSI-RSs). Fig. 2A shows CRSs (indicated as R, respectively) for antenna ports 0, 1, 2 and 3₀,R₁、R₂And R₃) UE-RS (indicated as R) for antenna port 5₅) And CSI-RS (indicated as R) for antenna port 15.

Fig. 2B shows an example of various channels within the DL subframe of a frame. The Physical Control Format Indicator Channel (PCFICH) is within symbol 0 of slot 0 and carries a Control Format Indicator (CFI) indicating whether the Physical Downlink Control Channel (PDCCH) occupies 1, 2 or 3 symbols (fig. 2B shows the PDCCH occupying 3 symbols). The PDCCH carries Downlink Control Information (DCI) within one or more Control Channel Elements (CCEs), each CCE includes nine RE groups (REGs), each REG including four consecutive REs in one OFDM symbol. The UE may be configured with a UE-specific enhanced pdcch (epdcch) that also carries DCI. The ePDCCH may have 2, 4, or 8 RB pairs (fig. 2B shows two RB pairs, each subset including one RB pair). A physical hybrid automatic repeat request (ARQ) (HARQ) indicator channel (PHICH) is also within symbol 0 of slot 0 and carries HARQ Indicators (HIs) indicating HARQ Acknowledgement (ACK)/negative ACK (nack) feedback based on a Physical Uplink Shared Channel (PUSCH). The Primary Synchronization Channel (PSCH) may be within symbol 6 of slot 0 within subframes 0 and 5 of one frame. The PSCH carries a Primary Synchronization Signal (PSS), which the UE uses to determine subframe/symbol timing and physical layer identity. The Secondary Synchronization Channel (SSCH) may be within symbol 5 of slot 0 within subframes 0 and 5 of one frame. The SSCH carries a Secondary Synchronization Signal (SSS) that the UE uses to determine the physical layer cell identification group number and radio frame timing. Based on the physical layer identity and the physical layer cell identity group number, the UE may determine a Physical Cell Identifier (PCI). Based on the PCI, the UE may determine the location of the DL-RS. A Physical Broadcast Channel (PBCH) carrying a Master Information Block (MIB) may be logically grouped with the PSCH and SSCH to form a Synchronization Signal (SS) block. The MIB provides the number of RBs, PHICH configuration, and System Frame Number (SFN) in the DL system bandwidth. The Physical Downlink Shared Channel (PDSCH) carries user data, broadcast system information, such as System Information Blocks (SIBs), which are not transmitted through the PBCH, and a paging message.

As shown in fig. 2C, some of the REs carry demodulation reference signals (DM-RS) for channel estimation at the base station. The UE may additionally transmit a Sounding Reference Signal (SRS) in the last symbol of the subframe. As described in more detail herein, in some embodiments, the SRS transmission may be measured by the receiving UE to determine the D2D channel measurements. The SRS may have a comb (comb) structure, and the UE may transmit the SRS on one comb. The base station may use SRS for channel quality estimation to enable frequency-based scheduling on the UL.

Fig. 2D shows an example of various channels within the UL subframe of a frame. A Physical Random Access Channel (PRACH) may be within one or more subframes within one frame based on a PRACH configuration. The PRACH may include six consecutive RB pairs within one subframe. The PRACH allows the UE to perform initial system access and achieve UL synchronization. The Physical Uplink Control Channel (PUCCH) may be located on the edge of the UL system bandwidth. The PUCCH carries Uplink Control Information (UCI) such as scheduling request, Channel Quality Indicator (CQI), Precoding Matrix Indicator (PMI), Rank Indicator (RI), and HARQ ACK/NACK feedback. The PUSCH carries data and may additionally be used to carry Buffer Status Reports (BSRs), Power Headroom Reports (PHR), and/or UCI.

Fig. 3 is a block diagram of a base station 310 in communication with a UE 350 in an access network. In the DL, IP packets from EPC 160 may be provided to controller/processor 375. Controller/processor 375 implements layer 3 and layer 2 functions. Layer 3 includes a Radio Resource Control (RRC) layer, and layer 2 includes a Packet Data Convergence Protocol (PDCP) layer, a Radio Link Control (RLC) layer, and a Medium Access Control (MAC) layer. The controller/processor 375 provides RRC layer functions associated with the broadcasting of system information (e.g., MIB, SIBs), RRC connection control (e.g., RRC connection paging, RRC connection establishment, RRC connection modification, and RRC connection release), inter-Radio Access Technology (RAT) mobility, and measurement configuration for UE measurement reporting; PDCP layer functions associated with header compression/decompression, security (ciphering, deciphering, integrity protection, integrity verification) and handover support functions; RLC layer functions associated with the delivery of upper layer Packet Data Units (PDUs), error correction by ARQ, concatenation, segmentation and reassembly of RLC Service Data Units (SDUs), re-segmentation of RLC data PDUs, and re-ordering of RLC data; and MAC layer functions associated with mapping between logical channels and transport channels, multiplexing of MAC SDUs onto Transport Blocks (TBs), demultiplexing of MAC SDUs from TBs, scheduling information reporting, error correction by HARQ, priority handling, and logical channel prioritization.

The Transmit (TX) processor 316 and the Receive (RX) processor 370 perform layer 1 functions associated with various signal processing functions. Layer 1, which includes the Physical (PHY) layer, may include error detection on transport channels, Forward Error Correction (FEC) encoding/decoding of transport channels, interleaving, rate matching, mapping onto physical channels, modulation/demodulation of physical channels, and MIMO antenna processing. The TX processor 316 processes the mapping to the signal constellation based on various modulation schemes (e.g., Binary Phase Shift Keying (BPSK), Quadrature Phase Shift Keying (QPSK), M-phase shift keying (M-PSK), M-quadrature amplitude modulation (M-QAM)). The coded and modulated symbols may then be split into parallel streams. Each stream may then be mapped to OFDM subcarriers, multiplexed with reference signals (e.g., pilots) in the time and/or frequency domain, and then combined together using an Inverse Fast Fourier Transform (IFFT) to generate a physical channel carrying a time-domain OFDM symbol stream. The OFDM streams are spatially precoded to produce a plurality of spatial streams. The channel estimates from channel estimator 374 may be used to determine coding and modulation schemes, as well as for spatial processing. The channel estimate may be derived from a reference signal and/or channel condition feedback transmitted by the UE 350. Each spatial stream may then be provided to a different antenna 320 via a separate transmitter 318 TX. Each transmitter 318TX may modulate an RF carrier with a respective spatial stream for transmission. The controller/processor and/or other exemplary components in base station 310 may represent one or more processing units that may be configured to support/implement certain D2D channel measurement and communication techniques as provided herein.

At the UE 350, each receiver 354RX receives a signal through its respective antenna 352. Each receiver 354RX recovers information modulated onto an RF carrier and provides the information to a Receive (RX) processor 356. The TX processor 368 and the RX processor 356 implement layer 1 functions associated with various signal processing functions. The RX processor 356 may perform spatial processing on the information to recover any spatial streams destined for the UE 350. If multiple spatial streams are destined for the UE 350, they may be combined into a single OFDM symbol stream by the RX processor 356. The RX processor 356 then converts the OFDM symbol stream from the time domain to the frequency domain using a Fast Fourier Transform (FFT). The frequency domain signal may include a separate OFDM symbol stream for each subcarrier of the OFDM signal. The symbols on each subcarrier, as well as the reference signal, are recovered and demodulated by determining the most likely signal constellation points transmitted by the base station 310. These soft decisions may be based on channel estimates calculated by channel estimator 358. The soft decisions are then decoded and deinterleaved to recover the data and control signals that were originally transmitted by the base station 310 on the physical channel. The data and control signals are then provided to a controller/processor 359, which implements layer 3 and layer 2 functions.

The controller/processor 359 can be associated with memory 360 that stores program codes and data. The memory 360 may be referred to as a computer-readable medium. In the UL, the controller/processor 359 provides demultiplexing between transport and logical channels, packet reassembly, deciphering, header decompression and control signal processing to recover IP packets from the EPC 160. Controller/processor 359 may also be responsible for error detection using ACK and/or NACK protocols to support HARQ operations. The controller/processor and/or other example components in the UE 350 may represent one or more processing units that may be configured to support/implement certain D2D channel measurement and communication techniques as provided herein.

Similar to the functionality described in connection with the DL transmission by base station 310, controller/processor 359 provides RRC layer functions associated with system information (e.g., MIB, SIB) acquisition, RRC connection, and measurement reporting; PDCP layer functions associated with header compression/decompression and security (ciphering, deciphering, integrity protection, integrity verification); RLC layer functions related to the transfer of upper layer PDUs, error correction by ARQ, concatenation, segmentation and reassembly of RLC SDUs, re-segmentation of RLC data PDUs, and re-ordering of RLC data; and MAC layer functions associated with mapping between logical channels and transport channels, multiplexing of MAC SDUs into TBs, demultiplexing of MAC SDUs from TBs, scheduling information reporting, error correction by HARQ, priority handling, and logical channel prioritization.

TX processor 368 may use channel estimates derived by channel estimator 358 from a reference signal or feedback transmitted by base station 310 to select an appropriate coding and modulation scheme and to facilitate spatial processing. The spatial streams generated by the TX processor 368 may be provided to different antennas 352 via separate transmitters 354 TX. Each transmitter 354TX may modulate an RF carrier with a respective spatial stream for transmission.

UL transmissions are processed at the base station 310 in a manner similar to that described in connection with the receiver function at the UE 350. Each receiver 318RX receives a signal through its corresponding antenna 320. Each receiver 318RX recovers information modulated onto an RF carrier and provides the information to an RX processor 370.

The controller/processor 375 can be associated with a memory 376 that stores program codes and data. The memory 376 may be referred to as a computer-readable medium. In the UL, the controller/processor 375 provides demultiplexing between transport and logical channels, packet reassembly, deciphering, header decompression, control signal processing to recover IP packets from the UE 350. IP packets from controller/processor 375 may be provided to EPC 160. Controller/processor 375 may also be responsible for error detection using ACK and/or NACK protocols to support HARQ operations.

Fig. 4 is a flow diagram illustrating an example method 400 for use at a base station in accordance with certain aspects of the present disclosure. The blocks shown in dashed lines are intended to be optional in some embodiments. Thus, for example, blocks 402, 403, 408, and 410 in example method 400 may each be optional, and blocks 404 and 406 may represent the complete example method 400 in some implementations.

With this in mind, at example block 402, the base station may determine whether the first UE and the second UE are D2D communication candidates. For example, such a determination made by the base station may consider, at least in part, one or more D2D channel measurements, which may be provided in one or more reports from one or more UEs. For example, in certain embodiments, the D2D channel measurements may include received signal strength measurements or some other similar signal parameter that may be used to determine whether D2D communication between the first UE and the second UE is possible. In some cases, the base station may also determine that the first UE and the second UE may be indicated as being within a threshold communication proximity of each other. For example, if a base station is serving two UEs, it may determine that the two UEs are indicated to be within a threshold communication proximity of each other. In another example, if the location (e.g., coordinates, range, etc.) of each UE is known or estimated, such a comparison may indicate that the two UEs may be within a threshold communication proximity of each other. In yet another example, one or both UEs may indicate to the base station that the other UE may be within a threshold communication proximity. For example, a UE may be configured to make D2D channel measurements based on an SRS or other similar transmission from another UE. In a similar manner, at example block 403, the base station may receive a request for D2D communication from the first UE, the second UE, or both. Such request(s) may inform, at least in part, the determination as made by the base station at block 402, or may otherwise indicate that the first UE and the second UE have been considered D2D communication candidates. By making this determination, a possible outcome, as shown in any of the exemplary (optional) blocks 402 and/or 403 in fig. 4, may be that the method 400 proceeds to block 404.

At example block 404, the base station may determine to provide a GUL resource allocation for D2D communications between the first UE and the second UE. For example, a first GUL resource allocation may be provided to a first UE and a second GUL resource allocation may be provided to a second UE. In some cases, such a GUL resource allocation may comprise, at least in part, one or more previously arranged GUL resource allocations for a given UE, while in other cases, such a GUL resource allocation may be new/different. In certain embodiments, the GUL resource allocation determination made at block 404 may consider, at least in part, various network condition(s), D2D channel measurement(s), report(s) from UE(s), D2D communication request(s) from UE(s), type of UE, service or other similar capabilities associated with the UE or its user, time or date of day, potential radio interference considerations, quality of service associated with D2D communications, and the like, or some combination thereof, to name a few.

At example block 406, the base station may transmit at least one indication to the first UE, the second UE, or both, the at least one indication identifying at least a portion of a GUL resource allocation for supporting D2D communications between the first UE and the second UE (e.g., as determined at block 404). The indication to the UE at block 406 may indicate, at least in part, one or more wireless signaling parameters for supporting at least a portion of the D2D communication. For example, the indication may inform the first UE to: D2D communications with a second UE are supported by transmitting D2D signals on a first GUL resource and receiving D2D signals from the second UE on a second GUL resource. Similarly, for example, the indication may inform the second UE to: D2D communications with the first UE are supported by transmitting D2D signals on the second GUL resources and receiving D2D signals from the first UE on the first GUL resources. As such, the indication according to example block 406 may include or otherwise correspond to a time-related parameter, a frequency-related parameter, a spatial-related parameter, a resource block-related parameter, a carrier-related parameter, a transmitter-related parameter, a transmit power-related parameter, or the like, or some combination thereof, to name a few examples. As a result of block 406, D2D communication between the first UE and the second UE will be established and may continue accordingly.

At example block 408 (which may be optional), the base station may monitor D2D communication between the first UE and the second UE (e.g., as established via block 406). Thus, for example, the base station may actively monitor some or all signals transmitted between the first UE, the second UE, or both via D2D communication. In one example, the base station may monitor the D2D communication signals to determine whether the GUL resource allocation(s) is sufficient, is being used efficiently, or the like. In a particular example, the base station may monitor, at least in part, D2D communication traffic and/or "keep alive" signals to determine whether D2D communications should continue or be altered in some manner. In certain example embodiments, a base station may monitor D2D communications at least in part by receiving one or more UE-to-base station reports/requests corresponding to ongoing (potentially problematic) D2D communications, signaling environment (e.g., link quality, D2D channel measurements, etc.), changes in UE/communication requirements, etc.

At example block 410 (which may be optional), the base station may determine that the D2D communication is to end as established at block 406. In some cases, the base station may end the D2D communication by altering one or more GUL resource allocations as determined at block 404 and notifying the affected UE(s). In some cases, at block 410, the base station may provide indirect communication between UEs involved in D2D communication. In some implementations, the D2D communication may be set to end at block 410 based on one or more events. For example, a need to change the GUL resource allocation(s), loss of D2D signaling, passage of a period of time, lack of a persistent valid signal, etc. may represent an event that may trigger, at least in part, the end of D2D communication according to block 410. As shown in fig. 4, the example method 400 may proceed from block 406 or possibly block 408 to block 410.

In some example embodiments, method 400 may allow a base station to handover one or both UEs to another base station at blocks 408 and/or 410 or where otherwise applicable. In some cases, such a handover may include ending the D2D communication as established at block 406. In some cases, the handover may be configured to maintain all or part of the ongoing or scheduled D2D communications, e.g., where monitoring of the D2D communications may also be transferred to the target base station in some manner, e.g., as part of the handover. In some embodiments, indirect communications between UEs involved in D2D communications may be rerouted via the first base station and the second base station. Some example signals that may support all or part of methods 400 and 500 (presented below) are also further described and illustrated in example paging flow 800 in fig. 8.

Attention is next drawn to fig. 5, which illustrates a flowchart of an example method 500 for use by a UE in accordance with certain aspects of the present disclosure. The blocks shown in dashed lines are intended to be optional in some embodiments. Thus, for example, blocks 502, 512, and 514 in exemplary method 500 may each be optional, and blocks 504 and 506 (including blocks 508 and 510) may represent the complete exemplary method 500 in some implementations.

With this in mind, at example (optional) block 502, the (first) UE may send a request to the base station for D2D communication, a report corresponding to D2D channel measurements, etc., which may be considered at least in part by the base station for D2D communications that may be established between the first UE and another (second) UE. In some cases, such requests, reports, etc. may be sent, for example, via existing/prior GUL resource allocations.

At example block 504, the first UE may receive an indication that a gil resource allocation has been or will be provided for use in D2D communications between the first UE and the second UE. As mentioned with respect to the example method 400 (e.g., at block 406), in some cases, the base station may send at least one indication to the first UE, the second UE, or both, the at least one indication identifying at least a portion of a GUL resource allocation for supporting D2D communications between the first UE and the second UE. Thus, in this example, the indication of the first UE at block 504 may indicate, at least in part, various wireless signaling parameters for providing at least a portion of the D2D communication. For example, the indication may inform the first UE to: D2D communications with a second UE are supported by transmitting D2D signals on a first GUL resource and receiving D2D signals from the second UE on a second GUL resource. As such, the indication according to example block 504 may include or otherwise correspond to a time-related parameter, a frequency-related parameter, a spatial-related parameter, a resource block-related parameter, a carrier-related parameter, a transmitter-related parameter, a transmit power-related parameter, or the like, or some combination thereof, to name a few examples.

At example block 506, the first UE may be configured to support D2D communication as indicated at block 504. Here, for example, at block 508, to support D2D communication, the first UE may transmit at least a first signal intended for the second UE via at least a first portion of the GUL resource allocation (as may be indicated at block 504). Similarly, at block 510, to support D2D communication, the first UE may receive at least a second signal intended for the first UE via at least a second portion of the GUL resource allocation (as may be indicated at block 504). In some further embodiments, at (optional) block 512, the first UE may support D2D communication at least in part by transmitting a first SRS, which may be used by the base station, the second UE, or both for possible channel measurements that may indicate whether D2D communication or other wireless communication with the first UE should continue, change in some manner, or possibly end. Such a first SRS may be transmitted via previously allocated GUL resources and/or via at least a portion of a GUL resource allocation associated with D2D communication.

In another example embodiment, at (optional) block 514, one or more continuously active signals may be sent via D2D communication with the intention of supporting/maintaining D2D communication, for example, possibly in the absence/delay of other D2D traffic. Here, for example, such a continuously active signal may be received by the second UE and/or the base station, and one or both of the second UE and the base station may continue to support D2D communication in view of the continuously active signal from the first UE. In a similar manner, it should also be appreciated that UEs and/or base stations involved in establishing and supporting D2D communications may also, when appropriate, monitor for ACK/NACK signals or the like that may inform decisions to maintain, alter, or possibly terminate D2D communications. Thus, for example, if a threshold number of NACKs or lack thereof are reached within a certain time period, the UE may make a decision to send a request, report, etc. to the base station to affect a possible change or end of D2D communication. Similarly, if the base station is monitoring D2D communications, the base station may change the D2D communications in some manner in response to such requests or reports and/or by monitoring D2D communications, e.g., end the D2D communications, reallocate the GUL resources, handover one or two UEs to another base station, etc.

Example methods 400 and 500 illustrate techniques by which the status of channel quality may be measured and considered in determining whether a UE may be a candidate for D2D communication. Some examples presented herein utilize SRS transmission for D2D channel measurements; however, other transmissions may also be measured using such techniques. For example, in LTE uplink, another potential reference signal that can be monitored is the UE-specific demodulation reference signal (DM-RS) because it is located in the middle of the PUSCH signal.

In order to determine whether transmission between the respective UEs can be switched to D2D based on the quality of the channel between the UEs, the base station may instruct the UEs to perform channel measurement via SRS transmission in a distributed manner. Channel quality may be an important factor in determining whether a channel may be used, which may be more important than the distance between UEs. However, switching the communication to D2D communication may cause additional interference to neighboring devices. This cost may also be weighed against the efficiency improvement when determining whether to switch to D2D communication. Note that even after D2D establishment (such as part of the example D2D support procedure), the base station may monitor D2D communication performance (e.g., RF and latency) because the UEs may move relative to each other, and if desired, the base station may decide to end the D2D communication and possibly switch to an indirect transmission route between the two UEs.

In one example, the channel conditions can be measured with existing UL SRS. In MuLTEfire, the UE may transmit UL SRS in PUCCH as part of an S subframe or in connection with aperiodic transmission in PUSCH according to a request from the gNB. The special subframe is used in TDD mode for switching from downlink to uplink. Such subframes may include GP, UpPTS, and DwPTS portions, with the GP portion including a guard period between the UpPTS and DwPTS portions. Here, the UpPTS includes an uplink pilot time slot. Such UpPTS may not include PUCCH or PUSCH, but may include PRACH and SRS. Such DwPTS includes downlink pilot time slots, which may include P-SSs. The SRS may be transmitted once, periodically, or aperiodically based on base station-directed scheduling. Subframes including such SRS transmissions may be indicated as potentially available along with SRS bandwidth by UE-specific or cell-specific configurations provided by the gNB. This configuration may indicate frequency and time domain resources that the UE may use. The subframe in which SRS transmission occurs is an example of a time domain resource. To enable D2D measurements to be used, for example, to determine channel quality between two UEs, as presented herein, a base station may request a monitored UE to transmit an aperiodic SRS in an upcoming short pucch (spucch), or, if the monitored UE is already transmitting UL traffic, to transmit an SRS using a Physical Uplink Shared Channel (PUSCH). Here, for example, the sPUCCH may include a PUCCH for independent operation in an unlicensed spectrum. The gNB may request the monitoring UE to monitor SRS transmissions from the monitored UE in upcoming sPUCCH/PUSCH transmissions and provide a corresponding report of such transmissions to the gNB.

Attention is next drawn to fig. 6, which is a schematic diagram illustrating some exemplary components that may be included within base station 600.

In some example embodiments, the base station 600 may include or otherwise represent an access point, a NodeB, an evolved NodeB, or the like. The base station 600 comprises a processing unit 602. The processing unit 602 may be a general purpose single-or multi-chip microprocessor (e.g., an ARM), a special purpose microprocessor (e.g., a Digital Signal Processor (DSP)), a microcontroller, a programmable gate array, or the like. The processing unit 602 may be referred to as a Central Processing Unit (CPU). Although only a single processing unit 602 is shown in the base station 600 of fig. 6, in alternative configurations, a combination of processors (e.g., an ARM and DSP) may be used.

Base station 600 may also include memory 606. The memory 606 may be any electronic component capable of storing electronic information. The memory 606 may be embodied as Random Access Memory (RAM), Read Only Memory (ROM), magnetic disk storage media, optical storage media, flash memory devices in RAM, on-board memory included with the processor, EPROM memory, EEPROM memory, registers, and so forth, including combinations thereof. As shown, data 614 and/or instructions 612 may sometimes be stored in memory 606. The instructions 612 may be executable by the processing unit 602, for example, to implement, at least in part, the techniques disclosed herein. Executing the instructions 612 may involve the use of data 614, which may be stored in the memory 606. When processing unit 602 executes instructions 1609, portions of instructions 612a may be loaded onto processing unit 602, and pieces of data 614a may be loaded onto processing unit 602.

Base station 600 may also include a transmitter 620 and a receiver 622 to allow transmission and reception of wireless signals to and from one or more UEs (not shown). The transmitter 620 and receiver 622 may be collectively referred to as a transceiver 604. One or more antennas 624a-b may be electrically coupled to the transceiver 604. The base station 600 may also include (not shown) multiple transmitters, multiple receivers, and/or multiple transceivers.

The various components of the base station 600 may be coupled together by one or more buses or the like, which may include, for example, a power bus, a control signal bus, a status signal bus, a data bus, etc. For clarity, the various buses are represented in FIG. 6 as bus 610.

Fig. 7 is a block diagram illustrating some exemplary components that may be included within UE 700.

The UE 700 may include a processing unit 702. The processing unit 702 may be a general purpose single-or multi-chip microprocessor (e.g., an ARM), a special purpose microprocessor (e.g., a Digital Signal Processor (DSP)), a microcontroller, a programmable gate array, or the like. The processing unit 702 may be referred to as a Central Processing Unit (CPU). Although only a single processing unit 702 is illustrated in the wireless communication device 700 of fig. 12, in alternative configurations, a combination of processors (e.g., an ARM and DSP) may be used.

The UE 700 may also include a memory 706. The memory 706 may be any electronic component capable of storing electronic information. The memory 706 may be embodied as Random Access Memory (RAM), Read Only Memory (ROM), magnetic disk storage media, optical storage media, flash memory devices in RAM, on-board memory included with the processor, EPROM memory, EEPROM memory, registers, and so forth, including combinations thereof.

As shown, sometimes data 714 and/or instructions 712 may be stored in memory 706. The instructions 712 may be executed by the processing unit 702 to implement the techniques disclosed herein. Executing the instructions 712 may involve the use of data 714 that may be stored in the memory 706. When processing unit 702 executes instructions 1709, portions of instructions 712a may be loaded onto processing unit 702 and pieces of data 714a may be loaded onto processing unit 702.

The UE 700 may also include a transmitter 720 and a receiver 722 to allow transmission and reception of wireless signals to and from other devices (not shown). The transmitter 720 and receiver 722 may be collectively referred to as a transceiver 704. One or more antennas 724a-b may be electrically coupled to the transceiver 704. The UE 700 may also include (not shown) multiple transmitters, multiple receivers, and/or multiple transceivers.

The various components of the UE 700 may be coupled together by one or more buses or the like, which may include a power bus, a control signal bus, a status signal bus, a data bus, and the like. For clarity, the various buses are shown in FIG. 7 as bus 710. It should be noted that the methods describe possible embodiments, and that the operations and steps may be rearranged or otherwise modified such that other embodiments are possible. In some examples, aspects from two or more of the methods may be combined. For example, aspects of each of the methods may include steps or aspects of the other methods, or other steps or techniques described herein.

Attention is next drawn to fig. 8, which includes an exemplary paging flow 800 for enabling D2D communication between a first UE 115-1 and a second UE115-2, which may be implemented at least in part by the techniques provided herein. As shown by paging flow 800, a first base station 105-1 and a second base station 105-2 are included in addition to the UE. In this example, the first base station 105-1 establishes D2D communication and there is an example handover to the second base station 105-2.

Signals 802 and 804 may represent one or more reports, requests, or other similar indications that may be transmitted from first UE 115-1 and UE115-2, respectively, to first base station 105-1 and may be considered, at least in part, by first base station 105-1 to determine whether to establish D2D communication. For example, refer to block 403 in method 400 and block 502 in method 500.

Signals 806 and 808 are shown as being transmitted by first base station 105-1 to first UE 115-1 and second UE115-2, respectively, and may represent one or more indications that D2D communication is or will be established between the two UEs. Signals 806 and 808 may identify at least a portion of a GUL resource allocation associated with D2D communications. For example, refer to blocks 404 and 406 in method 400 and block 504 in method 500. It should be understood that although separate signals for both UEs may be shown, in some embodiments, a shared/common signal may serve such a purpose.

As part of the D2D communication, the second UE115-2 may transmit a signal 810 to the first UE 115-1 and receive a signal 814 from the first UE 115-1. In this manner, for example, the first UE 115-1 and the second UE 115-12 may support, at least in part, D2D communication. For example, refer to block 506 in method 500. Also, as shown, a signal 810 from the second UE115-2 may be received by the first base station 105-1, as represented by signal 812. Similarly, a signal 814 from the first UE115-2 may be received by the first base station 105-1, as represented by signal 816. In this manner, for example, the first base station 105-1 may support or otherwise monitor, at least in part, D2D communications. For example, refer to block 408 in method 400.

As a further illustrative example, the signal 818 is shown as being sent by the first UE 115-1 to the second UE115-2 as part of the D2D communication and represents at least one persistent alive message. For example, refer to block 514 in method 500. As further shown, such persistent alive messages may also be received by the first base station 105-1, as represented by signal 820. For example, referring to block 408 of method 400, a base station may monitor all or a portion of the D2D communications. In another example, signal 818/820 may represent an ACK or NACK, e.g., as part of a HARQ process or the like.

The dashed line 822 is intended to represent some signals that may be generally expected to be received from the second UE115-2 as part of the D2D communication, but for some reason have not been received by the first UE 115-1 (as further shown by the tick portion). For example, the "lost" signal 822 may have been an expected traffic message, an ACK/NACK message, a continuously active message, etc. Signal 822 may be "lost" for a variety of reasons, e.g., it is not transmitted, it is attenuated, etc. Although not shown in fig. 8, it is also assumed that signal 822 is also not received by first base station 105-1 or second base station 105-2. In certain embodiments presented herein, D2D communication may be altered or ended based at least in part on the lack of transmission/reception of signal 822. For example, refer to blocks 408 and 410 in method 400 and blocks 506 and 514 in method 500.

As mentioned previously, it may be desirable to affect D2D communications in some way, e.g., change, end, switch, etc. An example of one type of change may be represented by signals 824 and/or 826 by which first base station 105-1 may indicate changes affecting D2D communications to first UE 115-1 and second UE115-2, respectively. For example, refer to blocks 408 and 410 in method 400. Here, for example, a new/different GUL resource allocation(s) may be indicated, or the end of the D2D communication may be indicated. In another example, signal(s) 824 and/or 826 may represent indirect signaling to support ongoing D2D communication.

Another exemplary modification may be represented by signal 828, where the first base station 105-1 may indicate to the second base station 105-2 via signal 828 that the first UE 115-1, the second UE115-2, or both, may be handed off. For example, refer to blocks 408 and 410 in method 400. Here, for example, in some cases, the D2D communication may end due to a handover. In other cases, D2D communication may continue in whole or in part after the handoff. Signals 830 and 832 may, for example, represent potential alterations or maintenance of D2D communication due to some handoff from first base station 105-1 to second base station 105-2.

The description herein is provided to enable any person skilled in the art to make or use the present disclosure. Various modifications to the disclosure will be readily apparent to those skilled 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 intended to be limited to the examples and designs described herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

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 embodiments are within the scope of the disclosure and the following claims. For example, due to the nature of software, the functions described above may be implemented using software executed by a processor, hardware, firmware, hard wiring, or a combination of any of these. Features implementing functions may also be physically located in various locations, including being distributed such that portions of functions are implemented at different Physical (PHY) locations. Also, as used herein, including in the claims, "or" as used in a list of items (e.g., a list of items beginning with a phrase such as "at least one of … …" or "one or more") indicates an inclusive list such that, for example, at least one of A, B or C represents a or B or C or AB or AC or BC or ABC (i.e., a and B and C).

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 can be accessed by a general purpose or special purpose computer. By way of example, and not limitation, non-transitory computer-readable media can comprise RAM, ROM, electrically erasable programmable read-only memory (EEPROM), Compact Disc (CD) ROM or other optical storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to carry or store desired program code means in the form of instructions or data structures and that can be accessed by a general-purpose or special-purpose computer, or a general-purpose or special-purpose processor. Also, any connection is properly termed a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, Digital Subscriber Line (DSL), or wireless technologies such as infrared, radio, and microwave, then the definition of medium includes the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave. Disk and disc, as used herein, includes 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.

The techniques described herein may be used for various wireless communication systems such as CDMA, TDMA, FDMA, OFDMA, single-carrier frequency division multiple access (SC-FDMA), and other systems. The terms "system" and "network" are often used interchangeably. A CDMA system may implement a radio technology such as CDMA2000, Universal Terrestrial Radio Access (UTRA), etc. CDMA2000 covers IS-2000, IS-95 and IS-856 standards. IS-2000 releases 0 and A are commonly referred to as CDMA 20001X, 1X, etc. IS-856(TIA-856) IS commonly referred to as CDMA 20001 xEV-DO, High Rate Packet Data (HRPD), etc. UTRA includes wideband CDMA (wcdma) and other variants of CDMA. A TDMA system may implement a radio technology such as global system for mobile communications (GSM). An OFDMA system may implement radio technologies such as Ultra Mobile Broadband (UMB), evolved UTRA (E-UTRA), IEEE 802.11 (Wireless Fidelity (Wi-Fi)), IEEE 802.16(WiMAX), IEEE 802.20, Flash-OFDM, etc. UTRA and E-UTRA are part of the Universal Mobile Telecommunications System (UMTS). The 3GPP LTE and LTE-advanced (LTE-A) are new versions of UMTS using E-UTRA. UTRA, E-UTRA, UMTS, LTE-A, and GSM are described in documents from an organization named "3 rd Generation partnership project" (3 GPP). CDMA2000 and UMB are described in documents from an organization named "3 rd generation partnership project 2" (3GPP 2). The techniques described herein may be used for the above-mentioned systems and radio technologies as well as other systems and radio technologies. However, the description herein describes an LTE system for purposes of example, and LTE terminology is used in much of the description above, although the techniques may be applicable to applications other than LTE.

In LTE/LTE-a networks, including the networks described herein, the term evolved node b (enb) may be used generally to describe a base station. One or more wireless communication systems described herein may include heterogeneous LTE/LTE-a networks, where different types of enbs provide coverage for various geographic areas. For example, each eNB or base station may provide communication coverage for a macro cell, a small cell, or other type of cell. The term "cell" is a 3GPP term that can be used to describe a base station, a carrier or Component Carrier (CC) associated with a base station, or a coverage area (e.g., sector, etc.) of a carrier or base station, depending on the context.

A base station may include, or may be referred to by those skilled in the art as, a base transceiver station, a radio base station, an Access Point (AP), a radio transceiver, a NodeB, an eNodeB (eNB), a home NodeB, a home eNodeB, or some other suitable terminology. The geographic coverage area of a base station can be divided into sectors that form a portion of the coverage area. One or more wireless communication systems described herein may include different types of base stations (e.g., macro cell base stations or small cell base stations). The UEs described herein may be capable of communicating with various types of base stations and network devices, including macro enbs, small cells, gnbs, relay base stations, and so on. For different technologies, there may be overlapping geographic coverage areas. In some cases, different coverage areas may be associated with different communication technologies. In some cases, the coverage area for one communication technology may overlap with the coverage area associated with another technology. Different technologies may be associated with the same base station or different base stations.

Wireless communication systems or systems described herein may support synchronous or asynchronous operation. For synchronous operation, the base stations may have similar frame timing, and transmissions from different base stations are approximately aligned in time. For asynchronous operation, the base stations may have different frame timings, and the transmissions from the different base stations may not be aligned in time. The techniques described herein may be used for synchronous or asynchronous operations.

The DL transmissions described herein may also be referred to as forward link transmissions, while the UL transmissions may also be referred to as reverse link transmissions. Each communication link described herein, including, for example, the wireless communication system of fig. 1, may include one or more carriers, where each carrier may be a signal composed of multiple subcarriers (e.g., waveform signals of different frequencies). Each modulated signal may be transmitted on a different subcarrier and may carry control information (e.g., reference signals, control channels, etc.), overhead information, user data, and so on. The communication links described herein may transmit bi-directional communications using Frequency Division Duplexing (FDD) (e.g., using paired spectrum resources) or Time Division Duplexing (TDD) operations (e.g., using unpaired spectrum resources). A frame structure (e.g., frame structure type 1) for FDD and a frame structure (e.g., frame structure type 2) for TDD may be defined.

Accordingly, aspects of the present disclosure may be provided for receiving at the time of transmission and transmitting at the time of reception. It should be noted that the methods describe possible embodiments, and that the operations and steps may be rearranged or otherwise modified such that other embodiments are possible. In some examples, aspects from two or more of the methods may be combined.

The various illustrative blocks and modules described in connection with the disclosure herein may be implemented or performed with a general purpose processor, a Digital Signal Processor (DSP), an ASIC, a Field Programmable Gate Array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional 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, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration). Thus, the functions described herein may be performed by one or more other processing units (or cores) on at least one Integrated Circuit (IC). In various examples, different types of ICs may be used (e.g., structured/platform ASICs, FPGAs, or another semi-custom IC), which may be programmed in any manner known in the art. The functions of each unit may also be implemented, in whole or in part, with instructions embodied in a memory, formatted to be executed by one or more general or special purpose processors.

In the drawings, 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 only the first reference label is used in the specification, the description applies to any one of the similar components having the same first reference label, regardless of the second reference label.

Claims (30)

1. A method for use at a first User Equipment (UE), the method comprising, at the first UE:

receiving, from a base station, an indication that an unlicensed uplink (GUL) resource allocation has been or will be provided for device-to-device (D2D) communication between the first UE and a second UE; and

supporting the D2D communication by:

transmitting a first signal intended for the second UE via at least a first portion of the GUL resource allocation, an

Receiving a second signal from the second UE via at least a second portion of the GUL resource allocation.

2. The method of claim 1, wherein:

the first portion of the GUL resource allocation and the second portion of the GUL resource allocation comprise the same GUL resource allocation; or

The first portion of the GUL resource allocation comprises at least a portion of a previous GUL resource allocation provided to the first UE to transmit signals intended for the base station.

3. The method of claim 1, and further comprising, at the first UE:

transmitting a request to the base station for the D2D communication, and wherein the indication received from the base station is in response to the request.

4. The method of claim 3, and further comprising, at the first UE:

measuring a D2D channel measurement of a Sounding Reference Signal (SRS) transmission by the second UE; and

determining whether to send the request based at least in part on the D2D channel measurements.

5. The method of claim 1, wherein supporting the D2D communication further comprises, at the first UE:

transmitting a first Sounding Reference Signal (SRS);

transmitting at least one continuously active signal to maintain the D2D communication;

or both.

6. The method of claim 5, wherein the first SRS are transmitted by the first UE via at least a first portion of the GUL resource allocation, and the first portion of the GUL resource allocation is different from a previous GUL resource allocation provided to the first UE to transmit a signal intended for the base station.

7. The method of claim 1, wherein the GUL resource allocation is provided as part of a MultEfire framework.

8. A first User Equipment (UE), the first UE comprising:

a receiver;

a transmitter; and

a processing unit coupled to the receiver and the transmitter and configured to:

obtaining, via the receiver, an indication from a base station that an unlicensed uplink (GUL) resource allocation has been or will be provided for device-to-device (D2D) communication between the first UE and a second UE; and

to support the D2D communication:

initiating, via the transmitter, transmission of a first signal intended for the second UE via at least a first portion of the GUL resource allocation, an

Obtaining, via the receiver, a second signal from the second UE via at least a second portion of the GUL resource allocation.

9. The first UE of claim 8, wherein:

the first portion of the GUL resource allocation and the second portion of the GUL resource allocation comprise the same GUL resource allocation; or

The first portion of the GUL resource allocation comprises at least a portion of a previous GUL resource allocation provided to the first UE to transmit signals intended for the base station.

10. The first UE of claim 8, wherein the processing unit is further configured to:

initiate transmission of a request for the D2D communication to the base station via the transmitter, and wherein the indication received from the base station is in response to the request.

11. The first UE of claim 10, wherein the processing unit is further configured to:

obtaining, via the receiver, D2D channel measurements for Sounding Reference Signal (SRS) transmissions by the second UE; and

determining whether to initiate transmission of the request based at least in part on the D2D channel measurements.

12. The first UE of claim 8, wherein to support the D2D communication, the processing unit is further configured to:

initiate transmission of a first Sounding Reference Signal (SRS) via the transmitter;

initiate transmission of at least one continuously active signal via the transmitter to maintain the D2D communication;

or both.

13. The first UE of claim 12, wherein the first SRS is transmitted by the first UE via at least a first portion of the gil resource allocation, and the first portion of the gil resource allocation is different from a previous gil resource allocation provided to the first UE to transmit signals intended for the base station.

14. The first UE of claim 8, wherein the GUL resource allocation is provided as part of a MuLTEfire framework.

15. A method for use at a base station, the method comprising, at the base station:

determining to provide a license-exempt uplink (GUL) resource allocation for device-to-device (D2D) communication between a first UE and a second UE; and

transmitting at least one indication to the first UE, the second UE, or both, wherein the at least one indication identifies at least a portion of the GUL resource allocation for use by the first UE, the second UE, or both, to support the D2D communication therebetween.

16. The method of claim 15, and further comprising, at the base station, monitoring the D2D communication at least in part by:

receiving a first signal via at least a first portion of the GUL resource allocation and a second signal via at least a second portion of the GUL resource allocation, the first signal being sent from the first UE to the second UE and the second signal being sent by the second UE to the first UE as part of the D2D communication.

17. The method of claim 16 wherein the first portion of the GUL resource allocation and the second portion of the GUL resource allocation comprise the same GUL resource allocation.

18. The method of claim 16, wherein the first portion of the GUL resource allocation comprises at least a portion of a previous GUL resource allocation provided to the first UE to transmit a signal intended for the base station.

19. The method of claim 16, wherein the first signal, the second signal, or both, comprise a continuously active signal intended to maintain the D2D communication.

20. The method of claim 15, and further comprising, at the base station:

ending the D2D communication based at least in part on a D2D channel measurement threshold parameter, a UE SRS threshold parameter, a D2D communication timeout threshold parameter, a D2D communication termination request, a base station handover determination, a GUL resource reallocation determination, or some combination thereof.

21. The method of claim 15, and further comprising, at the base station:

receive a request for the D2D communication from the first UE, the second UE, or both, and determine to provide the GUL resource allocation for the D2D communication based at least in part on the request.

22. The method of claim 15, and further comprising, at the base station:

determining that the first UE and the second UE are D2D communication candidates based at least in part on a report received from the first UE indicating D2D channel measurements, the D2D channel measurements being transmitted based on a Sounding Reference Signal (SRS) from the second UE.

23. The method of claim 15, wherein the GUL resource allocation is provided as part of a MultEfire framework.

24. A base station, comprising:

a receiver;

a transmitter; and

a processing unit coupled to the receiver and the transmitter and configured to:

determining to provide a license-exempt uplink (GUL) resource allocation for device-to-device (D2D) communication between a first UE and a second UE; and

initiate transmission of at least one indication to the first UE, the second UE, or both via the transmitter, wherein the at least one indication identifies at least a portion of the GUL resource allocation for use by the first UE, the second UE, or both to support the D2D communication therebetween.

25. The base station of claim 24, and wherein said processing unit is further configured to monitor, by said receiver, said D2D communication based, at least in part, on a first signal received via at least a first portion of said gil resource allocation and a second signal received via at least a second portion of said gil resource allocation, said first signal transmitted from said first UE to said second UE and said second signal transmitted by said second UE to said first UE as part of said D2D communication.

26. The base station of claim 25, wherein:

the first portion of the GUL resource allocation and the second portion of the GUL resource allocation comprise the same GUL resource allocation;

the first portion of the GUL resource allocation comprises at least a portion of a previous GUL resource allocation provided to the first UE to transmit signals intended for the base station;

the first signal, the second signal, or both comprise a continuously active signal intended to maintain the D2D communication;

or some combination thereof.

27. The base station of claim 24, wherein the processing unit is further configured to:

ending the D2D communication based at least in part on a D2D channel measurement threshold parameter, a UE SRS threshold parameter, a D2D communication timeout threshold parameter, a D2D communication termination request, a base station handover determination, a GUL resource reallocation determination, or some combination thereof.

28. The base station of claim 24, wherein the processing unit is further configured to:

obtaining, via the receiver, a request for the D2D communication from the first UE, the second UE, or both; and

determining to provide the GUL resource allocation for the D2D communication based at least in part on the request.

29. The base station of claim 24, wherein the processing unit is further configured to:

determining that the first UE and the second UE are D2D communication candidates based at least in part on a report of D2D channel measurements obtained from the first UE via the receiver indicating D2D channel measurements, the D2D channel measurements being based on Sounding Reference Signal (SRS) transmissions from the second UE.

30. The base station of claim 24, wherein the GUL resource allocation is provided as part of a MultEfire framework.

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