CN112314030B

CN112314030B - Device-to-device (D2D) communication management techniques

Info

Publication number: CN112314030B
Application number: CN201980040756.XA
Authority: CN
Inventors: P.古普塔; J.李; 李崇; H.王
Original assignee: Qualcomm Inc
Current assignee: Qualcomm Inc
Priority date: 2018-06-21
Filing date: 2019-06-18
Publication date: 2024-04-05
Anticipated expiration: 2039-06-18
Also published as: EP3811706A1; CN112314030A; WO2019246146A1

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 unlicensed 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

The present application claims priority and benefit from U.S. application Ser. No. 16/014,799, filed on U.S. patent and trademark office at month 21 of 2018, the entire contents of which are incorporated herein by reference as if fully set forth herein below, for all applicable purposes.

Technical Field

The following relates generally to wireless communications, and more particularly to techniques for supporting or otherwise managing device-to-device (D2D) communications, and in particular to techniques potentially for D2D communications 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 available system resources (e.g., broadcast spectrum with respect to time, frequency, space, and/or power related aspects). Examples of some 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 at municipal, national, regional, and even global levels. For example, fifth generation (5G) wireless communication technologies are contemplated, which may be referred to as New Radios (NRs), to extend and support various usage scenarios and applications relative to current mobile network generations. In one aspect, the 5G communication technique may include: an 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 Communications (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, 5G NR may provide greater flexibility in wireless communications. Such increased flexibility may be applied to different aspects of wireless communications, including various mechanisms and techniques for scheduling or conveying (e.g., signaling) information regarding transmitted assignments and/or feedback. Accordingly, new techniques for potential device-to-device (D2D) communications are needed, particularly D2D communications that use, at least in part, unlicensed uplink (GUL) resources in the 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 use, at least in part, the GUL resources in the 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 GUL resource allocation has been or will be provided for D2D communication 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 the 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, a first UE may be provided that includes 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 the 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 the second UE via at least a first portion of the 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 yet 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 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, in order to support D2D communication therebetween.

According to some other example aspects of the present disclosure, a base station may be provided that includes a receiver, a transmitter, and a processing unit. The processing unit may be coupled to the receiver and the transmitter and configured to determine that a GUL resource allocation is to be provided for D2D communication 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 in order to support D2D communication 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 in the system shown in fig. 1, in accordance with certain aspects of the present disclosure.

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

Fig. 5 is a flow chart illustrating an example method used by a UE to support D2D communications 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 D2D communication techniques, 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 cellular communication networks, 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 the devices (e.g., without having to communicate messages through a base station, relay, or other node). D2D communication may enable, for example, mesh network and device-to-network relay functionality. Some examples of D2D technologies include bluetooth pairing, wi-Fi Direct (Direct), miracast, and LTE-D. D2D communication may also be referred to as point-to-point (P2P) or side link communication.

D2D communication may be implemented using licensed or unlicensed frequency bands. D2D communication may avoid overhead related to 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 can support D2D communications using unlicensed frequency bands. MuLTEfire can be used in any unlicensed spectrum where there is competition for use of the spectrum, although it was originally intended to be deployed in the unlicensed band of 5GHz in the united states and potentially also in the shared band of 3.5 GHz. MuLTEfire implements a 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 μs) 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 different starting positions/times 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, at least partially utilizing 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 a D2D connection or channel between UEs across cells. The base station may provide a GUL resource allocation (e.g., an indication of activation/release, etc.) message to the UE. In some implementations, such GUL resource allocation messages 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 shared radio spectrum, a GUL transmission may be implemented in addition to 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 GUL resources for D2D communication with a second UE in the 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 by the base station than in the case of a distributed control mode, where the UE may be configured to have more control over D2D communication.

A technique is described in which 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 comprise radio spectrum licensed for a specific user/device for a specific purpose. The shared radio spectrum may include spectrum available for Wi-Fi, radio spectrum available for different radio access technologies, radio spectrum available for use by 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 some 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, 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 identifying all or an applicable portion of the GUL resource allocation for use by the first UE, the second UE, or both in order to support D2D communications therebetween.

For example, the base station may identify that the first UE and the second UE are 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, a base station may receive one or more requests for D2D communications from a first UE, a second UE, or both, and determine that D2D communications 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 communications may be provided based on other received information. For example, the base station may monitor/measure channel conditions, consider resource allocation, etc., which may at least partially inform the D2D communication determination.

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

The base station may be configured to end D2D communication, e.g., by changing the GUL 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 handoff determination, a GUL resource reallocation determination, some combination thereof, or the like.

To support D2D communications, the first UE and the second UE may receive together or independently 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, the first UE may support D2D communication by, for example, 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 GUL resource allocation and receiving a first signal from the first UE via at least a first portion of the GUL resource allocation.

As mentioned, in some 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 of 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 traffic, SRS, "keep alive" signals, etc., that may be used by the base station to monitor and maintain D2D communications, for example.

D2D communication may allow one of the UEs to communicate directly with another one of the UEs, which may increase throughput, decrease latency, extend range (coverage area), improve energy efficiency, or some combination thereof, to name a few non-limiting examples. Thus, D2D communication may potentially be beneficial to various social applications, such as gaming, media sharing, location-based services, and the like. In another example, such D2D communications may potentially be beneficial relative to wearable devices or other similar devices (e.g., smartphones, smartwatches, smart glasses, headphones, 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 communications 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 storage/available power.

Accordingly, those skilled in the art will recognize that the D2D channel measurement techniques provided herein by way of example may be beneficial to a variety of different or identical/similar types of UEs. Thus, for example, in some implementations, some UEs may include smart phones, tablet computers, laptops, positioning/tracking devices, wearable devices, display/eyewear devices, vehicles, machines, appliance robots, drones, internet of things (IoT) devices, circuits (e.g., controllers, sensors, actuators, data stores, etc.), etc., 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 being implementable for example frameworks (e.g., muLTEfire 1.1) or other similarly configured devices/networks. It should be understood, however, that the claimed subject matter is not intended to be limited thereto, unless otherwise specifically stated, as those skilled in the art will appreciate upon reading the present specification and accompanying drawings that such exemplary techniques may be implemented in other types of frameworks/protocols, networks, signals, etc.

Attention is now directed to fig. 1, which illustrates an example of a wireless communication system 100 supporting D2D communication, e.g., using at least in part, GUL resources in a shared radio spectrum, in accordance with aspects of the present disclosure. The wireless communication system 100 may include, for example, a base station 105, a UE 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 on.

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-range or short-range wireless communication technologies/frameworks. In an LTE/LTE-a/MuLTEfire network, the term evolved node B (eNB) may be generally used to describe base station 105, while the term UE may be generally used to describe 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, the eNB or base station 105 may provide communication coverage for a macrocell, 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.

Base station 105 may communicate wirelessly with UE 115 via one or more base station antennas. The base stations 105 described herein may include or may be referred to by those skilled in the art as base station transceivers, radio base stations, access points, radio transceivers, nodebs, enodebs (enbs), next generation Node bs or gigabit nodebs (any of which may be referred to as a gNB), home nodebs, home enodebs, or some other suitable terminology. The wireless communication system 100 may include different types of base stations 105 (e.g., macrocell 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 devices, 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 in which communications with individual 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 UEs 115 may utilize one or more carriers. The communication link 125 shown in the wireless communication system 100 may include an uplink transmission from the UE 115 to the base station 105 or a downlink transmission from the base station 105 to the UE 115. The downlink transmission may also be referred to as a forward link transmission, while the uplink transmission may also be referred to as a reverse link transmission.

The geographic coverage area 110 of a base station 105 may be divided into sectors that form only a portion of the geographic coverage area 110 and each sector may be associated with a cell. For example, each base station 105 may provide communication coverage for a macrocell, a small cell, a hotspot, or other type of cell, or various combinations thereof. In some examples, the base station 105 may be mobile and thus provide communication coverage for a mobile 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, heterogeneous LTE/LTE-a or NR networks, wherein 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 between neighboring cells operating via the same or different carriers. 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 other) 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 the geographic coverage area 110 over which the logical entity operates.

UEs 115 may be dispersed throughout wireless communication system 100, and sometimes such UEs 115 may be fixed or mobile. UE 115 may also be referred to as a mobile device, wireless device, remote device, handheld device, or subscriber device, or some other suitable terminology, where "device" may also be referred to as a unit, station, terminal, or client. The UE 115 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 UE 115 may also refer to a Wireless Local Loop (WLL) station, an internet of things (IoT) device, a internet of things (IoE) device, or an MTC device, etc., which may be implemented in various items such as appliances, vehicles, meters, etc.

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 a data communication technology that allows devices to communicate with each other or with the 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 to implement automatic behavior of the 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 communication (e.g., a mode that supports unidirectional communication via transmission or reception but not simultaneous transmission and reception). In some examples, half-duplex communications may be performed at a reduced peak rate. Other power saving techniques for UE 115 include entering a power-saving "deep sleep" mode when not engaged in active communication, or operating over a limited bandwidth (e.g., according to narrowband communication). In some cases, the UE 115 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 communications for these functions.

In some cases, the UE 115 may also be capable of other direct communication with other UEs 115 (e.g., using peer-to-peer (P2P), device-to-device (D2D) protocols, etc.). One or more UEs of a group of UEs 115 utilizing D2D communication may be within the geographic coverage area 110 of the base station 105. Other UEs 115 in the group may be outside of 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 UE 115 transmits to each other UE 115 in the group. In some cases, the base station 105 may facilitate scheduling/allocation of resources for D2D communications. In other cases, some D2D communications may be performed between UEs 115 without the participation of base station 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 through a backhaul link 132 (e.g., via S1 or other interfaces). The base stations 105 may communicate with each other directly (e.g., directly between the base stations 105) or indirectly (e.g., via the core network 130) over a backhaul link 134 (e.g., via an X2 or other interface).

The core network 130 may provide user authentication, access authorization, tracking, internet Protocol (IP) connectivity, and other access, routing, or mobility functions. The core network 130 may be an Evolved Packet Core (EPC) 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 delivered through an 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 connect to network operator IP services. 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 station 105, may include a subcomponent, such as an access network entity, which may be an example of an Access Node Controller (ANC). Each access network entity may communicate with UE 115 through a plurality of other access network transmitting entities, which may be referred to as radio heads, intelligent radio heads, or transmission/reception 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, since the length of the wavelength ranges from about one decimeter to one meter, the region of 300MHz to 3GHz is called an Ultra High Frequency (UHF) region or decimeter band. 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 UEs 115 located indoors. Transmission of UHF waves may be associated with smaller antennas and shorter distances (e.g., less than 100 km) than transmission of smaller frequencies and longer waves using 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-band, using a frequency band of 3GHz to 30 GHz. The SHF region includes frequency bands such as the 5GHz industrial, scientific, and medical (ISM) bands, which can be used in due course 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 (e.g., from 30GHz to 300 GHz), which is also referred to as the millimeter-frequency band. In some examples, wireless communication system 100 may support millimeter wave (mmW) communications between UE 115 and base station 105, and EHF antennas of the respective devices may be even smaller and more closely spaced than UHF antennas. In some cases, this may facilitate use of antenna arrays within UE 115 (e.g., for multiple-input multiple-output (MIMO) operations, such as spatial multiplexing, or for directional beamforming). However, propagation of EHF transmissions may experience 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 frequency bands across these frequency regions may vary from country to country or regulatory agency.

In some cases, the wireless communication system 100 may utilize both the licensed radio frequency spectrum band and the 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 frequency band, such as the 5GHz ISM band. When operating in the unlicensed/shared radio frequency spectrum band, wireless devices, such as base stations 105 and UEs 115, may employ listen-before-talk (LBT) procedures to ensure that the frequency channels are clear before transmitting data. In some cases, operation in the unlicensed/shared radio frequency spectrum may be combined with CCs operating in the licensed frequency spectrum 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 base station 105 or UE 115 may be located within one or more antennas or antenna arrays, which may support MIMO operation, 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, antennas or antenna arrays associated with base station 105 may be located in different geographic locations. The base station 105 may have an antenna array with multiple rows and columns of antenna ports that the base station 105 may use to support beamforming for communication with the UEs 115. Also, UE 115 may have one or more antenna arrays that may support various MIMO or beamforming operations.

The MIMO wireless system uses a transmission scheme between a transmission apparatus (e.g., base station 105) and a reception apparatus (e.g., UE 115) in which both the transmission apparatus and the reception apparatus are equipped with a plurality of antennas. MIMO communication may employ multipath signal propagation to increase utilization of the radio frequency spectrum band by transmitting or receiving different signals via different spatial paths, which may be referred to as spatial multiplexing. The 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 the different antennas or different combinations of antennas at a given device (e.g., orthogonal resources of the device associated with the spatial dimension) 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 implemented 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 UE 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 transmission directions. A receiving device (e.g., UE 115, 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 base station 105. For example, the receiving device may attempt multiple receiving directions by: the received signals are received via different antenna sub-arrays, processed according to different antenna sub-arrays, received according to different sets of receive beamforming weights applied to signals received at multiple antenna elements of an antenna array, or processed 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 that operates according to a layered protocol stack. In the user plane, communications at the bearer or Packet Data Convergence Protocol (PDCP) layer may be IP-based. In some cases, a Radio Link Control (RLC) layer may perform packet segmentation and reassembly to communicate over logical channels. A Medium Access Control (MAC) layer may perform priority 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 an RRC connection between the UE 115 and the base station 105 or core network 130 supporting radio bearers for user plane data. At the Physical (PHY) layer, transport channels may be mapped to physical channels.

In some cases, the UE 115 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 severe radio conditions (e.g., signal-to-noise 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 can be expressed in multiples of a basic time unit, e.g. can refer to T _s Sample period=1/30,720,000 seconds. The time intervals (T) of the communication resources may be organized according to radio frames each having a duration of 10 milliseconds (ms) _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 preceding each symbol period). Each symbol period may contain 2048 sample periods in addition to the cyclic prefix. In some cases, a subframe may be a minimum 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 bursts of shortened TTIs (sTTI) or in selected component carriers 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 a mini-slot of a mini-slot may be a minimum 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 slot aggregation, where multiple slots or small slots may be aggregated together for communication between a UE 115 and a base station 105.

The resource element may consist of one symbol period (e.g., the duration of one modulation symbol) and one subcarrier (e.g., the 15kHz frequency range). The resource block may contain 12 consecutive subcarriers (e.g., which together form one "carrier") in the frequency domain and 7 consecutive Orthogonal Frequency Division Multiplexing (OFDM) symbol periods (1 slot) in the time domain for a conventional cyclic prefix in each OFDM symbol, 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 within each symbol period). Thus, the more resource elements that the UE 115 receives and the higher the modulation scheme (e.g., the greater the number of bits that can 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, the 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 communication with the UE 115.

The term "carrier" refers to a collection of radio spectrum resources having a defined organization structure for supporting uplink or downlink communications over the communication link 125. For example, the carrier of the communication link 125 may include a portion of the 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). The carrier may be organized to include a plurality of physical channels, each of which 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 and control information or signaling to support decoding of the user data. The carrier may also include dedicated acquisition signaling (e.g., synchronization signals or system information, etc.) and control signaling to coordinate the operation of the carrier. 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 carrier according to various techniques. The physical control channels and physical data channels may be multiplexed on the downlink carrier using, for example, a Time Division Multiplexing (TDM) technique, a Frequency Division Multiplexing (FDM) technique, or a hybrid TDM-FDM technique. In some examples, control information transmitted in a physical control channel may be distributed among different control regions in a cascaded manner (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 the "system bandwidth" of the carrier or 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 20 MHz) for a carrier of a particular radio access technology. In some examples, the system bandwidth may refer to a minimum bandwidth unit used to schedule communications between the base station 105 and the UE 115. In other examples, the base station 105 or UE 115 may also support communication over carriers 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 the 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.

A device (e.g., base station or UE 115) of 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 of a set of carrier bandwidths. For example, the base station 105 or the UE 115 may perform some communications (e.g., wideband communications) according to a system bandwidth, and may perform some communications (e.g., narrowband communications) according to a smaller bandwidth. In some examples, the wireless communication system 100 may include a base station 105 and/or UE that supports simultaneous communications 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, a feature that may be referred to as Carrier Aggregation (CA) or multi-carrier operation. According to a carrier aggregation configuration, UE 115 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 characteristics, 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 sub-optimal 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 not available to UEs 115, which UEs 115 are not able 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 other CCs. A shorter symbol duration may be associated with an increased spacing between adjacent subcarriers. A device utilizing an eCC, such as UE115 or base station 105, may transmit a wideband signal within a shortened symbol duration (e.g., 16.67 microseconds) (e.g., according to a frequency channel or carrier bandwidth of 20, 40, 60, 80MHz, etc.). The TTIs 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 the 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, etc. The flexibility of eCC symbol duration and subcarrier spacing may allow eCC to be used across multiple spectrums. In some examples, NR sharing of spectrum may improve spectrum utilization and spectrum efficiency, especially through dynamic vertical sharing (e.g., across frequencies) and horizontal sharing (e.g., across time) of resources.

In various aspects, as further shown in fig. 1, the first UE 115-1 may be configured to support D2D communications with the second UE 115-2. Here, D2D communication is represented by communication link 150, for example. 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, the base station 105-1 may determine, e.g., based on serving node activity, location information, etc., that the UE 115-1 and the UE115-2 may be indicated as being within a threshold communication proximity of each other. In some cases, UE115-2 may be instructed (e.g., by base station 105-1) to transmit one or more particular SRS, 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 way, the UE may make D2D channel measurement(s) and send corresponding reports to the base station 105-1. The base station 105-1 that has identified the UE 115-1 and the UE115-2 as D2D communication candidates 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 disclosure. Fig. 2B is a diagram 230 illustrating an example of channels within a frame structure of a DL frame in accordance with 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 disclosure. Fig. 2D is a diagram 280 illustrating an example of channels within a frame structure of an UL frame in accordance with aspects of the present disclosure. Other wireless communication technologies may have different frame structures and/or different channels. A frame (10 ms) may be divided into 10 subframes of the same size. Each subframe may include two consecutive slots. A resource grid may be used to represent two slots, each slot comprising 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, the 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 the extended cyclic prefix, the 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. DL-RSs 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 3 ₀ ,R ₁ 、R ₂ And R is ₃ ) UE-RS (indicated as R) for antenna port 5 ₅ ) And a CSI-RS (indicated as R) for antenna port 15.

Fig. 2B shows an example of various channels within a 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 a PDCCH occupying 3 symbols). The PDCCH carries Downlink Control Information (DCI) within one or more Control Channel Elements (CCEs), each CCE including 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, one RB pair for each subset). A physical hybrid automatic repeat request (ARQ) (HARQ) indicator channel (PHICH) is also within symbol 0 of slot 0 and carries a HARQ Indicator (HI) that indicates 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. PSCH carries a Primary Synchronization Signal (PSS) that is used by the UE to determine subframe/symbol timing and physical layer identity. The Secondary Synchronization Channel (SSCH) can 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 PCI, the UE can determine the location of the DL-RS. A Physical Broadcast Channel (PBCH) carrying a Master Information Block (MIB) may be logically grouped with PSCH and SSCH to form a Synchronization Signal (SS) block. The MIB provides the number of RBs in the DL system bandwidth, PHICH configuration, and System Frame Number (SFN). The Physical Downlink Shared Channel (PDSCH) carries user data, broadcast system information such as System Information Blocks (SIBs) that are not transmitted over the PBCH, and paging messages.

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, SRS transmissions may be measured by a receiving UE to determine 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 UL.

Fig. 2D shows an example of various channels within a UL subframe of a frame. A Physical Random Access Channel (PRACH) may be within one or more subframes within a 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 a scheduling request, a Channel Quality Indicator (CQI), a Precoding Matrix Indicator (PMI), a Rank Indicator (RI), and HARQ ACK/NACK feedback. PUSCH carries data and may additionally be used to carry Buffer Status Reports (BSR), 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 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. Controller/processor 375 provides RRC layer functions associated with broadcast of system information (e.g., MIB, SIB), RRC connection control (e.g., RRC connection paging, RRC connection setup, 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 upper layer Packet Data Unit (PDU) delivery, 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 MAC SDUs onto Transport Blocks (TBs), demultiplexing MAC SDUs from TBs, scheduling information reporting, error correction by HARQ, prioritization and logical channel prioritization.

The Transmit (TX) processor 316 and the Receive (RX) processor 370 implement layer 1 functions associated with various signal processing functions. Layer 1, which includes a Physical (PHY) layer, may include error detection on a transport channel, forward Error Correction (FEC) encoding/decoding of a transport channel, interleaving, rate matching, mapping onto a physical channel, modulation/demodulation of a physical channel, and MIMO antenna processing. TX processor 316 processes the mapping to signal constellations 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 produce a physical channel carrying the time domain OFDM symbol stream. The OFDM streams are spatially precoded to produce multiple spatial streams. The channel estimates from channel estimator 374 may be used to determine the coding and modulation scheme, 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 the 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 via its respective antenna 352. Each receiver 354RX recovers information modulated onto an RF carrier and provides the information to the Receive (RX) processor 356.TX processor 368 and RX processor 356 implement layer 1 functions associated with various signal processing functions. RX processor 356 can perform spatial processing on the information to recover any spatial streams destined for UE 350. If multiple spatial streams are destined for the UE 350, they may be combined into a single OFDM symbol stream by an RX processor 356. 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 computed 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 that implements layer 3 and layer 2 functions.

The controller/processor 359 can be associated with a memory 360 that stores program codes and data. Memory 360 may be referred to as a computer-readable medium. In the UL, controller/processor 359 provides demultiplexing between transport and logical channels, packet reassembly, deciphering, header decompression, and control signal processing to recover IP packets from EPC 160. The controller/processor 359 may also be responsible for error detection using an ACK and/or NACK protocol 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 DL transmission by the base station 310, the 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 transmission 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 to TBs, demultiplexing of MAC SDUs from TBs, scheduling information reporting, error correction by HARQ, prioritization and logical channel prioritization.

TX processor 368 can use channel estimates derived by channel estimator 358 from reference signals or feedback transmitted by base station 310 to select an appropriate coding and modulation scheme and facilitate spatial processing. The spatial streams generated by TX processor 368 may be provided to different antenna 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 similar manner as described in connection with the receiver functionality 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 the RX processor 370.

The controller/processor 375 may be associated with a memory 376 that stores program codes and data. Memory 376 may be referred to as a computer-readable medium. In the UL, controller/processor 375 provides demultiplexing between transport and logical channels, packet reassembly, deciphering, header decompression, control signal processing to recover IP packets from 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 an ACK and/or NACK protocol to support HARQ operations.

Fig. 4 is a flow chart illustrating an example method 400 for use at a base station in accordance with certain aspects of the present disclosure. The boxes 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 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 some 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 the 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 has been estimated, such 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 SRS or other similar transmissions 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 at least partially inform 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 result, 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 communication 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 GUL resource allocations may include, at least in part, one or more previously arranged GUL resource allocations for a given UE, while in other cases, such GUL resource allocations may be new/different. In some implementations, the GUL resource allocation determination made at block 404 may take into account, at least in part, various network conditions(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 of day or date, potential radio interference considerations, quality of service associated with D2D communication, etc., or some combination thereof, to name a few.

At example block 406, 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 (e.g., as determined at block 404). The indication of the UE at block 406 may indicate, at least in part, one or more wireless signaling parameters for supporting at least a portion of D2D communications. For example, the indication may inform the first UE: D2D communication with the second UE is supported by transmitting D2D signals on the first GUL resources and receiving D2D signals from the second UE on the second GUL resources. Similarly, for example, the indication may inform the second UE: D2D communication with the first UE is 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, to name a few examples. Due to 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 communications 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 effectively used, etc. In particular examples, the base station may at least partially monitor D2D communication traffic and/or "keep-alive" signals to determine whether D2D communication should continue or be altered in some way. In some example embodiments, the 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 environments (e.g., link quality, D2D channel measurements, etc.), changes in UE/communication requirements, and/or the like.

At example block 410 (which may be optional), the base station may determine that the D2D communication as established at block 406 is to end. In some cases, the base station may end D2D communications by altering one or more GUL resource allocations and informing the affected UE(s) as determined in block 404. 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, a period of time elapsed, lack of a keep-alive signal, etc., may represent an event that may trigger, at least in part, ending of D2D communications 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, the method 400 may allow the base station to handover one or both UEs to another base station at blocks 408 and/or 410 or where applicable. In some cases, such a handoff may include ending the D2D communication as established at block 406. In some cases, the handoff may be configured to maintain all or part of the ongoing or scheduled D2D communication, e.g., where monitoring of the D2D communication may also be transferred to the target base station in some manner, e.g., as part of the handoff. In some embodiments, indirect communications between UEs involving 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 further described and illustrated in example paging flow 800 in fig. 8.

Attention is next drawn to fig. 5, which illustrates a flow chart of an example method 500 used by a UE in accordance with certain aspects of the present disclosure. The boxes 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 embodiments.

With this in mind, at example (optional) block 502, a (first) UE may send a request for D2D communication, a report corresponding to D2D channel measurements, etc. to a base station, which may be considered at least in part by the base station for D2D communication 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/previous GUL resource allocations.

At example block 504, the first UE may receive an indication that a GUL resource allocation has been or will be provided for D2D communication 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 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. 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 D2D communication. For example, the indication may inform the first UE: D2D communication with the second UE is supported by transmitting D2D signals on the first GUL resources and receiving D2D signals from the second UE on the second GUL resources. 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, 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, which may indicate whether D2D communication or other wireless communication with the first UE should continue, somehow change, or may end. Such 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 communications.

In another example embodiment, at (optional) block 514, one or more keep-alive signals may be sent via D2D communications, with the intention of supporting/maintaining D2D communications, e.g., possibly in the absence/delay of other D2D traffic. Here, for example, such a keep-alive signal may be received by the second UE and/or the base station, one or both of which may continue to support D2D communications in view of the keep-alive 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 monitor for ACK/NACK signals or the like as appropriate, which may inform decisions to maintain, alter, or possibly terminate D2D communications. Thus, for example, if a threshold number of NACKs is reached or lack of NACKs within a certain period of time, 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 D2D communications in response to such requests or reports and/or by monitoring D2D communications in some manner, e.g., ending the D2D communications, reallocating the GUL resources, handing over one or both UEs to another base station, etc.

Example methods 400 and 500 illustrate techniques by which conditions of channel quality may be measured and considered in determining whether a UE may be a D2D communication candidate. 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 may be monitored is a UE-specific demodulation reference signal (DM-RS) because it is located in the middle of the PUSCH signal.

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 make channel measurements via SRS transmission in a distributed manner. Channel quality may be an important factor in determining whether a channel can be used, which may be more important than the distance between UEs. However, switching communications to D2D communications may result in additional interference to neighboring devices. This cost may also be weighed against the increase in efficiency when determining whether to switch to D2D communication. Note that even after D2D setup (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 D2D communication and possibly switch to an indirect transmission route between the two UEs.

In one example, the channel conditions may be measured using existing UL SRS. In MuLTEfire, the UE may transmit UL SRS aperiodically in PUCCH as part of S subframes or in conjunction with PUSCH, according to a request from the gNB. The special subframes are used in TDD mode for switching from downlink to uplink. Such subframes may include GP, upPTS, and DwPTS portions, where the GP portion includes a guard period between the UpPTS and DwPTS portions. Here, the UpPTS includes an uplink pilot 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 the base station-indicated scheduling. Subframes including such SRS transmissions that may be available may be indicated by a UE-specific or cell-specific configuration provided by the gNB, along with SRS bandwidth. This configuration may indicate frequency and time domain resources that the UE may use. The subframes in which SRS transmission occurs are examples of time domain resources. To enable the D2D measurement to be used, for example, to determine the channel quality between two UEs, as presented herein, the base station may request the monitored UE to transmit aperiodic SRS in the upcoming short PUCCH (sPUCCH) or request the monitored UE to transmit SRS using a Physical Uplink Shared Channel (PUSCH) if the monitored UE is already transmitting UL traffic. Here, for example, the sPUCCH may include a PUCCH for independent operation in an unlicensed spectrum. The gNB may request that the monitoring UE monitor SRS transmissions from the monitored UE in upcoming pucch/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 a base station 600.

In certain 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., 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., ARM and DSP) may be used.

The base station 600 may also include a memory 606. Memory 606 may be any electronic component capable of storing electronic information. 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 using data 614 that may be stored in the memory 606. When the processing unit 602 executes the instructions 1609, various portions of the instructions 612a may be loaded onto the processing unit 602, and various pieces of data 614a may be loaded onto the 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 the receiver 622 may be collectively referred to as a transceiver 604. One or more antennas 624a-b may be electrically coupled to transceiver 604. The base station 600 may also include (not shown) multiple transmitters, multiple receivers, and/or multiple transceivers.

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

Fig. 7 is a block diagram illustrating some example components that may be included within a 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., 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 shown in the wireless communication device 700 of fig. 12, in alternative configurations, a combination of processors (e.g., ARM and DSP) may be used.

The UE 700 may also include a memory 706. 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, data 714 and/or instructions 712 may sometimes 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 using data 714 that may be stored in the memory 706. When the processing unit 702 executes the instructions 1709, various portions of the instructions 712a may be loaded onto the processing unit 702 and various pieces of data 714a may be loaded onto the processing unit 702.

The UE 700 may also include a transmitter 720 and a receiver 722 to allow for the transmission and reception of wireless signals to and from other devices (not shown). The transmitter 720 and the receiver 722 may be collectively referred to as a transceiver 704. One or more antennas 724a-b may be electrically coupled to 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, etc., which may include a power bus, a control signal bus, a status signal bus, a data bus, etc. For clarity, the various buses are shown in FIG. 7 as bus 710. It should be noted that these methods describe possible embodiments, and that operations and steps may be rearranged or otherwise modified so 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 other methods, or other steps or techniques described herein.

Attention is next drawn to fig. 8, which includes an exemplary paging flow 800 for allowing D2D communication between a first UE 115-1 and a second UE 115-2, which may be implemented at least in part by the techniques provided herein. As shown in 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 handoff 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 UE 115-2, 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, reference is made to block 403 in method 400 and block 502 in method 500.

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

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

As a further illustrative example, signal 818 is shown as being sent by first UE 115-1 to second UE 115-2 as part of D2D communication and represents at least one keep-alive message. For example, reference is made to block 514 in method 500. As further shown, such keep-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 part of a D2D communication. In another example, signals 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 generally be expected to be received from the second UE 115-2 as part of D2D communication, but for some reason have not been received by the first UE 115-1 (as further shown by the hooked-up portion). For example, the "lost" signal 822 may have been an expected traffic message, an ACK/NACK message, a keep alive message, etc. Signal 822 may be "lost" for a number 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 either first base station 105-1 or second base station 105-2. In certain implementations presented herein, D2D communications may be changed or ended based at least in part on lack of transmission/reception of signal 822. For example, reference is made 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., alter, end, switch, etc. An example of a type of change may be represented by signals 824 and/or 826 by which the first base station 105-1 may indicate to the first UE 115-1 and the second UE 115-2, respectively, a change affecting D2D communication. For example, reference is made to blocks 408 and 410 in method 400. Here, for example, new/different GUL resource allocation(s) may be indicated, or the end of D2D communication may be indicated. In another example, signal(s) 824 and/or 826 may represent indirect signaling to support ongoing D2D communications.

Another example modification may be represented by signal 828, which may indicate to the second base station 105-2 that the first UE 115-1, the second UE 115-2, or both may be handed off, via signal 828. For example, reference is made to blocks 408 and 410 in method 400. Here, for example, in some cases, D2D communication may end due to handover. In other cases, D2D communication may continue, in whole or in part, after handoff. Signals 830 and 832 may, for example, represent potential changes or maintenance of D2D communications 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 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 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 for execution by a processor, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium. Other examples and implementations are within the scope of the present disclosure and the appended claims. For example, due to the nature of software, the functions described above may be implemented using software executed by a processor, hardware, firmware, hardwired or a combination of any of these. Features that implement the functions may also be physically located in various places, including being distributed such that portions of the functions are implemented at different Physical (PHY) locations. Also, as used herein, including in the claims, an "or" as used in an item list (e.g., an item list 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. Non-transitory storage media may be any available media 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 Disk (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. Further, 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 a 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 generally used interchangeably. A CDMA system may implement a radio technology such as CDMA2000, universal Terrestrial Radio Access (UTRA), and the like. CDMA2000 covers IS-2000, IS-95, and IS-856 standards. IS-2000 release 0 and a are commonly referred to as CDMA2000 1X, etc. IS-856 (TIA-856) IS commonly referred to as CDMA2000 1xEV-DO, high Rate Packet Data (HRPD), or the like. UTRA includes Wideband CDMA (WCDMA) and other variations of CDMA. TDMA systems may implement radio technologies such as global system for mobile communications (GSM). OFDMA systems 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, and the like. UTRA and E-UTRA are part of the universal mobile telecommunications system (Universal Mobile Telecommunications System (UMTS)). 3GPP LTE and LTE-advanced (LTE-A) are new versions of UMTS that use E-UTRA. UTRA, E-UTRA, UMTS, LTE, 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" (3 GPP 2). The techniques described herein may be used for the systems and radio technologies mentioned above and 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 that of LTE.

In an LTE/LTE-a network including the networks described herein, the term evolved node B (eNB) may be generally used to describe a base station. One or more wireless communication systems described herein may include heterogeneous LTE/LTE-a networks in which different types of enbs provide coverage for respective geographic areas. For example, each eNB or base station may provide communication coverage for a macrocell, 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 station transceiver, 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 may be partitioned 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., macrocell 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 the like. 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, a coverage area for one communication technology may overlap with a coverage area associated with another technology. Different technologies may be associated with the same base station or different base stations.

The wireless communication system 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 transmissions from different base stations may not be aligned in time. The techniques described herein may be used for synchronous or asynchronous operation.

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 for FDD (e.g., frame structure type 1) and a frame structure for TDD (e.g., frame structure type 2) may be defined.

Accordingly, aspects of the present disclosure may be provided for reception at transmission and transmission at reception. It should be noted that these methods describe possible embodiments, and that operations and steps may be rearranged or otherwise modified so 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 (e.g., structured/platform ASICs, FPGAs, or another semi-custom IC) may be used, which may be programmed in any manner known in the art. The functions of each element may also be implemented, in whole or in part, with instructions embodied in a memory, which are formatted to be executed by one or more general or application-specific processors.

In the drawings, similar components or features may have the same reference label. In addition, 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 a first reference label is used in the specification, the description applies to any one of the similar components having the same first reference label, irrespective of the second reference label.

Claims

1. A method for use at a first user equipment, UE, the method comprising, at the first UE:

measuring the device-to-device D2D channel to obtain D2D channel measurements;

determining whether to send a request for D2D communication based on the D2D channel measurements;

transmitting the request for D2D communication based at least in part on determining whether to transmit the request;

receiving an indication from a network entity that an unlicensed uplink, GUL, resource allocation has been or will be provided for D2D communications between the first UE and a second UE in response to the request; and

the D2D communication is supported by:

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

A second signal is received from the second UE via at least a second portion of the GUL resource allocation.

2. The method according to 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 alternatively

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 network entity.

3. The method of claim 1, wherein measuring the D2D channel comprises measuring a sounding reference signal, SRS, transmission by the second UE.

4. The method of claim 1, wherein a first SRS is 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 signals intended for the network entity.

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

6. 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:

Measuring the device-to-device D2D channel to obtain D2D channel measurements;

obtaining, from a network entity and via the receiver, an indication that an unlicensed uplink, GUL, resource allocation has been or will be provided for D2D communications between the first UE and a second UE in response to the request; 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, and

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

7. The first UE of claim 6, wherein:

8. The first UE of claim 6, wherein the processing unit is further configured to:

Initiate, via the transmitter, a transmission of a request for the D2D communication to the network entity, and wherein the indication received from the network entity is in response to the request.

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

obtaining, via the receiver, D2D channel measurements of sounding reference signal, SRS, transmissions by the second UE; and

a determination is made whether to initiate transmission of the request based at least in part on the D2D channel measurement.

10. The first UE of claim 6, wherein to support the D2D communication, the processing unit is further configured to:

initiating transmission of a first sounding reference signal, SRS, via the transmitter;

initiating, via the transmitter, transmission of at least one keep-alive signal to maintain the D2D communication;

or both.

11. The first UE of claim 10, wherein the first SRS is 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 signals intended for the network entity.

12. The first UE of claim 6, wherein the GUL resource allocation is provided as part of a MuLTEfire framework.

13. A method for use at a network entity, the method comprising, at the network entity:

determining to provide unlicensed uplink, GUL, resource allocation for device-to-device, D2D, communications between a first UE and a second UE;

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; and

the D2D communication is monitored 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.

14. The method of claim 13, wherein the first portion of the GUL resource allocation and the second portion of the GUL resource allocation comprise a same GUL resource allocation.

15. The method of claim 13, 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 network entity.

16. The method of claim 13, wherein the first signal, the second signal, or both comprise a keep-alive signal intended to maintain the D2D communication.

17. The method of claim 13, and further comprising, at the network entity:

the D2D communication is ended 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 network entity handover determination, a GUL resource reallocation determination, or some combination thereof.

18. The method of claim 13, and further comprising, at the network entity:

a request for the D2D communication is received from the first UE, the second UE, or both, and the GUL resource allocation is determined to be provided for the D2D communication based at least in part on the request.

19. The method of claim 13, and further comprising, at the network entity:

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 based on sounding reference signal, SRS, transmissions from the second UE.

20. The method of claim 13, wherein the GUL resource allocation is provided as part of a MuLTEfire framework.

21. A network entity, comprising:

a receiver;

a transmitter; and

initiate transmission, via the transmitter, of 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, in supporting the D2D communication therebetween; and

the D2D communication is monitored by the receiver based at least in part on a first signal received via at least a first portion of the GUL resource allocation and a second signal received 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.

22. The network entity of claim 21, 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 network entity;

the first signal, the second signal, or both include a keep alive signal intended to maintain the D2D communication;

or some combination thereof.

23. The network entity of claim 21, wherein the processing unit is further configured to:

24. The network entity of claim 21, 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

the GUL resource allocation is determined to be provided for the D2D communication based at least in part on the request.

25. The network entity of claim 21, 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.

26. The network entity of claim 21, wherein the GUL resource allocation is provided as part of a MuLTEfire framework.

27. A non-transitory computer-readable medium having stored thereon code for use at a first user equipment, UE, the code comprising instructions executable by a processor to:

measuring the device-to-device D2D channel to obtain D2D channel measurements;

The D2D communication is supported by:

28. A non-transitory computer-readable medium having stored thereon code for use at a network entity, the code comprising instructions executable by a processor to: