Aspects of the disclosure relate to, at a wireless communication device, occupying a slot in a first subchannel, wherein the first subchannel comprises a sidelink subchannel in a licensed band, transmitting sidelink control in the first subchannel during the slot, except during a symbol gap indicated to include at least a last symbol of a plurality of symbols supported by the slot, seeking access to a secondary carrier in an unlicensed band, and transmitting sidelink traffic in the secondary carrier upon receiving the access to the secondary carrier. Other aspects, embodiments, and features are also claimed and described.

TECHNICAL FIELD

The technology discussed below relates generally to wireless communication systems, and more particularly to frame-based equipment (FBE) unlicensed band sidelink access that is assisted by sidelink in a licensed band.

INTRODUCTION

Scheduling access to licensed spectrum for sidelink communication between devices is performed efficiently. Presently, sidelink is used predominantly in the vehicle-to-vehicle (V2X) use case or domain. As sidelink use cases evolve in vertical domains other than the V2X domain, ever growing amounts of data transfer will present an increasing burden to the licensed spectrum, such as the Intelligent Transportation System (ITS) band presently handling V2X communication. Offloading of data to unlicensed spectrum is seen as one way to address the data bandwidth limitations of the licensed spectrum. However, scheduling access to unlicensed spectrum for sidelink communications is not as efficient as scheduling access to licensed spectrum for sidelink communications. The terms licensed spectrum, licensed band, and licensed bands may be used interchangeably. Likewise, the terms unlicensed spectrum, unlicensed band, and unlicensed bands may be used interchangeably.

As the demand for wireless communication increases, research and development continue to advance the communication technologies field. For example, techniques related to improved methods to schedule access to unlicensed spectrum for sidelink communication, between devices, may be useful, particularly for communications of all types between devices, where the communications are not necessarily scheduled by a network-type scheduling entity, such as, but not limited to, sidelink communications in the New Radio - Unlicensed (NR-U) domain.

BRIEF SUMMARY OF SOME EXAMPLES

In one example a method of wireless communication in a wireless communication network is disclosed. The method may include, at a wireless communication device, occupying a slot in a first subchannel, wherein the first subchannel comprises a sidelink subchannel in a licensed band, transmitting sidelink control in the first subchannel during the slot, except during a symbol gap indicated to include at least a last symbol of a plurality of symbols supported by the slot, seeking access to a secondary carrier in an unlicensed band, and transmitting sidelink traffic in the secondary carrier upon receiving the access to the secondary carrier.

In another example, a wireless communication device in a wireless communication network is disclosed. The wireless communication device includes a wireless transceiver, a memory, and a processor communicatively coupled to the wireless transceiver and the memory. According to one aspect, the processor and the memory may be configured to occupy a slot in a first subchannel, wherein the first subchannel comprises a sidelink subchannel in a licensed band, transmit sidelink control in the first subchannel during the slot, except during a symbol gap indicated to include at least a last symbol of a plurality of symbols supported by the slot, seek access to a secondary carrier in an unlicensed band, and transmit sidelink traffic in the secondary carrier upon receiving the access to the secondary carrier.

According to one aspect, a wireless communication device in a wireless communication network may include means for occupying a slot in a first subchannel, wherein the first subchannel comprises a sidelink subchannel in a licensed band, means for transmitting sidelink control in the first subchannel during the slot, except during a symbol gap indicated to include at least a last symbol of a plurality of symbols supported by the slot, means for seeking access to a secondary carrier in an unlicensed band, and means for transmitting sidelink traffic in the secondary carrier upon receiving the access to the secondary carrier.

In another example, an article of manufacture for use by a wireless communication device in a wireless communication network is described. The article of manufacture includes a non-transitory computer-readable medium having stored therein instructions executable by one or more processors of the wireless communication device. The instructions include instructions to occupy a slot in a first subchannel, wherein the first subchannel comprises a sidelink subchannel in a licensed band, transmit sidelink control in the first subchannel during the slot, except during a symbol gap indicated to include at least a last symbol of a plurality of symbols supported by the slot, seek access to a secondary carrier in an unlicensed band, and transmit sidelink traffic in the secondary carrier upon receiving the access to the secondary carrier.

DETAILED DESCRIPTION

Aspects described herein implement a heterogeneous carrier aggregation design for penetrating access control timing of New Radio Sidelink (NR SL) operating on a primary carrier in a licensed band to sidelink operating on a secondary carrier in an unlicensed band. The word heterogeneous is used to describe the design, which aggregates carriers from both the licensed and unlicensed spectrum together for one sidelink communication (e.g., one sidelink communication including sidelink control and sidelink traffic). As used herein, control refers to control messaging and traffic refers to non-control data, such as user data. Because the aggregated carriers are of two different types (e.g., carriers from licensed spectrum and carriers from unlicensed spectrum), the aggregation of the carriers is referred to as a heterogeneous aggregation. In contrast, a homogeneous aggregation would include carriers of only the licensed spectrum or carriers of only the unlicensed spectrum.

According to some aspects, there may be a benefit in offloading SL traffic from the primary carrier in the licensed band to the secondary carrier in the unlicensed band. For example, offloading the SL traffic may reduce some burden on the primary carrier by shifting the burden to the secondary carrier. As used herein, the primary carrier will refer to the carrier in the licensed band and the secondary carrier will refer to the carrier in the unlicensed band. According to aspects described herein, the primary carrier may carry all control information and the secondary carrier may carry traffic offloaded from the primary carrier. Furthermore, the secondary carrier may be relieved of any requirement for control, including, for example, sensing, resolution, access control, congestion control, and feedback. Instead, the aspects described herein may implement all control (including access control) for both the primary and secondary carriers to the primary carrier and shift all traffic from the primary carrier to the secondary carrier. In some aspects, the decisions made for the primary carrier may inform the decisions made for the secondary carrier.

Device-to-device communication, for example using sidelink, will become more frequent as time goes by. The 3rdGeneration Partnership Project (3GPP) standard setting body created standards and technical specification for sidelink in 4G Long Term Evolution (LTE). In support of the 5G rollout, 3GPP has also promulgated standards and specifications for sidelink in association with 5G standards. The exemplary processes and apparatus described herein may be described in terms of the 5G New Radio Sidelink (NR SL) standards; however, the disclosure is not limited to 5G NR or NR SL; the processes and apparatus described herein may find application with other wireless communication standards and specifications.

Presently, much work in NR SL is being performed in connection with Cellular Vehicle to Everything (C-V2X) (referred to generally herein as V2X) and/or Dedicated Short Range Communications (DSRC) use cases. These use cases may operate over licensed spectrum. For example, NR SL may operate in the ITS band (e.g., around 5.8-5.9 GHz) and/or in frequency spectrum owned by individual operators.

3GPP NR may further extend sidelink to other vertical domains (e.g., domains other than V2X). However, not every vertical domain can obtain or can have access to exclusive licensed spectrum like ITS or Industrial Internet of Things (IIoT) that is being used, for example, in Germany.

More users will benefit from sidelink if it could be used in unlicensed spectrum. To that end, 3GPP is currently promulgating standards and specifications for New Radio-Unlicensed (NR-U) operations, which provide, among other things, standards for use of sidelink in the unlicensed frequency bands.

ETSI has specified two channel access methodologies for unlicensed spectrum (e.g., the unlicensed 5 GHz band). The methodologies are referred to as load-based equipment (LBE) access and the frame-based equipment (FBE) access. LBE has been the dominating methodology due to its support for asynchronous channel access. LBE has been adopted by WiFi, 3GPP Licensed Assisted Access (LAA), and 3GPP NR-U. However, LBE is not considered to be “friendly” to Coordinated Multi-Point (CoMP) schemes and CoMP-like scheme that make use of simultaneous synchronous access from multiple nodes. This is unfortunate for NR SL, which has, to date, relied on a synchronous channel access engine at each UE.

FBE may be less-capable than other access schemes (like LBE) for the Uu interface yet shows good results for the PC-5 interface and for channel access in the unlicensed spectrum (e.g., the unlicensed 5 GHz band).

There are at least two reasons why FBE has not been adopted for the Uu interface. First, several FBE gNBs are not able to compete for airtime with the same number of LBE gNBs. However, this is not the case for SL because SL UEs are not competing with gNBs for airtime. Instead, they are competing for airtime among themselves. Second, competition among several FBE gNBs can lead to an unstable system. However, the aspects described herein may solve the problem of instability by arranging SL communication (e.g., coordinating SL communication) using a licensed SL carrier. Aspects described herein may overcome the obstacles found with FBE by using timing from channel access in a primary carrier in the licensed band to derive timing for FBE-based access over a secondary carrier in the unlicensed band.

The various concepts presented throughout this disclosure may be implemented across a broad variety of telecommunication systems, network architectures, and communication standards. Referring now toFIG.1, as an illustrative example without limitation, a schematic illustration of a wireless communication system100according to some aspects is provided. Various aspects of the present disclosure are illustrated with reference to the wireless communication system100. The wireless communication system100includes three interacting domains: a core network102, a radio access network (RAN)104, and a user equipment (UE)106. By virtue of the wireless communication system100, the UE106may be enabled to carry out data communication with an external data network110, such as (but not limited to) the Internet.

As illustrated, the RAN104includes a plurality of scheduling entities (schematically illustrated as scheduling entity108) also referred to herein as base stations or network access nodes. Broadly, a base station or network access node is a network element in a radio access network responsible for radio transmission and reception in one or more cells to or from a UE. In different technologies, standards, or contexts, a scheduling entity may variously be referred to by those skilled in the art as a base transceiver station (BTS), a radio base station, a radio transceiver, a transceiver function, a basic service set (BSS), an extended service set (ESS), an access point (AP), a Node B (NB), an eNode B (eNB), a gNode B (gNB), or some other suitable terminology.

Wireless communication between the RAN104and the UE106may be described as utilizing an air interface. Transmissions over the air interface from a base station (e.g., scheduling entity108) to one or more UEs (e.g., similar to UE106) may be referred to as downlink (DL) transmission. In accordance with certain aspects of the present disclosure, the term downlink may refer to a point-to-multipoint transmission originating at a scheduling entity108(described further below; e.g., base station). Another way to describe this scheme may be to use the term broadcast channel multiplexing. Transmissions from a UE (e.g., UE106) to a scheduling entity108(e.g., a base station) may be referred to as uplink (UL) transmissions. In accordance with further aspects of the present disclosure, the term uplink may refer to a point-to-point transmission originating at a scheduled entity (described further below; e.g., UE106).

In some examples, access to the air interface may be scheduled, wherein a scheduling entity108(e.g., a base station) allocates resources for communication among some or all devices and equipment within its service area or cell. Within the present disclosure, as discussed further below, the scheduling entity may be responsible for scheduling, assigning, reconfiguring, and releasing resources for one or more scheduled entities. That is, for scheduled communication, a plurality of UEs (e.g., a plurality of UE106), which may be scheduled entities, may utilize resources allocated by the scheduling entity108.

Base stations, represented in both the singular and the plural by scheduling entity108, are not the only entities that may function as scheduling entities. That is, in some examples, a UE may function as a scheduling entity, scheduling resources for one or more scheduled entities (e.g., one or more other UEs). For example, UE106may function as a scheduling entity while the UE122may function as scheduled entities. The communication between UE106and UE122may be referred to as sidelink124, which is described in connection withFIG.2herein.

As illustrated inFIG.1, a scheduling entity108may broadcast downlink traffic112and downlink control information114to one or more scheduled entities (e.g. one or more UE106). Broadly, the scheduling entity108is a node or device responsible for scheduling traffic in a wireless communication network, including the downlink traffic112and, in some examples, uplink traffic116and uplink control118from one or more scheduled entities (e.g. one or more UE106) to the scheduling entity108. On the other hand, the scheduled entity (e.g. one or more UE106) is a node or device that receives downlink control information114, including but not limited to scheduling information (e.g., a grant), synchronization or timing information, or other control information from another entity in the wireless communication network such as the scheduling entity108.

In general, scheduling entities, as graphically represented in the singular and plural by scheduling entity108, may include a backhaul interface for communication with a backhaul portion120of the wireless communication system100. The backhaul portion120may provide a link between a scheduling entity108and the core network102. Further, in some examples, a backhaul network may provide interconnection between the respective base stations (each similar to scheduling entity108). Various types of backhaul interfaces may be employed, such as a direct physical connection, a virtual network, or the like using any suitable transport network.

The various concepts presented throughout this disclosure may be implemented across a broad variety of telecommunication systems, network architectures, and communication standards. Referring now toFIG.2, as an illustrative example without limitation, a schematic illustration of a radio access network (RAN)200according to some aspects is provided. Various aspects of the present disclosure are illustrated with reference to the RAN200. The RAN200may implement any suitable wireless communication technology or technologies to provide radio access. As one example, the RAN200may operate according to 3rdGeneration Partnership Project (3GPP) New Radio (NR) specifications, often referred to as 5G. As another example, the RAN200may operate under a hybrid of 5G NR and Evolved Universal Terrestrial Radio Access Network (eUTRAN) standards, often referred to as LTE. The 3GPP refers to this hybrid RAN as a next-generation RAN, or NG-RAN. Of course, many other examples may be utilized within the scope of the present disclosure.

The geographic region covered by the RAN200may be divided into a number of cellular regions (cells) that can be uniquely identified by a user equipment (UE) based on an identification broadcasted over a geographical area from one base station (e.g., an access point (AP), a network access node).FIG.2illustrates cells202,204,206, and208, each of which may include one or more sectors (not shown). Cells202,204, and206may be referred to as macrocells and cell208may be referred to as a small cell. A sector is a sub-area of a cell. All sectors within one cell are served by the same base station. A radio link within a sector can be identified by a single logical identification belonging to that sector. In a cell that is divided into sectors, the multiple sectors within a cell can be formed by groups of antennas with each antenna, or array of antennas, responsible for communication with UEs in a portion of the cell.

In general, a respective base station (BS) serves each cell. Broadly, a base station is a network element in a radio access network responsible for radio transmission and reception in one or more cells to or from a UE. A BS may also be referred to by those skilled in the art as a network access node, a base transceiver station (BTS), a radio base station, a radio transceiver, a transceiver function, a basic service set (BSS), an extended service set (ESS), an access point (AP), a Node B (NB), an eNode B (eNB), a gNode B (gNB) or some other suitable terminology.

InFIG.2, two base stations, base station210and base station212are shown in cells202and204; and a third base station, base station214, is shown controlling a remote radio head (RRH)216in cell206. That is, a base station can have an integrated antenna or can be connected to an antenna or RRH216by feeder cables. In the illustrated example, cells202,204, and206may be referred to as macrocells, as the base stations210,212, and214support cells having a large size. Further, a base station218is shown in the cell208(e.g., a small cell, a microcell, picocell, femtocell, home base station, home Node B, home eNode B, etc.) which may overlap with one or more macrocells. In this example, the cell208may be referred to as a small cell, as the base station218supports a cell having a relatively small size. Cell sizing can be done according to system design as well as component constraints. It is to be understood that the RAN200may include any number of wireless base stations and cells. Further, a relay node may be deployed to extend the size or coverage area of a given cell. The base stations210,212,214,218provide wireless access points to a core network for any number of mobile apparatuses.

FIG.2further includes a quadcopter or drone, which may be configured to function as a base station, or more specifically as a mobile base station220. That is, in some examples, a cell may not necessarily be stationary, and the geographic area of the cell may move according to the location of a mobile base station220such as a quadcopter, drone, or backpack base station.

In general, base stations may include a backhaul interface for communication with a backhaul portion (not shown) of the network. The backhaul may provide a link between a base station and a core network (not shown), and in some examples, the backhaul may provide interconnection between the respective base stations. The core network may be a part of a wireless communication system and may be independent of the radio access technology used in the radio access network. Various types of backhaul interfaces may be employed, such as a direct physical connection, a virtual network, or the like using any suitable transport network.

The RAN200is illustrated supporting wireless communication for multiple mobile apparatuses. A mobile apparatus is commonly referred to as user equipment (UE) in standards and specifications promulgated by the 3rd Generation Partnership Project (3GPP), but may also be referred to by those skilled in the art as a mobile station (MS), a subscriber station, a mobile unit, a subscriber unit, a wireless unit, a remote unit, a mobile device, a wireless device, a wireless communications device, a remote device, a mobile subscriber station, an access terminal (AT), a mobile terminal, a wireless terminal, a remote terminal, a handset, a terminal, a user agent, a mobile client, a client, or some other suitable terminology. A UE may be an apparatus that provides a user with access to network services.

Within the RAN200, the cells may include UEs that may be in communication with one or more sectors of each cell. For example, UEs222and224may be in communication with base station210; UEs226and228may be in communication with base station212; UEs230and232may be in communication with base station214by way of RRH216; UE234may be in communication with base station218; and UE236may be in communication with mobile base station220. Here, each base station210,212,214,218, and220may be configured to provide an access point to a core network (not shown) for all the UEs in the respective cells. In another example, the mobile base station220(e.g., the quadcopter) may be configured to function as a UE. For example, the mobile base station220may operate within cell202by communicating with base station210.

Wireless communication between a RAN200and a UE (e.g., UE222or224) may be described as utilizing an air interface. Transmissions over the air interface from a base station (e.g., base station210) to one or more UEs (e.g., UE222and224) may be referred to as downlink (DL) transmission. In accordance with certain aspects of the present disclosure, the term downlink may refer to a point-to-multipoint transmission originating at a scheduling entity (described further below; e.g., base station210). Another way to describe this scheme may be to use the term broadcast channel multiplexing. Transmissions from a UE (e.g., UE222) to a base station (e.g., base station210) may be referred to as uplink (UL) transmissions. In accordance with further aspects of the present disclosure, the term uplink may refer to a point-to-point transmission originating at a scheduled entity (described further below; e.g., UE222).

For example, DL transmissions may include unicast or broadcast transmissions of control information and/or traffic information (e.g., user data traffic) from a base station (e.g., base station210) to one or more UEs (e.g., UEs222and224), while UL transmissions may include transmissions of control information and/or traffic information originating at a UE (e.g., UE222). In addition, the uplink and/or downlink control information and/or traffic information may be time-divided into frames, subframes, slots, and/or symbols. As used herein, a symbol may refer to a unit of time that, in an orthogonal frequency division multiplexed (OFDM) waveform, carries one resource element (RE) per sub-carrier. According to some aspects, a slot may carry 7 or 14 OFDM symbols. A subframe may refer to a duration of 1 ms. Multiple subframes or slots may be grouped together to form a single frame or radio frame. Of course, these definitions are not required, and any suitable scheme for organizing waveforms may be utilized, and various time divisions of the waveform may have any suitable duration.

In the RAN200, the ability for a UE to communicate while moving, independent of their location, is referred to as mobility. The various physical channels between the UE and the RAN are generally set up, maintained, and released under the control of an access and mobility management function (AMF), which may include a security context management function (SCMF) that manages the security context for both the control plane and the user plane functionality and a security anchor function (SEAF) that performs authentication. In various aspects of the disclosure, a RAN200may utilize DL-based mobility or UL-based mobility to enable mobility and handovers (i.e., the transfer of a UE’s connection from one radio channel to another). In a network configured for DL-based mobility, during a call with a scheduling entity, or at any other time, a UE may monitor various parameters of the signal from its serving cell as well as various parameters of neighboring cells. Depending on the quality of these parameters, the UE may maintain communication with one or more of the neighboring cells. During this time, if the UE moves from one cell to another, or if signal quality from a neighboring cell exceeds that from the serving cell for a given amount of time, the UE may undertake a handoff or handover from the serving cell to the neighboring (target) cell. For example, UE224may move from the geographic area corresponding to its serving cell, cell202, to the geographic area corresponding to a neighbor cell, cell206. When the signal strength or quality from the neighbor cell, cell206, exceeds that of its serving cell, cell202, for a given amount of time, the UE224may transmit a reporting message to its serving base station, base station210, indicating this condition. In response, the UE224may receive a handover command, and the UE may undergo a handover to the cell206.

In some examples, access to the air interface may be scheduled, wherein a scheduling entity (e.g., a base station) allocates resources (e.g., time-frequency resources) for communication among some or all devices and equipment within its service area or cell. Within the present disclosure, as discussed further below, the scheduling entity may be responsible for scheduling, assigning, reconfiguring, and releasing resources for one or more scheduled entities. That is, for scheduled communication, UEs or scheduled entities utilize resources allocated by the scheduling entity.

Base stations are not the only entities that may function as a scheduling entity. That is, in some examples, a UE may function as a scheduling entity, scheduling resources for one or more scheduled entities (e.g., one or more other UEs). For example, UE238is illustrated communicating with UEs240and242. In some examples, the UE238is functioning as a scheduling entity, while the UEs240and242may function as scheduled entities. In other examples, sidelink or other type of direct link signals may be communicated directly between UEs without necessarily relying on scheduling or control information from another entity. In one example, two or more UEs (e.g., UEs226and228) may communicate with each other using direct link signals227(e.g., sidelink, Bluetooth, and/or other types of direct link signals) without relaying that communication through a base station (e.g., base station212). In another example, UEs238,240, and242may communicate over a direct link in a device-to-device (D2D), peer-to-peer (P2P), vehicle-to-vehicle (V2V) network, vehicle-to-everything (V2X), and/or in a mesh network. In a mesh network example, UEs240and242may optionally communicate directly with one another in addition to communicating with a scheduling entity (e.g., UE238).

In some examples, UE238may be a transmitting sidelink device that reserves resources on a sidelink carrier for the transmission of sidelink signals to UEs240and242in a D2D or V2X network. Here, UEs240and242are each receiving sidelink devices. UEs240and242may, in turn, reserve additional resources on the sidelink carrier for subsequent sidelink transmissions.

In other examples, UEs238,240, and242may be P2P devices (e.g., Bluetooth, Zigbee, or Near Field Communication (NFC) devices) communicating over a P2P carrier. For example, UEs238,240, and242may be Bluetooth devices that communicate over a short-wavelength (e.g., 2.45 GHz) carrier. Each Bluetooth device (e.g., UEs238,240, and242) may operate at low power (e.g., 100 mW or less) to communicate over a short-range distance (e.g., 10 meters or less). In a Bluetooth network, the UEs238,240, and242may form an ad-hoc piconet and each pair of UEs (e.g., UEs238and240; UEs238and242; and UEs240and242) may communicate over a different frequency in a frequency-hopping manner. Within the piconet, one of the UEs (e.g., UE238) may function as the master, while the other UEs (e.g., UEs240and242) function as slaves. Each of the UEs238,240, and242may automatically detect and connect to one another.

In some examples, two or more UEs (e.g., UEs226and228) within the coverage area of a serving base, such as base station212, may communicate with both the base station212using cellular signals and with each other using direct link signals227(e.g., sidelink, Bluetooth, and/or other types of direct link signals) without relaying that communication through the base station212. In an example of a V2X network within the coverage area of the base station212, the base station212and/or one or both of the UEs226and228may function as scheduling entities to schedule sidelink communication between UEs226and228.

Two primary technologies that may be used by V2X networks include dedicated short-range communication (DSRC) based on IEEE 802.11p standards and cellular V2X based on LTE and/or 5G (New Radio) standards. Various aspects of the present disclosure may relate to New Radio (NR) cellular V2X networks, referred to herein as V2X networks, for simplicity. However, it should be understood that the concepts disclosed herein may not be limited to a particular V2X standard or may be directed to direct link (e.g., sidelink) networks other than V2X networks.

FIG.3illustrates an example of a wireless communication network300configured to support device-to-device (D2D) (e.g., sidelink) communication according to some aspects. In some examples, sidelink communication may include V2X communication. V2X communication involves the wireless exchange of information directly between not only vehicles (e.g., vehicles302and304) themselves, but also directly between vehicles302/304and infrastructure306, such as streetlights, buildings, traffic cameras, tollbooths or other stationary objects, vehicles302/304and mobile devices of pedestrians/cyclists308, and vehicles302/304and wireless communication networks (e.g., base station310). In some examples, V2X communication may be implemented in accordance with the New Radio (NR) cellular V2X standard defined by 3GPP, Release 16, or other suitable standard.

A V2X transmissions may include, for example, unicast transmissions, groupcast transmissions, and broadcast transmissions. Unicast describes a transmission, for example, from a vehicle (e.g., vehicle302) to one other vehicle (e.g., vehicle304). Groupcast arises when a group of UEs (e.g., vehicles302and304) form a cluster. Data may be groupcasted within the cluster. Broadcast describes a transmission from, for example, a UE (e.g., vehicle302) to surrounding receivers (e.g., vehicle304, infrastructure306(e.g., an RSU), mobile devices of pedestrians/cyclists308, the base station310of a network, or any combination thereof) in proximity to the transmitting UE.

V2X communication enable vehicles302and304to obtain information related to the weather, nearby accidents, road conditions, activities of nearby vehicles and pedestrians, objects nearby the vehicle, and other pertinent information that may be utilized to improve the vehicle driving experience and increase vehicle safety. For example, such V2X data may enable autonomous driving and improve road safety and traffic efficiency. For example, the exchanged V2X data may be utilized by a V2X connected vehicle302and304to provide in-vehicle collision warnings, road hazard warnings, approaching emergency vehicle warnings, pre-/post-crash warnings and information, emergency brake warnings, traffic jam ahead warnings, lane change warnings, intelligent navigation services, and other similar information. In addition, V2X data received by a V2X connected mobile device of a pedestrian/cyclist308may be utilized to trigger a warning sound, vibration, flashing light, etc., in case of imminent danger.

The sidelink communication between vehicles302and304or between a vehicle302or304and either infrastructure306or a pedestrian/cyclist308occurs over a proximity service (ProSe) PC5 interface312. In various aspects of the disclosure, the PC5 interface312or other direct interface may further be utilized to support D2D communication in other proximity use cases. Examples of other proximity use cases may include public safety or commercial (e.g., entertainment, education, office, medical, and/or interactive) based proximity services. As used herein, the term proximity service (ProSe) communication refers to the direct (e.g., D2D) communication between UEs in proximity use cases other than V2X. In the example shown inFIG.3, direct (e.g., ProSe) communication may occur between UEs314and316.

ProSe communication may support different operational scenarios, such as in-coverage, out-of-coverage, and partial coverage. Out-of-coverage refers to a scenario in which UEs314and316are outside of the coverage area of a base station (e.g., base station310), but each are still configured for ProSe communication. Partial coverage refers to a scenario in which one of the UEs (e.g., UE316) is outside of the coverage area of a base station (e.g., base station310), while the other UE (e.g., UE314) is in communication with the base station310. In-coverage refers to a scenario in which UEs314and316are in communication with the base station310(e.g., gNB) via a Uu (e.g., cellular interface) connection to receive ProSe service authorization and provisioning information to support ProSe operations.

Various aspects of the present disclosure will be described with reference to an OFDM waveform, schematically illustrated inFIG.4. It should be understood by those of ordinary skill in the art that the various aspects of the present disclosure may be applied, for example, to a DFT-s-OFDMA or an SC-FDMA waveform in substantially the same way as described herein below. That is, while some examples of the present disclosure may focus on an OFDM link for clarity, it should be understood that the same principles may be applied as well to DFT-s-OFDMA or SC-FDMA waveforms.

Scheduling of UEs or sidelink devices (hereinafter collectively referred to as wireless communication devise or SL UEs) for downlink, uplink, or sidelink transmissions typically involves scheduling one or more resource elements406within one or more sub-bands. Thus, a UE generally utilizes only a subset of the resource grid404. In some examples, an RB may be the smallest unit of resources that can be allocated to a UE. Thus, the more RBs scheduled for a UE, and the higher the modulation scheme chosen for the air interface, the higher the data rate for the UE. The RBs may be scheduled by a base station (e.g., gNB, eNB, etc.) or may be self-scheduled by a UE/sidelink device implementing D2D sidelink communication.

In this illustration, the RB408is shown as occupying less than the entire bandwidth of the subframe402, with some subcarriers illustrated above and below the RB408. In a given implementation, the subframe402may have a bandwidth corresponding to any number of one or more RBs408. Further, in this illustration, the RB408is shown as occupying less than the entire duration of the subframe402, although this is merely one possible example.

According to some examples, a frame may refer to a duration of 10 ms, with each frame sub-divided into 10 subframes402of 1 ms each. Each 1 ms subframe may consist of one or multiple adjacent slots. In the example shown inFIG.4, subframe403includes four slots410, as an illustrative example. In some examples, a slot may be defined according to a specified number of OFDM symbols with a given cyclic prefix (CP) length. For example, a slot may include 7 or 14 OFDM symbols with a nominal CP. Additional examples may include mini-slots, sometimes referred to as shortened transmission time intervals (TTIs), having a shorter duration (e.g., 1, 2, or 3 OFDM symbols). These mini-slots, or shortened TTIs, may in some cases be transmitted occupying resources scheduled for ongoing slot transmissions for the same or for different UEs. Any number of resource blocks may be utilized within a subframe or slot.

An expanded view of one of the slots410illustrates the slot as including a control region412and a data region414. In general, the control region412may carry control channels (e.g., PDCCH), and the data region414may carry data channels (e.g., PDSCH or PUSCH). Of course, a slot may contain all DL, all UL, or at least one DL portion and at least one UL portion. The simple structure illustrated inFIG.4is merely exemplary in nature, and different slot structures may be utilized, and may include one or more of each of the control region(s) and data region(s).

Although not illustrated inFIG.4, the various REs406within an RB408may be scheduled to carry one or more physical channels, including control channels, shared channels, data channels, etc. Other REs406within the RB408may also carry pilots or reference signals, including but not limited to a demodulation reference signal (DMRS) a control reference signal (CRS), or a sounding reference signal (SRS). These pilots or reference signals may provide for a receiving device to perform channel estimation of the corresponding channel, which may enable coherent demodulation/detection of the control and/or data channels within the RB408.

In some examples, the slot410may be utilized for broadcast or unicast communication. For example, a broadcast, multicast, or groupcast communication may refer to a point-to-multipoint transmission by one device (e.g., a base station, UE, or other similar device) to other devices. Here, a broadcast communication is delivered to all devices, whereas a multicast communication is delivered to multiple intended recipient devices. A unicast communication may refer to a point-to-point transmission by a one device to a single other device.

In an example of cellular communication over a cellular carrier via a Uu interface, for a DL transmission, the scheduling entity (e.g., a base station) may allocate one or more REs406(e.g., within the control region412) to carry DL control information including one or more DL control channels, such as a PBCH; a PSS; a SSS; a physical control format indicator channel (PCFICH); a physical hybrid automatic repeat request (HARQ) indicator channel (PHICH); and/or a physical downlink control channel (PDCCH), etc., to one or more scheduled entities (e.g., UEs). The PCFICH provides information to assist a receiving device in receiving and decoding the PDCCH. The PDCCH carries downlink control information (DCI) including but not limited to power control commands (e.g., one or more open loop power control parameters and/or one or more closed loop power control parameters), scheduling information, a grant, and/or an assignment of REs for DL and UL transmissions. The PHICH carries HARQ feedback transmissions such as an acknowledgment (ACK) or negative acknowledgment (NACK). HARQ is a technique well-known to those of ordinary skill in the art, wherein the integrity of packet transmissions may be checked at the receiving side for accuracy, e.g., utilizing any suitable integrity checking mechanism, such as a checksum or a cyclic redundancy check (CRC). If the integrity of the transmission confirmed, an ACK may be transmitted, whereas if not confirmed, a NACK may be transmitted. In response to a NACK, the transmitting device may send a HARQ retransmission, which may implement chase combining, incremental redundancy, etc.

In an UL transmission, the scheduled entity may utilize one or more REs406to carry UL control information (UCI) including one or more UL control channels, such as a physical uplink control channel (PUCCH), to the scheduling entity. UCI may include a variety of packet types and categories, including pilots, reference signals, and information configured to enable or assist in decoding uplink data transmissions. In some examples, the UCI may include a scheduling request (SR), i.e., request for the scheduling entity to schedule uplink transmissions. Here, in response to the SR transmitted on the UCI, the scheduling entity may transmit downlink control information (DCI) that may schedule resources for uplink packet transmissions. UCI may also include HARQ feedback, channel state feedback (CSF), or any other suitable UCI.

In addition to control information, one or more REs406(e.g., within the data region414) may be allocated for user data traffic. Such traffic may be carried on one or more traffic channels, such as, for a DL transmission, a physical downlink shared channel (PDSCH); or for an UL transmission, a physical uplink shared channel (PUSCH). In some examples, one or more REs406within the data region414may be configured to carry system information blocks (SIBs), carrying information that may enable access to a given cell.

In an example of sidelink communication over a sidelink carrier via a PC5 interface, the control region412of the slot410may include a physical sidelink control channel (PSCCH) including sidelink control information (SCI) transmitted by an initiating (transmitting) sidelink device (e.g., V2X or other sidelink device) towards a set of one or more other receiving sidelink devices. The PSCCH may include HARQ feedback information (e.g., ACK/NACK) that may be used to indicate a need, or lack of need, for retransmissions on the sidelink. The data region414of the slot410may include a physical sidelink shared channel (PSSCH) including the data transmitted by the initiating (transmitting) sidelink device within resources reserved over the sidelink carrier by the transmitting sidelink device.

The channels or carriers described above and illustrated inFIG.1,FIG.2, andFIG.3are not necessarily all the channels or carriers that may be utilized between a scheduling entity108and scheduled entities (e.g., one of more UE106,122), and those of ordinary skill in the art will recognize that other channels or carriers may be utilized in addition to those illustrated, such as other traffic, control, and feedback channels. For example, a UE, such as UE106may communicate with a second UE122via a sidelink124communication (e.g. a scheduled-entity-to-scheduled entity communication), for example, over a PC5 interface. The sidelink124communication may be carried, for example, in a licensed frequency domain using radio resources operating according to a 5G NR or NR SL specification and/or in an unlicensed frequency domain, using radio resources operating according to 5G new radio-unlicensed (NR-U) specifications.

In 5G NR, there may be four resource allocation modes of operation for sidelink (e.g., PC5) communications. In a first mode, Mode 1, a network access node (e.g., gNB) may allocate resources to wireless communication devices for sidelink communications between the wireless communication devices. In a second mode, Mode 2, the wireless communication devices may autonomously select sidelink resources for its own use. Signaling on the sidelink is the same between the two modes. Mode 3 and Mode 4 are generally directed to V2X, with Mode 4 being directed to self-scheduling of resources. Although Modes 3 and 4 are directed to V2X, the disclosures made herein may have applicability to at least Mode 2 and Mode 4. From a receiver’s point of view, there is no difference between the four modes.

In Mode 1, the network access node may provide resources in at least two ways. A first way may include having the network access node provide resources dynamically (e.g., a dynamic grant) to wireless communication devices, in response to requests for sidelink resources from wireless communication devices. In a second way, the network access node may activate preconfigured sidelink grants for sidelink communication among wireless communication devices. In Mode 1, sidelink feedback may be reported back to the network access node by a transmitting wireless communication device.

In Mode 2, a wireless communication device may schedule sidelink communication (e.g., PC5) by use of a sidelink control information (SCI) message. SCI may be produced in two stages. Stage 1 sidelink control information may be referred to as SCI-1 herein. Stage 2 sidelink control information may be referred to as SCI-2 herein.

SCI-1 may be transmitted on a physical sidelink control channel (PSCCH). SCI-1 may include information for resource allocation of a sidelink resource and for decoding of the second stage of sidelink control information (i.e., SCI-2). SCI-1 may identify a priority level of a payload. For example, ultra-reliable-low-latency communication (URLLC) traffic has a higher priority than text message traffic (e.g., short message service (SMS) traffic). SCI-1 may also include a physical sidelink shared channel (PSSCH) resource assignment and a resource reservation period (if enabled). Additionally, SCI-1 may include a PSSCH demodulation reference signal (DMRS) pattern (if more than one pattern is configured). The DMRS may be used by a receiver for radio channel estimation for demodulation of the associated physical channel. As indicated, SCI-1 may also include information about the SCI-2 message, for example, SCI-1 may disclose the size of SCI-2 by indicating an amount of time-frequency resources that are allotted for SCI-2, a number of a PSSCH DMRS port(s), and a modulation and coding scheme (MCS) index. SCI-1 may include other information that is useful for establishing and decoding a PSSCH resource.

SCI-2 may also be transmitted on the PSCCH and may contain information for decoding the PSSCH. According to some aspects, SCI-2 includes a 16-bit layer 1 (L1) destination identifier (ID), an 8-bit L1 source ID, a hybrid automatic repeat request (HARQ) process ID, a new data indicator (NDI), and a redundancy version (RV). SCI-2 may include other information that is useful for establishing and decoding a PSSCH resource.

Licensed use of sidelink in 5G (via NR SL standards) does provide a channel access scheme (e.g., sensing, reservation, and channel busy ratio (CBR) based QoS management). However, unlicensed use of sidelink (via NR-U) does not provide the same channel access scheme. For example, NR SL (e.g., as used for V2X) employs subchannel selection-based sensing, which is different from the NR-U Listen Before Talk (LBT)-type sensing. Moreover, these two types of sensing are not able to be integrated with one another.

The types of sensing, resolution, and QoS management used for NR-U (e.g., for V2X in the unlicensed spectrum) are less efficient than the types of sensing, resolution, and QoS management used for NR SL (e.g., sidelink in the licensed spectrum); accordingly, a UE communicating using sidelink in a wireless communications network under NR-U may use more processor time and overall power consumption to secure a subchannel in an unlicensed band (e.g., using a listen before talk (LBT) based sensing access scheme) in comparison to the same UE’s use of processing time and overall power consumption to secure a subchannel in a licensed band (e.g., using a subchannel selection based sensing access scheme). Furthermore, when using an LBT type of access scheme, even if a UE carefully selects subchannel in an unlicensed band, the selected subchannel can become unavailable (become invalid) in a last second before the UE’s transmission on the selected subchannel. This may be true because another UE, unaware of the first UE’s intent to use the subchannel, starts transmitting on the subchannel. As used herein, the phrase “at the last second” is meant to mean at a last instant of time prior to a transmission by a UE. The last instant of time may be measured, not in seconds, but in, for example, transmission time intervals, slot durations, or even OFDM symbol durations. The inefficiency caused by use of the LBT access scheme again results in a waste of processor time and overall power consumption in comparison to the same UE attempting to secure a similar subchannel in a licensed band. The additional processing time, receiver operation time (for use of LBT-based channel access), and transmitter time (in the case of transmitted traffic or data colliding with traffic or data from another UE) is a waste of resources (e.g., undesirably using processor time and/or undesirably using more battery power in unlicensed subchannel access in comparison to licensed subchannel access).

However, a direct application of the CBR type of access used in NR SL to NR-U may lead to starvation of an NR-U sidelink. For example, a subchannel can be sensed (e.g. as in C-V2X) as being busy due to interference received from a nearby WiFi node.

Various aspects of the disclosure may address the process of securing access and reducing wasted power by conveying sidelink communications in a distributed way over both licensed and unlicensed bands. For example, using concepts of carrier aggregation, a wireless communication device may make use of a primary carrier including one or more subchannels in a licensed band to handle control signaling and conduct access control (e.g., scheduling), while making use of a secondary carrier in an unlicensed band to handle traffic (e.g. user data). The access control may be performed in an efficient manner using NR SL licensed resources, while data can be offloaded onto subchannels in the unlicensed band using NR-U unlicensed resources. Use of a primary carrier in the licensed band for access control operations, to facilitate access (e.g., perform scheduling) to a secondary carrier in the unlicensed band, may result in less power consumption when compared to using the unlicensed band for all sidelink control and traffic communication. In addition, the carrier aggregation scheme described herein presents an added benefit in that an SL UE may need to only monitor the primary carrier (e.g., in the licensed band) for sidelink control information (SCI). More particularly, the SL UE may need to only monitor the primary carrier for SCI stage 1 (SCI-1) information. This eliminates a requirement or need for the SL UE to monitor the secondary carrier in the unlicensed band for SCI-1, for example.

FIG.5is a block diagram illustrating an example of a hardware implementation of a wireless communication device500employing a processing system514according to some aspects. The wireless communication device500may engage in sidelink (SL) communication. In accordance with various aspects of the disclosure, an element, or any portion of an element, or any combination of elements may be implemented with a processing system514that includes one or more processors, such as processor504. The wireless communication device500may be a wireless communication device or user equipment (UE) as illustrated and described in any one or more ofFIGS.1,2, and/or3. The wireless communication device500may be referred to as the wireless communication device500or an SL UE, interchangeably.

The wireless communication device500may be implemented with a processing system514that includes one or more processors, such as processor504. Examples of processors504include microprocessors, microcontrollers, digital signal processors (DSPs), field programmable gate arrays (FPGAs), programmable logic devices (PLDs), state machines, gated logic, discrete hardware circuits, and other suitable hardware configured to perform the various functionality described throughout this disclosure. In various examples, the wireless communication device500may be configured to perform any one or more of the functions described herein. That is, the processor504, as utilized in a wireless communication device500, may be used to implement any one or more of the methods or processes described below and illustrated, for example, inFIGS.6-11.

In this example, the processing system514may be implemented with a bus architecture, represented generally by the bus502. The bus502may include any number of interconnecting buses and bridges depending on the specific application of the processing system514and the overall design constraints. The bus502communicatively couples together various circuits including one or more processors (represented generally by the processor504), a memory505, and computer-readable media (represented generally by the computer-readable medium506). The bus502may also link various other circuits such as timing sources, peripherals, voltage regulators, and power management circuits, which are well known in the art, and therefore, will not be described any further.

A bus interface508provides an interface between the bus502and a transceiver510. The transceiver510provides a means for communicating with various other apparatus over a transmission medium (e.g., air interface). The transceiver510may further be coupled to one or more antennas/antenna array520. The bus interface508further provides an interface between the bus502and a user interface512(e.g., keypad, display, touch screen, speaker, microphone, control features, etc.). Of course, such a user interface512is optional, and may be omitted in some examples. In addition, the bus interface508further provides an interface between the bus502and a power source528, and between the bus502and an application processor530, which may be separate from a modem (not shown) of the wireless communication device500or processing system514.

One or more processors, such as processor504, in the processing system514may be responsible for managing the bus502and general processing, including the execution of software stored on the computer-readable medium506. Software shall be construed broadly to mean instructions, instruction sets, code, code segments, program code, programs, subprograms, software modules, applications, software applications, software packages, routines, subroutines, objects, executables, threads of execution, procedures, functions, etc., whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise. The software may reside on a computer-readable medium506. The software, when executed by the processor504, causes the processing system514to perform the various processes and functions described herein for any particular apparatus. The computer-readable medium506and the memory505may also be used for storing data that is manipulated by the processor504when executing software.

The computer-readable medium506may be a non-transitory computer-readable medium and may be referred to as a computer-readable storage medium or a non-transitory computer-readable medium. The non-transitory computer-readable medium may store computer-executable code (e.g., processor-executable code). The computer executable code may include code for causing a computer (e.g., a processor) to implement one or more of the functions described herein. A non-transitory computer-readable medium includes, by way of example, a magnetic storage device (e.g., hard disk, floppy disk, magnetic strip), an optical disk (e.g., a compact disc (CD) or a digital versatile disc (DVD)), a smart card, a flash memory device (e.g., a card, a stick, or a key drive), a random access memory (RAM), a read only memory (ROM), a programmable ROM (PROM), an erasable PROM (EPROM), an electrically erasable PROM (EEPROM), a register, a removable disk, and any other suitable medium for storing software and/or instructions that may be accessed and read by a computer. The computer-readable medium506may reside in the processing system514, external to the processing system514, or distributed across multiple entities including the processing system514. The computer-readable medium506may be embodied in a computer program product or article of manufacture. By way of example, a computer program product or article of manufacture may include the computer-readable medium506in packaging materials. In some examples, the computer-readable medium506may be part of the memory505. Those skilled in the art will recognize how best to implement the described functionality presented throughout this disclosure depending on the particular application and the overall design constraints imposed on the overall system.

In some aspects of the disclosure, the processor504may include communication and processing circuitry541configured for various functions, including for example communicating with a network core (e.g., a 5G core network), other scheduled entities, or any other entity, such as, for example, local infrastructure or an entity communicating with the wireless communication device500via the Internet, such as a network provider. In some examples, the communication and processing circuitry541may include one or more hardware components that provide the physical structure that performs processes related to wireless communication (e.g., signal reception and/or signal transmission) and signal processing (e.g., processing a received signal and/or processing a signal for transmission). In addition, the communication and processing circuitry541may be configured to receive and process uplink traffic and uplink control messages (e.g., similar to uplink traffic116and uplink control118ofFIG.1), transmit and process downlink traffic and downlink control messages (e.g., similar to downlink traffic112and downlink control114), and/or receive, transmit, and process sidelink traffic and control messages via the antennas/antenna array520and the transceiver510. The communication and processing circuitry541may further be configured to execute communication and processing software551stored on the computer-readable medium506to implement one or more functions described herein.

In some aspects of the disclosure, the processor504may include control channel monitoring circuitry542configured for various functions, including, for example, monitoring control channels and decoding control messages conveyed over a primary carrier in a licensed band. In some examples, the control channel monitoring circuitry542may include one or more hardware components that provide the physical structure that performs processes related to monitoring control channels and decoding control messages over a primary carrier in a licensed band. Monitored channels may include PDCCH and PSCCH. A control messages may include a grant of an allocation of the licensed and/or unlicensed spectrum to the wireless communication device500. Control messages may include sidelink control information (SCI) messages, including stage 1 SCI (SCI-1) messages and stage 2 SCI (SCI-2) messages. In addition, the control channel monitoring circuitry542may be configured to decode such messages using blind decoding (e.g., for SCI-1 messages) and/or decoding of one message using data obtained from another message (e.g., decoding an SCI 2 message with data obtained from an SCI-1 message). The control channel monitoring circuitry542may further be configured to execute control channel monitoring software552stored on the computer-readable medium506to implement one or more functions described herein.

In some aspects of the disclosure, the processor504may include slot transmission gap circuitry543configured for various functions, including, for example, transmitting sidelink control in a fist subchannel during a slot, or transmitting sidelink control in the first subchannel during the slot, except during a symbol gap that would be occupied with transmission of at least a last symbol of a plurality of symbols supported by the slot. In some examples, the slot transmission gap circuitry543may include one or more hardware components that provide the physical structure that performs processes related to transmitting sidelink control in the first subchannel during a slot, or transmitting sidelink control in the first subchannel during the slot, except during a symbol gap that would be occupied with transmission of at least a last symbol of a plurality of symbols supported by the slot. The slot transmission gap circuitry543may further be configured to execute slot transmission gap software553stored on the computer-readable medium506to implement one or more functions described herein.

In some aspects of the disclosure, the processor504may include licensed and unlicensed access control circuitry544configured for various functions, including, for example, seeking access to a subcarrier in an unlicensed band, or seeking access to a subcarrier in an unlicensed band during (or beginning during) a symbol gap in a transmission from a licensed channel. In some examples, the licensed and unlicensed access control circuitry544may include one or more hardware components that provide the physical structure that performs processes related to seeking access to a subcarrier in the unlicensed band, or seeking access to the subcarrier in an unlicensed band during (or beginning during) a symbol gap in a transmission from the licensed channel. The licensed and unlicensed access control circuitry544may also be configured to derive frame-based equipment (FBE) frame timing over an unlicensed band from timing in a licensed band and/or synchronize first channel access to a subcarrier in an unlicensed band to second channel access to a subcarrier in a licensed band. The licensed and unlicensed access control circuitry544may further be configured to execute licensed and unlicensed access control software554stored on the computer-readable medium506to implement one or more functions described herein.

In one configuration, the apparatus500for wireless communication includes means for occupying a slot in a first subchannel, where the first subchannel comprises a sidelink subchannel in a licensed band, means for transmitting sidelink control in the first subchannel during the slot, except during a symbol gap indicated to include at least a last symbol of a plurality of symbols supported by the slot, means for seeking access to a secondary carrier in an unlicensed band during the symbol gap, and means for transmitting sidelink traffic in the secondary carrier upon receiving access to the secondary carrier. In one aspect, the means for transmitting sidelink traffic in the secondary carrier upon receiving access to the secondary carrier transmits the sidelink traffic during or following the symbol gap. In one aspect, the aforementioned means may be the processor(s)504shown inFIG.5configured to perform the functions recited by the aforementioned means. In another aspect, the aforementioned means may be a circuit, or any apparatus configured to perform the functions recited by the aforementioned means.

NR SL may provide a channel busy ratio (CBR) and/or channel occupancy ratio (CR) based QoS management mechanism. While channel congestion control and QoS management based on CBR and/or CR may be well defined for sidelink in the licensed spectrum (e.g., NR SL), it may not be well defined, and may be difficult to perform, for unlicensed spectrum sidelink (e.g., NR-U).

For example, in Mode 2, used for licensed spectrum sidelink (NR SL), there may be a mechanism to control how many UEs are competing for channel access. However, the same mechanism may not exist for the unlicensed spectrum. Therefore, various aspects of the disclosure seek to regulate channel access and QoS of a secondary carrier in the unlicensed band by using measurements and measurement results based on channel access and QoS of a primary carrier in the licensed band (e.g., NR SL). The measurements and timing of the primary carrier (or subchannels thereof) in the licensed band may be applied to the secondary carrier in the unlicensed band. Because measurements and timing of the primary carrier are applicable to the secondary carrier, it may be sufficient to work with the primary carrier exclusively when determining channel access timing for both the primary and secondary carriers.

According to one aspect, a sidelink communication may anchor on a primary carrier in a licensed band for radio resource management (RRM) and quality of service (QoS) control for the secondary carrier in the unlicensed band. Frame-based equipment (FBE) channel access may be used for its relatively lower overhead and ease of implementation at the UE side.

With the various aspects of the disclosure described herein, a minimal (e.g., light) design for the unlicensed SL carrier may be realized (e.g., the unlicensed SL carrier may need no Master Information Block (MIB), System Information Block (SIB), or even Synchronization Signal Block (SSB)) as control may be carried on the SL licensed carrier with traffic being carried on the unlicensed carrier. According to some aspects, all control may be carried on the SL licensed carrier and all traffic may be carried on the unlicensed SL carrier. Additionally, using aspects described herein, coordination of reservations across nodes or links (e.g., for both the licensed carrier and the unlicensed carrier) can be reliably handled on the licensed carrier, in a way that is similar to how reservations work on the PC5 interface.

FIG.6is an illustration of two sets of time-frequency resources600according to some aspects herein. A first set602of time-frequency resources occupies a licensed band604of subchannels (e.g., ITS band of around 5.8 - 5.9 GHz). The licensed band604of subchannels includes a first subchannel606and a second subchannel608. The timing in the first set602of time-frequency resources may be based on resource blocks that have a width of one OFDM symbol. Accordingly, based on OFDM timing610, the time domain in the licensed band604of subchannels is divided into a plurality of slots. As depicted in the exemplary illustration of the first slot612, each slot may be divided into 14 OFDM symbols. Access control or scheduling in the licensed band604may be determined by a first standard for communication (including, for example, sidelink communication). One example of the first standard may be NR SL. Other standards, timing configurations, frequency bands and/or slot configurations may also be utilized with various aspects of the disclosure.

A second set614of time-frequency resources occupies an unlicensed band616of subchannels (e.g., around 5.6 - 5.7 GHz). The unlicensed band616of subchannels includes an aggregated subcarrier618. According to some aspects, the aggregated subcarrier may have a 20 MHz bandwidth and may be located in the 5 GHz unlicensed band. Timing in the unlicensed band616may be based on FBE frame timing620. An exemplary first frame622is depicted. Access control or scheduling in the unlicensed band616may be determined by a second standard for communication (including, for example, sidelink communication). One example of the second standard may be NR-U. Other standards, timing configurations, and/or frequency bands may be used with various aspects of the disclosure.

A first wireless communication device (not shown) (referred to herein as SL UE1) conducting sidelink communication and a second wireless communication device (not shown) (referred to herein as SL UE2) conducting sidelink communication may each monitor, for example, a physical sidelink control channel (PSCCH) to identify and decode a sidelink control information (SCI) message. More particularly, SL UE1 and SL UE2 may each monitor, for example, the PSCCH to identify and perform blind decoding of a stage 1 sidelink control information (SCI-1) message. An SCI-1 message may include a grant for time-frequency resources for sidelink communications. For example, one or more SCI-1 messages may have allocated the second slot624in the first subchannel606and the fifth slot628in the second subchannel608to SL UE1 for sidelink communication. The same or another SCI-1 message may have allocated the third slot626in the second subchannel608to SL UE2 for sidelink communication. Accordingly, the second slot624in the first subchannel606and the fifth slot 628 second subchannel608may each be occupied by SL UE1, while the third slot626in the second subchannel608may be occupied by SL UE2

Each of SL UE1 and SL UE2 may conduct sidelink communication by exchanging sidelink traffic (e.g., user data) messages and sidelink control messages. Each of SL UE1 and SL UE2 may make a determination to employ carrier aggregation as a way of organizing, transmitting, and receiving sidelink communications. Accordingly, each of SL UE1 and SL UE2 may designate a primary carrier and at least one secondary carrier. The primary carrier may carry sidelink control while the secondary carrier may carry sidelink traffic. The first subchannel606and the second subchannel608may be pre-designated as sidelink subchannels (sometimes referred to herein as carrier aggregation subchannels (CA subchannels).

Furthermore, each of SL UE1 and SL UE2 may offload (e.g., after making a determination to offload) the sidelink traffic from the subchannels (e.g., CA subchannels) in the licensed band604(e.g., ITS band of about 5.8-5.9 GHZ) to subchannels in the unlicensed band616(e.g., about 5.6 GHz to 5.7 GHz). The subchannels in the unlicensed band may be referred to herein as non-CA subchannels. In other words, each of SL UE1 and SL UE2 may aggregate (e.g., after making a determination to aggregate) a respective carrier in the unlicensed band to act as the secondary carrier and to carry, for example, the sidelink traffic in the unlicensed band616.

As mentioned above, access control for sidelink communication in the licensed band604, via NR SL for example, is more efficient than access control for sidelink communication in the unlicensed band616, via NR-U using FBE-based access control for example. By way of example, the timing associated with when a wireless communication device may occupy a channel is dynamic in NR-U FBE-based access control. In particular, a first wireless communication device may gain access to the channel by, for example, successfully completing an FBE LBT channel access procedure, that may result in a second wireless communication device being unable to use the channel for some unknown amount of time.

Aspects described herein may overcome at least the deficiencies of FBE-based access control for sidelink communication in the unlicensed band616that are exemplified herein. Aspects described herein may provide for an efficient offloading of sidelink traffic from the primary carrier in the licensed band604to the secondary carrier in the unlicensed band. Furthermore, aspects described herein may produce a reduction in cross-carrier interference during an FBE LBT access procedure in the unlicensed band616. Aspects described herein may also allow a wireless communication device (e.g., SL UE1, SL UE2) to derive frame-based equipment (FBE) frame timing620in the unlicensed band616from timing (e.g., OFDM timing610) in the licensed band604. In other words, the wireless communication device may derive frame-based equipment (FBE) frame timing over the unlicensed band from timing in the licensed band. Still further, aspects described herein may allow a wireless communication device to synchronize first channel access to a secondary carrier (e.g., an aggregated subcarrier618) in the unlicensed band616, based on second channel access to a first subchannel606and/or second subchannel608in the licensed band604.

As depicted inFIG.6, after a wireless communication device (e.g., SL UE1, SL UE2) occupies a SL subchannel (e.g., a CA subchannel) in a given slot, the wireless communication device may derive the FBE frame timing620for the secondary carrier (e.g., aggregated subcarrier618in unlicensed band616) from the OFDM timing610for the primary carrier (e.g., one or both of the first subchannel606and the second subchannel608in the licensed band604). The wireless communication device may occupy the SL subchannel with an enabling link. In other words, the wireless communication device may synchronize first channel access to the aggregated subcarrier618of the secondary carrier in the unlicensed band616, based on second channel access to the first subcarrier (e.g., first subchannel606and/or second subchannel608) in the licensed band604.

According to some aspects, using SL UE1 as an example, SL UE1 may occupy the second slot624of the first subchannel606(e.g., a first SL subchannel, a first CA subchannel) in the primary carrier in the licensed band604. SL UE1 may omit a transmission during at least the last OFDM symbol position630of the second slot624. In general, the duration of the omitted transmission may be referred to as a symbol gap. For exemplary and noon-limiting purposes, an example in which a transmission is omitted from the last OFDM symbol in a slot is described. The duration of the last OFDM symbol position630may be referred to herein as the last OFDM symbol gap632.

Last OFDM symbol positions that have no transmissions (e.g., last OFDM symbol position630) and idle intervals (e.g., idle interval636), which are time intervals in the unlicensed band616that overlap with at least a portion of the last OFDM symbol gap (e.g.,632) are both indicated by left-to-right downward sloping hash marks inFIG.6. An idle interval (e.g.,636) may begin coincident with the start of the last OFDM symbol positions (e.g., last OFDM symbol position630) or anywhere within the last OFDM symbol gap (e.g.,632). The last OFDM symbol gap (e.g., last OFDM symbol gap632) and the idle interval (e.g., idle interval636) do not necessarily have the same duration. The relationships between the various features ofFIG.6is illustrative and non-limiting.

SL UE1 may conduct an FBE listen before talk access procedure (LBT procedure634) to gain access to the aggregated subcarrier618in the unlicensed band616(e.g., the secondary carrier) by beginning the LBT process634at the start of, or anywhere within, the idle interval636. The idle interval at least partially overlaps with the last OFDM symbol gap632of the portion of the second slot624occupied by SL UE1. In other words, a wireless communication device may begin to seek access to a secondary carrier in an unlicensed band beginning at the start of the idle interval636or during any portion of the idle interval636that at least partially overlaps with the last OFDM symbol gap. Upon successful completion of the LBT process634(e.g., upon receiving access to the aggregated subcarrier618, that is, the secondary carrier), SL UE1 may offload the sidelink traffic to the third frame638of the secondary carrier (e.g., the third frame of the aggregated subcarrier618in the unlicensed band616).

Beginning the LBT procedure634at the start of, or anywhere within, the idle interval636helps to ensure that a transmission on a primary carrier in the licensed band604(e.g., in the ITS band of about 5.8-5.9 GHz) will not interfere with the LBT access procedure634that begins during the idle interval636. This result may be achieved when, for example, when SL UE1 omits transmission of the last OFDM symbol630from the slot624, as exemplified inFIG.6. The unlicensed band616may be, for example, at around 5.6 - 5.7 GHz. During FBE LBT, the wireless communication device measures the energy in the channel it is seeking to access. Therefore, if there are no transmissions in the primary carrier in the licensed band604(which as recognized from the examples above may be close in frequency to the frequency of the aggregated subcarrier618(e.g., the second carrier) in the unlicensed band616) during the FBE LBT access procedure634, it is less likely that the energy from a primary carrier in a licensed band604transmission will spill over into the channel being sensed for access in the secondary carrier.

Similarly, using SL UE2 as an example, SL UE2 may conduct an FBE LBT access procedure to gain access to the aggregated subcarrier618in the unlicensed band616(e.g., the secondary carrier) by beginning the LBT access procedure at the start of, or anywhere within, the idle interval646. The idle interval646at least partially overlaps with the last OFDM symbol gap644of the portion of the third slot626occupied by SL UE2. Upon successful completion of the LBT access procedure, SL UE2 may offload the sidelink traffic to the fourth frame640of the secondary carrier (e.g., the aggregated subcarrier618of the unlicensed band616).

Returning to using SL UE1 as an example, SL UE1 may conduct an FBE LBT access procedure to gain access to the aggregated subcarrier618in the unlicensed band616(e.g., the secondary carrier) by beginning the LBT process at the start of, or anywhere within, the respective idle interval. The respective idle interval at least partially overlaps with the respective last OFDM symbol gap of the portion of the fifth slot628occupied by SL UE1. Upon successful completion of the LBT access procedure, SL UE1 may offload the sidelink traffic to the sixth frame642of the secondary carrier (e.g., the aggregated subcarrier618of the unlicensed band616).

FIG.7is a flow chart illustrating an exemplary process700for use of carrier aggregation over licensed and unlicensed spectrum to perform SL communication between wireless communication devices (e.g., SL UEs) in a wireless communication network in accordance with some aspects of the present disclosure. As described below, some or all illustrated features may be omitted in a particular implementation within the scope of the present disclosure, and some illustrated features may not be required for implementation of all embodiments. In some examples, the process700(e.g., a method) may be carried out by the wireless communication device illustrated inFIG.5. In some examples, the process700may be carried out by any suitable apparatus or means for carrying out the functions or algorithm described below.

At block702, the wireless communication device may occupy a slot in a first subchannel, where the first subchannel comprises a sidelink subchannel in a licensed band. The wireless communication device may occupy the slot in the first subchannel after successful completion of an access procedure, for example.

At block704the wireless communication device may transmit sidelink control in the first subchannel during the slot, except during a symbol gap indicated to include at least a last symbol of a plurality of symbols supported by the slot.

At block706, the wireless communication device may seek access to a secondary carrier in an unlicensed band. According to some aspects, the wireless device may seek access to the secondary carrier beginning and/or during the symbol gap. The period during which the wireless communication device seeks access may be referred to as an idle interval. The idle interval may at least partially overlap with the symbol gap. According to some aspects, seeking access to the secondary carrier in the unlicensed band may include deriving frame-based equipment (FBE) frame timing over the unlicensed band from timing in the licensed band (e.g., OFDM timing). According to one aspect, seeking access to the secondary carrier in the unlicensed band may include synchronizing first channel access to the secondary carrier in the unlicensed band, based on second channel access to the first subchannel in the licensed band. According to another aspect, seeking access to the secondary carrier in the unlicensed band may include using a frame-based equipment (FBE) listen before talk (LBT) procedure to seek the access to the secondary carrier during an idle interval that at least partially overlaps with the symbol gap. According to another aspect, seeking access to the secondary carrier in the unlicensed band may include seeking the access to the secondary carrier in the unlicensed band during the symbol gap. According to some examples, the method may also include identifying a primary carrier that includes the first subchannel and monitoring only the primary carrier for sidelink control.

At block708, the wireless communication device may transmit sidelink traffic in the secondary carrier upon receiving (or obtaining) the access to the secondary carrier. According to one aspect, the wireless communication device may transmit sidelink traffic in the secondary carrier upon receiving (or obtaining) the access to the secondary carrier during or following the symbol gap.

According to other aspects, the wireless communication device may aggregate (e.g., after making a determination to aggregate) the sidelink control and the sidelink traffic to a primary carrier and the secondary carrier, respectively, and may further designate the licensed band to include the primary carrier and designate the unlicensed band to include the secondary carrier.

According to still other aspects, the wireless communication device may carry stage 1 sidelink control information over the first subchannel and carry enhanced stage 2 sidelink control information including at least one of modulation and coding scheme (MCD), hybrid automatic repeat request (HARQ), or transmission (TX) parameters for the secondary carrier over the first subchannel.

FIG.8Ais an example of a plurality subchannels802in a licensed band according to some aspects.FIG.8Bis an example of a plurality of resource blocks804(e.g., physical resource blocks) in an unlicensed band according to some aspects.FIG.8AandFIG.8Btogether constituteFIG.8.

Each of the plurality of subchannels802ofFIG.8Amay correspond a respective number of resource blocks in the frequency domain. Although the plurality of subchannels802ofFIG.8Aare all depicted as having the same frequency span (vertical span), the presentation is made for convenience and the frequency spans (and numbers of resource blocks) of the various subchannels may be different and/or the same as one another.

The lowest frequency on the frequency axis inFIG.8is identified as “Point A.” According to some aspects, Point A may represent a center frequency of a lowest subcarrier in the frequency domain. Point A may be used as common reference point for various subchannels and/or resource blocks. For example, the lowest subchannel (subchannel 0806) ofFIG.8Ais spaced apart from Point A by a first predetermined value. The lowest physical resource block (PRB 0818) ofFIG.8Bis spaced apart from Point A by a second predetermined value. The first predetermined value and the second predetermined value may be greater than, equal to, or lesser than the other.

The duration (in the time domain) of the column of the plurality of subchannels802and the column of the plurality of physical resource blocks804may be the same or different. By way of example, either or both of the durations may be a slot (e.g., first slot612, second slot624, third slot626, or fifth slot628ofFIG.6), or may be any duration, such as, for example, a subframe, a frame, or any other duration without limitation.

Wireless communication devices, for example, wireless communication device500, SL UE1, and/or SL UE2 may each perform an access procedure to gain access to and to occupy any of the plurality of subchannels802and may be referred to as CA subchannels, an SL subchannels, or a subchannel. By way of example and without limitation, SL UE1 may occupy subchannel 0806, SL UE2 may occupy subchannel 1808, SL UE3 may occupy subchannel 2810, SL UE4 may occupy subchannel 3812, SL UE5 may occupy subchannel 4814, and SL UE6 may occupy subchannel 5816. Additional subchannels may be occupied by additional respective SL UEs, as shown; however, inFIG.8A, the additional subchannels are not provided with reference numbers to avoid cluttering the drawing. The occupation of subchannels need not be sequential, nor must all subchannels be occupied. The appearance and configuration of the plurality of subchannels802inFIG.8Ais exemplary and non-limiting.

The plurality of physical resource blocks804ofFIG.8Bare each identified by a physical resource block number and an interlace index. In the example ofFIG.8B, 24 PRBs (PRB 0818- PRB 23840) are depicted. The number of PRBs is illustrative and not limiting. Not all PRBs are provided with reference numbers to avoid clutter the drawing. In the example ofFIG.8B, there are five interlaces (interlace index numbers 0-4). The quantity of five interlaces may correspond to a 30 kHz subcarrier spacing (SCS). Other numbers of interlaces and SCSs are within the scope of the disclosure. In the example ofFIG.8B, the interlaces begin at PRB 0818with interlace index 0 and repeat every five interlaces, such that each succeeding interlace 4 is adjacent to a next succeeding interlace 0.

In general,FIG.8depicts interlaced channel access over the secondary carrier805. InFIG.8, Frequency Division Multiplexing (FDM) is used in both the primary carrier803and the secondary carrier805. FDM (e.g., an interlaced waveform) may be used so that the unlicensed secondary carrier805may be shared by multiple wireless communication devices (e.g., SL UEs) that have occupied multiple CA subchannels (also referred to as subchannels and SL subchannels) in the primary carrier803. The interlaced waveform, (e.g., the interlaced waveform of the secondary carrier805ofFIG.8B) may be used for the unlicensed band of the secondary carrier805to meet occupied channel bandwidth (OCB) and/or power spectral density (PSD) regulations (such as various Governmental regulations imposed worldwide) by spreading the channel among a plurality of interlaced physical resource blocks in the secondary carrier805in the unlicensed band. Although both the primary carrier803and the secondary carrier805use FDM, the ways that the FDM is implemented are different between the primary carrier803and the secondary carrier805as depicted by a comparison ofFIG.8Aand the interlaced waveform ofFIG.8B.

A SL UE that occupies a given subchannel in the primary carrier803ofFIG.8Amay determine which interlace to use in a number of ways including, for example, by having a preconfigured set of subchannel and interlace combinations. In other words, a network operator for a given region or city, for example, may specify certain subchannel and interlace combinations, or specify interlace distributions according to some other way. The subchannel and interlace combinations may be preconfigured, for example, preloaded into wireless communication devices of the network operator or pushed down to or pulled down by the wireless communication devices from, for example, a server accessible to the wireless communication device via the Internet.

In the example ofFIG.8, SL UE1 has occupied subchannel 0806after completing an access procedure. In the example, subchannel 0806is associated with interlace 0 (interlace index 0), although it could be associated with any of interlaces 0-4. Through the association with interlace 0, SL UE1 is able to utilize subchannel 0806in the primary carrier803licensed band and also aggregate PRB 0818, PRB 5828, PRB 10832, PRB 15836, and PRB 20840in the secondary carrier805of the unlicensed band. The set of PRB 0818, PRB 5828, PRB 10832, PRB 15836, and PRB 20840is identified as each of these PRBs is associated with interlace index 0. The example includes PRB 0818through PRB 23842with 5 interlaces; however, this span and index combination is exemplary and non-limiting. For example, the span may include a span of 20 MHz, which may include more than the 24 physical resource blocks depicted in the example.

Also, in the example ofFIG.8, SL UE6 has occupied subchannel 5816after completing an access procedure. In the example, subchannel 5816is associated with interlace 3 (interlace index 3), although it could be associated with any of interlaces 0-4. Through the association with interlace 3, SL UE6 is able to utilize subchannel 5816in the primary carrier803licensed band and also aggregate PRB 3824, PRB 8830, PRB 13834, PRB 18838, and PRB 23842in the secondary carrier805of the unlicensed band. The set of PRB 3824, PRB 8830, PRB 13834, PRB 18838, and PRB 23842is identified as each of these PRBs is associated with interlace index 3. Like the previous example, the span of 24 PRBs, from PRB 0818to PRB 23842is exemplary and non-limiting. This number of PRBs or a different number of PRBs may correspond to a span of 20 MHz, which may include more than the 24 physical resource blocks depicted in the example.

In the primary carrier803licensed band, subchannel 1808may be occupied by SL UE2, subchannel 2810may be occupied by SL UE3, subchannel 3812may be occupied by subchannel SL UE4, and subchannel 4814may be occupied by SL UE5. In this example, none of these subchannels is associated with any interlace, therefore they may not interlace channel access over the secondary carrier805in the unlicensed band.

In the examples of subchannel 0806and subchannel 5816, corresponding to interlace index 0 and interlace index 3, respectively, a number of FDM channels over the secondary carrier (m_s = 5) which is smaller than the number of FDM channels over the primary carrier (m_p > 12). Therefore, consistent with the example, and according to some aspects, m_s ≤ m_p when it comes to mapping FDM subchannels in the primary carrier803to interlaced FDM channels in the secondary carrier805. Therefore, every subchannel in the primary carrier803in the licensed band may not have a counterpart in the secondary carrier805in the unlicensed band. However, through use of interlacing, a wireless communication device may share a portion of the unlicensed spectrum among a plurality of subchannels in the primary carrier803in the licensed spectrum.

The aspect of interlaced channel access over the secondary carrier805may be useful in several scenarios including, for example, when the primary carrier803may be used for low-latency safety-like small packet yet the secondary carrier805may be for large packet with relaxed latency. According to such aspects, the secondary carrier805in the unlicensed band can be shared by multiple SL UEs that have occupied multiple respective subchannels (CA subchannels, SL subchannels) in the primary carrier803licensed band. According to another example, a high-priority SL UE can occupy multiple subchannels (CA subchannels, SL subchannels) in the primary carrier803and hence yielding multiple dimensions in the secondary carrier805unlicensed band. Therefore, similar to the first example given above, a wireless communication device (e.g., SL UE1) may map a first subchannel (e.g., subchannel 0806) in a primary carrier803to a plurality of interlaced resource blocks (e.g., PRB 0818, PRB 5828, PRB 10832, PRB 15836, and PRB 20840) in the secondary carrier805of the unlicensed band. Similar to the second example given above, a wireless communication device (e.g., SL UE5) may map a first subchannel (e.g., subchannel 5816) in a primary carrier803to a plurality of interlaced resource blocks (e.g., PRB 3824, PRB 8830, PRB 13834, PRB 18838, and PRB 23842) in the secondary carrier805of the unlicensed band.

In some examples, the wireless communication device may have one transmission block remaining and can obtain another transmission block upon receiving the access to the secondary carrier. In such examples, a method disclosed herein may include having the wireless communication device transmit the sidelink control and the sidelink traffic in the first subchannel. In some of these examples, the sidelink control may include an enhanced stage 2 sidelink control information (eSCI-2) message that defines at least one of a modulation and coding scheme (MCS) of the secondary carrier, hybrid automatic repeat request (HARQ) feedback of the secondary carrier, or a transmission (TX) parameter for the secondary carrier. In some of these examples, the sidelink control may include a first stage 2 sidelink control information (first SCI-2) message and a pointer to a second stage 2 SCI (second SCI-2) message carried over the secondary carrier.

According to some aspects, a wireless communication device exemplified herein may transmit only sidelink control in the first subchannel. The sidelink control may include, for example SCI or SCI plus slot format indication (SFI). According to some aspects, the sidelink control may include a first stage 1 sidelink control information (first SCI-1) message and a pointer to a second stage 2 SCI (second SCI-2) message carried over the secondary carrier. According to other aspects, the sidelink control may include a stage one sidelink control information (SCI-1) message and an enhanced stage 2 sidelink control information (eSCI-2) message that defines at least one of a modulation and coding scheme (MCS) for the secondary carrier, hybrid automatic repeat request (HARQ) feedback for the secondary carrier, or a transmission (TX) parameter for the secondary carrier.

FIG.9is an example of a plurality subchannels902in a licensed band according to some aspects. Each of the plurality of subchannels902may correspond a respective number of resource blocks in the frequency domain. Although the plurality of subchannels902ofFIG.9are all depicted as having the same frequency span (vertical span), the presentation is made for convenience and the frequency spans (and numbers of resource blocks) of the various subchannels may be different and/or the same as one another.

The lowest frequency on the frequency axis inFIG.9is identified as “Point A.” According to some aspects, Point A may represent a center frequency of a lowest subcarrier in the frequency domain. Point A may be used as common reference point for various subchannels and/or resource blocks. For example, the lowest subchannel (subchannel 0906) ofFIG.9is spaced apart from Point A by a first predetermined value.

A plurality of wireless communication devices (e.g., SL UE1 - SL UE13) (similar to wireless communication device500ofFIG.5) may each perform an access procedure to gain access to and to occupy any of the plurality of subchannels902. By way of example and without limitation, SL UE1 may occupy subchannel 0906, SL UE2 may occupy subchannel 1908, SL UE3 may occupy subchannel 2910, SL UE4 may occupy subchannel 3912, SL UE5 may occupy subchannel 4914, and SL UE6 may occupy subchannel 5916. Additional subchannels may be occupied by additional respective SL UEs (e.g., SL UE7 - SL UE13), as shown; however, inFIG.9, the additional subchannels are not provided with reference numbers to avoid cluttering the drawing. The occupation of subchannels need not be sequential, nor must all subchannels be occupied. The appearance and configuration of the plurality of subchannels902inFIG.9is exemplary and non-limiting.

In the example ofFIG.9, two subchannels, subchannel 0906and subchannel 5916are mapped to interlaced channel access of a secondary carrier. The mapping of like-numbered subchannels occupied by like-numbered SL UEs was described in connection withFIG.8and will not be repeated here to avoid duplication. Subchannel 0906and subchannel 5916may be referred to as CA subchannels because, for example, they map to a carrier aggregated secondary channel (not shown, but similar to secondary carrier805ofFIG.8). On the other hand, subchannel 1908, subchannel 2910, subchannel 3912, subchannel 4914, and subchannels 6-12 (not provided with reference numbers to avoid cluttering the drawing) are not mapped to interlaced channel access over the secondary carrier.

To avoid hot competition for the CA subchannels in autonomous SL (e.g., Mode 2) or in LTE SL (e.g., Mode 4), a network entity or system may define respective carrier occupation ratios (CRs) under a congestion control network for CA subchannels and non-CA subchannels. Accordingly, for example, CA subchannels subchannel 0906and subchannel 5916may be defined for a first CR (e.g., CR1) while the remaining non-CA subchannels 1-4 and 6-12 may be defined for a different CR. However, as shown inFIG.9, the granularity of the CRs may be further resolved by grouping the subchannels into transmission pools (TX Pools) and defining CR values, for example, according to the respective TX Pool. By way of example and without limitation, subchannel 0906and subchannel 5916may be members of a first TX Pool918(TX Pool 1), subchannel 1908, subchannel 2910, subchannel 3912, and subchannel 4914may be members of a second TX Pool920(TX Pool 2), and subchannels 6-12 may be members of a third TX Pool922(TX Pool 3). The first TX Pool918may have a first CR (CR1), the second TX Pool920may have a second CR (CR2), and the third TX Pool922may have a third CR (CR3). When all subchannels are homogenous and there is one TX Pool, then there may be one CR. However, identifying some channels as CA subchannels and others as non-CA subchannels, the subchannels may be considered non-homogenous (or heterogenous) channels. Use of heterogeneous channels provides an ability to define two or more different CR values (e.g., CR levels). The different CR values may help to prevent all Mode 2 (or all Mode 4) wireless communication devices from competing for the CA subchannels. If only two CR levels are used, then, in the example ofFIG.9, CR2 may be set equal to CR3. In accordance with aspects described herein, the various CR values may be preconfigured (e.g., in the same way, for example, as described in connection with pre-configurations of interlaces (e.g., numbers of interlaces and values of interlace index numbers).

According to some aspects, a wireless communication device may use a first subchannel as an anchor in a primary carrier for interlaced channel access over a secondary carrier. In other words, the first subchannel may be, for example, a CA subchannel such as subchannel 0906and/or subchannel 5916ofFIG.9. The wireless communication device may obtain a first channel occupancy ratio (CR) that is associated with a first packet transmitted (or to be transmitted) over the first subchannel. For example, the first CR may be similar to CR1 of TX Pool918ofFIG.9. The first CR may be preconfigured; according to such an example, the first CR may be obtained from a memory of the wireless communication device, for example. The wireless communication device may identify a second subchannel that is not an anchor in the primary carrier for interlaced channel access over the secondary carrier. For example, the second subchannel may be any of non-CA subchannel 1908, non-CA subchannel 2910, non-CA subchannel 3912, non-CA subchannel 14914, and/or any of non-CA subchannels 6-12 ofFIG.9. The wireless communication device may obtain a second CR, different from the first CR, which is associated with a second packet transmitted in the second subchannel. For example, the second CR may be similar to CR2 of TX Pool 2920or CR3 of TX Pool922ofFIG.9. The wireless communication device may thereafter avoid competition for access to the first subchannel based on a difference between the first CR and the second CR.

According to some aspects, the CA subchannel may include only sidelink control, while according to other aspects the CA subchannel may include sidelink control and sidelink traffic.

According to some aspects, a wireless communication device may use a first subchannel as an anchor in a primary carrier for interlaced channel access over a secondary carrier. In other words, the first subchannel may be, for example, a CA subchannel such as subchannel 0906and/or subchannel 5916ofFIG.9. The wireless communication device may calculate a first channel occupancy ratio (CR) that is associated with a first packet transmitted over the first subchannel using a first weighting factor that is greater than 1. The wireless communication device may identify a second subchannel that is not an anchor in the primary carrier for interlaced channel access over the secondary carrier. For example, the second subchannel may be any of non-CA subchannel 1908, non-CA subchannel 2910, non-CA subchannel 3912, non-CA subchannel 14914, and/or any of non-CA subchannels 6-12 ofFIG.9. The wireless communication device may calculate a second CR that is associated with a second packet transmitted in the second subchannel. The wireless communication device may thereafter avoid competition for access to the first subchannel based on a difference between the first CR that was calculated with the weighting factor that is greater than 1 and the second CR.

According to some aspects, the CA subchannel may include only sidelink control, while according to other aspects the CA subchannel may include sidelink control and sidelink traffic.

FIG.10Ais an example of a plurality subchannels1002,1007in a licensed band according to some aspects.FIG.10Bis an example of a plurality of resource blocks1004,1009(e.g., physical resource blocks) in an unlicensed band according to some aspects.FIG.10AandFIG.10Btogether constituteFIG.10.

Each of the plurality of subchannels1002ofFIG.10Aoccur at time t0. Each of the plurality of subchannels1007ofFIG.10Aoccur at time t1. Each of the plurality of physical resource blocks1004ofFIG.10Boccur at time t0+1. Each of the plurality of physical resource blocks1009ofFIG.10Boccur at time t1+1. The plurality of subchannels1002ofFIG.10Aat time t0 may be associated with the plurality of physical resource blocks1004ofFIG.10Bat time t0+1. The plurality of subchannels1007ofFIG.10Aat time t1 may be associated with the plurality of physical resource blocks1009ofFIG.10Bat time t1+1. The time t0 is less than t1. The times t0 and t1 may be contiguous; however, they are not necessarily contiguous. The illustrations ofFIG.10AandFIG.10Bare illustrative and non-limiting.

The lowest frequency on the frequency axis inFIG.10is identified as “Point A.” According to some aspects, Point A may represent a center frequency of a lowest subcarrier in the frequency domain. Point A may be used as common reference point for various subchannels and/or resource blocks. For example, the lowest subchannel (subchannel 01006) ofFIG.10Ais spaced apart from Point A by a first predetermined value. The lowest physical resource block (PRB 01014) ofFIG.10Bis spaced apart from Point A by a second predetermined value. The first predetermined value and the second predetermined value may be greater than, equal to, or lesser than the other.

The duration (in the time domain) the plurality of subchannels1002,1007and the plurality of physical resource blocks1004,1009may be the same or different. By way of example, either or both of the durations may be a slot (e.g., first slot612, second slot624, third slot626, or fifth slot628ofFIG.6), or may be any duration, such as, for example, a subframe, a frame, or any other duration without limitation.

Wireless communication devices, for example, similar to wireless communication device500may each perform an access procedure to gain access to and to occupy any of the plurality of subchannels1002,1007. At time t0, subchannel 01006and subchannel 51010may be referred to as CA subchannels or SL subchannels. By way of example and without limitation, at t0, SL UE1 may occupy subchannel 01006, SL UE2 may occupy subchannel 11008, SL UE6 may occupy subchannel 51010and SL UE7 may occupy subchannel 61012.

However, at time t0, only subchannel 01006and subchannel 51010may be referred to as CA subchannels or SL subchannels. This is because, at time t0, subchannel 01006serves as an anchor for interlaced channel access over the secondary carrier1005with interlace 0. Specifically, subchannel 01006may be preconfigured to correspond with interlace 0 ofFIG.10Bat time t0+1. This is because, at time t0+1, in subchannel 01006at time t0 serving as anchor point for PRB 01014, PRB 51022, PRB 101030, PRB 151038and PRB 201046. Likewise, at time t0 subchannel 51010serves as an anchor for interlaced channel access over the secondary carrier1005with interlace 3. Specifically, subchannel 51010may be preconfigured to correspond with interlace 3 ofFIG.10Bat time t0+1. This is because, at time t0+1 in subchannel 51010at time t0 serving as anchor point for PRB 31018, PRB 81026, PRB 131034, and PRB 181042.

The mapping from CA subchannels in primary carrier1003may be time-varying according to a pattern as shown by comparison of the plurality of subchannels1002at time t0 and the same plurality of subchannels1007at time t1. In the example ofFIG.10A, although subchannel 01006and subchannel 51010were both CA subchannels at time t0, they are no longer CA subchannels at time t1. Instead, according to a patter, subchannel 11008and subchannel 61012are CA subchannels at time t1. This is because, at time t1 subchannel 11008serves as an anchor for interlaced channel access over the secondary carrier1005with interlace 2. Specifically, subchannel 11008may be preconfigured to correspond with interlace 2 ofFIG.10Bat time t1+1. This is because, at time t1+1 in subchannel 11008at time t1 serving as anchor point for PRB 21016, PRB 571024, PRB 121032, and PRB 171040. Likewise, at time t1 subchannel 61012serves as an anchor for interlaced channel access over the secondary carrier1005with interlace 4. Specifically, subchannel 61012may be preconfigured to correspond with interlace 4 ofFIG.10Bat time t1+1. This is because, at time t1+1 in subchannel 61012at time t1 serving as anchor point for PRB 41020, PRB 91028, PRB 141036, and PRB 191044.

Accordingly, as described above, the wireless communication device may map from CA subchannels in the primary carrier1003, according to a time-varying pattern. The time varying pattern may be preconfigured, similar to pre-configuration of interlaces, described earlier. According to some aspects, subchannels of a primary band including the first subchannel may be mapped, according to a time varying pattern, to pluralities of physical resource blocks in the secondary carrier.

In some examples, the wireless communication device may identify a primary carrier including the first subchannel and send hybrid automatic repeat request (HARQ) feedback of the secondary carrier over the primary carrier. The wireless communication device may send the HARQ feedback during a feedback opportunity of the first subchannel. The feedback opportunity may occur during a physical sidelink feedback channel opportunity. In one example, the wireless communication device may send the HARQ feedback of the secondary carrier over the primary carrier as code division multiplexed (CDM) message in the sidelink control.

A wireless communication device may report a channel quality indicator (QCI) and/or a rank indicator (RI) of the secondary carrier with CQI/RI of the first subchannel. According to some aspects, the reporting the CQI/RI of the secondary carrier with CQI/RI of the first subchannel may be sent in a medium access control element (MAC-CE) associated with the first subchannel.

According to some aspects, the wireless communication device may determine a first priority value associated with a sidelink control packet to be transmitted as the sidelink control in the first subchannel, determine a second priority value associated with a sidelink traffic packet, and transmit the sidelink traffic packet in the sidelink traffic if the second priority value is equal to the first priority value.

The wireless communication device may determine a first priority value, associated with a sidelink control packet to be transmitted as the sidelink control in the first subchannel, where the first priority value is selected from a closed set of values, determine a second priority value associated with a sidelink traffic packet, where the second priority value is selected from the closed set of values, determine a third priority value, relative to the first priority value, which may be indicative of lesser priority than the first priority value, and transmit the sidelink traffic packet in the sidelink control if the second priority value is greater than or equal to the third priority value.

The wireless communication device may also transmit a sidelink traffic packet in the sidelink traffic without regard to priority of the sidelink traffic packet.

According to some aspects, the wireless communication device may conduct load-balancing between a primary carrier including the first subchannel and the secondary carrier based on a channel busy ratio (CBR) determined for the primary carrier. Still further, according to some aspects, the load-balancing may further include conducting the load-balancing between a primary carrier including the first subchannel and the secondary carrier based on a channel busy ratio (CBR) determined for the primary carrier. In some examples, the conducting load-balancing may further include determining if the CBR exceeds a threshold and, if the CBR exceeds the threshold, determining to transmit a sidelink traffic packet in the sidelink traffic based on a determination of at least one of: whether a priority of the sidelink traffic packet is equal to a sidelink control packet, whether the priority of the sidelink traffic packet is within a predetermined delta of the sidelink control packet, or whether no priority of both the sidelink traffic packet is within a predetermined delta of the sidelink control packet. For example, for one CBR level over the primary carrier, the wireless communication device may transmit a packet over the secondary carrier if, for example, the priority of the sidelink control and sidelink traffic are equal, the priority of the sidelink traffic is slightly relaxed from that of the sidelink control (e.g., is less than a predetermined amount less than the priority of the sidelink control, or the priority of the sidelink control and sidelink traffic are not to be considered. For example, when CBR in primary is large, the wireless communication device may be preconfigured to ignore any determinations of priority and off-load traffic to the secondary carrier. As used herein, CBR may be measured or calculated over a TX Pool.

According to some aspects, the wireless communication device may seek access to the secondary carrier by deriving load-based equipment (LBE) frame timing over the unlicensed band from timing in the licensed band. According to still other aspects, the wireless communication device may seek access to the secondary carrier by using a load-based equipment (LBE) listen before talk (LBT) procedure to seek the access to the secondary carrier during an idle interval that at least partially overlaps with the symbol gap.

FIG.11is a flow diagram used by a wireless communication device to determine if content of a carrier aggregation subchannel (e.g., subchannels of a primary channel in the licensed band) should include control plus traffic or only control according to some aspects.

At block1102, the wireless communication device determines if it has at least one transmission block (TB) and can opportunistically obtain another TB if it passes the FBE LBT access control process. If the wireless communication device determines that it has at least one TB and can opportunistically obtain another TB if it passes the FBE LBT access control process, the process passes to block1104. At block1104, the wireless communication device selects Type-1 content, allowing the carrier aggregation subchannel (e.g., the in the licensed band) to carry control plus traffic. Thereafter, at block1106, the carrier aggregation subchannel carries the stage 1 SCI. Thereafter, the wireless communication device determines if the carrier aggregation subchannel should also carry an enhanced stage 2 SCI at block1108. If the wireless communication device determines, at block1108, that the carrier aggregation subchannel should also carry an enhanced stage 2 SCI, then, at block1110, the carrier aggregation subchannel is made to carry the enhanced stage 2 SCI, which in addition to parameters associated with a nominal stage 2 SCI, also defines the modulation coding scheme (MCS), HARQ, and related TX parameters for the secondary carrier. Thereafter, the process1100may end.

Returning to block1108, if the wireless communication device determines, at block1108, that the carrier aggregation subchannel should not also carry an enhanced stage 2 SCI, then, at block1112, the carrier aggregation subchannel is made to carry only stage 2 SCI for PSSCH or the primary carrier, and a pointer to the stage 2 SCI for the secondary carrier. Thereafter, the process1100may end.

Returning to block1102, if the wireless communication device determines that it does not have at least one TB and/or cannot opportunistically obtain another TB if it passes the FBE LBT access control process, the process passes to block1114. At block1114, the wireless communication device selects type-2 content, allowing the carrier aggregation subchannel (e.g., a subchannel of a primary carrier in the licensed band) to carry only control (e.g., SCI, or SCI plus sidelink feedback information (SFI)). According to some aspect, if the type-2 content is employed, then the primary carrier may be a relatively small size, as it is only carrying data. Thereafter, at block1116, the carrier aggregation subchannel carries the stage 1 SCI. Thereafter, the wireless communication device determines if the carrier aggregation subchannel should also carry an enhanced stage 2 SCI at block1118. If the wireless communication device determines, at block1118, that the carrier aggregation subchannel should also carry an enhanced stage 2 SCI, then, at block1120, the carrier aggregation subchannel is made to carry the enhanced stage 2 SCI for TX over secondary carrier. Thereafter, the process1100may end.

Returning to block1118, if the wireless communication device determines, at block1118, that the carrier aggregation subchannel should not also carry an enhanced stage 2 SCI, then, at block1122, the carrier aggregation subchannel is made to carry only the stage 1 SCI and leave the stage 2 SCI in the secondary carrier. Thereafter, the process1100may end.