WO2023097700A1

WO2023097700A1 - Channel occupancy time sharing

Info

Publication number: WO2023097700A1
Application number: PCT/CN2021/135540
Authority: WO
Inventors: Tao Tao; Timo Erkki Lunttila; Claudio Rosa; Navin Hathiramani
Original assignee: Nokia Shanghai Bell Co., Ltd.; Nokia Solutions And Networks Oy; Nokia Technologies Oy
Priority date: 2021-12-03
Filing date: 2021-12-03
Publication date: 2023-06-08

Abstract

Embodiments of the present disclosure relate to methods, devices, apparatuses, and computer readable medium of enhancement on positioning. The method comprises: receiving, at a first device and from a second device, a message comprising a configuration of reference signal based channel occupancy time, COT; monitoring, based on the configuration, a channel between the first device and a second device; and in accordance with a determination that a COT sharing condition is met based on the monitoring result, transmitting a first transmission to the second device during a target COT within a target time window, the target COT being acquired by using a high complexity listen-before-talk, LBT. In this way, the periodic discovery bursts or SSB transmissions within discovery burst transmission windows can be used for potential COT shared with to a low complexity UE. As such, the system performance, QoS and resource efficiency can be improved in unlicensed band.

Description

CHANNEL OCCUPANCY TIME SHARING

FIELD

Embodiments of the present disclosure generally relate to the field of telecommunication and in particular, to devices, methods, apparatus and computer readable storage media of channel occupancy time (COT) sharing.

BACKGROUND

LTE-LAA as the first time the notion of cellular-based access via unlicensed spectrum was introduced as a complementary tool for operators to augment their service offering and/or offloading heaving traffic from licensed band to unlicensed band on-demand. In addition, unlicensed spectrum also creates opportunities for enterprises without licensed spectrum holdings to deploy private networks for industrial use cases, such as, shipping ports, mines and airports. MulteFire was the first attempt to create a 3GPP technology based connectivity option for Internet of Things (IoT) deployments, exclusively operating in unlicensed spectrum, to help embrace the fourth industrial revolution.

With the arrival of 5G New Radio (NR) , operations in unlicensed band have also been introduced to support highly reliable low latency use cases in verticals, which is referred to as, New Radio in unlicensed spectrum (NR-U) . Massive industrial wireless sensor network (IWSN) use cases and requirements may include not only URLLC services with very high reliability requirements, but also relatively low-end services with the requirement of small device form factors, and/or being completely wireless with a battery life of several years. These realistic industrial use cases motivate the development of low complexity NR-U, to support low complexity low cost devices in the network when operating in unlicensed band.

SUMMARY

In general, example embodiments of the present disclosure provide a COT sharing solution.

In a first aspect, there is provided a first device. The first device comprises: at least one processor; and at least one memory including computer program codes. The at least one memory and the computer program codes are configured to, with the at least one processor, cause the first device to: a configuration of reference signal based channel occupancy time, COT; monitor, based on the configuration, a channel between the first device and the second device; and in accordance with a determination that a COT sharing condition is met based on the monitoring result, transmit a first transmission to the second device during a target COT within a target time window, the target COT being acquired by using a high complexity listen-before-talk, LBT.

In a second aspect, there is provided a second device. The second device comprises: at least one processor; and at least one memory including computer program codes. The at least one memory and the computer program codes are configured to, with the at least one processor, cause the second device to: transmit, to a first device, a message comprising a configuration of reference signal based channel occupancy time, COT; and upon transmitting a second transmission with a high complexity listen-before-talk, LBT at one of a group of occasions associated with a target COT within a target time window, receive, from the first device, a first transmission during the target COT.

In a third aspect, there is provided a method. The method comprises: receiving, at a first device and from a second device, a message comprising a configuration of reference signal based channel occupancy time, COT; monitoring, based on the configuration, a channel between the first device and a second device; and in accordance with a determination that a COT sharing condition is met based on the monitoring result, transmitting a first transmission to the second device during a target COT within a target time window, the target COT being acquired by using a high complexity listen-before-talk, LBT.

In a fourth aspect, there is provided a method. The method comprises: transmitting, at a second device and to a first device, a message comprising a configuration of reference signal based channel occupancy time, COT; and upon transmitting a second transmission with a high complexity listen-before-talk, LBT at one of a group of occasions associated with a target COT within a target time window, receiving, from the first device, a first transmission during the target COT.

In a fifth aspect, there is provided a first apparatus. The first apparatus comprises: means for receiving, from a second apparatus, a message comprising a configuration of reference signal t based channel occupancy time, COT; means for monitoring, based on the configuration, a channel between the first apparatus and the second apparatus; and means for in accordance with a determination that a COT sharing condition is met based on the monitoring result, transmitting a first transmission to the second device during a target COT within a target time window, the target COT being acquired by using a high complexity listen-before-talk, LBT.

In a sixth aspect, there is provided a second apparatus. The second apparatus comprises: means for transmitting, to a first apparatus, a message comprising a configuration of reference signal based channel occupancy time, COT; and means for upon transmitting a second transmission with a high complexity listen-before-talk, LBT at one of a group of occasions associated with a target COT within a target time window, receiving, from the first device, a first transmission during the target COT.

In a seventh aspect, there is provided a non-transitory computer readable medium. The non-transitory computer readable medium comprises program instructions for causing an apparatus to perform the method according to the third aspect.

In an eighth aspect, there is provided a non-transitory computer readable medium. The non-transitory computer readable medium comprises program instructions for causing an apparatus to perform the method according to the fourth aspect.

It is to be understood that the summary section is not intended to identify key or essential features of embodiments of the present disclosure, nor is it intended to be used to limit the scope of the present disclosure. Other features of the present disclosure will become easily comprehensible through the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

Some example embodiments will now be described with reference to the accompanying drawings, where:

FIG. 1 illustrates an example network environment in which example embodiments of the present disclosure may be implemented;

FIG. 2 illustrates a schematic diagram illustrating an example of COT sharing mechanism according to some example embodiments of the present disclosure;

FIG. 3 shows a signaling chart illustrating a COT sharing procedure according to some example embodiments of the present disclosure;

FIG. 4 illustrates a schematic diagram illustrating another example of COT sharing mechanism according to some example embodiments of the present disclosure;

FIG. 5 illustrates a flowchart of an example method implemented at a first device according to example embodiments of the present disclosure;

FIG. 6 illustrates a flowchart of an example method implemented at a second device according to example embodiments of the present disclosure;

FIG. 7 illustrates a simplified block diagram of an apparatus that is suitable for implementing example embodiments of the present disclosure; and

FIG. 8 illustrates a block diagram of an example computer readable medium in accordance with example embodiments of the present disclosure.

Throughout the drawings, the same or similar reference numerals represent the same or similar element.

DETAILED DESCRIPTION

Principle of the present disclosure will now be described with reference to some example embodiments. It is to be understood that these embodiments are described only for the purpose of illustration and help those skilled in the art to understand and implement the present disclosure, without suggesting any limitation as to the scope of the disclosure. The disclosure described herein can be implemented in various manners other than the ones described below.

In the following description and claims, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skills in the art to which this disclosure belongs.

References in the present disclosure to “one embodiment, ” “an embodiment, ” “an example embodiment, ” and the like indicate that the embodiment described may include a particular feature, structure, or characteristic, but it is not necessary that every embodiment includes the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

It shall be understood that although the terms “first” and “second” etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and similarly, a second element could be termed a first element, without departing from the scope of example embodiments. As used herein, the term “and/or” includes any and all combinations of one or more of the listed terms.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms “a” , “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” , “comprising” , “has” , “having” , “includes” and/or “including” , when used herein, specify the presence of stated features, elements, and/or components etc., but do not preclude the presence or addition of one or more other features, elements, components and/or combinations thereof.

As used in this application, the term “circuitry” may refer to one or more or all of the following:

(a) hardware-only circuit implementations (such as implementations in only analog and/or digital circuitry) and

(b) combinations of hardware circuits and software, such as (as applicable) :

(i) a combination of analog and/or digital hardware circuit (s) with software/firmware and

(ii) any portions of hardware processor (s) with software (including digital signal processor (s) ) , software, and memory (ies) that work together to cause an apparatus, such as a mobile phone or server, to perform various functions) and

(c) hardware circuit (s) and or processor (s) , such as a microprocessor (s) or a portion of a microprocessor (s) , that requires software (e.g., firmware) for operation, but the software may not be present when it is not needed for operation.

This definition of circuitry applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term circuitry also covers an implementation of merely a hardware circuit or processor (or multiple processors) or portion of a hardware circuit or processor and its (or their) accompanying software and/or firmware. The term circuitry also covers, for example and if applicable to the particular claim element, a baseband integrated circuit or processor integrated circuit for a mobile device or a similar integrated circuit in server, a cellular network device, or other computing or network device.

As used herein, the term “communication network” refers to a network following any suitable communication standards, such as Long Term Evolution (LTE) , LTE-Advanced (LTE-A) , Wideband Code Division Multiple Access (WCDMA) , High-Speed Packet Access (HSPA) , Narrow Band Internet of Things (NB-IoT) and so on. Furthermore, the communications between a terminal device and a network device in the communication network may be performed according to any suitable generation communication protocols, including, but not limited to, the first generation (1G) , the second generation (2G) , 2.5G, 2.75G, the third generation (3G) , the fourth generation (4G) , 4.5G, the fifth generation (5G) , a further sixth generation (6G) communication protocols, and/or any other protocols either currently known or to be developed in the future. Embodiments of the present disclosure may be applied in various communication systems. Given the rapid development in communications, there will of course also be future type communication technologies and systems with which the present disclosure may be embodied. It should not be seen as limiting the scope of the present disclosure to only the aforementioned system.

As used herein, the term “network device” refers to a node in a communication network via which a terminal device accesses the network and receives services therefrom. The network device may refer to a base station (BS) or an access point (AP) , for example, a node B (NodeB or NB) , an evolved NodeB (eNodeB or eNB) , a NR Next Generation NodeB (gNB) , a Remote Radio Unit (RRU) , a radio header (RH) , a remote radio head (RRH) , Integrated Access and Backhaul (IAB) node, a relay, a low power node such as a femto, a pico, and so forth, depending on the applied terminology and technology. The network device is allowed to be defined as part of a gNB such as for example in CU/DU split in which case the network device is defined to be either a gNB-CU or a gNB-DU.

The term “terminal device” refers to any end device that may be capable of wireless communication. By way of example rather than limitation, a terminal device may also be referred to as a communication device, user equipment (UE) , a Subscriber Station (SS) , a Portable Subscriber Station, a Mobile Station (MS) , or an Access Terminal (AT) . The terminal device may include, but not limited to, a mobile phone, a cellular phone, a smart phone, voice over IP (VoIP) phones, wireless local loop phones, a tablet, a wearable terminal device, a personal digital assistant (PDA) , portable computers, desktop computer, image capture terminal devices such as digital cameras, gaming terminal devices, music storage and playback appliances, vehicle-mounted wireless terminal devices, wireless endpoints, mobile stations, laptop-embedded equipment (LEE) , laptop-mounted equipment (LME) , USB dongles, smart devices, wireless customer-premises equipment (CPE) , an Internet of Things (loT) device, a watch or other wearable, a head-mounted display (HMD) , a vehicle, a drone, a medical device and applications (e.g., remote surgery) , an industrial device and applications (e.g., a robot and/or other wireless devices operating in an industrial and/or an automated processing chain contexts) , a consumer electronics device, a device operating on commercial and/or industrial wireless networks, and the like. In the following description, the terms “terminal device” , “communication device” , “terminal” , “user equipment” and “UE” may be used interchangeably.

In NR-U, a UE may communicate with a gNB or with another UE, where the UE initiating the communication takes a role of initiating device, while the gNB or the other UE takes a role of responding device. The initiating device has to acquire the “right” to access the channel for a certain period of time, which is referred to as the Channel Occupancy Time (COT) . To do this, a channel access procedure may be performed. Typically, there are two types of channel access procedure, i.e., channel access type 1 with random backoff, and channel access type 2 with one-shot clear channel assessment (CCA) .

The initiating device may apply an “extended” listen-before-talk (LBT) procedure where the channel must be deemed as free for an entire duration of a Contention Window (CW) . This “extended” LBT procedure is commonly known as LBT Category 4 (which may be referred to as LBT Cat. 4 hereinafter) which corresponds to the channel access type 1.

On the other hand, the responding device may share the COT acquired by the initiating device. In this case, the responding device is only required to perform a “reduced” LBT procedure. This “reduced” LBT procedure is commonly known as LBT Category 2 (which may be referred to as LBT Cat. 2 hereinafter) or LBT Category 1 (which may be referred to as LBT Cat. 1 hereinafter) . The LBT Category 2 and LBT Category 1 may correspond to the channel access type 2 which further includes the following variants:

· Type 2A (25 μs LBT Cat. 2) –in case the gap between DL to UL is ≥ 25 μs ;

· Type 2B (16 μs LBT Cat. 2) –in case the gap between DL to UL is exactly equal to 16 μs;and

· Type 2C (no LBT, LBT Cat. 1) –in case the gap between DL to UL is ≤ 16 μs.

Channel access type 1 and channel access type 2 differ in terms of implementation complexity and power consumption. In particular, the implementation complexity and power consumption of channel access type 1 is much larger than that of channel access type 2. Hence, most of the low complexity devices, such as, sensors, asset tracking beacons, etc., may only have capability of channel access type 2 to perform single-shot LBT or no LBT.

As low complexity devices only have limited LBT capability, transmissions from these devices may fully rely on the COT sharing mechanism. That is, a low complexity UE expects the gNB or another UE to acquire a COT, and then it is allowed to transmit data within the acquired COT.

However, in a scenario with heavy uplink (UL) traffic, a gNB may not acquire a COT at all, since the gNB has little data to be transmitted to a UE. In such a scenario, the UE has to wait until the gNB acquires a COT, which causes the UL transmission to be delayed. For example, if a UE expects to transmit a scheduling request (SR) to the gNB, the UE may have to wait for not only the next SR occasion, but also the SR occasion before which the gNB acquires a COT. This delay is intolerable for some services with high requirements on reliability, latency, Quality of Service (QoS) , for example, the URLLC service.

A straightforward way of handling the issue is that the gNB may try to acquire a COT before all SR and RACH (or other configured UL) occasions. However, it would incur a large DL overhead and redundancy. This is because the gNB will always occupy the channel and potentially cause interference to other nodes, regardless of whether the UE wants to transmit data or not. It is also worth mentioning that such a solution may potentially violate regulatory requirements, in case that the gNB actually has no downlink data, but have to transmit a “reservation signal” to occupy the channel.

In order to solve the above and other potential problems, embodiments of the present disclosure provide an improved COT sharing mechanism in unlicensed band. According to the COT sharing mechanism, a gNB utilizes periodic discovery bursts/Synchronization Signal and PBCH block, SSB, transmissions within discovery burst transmission windows as a potential COT provider to facilitate UL transmissions from a UE. To support transmissions within such discovery burst COTs, a set of SSB positions within the discovery burst transmission windows are predefined to be associated with a high complexity LBT, such as, Cat. 3 or Cat. 4 LBT, whereas the rest of SSB positions in the discovery burst transmission windows are still associated with a low complexity LBT, such as, Cat. 1 or Cat. 2 LBT. From the perspective of the UE, if the presence of an SSB in occasions associated with Cat. 4 LBT is detected, it would immediately know it is allowed to share the COT with SSB (s) for UL transmissions (e.g. SR, PRACH, CG UL) .

Additionally, or alternatively, for a case of no DL transmission for a certain period of time, the gNB and the UE will know that the next discovery burst or SSB position in the next discovery burst transmission window is to be associated with Cat. 4 LBT, so as to avoid the UE being unable to share the COT for a long time. Such a solution is also applicable to sidelink communications from to one UE to another UE. In this way, for the devices operating in unlicensed band, the channel access latency can be reduced, and thus improving the system performance and quality of services.

FIG. 1 illustrates an example network environment 100 in which embodiments of the present disclosure can be implemented. The network environment 100 includes a first device 110 and a second device 120. As shown in FIG. 1, the first device 110 may be implemented as a terminal device, which may be also referred to as the UE 110 or the terminal device 110 hereinafter. The second device 120 may be implemented as a base station, which may be also referred to as the base station 120 or the gNB 120 hereinafter.

The second device 120 provides radio coverage in a cell 102 where the first device 110 and the second device 120 may communicate with each other via a channel in unlicensed band. In particular, the direction from the first device 110 to the second device 120 may refer to uplink (UL) , and the direction from the second device 120 to the first device 120 may refer to downlink (DL) .

Before transmitting any data or control information, the second device 120 may perform a channel access procedure. The second device 120 may employ either a high complexity LBT including Cat. 3 LBT and Cat. 4 LBT or a low complexity LBT including Cat. 1 LBT and Cat. 2 LBT. In particular, the COT acquired via the low complexity LBT cannot be shared with the first device 110.

The first device 110 may be low complexity device, and thus has limited capability of LBT. In some example embodiments, due to limitations on processing capability, hardware structure, power consumption, etc., the first device 110 may not employ the high complexity LBT. In these cases, the first device 110 may transmit data within a COT acquired by the second device 120 and shared with it.

Typically, the second device 120 would employ Type2A/Category 2 LBT for Discovery burst/SSB transmissions. In some example embodiments, the second device 120 may employ the high complexity LBT for the Discovery burst/SSB transmissions, and thus, such discovery burst transmission windows can be used as COTs and shared with the first device 110. For descripting the example embodiments, the discovery burst/SSB transmissions are given for illustrative purpose, and the example embodiments can be applicable to various signal or data transmissions, including but not limited to, discovery reference signals (DRSs) , reference signals and so on. Therefore, the example embodiments are not limited in this regard.

In some example embodiments, the second device 120 may indicate whether the cell 102 supports the access of low complexity LBT device. For example, this may be implemented via broadcast signaling, such as, Physical Broadcast Channel (PBCH) , Remaining Minimum System Information (RMSI) , System Information Block (SIB) , or any other existing or new signaling.

To support UL transmissions within such discovery burst COTs, specific SSB positions within discovery burst transmission windows may be predefined to be associated with Cat. 4 LBT, while a rest of the SSB positions within the discovery burst transmission windows may be associated with Cat. 2 LBT. FIG. 2 illustrates a schematic diagram illustrating an example of COT sharing mechanism according to some example embodiments of the present disclosure.

As shown in FIG. 2, for a given beam, the SSB indexed with a lowest SSB index is assumed to be use the Cat. 4. That is, each of SSBs 201 and 211 that is transmitted at a first position within a discovery burst transmission window is the specific SSBs and thus to be associated with the Cat. 4 LBT. In addition, the rest SSBs in the discovery burst transmission windows, for examples SSBs 202 to 205 and 212 to 215 are associated with the Cat. 2 LBT.

By this way, the presence of the SSB 201 at the first position within the discovery burst transmission window indicates that the COT has been acquired by the second device 120 by using the Cat. 4 LBT, and thus upon detection of a discovery burst in the position of SSB 201, the first device 110 may determine that the COT can be shared for UL transmissions. The first device 110 may then perform Cat 2 or Cat 1 LBT, such as, Type 2A/B/C channel access, prior to UL transmissions within a predefined time window after the detection of the SSB.

Additionally or alternatively, the absence of the SSB 201 at the first position and the presence of any of the SSB 202 to 205 and 212 to 215 at the following positions indicate that the COT has been acquired by the second device 120 by using the Cat. 2 LBT. In this case, the first device 110 may determine that the COT cannot be shared for UL transmissions. In this case, the first device 110 has to wait for the next discovery burst transmission window.

It should be understood that, for the illustrative purpose, in the descriptions of the example embodiments, the first device 110 is given as the UE, and the second device 120 is given as the gNB. However, the proposed solution is not limited to the UL and DL transmissions between the UE and gNB, and it also applicable to sidelink transmissions between two UEs.

It is also to be understood that the number of the devices as shown in FIG. 1, the number of SSBs and the duration of the discovery burst transmission window shown in FIG. 2 are given only for illustrative purpose without suggesting any limitations. For example, the network environment 100 may include any suitable number of terminal devices and network devices adapted for implementing embodiments of the present disclosure. In addition, there may be more or less SSBs in a discovery burst transmission window. The present disclosure is not limited in these regards.

The communications in the network environment 100 may conform to any suitable standards including, but not limited to, LTE, LTE-evolution, LTE-advanced (LTE-A) , wideband code division multiple access (WCDMA) , code division multiple access (CDMA) and global system for mobile communications (GSM) and the like. Furthermore, the communications may be performed according to any generation communication protocols either currently known or to be developed in the future. Examples of the communication protocols include, but not limited to, the first generation (1G) , the second generation (2G) , 2.5G, 2.75G, the third generation (3G) , the fourth generation (4G) , 4.5G, the fifth generation (5G) , a future sixth generation (6G) and/or any further communication protocols.

Principle and implementations of the present disclosure will be described in detail below with reference to FIG. 3. FIG. 3 shows a signaling chart illustrating an example COT sharing procedure 300 according to some example embodiments of the present disclosure. For the purpose of discussion, the process 300 will be described with reference to FIGs. 1 to 2. The process 300 may involve the first device 110 and the second device 120.

In the process 300, the second device 110 transmits 302 an indication of whether the cell 102 supports access of low complexity LBT device. The indication may be transmitted via broadcast signaling, for example, PBCH, RMSI, SIB, or any other existing or new signaling. Upon receipt of the indication, the first device 110 may be aware that the channel access type 2 is supported in the cell 102.

The second device 102 may preconfigure at least one specific position in each of discovery burst transmission windows as a group of occasions for a discovery burst or SSB associated with high complexity LBT, such as, Cat. 3 or Cat. 4 LBT. In addition, the rest of the discovery burst transmission windows may be preconfigured for discovery bursts or SSBs associated with low complexity LBT, such as, Cat. 1 or Cat. 2 LBT.

By way of example, for a given beam, a SSB with the lowest SSB index is to be transmitted at the first position in the discovery burst transmission window by using Cat. 4 LBT. The subsequent SSBs at later positions in the same discovery burst transmission window are to be transmitted by using Cat. 2 LBT. Table 1 shows example configurations of SSBs at various positions indexed with corresponding indexes.

Table 1. Configurations of SSBs at various positions

As shown in the Table 1, only the colored SSBs are to be transmitted with Cat. 4 LBT, while other SSB are assumed to be transmitted with Cat. 2 LBT, with each of the colored SSB indexed with a corresponding SSB index being associated with a respective beam. If an SSB is detected at a position corresponding to the colored index, the first device 110 may know that the second device 120 has acquired access to the channel by using Cat4 LBT, and consequently initiated a COT for a predefined duration, during which the first device 110 is allowed to transmit on the channel by using Cat. 2 LBT, or no LBT. Otherwise, if an SSB is detected at a different location, which implies that the second device 120 has acquired access to the channel by using Cat 2. LBT, and thus no COT to be shared with the first device 110. Consequently, the next upcoming UL transmissions may be cancelled.

From the point of view of the channel access probability at the second device 120, as typically the second device 120 has enough time before starting a set of DRS transmissions to complete Cat 4 LBT, and if that for some reason is not successful, the second device 120 can use the more efficient Cat. 2 LBT for transmitting the remaining SSBs on the postponed positions in the discovery burst transmission window. Such a method may be more applicable for PRACH transmission.

The COT configuration described above may be preconfigured at the first device 110 and the second device 120. Alternatively, it may be indicated via dynamic signaling of the second device 120. In this case, the second device 120 transmits 304 a message comprising the COT configuration to the first device 110. In some example embodiments, the COT configuration may include, but not limited to, the specific position preconfigured for the discovery bursts or SSBs associated with high complexity LBT, the predetermined number X of periods for the discovery burst transmission window, and so on.

The first device 110 monitors 306 the possible transmission or activity of the second device 120 based on the COT configuration. In a case that the first device 110 determines that the COT sharing condition is met based on the monitoring result, for example, the first device 110 detects 308 a discovery burst or SSB transmitted with the Cat. 4 LBT at the specific position in a current discovery burst transmission window, the first device 110 may determine that the COT within the discovery burst transmission window is able to be shared for UL transmissions. The first device 110 then transmits 310 UL transmissions with Cat. 2 LBT or no LBT during the COT.

In a case that the first device 110 determines that the COT sharing condition is not met based on the monitoring result, for example, absence of discovery burst or SSB with the Cat. 4 LBT at the specific position in the current discovery burst transmission window, the first device 110 may determine that no COT within the discovery burst transmission window is to be shared for UL transmissions. The first device 110 may wait 312 for a discovery burst transmission window next to the current discovery burst transmission window.

Additionally, or alternatively, in some example embodiments, the second device 102 may predetermine a certain period of time that may include a predetermined number (e.g., X) of periods for the discovery burst transmission window. For example, duration of the discovery burst transmission window may be 6ms, and the period for the discovery burst transmission window may be 20ms. If no DL transmission other than the discovery burst transmission is transmitted during the period of time, the next discovery burst or SSB position in the next discovery burst transmission window is to be associated with Cat. 4 LBT. The predetermined number X may indicate a maximum period of time without COT available for sharing with the first device 110.

FIG. 4 illustrates a schematic diagram illustrating another example of COT sharing mechanism according to some example embodiments of the present disclosure. As shown in FIG, 4, the predetermined period of time spans two DRS periods during which only DRSs 401 and 411 associated with Cat. 2 LBT are transmitted, which means there is no COT available for sharing with the first device 110 for at least two DRS periods. In this case, the next discovery burst or SSB position 421 in the next discovery burst transmission window is to be associated with Cat. 4 LBT.

Now referring back to FIG. 3, during monitoring in 312, if there is no DL transmissions in at least one beam configured for the first device 110 or there is no COT initiated with Cat. 4 LBT for the predetermined number (e.g., X = 2) of periods for discovery burst transmission window, the first device 110 may determine 314 that the next discovery burst in the next discovery burst transmission window is assumed to be associated with Cat. 4 LBT, and thereby a corresponding COT initiated by the second device 120 is available to be shared with first device 110.

On the other hand, the second device 120 may make 314 the same decision. As such, the second device 120 may then transmit 318 the next discovery burst with Cat. 4 LBT at the specific position in the next discovery burst transmission window. After detecting the presence of the discovery burst, first device 110 may transmit 320 uplink transmissions on the channel with Cat. 2 LBT or no LBT.

The above embodiment may require the first device 110 to continuously monitor for transmission or activity from the second device 120 for at least X discovery burst transmission windows prior to UL transmission. For example, when operating in the RRC_CONNECTED mode, the first device 110 can keep monitoring the transmission/activity of the second device 120, which supports a fast configured UL transmission within the COT of discovery burst.

In order to reduce the overhead for monitoring the channel, in some example embodiments, the first device 110 may start monitoring from a specific position associated with system frame number (SFN) . In particular, the value X may be periodically reset subject to SFN. For example, the value X may be reset every [SFN mod YY = ZZ] . For example, when in the RRC_INACTIVE mode, the first device 110 has no need to keep monitoring DL activities during the entire X discovery burst transmission windows, thus it may start to monitor from a specific point, denoted by ZZ every YY SFN. The values of YY and ZZ may be configured by network as desired. However, this way is not limited to the RRC_INACTIVE mode, but more applicable for configured UL transmissions (e.g., CG-PUSCH, SR, and periodic CSI-RS) in both the RRC_CONNECTED mode and RRC_INACTIVE mode. For PRACH transmission, other solutions (e.g., embodiment A or explicit indication) can be used.

According to the example embodiments, there is provided an enhanced COT sharing mechanism, which is especially suitable for facilitating the transmissions of low complexity devices operating in unlicensed band. The COT sharing mechanism can help reduce channel access latency, and hence it is beneficial for URLLC services. In addition, the COT sharing mechanism is applicable not only for Uu interface, but also PC5 which supports sidelink operation in unlicensed band.

FIG. 5 illustrates a flowchart of an example method 500 implemented at a first device 110 according to example embodiments of the present disclosure. The method 500 can be implemented by a terminal device (e.g., UE) , for example, the first device 110 shown in FIG. 1. For the purpose of discussion, the method 500 will be described with reference to FIG. 1. It is to be understood that method 500 may further include additional blocks not shown and/or omit some shown blocks, and the scope of the present disclosure is not limited in this regard.

At 510, the first device 110 receives, from the second device 120, a message comprising a configuration of discovery burst based COT. The configuration may correspond to a COT sharing condition defining a condition that the COT is available to be shared with the first device 110 for a first transmission. The discovery burst may refer to discovery burst/SSB transmissions, including but not limited to, DRS or other reference signal.

In some example embodiments, before receiving the message, the first device 110 may receive, from the second device 120, an indication of supporting an access with a low complexity LBT. The low complexity LBT may include Cat. 2 LBT or no LBT. In this way, the first device 110 may be aware that accessing the channel by using Cat. 2 LBT or no LBT is supported during a shared COT.

At 520, the first device 110 monitors a channel between the first device 110 and the second device 120 based on the configuration.

At 530, the first device 110 determines whether a COT sharing condition is met based on the monitoring result.

If the COT sharing condition is met, at 540, the first device 110 transmits a first transmission to the second device during a target COT within a target time window. The target COT is acquired by using the high complexity LBT.

In a case where the first device 110 is a terminal device, and the second device 120 is a base station, the first transmission may be a UL transmission. Alternatively, in a case where the first device 110 is a first terminal device, and the second device 120 is a second terminal device, the first transmission may be a sidelink transmission.

Otherwise, if the COT sharing condition is not met based on the monitoring result, the first device 110 may wait for a time window next to the target time window.

In some example embodiments, the configuration may comprise a group of occasions (e.g., SSB positions) within the target time window, and the group of occasions is associated with a target COT.

The group of occasions may be preconfigured to be special SSB positions. Prior to a discovery burst transmission on the special SSB positions, the second device 120 may perform the high complexity LBT. The detection of a RS at such a special SSB position means that the channel is accessed by using the high complexity LBT, and thus the COT can be shared with the first device 110.

In the above embodiments, during monitoring, the first device 110 may determine whether at least one second transmission is detected at the group of occasions. If the at least one second transmission is detected at the group of occasions, the first device 110 may determine that the COT sharing condition is met. Otherwise, if no second transmission is detected at the group of occasions, the first device 110 may determine that the COT sharing condition is not met.

In some example embodiments, the configuration may indicates that, for each beam configured for the first device 110, a first SSB at a first one of the group of occasions is transmitted with the high complexity LBT, and at least one second SSB at a rest of the group of occasions is transmitted with a low complexity LBT.

In some example embodiments, the configuration may comprise indexes of a group of SSB associated with the group of occasions.

In some example embodiments, the group of occasions is associated with a plurality of beams each corresponding to one of a group of SSBs and a first occasion of the group of occasion is associated with a SSB transmission with the high complexity LBT.

In some example embodiments, the configuration may indicate a predetermined number of discovery burst transmission periods. During monitoring, the first device 110 may determine whether there is no second transmission is received from the second device 120 for the predetermined number of discovery burst transmission periods preceding the target time window. The second transmission may be a downlink transmission in a case that the second device 120 is the base station. Alternatively, the second transmission may be a sidelink transmission in a case that both of the first device 110 and the second device 120 are terminal devices.

If so, the first device 110 may determine that the COT sharing condition is met. Otherwise, if at least one second transmission is received from the second device for the predetermined number of discovery burst transmission periods preceding the target time window, the first device 110 may determine that the COT sharing condition is not met. The second transmission may be associated with a COT preceding the target COT.

In some example embodiments, the second transmission may be transmitted with a high complexity LBT which may be LBT category 3 or LBT category 4.

In some example embodiments, the first device 110 may monitor the channel from a predetermined point associated with a SFN to detect if there is any second transmission from the second device 120. If no second transmission is detected based on the monitoring result, the first device 110 may determine that no second transmission is received for the predetermined number of discovery burst transmission periods.

In some example embodiments, the target time window may be a discovery burst transmission window.

In some example embodiments, the first device 110 may be a first terminal device, and the second device 120 may be a network device or a second terminal device.

According to the COT sharing mechanism provided in the example embodiments, a gNB is capable of employing periodic discovery bursts or SSB transmissions within discovery burst transmission windows as potential COT providers to facilitate transmissions from a low complexity UE. To support transmissions within such discovery burst COTs, a set of SSB positions within the discovery burst transmission windows are predefined to be associated with a high complexity LBT, such as, Cat. 3 or Cat. 4 LBT, whereas the rest of SSB positions in the discovery burst transmission windows are still associated with a low complexity LBT, such as, Cat. 1 or Cat. 2 LBT.

From the perspective of the UE, if the presence of an SSB in occasions associated with Cat. 4 LBT is detected, it would immediately know it is allowed to share the COT with SSB (s) for UL transmissions (e.g. SR, PRACH, CG UL) .

FIG. 6 illustrates a flowchart of an example method 600 implemented at a second device according to example embodiments of the present disclosure. The method 600 can be implemented by a base station or gNB, such as, the second device 120 shown in FIG. 1. Additionally or alternatively, the method 600 can be implemented by a terminal device. For the purpose of discussion, the method 600 will be described with reference to FIG. 1. It is to be understood that method 600 may further include additional blocks not shown and/or omit some shown blocks, and the scope of the present disclosure is not limited in this regard.

At 610, the second device 120 transmits, to the first device 110, a message comprising a configuration of discovery burst based COT.

In some example embodiments, before transmitting the message, the second device 120 may transmit, to the first device 110, an indication of supporting an access with a low complexity LBT. The low complexity LBT may include Cat. 2 LBT or no LBT. In this way, the first device 110 may be aware that accessing the channel by using Cat. 2 LBT or no LBT is supported during a shared COT.

In some example embodiments, the configuration may comprise a group of occasions, and the group of occasions is associated with the target COT.

In some example embodiments, the configuration may indicate a COT sharing condition comprising the second transmission at one of the group of occasions indicating the target COT being shared with the first device 110.

In some example embodiments, the group of occasions may be associated with a plurality of beams configured for the first device 110, and each of the beams corresponds to one of a group of SSBs, and the configuration may indicate that a first occasion of the group of occasion is associated with a SSB transmission by using the high complexity LBT, and a rest of the group of occasions is associated with SSB transmission by using a low complexity LBT.

In some example embodiments, the configuration may comprise indexes of a group of SSBs associated with the group of occasions.

In some example embodiments, the group of occasions may be associated with a plurality of beams each corresponding to a group of SSBs.

At 620, the second device 120 transmits a second transmission with a high complexity LBT at one of a group of occasions associated with a target COT within a target time window.

In some example embodiments, the second device 120 may determine whether no second transmission is transmitted for a predetermined number of discovery burst transmission periods preceding the target time window. If so, the second device 120 may transmit the second transmission by using the high complexity LBT at the occasion.

In some example embodiments, the configuration may indicate a COT sharing condition comprising no second transmission for the predetermined number of discovery burst transmission periods indicating the target COT to be shared with the first device.

In some example embodiments, if no second transmission is transmitted from a predetermined point associated with a SFN, the second device 120 may transmit the second transmission by using the high complexity LBT at the occasion.

At 630, the second device 120 receives, from the first device 110, a first transmission during the target COT.

In some example embodiments, the first device 110 may be a first terminal device, and the second device 120 may be one of a network device and a second terminal device.

In some example embodiments, a first apparatus capable of performing any of the method 500 (for example, the first device 110) may comprise means for performing the respective steps of the method 500. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module.

In some example embodiments, the first apparatus comprises: means for receiving, from a second apparatus, a message comprising a configuration of reference signal based channel occupancy time, COT; means for monitoring, based on the configuration, a channel between the first apparatus and the second apparatus; and means for in accordance with a determination that a COT sharing condition is met based on the monitoring result, transmitting a first transmission to the second apparatus during a target COT within a target time window, the target COT being acquired by using a high complexity listen-before-talk, LBT.

In some example embodiments, the first apparatus further comprises: means for in accordance with a determination that the COT sharing condition is not met based on the monitoring result, waiting for a time window next to the target time window.

In some example embodiments, the configuration comprises a group of occasions within the target time window, and the group of occasions is associated with the target COT. The first apparatus further comprises: means for in accordance with a determination that at least one second transmission is detected at the group of occasions, determining that the COT sharing condition is met; and means for in accordance with a determination that no second transmission is transmitted with the high complexity LBT at the group of occasions, determining that the COT sharing condition is not met.

In some example embodiments, the configuration comprises: for each beam configured for the first apparatus, a first synchronization Signal and PBCH blocks, SSB at a first one of the group of occasions to be transmitted with the high complexity LBT, and at least one second SSB at a rest of the group of occasions to be transmitted with a low complexity LBT t.

In some example embodiments, the configuration comprises indexes of a group of Synchronization Signal and PBCH blocks, SSBs associated with the group of occasions.

In some example embodiments, the group of occasions is associated with a plurality of beams each corresponding to one of a group of Synchronization Signal and PBCH blocks, SSBs, and a first occasion of the group of occasion is associated with a SSB transmission with the high complexity LBT.

In some example embodiments, the first apparatus further comprises: means for in accordance with a determination that no second transmission is received from the second apparatus for a predetermined number of transmission periods preceding the target time window, determining that the COT sharing condition is met; and means for in accordance with a determination that at least one second transmission is received from the second apparatus for the predetermined number of transmission periods, determining that the COT sharing condition is not met.

In some example embodiments, the second transmission comprises one of downlink transmission and a data transmission transmitted with the high complexity LBT.

In some example embodiments, the means for monitoring the channel comprises: means for monitoring the channel from a predetermined point associated with a system frame number; and means for in accordance with a determination that no second transmission is detected based on the monitoring result, determining that no second transmission is received for the predetermined number of transmission periods.

In some example embodiments, the high complexity LBT comprises one of LBT category 3 and LBT category 4.

In some example embodiments, the first apparatus further comprises: means for before receiving the message, receiving, from the second apparatus, an indication of supporting an access with a low complexity listen-before-talk, LBT.

In some example embodiments, the target time window comprises a discovery burst transmission window.

In some example embodiments, the first apparatus comprises a first terminal device, and a second apparatus comprises one of a network device and a second terminal device.

In some example embodiments, a second apparatus capable of performing any of the method 600 (for example, the second device 120) may comprise means for performing the respective steps of the method 600. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module.

In some example embodiments, the second apparatus comprises: means for transmitting, to a first apparatus, a message comprising a configuration of reference signal based channel occupancy time, COT; and means for upon transmitting a second transmission with a high complexity listen-before-talk, LBT at one of a group of occasions associated with a target COT within a target time window, receiving, from the first apparatus, a first transmission during the target COT.

In some example embodiments, the configuration comprises the group of occasions within the target time window, and the group of occasions is associated with the target COT.

In some example embodiments, the configuration indicates a COT sharing condition comprising the second transmission at one of the group of occasions indicating the target COT being shared with the first apparatus.

In some example embodiments, the group of occasions is associated with a plurality of beams configured for the first apparatus, each of the beams corresponds to one of a group of Synchronization Signal and PBCH blocks, SSBs and the configuration indicates a first occasion of the group of occasion being associated with a SSB transmission by using the high complexity LBT, and a rest of the group of occasions being associated with SSB transmission by using a low complexity LBT.

In some example embodiments, the group of occasions is associated with a plurality of beams each corresponding to a group of Synchronization Signal and PBCH blocks, SSBs.

In some example embodiments, the second apparatus further comprises: means for in accordance with a determination that no second transmission is transmitted for a predetermined number of transmission periods preceding the target time window, transmitting the second transmission by using the high complexity listen-before-talk, LBT at the occasion.

In some example embodiments, the configuration indicates a COT sharing condition comprising no second transmission for the predetermined number of transmission periods indicating the target COT to be shared with the first apparatus.

In some example embodiments, the second apparatus further comprises: means for in accordance with a determination that no second transmission is transmitted from a predetermined point associated with a system frame number, transmitting the second transmission by using the high complexity listen-before-talk, LBT at the occasion.

In some example embodiments, the second apparatus further comprises: means for before transmitting the message, transmitting, to the first apparatus, an indication of supporting an access with a low complexity listen-before-talk, LBT.

FIG. 7 is a simplified block diagram of a device 700 that is suitable for implementing embodiments of the present disclosure. The device 700 may be provided to implement the communication device, for example the first device 110 and the second device 120 as shown in FIG. 1. As shown, the device 700 includes one or more processors 710, one or more memories 720 coupled to the processor 710, and one or more transmitters and/or receivers (TX/RX) 740 coupled to the processor 710.

The TX/RX 740 may be configured for bidirectional communications. The TX/RX 740 has at least one antenna to facilitate communication. The communication interface may represent any interface that is necessary for communication with other network elements.

The processor 710 may be of any type suitable to the local technical network and may include one or more of the following: general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on multicore processor architecture, as non-limiting examples. The device 700 may have multiple processors, such as an application specific integrated circuit chip that is slaved in time to a clock which synchronizes the main processor.

The memory 720 may include one or more non-volatile memories and one or more volatile memories. Examples of the non-volatile memories include, but are not limited to, a Read Only Memory (ROM) 724, an electrically programmable read only memory (EPROM) , a flash memory, a hard disk, a compact disc (CD) , a digital video disk (DVD) , and other magnetic storage and/or optical storage media. Examples of the volatile memories include, but are not limited to, a random access memory (RAM) 722 and other volatile memories that will not last in the power-down duration.

A computer program 730 includes computer executable instructions that may be executed by the associated processor 710. The program 730 may be stored in the ROM 724. The processor 710 may perform any suitable actions and processing by loading the program 730 into the RAM 722.

The embodiments of the present disclosure may be implemented by means of the program 730 so that the device 700 may perform any process of the disclosure as discussed with reference to FIG. 4. The embodiments of the present disclosure may also be implemented by hardware or by a combination of software and hardware.

In some embodiments, the program 730 may be tangibly contained in a computer readable medium which may be included in the device 700 (such as in the memory 720) or other storage devices that are accessible by the device 700. The device 700 may load the program 730 from the computer readable medium to the RAM 722 for execution. The computer readable medium may include any types of tangible non-volatile storage, such as ROM, EPROM, a flash memory, a hard disk, CD, DVD, and the like. FIG. 8 shows an example of the computer readable medium 800 in form of CD or DVD. The computer readable medium has the program 730 stored thereon.

Various embodiments of the present disclosure may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. Some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device. While various aspects of embodiments of the present disclosure are illustrated and described as block diagrams, flowcharts, or using some other pictorial representations. It is to be understood that the block, device, system, technique or method described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.

The present disclosure also provides at least one computer program product tangibly stored on a non-transitory computer readable storage medium. The computer program product includes computer-executable instructions, such as those included in program modules, being executed in a device on a target real or virtual processor, to carry out the

method

500 or 600 as described above with reference to FIGs. 5-6. Generally, program modules may include routines, programs, libraries, objects, classes, components, data structures, or the like that perform particular tasks or implement particular abstract data types. The functionality of the program modules may be combined or split between program modules as desired in various embodiments. Machine-executable instructions for program modules may be executed within a local or distributed device. In a distributed device, program modules may be located in both local and remote storage media.

Program code for carrying out methods of the present disclosure may be written in any combination of one or more programming languages. These program codes may be provided to a processor or controller of a general purpose computer, special purpose computer, or other programmable data processing device, such that the program codes, when executed by the processor or controller, cause the functions/operations specified in the flowcharts and/or block diagrams to be implemented. The program code may execute entirely on a machine, partly on the machine, as a stand-alone software package, partly on the machine and partly on a remote machine or entirely on the remote machine or server.

In the context of the present disclosure, the computer program codes or related data may be carried by any suitable carrier to enable the device, device or processor to perform various processes and operations as described above. Examples of the carrier include a signal, computer readable medium, and the like.

The computer readable medium may be a computer readable signal medium or a computer readable storage medium. A computer readable medium may include but not limited to an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, device, or device, or any suitable combination of the foregoing. More specific examples of the computer readable storage medium would include an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM) , a read-only memory (ROM) , an erasable programmable read-only memory (EPROM or Flash memory) , an optical fiber, a portable compact disc read-only memory (CD-ROM) , an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

Further, while operations are depicted in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In certain circumstances, multitasking and parallel processing may be advantageous. Likewise, while several specific implementation details are contained in the above discussions, these should not be construed as limitations on the scope of the present disclosure, but rather as descriptions of features that may be specific to particular embodiments. Certain features that are described in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment may also be implemented in multiple embodiments separately or in any suitable sub-combination.

Although the present disclosure has been described in languages specific to structural features and/or methodological acts, it is to be understood that the present disclosure defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.

Claims

A first device, comprising:

at least one processor; and

at least one memory including computer program codes;

the at least one memory and the computer program codes are configured to, with the at least one processor, cause the first device at least to:

receive, from a second device, a message comprising a configuration of reference signal based channel occupancy time, COT;

monitor, based on the configuration, a channel between the first device and the second device; and

in accordance with a determination that a COT sharing condition is met based on the monitoring result, transmit a first transmission to the second device during a target COT within a target time window, the target COT being acquired by using a high complexity listen-before-talk, LBT.
The first device of Claim 1, wherein the at least one memory and the computer program codes are configured to, with the at least one processor, further cause the first device to:

in accordance with a determination that the COT sharing condition is not met based on the monitoring result, wait for a time window next to the target time window.
The first device of Claim 1, wherein the configuration comprises a group of occasions within the target time window, and the group of occasions is associated with the target COT, and wherein the at least one memory and the computer program codes are configured to, with the at least one processor, further cause the first device to:

in accordance with a determination that at least one second transmission is detected at the group of occasions, determine that the COT sharing condition is met; and

in accordance with a determination that no second transmission is transmitted with the high complexity LBT at the group of occasions, determine that the COT sharing condition is not met.
The first device of Claim 3, wherein the configuration comprises: for each beam configured for the first device, a first synchronization Signal and PBCH blocks, SSB at a first one of the group of occasions to be transmitted with the high complexity LBT, and at least one second SSB at a rest of the group of occasions to be transmitted with a low complexity LBT.
The first device of Claim 3, wherein the configuration comprises indexes of a group of Synchronization Signal and PBCH blocks, SSBs associated with the group of occasions.
The first device of Claim 3, wherein the group of occasions is associated with a plurality of beams each corresponding to one of a group of Synchronization Signal and PBCH blocks, SSBs, and a first occasion of the group of occasion is associated with a SSB transmission with the high complexity LBT.
The first device of Claim 1, wherein the at least one memory and the computer program codes are configured to, with the at least one processor, further cause the first device to:

in accordance with a determination that no second transmission is received from the second device for a predetermined number of transmission periods preceding the target time window, determine that the COT sharing condition is met; and

in accordance with a determination that at least one second transmission is received from the second device for the predetermined number of transmission periods, determine that the COT sharing condition is not met.
The first device of Claim 7, wherein the second transmission comprises one of downlink transmission and a data transmission transmitted with the high complexity LBT.
The first device of Claim 7, wherein the at least one memory and the computer program codes are configured to, with the at least one processor, cause the first device to monitor the channel by:

monitoring the channel from a predetermined point associated with a system frame number; and

in accordance with a determination that no second transmission is detected based on the monitoring result, determining that no second transmission is received for the predetermined number of transmission periods.
The first device of Claim 1, wherein the high complexity LBT comprises one of LBT category 3 and LBT category 4.
The first device of Claim 1, wherein the at least one memory and the computer program codes are configured to, with the at least one processor, further cause the first device to:

before receiving the message, receive, from the second device, an indication of supporting an access with a low complexity listen-before-talk, LBT.
The first device of Claim 1, wherein the target time window comprises a discovery burst transmission window.
The first device of Claim 1, wherein the first device comprises a first terminal device, and a second device comprises one of a network device and a second terminal device.
A second device, comprising:

at least one processor; and

at least one memory including computer program codes;

the at least one memory and the computer program codes are configured to, with the at least one processor, cause the second device at least to:

transmit, to a first device, a message comprising a configuration of reference signal based channel occupancy time, COT; and

upon transmitting a second transmission with a high complexity listen-before-talk, LBT at one of a group of occasions associated with a target COT within a target time window, receive, from the first device, a first transmission during the target COT.
The second device of Claim 14, wherein the configuration comprises the group of occasions within the target time window, and the group of occasions is associated with the target COT.
The second device of Claim 15, wherein the configuration indicates a COT sharing condition comprising the second transmission at one of the group of occasions indicating the target COT being shared with the first device.
The second device of Claim 15, wherein the group of occasions is associated with a plurality of beams configured for the first device, each of the beams corresponds to one of a group of Synchronization Signal and PBCH blocks, SSBs and the configuration indicates a first occasion of the group of occasion being associated with a SSB transmission by using the high complexity LBT, and a rest of the group of occasions being associated with SSB transmission by using a low complexity LBT.
The second device of Claim 14, wherein the configuration comprises indexes of a group of Synchronization Signal and PBCH blocks, SSBs associated with the group of occasions.
The second device of Claim 14, wherein the group of occasions is associated with a plurality of beams each corresponding to a group of Synchronization Signal and PBCH blocks, SSBs.
The second device of Claim 14, wherein the at least one memory and the computer program codes are configured to, with the at least one processor, further cause the second device to:

in accordance with a determination that no second transmission is transmitted for a predetermined number of transmission periods preceding the target time window, transmit the second transmission by using the high complexity listen-before-talk, LBT at the occasion.
The second device of Claim 20, wherein the configuration indicates a COT sharing condition comprising no second transmission for the predetermined number of transmission periods indicating the target COT to be shared with the first device.
The second device of Claim 14, wherein the at least one memory and the computer program codes are configured to, with the at least one processor, further cause the second device to:

in accordance with a determination that no second transmission is transmitted from a predetermined point associated with a system frame number, transmit the second transmission by using the high complexity listen-before-talk, LBT at the occasion.
The second device of Claim 14, wherein the at least one memory and the computer program codes are configured to, with the at least one processor, further cause the second device to:

before transmitting the message, transmit, to the first device, an indication of supporting an access with a low complexity listen-before-talk, LBT.
The second device of Claim 14, wherein the high complexity LBT comprises one of LBT category 3 and LBT category 4.
The second device of Claim 14, wherein the first device comprises a first terminal device, and a second device comprises one of a network device and a second terminal device.
A method comprising:

receiving, at a first device and from a second device, a message comprising a configuration of reference signal based channel occupancy time, COT;

monitoring, based on the configuration, a channel between the first device and a second device; and

in accordance with a determination that a COT sharing condition is met based on the monitoring result, transmitting a first transmission to the second device during a target COT within a target time window, the target COT being acquired by using a high complexity listen-before-talk, LBT.
A method comprising:

transmitting, at a second device and to a first device, a message comprising a configuration of reference signal based channel occupancy time, COT; and

upon transmitting a second transmission with a high complexity listen-before-talk, LBT at one of a group of occasions associated with a target COT within a target time window, receiving, from the first device, a first transmission during the target COT.
A first apparatus comprising:

means for receiving, from a second apparatus, a message comprising a configuration of reference signal based channel occupancy time, COT;

means for monitoring, based on the configuration, a channel between the first apparatus and the second apparatus; and

means for in accordance with a determination that a COT sharing condition is met based on the monitoring result, transmitting a first transmission to the second device during a target COT within a target time window, the target COT being acquired by using a high complexity listen-before-talk, LBT.
A second apparatus comprising:

means for transmitting, to a first apparatus, a message comprising a configuration of reference signal based channel occupancy time, COT; and

means for upon transmitting a second transmission with a high complexity listen-before-talk, LBT at one of a group of occasions associated with a target COT within a target time window, receiving, from the first device, a first transmission during the target COT.
A non-transitory computer readable medium comprising program instructions for causing an apparatus to perform at least the method of Claim 26 or 27.