WO2022213242A1

WO2022213242A1 - Transmission control for unlicensed spectrum access

Info

Publication number: WO2022213242A1
Application number: PCT/CN2021/085555
Authority: WO
Inventors: Timo Erkki Lunttila; Tao Tao; Jianguo Liu
Original assignee: Nokia Shanghai Bell Co., Ltd.; Nokia Solutions And Networks Oy; Nokia Technologies Oy
Priority date: 2021-04-06
Filing date: 2021-04-06
Publication date: 2022-10-13
Also published as: CN117099464A

Abstract

Embodiments of the present disclosure relate to transmission control for unlicensed spectrum access. An electronic device performs a LBT procedure for a reference beam to determine a first beam which passes the LBT procedure among Tx beams, the reference beam having a beamwidth larger than the Tx beams. If the first beam is expected for transmission, the electronic device performs the transmission on the first beam, and adjust a first CWS specific to the first beam based on at least one of a feedback or a timing of the transmission. In this way, a LBT procedure for a wide beamwidth can be combined with beam specific CWS maintenance. Thus, associated overhead and complexity can be reduced and fair use of the unlicensed spectrum can be ensured.

Description

TRANSMISSION CONTROL FOR UNLICENSED SPECTRUM ACCESS

FIELD

Embodiments of the present disclosure generally relate to the field of telecommunication and in particular, to a transmission control for an unlicensed spectrum access.

BACKGROUND

For operation on an unlicensed spectrum, in particular, at 60GHz, it has been agreed that a channel access with a listen-before-talk (LBT) procedure can be supported for a device to initiate a channel occupancy. One aspect related to LBT procedure is contention window size (CWS) management.

Conventionally, beamwidths for the LBT procedure and for transmit beams are assumed to be the same from the CWS management point of view. It is rather suboptimal for narrow transmit beams as interference caused by different narrow beams may be quite different. For example, a failed transmission in one direction might trigger an increase of CWS, and hence slow down transmissions in all the directions, even if the transmissions to other directions could be successful. Thus, the CWS management needs to be further optimized.

SUMMARY

In general, example embodiments of the present disclosure provide a solution for transmission control.

In a first aspect, there is provided an electronic device. The electronic 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 electronic device to: perform a listen-before-talk procedure for a reference beam to determine a first beam which passes the listen-before-talk procedure among transmit beams, the reference beam having a beamwidth larger than the transmit beams; in accordance with a determination that the first beam is expected for transmission, perform the transmission on the first beam; and adjust a first contention window size specific to the first beam based on at least one of a feedback or a timing of the transmission.

In a second aspect, there is provided a method for transmission control. The method comprises: performing, at an electronic device, a listen-before-talk procedure for a reference beam to determine a first beam which passes the listen-before-talk procedure among transmit beams, the reference beam having a beamwidth larger than the transmit beams; in accordance with a determination that the first beam is expected for transmission, performing the transmission on the first beam; and adjusting a first contention window size specific to the first beam based on at least one of a feedback or a timing of the transmission.

In a third aspect, there is provided an apparatus for transmission control. The apparatus comprises: means for performing, at an electronic device, a listen-before-talk procedure for a reference beam to determine a first beam which passes the listen-before-talk procedure among transmit beams, the reference beam having a beamwidth larger than the transmit beams; means for performing the transmission on the first beam in accordance with a determination that the first beam is expected for transmission; and means for adjusting a first contention window size specific to the first beam based on at least one of a feedback or a timing of the transmission.

In a fourth 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 second 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 communication network in which example embodiments of the present disclosure may be implemented;

Fig. 2 illustrates a flowchart illustrating an example method for transmission control according to some embodiments of the present disclosure;

Fig. 3 illustrates a flowchart illustrating an example method for performing a LBT procedure according to some embodiments of the present disclosure;

Fig. 4 illustrates a flowchart illustrating another example method for performing a LBT procedure according to some embodiments of the present disclosure;

Fig. 5 illustrates a flowchart illustrating an example method for performing a CWS adjustment according to some embodiments of the present disclosure;

Fig. 6 illustrates a simplified block diagram of an apparatus that is suitable for implementing example embodiments of the present disclosure; and

FIG. 7 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 future fifth generation (5G) 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 NB (also referred to as a gNB) , a Remote Radio Unit (RRU) , a radio header (RH) , a remote radio head (RRH) , a relay, a low power node such as a femto, a pico, and so forth, depending on the applied terminology and technology.

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.

For the third generation partnership project (3GPP) new radio (NR) physical layer design, study has been made on required changes to NR using existing downlink (DL) or uplink (UL) NR waveform to support operation between 52.6 GHz and 71 GHz. Further, study has been made on channel access mechanism, considering potential interference to or from other nodes and assuming beam-based operation, in order to comply with the regulatory requirements applicable to unlicensed spectrum for frequencies between 52.6 GHz and 71 GHz.

Recently, a follow-up work item for channel access procedures was approved. The work item on the channel access mechanism may include: specifying both LBT and No-LBT related procedures, and for No-LBT case, specifying no additional sensing mechanism; studying, and if needed specifying, omni-directional LBT, directional LBT and receiver assistance in channel access; and studying, and if needed specifying, energy detection (ED) threshold enhancement.

The regulations for operation on 60 GHz unlicensed spectrum require use of a spectrum sharing or co-channel coexistence mechanism, but do not require any specific type of a mechanism. In some regions, separate regulatory requirements are defined for different use cases or deployments, e.g., for fixed outdoor equipment or point-to-point communications or for indoor-only use. However, the main trend targets indoor use and mandates the use of LBT. Correspondingly, it has been agreed that NR will support channel access with LBT as well as without LBT on 60 GHz.

Thus, further study will focus on LBT mechanisms such as omni-directional LBT, directional LBT and receiver assisted LBT type of schemes when channel access with LBT is used. Further, it is to be studied whether operation restrictions for channel access without LBT are needed, e.g., compliance with regulations, and/or in presence of ATPC, DFS, long term sensing, or other interference mitigation mechanisms. The mechanism and condition to switch between a channel access with LBT and a channel access without LBT is also to be studied if local regulation allows.

One of the open questions in 3GPP is how to perform a LBT procedure when the gNB’s transmissions are highly directive (i.e., use narrow beams) , while a beamwidth in the LBT procedure assumes to be a wide beam. It cannot always be assumed that the transmit (Tx) beam used for DL transmissions fully corresponds to the receive (Rx) beam used for data reception. In particular, use of a wide beam such as an omni-directional beam for LBT can be beneficial, as the same ED measurement in the LBT procedure is sufficient for several beams, and hence a complexity and a time required for the LBT procedure are minimized.

One aspect related to the LBT procedure is CWS management. For different channel access schemes, CWS management is different. Generally, the channel access schemes for NR-based access for unlicensed spectrum can be classified into the following categories.

Category 1: immediate transmission after a short switching gap. This is used for a transmitter to immediately transmit after a switching gap inside a channel occupancy time (COT) , without performing an LBT. The switching gap from reception to transmission is to accommodate a transceiver turnaround time and is no longer than 16 μs.

Category 2: LBT without random back-off. A duration of time that a channel is sensed to be idle before a transmitting entity transmits is deterministic.

Category 3: LBT with random back-off with a contention window of fixed size. The LBT procedure has the following procedure as one of its components. A transmitting entity draws a random number N within a contention window. The size of the contention window is specified by the minimum and maximum value of N. The size of the contention window is fixed. The random number N is used in the LBT procedure to determine a duration of time that a channel is sensed to be idle before the transmitting entity transmits on the channel.

Category 4: LBT with random back-off with a contention window of variable size. The LBT procedure has the following as one of its components. A transmitting entity draws a random number N within a contention window. The size of the contention window is specified by the minimum and maximum value of N. The transmitting entity can vary the size of the contention window when drawing the random number N. The random number N is used in the LBT procedure to determine a duration of time that a channel is sensed to be idle before the transmitting entity transmits on the channel.

For different transmissions in a COT and different channels or signals to be transmitted, different categories of channel access schemes can be used.

It can be seen that in Category 3 and 4, before a LBT procedure is successful and a device is permitted to transmit, a channel has to be sensed to be idle for a random number of times. The random number is drawn from a so-called contention window, and a size of the contention window (i.e., CWS) is specified by a minimum and a maximum value. In Category 3, the CWS is fixed, and in Category 4, the CWS varies depending on whether a transmission succeeds on the channel.

The present inventor observes that use of a wide beam for a LBT procedure can be beneficial. First, there is no need to switch between beams and implementation of the LBT procedure can be simplified. Second, instead of performing separate LBT for each beam, a single LBT will suffice, and thus the LBT procedure can be considerably speeded up. This avoids the need for switching gaps that are required when switching from one beam to another, and hence reduces overhead. However, it becomes an issue how to adjust the CWS in case of a beamwidth for LBT is wider than that of a Tx beam.

In order to solve the above and other potential problems, embodiments of the present disclosure provide an improved solution of CWS management in a scenario where a beamwidth for LBT is wider than the Tx beam. In the solution, a LBT procedure performed for a wide beamwidth is combined with beam specific CWS maintenance. The solution allows for maintaining and managing contention windows in the LBT procedure in a beam-specific manner, although an ED measurement is performed jointly for all or a part of the Tx beams.

In this way, overhead and complexity associated with the ED measurement can be reduced. Further, there is no need to switch the RX beam during the LBT procedure, which avoid the associated switching times. In addition, beam specific CWS management ensures fair use of the unlicensed spectrum.

Some example embodiments of the present disclosure will now be described in detail with reference to the figures. However, those skilled in the art would readily appreciate that the detailed description given herein with respect to these figures is for explanatory purpose as the present disclosure extends beyond theses limited embodiments.

EXAMPLE OF COMMUNICATION NETWORK

Fig. 1 illustrates an example communication network 100 in which embodiments of the present disclosure can be implemented. As shown in Fig. 1, the communication network 100 includes a first device 110 and a second device 120 served by the first device 110. The first device 110 and the second device 120 may communicate with each other via a channel such as a wireless communication channel.

As shown in Fig. 1, the first device 110 may have a plurality of beams such as

beams

111, 112 and 113, and the second device 120 may have a plurality of beams such as

beams

121, 122 and 123. A channel (or called as a sub-channel in this case) may be formed between one of

beams

111, 112 and 113 and one of

beams

121, 122 and 123. The first device 110 may transmit information to the second device 120 or receive information from the second device 120 via one or more of the

beams

111, 112 and 113. The second device 110 may transmit information to the second device 120 or receive information from the second device 120 via one or more of the

beams

111, 112 and 113. The number of the beams is not limited to that shown in FIG. 1, and more or less beams are also feasible.

In context of the present disclosure, when these beams are used for transmission, they are also referred to as Tx beams. When these beams are used for reception, they are also referred to as Rx beams. These beams may have the same or different beamwidth. Furthermore, one Tx beam may overlap with other Tx beams, or be fully covered by other Tx beams, that is, the coverage area of the different Tx beams may be fully or partially the same.

For illustration, the first device 110 is shown as a network device and the second device 120 is shown as a terminal device. Merely for illustration purpose and without suggesting any limitations as to the scope of the present disclosure, some embodiments will be described in the context where the first device 110 is a network device and the second device 120 is a terminal device. It is to be understood that, in other embodiments, the first device 110 may be a terminal device and the second device 120 may be a network device. In other words, the principles and spirits of the present disclosure can be applied to both uplink and downlink transmissions.

It is also to be understood that the number of first and second devices as shown in Fig. 1 are only for the purpose of illustration without suggesting any limitations. The network 100 may include any suitable number of first and second devices adapted for implementing embodiments of the present disclosure.

The communications in the network 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) communication protocols.

In some scenarios, the first device 110 or second device 120 may initiate a channel occupancy for unlicensed spectrum access. In this case, the first device 110 or second device 120 may perform channel clearance assessment (CCA) by performing a LBT procedure at a CCA slot to determine a channel which is idle, or in other words, to determine a Tx beam which passes the LBT procedure.

Conventionally, beamwidths for the LBT procedure and for Tx beams are assumed to be the same from the CWS management point of view. It is rather suboptimal for narrow Tx beams as interference caused by different narrow beams may be quite different. For example, a failed transmission in one direction might trigger an increase of CWS, and hence slow down transmissions in all the directions, even if the transmissions to other directions could be successful.

In view of this, embodiments of the present disclosure provide a solution for transmission control to combine a LBT procedure for a wide beam with beam-specific CWS maintenance. More details will be described below in connection with Figs. 2 to 5.

EXAMPLE IMPLEMENTATION OF TRANSMISSION CONTROL

Fig. 2 illustrates a flowchart illustrating an example method 200 for transmission control according to some embodiments of the present disclosure. The method 200 can be implemented at an electronic device such as the first device 110 or the second device 120 shown in Fig. 1. For the purpose of discussion, the method 200 will be described with reference to Fig. 1 and assuming that the method 200 is implemented at the first device 110. It is to be understood that method 200 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.

As shown in Fig. 2, at block 210, the first device 110 performs a LBT procedure for a reference beam to determine a first beam which passes the LBT procedure. According to embodiments of the present disclosure, the reference beam has a beamwidth larger than each of the Tx beams of the first device 110.

In some embodiments, the reference beam may cover at least one of the Tx beams. In this case, the first device 110 may perform a wide-beam LBT procedure before transmission. The wide beam covers at least one of the narrow Tx beams. In some alternative embodiments, the reference beam may be a quasi omni-directional beam. In this case, the reference beam may cover all the Tx beams. The first device 110 may perform a quasi omni-directional LBT procedure before transmission.

The performing of the LBT procedure will be detailed below in connection with Figs. 3 and 4. Fig. 3 illustrates a flowchart illustrating an example method 300 for performing a LBT procedure according to some embodiments of the present disclosure. The method 300 can be implemented at an electronic device such as the first device 110 or the second device 120 shown in Fig. 1. For the purpose of discussion, the method 300 will be described with reference to Fig. 1 and assuming that the method 300 is implemented at the first device 110. It is to be understood that method 300 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.

As shown in Fig. 3, at block 310, the first device 110 may initialize a CWS specific to each of the Tx beams. In other words, each of the Tx beams maintains separately a contention window, i.e., a backoff counter and a CWS, for the purpose of CCA or LBT. For this, the beam-specific CWS is initialized at the beginning of the LBT procedure.

In some embodiments, the first device 110 may use a common value to initialize the CWS per Tx beam. That is, initial values of the CWSs for the Tx beams are the same value. For example, the common value may be a random value. Of course, the common value may also be a predefined value.

In some alternative embodiments, the first device 110 may use a separate value to initialize the CWS per Tx beam. For example, the first device 110 may generate independently a random value by drawing [C_min, C_max] as the CWS per Tx beam. Here, C_min and C_max denote a minimum value and a maximum value for the CWSs. C_min and C_max may be predefined in any suitable ways.

At block 320, the first device 110 may generate, based on the CWS, a backoff counter specific to each of the Tx beams. In some embodiment, the first device 110 may generate, as an initial value of the backoff counter, a random number which is a positive integer less than or equal to the CWS. In other words, separately for each beam, the first device 110 may draw a random number within each beam-specific contention window [0, CWS] . Of course, any other suitable ways are also feasible for generating the backoff counter specific to each Tx beam.

At block 330, the first device 110 may perform an ED for the reference beam at a predefined CCA slot. In other words, before transmission on at least one of the Tx beams, the first device 110 may perform the ED based on CCA or LBT on the channel. In some embodiments where the reference beam covers at least one of the Tx beams, the first device 110 may perform a wide-beam LBT before transmission. In some embodiments where the reference beam is a quasi omni-directional beam, the first device 110 may perform a quasi omni-directional LBT before transmission. For LBT operation, the first device 110 may perform an ED on the operating channel, i.e., on the reference beam.

At block 340, the first device 110 may determine whether the detected energy is lower than an ED threshold. It is to be noted that the ED threshold may be predefined in any suitable ways. If the detected energy is not lower than (i.e., higher than or equal to) the ED threshold, the process returns to block 330 to continue performing the ED while the respective backoff counter remains unchanged. If the detected energy is lower than the ED threshold, the process proceeds to block 350.

At block 350, the first device 110 may decrement the backoff counter specific to each of one or more of the Tx beams that are covered by the reference beam. In some embodiments, the one or more Tx beams may be fully covered by the reference beam.

In some alternative embodiments, the one or more Tx beams may be expected for a subsequent transmission within a subsequent COT. In some still alternative embodiments, the one or more of the transmit beams may be expected for a subsequent reception from a further device (for example, the second device 120) within the subsequent COT. For example, if a Tx beam of the first device 110 is configured as a Quasi-Co-Location (QCL) reference for transmissions of another node (e.g., the second device 120) which a shared COT acquired by the first device 110 for a scheduled or configured UL transmission, the first device 110 may maintain the contention window for the Tx beam. In this case, the first device 110 may only decrement the backoff counters for the beams that the first device 110 intends to transmit or receive or both inside the subsequent COT.

At block 360, the first device 110 may determine whether the backoff counter specific to one of the Tx beams is decremented to zero. If the backoff counter specific to the one of the Tx beams is not decremented to zero, the process returns to block 330 to continue performing the ED. If the backoff counter specific to the one of the Tx beams is decremented to zero, the process proceeds to block 370. At block 370, the first device 110 may determine the one Tx beam as the first beam. In this way, a plurality of first beams may be determined.

Return to Fig. 2, upon the determination of the first beam, at block 220, the first device 110 determines whether the first beam is expected for a transmission. In other words, the first device 110 determines whether a transmission is expected to be performed on the first beam. If the first beam is expected for a transmission, the process proceeds to block 230.

At block 230, the first device 110 performs the transmission on the first beam. In some embodiments where the plurality of first beams are determined, the first device 110 may perform the transmission using one or more beams in the plurality of first beams. In some embodiments, the first device 110 may end the LBT procedure at a starting point of the transmission. In some embodiments, the first device 110 may transmit or receive information using the beams which backoff counters have reached zero.

In some alternative embodiments, the first device 110 may perform a further ED for the first beam at the last slot before the starting point of the transmission. If the detected energy in the further ED is lower than the ED threshold, the first device 110 may perform the transmission. That is, only if the detected energy is lower than the ED threshold at the last CCA slot before the starting point of the transmission, the first device 110 can transmit or receive information using the beams which backoff counters have reached zero. It is to be understood that the transmission on the first beam may also be performed in any other suitable ways.

For illustration, more detailed description will be made on the LBT procedure with reference to Fig. 4. Fig. 4 illustrates a flowchart illustrating another example method 400 for performing a LBT procedure according to some embodiments of the present disclosure. The method 400 can be implemented at an electronic device such as the first device 110 or the second device 120 shown in Fig. 1. For the purpose of discussion, the method 400 will be described with reference to Fig. 1 and assuming that the method 400 is implemented at the first device 110. It is to be understood that method 400 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.

As shown in Fig. 4, at block 401, the first device 110 may stay in an idle state. At block 402, the first device 110 may determine whether a transmission is expected to be performed in at least one of the Tx beams. If the transmission is unexpected to be performed, the first device 110 may remain in the idle state. If the transmission is expected to be performed, at block 403, the first device 110 may generate a backoff counter N. The operation on the generation of the backoff counter is similar to that described in connection with block 320 in Fig. 3, and thus is not repeated here for concise.

At block 404, the first device 110 may determine whether a channel for the reference beam is idle within 8μs. It is to be understood that 8μs is merely an example, and any other suitable values are also feasible. The first device 110 may perform the determination by performing an ED as that described in connection with block 330 in Fig. 3. In this case, the predefined CCA slot is 8μs.

If the channel for the reference beam is not idle (i.e., is busy) within 8μs, the first device 110 may return to the idle state. If the channel is idle within 8μs, the process proceeds to block 405. At block 405, the first device 110 may determine whether the backoff counter N is equal to zero (i.e., N=0) for one or more beams. If N≠0, the process proceeds to block 406. At block 406, the first device 110 may determine whether the channel for the reference beam is idle within 5μs. It is to be understood that 5μs is merely an example, and any other suitable values are also feasible. The first device 110 may perform the determination by performing an ED as that described in connection with block 330 in Fig. 3. In this case, the predefined CCA slot is 5μs.

If the channel for the reference beam is not idle (i.e., is busy) within 5μs, the first device 110 may return to block 404 to repeatedly perform the CCA. If the channel is idle within 5μs, the process proceeds to block 407. At block 407, the first device 110 may decrement the backoff counter N (i.e., N=N-1) . Then, the process returns to block 405 until N=0.

If determining at block 405 that N=0 for one or more beams, the process proceeds to block 408. At block 408, the first device 110 may determine whether the first device 110 is able to transmit information within a transmit opportunity (TxOP) . If the first device 110 is able to transmit information within the TxOP, the first device 110 may perform the transmission at block 409. Then, the first device 110 may return to the idle state.

If the first device 110 is unable to transmit information within the TxOP, the process may return to block 403 to repeatedly perform the LBT procedure. It is to be understood that the process of Fig. 4 merely an example and is not for limitation.

Based on a transmission on a beam, a CWS specific to the beam can be adjusted. With reference to Fig. 2 again, assuming that a first CWS is specific to the first beam determined in block 210. At block 240, the first device 110 adjusts the first CWS based on a feedback of the transmission on the first beam, a timing of the transmission on the first beam, or both. In some embodiments where there is a second beam at least partly overlapped with the first beam, the first device 110 may further adjust a second CWS specific to the second beam based on the adjustment for the first CWS. In some embodiments where there is a second beam at least partly overlapped with the first beam and the second beam does not perform a transmission in a COT, the first device 110 may further adjust a second CWS specific to the second beam based on the adjustment for the first CWS.

For clarity, more detailed description on the adjustment will be made below with reference to Fig. 5. Fig. 5 illustrates a flowchart illustrating an example method 500 for performing a CWS adjustment according to some embodiments of the present disclosure. The method 500 can be implemented at an electronic device such as the first device 110 or the second device 120 shown in Fig. 1. For the purpose of discussion, the method 500 will be described with reference to Fig. 1 and assuming that the method 500 is implemented at the first device 110. 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.

As shown in Fig. 5, at block 501, the first device 110 may determine whether the first beam is expected for transmission. The operation of block 501 is similar to that of block 220, and thus its detail is not repeated here. If the first beam is expected for transmission, the process proceeds to block 502. At block 502, the first device 110 may perform the transmission on the first beam. The operation of block 502 is similar to that of block 230, and thus its detail is not repeated here.

Upon the transmission, at block 503, the first device 110 may monitor a feedback for the transmission on a predefined reference resource. In some embodiments, the feedback may be a hybrid automatic repeat request (HARQ) feedback or decoding status of the transmission, for example, positive acknowledgement (ACK) or negative acknowledgement (NACK) .

The transmission on the first beam within a COT may involve a plurality of HARQ processes. In this case, a reference resource should be predefined so as to determine which one or more of the HARQ processes are used for the CWS adjustment. In some embodiments, the predefined reference resource may be a starting slot of the transmission. In other words, the predefined reference resource may be the starting slot of the most recent transmission on an operating channel on the first beam.

In some alternative embodiments, the predefined reference resource may be a duration from a start of a channel occupancy to earlier one of the following: an end of the first slot where at least one unicast data channel (for example, a physical downlink shared channel (PDSCH) from the first device 110 or a physical uplink shared channel (PUSCH) from the second device 120) is transmitted over all the resources allocated for the unicast data channel in a direction of the first beam, or an end of the first transmission burst that comprises the unicast data channel transmitted over all the resources allocated for the unicast data channel in the direction of the first beam. In some embodiments, if the channel occupancy includes a unicast data channel in the first beam direction, but it does not include any unicast data channel transmitted over all the resources allocated for that data channel, then, the duration of the first transmission burst by the first device 110 within the channel occupancy that contains unicast data channel may be the reference resource for the CWS adjustment.

At block 504, the first device 110 may determine whether the feedback is available. If the feedback is available, the first device 110 may adjust the first CWS based on the feedback. As shown in Fig. 5, the process proceeds to block 505. At block 505, the first device 110 may determine the feedback is ACK or NACK. If the feedback is ACK, the process proceeds to block 506. At block 506, the first device 110 may reset the first CWS to an initial value of the first CWS.

Similar with the adjustment of the first CWS, at block 507, the first device 110 may reset the second CWS specific to the second beam to an initial value of the second CWS. In some embodiments, the second beam may be fully overlapped with the first beam. In some embodiments, the second beam may be wider than the first beam and partly overlapped with the first beam. In some embodiments, the second beam may be narrower than the first beam and partly overlapped with the first beam. In some embodiments, the second beam does not perform a transmission in a COT. Of course, the second beam may also perform the transmission in the COT. The present disclosure does not make limitation for this.

If determining at block 505 that the feedback is NACK, the process proceeds to block 508. At block 508, the first device 110 may increase the first CWS. In some embodiments, the first device 110 may increase the first CWS in a linear manner. In some embodiments, the first device 110 may increase the first CWS in an exponential manner. In some embodiments, the first device 110 may increase the first CWS in a predefined manner.

At block 509, the first device 110 may determine whether the second beam is fully covered by the first beam. If the second beam is fully covered by the first beam, the process proceeds to block 510. At block 510, the first device 110 may also increase the second CWS. In some embodiments, the first device 110 may increase the second CWS in a linear manner. In some embodiments, the first device 110 may increase the second CWS in an exponential manner. In some embodiments, the first device 110 may increase the second CWS in a predefined manner.

If the second beam is not fully covered by the first beam, the process proceeds to block 511. At block 511, the first device 110 may maintain the second beam unchanged.

Return to block 504, if the feedback is unavailable, the first device 110 may adjust the first CWS based on the timing of the transmission. As shown in Fig. 5, the process proceeds to block 512. At block 512, the first device 110 may determine whether the transmission is a retransmission.

If the transmission is a retransmission, the process proceeds to block 508 to increase the first CWS. Accordingly, the first device 110 may also increase the second CWS or maintain the second CWS unchanged as described in blocks 509 to 511.

If determining at block 512 that the transmission is not a retransmission, the process proceeds to block 513. At block 513, the first device 110 may determine whether an interval between the transmission and the last adjustment of the first CWS is smaller than a threshold interval. If the interval is not smaller than (i.e., larger than or equal to) the threshold interval, the process proceeds to block 508 to increase the first CWS. Accordingly, the first device 110 may also increase the second CWS or maintain the second CWS unchanged as described in blocks 509 to 511.

If determining at block 513 that the interval is smaller than the threshold interval, the process proceeds to block 514. At block 514, the first device 110 may maintain the first CWS unchanged. Accordingly, the first device 110 may also maintain the second CWS unchanged at block 511.

As shown in Fig. 5, if determining at block 501 that the first beam is unexpected for transmission, the process proceeds to block 514 to maintain the first CWS unchanged. Accordingly, the first device 110 may also maintain the second CWS unchanged as shown in block 511. It is to be noted that the process of Fig. 5 merely is an example, and is not for limitation.

So far, the transmission control solution according to embodiments of the present disclosure has been described. It is to be understood that although the solution is described in connection with the first device 110 (i.e., a network device) , the solution also can be applied to the second device 120 (i.e., a terminal device) .

According to this solution, contention windows in a LBT procedure can be maintained or managed in a beam-specific manner while an ED measurement can be performed jointly for multiple Tx beams. Thus, overhead and complexity associated with the ED measurement can be reduced. Further, as there is no need to switch Rx beam during the LBT procedure, the associated switching time can be saved. In addition, beam-specific CWS management can ensure fair use of unlicensed spectrum.

EXAMPLE IMPLEMENTATION OF APPARATUS AND DEVICE

In some embodiments, an apparatus capable of performing any of the methods 200 to 500 (for example, the first device 110) may comprise means for performing the respective steps of the methods 200 to 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 embodiments, the apparatus comprises means for performing, at an electronic device, a listen-before-talk procedure for a reference beam to determine a first beam which passes the listen-before-talk procedure among transmit beams, the reference beam having a beamwidth larger than the transmit beams; means for performing the transmission on the first beam in accordance with a determination that the first beam is expected for transmission; and means for adjusting a first contention window size specific to the first beam based on at least one of a feedback or a timing of the transmission.

In some embodiments, the means for performing the listen-before-talk procedure may comprise: means for initializing a contention window size specific to each of the transmit beams; means for generating, based on the contention window size, a backoff counter specific to each of the transmit beams; means for performing an energy detection for the reference beam at a predetermined channel clearance assessment slot; means for decrementing the backoff counter specific to one or more of the transmit beams that are covered by the reference beam in accordance with a determination that the detected energy is lower than an energy detection threshold; and means for determining the one transmit beam as the first beam in accordance with a determination that the backoff counter specific to one of the transmit beams is decremented to zero.

In some embodiments, the means for generating the backoff counter may comprise: means for generating, as an initial value of the backoff counter, a random number which is a positive integer less than or equal to the contention window size.

In some embodiments, the one or more of the transmit beams may be expected for a subsequent transmission within a subsequent channel occupancy time. In some embodiments, the one or more of the transmit beams may be expected for a subsequent reception from a further device within a subsequent channel occupancy time.

In some embodiments, the reference beam may be a quasi omni-directional beam. In some embodiments, the reference beam may cover at least one of the transmit beams.

In some embodiments, the apparatus may further comprise means for ending the listen-before-talk procedure at a starting point of the transmission. In some embodiments, the means for performing the transmission may comprise means for performing a further energy detection for the first beam at the last slot before the starting point of the transmission; and means for performing the transmission in accordance with a determination that the detected energy in the further energy detection is lower than the energy detection threshold.

In some embodiments, the means for adjusting the first contention window size may comprise: means for monitoring the feedback on a predefined reference resource; means for adjusting the first contention window size based on the feedback in accordance with a determination that the feedback is available; and means for adjusting the first contention window size based on the timing in accordance with a determination that the feedback is unavailable.

In some embodiments, the predefined reference resource may be a starting slot of the transmission. In some embodiments, the predefined reference resource may be a duration from a start of a channel occupancy to earlier one of the following: an end of the first slot where at least one unicast data channel is transmitted over all the resources allocated for the unicast data channel in a direction of the first beam, or an end of the first transmission burst that comprises the unicast data channel transmitted over all the resources allocated for the unicast data channel in the direction of the first beam.

In some embodiments, the means for adjusting the first contention window size based on the feedback may comprise: means for resetting the first contention window size to a respective initial value in accordance with a determination that the feedback is a positive acknowledgement; and means for increasing the first contention window size in accordance with a determination that the feedback is a negative acknowledgement.

In some embodiments, the means for adjusting the first contention window size based on the timing may comprise: means for maintaining the first contention window size unchanged in accordance with a determination that an interval between the transmission and the last adjustment of the first contention window size is smaller than a threshold interval and the transmission is not a retransmission; and means for increasing the first contention window size in accordance with a determination that the transmission is a retransmission or the interval between the transmission and the last adjustment of the first contention window size is larger than the threshold interval.

In some embodiments, the means for increasing the first contention window size may comprise at least one of the following: means for increasing the first contention window size in a linear manner; means for increasing the first contention window size in an exponential manner; or means for increasing the first contention window size in a predefined manner.

In some embodiments, the apparatus may further comprise means for maintaining the first contention window size unchanged in accordance with a determination that the first beam is unexpected for the transmission.

In some embodiments, the apparatus may further comprise means for adjusting a second contention window size specific to a second beam among the transmit beams based on the adjustment for the first contention window size of the first beam, the second beam being at least partly overlapped with the first beam.

In some embodiments, the means for adjusting the second contention window size may comprise: means for resetting the second contention window size to a respective initial value in accordance with a determination that the feedback is a positive acknowledgement; means for increasing the second contention window size in accordance with a determination that the feedback is a negative acknowledgement and the second beam is fully covered by the first beam; and means for maintaining the second contention window size unchanged in accordance with a determination that the first contention window size is unchanged.

In some embodiments, the means for increasing the second contention window size may comprise at least one of the following: means for increasing the second contention window size in a linear manner; means for increasing the second contention window size in an exponential manner; or means for increasing the second contention window size in a predefined manner. In some embodiments, the electronic device may be a terminal device or a network device.

FIG. 6 is a simplified block diagram of a device 600 that is suitable for implementing embodiments of the present disclosure. The device 600 may be provided to implement a first device or a second device, for example the first device 110 or the second device 120 as shown in Fig. 1. As shown, the device 600 includes one or more processors 610, one or more memories 620 coupled to the processor 610, and one or more communication modules 640 (such as, transmitters and/or receivers) coupled to the processor 610.

The communication module 640 is for bidirectional communications. The communication module 640 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 610 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 600 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 620 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) 624, 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. Examples of the volatile memories include, but are not limited to, an random access memory (RAM) 622 and other volatile memories that will not last in the power-down duration.

A computer program 630 includes computer executable instructions that are executed by the associated processor 610. The program 630 may be stored in the ROM 624. The processor 610 may perform any suitable actions and processing by loading the program 630 into the RAM 622.

The embodiments of the present disclosure may be implemented by means of the program 630 so that the device 600 may perform any process of the disclosure as discussed with reference to Figs. 2 to 5. 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 630 may be tangibly contained in a computer readable medium which may be included in the device 600 (such as in the memory 620) or other storage devices that are accessible by the device 600. The device 600 may load the program 630 from the computer readable medium to the RAM 622 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. 7 shows an example of the computer readable medium 1600 in form of CD or DVD. The computer readable medium has the program 630 stored thereon.

Generally, 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, apparatus, 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 methods 200 to 500 as described above with reference to Figs. 2 to 5. Generally, program modules 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 apparatus, 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, apparatus 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, apparatus, 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

An electronic device comprising:

at least one processor; and

at least one memory including computer program code,

the at least one memory and the computer program code configured to, with the at least one processor, cause the electronic device to:

perform a listen-before-talk procedure for a reference beam to determine a first beam which passes the listen-before-talk procedure among transmit beams, the reference beam having a beamwidth larger than the transmit beams;

in accordance with a determination that the first beam is expected for transmission, perform the transmission on the first beam; and

adjust a first contention window size specific to the first beam based on at least one of a feedback or a timing of the transmission.
The electronic device of claim 1, wherein the electronic device is caused to perform the listen-before-talk procedure by:

initializing a contention window size specific to each of the transmit beams;

generating, based on the contention window size, a backoff counter specific to each of the transmit beams;

performing an energy detection for the reference beam at a predefined channel clearance assessment slot;

in accordance with a determination that the detected energy is lower than an energy detection threshold, decrementing the backoff counter specific to one or more of the transmit beams that are covered by the reference beam; and

in accordance with a determination that the backoff counter specific to one of the transmit beams is decremented to zero, determining the one transmit beam as the first beam.
The electronic device of claim 2, wherein the electronic device is caused to generate the backoff counter by:

generating, as an initial value of the backoff counter, a random number which is a positive integer less than or equal to the contention window size.
The electronic device of claim 2, wherein the one or more of the transmit beams are expected for a subsequent transmission within a subsequent channel occupancy time.
The electronic device of claim 2, wherein the one or more of the transmit beams are expected for a subsequent reception from a further device within a subsequent channel occupancy time.
The electronic device of claim 2, wherein the reference beam is a quasi omni-directional beam.
The electronic device of claim 2, wherein the reference beam covers at least one of the transmit beams.
The electronic device of claim 2, wherein the electronic device is further caused to end the listen-before-talk procedure at a starting point of the transmission.
The electronic device of claim 8, wherein the electronic device is caused to perform the transmission by:

performing a further energy detection for the first beam at the last slot before the starting point of the transmission; and

in accordance with a determination that the detected energy in the further energy detection is lower than the energy detection threshold, performing the transmission.
The electronic device of claim 1, wherein the electronic device is caused to adjust the first contention window size by:

monitoring the feedback on a predefined reference resource;

in accordance with a determination that the feedback is available, adjusting the first contention window size based on the feedback; and

in accordance with a determination that the feedback is unavailable, adjusting the first contention window size based on the timing.
The electronic device of claim 10, wherein the predefined reference resource is a starting slot of the transmission.
The electronic device of claim 10, wherein the predefined reference resource is a duration from a start of a channel occupancy to earlier one of the following:

an end of the first slot where at least one unicast data channel is transmitted over all the resources allocated for the unicast data channel in a direction of the first beam, or

an end of the first transmission burst that comprises the unicast data channel transmitted over all the resources allocated for the unicast data channel in the direction of the first beam.
The electronic device of claim 10, wherein the electronic device is caused to adjust the first contention window size based on the feedback by:

in accordance with a determination that the feedback is a positive acknowledgement, resetting the first contention window size to a respective initial value; and

in accordance with a determination that the feedback is a negative acknowledgement, increasing the first contention window size.
The electronic device of claim 10, wherein the electronic device is caused to adjust the first contention window size based on the timing by:

in accordance with a determination that an interval between the transmission and the last adjustment of the first contention window size is smaller than a threshold interval and the transmission is not a retransmission, maintaining the first contention window size unchanged; and

in accordance with a determination that the transmission is a retransmission or the interval between the transmission and the last adjustment of the first contention window size is larger than the threshold interval, increasing the first contention window size.
The electronic device of claim 13 or 14, wherein the electronic device is caused to increase the first contention window size by at least one of the following:

increasing the first contention window size in a linear manner;

increasing the first contention window size in an exponential manner; or

increasing the first contention window size in a predefined manner.
The electronic device of claim 1, wherein the electronic device is further caused to:

in accordance with a determination that the first beam is unexpected for the transmission, maintain the first contention window size unchanged.
The electronic device of claim 1, wherein the electronic device is further caused to:

adjust a second contention window size specific to a second beam among the transmit beams based on the adjustment for the first contention window size of the first beam, the second beam being at least partly overlapped with the first beam.
The electronic device of claim 17, wherein the electronic device is caused to adjust the second contention window size by:

in accordance with a determination that the feedback is a positive acknowledgement, resetting the second contention window size to a respective initial value;

in accordance with a determination that the feedback is a negative acknowledgement and the second beam is fully covered by the first beam, increasing the second contention window size; and

in accordance with a determination that the first contention window size is unchanged, maintaining the second contention window size unchanged.
The electronic device of claim 18, wherein the electronic device is caused to increase the second contention window size by at least one of the following:

increasing the second contention window size in a linear manner;

increasing the second contention window size in an exponential manner; or

increasing the second contention window size in a predefined manner.
The electronic device of claim 1, wherein the electronic device is a terminal device or a network device.
A method for transmission control, comprising:

performing, at an electronic device, a listen-before-talk procedure for a reference beam to determine a first beam which passes the listen-before-talk procedure among transmit beams, the reference beam having a beamwidth larger than the transmit beams;

in accordance with a determination that the first beam is expected for transmission, performing the transmission on the first beam; and

adjusting a first contention window size specific to the first beam based on at least one of a feedback or a timing of the transmission.
The method of claim 21, wherein performing the listen-before-talk procedure comprises:

initializing a contention window size specific to each of the transmit beams;

generating, based on the contention window size, a backoff counter specific to each of the transmit beams;

performing an energy detection for the reference beam at a predetermined channel clearance assessment slot;

in accordance with a determination that the detected energy is lower than an energy detection threshold, decrementing the backoff counter specific to one or more of the transmit beams that are covered by the reference beam; and

in accordance with a determination that the backoff counter specific to one of the transmit beams is decremented to zero, determining the one transmit beam as the first beam.
The method of claim 22, wherein generating the backoff counter comprises:

generating, as an initial value of the backoff counter, a random number which is a positive integer less than or equal to the contention window size.
The method of claim 22, wherein the one or more of the transmit beams are expected for a subsequent transmission within a subsequent channel occupancy time.
The method of claim 22, wherein the one or more of the transmit beams are expected for a subsequent reception from a further device within a subsequent channel occupancy time.
The method of claim 22, wherein the reference beam is a quasi omni-directional beam.
The method of claim 22, wherein the reference beam covers at least one of the transmit beams.
The method of claim 22, further comprising:

ending the listen-before-talk procedure at a starting point of the transmission.
The method of claim 28, wherein performing the transmission comprises:

performing a further energy detection for the first beam at the last slot before the starting point of the transmission; and

in accordance with a determination that the detected energy in the further energy detection is lower than the energy detection threshold, performing the transmission.
The method of claim 21, wherein adjusting the first contention window size comprises:

monitoring the feedback on a predefined reference resource;

in accordance with a determination that the feedback is available, adjusting the first contention window size based on the feedback; and

in accordance with a determination that the feedback is unavailable, adjusting the first contention window size based on the timing.
The method of claim 30, wherein the predefined reference resource is a starting slot of the transmission.
The method of claim 30, wherein the predefined reference resource is a duration from a start of a channel occupancy to earlier one of the following:

an end of the first slot where at least one unicast data channel is transmitted over all the resources allocated for the unicast data channel in a direction of the first beam, or

an end of the first transmission burst that comprises the unicast data channel transmitted over all the resources allocated for the unicast data channel in the direction of the first beam.
The method of claim 30, wherein adjusting the first contention window size based on the feedback by:

in accordance with a determination that the feedback is a positive acknowledgement, resetting the first contention window size to a respective initial value; and

in accordance with a determination that the feedback is a negative acknowledgement, increasing the first contention window size.
The method of claim 30, wherein adjusting the first contention window size based on the timing by:

in accordance with a determination that an interval between the transmission and the last adjustment of the first contention window size is smaller than a threshold interval and the transmission is not a retransmission, maintaining the first contention window size unchanged; and

in accordance with a determination that the transmission is a retransmission or the interval between the transmission and the last adjustment of the first contention window size is larger than the threshold interval, increasing the first contention window size.
The method of claim 33 or 34, wherein increasing the first contention window size comprising at least one of the following:

increasing the first contention window size in a linear manner;

increasing the first contention window size in an exponential manner; or

increasing the first contention window size in a predefined manner.
The method of claim 21, further comprising:

in accordance with a determination that the first beam is unexpected for the transmission, maintaining the first contention window size unchanged.
The method of claim 21, further comprising:

adjusting a second contention window size specific to a second beam among the transmit beams based on the adjustment for the first contention window size of the first beam, the second beam being at least partly overlapped with the first beam.
The method of claim 37, wherein adjusting the second contention window size comprises:

in accordance with a determination that the feedback is a positive acknowledgement, resetting the second contention window size to a respective initial value;

in accordance with a determination that the feedback is a negative acknowledgement and the second beam is fully covered by the first beam, increasing the second contention window size; and

in accordance with a determination that the first contention window size is unchanged, maintaining the second contention window size unchanged.
The method of claim 38, wherein increasing the second contention window size comprising at least one of the following:

increasing the second contention window size in a linear manner;

increasing the second contention window size in an exponential manner; or

increasing the second contention window size in a predefined manner.
The method of claim 21, wherein the electronic device is a terminal device or a network device.
An apparatus for transmission control, comprising:

means for performing, at an electronic device, a listen-before-talk procedure for a reference beam to determine a first beam which passes the listen-before-talk procedure among transmit beams, the reference beam having a beamwidth larger than the transmit beams;

means for performing the transmission on the first beam in accordance with a determination that the first beam is expected for transmission; and

means for adjusting a first contention window size specific to the first beam based on at least one of a feedback or a timing of the transmission.
A non-transitory computer readable medium comprising program instructions for causing an apparatus to perform the method according to any of claims 21 to 40.