WO2024074043A1

WO2024074043A1 - Methods and apparatuses for transmission over unlicensed spectra

Info

Publication number: WO2024074043A1
Application number: PCT/CN2023/094356
Authority: WO
Inventors: Xin Guo; Haipeng Lei; Xiaodong Yu; Zhennian SUN
Original assignee: Lenovo (Beijing) Limited
Priority date: 2023-05-15
Filing date: 2023-05-15
Publication date: 2024-04-11

Abstract

Embodiments of the present disclosure relate to methods and apparatuses for transmission over unlicensed spectra. According to an embodiment of the present disclosure, a user equipment can include: a transceiver; and a processor coupled to the transceiver and configured to: determine an operation with respect to a sidelink synchronization signal block (S-SSB) occasion according to one of the followings: whether it can be determined that the S-SSB occasion overlaps with a channel occupancy time (COT) for an SL transmission; or whether there is other radio access technology in an unlicensed spectrum associated with the S-SSB occasion; and perform the operation with respect to the S-SSB occasion based on the determination.

Description

METHODS AND APPARATUSES FOR TRANSMISSION OVER UNLICENSED SPECTRA

TECHNICAL FIELD

Embodiments of the present application are related to wireless communication technology, and more particularly, related to methods and apparatuses for transmission over unlicensed spectra.

BACKGROUND

A sidelink (SL) is a long-term evolution (LTE) feature introduced in 3rd generation partnership project (3GPP) Release 12, and enables a direct communication between proximal user equipments (UEs) , in which data does not need to go through a base station (BS) or a core network. An SL communication system has been introduced into 3GPP fifth generation (5G) wireless communication technology, in which a direct link between two UEs is called an SL.

SL synchronization information is carried in an SL synchronization signal block (S-SSB) . In an unlicensed spectrum, SL transmissions and S-SSB transmissions may both exist. Therefore, new designs for SL transmissions and S-SSB transmissions in unlicensed spectra are needed.

SUMMARY OF THE APPLICATION

Embodiments of the present application at least provide a technical solution for SL transmissions and S-SSB transmissions in unlicensed spectra.

According to some embodiments of the present application, a UE may include: a transceiver; and a processor coupled to the transceiver and configured to: determine an operation with respect to an S-SSB occasion according to one of the followings: whether it can be determined that the S-SSB occasion overlaps with a channel occupancy time (COT) for an SL transmission; or whether there is other radio access technology (RAT) in an unlicensed spectrum associated with the S-SSB occasion; and perform the operation with respect to the S-SSB occasion based on the determination.

In some embodiments of the present application, the processor is further configured to obtain a first configuration indicating a distribution of S-SSB occasions within an S-SSB period, wherein the first configuration indicates one of the followings: a time interval between two adjacent S-SSB occasions within the S-SSB period, wherein the time interval is greater than or equal to a minimum time interval which is greater than zero; a number of consecutive S-SSB occasion (s) included in an S-SSB group within the S-SSB period; a time offset between a starting of the S-SSB period and a starting of the first S-SSB group within the S-SSB period; a time interval between two adjacent S-SSB groups within the S-SSB period; or a number of S-SSB groups within the S-SSB period.

In some embodiments of the present application, the first configuration is configured, pre-configured, pre-defined, or defined per frequency range (FR) , per bandwidth part (BWP) , per carrier, per resource block (RB) set, or per resource pool (RP) .

In some embodiments of the present application, the first configuration is received via at least one of: a master information block (MIB) message, a system information block (SIB) message, a radio resource control (RRC) signaling, a medium access control (MAC) control element (CE) , or downlink control information (DCI) .

In some embodiments of the present application, the processor is further configured to determine whether the S-SSB occasion overlaps with the COT based on one of the followings: a distribution of S-SSB occasions within an S-SSB period; or information associated with the COT.

In some embodiments of the present application, the processor is further configured to obtain one of the followings: a first S-SSB access configuration for an inside-COT UE, indicating a first cyclic prefix extension (CPE) length or a listen before talk (LBT) type 2 having a first duration; a second S-SSB access configuration for an outside-COT UE, indicating a second CPE length different from the first CPE length or an LBT type 1; or a third S-SSB access configuration for the case that there is no other RAT in the unlicensed spectrum, indicating a third CPE length or an LBT type.

In some embodiments of the present application, in response to that the S-SSB occasion is determined to overlap with the COT, the operation includes performing a channel access to the S-SSB occasion by using the first S-SSB access configuration; in response to that the S-SSB occasion is not determined to overlap with any COT, the operation includes performing a channel access to the S-SSB occasion by using the second S-SSB access configuration; or in response to that no other RAT is determined to be in the unlicensed spectrum, the operation includes performing a channel access to the S-SSB occasion by using the third S-SSB access configuration.

In some embodiments of the present application, in response to that the S-SSB occasion is determined to overlap with the COT, the processor is further configured to determine whether there is a transmission on the first one or more symbols of the S-SSB occasion.

In some embodiments of the present application, in response to that no transmission is detected on the first one or more symbols of the S-SSB occasion, the operation includes performing transmission on remaining symbol (s) of the S-SSB occasion.

According to some embodiments of the present application, a BS may include: a transceiver; and a processor coupled to the transceiver and configured to transmit, via the transceiver, configuration information for transmission over SL in an unlicensed spectrum, wherein the configuration information includes one of the followings: a first configuration indicating a distribution of S-SSB occasions within an S-SSB period; a first S-SSB access configuration for an inside-COT UE, indicating a first CPE length or an LBT type 2 having a first duration; a second S-SSB access configuration for an outside-COT UE, indicating a second CPE length different from the first CPE length or an LBT type 1; or a third S-SSB access configuration for the case that there is no other RAT in the unlicensed spectrum, indicating a third CPE length or an LBT type.

In some embodiments of the present application, the configuration information is configured per FR, per BWP, per carrier, per RB set, or per RP.

In some embodiments of the present application, the processor is configured to transmit the configuration information via at least one of: a MIB message, a SIB message, an RRC signaling, a MAC CE, or DCI.

In some embodiments of the present application, the first configuration indicates one of the followings: a time interval between two adjacent S-SSB occasions within the S-SSB period, wherein the time interval is greater than or equal to a minimum time interval which is greater than zero; a number of consecutive S-SSB occasion (s) included in an S-SSB group within the S-SSB period; a time offset between a starting of the S-SSB period and a starting of the first S-SSB group within the S-SSB period; a time interval between two adjacent S-SSB groups within the S-SSB period; or a number of S-SSB groups within the S-SSB period.

According to some embodiments of the present application, a method performed by a UE may include: determining an operation with respect to an S-SSB occasion according to one of the followings: whether it can be determined that the S-SSB occasion overlaps with a COT for an SL transmission; or whether there is other RAT in an unlicensed spectrum associated with the S-SSB occasion; and performing the operation with respect to the S-SSB occasion based on the determination.

In some embodiments of the present application, the method may further includes obtaining a first configuration indicating a distribution of S-SSB occasions within an S-SSB period, wherein the first configuration indicates one of the followings: a time interval between two adjacent S-SSB occasions within the S-SSB period, wherein the time interval is greater than or equal to a minimum time interval which is greater than zero; a number of consecutive S-SSB occasion (s) included in an S-SSB group within the S-SSB period; a time offset between a starting of the S-SSB period and a starting of the first S-SSB group within the S-SSB period; a time interval between two adjacent S-SSB groups within the S-SSB period; or a number of S-SSB groups within the S-SSB period.

According to some embodiments of the present application, a method performed by a BS may include: transmitting configuration information for transmission over SL in an unlicensed spectrum, wherein the configuration information includes one of the followings: a first configuration indicating a distribution of S-SSB occasions within an S-SSB period; a first S-SSB access configuration for an inside-COT UE, indicating a first CPE length or an LBT type 2 having a first duration; a second S-SSB access configuration for an outside-COT UE, indicating a second CPE length different from the first CPE length or an LBT type 1; or a third S-SSB access configuration for the case that there is no other RAT in the unlicensed spectrum, indicating a third CPE length or an LBT type.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to describe the manner in which advantages and features of the application can be obtained, a description of the application is rendered by reference to specific embodiments thereof, which are illustrated in the appended drawings. These drawings depict only example embodiments of the application and are not therefore to be considered limiting of its scope.

FIG. 1 is a schematic diagram illustrating an exemplary wireless communication system according to some embodiments of the present application;

FIG. 2 illustrates an exemplary S-SSB slot according to some embodiments of the present application;

FIG. 3 illustrates an exemplary distribution of S-SSB occasions in the time domain according to some embodiments of the present application;

FIG. 4 illustrates exemplary locations of S-SSB occasion (s) and a COT for SL transmission in an RB set according to some embodiments of the present application;

FIG. 5 illustrates another exemplary distribution of S-SSB occasions in the time domain according to some embodiments of the present application;

FIG. 6 illustrates a flowchart of an exemplary method for transmission in an unlicensed spectrum according to some embodiments of the present application;

FIG. 7 illustrates an example of a CPE and a target S-SSB occasion according to some embodiments of the present application; and

FIG. 8 illustrates a simplified block diagram of an exemplary apparatus for transmission in an unlicensed spectrum according to some embodiments of the present application.

DETAILED DESCRIPTION

The detailed description of the appended drawings is intended as a description of preferred embodiments of the present application and is not intended to represent the only form in which the present application may be practiced. It should be understood that the same or equivalent functions may be accomplished by different embodiments that are intended to be encompassed within the spirit and scope of the present application.

While operations are depicted in the drawings in a particular order, persons skilled in the art will readily recognize that such operations need not be performed in the particular order as shown or in a sequential order, or that all illustrated operations need be performed, to achieve desirable results; sometimes one or more operations can be skipped. Further, the drawings can schematically depict one or more example processes in the form of a flow diagram. However, other operations that are not depicted can be incorporated in the example processes that are schematically illustrated. For example, one or more additional operations can be performed before, after, simultaneously, or between any of the illustrated operations. In certain circumstances, multitasking and parallel processing can be advantageous.

Reference will now be made in detail to some embodiments of the present application, examples of which are illustrated in the accompanying drawings. To facilitate understanding, embodiments are provided under specific network architecture and new service scenarios, such as 3GPP LTE and LTE advanced, 3GPP 5G new radio (NR) , 5G-Advanced, 6G, and so on. It is contemplated that along with developments of network architectures and new service scenarios, all embodiments in the present application are also applicable to similar technical problems; and moreover, the terminologies recited in the present application may change, which should not affect the principle of the present application.

FIG. 1 illustrates an exemplary wireless communication system 100 in accordance with some embodiments of the present application.

As shown in FIG. 1, the wireless communication system 100 includes at least one UE 101 and at least one BS 102. In particular, the wireless communication system 100 includes two UEs 101 (e.g., UE 101a and UE 101b) and one BS 102 for illustrative purpose. Although a specific number of UEs 101 and BS 102 are depicted in FIG. 1, it is contemplated that any number of UEs 101 and BSs 102 may be included in the wireless communication system 100.

According to some embodiments of the present disclosure, the UE (s) 101 may include computing devices, such as desktop computers, laptop computers, personal digital assistants (PDAs) , tablet computers, smart televisions (e.g., televisions connected to the Internet) , set-top boxes, game consoles, security systems (including security cameras) , vehicle on-board computers, network devices (e.g., routers, switches, and modems) , or the like.

According to some other embodiments of the present disclosure, the UE (s) 101 may include a portable wireless communication device, a smart phone, a cellular telephone, a flip phone, a device having a subscriber identity module, a personal computer, a selective call receiver, or any other device that is capable of sending and receiving communication signals on a wireless network.

According to some other embodiments of the present disclosure, the UE (s) 101 may include wearable devices, such as smart watches, fitness bands, optical head-mounted displays, or the like.

According to some embodiments of the present disclosure, the UE (s) 101 may include vehicle UEs (VUEs) and/or power-saving UEs (also referred to as power sensitive UEs) . The power-saving UEs may include vulnerable road users (VRUs) , public safety UEs (PS-UEs) , and/or commercial sidelink UEs (CS-UEs) that are sensitive to power consumption. In an embodiment of the present disclosure, a VRU may include a pedestrian UE (P-UE) , a cyclist UE, a wheelchair UE or other UEs which require power saving compared with a VUE.

Moreover, the UE (s) 101 may be referred to as a subscriber unit, a mobile, a mobile station, a user, a terminal, a mobile terminal, a wireless terminal, a fixed terminal, a subscriber station, a user terminal, or a device, or described using other terminology used in the art.

In a sidelink communication system, a transmission UE may also be named as a transmitting UE, a Tx UE, a sidelink Tx UE, a sidelink transmission UE, or the like. A reception UE may also be named as a receiving UE, an Rx UE, a sidelink Rx UE, a sidelink reception UE, or the like.

According to some embodiments of FIG. 1, UE 101a functions as a Tx UE, and UE 101b functions as an Rx UE. UE 101a may exchange sidelink messages with UE 101b through a sidelink, for example, via PC5 interface as defined in 3GPP TS 23.303. UE 101a may transmit information or data to other UE (s) within the sidelink communication system, through sidelink unicast, sidelink groupcast, or sidelink broadcast. For instance, UE 101a may transmit data to UE 101b in a sidelink unicast session. UE 101a may transmit data to UE 101b and other UE (s) in a groupcast group (not shown in FIG. 1) by a sidelink groupcast transmission session. Also, UE 101a may transmit data to UE 101b and other UE (s) (not shown in FIG. 1) by a sidelink broadcast transmission session.

Alternatively, according to some other embodiments of FIG. 1, UE 101b functions as a Tx UE and transmits sidelink messages, and UE 101a functions as an Rx UE and receives the sidelink messages from UE 101b.

In some embodiments of the present disclosure, UE 101a may communicate with UE 101b over licensed spectra, whereas in other embodiments, UE 101a may communicate with UE 101b over unlicensed spectra.

Both UE 101a and UE 101b in the embodiments of FIG. 1 may transmit information to BS 102 and receive control information from BS 102, for example, via LTE or NR Uu interface. BS 102 may be distributed over a geographic region. In certain embodiments of the present disclosure, BS 102 may also be referred to as an access point, an access terminal, a base, a base unit, a macro cell, a Node-B, an evolved Node B (eNB) , a gNB, a Home Node-B, a relay node, or a device, or described using other terminology used in the art. BS 102 is generally a part of a radio access network that may include one or more controllers communicably coupled to BS 102.

The wireless communication system 100 may be compatible with any type of network that is capable of sending and receiving wireless communication signals. For example, the wireless communication system 100 is compatible with a wireless communication network, a cellular telephone network, a time division multiple access (TDMA) based network, a code division multiple access (CDMA) based network, an orthogonal frequency division multiple access (OFDMA) based network, an LTE network, a 3GPP-based network, a 3GPP 5G network, a satellite communications network, a high-altitude platform network, and/or other communications networks.

In some embodiments of the present disclosure, the wireless communication system 100 is compatible with the 5G NR of the 3GPP protocol, wherein BS (s) 102 transmit data using an orthogonal frequency division multiplexing (OFDM) modulation scheme on the downlink (DL) and UE (s) 101 transmit data on the uplink (UL) using a discrete Fourier transform-spread-orthogonal frequency division multiplexing (DFT-S-OFDM) or cyclic prefix-OFDM (CP-OFDM) scheme. More generally, however, the wireless communication system 100 may implement some other open or proprietary communication protocols, for example, WiMAX, among other protocols.

In some embodiments of the present disclosure, BS (s) 102 may communicate using other communication protocols, such as the IEEE 802.11 family of wireless communication protocols. Further, in some embodiments of the present disclosure, BS (s) 102 may communicate over licensed spectrums, whereas in other embodiments, BS (s) 102 may communicate over unlicensed spectrums. The present disclosure is not intended to be limited to the implementation of any particular wireless communication system architecture or protocol. In yet some embodiments of the present disclosure, BS (s) 102 may communicate with UE (s) 101 using the 3GPP 5G protocols.

In NR, accommodating multiple uncoordinated UEs in an unlicensed spectrum requires channel access procedures defined for NR. Following a successful channel access procedure performed by a communicating node, the channel can be used by the communicating node during a period until the end of the period. Such a period may be referred to as a COT. During a COT, one or more transmissions may be exchanged between the communicating nodes, wherein a transmission may be a downlink transmission or an uplink transmission.

Dynamic channel access procedures are usually used by a BS or a UE to access a channel in an unlicensed spectrum. Dynamic channel access procedures may be based on listen-before-talk (LBT) , where a transmitter listens to potential transmission activity on a channel prior to transmitting and applies a random back-off time in some cases. Two main types of dynamic channel access procedures may be defined in NR. One is Type-1 dynamic channel access procedure, which is also referred to as LBT type 1 or LBT cat4. The other is Type-2 dynamic channel access procedure, which is also referred to as LBT type 2.

Type-1 dynamic channel access procedure may be used to initiate data transmission at the beginning of a COT. The initiator for the Type-1 dynamic channel access procedure may be either a BS or a UE. The Type-1 dynamic channel access procedure may be summarized as follows.

First, the initiator listens and waits until a channel (e.g., a frequency channel) is available during at least one period referred to as a defer duration. The defer duration may consist of 16 μs and a number (e.g., "m_p" in the following Table 1 or Table 2, which will be illustrated below) of 9 μs slots. As shown in Table 1 and Table 2, a value of "m_p" depends on a value of channel access priority class (CAPC) (represented as "p" ) . Accordingly, the defer duration depends on the value of CAPC as shown in the following Table 1 or Table 2. A channel is declared to be available if the received energy during at least 4 μs of each 9 μs slot is below a threshold.

Once the channel has been declared available during the defer duration, the transmitter starts a random back-off procedure during which it will wait a random period of time.

The UE starts the random back-off procedure by initializing a back-off timer with a random number within a contention window (CW) . The random number is drawn from a uniform distribution [0, CW] and represents that the channel must be available for a timer duration (e.g., denoted by the random number multiplying 9 μs) before transmission can take place. The value of "CW" may be selected from "allowed CW_p sizes" (the minimum value is represented as CW_min, p, and the maximum value is represented as CW_max, p) in the following Table 1 or Table 2, which depends on a value of CAPC.

The back-off timer is decreased by one for each sensing slot duration (e.g., 9 μs) the channel is sensed to be idle; whenever the channel is sensed to be busy, the back-off timer is put on hold until the channel has been idle for a defer duration.

Once the back-off timer has expired (e.g., the back-off timer is decreased to be 0) , the random back-off procedure is completed, and the transmitter has acquired the channel and can use it for transmission up to a maximum channel occupancy time (MCOT) (e.g., T_mcot, p in the following Table 1 or T_ulmcot, p in the following Table 2, which depends on a value of CAPC) .

The following Table 1 and Table 2 illustrate exemplary CAPC for DL and CAPC for UL, respectively, and corresponding values of m_p, CW_min, p, CW_max, p, T_mcot, p, T_ulmcot, p, and allowed CW_p sizes. Table 1 is the same as Table 4.1.1-1 in TS 37.213 and Table 2 is the same as Table 4.2.1-1 in TS 37.213. When a BS intends to initiate a channel occupancy for DL transmission, it may determine a CAPC value before performing a Type-1 channel access procedure, and then determine the corresponding values (e.g., m_p, CW_min, p, CW_max, p, T_mcot, p, and allowed CW_p sizes) used in the Type-1 channel access procedure according to Table 1. When a UE intends to initiate a channel occupancy for UL transmission, it may determine a CAPC value before performing a Type-1 channel access procedure, and then determine the corresponding values (e.g., m_p, CW_min, p, CW_max, p, T_ulmcot, p, and allowed CW_p sizes) used in the Type-1 channel access procedure according to Table 2.

Table 1: Channel Access Priority Class for DL

Table 2: Channel Access Priority Class for UL

The size of the contention window may be adjusted based on hybrid automatic repeat request (HARQ) reports received from the transmitter during a reference interval, which covers the beginning of the COT. For each received HARQ report, the contention window is (approximately) doubled up to the limit CW_max, p if a negative HARQ report (e.g., non-acknowledgement (NACK) ) is received. For a positive HARQ report (e.g., acknowledgement (ACK) ) , the contention window is reset to its minimum value, i.e., CW=CW_min, p.

Type-2 dynamic channel access procedure may be used for COT sharing and transmission of discovery bursts. Depending on a duration of a gap (also referred to as "COT sharing gap" ) in the COT, Type-2 dynamic channel access procedure may be further classified into the following three procedures, wherein which procedure to be used may be determined depending on the duration of the gap between two transmission bursts.

● Type 2A dynamic channel access procedure (also referred to as LBT cat2 or LBT type 2A) : which is used when the gap is 25 μs or more for transmission of the discovery bursts.

● Type 2B dynamic channel access procedure (also referred to as LBT type 2B) : which is used when the gap is 16 μs.

● Type 2C dynamic channel access procedure (also referred to as LBT type 2C) : which is used when the gap is 16 μs or less after the preceding transmission burst.

For Type 2C dynamic channel access procedure, no idle sensing is required between the transmission bursts. In such scenario, the duration of a transmission burst is limited to at most 584 μs. Such a short transmission burst may carry small amount of user data, uplink control information (UCI) such as HARQ status reports and channel state information (CSI) reports.

Type 2A dynamic channel access procedure and Type 2B dynamic channel access procedure may be similar to Type-1 dynamic channel access procedure but without the random back-off. That is, in Type 2A dynamic channel access procedure and Type 2B dynamic channel access procedure, if a channel is detected to be idle in the gap, it is declared to be available; if it is detected to be busy, the COT sharing has failed and the transmission cannot occur using COT sharing in this COT. If the COT sharing gap is 16 μs, Type 2B dynamic channel access procedure may be used and the channel must be detected to be idle in the 16 μs gap prior to the next transmission burst. If the COT sharing gap is 25 μs or longer, Type 2A dynamic channel access procedure may be used and the channel must be detected to be idle during at least 25 μs immediately preceding the next transmission burst.

The above embodiments provide several dynamic channel access procedures in an unlicensed spectrum for NR. These dynamic channel access procedures may also apply for sidelink transmissions in an unlicensed spectrum.

Sidelink synchronization information is carried in an S-SSB that consists of physical sidelink broadcast channel (PSBCH) , sidelink primary synchronization signal (S-PSS) and sidelink secondary synchronization signal (S-SSS) . FIG. 2 illustrates an exemplary S-SSB slot according to some embodiments of the present disclosure. In the embodiments of FIG. 2, a normal cyclic prefix (CP) is used.

Referring to FIG. 2, an S-SSB occupies one slot in the time domain and occupies 11 resource blocks (RBs) in the frequency domain. Each RB spans 12 subcarriers, thus the S-SSB bandwidth is 132 (11 × 12) subcarriers. In the example of FIG. 2, the S-SSB slot may include 14 OFDM symbols in total, e.g., symbol #0 to symbol #13. The S-PSS is transmitted repeatedly on the second and third symbols in the S-SSB slot, e.g., symbol #1 and symbol #2. The S-SSS is transmitted repeatedly on the fourth and fifth symbols in the S-SSB slot, e.g., symbol #3 and symbol #4. The S-PSS and the S-SSS occupy 127 subcarriers in the frequency domain, which are from the third subcarrier relative to the start of the S-SSB bandwidth up to the 129th subcarrier.

The S-PSS and the S-SSS are jointly referred to as the sidelink synchronization signal (SLSS) . The SLSS is used for time and frequency synchronization. By detecting the SLSS sent by a synchronization reference UE (also referred to as a SyncRef UE) , a UE is able to synchronize to the SyncRef UE and estimate the beginning of the frame and carrier frequency offsets.

The S-PSS may be generated from the maximum length sequences (m-sequences) that use the same design (i.e., generator polynomials, initial values and cyclic shifts, etc. ) which is used for generating the m-sequences in the primary synchronization signal (PSS) in the 3GPP documents. In NR Uu, there are three candidate sequences for PSS. However, only two candidate sequences are used for S-PSS.

The S-SSS may be generated from the Gold sequences that use the same design (i.e., generator polynomials, initial values and cyclic shifts, etc. ) which is utilized for generating the Gold sequences for the secondary synchronization signal (SSS) in the 3GPP documents. This results in 336 candidate sequences for S-SSS like for the SSS in NR Uu.

For the transmission of SLSS within an S-SSB, a SyncRef UE may select an S-PSS and an S-SSS out of the candidate sequences based on an SLSS identifier (ID) . The SLSS ID represents an identifier of the SyncRef UE and conveys a priority of the SyncRef UE as in LTE vehicle-to-everything (V2X) . Each SLSS ID corresponds to a unique combination of an S-PSS and an S-SSS out of the 2 S-PSS candidate sequences and the 336 S-SSS candidate sequences.

The main purpose of the PSBCH is to provide system-wide information and synchronization information that is required by a UE for establishing a sidelink connection. In the example of FIG. 2, the PSBCH is transmitted on the first symbol (e.g., symbol #0) and the eight symbols (e.g., symbol #5 to symbol #12) after the S-SSS in the S-SSB slot. In the case that an extended CP is used, the PSBCH is transmitted on the first symbol and the six symbols after the S-SSS in the S-SSB slot. The PSBCH occupies 132 subcarriers in the frequency domain. The PSBCH in the first symbol of the S-SSB slot is used for automatic gain control (AGC) . The last symbol, e.g., symbol #13, in the S-SSB slot is used as a guard symbol.

The structure of S-SSB slot in FIG. 2 is only for illustrative purpose. It is contemplated that along with developments of network architectures and new service scenarios, the S-SSB may have other structures (for example, the S-SSB may include 4 OFDM symbols or 6 OFDM symbols in the time domain) , which should not affect the principle of the present application.

In some embodiments, S-SSBs may be organized with a fixed periodicity. Such fixed periodicity may be referred to as an S-SSB period. There are one or more S-SSB occasions within an S-SSB period. A distribution of S-SSB occasions in the time domain may be determined based on at least one of the following parameters:

● S-SSB period, which indicates a length of an S-SSB period;

● T_Offset, which indicates a time offset between the starting of the S-SSB period and the first S-SSB occasion within the S-SSB period;

● T_Interval, which indicates a time interval between two adjacent S-SSB occasions within the S-SSB period: for example, T_interval may be defined in unit of slots and within a range of INTEGER (0…639) (i.e., a value of T_interval may be an integer between 0 and 639) ; or

● N, which indicates the number of S-SSB occasions within the S-SSB period.

In some embodiments, a UE may obtain a configuration including at least one of: S-SSB period, T_Offset, T_Interval, or N, and thus a distribution of S-SSB occasions in the time domain may be determined by the UE.

FIG. 3 illustrates an exemplary distribution of S-SSB occasions in the time domain according to some embodiments of the present disclosure.

FIG. 3 illustrates an S-SSB period as an example. Resource pool is also illustrated in the figure. A resource pool may define the overall time and frequency domain resources that can be used for SL transmission within a carrier. The SL transmission in the embodiments of the present application may refer to at least one of physical sidelink control channel (PSCCH) transmission or physical sidelink shared channel (PSSCH) transmission. In the time domain, the resource pool consists of a set of slots repeated over a resource pool period. Although the set of slots within the resource pool are logically organized in a consecutive way, actually the slots within the resource pool may be discretely distributed in the time domain.

As shown in FIG. 3, in the S-SSB period, N S-SSB occasions are included, which are labeled by S-SSB occasion #0, S-SSB occasion #1, S-SSB occasion #2, …, S-SSB occasion #N-1, respectively.

A length of the S-SSB period is marked as "S-SSB Period" in FIG. 3. There is a time offset between the starting of the S-SSB period and the first S-SSB occasion within the S-SSB period, which is marked as "T_Offset" in FIG. 3. There is a time interval between two adjacent S-SSB occasions (e.g., between the ending point of the former S-SSB occasion and the starting point of the latter S-SSB occasion) , which is marked as "T_Interval" in FIG. 3.

In 3GPP Release 16 (Rel-16) or Release 17 (Rel-17) , the S-SSB period may include 160ms, as specified in NR V2X. However, along with developments of network architectures and new service scenarios, the S-SSB period may have other values, which should not affect the principle of the disclosure.

In 3GPP Rel-16 or Rel-17, the S-SSB occasion (s) are excluded from a resource pool in the time domain. For example, the distribution of S-SSB occasion (s) in 3GPP Rel-16 or Rel-17 (also referred to as legacy S-SSB occasion (s) ) may be denoted by at least one of the following parameters: S-SSB period, T_Offset, T_Interval, or N as stated above.

The S-SSB transmissions in unlicensed spectrum may be subject to a channel access procedure as stated above. That is, transmitting S-SSB on a target S-SSB occasion requires a successful channel access procedure prior to the target S-SSB occasion. The channel access opportunities for transmitting S-SSB in unlicensed spectrum may be reduced due to resource collision or LBT failure. To compensate for the case that some S-SSB occasions are unavailable for transmitting S-SSB, in 3GPP Release 18 (Rel-18) , additional S-SSB occasion (s) are introduced for transmitting S-SSB in unlicensed spectrum to achieve the desired amount of channel access opportunities. The additional S-SSB occasion (s) may also be excluded from the resource pool in the time domain.

As a feature in unlicensed spectra, a COT-based transmission may be applied in sidelink. For example, for SL transmissions, a COT may be initiated by one UE (referred to as COT initiating UE) and shared to one or more other UEs (referred to as COT responding UEs) . The COT may be initiated by Type-1 dynamic channel access procedure. During the COT, one or more transmission bursts can be exchanged between the COT initiating UE and the one or more COT responding UEs, where a transmission burst corresponds to one direction of an SL transmission.

For NR Uu in unlicensed spectra, the length of MCOT may be up to 10ms. Such MCOT may also be applied for the sidelink. Accordingly, there may be a case where one or more S-SSB occasions overlap with a COT. An S-SSB occasion overlapping with a COT may refer to that the COT includes the S-SSB occasion or the S-SSB occasion is included in or within the COT.

FIG. 4 illustrates exemplary locations of S-SSB occasion (s) and a COT for sidelink transmission in an RB set according to some embodiments of the present application.

Referring to FIG. 4, in an RB set (e.g., RB set #j) , a COT for SL transmission may start from slot #i and has a length of 4 slots (e.g., including slot #i, slot #i+1, slot #i+2, and slot #i+3) . Each slot may include 14 OFDM symbols (e.g., from symbol 0 to symbol 13) . Within the COT, slot #i+2 is an S-SSB occasion, which may be either a legacy S-SSB occasion (defined in Rel-16 or Rel-17) or an additional S-SSB occasion (introduced in Rel-18) . Each of the other slots in the COT may be used for an SL transmission, which includes at least one of a PSCCH transmission and a PSSCH transmission.

The COT may be initiated by an LBT type 1 procedure before slot #i. Within the COT, a UE may perform SL transmissions in one or more slots. In the case that the UE performs SL transmissions in two or more consecutive slots (e.g., slot #i and slot #i+1, the UE may not need to perform LBT or may perform an LBT type 2 with a short duration (e.g., less than 16 μs) between the slots. That is, there may be no gap or may be a short gap between SL transmissions in two consecutive slots. For different kinds of transmissions in two consecutive slots, there may be a gap for LBT between the transmissions. For example, before the S-SSB transmission in slot #i+2 or the SL transmission in slot #i+3, there may exist a gap to perform LBT.

Although FIG. 4 illustrates that one S-SSB occasion overlaps with a COT, there may be cases where more than one S-SSB occasion overlaps with a COT. In addition, more S-SSB occasions typically result in more time-domain resources required. In such case, the COT-based sidelink transmission may be frequently interrupted by the S-SSB occasions. Then, how to reduce the risk of COT losing interrupted by other transmissions (e.g., S-SSB transmission) is critical to reduce performance loss for SL transmission over unlicensed spectra.

Given the above, embodiments of the present application provide solutions regarding how to reduce the COT losing for COT-based sidelink transmission in the case where a COT overlaps with one or more S-SSB occasions (regardless of legacy S-SSB occasion (s) or additional S-SSB occasion (s) ) . For example, embodiments of the present application provide configurations, signaling, and UE behaviors for reducing COT losing for COT-based sidelink transmission interrupted by other transmissions. More details will be described in the following text in combination with the appended drawings.

To solve the aforementioned technical problems, some embodiments of the present application provide solutions to decrease the number of interruptions to a COT caused by S-SSB occasion (s) . Such solutions may be implemented by adjusting the distribution of S-SSB occasion (s) within an S-SSB period. For example, the following embodiments 1 and 2 provide two solutions for adjusting the distribution of S-SSB occasion (s) within an S-SSB period, respectively.

Embodiment 1

In embodiment 1, to decrease the number of interruptions to a COT caused by S-SSB (s) , the time interval between two adjacent S-SSB occasions within an S-SSB period may be increased, so as to decrease the possibility that more than one S-SSB occasion overlaps with a COT.

In embodiment 1, a UE may obtain a configuration (e.g., configuration #1) indicating a distribution of S-SSB occasions within an S-SSB period. Configuration #1 may indicate a time interval (e.g., denoted by T_Interval) between two adjacent S-SSB occasions within the S-SSB period, wherein the time interval is greater than or equal to a minimum time interval which is greater than zero. The minimum time interval (e.g., denoted by T_Interval ^min) may be (pre-) configured or (pre-) defined in 3GPP standard documents. As an example, the minimum time interval may be greater than a maximum channel occupancy time (MCOT) . As another example, the minimum time interval may be determined based on subcarrier spacing (SCS) or FR.

In some embodiments, the UE may obtain configuration #1 based on configuration (i.e., configuration #1 is configured for the UE) . Configuration #1 being configured for the UE refers to that: configuration #1 may be transmitted by e.g. a BS (e.g., BS 102 as shown in FIG. 1) to the UE via at least one of: a SIB message, a MIB message, an RRC signaling, a MAC CE, or DCI, such that the UE may receive configuration #1 from the BS.

In some embodiments, the UE may obtain configuration #1 based on pre-configuration or (pre-) definition (i.e., configuration #1 is pre-configured or (pre-) defined for the UE) . Configuration #1 being pre-configured or (pre-) defined for the UE refers to that: configuration #1 may be hard-wired into the UE or stored on a subscriber identity module (SIM) or universal subscriber identity module (USIM) card for the UE, such that the UE may obtain configuration #1 within the UE.

In some embodiments, configuration #1 may be configured, pre-configured, or (pre-) defined per FR, per BWP, per carrier, per RB set, or per RP.

In some embodiments, configuration #1 may also include at least one of the following parameters: S-SSB period, T_Offset, or N, as stated above.

Configuration #1 may be applied for only legacy S-SSB occasion (s) , only additional S-SSB occasion (s) , or both legacy S-SSB occasion (s) and additional S-SSB occasion (s) . In the case that configuration #1 is applied for both legacy S-SSB occasion (s) and additional S-SSB occasion (s) , legacy S-SSB occasion (s) and additional S-SSB occasion (s) can be configured with the same group of parameters.

Embodiment 2

In embodiment 2, to decrease the number of interruptions to a COT caused by S-SSB (s) , partial S-SSB occasions within an S-SSB period may be organized in a consecutive way, so as to increase a length of physically consecutive slots for a resource pool. Then, a COT may be selected within the slots of the resource pool, which are physically organized in a consecutive way.

In embodiment 2, a number of consecutive S-SSB occasion (s) (physically consecutive in the time domain) within an S-SSB period may be referred to as an S-SSB group, an S-SSB cluster, an S-SSB window, or the like.

A UE may obtain a configuration (e.g., configuration #2) indicating a distribution of S-SSB occasions within an S-SSB period, which may indicate at least one of the followings:

● a number of consecutive S-SSB occasion (s) included in an S-SSB group within the S-SSB period;

● a time offset between a starting of the S-SSB period and a starting of the first S-SSB group within the S-SSB period;

● a time interval between two adjacent S-SSB groups within the S-SSB period; or

● a number of S-SSB groups within the S-SSB period.

Configuration #2 may be configured, pre-configured, or (pre-) defined for the UE. The aforementioned definitions regarding "configured, " "pre-configured, " and " (pre-) defined" may also apply here.

In some embodiments, configuration #2 may be configured, pre-configured, or (pre-) defined per FR, per BWP, per carrier, per RB set, or per RP.

In some embodiments, legacy S-SSB occasion (s) and additional S-SSB occasion (s) may be organized in the same manner. In such embodiments, configuration #2 may be applied for both legacy S-SSB occasion (s) and additional S-SSB occasion (s) . In other words, legacy S-SSB occasion (s) and additional S-SSB occasion (s) can be configured with the same group of parameters.

In some other embodiments, legacy S-SSB occasion (s) may be organized following the method defined in Rel-16 or Rel-17 (e.g., organized as the example illustrated in FIG. 3) , while additional S-SSB occasion (s) may be organized in the aforementioned grouping manner. In such embodiments, configuration #2 may be applied for only additional S-SSB occasion (s) .

FIG. 5 illustrates an exemplary distribution of S-SSB occasions in the time domain, which are organized in the aforementioned grouping manner, according to some embodiments of the present disclosure.

FIG. 5 illustrates an S-SSB period as an example. A length of the S-SSB period is marked as "S-SSB Period" in FIG. 5. The S-SSB period includes N1 S-SSB groups, which are S-SSB group #0, S-SSB group #1, …, and S-SSB group #N1-1. Each S-SSB group includes N2 consecutive S-SSB occasions, which are S-SSB occasion #0, S-SSB occasion #1, …, and S-SSB occasion #N2-1.

There is a time offset between the starting of the S-SSB period and a starting of the first S-SSB group within the S-SSB period, which is marked as "T_OffsetGroup" in FIG. 5. There is a time interval between two adjacent S-SSB groups (e.g., between the ending point of the former S-SSB group and the starting point of the latter S-SSB group) , which is marked as "T_{IntervalGroup}" in FIG. 5. Accordingly, the distribution of S-SSB occasions in the example of FIG. 5 may be defined by a configuration (e.g., configuration #2 as described above) which includes at least one of: the parameter "S-SSB Period, " the parameter "T_OffsetGroup, " the parameter "T_{IntervalGroup}, " the parameter "N1, " or the parameter "N2. "

The above embodiments provide solutions for adjusting the distribution of S-SSB occasion (s) within an S-SSB period to reduce the possibility that S-SSB occasion (s) overlaps with a COT. The following embodiments provide solutions regarding configurations and UE behaviors for reducing COT losing for COT-based sidelink transmission in the case where S-SSB occasion (s) overlaps with a COT. It is contemplated that these solutions can be implemented for any distribution of S-SSB occasions, which may include but are not limited to the distribution described in the aforementioned embodiment 1 or 2.

FIG. 6 illustrates a flowchart of an exemplary method 600 for transmission in an unlicensed spectrum according to some embodiments of the present application. The method 600 illustrated in FIG. 6 may be performed by a UE (e.g., UE 101a or UE 101b in FIG. 1) or other apparatus with the like functions. For example, the UE may be a Tx UE which attempts to transmit S-SSB on an S-SSB occasion or attempts to transmit a COT-based SL transmission.

As shown in FIG. 6, in step 601, the UE may determine an operation with respect to an S-SSB occasion according to one of the followings: whether it can be determined that the S-SSB occasion overlaps with a COT for an SL transmission; or whether there is other RAT in an unlicensed spectrum associated with the S-SSB occasion. In step 603, the UE may perform the operation with respect to the S-SSB occasion based on the determination.

The operation determined and performed by the UE may be different in different cases, several examples of which will be described in detail below.

Case 1

In case 1, the UE may attempt to transmit S-SSB on an S-SSB occasion, and the UE may determine that the S-SSB occasion overlaps with a COT for an SL transmission, i.e., the S-SSB occasion is determined to overlap with the COT.

In some embodiments, the UE may determine whether the S-SSB occasion overlaps with the COT based on at least one of the followings: a distribution of S-SSB occasions within an S-SSB period or information associated with the COT.

In some examples, the UE may obtain a configuration indicating the distribution of S-SSB occasions within an S-SSB period. As an example, the configuration may be configuration #1 or configuration #2 as described in embodiment 1 or 2. As another example, the configuration may be a configuration as defined in existing 3GPP specifications, e.g., including at least one of the parameters illustrated in FIG. 3. Then, the UE may determine the distribution of S-SSB occasions within an S-SSB period based on the configuration.

In some examples, the UE may obtain the information associated with the COT. For example, the UE may be a COT initiating UE which initiates the COT or may be a COT responding UE which obtains the information associated with the COT from the COT initiating UE. The COT initiating UE or the COT responding UE may be referred to as an inside-COT UE. The information associated with the COT may include at least one of: a starting slot of the COT, a duration of the COT, or a remaining duration of the COT.

In response to that the S-SSB occasion is determined to overlap with the COT, the UE may perform a channel access to the S-SSB occasion by using a first S-SSB access configuration for an inside-COT UE. That is, the operation determined in step 601 and performed in step 603 may include performing a channel access to the S-SSB occasion by using the first S-SSB access configuration.

The UE may obtain the first S-SSB access configuration based on configuration, pre-configuration, or (pre-) definition, i.e., the first S-SSB access configuration may be configured, pre-configured, or (pre-) defined for the UE. The aforementioned definitions regarding "configured, " "pre-configured, " and " (pre-) defined" may also apply here.

The first S-SSB access configuration may include at least one of: a first CPE length; or an LBT type 2 (e.g., LBT type 2A, LBT type 2B, or LBT type 2C) having a first duration. The first CPE length may be different from a second CPE length (which will be illustrated in detail in the following case 2) for an outside-COT UE (e.g., when a UE does not obtain information associated with a COT, the UE is referred to as an outside-COT UE to the COT) . In some embodiments, the first CPE length may be longer than the second CPE length. In some embodiments, the first duration may be short such that an earlier channel access opportunity to the S-SSB occasion may be obtained. For example, the first duration may be less than 16 μs.

In the embodiments of the present application, for the case that a CPE length larger than 0 is configured, pre-configured, or (pre-) defined for a UE, the UE may transmit a CPE from a CPE starting position until a starting boundary of a target transmission (e.g., S-SSB) in response to an LBT procedure to the target transmission (e.g., S-SSB) being successful. The CPE may contain a repetition of CP of the first symbol within the target transmission (e.g., S-SSB) . The length of CPE (i.e., a CPE length) indicates a time offset between the CPE starting position and the starting boundary of the target transmission (e.g., S-SSB) .

FIG. 7 illustrates an example of a CPE and a target S-SSB occasion according to some embodiments of the present application.

Referring to FIG. 7, the target S-SSB occasion may locate within an S-SSB slot in the time domain. The S-SSB slot may include 14 OFDM symbols, e.g., from symbol #0 to symbol #13. A CPE length, e.g., denoted by T_CPE in FIG. 7, may be configured, pre-configured, or (pre-) defined for a UE.

The UE may transmit a CPE from a CPE starting position (e.g., P1 in FIG. 7) until a starting boundary (e.g., P2 in FIG. 7) of the target S-SSB occasion in response to an LBT procedure to the target S-SSB occasion being successful. The CPE may contain a repetition of CP of symbol #0 within the target S-SSB occasion. The length of the CPE is equal to T_CPE.

When both the first CPE length and LBT type 2 are indicated by the first S-SSB access configuration, performing a channel access to the S-SSB occasion by using the first S-SSB access configuration may include performing an LBT type 2 as indicated in the first S-SSB access configuration before the S-SSB occasion, and transmitting a CPE with the first CPE length (from a CPE starting position to a starting boundary of the S-SSB occasion) in response to the LBT type 2 to the S-SSB occasion being successful.

The technical solution described with respect to case 1 may provide an earlier channel access opportunity to the S-SSB occasion for the COT initiating UE or COT responding UE, thereby avoiding COT losing caused by the S-SSB occasion being accessed by another UE.

Case 2

In case 2, the UE may attempt to transmit S-SSB on an S-SSB occasion, and the S-SSB occasion is not determined to overlap with any COT for SL transmission by the UE.

In an example of case 2, the UE may not obtain information associated with any COT for SL transmission overlapping with the S-SSB occasion. Accordingly, the UE cannot determine whether the S-SSB occasion overlaps with any COT.

In response to that the S-SSB occasion is not determined to overlap with any COT, the UE may perform a channel access to the S-SSB occasion by using a second S-SSB access configuration for an outside-COT UE. That is, the operation determined in step 601 and performed in step 603 may include performing a channel access to the S-SSB occasion by using the second S-SSB access configuration.

The UE may obtain the second S-SSB access configuration based on configuration, pre-configuration, or (pre-) definition, i.e., the second S-SSB access configuration may be configured, pre-configured, or (pre-) defined for the UE. The aforementioned definitions regarding "configured, " "pre-configured, " and " (pre-) defined" may also apply here.

The second S-SSB access configuration may indicate at least one of: a second CPE length which is different from the CPE length for an inside-COT UE (e.g., the first CPE length as described above with respect to case 1) , or an LBT type 1. For example, the second CPE may be shorter than the first CPE length.

When both the second CPE length and LBT type 1 are indicated by the second S-SSB access configuration, performing a channel access to the S-SSB occasion by using the second S-SSB access configuration may include performing an LBT type 1 as indicated in the second S-SSB access configuration before the S-SSB occasion, and transmitting a CPE with the second CPE length (from a CPE starting position to a starting boundary of the S-SSB occasion) in response to the LBT type 1 to the S-SSB occasion being successful.

According to the technical solution described with respect to case 2, when a UE cannot determine whether the S-SSB occasion overlaps with a COT, an earlier channel access opportunity to the S-SSB occasion may be provided for an COT initiating UE or COT responding UE other than the UE in the case where the S-SSB occasion is actually within a COT, thereby avoiding COT losing caused by S-SSB occasion being accessed by the UE.

Case 3

In case 3, the UE may attempt to transmit S-SSB on an S-SSB occasion, and the UE may determine that there is no other RAT in the unlicensed spectrum (e.g., an RB set) associated with the S-SSB occasion, i.e., no other RAT is determined to be in the unlicensed spectrum.

For example, whether there is other RAT in the unlicensed spectrum may be determined based on a higher layer (e.g., a layer higher than the physical layer) parameter, e.g., absenceOfAnyOtherTechnology as specified in 3GPP standard documents. In the case that the higher layer parameter indicates that there is no other RAT, the UE may determine that there is no other RAT in the unlicensed spectrum. In the case that the higher layer parameter indicates that there is other RAT (s) , the UE may determine that there is other RAT (s) in the unlicensed spectrum.

In response to that no other RAT is determined to be in the unlicensed spectrum, the UE may perform a channel access to the S-SSB occasion by using a third S-SSB access configuration for the case that there is no other RAT in the unlicensed spectrum. That is, the operation determined in step 601 and performed in step 603 may include performing a channel access to the S-SSB occasion by using the third S-SSB access configuration.

The UE may obtain the third S-SSB access configuration based on configuration, pre-configuration, or (pre-) definition, i.e., the third S-SSB access configuration may be configured, pre-configured, or (pre-) defined for the UE. The aforementioned definitions regarding "configured, " "pre-configured, " and " (pre-) defined" may also apply here.

The third S-SSB access configuration may indicate at least one of: a third CPE length; or an LBT type. In some embodiments, the third CPE length may be short. For example, the third CPE length may be less than 16 μs or may be equal to zero. The LBT type may be LBT type 1 or LBT type 2.

In some examples of case 3, when the third CPE length is equal to zero, performing a channel access to the S-SSB occasion by using the third S-SSB access configuration may include performing an LBT type as indicated in the third S-SSB access configuration and not transmitting a CPE before the S-SSB occasion.

According to the technical solution described with respect to case 3, when there is no other RAT, a COT initiating UE or COT responding UE may have a higher channel access opportunity for the slots within the COT than other UE (s) .

Case 4

In case 4, the UE may attempt to transmit an SL transmission within a COT, which may include an S-SSB occasion, and the UE does not transmit S-SSB on the S-SSB occasion. For example, the UE may be a COT initiating UE which initiates the COT or may be a COT responding UE to which the COT is shared.

In case 4, for example, as described in case 1, the UE may determine whether an S-SSB occasion overlaps with the COT based on at least one of the followings: a distribution of S-SSB occasions within an S-SSB period or information associated with the COT.

In response to that the S-SSB occasion is determined to overlap with the COT, the UE may perform sensing on the first one or more symbols of the S-SSB occasion, and determine whether there is a transmission on the first one or more symbols of the S-SSB occasion.

In response to determining that there is no transmission on the first one or more symbols of the S-SSB occasion (i.e., no transmission is detected on the first one or more symbols of the S-SSB occasion) , the UE may perform transmission on remaining symbol (s) of the S-SSB occasion. That is, the operation determined in step 601 and performed in step 603 may include performing transmission on remaining symbol (s) of the S-SSB occasion. The transmission on the remaining symbol (s) may be different from an S-SSB or SL transmission. For example, the UE may transmit dummy data on the remaining symbol (s) of the S-SSB occasion.

In response to determining that there is a transmission on the first one or more symbols of the S-SSB occasion, the UE may perform nothing on the S-SSB occasion. That is, the operation determined in step 601 and performed in step 603 may include performing nothing on the S-SSB occasion.

The solution described with respect to case 4 has no impact on S-SSB transmission. When there is no S-SSB transmission on the S-SSB occasion within the COT, the COT initiating UE or COT responding UE performing transmission on the remaining symbols of the S-SSB occasion can avoid COT losing for the COT initiating UE or COT responding UE.

According to some embodiments of the present application, when a UE attempts to receive S-SSB, the UE may detect each S-SSB occasion within the S-SSB period.

According to some embodiments of the present application, a BS may transmit configuration information for transmission over SL in an unlicensed spectrum to one or more UEs (e.g., the UE described in any of the above embodiments) . The configuration information may indicate at least one of the followings:

● a first configuration indicating a distribution of S-SSB occasions within an S-SSB period: for example, configuration #1 or configuration #2 as described above in embodiment 1 or 2;

● a first S-SSB access configuration for an inside-COT UE: for example, the first S-SSB access configuration as described above with respect to case 1;

● a second S-SSB access configuration for an outside-COT UE: for example, the second S-SSB access configuration as described above with respect to case 2; or

● a third S-SSB access configuration for the case that there is no other RAT in the unlicensed spectrum: for example, the third S-SSB access configuration as described above with respect to case 3.

In some embodiments, the configuration information may be configured per FR, per BWP, per carrier, per RB set, or per RP.

In some embodiments, the BS may transmit the configuration information via at least one of: a MIB message, a SIB message, an RRC signaling, a MAC CE, or DCI.

FIG. 8 illustrates a simplified block diagram of an exemplary apparatus 800 for transmission in an unlicensed spectrum according to some embodiments of the present application. In some embodiments, the apparatus 800 may be or include at least part of a UE (e.g., UE 101a or UE 101b in FIG. 1) . In some other embodiments, the apparatus 800 may be or include at least part of a BS (e.g., BS 102 in FIG. 1) .

Referring to FIG. 8, the apparatus 800 may include at least one transceiver 802 and at least one processor 806. The at least one transceiver 802 is coupled to the at least one processor 806.

Although in this figure, elements such as the transceiver 802 and the processor 806 are illustrated in the singular, the plural is contemplated unless a limitation to the singular is explicitly stated. In some embodiments of the present application, the transceiver 802 may be divided into two devices, such as receiving circuitry (or a receiver) and transmitting circuitry (or a transmitter) . In some embodiments of the present application, the apparatus 800 may further include an input device, a memory, and/or other components. The transceiver 802 and the processor 806 may be configured to perform any of the methods described herein (e.g., the methods described with respect to FIGS. 4-7 or other methods described in the embodiments of the present application) .

According to some embodiments of the present application, the apparatus 800 may be a UE (e.g., a Tx UE) , and the transceiver 802 and the processor 806 may be configured to perform operations of a UE in any of the methods as described with respect to FIGS. 4-7 or other methods described in the embodiments of the present application. For example, the processor 806 is configured to: determine an operation with respect to an S-SSB occasion according to one of the followings: whether it can be determined that the S-SSB occasion overlaps with a COT for an SL transmission; or whether there is other RAT in an unlicensed spectrum associated with the S-SSB occasion; and perform the operation with respect to the S-SSB occasion based on the determination.

According to some embodiments of the present application, the apparatus 800 may be a BS, and the transceiver 802 and the processor 806 may be configured to perform operations of a BS in any of the methods as described in the embodiments of the present application. For example, the processor 806 is configured to: transmit, via the transceiver 802, configuration information for transmission over SL in an unlicensed spectrum, wherein the configuration information includes one of the followings: a first configuration indicating a distribution of S-SSB occasions within an S-SSB period; a first S-SSB access configuration for an inside-COT UE, indicating a first CPE length or an LBT type 2 having a first duration; a second S-SSB access configuration for an outside-COT UE, indicating a second CPE length different from the first CPE length or an LBT type 1; or a third S-SSB access configuration for the case that there is no other RAT in the unlicensed spectrum, indicating a third CPE length or an LBT type

In some embodiments of the present application, the apparatus 800 may further include at least one non-transitory computer-readable medium. In some embodiments of the present disclosure, the non-transitory computer-readable medium may have stored thereon computer-executable instructions to cause the processor 806 to implement any of the methods as described above. For example, the computer-executable instructions, when executed, may cause the processor 806 to interact with the transceiver 802, so as to perform operations of the methods, e.g., as described with respect to FIGS. 4-7 or other methods described in the embodiments of the present application.

The method according to any of the embodiments of the present application can also be implemented on a programmed processor. However, the controllers, flowcharts, and modules may also be implemented on a general purpose or special purpose computer, a programmed microprocessor or microcontroller and peripheral integrated circuit elements, an integrated circuit, a hardware electronic or logic circuit such as a discrete element circuit, a programmable logic device, or the like. In general, any device on which resides a finite state machine capable of implementing the flowcharts shown in the figures may be used to implement the processor functions of this application. For example, an embodiment of the present application provides an apparatus for transmission in an unlicensed spectrum, including a processor and a memory. Computer programmable instructions for implementing a method for transmission in an unlicensed spectrum are stored in the memory, and the processor is configured to perform the computer programmable instructions to implement the method for transmission in an unlicensed spectrum. The method for transmission in an unlicensed spectrum may be any method as described in the present application.

An alternative embodiment preferably implements the methods according to embodiments of the present application in a non-transitory, computer-readable storage medium storing computer programmable instructions. The instructions are preferably executed by computer-executable components preferably integrated with a network security system. The non-transitory, computer-readable storage medium may be stored on any suitable computer readable media such as RAMs, ROMs, flash memory, EEPROMs, optical storage devices (CD or DVD) , hard drives, floppy drives, or any suitable device. The computer-executable component is preferably a processor but the instructions may alternatively or additionally be executed by any suitable dedicated hardware device. For example, an embodiment of the present application provides a non-transitory, computer-readable storage medium having computer programmable instructions stored therein. The computer programmable instructions are configured to implement a method for transmission in an unlicensed spectrum according to any embodiment of the present application.

While this application has been described with specific embodiments thereof, it is evident that many alternatives, modifications, and variations may be apparent to those skilled in the art. For example, various components of the embodiments may be interchanged, added, or substituted in the other embodiments. Also, all of the elements of each figure are not necessary for operation of the disclosed embodiments. For example, one of ordinary skill in the art of the disclosed embodiments would be enabled to make and use the teachings of the application by simply employing the elements of the independent claims. Accordingly, embodiments of the application as set forth herein are intended to be illustrative, not limiting. Various changes may be made without departing from the spirit and scope of the application.

In this disclosure, relational terms such as "first, " "second, " and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. The terms "comprises, " "comprising, " or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by "a, " "an, " or the like does not, without more constraints, preclude the existence of additional identical elements in the process, method, article, or apparatus that comprises the element. Also, the term "another" is defined as at least a second or more. The terms "including, " "having, " and the like, as used herein, are defined as "comprising. "

Claims

A user equipment (UE) , comprising:

a transceiver; and

a processor coupled to the transceiver and configured to:

determine an operation with respect to a sidelink (SL) synchronization signal block (S-SSB) occasion according to one of the followings:

whether it can be determined that the S-SSB occasion overlaps with a channel occupancy time (COT) for an SL transmission; or

whether there is other radio access technology (RAT) in an unlicensed spectrum associated with the S-SSB occasion; and

perform the operation with respect to the S-SSB occasion based on the determination.
The UE of Claim 1, wherein the processor is further configured to obtain a first configuration indicating a distribution of S-SSB occasions within an S-SSB period, wherein the first configuration indicates one of the followings:

a time interval between two adjacent S-SSB occasions within the S-SSB period, wherein the time interval is greater than or equal to a minimum time interval which is greater than zero;

a number of consecutive S-SSB occasion (s) included in an S-SSB group within the S-SSB period;

a time offset between a starting of the S-SSB period and a starting of the first S-SSB group within the S-SSB period;

a time interval between two adjacent S-SSB groups within the S-SSB period; or

a number of S-SSB groups within the S-SSB period.
The UE of Claim 2, wherein the first configuration is configured, pre-configured, pre-defined, or defined per frequency range (FR) , per bandwidth part (BWP) , per carrier, per resource block (RB) set, or per resource pool (RP) .
The UE of Claim 2, wherein the first configuration is received via at least one of: a master information block (MIB) message, a system information block (SIB) message, a radio resource control (RRC) signaling, a medium access control (MAC) control element (CE) , or downlink control information (DCI) .
The UE of Claim 1, wherein the processor is further configured to determine whether the S-SSB occasion overlaps with the COT based on one of the followings:

a distribution of S-SSB occasions within an S-SSB period; or

information associated with the COT.
The UE of Claim 1, wherein the processor is further configured to obtain one of the followings:

a first S-SSB access configuration for an inside-COT UE, indicating a first cyclic prefix extension (CPE) length or a listen before talk (LBT) type 2 having a first duration;

a second S-SSB access configuration for an outside-COT UE, indicating a second CPE length different from the first CPE length or an LBT type 1; or

a third S-SSB access configuration for the case that there is no other RAT in the unlicensed spectrum, indicating a third CPE length or an LBT type.
The UE of Claim 6, wherein:

in response to that the S-SSB occasion is determined to overlap with the COT, the operation includes performing a channel access to the S-SSB occasion by using the first S-SSB access configuration;

in response to that the S-SSB occasion is not determined to overlap with any COT, the operation includes performing a channel access to the S-SSB occasion by using the second S-SSB access configuration; or

in response to that no other RAT is determined to be in the unlicensed spectrum, the operation includes performing a channel access to the S-SSB occasion by using the third S-SSB access configuration.
The UE of Claim 1, wherein in response to that the S-SSB occasion is determined to overlap with the COT, the processor is further configured to determine whether there is a transmission on the first one or more symbols of the S-SSB occasion.
The UE of Claim 8, wherein in response to that no transmission is detected on the first one or more symbols of the S-SSB occasion, the operation includes performing transmission on remaining symbol (s) of the S-SSB occasion.
A base station (BS) , comprising:

a transceiver; and

a processor coupled to the transceiver and configured to transmit, via the transceiver, configuration information for transmission over sidelink (SL) in an unlicensed spectrum, wherein the configuration information includes one of the followings:

a first configuration indicating a distribution of SL synchronization signal block (S-SSB) occasions within an S-SSB period;

a first S-SSB access configuration for an inside-channel occupancy time (COT) UE, indicating a first cyclic prefix extension (CPE) length or a listen before talk (LBT) type 2 having a first duration ;

a second S-SSB access configuration for an outside-COT UE, indicating a second CPE length different from the first CPE length or an LBT type 1; or

a third S-SSB access configuration for the case that there is no other radio access technology (RAT) in the unlicensed spectrum, indicating a third CPE length or an LBT type.
The BS of Claim 10, wherein the configuration information is configured per frequency range (FR) , per bandwidth part (BWP) , per carrier, per resource block (RB) set, or per resource pool (RP) .
The BS of Claim 10, wherein the processor is configured to transmit the configuration information via at least one of: a master information block (MIB) message, a system information block (SIB) message, a radio resource control (RRC) signaling, a medium access control (MAC) control element (CE) , or downlink control information (DCI) .
The BS of Claim 10, wherein the first configuration indicates one of the followings:

a time interval between two adjacent S-SSB occasions within the S-SSB period, wherein the time interval is greater than or equal to a minimum time interval which is greater than zero;

a number of consecutive S-SSB occasion (s) included in an S-SSB group within the S-SSB period;

a time offset between a starting of the S-SSB period and a starting of the first S-SSB group within the S-SSB period;

a time interval between two adjacent S-SSB groups within the S-SSB period; or

a number of S-SSB groups within the S-SSB period.
A method performed by a user equipment (UE) , comprising:

determining an operation with respect to a sidelink (SL) synchronization signal block (S-SSB) occasion according to one of the followings:

whether it can be determined that the S-SSB occasion overlaps with a channel occupancy time (COT) for an SL transmission; or

whether there is other radio access technology (RAT) in an unlicensed spectrum associated with the S-SSB occasion; and

performing the operation with respect to the S-SSB occasion based on the determination.
The method of Claim 14, further comprising obtaining a first configuration indicating a distribution of S-SSB occasions within an S-SSB period, wherein the first configuration indicates one of the followings:

a time interval between two adjacent S-SSB occasions within the S-SSB period, wherein the time interval is greater than or equal to a minimum time interval which is greater than zero;

a number of consecutive S-SSB occasion (s) included in an S-SSB group within the S-SSB period;

a time offset between a starting of the S-SSB period and a starting of the first S-SSB group within the S-SSB period;

a time interval between two adjacent S-SSB groups within the S-SSB period; or

a number of S-SSB groups within the S-SSB period.