Method and apparatus for burst-based sidelink transmission

Abstract

Embodiments of the present disclosure relate to methods and devices for burst-based sidelink transmission. According to embodiments of the present disclosure, a method for wireless communication includes performing a first Type 1 channel access procedure for a sidelink transmission on a carrier starting from a first candidate starting symbol within a first slot, wherein the first candidate starting symbol is in a set of candidate starting symbols for the sidelink transmission, determining a channel occupancy time (COT) in response to the first Type 1 channel access procedure being successful, and performing the sidelink transmission on the carrier starting from the first candidate starting symbol within the first slot for the duration of the COT, wherein the sidelink transmission is continuous in time domain without any gap.

Description

TECHNICAL FIELD

[0001] Embodiments of the present disclosure relate to wireless communication technology, and more particularly, to methods and devices for sidelink transmissions over unlicensed spectrum. BACKGROUND

[0002] In a wireless communication system, user equipments (UEs), such as mobile devices, can communicate with another UE via a data path supported by an operator network, such as a cellular or Wi-Fi network infrastructure. The data path supported by the operator network can include a base station (BS) and multiple gateways.

[0003] In a case where two UEs are relatively close to each other, a radio link or sidelink can be established between the two UEs to provide device-to-device (D2D) communication without going through a direct link to a BS. The term “sidelink” can refer to a direct radio link established for communication between devices (e.g., UEs) rather than via the cellular infrastructure (uplink and downlink) as discussed above. In this case, the “sidelink” is also referred to as a D2D communication link. The D2D communication link can be used in any suitable telecommunication network according to various standards, where the telecommunication network can configure a resource pool for the UEs to use during this D2D communication.

[0004] D2D communication has evolved into vehicle-to-everything (V2X) communication in a long term evolution (LTE) sidelink standard. V2X communication technology covers communication involving vehicles as a source or destination of messages. In a new radio (NR) communication system, a transmitting (Tx) UE can send a sidelink transmission to a specific receiving (Rx) UE in unicast mode, to a group of Rx UEs in groupcast mode, or to Rx UEs within a certain range in broadcast mode.

[0005] A UE can operate in both licensed spectrum and unlicensed spectrum. For transmissions over unlicensed spectrum, to achieve fair coexistence with other wireless systems, a UE is required to perform a channel access procedure, also known as a “listen-before-talk” (LBT) procedure, before transmitting over the unlicensed spectrum. In the LBT procedure, the UE performs energy detection on a certain channel. If the detected energy is below a predefined threshold, the channel is considered empty and available for transmission, and then the LBT procedure is successful. Only when the LBT procedure is successful, the UE can start transmission on the channel and occupy the channel up to a maximum channel occupancy time (MCOT); otherwise, the UE cannot start transmission and continues to perform another LBT procedure until the LBT procedure is successful. Sidelink transmissions can also be performed over unlicensed spectrum. SUMMARY

[0006] According to embodiments of the present disclosure, a method for wireless communication can include performing a first Type 1 channel access procedure for a sidelink transmission on a carrier starting from a first candidate starting symbol within a first slot, wherein the first candidate starting symbol is in a set of candidate starting symbols for the sidelink transmission; determining a channel occupancy time (COT) in response to the first Type 1 channel access procedure being successful; and performing the sidelink transmission on the carrier starting from the first candidate starting symbol within the first slot for the duration of the COT, wherein the sidelink transmission is continuous in time domain without any gap.

[0007] According to another embodiment of the present disclosure, a method for wireless communication can include detecting a sidelink transmission on a carrier starting from a first candidate starting symbol of a first slot, wherein the first candidate starting symbol is in a set of candidate starting symbols for the sidelink transmission; and receiving the sidelink transmission starting from the first candidate starting symbol within the first slot in response to the sidelink transmission on the carrier starting from the first candidate starting symbol being detected, wherein the sidelink transmission is continuous in time domain without any gap.

[0008] According to yet another embodiment of the present disclosure, an apparatus can include a non-transitory computer-readable medium having stored thereon computer-executable instructions, reception circuitry, transmission circuitry, and a processor coupled to the non-transitory computer-readable medium, the reception circuitry, and the transmission circuitry. The computer-executable instructions can cause the processor to implement a method recited in any embodiment of the present disclosure.

[0009] The details of one or more examples are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims. BRIEF DESCRIPTION OF DRAWINGS

[0010] In order to describe the manner in which the advantages and features of the disclosure can be obtained, a description of the disclosure is rendered by reference to particular embodiments thereof which are illustrated in the appended drawings. These drawings depict only example embodiments of the disclosure and are therefore not to be considered limiting of its scope.

[0011] Figure 1 A schematic diagram illustrating a wireless communication system in accordance with some embodiments of the present application;

[0012] Figure 2 (a) through (d) illustrate some example sets of candidate starting positions within a slot for a sidelink transmission in accordance with some embodiments of the present disclosure;

[0013] Figure 3 A flowchart illustrating a method for a sidelink transmission in accordance with embodiments of the present disclosure;

[0014] Figure 4 (a) through (f) illustrate some example sets of candidate ending positions within a slot for sidelink transmission according to some embodiments of the present disclosure;

[0015] Figure 5 A flowchart illustrating a method for sidelink transmission according to embodiments of the present disclosure is described;

[0016] Figure 6 An example block diagram illustrating a device according to embodiments of the present disclosure; and

[0017] Figure 7 An example block diagram illustrating a device according to another embodiment of the present disclosure. DETAILED DESCRIPTION

[0018] The detailed description set forth below of the presently preferred embodiments of the disclosure is intended as a description of the present implementation and is not intended to represent the only forms in which the present implementation can be constructed or utilized. It is understood that the same or equivalent functions can be accomplished by different embodiments that are intended to be encompassed within the spirit and scope of the present disclosure.

[0019] Reference will now be made in detail to some embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings. In order to facilitate understanding, the embodiments are provided under a specific network architecture and a new service scenario, such as 3GPP (Third Generation Partnership Project) 5G, 3GPP LTE Release 8, etc. It is very clear to those skilled in the art that the embodiments in the present disclosure are also applicable to similar technical problems as the network architecture and the new service scenario develop.

[0020] Figure 1 A schematic diagram illustrating a wireless communication system 100 according to some embodiments of the present application is described.

[0021] As shown in Figure 1 Wireless communication system 100 can include base stations (e.g., BS 120) and some UEs 110 (e.g., UE 110a, UE 110b, and UE 110c). Although a specific number of UEs 110 and one BS 120 are depicted in Figure 1 wireless communication system 100 can also include more BSs and more or less UEs within and outside the coverage of the BSs.

[0022] The UE and base station may support communication based on, for example, 3G, Long Term Evolution (LTE), LTE-Advanced (LTE-A), New Radio (NR), or (some) other suitable protocols. For example, BS 120 may include an eNB or gNB. UE 110a, UE 110b, or UE 110c may include, for example, but not limited to, computing devices, wearable devices, mobile devices, IoT (Internet of Things) devices, vehicles, etc. Those skilled in the art will understand that the terminology described in this disclosure may change as technology develops and advances, but this should not affect or limit the principles and spirit of this disclosure.

[0023] BS 120 may define one or more cells, and each cell may have a coverage area 130. In the exemplary wireless communication system 100, some UEs (e.g., UE 110a and UE 110b) are within the coverage area of ​​BS 120, which may not be... Figure 1 The specific base station 120 shown may be any of the base stations 120 in a wireless communication system, and some UEs (e.g., UE 110c) may be outside the coverage area of ​​the base station 120. For example, in the case where the wireless communication system includes two base stations, UE 110a being within the coverage area of ​​either of the two base stations 120 means that UE 110a is within the coverage area of ​​the base station 120 in the wireless communication system (i.e., within the coverage area); and UE 110a being outside the coverage area of ​​either base station 120 means that UE 110a is outside the coverage area of ​​the base station 120 in the wireless communication system (i.e., outside the coverage area).

[0024] Still referencing Figure 1 UE 110a and UE 110b can be connected via, for example, a Uu link (from... Figure 1 (Indicated by the dashed arrow in the diagram) communicates with BS120. UE 110a, UE 110b, and UE 110c can communicate via a secondary link (from...). Figure 1 The solid arrows in the diagram indicate that UEs communicate with each other and can form UE groups. During secondary link communication, the transmitting UE (hereinafter referred to as "Tx UE") can transmit signaling, data, or both to the receiving UE (hereinafter referred to as "Rx UE"). For example, see Reference Figure 1 A Tx UE (e.g., UE 110a) can transmit data to an Rx UE (e.g., UE 110b or UE 110c).

[0025] BS (for example, Figure 1 BS 120) and UE (e.g., Figure 1The UEs 110a, 110b, and 110c in the example of FIG. 1A can be configured to operate in licensed frequency spectrum (e.g., in the 600 MHz, 700 MHz, 800 MHz, 900 MHz, 1.4 GHz, 2.1 GHz, 2.6 GHz, 3.5 GHz, 4.9 GHz, 5.0 GHz, or 7.125 GHz bands) and / or unlicensed frequency spectrum (e.g., in the 5.0 GHz band). When operating in unlicensed frequency spectrum (e.g., the 5.0 GHz band), the UEs 110a, 110b, and 110c can employ LBT procedures to ensure the channel is clear before communicating in the band. For example, the UEs 110a, 110b, and 110c can perform a listen-before-talk (LBT) procedure before transmitting on the channel. The LBT procedure can include performing energy detection, where the UEs 110a, 110b, and 110c can determine whether the channel is busy (e.g., if the signal strength of other transmissions is below a threshold) or idle (e.g., if the signal strength of other transmissions is below the threshold). If the channel is determined to be idle, the UEs 110a, 110b, and 110c can transmit on the channel. If the channel is determined to be busy, the UEs 110a, 110b, and 110c can refrain from transmitting on the channel. The UEs 110a, 110b, and 110c can also perform LBT procedures before switching from a first band to a second band (e.g., from the 5.0 GHz band to the 7.125 GHz band).

[0026] When unlicensed spectrum is used for sidelink transmissions between UEs (e.g., between a Tx UE and an Rx UE), the Tx UE is required to perform an LBT procedure before performing any sidelink transmission. The LBT procedure is performed based on energy detection in each sensing slot. In detail, if the energy detected on a channel in one sensing slot is below an energy detection threshold, the channel is considered to be empty or idle or available in that sensing slot; otherwise, the channel is considered to be occupied or unavailable in that sensing slot. For a Type 1 channel access procedure (also referred to as an “LBT Category 4 or LBT Cat. 4 procedure”), energy detection is typically required to be performed in a range from several sensing slots to hundreds of sensing slots. At the beginning of the LBT Cat. 4 procedure, a random backoff counter is selected from a contention window. The random backoff counter is decremented by 1 each time the Tx UE detects that the channel is empty in one sensing slot. When the random backoff counter decrements to zero, the channel is considered to be available and the LBT Cat. 4 procedure is successful. Then, the Tx UE can determine a COT that is no larger than an MCOT and start a sidelink transmission on the channel within the COT. In the LBT Cat. 4 procedure, the contention window is updated continuously based on hybrid automatic repeat request (HARQ)-acknowledgement (ACK) feedback from the Rx UE. A more detailed Type 1 channel access procedure is specified in the 3GPP standard document TS 37.213. Thus, the time point at which the LBT Cat. 4 procedure will be successful is unpredictable, and thus the time point at which the sidelink transmission can start is also unpredictable.

[0027] For simplicity, sidelink transmission can be limited to always start from the first symbol of a slot, which typically contains 14 symbols, e.g., symbol 0 to symbol 13. However, this limitation will inevitably cause resource waste unless the Tx UE happens to grab the channel from symbol 0 of the slot. For example, if the Tx UE grabs the channel from symbol 1 of the slot (i.e., COT starts from symbol 1 of the slot) and waits for transmission starting from symbol 0 of the next slot, a total of 13 symbols (i.e., symbol 1 to symbol 13 of the slot) will be wasted. Therefore, it is beneficial to allow multiple starting positions or symbols for sidelink transmission.

[0028] On the other hand, MCOT can have different durations (e.g., 4 ms in Japan and 6 ms, 8 ms, or 10 ms in European countries). Therefore, if the Tx UE does not grab the channel from symbol 0, it can not end the transmission at symbol 13 in the last slot of the COT. If only the last symbol, e.g., symbol 13, of a slot can be the last symbol for sidelink transmission, it will also cause resource waste of the last slot, provided that the entire last slot cannot be occupied due to the limitation of MCOT. Therefore, allowing multiple ending positions or symbols for sidelink transmission can also reduce or avoid resource waste.

[0029] Figure 2 (a) to 2(d) illustrate some example candidate starting position sets within a slot for sidelink transmission according to some embodiments of the present disclosure. In Figure 2 In (a) to 2(d), the dark positions in a slot represent candidate starting positions for sidelink transmission. In the first embodiment as shown in Figure 2 In the first embodiment as shown in (a), the candidate starting position set includes symbol 0, 2, 4, 6, 8, 10, and 12. In the second embodiment as shown in Figure 2 In the second embodiment as shown in (b), the candidate starting position set includes symbol 0, 3, 6, and 9. In the third embodiment as shown in Figure 2 In the third embodiment as shown in (c), the candidate starting position set includes symbol 0, 4, and 8. In the fourth embodiment as shown in Figure 2 In the fourth embodiment as shown in (d), the candidate starting position set includes symbol 0 and 7. It should be appreciated that other sets including other combinations of candidate starting positions are also applicable. The minimum candidate starting position set can include only one symbol of a slot, e.g., symbol 0. The maximum candidate starting position set can include all symbols of a slot, e.g., symbol 0, 1, 2, 3, …, and 13.

[0030] A set of candidate starting positions for sidelink transmission can be configured via higher layer signaling (e.g., radio resource control (RRC) signaling), e.g., by a base station (e.g., gNB) or a Tx UE. The Tx UE can also signal the set of candidate starting positions to a Rx UE via RRC signaling. Additionally or alternatively, the set of candidate starting positions can be pre-configured during implementation or pre-defined in the standard. The selection of a candidate starting position from the set of candidate starting positions should consider several principles, including but not limited to: (1) efficient resource utilization; (2) Rx UE blind detection effort; and (3) channel variation and LBT success probability between two consecutive candidate starting positions. These principles can be considered individually or in any combination. The more candidate starting positions the set contains, the more efficient the resource utilization can be and the more blind detection effort the Rx UE needs to make.

[0031] Figure 3 A flowchart of a method 300 for sidelink transmission according to embodiments of the disclosure is illustrated, which can be performed at a Tx UE or other apparatus having similar functionality. As shown in Figure 3 In step 302, a first type 1 channel access procedure (e.g., a first LBT Cat. 4 procedure) for sidelink transmission on the carrier can be performed, e.g., by the Tx UE, before a first candidate starting symbol (e.g., symbol 0) in a set of candidate starting symbols (e.g., Figure 2 illustrated in any one of (a) to (d) in a slot.

[0032] When the first channel access procedure fails (i.e., the “No” branch of step 304), the method 300 can return to step 302 and a second type 1 channel access procedure (e.g., a second LBT Cat. 4 procedure) for sidelink transmission on the carrier can be performed, e.g., by the Tx UE, before a second candidate starting symbol in the set of candidate starting symbols in the slot. The second candidate starting symbol can be after the first candidate starting symbol in the set of candidate starting symbols, i.e., the second candidate starting symbol is later in time domain than the first candidate starting symbol. For example, the second candidate starting symbol can be Figure 2 symbol 2 in the embodiments of (a), Figure 2 symbol 3 in the embodiments of (b), Figure 2 symbol 4 in the embodiments of (c), or Figure 2Symbol 7 in the embodiment of (d). In embodiments of the disclosure, if the random backoff counter of the first LBT Cat.4 procedure does not count down to zero at the first candidate starting symbol, the first LBT Cat.4 procedure is considered to fail and is immediately terminated by the Tx UE. If the second Type 1 channel access procedure still fails, a third Type 1 channel access procedure (e.g., a third LBT Cat.4 procedure) for a sidelink transmission on the carrier can be performed, e.g., by the Tx UE, before a third candidate starting symbol in the set of candidate starting symbols of the slot, and so on until a Type 1 channel access procedure is successful for a candidate starting symbol of the slot. If Type 1 channel access procedures fail for all candidate starting symbols of the slot, the Tx UE can perform Type 1 channel access procedures for each candidate starting symbol of the next slot in the same way.

[0033] If the channel access procedure is successful for any candidate starting symbol of the slot (i.e., the “Yes” branch of step 304), the method 300 can proceed to step 306, and a COT can be determined, e.g., by the Tx UE, in response to the successful channel access procedure. Then, in step 308, within the COT, a sidelink transmission on the carrier can be performed, e.g., by the Tx UE, to the Rx UE starting from the candidate starting symbol corresponding to the successful channel access procedure. For example, if the first Type 1 channel access procedure is successful, the Tx UE can perform the sidelink transmission on the carrier starting from the first candidate starting symbol; and if the second Type 1 channel access procedure is successful, the Tx UE can perform the sidelink transmission on the carrier starting from the second candidate starting symbol. In step 310, a HARQ-ACK feedback corresponding to the sidelink transmission can be received, e.g., by the Tx UE, from the Rx UE.

[0034] According to embodiments of the disclosure, to avoid the risk of losing the occupied channel, the Tx UE can perform the sidelink transmission in a sidelink transmission burst without any gap in time domain. That is, the sidelink transmission within the COT is continuous in time domain without any gap.

[0035] The sidelink transmission can span one or more slots within a COT. Within each of the one or more slots, the sidelink transmission can include a physical sidelink control channel (PSCCH) and an associated physical sidelink shared channel (PSSCH) scheduled by a sidelink control information (SCI) format carried on the PSCCH. The associated PSSCH can have various multiplexing manners with the PSCCH. The SCI format can be used to indicate a starting position of the associated PSSCH to the Rx UE. In an embodiment of the disclosure, the SCI format carried on the PSCCH can indicate an index of a starting symbol of the associated PSSCH. In another embodiment of the disclosure, the SCI format carried on the PSCCH can indicate an offset between a starting symbol of the associated PSSCH and a starting symbol of the PSCCH. In yet another embodiment of the disclosure, the SCI format carried on the PSCCH can indicate an offset between a starting symbol of the associated PSSCH and an ending symbol of the PSCCH. In some other embodiments of the disclosure, the starting position of the associated PSSCH in a slot is default and not explicitly indicated by the SCI format. According to an embodiment of the disclosure, the starting position of the associated PSSCH is always the same as the starting position of the PSCCH, i.e., the PSCCH and the associated PSSCH start from the same symbol in a slot. For example, in case of a successful first type 1 channel access procedure for a first candidate starting symbol of a slot, the Tx UE can transmit the PSCCH and its associated PSSCH starting from the first candidate starting symbol within the slot. According to another embodiment of the disclosure, the associated PSSCH can always be transmitted right after the ending symbol of the PSCCH. According to some other embodiments of the disclosure, the offset between the starting symbol of the associated PSSCH and the starting or ending symbol of the PSCCH can be configured via RRC signaling, e.g., by a base station (e.g., gNB) or the Tx UE. The Tx UE can also signal the offset to the Rx UE via RRC signaling. Additionally or alternatively, the offset can be pre-configured or pre-defined in the standard.

[0036] In some embodiments of the disclosure, the SCI format carried on the PSCCH in each slot can indicate an ending position of the associated PSSCH. As discussed above, to save resources, it is beneficial to allow multiple ending positions for the sidelink transmission. Thus, the ending position of the associated PSSCH can be selected from a set of candidate ending positions for the sidelink transmission.

[0037] The set of candidate ending positions for sidelink transmission can be configured via RRC signaling, e.g., by a base station (e.g., gNB) or Tx UE. The Tx UE can also signal the set of candidate ending positions to the Rx UE via RRC signaling. Additionally or alternatively, the set of candidate ending positions can be pre-configured during implementation or pre-defined in the standard. The selection of a candidate ending position from the set of candidate ending positions should consider several principles, including but not limited to: (1) efficient resource utilization; (2) Rx UE decoding complexity; (3) channel variation between two consecutive candidate ending positions; (4) leaving a gap in the last slot of the COT for other UEs to perform LBT procedure; (5) leaving a gap within the COT for a physical sidelink feedback channel (PSFCH) corresponding to the sidelink transmission; and (6) leaving a gap before the PSFCH for the Rx UE to decode the sidelink transmission and / or perform LBT procedure for transmitting the PSFCH. These principles can be considered individually or in any combination. The minimum set of candidate ending positions can include only one symbol of a slot, e.g., symbol 13. The maximum set of candidate ending positions can include all symbols of a slot, e.g., symbols 0, 1, 2, 3, …, and 13. The more candidate ending positions the set includes, the more efficient the resource utilization can be and the more decoding work the Rx UE needs to do.

[0038] Figure 4 (a) through (f) illustrate some example sets of candidate ending positions within a slot for sidelink transmission according to some embodiments of the present disclosure. In Figure 4 In (a) through (f), the dark positions in the slot represent candidate ending positions for sidelink transmission.

[0039] In the first embodiment shown in (a), the set of candidate ending positions includes symbols 1, 3, 5, 7, 9, 11, and 13. In the second embodiment shown in (b), the set of candidate ending positions includes symbols 3, 7, 11, and 13. In the third embodiment shown in (c), the set of candidate ending positions includes symbols 4, 8, and 13. In the fourth embodiment shown in (d), the set of candidate ending positions includes symbols 6 and 13. Figure 4 Figure 4 Figure 4 Figure 4 Figure 4 The embodiments illustrated in (a) through (d) consider providing multiple candidate ending positions in selecting the set of candidate ending positions to achieve more efficient channel usage.

[0040] Figure 4 ​​​​(e) illustrates embodiments according to the present disclosure for providing multiple candidate end positions to fit a gap for other UEs to perform a Type 2 channel access procedure, also referred to as "LBT Cat.2 procedure", which is a different LBT procedure than Type 1 channel access procedure. Type 2 channel access procedure requires one energy detection within a sensing interval of at least 16us or 25us. There is no random backoff counter generation and decrement procedure in Type 2 channel access procedure, which is the main difference compared to Type 1 channel access procedure. More detailed procedures of Type 2 channel access procedure are specified in 3GPP standard document TS 37.213. As Figure 4 As shown in (e), the set of candidate end positions in a slot can include symbol 12 and 13. If the Tx UE needs to reserve one symbol for other UEs to contend for occupying the channel starting from the next slot, the SCI format carried on the PSCCH in the slot can indicate symbol 12 as the end symbol of the associated PSSCH in the slot so that other UEs can perform LBT procedure in symbol 13; otherwise, the SCI format carried on the PSCCH in the slot can indicate symbol 13 as the end symbol of the associated PSSCH in the slot.

[0041] In Figure 4 In the embodiments shown in (e), a gap including only one symbol (e.g., symbol 13) can be reserved for other UEs to perform LBT procedure. It should be appreciated that different candidate end positions can be included in the set of candidate end positions to accommodate different gap durations required to perform LBT procedure. The required gap duration depends on the subcarrier spacing value. Therefore, the set of candidate end positions also depends on the subcarrier spacing value. For example, in case of 15kHz subcarrier spacing and 30kHz subcarrier spacing, a gap of at least one symbol is required, therefore the set of candidate end positions can include symbol 12 and 13. In case of 60kHz subcarrier spacing, a gap of at least two symbols is required, therefore the set of candidate end positions can include symbol 11 and 13. In case of 120kHz subcarrier spacing, a gap of at least three or four symbols is required, therefore the set of candidate end positions can include symbol 9, 10 and 13; or include symbol 9 and 13.

[0042] Figure 4 (f) illustrates embodiments according to the present disclosure for providing multiple candidate end positions to fit a first gap for other UEs to perform a Type 2 channel access procedure (e.g., LBT Cat.2 procedure), to fit a second gap for a Rx UE to transmit PSFCH, and to fit a third gap for the Rx UE to perform a Type 2 channel access procedure for transmitting PSFCH.

[0043] After receiving the sidelink transmission from the Tx UE, the Rx UE can transmit the HARQ-ACK feedback corresponding to the sidelink transmission to the Tx UE on the PSFCH. To transmit the PSFCH on the unlicensed spectrum, the Rx UE also needs to perform an LBT procedure before transmitting the PSFCH. As discussed above, the LBT Cat.4 procedure can result in unpredictable sensing time. If the LBT Cat.4 procedure for transmitting the PSFCH fails or succeeds under long sensing time, the PSFCH can be dropped. According to embodiments of the disclosure, the Tx UE reserves resources for the PSFCH within the COT initiated by the Tx UE, so that the Rx UE can perform a shorter LBT Cat.2 procedure before transmitting the PSFCH on the reserved resources, and the channel access success probability can be higher. To perform the LBT Cat.2 procedure, the Tx UE can reserve an LBT gap before the resources reserved for the PSFCH.

[0044] As Figure 4 As shown in (f), the set of candidate ending positions in a slot can include symbols 9, 12, and 13. If the Tx UE needs to reserve both the PSFCH resources in a slot and one symbol for other UEs to contend for occupying the channel starting from the next slot, the SCI format carried on the PSCCH in the slot can indicate symbol 9 as the ending symbol of the associated PSSCH in the slot, so that four symbols are left and not used for transmitting the associated PSSCH. The four symbols can be reserved as a first gap of one symbol (e.g., symbol 13) at the end of the slot for other UEs to perform the LBT procedure, as shown in (g). Figure 4 As shown in (e), a second gap of two symbols (e.g., symbols 11 and 12) is reserved for the Rx UE to transmit the PSFCH, and a third gap of one symbol (e.g., symbol 10) between the ending symbol of the PSSCH (e.g., symbol 9) and the starting symbol of the PSFCH (e.g., symbol 11) is reserved for the Rx UE to perform the LBT procedure. If one Tx UE needs to reserve only one symbol for other UEs to contend for occupying the channel starting from the next slot, the SCI format carried on the PSCCH in the slot can indicate symbol 12 as the ending symbol of the associated PSSCH in the slot, so that other UEs can perform the LBT procedure in symbol 13. If the Tx UE does not need to reserve the PSFCH resources or the LBT gap in the slot, the SCI format carried on the PSCCH in the slot can indicate symbol 13 as the ending symbol of the associated PSSCH in the slot.

[0045] In Figure 4In the embodiments shown in (f), a gap comprising only one symbol (e.g., symbol 10 or symbol 13) can be reserved for the Rx UE or other UEs to perform an LBT procedure (e.g., LBT Cat. 2 procedure). It should be appreciated that different candidate ending positions can be included in the candidate ending position set to accommodate different gap durations required to perform the LBT procedure. The required gap duration depends on the subcarrier spacing value. The candidate ending position set thus also depends on the subcarrier spacing value. For example, in the case of 15 kHz subcarrier spacing and 30 kHz subcarrier spacing, a gap of at least one symbol is required, and thus the candidate ending position set can include symbols 9, 12, and 13. In the case of 60 kHz subcarrier spacing, a gap of at least two symbols is required, and thus the candidate ending position set can include symbols 7, 11, and 13. In the case of 120 kHz subcarrier spacing, a gap of at least four symbols is required, and thus the candidate ending position set can include symbols 3, 9, and 13.

[0046] In Figure 5 In the embodiments shown in (f), a gap comprising two symbols (e.g., symbols 11 and 12) can be reserved for the Rx UE to transmit the PSFCH. It should be appreciated that different candidate ending positions can be included in the candidate ending position set to accommodate PSFCHs having different numbers of symbols.

[0047] Any of the first, second, and third gaps described above can be made by puncturing (i.e., puncturing data mapped on each symbol within the gap when not transmitted) or rate matching (i.e., not mapping data on each symbol within the gap during the resource mapping procedure).

[0048] The embodiments shown in (a) through 4(f) are provided for illustration purposes. One of skill in the art will appreciate that other sets including other combinations of candidate ending positions are also applicable. Figure 5 (a) through 4(f). One of skill in the art will appreciate that other sets including other combinations of candidate ending positions are also applicable.

[0049] According to some embodiments of the disclosure, the first N consecutive symbols in the first slot of the sidelink transmission can be used as automatic gain control (AGC) symbols, and the other slots of the sidelink transmission do not include any AGC symbols. For example, in the first slot, the first N consecutive symbols are a repetition of the next N consecutive symbols in a one-to-one mapping. Alternatively, in the first slot, each of the first N consecutive symbols is a repetition of the (N+1)th symbol. The number N of AGC symbols depends on the subcarrier spacing value. For example, in the case of 15 kHz subcarrier spacing and 30 kHz subcarrier spacing, at least one symbol is required for AGC purposes. In the case of 60 kHz subcarrier spacing, at least two symbols are required for AGC purposes. In the case of 120 kHz subcarrier spacing, at least four symbols are required for AGC purposes.

[0050] Figure 2 A flowchart illustrating a method 500 for secondary link transmission according to an embodiment of this disclosure is provided. For simplicity, method 500 is described below with respect to an Rx UE. It should be understood that method 500 may be performed by other devices having similar functionality.

[0051] like Figure 2 As shown, in step 502, the Rx UE may perform a blind detection procedure starting from the first candidate start symbol of the time slot (e.g., symbol 0) to detect sublink transmissions on the carrier, wherein the first candidate start symbol is in the set of candidate start symbols used for sublink transmissions (e.g., ...). Figure 2 The candidate start location set (as described in any of (a) to (d)) is used. For example, the Rx UE can detect the presence of an SCI format from a first candidate start symbol. The candidate start location set for secondary link transmission can be configured via RRC signaling, for example by the base station (e.g., gNB) or the Tx UE. The Tx UE can also signal the candidate start location set to the Rx UE via RRC signaling. Alternatively or concurrently, the candidate start location set can be preconfigured during implementation or predefined in the standard.

[0052] If a secondary link transmission starting from the first candidate start symbol of the time slot is not detected (i.e., the "No" branch of step 504), for example, if the SCI format is not detected from the first candidate start symbol, then method 500 may return to step 502, and the RxUE may detect secondary link transmissions on the carrier starting from the second candidate start symbol in the candidate start symbol set of the time slot. The second candidate start symbol in the candidate start symbol set may follow the first candidate start symbol. For example, the second candidate start symbol may be... Figure 2 In the embodiment of (a), symbol 2, Figure 2 In the embodiment of (b), symbol 3, Figure 4 (c) In the embodiment, symbol 4 or Figure 5 Symbol 7 in embodiment (d). If a secondary link transmission starting from the second candidate start symbol is still not detected, then the Rx UE may start detecting the secondary link transmission from the third candidate start symbol in the candidate start symbol set of the time slot, and so on, until a secondary link transmission is detected from the candidate start symbol of the time slot. If the Rx UE fails to detect the secondary link transmission from any candidate start symbol of the time slot, then the Rx UE may start detecting the secondary link transmission from each candidate start symbol of the next time slot in the same manner.

[0053] If a sidelink transmission starting from a candidate starting symbol of a slot is detected (i.e., the “Yes” branch of step 504), e.g., an SCI format is detected from the candidate starting symbol, the method 500 can proceed to step 506, and the Rx UE can receive the sidelink transmission from the candidate starting symbol. For example, if a sidelink transmission starting from the first candidate starting symbol is detected, the Rx UE can receive the sidelink transmission on the carrier from the first candidate starting symbol; if a sidelink transmission starting from the second candidate starting symbol is detected, the Rx UE can receive the sidelink transmission on the carrier from the second candidate starting symbol. According to embodiments of the present disclosure, the sidelink transmission is continuous in time domain without any gap.

[0054] The sidelink transmission can span one or more slots. Within each slot of the one or more slots, the sidelink transmission can include a PSCCH and an associated PSSCH scheduled by an SCI format carried on the PSCCH. The associated PSSCH can have various multiplexing manners with the PSCCH. The SCI format can indicate a starting position of the associated PSSCH to the Rx UE, and the Rx UE can determine the starting position of the associated PSSCH by decoding the SCI format. In embodiments of the present disclosure, the SCI format carried on the PSCCH can indicate an index of a starting symbol of the associated PSSCH. In another embodiment of the present disclosure, the SCI format carried on the PSCCH can indicate an offset between the starting symbol of the associated PSSCH and the starting symbol of the PSCCH. In yet another embodiment of the present disclosure, the SCI format carried on the PSCCH can indicate an offset between the starting symbol of the associated PSSCH and the ending symbol of the PSCCH. In some other embodiments of the present disclosure, the starting position of the associated PSSCH in a slot is default and not explicitly indicated by the SCI format. According to embodiments of the present disclosure, the starting position of the associated PSSCH is always the same as the starting position of the PSCCH, i.e., the PSCCH and the associated PSSCH start from the same symbol in a slot. For example, in a case where a sidelink transmission starting from the first candidate starting symbol is detected, the Rx UE can receive the PSCCH and its associated PSSCH from the first candidate starting symbol within a slot. According to another embodiment of the present disclosure, the associated PSSCH can always be transmitted right after the ending symbol of the PSCCH. According to some other embodiments of the present disclosure, the offset between the starting symbol of the associated PSSCH and the starting symbol or the ending symbol of the PSCCH can be configured via RRC signaling, e.g., by a base station (e.g., a gNB) or a Tx UE. The Tx UE can also signal the offset to the Rx UE via RRC signaling. Additionally or alternatively, the offset can be pre-configured or pre-defined in the standard.

[0055] In some embodiments of the disclosure, the SCI format carried on the PSCCH in each slot can indicate the ending position of the associated PSSCH, and the Rx UE can determine the ending position of the associated PSSCH by decoding the SCI format. The ending position of the associated PSSCH is in a set of candidate ending positions for the sidelink transmission (e.g., the set specified in any one of (a) to (f) in the disclosure). The set of candidate ending positions for the sidelink transmission can be configured via RRC signaling, e.g., by a base station (e.g., gNB) or a Tx UE. The Tx UE can also signal the set of candidate ending positions to the Rx UE via RRC signaling. Additionally or alternatively, the set of candidate ending positions can be pre-configured during implementation or pre-defined in the standard. Figure 4 (a) to (f) in the disclosure. The set of candidate ending positions for the sidelink transmission can be configured via RRC signaling, e.g., by a base station (e.g., gNB) or a Tx UE. The Tx UE can also signal the set of candidate ending positions to the Rx UE via RRC signaling. Additionally or alternatively, the set of candidate ending positions can be pre-configured during implementation or pre-defined in the standard.

[0056] Referring back to Figure 4 After receiving the sidelink transmission, the Rx UE can determine the resource for HARQ-ACK feedback corresponding to the sidelink transmission in step 508. The HARQ-ACK feedback is to be transmitted on the PSFCH to the Tx UE. According to embodiments of the disclosure, the resource for the HARQ-ACK feedback is reserved within the COT initiated by the Tx UE. For example, symbols 11 and 12 in the last slot of the COT can be reserved for the Rx UE to transmit the PSFCH, as discussed above with reference to Figure 6 (f) in the disclosure. It should be appreciated that the PSFCH resource can be reserved in other symbols or other slots within the COT initiated by the Tx UE.

[0057] In step 510, the Rx UE can perform a channel access procedure within a gap between the ending symbol of the sidelink transmission and the starting symbol of the resource determined in step 508 for the HARQ-ACK feedback corresponding to the sidelink transmission. In the case where the resource is reserved within the COT initiated by the Tx UE, the Rx UE can perform an LBT Cat.2 procedure within the gap, which requires a shorter sensing time and a higher channel access success probability compared to an LBT Cat.4 procedure. The number of symbols within the gap depends on the subcarrier spacing value of the carrier. For example, a gap of at least one symbol is required in the case of 15 kHz subcarrier spacing and 30 kHz subcarrier spacing. A gap of at least two symbols is required in the case of 60 kHz subcarrier spacing. A gap of at least three or four symbols is required in the case of 120 kHz subcarrier spacing. The gap for the Rx UE to perform the LBT Cat.2 procedure can be reserved within the COT initiated by the Tx UE, e.g., as discussed above with reference to Figure 3 (f) in the disclosure.

[0058] In response to the channel access procedure being successful, in step 512, the Rx UE can transmit HARQ-ACK feedback corresponding to the sidelink transmission on the resources determined in step 508.

[0059] Figure 6 An example block diagram of a device 600 according to embodiments of the disclosure is illustrated. In some embodiments of the disclosure, the device 600 can be a Tx UE or other apparatus having similar functionality that can perform at least the methods illustrated in Figure 6

[0060] As shown in Figure 3 , the device 600 can include at least one receiving circuitry 602, at least one transmitting circuitry 604, at least one non-transitory computer- readable medium 606, and at least one processor 608 coupled to the at least one receiving circuitry 602, the at least one transmitting circuitry 604, and the at least one non-transitory computer-readable medium 606.

[0061] Although elements such as the receiving circuitry 602, the transmitting circuitry 604, the non-transitory computer-readable medium 606, and the processor 608 are described in the singular form in Figure 7 , the plural form is contemplated unless expressly stated to the contrary. In some embodiments of the disclosure, the at least one receiving circuitry 602 and the at least one transmitting circuitry 604 are combined into a single device, such as a transceiver. In certain embodiments of the disclosure, the device 600 can further include an input device, a memory, and / or other components.

[0062] In some embodiments of the disclosure, the at least one non-transitory computer- readable medium 606 can have stored thereon computer-executable instructions that are programmed to cause the at least one processor 608, utilizing the at least one receiving circuitry 602 and the at least one transmitting circuitry 604, to perform steps of a method such as described in the views of Figure 5 , for example. When executed, the instructions can cause the at least one processor 608 to perform a Type 1 channel access procedure for a sidelink transmission on a carrier starting from a first candidate starting symbol within a slot and determine a COT in response to the Type 1 channel access procedure being successful. The instructions can further cause the at least one processor 608 to perform a sidelink transmission on the carrier starting from the first candidate starting symbol utilizing the at least one transmitting circuitry 604. The instructions can further cause the at least one processor 608 to receive HARQ-ACK feedback corresponding to the sidelink transmission utilizing the at least one receiving circuitry 602.

[0063] Figure 7 ​An example block diagram of a device 700 according to another embodiment of the disclosure is illustrated. In some embodiments of the disclosure, the device 700 can be a Rx UE or other apparatus having similar functionality that can perform at least the methods described in Figure 7

[0064] As shown in Figure 5 The device 700 can include at least one receiving circuitry 702, at least one transmitting circuitry 704, at least one non-transitory computer-readable medium 706, and at least one processor 708 coupled to the at least one receiving circuitry 702, the at least one transmitting circuitry 704, the at least one non-transitory computer-readable medium 706.

[0065] Although elements such as the receiving circuitry 702, the transmitting circuitry 704, the non-transitory computer-readable medium 706, and the processor 708 are described in the singular form in ​ , consider the plural form, unless explicitly stated otherwise. In some embodiments of the disclosure, the at least one receiving circuitry 702 and the at least one transmitting circuitry 704 are combined into a single device, such as a transceiver. In certain embodiments of the disclosure, the device 700 can further include an input device, a memory, and / or other components.

[0066] In some embodiments of the disclosure, the at least one non-transitory computer- readable medium 706 can have stored thereon computer-executable instructions that are programmed to cause the at least one processor 708, with the at least one receiving circuitry 702 and the at least one transmitting circuitry 704, to perform steps of the methods described, for example, in the views of ​ When executed, the instructions can cause the at least one processor 708 to detect a sidelink transmission on the carrier starting from a first candidate starting symbol of a slot. In response to the sidelink transmission on the carrier starting from the first candidate starting symbol being detected, the instructions can cause the at least one processor 708 to receive the sidelink transmission from the first candidate starting symbol with the at least one receiving circuitry 702. The instructions can further cause the at least one processor 708 to determine a resource reserved for HARQ-ACK feedback to the sidelink transmission, and perform a Type 2 channel access procedure within a gap between an ending symbol of the sidelink transmission and a starting symbol of the resource. The instructions can further cause the at least one processor 708 to transmit the HARQ-ACK feedback with the at least one transmitting circuitry 704 in response to the Type 2 channel access procedure being successful.

[0067] ​Those of ordinary skill in the art will appreciate that the steps of a method described in connection with the aspects disclosed herein can be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module can reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. Additionally, in some aspects, the steps of a method can reside as one or any combination or set of codes and / or instructions on a non-transitory computer-readable medium, which can be incorporated into a computer program product.

[0068] Although the present disclosure has been described with reference to specific embodiments, it will be apparent to those skilled in the art that many alternatives, modifications and variations to the embodiments described herein can be made. For example, various elements of the described embodiments can be interchanged, added or removed in other embodiments. Also, all of the elements of each figure can not be necessary for operation of the disclosed embodiments. For example, one of ordinary skill in the art will be able to make and use the teachings of the present disclosure by simply employing the elements of the independent claims. Accordingly, the embodiments of the present disclosure as set forth herein are intended to be illustrative, not limiting. Various changes can be made without departing from the spirit and scope of the disclosure.

[0069] In this document, the terms "includes," "including," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that includes elements not expressly listed or inherent to such process, method, article, or apparatus can include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element preceded by "a" or "an" does not, without further constraints, preclude the existence of more than one of such elements. Further, the term "another" is defined as at least a second or more. The terms "has," "have," and "having" are defined as "including."

Claims

1. A method for wireless communication, comprising: performing a first Type 1 channel access procedure for a sidelink transmission on a carrier starting from a first candidate starting symbol within a first slot, wherein the first candidate starting symbol is in a set of candidate starting symbols for the sidelink transmission; determining a channel occupancy time (COT) in response to the first Type 1 channel access procedure for the sidelink transmission starting from the first candidate starting symbol being successful; and performing the sidelink transmission on the carrier starting from the first candidate starting symbol within the first slot for the COT; in response to the first Type 1 channel access procedure for the sidelink transmission starting from the first candidate starting symbol being unsuccessful, performing a second Type 1 channel access procedure for the sidelink transmission starting from a second candidate starting symbol within the first slot, wherein the second candidate starting symbol is in the set of candidate starting symbols, and in response to the second Type 1 channel access procedure being successful, determining a COT, and performing the sidelink transmission on the carrier starting from the second candidate starting symbol for the COT, wherein the sidelink transmission is contiguous in time domain without a gap.

2. The method of claim 1, wherein the second candidate starting symbol is after the first candidate starting symbol in the set of candidate starting symbols.

3. The method of claim 1, wherein the sidelink transmission within the first slot comprises a first physical sidelink control channel (PSCCH) and a first physical sidelink shared channel (PSSCH) transmitted from the first candidate starting symbol, and the first PSSCH is scheduled by a first sidelink control information (SCI) format carried on the first PSCCH.

4. An apparatus, comprising: receiver circuitry: transmitter circuitry; and a processor coupled to the receiver circuitry and the transmitter circuitry, the processor configured to cause the apparatus to: perform a first Type 1 channel access procedure for a sidelink transmission on a carrier starting from a first candidate starting symbol within a first slot, wherein the first candidate starting symbol is in a set of candidate starting symbols for the sidelink transmission; determine a channel occupancy time (COT) in response to the first Type 1 channel access procedure for the sidelink transmission starting from the first candidate starting symbol being successful; and perform the sidelink transmission on the carrier starting from the first candidate starting symbol within the first slot for the COT; in response to the first Type 1 channel access procedure for the sidelink transmission starting from the first candidate starting symbol being unsuccessful, perform a second Type 1 channel access procedure for the sidelink transmission starting from a second candidate starting symbol within the first slot, wherein the second candidate starting symbol is in the set of candidate starting symbols, and in response to the second Type 1 channel access procedure being successful, determine a COT, and perform the sidelink transmission on the carrier starting from the second candidate starting symbol for the COT, wherein the sidelink transmission is contiguous in time domain without a gap.

5. The apparatus of claim 4, wherein the sidelink transmission within the first time slot comprises a first physical sidelink control channel (PSCCH) and a first physical sidelink shared channel (PSSCH) transmitted from the first candidate starting symbol, and the first PSSCH is scheduled by a first sidelink control information (SCI) format carried on the first PSCCH.

6. The apparatus of claim 5, wherein the first SCI format indicates one or more of: an index of a starting symbol of the first PSSCH; an offset between a starting symbol of the first PSSCH and a starting symbol of the first PSCCH; or an offset between a starting symbol of the first PSSCH and an ending symbol of the first PSCCH.

7. The apparatus of claim 5, wherein comprises one or more of: the first PSSCH is transmitted from the first candidate starting symbol; or the first PSSCH is transmitted after an ending symbol of the first PSCCH.

8. The apparatus of claim 5, wherein comprises one or more of: an offset between a starting symbol of the first PSSCH and a starting symbol of the first PSCCH is obtained by one or more of: configured via radio resource control (RRC) signaling, pre-configured, or pre-defined; or an offset between a starting symbol of the first PSSCH and an ending symbol of the first PSCCH is obtained by one or more of: configured via radio resource control (RRC) signaling, pre-configured, or pre-defined.

9. The apparatus of claim 4, wherein, among the set of candidate starting symbols, the second candidate starting symbol is after the first candidate starting symbol.

10. The apparatus of claim 4, wherein the processor is further configured to cause the apparatus to perform operations of: reserving resources for a hybrid automatic repeat request (HARQ)-acknowledgement (ACK) feedback corresponding to the sidelink transmission within the COT; reserving a gap between an ending symbol of the sidelink transmission and a starting symbol of the resources; and receiving the HARQ-ACK feedback.

11. The apparatus of claim 10, wherein the processor is further configured to cause the apparatus to use the gap to perform a type 2 channel access procedure for transmission of the HARQ-ACK feedback.

12. The apparatus of claim 11, wherein a number of symbols within the gap is based at least in part on a subcarrier spacing value of the carrier.

13. An apparatus comprising: receiver circuitry: transmitter circuitry; and a processor coupled to the receiver circuitry and the transmitter circuitry, the processor configured to cause the apparatus to perform operations of: detecting a sidelink transmission on a carrier starting from a first candidate starting symbol of a first time slot, wherein the first candidate starting symbol is in a set of candidate starting symbols for the sidelink transmission; in response to the sidelink transmission on the carrier starting from the first candidate starting symbol being detected, receiving the sidelink transmission starting from the first candidate starting symbol within the first slot; in response to the sidelink transmission on the carrier starting from the first candidate starting symbol not being detected, detecting the sidelink transmission on the carrier starting from a second candidate starting symbol in the first slot, wherein the second candidate starting symbol is in the set of candidate starting symbols; and in response to the sidelink transmission on the carrier starting from the second candidate starting symbol being detected, receiving the sidelink transmission starting from the second candidate starting symbol within the first slot, wherein the sidelink transmission is continuous in time domain without a gap.

14. The apparatus of claim 13, wherein the sidelink transmission within the first slot comprises a first physical sidelink control channel (PSCCH) and a first physical sidelink shared channel (PSSCH) transmitted from the first candidate starting symbol, and the first PSSCH is scheduled by a first sidelink control information (SCI) format carried on the first PSCCH.

15. The apparatus of claim 14, wherein the first SCI format indicates one or more of: an index of a starting symbol of the first PSSCH; an offset between a starting symbol of the first PSSCH and a starting symbol of the first PSCCH; or an offset between a starting symbol of the first PSSCH and an ending symbol of the first PSCCH.

16. The apparatus of claim 14, wherein comprises one or more of: the first PSSCH is transmitted from the first candidate starting symbol; or the first PSSCH is transmitted after an ending symbol of the first PSCCH.

17. The apparatus of claim 14, wherein comprises one or more of: an offset between a starting symbol of the first PSSCH and a starting symbol of the first PSCCH is obtained by one or more of: configured via radio resource control (RRC) signaling, pre-configured, or pre-defined; or an offset between a starting symbol of the first PSSCH and an ending symbol of the first PSCCH is obtained by one or more of: configured via radio resource control (RRC) signaling, pre-configured, or pre-defined.

18. The apparatus of claim 13, wherein the second candidate starting symbol is after the first candidate starting symbol in the set of candidate starting symbols.

19. The apparatus of claim 13, wherein the processor is further configured to cause the apparatus to perform operations of: determining a resource reserved for hybrid automatic repeat request (HARQ)-acknowledgement (ACK) feedback corresponding to the sidelink transmission; performing a type 2 channel access procedure in a gap between an ending symbol of the sidelink transmission and a starting symbol of the resource; and transmitting the HARQ-ACK feedback in response to the type 2 channel access procedure being successful.

20. A method for wireless communication, comprising: receiving a first physical sidelink control channel (PSCCH) and a first physical sidelink shared channel (PSSCH) in a first slot, wherein the first PSSCH is scheduled by a first sidelink control information (SCI) format carried on the first PSCCH; in response to the first PSSCH being transmitted from a first candidate starting symbol in the first slot, receiving the first PSSCH starting from the first candidate starting symbol; and in response to the first PSSCH not being transmitted from the first candidate starting symbol in the first slot, receiving the first PSSCH starting from a second candidate starting symbol in the first slot, wherein the second candidate starting symbol is after the first candidate starting symbol in the first slot.

21. The method of claim 20, wherein the first PSSCH is transmitted from the first candidate starting symbol or after an ending symbol of the first PSCCH.

22. The method of claim 20, wherein an offset between a starting symbol of the first PSSCH and a starting symbol of the first PSCCH is obtained by one or more of: configured via radio resource control (RRC) signaling, pre-configured, or pre-defined.

23. The method of claim 20, wherein an offset between a starting symbol of the first PSSCH and an ending symbol of the first PSCCH is obtained by one or more of: configured via radio resource control (RRC) signaling, pre-configured, or pre-defined.

24. The method of claim 20, further comprising: determining a resource reserved for hybrid automatic repeat request (HARQ)-acknowledgement (ACK) feedback corresponding to the first PSSCH; performing a type 2 channel access procedure in a gap between an ending symbol of the first PSSCH and a starting symbol of the resource; and transmitting the HARQ-ACK feedback in response to the type 2 channel access procedure being successful.

20. The apparatus of claim 19, wherein a number of symbols within the gap is based at least in part on a subcarrier spacing value of the carrier.

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