Channel access procedure selection for sidelink communication in unlicensed spectrum

Abstract

A user equipment (UE) for a wireless communication network, such as a 3rd generation partnership project (3GPP) network, is described. The UE is configured to communicate with one or more further UEs in a wireless communication network via a sidelink (SL) using a set of resources in an unlicensed spectrum. In order to perform SL transmissions on a set of resources in an unlicensed spectrum, a UE is used to perform a channel access procedure (CAP) to evaluate availability of the set of resources used to perform the SL transmissions. The UE is to select a CAP for evaluating availability of a set of resources for performing SL transmissions based on criteria.

Description

[0001] manual

[0002] The present invention relates to the field of wireless communication systems or networks, and more particularly to direct communication between user equipments via sidelink using resources in unlicensed spectrum. Embodiments relate to channel access procedure selection for such sidelink communication in unlicensed spectrum.

[0003] FIG. 1 is a schematic diagram of an example of a terrestrial wireless network 100. As shown in FIG. 1(a), the terrestrial wireless network 100 includes a core network 102 and one or more radio access networks RAN1, RAN2, . . . RAN N Figure 1(b) shows the radio access network RAN n Schematic diagram of an example of a radio access network RAN n One or more base stations gNB1 to gNB5 may be included, each serving a specific area around the base station, schematically represented by corresponding cells 1061 to 1065. The base station provides services to users within the cell. One or more base stations can provide services to users in licensed and / or unlicensed frequency bands. The term base station (BS) refers to a gNB in ​​a 5G network, an eNB in ​​UMTS / LTE / LTE-A / LTE-A Pro, or a BS in other mobile communication standards. Users can be fixed devices or mobile devices. The wireless communication system can also be accessed by mobile or fixed IoT devices connected to the base station or user. Mobile devices or fixed devices may include physical devices, ground vehicles (such as robots or cars), aerial vehicles (such as manned or unmanned aerial vehicles (UAVs), the latter also known as drones), buildings and other items or devices with embedded electronic devices, software, sensors, actuators, etc., as well as network connections that enable these devices to collect and exchange data through existing network infrastructure. Figure 1(b) shows an exemplary view of five cells, however, the RAN n More or fewer such cells may be included, and the RAN nIt is also possible to include only one base station. Figure 1(b) shows two users UE1 and UE2, also referred to as user equipment (device) or user equipment (equipment), which are in cell 1062 and served by base station gNB2. Another user UE3 is shown in cell 1064 served by base station gNB4. Arrows 1081, 1082 and 1083 schematically represent uplink / downlink connections for transmitting data from users UE1, UE2 and UE3 to base stations gNB2, gNB4 or for transmitting data from base stations gNB2, gNB4 to users UE1, UE2, UE3. This can be achieved in a licensed band or an unlicensed band. In addition, Figure 1(b) shows two IoT devices 1101 and 1102 in cell 1064, which can be fixed devices or mobile devices. Device 1101 accesses the wireless communication system via base station gNB4 to receive and send data, as schematically represented by arrow 1121. Device 1102 accesses the wireless communication system via user UE3, as schematically represented by arrow 1122. The corresponding base stations gNB1 to gNB5 can be connected to the core network 102, for example, via the S1 interface, via corresponding backhaul links 1141 to 1145, which are schematically represented by arrows pointing to "core" in Figure 1(b). The core network 102 can be connected to one or more external networks. The external network can be the Internet, or it can be a private network, such as an intranet or any other type of campus network, such as a private WiFi communication system or a 4G or 5G mobile communication system. In addition, some or all of the corresponding base stations gNB1 to gNB5 can be connected to each other, for example, via the S1 or X2 interface or the XN interface in NR, via corresponding backhaul links 1161 to 1165, which are schematically represented by arrows pointing to "gNB" in Figure 1(b). The sidelink channel allows direct communication between UEs, also known as device-to-device (D2D) communication. The sidelink interface in 3GPP is named PC5.

[0004] For data transmission, a physical resource grid may be used. The physical resource grid may include a set of resource elements to which various physical channels and physical signals are mapped. For example, the physical channels may include a physical downlink shared channel PDSCH, an uplink shared channel PUSCH, and a sidelink shared channel PSSCH (carrying user-specific data, also referred to as downlink, uplink, and sidelink payload data), a physical broadcast channel PBCH, and a physical sidelink broadcast channel PSBCH (carrying, for example, a master information block (MIB) and one or more system information blocks (SI), one or more sidelink information blocks (SLIBs), if supported, a physical downlink control channel PDCCH, an uplink control channel PUCCH, and a sidelink control channel PSSCH (carrying, for example, downlink control information DCI, uplink control information UCI, and sidelink control information SCI), and a physical sidelink feedback channel PSFCH (carrying PC5 feedback responses). The sidelink interface may support 2-stage SCI, i.e., a first control region containing some parts of the SCI, also referred to as the first stage SCI, and optionally, a second control region containing the second part of the control information, also referred to as the second stage SCI.

[0005] For the uplink, the physical channel may further include a physical random access channel PRACH or RACH, which the UE uses to access the network once it is synchronized and obtains the MIB and SIB. Physical signals may include reference signals or symbols (RS), synchronization signals, etc. The resource grid may include frames or radio frames with a specific duration in the time domain and a given bandwidth in the frequency domain. A frame may have a certain number of subframes of a predetermined length, such as 1 millisecond. Each subframe may include one or more time slots of 12 or 14 OFDM symbols, depending on the cyclic prefix (CP) length. The frame may also have a smaller number of OFDM symbols, for example, when utilizing a shortened transmission time interval (sTTI, shortened transmission time interval) or a micro-slot / non-slot-based frame structure that includes only a few OFDM symbols.

[0006] The wireless communication system may be any single tone or multi-carrier system using frequency division multiplexing, such as an orthogonal frequency division multiplexing (OFDM) system, an orthogonal frequency division multiple access (OFDMA) system, or any other signal based on inverse fast Fourier transform IFFT with or without cyclic prefix CP, such as discrete Fourier transform-spread OFDM (DFT-s-OFDM). Other waveforms may also be used, such as non-orthogonal waveforms for multiple access, such as filter bank multi-carrier (FBMC), generalized frequency division multiplexing (GFDM), or universal filtering multi-carrier (UFMC). The wireless communication system may operate according to 3GPP's LTE, LTE-advanced, LTE-advancedPro standards or 5G or 3GPP NR (New Radio) standards, or NR-U, New Radio unlicensed (specified in the above-mentioned LTE and NR specifications).

[0007] The wireless network or communication system depicted in Figure 1 can be a heterogeneous network with different overlapping networks, such as a macrocell network, each macrocell including a macro base station (such as base stations gNB1 to gNB5), and a small cell base station base station (not shown in Figure 1), such as a femto base station or a pico base station. In addition to the above-mentioned terrestrial wireless networks, there are also non-terrestrial wireless communication networks NTN, including space transceivers such as satellites and / or airborne transceivers such as drone systems. The operation of the non-terrestrial wireless communication network or system can be similar to the terrestrial system described in the above reference Figure 1, for example according to the LTE-Advanced Pro specification or the 5G or NR (NewRadio) specification.

[0008] In a mobile communication network, for example, in a network similar to that described above with reference to FIG. 1 , such as an LTE or 5G / NR network, there may be UEs that communicate directly with each other through one or more side link SL channels, for example, using a PC5 / PC3 interface or WiFi direct connection. UEs that communicate directly with each other through side links may include vehicles that communicate directly with other vehicles (V2V communication), vehicles that communicate with other entities of a wireless communication network (V2X communication), such as roadside units RSU, roadside entities (such as traffic lights, traffic signs, or pedestrians). Depending on the specific network configuration, the RSU may have the functionality of a BS or a UE. Other UEs may not be vehicle-related UEs, and may include any of the above devices. These devices may also communicate directly with each other using SL channels, i.e., D2D communication.

[0009] When considering two UEs communicating directly via a sidelink, the two UEs can be served by the same base station or different base stations, and the base station can provide sidelink resource allocation configuration or assistance to the UE. For example, both UEs can be within the coverage area of ​​a base station, such as one of the base stations shown in Figure 1. This is called the "in coverage" scenario. Another scenario is called the "out of coverage" scenario. It should be noted that "out of coverage" does not mean that the two UEs are necessarily outside the cell shown in Figure 1, but rather that these UEs:

[0010] - may not be connected to the base station, e.g. they are not in RRC connected state, resulting in the UE not being able to receive any sidelink resource allocation configuration or assistance from the base station, and / or

[0011] - may be connected to a base station, but due to one or more reasons, the base station may not provide sidelink resource allocation configuration or assistance to the UE, and / or

[0012] -It is possible to connect to base stations that do not support NR V2X services, such as GSM, UMTS, LTE base stations.

[0013] FIG2(a) is a schematic diagram of a coverage scenario in which two UEs in direct communication with each other are both connected to a base station. The coverage area of ​​the base station gNB is shown in FIG200, which substantially corresponds to the cell shown in FIG1. ​​The UEs in direct communication with each other include a first vehicle 202 and a second vehicle 204, both of which are located within the coverage area 200 of the base station gNB. Both vehicles 202 and 204 are connected to the base station gNB and, in addition, are directly connected to each other via a PC5 interface. Scheduling and / or interference management of V2V traffic is assisted by the gNB through control signaling on the Uu interface (radio interface between the base station and the UE). That is, the gNB provides SL resource allocation configuration or assistance to the UE, and the gNB allocates resources for V2V communication via a side link. This configuration is also referred to as a mode 1 configuration in NRV2X or a mode 3 configuration for LTE V2X. Thus, in Mode 1, a SL UE (e.g., UE 202) is connected to the gNB via a Uu interface, and the gNB coordinates the resources of UE 202 for transmitting control and / or data to another UE (e.g., UE 204) via a SL interface (referred to as PC5 in NR).

[0014] FIG2( b) is a schematic diagram of an out-of-coverage scenario, in which UEs communicating directly with each other are not connected to a base station, although they may be physically located within a cell of a wireless communication network, or some or all of the UEs communicating directly with each other are connected to a base station, but the base station does not provide SL resource allocation configuration or assistance. The three vehicles 206, 208, and 210 shown communicate directly with each other via a side link, for example, using a PC5 interface. The scheduling and / or interference management of V2V traffic is based on an algorithm implemented between vehicles. This configuration is also referred to as a Mode 2 configuration in NR V2X or a Mode 4 configuration in LTE V2X. As described above, the out-of-coverage scenario in FIG2( b) does not necessarily mean that the corresponding Mode 2 UE in NR or Mode 4 UE in LTE is outside the coverage 200 of the base station, but means that the corresponding Mode 2 UE in NR or Mode 4 UE in LTE is not served by the base station, is not connected to a base station in the coverage area, or is connected to a base station but does not receive SL resource allocation configuration or assistance from the base station. Therefore, in the coverage area 200 shown in FIG. 2( a ), in addition to the UEs 202 and 204 of NR mode 1 or LTE mode 3, there may also be UEs 206, 208, and 210 of NR mode 2 or LTE mode 4. In addition, FIG. 2( b ) schematically shows an out-of-coverage UE that uses a relay to communicate with the network. For example, UE 210 may communicate with UE 212 via a side link, and UE 212 may be connected to the gNB via a Uu interface. Therefore, UE 212 may relay information between the gNB and UE 210. Therefore, the SLUEs (e.g., UEs 206-210) do not need to be connected to the gNB and perform perception and use of resource allocation or random access-based resource allocation, such as when transmitting from UE 206 to UE 208. However, in order to successfully exchange data, the UEs 206-210 need to have basic configuration. This information may be pre-configured or may be configured when the UE is within the coverage of the gNB. To this end, the gNB may provide basic configuration, such as basic information, which may be transmitted via a broadcast channel, for example, using a system information block (SIB). The BS may also assist the Mode 2 UE to provide basic information about which resource pool (RP) to use or may serve as a synchronization source.

[0015] Although Figures 2(a) and 2(b) show vehicle-mounted UEs, it is worth noting that the in-coverage scenario and out-of-coverage scenario also apply to non-vehicle UEs. In other words, any UE (such as a handheld device) that directly communicates with another UE using an SL channel can be in coverage and out of coverage.

[0016] In the above-mentioned vehicle-mounted user equipment (UE) scenario, multiple such user equipments can form a user equipment group, also referred to as a group, and the communication within the group or between group members can be carried out via a side link interface (such as a PC5 interface) between the user equipments. For example, the above-mentioned scenario using vehicle-mounted user equipment can be applied to the field of transportation industry, in which multiple vehicles equipped with vehicle-mounted user equipment can be grouped together through remote driving applications and other means. Other use cases that can group multiple user equipments together for mutual side link communication include, for example, factory automation and power distribution. In the case of factory automation, multiple mobile or fixed machines in a factory can be equipped with user equipments and combined together for side link communication, for example, for controlling the operation of the machines, such as motion control of robots. In the case of power distribution, entities within the distribution network can be equipped with corresponding user equipments, which can be grouped together in a certain area of ​​the system to communicate with each other via side link communication, so as to monitor the system and handle distribution network faults and power outages.

[0017] It should be noted that the information in the previous section is only for enhancing understanding of the background of the invention and therefore it may contain information that does not constitute the prior art that is already known to a person of ordinary skill in the art.

[0018] In summary, the sidelink in a wireless communication system or network may need to be improved or enhanced.

[0019] Now, embodiments of the present invention are described in further detail with reference to the accompanying drawings:

[0020] FIG1 is a schematic diagram of an example of a terrestrial wireless network;

[0021] Figure 2(a) is a schematic diagram of a scene within the coverage area;

[0022] Figure 2(b) is a schematic diagram of a scenario outside the coverage area;

[0023] Figure 3 is a schematic diagram of a wireless communication system for implementing an embodiment of the present invention, the system comprising a transmitter (such as a base station) and one or more receivers (such as user equipment (UE));

[0024] Figure 4 A user equipment UE according to an embodiment of the present invention is shown;

[0025] Figure 5 An embodiment showing how to handle a failed initial CAP for a data transfer via a SL with a particular PDB, and

[0026] Figure 6 An example of a computer system is shown, on which the units or modules described according to the method of the present invention and the steps of the method can be executed.

[0027] Embodiments of the present invention will now be described in more detail with reference to the accompanying drawings, wherein the same or similar elements are designated with the same reference numerals.

[0028] In a mobile communication system or network, as described above with reference to FIG. 1, for example, in an LTE or 5G / NR network, each entity may use one or more frequency bands for communication. A frequency band includes a starting frequency, an ending frequency, and all intermediate frequencies between the starting frequency and the ending frequency. In other words, the starting frequency, the ending frequency, and the intermediate frequencies may define a certain bandwidth, such as 20 MHz. A frequency band may also be referred to as a carrier, a bandwidth part (BWP), a subband, a resource pool, etc.

[0029] When a single frequency band is used, the communication may be referred to as single-band operation, for example, the UE sends / receives radio signals to / from another network entity on a frequency within the frequency band (eg, a 20 MHz band).

[0030] When two or more frequency bands are used, the communication may be referred to as multi-band operation or broadband operation or carrier aggregation operation. The frequency bands may have different bandwidths or may have the same bandwidth, such as 20 MHz. For example, in the case where the frequency bands have the same bandwidth, the UE may send / receive radio signals to / from another network entity at frequencies within two or more 20 MHz frequency bands, so that the frequency range of the radio communication may be a multiple of 20 MHz. The two or more frequency bands may be continuous / adjacent frequency bands, or some or all of the frequency bands may be separated in the frequency domain.

[0031] Multi-band operation may include frequency bands in the licensed spectrum, frequency bands in the unlicensed spectrum, or frequency bands in both the licensed spectrum and the unlicensed spectrum.

[0032] Carrier aggregation (CA) is an example of using two or more frequency bands in the licensed spectrum and / or unlicensed spectrum. Mixed combinations are also possible, for example, one or more frequency bands in the licensed band and one or more frequency bands in the unlicensed band. In addition, CA can also be used to aggregate additional carriers in one direction only, for example as supplementary carriers to improve transmission via UL, DL or SL.

[0033] 5G New Radio (NR) may support operation in an unlicensed spectrum so that single-band operation or multi-band operation may include a band or sub-band or resource pool in an unlicensed spectrum. The unlicensed spectrum may include bands that can coexist with IEEE802.11, such as bands within the 5 GHz and / or 6 GHz spectrum. For example, due to regulatory requirements, NR-U may support bandwidths of integer multiples of 20 MHz. The purpose of dividing into sub-bands is to minimize interference to coexisting systems (such as IEEE 802.11 systems), which may operate in the same band with one or more channels having the same bandwidth (such as a 20 MHz channel). Other examples of coexistence systems may use sub-bands with sub-band sizes and nominal frequencies different from those of the above-mentioned IEEE 802.11 systems. For example, the unlicensed spectrum may include a 5 GHz band, a 6 GHz band, a 24 GHz band, and a 60 GHz band. Examples of such unlicensed bands include industrial, scientific and medical (ISM) bands, which are reserved internationally for the use of radio frequency energy for industrial, scientific and medical purposes other than telecommunications.

[0034] During operation using unlicensed subbands, each subband may perform Listen-before-talk (LBT) separately. This may result in one or more subbands being busy or occupied due to interference, for example, from other communication systems coexisting in the same band, such as other public land mobile networks (PLMNs) or systems operating in accordance with the IEEE 802.11 specification or systems operating in accordance with the ETSI Broadband Radio Access Network (BRAN) specification. In this case, the transmitter (transmitting gNB or transmitting UE) can only transmit on subbands that are detected to be not busy (also called idle or unoccupied subbands). For example, when transmitting in the 5 GHz unlicensed operating band spanning more than 20 MHz, the transmitter (such as a gNB or UE) performs Listen-before-talk (LBT) separately on each subband. Once the LBT results for each subband are obtained, the device (e.g., gNB in ​​downlink (DL) or UE in uplink (UL)) can transmit on subbands determined to be idle or unoccupied, i.e., on winning subbands. Transmissions are not allowed on occupied, busy, or unacquired subbands.

[0035] In order to access resources or channels in the unlicensed spectrum, a so-called NR-U channel access is performed, which requires the use of a channel access procedure, which is a sensing-based procedure for evaluating whether a channel is available for transmission. The basic unit of sensing may be a sensing slot with a certain duration, such as T si =9μs. If the base station or UE senses the channel during the sensing time slot duration and determines that the power detected is less than the energy detection threshold for at least a period of time (such as 4μs) during the sensing time slot duration, then the sensing time slot duration T is considered to be si is idle. Otherwise, the perceived time slot duration is considered to be busy. When the channel is available or not busy, one or more transmissions can be performed on the channel. The so-called channel occupancy refers to one or more transmissions performed by the base station or UE on one or more channels after the base station or UE performs the corresponding channel access procedure. Channel occupancy time refers to the total time that the base station or UE and any other base station or UE share the channel occupancy to perform one or more transmissions on the channel after the base station or UE performs the channel access procedure. In order to determine the channel occupancy time, if the transmission gap is less than or equal to a certain period (such as 25μs), the gap duration is included in the channel occupancy time. Transmissions between the base station and the corresponding UE can share the channel occupancy time.

[0036] There can be various types of channel access procedures (CAP), for example:

[0037] - Type 1 CAP, the duration that the channel must be idle before transmission can be random. For example, the base station or UE can determine an initial counter N that ranges from 0 to the contention window CW p Randomly select between min,p ≤CW p ≤CW max,p , C.W. min,p and CW max,p Subject to the channel access procedure class (CAPC), when the channel is perceived to be idle for a period of time, the value of N will be decremented, and transmission can only be performed when N is 0.

[0038] - Type 2A: The duration of time that the channel must be perceived to be idle before transmission may be determined, and the channel may need to be idle for a sensing interval of a first duration (eg 25 μs).

[0039] - Type 2B: The time duration that the channel must be perceived to be idle before transmission may be determined, and the channel may need to be idle for a sensing interval of a second duration (eg 16 μs) that is shorter than the first duration.

[0040] - Type 2C: This type does not perform any sensing of the channel before transmission, and the duration of the corresponding transmission may have a predefined duration, for example, may be at most 583 μs.

[0041] For downlink (DL), multi-channel access, there may be corresponding types of DL multi-channel access procedures, for example:

[0042] - Type A: This type requires the base station to perform Type 1 LBT on each channel.

[0043] -Type B: This type requires the base station to perform Type 1 LBT on one of the multiple channels and sense the other channels within a sensing interval of at least a certain duration (such as 25μs) before performing transmission, optionally with constraints: the selection of the channel can be random, or the channel cannot be selected more than once every 1 second.

[0044] For uplink (UL) multi-channel access procedures, the UE may start transmission on the channel indicated by the base station or perform uplink transmission on the configured resources. The UE performs single channel sensing or access procedures only on a channel indicated by the base station, such as type 1 or type 2.

[0045] The following table shows the scenarios in which the UE uses different channel access procedures, and more specifically, under what scenarios or circumstances the UE uses a type 1 channel access procedure or a type 2 channel access procedure for PUSCH.

[0046]

[0047]

[0048] As described above, user devices can communicate directly with each other using sidelinks. In addition to implementing sidelink communications in licensed spectrum, sidelink communications can also be implemented in unlicensed or unlicensed spectrum. For example, one or more unlicensed sub-bands can be used for sidelink communications between two user devices. In other words, in addition to being implemented in licensed spectrum, sidelinks can also be implemented in unlicensed spectrum.

[0049] When implementing sidelink communications in unlicensed spectrum, improvements and enhancements are needed to allow the SL UE to select an appropriate channel access procedure CAP before performing transmissions on the sidelink. The present invention addresses this need by allowing a sidelink (SL) UE to select a CAP for evaluating resource availability in the unlicensed spectrum to perform SL transmissions based on whether certain criteria and / or conditions and / or scenarios are applicable.

[0050] According to the first embodiment, when the UE operates in Mode 1, it can select the CAP to be used in response to a corresponding indication from a network entity (e.g., a base station). This embodiment is advantageous because the network entity in Mode 1 controls the use of the resource pool and schedules other UEs to use the resources within the pool. Assuming that the gNB also has some information about the availability of resources used by other non-3GPP RATs, the gNB has a bird's eye view of the resource allocation and scheduling status of the resource pool, and can therefore indicate to the UE which type of CAP it needs to use to ensure that the UE can transmit successfully. This is the case as long as the resource pool is only used by 3GPP users, even if the network entity has no information about the usage status of the resource pool by other non-3GPP UEs.

[0051] According to a second embodiment, an indication of which CAP to use may be received from a network entity of a wireless communication network, such as a 3GPP network entity such as a base station, another SLUE, a network function such as an entity provided by a core network such as a 5GC, a road side unit (RSU) or a relay device, or from a network entity of a different or further wireless communication network, such as a non-3GPP device such as a WiFi access point. The network entity provides a channel occupancy time COT (channel occupancy time) shared with the transmitting UE for SL transmission. This embodiment has an advantage because by initiating COT sharing, the network entity essentially reserves a subband for use between the network entity and the UE. The network entity initiates the COT by executing a CAP to determine the availability of the subband and is therefore able to suggest a CAP type to be executed by the UE before it uses the same subband.

[0052] According to a third embodiment, a UE may select a CAP based on whether a network entity (such as a base station or another SLUE) of a wireless communication network that provides resource approval for sidelink transmission is aware of the availability of resources in an unlicensed spectrum for performing SL transmission. The network entity that provides the approval may also perform sensing of resources in the unlicensed spectrum, such as in an unlicensed sidelink resource pool (SL-URP). In addition, the network entity may receive its sensing results from other entities within the network, for example, by using inter-UE coordination (IUC) or from respective assistance information messages (AIMs), indicating which resources are available / unavailable for communication in the unlicensed spectrum. This embodiment has advantages because, as previously described, the network entity has information about the occupancy status of the resource pool, which is related to other non-3GPP UEs using the same set of resources. Since the network entity uses this information when scheduling resources to the UE through approval, the UE can be more confident in the quality of the resources provided and believe that the possibility of resource conflicts with other non-3GPP UEs is extremely small.

[0053] According to the fourth embodiment, the CAP may be selected based on the type of SL physical (PHY) channel to be transmitted by the SL transmission. This embodiment is advantageous because the UE may decide whether to perform a CAP of a longer duration to determine the occupancy of the used resources, or to perform a CAP of a shorter duration, based on the channel characteristics and the transmission to be performed. For example, in order to ensure reliability and minimize retransmissions, the UE may need to perform a CAP of a longer duration for control and data transmission of high priority SL transmissions, and use a CAP of a shorter duration for PSFCH transmissions, because it is more time sensitive based on the remaining PDBs.

[0054] According to a fifth embodiment, a CAP may be selected based on one or more specific characteristics of the SL transmission. This embodiment is advantageous because the UE's goal is to attempt to perform the transmission in the most reliable and delay-efficient manner at the first possible opportunity or in the initial transmission itself. By selecting a CAP based on the transmission characteristics, the UE can ensure that this is done while improving resource efficiency by avoiding failed transmissions and multiple retransmissions.

[0055] According to the sixth embodiment, the UE may select a CAP based on the configuration of resources in the unlicensed spectrum used to perform SL transmission. This embodiment has an advantage because the initial transmission and retransmission or the first periodic transmission and subsequent transmissions may occur between different subbands. Providing the UE with the ability to select a CAP independent of these factors may enable the UE to minimize the duration of the CAP while ensuring successful transmission.

[0056] According to the seventh embodiment, a CAP may be selected based on the structure of a resource pool in an unlicensed spectrum for SL transmission. This embodiment has an advantage because the UE must ultimately ensure that the resources it selects are indeed not occupied by other non-3GPP UEs. For example, when the resource pool configuration supports interleaving, the UE must ensure that a CAP is performed on each subband or RB set to check their availability before transmission. Selecting a CAP accordingly can ensure successful transmission.

[0057] According to the eighth embodiment, the selection of CAP depends on whether transmission is performed using continuous or non-continuous resources over time within the SL-URP. This embodiment has advantages because, similar to the configuration of resources, the resource pool configuration allows continuous or non-continuous frequency-based subchannels and continuous or non-continuous time slots. By adjusting the CAP type used for these different resource pool configurations, the UE can reduce the time to carry the CAP while ensuring successful transmission.

[0058] According to the ninth embodiment, a CAP may be selected based on the presence of a radio access technology (RAT) that uses a different RAT than the UE uses for SL transmission. This embodiment has an advantage because if the resource pool is configured only for 3GPP UEs, the UE may avoid performing a CAP altogether, thereby eliminating any resource competition with other non-3GPP UEs. Existing sensing mechanisms are sufficient to determine the availability of these resources.

[0059] The embodiment of the present invention may be implemented in a wireless communication system as shown in FIG. 1 , FIG. 2( a ) or FIG. 2( b ), which includes a base station and a user, such as a mobile terminal or an IoT device. Figure 3 is a schematic diagram of a wireless communication system, which includes a transmitter 300 (such as a base station) and one or more receivers 302, 304 (such as user equipment UE). The transmitter 300 and the receivers 302, 304 can perform communication via one or more wireless communication links or channels 306a, 306b, 308 (such as radio links). The transmitter 300 may include one or more antennas ANT T Or an antenna array having multiple antenna elements, a signal processor 300a and a transceiver 300b are coupled to each other. The receivers 302 and 304 include one or more antennas ANT UE Or an antenna array with multiple antennas, a signal processor 302A, 304a and a transceiver 302b, 304b are coupled to each other. The base station 300 and the UE 302, 304 can perform communication via respective first wireless communication links 306a and 306b (such as radio links using Uu interfaces), and the UE 302, 304 can communicate with each other via a second wireless communication link 308 (such as a radio link using PC5 or a side link SL interface). When the UE is not served by the base station or is not connected to the base station, for example, the UE is not in an RRC connected state, or more generally, when the base station does not provide SL resource allocation configuration or assistance, the UE can communicate with each other via the side link. Figure 3 systems or networks, Figure 3 One or more UEs 302, 304 and Figure 3 The base station 300 may operate according to the inventive teachings described herein.

[0060] User Equipment

[0061] The present invention provides a user equipment UE for a wireless communication network (such as a third generation partnership project 3GPP network),

[0062] The UE is used to communicate with one or more other UEs in the wireless communication network via a side link SL using a resource set in an unlicensed spectrum.

[0063] The UE is used to perform a channel access procedure CAP to evaluate the availability of a resource set for performing SL transmission, so as to perform SL transmission on the resource set in the unlicensed spectrum;

[0064] Therein, the UE is configured to select a CAP for evaluating the availability of a resource set for performing SL transmission based on a criterion.

[0065] According to an embodiment, the criteria for selecting a CAP are one or more of the following:

[0066] - an indication of a wireless communication network or another network entity of a wireless communication network, or

[0067] - an indication from a network entity of the wireless communication network, indicating initiation of a channel occupation time (COT) for SL transmission shared with the UE, or

[0068] - whether a network entity of the wireless communication network that provides approval for a resource set for SL transmission is aware of the availability of the resource set in the unlicensed spectrum for performing the SL transmission, or

[0069] - configuration of resource sets in the unlicensed spectrum for performing SL transmissions, or

[0070] - one or more specific characteristics of a SL transmission, or

[0071] - The type of SL physical (PHY) channel over which the SL transmission is to be transmitted, or

[0072] - a resource pool structure of resource sets in the unlicensed spectrum for SL transmission,

[0073] - There are transmissions using a radio access technology (RAT) that is different from the RAT used by the UE for SL transmissions.

[0074] According to an embodiment, the UE is configured to receive information on COT configuration from a network entity providing COT information on the COT configuration, the information indicating a CAP to be performed by the UE.

[0075] According to an embodiment, in the case where the network entity is aware of the availability of resources, the UE is configured to perform one or more of the following:

[0076] -Not performing CAP, or

[0077] - performing a CAP or a first CAP in the case where the SL transmission has one or more specific characteristics, and / or

[0078] - In case the SL transmission does not have one or more specific characteristics, the second CAP is performed or not performed, and the first CAP and the second CAP are different.

[0079] According to an embodiment, in the case where the network entity is not aware of the availability of resources, the UE will perform one or more of the following:

[0080] -Perform CAP, or

[0081] - In case the SL transmission has one or more specific characteristics, a first CAP is performed, and, in case the priority of the SL transmission does not have one or more specific characteristics, a second CAP is performed or no CAP is performed, the first CAP and the second CAP are different.

[0082] According to an embodiment, the UE is configured to select a CAP based on whether the SL transmission transmits one or more of the following:

[0083] - Physical Sidelink Control Channel PSCCH,

[0084] - Physical side link shared channel PSSCH,

[0085] - Physical Sidelink Feedback Channel PSFCH,

[0086] - Physical side link broadcast channel PSBCH,

[0087] - Stage I SCI,

[0088] -Phase II SCI.

[0089] According to an embodiment, in case that the SL transmission transmits a physical sidelink control channel PSCCH and / or a physical sidelink shared channel PSSCH, the UE is configured to select a CAP according to one or more specific characteristics of the SL transmission.

[0090] According to an embodiment, in case that the SL transmits the physical side link feedback channel PSFCH,

[0091] - the UE is configured to perform a CAP that provides faster access or shorter duration than a CAP used to transmit SL transmissions on a channel other than the PSFCH, or

[0092] - In case the UE cannot find an available PSFCH timeslot within the packet delay budget (PDB) of the TB for SL transmission, the UE is configured to change from the currently used CAP to a new CAP that provides faster access or shorter duration compared to the currently used CAP.

[0093] According to an embodiment, in the case where the SL transmission transmits a physical side link control channel PSCCH or a physical side link shared channel PSSCH in the first COT and transmits a physical side link feedback channel PSFCH in the second COT, and in the case where resources between the first COT and the second COT are used by other UEs using another COT,

[0094] - the UE is configured to perform a first CAP for transmission of a PSCCH or a PSSCH and to perform a second CAP for transmission of a PSFCH, or

[0095] - In case the UE does not enable feedback for blind transmission, the UE is used to perform CAP only on PSCCH or PSSCH.

[0096] According to an embodiment, one or more specific features of SL transmission include one or more of the following:

[0097] -The priority of the SL transmission is equal to or higher than the configured or preconfigured threshold,

[0098] - The packet delay budget PDB or delay of the SL transmission is equal to or higher than the configured or preconfigured threshold,

[0099] - Whether the SL transmission is periodic or aperiodic,

[0100] - Whether the SL transmission is an initial transmission or a retransmission, wherein if the SL transmission is an initial transmission, the UE performs a first CAP or does not perform the first CAP, and if the SL transmission is a retransmission, the UE performs a second CAP,

[0101] - whether the resources used for SL transfer are selected through a re-evaluation process,

[0102] - Whether the resources used for SL transmission are selected through preemption,

[0103] - the type of sensing used to select resources for SL transmission, such as full sensing, partial sensing, random resource selection,

[0104] - Based on the operating mode, SL transmission is performed in Mode 1 or Mode 2,

[0105] - Whether the SL transmission includes Inter-UE Coordination (IUC) or Assistance Information Message (AIM),

[0106] -Whether the SL transmission belongs to a specific propagation type, such as unicast, multicast, or broadcast,

[0107] -UE location, distance to the receiving UE (RX UE), minimum communication range (MCR), area where the UE is located (e.g. area ID),

[0108] -QoS profile for SL transport.

[0109] According to an embodiment, one or more specific characteristics of SL transmission include priority of SL transmission, wherein if the SL transmission has a first priority, the UE will execute a first CAP, and if the SL transmission has a second priority, the UE will execute a second CAP, and the first priority and the second priority are different.

[0110] According to an embodiment, one or more specific characteristics of the SL transmission include a priority of the SL transmission, wherein if the priority of the SL transmission is equal to or higher than a configured or preconfigured threshold, the UE will execute a first CAP, and if the priority of the SL transmission is lower than the threshold, the UE will execute a second CAP or not execute the second CAP.

[0111] According to an embodiment, one or more specific features of SL transmission include a packet delay budget (PDB) of SL transmission, wherein, in a case where the PDB reaches or is higher than a configured or pre-configured threshold, the UE will perform a first CAP or will not perform the first CAP, and in a case where the PDB is lower than the threshold, the UE will perform a second CAP, or in a case where the PDB reaches or is higher than the configured or pre-configured threshold, the UE will not perform the second CAP.

[0112] According to an embodiment, in the event that the first CAP is performed on the primary band and fails, for example, the UE will perform SL transmission on other resources (such as another carrier or subchannel or subband or bandwidth portion in the licensed or unlicensed spectrum) by performing the following:

[0113] - a first CAP or a second CAP in the case of a transmission performed on an unlicensed set of resources, wherein the first CAP is the same as that originally performed, e.g. on the primary frequency band, and the second CAP is different from the first CAP, or

[0114] - In case the transfer is performed on the authorized resource set, there is no CAP.

[0115] According to an embodiment, one or more specific characteristics of SL transmission include the periodicity of SL transmission, wherein

[0116] - the UE is configured to perform a first CAP in case of aperiodic SL transmission and a second CAP in case of periodic SL transmission, or

[0117] -UE is used to perform the same CAP for aperiodic SL transmission or retransmission,

[0118] - The UE is configured to implement different CAPs for periodic SL transmissions so that each transmission of a transport block TB uses a different CAP, wherein the CAP is indicated by the resource reservation periodicity.

[0119] According to an embodiment, one or more specific characteristics of the SL transmission include whether the SL transmission is an initial transmission or a retransmission on resources reserved within a certain number of future time slots using a time resource indicator value (TRIV) and / or a frequency resource indicator value (FRIV) within a certain number of future frequency resources (e.g., subchannels), wherein, if the SL transmission is an initial transmission, the UE is used to perform a first CAP or no CAP, and if the SL transmission is a retransmission, the UE is used to perform a second CAP.

[0120] According to an embodiment, one or more specific features of SL transmission include new resources for SL transmission after re-evaluating or preempting initial resources scheduled for SL transmission, and wherein the UE is configured to perform a first CAP for checking the availability of the new resources, which is faster or of shorter duration than a second CAP for checking the availability of the initial resources.

[0121] According to an embodiment, one or more specific characteristics of SL transmission include the type of sensing performed by the UE to determine available resources for SL transmission, wherein

[0122] - In the case of full awareness, the UE does not perform a CAP or performs a CAP with a duration less than some configured or pre-configured threshold, such as a minimum duration CAP, e.g. a Type 2C CAP, or

[0123] - In case of partial sensing, when the amount of resources sensed by the UE is below a configured or pre-configured threshold, the UE shall perform CAP, or

[0124] - In case of random selection of resources, the UE shall perform CAP.

[0125] According to an embodiment, one or more specific features of SL transmission include an operation mode in which SL transmission is used to transmit TBs, wherein

[0126] - In case of Mode 1 transmission, if the gNB is aware of the availability of resources provided to the UE, the UE does not perform a CAP or performs a CAP of the shortest duration,

[0127] - In case of Mode 1 transmission, if the gNB is not aware of the availability of resources to be provided to the UE, the UE shall perform CAP,

[0128] - In case of Mode 2 transmission, the UE shall decide whether to perform CAP and the type of CAP to be performed based on one or more specific characteristics of the SL transmission.

[0129] According to an embodiment, one or more characteristic features of the SL transmission include whether the SL transmission contains inter-UE coordination (IUC) information, wherein

[0130] - In case the SL transmission includes IUC information and data, the UE performs the first CAP, and

[0131] - In case the SL transmission includes only IUC information, the UE shall execute a second CAP which provides faster access or is of shorter duration than the first CAP.

[0132] According to an embodiment, one or more characteristics of the SL transmission include whether the resources to be used for the SL transmission are obtained from an inter-UE coordination (IUC) message, wherein

[0133] - The UE does not implement CAP, or

[0134] - the UE shall perform the CAP based on the priority or characteristics of the intended transmission, wherein the UE shall perform the CAP if the SL transmission has a first priority or one or more specific characteristics, and shall not perform the CAP if the SL transmission has a second priority or does not have one or more specific characteristics (the first priority and the second priority are different), or

[0135] - The UE shall execute the CAP indicated in the IUC message, or

[0136] -The UE performs CAP according to whether other UEs providing the IUC message perform CAP, wherein if other UEs do not perform CAP on the resources indicated in the IUC, the UE performs a first CAP, and if other UEs have performed CAP on the indicated resources, the UE does not perform CAP or performs a second CAP.

[0137] According to an embodiment, the IUC message includes one or more of the following:

[0138] - a preferred set of resources for transmission via the SL,

[0139] - a non-preferred set of resources for transmission via the SL,

[0140] -Conflict indication.

[0141] According to an embodiment,

[0142] One or more specific features of the SL transmission include replacing an initially selected resource for the SL transmission with a new resource, such as by the UE performing a resource reselection procedure in response to receiving an inter-UE coordination (IUC) message from another UE including a conflict indication or a large number of non-preferred resources, and

[0143] The UE is configured to implement a CAP different from the CAP used when initially selecting the resource.

[0144] According to an embodiment, the UE is configured to perform one or more of the following operations in response to the IUC message:

[0145] - aggregate another carrier,

[0146] - switch to another licensed frequency band,

[0147] - switch to another unlicensed band,

[0148] -Stop the transmission.

[0149] According to an embodiment, one or more specific characteristics of the SL transmission include the propagation type of the SL transmission, wherein

[0150] - in the unicast case, the UE performs a first type CAP with a first duration,

[0151] - In case of groupcast or broadcast, the UE performs a second type of CAP having a second duration, the first duration being shorter or longer than the second duration.

[0152] According to an embodiment, one or more specific features of SL transmission related to UE location include one or more of the following:

[0153] - the transmission distance of the SL transmission, e.g., the distance between the UE and another UE to which the SL transmission is directed, e.g., the physical distance between the UEs,

[0154] - starting location of the SL transmission, such as the location of the UE, such as the area where the UE is located or coordinates indicating the location of the UE, such as longitude and / or latitude and / or altitude,

[0155] -Required minimum communication range (MCR),

[0156] - the path loss experienced by the SL transmission while transmitting, for example, as measured by the signal-to-noise ratio (SNR), signal-to-interference-and-noise ratio (SINR), received signal strength indication (RSSI), or reference signal received power (RSRP),

[0157] - The identity ID of a given UE.

[0158] According to an embodiment, the resource configuration in the unlicensed spectrum comprises a plurality of resource sets, each of the plurality of resource sets being associated with a specific CAP to be used, wherein the resource set comprises a bandwidth portion or a resource pool or a subband or a subchannel or an aggregated carrier.

[0159] According to an embodiment, the UE is configured to receive an indication from a network entity in response to a request of the UE via unicast or as a groupcast or broadcast, the indication comprising configuration on how to initiate a COT or how to initiate a COT and a future COT.

[0160] According to an embodiment, the future COT is one or more of the following:

[0161] - the next n future COTs, e.g., the next 5 COTs executed by the UE,

[0162] - the next n future transmissions, e.g., COT for the next 5 transmissions,

[0163] - the future COT until the timer expires, e.g. the COT for the next 100 milliseconds,

[0164] - until there is another future COT configured, e.g. in response to a new configuration,

[0165] - Future COT until an event occurs, such as HARQ decoding failure reaching a configured or preconfigured threshold or in response to a certain IUC message.

[0166] According to an embodiment, the UE is configured to perform, according to whether a resource pool in an unlicensed spectrum available for SL transmission supports interlacing:

[0167] - the first CAP for SL transmission in case the resource pool supports interlacing or in case the SL transmission spans different interlacings,

[0168] - Second CAP in case the resource pool does not support interlacing.

[0169] According to an embodiment, the UE performs, based on the similarity of current resources for current SL transmission and future resources for future transmission or retransmission (these resources have been reserved within a certain number of future time slots using a time resource indication value (TRIV) and / or within a certain number of future frequency resources (e.g., subchannels) using a frequency resource indication value (FRIV):

[0170] - In case the current resource and the future resource are in the same subband or subchannel, do not perform CAP or perform the first CAP for the future SL transmission, or

[0171] - Performing a second CAP for future SL transmission in case the current resources and the future resources are in different resource block RB sets in different subbands or subchannels.

[0172] According to an embodiment, the UE performs, according to whether the SL transmission uses continuous resources or non-contiguous resources in a resource pool in an unlicensed spectrum that can be used for SL transmission:

[0173] - In case the resources are contiguous, perform first CAP or no CAP for SL transfer, or

[0174] - In case the resources are non-contiguous, a second CAP is performed for SL transmission.

[0175] According to an embodiment, the UE performs, based on the presence of a transmission using a RAT different from the radio access technology RAT used by the UE for SL transmission:

[0176] - performing a first CAP or no CAP for SL transmission in case the subband, subchannel or resource pool for SL transmission is allocated only to the RAT used by the UE to perform SL transmission, or

[0177] - performing a second CAP for SL transmission in case the subband, subchannel or resource pool used for SL transmission is shared by different RATs, or

[0178] - In case of semi-static sub-band, sub-channel or resource pool definition, there is no CAP.

[0179] According to an embodiment, the CAP that the UE expects to perform includes one or more of the following:

[0180] ● Implement Listen Before Talk (LBT) procedures on resources,

[0181] ● One or more energy levels on the resource are detected, such as received signal strength indication (RSSI), signal-to-noise ratio (SNR), or signal-to-noise-and-interference ratio (SINR),

[0182] · measuring pilot symbols transmitted on the resource and / or determining one or more measurement values, such as 3GPP reference signal received power (RSRP) or 3GPP reference signal received quality (RSRQ),

[0183] Decode the Side Link Assistance Information Message (SL AIM),

[0184] Decode the sidelink inter-UE coordination message (IUC),

[0185] Decode the AIM information,

[0186] Decode a control message transmitted on a resource (e.g., 3GPP Downlink Control Information (DCI) or 3GPP Sidelink Control Information (SCI), or an IEEE 802.11 Physical Layer Convergence Protocol (PLCP) header), or extract information about one or more transmissions, such as a transmission that is in progress or about to be performed, or the remaining duration of a transmission that is in progress.

[0187] According to an embodiment, the LBT procedure includes:

[0188] - Type 1 CAP, sensing the channel for SL transmission at random times, or

[0189] - Type 2 ACAP, sensing the channel for SL transmission 25μs, or

[0190] - Type 2B CAP, sensing channel 16μs for SL transmission,

[0191] - Type 2C CAP, not aware of the channel used for SL transmission, or

[0192] - New CAP type to sense the channel for SL transmission with a duration of configured or preconfigured time.

[0193] According to an embodiment, CAP evaluates the availability of a channel for performing SL transmission based on perception, wherein, when the channel is sensed within a certain time and it is determined that the detected power for at least a certain time within a certain duration is less than an energy detection threshold, the channel is considered to be idle for a certain duration, otherwise, the channel is considered to be busy.

[0194] According to an embodiment, the difference between the first CAP and the second CAP depends on the duration of LBT, sensing or measurement that the UE must perform to determine whether the resources are occupied by other UEs.

[0195] According to an embodiment, the network entity is one of:

[0196] - Base station, or

[0197] - further UE, or

[0198] - Network functions, such as entities provided by the core network, such as 5GC, or

[0199] - non-3GPP devices, such as WiFi access points, or

[0200] -RSU or relay unit.

[0201] system

[0202] The present invention provides a wireless communication system, such as a 3rd Generation Partnership Project 3GPP system, comprising one or more user equipments UE of the present invention and one or more base stations.

[0203] According to an embodiment, the UE includes one or more of the following: a power-limited UE, or a handheld UE (such as a UE used by pedestrians (also referred to as a vulnerable road user VRU or a pedestrian UE (P-UE)), or a body-worn or handheld UE used by public safety personnel and emergency personnel (also referred to as a public safety UE (PS-UE)), or an IoT UE, such as a sensor, an actuator, or a UE provided in a campus network for performing repetitive tasks and requiring regular input from a gateway node, or a mobile terminal, or a fixed terminal, or a cell IoT-UE, or a SL UE, or vehicle-mounted UE, or vehicle-mounted group leader UE (GL-UE), or scheduling UE (S-UE), or IoT or narrowband IoT (NB-IoT) device, or ground-based vehicle, or aerial vehicle, or drone, or mobile base station, or roadside unit (RSU), or building, or any other item or device providing network connectivity, enabling the item / device to communicate using a wireless communication network, such as a sensor or actuator, or any other item or device with network connectivity, enabling the item / device to communicate using a side link of a wireless communication network, such as a sensor or actuator, or any network entity with side link capability, and,

[0204] The base station includes one or more of the following: a macro cell base station, or a small cell base station, or a central unit of a base station, or a distributed unit of a base station, or an integrated access and backhaul (IAB) node, or a roadside unit RSU, or a UE, or a SLUE, or a group leader UE (GL-UE), or a relay, or a remote radio head, or an AMF, or an SMF, or a core network entity, or a mobile edge computing (MEC) entity, or a network slice in the context of NR or 5G core, or any transmit / receive point (TRP), enabling an item or device to communicate using a wireless communication network, and the item or device is provided with network connectivity to communicate using the wireless communication network.

[0205] method

[0206] The present invention provides a method for operating a user equipment UE in a wireless communication network such as a third generation partnership project 3GPP network, the method comprising:

[0207] communicating, by the UE, with one or more further UEs in a wireless communication network via a side link SL using a set of resources in an unlicensed spectrum,

[0208] performing a channel access procedure CAP by the UE to evaluate availability of a resource set for performing SL transmission in order to perform SL transmission on the resource set in the unlicensed spectrum,

[0209] The CAP for evaluating the availability of a resource set for performing SL transmission is selected by the UE based on criteria.

[0210] Computer program product

[0211] An embodiment of a first aspect of the present invention provides a computer program product, the computer program product comprising instructions, which, when the program is executed by a computer, causes the computer to perform one or more methods according to the present invention.

[0212] Embodiments of aspects of the present invention are now described in more detail with reference to the accompanying drawings. It should be noted that the aspects or embodiments summarized and described below may be combined so as to implement some or all aspects / embodiments in one embodiment. In addition, it should be noted that when "resources" are mentioned in this description, resources should be understood to include one or more of the following:

[0213] - one or more symbols,

[0214] - one or more time slots or subframes or frames,

[0215] - one or more frequencies or carriers or subchannels or groups of subchannels,

[0216] - one or more frequency bands, such as unlicensed sub-bands,

[0217] - one or more bandwidth portions,

[0218] - one or more resource pools,

[0219] - one or more LBT sub-bands,

[0220] - One or more spatial resources, for example using spatial multiplexing.

[0221] In addition, it should be noted that when a "resource set" is mentioned in this specification, the resource set may include one or more resources, and the definition of the resource is as described above.

[0222] Figure 4 According to an embodiment of the present invention, a user equipment UE is shown. UE 400 (also referred to as a side link UE (SL-UE)) includes one or more antennas 402 and a signal processor 404 for performing one or more operations, such as operations involving antenna 402, such as sending / receiving data (such as payload data or control data or inter-UE coordination (IUC) messages). UE 400 operates in a wireless communication system, as described above with reference to FIGS. 1 to 4 Figure 3The system described is, for example, a 3rd Generation Partnership Project 3GPP system or network. UE 400 is used to communicate with other UEs (such as UE 406) using a side link or PC5 interface, as shown at 408. In addition, UE 400 can be connected to a base station or gNB 410. gNB 410 includes a signal processor 410a and one or more antennas 410b for wireless communication with other network entities (such as UE 400 and UE 406). When operating in mode 1, UE 400 receives resources allocated by gNB 410 via Uu interface 412, which will be used by UE 400 for communication via side link 408. As described above, when operating in mode 2, UE 400 may not be connected to gNB 410 and perform sense and access resource allocation or random access based resource allocation, such as when transmitting to UE 406.

[0223] Figure 4 A spectrum 414, such as a radio spectrum, is further schematically shown, including resources to be used for communication within a wireless communication system or network. The resources that can be used for SL communication can include one or more of the following: one or more symbols, one or more time slots or subframes or frames, one or more resource blocks (RBs) or frequencies or carriers or subchannels or subchannel groups, one or more frequency bands. As shown, the spectrum 414 includes a licensed spectrum 416 and an unlicensed spectrum 418. The licensed spectrum 416 is a portion of the spectrum reserved for wireless communication systems including UEs 400 and 406 and base stations 410. In other words, the resources in the licensed spectrum are used exclusively by wireless systems according to regulations of regulatory agencies and entities. The unlicensed spectrum 418 includes resources that can be used by multiple wireless communication systems, such as another wireless communication system that complies with the 3GPP standard but is operated by a different operator, or a system that uses a different radio access technology (such as WiFi or Bluetooth).

[0224] According to an embodiment, for sidelink communication, a resource pool 420 (also referred to as a sidelink resource pool SL-RP) may be provided, and the UE 400 configures or preconfigures the resource pool 420. Although only one resource pool is depicted in the figure, multiple such resource pools may be configured or preconfigured. The resource pool may include resources only from the unlicensed spectrum 418 or only from the licensed spectrum 416, or as Figure 4 In the illustrated embodiment, resources may be included only from the licensed spectrum 416 and from the unlicensed spectrum 420. According to further embodiments, resources in the unlicensed spectrum may be aggregated using carrier aggregation.

[0225] According to an embodiment of the present invention, UE 400 may need to perform a suitable channel access procedure, such as one of the channel access procedures CAP described above, before performing transmission via side link 408 using resources from unlicensed spectrum 420a. According to the method of the present invention, initially, UE 400 determines whether specific standards and / or conditions and / or specific scenarios apply (as shown in 422), and selects a CAP to be used based on the determination (as shown in 426). It is worth noting that selecting a CAP may also include determining that a CAP is not required. Once a CAP is selected, in order to perform the required SL transmission on the resources in the unlicensed spectrum, UE 400 will perform the selected channel access procedure to evaluate the availability of resources in the unlicensed spectrum that can be used for SL transmission (e.g., SL transmission to UE 406 via side link 408).

[0226] First embodiment

[0227] According to the first embodiment of the present invention, UE 400 selects the CAP to be used according to the indication of the network entity of the wireless communication network. For example, when UE 400 operates in mode 1, the base station or gNB 410 may indicate the CAP to be used to UE 400. For example, gNB 410 may include the CAP to be used together with the approval of the resources in the unlicensed spectrum to be used for SL transmission. The CAP to be used may be part of the approval or may be signaled separately from the actual approval. In the case where UE 400 operates in mode 2, the CAP may be signaled by UE 406. For example, in mode 1, gNB 410 may provide configuration approval or dynamic approval to UE 400. In the case where configuration approval is provided using RRC signaling through RRC information elements, gNB 410 may also include parameters indicating the type of CAP that the UE must use. Similarly, when dynamic approval is provided to UE 400 using downlink control information (DCI) signaling, gNB 410 may also include similar parameters regarding which type of CAP the UE uses for the resources included in the approval.

[0228] Second embodiment

[0229] As described above, during the channel occupancy time (COT), the network entity performing the channel access procedure can share the channel occupancy with other entities of the wireless communication network. According to the second embodiment of the present invention, the network entity providing the COT (such as the gNB 410 or further the SL UE 406) can provide the UE 400 with information about the COT configuration. This information may include the type of CAP that the UE 400 will use. In other words, based on the COT initiated by the gNB 410 or the UE 406, the so-called COT sharing information can be provided to the UE 400, which indicates which CAP the UE 400 using the COT of other entities is to execute.

[0230] Figure 4 4281, in the case where UE 400 operates in Mode 1, UE 400 may request CAP configuration from gNB 410, for example, using a CAP request. Figure 4 As shown in 4301, gNB 410 may broadcast the CAP to be used to all UEs. If UE 400 operates in Mode 2 but manages to read the broadcast channel from gNB 410, the CAP to be used may be received from gNB 410, as shown in 4301. On the other hand, in the case where UE 400 and UE 406 operate in Mode 2 without being connected to gNB 410, as described above with reference to FIG. 2(b), UE 406 may receive the CAP configuration from UE 400 by using inter-UE coordination (IUC). For example, UE 406 may request UE 400 to provide a CAP, as shown in 4282, and in response, receive the CAP to be used from UE 400, as shown in 4302.

[0231] For example, the UE may receive an indication from the network entity in response to a request of the UE via unicast or as a multicast or broadcast, and the indication may include configurations on how to initiate the COT or how to initiate the COT and future COTs. The future COT may be one or more of the following:

[0232] - the next n future COTs, e.g., the next 5 COTs executed by the UE,

[0233] - the next n future transmissions, e.g., COT for the next 5 transmissions,

[0234] - the future COT until the timer expires, e.g. the COT for the next 100 milliseconds,

[0235] - until there is another future COT configured, e.g. in response to a new configuration,

[0236] - Future COT until an event occurs, such as HARQ decoding failure reaching a configured or preconfigured threshold or in response to a certain IUC message.

[0237] In other embodiments, UE 400 may broadcast the CAP, which is then received by UE 406, without sending request 4282. In the case where the CAP is sent without a request, the CAP may be piggybacked on another message transmitted by UE 400.

[0238] According to other embodiments, UE 400 may simply transmit the CAP to surrounding UEs, similar to a polling message, in order to support surrounding UEs on an access procedure type for a portion of the unlicensed spectrum (e.g., a portion of the resource pool for sidelink communication). In this case, the UE 400 that sends the CAP may be a coordinating UE. It is worth noting that UE 400 is not necessarily a mobile UE, but may also be a fixed unit, such as a roadside unit (RSU), whose role is to provide support for coordinated resources for V2X communication.

[0239] Third embodiment

[0240] According to a third embodiment of the present invention, the UE may select a CAP based on whether a network entity of a wireless communication network that provides resource approval for sidelink communication is aware of the availability of resources in an unlicensed spectrum for performing SL transmission. For example, in a case where the network entity is aware of the availability of resources, the UE may not perform the CAP. According to other examples, the UE may perform different CAPs based on whether the SL transmission has one or more specific characteristics. In other words, in a case where the SL transmission has one or more specific characteristics, the UE may perform a CAP, such as a first CAP with a longer duration, and in a case where the SL transmission does not have one or more specific characteristics, the UE may or may not perform a further CAP, such as a second CAP with a shorter duration.

[0241] For example, if the network entity is aware of the availability of resources and provides resources for the initial transmission that the UE uses immediately, the UE does not need to perform CAP for the initial transmission. However, since the resources for the retransmission are scheduled in a later time slot, the UE must perform some type of CAP.

[0242] According to other embodiments, the UE may perform a CAP in any case without the network entity being aware of the availability of resources. According to other examples, the UE may perform a CAP based on whether the SL transmission has one or more specific characteristics. In other words, the UE may perform a CAP if the SL transmission has one or more specific characteristics, otherwise, the UE does not perform a CAP if the SL transmission does not have one or more specific characteristics. Since the network entity is unaware of the resource availability and occupancy of other non-3GPP UEs using these resources, it is determined by the UE based on the nature of the transmission it intends to perform. For example, the UE may perform a longer duration CAP for a high priority transmission to ensure that the resources are indeed available, while it may choose to perform a shorter duration CAP for a low priority transmission. Similarly, if the remaining PDB of the transmission is small or is about to expire, the UE may choose to perform a shorter CAP in an attempt to complete the transmission before the PDB expires.

[0243] A network entity (e.g., gNB 410 or UE 406) may perform resource sensing of the unlicensed spectrum to be included in the approved spectrum to determine the availability of transmission resources. According to other embodiments, each network entity receives information from other network entities, such as by forwarding information using IUC or Assistance Information Messages (AIM), regarding the availability of certain resources in the unlicensed spectrum sensed by the other entities.

[0244] Thus, the gNB 410 or UE 406 may understand the availability of resources to be used for transmission in the unlicensed spectrum based on its own perception results and / or from information included in one or more AIMs.

[0245] According to an embodiment, if the gNB 410 or UE 406 is capable of performing certain sensing and / or is capable of receiving reports from other network entities, such as information including information about resources occupied by other RATs, the gNB 410 or UE 400 may provide such functionality to the UE 400. In response to receiving this information, the UE 400 may determine that no CAP needs to be performed. According to a further embodiment, the UE 400 may link this decision to a specific attribute of the transmission to be performed, such as the transmission priority, instead of not performing any CAP. For example, if the transmission to be performed has a high priority, that is, the priority exceeds a certain threshold, although the gNB 410 or UE 406 indicates that they are aware of the availability of resources for the transmission and provide the sensed or checked available resources, the UE 400 may still decide to perform a certain CAP for such high priority transmission, such as the Type 1 CAP described above. Thereby improving the reliability of the transmission. On the other hand, for transmissions with lower priorities, such as transmissions with a priority lower than the above threshold, the reliability of the transmission may not be so important, so the UE 400 may decide that no CAP is required for such low priority transmissions. Regarding the above threshold, it should be noted that the threshold may be configured or pre-configured on the UE 400, or may be a resource pool configuration or a system-wide configuration.

[0246] In the event that the gNB 410 or UE 406 indicates to the UE 400 that they are not aware of the availability of resources to be used for transmissions in the unlicensed spectrum (e.g., because they do not perform any sensing and do not rely on AIM or any measurement reports from other UEs), the UE 400 determines that it is necessary to perform a CAP for each resource or channel indicated in the grant received from the gNB 410 or UE 406. For example, depending on the specific attributes of the transmission to be performed, a specific type of CAP may be selected. For example, a high priority transmission as described above may require the performance of a Type 1 CAP, while other transmissions (such as low priority transmissions or retransmissions of an initial transmission) may require the performance of a Type 2 CAP.

[0247] It should be noted that different types of CAPs differ in the duration that the UE performs LBT, senses, or measures the resources that the UE intends to use for transmission. For example, the first CAP may last longer (such as a Type 1 CAP), which depends on the Channel Access Priority (CAPC) table (see Table 4.2.1-1 in TS37.213), while the second CAP may last shorter, such as the Type 2 CAP described above.

[0248] Fourth embodiment

[0249] According to the sixth embodiment of the present invention, UE 400 may decide the CAP to be used according to the type of physical (PHY) channel transmitted by the SL transmission, that is, whether the SL transmission transmits one or more of the following: physical side link control channel PSCCH, physical side link shared channel PSSCH, physical side link feedback channel PSFCH and physical side link broadcast channel PSBCH. This may also depend on the type of transmission performed in these channels, that is, the first stage SCI on PSCCH or the second stage SCI on PSSCH. In the case where the SL transmission transmits the physical side link control channel PSCCH and / or the physical side link shared channel PSSCH, the UE may select the CAP according to one or more specific characteristics of the SL transmission. For example, if UE 400 transmits PSCCH or PSCCH, UE 400 may perform type 1 CAP for transmissions with specific attributes (e.g., high priority), and vice versa, type 2 CAP may be used, for example, for transmissions with lower priority.

[0250] According to an embodiment, if UE 400 transmits a physical sidelink feedback channel PSFCH, the UE performs a CAP (e.g., a type 2 CAP) that provides faster access or shorter duration than a CAP (e.g., a type 1 CAP) used to transmit SL transmission on a channel other than PSFCH (e.g., PSCCH or PSCCH). If the UE cannot find an available PSFCH time slot within the packet delay budget (PDB) of the TB of the SL transmission, the UE can change from the currently used CAP to a new CAP that provides faster access than the currently used CAP, such as changing from a type 2A or type 2B CAP to a type 2C CAP. The advantage of the UE being able to change the CAP based on the PDB is that it can select a CAP of shorter duration, such as a type 2C CAP, which only requires the UE to wait before accessing the channel or resource, compared to a type 2A CAP that expects the UE to perform LBT before accessing the channel or resource.

[0251] According to an embodiment, UE 400 will independently perform CAP for each transmission of PSCCH or PSSCH and each PSFCH used for the transmission, provided that they belong to different COTs and the resources in between are used by different UEs using another COT. This is because different COTs may point to different subbands, which means that there are different resources on different subchannels. Therefore, a UE performing CAP on one COT does not indicate the availability of resources on another COT. For example, if the UE performs Type 1 CAP on PSCCH and PSSCH on one COT for control and data transmission, the UE may choose to perform Type 2C CAP on feedback transmission on another COT.

[0252] In the case where the UE 400 performs blind transmission without feedback enabled, the UE 400 is expected to perform CAP only on PSCCH / PSCCH. This is because for blind transmission, the UE does not need to send any feedback for the transmission, and therefore does not need to access PSFCH.

[0253] Fifth embodiment

[0254] According to the fifth embodiment of the present invention, UE 400 may decide the CAP to be used according to one or more characteristics of the SL transmission to be performed.

[0255] According to an embodiment, the priority of the transmission may be mapped to a channel access procedure category (CAPC) table. The CAPC table (see Table 4.2.1-1 of TS37.213) provides a mapping between contention window sizes for different transmissions with priority values ​​ranging from 1 to 4. Assuming that these priority values ​​are mapped to PQI priority values ​​ranging from 1 to 8, each transmission can be assigned a certain range of contention window sizes. Based on each priority, the UE can choose to perform different types of CAPs with different durations. For example, the contention window size range for high priority transmissions with priority values ​​mapped to channel access priority category 1 is 3 to 7. This determines the duration that the UE must perform LBT or sensing to determine the availability of a given resource. Therefore, a longer duration enables the UE to specifically determine the availability of resources.

[0256] According to an embodiment, the packet delay budget PDB of the transmission to be performed may be mapped to the remaining COT timer.

[0257] According to an embodiment, the CAP may be determined based on whether the SL transmission is a non-periodic transmission or part of a series of periodic transmissions. For example, the UE 400 may use the same CAP for non-periodic transmissions, i.e., use the same CAP for each single or one-time transmission, and also apply the same CAP if retransmission is required. According to other embodiments, the UE 400 may use different CAPs for periodic transmissions, and the CAP may be indicated by resource reservation periodically, and each transmission of the transport block TB uses one CAP.

[0258] According to an embodiment, the CAP may be selected based on whether the transmission is an initial transmission or a retransmission to future resources, which may have been reserved using, for example, a time resource indication value (TRIV) or a frequency resource indication value (FRIV), etc. In this case, the UE may use different CAPs for initial transmissions and retransmissions.

[0259] According to an embodiment, UE 400 may select a CAP based on whether a resource for transmission is selected after re-evaluation or preemption of the initially selected resource. For example, UE 400 may use a first type of CAP (e.g., a Type 1 CAP) to access the initially determined transmission resource. However, the result may be that the resource is preempted or needs to be re-evaluated. In this scenario, the UE, after re-evaluation / preemption, uses a CAP (e.g., a Type 2 CAP of shorter duration) that checks the availability of resources or channels faster than the CAP used to check the availability of the initial resource for the resource for transmission.

[0260] According to an embodiment, the CAP to be used may be selected according to the type of sensing performed by the UE to determine the resources for transmission.Different types of CAPs may be used depending on whether the resource selection is as a full resource selection, a partial resource selection or a random resource selection.

[0261] According to an embodiment, when transmitting a transport block (TB), the CAP may be determined based on the operation mode of the UE 4000. For example, different CAPs may be selected depending on whether the UE operates in mode 1 (see FIG. 2(a) ) or in mode 2 (see FIG. 2(b) ).

[0262] According to an embodiment, a CAP may be selected based on whether the transmission includes IUC information (e.g., AIM). UE 400 may use the same CAP as the data transmitted with IUC. In the case of IUC transmission alone, the UE may use a separate or different type of CAP (allowing faster access to resources), such as a Type 2 CAP.

[0263] According to an embodiment, UE 400 may decide CAP based on whether to utilize resources obtained from an IUC message (such as AIM). For example, when receiving an IUC message from UE 406, UE 400 assumes that UE 406 performs a certain type of CAP before providing IUC information, and thus may decide not to perform any CAP, or perform CAP only for transmissions with specific attributes (such as the priority explained above). If UE 406 performs a Type 1 CAP before providing IUC information, UE 400 may decide to use a Type 2C CAP.

[0264] According to an embodiment, the UE 400 may transmit to the UE 406 a signal for the UE 400 to indicate to the UE 406 the type of the CAP of the IUC message or the AIM.

[0265] According to an embodiment, UE 400 may determine the CAP to be used according to the type of propagation (eg, multicast, unicast, or broadcast).

[0266] According to an embodiment, the UE 400 may determine the CAP to be used according to the location of the UE 400, its distance from the receiving UE, the minimum communication range, or the area in which it is located.

[0267] According to an embodiment, UE 400 may determine the CAP to be used according to the QoS profile attached to the transmission it intends to perform.

[0268] In the embodiments just described, one or more specific features of SL transmission are mentioned. The one or more specific features of SL transmission include one or more of the following:

[0269] -The priority of the SL transmission is equal to or higher than the configured or preconfigured threshold.

[0270] If the SL transmission is a high priority transmission (priority ≥ threshold), the UE can use type 1 CAP to ensure that resources are indeed available and avoid retransmissions. If the SL transmission is a low priority transmission (priority < threshold), the UE can use type 2 CAP or even no CAP. This is because the UE needs to ensure the availability of resources before transmitting high priority transmissions to avoid any resource conflicts while reducing or completely avoiding retransmissions. This is to improve the performance and resource efficiency of the system. On the other hand, low priority transmissions can perform CAPs of shorter duration, or avoid CAPs completely, even if retransmissions must be performed when LBT fails. In other words, low priority transmissions can be regarded as best-effort transmissions that utilize available resources, taking into account that even if low priority transmissions fail, upper layers can handle retransmissions or packet losses. Such an operation may not have a negative impact on the end-to-end performance of the system because it has a lower priority. In highly congested systems, low priority transmissions will be affected by more LBT failures and performance will be degraded.

[0271] Another viewpoint may be that high priority transmissions use CAPs of shorter duration than low priority transmissions to ensure quicker access to the channel and reduce latency.

[0272] - The Packet Delay Budget (PDB) or delay of the SL transmission is equal to or greater than the configured or preconfigured threshold.

[0273] For example, in the case where the remaining PDB is small, which means that there is not much time left for the UE to attempt to complete the transmission, the UE may choose not to perform the CAP and simply transmit, or only perform the Type 2C CAP.

[0274] On the other hand, if there is enough time to complete the transmission, the UE can perform a CAP with a longer duration, such as Type 1 CAP.

[0275] If, for example, a first CAP is performed on the primary band and fails, the UE will perform a SL transmission on other resources, such as another carrier or subchannel or subband or bandwidth portion in the licensed or unlicensed spectrum. In this case, if transmitting on unlicensed resources, the UE can perform a first CAP or a second CAP, where the first CAP is the same as the one originally performed, such as on the primary band, and the second CAP is different from the first CAP. If transmitting on licensed resources, no CAP is performed.

[0276] -Whether SL transmission is periodic or aperiodic.

[0277] For example, in the case of periodic transmission, currently, the resource reservation period indicates the transmission time of the next periodic TB within the same subchannel and resource pool. If the period is less than the preconfigured or configured threshold, i.e., the periodicity is low, the UE can determine that the next periodic resource can be obtained from the previously performed CAP belonging to the same COT and the same subband. In this case, the UE can avoid performing a CAP on subsequent TBs, or perform a Type 2C CAP. On the other hand, if the periodicity is high, the UE is expected to perform a full CAP of Type 1 to ensure that the channel is available.

[0278] - Whether the SL transmission is an initial transmission or a retransmission, wherein if the SL transmission is an initial transmission, the UE performs the first CAP or does not perform the first CAP, and if the SL transmission is a retransmission, the UE performs the second CAP.

[0279] For example, if the transmission is an initial transmission and the resources are provided by the gNB (Mode 1 - see Figure 2(a)), and the gNB has some knowledge of the availability of the resources, then the UE can avoid CAP altogether or only perform a Type 2 CAP, such as Type 2C. If the gNB has no knowledge of the availability, then the UE can use either Type 1 or Type 2. For initial transmissions in Mode 2 (see Figure 2(b)), the UE performs Type 1 unless other features such as priority, PDB, etc. take precedence. For retransmissions, since these resources are only reserved for the future, no LBT check is performed, so the UE performs Type 1 unless other features take precedence.

[0280] - Whether the resources used for SL transmission are selected through a re-evaluation procedure and / or preemption.

[0281] Since the UE performs these resource selection procedures before a predefined or defined time, the UE may only perform Type 2 CAP, such as Type 2C,

[0282] - The sensing type used to select SL transmission resources, such as full sensing, partial sensing, and random resource selection.

[0283] For example, when executing Fully awareIn the case of unlicensed bands, the UE may be able to avoid CAP or perform a CAP of minimum duration, such as Type 2C. This is because the UE is performing appropriate sensing of the channel anyway, and in the case that the unlicensed band is only used by 3GPP RAT, sensing alone is sufficient to determine whether the resources are indeed available. Only when the band is shared with other RATs does the UE need to perform a CAP like Type 2C.

[0284] for Partial perception , the UE does not perform sensing on all time slots, but only on a subset of them. In this case, the sensing result itself cannot determine the availability of resources. Depending on the detection rate and priority, the UE can decide to perform CAP type 1 or type 2. If the UE performs sensing on most resources (high detection rate ≥ threshold), then type 2 CAP can be performed. If the detection rate is low (< threshold), then the UE can perform type 1. This also applies to priority. For high priority transmission, type 1 CAP is performed to ensure resource availability.

[0285] for Random resource selection , since the UE does not perform sensing at all, the UE must enforce a CAP, preferably type 1. This can also be related to priority or other transmission characteristics, that is, different types of CAP can be applied depending on the priority.

[0286] - Depending on the operating mode, SL transfer is performed in Mode 1 or Mode 2.

[0287] For example, in Mode 1 (see Figure 2(a)), the gNB provides resources to the UE. If the gNB performs a certain type of CAP (such as LBT or selecting resources based on reports), the UE can avoid CAP or only perform Type 2 CAP. In Mode 2 (see Figure 2(b)), the UE performs CAP based on other transmission parameters (such as priority, etc.).

[0288] - Whether the SL transmission contains Inter-UE Coordination (IUC) or Assistance Information Message (AIM), or whether it is based on resources indicated in the IUC message or AIM.

[0289] When referring to the UE using resources obtained from another UE through IUC, it is assumed that the other UE has performed a certain type of CAP before sending the IUC. Therefore, when receiving the IUC, the UE can avoid performing a CAP or perform a type 2 CAP, (for example, depending on the priority). For example, in the case where the SL transmission includes IUC information and data, the UE performs a first CAP, and in the case where the SL transmission only includes IUC information, the UE can only perform a second CAP, and the second CAP provides faster access than the first CAP. According to an embodiment, if the IUC is paired with data, the UE can decide which CAP to use based solely on the data transmission, because the IUC is technically piggybacked on the data transmission. The UE can also perform a CAP based on whether the other UE that provides the IUC message to the UE has performed a CAP on the resources indicated in the IUC. In the case where the other UE does not perform a CAP, the UE must perform a CAP with a longer duration, such as a type 1 CAP, and in the case where the other UE performs a CAP, the UE can avoid performing a CAP or perform a CAP with a shorter duration (such as a type 2 CAP).

[0290] The IUC message or AIM may contain one or more of the following: a preferred resource set for transmission via SL, a non-preferred resource set for transmission via SL, a conflict indication. A conflict indication may be specified in Release 17, where the first UE detects a possible resource conflict for a single future resource reserved by a second UE and a third UE. The first UE then sends a conflict indication to the second UE or third UE, which may be just a 1-bit indication on the PSFCH, informing the UE not to use the reserved resource. This can basically be seen as a single non-preferred resource that the second UE / third UE must avoid / not use.

[0291] According to an embodiment, the initially selected resources for SL transmission may be replaced by new resources, for example, by a resource reselection procedure performed by the UE in response to receiving an IUC message from another UE (including a conflict indicator or a large number of non-preferred resources). In this case, the CAP executed by the UE is different from the CAP used for the initially selected resources. The new CAP may depend on transmission characteristics such as priority, PDB, etc. For example, in response to the IUC message, the UE may perform one or more of the following operations: aggregate another carrier, switch to another licensed frequency band, switch to another unlicensed frequency band, abandon transmission.

[0292] -Whether the SL transmission belongs to a certain propagation type, such as unicast, multicast, or broadcast.

[0293] For example, in a unicast case, the UE may execute a first type CAP with a first duration, such as a type 1 CAP; and in a multicast or broadcast case, the UE may execute a second type CAP with a second duration, such as a type 2 CAP, and the first duration is shorter than the second duration.

[0294] -UE location, distance to the receiving UE (RX UE), minimum communication range (MCR), path loss, and the area where the UE is located (such as area ID).

[0295] The distance may refer to the transmission distance of the SL transmission, such as the distance between the UE and another UE to which the SL transmission is directed, such as the physical distance between the UEs.

[0296] The location may be a starting location of SL transmission, such as a location of the UE, such as an area where the UE is located or coordinates indicating the location of the UE, such as longitude and / or latitude and / or altitude,

[0297] The path loss may be the path loss experienced when the SL is transmitted, for example, measured by a signal-to-noise ratio (SNR), a signal-to-interference-and-noise ratio (SINR), a received signal strength indication (RSSI), or a reference signal received power (RSRP).

[0298] The UE ID of the RX UE can be used, and the TX UE can use the area information to identify its location to allow the TX UE to determine its distance from the RX UE. The location, UE ID, and path loss can be used to determine the distance between UEs. When determining the distance between UEs, if the distance is greater than a certain threshold, the TX UE can use Type 1 CAP because the resources are susceptible to more interference and the availability of resources needs to be checked. If the distance is less than the threshold (the UEs are closer), the UE can use Type 2 CAP to determine the availability of resources.

[0299] The MCR can be used to determine whether the RX UE must send feedback to the TX UE. If the RX UE is within the MCR range, but the distance is still large, i.e., above the threshold, the UE performs a Type 1 CAP, otherwise, if the RX UE is closer (the distance is less than the threshold), the TX UE may perform a Type 2 CAP. For example, according to Release 16, the TX UE includes the MCR in the sidelink control information SCI, requiring the RX UE to transmit feedback only within the range indicated by the MCR.

[0300] According to certain embodiments, the UE may perform a first CAP. However, the CAP may not be successful or may fail. Therefore, in the event that the first CAP is performed and fails, for example on the primary frequency band, the UE will perform SL transmission on other resources, other carriers or subchannels or subbands or bandwidth portions in the authorized or unlicensed spectrum. In this case, if transmitting on unlicensed resources, the UE may perform a first CAP or a second CAP, and the first CAP is the same as the one originally performed, for example on the primary frequency band, and the second CAP is different from the first CAP. If the other resources used for transmission are authorized resources, the CAP is not performed. Figure 5 An embodiment of how to handle a failed initial CAP when performing data transmission on a SL with a specific PDB is shown. The following also applies to other attributes or characteristics of SL transmissions, such as the above-mentioned priority, propagation type, data size, transmission or retransmission type, physical layer channel type, etc. As shown in the figure, a SL transmission that fails a CAP on an unlicensed carrier can be transmitted on another carrier:

[0301] - unlicensed carriers, for example by using different CAP types to gain easier channel access,

[0302] - Licensed carriers, e.g. where the UE does not need to contend with non-3GPP RATs and may therefore more easily obtain the required resources when the UE operates in the following modes:

[0303] ○ Using approved Mode 1 from a base station (such as a gNB), and

[0304] ○ Mode 2 that performs random resource selection or full or partial sensing.

[0305] Sixth embodiment

[0306] According to the fourth embodiment of the present invention, UE 400 may determine a specific configuration of resources in an unlicensed spectrum that are configured to be used to perform a side link transmission. For example, UE 400 may decide the CAP to be used based on a resource pool configuration or a subband level configuration provided by gNB 410, and gNB 410 further instructs UE 400 to use a specific type of CAP for a given resource pool, RP or subband or a given subchannel. This is because the initial transmission and the retransmission may span different subbands or resources. The first periodic transmission and the subsequent periodic transmission may also span different subbands or resources. Providing the UE with the ability to independently select a CAP for each transmission based on the resource location allows the UE to minimize the duration of the CAP while ensuring successful transmission. For example, if the resources of different TBs of periodic transmissions are located in the same subband, the UE may perform a CAP of longer duration for the first transmission of these periodic transmissions and shorten the duration of the subsequent transmission. On the other hand, if these periodic transmissions occur in different subbands, the UE may perform a CAP of longer duration for each subband to determine the availability of resources because the UE has no information about the availability of resources in advance.

[0307] Seventh embodiment

[0308] According to the seventh embodiment of the present invention, UE 400 selects the CAP to be used based on the resource pool structure, more specifically, selects the CAP to be used based on the structure of the resource pool 420, which defines the unauthorized resources to be used for SL transmission. According to the embodiment, if the resource pool supports interlacing, the UE 400 performs a type 1 CAP. When the resource pool supports interlacing, the RBs are not continuous in frequency, but are distributed over different sets of RBs. Therefore, the UE must perform CAP on each interlacing to ensure that they are indeed available before transmission. If the resource pool does not support interlacing, but there are only continuous resource blocks in the resource pool, or the transmission spans different interlacings, such as PSFCH transmission, the UE 400 performs a type 2 CAP. In this case, the RBs are continuous and form a single subchannel (or subband). Therefore, the UE needs to perform CAP on the single subchannel to ensure resource availability before transmission.

[0309] In the case of periodic transmission (as indicated by TRIV or FRIV), if the resources for retransmission or future transmission are reserved in the same subband as the initial transmission, the UE may perform a Type 2 CAP for the future transmission. On the other hand, if the resources for the future transmission are in a different subband or a different set of resource blocks, the UE 400 may perform a Type 1 CAP on each resource before performing the transmission when wideband transmission is considered.

[0310] In the case where the current resources and future resources are located in the same subband, the UE may not perform CAP or perform a first CAP for future SL transmissions. If the retransmission is on the same subband / subchannel as the initial transmission, the UE may avoid performing CAP or perform a CAP of shorter duration (such as Type 2) for the retransmission. This is because the UE has already performed Type 1 CAP for the initial transmission. According to other examples, if the current resources and future resources are located in different sets of resource blocks (RBs) spanning different subbands or subchannels, the UE may perform a second CAP for future SL transmissions. If the retransmission is scheduled on a different subchannel compared to the initial transmission, the UE will perform Type 1 CAP because it has no prior information about the subchannel availability, which may come from the initial transmission because the initial transmission occurs in a different subchannel.

[0311] Eighth embodiment

[0312] According to the eighth embodiment of the present invention, UE 400 can decide the CAP to be used based on whether the transmission to be performed uses continuous or non-continuous resources that vary over time within the SL-URP. For example, a continuous resource pool can be defined by setting the bitmap to 1 in all positions to avoid interruptions within the COT and avoid UEs (such as UEs from other RATs) from using the channel. In the case where the resources are continuous, the UE can perform a first CAP or no CAP for the SL transmission. If it is continuous, the UE can perform a CAP once and reuse the same subband for the remainder of the COT without performing a CAP. However, it can perform a CAP based on the transmission characteristics (see above). In the case where the resources are discontinuous, the UE can perform a second CAP for the SL transmission. If the resources are discontinuous, the UE will perform a CAP each time it accesses the channel because UEs of other RATs may occupy the channel during gaps or discontinuities. Therefore, the UE must perform type 1 to ensure the availability of resources before transmission.

[0313] Ninth embodiment

[0314] According to the ninth embodiment of the present invention, UE 400 will select CAP according to the presence of other RATs. For example, in the case where a certain resource (such as a subband) is designated to be used only for 3GPP sidelink communication in an unlicensed band, a first type of CAP can be used, while when the resource or subband is shared between different RATs, another type of CAP can be used. If the subband / resource pool is only used by 3GPP RAT users, the UE can avoid CAP completely because it does not compete with other RAT UEs. If the band is shared, the UE must perform a Type 1 or Type 2 CAP because it is competing with other RAT UEs.

[0315] According to an embodiment, where semi-static subband definition is allowed, and the subband only supports 3GPP sidelink transmissions in the unlicensed band, the UE does not need to perform any CAP, but is allowed to perform resource allocation using traditional procedures. If the subband / resource pool is only used by 3GPP RAT users, the UE can avoid CAP completely because it does not compete with other RAT UEs.

[0316] General

[0317] The embodiments of the present invention have been described in detail above. Each embodiment and aspect may be implemented separately or two or more embodiments or aspects may be implemented in combination.

[0318] According to an embodiment, CAP evaluates the availability of a channel for performing SL transmission based on perception, wherein when the channel is sensed within a certain duration and it is determined that the detected power for at least a certain time within the certain duration is less than an energy detection threshold, the channel is considered to be idle for a certain duration, otherwise the channel is considered to be busy. For example, perception can be performed within a certain group of carriers within a certain duration, for example, the energy detected on 5 out of 10 carriers within a subchannel or subband exceeds a certain threshold. This scheme can be pre-configured or configured by the network / base station, and can also vary depending on the frequency band and / or digital technology used for a given frequency band / subchannel / bandwidth portion.

[0319] Depending on the embodiment, the wireless communication system may include a terrestrial network or a non-terrestrial network, or a network or network segment using an airborne vehicle or a space vehicle as a receiver, or a combination thereof.

[0320] According to an embodiment of the present invention, the user equipment includes one or more of the following: a power-limited UE, or a handheld UE (such as a UE used by pedestrians (also known as a vulnerable road user VRU) or a pedestrian UE (P-UE)), or a body-held or handheld UE used by public safety personnel and emergency personnel (also known as a public safety UE (PS-UE)), or an IoT UE, such as a sensor, actuator or UE provided in a campus network that performs repetitive tasks and requires regular input from a gateway node, or a mobile terminal, or a fixed terminal, or a cell IoT-UE, or a vehicle UE, or a vehicle group leader (GL) UE, or a sidelink relay, or an IoT or narrowband IoT (NB-IoT) device, or a wearable device (such as a smart watch, or a fitness tracker or smart glasses), or a ground-based vehicle, or an aerial vehicle, or a drone, or a mobile base station, or a roadside unit (RSU), or a building, or any other item or device that provides network connectivity to enable the item / device to communicate using a wireless communication network, such as a sensor or actuator, or any other item or device with network connectivity to enable the item / device to communicate using a sidelink of a wireless communication network, such as a sensor or actuator, or any network entity with sidelink capability.

[0321] According to an embodiment of the present invention, the network entity includes one or more of the following: a macro cell base station, or a small cell base station, or a central unit of a base station, or an integrated access and backhaul (IAB) node, or a distributed unit of a base station, or a roadside unit RSU or a remote radio head, or an AMF, or an MME, or an SMF, or a core network entity, or a mobile edge computing (MEC) entity, or a network slice in the context of NR or 5G core, or any sending / receiving point TRP, enabling an item or device to communicate using a wireless communication network, and the item or device is provided with network connectivity to communicate using the wireless communication network.

[0322] Although some aspects of the concepts are described in the context of an apparatus, it is clear that these aspects also represent a description of a corresponding method, where a block or device corresponds to a method step or a feature of a method step. Similarly, various aspects described in the context of a method step also represent a description of a corresponding block or item or feature of a corresponding apparatus.

[0323] The various elements and functions of the present invention can be implemented in hardware using analog and / or digital circuits, can be implemented in software by executing instructions through one or more general or special processors, or can be implemented as a combination of hardware and software. For example, embodiments of the present invention can be implemented in the environment of a computer system or other processing system. Figure 6An example of a computer system 600 is shown. The units or modules and the method steps performed by these units can be executed on one or more computer systems 600. The computer system 600 includes one or more processors 602, such as a dedicated or general-purpose digital signal processor. The processor 602 is connected to a communication infrastructure 604, such as a bus or a network. The computer system 600 includes a main memory 606 (such as a random access memory RAM) and an auxiliary memory 608 (such as a hard drive and / or a removable storage drive). The auxiliary memory 608 can load computer programs or other instructions into the computer system 600. The computer system 600 can also include a communication interface 610 to allow software and data to be transmitted between the computer system 600 and external devices. The communication can be an electronic, electromagnetic, optical or other signal that can be processed by the communication interface. The communication can use wires or cables, optical fibers, telephone lines, cellular phone links, radio frequency links and other communication channels 612.

[0324] The terms "computer program medium" and "computer readable medium" are generally used to refer to tangible storage media, such as a removable storage unit or a hard disk installed in a hard drive. These computer program products are a means of providing software to the computer system 600. The computer program, also known as computer control logic, is stored in the main memory 606 and / or the secondary memory 608. The computer program can also be received via the communication interface 610. When the computer program is executed, the computer system 600 is enabled to implement the present invention. In particular, when the computer program is executed, the processor 602 is enabled to implement the process of the present invention, such as any method described in the present invention. Accordingly, such a computer program can represent a controller of the computer system 600. In the case of using software to implement the disclosure, the software can be stored in a computer program product and loaded into the computer system 600 using a removable storage drive, an interface (such as the communication interface 610).

[0325] The implementation in hardware or software can be performed using digital storage media, such as cloud storage, floppy disk, DVD, Blu-ray, CD, ROM, PROM, EPROM, EEPROM or flash memory, which have electronically readable control signals stored thereon and can cooperate with or be able to cooperate with a programmable computer system to perform the corresponding method. Therefore, the digital storage medium can be computer readable.

[0326] Some embodiments according to the invention comprise a data carrier having electronically readable control signals, which are capable of cooperating with a programmable computer system, such that the system performs one of the methods described herein.

[0327] Generally, the embodiments of the present invention can be implemented as a computer program product with a program code, when the computer program product runs on a computer, the program code can be used to perform one of the methods.For example, the program code can be stored on a machine readable carrier.

[0328] Other embodiments comprise the computer program for performing one of the methods described herein, stored on a machine readable carrier. In other words, therefore, one embodiment of the inventive method is a computer program having a program code for performing one of the methods described herein, when the computer program runs on a computer.

[0329] Therefore, a further embodiment of the method of the present invention is a data carrier or a digital storage medium or a computer-readable medium, on which a computer program for performing one of the methods described herein is recorded. Therefore, a further embodiment of the method of the present invention is a data stream or a signal sequence representing a computer program for performing one of the methods described herein. For example, the data stream or signal sequence can be configured to be transmitted via a data communication connection (e.g., via the Internet). Further embodiments include processing means, such as a computer or a programmable logic device, configured to or adapted to perform one of the methods described herein. Further embodiments include a computer on which a computer program for performing one of the methods described herein is installed.

[0330] In some embodiments, a programmable logic device, such as a field programmable gate array, may be used to perform some or all of the functions of the methods described herein. In some embodiments, a field programmable gate array may be used in conjunction with a microprocessor to perform one of the methods described herein. Typically, the method is preferably performed by any hardware device.

[0331] The above embodiments are merely illustrative of the principles of the present invention. It is understood that modifications and variations of the arrangements and details described herein will be apparent to other persons skilled in the art. Therefore, it is intended that the present invention be limited only by the scope of the patent claims to be presented, and not by the specific details presented herein by way of description and explanation of the embodiments.

Claims

1. A user equipment UE for a wireless communication network such as a 3rd Generation Partnership Project 3GPP network, in, The UE is configured to communicate with one or more further UEs in a wireless communication network via a side link SL using a set of resources in an unlicensed spectrum, The UE is used to perform a channel access procedure CAP to evaluate the availability of a resource set for performing SL transmission, so as to perform SL transmission on the resource set in the unlicensed spectrum, Therein, the UE is configured to select a CAP for evaluating availability of a resource set for performing SL transmission based on a criterion.

2. The user equipment UE according to claim 1, wherein: The criteria used to select the CAP are one or more of the following: - an indication of the wireless communication network or of a network entity of a further wireless communication network, or - an indication by a network entity of the wireless communication network, the indication initiating a channel occupation time COT for SL transmission to be shared with the UE, or - whether a network entity of the wireless communication network that provides approval for a resource set for SL transmission is aware of the availability of the resource set in the unlicensed spectrum for performing the SL transmission, or - configuration of resource sets in the unlicensed spectrum for performing SL transmissions, or - one or more specific characteristics of a SL transmission, or -The type of SL physical PHY channel on which the SL transmission will be transmitted, or - a resource pool structure of resource sets in the unlicensed spectrum for SL transmission, - There is a transmission using a radio access technology RAT different from the one used by the UE for SL transmission.

3. The user equipment UE according to claim 1 or 2, wherein: The UE is configured to receive information on COT configuration from a network entity that provides COT information on COT configuration, the information indicating a CAP to be performed by the UE.

4. A user equipment UE as claimed in any one of the preceding claims, wherein: The UE is configured to perform one or more of the following when the network entity is aware of the availability of resources: - not performing CAP, or - performing a CAP or a first CAP in the case where the SL transmission has one or more specific characteristics, and / or - In case the SL transmission does not have one or more specific characteristics, the second CAP is performed or the second CAP is not performed, and the first CAP is different from the second CAP.

5. A user equipment UE as claimed in any one of the preceding claims, wherein: The UE is configured to perform one or more of the following when the network entity is unaware of the availability of resources: -Perform CAP, or - In case the SL transmission has one or more specific characteristics, a first CAP is executed, and in case the priority of the SL transmission does not have one or more specific characteristics, a second CAP is executed or no CAP is executed, the first CAP being different from the second CAP.

6. A user equipment UE as claimed in any one of the preceding claims, wherein: The UE is used to select the CAP based on whether the SL transmission transmits one or more of the following: - Physical Sidelink Control Channel PSCCH, - Physical side link shared channel PSSCH, - Physical Sidelink Feedback Channel PSFCH, - Physical side link broadcast channel PSBCH, - Stage I SCI, -Phase II SCI.

7. The user equipment UE according to claim 6, wherein: The UE is configured to select a CAP according to one or more specific characteristics of the SL transmission when the SL transmission transmits a physical sidelink control channel PSCCH and / or a physical sidelink shared channel PSSCH.

8. The user equipment UE according to claim 6 or 7, wherein: In case of SL transmission of the Physical Sidelink Feedback Channel PSFCH, - the UE is configured to perform a CAP that provides faster access or shorter duration than a CAP used to transmit SL transmissions on a channel other than the PSFCH, or -If the UE cannot find an available PSFCH slot within the packet delay budget PDB of the TB for SL transmission, the UE is configured to change from the currently used CAP to a new CAP that provides faster access or shorter duration compared to the currently used CAP.

9. A user equipment UE as claimed in any one of the preceding claims, wherein: In the case where the SL transmission transmits a physical sidelink control channel PSCCH or a physical sidelink shared channel PSSCH in the first COT and transmits a physical sidelink feedback channel PSFCH in the second COT, and in the case where resources between the first COT and the second COT are used by a further UE using another COT, - the UE is configured to perform a first CAP for transmissions on the PSCCH or SSCH and a second CAP for transmissions on the PSFCH, or - If the UE does not enable feedback for blind transmission, the UE is used to perform CAP only for PSCCH or PSSCH.

10. The user equipment UE according to any one of the preceding claims, wherein: One or more specific characteristics of SL transmission include one or more of the following: -The priority of the SL transmission is equal to or higher than the configured or preconfigured threshold, - The packet delay budget PDB or delay of the SL transmission is equal to or higher than the configured or preconfigured threshold, - Whether the SL transmission is periodic or aperiodic, - whether the SL transmission is an initial transmission or a retransmission, wherein the UE is configured to perform a first CAP or not perform the first CAP if the SL transmission is an initial transmission, and the UE is configured to perform a second CAP if the SL transmission is a retransmission, - whether the resources used for SL transfer are selected through a re-evaluation process, - whether the resources used for SL transmission are selected through preemption, - the type of sensing used to select SL transmission resources, such as full sensing, partial sensing, random resource selection, - Based on the operating mode, SL transmission is performed in Mode 1 or Mode 2, -Whether the SL transmission contains inter-UE coordination IUC or assistance information message AIM, -Whether the SL transmission is of a specific transmission type, such as unicast, multicast, or broadcast, -UE location, distance to receiving UE RX UE, minimum communication range MCR, area where UE is located such as area ID, -QoS profile for SL transport.

11. A user equipment UE as claimed in any one of the preceding claims, wherein: One or more specific features of the SL transmission include a priority of the SL transmission, wherein the UE is configured to perform a first CAP when the SL transmission has a first priority, and the UE is configured to perform a second CAP when the SL transmission has a second priority, the first priority being different from the second priority.

12. A user equipment UE as claimed in any one of the preceding claims, wherein: One or more specific characteristics of the SL transmission include a priority of the SL transmission, wherein the UE is configured to perform a first CAP if the SL transmission has a priority equal to or higher than a configured or preconfigured threshold, and the UE is configured to perform a second CAP or not perform the second CAP if the SL transmission has a priority lower than the threshold.

13. A user equipment UE as claimed in any one of the preceding claims, wherein: One or more specific features of the SL transmission include a packet delay budget PDB for the SL transmission, wherein the UE is configured to perform or not perform a first CAP if the PDB is equal to or higher than a configured or preconfigured threshold, and the UE is configured to perform a second CAP if the PDB is lower than the threshold, or the UE is configured not to perform the second CAP if the PDB is equal to or higher than the configured or preconfigured threshold.

14. A user equipment UE as claimed in any one of the preceding claims, wherein: The UE is configured to perform SL transmission in case of failure of performing the first CAP on, for example, the primary frequency band, by performing the following in other resources such as another carrier or subchannel or subband or bandwidth portion in the licensed or unlicensed spectrum: - a first CAP or a second CAP in case of transmission on an unlicensed resource set, where the first CAP is the same as originally performed, for example, on the primary band, and the second CAP is different from the first CAP, or - In case of transmission on the authorized resource set, there is no CAP.

15. A user equipment UE as claimed in any one of the preceding claims, wherein: One or more specific characteristics of SL transmission include the periodicity of SL transmission, wherein - the UE is configured to perform a first CAP in case of aperiodic SL transmission, and the UE is configured to perform a second CAP in case of periodic SL transmission, or -UE is used to perform the same CAP for aperiodic SL transmission or retransmission, - The UE is configured to implement different CAPs for periodic SL transmissions so that each transmission of a transport block TB uses a different CAP, wherein the CAP is indicated by the resource reservation periodicity.

16. A user equipment UE as claimed in any one of the preceding claims, wherein: One or more specific characteristics of the SL transmission include whether the SL transmission is an initial transmission or a retransmission using a time resource indication value TRIV within a certain number of future time slots and / or using a frequency resource indication value FRIV on a certain number of future frequency resources such as resources reserved within a subchannel, wherein the UE is configured to perform a first CAP or no CAP when the SL transmission is an initial transmission, and the UE is configured to perform a second CAP when the SL transmission is a retransmission.

17. A user equipment UE as claimed in any one of the preceding claims, wherein: One or more specific features of SL transmission include new resources for SL transmission after re-evaluating or preempting initial resources scheduled for SL transmission, and wherein the UE performs a first CAP for checking the availability of the new resources, which is faster or of shorter duration than a second CAP for checking the availability of the initial resources.

18. A user equipment UE as claimed in any one of the preceding claims, wherein: One or more specific characteristics of SL transmission include the type of sensing performed by the UE to determine available resources for SL transmission, where: - The UE is configured not to perform a CAP in the case of full awareness, or to perform a CAP with a duration less than a certain configured or pre-configured threshold, such as a minimum duration CAP, e.g. a Type 2C CAP, or - The UE is configured to perform CAP in the case of partial perception if the amount of resources perceived by the UE is below a configured or pre-configured threshold, or -UE is used to perform CAP with random selection of resources.

19. A user equipment UE as claimed in any one of the preceding claims, wherein: One or more specific features of SL transmission include an operating mode of SL transmission for transmitting TBs, wherein: -UE is configured to perform no CAP or a CAP of minimum duration if the gNB is aware of the availability of resources provided to the UE in case of Mode 1 transmission, -UE is used to perform CAP in case of Mode 1 transmission if the gNB is not aware of the availability of resources provided to the UE, -The UE is used to decide whether to perform CAP and the type of CAP to be performed based on one or more specific characteristics of the SL transmission in the case of Mode 2 transmission.

20. The user equipment (UE) as claimed in any one of the preceding claims, wherein: One or more specific characteristics of the SL transmission include whether the SL transmission contains inter-UE coordinated IUC information, where: - the UE is configured to perform a first CAP in case the SL transmission includes IUC information and data, and -The UE is configured to perform a second CAP when the SL transmission includes only IUC information, the second CAP providing faster access or shorter duration than the first CAP.

21. A user equipment (UE) as claimed in any one of the preceding claims, wherein: One or more specific features of the SL transmission include whether the resources to be used for the SL transmission are obtained from the inter-UE coordination IUC message, where: - The UE is not configured to perform CAP, or - the UE is configured to perform the CAP based on the priority or characteristics of the intended transmission, wherein the UE is configured to perform the CAP if the SL transmission has a first priority or one or more specific characteristics, and the UE is configured not to perform the CAP if the SL transmission has a second priority or does not have the one or more specific characteristics, the first priority being different from the second priority, or - the UE is used to perform the CAP indicated in the IUC message, or -The UE is configured to perform CAP depending on whether the further UE providing the IUC message performs CAP, wherein the UE is configured to perform a first CAP if the further UE has not performed CAP on the resources indicated in the IUC, and the UE is configured to not perform CAP or perform a second CAP if the further UE has performed CAP on the indicated resources.

22. The user equipment UE according to claim 21, wherein: An IUC message contains one or more of the following: - a preferred set of resources for transmission via the SL, - a non-preferred set of resources for transmission via the SL, -Conflict indication.

23. A user equipment (UE) as claimed in any one of the preceding claims, wherein: One or more specific features of SL transmission include: replacing initially selected resources for SL transmission with new resources, for example, by a resource reselection process performed by the UE in response to receiving an inter-UE coordination (IUC) message from another UE including a conflict indication or a large amount of non-preferred resources, and The UE is configured to implement a CAP different from the CAP used by the initially selected resource.

24. The user equipment UE according to claim 23, wherein: The UE is configured to perform one or more of the following operations in response to the IUC message: - aggregate another carrier, - switch to another licensed frequency band, - switch to another unlicensed band, -Stop the transmission.

25. A user equipment (UE) as claimed in any one of the preceding claims, wherein: The one or more specific characteristics of the SL transmission include the propagation type of the SL transmission, wherein: - the UE is configured to perform a first type of CAP having a first duration in a unicast case, - The UE is configured to perform a second type of CAP having a second duration in case of groupcast or broadcast, the first duration being shorter or longer than the second duration.

26. A user equipment (UE) as claimed in any one of the preceding claims, wherein: The one or more specific characteristics of the SL transmission related to the UE location include one or more of the following: - the transmission distance of the SL transmission, e.g. the distance between the UE and the further UE to which the SL transmission is directed, e.g. the physical distance between the UEs, - starting location of the SL transmission, such as the location of the UE, such as the area where the UE is located or coordinates indicating the location of the UE, such as longitude and / or latitude and / or altitude, - the minimum communication distance MCR required, - the path loss experienced by the SL transmission while transmitting, for example, measured by the signal-to-noise ratio SNR, the signal-to-interference-plus-noise ratio SINR, the received signal strength indicator RSSI or the reference signal received power RSRP, - The identity ID of a given UE.

27. A user equipment (UE) as claimed in any one of the preceding claims, wherein: The resource configuration in the unlicensed spectrum comprises a plurality of resource sets, each of the plurality of resource sets being associated with a specific CAP to be used, and wherein the resource sets comprise bandwidth portions or resource pools or subbands or subchannels or aggregated carriers.

28. A user equipment (UE) as claimed in any one of the preceding claims, wherein: The UE is configured to receive an indication from a network entity in response to a request of the UE via unicast or as a multicast or broadcast, wherein the indication includes configuration on how to initiate the COT or how to initiate the COT and future COTs.

29. The user equipment UE according to claim 28, wherein: Future COT is one or more of the following: - the next n future COTs, e.g., the next 5 COTs performed by the UE, - the next n future transmissions, e.g., COT for the next 5 transmissions, - the future COT until the timer expires, e.g. the COT for the next 100 milliseconds, - until there is another future COT configured, e.g. in response to a new configuration, - Future COT until an event occurs, such as HARQ decoding failure reaching a configured or preconfigured threshold or in response to a certain IUC message.

30. A user equipment (UE) as claimed in any one of the preceding claims, wherein: The UE is configured to perform, according to whether the resource pool in the unlicensed spectrum available for SL transmission supports interlacing: - the first CAP for SL transmission in case the resource pool supports interlacing or in case the SL transmission spans different interlacings, - Second CAP in case the resource pool does not support interlacing.

31. A user equipment (UE) as claimed in any one of the preceding claims, wherein: The UE is configured to perform, according to the similarity between the current resources used for the current SL transmission and the future resources reserved for future transmission or retransmission within a certain number of future time slots using the time resource indication value TRIV and / or the frequency resource indication value FRIV within a certain number of future frequency resources such as a subchannel: No CAP or first CAP for future SL transmissions in case current and future resources are located in the same subband or subchannel, • A second CAP for future SL transmissions in case the current resources and the future resources are in different resource block RB sets in different subbands or subchannels.

32. A user equipment (UE) as claimed in any one of the preceding claims, wherein: The UE is configured to execute, according to whether the SL transmission uses continuous resources or non-continuous resources in a resource pool in an unlicensed spectrum available for the SL transmission: - First CAP or no CAP for SL transmission in case the resources are contiguous, or - A second CAP for SL transmission in case the resources are non-contiguous.

33. A user equipment (UE) as claimed in any one of the preceding claims, wherein: The UE is configured to, based on the presence of a transmission using a RAT different from the RAT used by the UE for SL transmissions, perform: - a first CAP or no CAP for SL transmission in the case where the subband, subchannel or resource pool for SL transmission is allocated only to the RAT used by the UE to perform SL transmission, or - a second CAP for SL transmission in case the subband, subchannel or resource pool used for SL transmission is shared by different RATs, or - In case of semi-static sub-band, sub-channel or resource pool definition, there is no CAP.

34. The user equipment (UE) as claimed in any one of the preceding claims, wherein the CAP that the UE desires to perform includes one or more of the following: Implement the Listen Before Talk (LBT) process on resources, · Detecting one or more energy levels on the resource, such as received signal strength indication RSSI, signal-to-noise ratio SNR or signal-to-noise-interference ratio SINR, · measuring pilot symbols transmitted on the resource and / or determining one or more measurement values, such as 3GPP reference signal received power RSRP or 3GPP reference signal received quality RSRQ, Decode the sidelink auxiliary information message SL AIM, Decode the sidelink inter-UE coordination message IUC, Decode the auxiliary information AIM, ●Decode control messages transmitted on resources, such as 3GPP downlink control information DCI, or 3GPP sidelink control information SCI, or IEEE 802.11 physical layer convergence protocol PLCP header, or extract information about one or more transmissions, such as a transmission that is being performed or about to be performed, or the remaining duration of a transmission that is being performed.

35. The user equipment UE of claim 34, wherein the LBT procedure comprises: - Type 1 CAP, which senses the channel for SL transmission for a random duration of time, or - Type 2A CAP, sensing the channel for SL transmission 25μs, or - Type 2B CAP, sensing channel 16μs for SL transmission, - Type 2C CAP, not aware of the channel used for SL transmission, or - New CAP type to sense the channel for SL transmission with a duration of configured or preconfigured time.

36. A user equipment UE as claimed in any one of the preceding claims, wherein the CAP evaluates the availability of a channel for performing SL transmission based on perception, wherein, When a channel is sensed within a specific duration and it is determined that the detected power for at least a specific time within the specific duration is less than the energy detection threshold, the channel is considered idle for a certain duration, otherwise, the channel is considered busy.

37. A User Equipment (UE) as claimed in any one of the preceding claims, wherein the difference between the first CAP and the second CAP depends on the duration of LBT, sensing or measurements that the UE has to perform to decide whether the resources are occupied by a further UE.

38. A user equipment (UE) as claimed in any one of the preceding claims, wherein the network entity is one of: - Base station, or - further UE, or - Network functions, such as entities provided by the core network, such as 5GC, or - non-3GPP devices, such as WiFi access points, or -RSU or relay unit.

39. A wireless communication system such as a 3rd Generation Partnership Project 3GPP system, comprising one or more user equipments UE and one or more base stations as claimed in any one of the preceding claims.

40. The user equipment UE according to claim 39, wherein: UE includes one or more of the following: limited power UE, or handheld UE such as UE used by pedestrians, also known as vulnerable road users VRU or pedestrian UE P-UE, or body-worn or handheld UE used by public safety personnel and emergency personnel, also known as public safety UEPS-UE, or IoT UE, such as sensors, actuators or UEs provided in a campus network to perform repetitive tasks and require regular input from a gateway node, or mobile terminal, or fixed terminal, or cell IoT-UE, or SL UE, or vehicle UE, or vehicle group leader UE (GL-UE), or dispatch UE (S-UE), or IoT or narrowband IoT NB-IoT device, or ground-based vehicle, or aircraft, or drone, or mobile base station, or roadside unit RSU, or building, or any other item or device providing network connectivity enabling the item / device to communicate using a wireless communication network, such as a sensor or actuator, or any other item or device with network connectivity enabling the item / device to communicate using a sidelink of a wireless communication network, such as a sensor or actuator, or any network entity with sidelink capability, and The base station includes one or more of the following: a macro cell base station, or a small cell base station, or a central unit of a base station, or a distributed unit of a base station, or an integrated access and backhaul IAB node, or a roadside unit RSU, or a UE, or a SL UE, or a group leader UE (GL-UE), or a relay, or a remote radio head, or an AMF, or an SMF, or a core network entity, or a mobile edge computing (MEC) entity, or a network slice in the context of an NR or 5G core, or any sending / receiving point TRP, enabling an item or device to communicate using a wireless communication network, and the item or device is provided with network connectivity to communicate using the wireless communication network.

41. A method for operating a user equipment (UE) for a wireless communication network such as a 3rd Generation Partnership Project (3GPP) network, the method comprising: communicating, by the UE, with one or more further UEs in a wireless communication network via a side link SL using a set of resources in an unlicensed spectrum, A channel access procedure CAP is performed by the UE to evaluate the availability of a resource set for performing SL transmission, so as to perform SL transmission on the resource set of the unlicensed spectrum, The CAP for evaluating the availability of a resource set for performing SL transmission is selected by the UE based on criteria.

42. A non-transitory computer program product comprising a computer-readable medium storing instructions which, when executed on a computer, perform the method of claim 41.

Images