110 receives 235 the explicit request for coordination information from the UE 120, the UE 110 may prepare to transmit coordination information. For example, the UE 110 determines 275 a resource collision status for the UE 120. That is, the UE 110 determines whether a potential resource collision is present for the UE 120. Details regarding determining 275 the resource collision status for the UE 120 may be described with respect to FIG. 7 below.

With the determined resource collision status, the UE 110 transmits 280 coordination information to the UE 120. The coordination information indicates the determined resource collision status. For example, the coordination information may indicate presence of a potential resource collision. The UE 120 receives 285 the coordination information from the UE 110.

If the coordination information received from the UE 110 indicating presence of the potential resource collision, the UE 120 determines 290 to reselect a resource to replace a potentially collided resource. The UE 120 may perform a following SL transmission using the reselected resource. Details regarding resource reselection based on the coordination information will be described in details with respect to FIG. 8 below.

General procedures regarding SL transmission with the coordination information in scheme 1 and scheme 2 have been described with respect to FIGS. 2A and 2B. From now on, details regarding several steps in the above procedures will be described with respect to FIGS. 3-8 below.

Conditions to Transmit Coordination Information

Conventionally, the UE-A may transmit coordination information to the UE-B in response to the explicit request, or otherwise makes a determination to transmit the coordination information to the UE-B. However, it lacks detail conditions regarding how to determine whether to transmit the coordination information or not.

FIG. 3 illustrates a flowchart illustrating an example method 300 of determination of coordination information transmission according to some embodiments of the present disclosure. For the purpose of discussion, the method 300 will be described with reference to FIGS. 1, 2A and 2B. The method 300 may be implemented at a UE-A, for example, the UE 110. For the purpose of discussion, the method 300 will be described from the perspective of the UE 110.

At block 310, the UE 110 determines whether to transmit coordination information to the UE 120 based on at least one condition. The condition to transmit the coordination information may depend on the specific scheme. For example, different conditions may be applied for scheme 1 and scheme 2.

In scheme 1 as shown in FIG. 2A, a condition may be that a configuration of the UE 110 enables a transmission of the coordination information to the UE 120. For example, the UE 110 may be configured by higher layer to transmit the coordination information to the UE 120. If this condition is met, the UE 110 determines to transmit the coordination information to the UE 120.

In scheme 1, another condition may be that a channel status determined by the UE 110 indicates a busy status. For example, the UE 110 detects a channel busy ratio (CBR) higher than a threshold, which means that the channel is busy. A busier channel at higher CBR level will have more collision chances, which implies the need of the coordination information. In this situation, the condition is met, and then the UE 110 determines to transmit the coordination information to the UE 120.

In scheme 2 as shown in FIG. 2B, similar to scheme 1, a condition may be that a channel status determined by the UE 110 indicates a busy status. For example, the UE 110 detects a channel busy ratio (CBR) higher than a threshold, which means that the channel is busy. The threshold may be configured or preconfigured per resource pool. In this situation, the condition is met, and then the UE 110 determines to transmit the coordination information to the UE 120.

In scheme 2, another condition may be that a potential resource collision for the UE 120 is determined based on the control information from the UE 120. For example, the control information such as the SCI from the UE 120 indicates a need of the coordination information. In this situation, the UE 110 determines to transmit the coordination information to the UE 120.

Alternatively or in addition, in scheme 2, if the UE 110 determines that a time gap between reception time of the control information (such as the SCI from the UE 120) and time of the resource collision (such as time of a potentially collided resource) exceeds a time threshold, the UE 110 determines to transmit the coordination information to the UE 120.

In some example embodiments, in scheme 2, if the UE 110 determines that a priority of data indicated by the control information exceeds a threshold priority, the UE 110 determines to transmit the coordination information to the UE 120. The data is to be transmitted by a potentially collided resource. For example, if the UE 110 detects that the data priority of the potentially collided resource of the UE 120 is higher than a configured or (pre)configured threshold priority, the UE 110 determines to transmit the coordination information to the UE 120.

Alternatively or in addition, in scheme 2, if the UE 110 determines that a time gap between expected transmission time of the coordination information and time of the potential resource collision exceeds a time threshold, the UE 110 determines to transmit the coordination information to the UE 120.

In some example embodiments, in scheme 2, if the UE 110 determines that the resource collision is determined based on the control information from the UE 120 and further control information from UE 130, the UE 110 determines to transmit the coordination information to the UE 120. For example, if the control information from the UE 120 indicates that the UE 120 reserves a particular resource while the further control from the UE 130 indicates that the UE 130 reserves the particular resource as well, the UE 110 may determine a potential resource collision on the particular resource.

In some example embodiments, in scheme 2, if the UE 110 determines that a distance between the UE 110 and the UE 120 is less than a threshold distance, the UE 110 may determine a potential resource collision on the particular resource. For example, in groupcast feedback option 1, the SCI stage 2 of the UE 120 has zone ID. The UE 110 may calculate the distance between the UE 110 and the UE 120 based on the zone ID comprised in the SCI received from the UE 120.

If at block 310, the UE 110 determines to transmit the coordination information to the UE 120, the method 300 will proceed to the block 320. At block 320, the UE 110 transmits, via a transceiver of the UE 110, the coordination information to the UE 120. The coordination information concerns a transmission to be performed by the UE 120. The coordination information indicates the UE 120 to perform resource selection. For example, the UE 120 may perform the resource selection based on the coordination information to select a resource for the transmission to be performed by the UE 120. In some embodiments, for example in the case of scheme 1, the coordination information may indicate a resource set non-preferred for the UE 120 without a resource set preferred for the UE 120. Alternatively, in some examples in the case of scheme 2, the coordination information may indicate a potential resource collision for the UE 120.

The above mentioned conditions may help the UE 110 to determine whether to transmit the coordination information to the UE 120. In this way, the UE 110 may transmit the coordination information without the explicit request from the UE 120. For example, a UE-A, for example a road-side unit which has powerful sensing ability, can transmit the coordination information based on its sensing results to help one or more neighbor UEs (for example, a UE-B such as the UE 120 or the UE 130) to enhance their resource selection reliability. Using the above described determination of transmission of the coordination information, the SL transmission will be enhanced.

Determination of a Resource Set

As mentioned above, in scheme 1, the UE 110 determines 240 a resource set for the UE 120. The resource set may be indicated in the coordination information. Conventionally, if the UE-A identifies that Reference Signal Received Power (RSRP) of resources excluding those overlapping with reserved resource(s) of other UE(s) exceeds a RSRP threshold, and the UE-A identifies additional conditions for example a condition that the resource(s) satisfies the UE-B's requirement, the UE-A may determine those resource(s) satisfying those conditions as a preferred resource for the UE-B. In addition, the UE-A may determine a non-preferred resource for the UE-B under other conditions regarding the RSRP. However, further conditions regarding how to determine a preferred or non-preferred resource set for the UE-B still needs improvement.

FIG. 4 illustrates a flowchart illustrating an example method 400 of determining a resource set to be indicated by coordination information according to some embodiments of the present disclosure. For the purpose of discussion, the method 400 will be described with reference to FIGS. 1 and 2A. The method 400 may be implemented at a UE-A, for example, the UE 110. For the purpose of discussion, the method 400 will be described from the perspective of the UE 110.

At block 410, the UE 110 determines at least one resource set for the UE 120 based on at least one of: measured power of a signal associated with on a resource, control information from the UE 130, and a priority of data to be transmitted using a resource reserved by the UE 120.

The measured power is on a resource whose reservation is on a candidate resource in the resource set. For example, the candidate resource in the resource set is on slot n. If the UE 120 receives a signal on slot m (m<n) whose measured power (RSRP) is high, and whose resource reservation is for the resource on slot n. When the UE 120 performs resource selection, the UE 120 may determine that the candidate resource on the slot n is not usable any more.

The measured power may be RSRP. For example, if the RSRP associated with the resource is below a first threshold, the UE 110 may add the resource into a first resource set preferred for the UE 120. Alternatively or in addition, if the RSRP associated with the resource exceeds a second threshold, the UE 110 may add the resource into a second resource set non-preferred for the UE 120.

It is to be understood that the first threshold and the second threshold may be configured or preconfigured by a resource pool or based on PC5-Radio Resource Control (RRC) configuration. The first threshold and the second threshold may be the same or different.

In some example embodiments, if the UE 110 determines that a further resource is not reserved based on the control information from the UE 130, the UE 110 may add the further resource into the first resource set preferred for the UE 120. For example, the UE 110 may perform sensing and not detect SCI from a UE other than the UE 120, for example the SCI from the UE 130, reserving the further resource, the UE 110 may add the further resource into the first resource set preferred for the UE 120.

In some example embodiments, if the UE 110 determines that the measured power of the signal associated with the resource exceeds a third threshold, the UE 110 may add the resource into the second resource set non-preferred for the UE 120. The third threshold is determined based on a priority of data to be transmitted using the resource and a configured or preconfigured data priority level. The data priority level may be configured or preconfigured by a resource pool or based on PC5-RRC configuration. The data priority level for preferred resource set and for non-preferred resource set may be different.

At block 420, the UE 110 transmits, via a transceiver of the UE 110 and to the UE 120, the coordination information concerning a transmission to be performed by the UE 120. The coordination information indicates the at least one resource set. For example, the coordination information may indicate a resource set preferred for the UE 120 such as the first resource set or a resource set non-preferred for the UE 120 such as the second resource set as determined by procedures discussed above. The UE 120 may perform resource selection based on the coordination information to select a resource for the transmission performed by the UE 120.

The above mentioned procedures may help the UE 110 to determine a preferred or non-preferred resource set for the UE 120. In this way, the UE 120 may easier determine a target resource based on the coordination information indicative of a resource set determined by the UE 110. Using the above described determination of a resource set for the UE 120, the SL transmission will be enhanced. The determination of a target resource by the UE 120 may be described with respect to FIG. 5 below.

Determination of a Target Resource

Conventionally, the UE-B may determine a target resource based on the coordination information received from the UE-A and the sensing result of the UE-B (if available). However, it lacks detail conditions and methods regarding how to determine the target resource for the UE-B.

FIG. 5 illustrates a flowchart illustrating an example method 500 of target resource determination based on coordination information according to some embodiments of the present disclosure. For the purpose of discussion, the method 500 will be described with reference to FIGS. 1 and 2A. The method 500 may be implemented at a UE-B, for example, the UE 120. For the purpose of discussion, the method 500 will be described from the perspective of the UE 120.

At block 510, the UE 120 receives, via a transceiver of the UE 120 and from the UE 110, coordination information concerning a transmission to be performed by the UE 120. The coordination information indicates a resource set preferred for the UE 120 to perform resource selection.

At block 520, the UE 120 determines at least one target resource for the transmission based on the coordination information and additional information. For example, the UE 120 determines the at least one target resource based on the resource set indicated by the coordination information and at least one additional information. Examples of the additional information may include but not limited to: measured power of a signal associated with a resource in the resource set, reception time of the coordination information, and a reception scheduled for the UE 120 on a resource in the resource set.

In some example embodiments, the UE 120 may receive, from a further UE-A (for example a further UE-A in the communication network 100), further coordination information indicating a further resource set preferred for the UE 120 to perform resource selection. The at least one target resource is determined further based on the further resource set. For example, if the UE 120 receives multiple resource sets preferred for the UE 120 from multiple UE-As, the final resource set preferred for the UE 120 may be a union or an inter-section of these resource sets.

In some example embodiments, if the UE 120 determines that a time gap between the reception time of the coordination information and a delay limit for the transmission is less than a time threshold, the UE 120 may perform random resource selection to select the at least one target resource. For example, if the coordination information is received close or after data packet delay budget (PDB), or the time gap between the reception time of the coordination information and the data PDB is less than a time threshold, the UE 120 may perform random resource selection or not rely on the coordination information for its resource selection. It is to be understood that the time threshold may be configured or preconfigured.

In some example embodiments, the UE 120 may perform sensing. In this situation, the UE 120 may determine the at least one target resource based on the coordination information and the sensing result. For example, if the UE 120 determines that measured power of a signal associated with a resource in the resource set exceeds a power threshold, the UE 120 may select a further resource exclusive of the resource set to be one of the at least one target resource.

For example, if the RSRP measurement at the UE 120 corresponding to the resource in the resource set preferred for the UE 120 exceeds a RSRP threshold, the UE 120 may perform resource selection based on its sensing result to select a further resource exclusive of the resource set to be one of the at least one target resource. In some example embodiments, the RSRP threshold is determined based on a priority of data to be transmitted using the resource in the resource set. Alternatively, in some example embodiments, the RSRP threshold is configured or preconfigured by a resource pool.

In some example embodiments, in the situation that the UE 120 performs sensing, if the UE 120 determines that time of a resource in the resource set is to be used for the reception scheduled for the UE 120, the UE 120 may select a further resource exclusive of the resource set to be one of the at least one target resource. In this way, the UE 120 may not select the resource to be used for the reception scheduled for the UE 120, thus will prevent the UE 120 from SL transmission due to half duplex.

In some example embodiments, in the situation that the UE 120 performs no sensing, the UE 120 may determine the at least one target resource based on the coordination information. For example, if the UE 120 determines that the number of the at least one target resource is less than the number of resources in the preferred resource set indicated by the coordination information, the UE 120 may randomly select the at least one target resource from the preferred resource set. If the UE 120 determines that the number of the at least one target resource exceeds the number of resources in the preferred resource set, the UE 120 may determine each resource in the preferred resource set and at least one further resource to be the at least one target resource. The at least one further resource is exclusive of the resource set. For example, the UE 120 may randomly select the at least one further resource.

Several example embodiments regarding determination of the at least one target resource have been described above, a further embodiment will be described with respect to FIG. 6 below. FIG. 6 illustrates a flowchart illustrating an example method 600 of target resource determination based on coordination information and sensing result according to some embodiments of the present disclosure. For the purpose of discussion, the method 600 will be described with reference to FIGS. 1 and 2A. The method 600 may be implemented at a UE-B, for example, the UE 120. For the purpose of discussion, the method 600 will be described from the perspective of the UE 120.

At block 610, the UE 120 performs sensing. At block 620, the UE 120 receives, from the UE 110, coordination information concerning a transmission to be performed by the UE 120. The coordination information indicates a resource set preferred for the UE 120 to perform resource selection. The UE 120 may select a resource for the transmission based on the coordination information.

At block 630, the UE 120 determines whether to remove a resource in the resource set based on the at least one of the measured power, the reception time and the reception scheduled for the UE. The determination process is similar to the determination described with respect to FIG. 5. If at block 630, the UE determines to remove the resource in the resource set, the method 600 will proceed to block 640.

At block 640, the UE 120 updates the resource set by removing the resource. At block 650, the UE 120 determines whether the number of the at least one target resource is less than the number of resources in the updated resource set. If at block 650, the UE 120 determines that the number of the at least one target resource is less than the number of resources in the updated resource set, then the method 600 will proceed to block 660. At block 660, the UE 120 may select the at least one target resource from the updated resource set.

If at block 650, the UE 120 determines that the number of the at least one target resource exceeds the number of resources in the updated resource set, then the method 600 will proceed to block 670. At block 670, the UE 120 may determine each resource in the updated resource set and at least one further resource to be the at least one target resource. The at least one further resource is exclusive of the updated resource set. For example, the UE 120 may select the at least one further resource based on its sensing result, such as via a legacy resource selection procedure.

By determining the at least one target resource based on the coordination information and additional further information, it may avoid the UE 120 from selecting a potentially collided resource. In addition, it may avoid the SL transmission due to half duplex. Using the above described determination of target resource, the SL transmission will be enhanced.

Determination of a Resource Collision Status

As mentioned above, in scheme 2, if the UE 110 determines to transmit the coordination information to the UE 120, or receives an explicit request for the coordination information from the UE 120, the UE 110 may determine 275 the resource collision status for the UE 120.

Conventionally, if the UE-A identifies that an expected or potential resource collision occurs on the resource(s) satisfying at least one condition, the UE-A may determine presence of the expected or potential resource collision. The at least one condition comprises for example that other UE(s) reserves reserved resource(s) are fully or partially overlapping with resource(s) indicated by SCI of a UE-B. However, it still needs to specify additional criteria and details including signaling regarding the indication of a potential resource collision.

FIG. 7 illustrates a flowchart illustrating an example method 700 of determination of a potential resource collision indicated by coordination information according to some embodiments of the present disclosure. For the purpose of discussion, the method 700 will be described with reference to FIGS. 1 and 2B. The method 700 may be implemented at a UE-A, for example, the UE 110. For the purpose of discussion, the method 700 will be described from the perspective of the UE 110.

At block 710, the UE 110 receives, via a transceiver of the UE 110 and from the UE 120, control information indicating a resource reserved by the UE 120. For example, the UE 110 may receive SCI from the UE 120. At block 720, the UE 110 determines 720 a resource collision status of the UE 120 with a further UE such as the UE 130. For example, the UE 110 determines the resource collision status based on at least further information. Examples of further information may include but not limited to: the control information from the UE 120, further control information from the UE 130, measured power of a signal from the UE 120 or further measured power of a signal from the UE 130, and time of the potential resource collision.

For example, the UE 110 may perform sensing and receive the control information from the UE 120 and the further control information from the UE 130. If the control information from the UE 120 and the further control information from the UE 130 indicate that both the UE 120 and the UE 130 reserve a same resource, the UE 110 may determine that a potentially collided resource is reserved by both the UE 120 and the UE 130. The UE 110 may also determine the potentially collided resource based on other conditions.

In some example embodiments, if the UE 110 determines that the potentially collided resource is reserved by both the UE 120 and the UE 130 and that a priority of data to be transmitted using the potentially collided resource by the UE 120 exceeds a threshold priority, the UE 110 may determine the resource collision status as presence of a potential resource collision. The priority of data is indicated by the control information from the UE 120, for example the SCI from the UE 120. The threshold priority is configured or preconfigured.

Alternatively or in addition, if the UE 110 determines that a potentially collided resource is reserved by both the UE 120 and the UE 130 and that a priority of data to be transmitted using the potentially collided resource by the UE 130 exceeds a threshold priority, the UE 110 may determine the resource collision status as presence of a potential resource collision. The priority of data is indicated by the further control information from the UE 130, for example the SCI from the UE 130. The threshold priority is configured or preconfigured.

In some example embodiments, if the UE 110 determines that a resource is reserved by both the UE 120 and the UE 130 and that a distance between the UE 120 and the UE 110 is less than a threshold distance, the UE 110 may determine the resource collision status as presence of a potential resource collision. The distance is determined based on the control information from the UE 120. For example, the UE 110 may calculate the distance based on the SCI using groupcast feedback option 1 (i.e., negative acknowledgement (NACK) only scheme) from the UE 120. The threshold distance is configured or preconfigured.

Alternatively or in addition, if the UE 110 determines that a resource is reserved by both the UE 120 and the UE 130 and that a distance between the UE 130 and the UE 110 is less than a threshold distance, the UE 110 may determine the resource collision status as presence of a potential resource collision. The distance is determined based on the further control information from the UE 130. For example, the UE 110 may calculate the distance based on the SCI using groupcast feedback option 1 (i.e., negative acknowledgement (NACK) only scheme) from the UE 130. The threshold distance is configured or preconfigured.

In some example embodiments, if the UE 110 determines that a resource is reserved by both the UE 120 and the UE 130 and that the control information from the UE 120 indicates that a partial sensing or no sensing is performed by the UE 120, the UE 110 may determine the resource collision status as presence of a potential resource collision.

Alternatively or in addition, if the UE 110 determines that a resource is reserved by both the UE 120 and the UE 130 and that the further control information from the UE 130 indicates that a partial sensing or no sensing is performed by the UE 130, the UE 110 may determine the resource collision status as presence of a potential resource collision.

In some example embodiments, if the UE 110 determines that a resource is reserved by both the UE 120 and the UE 130 and that the control information from the UE 120 indicates a periodic resource reservation performed by the UE 120, the UE 110 may determine the resource collision status as presence of a potential resource collision.

Alternatively or in addition, if the UE 110 determines that a resource is reserved by both the UE 120 and the UE 130 and that the further control information from the UE 130 indicates a periodic resource reservation performed by the UE 130, the UE 110 may determine the resource collision status as presence of a potential resource collision.

In some example embodiments, if the UE 110 determines that a potentially collided resource is reserved by both the UE 120 and the UE 130 and that the measured power of a signal from the UE