Preemption in Sidechain Communication

Abstract

The present application provides a method for preempting transmission resources in a cellular network sidelink communication. Resource reservation information that conflicts with previously reserved resources is used as a preemption indication.

Description

Technical Field

[0001] The present application relates to a wireless communication system, and more specifically to a distributed SL resource allocation and preemption mechanism in a sidelink (SL) communication environment, such as in a cellular vehicle-to-everything (V2X) application. Background Art

[0002] In Release 16 Vehicle-to-Everything Work Item (Rel.16 V2X WI), in addition to the classic use cases inherited from traditional LTE V2X, the 3rd Generation Partnership Project (3GPP) also introduced new applications for V2X communications, such as assisted / autonomous driving and car platooning. Therefore, different packet priorities and delay budgets are considered in NR V2X.

[0003] In order to meet the new requirements of User Equipment (UE) operating in Mode 2 in terms of strict reliability and latency, the UE should be allowed to access the channel within its packet delay budget while maintaining a sufficient reliability level. Therefore, the study of preemption operations in V2X Mode 2 has received great attention. Resource preemption involves the opportunistic use of block resources that have been reserved or allocated to the UE for future transmissions (preempted) in whole or in part by the UE (preemptor) to allow data transmission with higher Quality of Service (QoS). The preempting UE should notify the preempted UE of the resource preemption and suppress transmission, thereby avoiding packet collisions on the resources. In addition, the preempted UE should select a new resource to resume its preempted transmission.

[0004] In LTE V2X Mode 4 (equivalent to NR V2X Mode 2), there is no clear mechanism for a UE with a higher priority data packet to preempt a UE that has reserved lower priority resources. The present disclosure aims to solve the sidelink (SL) preemption problem of NR V2X Mode 2 operation. The lack of a centralized node (such as a next generation node base station (gNB)) with a clear overview of resource scheduling status and control of preemption operation status leads to ambiguity in the role of each UE, i.e., when a preempting UE is allowed to preempt SL resources, and when the preempted UE needs to monitor potential preemption indications (PI). In addition, monitoring PI consumes power and wastes duplexing time, and should only be performed when necessary. Regarding preemption, many companies in the 3GPP group have proposed the need for a preemption mechanism in V2X Mode 2.

[0005] In many technical documents (Tdocs) of the 97th meeting (#97) of the Radio Access Network working group #1 (RAN1), preemption is considered to be related to V2X Mode 2 to effectively meet the QoS requirements in high congestion scenarios. The discussion of the preemption mechanism was proposed in the feature-lead-summary of AI 7.2.4.2.2 Mode-2 Resource Allocation R1-1907771 (and R1-1907699):

[0006] ●Support Mode-2 resource preemption mechanism

[0007] ○ If enabled, the preemption mechanism should trigger resource reselection or resource release to prevent conflicts with higher priority UE resources

[0008] ○FFS other details

[0009] We outline below some of the companies’ recommendations for resource preemption for V2X Mode 2:

[0010] OPPO R1-1904922&R1-1906477:

[0011] To ensure that the target Physical sideLink Shared Channel (PSSCH) resource reservation is received by others, the preemption information can be sent twice in two Physical sideLink Control Channel (PSCCH) resources separated in time and frequency to prevent some UEs from not receiving the message in the first transmission due to half-duplex issue or conflict with other preempted Transmits (Tx).

[0012] Ericsson R1-1905477:

[0013] We believe that the sidelink control information (SCI) also carries other data directly related to resource utilization, such as requests for hybrid automatic repeat request (HARQ) feedback and preemption information. The former allows the decoding UE to identify which resources are used for physical feedback control channel (PSFCH) transmissions and avoid using them. The latter allows the preempted UE to stop transmitting. We believe that these fields should be included in the SCI and extracted by the sensing program.

[0014] Ericsson R1-1907136:

[0015] Consider the following alternatives for signaling preemption signaling:

[0016] ●Alternative 1: Independent PSCCH spanning the entire slot.

[0017] ●Alternative 2: PSCCH+PSSCH carries emergency data.

[0018] LG R1-1905439:

[0019] "Time Division Multiplexing (TDM) transmission of (Standalone, SA) and data" is conducive to preemption. If there is a gap between the data and the SA containing the preemption indication, the UE can have more opportunities to detect the preemption indication. This means that better conflict avoidance can be achieved between packet transmissions of different priorities. In addition, the Roadside Unit (RSU) relay mechanism can be considered for preemption operations. That is, if the UE needs to preempt resources for high-priority packet transmission, it sends a request message with a preemption indication or resources to a nearby RSU. The RSU can then relay this type of information to other UEs, and these UEs can avoid selecting preempted resources. Summary of the invention

[0020] In this disclosure, the preemption mechanism and related issues when all involved UEs are out of coverage (i.e., V2X Mode 2) are discussed. We propose a simplified signaling preemption design with little standardization work for distributed preemption decisions, allowing both parties to make autonomous decisions to be part of the preemption operation. The decision is mainly based on the load of the sidelink channel. Therefore, it can be appropriately based on the estimated channel busy rate (CBR) of all UEs intending to transmit in the SL resource pool. A suitable threshold can be defined in terms of channel load (or CBR) to trigger users to start listening for potential preemption. This can be made more meaningful by defining a composite threshold with traffic priority and channel load. When the sidelink channel load (e.g., in terms of CBR) exceeds a certain threshold, users with high priority traffic will also preempt other users. That is, the UE that may be preempted will monitor potential PIs, while the preemption will send PIs. In order to guarantee the reception of the preemption, different thresholds can be defined for the preemptor and the preempted UEs. A more reliable approach is to indicate in the sidelink control data (SCI) from low priority UEs that they are listening for preemption signaling. Furthermore, we propose improvements to help UEs select and reserve SL resources to be preempted for transmission.

[0021] The current disclosure aims to provide:

[0022] ●There is no ambiguous distributed preemption mechanism in the absence of a centralized control node.

[0023] ●Reduce the preemption monitoring overhead of UEs that may be preempted.

[0024] ● Provide enhanced QoS for UEs intending to transmit high priority and / or delay-constrained data packets.

[0025] ●Reduce the risk of data packet collision.

[0026] The present disclosure provides a method for allocating and preempting sidelink communication transmission resources in a cellular wireless communication system, the method comprising the following steps: at a first UE, receiving transmission resource reservation information from a second UE, the reservation information being used for a first transmission resource, the first transmission resource being used for a sidelink transmission of a first priority of the second UE; at the first UE, selecting a second transmission resource for the sidelink transmission of the first UE with a second priority higher than the first priority, the second transmission resource overlapping with at least a portion of the first transmission resource; and at the first UE, sending sidelink control data information, the sidelink control data information indicating the reservation information of the first UE for the second transmission resource, and indicating to the second UE that the overlapping first transmission resource is preempted.

[0027] The present disclosure also provides a method for allocating and preempting sidelink communication transmission resources in a cellular wireless communication system, the method comprising the following steps: at a first UE, sending first transmission resource reservation information, the reservation information is for a first transmission resource, the first transmission resource is for a sidelink transmission of a first priority of the first UE; and at the first UE, receiving sidelink control data information from a second UE, the sidelink control data information indicating reservation information of a second transmission resource of the second UE, the second transmission resource being used for a sidelink transmission of the second UE with a priority higher than the first priority, wherein the second transmission resource overlaps with the first transmission resource, and the overlap of the second transmission resource with the first transmission resource indicates to the first UE that the overlapping first transmission resource is preempted. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figures 1 to 5 Various examples of sidechain communication preemption are shown;

[0029] Figure 6 Selected elements of a cellular communication system are shown. DETAILED DESCRIPTION

[0030] In out of coverage situations, New Radio mode 2 sidelink (NR mode 2 SL) resource allocation is used, where the User Equipment (UE) autonomously selects its transmission resources based on the results of a sensing procedure. The sensing operation allows reducing SL resource conflicts, where a UE intending to transmit should detect the SL resource reservation pattern of other UEs. Resources that exceed a given threshold in Reference Signal Received Power (RSRP) are first excluded in the SL resource selection procedure, followed by resources that exceed a given threshold in Received Signal Strength Indication (RSSI). Similarly, when an available SL resource is selected, the UE announces the SL resource reservation indication in broadcast signaling before transmitting on that resource. Packet priority and packet delay budget are parameters that may affect the Quality of Service (QoS) of packet transmission. In the discussion of Radio Access Networkworking group#1 New Radio Vehicle-to-Everything mode 2 (RAN1 NR V2X mode 2), most companies support including the reserved resources and QoS / priority data in the SL resource reservation sidelink control information (SCI). In order to meet the required QoS in the congested SL resource pool, the UE carrying high-priority data packets can preempt the transmission of low-priority data packets.

[0031] The preemption mechanism relies on detecting the SL resource reservation sent by the low priority UE and the preemption indication information sent by the high priority UE to notify that the preempted SL resources will be used by another UE and the lower priority UE should suppress transmission to avoid packet collision.

[0032] In the New Radio User Universal interface context (NR-Uu context), resource allocation and preemption are controlled by a centralized entity, the next Generation Node Base (gNB), which usually receives the PI and forwards it to the affected UE to stop the transmission. In mode 2V2X, there is no centralized node, forcing the preempting and preempted UEs to autonomously decide and execute the preemption mechanism. That is, a UE that wants to preempt a given SL resource must send a PI. This preemption indication needs to be sent in advance with appropriate reliability and sufficient time before the target preempted resource so that the preempted UE can receive and process it. In order to be able to stop the reserved transmission, the UE should be able to autonomously decide when and how to listen to the PI. A straightforward approach could be for the UE after sending the resource reservation indication to listen to the potential PI before actually sending it.

[0033] While the classic preemption approach in Mode 2 above works, it results in a large monitoring overhead for the potentially preempted UE. Therefore, the preempted UE must autonomously limit the number of monitoring opportunities without the help of the gNB. Similarly, in a distributed system, it is unclear when a UE can send a preemption indication.

[0034] Therefore, we propose that preemption triggering (by the preempting UE) and monitoring (by other UEs that may preempt) are mainly determined by the UE based on the packet priority and channel occupancy generated by the sensing procedure. Based on these parameters, a UE with a high priority packet knows whether it has the right to preempt a given SL resource. Similarly, a UE that has reserved SL resources for future transmission knows whether it may be preempted and how the monitoring should be performed (timing and periodicity).

[0035] From the perspective of the UE performing preemption, preemption can be triggered primarily based on when the user gets high priority traffic but the channel load is so high that the data packets cannot be expected to meet their QoS targets.

[0036] The present disclosure proposes a simple, elegant and effective preemption design method for V2X Mode 2. In this method, the preemption decision is based on the load of the sidelink channel. Therefore, it can be appropriately based on the Channel Busy Ratio (CBR) estimated by all UEs intending to transmit in the SL resource pool. CBR can be calculated in different ways to indicate the load of the sidelink channel. A first definition of CBR can be the ratio of available resources in the sidelink channel. A second definition can consider the continuity of available resources across the sidelink channel. That is, if many small available resources are too dispersed in the channel, then they are unlikely to be used by UEs that tend to transmit on a single continuous resource block.

[0037] CBR can be calculated in a number of ways:

[0038] ●Option 1: Ratio of available resources in the sidechain channel.

[0039] ●Option 2: Consider the ratio of the distribution of available resources on the sidechain channels.

[0040] As a typical mechanism, in mode 2 users who want to send packets need to listen to the sidelink channel, so they have an overview of the channel load. A suitable threshold in terms of channel load (or CBR) can be defined to trigger users to start listening for potential preemption. This can be made more meaningful by defining a composite threshold with traffic priority and channel load. Thus, users transmitting low priority traffic are more likely to be preempted, and therefore listen to the CBR early for potential PI.

[0041] A composite CBR threshold with traffic priority is defined to make UEs with the lowest packet priority perform more listening for potential PI.

[0042] When the sidelink channel load (e.g. in terms of CBR) exceeds a certain threshold, users with high priority traffic may preempt other users. That is, the UE that may be preempted will monitor potential PIs, while the user performing the preemption will send PIs. In order to guarantee reception of the preemption, different thresholds can be defined for the UE performing the preemption and the UE being preempted. Different thresholds at both ends of the preemption help to comply with the fact that the sensing performed at these two users may result in different channel load overviews, because these users are not necessarily located at the same location. However, these users will not be far apart, because the UE performing the preemption is able to listen and decode resource reservation indications from other users before sending the PI.

[0043] Different suitable channel load thresholds result in UEs with a higher chance of being preempted listening to the PI and stopping their transmission on the resources that were reserved before receiving the PI. However, when the user does not listen to the PI or the decoding fails, both cases will result in the user with previous reservations not stopping their transmission on the reserved resources and some transmissions will face conflicts.

[0044] In order to avoid that a UE sending or planning to send a PI is not clear whether its target user, i.e. the user whose resources it plans to preempt, is listening to the PI, the present disclosure proposes another novel strategy. When the channel load exceeds the threshold at which a user may be preempted, the user sends a preemption-ready indication (possibly a single bit flag) in the resource reservation indication. As part of the normal sensing procedure, all nearby users decoding the resource reservation indication thus obtain the information that this particular user will be listening to a potential PI. Now, if another user with high priority traffic needs to preempt to be able to transmit its data packets within its QoS target, it will only preempt users that have indicated a "preemption-ready" indication in a part of the resource reservation indication.

[0045] To avoid missing the detection of the PI indication, a 1-bit pre-emption-READY flag may be included in the resource reservation SCI from the UE that may be preempted to inform other UEs that they are ready to listen to the PI.

[0046] In addition to handling the distributed decision of when preemption can be performed, when users listen to PI and when to send it, another most important invention of the present disclosure is related to preemption signaling. NR-Uu standardizes independent preemption signaling, which notifies previously scheduled users about preemption events. The present disclosure proposes to serve the purpose of resource preemption with normal scheduling indications. UEs with higher priority traffic will select the appropriate UE to preempt, but no explicit preemption signaling will be sent. It sends a scheduling indication that provides resource indications, possibly together with other control parameters. The scheduling indication is sent in a predefined (preconfigured) time window associated with the target resource. Therefore, UEs that have made previous reservations will listen to scheduling indications from neighboring UEs within this predefined time window. The resource reservation indication sent here together with the resources overlapping the previous scheduling is therefore used for the purpose of preemption, resulting in a very efficient preemption signaling design. It is worth noting that, in a sense, this design can preempt multiple lower priority previous schedules with a single scheduling without any additional signaling overhead.

[0047] To reduce signaling, in a preemption environment, the reserved SCI may be used as a reservation indication for all UEs, or as a preemption indication for UEs whose previously reserved resources fully or partially overlap with the sent reserved SCI.

[0048] A. Preemption based on insufficient resources:

[0049] A UE with packets to transmit should perform a sensing procedure in a window in which it learns the transmission patterns in the SL resource pool and then excludes the resources that have been reserved when it intends to transmit. We recommend that the UE starts listening for preemption indications after exceeding a given resource occupancy threshold. A simple approach is to define a single threshold based on channel occupancy, such as a CBR value, above which the user starts monitoring the PI. A more meaningful approach is to define multiple channel load values ​​for different traffic priorities that the user is transmitting. The rationale behind this is that if preemption is required, it makes sense to preempt the lowest priority traffic among the packets occupying the resources.

[0050] Furthermore, the channel occupancy metric used for (de)activating preemption monitoring may take into account the size of the resources to be reserved so that it reflects the occupancy at the time of transmission. For example, if a channel is empty but a planned transmission uses all available resources for a period of time, then for the decision of preemption monitoring it may be considered as having the maximum channel occupancy.

[0051] A preemptive user can only preempt resources reserved for lower priority packets. Figure 1 In Figure 1, we describe a typical scenario of preemption based on lack of resources. For UE1 (blue) and UE2 (orange), UE1 has a packet with priority p1 to transmit. Before resource selection, the UE should perform a sensing procedure in order to exclude resources that have been reserved by other UEs. After selecting a suitable SL resource, it sends an SL resource reservation indication and reserves it. This reservation can be sent as the first phase of a two-phase SCI or as a single-phase SCI. If the UE1 sensing result indicates that the SL resource occupancy exceeds a threshold C1, UE1 needs to perform PI monitoring before its transmission. This short-term PI monitoring procedure can coincide with the last or last few SCI transmission opportunities before its transmission moment. In this way, UE1 can autonomously decide whether it may be preempted, and in this case, the PI monitoring overhead can be reduced.

[0052] Obviously, if UE1 has a packet with the highest priority, it can be exempted from monitoring PI.

[0053] Now assume that UE2 performs a transmission sensing procedure that overlaps with UE1's reservation information, for example, UE2 knows the parameters of future UE1 transmissions on a given SL resource. Now, if UE2 has a packet with priority P2 (and P2>P1), and the result of its sensing procedure indicates that the channel occupancy exceeds a threshold C2, then it can decide to preempt UE1's transmission to meet its QoS. The preempted channel occupancy C2 should be higher than or equal to the preempted channel occupancy C1, i.e., C2>=C1. The reason is that it should be more difficult for UE2 to make a preemption decision autonomously than to preempt a monitoring decision, in order to reduce the number of preemption decisions and limit its use to only extreme cases, thereby reducing the number of collision events.

[0054] A conservative CBR threshold can be set to limit the preemption usage of UEs with high priority packets and ensure that UEs that may be preempted are monitored for preemption.

[0055] In order to inform the preempted UE1 of the SL resource preemption, UE2 should send the SL resource PI at the last or last few opportunities before the target UE1 transmission is preempted.

[0056] NR-Uu has defined a preemption mechanism and standardized a specific group common DCI (Downlink Control Indicator) for the purpose of transmission in a specific configured control resource CORESET (Control Resource set). This design becomes complicated in V2X Mode 2 due to the absence of any centralized scheduler. The present disclosure proposes a very elegant design here, allowing a general SCI to be used as a PI in the case where resource scheduling occurs on previously reserved resources. Therefore, the PI can be sent as a general SL resource reservation SCI for UE2 transmission. UE1 monitors the last / last few SCIs before its transmission, comparing its reserved SL resources with the preempted SL resources indicated in the PI. If the reserved resources partially overlap with the SL resources reserved by UE2, UE1 will stop transmission and start a new sensing / reservation procedure for another SL resource.

[0057] The PI is sent in the last / last few SCI opportunities before the transmission time. The number of SCI opportunities to be monitored can be preconfigured.

[0058] In order to limit the decoding complexity of the potential PI for the user, it is reasonable to define a window within which the UE performing the preemption will send its resource reservation as a preemption indication. This SCI (or the first stage of the SCI) will arrange the SL resources for its intended recipient as a general SCI, and in addition, it also acts as a preemption indication for UEs that have reserved overlapping resources in the previous control (SCI). This dual utilization forms a very effective preemption signaling, increasing system efficiency.

[0059] A preemption indication affects multiple UEs that intend to transmit low - priority UEs. In Figure 2 , we illustrate this scenario. UE1, UE2, and UE3 intend to transmit data packets with priorities P1, P2, and P3 respectively, where P1 < P2 < P3. The CBR threshold can be calculated according to the priority of the data packet to be transmitted. A conservative threshold can be selected to avoid UEs with low - priority data packets to transmit from missing the PI. Therefore, we assume C3 < C2 < C1. Low - priority data - packet UEs may be affected differently. Although the resources selected by the preempting UE can overlap with other UEs' resources arbitrarily, completely, or partially, it is preferable to partially preempt the resources reserved for higher - priority data packets. That is, in Figure 2 the example shown, UE3 partially preempts the resources reserved by UE2 and completely preempts the resources reserved by UE1 (because the priority of UE1 data packet P1 < the priority of UE2 data packet P2). Regarding the reliability level of the PI transmitted to multiple UEs, each preempted UE should receive it at a sufficient aggregation level to be able to decode it. Therefore, the UE that performs the preemption must select the maximum value among all required aggregation levels to ensure a high probability of PI decoding.

[0060] B. Preemption Based on a Finite Delay Budget:

[0061] In this section, we will address the problem of the expiration of the delay budget for data packets of all packet types and priorities. For example, the case where a data packet with any priority fails to select SL resources after one or more sensing windows and the delay budget is about to expire. Note that a UE can only preempt the resources reserved for higher - priority data packets. To allow the data packet to be transmitted within the time budget, some solutions are proposed:

[0062] 1. Short - term Sensing Instead of Long - term Sensing Plus Preemption

[0063] In Figure 3 the described scheme, UE2, for which a data packet with a given priority is approaching the transmission deadline, will perform a short - term sensing window instead of the classical long - term sensing window to allow for a quick sensing and preemption procedure. As described in the previous section, the monitoring decision of the UE1 PI is based on the CBR generated by its sensing procedure. The preemption decision of UE2 is also based on the CBR generated by its short - term sensing window. The CBR threshold C2 can be kept at a nominal value or decreased according to the remaining time budget before the transmission deadline. The CBR threshold of the UE that performs the preemption should, in any case, be higher than or equal to the CBR of the preempted UE.

[0064] The CBR threshold of the potentially pre - empting UE can be kept at a nominal value or decreased according to the remaining time budget before the transmission deadline.

[0065] Then, UE2 selects a SL resource to preempt to satisfy its packet size and delay budget, and sends the SL resource reservation information in a broadcast manner, which will be regarded as a preemption indication from the perspective of the preempted UE1. As mentioned above, preemption can only be for lower priority packets.

[0066] 2. Progressive perception of window size:

[0067] In case SL resource selection still fails after one / more sensing procedures, the UE intending to send packets of a given priority level may switch to sensing windows of gradually decreasing sizes and enable preemption if the CBR threshold is met.

[0068] A UE that fails once or multiple times may reserve resources using sensing windows of gradually decreasing sizes.

[0069] 3. Progressive CBR with fixed perception window size:

[0070] In case SL resource selection still fails after one / more sensing procedures, the UE that intends to send a packet of a given priority can gradually reduce the CBR threshold for preemption decision. The advantage of gradually relaxing the threshold constraint is that it allows UEs with critical time budget to access the medium more easily, thereby meeting the QoS requirements of all packet priorities. The CBR threshold of the UE performing preemption should be higher than or equal to the CBR of the preempted UE in any case.

[0071] Gradually lower CBR thresholds for preemption decisions may be used by UEs that fail once or multiple times to reserve resources.

[0072] Note that as the first preemption triggering case, even if the UE decides to preempt SL resources due to the packet delay budget constraint, if the packet is of low priority, the UE should perform sufficient short-term sensing before its transmission because it itself may be preempted by another UE.

[0073] C. Enhanced functions:

[0074] 1. Preempt SL resource selection parameters:

[0075] In addition to CBR as the main trigger for SL resource preemption decision, other parameters may be involved to fine-tune the preemption SL resource selection procedure. For a UE performing preemption, if two resource blocks have the same latency and reliability, the resource that affects a smaller number of users should be prioritized. Then, the SL resource that represents the largest difference between the preempted and preempted packets should be prioritized.

[0076] In addition, if the SL resource reservation information indicates the transmission order in the sensing procedure, such as first transmission, retransmission 1, retransmission 2, etc., it should tend to preempt the retransmission resources with higher priority to avoid penalizing the first transmission.

[0077] Higher order retransmission resources should be prioritized to avoid penalizing the first transmission.

[0078] 2. Preemption indication reliability:

[0079] To avoid packet collisions, the UE performing the preemption should ensure that the preempted UE, preferably its intended recipient, successfully receives the preemption indication (to reduce unnecessary decoding work of the preempted SL resources). Therefore, the PI should be sent in broadcast mode. In addition, if the SCI is considered as a means of SL resource reservation and preemption, the modulation and coding scheme (MCS) and aggregation level of the PSCCH carrying the SCI should be selected in a way that ensures successful decoding by the preempted UE. If the available resources of the PSCCH cannot guarantee successful reception, the UE intending to preempt should cancel its preemption decision.

[0080] If the available resources of PSCCH cannot guarantee successful reception at the preempted UE side, the UE intending to preempt should cancel its preemption decision.

[0081] 3. Preemption signaling:

[0082] In this application document, SCI is considered as potential signaling of SL resource reservation information, which can be used as a preemption indication from the perspective of the preempted UE. Although this solution does not require new signaling standardization work, it is still valid for any PI signaling, such as in existing or new dedicated channels.

[0083] 4. Preemptive capability communication between UEs:

[0084] If a connection is being or has been established between users, the preemption monitoring capability can be notified through Radio Resource Control (RRC) or equivalent distributed configuration information. Therefore, the UE performing the preemption should select the resources reserved by the UE with preemption monitoring capability. This capability communication can help avoid incompatibility between UEs, where a UE that does not support V2X Mode 2 preemption is preempted by a UE that supports the function.

[0085] The preemption monitoring capability may be signaled via RRC or an equivalent distributed configuration message.

[0086] 5. Explicit preemption monitoring ads:

[0087] The decoding of the preemption indication should be ensured to ensure that the risk of collision between packets due to preemption is low. Therefore, a UE that may be preempted can include a 1-bit flag "pre-emption-READY" in its reserved SCI to inform other UEs of its ability to preempt monitoring. Figure 4 The figure illustrates a situation where UE1 and UE2 reserve adjacent resources for their packets of priority P1 and P2, respectively. For its transmission, UE1 supports the preemption option and includes a 1-bit "pre-emption-Ready" flag in its reservation SCI. Then, another UE3, which intends to send a high priority (priority P3) packet, decides to preempt future transmissions of UE1 and UE2. Only UE1 monitors any potential PI that affects its transmission. As a result, UE1 avoids collisions, but UE2 does not.

[0088] In order to minimize the risk of collision, a UE intending to preempt must preferably select the resources of an affected UE that has sent a "pre-emption-Ready" flag.

[0089] 6. Packet Priority Preemption in a Specific CORESET:

[0090] In the sidelink, the control resource set can depend on the packet priority, i.e. each UE intending to send a packet of priority P1 should send a resource reservation indication in a specific coreset of the specified priority P1. In this way, another UE intending to send a packet with high priority P2 (P2>P1) and when the CBR value exceeds a given threshold, it can preempt the transmission of a lower priority, such as P1. Then, it sends its resource reservation indication, which also serves as a preemption indication in the coreset specific to the priority of the preempted packet. Therefore, the lower priority UE, after its reservation action, should only monitor the coreset specific to its packet priority P1, which reduces the PI monitoring overhead. This mechanism is as follows Figure 5 shown.

[0091] Resource reservation and preemption for a given packet priority should be transmitted in the coreset specific to that priority.

[0092] Figure 6A schematic diagram of three base stations (e.g., eNBs or gNBs, depending on the particular cellular standard and terminology) is depicted, which form a cellular network in which the above disclosure may be implemented. Typically, each base station will be deployed by a cellular network operator to provide geographic coverage for UEs in an area. The base stations form a Radio Area Net (RAN). Each base station provides wireless coverage for UEs in its area or cell. The base stations are interconnected via an X2 interface and connected to the core network via an S1 interface. It is understandable that only basic details are depicted in order to illustrate the key features of the cellular network. A PC5 interface is provided between UEs for sidelink (SL) communication. With Figure 6 The related interface and component names are used as examples only, and different systems operating on the same principles may use different nomenclature.

[0093] Each base station contains hardware and software that implements RAN functions, including communication with the core network and other base stations, control and data signal transmission between the core network and UEs, and maintaining wireless communications with UEs associated with each base station. The core network includes hardware and software that implements network functions, such as overall network management and control, and routing of calls and data.

[0094] Although not shown in detail, any device or apparatus forming part of the network may include at least a processor, a storage unit and a communication interface, wherein the processor unit, the storage unit and the communication interface are configured to perform the method of any aspect of the present invention. The following further describes options and selections.

[0095] Embodiments of the present invention, in particular the signal processing functions of the gNB and UE, may be implemented using computing systems or architectures known to those skilled in the relevant art. Computing systems, such as desktop computers, laptops or notebook computers, handheld computing devices (personal digital assistants (PDAs), mobile phones, palmtops, etc.), mainframes, servers, clients, or any other type of dedicated or general-purpose computing devices, etc., may be suitable for a given application or environment. The computing system may include one or more processors, which may be implemented using a general-purpose or dedicated processing engine, such as a microprocessor, microcontroller, or other control module.

[0096] The computing system may also include a main memory, such as a random access memory (RAM) or other dynamic memory, for storing information and instructions executed by the processor. Such a main memory may also be used to store temporary variables or other intermediate information during the execution of instructions by the processor. The computing system may also include a read-only memory (ROM) or other static storage device for storing static information and instructions for the processor.

[0097] The computing system may also include an information storage system, which may include, for example, a media drive and a removable storage interface. The media drive may include a drive or other mechanism to support fixed or removable storage media, such as a hard drive, a floppy disk drive, a tape drive, an optical drive, a compact disk (CD) or a digital video drive (DVD) (RTM) read or write drive (R or RW), or other removable or fixed media drives. The storage medium may include, for example, a hard disk, a floppy disk, a tape, an optical disk, a CD or a DVD, or other fixed or removable media read and written by a media drive. The storage medium may include a computer-readable storage medium having specific computer software or data stored therein.

[0098] In alternative embodiments, the information storage system may include other similar components for allowing computer programs or other instructions or data to be loaded into the computing system. Such components may include, for example, removable storage units and interfaces, such as program cartridges and cartridge interfaces, removable memory (e.g., flash memory or other removable memory modules) and memory slots, and other removable storage units and interfaces that allow software and data to be transferred from the removable storage units to the computing system.

[0099] The computing system may also include a communication interface. Such a communication interface may be used to allow software and data to be transferred between the computing system and external devices. Examples of communication interfaces may include a modem, a network interface (e.g., an Ethernet or other NIC card), a communication port (e.g., a Universal Serial Bus (USB) port), a PCMCIA slot and card, etc. The software and data transferred via the communication interface are in the form of signals, which may be electronic, electromagnetic, optical, or other signals that can be received by the communication interface medium.

[0100] In this document, the terms "computer program product," "computer-readable medium," and the like may be generally used to refer to tangible media, such as memory, storage devices, or storage units. These and other forms of computer-readable media may store one or more instructions for use by a processor comprising a computer system to cause the processor to perform specified operations. Such instructions, generally referred to as "computer program code" (which may be grouped in the form of a computer program or otherwise), when executed, enable a computing system to perform the functions of embodiments of the present invention. Note that the code may directly cause a processor to perform a specified operation, be compiled to perform such operation, and / or be combined with other software, hardware, and / or firmware elements (e.g., libraries for performing standard functions) to perform such operation.

[0101] The non-transitory computer-readable medium may include at least one selected from the group consisting of a hard disk, a CD-ROM, an optical storage device, a magnetic storage device, a read-only memory, a programmable read-only memory, an erasable programmable read-only memory, an EPROM, an electrically erasable programmable read-only memory, and a flash memory. In embodiments where software is used to implement the components, the software may be stored in a computer-readable medium and loaded into a computing system using, for example, a removable storage drive. The control module (in this example, software instructions or executable computer program code) when executed by a processor in a computer system causes the processor to perform the functions of the present invention as described herein.

[0102] Furthermore, the inventive concept can be applied to any circuit that performs signal processing functions within a network component. It is further contemplated that, for example, a semiconductor manufacturer can employ the inventive concept in the design of a standalone device, such as a microcontroller of a digital signal processor (DSP), or an application specific integrated circuit (ASIC) and / or any other subsystem element.

[0103] It should be understood that, for the sake of clarity, the above description describes embodiments of the present invention with reference to a single processing logic. However, the inventive concept can also be implemented by a plurality of different functional units and processors to provide signal processing functions. Therefore, references to specific functional units are only considered as references to appropriate means for providing the described functions, rather than representing a strict logical or physical structure or organization.

[0104] The various aspects of the present invention can be implemented in any suitable form, including hardware, software, firmware or any combination of these. The present invention can be optionally implemented at least in part as computer software running on one or more data processors and / or digital signal processors or configurable module components such as FPGA devices.

[0105] Therefore, the components and assemblies of the embodiments of the present invention can be implemented physically, functionally and logically in any suitable manner. In fact, the function can be implemented in a single unit, in multiple units or as a part of other functional units. Although the present invention has been described in conjunction with some embodiments, it is not limited to the specific form set forth herein. On the contrary, the scope of the present invention is limited only by the appended claims.

[0106] Additionally, although a feature may appear to be described in connection with particular embodiments, one skilled in the art will recognize that various features of the described embodiments may be combined in accordance with the invention.In the claims, the term "comprising" does not exclude the presence of other components or steps.

[0107] Furthermore, although individually listed, a plurality of means, components or method steps may be implemented by, for example, a single unit or processor. Furthermore, although individual features may be included in different claims, these may be advantageously combined, and the inclusion in different claims does not imply that a combination of features is not feasible and / or advantageous. Furthermore, the inclusion of a feature in one claim category does not imply a limitation to that category, but rather indicates that the feature is equally applicable to other claim categories where appropriate.

[0108] Furthermore, the order of features in the claims does not imply any specific order in which the features must be performed and in particular the order of individual steps in a method claim does not imply that the steps must be performed in this order. On the contrary, the steps may be performed in any suitable order. Furthermore, singular references do not exclude a plurality. Thus, references to "a", "an", "first", "second" etc do not exclude a plurality.

[0109] Although the present invention has been described in conjunction with some embodiments, it is not limited to the specific form set forth herein. On the contrary, the scope of the present invention is limited only by the appended claims. In addition, although it seems that features have been described in conjunction with specific embodiments, it will be appreciated by those skilled in the art that the various features of the described embodiments may be combined in accordance with the present invention. In the claims, the terms "comprise" or "comprising" do not exclude the presence of other elements.

Claims

1. A method for allocating and preempting sidelink communication transmission resources in a cellular wireless communication system, characterized in that: The method comprises the following steps: At a first user equipment (UE), receiving transmission resource reservation information from a second user equipment, the reservation information being used for a first transmission resource, the first transmission resource being used for a sidelink transmission of a first priority of the second user equipment; At the first user equipment, selecting a second transmission resource for sidelink transmission of the first user equipment with a second priority higher than the first priority, wherein the second transmission resource overlaps with at least a portion of the first transmission resource; At the first user equipment, sending sidelink control data information, where the sidelink control data information indicates reservation information of the second transmission resource by the first user equipment and indicates to the second user equipment that the overlapping first transmission resource is preempted; The method further comprises: At the first user equipment, estimating a channel busy rate CBR of a sidelink resource pool associated with the sidelink channel, wherein the CBR represents a load of the sidelink channel; and selecting the second transmission resource or making a preemption decision based on whether the estimated CBR is greater than a predefined CBR threshold; Wherein, the first user equipment that still fails to reserve resources after a predetermined number of attempts lowers the predefined CBR threshold.

2. The method according to claim 1, wherein the CBR is the ratio of available resources in the side chain resource pool.

3. The method according to claim 1, wherein the CBR is a ratio that takes into account the dispersion of available resources on the sidelink channel.

4. The method according to claim 1, wherein the predefined CBR threshold is a threshold that takes communication service priority into consideration.

5. The method of claim 1, wherein the predefined CBR threshold of the first user equipment is reduced based on a remaining time budget before a sidelink transmission deadline.

6. The method according to claim 1, wherein a preemption indication PI is sent by the first user equipment in the last N sidelink control information SCI opportunities before the sidelink transmission moment, wherein the number N of SCI opportunities for monitoring PI is preconfigurable.

7. A method for allocating and preempting sidelink communication transmission resources in a cellular wireless communication system, characterized in that: The method comprises the following steps: At a first user equipment (UE), sending reservation information of a first transmission resource, where the reservation information is used for a first transmission resource, where the first transmission resource is used for a sidelink transmission of a first priority of the first user equipment; At the first user equipment, receiving sidelink control data information from a second user equipment, wherein the sidelink control data information indicates reservation information of a second transmission resource of the second user equipment, the second transmission resource being used for sidelink transmission performed by the second user equipment with a priority higher than the first priority, wherein the second transmission resource overlaps with the first transmission resource, and the reservation information of the second transmission resource indicates to the first user equipment that the overlapping first transmission resource is preempted; The method further comprises: At the second user equipment, estimating a channel busy rate CBR of a sidelink resource pool associated with the sidelink channel, wherein the CBR represents a load of the sidelink channel; and The second user equipment selects the second transmission resource or makes a preemption decision based on whether the estimated CBR is greater than a predefined CBR threshold; The second user equipment that still fails to reserve resources after a predetermined number of attempts lowers the predefined CBR threshold.

8. The method according to claim 7, wherein the CBR is a ratio of available resources in the side chain resource pool.

9. The method according to claim 7, wherein the CBR is a ratio that takes into account the dispersion of available resources on the sidelink channel.

10. The method according to claim 7, wherein the predefined CBR threshold is a threshold that takes communication service priority into consideration.

11. The method of claim 7, wherein the predefined CBR threshold of the first user equipment is reduced based on a remaining time budget before a sidelink transmission deadline.

12. The method according to claim 7, wherein a preemption indication PI is sent by the first user equipment in the last N sidelink control information SCI opportunities before the sidelink transmission moment, wherein the number N of SCI opportunities for monitoring PI is preconfigurable.

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