CN116325903A - Periodic reservation for sidelink communication in cellular networks - Google Patents

Abstract

A method for reselecting periodic resource reservations when conflicts are detected. The reselection process can reselect all resources forming a periodic resource reservation, or only a subset. The resource after reselection can be canceled. The UE may reuse the reselected resources for another transmission than originally intended.

Description

Periodic reservation for sidelink communication in cellular networks

technical field

The following disclosure relates to periodic resource reservations in cellular networks, and in particular to such reservations for sidelink communications.

Background technique

Wireless communication systems, such as third generation (3G) mobile phone standards and technologies are well known. Such 3G standards and technologies have been developed by the Third Generation Partnership Project (3GPP) (RTM). Third generation wireless communications have been generally developed to support macro-cell mobile phone communications. Communication systems and networks have evolved towards broadband and mobile systems.

In a cellular wireless communication system, a user equipment (User Equipment, UE) is connected to a radio access network (Radio Access Network, RAN) through a wireless link. The RAN includes a set of base stations that provide radio links to UEs located in cells covered by the base stations, and an interface that provides overall network control to the Core Network (CN). It should be understood that the RAN and CN each perform respective functions related to the overall network. For convenience, the term "cellular network" will be used to refer to the combined RAN and CN, and it should be understood that the term is used to refer to the corresponding systems for performing the disclosed functions.

The 3rd Generation Partnership Project developed the so-called Long Term Evolution (LTE) (RTM) system, the Evolved Universal Mobile Telecommunications System Territorial Radio Access Network (E-UTRAN) , for mobile access networks where one or more macro cells are supported by a base station called eNodeB or eNB (Evolved NodeB). More recently, LTE is being developed further towards so-called 5G or NR (New Radio) systems, where one or more cells are supported by base stations known as gNBs. NR is proposed to use Orthogonal Frequency Division Multiplexed (OFDM) physical transmission format.

The NR protocol is intended to provide the option to operate in unlicensed radio bands known as NR-U. When operating in unlicensed radio bands, gNBs and UEs have to compete with other devices for physical medium/resource access. For example, Wi-Fi (RTM), NR-U and LAA can use the same physical resources.

The trend of wireless communication is to provide services with lower latency and higher reliability. For example, NR is designed to support Ultra-reliable and low-latency communications (URLLC), while massive Machine-Type Communications (mMTC) is designed to support small packet sizes (typically 32 bytes) provide low latency and high reliability. A user-plane latency of 1 ms with a reliability of 99.99999% is proposed, and a packet loss rate (packet loss rate) of 10 ⁻⁵ or 10 ⁻⁶ is proposed at the physical layer.

The mMTC service is designed to support a large number of devices over a long lifetime over an energy-efficient communication channel, where data transfers to and from each device occur sporadically and infrequently. For example, a cell can be expected to support thousands of devices.

The following disclosure relates to various improvements to cellular radio communication systems.

Contents of the invention

This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

A method of changing periodic resource reservations for sidelink communications is provided. A UE with a periodic resource reservation listens for reservations that may conflict with the transmission resources of the periodic resource reservation and determines the level of conflict between the periodic resource reservation and the colliding transmission. The UE compares the level of collision with a threshold to determine whether to trigger a preemption procedure. Such a process may result in reselection of a periodic resource reservation, or only one or more periods of a periodic resource reservation.

The UE may then reselect new resources based on this determination. The new resources may be new periodic resource reservations or simply replace some of the original resources and/or periodic aperiodic resource reservations.

A resource reselection method related to periodic resource reservation is also provided, the method is executed in the UE, and includes the following steps: reserving periodic resources for sidelink communication; identifying and conflicts for resources; and reselecting resources in at least one cycle of the periodic resources, wherein the reselection process depends on the level of conflict identified.

Only conflicting resources or periods can be reselected.

All resources or periods for recurring resources can be reselected.

The level of conflict may depend on the number or fraction of cycles in which a conflict is detected.

The level of conflict may depend on the fraction of resources that conflict each cycle.

The reselection process may reserve new periodic resources.

The reselection process may reserve new aperiodic resources.

The UE may use sources of reselected resources without conflicts for transmissions other than those originally reserved.

The level of the conflict may be determined by comparing the identified conflict to a predetermined threshold.

The predetermined threshold may be indicated to the UE in higher layer signaling.

The predetermined threshold may be defined on a resource pool or UE basis.

The level of conflict may be determined by comparing the identified conflicts with two predetermined thresholds, below which a reselection of aperiodic resources is performed and above a second threshold where reselection of periodic resources is performed Select, the UE selects the type of reselection when it is between the first and second thresholds.

After the reselection process, reserved periodic resources can be canceled.

Reserved periodic resources can be canceled using SCI messages.

The SCI messages may include Phase 1 SCI messages.

The SCI messages may include Phase 2 SCI messages.

The SCI message may include an explicit cancellation indication.

The SCI message may include the identity of the resource to be revoked.

The identity can include the frequency of the resource as well as the time.

There is also provided a UE configured to perform the method described herein.

Description of drawings

Further details, aspects and embodiments of the invention will be described, by way of example only, with reference to the accompanying drawings. Components in the figures are shown for simplicity and clarity and have not necessarily been drawn to scale. Like reference numerals have been included in the respective drawings for ease of understanding.

Figures 1 and 2 show schematic diagrams of selected elements of a cellular communication network;

Figure 3 shows the method of resource reselection; and

Figure 4 shows an example of resource reselection.

Detailed ways

Those skilled in the art will recognize and understand that the details of the described examples are illustrations of some embodiments only, and that the teachings set forth herein apply to various alternative arrangements.

Figure 1 shows a schematic diagram of three base stations (eg eNB or gNB depending on the particular cellular standard and terminology) forming a cellular network. Typically, each base station will be deployed by a cellular network operator to provide geographic coverage for UEs in that area. The base stations form a radio area network (Radio Area Network, RAN). Each base station provides wireless coverage to UEs in its area or cell. The base stations are interconnected through the X2 interface and connected to the core network through the S1 interface. It should be understood that for the purpose of illustrating key features of a cellular network, only essential details are shown. A PC5 interface is provided between UEs for sidelink communication. Interface and component names related to Figure 1 are used as examples only, different systems operating on the same principles may use different nomenclature.

Each base station includes hardware and software to implement the functions of the RAN, including communication with the core network and other base stations, control and data signaling between the core network and UEs, and maintaining wireless communication with the UEs associated with each base station. The core network includes the hardware and software that implement network functions, such as overall network management and control, and the routing of calls and data.

In addition to the uplink (uplink)/downlink communication (downlink) between UEs and the base station, sidelink communication in which UEs directly communicate with each other can also be realized. Figure 2 shows base stations 102 forming a RAN, and sidelink transmitter (SL Tx UE) UE 150 and sidelink receiver (SL Rx UE) UE 152 in the RAN. UEs 150 and 152 are described as transmitters and receivers only for explanation during a particular communication, and their roles may likewise be reversed. The base station 102 is arranged to communicate wirelessly with each of the SL Tx UE 150 and the SL Rx UE 152 over respective connections 154 . The SL Tx UE 150 and the SL Rx UE 152 are arranged to communicate wirelessly with each other via a sidelink 156 .

The sidelink transmission utilizes TDD (half-duplex) with conventional Uu transmission between the base station and UE on a dedicated carrier or a shared carrier. A resource pool of transmission resources is used to manage resources and allocations and to manage interference between potentially concurrent transmissions. A resource pool is a set of time-frequency resources from which resources can be selected for transmission. UEs can be configured with multiple transmit and receive resource pools.

Two modes of operation are used for resource allocation for sidelink communication, depending on whether UEs are within the coverage of the cellular network or not. In Mode 1, V2X communication operates within the coverage of base stations (e.g. eNBs or gNBs). All scheduling and resource assignment can be done by the base station.

Mode 2 applies when the sidelink service is operating outside the coverage of the cellular base station. Here UEs need to schedule by themselves. Perception-based resource allocation of transmission resources is typically used by UEs for fair utilization. It is expected that resource selection will consist of two steps. In a first step, the UE will identify the resources considered available for selection, and in a second step, a specific resource will be selected for transmission. The first step can be done by starting from a set of all resources within the selection window and removing those resources that are not considered candidates (e.g. reserved by another UE with SL-RSRP above a threshold resources) to proceed. The step of selecting resources may be a random selection, possibly with constraints such as HARQ timing and delay between resources.

In Mode 2, UEs select the transmission resources they wish to use for transmission and transmit Sidelink Control Information (SCI) messages indicating these resources. The SCI informs the receiver (could be a single UE in unicast, a group of UEs in multicast, or all reachable UEs in broadcast) the details of the transmission it can expect.

In NR, resource pools can be configured to allow reserving periodic resources for sidelink communications. When reserving periodic resources, the SCI message includes an indication of the reserved period, which may be based on configuration from higher layers, which may be received in RRC signaling (RRC signaling).

A particular problem that can arise with periodic reservations is that repeated collisions can occur if two UEs select overlapping resources with the same periodicity. Similarly, reservations with a common multiple period collide periodically (eg 10ms and 15ms will collide every 30ms (half or third of the time). Each collision can cause a transmission error or cause Pre-emption, causing UE to reselect (reselect) resources, which requires additional signaling and processing. Since there is no way to cancel periodic resource reservation, when UE reselects resources, two sets of resources are reserved, May result in resources not being used.

The following disclosure provides techniques aimed at improving periodic resource selection for sidelink communications. Specifically, in case a UE has reserved periodic resources and the UE receives an indication that another UE has reserved overlapping resources, which means preemption, the UE at least reselects the reserved overlapping resources.

In the current disclosure, the term "periodic resource reservation" is used to refer to the reservation of a resource pattern that repeats in the time and frequency domains with a given period (usually indicated in the first stage SCI) (a reservation of apattern ofresources) (usually indicated in Phase 1 SCI). The term "period" is used to refer to a single occurrence of a resource pattern within a periodic resource. A single period corresponds to a reserved initial transmission and associated retransmissions reserved.

Conflicts may occur on a subset of the cycles of a periodic resource reservation, or on all cycles. For example, a dynamic grant may only conflict/preempt for one cycle, while subsequent cycles of the periodic reservation are still available. In the case of conflicts in only a few cycles, it may be inefficient to reselect resources for all cycles, as this would result in unused resources for a different cycle than the conflict. Similarly, it is also inefficient to reselect individual cycles when there are a large number of conflicts.

In a first reselection method, a UE with periodic resource reservation detects a conflict with resources in at least a subset of the reservation period. The UE triggers a pre-emption procedure, where the UE performs a reselection procedure only for periods with conflicts and reserves reservations for non-conflicted periods. Non-conflicting resources can also be reselected if it is determined that this is preferred. For example, if the reselected resource for the conflicting resource collides with other resources (for example, the time interval between two retransmissions does not satisfy the HARQ/PSFCH constraint), more resources may need to be reselected. Some previously selected resources may also be reselected if during step 1 they are no longer available but do not meet the criteria to trigger preemption. Additionally, the selection process in step 2 of the process can be configured to only allow reselection of all resources within a given period. Reselecting resources only in certain periods (eg, a period) can be described as aperiodic reselection.

In the second reselection method, a UE that detects a collision and has a periodic resource reservation can choose to reselect a new periodic resource reservation to replace all the periods of the previous one. This method can be used even if only some resources are in conflict. Once a new periodic resource reservation is made, the previous reservation will be discarded and not used by the UE for this periodic transmission.

In cases where resources will not be used by the UE for the original transmission, the UE can choose to use these resources for another transmission, leave them unused, or use the cancellation procedure as described below.

The UE may choose one of these methods based on a predefined configuration, which may specify that a preempted periodic reservation is reselected as a new periodic resource, or one or more aperiodic resources (along with the original reservation) non-conflicting resources). The configuration may be defined by higher layer (RRC) signaling or other configuration methods. The configuration can be defined by resource pool, UE, cell or according to UE capability. Improved granularity in the configuration can be provided by indicating in the configuration whether the UE is allowed to reselect periodic resources, or it must perform aperiodic reselection. The UE can then decide how to behave in different situations.

The choice of which method to use can be based on an estimate of how many resources or cycles suffer from conflicts, as shown in Figure 3. At step 300, the UE detects a conflict with a periodic resource reservation it has made and starts a preemption/reselection procedure. In step 301, the UE evaluates the number of periods and/or resources within the periodic resource reservation for which collisions are expected to occur. If the number of conflicts is high (e.g., the UE may detect that the conflicting/preempting reservation is a periodic resource reservation with the same period as the UE's original reservation), the UE performs a periodic resource reservation to reselect the entire original reservation (step 302). On the contrary, if the UE determines that the number of conflicts is small, it performs aperiodic reselection in step 303 to replace only conflicting resources.

The determination of high or low may be based on a preset threshold determined by the UE or signaled to the UE eg in higher layer (RRC) signaling. More than one threshold can be configured, so that in the central area, the UE can decide which technology to choose by itself. In one example, a small number of conflicts may be 2 cycles requiring reselection, and/or a large number of conflicts may be 5 cycles requiring reselection. Thresholds can also be defined as a fraction of the number of cycles in periodic resource selection. For example, aperiodic reselection may be used if less than (in a particular example) 10% or 50% of the cycles suffer from collisions and require reselection.

The evaluation of conflicts requires calculating the conflicts that will occur between resources reserved by a periodic resource and resources reserved by another periodic resource. Conflicts can also arise between recurring resource reservation resources and other aperiodic resource reservations. For example, the accumulation of aperiodic reservations may conflict with multiple periods of periodic resource reservations. The methods discussed here treat conflicts with any other type of reservation equally. Therefore, when evaluating conflicts, it may be necessary to evaluate the accumulation of all other reservations, not just periodic reservations. This depends on the resources reserved by each reservation and the period of each reservation.

The criteria used may be a function of counting the number of conflicting resources for a single conflict (may help assess the penalty for unused resources if a new periodic reservation is made) and/or periodic resource reservations that include at least one conflict The number of cycles (given an indication of control signaling overhead, counting the number of required reselections and SCI reservations). As noted above, criteria can also be based on fractions or ratios rather than absolute counts.

Criteria can be evaluated over a defined time period, which can be a configured number of cycles, a time in the future (in milliseconds or logical slots) (e.g. T_scal/C_resel) and/or a periodic resource reservation The number of cycles remaining (or the minimum or maximum of these) is left in memory. The period may be defined by a standard, and/or defined according to the configuration of the UE. Thresholds may depend on the method and time period used to calculate conflicts, so configurations should be defined as a set to ensure predictable behavior.

In one example, the time period for evaluation may be the minimum of the configuration time (T_scal) and the remaining time of the periodic resource reservation. The first periodic resource reservation for the first UE may have a period of 20 milliseconds with 3 transmissions in each period. There are 3 cycles (20ms) left in the reservation. The second UE makes preemptive reservations consisting of 10 ms periods, generating a collision in each period. This can be counted as 1 out of 3 (1/3) transmissions per period of the first reservation having a collision, and three (100%) of the remaining first reservation periods having at least one collision, Or three (50%) of the second (preemptive) cycle had at least one conflict. In this example, the threshold could be set to 25% of the remaining period with at least one conflict, in which case periodic reselection would occur. More complex evaluations can be made using more than one criterion, each possibly with different thresholds.

Different criteria and thresholds can be applied according to the priorities of each reservation, which can be configured through higher layer signaling (RRC).

As mentioned above, it is currently not possible for UEs to cancel earlier periodic resource reservations, so they may become unused if resources are reselected. Therefore, the method discussed above can be extended to allow the UE to cancel and reselect periodic resource reservations (or as a stand-alone process).

In the first method, the UE provides a dedicated signal for transmission to cancel the periodic resource reservation. In one example, the field is provided in an SCI message format for indicating cancellation. The UE may include the cancellation in the SCI message for selecting new resources, or in an independent message (standalone message).

This indication may be provided in a Phase 1 SCI message. In order to avoid changing the size of the existing message format (which will increase the complexity of decoding), a reserved bit (reserved bit) of the SCI can be used to indicate that the SCI message is a cancellation message (cancellation message). The message should indicate the periodically reserved resource to be canceled, and the source identity that helps ensure that receiving UEs cancel the correct reservation. For example, the frequency and time fields of the SCI can be used to indicate those respective parameters of the reservation to be canceled. The source identity can be defined as the identity (typically 16 bits) transmitted in the original Phase 2 SCI. These can include the positions of unneeded bits in the cancel SCI. For example, MCS, DMRS mode and number of ports, reservation period and beta_offset indicator fields may be used. May include the full original source ID, or a shorter version (e.g. 8 LSBs). A cancellation SCI may be transmitted as a standalone transmission without an associated second stage SCI. Using Phase 1 SCI should allow faster and more reliable decoding than Phase 2 SCI and allow receiving UEs to get cancellation indications sooner.

In the current sidelink transmission design, the first-stage SCI, the second-stage SCI and the sidelink data are always mapped in the time-frequency resource in the form of a rectangle. Certain resources of the sidelink resource pool can be dedicated where independent Phase 1 SCIs can be transmitted. This dedicated resource can be used to transmit a cancellation SCI (cancellation SCI), and possibly accommodate new control transmissions with no associated data.

In order to limit the increased blind decoding (blind decoding) due to the addition of the first-stage SCI format, the cancellation of SCI (and other special signaling first-stage SCI formats, if required) can be restricted to certain pre-configured time slots and sub-channels , and/or functions that map to reserved resources.

In an alternative configuration, a cancellation indication may be provided in the second phase SCI message, eg no data or dummy data in the payload. In this configuration, the first-stage SCI points to the second-stage SCI in a conventional manner, and also indicates that the second-stage CSI is a cancel SCI. The only purpose of SCI transmission in the second stage is to cancel the reservation, no data is being transmitted, so that it can be limited to a single sub-channel transmission.

As mentioned above, the cancel message should indicate the time/frequency resource (or point to the point at which the reservation was performed) that was canceled. It may be beneficial to also indicate the identity of the reservation source, the identity of the destination of the reserved resources and/or the HARQ ID which may further reduce ambiguity.

When the cancellation indication is carried in the second stage SCI, a high reliability transport format may be chosen, especially since many bits may not be needed and the entire radio resource may be utilized. Multiple cancellations can be sent using the same resource with multiplexed phase 2 SCI messages, or a new format can be defined including multiple cancellation indications.

In a further example, the cancel phase 2 SCI may be sent (multiplexed) with the regular transmission. Thus, the transfer will consist of a Phase 1 SCI, a Phase 2 SCI for the data, and a Phase 2 Cancellation SCI for the cancellation and payload data. The multiplexing order (cancellation SCI before second phase SCI of data) may implicitly indicate that at least one second phase SCI is expected after the cancellation SCI. Alternatively, the first stage SCI may indicate the number of expected second stage SCIs.

In another example, the second stage SCI format may be defined to include cancellation information and normal data information.

In all examples, the first-stage SCI uses a second-stage format indicator field to indicate the format of the second-stage SCI that can be expected in the PSSCH.

In another method, a part of the previous periodic resource reservation can be used to directly indicate the new resource by changing the SCI transmitted in the relevant period. For example, if only one of the three resources in a period collides, the SCI transmitted in this period only indicates non-conflicting resources. Other UEs are aware of previous periodic reservations, and thus can unambiguously infer that the new SCI represents an update of the previous reservations for that period. When using this technique, preemption can be applied on subsequent transmission resources, so processing must be notified sufficiently early (eg, processing time T3) before resources will collide. Therefore, UEs must be configured to transmit collision reservations early enough.

An indication may be provided in the configuration whether the changed reservation is for a specific period only, or for all future periods of the periodic resource reservation. Alternatively, the indication may be provided in the SCI reserving the changed resource.

Figure 4(a) shows an example where all periods of reserved resources change (periodic reselection), while Figure 4(b) shows an example where only one period changes (aperiodic reselection).

In another approach, the SCI (not necessarily part of the previous reservation) may include an indication that the reservation replaces the previous periodic reservation. In order to determine which reservations are canceled by the new SCI, receiving UEs need to decode the second-stage SCI to identify SRC, DST, and HARQ ID to be able to associate the new reservation with the previous reservation that was replaced. While this may increase processing complexity (and require storing sensed SCI information), this approach may enable reselection to be performed at any time and send new reservations on previously unreserved resources. This approach also relaxes constraints on resource selection time (since there is no need to allow time to process conflicts before they occur).

Various methods have been described for managing changes and cancellations of periodic resource reservations for sidelink communications.

Although not shown in detail, any apparatus or device forming part of a network may comprise at least a processor, a storage unit and a communication interface configured to perform the method of any aspect of the invention. Further options and selections are described below.

The signal processing function of the embodiment of the present invention, especially the gNB and the UE, can be implemented using a computing system or architecture known to those skilled in the relevant art. For a given application process or environment, using a computing system such as a desktop, laptop or notebook computer, handheld computing device (PDA, cell phone, PDA, etc.), mainframe, server, client, or any other type of dedicated or A general purpose computing device is desirable or appropriate. A computing system may include one or more processors, which may be implemented using a general or special purpose processing engine such as a microprocessor, microcontroller or other control module.

The computing system may also include main memory, such as Random Access Memory (RAM) or other dynamic memory, for storing information and instructions for execution by the processor. Such main memory may also be used for storing temporary variables or other intermediate information during execution of instructions executed by the processor. The computing system may also include a read only memory (Read Only Memory, ROM) or other static storage devices for storing static information and instructions of the processor.

The computing system may also include an information storage system, which may include, for example, media drives and removable storage interfaces. A media drive may include a drive or other mechanism that supports fixed or removable storage media, such as a hard drive, floppy disk drive, tape drive, optical drive, compact disc (CD) or digital video drive (Digital Video Drive, DVD) (RTM ), read or write drives (Read or Write Drive, R or RW), or other removable or fixed media drives. The storage media may include, for example, hard disks, floppy disks, magnetic tape, optical disks, CDs or DVDs, or other fixed or removable media that is read from and written to by a media drive. The storage media may include computer-readable storage media in which specific computer software or data is stored.

In alternative embodiments, the information storage system may include other similar components for allowing computer processes 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 process cartridges and cartridge interfaces, removable memory (e.g., flash memory or other removable memory modules) and memory slots, and other removable storage units as well as allowing software and data An interface for transferring from a removable storage unit to a computing system.

The computing system may also include a communication interface. Such communication interfaces can be used to allow software and data to be transferred between the computing system and external devices. Examples of communications interfaces may include modems, network interfaces such as Ethernet or other NIC cards, communications ports such as Universal Serial Bus (USB) ports, PCMCIA slots and cards, and the like. The software and data transmitted via the communication interface are in the form of signals, which may be electronic, electromagnetic and optical or other signals capable of being received by the communication interface medium.

In this document, the terms "computer process product", "computer readable medium" and the like may be used generally to refer to tangible media such as memory, storage, 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, commonly referred to as "computer procedure code" (which may be grouped in a computer procedure or other grouping), when executed, enable a computing system to perform the functions of embodiments of the invention. Note that code may directly cause the processor to perform specified operations, be compiled to do so, and/or be combined with other software, hardware, and/or firmware elements (e.g., libraries to perform standard functions) to do so .

The non-transitory computer readable medium may include at least one 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 ROM, EPROM, Electrically Erasable Programmable ROM, and Flash. In embodiments where the components are implemented using software, the software may be stored on a computer readable medium and loaded into the computing system using, for example, a removable storage drive. When executed by a processor in a computer system, the control module (in this example, software instructions or executable computer process code) causes the processor to perform the functions of the invention as described herein.

Furthermore, the inventive concept may be applied to any circuit for performing signal processing functions within a network component. It is further conceived that, for example, a semiconductor manufacturer may design a stand-alone device, such as a digital signal processor (Digital Signal Processor, DSP) microcontroller, or an application-specific integrated circuit (Application-Specific Integrated Circuit, ASIC), and/or any Other subsystem elements employ the inventive concepts.

It should be appreciated that, for clarity, the foregoing description has described embodiments of the 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 functionality. Hence, references to specific functional units are only to be seen as references to suitable means for providing the described functionality rather than indicative of a strict logical or physical structure or organization.

Aspects of the invention can be implemented in any suitable form including hardware, software, firmware or any combination of these. The invention may optionally be implemented at least partly as computer software running on one or more data processors and/or digital signal processors or configurable modular components such as FPGA devices.

Accordingly, the components and components of an embodiment of the invention may be physically, functionally and logically implemented in any suitable way. Indeed the functionality may be implemented in a single unit, in a plurality of units or as part of other functional units. Although this invention has been described in connection with some embodiments, it is not intended to be limited to the specific forms set forth herein. Rather, the scope of the present invention is limited only by the appended claims. Additionally, although a feature may appear to be described in connection with particular embodiments, one skilled in the art would 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 elements or steps.

Furthermore, although individually listed, a plurality of means, components or method steps may be implemented by eg a single unit or processor. Additionally, although individual features may be included in different claims, these may possibly 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 category of claims does not imply a limitation to that category but rather indicates that the feature is equally applicable to other claim categories as appropriate.

Furthermore, the order of features in the claims do 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. Rather, the steps may be performed in any suitable order. Furthermore, references in the singular do not exclude the plural. Thus references to "a", "an", "first", "second" etc do not preclude a plurality.

While this invention has been described in connection with some embodiments, it is not intended to be limited to the specific forms set forth herein. Rather, the scope of the present invention is limited only by the appended claims. Additionally, although a feature may appear to be described in connection with particular embodiments, one skilled in the art would recognize that various features of the described embodiments may be combined in accordance with the invention. In the claims, the terms "comprises" or "comprises" do not exclude the presence of other elements.

Claims (20)

1. A resource reselection method related to periodic resource reservation, the method is performed in UE, comprising the following steps: Reserve periodic resources for sidelink communications; identifying a conflict with the resource for at least one period of the periodic resource; and A resource is reselected in at least one cycle of the periodic resource, wherein the reselection process depends on the level of the identified conflict. 2. The method of claim 1 , wherein only conflicting resources or periods are reselected. 3. The method of claim 1, wherein all resources or periods of periodic resources are reselected. 4. A method as claimed in any one of the preceding claims, wherein the level of collision is dependent on the number or fraction of periods in which a collision is detected. 5. A method as claimed in any one of the preceding claims, wherein the level of conflict is dependent on the fraction of resources that collide each period. 6. A method according to any one of the preceding claims, wherein the reselection process reserves new periodic resources. 7. A method according to any one of claims 1 to 5, wherein the reselection procedure reserves new aperiodic resources. 8. The method according to any one of the preceding claims, wherein the UE uses the reselected resources without conflicts for other transmissions than the original reservation. 9. A method according to any one of the preceding claims, wherein the level of the conflict is determined by comparing the identified conflict with a predetermined threshold. 10. The method according to claim 9, wherein the predetermined threshold is indicated to the UE in higher layer signaling. 11. The method according to claim 9 or 10, wherein the predetermined threshold is defined on a resource pool or UE basis. 12. The method of claim 1, wherein the level of the conflict is determined by comparing the identified conflict with two predetermined thresholds, wherein below a first threshold a reselection of aperiodic resources is performed, above Periodic resource reselection is performed when the second threshold is between the first and second thresholds, and the UE selects the type of reselection. 13. A method according to any one of the preceding claims, wherein the reserved periodic resources are canceled after a reselection procedure. 14. The method of claim 13, wherein a reserved periodic resource is canceled using an SCI message. 15. The method of claim 14, wherein the SCI message comprises a Phase 1 SCI message. 16. A method as claimed in any one of claims 13 to 15, wherein the SCI message comprises a phase two SCI message. 17. A method as claimed in any one of claims 13 to 16, wherein the SCI message includes an explicit cancellation indication. 18. A method as claimed in any one of claims 13 to 17, wherein the SCI message includes the identity of the resource to be revoked. 19. The method of claim 18, wherein the identity includes frequency and time of the resource. 20. A UE configured to perform the method of any one of the preceding claims.

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