WO2022017477A1

WO2022017477A1 - Periodic reservations for sidelink communications in cellular networks

Info

Publication number: WO2022017477A1
Application number: PCT/CN2021/107966
Authority: WO
Inventors: Virgile Garcia; Umer Salim
Original assignee: Huizhou Tcl Cloud Internet Corporation Technology Co., Ltd.
Priority date: 2020-07-22
Filing date: 2021-07-22
Publication date: 2022-01-27
Also published as: CN116325903A

Abstract

A method for reselection of periodic resource reservations upon detection of a collision is disclosed. The method is performed at a UE and comprises the steps of: reserving periodic resources for sidelink communications; identifying a collision with resources in at least one period of the periodic resources; and reselecting resources in at least one period of the periodic resources, wherein the reselection process is dependent on the level of identified collision. The UE may re-use reselected resources for another transmission than original intended.

Description

Periodic Reservations For Sidelink Communications 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

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

In cellular wireless communication systems User Equipment (UE) is connected by a wireless link to a Radio Access Network (RAN) . The RAN comprises a set of base stations which provide wireless links to the UEs located in cells covered by the base station, and an interface to a Core Network (CN) which provides overall network control. As will be appreciated the RAN and CN each conduct respective functions in relation to the overall network. For convenience the term cellular network will be used to refer to the combined RAN &CN, and it will be understood that the term is used to refer to the respective system for performing the disclosed function.

The 3rd Generation Partnership Project has developed the so-called Long Term Evolution (LTE) system, namely, an Evolved Universal Mobile Telecommunication System Territorial Radio Access Network, (E-UTRAN) , for a mobile access network where one or more macro-cells are supported by a base station known as an eNodeB or eNB (evolved NodeB) . More recently, LTE is evolving further towards the so-called 5G or NR (new radio) systems where one or more cells are supported by a base station known as a gNB. NR is proposed to utilise an Orthogonal Frequency Division Multiplexed (OFDM) physical transmission format.

The NR protocols are intended to offer options for operating in unlicensed radio bands, to be known as NR-U. When operating in an unlicensed radio band the gNB and UE must compete with other devices for physical medium/resource access. For example, Wi-Fi (RTM) , NR-U, and LAA may utilise the same physical resources.

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

mMTC services are intended to support a large number of devices over a long life-time with highly energy efficient communication channels, where transmission of data to and from each device occurs sporadically and infrequently. For example, a cell may be expected to support many thousands of devices.

The disclosure below relates to various improvements to cellular wireless communications systems.

Summary

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.

There is provided a method of varying periodic resource reservations for sidelink communications. A UE with a periodic resource reservation listens for reservations which may collide with transmission resources of the periodic resource reservation and determines the level of collision 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 pre-emption procedure. Such a procedure may lead to reselection of the periodic resource reservation, or only one or more period of the periodic resource reservation.

The UE may subsequently reselect new resources in accordance with the determination. The new resources may be a new periodic resource reservation or an aperiodic resource reservation replacing only some of the original resources and/or periods.

There is also provided a method for reselection of resources in relation to a periodic resource reservation, the method being performed at a UE and comprising the steps of reserving periodic resources for sidelink communications; identifying a collision with resources in at least one period of the periodic resources; and reselecting resources in at least one period of the periodic resources, wherein the reselection process is dependent on the level of identified collision.

Only resources or periods which collide may be reselected.

All resources or periods of the periodic resources may be reselected.

The level of collision may be dependent on the number or portion of periods in which a collision is detected.

The level of collision may be dependent on the portion of resources in each period which collide.

The reselection process may reserve new periodic resources.

The reselection process may reserve new aperiodic resources.

Reselected resources without a collision may be utilised by the UE for other transmissions than for which the original reservation was made.

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

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

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

The level of collision may be determined by comparison of the identified collisions with two predetermined thresholds, wherein below a first of the thresholds reselection of aperiodic resources is performed, above a second of the thresholds reselection of periodic resources is performed, and between the first and second thresholds the UE selects the type of reselection.

After the reselection process the reserved periodic resources may be cancelled.

The reserved periodic resources may be cancelled using an SCI message.

The SCI message may comprise a first-stage SCI message.

The SCI message may comprise a second-stage SCI message.

The SCI message may include an explicit cancellation indication.

The SCI message may include the identity of the resources to be cancelled.

The identity may include the frequency and time of the resources.

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

Brief description of the drawings

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

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

Figure 3 shows a method of resource reselection; and

Figure 4 shows an example of resource reselection.

Detailed description of the preferred embodiments

Those skilled in the art will recognise and appreciate that the specifics of the examples described are merely illustrative of some embodiments and that the teachings set forth herein are applicable in a variety of alternative settings.

Figure 1 shows a schematic diagram of three base stations (for example, eNB or gNBs depending on the particular cellular standard and terminology) forming a cellular network. Typically, each of the base stations will be deployed by one cellular network operator to provide geographic coverage for UEs in the area. The base stations form a Radio Area Network (RAN) . Each base station provides wireless coverage for UEs in its area or cell. The base stations are interconnected via the X2 interface and are connected to the core network via the S1 interface. As will be appreciated only basic details are shown for the purposes of exemplifying the key features of a cellular network. A PC5 interface is provided between UEs for SideLink (SL) communications. The interface and component names mentioned in relation to Figure 1 are used for example only and different systems, operating to the same principles, may use different nomenclature.

The base stations each comprise hardware and software to implement the RAN’s functionality, including communications with the core network and other base stations, carriage of control and data signals between the core network and UEs, and maintaining wireless communications with UEs associated with each base station. The core network comprises hardware and software to implement the network functionality, such as overall network management and control, and routing of calls and data.

In addition to uplink/downlink communications between UEs and base stations, sidelink communications may also be implemented in which UEs communicate directly with each other. Figure 2 illustrates a base station 102 forming a RAN, and a sidelink transmitter (SL Tx UE) UE 150 and a sidelink receiver (SL Rx UE) UE 152 in the RAN.

UEs

150 and 152 are described as transmitter and receiver only for the purposes of explanation during a particular communication, and their roles may equally be reversed. The base station 102 is arranged to wirelessly communicate over respective connections 154 with each of the SL Tx UE 150 and the SL Rx UE 152. The SL Tx UE 150 and the SL Rx UE 152 are arranged to wirelessly communicate with each other over a sidelink 156.

Sidelink transmissions utilise TDD (half duplex) on either a dedicated carrier, or a shared carrier with conventional Uu transmissions between a base station and UE. Resource pools of transmission resources are utilised to manage resource and allocation and manage interference between potentially concurrent transmissions. A resource pool is a set of time-frequency resources from which resources for a transmission can be selected. 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 the UEs are within coverage of a cellular network. In Mode 1, the V2X communication is operating in-coverage of the base stations (eg eNBs or gNBs) . All the scheduling and the resource assignments may be made by the base stations.

Mode 2 applies when the sidelink services operate out-of-coverage of cellular base stations. Here the UEs need to schedule themselves. For fair utilization, sensing-based resource allocation of transmission resources is generally utilised by the UEs. It is expected that resource selection will comprise two steps. In a first step a UE will identify resources that are considered available for selection, and in a second step specific resources will be selected for a transmission. The first step may be conducted by starting with a set of all resources within a selection window and removing those which are not considered candidates (for example resources reserved by another UE with an SL-RSRP above a threshold) . The step of selecting resources may be a random selection, potentially with constraints such as HARQ timing and delay between resources.

In Mode 2, UEs select transmission resources they wish to use for a transmission and transmita Sidelink Control Information (SCI) message indicating those resources . The SCI notifies the recipient (which may be a single UE in unicast, a group of UEs in groupcast, or all reachable UEs in broadcast) of the details of the transmission it can expect.

In NR, a resource pool may be configured to permit periodic resources to be reserved for sidelink communications. When reserving periodic resources an SCI message includes an indication of the reservation period, which may be based on the configuration from higher layers, which may be received in RRC signalling.

A particular issue that may arise with periodic reservations is the occurrence of repeated collisions if two UEs select overlapping resources with the same periods. Similarly, reservations whose period has a common multiple will also collide on a regular basis (e.g. 10ms and 15ms will collide every 30ms (half or one-third of the occurrences) . Each collision leads to a transmission error or leads to a pre-emption causing a UE to reselect resources, which requires additional signalling and processing. Since there is no method to cancel a reservation of periodic resources, when a UE reselects resources two sets are reserved and may lead to unused resources.

The following disclosure provides techniques intended to improve periodic resource selection for sidelink communications. In particular, where a UE has reserved periodic resources and the UE receives an indication that another UE has reserved overlapping resources which implies pre-emption, the UE reselects at least the reserved overlapping resources.

In the current disclosure the term “periodic resource reservation” is used to refer to a reservation of a pattern of resources (typically indicated in the 1st stage SCI) in the time and frequency domain that is repeated with a given period (also typically indicated in the 1st stage SCI) . The term “period” is used to refer to a single occurrence of the pattern of resources within the periodic resources. A single period corresponds to the initial transmission and associated retransmissions reserved.

A collision may occur on a subset of the periods of a periodic resource reservation, or all periods. For example, a dynamic grant may collide/pre-empt only one period, with subsequent periods of the periodic reservation remaining available. Where only a small number of periods collide it may be inefficient to reselect resources of all periods as this would lead to unused resources in the periods different to the collided one (s) . Similarly, reselecting individual periods when a large number collide is also inefficient.

In a first method of reselection, a UE with a periodic resource reservation detects a collision with the resources in at least a subset of the periods of the reservation. The UE triggers a pre-emption procedure in which the UE performs a reselection procedure only for the periods with a collision and retains the reservation of the non-collided periods. The non-collided resources can also be re-selected if this is determined to be preferable. For example, if the reselected resources for the collided one creates a conflict with other resources (e.g. the time gaps between two retransmissions do not meet the HARQ/PSFCH constraints) it may be necessary to reselect further resources. If during step 1 some previously selected resources are no longer available but did not meet the criterion to trigger pre-emption those resources may also be reselected. Also, the selection procedure in step 2 of the process may be configured to only allow reselection of all resources for a given period. Reselecting resources in only some of the periods (for example one) may be described as an aperiodic reselection.

In a second method of reselection, a UE with a periodic resource reservation which detects a collision may elect to reselect a new periodic resource reservation to replace all periods of the previous one. This method may be used even if only some of the resources have a collision. Once a new periodic resource reservation is made the previous reservation is discarded and not utilised by the UE for that periodic transmission.

Where resources will be unused by the UE for the original transmission, the UE may elect to use those resources for another transmission, leave them unused, or use a cancellation procedure as discussed below.

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

The choice of which method to use may be based be on an estimate of how many resources or periods suffer collisions, as shown in Figure 3. At step 300 the UE detects a collision with a periodic resource reservation it has made and starts a pre-emption/reselection procedure. At step 301 the UE assesses the number of periods and/or resources within the periodic resource reservation that are expected to collide. If the number of collisions is high (For example, the UE may detect that the colliding/pre-empting 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) . In contrast, if the UE determines a low number of collisions an aperiodic reselection is performed at step 303 to replace only the collided resources.

The high or low determination may be conducted based on a pre-set threshold which is determined by the UE or signalled to the UE, for example in higher layer (RRC) signalling. More than one threshold may be configured such that in the central region the UE has discretion as to which technique to select. In an example, a small number of collisions may be 2 periods which require reselection, and/or a large number of collisions may be 5 periods which require reselection. The thresholds could also be defined as a portion of the number of periods in the periodic resource selection. For example, aperiodic reselection may be used if less than (in specific examples) 10%or 50%of periods suffer a collision and require reselection.

The evaluation of collisions requires calculation of the collisions that will occur between resources of the periodic resource reservation and another periodic resource reservation. It is also possible that collisions will occur between the periodic resource reservation resources and other non-periodic resource reservations. For example an accumulation of aperiodic reservations may collie with a number of periods of the periodic resource reservation. The methods discussed herein may treat collisions with any other type of reservation equally. When evaluating collisions it may therefore be necessary to evaluate the accumulation of all other reservations, not only a periodic reservation. This is dependent on the resources reserved by each reservation and the periodicity of each reservation.

The criterion used may be a function of the number of collided resources which counts individual collisions (and may assist in assessing the loss of unused resources if a new period reservation is made) , and/or the number of periods of the period resource reservation that include at least one collision (which counts the number of required reselection and SCI reservations, giving an indication of control signalling overhead) . As noted above the criterion may also be based on portions or ratios rather than an absolute count.

The criterion may be assessed over a defined time period, which may be a configured number of periods, time in the future (in ms or logical slots) (e. g T_scal/C_resel) , and/or the number of periods remaining in the periodic resource reservation (or the minimum or maximum of these) . The period may be defined by standards, and/or according to the UE’s configuration. The thresholds are likely to be dependent on the method used to count collisions, and the time period, and hence the configuration should be defined as a set to ensure predictable behaviour.

In an example, the time period for evaluation may be the minimum of a configured time (T_scal) and the time remaining of the periodic resource reservation. A first periodic resource reservation by a first UE may have a 20ms period, with 3 transmissions in each period. There are 3 periods (of 20ms) remaining in the reservation. A second UE makes a pre-empting reservation consisting of 10ms periods, creating one collision in each period. This could be counted as 1 out of 3 (1/3) transmissions per period of the first reservation have collisions, 3 (100%) of the remaining first reservation periods have at least one collision, or 3 (50%) of the second (pre-empting) periods have at least one collision. In this example, a threshold could be set as 25%of remaining periods having at least one collision, in which case a periodic reselection would be made. More complex assessments can be made to use more than one criterion, potentially with different thresholds for each.

Different criteria and thresholds may be applied dependent on the priorities of each reservation, which may be configured via higher layer signalling (RRC) .

As set out above, it is not currently possible for UEs to cancel an earlier periodic resource reservation, such that if the resources are reselected they may go unused. The methods discussed above may therefore be extended to permit a UE to cancel a periodic resource reservation in conjunction with reselection (or as a standalone process)

In a first method a dedicated signal is provided for transmission by a UE to cancel a periodic resource reservation. In an example a field is provided in an SCI message format which is used to indicate a cancellation. The UE can include the cancellation in an SCI message selecting new resources, or in a standalone message.

The indication may be provided in the first-stage SCI message. To avoid changing the size of existing message formats (which would increase decoding complexity) a reserved bit of the SCI may be used to indicate that the SCI message is a cancellation message. The message should indicate the periodic reserved resources to cancel, and a source identity to help ensure receiving UEs cancel the correct reservation. For example, the frequency and time fields of the SCI may be used to indicate those respective parameters of the reservation to be cancelled. The source identity may be defined as the identity transmitted in the original second-stage SCI (typically 16 bits) . These may be included in place of bits not required in the cancellation SCI. For example, the MCS, number of DMRS patterns and ports, reservation period, and beta_offset indicator fields may be utilised. The full original source identity can be included, or a shorter version (for example the 8 LSBs) . The cancellation SCI may be transmitted as a standalone transmission without a related second-stage SCI. Utilising the first-stage SCI should make decoding faster and more reliable than using a second-stage SCI, and makes the cancellation indication available sooner to receiving UEs.

In the current sidelink transmission design first-stage SCI, second-stage SCI and sidelink data are always mapped in the form of a rectangle in time-frequency resources. A specific resource of the sidelink resource pool can be dedicated where standalone first-stage SCIs may be transmitted. This dedicated resource can be used to transmit a cancellation SCI, and potentially accommodate new control transmissions without associated data.

To restrict the increase in blind decoding due to adding first-stage SCI formats, cancellation SCIs (as well as other special signalling first-stage SCI formats if required) can be restricted to certain slots and sub channels that are preconfigured, and/or mapped as a function of the resources reserved.

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

As noted above, a cancellation message should indicate the time/frequency resources being cancelled (or a point to the resource that performed the reservation) . It may be beneficial to also indicate the identity of the source of the reservation, the identity of the destination of the reserved resources, and/or the HARQ ID which may reduce ambiguity further.

When carrying the cancellation indication in a second-stage SCI a high-reliability transmission format may be selected, particularly as not many bits may be required and the whole radio resource may be utilised. Multiple cancellations can be sent using the same resources with multiplexed second-stage SCI messages, or a new format can be defined including more than one cancellation indication.

In a further example, a cancellation second-stage SCI can be sent together (multiplexed) with a regular transmission. The transmission would thus include a first-stage SCI, a second-stage SCI for data, and a second-stage cancellation SCI for cancellation and the payload data. The multiplexing order (cancellation SCI before the second-stage SCI for data) can implicitly indicate that at least one further second-stage SCI is expected after the cancellation SCI. Alternatively, the first-stage SCI may indicate the number of second-stage SCI’s to be expected.

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

In all examples the first-stage SCI indicates the format of the second-stage SCI that can be expected in the PSSCH using the second-stage format indicator field.

In an alternative approach, part of the previous periodic resource reservation may be utilised by changing the SCI for the transmission in the relevant period to directly indicate the new resources. For example, if only one out of three resources in one period collides, the SCI for the transmission in that period indicates only the non-collided resources. Other UEs are awareof the previous periodic reservation and can hence unambiguously infer that the new SCI represents updated information of the previous reservation for that period. When using this technique, pre-emption can be applied on a subsequent transmission resource, and hence must be announced at an early enough time for processing (e.g. processing time T3) before the resource that will collide. UEs must thus be configured to transmit conflicting reservations sufficiently early.

An indication may be provided in configuration whether changed reservations are for a particular period only, or for all future periods of the periodic resource reservation. Alternatively, this indication may be provided in the SCI reserving the changed resources.

Figure 4 (a) shows an example in which all periods of the reserved resources are changed (periodic reselection) , whereas Figure 4 (b) shows an example in which only one period is changed (aperiodic reselection) .

In a further method, an SCI (not necessarily part of a previous reservation) may include an indication that the reservation replaces a previous periodic reservation. To determine which reservation (s) is/are cancelled by the new SCI, receiving UEs need to decode the second stage SCI to identify SRC, DST, and HARQ ID to be able to relate the new reservation to the previous one that is replaced. Although this may increase the complexity of processing (and need sensed SCI information to be stored) this method may enable reselection to be performed at anytime and to send the new reservation on previously unreserved resources. This approach also relaxes constraints on resource selection timing (since there is no need to allow time for processing before a collision occurs) .

Various methods for managing variation and cancellation of period resource reservations for sidelink communications have been described.

Although not shown in detail any of the devices or apparatus that form part of the network may include at least a processor, a storage unit and a communications interface, wherein the processor unit, storage unit, and communications interface are configured to perform the method of any aspect of the present invention. Further options and choices are described below.

The signal processing functionality of the embodiments of the invention especially the gNB and the UE may be achieved using computing systems or architectures known to those who are skilled in the relevant art. Computing systems such as, a desktop, laptop or notebook computer, hand-held computing device (PDA, cell phone, palmtop, etc. ) , mainframe, server, client, or any other type of special or general purpose computing device as may be desirable or appropriate for a given application or environment can be used. The computing system can include one or more processors which can be implemented using a general or special-purpose processing engine such as, for example, a microprocessor, microcontroller or other control module.

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

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 disk drive, a floppy disk drive, a magnetic tape drive, an optical disk drive, a compact disc (CD) or digital video drive (DVD) (RTM) read or write drive (R or RW) , or other removable or fixed media drive. Storage media may include, for example, a hard disk, floppy disk, magnetic tape, optical disk, CD or DVD, or other fixed or removable medium that is read by and written to by media drive. The storage media may include a computer-readable storage medium having particular computer software or data stored therein.

In alternative embodiments, an 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, a removable storage unit and an interface , such as a program cartridge and cartridge interface, a removable memory (for example, a flash memory or other removable memory module) and memory slot, and other removable storage units and interfaces that allow software and data to be transferred from the removable storage unit to computing system.

The computing system can also include a communications interface. Such a communications interface can be used to allow software and data to be transferred between a computing system and external devices. Examples of communications interfaces can include a modem, a network interface (such as an Ethernet or other NIC card) , a communications port (such as for example, a universal serial bus (USB) port) , a PCMCIA slot and card, etc. Software and data transferred via a communications interface are in the form of signals which can be electronic, electromagnetic, and optical or other signals capable of being received by a communications interface medium.

In this document, the terms ‘computer program product’ , ‘computer-readable medium’ and the like may be used generally to refer to tangible media such as, for example, a memory, storage device, or storage unit. These and other forms of computer-readable media may store one or more instructions for use by the processor comprising the computer system to cause the processor to perform specified operations. Such instructions, generally 45 referred to as ‘computer program code’ (which may be grouped in the form of computer programs or other groupings) , when executed, enable the computing system to perform functions of embodiments of the present invention. Note that the code may directly cause a 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 for performing standard functions) to do so.

The non-transitory computer readable medium may comprise at least one from a 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, EPROM, an Electrically Erasable Programmable Read Only Memory and a Flash memory. In an embodiment where the elements are implemented using software, the software may be stored in a computer-readable medium and loaded into computing system using, for example, removable storage drive. A control module (in this example, software instructions or executable computer program code) , when executed by the processor in the computer system, causes a processor to perform the functions of the invention as described herein.

Furthermore, the inventive concept can be applied to any circuit for performing signal processing functionality within a network element. It is further envisaged that, for example, a semiconductor manufacturer may employ the inventive concept in a design of a stand-alone device, such as a microcontroller of a digital signal processor (DSP) , or application-specific integrated circuit (ASIC) and/or any other sub-system element.

It will be appreciated that, for clarity purposes, the above description has described embodiments of the invention with reference to a single processing logic. However, the inventive concept may equally be implemented by way of a plurality of different functional units and processors to provide the signal processing functionality. Thus, 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 organisation.

Aspects of the invention may 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 module components such as FPGA devices.

Thus, the elements 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 the present invention has been described in connection with some embodiments, it is not intended to be limited to the specific form set forth herein. Rather, the scope of the present invention is limited only by the accompanying claims. Additionally, although a feature may appear to be described in connection with particular embodiments, one skilled in the art would recognise 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, elements or method steps may be implemented by, for example, 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. Also, the inclusion of a feature in one category of claims does not imply a limitation to this category, but rather indicates that the feature is equally applicable to other claim categories, as appropriate.

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. Rather, the steps may be performed in any suitable order. In addition, singular references do not exclude a plurality. Thus, references to ‘a’ , ‘an’ , ‘first’ , ‘second’ , etc. do not preclude a plurality.

Although the present invention has been described in connection with some embodiments, it is not intended to be limited to the specific form set forth herein. Rather, the scope of the present invention is limited only by the accompanying claims. Additionally, although a feature may appear to be described in connection with particular embodiments, one skilled in the art would recognise that various features of the described embodiments may be combined in accordance with the invention. In the claims, the term ‘comprising’ or “including” does not exclude the presence of other elements.

Claims

A method for reselection of resources in relation to a periodic resource reservation, the method being performed at a UE and comprising the steps of

reserving periodic resources for sidelink communications;

identifying a collision with resources in at least one period of the periodic resources; and

reselecting resources in at least one period of the periodic resources, wherein the reselection process is dependent on the level of identified collision.
The method according to claim 1, wherein only resources or periods which collide are reselected.
The method according to claim 1, wherein all resources or periods of the periodic resources are reselected.
The method according to any preceding claim, wherein the level of collision is dependent on the number or portion of periods in which a collision is detected.
The method according to any preceding claim, wherein the level of collision is dependent on the portion of resources in each period which collide.
The method according to any preceding claim, wherein the reselection process reserves new periodic resources.
The method according to any of claims 1 to 5, wherein the reselection process reserves new aperiodic resources.
The method according to any preceding claim, wherein reselected resources without a collision are utilised by the UE for other transmissions than for which the original reservation was made.
The method according to any preceding claim wherein the level of collision is determined by comparing the identified collisions to a predetermined threshold.
The according to claim 9, wherein the predetermined threshold is indicated to the UE in higher layer signalling.
The method according to claim 9 or claim 10, wherein the predetermined threshold is defined on a resource pool or UE basis.
The method according to claim 1, wherein the level of collision is determined by comparison of the identified collisions with two predetermined thresholds, wherein below a first of the thresholds reselection of aperiodic resources is performed, above a second of the thresholds reselection of periodic resources is performed, and between the first and second thresholds the UE selects the type of reselection.
The method according to any preceding claim, wherein after the reselection process the reserved periodic resources are cancelled.
The method according to claim 13, wherein the reserved periodic resources are cancelled using an SCI message.
The method according to claim 14, wherein the SCI message comprises a first-stage SCI message.
The method of claims 13 to 15, wherein the SCI message comprises a second-stage SCI message.
The method according to claims 13 to 16, wherein the SCI message includes an explicit cancellation indication.
The method according to claims 13 to 17, wherein the SCI message includes the identity of the resources to be cancelled.
The method of claim 18, wherein the identity includes the frequency and time of the resources.
A UE configured to perform the method of any preceding claim.