WO2022017476A1

WO2022017476A1 - Periodic reservations for sidelink communications in cellular networks

Info

Publication number: WO2022017476A1
Application number: PCT/CN2021/107965
Authority: WO
Inventors: Virgile Garcia; Umer Salim; Mohamed-Achraf Khsiba
Original assignee: Huizhou Tcl Cloud Internet Corporation Technology Co., Ltd.
Priority date: 2020-07-24
Filing date: 2021-07-22
Publication date: 2022-01-27
Also published as: CN116034623A

Abstract

Methods for assessing existing transmission resource reservations during transmission resource reservation. The methods consider whether existing reservations are periodic or aperiodic, and may also consider other characteristics such as RSRP, number of collisions, and relative periodicities. Transmission resources may be excluded from selection based on the characteristics and whether the reservations are periodic or aperiodic.

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 are provided various methods to assist selection of periodic resources for reservations.

There is provided a method of selecting resources for a sidelink transmission in a cellular communication network comprises the steps of evaluating existing resource reservations, identifying periodic reservations, and marking the resources of those reservations as unavailable for selection.

There is also provided a method of selecting resources for a sidelink transmission in a cellular communication network comprises the steps of evaluating existing resource reservations, identifying periodic reservations, and applying a different threshold for periodic reservations than for aperiodic reservations to assess whether the relevant resources are available for selection. The thresholds may be in relation to the SL-RSRP of the reservation message for the relevant reservation. The threshold may be dependent on the priority of the reservations, and may be configured such that functionality of conventional priority systems is not affected.

There is also provided a method of selecting resources for a sidelink transmission in a cellular communication network comprises the steps of evaluating existing resource reservations, identifying periodic reservations, and comparing the period of existing periodic reservations to the period of the current reservation, wherein reservations with the same period, or where the periods are multiples, are not permitted.

There is also provided a method of selecting transmission resources for sidelink transmissions in a cellular communications network, the method performed at a UE and comprising the steps of identifying existing periodic transmission resource reservations; and marking the transmission resources of those reservations as unavailable for selection for reservation by the UE.

There is also provided a method of selecting transmission resources for sidelink transmissions in a cellular communications network, the method performed at a UE and comprising the steps of identifying existing transmission resource reservations; categorising existing transmission resource reservations as periodic or aperiodic reservations; marking transmission resources of the identified existing transmission resource reservations as unavailable based on a comparison of a characteristic of those transmission resources to a threshold, wherein the threshold is dependent on whether the respective reservation is periodic or aperiodic.

The threshold for periodic reservations may be higher than the threshold for aperiodic reservations.

The threshold for periodic reservations may be equal to the threshold for aperiodic reservations with an offset applied.

The offset may be predefined.

The offset may be dependent on the difference in priority between the existing reservation and a new reservation.

The threshold may also be dependent on the priority of the respective reservation.

The characteristic may be adjusted dependent on whether the existing reservation is periodic or aperiodic.

The characteristic may be the SL-RSRP of the reservation message for the transmission resources.

The method may further comprise the step of comparing the period of a new reservation with the periods of the existing periodic reservations, and marking resources of existing periodic reservations having the same period as the new reservation as unavailable.

The method may further comprise the step of identifying the number of collisions between existing periodic reservations and a new periodic reservations, and marking the transmission resources of the existing reservations as unavailable if the number of collisions exceeds a threshold.

There is also provided a method of selecting transmission resources for sidelink transmissions in a cellular communications network, the method performed at a UE and comprising the steps of identifying existing periodic transmission resource reservations; determining the period of the existing periodic transmission resource reservations; and marking the transmission resources of those reservations as unavailable for selection for a new periodic reservation by the UE if the period of the new reservation is the same or a multiple of the period of an existing reservation.

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 2 shows a method of resource reselection; and

Figures 3 to 7 show flow charts of methods for selection of resources.

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 transmit a 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.

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.

The following disclosure provides techniques intended to improve periodic resource selection for sidelink communications. In particular, the resource selection process is adapted to differentiate between periodic resource reservations, and aperiodic (e.g. dynamic grant) resource reservations. When a resource pool is configured to permit periodic reservations all 1 ^st stage SCIs include the reservation period and are hence inherently periodic. However, if an SCI specifies a period of 0ms the SCI is treated as aperiodic reservation.

Coordination between UEs is introduced with the aim of reducing interference between transmissions, and to reduce pre-emption and reselections, thereby improving overall system performance. In particular, resources of previous periodic reservations may be marked as unavailable for selection by a later periodic reservation or may be differentiated from aperiodic reservations when determining whether they are available. Further differentiation may be provided based on the similarity between the periods of the previous and new reservations.

The methods discussed herein are applicable to both initial selection of resources, and also reselection.

As set out above, resources reserved by a signal with an SL-RSRP above a predefined threshold are considered unavailable at step 1 of the resource selection process. This process may be modified such that all resources of a periodic reservation are considered unavailable, regardless of the SL-RSRP level of the signal making the reservation. There is still effectively a threshold for resources to be unavailable since the UE must have been able to receive and decode the SCI, meaning the SL-RSRP was not too low.

This behaviour may be configured by the network, for example using higher layer (RRC) signalling. The configuration may be made for a particular cell, or on a resource pool basis. Furthermore, the behaviour can be enabled for all periodic resource reservations or on selected priorities. For example, higher-priority reservations may always be unavailable, whereas lower-priority reservations may be available depending on the SL-RSRP of the reserving message. Similarly, previous reservations with a priority higher than the new reservation may be always unavailable. As noted the activation, and the required thresholds, may be configured using higher layer (RRC) signalling. In an example, reservations for specific priorities may be made always available or always unavailable by setting the corresponding thresholds to positive or negative infinity (or another extreme value that could not be achieved in an operating system) . Such values may be stored in a dedicated table of priority thresholds as discussed below.

A binary decision on availability is expected to be straightforward to implement and gives good predictability but may limit flexibility and reduce spectrum utilisation. A more refined approach may be taken by utilising different criterion for the availability of resources of previous periodic reservations and aperiodic reservations. Figure 3 shows an example in which different SL-RSRP thresholds may be applied to periodic and aperiodic reservations.

At step 300, step 1 of the resource selection process is started and at step 301 received reservations are evaluated to determine the RSRP, priority and/or aperiodic/periodic type (and potentially other parameters) . If a reservation is determined to be periodic the method proceeds to step 302 and applies a first RSRP threshold which is configured for periodic reservations. If the reservation is determined to be aperiodic the method proceeds to step 303 and applies a second RSRP threshold which is configured for aperiodic reservations. At step 304 the SL-RSRP of the reservation message is compared to the relevant threshold. If the SL-RSRP exceeds the relevant threshold the resource is considered not available at step 305, and if the SL-RSRP is below the relevant threshold the resources are considered available at step 306. Generally the threshold for a periodic reservation is higher than the threshold for an aperiodic reservation. That is, periodic reservations are given increased protection against pre-emption and collisions.

The thresholds may also be dependent on other factors such as priority of the respective reservations as discussed above. The thresholds may be configured by higher layer (RRC) signalling, and may be defined per resource pool, cell, or other appropriate granularity. The applicable thresholds should be defined such that the general behaviour regarding priority is maintained. For example, it should be avoided that a periodic reservation is protected from a later higher-priority reservation.

The method of Figure 3 relies upon specific threshold values being defined for reservation types and priorities. This configuration data may be reduced using the method shown in Figure 4 in which an offset is applied in the assessment of periodic reservations.

In Figure 4

steps

300 and 301 are as described in relation to Figure 3. However, if the reservation is periodic, at step 400 the UE applies an offset to the RSRP thresholds. The offset may be a (pre) configured fixed offset, for example 2dB or 3dB which is applied to the standard table of thresholds. Alternatively, the offset may be defined based on the difference in priority between the two reservations (i.e. the detected reservation and the reservation for which resources are being identified by the UE) . For example, the offset may be defined as x dB * (prioroity_tx –priority_rx) (where x may be 3) . The offset may also be capped to avoid exceeding the threshold for a lower priority transmission which affect normal operation of the priority system. For example: -

Th_periodic (P_rx, P_tx) = max (Th_aperiodic (P_rx, P_tx) -offset (P_rx, P_tx) , Th_aperiodic (P_rx-1, P_tx) )

Steps 304 –306 are then conducted as described in relation to Figure 3 but based on the relevant thresholds.

In an alternative approach for Figure 4, the measured SL-RSRP values may be adjusted as described for the thresholds in Figure 4 and compared to unadjusted threshold. As will be apparent the adjustment will be in the opposite direction to that made to the thresholds, but the principles are the same. The effect of both approaches is that resources of periodic reservations are less likely to be selected than aperiodic resources by the UE for the new transmission.

In a further example, shown in Figure 5, the relative periodicity of the previous and new reservations may be considered.

Steps

300 and 301 are as discussed previously, but at step 500 the periodicity of previous periodic reservation is assessed in comparison to the period of the new reservation. If the periods are the same the resources are marked as unavailable at step 501, but if the resources have a different period the method continues to consider the SL-RSRP against a threshold at step 502. The threshold process may be as disclosed hereinbefore in relation to any of the previous examples or using conventional methods. If the threshold fails the resources are marked unavailable, or if it is passed the resources are considered available at step 503.

The method of Figure 5 avoids a situation in which resources in every period of a periodic reservation will collide (since the periodicities are the same) but may permit less regular collisions (subject to the threshold test) . In a modification of the method of Figure 5, resources may be considered unavailable if the periodicities of an existing reservation and the new reservation are multiples of each other (since this will lead to repeated collisions) .

The comparison of periodicities may consider how frequently collisions will occur, as shown in Figure 6. For example, a pair of reservations with periodicities of 10ms and 15ms will collide every 30ms (i.e. every 3 and 2 periods respectively) . The comparison criterion may be based on the ratio of periods with collisions. At step 600 the relevant metric is compared to a threshold for collisions and if the threshold is failed the resources are marked as unavailable at step 601. If the threshold passes the resources are considered to be available at step 503.

If either or both reservation has a ratio of collisions higher than a (pre) configured threshold the resources are marked as unavailable at step 601. The ratio may be defined according to the parameters discussed hereinbefore, for example dependent on priority.

The threshold comparison at step 502 may be performed using any of the techniques discussed hereinbefore or using conventional techniques.

Figure 7 shows a further method in which assessment of collisions is used during step 2 of the resource selection process, applied after step 1 is performed in the conventional manner At step 700 the UE selects resources it intends to reserve during step 2 of the resource selection process. At step 701 the UE determines if the reservation is a periodic reservation, and if not the selection is considered valid at step 702. If the reservation is periodic, at step 703 the UE assesses the collisions with the previously reserved resources. The assessment may be based on any of the criteria discussed above and below.

If the number of collisions is small (step 704) , for example below a threshold the selection is considered valid at step 702. The threshold may be defined on any appropriate basis, for example by resource pool or per UE, and as discussed previously may be dependent on priority.

If the number of collisions is not considered small (i.e. the threshold is exceeded) , the UE assesses (step 705) whether reservations with collisions in excess of the threshold may be permitted. If such reservations are not permitted the UE returns to step 700 to select different resources. However, reservations with a large number of collisions (for example in excess of a second threshold) may be permitted because the collisions are likely to trigger pre-emption by the UE with the existing reservation and reselection of a new periodic reservation. The reselection procedure is relatively inexpensive in control overhead, and the high number of collisions implies a low number of resources will be left unused. Accordingly, at step 706 the UE checks with the second threshold is exceeded and moves to step 702 or 700 accordingly. As will be apparent, the steps 704 –706 may be condensed into a set of checks against the appropriate thresholds. The effect of the steps is that reservations with collisions below a first threshold and above a second threshold may be permitted according to configuration.

The threshold for use at step 706 may be defined according to any of the principles discussed hereinbefore.

Described below are various examples of measures and criteria to evaluable collisions between period resource reservations. This measures and criteria may be used in any of the relevant methods described above. The intention of the criteria is to evaluate collisions that will occur, and the potential cost due to triggering pre-emption and reselection.

The collisions that will occur are a function of the overlap between resources in each period of the periodic reservations, and the relation of the periodicity of the two reservations. Measures which may be used to evaluate collisions include the number of collided resources which counts the individual collisions which will occur, which also provides an indication of the loss due unused reservation if the whole previous periodic reservation is reselected. The number of periods that include at least one collision may be utilised which gives an indication of the number of reselections and SCI reservations that will be triggered by the collisions. As noted previously, any measure may be based on ratio values rather than absolute numbers

The measure and criteria 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.

The various measures/criteria may be defined different values for UEs in different situations or configurations, for example as discussed above they may be dependent on priority of the reservations. The thresholds, criteria, and measures may be configured using higher layer (RRC) signalling and configuration.

All aspects of configuration discussed above in relation to RRC configuration may also be configured, or updated, on a dynamic basis using appropriate signalling processes.

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 of selecting transmission resources for sidelink transmissions in a cellular communications network, the method performed at a UE and comprising the steps of

identifying existing periodic transmission resource reservations; and

marking the transmission resources of those reservations as unavailable for selection for reservation by the UE.
A method of selecting transmission resources for sidelink transmissions in a cellular communications network, the method performed at a UE and comprising the steps of

identifying existing transmission resource reservations;

categorising existing transmission resource reservations as periodic or aperiodic reservations;

marking transmission resources of the identified existing transmission resource reservations as unavailable based on a comparison of a characteristic of those transmission resources to a threshold, wherein the threshold is dependent on whether the respective reservation is periodic or aperiodic.
The method of claim 2, wherein the threshold for periodic reservations is higher than the threshold for aperiodic reservations.
The method of claim 2 or claim 3, wherein the threshold for periodic reservations is equal to the threshold for aperiodic reservations with an offset applied.
The method of claim 4, wherein the offset is predefined.
The method of claim 5, wherein the offset is dependent on the difference in priority between the existing reservation and a new reservation.
The method according to any of claims 2 to 7, wherein the threshold is also dependent on the priority of the respective reservation.
The method according to claim 2, wherein the characteristic is adjusted dependent on whether the existing reservation is periodic or aperiodic.
The method according to any of claims 2 to 8, wherein the characteristic is the SL-RSRP of the reservation message for the transmission resources.
The method according to any of claims 2 to 9, further comprising the step of comparing the period of a new reservation with the periods of the existing periodic reservations, and marking resources of existing periodic reservations having the same period as the new reservation as unavailable.
The method according to any of claims 2 to 10, further comprising identifying the number of collisions between existing periodic reservations and a new periodic reservations, and marking the transmission resources of the existing reservations as unavailable if the number of collisions exceeds a threshold.
A method of selecting transmission resources for sidelink transmissions in a cellular communications network, the method performed at a UE and comprising the steps of

identifying existing periodic transmission resource reservations;

determining the period of the existing periodic transmission resource reservations; and

marking the transmission resources of those reservations as unavailable for selection for a new periodic reservation by the UE if the period of the new reservation is the same or a multiple of the period of an existing reservation.