WO2022028428A1

WO2022028428A1 - Sidelink Resource Selection

Info

Publication number: WO2022028428A1
Application number: PCT/CN2021/110369
Authority: WO
Inventors: Umer Salim; Virgile Garcia
Original assignee: Huizhou Tcl Cloud Internet Corporation Technology Co., Ltd.
Priority date: 2020-08-03
Filing date: 2021-08-03
Publication date: 2022-02-10
Also published as: CN116326012A

Abstract

A method for selecting resources for a transmission is disclosed. The method comprises: receiving a set of threshold valuesof Reference Signal Received Power, the set of threshold values including a threshold valueof Reference Signal Received Power for each potential combination of transmission priority value and reservation priority value; sensing a set of resources within a resource selection window for the transmission, wherein each resource in the set ofresources is associated with a value of Reference Signal Received Power; receiving a value of priority of the transmission; identifying, from the set of resources, a first subset of resources, wherein the first subset of resources comprises resources which are selectable for the transmission based on the set of threshold values and the value of priority of the transmission; determining the proportion of the number of resources in the first subset of resources relative to the number of resources in the set of resources; andin the event that the proportion of the number of resources in the first subset of resources relative to the number of resources in the set of resources is greater than or equal to a predetermined proportion, selecting at least one resource of the first subset of resources for the transmission.

Description

Sidelink Resource Selection

Technical Field

The following disclosure relates sidelink resource selection, in particular for avoiding collisions of transmissions.

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) . 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.

NR has added a lot of capabilities and technical features to the wireless strategies going way beyond LTE for operation on licensed spectrum. In addition, 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, 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 1 ms has been proposed with a reliability of 99.99999%, and at the physical layer a packet loss rate of 10-5 or 10-6 has 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.

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.

Figure 1 shows selected elements of a cellular wireless communication network;

Figure 2 shows selected elements in a Radio Area Network of the cellular wireless communication network of Figure 1;

Figure 3 shows a method of resource selection;

Figure 4 shows a table of resources;

Figures 5A and 5B show tables of available resources from Figure 4 using the method of Figure 3;

Figure 6 shows a method of resource selection;

Figure 7 shows a table of excluded resources from Figure 4 using the method of Figure 6;

Figure 8 shows a table of available resources from Figure 4 using the method of Figure 6;

Figure 9 shows a method of resource selection;

Figure 10 shows a table of available resources from Figure 4 using the method of Figure 9;

Figure 11 shows a method of resource selection; and

Figure 12 shows a table of available resources from Figure 4 using the method of Figure 11.

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 102 (for example, eNB or gNBs depending on the particular cellular standard and terminology) forming a cellular network. Typically, each of the base stations 102 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 102 provides wireless coverage for UEs in its area or cell. The base stations 102 are interconnected via the X2 interface and are connected to a core network 104 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. 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 102 each comprise hardware and software to implement the RAN’s functionality, including communications with the core network 104 and other base stations 102, 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 104 comprises hardware and software to implement the network functionality, such as overall network management and control, and routing of calls and data.

In vehicle-to-vehicle (V2V) applications, the UEs may be incorporated into vehicles such as cars, trucks and buses. These vehicular UEs are capable of communicating with each other in in-coverage mode, where a base station manages and allocates the resources and in out-of-coverage mode, without any base station managing and allocating the resources. In vehicle-to-everything (V2X) applications, the vehicles may be communicating not only with other vehicles, but also with infrastructure, pedestrians, cellular networks and potentially other surrounding devices. V2X use cases include:

Vehicles Platooning -this enables the vehicles to dynamically form a platoon travelling together. All the vehicles in the platoon obtain information from the leading vehicle to manage this platoon. This information allows the vehicles to drive closer than normal in a coordinated manner, going to the same direction and travelling together.

Extended Sensors -this enables the exchange of raw or processed data gathered through local sensors or live video images among vehicles, road site units, devices of pedestrian and V2X application servers. The vehicles can increase the perception of their environment beyond of what their own sensors can detect and have a broader and holistic view of the local situation. High data rate is one of the key characteristics.

Advanced Driving -this enables semi-automated or full-automated driving. Each vehicle and/or RSU shares its own perception data obtained from its local sensors with vehicles in proximity and that allows vehicles to synchronize and coordinate their trajectories or manoeuvres. Each vehicle shares its driving intention with vehicles in proximity too.

Remote Driving -this enables a remote driver or a V2X application to operate a remote vehicle for those passengers who cannot drive by themselves or remote vehicles located in dangerous environments. For a case where variation is limited and routes are predictable, such as public transportation, driving based on cloud computing can be used. High reliability and low latency are the main requirements.

Figure 2 illustrates a base station 102 forming a RAN, and a transmitter (Tx) UE 150 and a receiver (Rx) UE 152 in the RAN. The base station 102 is arranged to wirelessly communicate over respective connections 154 with each of the Tx UE 150 and the Rx UE 152. The Tx UE 150 and the 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 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 V2X services operate out-of-coverage of cellular base stations. Here the UEs need to schedule themselves. For fair utilization, sensing-based resource allocation is generally adopted at the UEs. In Mode 2, UEs reserve resources for a transmission by transmitting a Sidelink Control Information (SCI) message indicating the resources to be used. 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. UEs may reserve transmission resources both for a first transmission of a Transport Block (TB) of data, and also for transmitting repetitions of the TB to improve reliability if the initial transmission fails.

Figure 3 illustrates a method 300 of resource selection in Mode 2 carried out by a UE. At step 302, a processor of the UE receives initial Reference Signal Received Power (RSRP) thresholds. These thresholds are configured for each pair of priority values, where one priority is the priority of own transmission for which UE is performing resource selection, and the other priority is the priority of the detected packet. At step 304, the processor of the UE receives a priority for the intended transmission, P_tx. At step 306, the processor of the UE receives a value, X, for the percentage of identified resources. The value of X may be a percentage between 0 and 100 and is preferably 20, 35 or 50.

At step 308, the UE senses resources within the resource selection window for the intended transmission. The resource selection window includes the future resources over which the UE may select the suitable resource for transmission. This includes the UE receiving a value for priority of the sensed reservation, P_rx, and an RSRP value in dB. RSRP value is the estimated RSRP value for the received reservation, and P_rx is the priority of the detected transmission/reservation as indicated in sidelink control information. At step 310, the processor of the UE identifies, based on the RSRP thresholds and value of P_tx, which of the sensed resources from step 308 are selectable. The identification at step 310may comprise the processor of the UE comparing the RSRP of the detected reservation with the threshold to identify this resource as candidate or not. All the resources having received RSRP larger than the RSRP threshold for the relevant priority pair may be removed from the candidate list. At step 312, the processor of the UE determines the proportion of selectable resources relative to the number of sensed resources from step 308. If the proportion of resources available for selection identified at step 312 is greater than or equal to X, then the method 300 proceeds to step 314. At step 314, the processor of the UE selects resource (s) to use from the resources available for selection identified at step 312. Selection of resources at step 314 may bea random selection form the resources available for selection identified within some constraints, e.g. Hybrid automatic repeat request (HARQ) feedback timing or delay between the resources when multiple resources need to be selected.

If following step 312, the proportion of resources available for selection identified at step 312 is less than X, then the method 300 proceeds to step 316. At step 316, the processor of the UE increases the RSRP thresholds. The increase of the RSRP thresholds may be by 3dB. In some cases, the increase in the RSRP thresholds can be by a fixed configured offset value applied to all thresholds for the priority pairs. The method 300 then returns to step 310 in which the processor of the UE identifies, based on the (increased) RSRP thresholds and value of P_tx, which of the sensed resources from step 308 are selectable.

At the RSRP thresholds may be increased at step 316, this may mean that the resources for the transmissions detected at step 308 with priority higher than the UE’s intended transmission priority, P_tx, become part of available candidate resources. As resources may be randomly selected from the identified resources at step 314, this can result in selection of resources for UE transmission which will collide with detected reserved resources of high priority transmission.

Moreover, if a UE detects a reservation on its already-reserved resource, the UE may trigger re-section of its already selected resource if the new reservation is for a high priority transmission. On the other hand, if the prior reserved resource has higher priority, the UE which made that prior reservation may not trigger resource reselection. Thus, high priority transmissions are at risk of collision which could lead to failure to meet reliability targets for the transmissions.

Figure 4 illustrates an example in which a UE senses (i.e. at step 308) twenty resources each with a value for priority of the sensed reservation, P_rx, and an RSRP value in dB. This table can be considered as the resources included in the resource selection window. The horizontal axis may show time dimension and the vertical axis may indicate frequency dimension (in the form of sub-channels or other suitable granularity) . In this example, only three priority values for Point-to-Point Protocol (PPP) are used: 0, 1 and 2, where a lower value means higher priority. Table 1 provides an example initial threshold configuration for resource selection in Mode 2:

Table 1

Using the configuration of Table 1 and taking P_tx = 1 and X = 20% (i.e. steps 302 to 306) , it can be seen that three of the sensed resources of Figure 4 are available for selection (i.e. step 310) . The available resources for this case are shown in Figure 5A. The UE determines at step 312 that 3/20 = 15%resources are available. This is below the 20%configured value of X and so condition for X is not achieved at the first iteration using the configuration of thresholds in Table 1. Accordingly, the thresholds are increased by 3dB iteratively until X is reached (i.e. step 316) . Table 2 provides an example threshold configuration for resource selection iterated twice with an increase of 3dB for each iteration from the initial configuration of Table 1. The readers will note the thresholds updated by 6 dB (2 iterations of 3 dB) for the 2 ^nd column which is for the priority of intended transmission P_tx = 1.

Table 2

Using the configuration of Table 2 and remaining with P_tx = 1 and X = 20%, it can be seen that six of the sensed resources of Figure 3 are available for selection. The available resources for this case are shown in Figure 5B. The UE determines at step 312 that 6/20 = 30%resources are available. This is above the 20%and so X is achieved using the configuration of Table 2. The UE can then select from the six available resources (i.e. step 314) . However, resources with higher priority, i.e. P_rx = 0, have been made available and therefore there is a risk of collision with transmissions that have a higher priority.

Methods are discussed below in relation to avoiding collisions in Mode 2 resource selection.

Figure 6 illustrates a method 600 of resource selection in Mode 2 carried out by a UE. The method 600 is substantially the same as method 300. Method 600 includes a step 602 between

steps

308 and 310. At step 602, the processor of the UE excludes from selection any resources from the set of sensed resources for which SCIs are detected with priority P_rx higher than an offset from the priority of intended transmission, P_tx. The offset is an integer value, e.g. 1, 2 or 3. The offset may be 0 which would exclude resources having the same priority. Accordingly, when a UE selects resources for sidelink transmission with a given priority, P_tx, all the resources for which it has detected reservations, periodic or aperiodic, in the resource selection window with priority P_rx higher than P_tx minus the offset (as a lower value means higher priority) , are excluded from the resource selection window.

This avoids the resource allocation resulting in collisions with high priority transmissions because the UE cannot select resources at step 314 that have priority P_rx higher than the priority of intended transmission P_tx from the set of sensed resources.

Returning to the example of the sensed resources of Figure 4 with P_tx remaining as 1, the excluded resources for this case, i.e. with P_rx = 0, are shown in Figure 7. In this case, all the resources in the selection window with priority higher than the intended transmission are excluded. This is achieved with an offset value of 1. After excluding the higher priority reservation resources, the higher priority resources are not available even if they pass the RSRP thresholds after a 3dB increase. The thresholds are increased by 3dB iteratively until X is reached (i.e. step 316) . Table 3 provides an example threshold configuration for resource selection iterated four times by 3dB from the initial configuration of Table 1:

Table 3

Using the configuration of Table 3 and remaining with P_tx = 1 and X = 20%, it can be seen that 11 of the sensed resources of Figure 3 are available for selection. The available resources for this case are shown in Figure 8. The UE determines at step 312 that 55%of resources are available. This is above the 20%and so X is achieved using the configuration of Table 3. The UE can then select from the available resources (i.e. step 314) . These may overlap with existing reservations. However, a pre-emption mechanism may be triggered, if needed by the UEs that have performed the reservation. In this example, the “low RSRP-high priority” reservation is also excluded, which provides a safer transmission for that high priority transmission.

Figure 9 illustrates a method 900 of resource selection in Mode 2 carried out by a UE. The method 900 is substantially the same as method 300. Method 900 includes a step 902 which may be carried out between step 302 and step 310. At step 902, the processor of the UE sets the RSRP thresholds for all pairs where P_rx has higher priority than P_tx to very low values, e.g. minus infinity. A resource pool may be configured with a “collision avoidance” flag. When collision avoidance is activated by indicating an appropriate value for this flag as part of resource pool configuration, UEs performing resource selection or reselection may carry out step 902.

This avoids the resource allocation resulting in collisions with high priority transmissions because the UE does not identify (at step 310) resources that have priority P_rx higher than the priority of intended transmission from the set of sensed resources, P_tx.

Returning to the example of the sensed resources of Figure 4 with P_tx remaining as 1, Table 4 provides an example threshold configuration for resource selection in which the RSRP thresholds for all pairs where P_rx has higher priority than P_tx to very lowvalues has been set to negative infinity as well as iterated four times by 3dB from the initial configuration of Table 1. This table has updated RSRP thresholds for all P_tx, P_rx pairs with P_rx having higher priority (lower value) . In resource selection, as the UE will only use RSRP thresholds having the P_tx equal to the priority of intended transmission, only the relevant thresholds associated to this P_tx may be updated. For the example with P_tx = 1, it would imply update of only the column associated to P_tx =1.

Table 4

Using the configuration of Table 4 and remaining with P_tx = 1 and X = 20%, it can be seen that 11 of the sensed resources of Figure 3 are available for selection. The available resources for this case are shown in Figure 10. The UE determines at step 312 that 55%of resources are available. This is above the 20%and so X is achieved using the configuration of Table 4. The UE can then select from the available resources (i.e. step 314) .

Figure 11 illustrates a method 1100 of resource selection in Mode 2 carried out by a UE. The method 1100 is substantially the same as method 300. Method 1100 replaces step 316 of method 300 with

steps

1102 and 1104 which are carried out if insufficient resources are available following step 312. At step 1102, the processor of the UE freezes, i.e. locks or fixes, any RSRP threshold pairs with detected priority P_rx higher than an offset from P_tx. The offset is an integer value, e.g. 1, 2 or 3. This offset can be used with value of 0, resulting in freezing of thresholds with the same P_rx priority as of P_tx. At step 1104, the processor of the UE increases the RSRP thresholds unless they are frozen. The increase of the RSRP thresholds may be by 3dB, similar to step 316.

This approach for resource selection avoids harmful collisions over the resources reserved with higher priority transmissions. In particular, although method 1100 may result in a finally selected resource which may collide with a higher priority reservation, the collisions will not be detrimental as they will happen only under the restrictions that the detected higher priority reservations must have estimated RSRP below the initially configured RSRP threshold, and while the resource identification step may have multiple iterations, the freezing of RSRP thresholds associated with higher priority does not permit inclusion of resources reserved with higher priority being part of identified resources with RSRP larger than the initially configured RSRP threshold. In other words, the “low RSRP-high priority” reservation is kept available, as it passed the initial criterion. But other high priority reservations will not be considered further and protected by not being made available for selection. This enables increased flexibility in setting an acceptable threshold for resource spatial reuse with a safer approach toward high priority.

Returning to the example of the sensed resources of Figure 4 with P_tx remaining as 1, Table 5provides an example threshold configuration for resource selection in which the RSRP threshold for {P_tx = 1, P_rx = 0} has been frozen at its initial value (as per Table 1) whilst other RSRP valuesiterated four times by 3dB from the initial configuration of Table 1:

Table 5

Using the configuration of Table 5 and remaining with P_tx = 1 and X = 20%, it can be seen that 12 of the sensed resources of Figure 3 are available for selection, after 4 iterations. The available resources for this case are shown in Figure 12. The UE determines at step 312 that 60%of resources are available. This is above the 20%and so X is achieved using the configuration of Table 5. The UE can then select from the available resources (i.e. step 314) . In the

methods

600, 900, 1100 described above avoid collision of resources based on the priority of the transmission for which UE is performing resource allocation, P_tx. In alternative scenarios, a resource pool configuration may include a field indicating a pivotal priority, P_p. This priority indicates the priority point beyond which all the transmissions need to be protected. A UE performing resource allocation with method 600 will then exclude all the resources for which it detects priority equal or higher than the indicated pivotal priority P_p. A UE performing method 900 will set low RSRP thresholds to all pairs where P_rx has equal or higher priority than P_p. A UE performing method 1100 will freeze RSRP thresholds in step 1102 for all priority pairs where P_rx has equal or higher priority than P_p. The resource selection methods discussed above have been described where prioritization is always performed with respect to the priority of Tx UE P_tx performing resource selection. In this alternative method, a set of priorities, indicated by P_p, is always protected with the methods described earlier, irrespective of P_tx. This safeguards transmissions having priority equal to or higher than the pivotal priority. Thus, UEs performing resource allocation in this resource pool exclude resources or have the RSRP thresholds frozen for priorities higher than this pivotal priority. This method is particularly beneficial for high priority applications such as having URLLC constraints.

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) 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 selecting resources for a transmission, the method comprising:

receiving a set of threshold valuesof Reference Signal Received Power, the set of threshold values including a threshold valueof Reference Signal Received Power for each potential combination of transmission priority value and reservation priority value;

sensing a set of resources within a resource selection window for the transmission, wherein each resource in the set of resources is associated with a value of Reference Signal Received Power;

receiving a value of priority of the transmission;

identifying, from the set of resources, a first subset of resources, whereinthe first subset of resources comprises resources which are selectable for the transmission based on the set of threshold values and the value of priority of the transmission;

determining the proportion of the number of resources in the first subset of resources relative to the number of resources in the set of resources; and

in the event that the proportion of the number of resources in the first subset of resources relative to the number of resources in the set of resourcesis greater than or equal to a predetermined proportion, selecting at least one resource of the first subset of resources for the transmission.
The method of claim 1, comprising receiving the predetermined proportion.
The method of any preceding claim, comprising, in the event that the proportion of the number of resources in the first subset of resources relative to the number of resources in the set of resourcesis less than the predetermined proportion:

increasing each of the threshold values in the set of threshold values;

identifying a second subset of resources, wherein the second subset of resources comprises resources of the set of resources which are selectable for the transmission based on the increased threshold values and the value of priority of the transmission;

determining the proportion of the number of resources in the second subset of resources relative to the number of resources in the set of resources; and

in the event that the proportion of the number of resources in the second subset of resources relative to the number of resources in the set of resources is greater than or equal to the predetermined proportion, selecting at least one resource of the second subset of resources for the transmission.
The method of claim 3, wherein increasing each of the threshold values in the set of threshold valuesincludes increasing each threshold value by 3 dB.
The method of any of claims 1 to 4, wherein each resource in the set of resources is associated with a reservation priority value, the method comprising:

prior to identifying the first subset of resources, excluding, from the set of resources, any resources having areservation priority value that is greater than a predetermined offset above the value of priority of the transmission.
The method of any of claims 1 to 4, comprising:

prior to identifying the first subset of resources, settingthe threshold value to a low valuefor each combination of transmission priority value and reservation priority valuein the set of threshold values in which the reservation priority valueis higher than the transmission priority value.
The method of claim 6, where the low value is negative infinity.
The method of any of claims 1 or 2, comprising, in the event that the proportion of the number of resources in the first subset of resources relative to the number of resources in the set of resources is less than the predetermined proportion:

freezing the threshold value for each combinationof transmission priority value and reservation priority value in the set of threshold values in which the reservation priority value is greater than a predetermined offset above the transmission priority value; and

increasing each of the threshold values in the set of threshold values unless the threshold value is frozen.
The method of claim 8, wherein increasing each of the threshold values in the set of threshold values unless the threshold value is frozen includes increasing the threshold values by 3 dB.
The method of any of claims 5, 8 or 9, wherein the predetermined offset is an integer value.
The method of claim 10, wherein the predetermined offset is 0, 1, 2, or 3.
The method of any proceeding claim, wherein the steps are performed at or by a UE.
A UE comprising a processor arranged to perform the method of any one of claims 1 to 12.
A non-transitory computer readable mediumstoring instructions, which when executed by a computer, perform the method of any one of claims 1 to 12.