Method for resource selection

A method for resource selection is disclosed. The method includes performing, by a UE, a first sensing operation to determine available resources in a resource pool; transmitting, by the UE, first data using a first set of available resources, the first set of available resources having been selected from the resource pool in accordance with the first sensing operation; performing, by the UE, concurrently with the first sensing operation and resource selection of the first set of available resources and independently from the first sensing operation, a second sensing operation to determine other available resources in the resource pool; and transmitting, by the UE, second data using a second set of available resources, the second set of available resources having been selected from the resource pool in accordance with the second sensing operation, wherein the first set of available resources and the second set of available resources are independently selected.

TECHNICAL FIELD

The present disclosure relates generally to a system and method for selecting resources and, in particular embodiments, to a system and method for improved transmission reliability between user equipment in V2V/V2X technology.

BACKGROUND

Vehicle-to-Vehicle (V2V) and Vehicle-to-Everything (V2X) technologies have been standardized by the 3rd Generation Partnership Project (3GPP) in Release 14 (Rel-14). V2V/V2X services are supported on the sidelink and reuse much of the Device-to-Device (D2D) work already standardized in Rel-12 and Rel-13. The term “sidelink” refers to communication performed between one user equipment (UE) and one or more other UEs without data being transmitted through an Evolved Node B (eNB) or other centralized controller. In particular, V2V/V2X messages are broadcast by a source without a priori knowledge of a receiver.

In Rel-15, the V2V/V2X work is expected to continue for both Long Term Evolution (LTE) and New Radio (NR) Scalable Network. In particular, it is likely that more advanced vehicular services such as platooning, automated merging, and a general move towards autonomous cars will be standardized. The work has already started in the 3GPP Service and System Aspects Group 1 (SA1), where requirements for V2V/V2X services are being drafted.

One of the requirements for advanced V2V/V2X services is the need for higher transmission reliability, for both multicast and unicast transmission. With transmission mode-4 (UE being autonomous without eNB allocating resources), the Rel-14 V2V/V2X solution might not provide adequate reliability. Thus, there is a need for techniques for improved mode-4 reliability.

SUMMARY

In accordance with an embodiment of the present disclosure, a method for resource selection comprises performing, by a UE, a first sensing operation to determine available resources in a resource pool; transmitting, by the UE, first data using a first set of available resources, the first set of available resources having been selected from the resource pool in accordance with the first sensing operation; performing, by the UE, concurrently with the first sensing operation and resource selection of the first set of available resources and independently from the first sensing operation, a second sensing operation to determine other available resources in the resource pool; and transmitting, by the UE, second data using a second set of available resources, the second set of available resources having been selected from the resource pool in accordance with the second sensing operation, wherein the first set of available resources and the second set of available resources are independently selected.

In the previous embodiment, the first data and the second data might be the same data. In any of the previous embodiments, the first data and the second data might be two consecutive data packets. In any of the previous embodiments, the first set of available resources and the second set of available resources might be selected on different subframes. In any of the previous embodiments, the first set of available resources might be used in odd resource intervals and the second set of available resources might be used in even resource intervals. In any of the previous embodiments, the first set of available resources and the second set of available resources might be used in the same resource interval. In any of the previous embodiments, selection of the first set of available resources and selection of the second set of available resources might be performed before a reselection of resources. In any of the previous embodiments, resource reselections for the first set of available resources and the second set of available resources might occur at different times. In any of the previous embodiments, the first set of available resources and the second set of available resources might be in consecutive data blocks. In any of the previous embodiments, the method might further comprise performing, by the UE, concurrently with the first sensing operation and the second sensing operation and independently from the first sensing operation and the second sensing operation, a third sensing operation to determine additional other available resources in the resource pool; and transmitting, by the UE, third data using a third set of available resources, the third set of available resources having been selected from the resource pool in accordance with the third sensing operation. In any of the previous embodiments, the first sensing operation and the second sensing operation might comprise sidelink mode-4 sensing operations.

In accordance with another embodiment of the present disclosure, a UE comprises a transmitter configured to transmit first data using a first set of available resources, the first set of available resources having been selected from the resource pool in accordance with a first sensing operation performed by the UE to determine available resources in a resource pool. The transmitter is further configured to transmit second data using a second set of available resources, the second set of available resources having been selected from the resource pool in accordance with a second sensing operation performed by the UE, concurrently with the first sensing operation and resource selection of the first set of available resources and independently from the first sensing operation, to determine other available resources in the resource pool, wherein the first set of available resources and the second set of available resources are independently selected.

In the previous embodiment, the first data and the second data might be the same data. In any of the previous embodiments, the first data and the second data might be two consecutive data packets. In any of the previous embodiments, the first set of available resources and the second set of available resources might be selected on different subframes. In any of the previous embodiments, the first set of available resources might be used in odd resource intervals and the second set of available resources might be used in even resource intervals. In any of the previous embodiments, the first set of available resources and the second set of available resources might be used in the same resource interval. In any of the previous embodiments, selection of the first set of available resources and selection of the second set of available resources might be performed before a reselection of resources. In any of the previous embodiments, resource reselections for the first set of available resources and the second set of available resources might occur at different times. In any of the previous embodiments, the first set of available resources and the second set of available resources might be in consecutive data blocks. In any of the previous embodiments, the transmitter might be configured to transmit third data using a third set of available resources, the third set of available resources having been selected from the resource pool in accordance with a third sensing operation performed, concurrently with the first sensing operation and the second sensing operation and independently from the first sensing operation and the second sensing operation, to determine additional other available resources in the resource pool. In any of the previous embodiments, the first sensing operation and the second sensing operation might comprise sidelink mode-4 sensing operations.

In accordance with another embodiment of the present disclosure, a device comprises a non-transitory memory storage comprising instructions and one or more processors in communication with the memory storage. The one or more processors execute the instructions to transmit first data using a first set of available resources, the first set of available resources having been selected from the resource pool in accordance with a first sensing operation performed by the device to determine available resources in a resource pool, and transmit second data using a second set of available resources, the second set of available resources having been selected from the resource pool in accordance with a second sensing operation performed by the device, concurrently with the first sensing operation and resource selection of the first set of available resources and independently from the first sensing operation, to determine other available resources in the resource pool, wherein the first set of available resources and the second set of available resources are independently selected.

In the previous embodiment, the first data and the second data might be the same data. In any of the previous embodiments, the first data and the second data might be two consecutive data packets. In any of the previous embodiments, the first set of available resources and the second set of available resources might be selected on different subframes. In any of the previous embodiments, the first set of available resources might be used in odd resource intervals and the second set of available resources might be used in even resource intervals. In any of the previous embodiments, the first set of available resources and the second set of available resources might be used in the same resource interval. In any of the previous embodiments, selection of the first set of available resources and selection of the second set of available resources might be performed before a reselection of resources. In any of the previous embodiments, resource reselections for the first set of available resources and the second set of available resources might occur at different times. In any of the previous embodiments, the first set of available resources and the second set of available resources might be in consecutive data blocks. In any of the previous embodiments, the one or more processors might further execute the instructions to perform, concurrently with the first sensing operation and the second sensing operation and independently from the first sensing operation and the second sensing operation, a third sensing operation to determine additional other available resources in the resource pool; and transmit third data using a third set of available resources, the third set of available resources having been selected from the resource pool in accordance with the third sensing operation. In any of the previous embodiments, the first sensing operation and the second sensing operation might comprise sidelink mode-4 sensing operations.

An advantage of the disclosed embodiments is that the number of consecutive packet losses for V2X mode-4 transmissions might be decreased.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

Transmission mode-4 provides an autonomous resource selection process, wherein a UE autonomously selects time/frequency transmission resources from a V2X sidelink transmission resource pool to transmit a V2V or V2X message. While the embodiments disclosed herein are described with respect to LTE-based V2V/V2X transmission systems, the embodiments might also apply to NR-based V2V/V2X systems where UEs autonomously select resources using a resource selection process similar to mode-4, with a sensing phase. The embodiments might also apply when LTE V2V/V2X and NR V2V/V2X (and/or possibly another system) share the same band.

FIG. 1illustrates an embodiment of a resource pool no with respect to a cell120of a base station, such as an eNB130, and a UE140. The resource pool110might be available for in-coverage UEs (i.e., UEs covered by the cell120) and out-of-coverage UEs (i.e., UEs not covered by the cell120). The resource pool110might be provided by the network through the eNB130(for in-coverage UEs) or by preconfiguration (for out-of-coverage UEs). The resource pool110might be available for idle UEs (RRC_IDLE) or for connected UEs (RRC_CONNECTED). If a mapping between the zones in the cell120and the V2X sidelink transmission resource pool110is configured, the UE140might select from the V2X sidelink resource pool110based on the zone where the UE140is located.

UEs, such as UEs in V2X vehicles, may be synchronized such that the UEs are able to sense and reserve periodic time/frequency resources in the sidelink transmission resource pool for V2X traffic. That is, a UE might observe data traffic in a cell and determine which resources in the resource pool are occupied and which resources are available. Such a procedure might be referred to as sensing. After performing a sensing operation, the UE might select available resources in the resource pool for its data transmissions.

However, it might happen that two UEs perform a sensing operation at approximately the same time, discover at approximately the same time that the same resources are available, and select those same resources at approximately the same time for their data transmissions. In such a case, the UEs will collide until one of the two UEs reselects the resources or until the distance between the two UEs is sufficiently large. Such processes might take several seconds. If the UEs broadcast data under mode-4 transmission, there is no feedback, and the transmitting UEs are not aware of the collisions. Given that resource reselection is a relatively rare occurrence, a receiving UE might be prevented from receiving data packets from one or more transmitting UEs for a large number of transmissions of consecutive data packets, as illustrated inFIG. 2.

InFIG. 2, data is semi-persistently transmitted on a resource210in a plurality of intervals220. The length of a resource interval220typically is 100 milliseconds (ms) but might be different. In this example, collisions occur in the first six intervals220a-220f, and thus transmission failures occur in those intervals220a-220f. (The failures are marked with exclamation marks inFIG. 2.) That is, as described above, if a transmission by a UE on a resource collides with a transmission by another UE, a receiving UE is not able to receive data from the transmitting UEs. The selected resource210remains the same until a reselection230is triggered and another resource240is selected. The reselection230is a procedure whereby a UE occasionally chooses a different set of transmission resources to introduce randomness and adaptation to a changing environment. Reselection might be automatically triggered after a defined length of time or after a defined number of transmissions. After the reselection230, the transmitting UE is able to transmit its data via the reselected resources240, and the receiving UE might be able to receive the data because no other UE is transmitting data on those resources. (Successful transmission is marked with check marks inFIG. 2.)

In an exemplary case, the fraction of receiving UEs experiencing n consecutive packet losses is shown in the diagram300ofFIG. 3. As is apparent, the fraction of receiving UEs experiencing consecutive packet losses is significant. For instance, more than 2% of vehicles experience at least 10 consecutive packet losses. It is noted that, depending on parameters, the proportion of UEs experiencing consecutive packet losses can be much larger (e.g., for shorter interval periodicities, e.g., 20 ms). The number of consecutive packet losses might be too large for the advanced connected vehicle services being considered for 5thGeneration (5G) systems. Therefore, there is a need for a solution to lower the number of consecutive packet losses for V2X mode-4.

Embodiments of the present disclosure provide at least one solution to this need. In an embodiment, a UE concurrently performs at least two independent mode-4 resource selection procedures, S1and S2. The UE might select resources according to a resource selection procedure S1on odd subframes, and the UE might select resources according to a resource selection procedure S2on even subframes. The resource selection procedures S1and S2run independently (except for some possible rules to prevent self-collision, such as preventing the resource selection procedures S1and S2from selecting resources on the same subframe). That is, the resources selected by the S1and S2procedures are different from one another, and the resource reselection times may be different.

By using two independent sensing and selection procedures or methods, “resource selection diversity” can be achieved. If the probability of two UEs colliding on a given resource interval is 1/N, the probability of two UEs colliding for two consecutive transmissions is 1/N2for the same two UEs.

Embodiments of sensing and selection methods are shown inFIGS. 4 and 5. The embodiment ofFIG. 4shows eight resource intervals411-418. A first transmitting UE selects, according to a first selection procedure S1, resources421,423in odd resource intervals411,413and transmits data on those resources421,423. In this example, the selected resources421,423are also selected, by coincidence, by a second transmitting UE that also attempts to transmit its data on those resources421,423. Because of this collision, a receiving UE will not receive any data from the transmitting UEs. (The failure is marked with exclamation marks inFIG. 4.) However, the first transmitting UE has also selected, according to a second selection procedure S2, resources422,424in even resource intervals412,414and transmits the same data on those resources422,424that was transmitted in resources421,423. In this example, the selected resources422,424are not selected by the second transmitting UE to transmit its data, so the receiving UE receives the data from the first transmitting UE on resources422,424. (Successful transmission is marked with check marks inFIG. 4.) It should be understood that terms such as “first” and “second” are used herein to differentiate UEs from one another and do not imply any sort of sequence.

Assuming that the data blocks allocated to the resources421-424are consecutive data blocks, the receiving UE at least receives every other data block. Moreover, as can be seen fromFIG. 4, after reselection430in the first selection procedure S1, the data blocks are transmitted on the resources425-427of the odd and the even resource intervals415-417. After reselection440in the second selection procedure S2, the data blocks on the resource428of the even interval418cannot reach the receiving UE, but the data blocks on the resources425,427of the odd resource intervals415,417can still be received by the receiving UE. It may be noted that the same data is transmitted on different resources, such as on resource421and resource422, before any reselection operation430or440is performed.

The length of the resource interval may be 100 ms as indicated inFIG. 4. Alternatively, the length can be 20 ms, 50 ms, or a multiple of 100 ms, such as 200 ms or 300 ms up to 1 second (s) or 1.5 s. Alternatively, the lengths can be equal to or longer than 20 ms, 50 ms or 100 ms or equal to or shorter than 500 ms, 1 s or 1.5 s.

In various embodiments, the selection procedure S can be extended to k independent sensing and selection procedures S1-Skwith each procedure independently sensing and selecting one or more resources in a resource interval and eventually allocating data blocks to the resources in that resource interval. The periodicity for the k procedures is k. That is, every k resource interval, the same resource is selected, and a data block is allocated until reselection for the resource interval.

In various other embodiments, the different and independent sensing and resource selection procedures S1-Skcould be performed during the same resource interval. This is shown in the embodiment ofFIG. 5. For example, resources431are selected according to a first selection procedure, and resources433are selected according to a second selection procedure. The transmissions on the two resources in the same resource interval can be the same data packet and can correspond to different Hybrid Automatic Repeat Request (HARQ) transmissions. Alternatively, the transmissions on the two resources can be different data packets, such as consecutive data packets.

In various embodiments, the reselections of the resources of the first and second resource selection procedures S1and S2may be triggered at different times. In various other embodiments, the reselections may be triggered at the same time. In other embodiments, for more than two independent resource selection procedures, some of the procedures trigger the reselection at different times while others trigger the reselection at the same time.

In yet other embodiments, the sensing and resource selection procedures can be performed as a combination of the embodiments ofFIGS. 4 and 5.

FIG. 6shows an embodiment method600for configuring a UE with a number of resource selection processes and for transmitting data according to at least a subset of the number of resource selection processes. At step610, a resource selection configuration is provided for a transmitting UE. The UE may provide or obtain a resource selection configuration. This can be done in several ways.

In one option, the UE obtains a number of resource selection processes through a broadcast message from the network, e.g., via the base station or eNB. For instance, the number of resource selection processes may be broadcast in the System Information Block 21 (SIB21), as shown in the text box700ofFIG. 7. Alternatively, the number of resource selection processes may be broadcast in an equivalent message, such as in a maximum number of resource selection processes field, maxNumberResourceProcesses, or a similar message or field.

In another option, the UE obtains the number of resource selection processes through a dedicated message from the network, base station or eNB, either as a dedicated Radio Resource Control (RRC) message (with a message format similar to the previous option) or as a physical layer message, such as in Downlink Control Information (DCI).

In another option, the UE is preconfigured with a given number of resource selection processes.

In another option, the UE autonomously selects the number of resource selection processes.

The number of resource selection processes may be service-dependent. For instance, for basic V2X safety features, the number of resource selection processes may be one, whereas for platooning services, the number of resource selection processes might be two, three, five, or more. The number of resource selection processes may depend on quality of service (QoS) requirements, reliability requirements, etc.

In an embodiment, a UE may be initialized or configured with the different resource selection processes before an actual transmission can occur. For example, the UE may perform initial resource sensing (for 1 s in V2X Rel-14) and map resource intervals that need to be excluded. The initializing and configuration can be done any time before data is transmitted.

Returning toFIG. 6, at optional step620, the configuration may be indicated to other network devices. In some cases, an eNB might inform a UE of the selection processes the UE is to use. In some cases, a UE might use control signaling to inform other UEs of the selection processes the UE is using. In various embodiments, there are benefits in having the UE indicate the number of resource selection processes the UE uses and which resource selection is currently used. This can be done in several ways. For example, a new message may be defined to convey this information to other UEs. In other examples, one or more new fields may be added in a Sidelink Control Information (SCI) message. For instance, an index may be associated with each resource selection process. When a transmission occurs for a given resource selection process, the UE may add the corresponding index in the SCI associated with the data transmission.

At step630, the resource selection procedures are mapped to the resource intervals. The UE may use different resource selection processes for the same or for different consecutive data packet transmissions. Different packet transmissions may be mapped to different resource intervals. For instance, if the transmission periodicity is 100 ms, the UE may use two resource selection processes, S1and S2, each with a 200 ms periodicity and intertwined as shown inFIG. 4. Odd resource intervals may be allocated to the resource selection procedure S1, and even resource intervals may be allocated to the resource selection procedure S2. Alternatively, each transmission may be allocated two HARQ transmissions in the same resource interval, the first transmission using resources selected in S1and the second transmission using resources selected in S2. This alternative is shown inFIG. 5.

At step640, the UE transmits data on the resources that were determined by the resource selection and allocation processes. This step includes transmitting the actual data block on the physical sidelink shared channel (PSSCH) and transmitting the associated Scheduling Assignment (SA), if any, on the physical sidelink control channel (PSCCH). Each sensing and selecting procedure may be performed as described with respect toFIG. 8.

FIG. 8shows a method for sensing and selecting resources and for transmitting data in a single resource selection process800, such as the selection procedures S1and S2described above. In an embodiment, a UE might perform two or more of these resource sensing and selection processes800independently and concurrently. Each process800might include sensing available resources in a resource pool, selecting and reserving a resource, and transmitting a data block on the selected resource. Alternatively, the sensing procedure of a UE might include the UE sensing the medium for a given duration (about 1 s in Rel-14), the UE identifying and marking some resources as free, and the UE selecting one resource and using the selected resource until reselection is triggered.

At step810, the UE decodes other UEs' SA and measures the corresponding PSSCH energy. At step820, the UE collects sensing information of other UEs' resource occupancy by collecting PSSCH energy measurements. At step830, the UE excludes high energy resources and forms a candidate resource set comprising low energy resources. At step840, the UE selects a resource for transmitting a data block from the candidate resource set and transmits data blocks semi-persistently on that resource block. At decision block850, the UE evaluates whether to trigger resource reselection. If no reselection is necessary or desired, the UE continues to transmit data blocks on the selected resource, and the process moves back to step840. If resource reselection is necessary or desired, a reselection process is triggered, and the process moves back to step820in order to determine a new resource to be selected in the resource pool.

FIG. 9is a flowchart illustrating an embodiment method900for sensing and selecting resources and for transmitting data on the selected resources. At block910, a UE performs a first sensing operation to determine available resources in a resource pool. At block920, the UE selects a first set of available resources from the resource pool in accordance with the first sensing operation. At block930, concurrently with the first sensing operation and resource selection of the first set of available resources and independently from the first sensing operation, the UE performs a second sensing operation to determine other available resources in the resource pool. At block940, the UE selects a second set of available resources from the resource pool in accordance with the second sensing operation. At block950, the UE transmits first data using the first set of available resources. At block960, the UE transmits second data using the second set of available resources. The first data and the second data might be the same data. Alternatively or additionally, the first data and the second data might be two consecutive data packets. The UE might use the first set of available resources and the second set of available resources in alternating time intervals, as inFIG. 4. Alternatively, the UE might use the first set of available resources and the second set of available resources in the same time interval, as inFIG. 5.

FIG. 10is a block diagram illustrating an embodiment processing system1000for performing methods described herein, which may be installed in a host device. As shown, the processing system1000includes a processor1004, a memory1006, and interfaces1010-1014, which may (or may not) be arranged as shown in the figure. The processor1004may be any component or collection of components adapted to perform computations and/or other processing related tasks, and the memory1006may be any component or collection of components adapted to store programming and/or instructions for execution by the processor1004. In an embodiment, the memory1006includes a non-transitory computer readable medium. The interfaces1010,1012,1014may be any component or collection of components that allow the processing system moo to communicate with other devices/components and/or a user. For example, one or more of the interfaces1010,1012,1014may be adapted to communicate data, control, or management messages from the processor1004to applications installed on the host device and/or a remote device. As another example, one or more of the interfaces1010,1012,1014may be adapted to allow a user or user device (e.g., personal computer (PC), etc.) to interact/communicate with the processing system1000. The processing system1000may include additional components not depicted in the figure, such as long term storage (e.g., non-volatile memory, etc.).

In some embodiments, one or more of the interfaces1010,1012,1014connects the processing system moo to a transceiver adapted to transmit and receive signaling over the telecommunications network.FIG. 11is a block diagram illustrating a transceiver1100adapted to transmit and receive signaling over a telecommunications network. The transceiver1100may be installed in a host device. As shown, the transceiver1100comprises a network-side interface1102, a coupler1104, a transmitter1106, a receiver1108, a signal processor1110, and a device-side interface1112. The network-side interface1102may include any component or collection of components adapted to transmit or receive signaling over a wireless or wireline telecommunications network. The coupler1104may include any component or collection of components adapted to facilitate bi-directional communication over the network-side interface1102. The transmitter1106may include any component or collection of components (e.g., up-converter, power amplifier, etc.) adapted to convert a baseband signal into a modulated carrier signal suitable for transmission over the network-side interface1102. The receiver1108may include any component or collection of components (e.g., down-converter, low noise amplifier, etc.) adapted to convert a carrier signal received over the network-side interface1102into a baseband signal. The signal processor1110may include any component or collection of components adapted to convert a baseband signal into a data signal suitable for communication over the device-side interface(s)1112, or vice-versa. The device-side interface(s)1112may include any component or collection of components adapted to communicate data-signals between the signal processor1110and components within the host device (e.g., the processing system1000, local area network (LAN) ports, etc.).

At the receiving end, the receiving UE may operate as currently known. In an embodiment, the UE may receive the resource selection process index in the SCI as described above. This may need a new SCI format. Alternatively, some of the currently reserved bits of SCI format 1 may be used to indicate the resource selection process index, and/or the maximum number of resource selection processes. A receiving UE may benefit from decoding this information.

At the network, base station or eNB, depending on the embodiment, some changes may be needed. In an embodiment, if the number or maximum number of resource selection processes is broadcast by the network, base station or eNB, a new field may be needed in SIB21 or a similar message. If dedicated RRC signaling is used, a new information element, or a new field in an information element may be needed. Alternatively, if the resource selection process management is fully under the control of the transmitting UE, no change at the network, base station or eNB is needed.