Sidelink HARQ

Abstract

The invention relates to a sidelink HARQ. A user equipment (UE) communicates with a further UE via a sidelink and with a cell of a network via an uplink. The UE receives a hybrid automatic repeat request (HARQ) acknowledgement (ACK) timing parameter from a network; generating a sidelink HARQ-ACK codebook based on a signaling exchange with a further UE, wherein the sidelink HARQ-ACK codebook is constructed in a decreasing order of one or more physical sidelink shared channel (PSSCH) transmission slots associated with a configured physical sidelink feedback channel (PSFCH) occasion; and transmitting an indication of the side link HARQ-ACK codebook to the cell of the network.

Description

[0001] This application is a divisional application of Chinese patent application 202110183880.0, with the filing date of February 10, 2021 and the invention name “Sidelink HARQ”. Technical Field

[0002] The present disclosure relates to sidelink HARQ. Background Art

[0003] A user equipment (UE) may be configured with multiple communication links. For example, a UE may receive a signal from a cell of a corresponding network via a downlink, and may transmit a signal to a cell of a corresponding network via an uplink. A UE may also be configured to communicate with another UE via a side link. The term "side link" refers to a communication link that may be used for device-to-device (D2D) communication. Therefore, a side link may facilitate communication between a UE and another UE without using a cell.

[0004] When a sidelink is configured, the UE may utilize hybrid automatic repeat request (HARQ) signaling. Generally speaking, HARQ signaling refers to a signaling exchange in which information and / or data is sent from a transmitting device to a receiving device and feedback is provided to the transmitting device in response. The feedback may indicate to the transmitting device whether a retransmission is to be performed. HARQ feedback may also be provided to a cell of the network. Therefore, although information and / or data transmitted directly from a UE to another UE via a sidelink does not pass through a cell, HARQ feedback may be provided to the network via a cell. Summary of the invention

[0005] Some exemplary embodiments relate to a user equipment (UE) having: a transceiver configured to communicate with another UE via a sidelink and to communicate with a cell of a network via an uplink; and a processor communicatively coupled to the transceiver and configured to perform operations. The operations include: receiving hybrid automatic repeat request (HARQ) acknowledgement (ACK) timing parameters from the network; generating a sidelink HARQ-ACK codebook based on a signaling exchange with the other UE, wherein the sidelink HARQ-ACK codebook is constructed in a decreasing order of one or more physical sidelink shared channel (PSSCH) transmission time slots associated with a configured physical sidelink feedback channel (PSFCH) opportunity; and transmitting an indication of the sidelink HARQ-ACK codebook to the cell of the network.

[0006] Other exemplary embodiments relate to a user equipment (UE) having: a transceiver configured to communicate with another UE via a sidelink and to communicate with a cell of a network via an uplink; and a processor communicatively coupled to the transceiver and configured to perform operations. The operations include: receiving an indication that the network does not allocate physical uplink control channel resources (PUCCH) for providing sidelink hybrid automatic repeat request (HARQ) feedback to the network; and transmitting HARQ feedback to the other UE.

[0007] Still other exemplary embodiments relate to a user equipment (UE) having: a transceiver configured to communicate with another UE via a sidelink; and a processor communicatively coupled to the transceiver and configured to perform operations. The operations include: determining candidate physical sidelink feedback channel (PSFCH) resources, wherein the candidate PSFCH resources correspond to a resource pool, and wherein determining the candidate PSFCH resources is based on resource pool configuration information; and transmitting hybrid automatic repeat request (HARQ) feedback on one or more of the PSFCH resources.

[0008] Another exemplary embodiment relates to a user equipment (UE) having: a transceiver configured to communicate with another UE via a side link; and a processor communicatively coupled to the transceiver and configured to perform operations. The operations include: initiating a first resource selection process, wherein the first resource selection process includes a first sensing window and a first resource selection window; transmitting data on one or more resources in the first resource selection window; determining whether an acknowledgment (ACK) has been received in response to transmitting on the one or more resources in the first resource selection window; when the ACK is not received, initiating a second resource selection process, wherein the second resource selection process includes a second sensing window and a second resource selection window; and transmitting the data on one or more resources in the second resource selection window. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 Exemplary network arrangements are shown according to various exemplary embodiments.

[0010] Figure 2 An exemplary UE according to various exemplary embodiments is shown.

[0011] Figure 3 Methods for sidelink HARQ-ACK codebook construction according to various exemplary embodiments are shown.

[0012] Figure 4a An exemplary table of candidate PSSCH transmission opportunities is shown.

[0013] Figure 4b An exemplary scenario illustrating candidate PSSCH transmission opportunities associated with PSFCH is shown.

[0014] Figure 5 Methods for candidate PSFCH resource determination according to various exemplary embodiments are shown.

[0015] Figure 6 Methods of candidate segment resource reselection for retransmission according to various exemplary embodiments are shown.

[0016] Figure 7 An exemplary timeline and process for segment resource reselection according to various exemplary embodiments is shown. DETAILED DESCRIPTION

[0017] The exemplary embodiments may be further understood with reference to the following description and the associated drawings, wherein similar elements have the same reference numerals. The exemplary embodiments relate to implementing a hybrid automatic repeat request (HARQ) mechanism for sidelink communications. As will be explained in more detail below, in a first aspect, the exemplary embodiments relate to providing HARQ feedback for sidelink communications to a cell of a network. In a second aspect, the exemplary embodiments relate to selecting resources to be used to transmit HARQ feedback and perform retransmissions via a sidelink.

[0018] The exemplary embodiments are described with respect to UE. However, reference to UE is provided for illustration purposes only. The exemplary embodiments may be used with any electronic component configured with hardware, software and / or firmware for exchanging information (e.g., control information) and / or data with a network. Therefore, the UE described herein is used to represent any suitable electronic device.

[0019] Exemplary embodiments are also described with reference to side links. The term "side link" generally refers to a communication link between a UE and another UE. A side link provides direct device-to-device (D2D) communication, wherein information and / or data exchanged between a UE and another UE via a side link does not pass through a cell. In some configurations, a single side link provides bidirectional communication between a UE and another UE. In other configurations, a single side link provides unidirectional communication between a UE and another UE. Exemplary embodiments may be applied to bidirectional side links or unidirectional side links.

[0020] Both the Long Term Evolution (LTE) and 5G New Radio (NR) standards support sidelink communications. In some configurations, the network may provide the UE with information indicating how to establish, maintain and / or utilize the sidelink. Therefore, when the information and / or data exchanged through the sidelink does not pass through the cell, the UE and the network may exchange information associated with the sidelink. In other configurations, the sidelink is not controlled by the network. In any configuration, the UE and another UE may still perform a synchronization process, a discovery process and exchange control information corresponding to the sidelink.

[0021] Exemplary embodiments are also described with reference to HARQ signaling. HARQ signaling generally refers to a signaling exchange in which information and / or data are sent from a transmitting device to a receiving device and feedback is provided to the transmitting device in response. Throughout the specification, the term "UE" may be used to represent a transmitting device, and the term "another UE" may be used to represent a receiving device. For example, consider a scenario in which a UE is configured with a side link to another UE. Initially, the UE may transmit information and / or data to another UE via a side link. In response, the UE may receive feedback from another UE. The feedback may indicate whether the other UE successfully received the information and / or data transmitted by the UE. If the feedback indicates that one or more parts of the information and / or data were not successfully received by another UE, the UE may perform a retransmission.

[0022] Throughout the specification, reference may be made to a physical sidelink control channel (PSCCH), a physical sidelink shared channel (PSSCH), and a physical sidelink feedback channel (PSFCH). PSCCH may refer to a communication channel configured to carry control information related to the sidelink between a transmitting device (e.g., a UE) and a receiving device (e.g., another UE). PSSCH may refer to a communication channel configured to carry payload data between a transmitting device and a receiving device. PSFCH may refer to a communication channel configured to carry feedback related to the sidelink between a transmitting device and a receiving device. Feedback may include HARQ feedback, such as acknowledgement (ACK) and negative acknowledgement (NACK).

[0023] Throughout this specification, reference may also be made to a physical uplink control channel (PUCCH). A PUCCH may refer to a communication channel between a UE and a cell of a network. An exemplary embodiment relates to providing HARQ feedback associated with a sidelink to a network via a PUCCH. Thus, a receiving device (e.g., another UE) may be configured to provide HARQ feedback associated with a sidelink to a transmitting device (e.g., a UE) via a PSFCH, and to provide HARQ feedback associated with a sidelink to the network via a PUCCH.

[0024] In a first aspect, an exemplary embodiment relates to constructing a sidelink HARQ-ACK codebook. Those skilled in the art will appreciate that a HARQ-ACK codebook generally refers to a mechanism that can be used to multiplex HARQ feedback. As will be described in more detail below, the sidelink HARQ-ACK codebook is configured to include multiple instances of HARQ feedback related to the sidelink. The sidelink HARQ-ACK codebook can then be reported to a cell of the network via a PUCCH.

[0025] In a second aspect, exemplary embodiments relate to resources to be used for HARQ signaling via a sidelink. As will be described in more detail below, some exemplary embodiments may involve determining candidate PSFCH resources that may be used to provide feedback to a transmitting device. Other exemplary embodiments may involve selecting resources that may be used by a transmitting device to perform retransmissions via a sidelink. The exemplary techniques described herein may be used with currently implemented sidelink HARQ processes, future implementations of sidelink HARQ processes, or independently of other sidelink HARQ processes.

[0026] Figure 1 An exemplary network arrangement 100 according to various exemplary embodiments is shown. The exemplary network arrangement 100 includes UEs 110, 112. Those skilled in the art will appreciate that the UEs 110, 112 may be any type of electronic component configured to communicate via a network, such as a component of a connected car, a mobile phone, a tablet, a smartphone, a phablet, an embedded device, a wearable device, an Internet of Things (IoT) device, etc.

[0027] Throughout the specification, the terms "UE 110", "UE" and "transmitting device" can be used interchangeably. In addition, the terms "UE 112", "additional UE" and "receiving device" can also be used interchangeably. It should also be understood that an actual network arrangement may include any number of UEs used by any number of users. Therefore, the example with two UEs 110, 112 is provided for illustration purposes only.

[0028] UE 110, 112 can communicate directly with one or more networks. In the example of network configuration 100, the networks with which UE 110, 112 can wirelessly communicate are 5G NR radio access network (5G NR-RAN) 120, LTE radio access network (LTE-RAN) 122, and wireless local area network (WLAN) 124. These types of networks support vehicle-to-everything (V2X) and / or sidelink communications. However, UE 110 can also communicate with other types of networks, and UE 110 can also communicate with the network via a wired connection. Therefore, UE 110, 112 may include a 5G NR chipset that communicates with 5G NR-RAN 120, an LTE chipset that communicates with LTE-RAN 122, and an ISM chipset that communicates with WLAN 124.

[0029] 5G NR-RAN 120 and LTE-RAN 122 may be part of cellular networks that may be deployed by cellular providers (e.g., Verizon, AT&T, Sprint, T-Mobile, etc.). These networks 120, 122 may include, for example, cells or base stations (NodeB, eNodeB, HeNB, eNBS, gNB, gNodeB, macrocell base stations, microcell base stations, small cell base stations, femtocell base stations, etc.) configured to send and receive traffic from UEs equipped with appropriate cellular chipsets. WLAN 124 may include any type of wireless local area network (WiFi, hotspot, IEEE 802.11x network, etc.).

[0030] The UEs 110, 112 may be connected to the 5G NR-RAN via a gNB 120A. The gNB 120A may be configured with the necessary hardware (e.g., antenna array), software, and / or firmware to perform massive multiple-input multiple-output (MIMO) functionality. Massive MIMO may refer to a base station configured to generate multiple beams for multiple UEs. Reference to a single gNB 120A is for illustrative purposes only. The exemplary embodiments may apply to any appropriate number of gNBs. The UEs 110, 112 may also be connected to the LTE-RAN 122 via an eNB 122A.

[0031] Those skilled in the art will appreciate that any associated process may be performed for the UE 110, 112 to connect to the 5G NR-RAN 120 and the LTE-RAN 122. For example, as discussed above, the 5G NR-RAN 120 and the LTE-RAN 122 may be associated with a particular cellular provider at which the UE 110, 112 and / or its user has a contract and credential information (e.g., stored on a SIM card). Upon detecting the presence of the 5G NR-RAN 120, the UE 110, 112 may transmit the corresponding credential information in order to associate with the 5G NR-RAN 120. More specifically, the UE 110, 112 may be associated with a particular base station (e.g., gNB 120A of the 5G NR-RAN 120, eNB 122A of the LTE-RAN 122).

[0032] UE 110, 112 may also communicate directly with each other using a side link. The side link is a direct D2D communication link. Therefore, information and / or data transmitted directly to another endpoint (e.g., UE 110 or UE 112) does not pass through a cell (e.g., gNB 120A, eNB 122A). In some embodiments, UE 110, 112 may receive information from the cell about how to establish, maintain and / or utilize the side link. Therefore, the network (e.g., 5G NR-RAN 120, LTE-RAN 122) may control the side link. In other embodiments, UE 110, 112 may control the side link. Regardless of how the side link is controlled, UE 110, 112 may simultaneously maintain a downlink / uplink to the currently occupied cell (e.g., gNB 120A, eNB 122A) and a side link to another UE.

[0033] In addition to the networks 120, 122, and 124, the network arrangement 100 includes a cellular core network 130, the Internet 140, an IP multimedia subsystem (IMS) 150, and a network service backbone 160. The cellular core network 130 can be viewed as an interconnected collection of components that manage the operation and traffic of the cellular network. The cellular core network 130 also manages the traffic flowing between the cellular network and the Internet 140. The IMS 150 can be generally described as an architecture for delivering multimedia services to the UE 110 using the IP protocol. The IMS 150 can communicate with the cellular core network 130 and the Internet 140 to provide multimedia services to the UE 110. The network service backbone 160 communicates directly or indirectly with the Internet 140 and the cellular core network 130. The network service backbone 160 can be generally described as a set of components (e.g., servers, network storage arrangements, etc.) that implement a set of services that can be used to extend the functionality of the UE 110 to communicate with various networks.

[0034] Figure 2An exemplary UE 110 is shown according to various exemplary embodiments. Figure 1 100 is used to describe the UE 110. The UE 110 may include a processor 205, a memory arrangement 210, a display device 215, an input / output (I / O) device 220, a transceiver 225, an antenna panel 230, and other components 235. The other components 235 may include, for example, a SIM card, an embedded SIM (eSIM), an audio input device, an audio output device, a power source, a data acquisition device, a port for electrically connecting the UE 110 to other electronic devices, etc. Figure 2 The UE 110 shown may also represent UE 112.

[0035] The processor 205 may be configured to execute multiple engines of the UE 110. For example, the engines may include a sidelink HARQ engine 235. The sidelink HARQ engine 235 may perform various operations related to using HARQ for the sidelink. These operations may include, but are not limited to, providing an indication of sidelink HARQ feedback to the network, selecting resources for delivering HARQ feedback to the transmitting device, selecting resources for retransmission, etc.

[0036] The above engines are each an application (e.g., a program) executed by the processor 205 for exemplary purposes only. The functions associated with the engine may also be represented as an independent combined component of the UE 110, or may be a modular component coupled to the UE 110, for example, an integrated circuit with or without firmware. For example, an integrated circuit may include an input circuit for receiving a signal and a processing circuit for processing the signal and other information. The engine may also be embodied as an application or multiple separate applications. In addition, in some UEs, the functionality described for the processor 205 is shared between two or more processors such as a baseband processor and an application processor. The exemplary embodiments may be implemented in any of these or other configurations of the UE.

[0037] The memory arrangement 210 may be a hardware component configured to store data related to operations performed by the UE 110. The display device 215 may be a hardware component configured to display data to a user, and the I / O device 220 may be a hardware component that enables user input. The display device 215 and the I / O device 220 may be separate components or may be integrated together (such as a touch screen). The transceiver 225 may be a hardware component configured to establish a connection with the 5G NR-RAN 120, the WLAN 122, etc. Thus, the transceiver 225 may operate on multiple different frequencies or channels (e.g., a continuous frequency group).

[0038] For downlink communications, UE 110 may be configured to provide a HARQ-ACK codebook to a corresponding cell of the network. The cell may provide HARQ-ACK feedback timing information to UE 110 in downlink control information (DCI). Using the HARQ-ACK feedback timing information, UE 110 may multiplex downlink HARQ-ACK on the allocated PUCCH resources. As described above, the exemplary embodiment relates to constructing a sidelink HARQ-ACK codebook for a cell to be provided to the network via PUCCH. In order to construct the sidelink HARQ-ACK codebook, various modifications may be made to the process that can be used to construct the downlink HARQ-ACK codebook. Therefore, when describing the construction of the sidelink HARQ-ACK codebook, the exemplary embodiment may refer to the terms conventionally associated with the construction of the downlink HARQ-ACK codebook.

[0039] Figure 3 A method 300 for sidelink HARQ-ACK codebook construction according to various exemplary embodiments is shown. Figure 2 UE 110 and Figure 1 The method 300 is described with reference to the network arrangement 100 .

[0040] In method 300, within the context of sidelink HARQ signaling, UE 110 may represent a transmitting device. For example, UE 110 and UE 112 may establish a sidelink. UE 110 may transmit data to UE 112 via PSSCH. In response, UE 112 may provide HARQ feedback to UE 110 via PSFCH. UE 110 may also have a connection to a cell of a corresponding network. For example, UE 110 may camp on gNB 120A of 5G NR-RAN 120. Method 300 will be described with reference to UE 110 generating a sidelink HARQ-ACK codebook representing HARQ feedback received from UE 112. The sidelink HARQ-ACK codebook may then be provided by UE 110 to the currently camped cell via PUCCH.

[0041] UE 110 may receive sidelink HARQ-ACK feedback timing information from the network at 305. The sidelink HARQ-ACK feedback timing information may provide a basis for generating a sidelink HARQ-ACK codebook at UE 110.

[0042] HARQ-ACK feedback timing information may be received from the network in the DCI. For example, DCI format 3_0 may be configured to include a PSFCH to HARQ feedback timing indicator. However, reference to DCI format 3_0 is provided for illustrative purposes only. The exemplary embodiments may be applied to include HARQ-ACK feedback timing information in any suitable type of DCI or signaling exchange performed with the network.

[0043] Similar to the K1 parameter used for downlink HARQ-ACK codebook construction, which indicates the time slot offset between physical downlink shared channel (PDSCH) reception and PUCCH transmission, the PSFCH to HARQ feedback timing indicator indicates the time slot duration between the last PSFCH opportunity and PUCCH transmission. An example of the PSFCH to HARQ feedback timing indicator is shown in Figure 4b An exemplary scenario 450 is shown.

[0044] There may be a situation where the network does not provide PUCCH resources for the sidelink HARQ-ACK codebook. In the absence of PUCCH resources, UE 110 may not be able to report sidelink HARQ-ACK feedback to the network. In these types of scenarios, the network may indicate to UE 110 that there are no PUCCH resources allocated for sidelink HARQ-ACK feedback. In some embodiments, the indication may be provided in an information element (IE). To provide an example, a PUCCH-config-SL IE may be included in DCI format 3_0, which indicates to UE 110 whether PUCCH resources are configured to sidelink HARQ feedback. In other embodiments, the indication may be included in a field of DCI. To provide an example, a field in DCI format 3_0 may be configured to include information related to providing sidelink HARQ feedback in the uplink. A specific type of element may be specified to indicate that there are no PUCCH resources allocated for sidelink HARQ-ACK feedback. In this example, a field in DCI format 3_0 may be configured to include up to eight elements. If one of the elements is set to an infinite value, this may indicate to UE 110 that there are no PUCCH resources allocated for sidelink HARQ-ACK feedback. However, the above example is provided for illustrative purposes only. The exemplary embodiments may be applied to networks that utilize any suitable mechanism to indicate to UE 110 that there are no PUCCH resources allocated for sidelink HARQ-ACK feedback.

[0045] In 310, UE 110 generates a sidelink HARQ-ACK codebook. As described above, the sidelink HARQ-ACK codebook may be generated using multiple PSFCH to HARQ feedback timing indicators, each corresponding to a different PSFCH opportunity. The sidelink HARQ-ACK codebook may be constructed in descending order of the multiple PSFCH to HARQ feedback timing indicators.

[0046] It should be understood that, unlike the downlink HARQ-ACK codebook construction that depends on the downlink subcarrier spacing, the sidelink HARQ-ACK codebook construction uses the sidelink subcarrier spacing. In addition, to determine the time slot configuration for the sidelink, UE110 may utilize sidelink parameters similar to the cell-specific high-layer parameters "TDD-UL-DL-ConfigurationCommon" and "TDD-UL-DL-ConfigurationDedicated".

[0047] When constructing the downlink HARQ-ACK codebook, for each K1 value, the configured PDSCH time domain resource allocation list provides a table for candidate PDSCH reception. PDSCH resources are independent of sidelink HARQ signaling. Therefore, when constructing the sidelink HARQ-ACK codebook, the PDSCH time resources are replaced by the PSSCH time resources associated with the last PSFCH opportunity.

[0048] The timeslot offset between the PSSCH and its corresponding PFSCH is configured per resource pool. The timeslot offset may also depend on the resource pool logical timeslot and PSFCH periodicity configuration. The time mapping from the PSFCH opportunity to its associated PSSCH may be a one-to-many mapping. In addition, the pre-configured PSSCH time resources associated with the last PSFCH opportunity provide a table for candidate PSSCH transmissions. Thus, each possible PSSCH transmission timeslot leading to a PSFCH opportunity at a given offset from the PUCCH is used as a candidate opportunity to be further processed.

[0049] The sidelink HARQ-ACK codebook may be constructed in descending order of the PSSCH transmission slots associated with the configured PSFCH opportunities. For downlink communications, the K0 parameter representing the duration between a downlink grant (e.g., DCI) and the corresponding PDSCH reception may be used for HARQ-ACK codebook construction. For sidelink HARQ-ACK codebook construction, K0 may be represented by the duration (e.g., slot) between the PSSCH and the corresponding PSFCH.

[0050] Figure 4aAn exemplary table 400 of candidate PSSCH transmission opportunities is shown. The exemplary table 400 includes a column 405 that displays a row index value. The row index value may be indicated in the time domain resource allocation field of the DCI and corresponds to the PSSCH time domain resource allocation. The exemplary table 400 also includes a column 410 that displays the duration (e.g., K0) between the PSSCH and the PSFCH for each row number. The duration between the PSSCH and the PSFCH may be expressed in units of time slots.

[0051] Figure 4b An exemplary scenario 450 illustrating candidate PSSCH transmission opportunities associated with PSFCH is shown. The exemplary scenario 450 shows that PUCCH transmission 455 is scheduled for the first time and PSFCH transmission 460 is scheduled for the second time. The duration between PSFCH 460 and PUCCH 455 may be indicated by the PSFCH to HARQ feedback timing indicator included in the DCI received in 305. This duration is similar to the K1 value used in the downlink HARQ-ACK codebook construction.

[0052] In the exemplary scenario 450, the PSFCH 460 is shown as being included in a time slot 495, which is one of the six time slots 490-495 shown in the example. In addition, in the example, time slot 490 is shown as including a PSSCH opportunity 480, time slot 491 is shown as including a PSSCH opportunity 481, time slot 492 is shown as including a PSSCH opportunity 482, and time slot 493 is shown as including a PSSCH opportunity 483. The sidelink HARQ feedback corresponding to each PSSCH opportunity 480-483 will be included in the associated PSFCH transmission 460 to be received by the UE 110 in response to transmitting at the PSSCH opportunity 480-483. The HARQ feedback corresponding to each PSSCH opportunity 480-483 will also be included in the PUCCH transmission 455 to be provided by the UE 110 to the cell of the corresponding network.

[0053] As described above, the sidelink K0 value may represent the duration between a PSSCH opportunity and a PSFCH. In exemplary scenario 450, the sidelink K0 value for PSSCH opportunity 480 is equal to five time slots, the sidelink K0 value for PSSCH opportunity 481 is equal to four time slots, the sidelink K0 value for PSSCH opportunity 482 is equal to three time slots, and the sidelink K0 value for PSSCH opportunity 483 is equal to two time slots.

[0054] Returning to method 300, from the perspective of UE 110, the sidelink HARQ-ACK codebook may be a collection of data representing multiple instances of HARQ feedback for the sidelink with UE 112. The multiple instances of HARQ feedback may be configured as a matrix or a bitmap.

[0055] If simultaneous PSSCH transmissions in a single time slot are configured, UE 110 may generate the sidelink HARQ-ACK codebook using the frequency first, time second rule. For example, UE 110 may be configured with multiple side links, and therefore, multiple PSSCH opportunities may occur in the same time slot. Each PSSCH may be configured to be transmitted at a different frequency. Therefore, each instance of sidelink HARQ feedback may be associated with a time slot (e.g., time) and a frequency. There may be multiple PSSCH opportunities in each time slot, but not on each frequency. Therefore, all candidate PSSCH opportunities with different frequency positions in the same time slot are first packaged in the sidelink HARQ-ACK codebook.

[0056] In 315, a representation of the sidelink HARQ-ACK codebook is transmitted to the network. For example, UE 110 may transmit a matrix on a PUCCH resource to a currently camped cell, the matrix including an indication of multiple instances of HARQ feedback for the sidelink with UE 112. Method 300 then ends.

[0057] The method 300 is described with reference to constructing a Type 1 HARQ-ACK codebook (e.g., semi-static) to report sidelink HARQ feedback to the network. However, those skilled in the art will appreciate that similar techniques may be used to construct a Type 2 HARQ-ACK codebook (e.g., dynamic) to report sidelink HARQ feedback to the network.

[0058] Another aspect of the exemplary embodiments relates to determining candidate PSFCH resources that may be used to provide feedback to a transmitting device. In other words, how a receiving device determines network resources to use for PSFCH transmissions.

[0059] Figure 5 A method 500 for candidate PSFCH resource determination according to various exemplary embodiments is shown. Figure 2 UE 110 and Figure 1 The method 500 is described with reference to the network arrangement 100 .

[0060] In method 500, within the context of sidelink HARQ signaling, UE 110 may represent a receiving device. For example, UE 110 and UE 112 may establish a sidelink. UE 112 may transmit data to UE 110 via PSSCH. In response, UE 110 may provide HARQ feedback to UE 112 via PSFCH.

[0061] In 505, UE 110 determines the type of side link configuration. The type of side link configuration may include, but is not limited to, unicast option 1, unicast option 2, multicast option 1, multicast option 2, and resource pool. In some embodiments, the determination of the type of side link configuration may be based on information received from a cell of the network in DCI and / or radio resource control (RRC) signaling. In other embodiments, the determination of the type of side link configuration may be based on information received from another UE (e.g., UE 112) during a synchronization process, a discovery process, or any other process for exchanging control information between UEs. The above examples are provided for illustrative purposes only, and those skilled in the art will understand the type of information that UE 110 can use to determine the type of side link configuration.

[0062] Multicast Option 1 can be characterized as a NACK-only scheme. For example, the receiving device is configured to transmit a HARQ NACK on the PSFCH if the receiving device fails to decode at least a portion of a transport block received on the PSSCH. Otherwise, the receiving device does not provide any HARQ feedback on the PSFCH.

[0063] Unicast and multicast Option 2 can be characterized as an ACK / NACK scheme. For example, the receiving device is configured to transmit a HARQ ACK on the PSFCH if the receiving device is able to decode a transport block received on the PSSCH. The receiving device is configured to transmit a HARQ NACK on the PSFCH if the receiving device fails to decode at least a portion of a transport block received on the PSSCH.

[0064] A resource pool may refer to a set of time and frequency resources that may be used for sidelink transmission and reception. A receiving device may be (pre-)configured with one or more resource pools.

[0065] In 510, UE 110 determines candidate PSFCH resources based on the type of sidelink configuration. Candidate PSFCH is a set of physical resource blocks (PRBs) that can be used to provide HARQ feedback to a transmitting device (e.g., UE 112). For unicast and multicast option 1, candidate PSFCH resources are determined based on the starting subchannel and time slot for PSSCH. For multicast option 2, candidate PSFCH resources are determined based on the subchannel and time slot for PSSCH. For resource pool configuration, an indication may be provided to UE 110 as to whether candidate PSFCH resources are determined based on i) the starting subchannel and time slot for PSSCH or ii) the subchannel and time slot for PSSCH.

[0066] In 515, UE 110 transmits HARQ feedback to a transmitting device (e.g., UE 112) on the determined PSFCH resources. For example, the HARQ feedback may be transmitted using the PRBs determined in 510. Within a set of PRBs configured for PSFCH, a first set of PRBs is associated with a first subchannel in a first slot associated with a PSFCH slot, a second set of PRBs is associated with a first subchannel in a second slot associated with a PSFCH slot, and so on. Subsequently, method 500 ends.

[0067] Another aspect of the exemplary embodiments relates to selecting network resources that can be used for retransmission. In other words, how a sending device selects resources for retransmission to a receiving device.

[0068] Figure 6 A method 600 of reselecting candidate segment resources for retransmission is shown according to various exemplary embodiments. Figure 2 UE 110 and Figure 1 The method 600 is described with reference to the network arrangement 100 of FIG.

[0069] In method 600, within the context of sidelink HARQ signaling, UE 110 may represent a transmitting device. For example, UE 110 and UE 112 may establish a sidelink. UE 110 may transmit data to UE 112 via PSSCH. In response, UE 112 may provide HARQ feedback to UE 110 via PSFCH. If UE 110 receives NACK (or ambiguous feedback), UE 110 may be triggered to perform a retransmission on PSSCH.

[0070] Figure 7 An exemplary timeline and process for segment resource reselection is shown. Figure 7 It is intended to supplement the description of method 600 .

[0071] At 605, a resource selection process is initiated for the first segment. Resource selection may utilize a sensing window having a predetermined duration. During the sensing window, UE 110 may generate a set of resource candidates in a corresponding resource selection window. Where N 最大值 Indicates the number of resources to be selected in the resource selection window. N 最大值 Indicates the maximum number of resources that can be reserved in the sidelink control information (SCI) for a transport block. The first segment may represent both the first sensing window and the first selection window. As described below, if an ACK is not received in response to one or more transmissions performed in the first segment, an additional segment may be utilized.

[0072] The resource selection window can be [n1+T 1，1 , n1+T1，2 ], where n1 represents the time when a new transport block is ready for delivery. 1，2 The lower bound of may be based on factors including, but not limited to, data priority, remaining packet delay budget, (pre-)configured number of retransmissions N, and N 最大值 Generally speaking, the larger the N and the smaller the N 最大值 The smaller the T 1，2 Similarly, the smaller N and the larger N 最大值 The smaller the T 1，2 .exist Figure 7 In the example shown, the (pre-)configured number of retransmissions N is equal to eight.

[0073] In 610, UE 110 transmits on one or more of the selected resources in the first selection window. For example, if three resources are reserved in the selection window, UE 110 may initially transmit on the first selected resource in the first segment. Then, if possible and an ACK has not been received for the transmission on the first selected resource, UE 110 may transmit on the second selected resource in the first segment. If an ACK has been received, there is no need to retransmit on the second selected resource because the receiving device has successfully received the data payload. Then, if possible and an ACK has not been received for the transmission on the second selected resource, UE 110 may transmit on the third selected resource. Figure 7 In the example shown, N 最大值 is set to three. Thus, three resources m1, m2, m3 are shown as reserved in the selection window for the first segment.

[0074] In 615, UE 110 determines whether an ACK has been received in response to one or more transmissions performed in the first selection window. As described above, if an ACK has been received, this indicates that the receiving device (e.g., UE 112) has successfully received the data payload. Therefore, if an ACK has been received, method 600 ends. If an ACK has not been received, method 600 continues to 620. Figure 7 In the example shown, no ACK is received for any transmission performed in the resource selection window for the first segment. In contrast, a NACK is depicted as being received in response to one or more transmissions performed in the selection window for the first segment.

[0075] At 620, a resource selection process for the second segment is initiated. Thus, a sensing window for the second segment and a selection window for the second segment are configured. UE 110 may be configured to perform the j-th selection process. Where j may represent any suitable number of segments (e.g., 2, 3, 5, 10, 20, etc.). Figure 7 In the example shown, three sectors are shown.

[0076] In some embodiments, the resources for the first segment may have been reserved in the SCI of the previous transmission block. Therefore, in these types of scenarios, there is no need to perform a resource selection process. However, if an ACK is not received in response to a transmission performed on the reserved resources, 615-625 of method 600 may still be used for retransmissions.

[0077] UE 110 may be configured with a transmission budget. The number of resources selected in the second segment may take into account the transmission budget. For example, min{N 最大值 , N rem} resources. rem represents the remaining transmission budget and is the difference between the (pre-)configured number of retransmissions N and the total number of retransmissions that have occurred for the existing transport blocks (e.g., data subject to retransmission). 最大值 , N rem} is within the resource selection window for the second segment. The SCI for transmissions occurring in segments other than the first segment does not include a resource reservation period. In addition, there is no time difference restriction between segment j-1 and the current segment. Therefore, in Figure 7 In the example shown, the first segment overlaps the second segment, and the second segment overlaps the third segment.

[0078] In 625, UE 110 transmits on one or more of the selected resources in the second selection window. For example, if three resources are reserved in the second selection window, UE 110 may initially transmit on the first selected resource in the second segment. Then, if possible and an ACK has not been received for the transmission on the first selected resource, UE 110 may transmit on the second selected resource in the second segment. If an ACK has been received, there is no need to retransmit on the second selected resource because the receiving device has successfully received the data payload. Then, if possible and an ACK has not been received for the transmission on the second selected resource, UE 110 may transmit on the third selected resource. Figure 7 In the example shown, three resources m4, m5, m6 are shown as reserved in the selection window α for the first segment. As described above, the number of selected resources may be based on min{N 最大值 , Nrem}.

[0079] The method 600 then returns to 615 where the UE 110 determines whether an ACK has been received. The process may repeat itself until an ACK is received or a maximum number of retransmissions have been performed. Figure 7 In the example shown, no ACK is received in response to any transmission performed in the second selection window. Therefore, a selection process for the third segment is initiated. However, as described above, the (pre)configured number of retransmissions N is equal to eight. Since six resources have been used for retransmissions, e.g., m1, m2, m3, m4, m5, m6, only two resources are selected in the third selection window. It will be appreciated by those skilled in the art that similar schemes can be applied to both retransmissions based on HARQ feedback and blind retransmissions.

[0080] Other aspects of the exemplary embodiments relate to selecting a UE to be used as a synchronization source. In 5G NR, signaling via a physical sidelink broadcast channel (PSBCH) may include various components, including but not limited to DFN, TDD configuration indication, slot index, coverage indicator, cyclic redundancy check (CRC), payload, etc. In this example, the PSBCH includes a 10-bit DFN, a 12-bit TDD configuration indication, a 7-bit slot index, a 1-bit coverage indicator, a reserved bit, and a 24-bit CRC, with a total payload size of 56 bits.

[0081] The synchronization source priority can have two configurations: Global Navigation Satellite System (GNSS) based synchronization or gNB / eNB based synchronization. In GNSS based synchronization, the priority of the synchronization source can be ordered as follows: GNSS has the highest priority, UEs directly synchronized to GNSS have the second highest priority, UEs indirectly synchronized to GNSS have the third highest priority, gNB / eNB has the fourth highest priority, UEs directly synchronized to gNB / eNB have the fifth highest priority, UEs indirectly synchronized to gNB / eNB have the sixth highest priority, and the remaining UEs have the lowest priority.

[0082] In gNB / eNB based synchronization, the priorities of synchronization sources may be ranked as follows: gNB / eNB has the highest priority, UEs directly synchronized to gNB / eNB have the second highest priority, UEs indirectly synchronized to gNB / eNB have the third highest priority, GNSS has the fourth highest priority, UEs directly synchronized to GNSS have the fifth highest priority, UEs indirectly synchronized to GNSS have the sixth highest priority, and the remaining UEs have the lowest priority.

[0083] Therefore, in GNSS-based synchronization or gNB / eNB-based synchronization, another UE can be selected as the synchronization source. In LTE Vehicle-to-Everything (V2X), the UE associated with the highest sidelink reference signal received power (RSRP) can be selected as the synchronization source. In NR V2X, if the UE with the lowest sidelink synchronization signal (SLSS) ID is associated with a sidelink RSRP above a threshold, then this UE can be selected as the synchronization source. This allows multiple independent clusters to be merged.

[0084] If two independent clusters have the same SLSSID, one of the following schemes (or a combination thereof) may be implemented. In the first scheme, the UE with the strongest sidelink RSRP may be selected as the synchronization source. In the second scheme, the UE associated with the in-coverage indicator of PSBCH ON may be selected as the synchronization source. In the third scheme, the UE with the smallest number of hops may be selected as the synchronization source (if the number of hops is included in the PSBCH). The UE with the smallest number of hops may be selected because the smallest number of hops indicates that the UE is closer to an independent UE-type synchronization source with a smaller timing offset. In the fourth scheme, the UE with the largest number of hops (if the number of hops is included in the PSBCH) may be selected as the synchronization source. The UE with the largest number of hops may be selected because the largest number of hops indicates a larger cluster that will affect the coverage area.

[0085] Example

[0086] A first embodiment includes a user equipment (UE) comprising: a transceiver configured to communicate with another UE via a sidelink and to communicate with a cell of a network via an uplink; and a processor communicatively coupled to the transceiver and configured to perform operations. The operations include: receiving an indication that the network does not allocate physical uplink control channel resources (PUCCH) for providing sidelink hybrid automatic repeat request (HARQ) feedback to the network; and transmitting HARQ feedback to the other UE.

[0087] A second embodiment comprises the UE of the first embodiment, wherein the indication is received via downlink control information (DCI).

[0088] The third embodiment includes the UE of the second embodiment, wherein the DCI is format 3_0 DCI.

[0089] A fourth embodiment includes a user equipment (UE), the user equipment comprising: a transceiver, the transceiver configured to communicate with another UE via a side link; and a processor, the processor being communicatively coupled to the transceiver and configured to perform operations. The operations include: initiating a first resource selection process, wherein the first resource selection process includes a first sensing window and a first resource selection window; transmitting data on one or more resources in the first resource selection window; determining whether an acknowledgment (ACK) has been received in response to transmitting on the one or more resources in the first resource selection window; when the ACK is not received, initiating a second resource selection process, wherein the second resource selection process includes a second sensing window and a second resource selection window; and transmitting the data on one or more resources in the second resource selection window.

[0090] The fifth embodiment includes the UE of the fourth embodiment, wherein the operation further includes: generating a set of resource candidates in the corresponding resource selection window, wherein N 最大值 Indicates the maximum number of resource candidates reserved in the Sidelink Control Information (SCI) for a transport block.

[0091] A sixth embodiment includes the UE of the fourth embodiment, wherein the size of the first resource selection window is based on one of a time when a new transport block is ready for delivery, a data priority, a remaining packet delay budget, or a configured number of retransmissions.

[0092] Those skilled in the art will appreciate that the exemplary embodiments described above may be implemented with any suitable software configuration or hardware configuration or combination thereof. Exemplary hardware platforms for implementing the exemplary embodiments may include, for example, Intel x86-based platforms with compatible operating systems, Windows OS, Mac platforms and MAC OS, mobile devices with operating systems such as iOS, Android, etc. In other examples, the exemplary embodiments of the above methods may be embodied as a program including lines of code stored on a non-transitory computer-readable storage medium, which, when compiled, may be executed on a processor or microprocessor.

[0093] Although this patent application describes various combinations of various embodiments each having different features, those skilled in the art will understand that any feature of an embodiment may be combined with features of other embodiments in any manner not publicly denied or with features that are not functionally or logically inconsistent with the operation or function of the device of the embodiments disclosed in the present invention.

[0094] It is understood that the use of personally identifiable information should be subject to privacy policies and practices that are generally recognized to meet or exceed industry or government requirements for maintaining user privacy. Specifically, personally identifiable information data should be managed and processed to minimize the risk of unintentional or unauthorized access or use, and the nature of the authorized use should be clearly stated to users.

[0095] It will be apparent to those skilled in the art that various modifications may be made to the present disclosure without departing from the spirit or scope of the present disclosure. Therefore, the present disclosure is intended to cover modifications and variations of the present disclosure, provided that these modifications and variations are within the scope of the appended claims and their equivalents.

Claims

1. A method comprising: receiving a physical sidelink feedback channel (PSFCH) to hybrid automatic repeat request (HARQ) feedback timing indicator from a network via downlink control information (DCI) format 3_0; generating an indication of a sidelink HARQ-ACK codebook for one or more physical sidelink shared channel (PSSCH) transmissions associated with a configured physical sidelink feedback channel (PSFCH) opportunity; as well as Based on the PSFCH to HARQ feedback timing indicator of DCI format 3_0, an indication of the sidelink HARQ-ACK codebook is sent to the network in the time slot.

2. The method of claim 1 , wherein the indication of the sidelink HARQ-ACK codebook is also sent in the time slot based on a configured PSFCH opportunity.

3. The method of claim 1 , wherein the indication of the sidelink HARQ-ACK codebook is sent to the network via a physical uplink control channel (PUCCH).

4. The method according to claim 3, further comprising: The receive PUCCH resource is allocated to transmit an indication of the sidelink HARQ-ACK codebook.

5. The method of claim 1, wherein the PSFCH to HARQ feedback timing indicator of the DCI format 3_0 includes a plurality of time slots.

6. The method of claim 1, wherein the sidelink HARQ-ACK codebook comprises a semi-static codebook.

7. The method of claim 1, wherein the sidelink HARQ-ACK codebook comprises a type 1 codebook or a type 2 codebook.

8. A processor configured to: receiving a physical sidelink feedback channel (PSFCH) to hybrid automatic repeat request (HARQ) feedback timing indicator from a network via downlink control information (DCI) format 3_0; generating an indication of a sidelink HARQ-ACK codebook for one or more physical sidelink shared channel (PSSCH) transmissions associated with a configured physical sidelink feedback channel (PSFCH) opportunity; and Based on the PSFCH to HARQ feedback timing indicator of the DCI format 3_0, configure the indication of the sidelink HARQ-ACK codebook for transmission to the network in a time slot.

9. The processor of claim 8, wherein the indication of the sidelink HARQ-ACK codebook is also sent in the time slot based on a configured PSFCH opportunity.

10. The processor of claim 8, wherein the indication of the sidelink HARQ-ACK codebook is sent to the network via a physical uplink control channel (PUCCH).

11. The processor of claim 10, further configured to: The receive PUCCH resource is allocated to transmit an indication of the sidelink HARQ-ACK codebook.

12. The processor of claim 8, wherein the PSFCH to HARQ feedback timing indicator of the DCI format 3_0 comprises a plurality of time slots.

13. The processor of claim 8, wherein the sidelink HARQ-ACK codebook comprises a semi-static codebook.

14. The processor of claim 8, wherein the sidelink HARQ-ACK codebook comprises a type 1 codebook or a type 2 codebook.

15. A user equipment (UE), comprising: a transceiver configured to communicate with another UE via a sidelink and with a network via an uplink; as well as a processor communicatively coupled to the transceiver and configured to: receiving a physical sidelink feedback channel (PSFCH) to hybrid automatic repeat request (HARQ) feedback timing indicator from the network via downlink control information (DCI) format 3_0; as well as generating an indication of a sidelink HARQ-ACK codebook for one or more physical sidelink shared channel (PSSCH) transmissions associated with a configured physical sidelink feedback channel (PSFCH) opportunity, The transceiver is configured to send an indication of the sidelink HARQ-ACK codebook to the network in a time slot based on the PSFCH to HARQ feedback timing indicator of the DCI format 3_0.

16. The UE of claim 15, wherein the indication of the sidelink HARQ-ACK codebook is also sent in the time slot based on a configured PSFCH opportunity.

17. The UE of claim 15, wherein the indication of the sidelink HARQ-ACK codebook is sent to the network via a physical uplink control channel (PUCCH).

18. The UE according to claim 17, wherein the processor is further configured to: The receive PUCCH resource is allocated to transmit an indication of the sidelink HARQ-ACK codebook.

19. The UE of claim 15, wherein the PSFCH to HARQ feedback timing indicator of the DCI format 3_0 includes a plurality of time slots.

20. The UE of claim 15, wherein the sidelink HARQ-ACK codebook comprises a semi-static codebook.

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