Apparatus and method for allocating resources for sidelink positioning

Abstract

Apparatuses and methods for allocating resources for sidelink positioning are disclosed. For example, a UE (120a) is disclosed for transmitting an allocation of time and frequency resources for the transmission of one or more sidelink positioning reference signals (SL-PRSs), for example, for the transmission of one or more sidelink positioning reference signals (SL-PRSs). The UE (120a) is configured to transmit the allocation using a two-stage allocation, the two-stage allocation includes a first-stage allocation of one or more first time and frequency resources of a plurality of time and frequency resources having a first granularity and a second-stage allocation of one or more second time and frequency resources of the plurality of time and frequency resources having a second granularity, the one or more second time and frequency resources are a subset of the one or more first time and frequency resources.

Description

Technical Field

[0001] The present disclosure relates to sidelink communications in a wireless communication network. More particularly, the present disclosure relates to an apparatus and method for allocating resources for sidelink positioning in a wireless communication network. Background Art

[0002] Since Release 12 of the Long-Term Evolution (LTE) of the 3rd Generation Public Partnership (3GPP) standards, communications between mobile devices (also known as user equipment (UE)) have been standardized in the form of sidelink (SL) communications. Resources for sidelink communications can be allocated by the network if the UE is within network coverage and is using licensed spectrum, or can be allocated by each UE in an autonomously distributed manner when the UE is out of network coverage or is using unlicensed spectrum.

[0003] Some vehicle-to-everything (V2X) and public safety use cases can benefit from sidelink positioning, which is based on the transmission and reception of sidelink positioning reference signals (SL-PRS). The 3rd Generation Partnership Project (3GPP) is currently studying SL positioning in its Release 18 (Rel.18) as part of a study project to extend and improve new radio (NR) positioning. Summary of the Invention

[0004] An object of the present disclosure is to provide an apparatus and method for allocating time and frequency resources for transmission of SL-PRS in a wireless communication network.

[0005] The above and other objects are achieved by the subject matter claimed in the independent claims. Other implementations are apparent from the dependent claims, the description and the drawings.

[0006] According to a first aspect, a user equipment (UE) is provided for sending a time and frequency resource allocation, the time and frequency resource allocation being used for the transmission of one or more sidelink positioning reference signals (SL-PRS). The UE is used to send the allocation using two-level allocation, the two-level allocation comprising a first-level allocation indicating one or more first time and frequency resources in a plurality of time and frequency resources with a first granularity and a second-level allocation indicating one or more second time and frequency resources in the plurality of time and frequency resources with a second granularity, wherein the one or more second time and frequency resources are a subset of the one or more first time and frequency resources. As used herein, the one or more second time and frequency resources being a subset of the one or more first time and frequency resources includes the following case: the one or more second time and frequency resources include all of the one or more first time and frequency resources, that is, the first time and frequency resource and the second time and frequency resource are the same.

[0007] In another possible implementation, the UE is configured to send first-level sidelink control information (SCI), where the first-level SCI includes the first-level allocation.

[0008] In another possible implementation, the UE is configured to send second-level sidelink control information SCI, where the second-level SCI includes the second-level allocation.

[0009] In another possible implementation, the first-level SCI includes information indicating the existence of the second-level allocation.

[0010] In another possible implementation, the first-level SCI further includes information about the format of the second-level SCI, and / or one or more reserved bits of the first-level SCI include the information indicating the existence of the second-level allocation.

[0011] In another possible implementation, the multiple time and frequency resources include multiple time slots and multiple sub-channels.

[0012] In another possible implementation, the UE is configured to send the two-level allocation, ie, the first allocation and the second allocation, within the multiple time slots and one or more subchannels of the multiple subchannels.

[0013] In another possible implementation, the UE is configured to send control information associated with the one or more SL-PRSs in the multiple time slots carrying the two-level allocation and the one or more subchannels of the multiple subchannels.

[0014] In another possible implementation, the UE is configured to send the two-stage allocation in a time slot prior to one or more time slots, where the time slot includes the first time and frequency resources indicated by the two-stage allocation.

[0015] In another possible implementation manner, the UE is configured to send the two-stage allocation in a time slot of the first time and frequency resource including the two-stage allocation indication.

[0016] In another possible implementation, the UE is configured to send the one or more SL-PRSs on the second time and frequency resources indicated by the second level allocation, that is, using the second time and frequency resources indicated by the second level allocation.

[0017] In another possible implementation, the UE is used to send the one or more SL-PRSs on the second time and frequency resources indicated by the first level allocation and the second level allocation, that is, using the second time and frequency resources indicated by the first level allocation and the second level allocation.

[0018] In another possible implementation, the UE is configured to send the time and frequency resource allocation using the two-stage allocation, and the two-stage allocation is used for another UE to send one or more SL-PRSs of the one or more SL-PRSs.

[0019] In another possible implementation, the first granularity is a sub-channel of a time slot, that is, a sub-channel of a size of a time slot.

[0020] In another possible implementation, the plurality of time and frequency resources include one or more configured or pre-configured semi-dedicated SL-PRS resources with the second granularity.

[0021] In another possible implementation, the multiple time and frequency resources include one or more configured or pre-configured semi-dedicated SL-PRS resources, wherein the UE and / or another UE is used to send the one or more SL-PRS on one or more SL-PRS resources among the one or more SL-PRS resources, i.e., using one or more SL-PRS resources among the one or more SL-PRS resources.

[0022] In another possible implementation, the UE is configured to send the two-level allocation in one or more time and frequency resources among the multiple time and frequency resources that are different from the one or more SL-PRS resources.

[0023] In another possible implementation, the UE is used to send data in one or more time and frequency resources among the multiple time and frequency resources, and the one or more time and frequency resources include one or more SL-PRS resources among the one or more SL-PRS resources.

[0024] In another possible implementation, the UE is configured to send information associated with one or more SL-PRS resources among the one or more SL-PRS resources in one or more time and frequency resources among the multiple time and frequency resources.

[0025] In another possible implementation, the UE is configured to receive configuration information about the one or more SL-PRS resources from a base station or from another second UE.

[0026] In another possible implementation, the UE is configured to send one or more identifiers of one or more UEs that intend to send the one or more SL-PRSs on the second time and frequency resources, i.e., using the second time and frequency resources.

[0027] In another possible implementation, the UE is configured to send one or more identifiers of one or more UEs that intend to receive the one or more SL-PRSs on the second time and frequency resources, i.e., using the second time and frequency resources.

[0028] According to a second aspect, a method is provided for sending a time and frequency resource allocation for the transmission of one or more sidelink positioning reference signals (SL-PRS). The method comprises the following steps: sending the allocation using a two-level allocation, the two-level allocation comprising a first-level allocation indicating one or more first time and frequency resources of a plurality of time and frequency resources with a first granularity and a second-level allocation indicating one or more second time and frequency resources of the plurality of time and frequency resources with a second granularity, wherein the one or more second time and frequency resources are a subset of the one or more first time and frequency resources. As used herein, the one or more second time and frequency resources being a subset of the one or more first time and frequency resources includes the following case: the one or more second time and frequency resources include all of the one or more first time and frequency resources, that is, the first time and frequency resource and the second time and frequency resource are the same.

[0029] The method provided in the second aspect of the present disclosure can be performed by the UE provided in the first aspect of the present disclosure. Therefore, other features of the method provided in the second aspect of the present disclosure are directly obtained from the functions of the UE provided in the first aspect of the present disclosure and its different implementations described above and below.

[0030] According to a third aspect, a user equipment (UE) is provided for receiving a time and frequency resource allocation, the time and frequency resource allocation being used for the transmission of one or more sidelink positioning reference signals (SL-PRS). The UE is used to receive the allocation using two-level allocation, the two-level allocation comprising a first-level allocation indicating one or more first time and frequency resources in a plurality of time and frequency resources with a first granularity and a second-level allocation indicating one or more second time and frequency resources in the plurality of time and frequency resources with a second granularity, wherein the one or more second time and frequency resources are a subset of the one or more first time and frequency resources. As used herein, the one or more second time and frequency resources being a subset of the one or more first time and frequency resources includes the following case: the one or more second time and frequency resources include all of the one or more first time and frequency resources, that is, the first time and frequency resource and the second time and frequency resource are the same.

[0031] In another possible implementation, the UE is configured to receive first-level sidelink control information (SCI), where the first-level SCI includes the first-level allocation.

[0032] In another possible implementation manner, the UE is configured to determine that the first-level SCI includes the first-level allocation by determining that the first-level SCI indicates the second-level allocation.

[0033] In another possible implementation, the UE is configured to receive second-level sidelink control information (SCI), where the second-level SCI includes the second-level allocation.

[0034] In another possible implementation, the first-level SCI includes information indicating the existence of the second-level allocation.

[0035] In another possible implementation, the first-level SCI further includes information about the format of the second-level SCI, and / or one or more reserved bits of the first-level SCI include the information indicating the existence of the second-level allocation.

[0036] In another possible implementation, the multiple time and frequency resources include multiple time slots and multiple sub-channels.

[0037] In another possible implementation, the UE is configured to receive the two-level allocation, ie, the first allocation and the second allocation, in the multiple time slots and one or more subchannels of the multiple subchannels.

[0038] In another possible implementation, the UE is configured to receive control information associated with the one or more SL-PRSs in the multiple time slots carrying the two-level allocation and the one or more subchannels of the multiple subchannels.

[0039] In another possible implementation, the UE is configured to receive the two-stage allocation in a time slot prior to one or more time slots, where the time slot includes the first time and frequency resources indicated by the two-stage allocation.

[0040] In another possible implementation manner, the UE is configured to receive the two-stage allocation in a time slot of the first time and frequency resource including the two-stage allocation indication.

[0041] In another possible implementation, the UE is configured to send the one or more SL-PRSs on the second time and frequency resources indicated by the second level allocation, that is, using the second time and frequency resources indicated by the second level allocation.

[0042] In another possible implementation, the UE is used to send the one or more SL-PRSs on the second time and frequency resources indicated by the first level allocation and the second level allocation, that is, using the second time and frequency resources indicated by the first level allocation and the second level allocation.

[0043] In another possible implementation, the UE is configured to receive the one or more SL-PRSs on the second time and frequency resources indicated by the second level allocation, that is, using the second time and frequency resources indicated by the second level allocation.

[0044] In another possible implementation, the UE is configured to receive the one or more SL-PRSs on the second time and frequency resources indicated by the first level allocation and the second level allocation, i.e., using the second time and frequency resources indicated by the first level allocation and the second level allocation.

[0045] In another possible implementation, the first granularity is a sub-channel of a time slot, that is, a sub-channel of a size of a time slot.

[0046] In another possible implementation, the plurality of time and frequency resources include one or more configured or pre-configured semi-dedicated SL-PRS resources having the second granularity, ie, the same resolution as the one or more second time and frequency resources.

[0047] In another possible implementation, the multiple time and frequency resources include one or more configured or pre-configured semi-dedicated SL-PRS resources, wherein the UE and / or another UE is used to send the one or more SL-PRS on one or more SL-PRS resources among the one or more SL-PRS resources, i.e., using one or more SL-PRS resources among the one or more SL-PRS resources.

[0048] In another possible implementation, the UE is configured to receive the two-level allocation in one or more time and frequency resources among the multiple time and frequency resources that are different from the one or more SL-PRS resources.

[0049] In another possible implementation, the UE is used to send data in one or more time and frequency resources among the multiple time and frequency resources, and the one or more time and frequency resources include one or more SL-PRS resources among the one or more SL-PRS resources.

[0050] In another possible implementation, the UE is used to receive data in one or more time and frequency resources among the multiple time and frequency resources, and the one or more time and frequency resources include one or more SL-PRS resources among the one or more SL-PRS resources.

[0051] In another possible implementation, the UE is configured to send information associated with one or more SL-PRS resources among the one or more SL-PRS resources in one or more time and frequency resources among the multiple time and frequency resources.

[0052] In another possible implementation, the UE is configured to receive, in one or more time and frequency resources among the multiple time and frequency resources, information associated with one or more SL-PRS resources among the one or more SL-PRS resources.

[0053] In another possible implementation, the UE is configured to receive configuration information about the one or more SL-PRS resources from a base station or from another second UE.

[0054] In another possible implementation, the UE is configured to receive one or more identifiers of one or more UEs that intend to send the one or more SL-PRSs on the second time and frequency resources, i.e., using the second time and frequency resources.

[0055] In another possible implementation, the UE is configured to receive one or more identifiers of one or more UEs that intend to receive the one or more SL-PRSs on the second time and frequency resources, i.e., using the second time and frequency resources.

[0056] According to a fourth aspect, a method is provided for receiving a time and frequency resource allocation for the transmission of one or more sidelink positioning reference signals (SL-PRS). The method comprises the following steps: receiving the allocation using a two-level allocation, the two-level allocation comprising a first-level allocation indicating one or more first time and frequency resources in a plurality of time and frequency resources with a first granularity and a second-level allocation indicating one or more second time and frequency resources in the plurality of time and frequency resources with a second granularity, wherein the one or more second time and frequency resources are a subset of the one or more first time and frequency resources. As used herein, the one or more second time and frequency resources being a subset of the one or more first time and frequency resources includes the following case: the one or more second time and frequency resources include all of the one or more first time and frequency resources, that is, the first time and frequency resource and the second time and frequency resource are the same.

[0057] The method provided in the fourth aspect of the present disclosure may be performed by the UE provided in the third aspect of the present disclosure. Therefore, other features of the method provided in the fourth aspect of the present disclosure are directly derived from the functionality of the UE provided in the third aspect of the present disclosure and its different implementations described above and below.

[0058] According to the fifth aspect, a computer program product is provided, comprising a computer-readable storage medium for storing program code, wherein when the program code is executed by a computer or a processor, the program code causes the computer or the processor to perform the method provided in the second aspect or the method provided in the fourth aspect.

[0059] The details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features, objects, and advantages are apparent from the description, drawings, and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] The embodiments of the present disclosure are described in detail below with reference to the accompanying drawings.

[0061] Figure 1 A schematic diagram of a wireless communication network with multiple UEs provided by an embodiment is shown, which is used to send and / or receive time and frequency resource allocation, wherein the time and frequency resource allocation is used for transmission of one or more sidelink positioning reference signals.

[0062] Figure 2 A schematic diagram of two-level allocation of time and frequency resources implemented by a UE according to an embodiment is shown, where the two-level allocation of time and frequency resources is used for transmission of one or more sidelink positioning reference signals.

[0063] Figure 3 A schematic diagram of a semi-dedicated SL-PRS resource implemented by a UE according to an embodiment is shown, wherein the semi-dedicated SL-PRS resource is used for two-level allocation of time and frequency resources, and the two-level allocation of time and frequency resources is used for the transmission of one or more sidelink positioning reference signals.

[0064] Figure 4 A schematic diagram of two-level allocation of time and frequency resources implemented by a UE according to an embodiment is shown, where the two-level allocation of time and frequency resources is used for transmission of one or more sidelink positioning reference signals.

[0065] Figure 5 A schematic diagram of two-level allocation of time and frequency resources implemented by a first UE and a second UE according to an embodiment is shown, where the two-level allocation of time and frequency resources is used for transmission of one or more sidelink positioning reference signals.

[0066] Figure 6a A schematic diagram of two-level allocation of time and frequency resources implemented by a UE according to an embodiment is shown, where the two-level allocation of time and frequency resources is used for transmission of one or more sidelink positioning reference signals.

[0067] Figure 6b A schematic diagram of two-level allocation of time and frequency resources implemented by a UE according to an embodiment is shown, where the two-level allocation of time and frequency resources is used for transmission of one or more sidelink positioning reference signals.

[0068] Figure 7a A schematic diagram of configuration steps implemented by a transmitting UE according to an embodiment is shown for a two-level allocation of time and frequency resources for transmission of one or more sidelink positioning reference signals.

[0069] Figure 7b A schematic diagram of configuration steps implemented by a receiving UE according to an embodiment is shown for a two-level allocation of time and frequency resources for transmission of one or more sidelink positioning reference signals.

[0070] Figure 8 A signaling diagram of a two-level allocation of time and frequency resources implemented by a UE according to an embodiment is shown, where the two-level allocation of time and frequency resources is used for transmission of one or more sidelink positioning reference signals.

[0071] Figure 9A flowchart of processing steps implemented by a transmitting UE for two-level allocation of time and frequency resources implemented by a UE according to an embodiment is shown, wherein the two-level allocation of time and frequency resources is used for the transmission of one or more sidelink positioning reference signals.

[0072] Figure 10 A schematic diagram of processing steps implemented by a transmitting UE is shown for a two-level allocation of time and frequency resources for transmission of one or more sidelink positioning reference signals, according to an embodiment.

[0073] Figure 11 A schematic diagram of processing steps implemented by a transmitting UE is shown for a two-level allocation of time and frequency resources for transmission of one or more sidelink positioning reference signals, according to an embodiment.

[0074] Figure 12 A flowchart illustrating processing steps implemented by a transmitting UE according to an embodiment is shown for a two-level allocation of time and frequency resources for transmission of one or more sidelink positioning reference signals.

[0075] Figure 13 A schematic diagram of two-level allocation of time and frequency resources implemented by a UE according to an embodiment is shown, where the two-level allocation of time and frequency resources is used for transmission of one or more sidelink positioning reference signals.

[0076] Figure 14 A flowchart illustrating processing steps implemented by a receiving UE according to an embodiment is shown for a two-level allocation of time and frequency resources for transmission of one or more sidelink positioning reference signals.

[0077] Figure 15 A schematic diagram of a semi-dedicated SL-PRS resource implemented by a UE according to an embodiment is shown, wherein the semi-dedicated SL-PRS resource is used for two-level allocation of time and frequency resources, and the two-level allocation of time and frequency resources is used for the transmission of one or more sidelink positioning reference signals.

[0078] Figure 16 A signaling diagram of two-level allocation of time and frequency resources based on semi-dedicated SL-PRS resources implemented by a UE according to an embodiment is shown, where the two-level allocation of time and frequency resources is used for transmission of one or more sidelink positioning reference signals.

[0079] Figure 17It is a flowchart of a method for sending two-level allocation of time and frequency resources provided by an embodiment, wherein the two-level allocation of time and frequency resources is used for the transmission of one or more sidelink positioning reference signals.

[0080] Figure 18 1 is a flowchart of a method for receiving two-stage allocation of time and frequency resources provided by an embodiment, wherein the two-stage allocation of time and frequency resources is used for transmission of one or more sidelink positioning reference signals.

[0081] In the following, identical reference numerals refer to identical or at least functionally equivalent features. DETAILED DESCRIPTION

[0082] In the following description, reference is made to the accompanying drawings that form part of the present disclosure and illustrate specific aspects of embodiments of the present disclosure or specific aspects in which embodiments of the present disclosure may be used. It should be understood that the embodiments of the present disclosure may be used in other aspects and include structural or logical changes not depicted in the accompanying drawings. Therefore, the following detailed description should not be understood in a restrictive sense, and the scope of the present disclosure is defined by the appended claims.

[0083] For example, it should be understood that the disclosure related to describing a method may also apply to a corresponding device or system for performing the method, and vice versa. For example, if one or more specific method steps are described, the corresponding device may include one or more units (e.g., functional units) to perform the one or more method steps described (e.g., one unit performs one or more steps, or multiple units perform one or more of the multiple steps respectively), even if the one or more units are not explicitly described or illustrated in the drawings. On the other hand, for example, if a specific device is described based on one or more units (e.g., functional units), the corresponding method may include a step to perform the function of the one or more units (e.g., one step performs the function of the one or more units, or multiple steps perform the function of one or more of the multiple units respectively), even if the one or more steps are not explicitly described or illustrated in the drawings. In addition, it should be understood that, unless otherwise stated, the features of the various exemplary embodiments and / or aspects described herein may be combined with each other.

[0084] Figure 1A schematic diagram of a wireless communication network provided by an embodiment is shown, for sending and / or receiving time and frequency resource allocations for transmission of one or more sidelink positioning reference signals (SL-PRS), wherein the wireless communication network, in particular a cellular communication network 100, has a base station 110 defining a cell of the wireless communication network 100 and a plurality of user equipment (UE) 120a to 120d. As an example, in Figure 1 In the example embodiment, UE 120a sends a time and frequency resource allocation for the transmission of one or more sidelink positioning reference signals SL-PRS.

[0085] like Figure 1 As shown, UE 120a may include processing circuitry 121a and a communication interface 123a, particularly an antenna, for communicating with a base station 110 in a wireless network 100 and performing sidelink communications with other UEs 120b to 120d. The processing circuitry 121a may be implemented in hardware and / or software. The hardware may include digital circuitry, or both analog and digital circuitry. The digital circuitry may include components such as an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), a digital signal processor (DSP), or one or more general-purpose processors. In addition, UE 120a may include a memory 125a for storing executable program code that, when executed by the processing circuitry 121a, enables UE 120a to perform the functions and operations described herein. Similar to UE 120a, other UEs 120b to 120d may also include processing circuitry, a communication interface, and a memory.

[0086] As an example, several detailed embodiments are further described below in which UE 120a (also referred to as a first UE) is transmitting a time and frequency resource allocation for transmission of one or more SL-PRSs, and UEs 120b through 120d may receive such allocations. Furthermore, as an example, UE 120d may be a legacy UE 120d, as defined in more detail below.

[0087] The embodiments disclosed herein relate to the allocation of time and frequency resources for the transmission of SL-PRS in the sidelink. Transmissions in the sidelink may use an orthogonal frequency division multiplexing (OFDM) waveform with a cyclic prefix (CP). In the time domain, resources may consist of time slots. A time slot includes multiple OFDM symbols, for example, 14 or 12 OFDM symbols, depending on whether a normal CP or an extended CP is used. hereinafter, OFDM symbols are referred to as symbols, and it is assumed that a time slot includes 12 symbols. In the frequency domain, resources may consist of resource blocks (RBs). An RB includes multiple adjacent subcarriers, for example, 12 subcarriers, having the same subcarrier spacing for the OFDM waveform.

[0088] For data transmission in the sidelink, for example, in NR-V2X in 3GPP Rel.16 / 17, a subset of available resources can be (pre-)configured by UE 120a to 120d for its SL transmission. The subset of available resources used for SL transmission is called a resource pool (RP). (Pre-) configuration refers to (a) a configuration defined by the network and signaled to UE 120a to 120d by the network device base station 110, that is, when UE 120a to 120d is within the network coverage; or (b) a configuration predefined in UE 120a to 120d, for example, when UE 120a to 120d is not within the network coverage. The network device base station 110 can be a next generation node B (gNB), a base station (BS), a roadside unit (RSU), a transmit / receive point (TRP), etc. UEs 120a to 120d may be mobile phones, handheld devices, devices on vehicles, devices on robots, etc. Hereinafter, the term gNB is used with the understanding that this unit may generally be implemented as network device 110. As described above, as an example, UE 120d may be a conventional UE 120d, while UEs 120a to 120c are implemented according to the embodiments disclosed herein.

[0089] In the time domain, the RP consists of continuous or non-continuous time slots. Within a time slot, all symbols or only a subset of available symbols can be (pre-)configured for sidelink transmission. Resource blocks within a resource pool are also called physical resource blocks (PRBs). In the frequency domain, the RP is divided into a (pre-)configured number of continuous subchannels. A subchannel consists of a set of adjacent PRBs in a time slot. The number of PRBs in a subchannel is (pre-)configured within the resource pool. A subchannel represents the smallest unit for scheduling data transmission in the sidelink. Transmissions in the sidelink can occupy one or more subchannels.

[0090] Data is organized in transport blocks (TBs), for example, a TB can contain an entire data packet. In NR V2X, the data payload (i.e., TB) is carried in the physical sidelink shared channel (PSSCH). Depending on the size of the data packet, the PSSCH carrying the TB can occupy one or more subchannels. The sidelink control information (SCI) associated with the TB is sent in two levels: first-level SCI and second-level SCI. The first level is carried in the physical sidelink control channel (PSCCH). The PSCCH is multiplexed with the associated PSSCH in non-overlapping resources within one or more subchannels occupied by the PSSCH. To assist in decoding the PSCCH, a demodulation reference signal (DMRS) is sent within the PSCCH, called the PSCCH DMRS. The second-level SCI is multiplexed in time and frequency with the TBs in the PSSCH. To aid in decoding the PSSCH, a demodulation reference signal (DMRS) is transmitted within the PSSCH, referred to as the PSSCH DMRS. For TB transmission, transmitting UEs (Tx UEs) 120a to 120d transmit the PSCCH (carrying the first-level SCI) along with the second-level SCI multiplexed with the TBs in the PSSCH in one or more subchannels.

[0091] The first-level SCI indicates one or more resources for the current TB transmission and may also indicate resources reserved for retransmissions of the same TB. The current TB transmission may be referred to as an initial transmission. The initial transmission may correspond to a retransmission. The one or more resources used for transmission include one or more subchannels in a time slot. The one or more resources for transmission may be determined by the frequency resource location and time resource location of the resource. The frequency resource location of the resource may be indicated by the starting subchannel index for transmission and the number of consecutively allocated subchannels. The time resource location may be indicated by a time slot index. The starting subchannel and resource time slot of the current TB transmission correspond to the subchannel and time slot where the PSCCH (carrying the first-level SCI associated with the TB) is located. Based on this, the resources for the current transmission may be determined by an indication of the number of consecutive subchannels occupied by the current transmission. The resources for retransmission are indicated by a frequency indication value and a time indication value, which specify the starting subchannel index for retransmission, the number of consecutively allocated subchannels, and the subsequent time slot index.

[0092] In addition, the first-level SCI may also indicate a resource reservation period, which is the time period between resources selected for the transmission of consecutive TBs. This period indicates the period of resources selected by UE 120a-120d and is referred to as a resource reservation interval (RRI) in NR V2X. Using the RRI in the first-level SCI, UE 120a-120d can indicate that one or more subchannels used for the current transmission of a TB can be reserved after the RRI used for the transmission of a new TB. Multiple RRIs can be (pre-)configured in the resource pool.

[0093] Decoding of the first-level SCI can then support UEs 120a to 120d to understand the one or more subchannels occupied by the current transmission of the TB carried in the PSSCH, as well as to understand the one or more subchannels reserved for future transmissions (retransmissions) of the same TB or a new TB. The first-level SCI also indicates the priority of the TB carried in the associated PSSCH. In addition, the first-level SCI also indicates the format of the second-level SCI, as the second-level SCI can have a variable length. The second-level SCI indicates the source ID and destination ID of the TB. Decoding the second-level SCI supports receiving UEs (Rx UEs) 120a to 120d to understand the source and destination of the TB, that is, supports Rx UEs 120a to 120d to understand whether it is the target Rx UE 120a to 120d of the TB carried in the PSSCH.

[0094] For data transmission, i.e., for TB transmission, subchannels within the resource pool can be selected based on two resource allocation modes, namely, Mode 1 and Mode 2. In Mode 1, one or more subchannels for data transmission are allocated by the network, i.e., the base station or gNB 110 indicates to the UEs 120a to 120d the resources to be used for data transmission. In Mode 2, the UEs 120a to 120d can autonomously select one or more subchannels for data transmission.

[0095] For transmission in Mode 2, UEs 120a to 120d identify candidate resources in a selection window based on a sensing process within a set of time slots of the resource pool. This set of time slots is called a sensing window. As part of the sensing process, UEs 120a to 120d search for PSCCH at all potential PSCCH locations in each subchannel of these time slots and, if PSCCH is found, decode the first-level SCI. Based on the decoded first-level SCI, UEs 120a to 120d learn about the resources that other UEs 120a to 120d have reserved for their transmissions. In addition, UEs 120a to 120d measure the reference signal received power (RSRP) of the transmission associated with the received first-level SCI. Whether UEs 120a to 120d should measure RSRP based on PSCCH DMRS or PSSCH DMRS can be (pre-)configured for each resource pool. The measured RSRP and the resources reserved by the corresponding first-level SCI are considered as sensing results of Mode 2 sensing from UEs 120a to 120d.

[0096] In Mode 2, UEs 120a-120d determine candidate resources within the selection window after eliminating resources within the selection window based on half-duplex operation and sensing results. Due to half-duplex operation, UEs 120a-120d are unable to sense reservations from other UEs 120a-120d during the time slots of the sensing window in which UEs 120a-120d are transmitting. Based on this, when UEs 120a-120d are transmitting, UEs 120a-120d eliminate time slots in the selection window that have potential reserved resources due to the RRI period indicated in the first level transmitted in the time slots of the sensing window. UEs 120a-120d may also eliminate time slots that, if selected by UEs 120a-120d for use with a given RRI period (selected by UEs 120a-120d for their transmissions), could cause future conflicts with potentially reserved resources of other UEs 120a-120d. Furthermore, based on the sensing results, UE 120a-120d excludes reserved resources from the selection window that have an associated measured RSRP greater than a (pre-)configured threshold, which depends on the priority of the TB to be transmitted by UE 120a-120d. UE 120a-120d may also exclude resources that, if selected by UE 120a-120d for use within a given RRI period, could cause future conflicts with reserved resources of other UEs 120a-120d. After exclusion, UE 120a-120d checks whether the percentage of remaining available candidate resources within the selection window is above a threshold, which depends on the priority of the TB to be transmitted by UE 120a-120d. If this is not the case, the RSRP threshold used to exclude reserved resources is increased by 3dB, and the resource exclusion based on the sensing results is repeated. From the remaining candidate resources in the selection window, UE 120a-120d randomly selects resources for initial transmission and retransmission of the TB. The UEs 120a through 120d may use the selected resources for sending multiple TBs over multiple periods (ie, using a given RRI selected by the UEs 120a through 120d).

[0097] The mechanisms of enhanced Mode 2 operation include re-evaluation and pre-emption. With re-evaluation, UE 120a to 120d can check whether the selected resources for a TB have been reserved by another UE 120a to 120d based on new sensing results before UE 120a to 120d transmits the TB. If so, UE 120a to 120d discards the selected resources and selects new resources for the TB. With pre-emption, similar to the re-evaluation mechanism, UE 120a to 120d can also check whether the selected resources for the TB have been reserved. However, with pre-emption, if other UE 120a to 120d has already reserved resources for a certain transmission with a higher priority compared to the UE's transmission priority, UE 120a to 120d only selects new resources for its TB transmission. If the priority associated with the reserved resources is higher than a (pre-)configured threshold within the resource pool, UE 120a to 120d can also select new resources for its transmission.

[0098] Regarding SL-PRS resource allocation, 3GPP has discussed the introduction of Scheme 1 and Scheme 2, which are similar to Mode 1 (i.e., network control) and Mode 2 (UE autonomous selection) for data transmission, respectively. Hereinafter, Scheme 1 will be referred to as Mode 1 and Scheme 2 will be referred to as Mode 2.

[0099] The transmission of SL-PRS requires time and frequency resources in the sidelink. Similar to data transmission in the sidelink, resources in a resource pool can be used for SL-PRS transmission. To this end, 3GPP has discussed whether to use a dedicated shared resource pool and / or a shared resource pool for SL-PRS, including (pre-)configuring either of them. A dedicated resource pool refers to a resource pool that has resources for SL-PRS transmission and possibly for transmission of SCI or other information associated with the SL-PRS resources. A PSCCH can be transmitted in a dedicated resource pool, where the PSCCH carries SCI related to one or more SL-PRS transmissions. A PSSCH associated with one or more SL-PRS transmissions can also be transmitted in a dedicated resource pool, for example, a PSSCH carrying measurement reports for one or more SL-PRS transmissions. A shared resource pool refers to a resource pool that has resources for data and SL-PRS transmissions and for transmitting information associated with these transmissions (e.g., SCI). In addition, 3GPP has agreed that backward compatibility for legacy UEs (e.g., exemplary UE 120d) should be supported in the shared resource pool. A legacy UE (e.g., exemplary UE 120d) refers to a UE of a previous version in NRV2X, i.e., Rel.16 or Rel.17 UE. Non-legacy as used herein corresponds to a UE of a higher version (e.g., Rel.18), e.g. Figure 1 UEs 120a to 120c are shown.

[0100] Data transmission is allocated in units of subchannels. SL-PRS can span multiple PRBs (e.g., the entire resource pool) in the frequency domain and occupy multiple symbols in the time domain. Therefore, one SL-PRS resource may not correspond to one or more subchannels. Therefore, the resource granularity of data transmission and SL-PRS in the sidelink may be different. The shared resource pool needs to support resource selection and scheduling for these two types of transmission with different resource granularity.

[0101] In addition, some have proposed multiplexing the SL-PRS with the PSSCH. However, a UE 120a-120c that wishes to transmit the SL-PRS may not always need to transmit the PSSCH. Furthermore, the SL-PRS may need to span multiple subchannels, while the PSSCH may not occupy as many subchannels. Furthermore, the SL-PRS may not need to span all symbols in a slot.

[0102] The shared resource pool should support data transmission from Rel.16 / 17 / 18 Tx UE 120d to Rel.16 / 17 / 18 Rx UEs, as well as SL-PRS transmission from Rel.18 Tx UEs 120a to 120c to Rel.18 Rx UEs 120a to 120c. Because Rel.16 / 17 Rx UE 120d does not need to receive SL-PRS, backward compatibility for legacy Rx UEs 120d in the shared resource pool is ensured as long as these Rx UEs 120d can receive their intended data. Backward compatibility with Rel.16 / 17 Tx UE 120d is required in both Solution 1 (Mode 1) and Solution 2 (Mode 2). In Mode 1, data and SL-PRS resources can be configured by the network for Rel.16 / 17 Tx UE 120d and Rel.18 Tx UEs 120a to 120c. To ensure backward compatibility, Rel.16 / 17 Tx UE 120d performing Mode 2 sensing needs to be aware of SL-PRS resources reserved by Rel.18 Tx UEs 120a to 120c, but cannot identify these resources as being used for SL-PRS. However, Rel.16 / 17 Tx UE 120d performing Mode 2 sensing can only be aware of resource reservations at the subchannel granularity. On the other hand, Rel.18 Tx UEs 120a to 120c performing Mode 2 sensing (for transmitting SL-PRS) need to be aware of SL-PRS resource reservations (performed by other Rel.18 Tx UEs 120a to 120c) at the SL-PRS resource granularity.

[0103] Using a dedicated resource pool may be inefficient because the resources dedicated to SL-PRS may not always be used, while reducing the available resources for data transmission in the sidelink. A shared resource pool can better utilize resources, but may require backward compatibility. In addition, the shared resource pool needs to accommodate the scheduling of transmissions with different resource granularity. In addition, multiplexing SL-PRS within PSSCH may require that PSSCH needs to be sent together with SL-PRS, and the PSSCH spans more subchannels than necessary. Multiplexing SL-PRS within PSSCH may limit the design of SL-PRS.

[0104] Embodiments disclosed herein provide a shared resource pool for supporting data transmission and SL-PRS transmission (i.e., for Rel.18 UEs 120a to 120c), taking into account different resource granularity for the two transmission types, for example, in units of subchannels for data transmission and in units of SL-PRS resources for SL-PRS. The design of the shared resource pool ensures backward compatibility with legacy UEs 120d (i.e., Rel.16 and Rel.17 UEs 120d). Data transmission in the shared resource pool can be performed by all UEs (i.e., Rel.16 / 17 / 18 UEs 120a to 120d). SL-PRS transmission can be performed by non-legacy UEs (i.e., Rel.18 UEs 120a to 120c).

[0105] like Figure 2 As shown, the embodiments disclosed herein generally provide a two-level allocation scheme (also referred to as two-level reservation) for one or more SL-PRS resources. A first-level allocation 210a (also referred to as first-level reservation) allocates (i.e., reserves) a set of contiguous subchannels comprising one or more SL-PRS resources. A second-level allocation 210b (also referred to as second-level reservation) allocates (i.e., reserves) one or more resources within the set of subchannels for one or more SL-PRS resources. Time and frequency resource allocation is also referred to as reservation, and the terms "allocation" and "reservation" are used interchangeably herein.

[0106] More specifically, to send a time and frequency resource allocation for transmission of one or more SL-PRSs, for example, UE 120a is configured to send an allocation using a two-level allocation, the two-level allocation including a first-level allocation 210a having a first granularity indicating one or more first time and frequency resources 220 among a plurality of time and frequency resources 200 and a second-level allocation 210b having a second granularity indicating one or more second time and frequency resources 230 among the plurality of time and frequency resources 200, wherein the one or more second time and frequency resources 230 are a subset of the one or more first time and frequency resources 220. As used herein, the one or more second time and frequency resources 230 being a subset of the one or more first time and frequency resources 220 includes the case where the one or more second time and frequency resources 230 include all of the one or more first time and frequency resources 220, i.e., the first time and frequency resources 220 and the second time and frequency resources 230 are the same.

[0107] Similarly, to receive a time and frequency resource allocation for transmission of one or more SL-PRSs, for example, UE 120b is configured to receive an allocation using a two-level allocation, the two-level allocation including a first-level allocation 210a having a first granularity indicating one or more first time and frequency resources 220 in a plurality of time and frequency resources 200 and a second-level allocation 210b having a second granularity indicating one or more second time and frequency resources 230 in the plurality of time and frequency resources 200. As described above, the one or more second time and frequency resources 230 are a subset of the one or more first time and frequency resources 220.

[0108] The advantage of two-level allocation is that it supports allocating SL-PRS resources in a shared resource pool while supporting allocating SL-PRS resources at a different granularity from data transmission. Figure 2The example shown depicts a two-level allocation of one SL-PRS resource within a symbol. SL-PRS resources within a subchannel set may span multiple symbols and may span the subchannel set in a comb-like pattern or structure. The first-level allocation 210a is intended for all UEs 120a to 120d, i.e., both legacy and non-legacy UEs 120a to 120d that wish to transmit or receive data or SL-PRS, while the second-level allocation 210b is intended for (non-legacy) UEs 120a to 120c that wish to transmit or receive SL-PRS. Both levels of allocations may be sent by Rel.18 Tx UEs 120a to 120c that wish to reserve SL-PRS resources for future transmission of SL-PRS. With first-level reservation 210a, Rel.18 Tx UE 120a-120c indicates reservation of the entire subchannel set, while it may actually be aiming to reserve only a portion of the resources within the subchannel set, i.e., one or more resources within the subchannel set for one or more SL-PRS resources. Second-level reservation 210b is used to identify and reserve one or more SL-PRS resources. Second-level reservation 210b only needs to be received and interpreted by Rel.18 UEs 120a-120c, i.e., Tx UEs 120a-120c performing Mode 2 sensing to transmit SL-PRS and / or Rx UEs 120a-120c receiving SL-PRS.

[0109] In one embodiment, the first-level allocation 210a can be sent in the first-level SCI carried in the PSCCH within a subchannel. The first-level allocation 210a can be indicated by one of up to two allocations within the first-level SCI, where the first-level SCI is used for resource allocation for retransmission of a TB. This has the advantage of ensuring backward compatibility. In particular, the advantage of sending the first-level allocation 210a in the first-level SCI is that it can be interpreted by Mode 2 sensing UEs (Rel. 16 / 17 / 18) 120a to 120d intending to transmit data, without requiring those UEs 120a to 120d to understand that the reservation (i.e., allocation) is for SL-PRS. For Rel. 16 / 17 Tx UE 120d performing Mode 2 sensing (i.e., to transmit data), the first-level allocation 210a of the SL-PRS resources will be transparent, i.e., UE 120d does not need to be aware that these resources are reserved for SL-PRS. This is regardless of whether all resources within the subchannel set are actually allocated with the second-level allocation 210b.

[0110] In one embodiment, if the allocation involves a given number of subchannels, e.g., all subchannels of a resource pool in a future time slot, the Rel.18 Rx UEs 120a-120c may be configured to interpret the allocation carried in the first-level SCI as a first-level allocation 210a of SL-PRS resources. In this case, the Rel.18 UEs 120a-120c may be configured to only be allocated a given number of contiguous subchannels, e.g., all subchannels in the RP, for allocation of SL-PRS resources. Furthermore, if the allocation involves a given set of subchannels (hereinafter referred to as semi-dedicated resources), the Rel.18 Rx UEs 120a-120c may be configured to interpret the allocation carried in the first-level SCI as a first-level allocation 210a of SL-PRS resources. In this case, the Rel.18 UEs 120a-120c may be configured to only be allocated a given set of contiguous subchannels. Rel. 18 Rx UEs 120a-120c may also be configured to interpret the allocation carried in the first-level SCI as the first-level allocation 210a of SL-PRS resources based on the presence of the second-level allocation 210b of SL-PRS resources. Thus, according to one embodiment, only after the Rx UE 120a-120c becomes aware of the presence of the second-level allocation 210b does it recognize that the allocation in the first-level SCI is the first-level allocation 210a of SL-PRS resources. If the UE 120a-120c has determined that the allocation is the first-level allocation 210a, it proceeds to decode the second-level allocation 210b to determine one or more allocated SL-PRS resources.

[0111] In one embodiment, the second-level allocation 210b may be transmitted along with the first-level allocation 210a. Specifically, the second-level allocation 210b may be transmitted within a subchannel that also carries the associated first-level allocation 210a. This has the advantage that Rel.18 UEs 120a-120c (i.e., UEs 120a-120c performing Mode 2 sensing to transmit SL-PRS and / or SL-PRS Rx UEs 120a-120c) only need to examine the first-level allocation 210a and second-level allocation 210b within one subchannel to determine one or more allocated SL-PRS resources. Specifically, the second-level allocation 210b may be transmitted within the second-level SCI. The second-level allocation 210b may also be transmitted within the PSSCH associated with the PSCCH carrying the first-level allocation 210a. The presence of the second-level allocation 210b within the subchannel may be indicated based on control information within the subchannel. Specifically, the presence of the second-level allocation 210b may be indicated using one of the reserved bits in the first-level SCI. In addition, an indication of the second-level SCI format associated with the SL-PRS may also be used. The second-level SCI associated with the SL-PRS may carry the second-level allocation 210b and may be sent in the same subchannel that carries the corresponding first-level SCI. The second-level SCI associated with the SL-PRS may also carry other information associated with the SL-PRS.

[0112] In one embodiment, the first-level allocation 210a and the second-level allocation 210b may be sent by the UEs 120a to 120c in subchannels in a time slot preceding the set of allocated subchannels, i.e., in subchannels of a previous time slot. This has the advantage that the UEs 120a to 120c are aware of the allocated resources before the SL-PRS transmission.

[0113] In one embodiment, the sub-channel carrying the two-level allocation can be used to transmit other relevant information associated with the allocated SL-PRS transmission or necessary for receiving the allocated SL-PRS. This information may include the configuration and parameters of the SL-PRS for each SL-PRS resource, such as the sequence type used for the SL-PRS (e.g., Zaduff-Chu sequence, Gold sequence, etc.), sequence identifier, sequence initialization, SL-PRS periodicity, resource repetition, comb tooth size, staggered arrangement, quasi-co-location information, power control parameters for SL-PRS transmission, etc. This relevant information can be sent in the SCI (e.g., the second-level SCI) or in the PSSCH in the sub-channel carrying the two-level allocation.

[0114] For Rel.18 Tx UEs 120a to 120c that transmit two-level allocation, resource allocation of subchannels may follow conventional resource allocation procedures, i.e., Mode 1 or Mode 2. Furthermore, resource allocation of SL-PRS may also be based on Mode 1 and Mode 2 procedures applicable to SL-PRS, which will be described in more detail below.

[0115] In one embodiment, the priority of the reserved SL-PRS resources may be signaled in the SCI (eg, second level SCI) or the PSSCH in the subchannel carrying the secondary reservation.

[0116] In one embodiment, the first-level allocation 210a and the second-level allocation 210b may be sent by UEs 120a to 120c within the allocated set of subchannels. This means that the first-level allocation and the second-level allocation are sent within the semi-dedicated resources that include the SL-PRS resources indicated by the two-level allocation. The first-level allocation and the second-level allocation are then sent in the same time slot as the SL-PRS. This has the advantage that UEs 120a to 120c may receive the SL-PRS and the associated first-level allocation and second-level allocation in the same time slot. In addition, the source ID and destination ID of the SL-PRS may also be sent within the allocated set of subchannels. For both the shared resource pool and the dedicated resource pool, it may be considered to send the SL-PRS with the associated first-level allocation and second-level allocation in the same time slot (i.e., within the allocated subchannel).

[0117] In one embodiment, the set of subchannels reserved by the first level allocation 210a may correspond to the semi-dedicated resources 260 of the SL-PRS. Figure 3 As shown, the semi-dedicated resources 260 for SL-PRS may correspond to a set of (pre-)configured subchannels in a (pre-)configured time slot within the resource pool. Figure 3 As shown, multiple SL-PRS resources may be (pre-)configured within the semi-dedicated resources 260 . Figure 3An example of SL-PRS resources within one symbol is shown. The SL-PRS resources within the semi-dedicated resources 260 may span multiple symbols and may span a set of subchannels in a comb pattern or structure. Multiple SL-PRS resources may be multiplexed within the semi-dedicated resources 260. Multiple semi-dedicated resources 260 for SL-PRS may be (pre-)configured in a resource pool. The (pre-)configuration of the semi-dedicated resources 260 has the advantage of enabling Rel. 18 UEs 120a to 120c to have a common understanding of the SL-PRS resources. In particular, it allows the UEs 120a to 120c (i.e., Rel. 18 UEs) to know the set of subchannels on which SL-PRS may be transmitted, as well as the configuration of the SL-PRS resources (i.e., the time / frequency allocation of the SL-PRS resources) within the set of subchannels (i.e., within the semi-dedicated resources 260). In particular, the semi-dedicated resources 260 may be (pre-)configured in a shared resource pool. This has the advantage that sub-channels within the semi-dedicated resources can be considered for SL-PRS in the shared resource pool.

[0118] In one embodiment, different numbers of sub-channels may be (pre-)configured for different semi-dedicated resources 260, for example, to support SL-PRS resources with different bandwidths, such as Figure 3 More specifically, the semi-dedicated resources 260 may include all sub-channels in the time slots of the resource pool. This has the advantage that the SL-PRS resources may occupy the entire bandwidth of the resource pool.

[0119] In one embodiment, the semi-dedicated resources 260 may be configured by the network 110 (i.e., base station 110), for example, when the UEs 120a to 120c are within network coverage, or may be pre-configured for use outside of network coverage. Configuration by the network 110 (i.e., base station 110) has the advantage that the configuration of the semi-dedicated resources 260 can be adjusted by the network 110 (i.e., base station 110), for example, based on traffic load and requests for SL-PRS resources. Pre-configuration has the advantage that the semi-dedicated resources 260 can be used outside of network coverage. In one embodiment, the semi-dedicated resources 260 may also be dynamically configured, i.e., configured among a group of UEs 120a to 120c. This allows the UEs 120a to 120c within the group to have a common understanding of the SL-PRS resources within the group.

[0120] In one embodiment, the semi-dedicated resources 260 only need to be (pre-)configured for Rel. 18 UEs 120a to 120c, as they need to be aware of the semi-dedicated resources 260 used for SL-PRS. For Rel. 16 / 17 UE 120d, the semi-dedicated resources 260 are transparent and correspond to normal subchannels like other subchannels in the resource pool. Resource allocation for SL-PRS can be performed based on Mode 1 and Mode 2. In Mode 1, the network 110 (i.e., base station 110) can allocate resources within the semi-dedicated resources 260 for SL-PRS or data transmission, for example, upon request. If resources are allocated for SL-PRS, the network 110 (i.e., base station 110) can indicate the SL-PRS resources that a given Tx UE 120a to 120c can use. In Mode 2, if Rel.16 / 17 Tx UE 120d has sensed that a subchannel within semi-dedicated resources 260 is idle, it may use that subchannel. In Mode 2, if Rel.18 Tx UEs 120a to 120c have sensed that a SL-PR within semi-dedicated resources 260 is idle, it may use that SL-PR. Due to the two-level reservation of SL-PRS resources, the Mode 2 sensing process for finding SL-PRS resources may be enhanced to support selection of SL-PRS resources, as described in more detail below in the context of various more detailed embodiments.

[0121] The reservation (i.e., allocation) of SL-PRS resources within the semi-dedicated resources 260 is indicated by a two-stage reservation sent in a subchannel that is sent in the time slot preceding the time slot with the semi-dedicated resources 260. For the embodiments disclosed herein, there is no need to send SCI or other related information required to receive SL-PRS within the semi-dedicated resources 260. The information required to receive SL-PRS can be sent in the subchannel that carries the corresponding two-stage reservation. The advantage of not having any SCI or other information related to SL-PRS within the semi-dedicated resources 260 is that all resources within the semi-dedicated resources 260 can be used for SL-PRS resources. If the semi-dedicated resources 260 span all subchannels in the time slot of the resource pool, the entire time slot can be used for SL-PRS resources, for example, 12 SL-PRS resource plus resources as well as automatic gain control (AGC) symbols and guard symbols. If SCI or other information associated with the SL-PRS is multiplexed with the SL-PRS in non-overlapping resources within the semi-dedicated resources 260, i.e., multiplexed in first-level SCI carried in the PSCCH within the semi-dedicated resources 260, this may reduce the resources available for the SL-PRS, e.g., resulting in a smaller number of SL-PRS resources within the semi-dedicated resources 260. Furthermore, if SCI or other information associated with the SL-PRS is multiplexed with the SL-PRS in overlapping resources within the semi-dedicated resources 260, this may impact positioning estimation using the SL-PRS. In this regard, multiplexing second-level SCI with the SL-PRS resources, i.e., within the semi-dedicated resources 260, may be undesirable. However, in embodiments disclosed herein, SCI associated with the SL-PRS may be transmitted within the semi-dedicated resources 260, e.g., at the expense of reducing the resources available for the SL-PRS. The SCI may be transmitted in the PSCCH. This can be considered as transmitting the SCI along with the SL-PRS transmission in the same time slot, similar to how SCI is transmitted along with data transmission in one or more subchannels.

[0122] Multiple first-level allocations (i.e., reservations) may also be sent to indicate the allocation of multiple semi-dedicated resources 260. Two first-level allocations 210a, 210a' may be indicated by two allocations within a first-level SCI, which may be used in a conventional system to allocate resources for two retransmissions of a TB. Multiple first-level allocations may also be indicated by allocating multiple semi-dedicated resources 260 with a period. Multiple first-level allocations 210a, 210a' of multiple semi-dedicated resources 260 with a period may be indicated by an RRI sent within a first-level SCI carried in a PSCCH, which is used in a conventional system to indicate periodic reserved resources for future TB transmissions. In addition, the second-level allocation 210b may also indicate multiple SL-PRS resources at different reserved semi-dedicated resources 260. An example of a two-level allocation of multiple semi-dedicated resources is shown in FIG. Figure 4 For each first-level allocation 210a, 210a', the second-level allocation 210b, 210b' can be the same or different. For example, for a semi-dedicated resource 260 with periodic reservation, the second-level allocation 210b, 210b' can be the same, that is, the reserved SL-PRS resources within the semi-dedicated resource 260 are the same (see Figure 4 For each first-level allocation 210a, 210a', there may be a second-level allocation 210b, 210b', i.e., when the reserved semi-dedicated resources 260 span different numbers of subchannels, different second-level allocations 210b, 210b' may be needed to indicate different SL-PRS resources reserved in each semi-dedicated resource 260.

[0123] If multiple Rel.18 Tx UEs 120a to 120c allocate (ie, reserve) different SL-PRS resources within the semi-dedicated resources 260, the multiple Rel.18 Tx UEs 120a to 120c may send first level allocations 210a, 210a' of the same semi-dedicated resources 260, such as Figure 5 More specifically, Figure 5As shown, first-level allocation 210a and second-level allocation 210b of a first two-level allocation can allocate first resource 220 and second resource 230, while first-level allocation 210a' and second-level allocation 210b' of another two-level allocation can allocate first resource 220' and second resource 230'. Because multiple allocations for the same set of subchannels can be sent, this increases the likelihood that semi-dedicated resources 260 will be used for SL-PRS transmission rather than data transmission. If one or more subchannels within semi-dedicated resources 260 have already been allocated by another UE 120b, 120c, Rel.18 Tx UE 120a can preempt one or more subchannels by allocating one or more SL-PRS within semi-dedicated resources 260. In this case, SL-PRS transmission can be prioritized (pre-configured) over data transmission by other UEs to enable preemption mechanisms as detailed in the embodiments.

[0124] The set of subchannels are referred to as semi-dedicated resources because they can be used for both data transmission and SL-PRS transmission, i.e., they are not fully dedicated to SL-PRS. However, the embodiments disclosed herein enable the use of those resources for SL-PRS transmission. Furthermore, the embodiments disclosed herein enable UEs 120a through 120c to have a common understanding of SL-PRS resources within the semi-dedicated resources.

[0125] Furthermore, according to embodiments disclosed herein, the source ID and destination ID of the SL-PRS transmission may be sent within the same subchannel that carries the first level allocation 210a and the second level allocation 210b, as shown in FIG. Figure 6a As shown. More specifically, the source ID / destination ID may be carried in the second-level SCI within the subchannel carrying the two-level allocation. The source ID is an identifier of the UE that is sending the transmission (i.e., the transmission of the SL-PRS). The destination ID is an identifier of one or more UEs that are one or more intended receivers of the transmission (i.e., the SL-PRS transmission). The destination ID may be checked by Rel.18 Rx UEs 120a to 120c to determine whether they are the target receivers of the allocated SL-PRS resources to be sent within the semi-dedicated resources 260. Transmitting the source ID and destination ID within the subchannel transmitting the two-level allocation enables Rel.18 Rx UEs 120a to 120c to know in advance whether it is the target Rx UE for the SL-PRS in the semi-dedicated resources 260.

[0126] In the case of multiple first-level allocations and second-level allocations, a destination ID and source ID may be provided for each first-level allocation and second-level allocation. For multiple first-level allocations and second-level allocations, the destination ID and source ID may be the same. Furthermore, the UE 120a to 120c that transmits the two-level allocation of SL-PRS resources may or may not be the same UE 120a to 120c that transmits the SL-PRS resources. Thus, the destination ID may be an identifier of a UE 120a to 120c different from the UE 120a to 120c that transmits the two-level allocation. This has the advantage that a UE 120a to 120c can transmit a reservation of SL-PRS resources that should be transmitted by another UE 120a to 120c.

[0127] Figure 6b Shown Figure 6a A variation of the embodiment shown is one in which the first UE 120a sends a two-stage reservation of SL-PRS resources, which should be sent by the second UE 120b and the third UE 120c. More specifically, by Figure 6b In the two-level allocation shown, the first UE 120a reserves a second resource 230′ for the second UE 120b and a second resource 230″ for the third UE 120c. In this embodiment, the UEs 120a to 120c may be part of a group of UEs. The first UE 120a may be the group leader and obtain resources for SL-PRS transmission for the UEs 120a to 120c in the group.

[0128] As described above, the UEs 120a to 120c disclosed herein may include handheld devices, in-vehicle devices, and the like. These devices communicate with each other in the SL of the wireless communication network 100 and may transmit and receive reference signals in the sidelink for positioning. Furthermore, as described above, one objective of the present invention is to enable sharing of resources within a resource pool for data transmission and SL-PRS transmission with different granularities.

[0129] Figure 7aA first main embodiment is shown in FIG, wherein (pre-)configuration of UEs 120a to 120c for semi-dedicated SL-PRS resources 260 and for transmission of a two-level allocation of SL-PRS resources. The configuration may be provided by the network 110 (i.e., the base station 110) or by another UE 120a to 120c, or may be pre-configured within the UE 120a to 120c. The (pre-)configuration of the semi-dedicated resources 260 may include (pre-)configuration and indication of the time slots in the resource pool containing the semi-dedicated resources 260, as well as the frequency resource location (i.e., the starting subchannel index) and the number of consecutive subchannels for each semi-dedicated resource 260. Furthermore, the (pre-)configuration may include the periodicity of the semi-dedicated resources 260. Furthermore, the (pre-)configuration may include (pre-)configuration of the SL-PRS resources within each subchannel, i.e., how many SL-PRS resources are in each semi-dedicated resource 260, and the time and frequency allocation of each SL-PRS resource within the semi-dedicated resource 260. The (pre-)configuration may also include SL-PRS parameters for each SL-PRS resource, such as the SL-PRS sequence type (e.g., Zaduff-Chu sequence, Gold sequence, etc.), a sequence identifier, parameters for sequence initialization, SL-PRS periodicity, resource repetition, comb size, staggering, quasi-co-location information, power control parameters for SL-PRS transmission, etc. The (pre-)configuration of semi-dedicated resources enables UEs 120a to 120c (i.e., Rel. 18 UEs) to have a common understanding of the SL-PRS resources in the shared resource pool. In particular, the (pre-)configuration of semi-dedicated resources 260 enables UEs 120a to 120c to understand the resources on which they can transmit SL-PRS. The (pre-)configured semi-dedicated resources 260 may consist of all subchannels in a timeslot in the resource pool. In particular, all (pre-)configured semi-dedicated resources 260 may each span all subchannels in the resource pool.

[0130] Figure 7aFurther shown is a (pre-)configuration for transmitting a two-level allocation. The (pre-)configuration indicates to a UE 120-c how it should transmit the first-level allocation 210a and the second-level allocation 210b of SL-PRS resources. The (pre-)configuration for the two-level allocation may include an indication 240 indicating where and how the first-level allocation 210a and the second-level allocation 210b should be transmitted, i.e., the location within a subchannel. The (pre-)configuration may indicate that the UE 120a-120c should transmit the first-level allocation 210a in the first-level SCI carried in the PSCCH. The (pre-)configuration may include an indication 240 indicating that a UE 120a-120c that reserves SL-PRS resources may only transmit one or more first-level allocations 210a of one or more semi-dedicated resources 260. The (pre-)configuration may also include an indication 240 indicating that a UE 120a-120c that allocates SL-PRS resources should indicate the presence of the second-level allocation 210b of SL-PRS resources using a reserved bit in the first-level SCI. The (pre-)configuration may include an indication 240 indicating that the UE 120a-120c allocated SL-PRS resources should indicate the presence of the second-level allocation 210b of the SL-PRS resources using an indication in the first-level SCI of the second-level SCI format associated with the SL-PRS. The (pre-)configuration may indicate that the UE 120a-120c should transmit the second-level allocation in the second-level SCI. The second-level SCI may be associated with the first-level SCI carrying the first-level allocation 210a. The (pre-)configuration may indicate that the UE 120a-120c should transmit the first-level allocation 210a and the second-level allocation 210b together in one subchannel. Based on the (pre-)configuration for the two-level allocation transmission, the UE 120a-120c then understands how to transmit the two-level allocation of SL-PRS resources.

[0131] Figure 7b A second main embodiment is shown in FIG, which shows the (pre-) configuration of UEs 120a to 120c for a two-level allocation of semi-dedicated resources 260 and resources for receiving SL-PRS. This configuration may be provided by the network 110 or may be pre-configured within the UEs 120a to 120c. The (pre-) configuration of the semi-dedicated resources 260 corresponds to the (pre-) configuration of the semi-dedicated resources 260 previously described in the context of the first main embodiment. The (pre-) configuration of the semi-dedicated resources 260 enables the UEs 120a to 120c to have a common understanding of the SL-PRS resources in the shared resource pool. In particular, the (pre-) configuration of the semi-dedicated resources 260 enables the UEs 120a to 120c to understand the resources on which they can receive SL-PRS.

[0132] Figure 7bFurther shown is a (pre-)configuration for receiving a two-level allocation. The (pre-)configuration indicates to the UEs 120a to 120c where to find and how to determine the first-level allocation 210a and the second-level allocation 210b of SL-PRS resources, i.e., their location within a subchannel. The (pre-)configuration may indicate that the first-level allocation 210a and the second-level allocation 210b are transmitted together, for example, in a subchannel. The (pre-)configuration may indicate that the first-level allocation 210a may be located in the first-level SCI carried in the PSCCH. The (pre-)configuration may indicate that the allocation of one or more semi-dedicated resources 260 corresponds to one or more first-level allocations 210a of one or more SL-PRS resources. The (pre-)configuration may include an indication that the UEs 120a to 120c should interpret the resource allocation in the first-level SCI as the first-level allocation 210a of one or more SL-PRS resources based on the presence of the second-level allocation 210b of the one or more SL-PRS resources. The (pre-)configuration may indicate that the presence of the second-level allocation 210b for one or more SL-PRSs may be indicated using one of the reserved bits in the first-level SCI or an indication in the first-level SCI in the second-level SCI format associated with the SL-PRS. The (pre-)configuration may also indicate that the presence of the second-level allocation 210b may be indicated by an allocation in the first-level SCI for a given number of subchannels or by an allocation in the first-level SCI for semi-dedicated resources 260. In this case, in one embodiment, it may be configured to allow only Rel. 18 UEs 120a to 120c to be allocated a given number of contiguous subchannels, e.g., all subchannels in the RP, for allocation of one or more SL-PRS resources. Legacy UE 120d is then configured not to allocate more than the given number of subchannels for data transmission. The (pre-)configuration may also indicate that the second-level allocation 210b is located in the second-level SCI. In particular, the second-level SCI may be associated with the first-level SCI carrying the first-level allocation 210a. Based on the (pre-)configuration for receiving the two-level allocation, the UEs 120a to 120c then know how to receive the two-level allocation of one or more SL-PRS resources and, therefore, where to receive the SL-PRS.

[0133] Figure 8 In the third main embodiment shown in FIG, for the scenario in network coverage, the base station or gNB 110 provides the configuration for SL-PRS and semi-dedicated resources 260 for two-level allocation to the UEs 120a to 120d. In one embodiment, both configurations can be provided only to Rel.18 UEs 120a to 120c, i.e., the legacy UE 120d has no knowledge of the configuration related to SL-PRS. This means that the configuration can be release specific. Figure 8In the example, it is assumed that the first UE 120a (UE 1) and the second UE 120b (UE 2) are Rel. 18 UEs. The configuration for the SL-PRS and the semi-dedicated resources 260 for two-level allocation may be included in an information element of the configuration information specifying a resource pool (e.g., SL-ResourcePool), which is signaled by the network to the UEs 120a and 120b.

[0134] If gNB 110 has already configured a resource pool for sidelink communication (i.e., for data transmission in the sidelink), gNB 110 may also configure a resource pool for SL-PRS transmission. The resource pool becomes a shared pool for both sidelink communication and SL-PRS transmission. Configuring the resource pool as a shared resource pool can only be performed for Rel.18 UEs 120a-120c. Configuring the resource pool as a shared resource pool may correspond to configuring the resource pool for SL-PRS and / or for semi-dedicated resources 260 for two-stage allocation. Therefore, when Rel.18 UEs 120a-120c are provided with the configuration for SL-PRS and / or for semi-dedicated resources 260 for two-stage allocation, they understand that the resource pool is a shared resource pool. The configuration for SL-PRS and semi-dedicated resources 260 for two-stage allocation may be provided to Rel.18 UEs 120a-120c, and gNB 110 may then provide additional configuration to configure the resource pool as a shared resource pool. The legacy UE 120d has no knowledge of the shared resource pool.

[0135] like Figure 8 As shown in step 801, gNB 110 provides the configuration of semi-dedicated resources 260 to Rel.18 UEs (e.g., first UE 120a and second UE 120b). Figure 8 The configuration includes the configuration and indication of the semi-dedicated resources 260, as previously described in the context of the first main embodiment. The configuration of the semi-dedicated resources 260 provided to the UEs 120a to 120c enables the UEs 120a to 120c to have a common understanding of the SL-PRS resources in the shared resource pool. In particular, the configuration of the semi-dedicated resources 260 enables the Tx UE (e.g., UE 120a) to understand the resources on which it can transmit SL-PRS, and enables the Rx UE (e.g., UE 120b) to understand the resources on which it can receive SL-PRS.

[0136] In addition, gNB 110 provides a two-level allocation configuration to Rel.18 UEs 120a to 120c ( Figure 8Step 803 of the present invention. The configuration includes configuration for transmission and reception of two-level allocation. The configuration indicates to the Tx UE (e.g., UE 120a) where and how it should transmit the first-level allocation 210a and the second-level allocation 210b of SL-PRS resources, i.e., within the subchannels, and indicates to the Rx UE (e.g., UE 120b) where it should look for and how to determine the first-level allocation 210a and the second-level allocation 210b of SL-PRS resources. The configuration of the two-level allocation corresponds to the configuration of the two-level allocation for transmission and reception previously described in the context of the first and second main embodiments, respectively. In particular, it can be configured to allow only Rel.18 UEs 120a to 120c to reserve a given number of consecutive subchannels, e.g., all subchannels in the RP, for reserving SL-PRS resources. The legacy UE 120d can be configured to reserve up to a given number of subchannels minus one for transmission, i.e., the legacy UE 120d is not allowed to reserve a given number of subchannels for transmission. Rel.18 UEs 120a to 120c may also be configured to interpret the reservation of a given number of subchannels as a first level reservation 210a of SL-PRS and then search for a second level reservation 210b within the same subchannels to determine one or more reserved SL-PRS resources within the reserved given number of subchannels.

[0137] exist Figure 8 In the exemplary embodiment shown, it is assumed that UEs 120a and 120b are configured to transmit and receive first-level reservations 210a and second-level reservations 210b in first-level SCI and second-level SCI, respectively. UEs 120a and 120b are further configured such that the presence of second-level reservations 20b is indicated by an indication of the second-level SCI format associated with the SL-PRS. Based on the presence of the second-level SCI associated with the SL-PRS, UEs 120a and 120b understand that the reservation carried in the first-level SCI corresponds to the first-level reservation 210a for SL-PRS resources.

[0138] Resource selection for SL-PRS resources can be done using Mode 1 resource allocation due to the availability of network coverage. Resource selection can also be performed using Mode 2 resource allocation when within network coverage. Figure 8 In the illustrated embodiment, SL-PRS resources are selected based on Mode 1 resource allocation. In this case, the first UE 120a requests resources ( Figure 8805). The first UE 120a may also acquire resources based on autonomous resource selection (e.g., using Mode 2). The first UE 120a may also provide other relevant information that enables the gNB 110 to determine appropriate resources for the SL-PRS, i.e., positioning requirements, bandwidth requirements for the SL-PRS, etc. The gNB 110 provides the resource configuration (i.e., one subchannel) to the first UE 120a ( Figure 8 The configuration may include time and frequency allocation of resources. gNB 110 provides one or more resources ( Figure 8 809 ), indicating which SL-PRS resource(s) on which semi-dedicated resource(s) 260 the first UE 120a should use for its one or more SL-PRS transmissions.

[0139] After gNB 110 has provided resource configuration for two-level reservation and associated SL-PRS, first UE 120a sends first-level reservation 210a and second-level reservation 210b together in the configured resources ( Figure 8 More specifically, the first UE 120a transmits a first level reservation 210a in a first level SCI and a second level reservation 210b in an associated second level SCI, wherein the format of the second level SCI is associated with the SL-PRS. Within the second level SCI carried in the resource, the first UE 120a may also transmit a source ID and a destination ID of the SL-PRS within the second level SCI ( Figure 8 Step 815 of the present embodiment. The second UE 120b receives the two-level reservation and the source ID and destination ID of the SL-PRS. The second UE 102b is operable to interpret the two-level reservation of the SL-PRS based on the configuration provided by the gNB 110. The second UE 120b also understands that the second UE 120b will receive the SL-PRS resources within the semi-dedicated resources 260 where the SL-PRS is located. Thereafter, the first UE 120a transmits the SL-PRS on the configured SL-PRS resources ( Figure 8 The second UE 120b receives the SL-PRS sent by the first UE 120a. The other UE 120c may be configured to send the SL-PRS on other SL-PRS resources within the semi-dedicated resources on which the first UE 120a sends the SL-PRS.

[0140] Figure 9 FIG. 4 is a flow chart illustrating a fourth main embodiment of Mode 2 resource allocation based on SL-PRS resources. More specifically, Figure 9The steps for selecting SL-PRS resources based on a Mode 2 sensing procedure with two-level reservation are shown. The complete procedure is applicable only to Rel. 18 UEs 120a to 120c, since the legacy UE 120d has no knowledge of the SL-PRS within the resource pool.

[0141] UEs 120a to 120c first search for PSCCH ( Figure 9 Similar to the conventional Mode 2 sensing, i.e., the Mode 2 sensing process in Rel. 16 and Rel. 17, UEs 120a to 120c may search for PSCCH at all potential locations of PSCCH in each subchannel in a time slot of the resource pool (e.g., in a time slot of the sensing window). The presence of PSCCH may be detected based on the PSCCH DMRS. If PSCCH is found ( Figure 9 903), the UEs 120a to 120c decode the first level SCI carried by the PSCCH and determine one or more resource reservations indicated by the first level SCI ( Figure 9 Then, the UE 120a to 120c needs to determine whether the indicated resource reservation is for data transmission or for SL-PRS transmission. The UE 120a to 120c checks whether the resource reservation indicated by the first level SCI corresponds to the first level reservation 210a of SL-PRS resources ( Figure 9 907). This can be determined in various ways. UEs 120a-120c may determine that the resource reservation for a given number of subchannels corresponds to first-level reservation 210a of SL-PRS resources. UEs 120a-120c may also determine that the resource reservation for semi-dedicated resources 260 corresponds to first-level reservation 210a of SL-PRS resources. UEs 120a-120c may also determine that the resource reservation is first-level reservation 210a based on the presence of second-level reservation 210b. The presence of second-level reservation 210b may be indicated by one of the reserved bits in the first-level SCI or by an indication of the second-level SCI format associated with the SL-PRS.

[0142] If the UE 120a to 120c detects the first level reservation 210a of SL-PRS resources, it proceeds to decode the second level reservation 210b of SL-PRS resources ( Figure 9 913). The UE 120a to 120c understands where and how to find the second-level reservation 210b based on (pre-) configuration. The second-level reservation 210b may be carried in the same subchannel that carries the first-level reservation 210a. In particular, the second-level reservation 210b may be carried in a second-level SCI associated with the first-level SCI. After decoding the second-level reservation 210b, the UE 120a to 120c determines the reserved SL-PRS resources ( Figure 9Step 915).

[0143] If the one or more resource reservations indicated by the first-level SCI do not correspond to the first-level reservation 210a, the UEs 120a to 120c check whether the resource reservations indicate reservation of one or more subchannels within the semi-dedicated resources 260 for SL-PRS ( Figure 9 Resource reservation may also be based on the periodicity of the reserved resources, ie, based on the RRI. In this way, the UEs 120a to 120c may determine one or more reserved subchannels within the semi-dedicated resources.

[0144] Based on the resource reservation within the semi-dedicated resources 260, i.e., the resource reservation of the SL-PRS resources or one or more subchannels within one or more semi-dedicated resources, the UEs 120a to 120c may then perform resource selection of the SL-PRS resources ( Figure 9 To this end, it may perform resource exclusion based on resource reservation within the semi-dedicated resources 260.

[0145] Figure 10 FIG. 2 shows another embodiment of a Mode 2 sensing process at UEs 120a to 120c (ie, for Rel. 18 UEs) for resource selection of SL-PRS. Figure 10As shown in step 1001 of , UEs 120a to 120c may determine the reservation of one or more subchannels within the semi-dedicated resources, for example based on the process previously described in the context of the fourth main embodiment. The reserved subchannels may be indicated in a first-level SCI carried in a PSCCH received by the UEs 120a to 120c. The UEs 120a to 120c also determine one or more RSRPs associated with the one or more reserved subchannels. The RSRP may be measured based on a DMRS within a PSCCH, the PSCCH carrying a first-level SCI indicating the one or more reserved subchannels. These one or more RSRPs will be considered for resource exclusion in the mode 2 sensing process. The UEs 120a to 120c are (pre-)configured to measure the RSRP associated with the resource reservation using a PSCCH DMRS based on a PSCCH, the PSCCH carrying a first-level SCI indicating the resource reservation. In particular, the (pre-)configuration for measuring RSRP based on the PSCCH DMRS for resource selection may be part of the (pre-)configuration of the resource pool. In this case, all UEs 120a to 120c using the resource pool can measure the RSRP associated with the resource reservation based on the PSCCH DMRS of the corresponding PSCCH. The (pre-)configuration can be indicated by a higher-layer parameter, namely sl-RS-ForSensing. The (pre-)configuration can be indicated within the (pre-)configuration of the SL-ResourcePool information element, i.e., by setting the parameter sl-RS-ForSensing-r16 to pscch. In addition, the UEs 120a to 120c can determine the priority associated with the transmission on one or more reserved subchannels. The priority can be indicated in the first-level SCI, which indicates the resource reservation of one or more subchannels.

[0146] like Figure 10As shown in step 1003, UEs 120a to 120c may determine the reservation of SL-PRS resources, for example, based on the process previously described in the context of the fourth main embodiment. The reserved SL-PRS resources may be determined using a two-level reservation, namely, a first-level reservation 210a carried in a first-level SCI and a second-level reservation 210b carried in a second-level SCI. UEs 120a to 120c may also determine one or more RSRPs associated with one or more reserved SL-PRS resources. The RSRP associated with the reserved SL-PRS resources may be measured based on the SL-PRS transmitted on the reserved SL-PRS resources. This may be considered when the UE transmitting the SL-PRS and the UE transmitting the two-level reservation are different. RSRP may also be measured based on the DMRS within the PSCCH carrying the first-level SCI, which indicates the first-level reservation 210a. This may be considered when the UE transmitting the SL-PRS and the UE transmitting the two-level reservation are the same. One or more RSRPs will be considered for resource exclusion during Mode 2 sensing. UEs 120a to 120c may be (pre-)configured to measure RSRP associated with a first-level reservation 210a for SL-PRS resources based on PSCCH DMRS of a PSCCH, the PSCCH carrying a first-level SCI indicating the first-level reservation 210a. In particular, the (pre-)configuration for measuring RSRP based on PSCCH DMRS for resource selection may be part of the (pre-)configuration of a resource pool for Rel. 18 UEs 120a to 120c. The (pre-)configuration may be indicated by a higher-layer parameter. This may be indicated in the (pre-)configuration of the SL-ResourcePool information element. Furthermore, UEs 120a to 120c may determine a priority associated with the reserved SL-PRS resources. The priority may be indicated in the first-level SCI or in a second-level SCI associated with the first-level SCI carrying the first-level reservation 210a.

[0147] like Figure 10As shown in step 1005 of , the UEs 120a to 120c then perform SL-PRS resource selection based on the one or more reserved subchannels within the semi-dedicated resources 260, the RSRP associated with the one or more reserved subchannels, the priority associated with transmissions on the one or more reserved subchannels, the reserved SL-PRS resources, the RSRP associated with the reserved SL-PRS resources, and optionally, the priority associated with the reserved SL-PRS resources. The UEs 120a to 120c first determine candidate SL-PRS resources. To determine the candidate resources, the UEs 120a to 120c may exclude resources based on the reserved resources within the semi-dedicated resources 260 and the associated RSRP and priority of the reserved resources. For example, if more than X subchannels are reserved within the semi-dedicated resources 260, the UEs 120a to 120c may then exclude all SL-PRS resources within the semi-dedicated resources 260. For resource exclusion, the UEs 120a to 120c may be (pre-)configured to exclude resources based on the associated RSRP and the priority of the reserved subchannels. For example, if more than X subchannels are reserved within the semi-dedicated resources 260 whose RSRP is higher than the RSRP threshold RSRP1, the UEs 120a to 120c may then exclude all SL-PRS resources within the semi-dedicated resources 260. Furthermore, if more than X subchannels are reserved within the semi-dedicated resources 260 whose priority is higher than the priority of the SL-PRS that the UEs 120a to 120c want to transmit, the UEs 120a to 120c may then exclude all SL-PRS resources within the semi-dedicated resources 260. Exclusion of the semi-dedicated resources 260 may be based on both the associated RSRP and the priority of the reserved resources.

[0148] UEs 120a-120c may also exclude SL-PRS resources based on reserved SL-PRS resources. That is, if SL-PRS resources within the semi-dedicated resources 260 have been reserved, then UEs 120a-120c may exclude these SL-PRS resources. For resource exclusion, UEs 120a-120c may consider the RSRP and priority of the reserved SL-PRS resources. For example, if a UE 120a-120c has an associated RSRP greater than an RSRP threshold of RSRP2, then UEs 120a-120c may exclude SL-PRS resources within the semi-dedicated resources 260. Furthermore, if a UE 120a-120c has an associated priority that is greater than the priority of the SL-PRS that the UE 120a-120c intends to transmit, then the UE 120a-120c may exclude SL-PRS resources within the semi-dedicated resources 260. Excluding half SL-PRS resources may be based on two conditions: the associated RSRP and the priority of the reserved SL-PRS resources.

[0149] UEs 120a to 120c may also exclude resources based on half-duplex constraints similar to the conventional mode 2 sensing process. The SL-PRS resources remaining after resource exclusion, i.e., the remaining SL-PRS resources within the selection window, are considered candidate SL-PRS resources. UEs 120a to 120c may then select SL-PRS resources among the candidate SL-PRS resources, e.g., UEs 120a to 120c may randomly select SL-PRS resources. If the percentage of candidate resources in semi-dedicated is lower than a (pre-) configured threshold, UEs 120a to 120c may increase the RSRP threshold for excluding resources by a given amount, e.g., 3 dB, and repeat the process for excluding resources. The values ​​of X, RSRP1, and RSRP2 may be (pre-) configured to the UE, e.g., Figure 10 shown.

[0150] Figure 11 A flow chart illustrating another embodiment is shown, in which only the reservation of SL-PRS resources for resource selection using mode 2 is considered, i.e., resources are excluded based on the reserved SL-PRS resources, and not based on the reserved subchannels within the semi-dedicated resources. Figure 11 The description of steps 1101 and 1103 is similar to that of the previous embodiment, but does not take into account the reserved sub-channels within the semi-dedicated resources. Figure 11 In the illustrated embodiment, a Rel. 18 UE 120a-120c may reserve resources for an SL-PRS within the semi-dedicated resources 260, even if one or more subchannels within the semi-dedicated resources 260 have already been reserved for data transmission by another UE 120a-120d. The Rel. 18 UE 120a-120c may ignore the subchannel reservation within the semi-dedicated resources 260 (i.e., for data transmission). The Rel. 18 UE 120a-120c may be unaware of the subchannel reservation within the semi-dedicated resources 260. If one or more subchannels within the semi-dedicated resources 260 have already been reserved, and a Rel. 18 UE 120a-120c wishes to transmit an SL-PRS, this may result in a conflict, i.e., a conflict between the SL-PRS transmission by the Rel. 18 UE 120a-120c and the data transmission by the other UE 120a-120d. To avoid this, a preemption mechanism may be considered, in which the transmission of an SL-PRS takes precedence over the data transmission. To this end, the SL-PRS is (pre-)configured to have a higher priority than data transmissions of different service types. To this end, a preemption mechanism can be enabled in the resource pool. Preemption in the resource pool can be enabled using parameters (e.g., sl-PreemptionEnable-r16) within an information element (i.e., the SL-ResourcePool information element) that provides (pre-)configuration of the resource pool.

[0151] Furthermore, a legacy UE 120 d intending to transmit data may be (pre-)configured, i.e., with the preemption mechanism enabled, to check before transmitting whether other UEs 120 a to 120 d have already reserved the same subchannel for a transmission having a higher priority. Since the preemption mechanism is enabled, collisions may be avoided because if a UE 120 a to 120 d receives a reservation for a semi-dedicated resource (from a Rel. 18 UE 120 a to 120 c intending to transmit an SL-PRS) for a transmission having a higher priority than the intended transmission of the UE 120 a to 120 d, it will discard the subchannel reservation within the semi-dedicated resource.

[0152] Furthermore, the Rel. 18 UEs 120a to 120c that intend to transmit data may be (pre-)configured to exclude all resources in the semi-dedicated resources 260 during resource selection in Mode 2. The Rel. 18 UEs 120a to 120c may be aware of the semi-dedicated resources 260. In doing so, the Rel. 18 UEs 120a to 120c will not select subchannels within the semi-dedicated resources 260 for data transmission.

[0153] Figure 12 A flowchart illustrating processing steps for another embodiment of resource selection taking into account SL-PRS and resources carrying two levels of reservation is shown. After a UE 120a to 120c is triggered to send SL-PRS, e.g., by the UE's own higher layers or by another UE 120a to 120c, the UE 120a to 120c selects SL-PRS resources ( Figure 12 1201). Resource selection of SL-PRS resources may be performed using either Mode 1 resource allocation or Mode 2 resource allocation. UEs 120a to 120c also select resources for transmitting two-level reservations ( Figure 12 The resource used to transmit the secondary reservation may include one subchannel. Resource selection for the resource may be performed using either Mode 1 resource allocation or Mode 2 resource allocation. After selecting the SL-PRS resource and the resource that should carry the two-level reservation, the UEs 120a to 120c transmit the two-level reservation on the selected resource and transmit the SL-PRS on the selected SL-PRS resource. Figure 12 The UEs 120a to 120c may transmit the two-stage reservation using a transmission power greater than the transmission power for data transmission (i.e., PSSCH). In this exemplary embodiment, the UEs 120a to 120c that transmit the two-stage reservation of SL-PRS resources may be the same UEs 120a to 120c that transmit the SL-PRS resources ( Figure 12 Step 1207). However, as mentioned above, this may not be the case in general.

[0154] Figure 13 Another embodiment of transmitting two levels of reservation on a selected subchannel is shown. The first level reservation of SL-PRS is sent in a first level SCI carried in a PSCCH within a selected subchannel. In Rel.16 / 17NR V2X, the first level SCI may indicate a reservation for the initial transmission of a TB (i.e., the current transmission), as well as a reservation for one or two subsequent resources, for example, for retransmissions of the TB. The reservation includes an indication of the frequency resource location (i.e., the starting subchannel index and the number of subchannels occupied by the transmission) and the time resource location (i.e., the time slot) of the transmission. According to the embodiments disclosed herein, two levels of reservation of SL-PRS resources may be sent in one subchannel. The first level reservation 210a is sent in a first level SCI carried by a PSCCH, which is sent within a subchannel, such as Figure 13 As shown. The first-level reservation 210a indicates the reservation of semi-dedicated resources 260, and in this example, the reservation occupies all subchannels in the resource pool. Since the transmission of the two-level reservation occupies one subchannel, the reservation for the current transmission of the two-level reservation (i.e., the initial transmission) only needs to indicate that one subchannel is occupied. On the other hand, the first-level reservation 210a indicates that all subchannels in the semi-dedicated state (i.e., all subchannels in the resource pool) are reserved for the transmission of SL-PRS. In Rel.16 / 17NR V2X, it is assumed that the number of subchannels occupied by the initial transmission and the retransmission is the same, that is, the resource reservation for the initial transmission and the resource reservation for the retransmission reserve the same number of consecutive subchannels. However, the transmission of the two-level reservation may not need to occupy the same number of subchannels as the reserved semi-dedicated resources. The first-level reservation 210a can be indicated by the resource reservation carried by the first-level SCI, which is usually used to indicate the resource reservation for the retransmission. This will mean that the current transmission of the two-level reservation also occupies the same number of channels as the reserved semi-dedicated resources. To this end, according to embodiments disclosed herein, Rel.18 UEs 120a-120c are (pre-)configured to ignore the larger implicit reservation for the two-stage reservation transmission. After UE 120a-120c has determined the presence of first-stage reservation 210a (i.e., it has detected the presence of second-stage reservation 210b), UE 120a-120c knows that the reservation indicated in the first-stage SCI is associated with the SL-PRS (i.e., it is the first-stage reservation 210a), and therefore, it can ignore the larger "dummy" reservation currently transmitted in the two-stage reservation. It only needs to use the PSCCH carrying the first-stage SCI associated with the SL-PRS reservation to decode the information within the subchannel. In this way, the larger reservation currently transmitted in the two-stage reservation is the dummy reservation. Rel.18 UEs 120a-120c can also be (pre-)configured to ignore this larger "dummy" reservation for its Mode 2 sensing process.

[0155] Figure 14 1 shows a flow chart of an embodiment of receiving SL-PRS. UE 120a to 120c first checks whether it has been (pre-) configured to receive SL-PRS ( Figure 14 Step 1401 of FIG. 1402 is performed. The (pre-)configuration may be per UE 120a to 120c or per resource pool. UE 120a to 120c may be (pre-)configured not to receive SL-PRS, thereby avoiding searching for two-stage reservation and reducing its power consumption. If UE 120a to 120c is (pre-)configured to receive SL-PRS, UE 120a to 120c then searches for PSCCH ( Figure 14 Similar to the conventional process in Rel. 16 and Rel. 17, UEs 120a to 120c may search for PSCCH at all potential locations of PSCCH in each subchannel in the time slot of the resource pool. The presence of PSCCH may be detected based on the PSCCH DMRS. If PSCCH is found ( Figure 14 1405), the UEs 120a to 120c decode the first level SCI carried by the PSCCH and determine one or more resource reservations indicated by the first level SCI ( Figure 14 Then, the UEs 120a to 120c determine whether the indicated resource reservation is for data transmission or for SL-PRS transmission ( Figure 14 UE 120a to 120c checks whether the resource reservation indicated by the first level SCI corresponds to the first level reservation 210a of SL-PRS resources ( Figure 14 1409). This can be determined in various ways. UEs 120a-120c may determine that the resource reservation for a given number of subchannels corresponds to first-level reservation 210a of SL-PRS resources. UEs 120a-120c may also determine that the resource reservation for semi-dedicated resources 260 corresponds to first-level reservation 210a of SL-PRS resources. UEs 120a-120c may also determine that the resource reservation is first-level reservation 210a based on the presence of second-level reservation 210b. The presence of second-level reservation 210b may be indicated by one of the reserved bits in the first-level SCI or by an indication of the second-level SCI format associated with the SL-PRS.

[0156] If the UEs 120a to 120c detect the first level reservation of SL-PRS resources, the UEs 120a to 120c proceed to determine the destination ID of the reserved SL-PRS resources ( Figure 141411). UEs 120a to 120c, based on their (pre-)configuration, know where and how to find the destination ID. The destination ID may be sent along with the source ID. The destination ID may be sent in the same subchannel that carries the first-level reservation 210a. In particular, the source ID and destination ID may be carried in a second-level SCI associated with the first-level SCI.

[0157] After determining the destination ID, UEs 120a to 120c check whether they are target Rx UEs for SL-PRS ( Figure 14 If the UE 120a to 120c is the target Rx UE of the reserved SL-PRS resources, the UE 120a to 120c proceeds to determine the second level reservation 210b of the SL-PRS resources ( Figure 14 1415). UEs 120a-120c understand where and how to find the second-level reservation 210b based on their (pre-)configuration. Second-level reservation 210b may be carried in the same subchannel as first-level reservation 210a. In particular, second-level reservation 210b may be carried in a second-level SCI associated with the first-level SCI. After decoding second-level reservation 210b, UEs 120a-120c determine the reserved SL-PRS resources.

[0158] After the UE 120a to 120c has determined the first level reservation 210a and the second level reservation 210b of SL-PRS resources, it knows in which semi-dedicated resource 260 and in which SL-PRS resource it should receive SL-PRS ( Figure 14 Step 1417).

[0159] Figure 15 An embodiment of the time and frequency allocation of several SL-PRS resources within the semi-dedicated resources is shown. Figure 15 In the example shown, eight SL-PRS resources are depicted, where each SL-PRS resource spans four symbols, and all subchannels in the semi-dedicated resource are arranged in a comb pattern. For simplicity, only the frequency chunks within the semi-dedicated resource are depicted, but the comb pattern can be repeated in the rest of the semi-dedicated resource. Figure 15Also shown are automatic gain control (AGC) symbols and gap or guard symbols. The AGC symbols enable the Rx UE to adjust the dynamic range based on the received signal. The guard symbols support switching from transmission to reception or vice versa. Due to half-duplex constraints, UEs 120a to 120c may not be able to receive SL-PRS while transmitting SL-PRS, i.e., in the same symbol. Thus, UEs 120a to 120c transmitting SL-PRS resource 1 cannot receive SL-PRS resource 2. However, UEs 120a to 120c transmitting SL-PRS resource 1 can receive SL-PRS resource 5. The depicted example enables UEs 120a to 120c to transmit SL-PRS in SL-PRS resources 1, 2, 3, or 4 and receive SL-PRS in SL-PRS resources 5, 6, 7, or 8. This enables UEs 120a to 120c to transmit and receive SL-PRS within the same semi-dedicated resources (i.e., within the same time slot). More SL-PRS resources may be multiplexed within the semi-dedicated resources, i.e., by having one AGC symbol followed by 12 SL-PRS resources (eg, in a comb pattern) and finally a guard symbol within 14 symbols in a slot.

[0160] Figure 16 Another embodiment is shown for the case of a group of UEs 120a to 120c in an out of network coverage scenario. Figure 16 shows a signaling diagram, where the configuration of semi-dedicated resources ( Figure 16 Step 1601 of the present invention is dynamically completed between the group of UEs 120a to 120c. This allows the UEs 120a to 120c in the group to have a common understanding of the SL-PRS resources in the group. The configuration can be provided by one UE 120a to the other UEs 120b, 120c, or the UEs 120a to 120c can agree on the configuration together. Pre-configuration for sending and receiving two-level reservations ( Figure 16 The pre-configuration may be performed as in the above-described embodiment. The first UE 120a (UE 1) may instruct the second UE 120b (UE 2) to select SL-PRS resources ( Figure 16 The second UE 102b selects resources for sending the two-level reservation and for the SL-PRS resources for the first UE 120a and the second UE 120b ( Figure 161607 and 1609). As an example, the second UE 120b selects two SL-PRS resources within one semi-dedicated resource 260 for two transmissions of SL-PRS, i.e., one SL-PRS will be sent by the first UE 120a and one SL-PRS will be sent by the second UE 120b. The two SL-PRS resources can be multiplexed within one semi-dedicated resource, as described in the aforementioned embodiments. Resource selection can be accomplished using Mode 2 resource allocation, i.e., as described in the aforementioned embodiments. UEs 120a to 120c can also be within network coverage and select resources based on Mode 2 resource allocation. The second UE 102b selects a subchannel for sending the two-level reservation and the source ID and destination ID for sending the two SL-PRS resources. The two selected SL-PRS resources are denoted as SL-PRS1 and SL-PRS2, respectively, and are sent by the first UE 120a and the second UE 120b, respectively. Then, the second UE 120b sends the two-level reservation ( Figure 16 1611a, 1611b and 1613a, 1613b) and the source ID and destination ID of SL-PRS1 and SL-PRS2 ( Figure 16 1615a, 1615b) is received by the first UE 120a and the third UE 120c (UE 3). The first UE 120a and the third UE 120c determine that there is a first-level reservation 210a of SL-PRS resources. The third UE 120c also determines that it is the target receiver of two SL-PRS resources based on the destination ID. The first UE 120a determines that the second UE 120b has reserved SL-PRS resources for the first UE 120a, i.e., based on the source ID of SL-PRS1. The first UE 120a then transmits SL-PRS1 ( Figure 16 Then, the second UE 120b sends SL-PRS2 on the selected SL-PRS resource ( Figure 16 The third UE 120c receives SL-PRS1 and SL-PRS2 based on the two-level reservation and destination ID of the two SL-PRS resources received in the selected subchannel. In the illustrated example, the first UE 120a is configured to check the two-level reservation sent by the second UE 120b.

[0161] Figure 1717 is a flow chart of a method 1700 according to an embodiment for transmitting a two-level allocation of time and frequency resources for transmission of one or more sidelink positioning reference signals. The method 1700 includes step 1701 of transmitting an allocation using the two-level allocation, the two-level allocation including a first-level allocation 210a of one or more first time and frequency resources 220 from a plurality of time and frequency resources 200 having a first granularity and a second-level allocation 210b of one or more second time and frequency resources 230 from the plurality of time and frequency resources 200 having a second granularity, wherein the one or more second time and frequency resources 230 are a subset of the one or more first time and frequency resources 220.

[0162] Figure 18 18 is a flow chart of a method 1800 according to an embodiment for receiving a two-level allocation of time and frequency resources for transmission of one or more sidelink positioning reference signals. The method 1800 includes step 1801 of receiving an allocation using a two-level allocation, the two-level allocation including a first-level allocation 210a of one or more first time and frequency resources 220 from a plurality of time and frequency resources 200 having a first granularity and a second-level allocation 210b of one or more second time and frequency resources 230 from the plurality of time and frequency resources 200 having a second granularity, wherein the one or more second time and frequency resources 230 are a subset of the one or more first time and frequency resources 220.

[0163] Those skilled in the art will understand that the "blocks" ("units") in the various figures (methods and devices) represent or describe the functions of an embodiment of the present invention (and not necessarily independent "units" in hardware or software), thereby equally describing the functions or features of the device embodiments and the method embodiments (unit = step).

[0164] In the several embodiments provided in this application, it should be understood that the disclosed systems, devices, and methods can be implemented in other ways. For example, the device embodiments described are merely exemplary. For example, the unit division is merely a logical function division, and in actual implementation, it may be another division. For example, multiple units or components can be merged or integrated into another system, or some features can be ignored or not performed. In addition, the mutual coupling or direct coupling or communication connection shown or discussed can be achieved through some interfaces. The indirect coupling or communication connection between devices or units can be achieved through electronic, mechanical or other forms.

[0165] The units described as discrete parts may or may not be physically separate, and the parts shown as units may or may not be physical units. They may be located in one location or distributed across multiple network units. Some or all of these units may be selected to achieve the purpose of this embodiment as needed.

[0166] Furthermore, the functional units in the embodiments of the present invention may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit.

Claims

1. A user equipment (UE) (120a) configured to send a time and frequency resource allocation for transmission of one or more sidelink positioning reference signals (SL-PRS), wherein: The UE (120a) is configured to send the allocation using a two-level allocation, the two-level allocation comprising a first-level allocation (210a) of one or more first time and frequency resources (220) of a plurality of time and frequency resources (200) having a first granularity and a second-level allocation (210b) of one or more second time and frequency resources (230) of the plurality of time and frequency resources (200) having a second granularity, wherein the one or more second time and frequency resources (230) are a subset of the one or more first time and frequency resources (220).

2. The UE (120a) according to claim 1, wherein The UE (120a) is configured to send first-level sidelink control information (SCI), wherein the first-level SCI includes the first-level allocation (210a).

3. The UE (120a) according to claim 2, wherein The UE (120a) is configured to send second-level sidelink control information (SCI), wherein the second-level SCI includes the second-level allocation (210b).

4. The UE (120a) according to claim 3, wherein The first level SCI includes information indicating the presence of the second level allocation (210b).

5. The UE (120a) according to claim 4, wherein The first level SCI further comprises information on the format of the second level SCI, and / or one or more reserved bits of the first level SCI comprise said information indicating said presence of the second level allocation (210b).

6. The UE (120a) according to any one of the preceding claims, wherein: The plurality of time and frequency resources (200) includes a plurality of time slots and a plurality of sub-channels.

7. The UE (120a) according to claim 6, wherein The UE (120a) is configured to transmit the two-level allocation within the plurality of time slots and one or more subchannels of the plurality of subchannels.

8. The UE (120a) according to claim 7, wherein The UE (120a) is configured to transmit control information associated with the one or more SL-PRSs within the plurality of time slots and the one or more subchannels of the plurality of subchannels carrying the two-level allocation.

9. The UE (120a) according to any one of claims 6 to 8, wherein: The UE (120a) is configured to transmit the two-level allocation in a time slot comprising the first time and frequency resources (220) one or more time slots prior.

10. The UE (120a) according to any one of claims 6 to 8, wherein: The UE (120a) is configured to transmit the two-level allocation in a time slot comprising the first time and frequency resources (220).

11. The UE (120a) according to any one of the preceding claims, wherein: The UE (120a) is configured to transmit the one or more SL-PRSs on the second time and frequency resources (230) indicated by the second level allocation (210b).

12. The UE (120a) according to any one of the preceding claims, wherein: The UE (120a) is configured to transmit the one or more SL-PRSs on the second time and frequency resources (230) indicated by the first level allocation (210a) and the second level allocation (210b).

13. The UE (120a) according to any one of the preceding claims, wherein: The UE (120a) is configured to transmit the time and frequency resource allocation using the two-level allocation for another UE (120b, 120c) to transmit one or more of the one or more SL-PRSs.

14. The UE (120a) according to any one of the preceding claims, wherein: The first granularity is a sub-channel of a time slot.

15. The UE (120a) according to claim 14, wherein The plurality of time and frequency resources (200) includes one or more SL-PRS resources (260) having the second granularity.

16. The UE (120a) according to any one of the preceding claims, wherein: The plurality of time and frequency resources (200) include one or more SL-PRS resources (260), and the UE (120a) and / or another UE (120b, 120c) is configured to transmit the one or more SL-PRSs on one or more of the one or more SL-PRS resources (260).

17. The UE (120a) according to claim 16, wherein The UE (120a) is configured to transmit the two-level allocation in one or more time and frequency resources of the plurality of time and frequency resources (200) that are different from the one or more SL-PRS resources (260).

18. The UE (120a) according to claim 17, wherein The UE (120a) is configured to transmit data in one or more time and frequency resources of the plurality of time and frequency resources (200), the one or more time and frequency resources including one or more SL-PRS resources of the one or more SL-PRS resources (260).

19. The UE (120a) according to claim 17, wherein The UE (120a) is configured to transmit information associated with one or more of the one or more SL-PRS resources (260) in one or more of the plurality of time and frequency resources (200).

20. The UE (120a) according to claim 15 or 16, wherein The UE (120a) is configured to receive configuration information about the one or more SL-PRS resources (260) from a base station (110) or from a second another UE (120b, 120c).

21. The UE (120a) according to any one of the preceding claims, wherein: The UE (120a) is configured to send one or more identifiers of one or more UEs (120b, 120c) that intend to send the one or more SL-PRSs on the second time and frequency resources (230).

22. The UE (120a) according to any one of the preceding claims, wherein: The UE (120a) is configured to send one or more identifiers of one or more UEs (120b, 120c) that intend to receive the one or more SL-PRSs on the second time and frequency resources (230).

23. A method (1700) for transmitting a time and frequency resource allocation for transmission of one or more sidelink positioning reference signals (SL-PRS), wherein: The method (1700) comprises sending (1701) the allocation using a two-level allocation comprising a first level allocation (210a) of one or more first time and frequency resources (220) of a plurality of time and frequency resources (200) having a first granularity and a second level allocation (210b) of one or more second time and frequency resources (230) of the plurality of time and frequency resources (200) having a second granularity, wherein the one or more second time and frequency resources (230) are a subset of the one or more first time and frequency resources (220).

24. A user equipment (UE) (120b) for receiving a time and frequency resource allocation for transmission of one or more sidelink positioning reference signals (SL-PRS), wherein: The UE (120b) is configured to receive the allocation using a two-level allocation, the two-level allocation comprising a first level allocation (210a) of one or more first time and frequency resources (220) of a plurality of time and frequency resources (200) having a first granularity and a second level allocation (210b) of one or more second time and frequency resources (230) of the plurality of time and frequency resources (200) having a second granularity, wherein the one or more second time and frequency resources (230) are a subset of the one or more first time and frequency resources (220).

25. The UE (120b) according to claim 24, wherein The UE (120b) is configured to receive first-level sidelink control information (SCI), wherein the first-level SCI includes the first-level allocation (210a).

26. The UE (120b) according to claim 25, wherein The UE (120b) is configured to determine that the first level SCI includes the first level allocation (210a) by determining that the first level SCI indicates the second level allocation (210b).

27. The UE (120b) according to claim 25 or 26, wherein The UE (120b) is configured to receive second-level sidelink control information (SCI), wherein the second-level SCI includes the second-level allocation (210b).

28. The UE (120b) according to claim 26 or 27, wherein The first level SCI includes information indicating the presence of the second level allocation (210b).

29. The UE (120b) according to claim 27 or 28, wherein The first level SCI further comprises information on the format of the second level SCI, and / or one or more reserved bits of the first level SCI comprise said information indicating said presence of the second level allocation (210b).

30. The UE (120b) according to any one of claims 24 to 29, wherein The plurality of time and frequency resources (200) includes a plurality of time slots and a plurality of sub-channels.

31. The UE (120b) according to claim 30, wherein The UE (120b) is configured to receive the two-level allocation within the plurality of time slots and one or more subchannels of the plurality of subchannels.

32. The UE (120b) according to claim 31, wherein The UE (120b) is configured to receive control information associated with the one or more SL-PRSs within the plurality of time slots and the one or more subchannels of the plurality of subchannels carrying the two-level allocation.

33. The UE (120b) according to any one of claims 30 to 32, wherein The UE (120b) is configured to receive the two-level allocation in a time slot comprising the first time and frequency resources (220) one or more time slots prior.

34. The UE (120b) according to any one of claims 30 to 32, wherein: The UE (120b) is configured to receive the two-level allocation in a time slot comprising the first time and frequency resources (220).

35. The UE (120b) according to any one of claims 24 to 34, wherein The UE (120b) is configured to transmit the one or more SL-PRSs on the second time and frequency resources (230) indicated by the second level allocation (210b).

36. The UE (120b) according to any one of claims 24 to 34, wherein The UE (120b) is configured to transmit the one or more SL-PRSs on the second time and frequency resources (230) indicated by the first level allocation (210a) and the second level allocation (210b).

37. The UE (120b) according to any one of claims 24 to 36, wherein The UE (120b) is configured to receive the one or more SL-PRSs on the second time and frequency resources (230) indicated by the second level allocation (210b).

38. The UE (120b) according to any one of claims 24 to 35, wherein The UE (120b) is configured to receive the one or more SL-PRSs on the second time and frequency resources (230) indicated by the first level allocation (210a) and the second level allocation (210b).

39. The UE (120b) according to any one of claims 24 to 38, wherein The first granularity is a sub-channel of a time slot.

40. The UE (120b) of claim 39, wherein: The plurality of time and frequency resources (200) includes one or more SL-PRS resources (260) having the second granularity.

41. The UE (120b) according to any one of claims 24 to 40, wherein The plurality of time and frequency resources (200) include one or more SL-PRS resources (260), and the UE (120b) and / or another UE (120a, 120c) are configured to transmit the one or more SL-PRSs on one or more of the one or more SL-PRS resources (260).

42. The UE (120b) of claim 41, wherein: The UE (120b) is configured to receive the two-level allocation in one or more time and frequency resources of the plurality of time and frequency resources (200) that are different from the one or more SL-PRS resources (260).

43. The UE (120b) of claim 42, wherein: The UE (120b) is configured to transmit data in one or more time and frequency resources of the plurality of time and frequency resources (200), the one or more time and frequency resources including one or more SL-PRS resources of the one or more SL-PRS resources (260).

44. The UE (120b) of claim 42, wherein: The UE (120b) is configured to receive data in one or more time and frequency resources of the plurality of time and frequency resources (220), the one or more time and frequency resources including one or more SL-PRS resources of the one or more SL-PRS resources (260).

45. The UE (120b) of claim 42, wherein: The UE (120b) is configured to transmit information associated with one or more of the one or more SL-PRS resources (260) in one or more of the plurality of time and frequency resources (200).

46. ​​The UE (120b) of claim 42, wherein: The UE (120b) is configured to receive, in one or more time and frequency resources of the plurality of time and frequency resources (200), information associated with one or more SL-PRS resources of the one or more SL-PRS resources (260).

47. The UE (120b) according to any one of claims 40 to 44, wherein The UE (120b) is configured to receive configuration information about the one or more SL-PRS resources from a base station (110) or from a second another UE (120a, 120b).

48. The UE (120b) according to any one of claims 24 to 47, wherein The UE (120b) is configured to receive one or more identifiers (240) of one or more UEs (120a, 120c) that intend to transmit the one or more SL-PRSs on the second time and frequency resources (230).

49. The UE (120b) according to any one of claims 24 to 48, wherein The UE (120b) is configured to receive one or more identifiers (240) of one or more UEs (120a, 120c) that intend to receive the one or more SL-PRSs on the second time and frequency resources (230).

50. A method (1800) for receiving a time and frequency resource allocation for transmission of one or more sidelink positioning reference signals (SL-PRS), wherein: The method (1800) comprises receiving (1801) the allocation using a two-level allocation comprising a first-level allocation (210a) of one or more first time and frequency resources (220) of a plurality of time and frequency resources (200) having a first granularity and a second-level allocation (210b) of one or more second time and frequency resources (230) of the plurality of time and frequency resources (200) having a second granularity, wherein the one or more second time and frequency resources (230) are a subset of the one or more first time and frequency resources (220).

51. A computer program product comprising a computer-readable storage medium for storing program code, wherein when the program code is executed by a computer or a processor, the program code causes the computer or the processor to perform the method (1700) according to claim 23 or the method (1800) according to claim 50.

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