Transmitting apparatus, method and integrated circuit

Abstract

The invention relates to a transmitting device, a method and an integrated circuit, a transmitting device for transmitting data to one or more receiving devices via a sidelink interface, wherein the transmission of data comprises a first transmission of data and one or more retransmissions of data following the first data transmission, the transmitting device comprising: a processor performing a resource sensing procedure for selecting radio resources available for the transmitting device to transmit data at a later point in time, the processor performing an autonomous radio resource allocation based on the outcome of the resource sensing procedure during a sensing window to select time-frequency radio resources within a transmission window to be used for performing the first transmission of data, and the processor determining a data transmission timing pattern out of a plurality of data transmission timing patterns, each data transmission timing pattern indicating a transmission timing for performing one or more transmissions of data, a transmitting unit, the transmitting unit performing the first data transmission using the selected time-frequency radio resources and performing the one or more data retransmissions relative to the first data transmission in the transmission timing defined by the determined data transmission timing pattern.

Description

[0001] This application is a divisional application of Chinese Patent Application No. 201780048824.8, filed on July 31, 2017, entitled "Improved Initial Transmission and Retransmission of Data for V2X Transmission", filed by Panasonic Corporation (USA). Technical Field

[0002] This disclosure relates to improved data transmission and resource allocation via a sidelink interface. Corresponding methods and apparatus for use in this invention are provided. Background Technology

[0003] Long Term Evolution (LTE)

[0004] Third-generation mobile systems (3G) based on WCDMA radio access technology are being widely deployed globally. The first step in enhancing or developing this technology requires the introduction of High-Speed ​​Downlink Packet Access (HSDPA) and Enhanced Uplink, also known as High-Speed ​​Uplink Packet Access (HSUPA), to provide a highly competitive radio access technology.

[0005] To prepare for increased user demand and compete with new radio access technologies, 3GPP introduced a new mobile communication system called Long Term Evolution (LTE). LTE is designed to meet operators' needs for high-speed data and media transmission, as well as high-capacity voice support, over the next decade. Providing high bit rates is a key feature of LTE.

[0006] The work item (WI) specification for the Long Term Evolution (LTE), known as Evolved UMTS Terrestrial Radio Access (UTRA) and UMTS Terrestrial Radio Access Network (UTRAN), has been finalized as Version 8 (LTE Rel. 8). The LTE system represents an efficient packet-based radio access and radio access network, providing fully IP-based functionality with low latency and low cost. In LTE, several scalable transmission bandwidths, such as 1.4, 3.0, 5.0, 10.0, 15.0, and 20.0 MHz, are specified to allow for flexible system deployment using a given spectrum. In the downlink, Orthogonal Frequency Division Multiplexing (OFDM)-based radio access is employed due to its inherent immunity to multipath interference (MPI) caused by low symbol rates, the use of cyclic prefixes (CP), and its affinity for different transmission bandwidth arrangements. In the uplink, Single-Carrier Frequency Division Multiple Access (SC-FDMA)-based radio access is employed because, considering the limited transmission power of User Equipment (UE), providing wide-area coverage is prioritized over improving peak data rates. It employs many key block radio access technologies, including multiple-input multiple-output (MIMO) channel transmission technology, and implements an efficient control signaling structure in LTE Rel.8 / 9.

[0007] LTE architecture

[0008] Overall LTE architecture as follows Figure 1 As shown, E-UTRAN consists of Evolved Node Bs (eNodeBs) that provide E-UTRA user plane (PDCP / RLC / MAC / PHY) and control plane (RRC) protocol terminals to User Equipment (UE). The eNodeB (eNB) hosts the Physical (PHY), Media Access Control (MAC), Radio Link Control (RLC), and Packet Data Control Protocol (PDCP) layers, including user plane header compression and encryption. It also provides Radio Resource Control (RRC) functions corresponding to the control plane. It performs numerous functions, including radio resource management, admission control, scheduling, implementation of negotiated uplink Quality of Service (QoS), cell information broadcasting, encryption / decryption of user and control plane data, and compression / decompression of downlink / uplink user plane packet headers. eNodeBs interconnect with each other via the X2 interface.

[0009] The eNodeB also connects to the EPC (Evolved Packet Core) via the S1 interface, more specifically to the MME (Mobility Management Entity) via the S1-MME, and to the Serving Gateway (SGW) via the S1-U. The S1 interface supports many-to-many relationships between the MME / Serving Gateway and the eNodeB. The SGW routes and forwards user packets, and also acts as a mobility anchor for the user plane during handovers between eNodeBs, and as an anchor for mobility between LTE and other 3GPP technologies (terminating the S4 interface and relaying traffic between 2G / 3G systems and the PDN GW). For idle user equipment, the SGW terminates the downlink data path and triggers paging when downlink data arrives at the user equipment. It manages and stores user equipment context, such as parameters of IP bearer services or intra-network routing information. It also performs replication of user services under lawful interception.

[0010] The MME is a key control node in the LTE access network. It is responsible for idle-mode UE tracking and paging processes, including retransmissions. It is involved in bearer activation / deactivation processes and is also responsible for selecting the SGW for UEs during initial attachment and during intra-LTE handovers involving core network (CN) node relocation. It is responsible for authenticating users (through interaction with the HSS). Non-access stratum (NAS) signaling terminates at the MME, which is also responsible for generating and assigning temporary identifiers to UEs. It checks UE authorization to pre-occupy the service provider's Public Land Mobile Network (PLMN) and enforces UE roaming restrictions. The MME is the termination point in the network for encryption / integrity protection of NAS signaling and handles security key management. The MME also supports lawful interception of signaling. The MME also provides control plane functions for mobility between LTE and 2G / 3G access networks, where the S3 interface terminates at the MME from the SGSN. The MME also terminates the S6a interface toward the home HSS for roaming UEs.

[0011] Component carrier structure in LTE

[0012] In 3GPP LTE systems, downlink component carriers are subdivided in the time-frequency domain into so-called subframes. In 3GPP LTE, as... Figure 2 As shown, each subframe is divided into two downlink time slots, where the first downlink time slot includes the control channel region (PDCCH region) within the first OFDM symbol. Each subframe consists of a given number of OFDM symbols in the time domain (12 or 14 OFDM symbols in 3GPP LTE (Release 8), where each OFDM symbol spans the entire bandwidth of the component carrier. OFDM symbols are therefore composed of multiple modulated symbols transmitted on each subcarrier. In LTE, the transmitted signal in each time slot is... subcarriers and OFDM symbol resource grid description. This refers to the number of resource blocks within the bandwidth. It depends on the downlink transmission bandwidth configured in the cell and should meet the following requirements. in and These are the minimum and maximum downlink bandwidths, respectively, which are supported by the current version of the specification. This refers to the number of subcarriers within a resource block. For a normal cyclic prefix subframe structure, and

[0013] Assuming a multi-carrier communication system employing OFDM, such as in 3GPP Long Term Evolution (LTE), the smallest resource unit that can be allocated by the scheduler is a "resource block". A physical resource block (PRB) is defined as a contiguous block of OFDM symbols in the time domain (e.g., 7 OFDM symbols) and such... Figure 2 The frequency domain shown represents consecutive subcarriers (e.g., 12 subcarriers for component carriers). In 3GPP LTE (Release 8), a physical resource block is therefore composed of resource elements corresponding to a time slot in the time domain and 180 kHz in the frequency domain (for further details regarding the downlink resource grid, see, for example, 3GPP TS 36.211, “Evolve Universal Terrestrial Radio Access (E-UTRA); Physical Channels and Modulation (Release 8)”, current version 13.1.0, Section 6.2, available at http: / / www.3gpp.org and incorporated herein by reference).

[0014] A subframe consists of two time slots, such that there are 14 OFDM symbols in the subframe when using the so-called "normal" CP (Cyclic Prefix), and 12 OFDM symbols in the subframe when using the so-called "extended" CP. For the sake of terminology, in the following text, time-frequency resources equivalent to the same consecutive subcarriers spanning the entire subframe are referred to as a "resource block pair" or equivalent "RB pair" or "PRB pair".

[0015] The term "component carrier" refers to a combination of several resource blocks in the frequency domain. In future LTE versions, the term "component carrier" will no longer be used; instead, the term will change to "cell," which refers to a combination of downlink and optional uplink resources. The system information transmitted on downlink resources indicates the link between the carrier frequencies of the downlink and uplink resources.

[0016] Similar assumptions about component carrier structures will also apply to subsequent versions.

[0017] Carrier aggregation in LTE-A is used to support wider bandwidth.

[0018] The spectrum for IMT-Advanced was determined at the World Radiocommunication Conference (WRC-07) in 2007. Although the overall spectrum for IMT-Advanced was identified, the actual available frequency bandwidth varied by region or country. However, following the decision on the overview of available spectrum, standardization of the radio interface began within the 3rd Generation Partnership Project (3GPP). At the 3GPP TSG RAN#39 meeting, a research project description for “Further Advancements for E-UTRA (LTE-Advanced)” was approved. This research project covered the technical components considered in the evolution of E-UTRA, such as meeting the requirements of IMT-Advanced.

[0019] LTE-Advanced Systems can support a bandwidth of 100MHz, while LTE systems can only support 20MHz. Currently, the lack of radio spectrum has become a bottleneck for the development of wireless networks, making it difficult to find a sufficiently wide spectrum band for LTE-Advanced Systems. Therefore, there is an urgent need to find ways to obtain a wider radio spectrum band, and one possible answer is carrier aggregation.

[0020] In carrier aggregation, two or more component carriers are aggregated to support a wider transmission bandwidth of up to 100MHz. Several cells in an LTE system are aggregated into a wider channel in an LTE-Advanced system, which is wide enough for 100MHz, even if these cells in LTE may be in different frequency bands.

[0021] All component carriers can be configured to be LTE Rel.8 / 9 compatible, at least as long as the bandwidth of the component carriers does not exceed the supported bandwidth of the LTE Rel.8 / 9 cell. Not all component carriers aggregated by user equipment need to be Rel.8 / 9 compatible. Existing mechanisms (such as blocking) can be used to prevent Rel-8 / 9 user equipment from pre-occupying component carriers.

[0022] User equipment can receive or transmit simultaneously on one or more component carriers (corresponding to multiple serving cells) depending on its capabilities. LTE-A Rel.10 user equipment with receive and / or transmit capabilities for carrier aggregation can receive and / or transmit simultaneously on multiple serving cells, while LTE Rel.8 / 9 user equipment can only receive and transmit on a single serving cell, provided that the component carrier structure conforms to the Rel.8 / 9 specification.

[0023] Carrier aggregation is supported for both continuous and non-continuous component carriers, where each component carrier (using 3GPP LTE (version 8 / 9) digitization) is limited to a maximum of 110 resource blocks in the frequency domain.

[0024] 3GPP LTE-A (Release 10) compliant user equipment can be configured to aggregate different numbers of component carriers originating from the same eNodeB (base station), as well as potentially different bandwidths in the uplink and downlink. The number of configurable downlink component carriers depends on the UE's downlink path aggregation capability. Conversely, the number of configurable uplink component carriers depends on the UE's uplink aggregation capability. Currently, it may not be possible to configure mobile terminals with more uplink component carriers than downlink component carriers. In typical TDD deployments, the number of component carriers in the uplink and downlink, as well as the bandwidth of each component carrier, are the same. Component carriers originating from the same eNodeB do not need to provide the same coverage.

[0025] The spacing between the center frequencies of consecutive aggregated component carriers should be a multiple of 300kHz. This is to ensure compatibility with the 100kHz frequency grating of 3GPP LTE (Revision 8 / 9) while maintaining the orthogonality of subcarriers with a 15kHz spacing. Depending on the aggregation scenario, an n×300kHz spacing can be facilitated by inserting a small number of unused subcarriers between consecutive component carriers.

[0026] The aggregation of multiple carriers is only exposed to the MAC layer. For both uplink and downlink, a HARQ entity is required in the MAC for each aggregated component carrier. (In the absence of a SU-MIMO for the uplink) At most one transport block exists for each component carrier. The transport block and its potential HARQ retransmissions need to be mapped onto the same component carrier.

[0027] When carrier aggregation is configured, a mobile terminal has only one RRC connection with the network. During RRC connection establishment / re-establishment, a cell provides security inputs (one ECGI, one PCI, and one ARFCN) and non-access stratum mobility information (e.g., TAI) similar to those in LTERel.8 / 9. After RRC connection establishment / re-establishment, the component carriers corresponding to the cell are called the downlink primary cell (PCell). In connected state, each user equipment always configures one and only one downlink PCell (DL PCell) and one uplink PCell (UL PCell). Within the configured set of component carriers, other cells are called secondary cells (SCells); the carriers of the SCells are the downlink secondary component carriers (DL SCC) and the uplink secondary component carriers (UL SCC). A maximum of five serving cells, including PCells, can be configured for a UE.

[0028] MAC layer / entity, RRC layer, physical layer

[0029] The LTE Layer 2 user plane / control plane protocol stack comprises four sublayers: RRC, PDCP, RLC, and MAC. The Media Access Control (MAC) layer is the lowest sublayer in the Layer 2 architecture of the LTE radio protocol stack and is defined by, for example, the 3GPP technical standard TS 36.321 of current version 13.2.0. Connections to the physical layer are made via transport channels, and connections to the RLC layer are made via logical channels. The MAC layer therefore performs multiplexing and demultiplexing between the logical and transport channels: the MAC layer on the transport side constructs MAC PDUs (called transport blocks) from MAC SDUs received via the logical channel, and the MAC layer on the receiver side recovers MAC SDUs from MAC PDUs received via the transport channel.

[0030] The MAC layer provides data transmission services to the RLC layer via logical channels (see subclauses 5.4 and 5.3 of TS 36.321, which are incorporated herein by reference). These logical channels are either control logical channels carrying control data (e.g., RRC signaling) or service logical channels carrying user plane data. Conversely, data from the MAC layer is exchanged with the physical layer via transport channels, which are classified as downlink or uplink. Data is multiplexed into the transport channels according to its transmission method in the air.

[0031] The physical layer is responsible for the actual transmission of data and control information via the air interface; that is, the physical layer carries all information from the MAC transport channel through the air interface on the transport side. Some important functions performed by the physical layer include coding and modulation, adaptive link control (AMC), power control, cell search (for initial synchronization and handover purposes), and other measurements for the RRC layer (within and between LTE systems). The physical layer performs transmission based on transport parameters such as modulation scheme, coding rate (i.e., modulation and coding scheme, MCS), and the number of physical resource blocks. More information about the functions of the physical layer can be found in the current version 13.1.1 of 3GPP technical standard 36.213 (which is incorporated herein by reference).

[0032] The Radio Resource Control (RRC) layer controls communication between the UE and eNB at the radio interface, as well as the mobility of the UE moving across several cells. The RRC protocol also supports the transmission of NAS information. For UEs in RRC_Idle mode, RRC supports notifications from the network of incoming calls. RRC connection control covers all processes related to the establishment, modification, and release of RRC connections, including paging, measurement configuration and reporting, radio resource configuration, initial security activation, and the establishment of signaling radio bearers (SRBs) and radio bearers carrying user data (data radio bearers, DRBs).

[0033] The Radio Link Control (RLC) sublayer primarily includes ARQ functionality and supports data segmentation and concatenation. Specifically, the RLC layer performs framing of RLC SDUs to fit them into sizes indicated by the MAC layer. Both of these processes minimize protocol overhead, independent of the data rate. The RLC layer connects to the MAC layer via logical channels. Each logical channel transmits different types of traffic. The layer above the RLC layer is typically the PDCP layer, but in some cases, it is the RRC layer. This is because RRC messages transmitted on the logical channels BCCH (Broadcast Control Channel), PCCH (Paging Control Channel), and CCCH (Common Control Channel) do not require security protection and therefore bypass the PDCP layer to directly enter the RLC layer.

[0034] Uplink Access Scheme for LTE

[0035] For uplink transmission, power-efficient user terminal transmission is required to maximize coverage. Single-carrier transmission, combined with FDMA with dynamic bandwidth allocation, has been selected as the evolved UTRA uplink transmission scheme. The main reason for the preference for single-carrier transmission compared to multi-carrier signaling (OFDMA) is the lower peak-to-average power ratio (PAPR), and the corresponding improved power amplifier efficiency and improved coverage (higher data rates for a given terminal peak power). During each time interval, the eNodeB allocates unique time / frequency resources to users for transmitting user data, thereby ensuring intra-cell orthogonality. Orthogonal access in the uplink promises improved spectral efficiency by eliminating intra-cell interference. Interference due to multipath propagation is addressed at the base station (eNodeB), which is aided by inserting a cyclic prefix into the transmitted signal.

[0036] The basic physical resources used for data transmission include frequency resources of size BWgrant for a time interval, such as subframes, on which encoded information bits are mapped. It should be noted that a subframe (also called a Transmission Time Interval (TTI)) is the minimum time interval used for user data transmission. However, by concatenating subframes, frequency resources BWgrant can be allocated to users for a longer period than a single TTI.

[0037] Layer 1 / Layer 2 control signaling

[0038] To inform scheduled users of their allocation status, transmission format, and other transmission-related information (e.g., HARQ information, Transmission Power Control (TPC) commands), L1 / L2 control signaling is transmitted along with data on the downlink. Assuming user allocation can change based on different subframes, L1 / L2 control signaling is multiplexed with downlink data within the subframe. It should be noted that user allocation can also be performed on a TTI (Transmission Time Interval), where the TTI length can be a multiple of the subframe length. The TTI length can be fixed for all users in the service area, different for different users, or even dynamic for each user. Typically, L1 / 2 control signaling only needs to be transmitted once per TTI. Without loss of generality, the following assumption is made that the TTI equals one subframe.

[0039] L1 / L2 control signaling is transmitted on the Physical Downlink Control Channel (PDCCH). The PDCCH carries messages as Downlink Control Information (DCI), which in most cases include resource allocation and other control information for mobile terminals or UE groups. Several PDCCHs can be transmitted in a single subframe.

[0040] Typically, the information transmitted in L1 / L2 control signaling for allocating uplink or downlink radio resources (specifically LTE(-A) version 10) can be categorized into the following items:

[0041] - User ID This indicates the assigned user. This is typically included in the checksum by masking the CRC with the user's identity.

[0042] - Resource allocation information This indicates the allocation of resources (e.g., resource blocks, RBs) to a user. Alternatively, this information is referred to as Resource Block Allocation (RBA). Note that the number of RBs allocated to a user can be dynamic;

[0043] - Carrier indicator If the control channel allocation transmitted on the first carrier involves resources on the second carrier, i.e., resources on or associated with the second carrier, then the carrier indicator is used (cross-carrier scheduling);

[0044] - Modulation and coding schemes Determine the modulation scheme and coding rate to be used;

[0045] - HARQ Information Examples such as New Data Indicator (NDI) and / or Redundant Version (RV) are particularly useful in the retransmission of data packets or portions thereof;

[0046] - Power control commands It is used to adjust the transmission power of the allocated uplink data or control information transmission;

[0047] - Reference signal information Such as the applied cyclic shift and / or orthogonal overlay code index, used for transmitting or receiving reference signals related to allocation;

[0048] - Uplink or downlink allocation index This is used to identify the allocation order, which is particularly useful in TDD systems;

[0049] - Frequency hopping information For example, indicating whether and how to apply resource hopping to increase frequency diversity;

[0050] - CSI Request This is used to trigger the transmission of channel state information in the allocated resources; and

[0051] - Multi-cluster information This is a flag used to indicate and control whether a transmission occurs in a single cluster (a contiguous set of RBs) or in multiple clusters (at least two non-contiguous sets of contiguous RBs). Multi-cluster allocation has been introduced through 3GPP LTE-(A) Release 10.

[0052] It should be noted that the above list is not exhaustive and depends on the DCI format used; not all of the mentioned information items need to be present in every PDCCH transmission.

[0053] Downlink control information occurs in several formats, which differ in overall size and the information contained in their fields as described above. The different DCI formats currently defined for LTE are as follows and are described in detail in 3GPP TS 36.212 “Multiplexing and channel coding,” section 5.3.3.1 (current version v13.1.0 is available at http: / / www.3gpp.org and is incorporated herein by reference). 3GPP technical standard TS 36.212, current version 13.1.0, defines control information for the sidelink interface in sub-clause 5.4.3 (which is incorporated herein by reference).

[0054] Semi-persistent scheduling (SPS)

[0055] In both downlink and uplink, the eNodeB dynamically allocates resources to user equipment (UEs) each transmission interval via the L1 / L2 control channel (PDCCH), where UEs are addressed via their specific C-RNTIs. As previously mentioned, the CRC of the PDCCH is masked by the C-RNTI of the addressed UE (so-called dynamic PDCCH). Only UEs with matching C-RNTIs can correctly decode the PDCCH content, i.e., the CRC check is positive. This PDCCH signaling is also known as dynamic (scheduled) granting. UEs monitor the L1 / L2 control channel used for dynamic granting each transmission interval to find the possible allocations (downlink and uplink) to which they are assigned.

[0056] Furthermore, E-UTRAN can continuously allocate uplink / downlink resources for initial HARQ transmissions. When needed, retransmissions are explicitly signaled via the L1 / L2 control channels. Because retransmissions are dynamically scheduled, this operation is called semi-persistent scheduling (SPS), where resources are allocated to user equipment on a semi-persistent basis (semi-persistent resource allocation). The benefit is that PDCCH resources used for initial HARQ transmissions are preserved. Semi-persistent scheduling can be used in PCells in version 10, but not in SCells.

[0057] One example of a service that can be scheduled using semi-persistent scheduling is Voice over IP (VoIP). During a conversation burst, VoIP packets are generated at the codec every 20ms. Therefore, the eNodeB can continuously allocate uplink or corresponding downlink resources every 20ms, which can then be used for the transmission of VoIP packets. Generally, semi-persistent scheduling is beneficial for services with predictable traffic behavior (i.e., constant bit rate, periodic packet arrival times).

[0058] While resources have been continuously allocated for the initial transmission, the User Equipment (UE) also monitors the PDCCH in the subframe. Dynamic (scheduled) granting, i.e., the PDCCH with a C-RNTI mask CRC, can replace semi-persistent resource allocation. If the UE finds its C-RNTI on the L1 / L2 control channel in the subframe while having allocated semi-persistent resources, the L1 / L2 control channel allocation replaces persistent resource allocation for the transmission time interval, and the UE adheres to dynamic granting. When the UE does not find dynamic granting, it will transmit / receive according to the semi-persistent resource allocation.

[0059] The configuration of semi-persistent scheduling is accomplished by RRC signaling. For example, the periodicity of persistent allocation, such as a PS_ period, is signaled within Radio Resource Control (RRC) signaling. Activation of persistent allocation, along with equally precise timing, physical resource, and transport format parameters, is sent via PDCCH signaling. Based on the SPS activation PDCCH for each PS_ period, once semi-persistent scheduling is activated, the user equipment follows the semi-persistent resource allocation. Essentially, the user equipment stores the SPS activation PDCCH content and follows the PDCCH periodically as signaled.

[0060] To distinguish between dynamic PDCCH and PDCCH activated by semi-persistent scheduling (also known as SPS-activated PDCCH), a separate identifier is introduced. Essentially, the CRC of the SPS-activated PDCCH is masked by this additional identifier, referred to below as SPSC-RNTI. The SPS C-RNTI is also 16 bits in size, the same as the regular C-RNTI. Furthermore, the SPS C-RNTI is also user equipment specific; each user equipment configured for semi-persistent scheduling is assigned a unique SPS C-RNTI.

[0061] When a user equipment (UE) detects that a semi-persistent resource allocation has been activated by the corresponding SPS-activated PDCCH, the UE will store the PDCCH content (i.e., the semi-persistent resource allocation) and apply it every semi-persistent scheduling interval (i.e., periodic notification via RRC signaling). As mentioned, dynamic allocation, i.e., signaling notification on a dynamic PDCCH, is only a "one-time allocation." SPS allocation retransmissions are also signaled using the SPS C-RNTI. To distinguish between SPS activation and SPS retransmission, the NDI (New Data Indicator) bit is used. SPS activation is indicated by setting the NDI bit to 0. An SPS PDCCH with the NDI bit set to 1 indicates a retransmission of the initial transmission used for semi-persistent scheduling.

[0062] Similar to the activation of semi-persistent scheduling, the eNodeB can also deactivate semi-persistent scheduling, also known as SPS resource release. Several options exist for signaling the release of semi-persistent scheduling resources. One option would be to use PDCCH signaling, where some PDCCH fields are set to certain predefined values, indicating an SPS PDCCH with zero-size resource allocation. Another option would be to use MAC control signaling. LTE Device-to-Device (D2D) Proximity Service (ProSe)

[0063] Proximity-based applications and services represent an emerging social technology trend. Identified areas include commercial services and public safety-related services that will be of interest to operators and users. Introducing Proximity Services (ProSe) functionality in LTE allows the 3GPP industry to serve this developing market while simultaneously addressing the pressing needs of several public safety communities working together on LTE.

[0064] Device-to-device (D2D) communication is a technology introduced by LTE-Rel.12, which allows D2D to serve as the underlying layer of cellular networks to improve spectral efficiency. For example, if the cellular network is LTE, then all physical channels carrying data use SC-FDMA for D2D signaling. In D2D communication, user equipment uses cellular resources instead of radio base stations to transmit data signals to each other via a direct link. Throughout the invention, the terms "D2D," "ProSe," and "sidelink" are used interchangeably.

[0065] D2D communication in LTE focuses on two areas: discovery and communication.

[0066] ProSe (Proximity-Based Service) Direct Discovery is defined as the process by which a ProSe-enabled UE uses E-UTRA direct radio signals via the PC5 interface to discover other ProSe-enabled UEs in its vicinity.

[0067] In D2D communication, UEs use cellular resources instead of base stations (BS) to transmit data signals to each other via a direct link. D2D users communicate directly while remaining under control at the BS, i.e., at least within the coverage area of ​​the eNB. Therefore, D2D can improve system performance by reusing cellular resources.

[0068] It is assumed that D2D operates in the uplink LTE spectrum (in the case of FDD) or in the uplink subframe of a cell that provides coverage (in the case of TDD, except when outside the coverage area). Furthermore, D2D transmission / reception does not use full-duplex on a given carrier. From the perspective of a single UE, D2D signal reception and LTE uplink transmission do not use full-duplex on a given carrier; that is, D2D signal reception and LTE UL transmission cannot be performed simultaneously.

[0069] In D2D communication, when a specific UE1 has a transmit role (transmitting user equipment or transmitting terminal), UE1 sends data, and another UE2 (receiving user equipment) receives it. UE1 and UE2 can change their transmit and receive roles. A transmission from UE1 can be received by one or more UEs, such as UE2.

[0070] ProSe Direct Communication Layer - 2 Link

[0071] In short, ProSe direct one-to-one communication is achieved by establishing a secure Layer-2 link on PC5 between two UEs. Each UE has a Layer-2 ID for unicast communication, which is included in the source Layer-2 ID field of each frame it transmits on the Layer-2 link and the target Layer-2 ID of each frame it receives on the Layer-2 link. The UE needs to ensure that the Layer-2 ID used for unicast communication is at least locally unique. Therefore, the UE should be prepared to use unspecified mechanisms to handle Layer-2 ID conflicts with neighboring UEs (e.g., self-assigning a new Layer-2 ID for unicast communication when a conflict is detected). The Layer-2 link used for ProSe direct one-to-one communication is identified by the combination of the Layer-2 IDs of the two UEs. This means that a UE can participate in multiple Layer-2 links to perform ProSe direct one-to-one communication using the same Layer-2 ID.

[0072] ProSe direct one-to-one communication consists of the following process, as detailed in section 7.1.2 of the current version v13.0.0 of TR 23.713, which is incorporated herein by reference:

[0073] • Establish a secure Layer-2 link via PC5.

[0074] • IP address / prefix allocation.

[0075] • Layer-2 link maintenance on PC5.

[0076] • Release the Layer-2 link on PC5.

[0077] Figure 3 The diagram illustrates how to establish a secure Layer-2 link over a PC5 interface.

[0078] 1. UE-1 sends a direct communication request message to UE-2 to trigger mutual authentication. The link initiator (UE-1) needs to know the peer's (UE-2) Layer-2 ID in order to perform step 1. As an example, the link initiator can learn the peer's Layer-2 ID by first performing a discovery process or by participating in ProSe one-to-many communication that includes the peer.

[0079] 2. UE-2 initiates the mutual authentication process. Successful completion of the authentication process establishes a security layer-2 link via PC5.

[0080] UEs participating in isolated (non-relay) one-to-one communication can also use link-local addresses. The PC5 signaling protocol should support a keep-alive function to detect when a UE is out of ProSe communication range, allowing them to continue implicit Layer-2 link release. Layer-2 link release on PC5 can be performed using a disconnect request message transmitted to another UE, which also deletes all associated context data. Upon receiving the disconnect request message, the other UE responds with a disconnect response message and deletes all context data associated with the Layer-2 link.

[0081] ProSe direct communication related features

[0082] 3GPP TS 36.300, current version 13.3.0, defines the following features for ProSe direct communication in sub-clause 8.3:

[0083] · SL-RNTI : A unique identifier used for direct communication scheduling within ProSe;

[0084] · Source Layer-2 ID : Identifies the sender of data in ProSe direct communication on the side link. The source layer-2 ID is 24 bits long and, together with the ProSe layer-2 target ID and LCID, is used to identify the RLC UM entity and PDCP entity in the receiving unit;

[0085] · Target Layer - 2ID : Identifies the target of data in ProSe direct communication on the side link. The target layer-2 ID is 24 bits long and is split into two bit strings in the MAC layer:

[0086] • A bit string is the LSB portion (8 bits) of the target layer-2 ID and is forwarded to the physical layer as the side link control layer-1 ID. This identifies the destination of the expected data in the side link control and is used to filter packets in the physical layer.

[0087] The second bit string is the MSB portion (16 bits) of the target layer-2ID and is carried within the MAC header. This is used for filtering packets at the MAC layer.

[0088] Access layer signaling is not required for group formation and for configuring the source-2 ID, target-2 ID, and sidelink control L1 ID in the UE. These features are provided by higher layers or derived from features provided by higher layers. In the case of multicast and broadcast, the ProSe UE ID provided by the upper layer is directly used as the source-2 ID, and the ProSe layer-2 group ID provided by the upper layer is directly used as the target-2 ID in the MAC layer. In the case of one-to-one communication, the upper layer provides the source-2 ID and target-2 ID.

[0089] Radio resource allocation for short-range services

[0090] From the perspective of the UE, UEs initiated by ProSe can operate in two modes for resource allocation:

[0091] Mode 1 refers to the resource allocation mode scheduled by the eNB, where the UE requests transmission resources from the eNB (or version-10 relay node), and the eNodeB (or version-10 relay node) schedules the resources used by the UE in turn to transmit direct data and direct control information (e.g., scheduling assignment). The UE needs an RRC connection to transmit data. Specifically, the UE sends a scheduling request (D-SR or random access) to the eNB in ​​a conventional manner, followed by a transmission sidelink buffer status report (BSR) (see also the section "Transmission Procedures for D2D Communication" below). Based on the BSR, the eNB can determine that the UE has data for ProSe direct communication transmission and can estimate the resources required for transmission.

[0092] On the other hand, Mode 2 refers to the UE autonomous resource selection mode, where the UE selects resources (time and frequency) from a resource pool to transmit direct data and direct control information (i.e., SA). For example, at least one resource pool is defined through the content of SIB18, specifically the commTxPool Normal Common field. These specific resource pools are broadcast within the cell and are subsequently generally available to all UEs in the cell that are still in the RRC_Idle state. Effectively, the eNB can define up to four different instances of the pool, four resource pools for transmitting SA messages and direct data respectively. However, in Rel-12, the UE should always use the first resource pool defined in the list, even if it is configured with multiple resource pools. This restriction is removed for Rel-13, allowing the UE to transmit on multiple configured resource pools within a single SC cycle. The following further outlines (further explained in TS36.321) how the UE selects the resource pool for transmission.

[0093] Alternatively, another resource pool can be defined by the eNB using the commTxPool Exceptional field and signaled in SIB18, which can be used by the UE in special circumstances.

[0094] The resource allocation mode that the UE will use can be configured by the eNB. Furthermore, the resource allocation mode that the UE will use for D2D data communication can also depend on the RRC status, i.e., RRC_Idle or RRC_Connected, and the UE's coverage status, i.e., within or outside coverage. If the UE has a serving cell (i.e., the UE is RRC_Connected or pre-occupied on a cell in RRC_Idle), then the UE is considered to be within coverage.

[0095] Figure 4 The illustration shows the use of transmit / receive resources for overlay (LTE) and underlying (D2D) systems.

[0096] Basically, the eNodeB controls whether the UE can apply mode 1 or mode 2 transmission. Once the UE knows the resources it can send (or receive) for D2D communication, it only uses the corresponding resources for the corresponding send / receive. For example, in Figure 4 In this context, D2D subframes will be used solely for receiving or transmitting D2D signals. Since the UE, acting as a D2D device, will operate in half-duplex mode, it can receive or transmit D2D signals at any time. Similarly, Figure 4 The other subframes shown in the diagram can be used for LTE (coverage) transmission and / or reception.

[0097] Transmission process for D2D communication

[0098] According to Rel. 12 / 13, the D2D data transmission process varies depending on the resource allocation mode. As described above for Mode 1, the eNB explicitly schedules resources for scheduling assignment and D2D data communication after a corresponding request from the UE. Specifically, the eNB may inform the UE that D2D communication is generally permitted, but Mode 2 resources (i.e., resource pools) are not provided; this can be done, for example, by the UE exchanging a D2D communication interest indication and a corresponding response, a D2D communication response, where the corresponding exemplary ProseCommConfig information element will not include commTxPool Normal Common. This means that a UE wishing to initiate direct communication involving transmissions must request the E-UTRAN to allocate resources for each individual transmission. Therefore, in this case, the UE must request resources for each individual transmission, and the different steps of the request / authorization process are exemplarily listed below for the Mode 1 resource allocation:

[0099] Step 1: The UE sends an SR (Schedule Request) to the eNB via PUCCH;

[0100] Step 2: The eNB authorizes UL resources via PDCCH (for the UE to transmit the sidelink BSR), which are then scrambled by C-RNTI;

[0101] Step 3: The UE sends a D2D / sidelink BSR indicating the buffer status via PUSCH;

[0102] Step 4: The eNB authorizes D2D resources (for UE to transmit data) via PDCCH, and scrambles the data using D2D-RNTI.

[0103] • Step 5: The D2D Tx UE transmits SA / D2D data according to the authorization received in step 4.

[0104] Scheduling assignment (SA), also known as SCI (Sidelink Control Message), is a compact (low payload) message containing control information, such as time-frequency resources, modulation and coding schemes, and pointers to group target IDs for corresponding D2D data transmission. The SCI transmits sidelink scheduling information for one target ID. The content of the SA (SCI) is substantially the same as the grant received in step 4 above. The D2D grant and SA content (i.e., SCI content) are defined in 3GPP technical standard 36.212, current version 13.1.0, subclause 5.4.3, which is incorporated herein by reference, thereby specifically defining SCI format 0 (see the content of SCI format 0 above).

[0105] On the other hand, for mode 2 resource allocation, steps 1-4 above are essentially unnecessary, and the UE autonomously selects radio resources for SA and D2D data transmission from the transmission resource pool configured and provided by the eNB.

[0106] Figure 5 An exemplary illustration is provided for scheduling assignments and D2D data transmission for two UEs (UE-1 and UE-2), wherein the resources for sending scheduling assignments are periodic, and the resources for D2D data transmission are indicated by the corresponding scheduling assignments.

[0107] Figure 6 The illustration shows a specific example of D2D communication timing for mode 2 autonomous scheduling during an SA / data period (also known as an SC period or side link control period). Figure 7 The diagram illustrates the D2D communication timing for Mode 1eNB scheduling assignments during a single SA / data period. In Rel. 13, 3GPP defines an SC period as a time segment consisting of scheduled transmissions and their corresponding data. (The diagram is from...) Figure 6 As can be seen, the UE sends a scheduling assignment after the SA offset time, which uses the transport pool resources for Mode 2 scheduling assignment SA_Mode2_Tx_pool. The first transmission of SA is followed by, for example, three retransmissions of the same SA message. Subsequently, the UE begins D2D data transmission at a configured offset (Mode 2 data_offset) after the first subframe of the SA resource pool (given by SA_offset), specifically the T-RPT bitmap / mode. A D2D data transmission of a MACPDU (i.e., transport block) includes its first initial transmission and several retransmissions. For illustration... Figure 6 (and Figure 7 Assuming three retransmissions are performed (i.e., the 2nd, 3rd, and 4th transmissions of the same MAC PDU), the T-RPT bitmap (Transmission Time Resource Mode, T-RPT) of Mode 2 essentially defines the timing of MAC PDU transmission (first transmission) and its retransmissions (2nd, 3rd, and 4th transmissions). SA mode essentially defines the timing of the initial SA transmission and its retransmissions (2nd, 3rd, and 4th transmissions). More information on T-RPT can be found in 3GPP technical standard 36.213v.13.1.1, specifically in Section 14, “UE procedures related to the Sidelink,” which is incorporated herein by reference.

[0108] As currently specified in the standard, for a sidelink grant, whether transmitted by the eNB or selected by the UE itself, the UE can transmit multiple transport blocks and MAC PDUs (only one per subframe (TTI), i.e., transmitted one after another), but only to one ProSe target group. Furthermore, a retransmission of a transport block must be completed before the first transmission of the next transport block begins; that is, each sidelink grant uses only one HARQ procedure to transmit multiple transport blocks. Additionally, the UE can have and use multiple sidelink grants in each SC cycle, but select a different ProSe target for each of them. Therefore, in an SC cycle, the UE can transmit data to only one ProSe target at a time.

[0109] As from Figure 7 It is evident that for the eNB scheduling resource allocation mode (Mode 1), D2D data transmission, more specifically T-RPT mode / bitmap, begins in the next UL subframe after the last SA transmission repetition in the SA resource pool. For example... Figure 6 As explained, the T-RPT bitmap (Transmission Time Resource Mode, T-RPT) of Mode 1 basically defines the timing of MAC PDU transmission (first transmission) and its retransmissions (second, third and fourth transmissions).

[0110] The sidelink data transmission procedure can be found in Section 5.14 of the 3GPP standard document TS 36.321v13.2.0, which is incorporated herein by reference. It details Mode 2 autonomous resource selection, distinguishing between configurations with a single radio resource pool or multiple radio resource pools.

[0111] The above discussion pertains to the current state of the 3GPP standard for D2D communication. However, it should be noted that there is ongoing discussion about how to further improve and enhance D2D communication, which may lead to some changes to D2D communication in future versions. The invention described later also applies to those subsequent versions.

[0112] For example, with the currently developing 3GPP Rel.14, 3GPP may decide to change the transmission timing so that it is no longer based on the SC period as described above, but rather on something different (e.g., based on the same / similar subframes as the Uu interface transmission). Accordingly, the detailed examples above regarding how transmissions can be performed via the sidelink (PC5) interface are merely exemplary and can be applied to Rel.13, but may not be applicable to subsequent versions of the corresponding 3GPP standard.

[0113] Furthermore, in future versions of the D2D framework, particularly those integrated with vehicle communication, fixed T-RPT-based transmissions may no longer be used.

[0114] ProSe network architecture and ProSe entities

[0115] Figure 8 The diagram illustrates a high-level exemplary architecture for non-roaming scenarios, which includes different ProSe applications in corresponding UE A and UE B, as well as ProSe application servers and ProSe functions in the network. Figure 8 The exemplary architecture is taken from Chapter 4.2 “Architectural Reference Model” of TS23.303v.13.2.0, which is incorporated herein by reference.

[0116] The functional entities are presented and described in detail in Sub-clause 4.4 “Function Entities” of TS 23.303, which is incorporated herein by reference. ProSe functions are logical functions that perform the network-related operations required by ProSe and play different roles for each ProSe function. ProSe functions are part of the 3GPP EPC and provide all relevant network services related to proximity services, such as authorization, authentication, and data processing. For ProSe direct discovery and communication, the UE can obtain a specific ProSe UE identifier, other configuration information, and authorization from the ProSe function through the PC3 reference point. Multiple ProSe functions can be deployed in a network, but for ease of illustration, a single ProSe function is presented. A ProSe function consists of three main sub-functions that perform different roles based on ProSe characteristics: Direct Provided Function (DPF), Direct Discovery Name Management Function, and EPC-level Discovery Function. The DPF is used to provide the UE with the necessary parameters for using ProSe direct discovery and ProSe direct communication.

[0117] The term "UE" used in this connection refers to a ProSe-enabled UE that supports ProSe functionality, such as:

[0118] • Exchange ProSe control information between ProSe-enabled UEs and ProSe functions via the PC3 reference point.

[0119] • A process for enabling direct ProSe discovery for other ProSe-enabled UEs via the PC5 reference point.

[0120] • Used for one-to-many ProSe direct communication via PC5 reference point.

[0121] • Acts as a ProSe UE-to-Network Relay. Remote UEs communicate with the ProSe UE-to-Network Relay via a PC5 reference point. The ProSe UE-to-Network Relay uses Layer-3 packet forwarding.

[0122] • Exchange control information between ProSe UEs via PC5 reference points, such as for UE-to-network relay detection and ProSe direct discovery.

[0123] • ProSe control information is exchanged between another ProSe-enabled UE and the ProSe function via the PC3 reference point. In the case of ProSe UE-to-network relay, the remote UE will send the control information via the PC5 user plane to relay to the ProSe function via the LTE-Uu interface.

[0124] • Configuration of parameters (e.g., including IP address, ProSe Layer-2 group ID, group security material, radio resource parameters). These parameters can be pre-configured in the UE, or, if within coverage area, provided to the ProSe function in the network by signaling at the PC3 reference point.

[0125] The ProSe application server supports the storage of EPC ProSe user IDs and ProSe function IDs, as well as the mapping between application layer user IDs and EPC ProSe user IDs. The ProSe application server (AS) is an entity outside the 3GPP scope. ProSe applications in the UE communicate with the ProSe AS via application layer reference point PC1. The ProSe AS connects to the 3GPP network via reference point PC2.

[0126] Vehicle Communication - V2X Service

[0127] In Rel. 14, a new research project was established within 3GPP to consider the usefulness of new LTE features for the automotive industry, including Proximity Service (ProSe) and LTE-based broadcast services. The aforementioned ProSe functionality is therefore considered to provide a good foundation for V2X services. Changes to the D2D framework are discussed regarding how vehicle communication transmission can be enhanced. For example, the T-RPT mode may no longer be used. Furthermore, frequency division multiplexing is foreseeable as an alternative to or in addition to TDD for data transmission and SA as previously described. Cooperative services in vehicle contexts are becoming crucial for future connected vehicles in the field of ITS (Intelligent Transportation Systems) research. They should reduce road traffic fatalities, improve road capacity, reduce carbon emissions from road transport, and enhance the user experience during travel.

[0128] V2X communication is the transmission of information from a vehicle to any entity that may affect the vehicle, and vice versa. This information exchange can be used to improve safety, mobility, and environmental applications, including driver-assisted vehicle safety, speed adaptation and warnings, emergency response, travel information, navigation, traffic operations, commercial fleet planning, and payment transactions.

[0129] LTE support for V2X services includes three different use cases, as follows:

[0130] • V2V: Covers LTE-based communication between vehicles.

[0131] • V2P: Covers LTE-based communication between vehicles and personal devices (e.g., handheld terminals carried by pedestrians, cyclists, drivers, or passengers).

[0132] • V2I: Covers LTE-based communication between vehicles and roadside units.

[0133] These three types of V2X can use “cooperative perception” to provide smarter services to end users. This means that transportation entities, such as vehicles, roadside infrastructure, and pedestrians, can gather knowledge of their local environment (e.g., information received from other vehicles or nearby sensor devices) to process and share that knowledge in order to provide smarter services, such as cooperative collision warnings or autonomous driving.

[0134] Regarding V2V communication, when licensing, authorization, and proximity criteria are met, E-UTRAN allows UEs in close proximity to each other (in vehicles) to exchange V2V-related information using E-UTRA(N). The proximity criteria can be configured by the MNO (Mobile Network Operator). However, UEs supporting V2V services can exchange this information whether or not it is provided by an E-UTRAN supporting V2X services.

[0135] Devices supporting V2V applications (vehicle UEs) transmit application layer information (e.g., information about their location, dynamics, and attributes as part of V2V services). The V2V payload must be flexible to accommodate different information content and can transmit information periodically according to the configuration provided by the MNO.

[0136] V2V is primarily broadcast-based; V2V includes the exchange of V2V-related application information between different devices directly and / or due to the limited direct communication range of V2V, and the exchange of V2V-related application information between different devices via infrastructure that supports V2X services (such as RSU, application servers, etc.).

[0137] Regarding V2I communication, devices that support V2I applications send application layer information to roadside units, which in turn can send the application layer information to a group of devices or devices that support V2I applications.

[0138] It also introduces V2N (vehicle to network, eNB / CN), where one party is the UE and the other is the service entity, both of which support V2N applications and communicate with each other via the LTE network.

[0139] Regarding V2P communication, when the licensing, authorization, and proximity criteria are met, E-UTRAN allows UEs that are close to each other to exchange V2P-related information using E-UTRAN. The proximity criteria can be configured by the MNO. However, UEs supporting V2P services can exchange this information even when it is not provided by an E-UTRAN supporting V2X services.

[0140] UEs supporting V2P applications transmit application layer information. This information can be broadcast by vehicles with UEs supporting V2X services (e.g., warnings to pedestrians) and / or by pedestrians with UEs supporting V2X services (e.g., warnings to vehicles).

[0141] V2P includes exchanging V2P-related application information between different UEs (one for vehicles and another for pedestrians) directly and / or due to the limited direct communication range of V2P, via infrastructure that supports V2X services (such as RSUs, application servers, etc.).

[0142] For the new research project V2X, 3GPP provides specific terminology and definitions in TR 21.905, current version 13.0.0, which can be reused for the application.

[0143] Roadside Unit (RSU): An entity that supports V2I services can transmit to and receive from the UE using V2I applications. RSUs can be implemented in eNBs or fixed UEs.

[0144] V2I service: A type of V2X service in which one party is the UE and the other party is the RSU, both of which use V2I applications.

[0145] V2N service: A type of V2X service in which one party is the UE and the other party is the service entity, both of which use V2N applications and communicate with each other via LTE network entities.

[0146] V2P service: A type of V2X service in which both parties communicating are UEs using V2P applications.

[0147] V2V service: A type of V2X service in which both parties communicating are UEs using V2V applications.

[0148] V2X service: A type of communication service involving the use of V2V applications to transmit or receive UEs via 3GPP transmissions. Based on the other party involved in the communication, it can be further divided into V2V service, V2I service, V2P service, and V2N service.

[0149] Many ITS services share common communication requirements:

[0150] • Periodic status exchange. ITS services typically need to know the status of vehicles or roadside terminals. This means periodically exchanging packets containing information about location, speed, identifiers, etc.

[0151] • Asynchronous notifications. These messages are used to notify specific service events. Unlike previous status messages, reliably delivering these messages to a single endpoint or a group of endpoints is often a critical requirement.

[0152] Examples of the first type of communication can be found in traffic efficiency services or safety services such as remote vehicle monitoring, where the traffic efficiency service collects periodic status data from vehicles, and in safety services such as cooperative collision avoidance, which require information about the movement of surrounding vehicles to detect potential collisions. Asynchronous notifications are primarily found in safety services, such as warnings for slippery surfaces or after a collision.

[0153] Different message types will be defined for V2V communication. ETSI has already defined two different message types for Intelligent Transport Systems (ITS), see the corresponding European standards ETSI EN 302 637-2v1.3.1 and ETSI EN 302 637-3v1.2.1:

[0154] • Collaborative perception messages (CAM) are continuously triggered by vehicle dynamics to reflect the vehicle's status.

[0155] • Decentralized Environmental Notification Messages (DENMs) are triggered only when a vehicle-related safety event occurs.

[0156] Since V2V and ITS standardization are still in their early stages, it is expected that other messages may be defined in the future.

[0157] CAM messages are continuously (periodically) broadcast by ITS-S to exchange status information with other ITS-S, and therefore have a greater impact on traffic load than event-triggered (non-periodic) DENM messages. Essentially, CAM messages are heartbeat messages periodically broadcast by each vehicle to its neighbors, providing information on presence, location, temperature, and basic status. In contrast, DENMs are broadcast event-triggered messages to warn road users of hazardous events. Therefore, the service characteristics of CAM messages as defined by ETSI for ITS are considered more representative of V2V services.

[0158] Cooperative Awareness Messages (CAMs) are messages exchanged between ITS-Ss within the ITS network to create and maintain awareness of each other and support cooperative performance of vehicles using the road network. Point-to-multipoint communication should be used to transmit CAMs, enabling CAMs to be transmitted from the originating ITS-S to the receiving ITS-S located within direct communication range of the originating ITS-S. CAM generation should be triggered and managed by the Cooperative Awareness Basic Service, which defines the time interval between two consecutive CAM generation. Currently, the upper and lower limits for the transmission interval are 100ms (i.e., a CAM generation rate of 10Hz) and 1000ms (i.e., a CAM generation rate of 1Hz). The basic principle of ETSI ITS is to send CAMs when new information (e.g., new position, new acceleration, or new heading value) is available to share. Accordingly, when vehicles are moving slowly and at a constant heading and speed, a high CAM generation rate does not provide any real benefit, as the CAMs only show minimal differences. Depending on vehicle dynamics (e.g., speed, acceleration, and heading), the transmission frequency of a vehicle's CAM varies between 1Hz and 10Hz. For example, the slower the vehicle travels, the fewer CAMs are triggered and transmitted. Vehicle speed is a major factor affecting CAM service generation.

[0159] The periodic collaborative sensing messages have been described above. However, it should be noted that while some of the information described above has been standardized, other information, such as periodicity and message size, has not been standardized and is based on assumptions. Furthermore, standardization may change in the future, and therefore may also change the way CAMs are generated and transmitted.

[0160] As described above, to enable the vehicle UE to have radio resources on the sidelink for CAM transmission, Mode 1 and / or Mode 2 radio resource allocation are envisioned. For Mode 1 radio resource allocation, the eNB allocates resources for each SA message and data for each SA cycle. However, when there is heavy traffic (e.g., high-frequency periodic traffic), the overhead on the Uu link from the UE to the eNB can be significant.

[0161] As can be clearly seen from the above, many V2V services are periodic, which has led 3GPP to agree that for sidelink V2V communication mode 1 (i.e., radio resource allocation scheduled by eNB), eNB and UE will support sidelink semi-persistent radio resource allocation.

[0162] The agreement supports sensing mechanisms, along with semi-persistent transmission, for autonomous resource control / selection mechanisms to assist V2X sidelinks. The UE will indicate within the PSCCH (SA / SCI) that it has data regarding a selected set of periodically occurring resources until resource selection occurs. This resource reservation information (signaled within the SCI) can be used by other UEs intending to transmit V2X messages for resource selection, preventing resources already reserved / booked by other UEs from being considered for radio resource selection. This resource reservation / booking process is particularly suitable for services with specific periodic packet arrivals, such as CAM messages.

[0163] The indication of reserved radio resources in the scheduling information described above can be monitored (“sensed”) by other (vehicle) equipment. Typically, the sensing process collects information about radio resources and thus allows for prediction of future radio resources that can be used during resource allocation to identify a set of resource candidates for transmission. 3GPP has agreed on very few things, but it can be assumed that the sensing process classifies time-frequency resources into:

[0164] • "Unavailable" resources. These are resources that the UE is not allowed to transmit because they have been reserved / booked by other UEs.

[0165] • “Candidate (or available) resources”. These are the resources on which the UE can / is able to perform transmissions.

[0166] Furthermore, 3GPP agrees to perform energy measurements for the sensing procedure, although the agreement does not provide any details on how or what kind of energy measurements will be performed. Energy-based sensing can be understood as the process by which the UE measures the received signal strength on the PSSCH radio resources and / or PSCCH radio resources. Energy-based sensing can essentially help identify near-field and long-field interference.

[0167] In addition, it was discussed whether the priority of data (or the corresponding radio resource reservation) was indicated in the scheduling assignment (SCI) so that it could be used in the resource allocation process, although no agreement was reached on how to effectively use the priority.

[0168] Another topic that arose during the discussion was the use of channel (i.e., PC5 interface) congestion levels for resource allocation processes, which may be similar to the Channel Busy Rate (CBR) known in ETSI standards (see, for example, ETSI EN 302 571v2.0.0 and 102 687v1.1.1). Again, no details were discussed in this regard, let alone protocols on how to accurately use such congestion levels.

[0169] As described above Figure 6 and Figure 7 As explained, to increase transmission reliability, each transport block and scheduling assignment is repeatedly transmitted on the side link; that is, the initial transmission of the scheduling assignment or data is repeated once or multiple times. The ongoing discussions in 3GPP do not distinguish between the initial and repeated transmissions of the data ISA, and it remains unclear how to achieve semi-persistent scheduling and resource awareness for V2X transmissions in this regard.

[0170] Sensing and semi-persistent scheduling should be implemented in a simple manner so as not to unduly increase the complexity of the UE. Although there is a general agreement on sensing and resource reservation for V2X transmissions over the PC5 interface, implementing these mechanisms in current systems may lead to problems and inefficiencies. Summary of the Invention

[0171] Non-limiting and exemplary embodiments provide an improved transmission process for a transmitting device to perform initial transmission and retransmission of data via a sidelink interface. The independent claims provide non-limiting and exemplary embodiments. Advantageous embodiments are limited by the dependent claims.

[0172] According to one aspect of the present invention, a transmitting device for transmitting data to one or more receiving devices via a sidelink interface is disclosed, wherein the data transmission includes a first transmission of data and one or more retransmissions of data after the first data transmission. The transmitting device includes: a processor that performs a resource sensing process for selecting radio resources available for the transmitting device to transmit data at a later time point; the processor performs autonomous radio resource allocation based on the results of the resource sensing process during a sensing window to select time-frequency radio resources within the transmission window to be used for the first data transmission; and the processor determines a data transmission timing pattern among a plurality of data transmission timing patterns, each data transmission timing pattern indicating a transmission timing for performing one or more data transmissions; and a transmitting unit that uses the selected time-frequency radio resources to perform the first data transmission and performs one or more data retransmissions relative to the first data transmission with a transmission timing defined by the determined data transmission timing pattern.

[0173] According to another aspect of the invention, a method is disclosed for a transmitting device to transmit data to one or more receiving devices via a sidelink interface, wherein the data transmission includes a first transmission of data and one or more retransmissions of data after the first data transmission. The method includes the following steps performed by the transmitting device: performing a resource sensing process to select radio resources available for the transmitting device to transmit data at a later time point; performing autonomous radio resource allocation based on the results of the resource sensing process during a sensing window to select time-frequency radio resources within the transmission window to be used for the first data transmission; determining a data transmission timing pattern among a plurality of data transmission timing patterns, each data transmission timing pattern indicating a transmission timing for performing one or more data transmissions; performing the first data transmission using the selected time-frequency radio resources; and performing one or more data retransmissions relative to the first data transmission with a transmission timing defined by the determined data transmission timing pattern.

[0174] According to another aspect of this disclosure, an integrated circuit is disclosed that controls the processing of a transmitting device for transmitting data to one or more receiving devices via a sidelink interface, wherein the data transmission includes a first transmission of data and one or more retransmissions of data after the first data transmission, the processing including: performing a resource sensing process for selecting radio resources available for the transmitting device to transmit data at a later time point; performing autonomous radio resource allocation based on the result of the resource sensing process during a sensing window to select time-frequency radio resources within the transmission window to be used for performing the first data transmission; determining a data transmission timing pattern among a plurality of data transmission timing patterns, each data transmission timing pattern indicating a transmission timing for performing one or more data transmissions; performing the first data transmission using the selected time-frequency radio resources; and performing one or more data retransmissions relative to the first data transmission with a transmission timing defined by the determined data transmission timing pattern.

[0175] According to a first aspect, a transmitting device is provided for performing initial data transmission and data retransmission with other devices via a sidelink interface. It is assumed that a resource sensing process is continuously performed by the transmitting device to acquire information about future radio resources. According to one example, the radio resource sensing includes at least monitoring scheduling assignments sent by other devices that reserve radio resources at a later time point, which can then be excluded from the selection of the radio resources. Sensing may also optionally include measuring the received signal energy in the radio resources. Other information may also be collected during the sensing process in the future.

[0176] According to the first aspect, a data retransmission (e.g., the initial transmission) has a "higher priority" than the remaining (re)transmissions because the vehicle UE performs a resource allocation process to select radio resources for the initial data retransmission based on information obtained from the radio sensing process within the sensing window before data is available for transmission. Therefore, the radio resources selected for the (initial) transmission should not cause conflicts with transmissions from other UEs and should therefore be transmitted with high reliability. On the other hand, less flexibility is used in selecting the radio resources to be used for the remaining data (re)transmissions in order to reduce signaling overhead. Specifically, for the remaining data (re)transmissions, the vehicle UE should select a suitable data transmission timing pattern (hereinafter also referred to as T-RPT), which defines the timing of one or more data transmissions and is used by the vehicle UE, wherein the first data transmission is used as a reference to perform the remaining data (re)transmissions. The scheduling information for data transmission transmitted by the vehicle UE correspondingly indicates the time and frequency resources used for the initial transmission and the data transmission timing pattern from which the receiving entity derives the transmission timing for the first and all retransmissions by the vehicle UE. Regarding frequency resources, data retransmission performed by the vehicle UE can use the same frequency used for the initial data transmission, or a frequency derived from the initially used frequency based on frequency hopping mode; in the latter variant, the scheduling information should also indicate whether frequency hopping will be used to determine the frequency for data retransmission.

[0177] According to one variant, the selected data transmission timing pattern will have already identified all transmissions or retransmissions to be performed on the data. Accordingly, the (re)transmission will be completed within the time period given by the data transmission timing pattern; for example, within 8 subframes in the case of the 8-bit data transmission timing pattern.

[0178] According to another variation of the first aspect, the selected data transmission timing pattern will indicate only a single transmission, wherein the single-transmission data transmission timing pattern will be repeated throughout the transmission window after the first data transmission. By sequentially positioning the selected single-transmission data transmission timing pattern, various data retransmission candidates are defined at those locations indicating the recurring timing pattern of the transmission. The vehicle UE will have to select from the various data retransmission candidates those that will actually be used for data retransmission. The selection of the single-transmission T-RPT can be performed by the vehicle UE using information obtained from the resource sensing process, such that the resulting data transmission candidates, and especially the data retransmission candidates selected later for actual use, are optimal from the perspective of collision rate and interference.

[0179] The selection of data retransmission candidates can be performed randomly or based on the results of the sensing process described above, in order to improve transmission reliability and avoid transmission conflicts with other UEs. Which data retransmission candidate the vehicle UE actually uses must subsequently be indicated to the receiving entity, for example, as part of the scheduling information for data transmission transmitted by the vehicle UE. Regarding frequency resources, data retransmission performed according to the selected data retransmission candidate can use the frequency already used by the vehicle UE for initial data transmission, or it can follow a frequency hopping pattern starting from the frequency used for initial data transmission.

[0180] According to another variation of the first aspect, the selection of the primary transmission T-RPT is based on the sensing results of the resource sensing process as follows. The vehicle UE first determines the preferred data retransmission candidate (e.g., the second-highest possible data retransmission candidate) throughout the entire transmission window (after the first data transmission). This data retransmission candidate is then used to determine the primary transmission T-RPT, which, when repeated throughout the transmission window, has a "1" consistent with the preferred data retransmission candidate. Therefore, the frequency and time domain resources (i.e., the preferred data transmission candidates) for the initial transmission and for the primary data retransmission are freely determined by the vehicle UE based on the sensing results, thereby improving the reliability of data transmission and reducing the collision rate. For this variation, the scheduling information should not only indicate the time-frequency radio resources for the initial transmission but also the frequency resources for the preferred data retransmission. This can be accomplished, for example, by providing a frequency offset regarding the frequency indication provided for the initial data transmission. As previously mentioned, the T-RPT is indicated in the scheduling assignment so that the transmission timing of all retransmissions is provided using the initial data transmission as a reference.

[0181] According to another aspect, radio resources available for data transmission by the vehicle UE should generally be divided into radio resources for initial data transmission and radio resources for data retransmission. Separating radio resources will ensure that data retransmission and initial transmission will not conflict, thereby protecting the most important initial transmission.

[0182] Accordingly, in a general first aspect, the technology disclosed herein is characterized by a transmitting device for transmitting data to one or more receiving devices via a sidelink interface. The data transmission includes a first transmission of data and one or more retransmissions of data following the first data transmission. A receiving unit and a processor of the transmitting device perform a resource sensing process to acquire information about radio resources available for the transmitting device to transmit data at a later time. After the data becomes available for transmission, the processor performs autonomous radio resource allocation based on the information acquired by the resource sensing process during a sensing window prior to the data becoming available for transmission, to select time-frequency radio resources within the transmission window to be used for performing the first data transmission. The processor determines a data transmission timing pattern among multiple data transmission timing patterns, each data transmission timing pattern indicating the transmission timing for performing one or more data transmissions. The transmitting unit of the transmitting device performs the first data transmission using the selected time-frequency radio resources and performs one or more data retransmissions with the transmission timing defined by the determined data transmission timing pattern relative to the first data transmission.

[0183] Accordingly, in a general first aspect, the technology disclosed herein is characterized by a method for a transmitting device to transmit data to one or more receiving devices via a sidelink interface. The data transmission includes a first transmission of data and one or more retransmissions of data following the first data transmission. The method includes the following steps performed by the transmitting device: A resource sensing process is performed to acquire information about radio resources available for the transmitting device to transmit data at a later time. After the data becomes available for transmission, an autonomous radio resource allocation is performed based on the information acquired by the resource sensing process during a sensing window prior to the data becoming available for transmission, to select time-frequency radio resources within the transmission window to be used for performing the first transmission of data. The transmitting device determines a data transmission timing pattern among a plurality of data transmission timing patterns, each data transmission timing pattern indicating the transmission timing for performing one or more data transmissions. The transmitting device uses the selected time-frequency radio resources to perform the first data transmission and performs one or more data retransmissions with the transmission timing defined by the determined data transmission timing pattern relative to the first data transmission.

[0184] Other benefits and advantages of the disclosed embodiments will become apparent from the specification and drawings. Benefits and / or advantages may be provided individually by the various embodiments and features disclosed in the specification and drawings, and need not all be provided in order to obtain one or more of them.

[0185] These general and specific aspects can be implemented using systems, methods, and computer programs, as well as any combination of systems, methods, and computer programs. Brief description of the attached diagram

[0186] In the following description, exemplary embodiments will be illustrated in more detail with reference to the accompanying drawings and figures.

[0187] Figure 1 An exemplary architecture of a 3GPP LTE system is shown.

[0188] Figure 2 An exemplary downlink resource grid is shown for a downlink slot of a subframe defined by 3GPP LTE (version 8 / 9).

[0189] Figure 3 The diagram illustrates how to establish a Layer-2 link for ProSe communication on a PC5.

[0190] Figure 4 The diagram illustrates the use of transmit / receive resources for overlay (LTE) and underlying (D2D) systems.

[0191] Figure 5 The diagram illustrates the scheduling assignment and D2D data transmission for two UEs.

[0192] Figure 6 The diagram illustrates the D2D communication timing for UE autonomous scheduling mode 2.

[0193] Figure 7 The diagram illustrates the D2D communication timing for eNB scheduling mode 1.

[0194] Figure 8 The diagram illustrates an exemplary architecture model of ProSe for non-roaming scenarios.

[0195] Figure 9 The diagram illustrates the frequency-time radio resources of the vehicle UE, which are divided into transmission and sensing windows at time P when data becomes available for transmission.

[0196] Figure 10 This is a sequence diagram of UE behavior according to an exemplary implementation of the first embodiment.

[0197] Figure 11 and Figure 12 The illustration shows a transmission window and a sequence of subframes for initial data transmission and data retransmission according to an exemplary implementation of the first embodiment.

[0198] Figure 13 and Figure 14 The illustration shows a transmission window and a sequence of subframes for initial data transmission and data retransmission according to another exemplary implementation of the first embodiment.

[0199] Figure 15The illustration shows a transmission window and a sequence of subframes for initial data transmission and data retransmission according to an improved implementation of the first embodiment.

[0200] Figure 16 The illustration shows a transmission window and a sequence of subframes for initial data transmission and data retransmission according to an additional improved implementation of the first embodiment. Detailed Implementation

[0201] A mobile station, mobile node, user terminal, or user equipment is a physical entity within a communication network. A node can have multiple functional entities. A functional entity is a software or hardware module that refers to other functional entities of the node or network that implement and / or provide a predetermined set of functions. A node can have one or more interfaces that attach the node to a communication facility or medium through which the node can communicate. Similarly, a network entity can have logical interfaces that attach functional entities to a communication facility or medium through which it can communicate with other functional entities or communication nodes.

[0202] The term “radio resources” as used in the collection of claims and applications should be understood broadly to refer to physical radio resources, such as time and frequency resources.

[0203] The term "direct communication transmission" as used in this application should be broadly understood to refer to transmission directly between two user equipments, i.e., transmission without traversing a radio base station (e.g., an eNB). Accordingly, direct communication transmission is performed on a "direct sidelink connection," a term used for connections established directly between two user equipments. For example, in 3GPP, the terminology used is D2D (device-to-device) communication, or ProSe communication, or sidelink communication. The terms "direct sidelink connection" and "sidelink interface" should be broadly understood and can be understood in the 3GPP context as the PC5 interface described in the background section.

[0204] The term "ProSe" or its unabbreviated form "proximity service" as used in this application applies to the context of proximity-based applications and services in LTE systems, as exemplarily illustrated in the Background section. Other terms such as "D2D" are also used in this context to refer to device-to-device communication for proximity services.

[0205] The term "vehicle mobile terminal" as used throughout this application should be understood in the context of the new 3GPP research project, specifically the work item V2X (Vehicle-to-Everything) described in the Background section. Accordingly, "vehicle mobile terminal" should be broadly understood as a mobile terminal specifically installed in a vehicle (e.g., a car, commercial truck, motorcycle, etc.) to perform vehicle communication, i.e., to transmit vehicle-related information to other entities (such as vehicles, infrastructure, pedestrians), for example, for safety or driver assistance purposes. Optionally, the vehicle mobile terminal may access information available at a navigation system (assuming it is also installed in the vehicle), such as map information.

[0206] The term “autonomous radio resource allocation” (as opposed to “radio base station controlled radio resource allocation”) used throughout the application can be understood exemplarily in the context of 3GPP near-field services, thereby allowing two modes for resource allocation: mode 1, in which the radio base station controls the allocation (i.e., radio base station controlled radio resource allocation), and mode 2, in which the terminal (or transmitting device) (in the absence of a radio base station) autonomously selects resources according to its own discretion (i.e., autonomous radio resource allocation).

[0207] The term "data transmission timing pattern" used throughout this application can be understood, by way of example, as information defining transmission timing, such as T-RPT (Transmission Time Resource Pattern) known in the context of 3GPP D2D technology. Depending on the actual implementation, the data transmission timing pattern may be used to indicate the first data transmission and the retransmission of data, or only to indicate the retransmission of data when the first data transmission is indicated.

[0208] As explained in the background section, 3GPP has introduced a new research project for LTE-assisted vehicle communications, which should be based on the ProSe process to exchange V2X services between various vehicle mobile terminals and other stations. Furthermore, the V2X service should support a semi-persistent radio resource allocation, and it has been agreed that mechanisms for radio resource reservation and awareness will be supported for the terminals, particularly for UE-autonomous resource allocation mode (also known as Mode 2). However, only general agreements have been reached regarding sensing and radio resource reservation, without providing details on how to implement these agreements and how to adapt other mechanisms to ensure effective and perfect operation. For example, it is unclear how exactly to implement resource sensing mechanisms and radio resource reservation.

[0209] The following will be referenced Figure 9 Explain one possible solution. Figure 9The frequency-time radio resources of a vehicle UE (typically a transmitting device) data resource pool are illustrated in an exemplary and simplified manner. PRB pairs (Physical Resource Block pairs; 12 subcarriers per subframe) are used as units for the frequency-time radio resources illustrated in the exemplary diagram. It is assumed that data becomes available for transmission at time P (i.e., a packet arrives), and data transmission (and retransmission) should end at time L; this time period can be represented as a transmission window and depends on the delay requirements of the data to be transmitted (e.g., 100 ms; L = P + 100 ms). The results of a sensing process obtained within a sensing window of, for example, 1000 ms before packet arrival should be considered for the radio resource allocation process to be performed by the vehicle UE to select the frequency-time radio resources (and possibly other transmission parameters) for transmitting data. It is exemplarily assumed that three (physical) resource block pairs are required to transmit data (furthermore, according to current standardization, the resource blocks should be contiguous).

[0210] One piece of information obtained from the sensing process is that a specific radio resource in the transmission window has been reserved by another device and therefore should not be used by the vehicle UE; the corresponding box for the reserved radio resource is represented by a vertical stripe. The complete list of radio resource candidates (every three consecutive resource block pairs) available for the vehicle UE to transmit data within the transmission window is shown in [the table / section / etc.]. Figure 9 The diagram in the middle is framed. There are a total of six candidates within the transmission window, all of which can be ranked based on one or more specific characteristics. As an example, the ranking process can rank various radio resource candidates based on energy measurements performed during the sensing process within the sensing window. More specifically, energy (e.g., received signal strength) can be measured across the entire sensing window for the relevant radio resource candidate. Figure 9 As shown, it is exemplarily assumed that the corresponding radio resource candidates are ranked from 1 to 4 based on energy measurements. Accordingly, radio resource candidate 2, which has the same corresponding frequency radio resource in the sensing window, is ranked the same. This also applies to the two candidate resources 3. Figure 9 The corresponding radio resources for the sensing window are illustrated with diagonal stripes, and the measured energy is averaged to predict the energy of radio resource candidate 2. Similarly, Figure 9 The corresponding frequency-time radio resources in the sensing window used for energy measurement of resource candidate 4 are plotted as horizontal stripes. Although not shown in the diagram for ease of illustration... Figure 9 The diagram shows that, however, corresponding energy measurements and processing are also performed for the radio resources within the sensing windows corresponding to candidates 1 and 3.

[0211] For example, assume the vehicle UE performs four transmissions for a single transport block: a first transmission and three retransmissions. One possible implementation would be to use the results of a resource sensing process for each data transmission—the first transmission and the retransmissions. (As presented above...) Figure 9 In this example, the vehicle UE can therefore select four of the highest-ranked resource candidates to transmit four (re)transmissions. The solution is flexible and efficient for transmitting data (i.e., a transport block) using the best available radio resources in both the time and frequency domains.

[0212] However, to indicate the radio resources (i.e., time and frequency within the transmission window) for each (re)transmission by the receiving entity, a scheduling assignment can be sent for each (re)transmission. Alternatively, a scheduling assignment can be transmitted that includes all the necessary information for the receiving entity to receive and correctly decode the first retransmission and all retransmissions. In either case, this significantly increases signaling overhead compared to existing solutions. Figure 6 In the prior art, a scheduling assignment is transmitted for all (re)transmissions, indicating the time-frequency resources for all transmissions and the corresponding T-RPT mode, which uniquely defines the timing of all (re)transmissions. In the prior art, the frequency resources used for retransmissions are the same as those used for the first data transmission (explicitly indicated in the SA) or follow a frequency hopping pattern starting from the frequency resources used for the first data transmission (the scheduling assignment indicates whether a frequency hopping pattern is used). If there is no fixed time and / or frequency relationship between the first transmission and the retransmission, then separate information regarding the actual time-frequency radio resources used needs to be provided to the receiving entity for each transmission.

[0213] Furthermore, the receiving entity needs to be able to correlate the first transmission and retransmissions of a transport block together, for example, to achieve soft combination of data. In this regard, a bitmap of length LP can be signaled (100 bits would be able to indicate transmissions within a 100ms transmission window), thus indicating the subframes in which transmissions occurred, allowing the receiving entity to correlate all transmissions of a transport block together. However, the bitmap will be long, and therefore will additionally increase signaling overhead. Moreover, the transmission window can have different lengths, and therefore the bitmap must be very long to indicate the longest possible transmission window, or the size of the bitmap will vary depending on the length of the transmission window, either of which would be disadvantageous.

[0214] The above provides a possible solution for the sensing process and corresponding radio resource allocation for the first transmission and retransmission of the same data, although it involves several drawbacks and problems.

[0215] The inventors have devised the following exemplary embodiments to mitigate the aforementioned disadvantages and problems.

[0216] Specific implementations of the various embodiments will be implemented in the broad specifications given by the 3GPP standard and are described in part in the background section, wherein specific key features are added as illustrated in the following embodiments. It should be noted that the embodiments can be advantageously used, for example, in mobile communication systems, such as the 3GPP LTE-A (versions 10 / 11 / 12 / 13 / 14 or later) communication systems described in the above background section. However, the embodiments are not limited to their use in these specific exemplary communication networks.

[0217] The description should not be construed as limiting the scope of this disclosure, but rather as examples of various embodiments to better understand the disclosure. Those skilled in the art will recognize that the general principles of the disclosure set forth in the claims can be applied to different contexts and in ways not explicitly described herein. Several assumptions are made for illustrative purposes; however, these assumptions should not limit the scope of the following embodiments.

[0218] Various embodiments primarily focus on improving how the transmitting device performs radio resource allocation and data transmission via a sidelink interface, and improvements are also suggested for the scheduling assignments transmitted by the device for data transmission. Details will become apparent from the embodiments described below. Other functionalities (i.e., functionalities unchanged in the various embodiments) may remain exactly the same as those described in the Background section, or may be changed without affecting the various embodiments.

[0219] As illustrated in the background section, an exemplary scenario in which the various embodiments can be applied is V2X communication. Therefore, the transmitting and receiving devices can be, for example, a UE in a vehicle, a roadside unit, a "normal" mobile terminal carried by a pedestrian, etc. Furthermore, the data can be (periodic) vehicle data, such as CAM messages, which should be continuously exchanged between various vehicle entities, and for which resource sensing procedures and semi-persistent resources have been discussed in 3GPP. Although the following exemplary embodiments will be described in conjunction with this V2X communication scenario for illustrative purposes, the invention is not limited thereto.

[0220] First Embodiment

[0221] The first embodiment for solving the above-mentioned problems will be described in detail below. Different implementations and variations of the first embodiment will also be described.

[0222] As described above, and exemplarily as illustrated in the background section of this application, it is assumed that the vehicle UE is installed in a vehicle and is capable of performing vehicle communication based on a D2D framework. Accordingly, vehicle data (e.g., periodic and non-periodic data) should be transmitted by the vehicle UE to other entities to which the data is of interest. It is assumed that the UE supports and primarily performs Mode 2 radio resource allocation and has been appropriately configured with the necessary resource pools (for data and scheduling assignment) to autonomously select radio resources for transmitting scheduling information and data via the PC5 (sidelink) interface.

[0223] The periodic data to be transmitted by the vehicle UE will be exemplified by the Cooperative Aware Message (CAM), detailed in the Background section. As described in the Background section, 3GPP has generally approved the inclusion of sensing and radio resource reservation in future versions of the standard for the transmission of periodic vehicle data. Specifically, radio resource reservation on the transmission side allows for a “semi-persistent” radio resource allocation, for example, reserving the same resources currently in use for the transmission of other packets of periodic data at one or more later times. Therefore, at those later times, the vehicle UE does not need to perform resource selection / request (Mode 1 or Mode 2 resource allocation) again to be able to transmit periodic data. Radio resource reservation can be implemented in different ways and has not yet been determined by 3GPP. For example, radio resource reservation can be completed for the next transmission instance or over a longer time period (i.e., not just for the next transmission instance of periodic data). Scheduling information (SCI) transmitted along with the sidelink data identifies the radio resources used for transmission and thus allows the receiving entity to correctly receive and process / decode the sidelink data. Scheduling information can also be used, for example, to indicate radio resource reservation by indicating the timing or periodicity of data, so that the receiving entity can determine the time for reserving radio resources (e.g., subframes).

[0224] The vehicle UE should further and continuously perform the radio sensing process as described in the background section to obtain information about future radio resources. This information can then be used during a Mode 2 radio resource allocation process performed by the vehicle UE to select radio resources (and possibly other transmission parameters) for transmitting data (optionally, or corresponding scheduling assignments). The sensing process includes, for example, decoding scheduling assignments transmitted by other devices to identify reserved radio resources. Optionally, the sensing process also includes energy measurements (e.g., received signal strength, RSSI) of the entire frequency resource for data transmission configured for the vehicle UE.

[0225] One possible implementation option for the resource sensing process is that each UE has a distribution map containing predictions of frequency resources spanning, for example, 100 ms (e.g., at most 1 second) from the start of the next subframe. Subsequently, at time P when a packet arrives in the buffer in the UE, the UE has prepared a distribution map of all frequency resources for subframes P to L (which may be called the transmission window), where L essentially corresponds to the maximum time span until a packet should be transmitted (according to QoS). The frequency distribution map can distinguish between unavailable and available radio resources (and may also include information about the predicted energy levels of different radio resources). Other implementations of the radio sensing process are also possible, for example, where the UE does not continuously update this future resource distribution map, but instead predicts radio resources from past measurements within the sensing window only when needed.

[0226] Data transmission includes an initial data transmission and one or more retransmissions. For example, the following primarily assumes a total transmission count of four, or the difference being that three retransmissions are performed in addition to the initial data transmission. The total transmission count can be predetermined (e.g., by a standard or network operator) or configurable (e.g., by the eNodeB controlling the vehicle UE, or by the vehicle UE itself). If the total transmission count is configurable, the data receiver must know in some way the total transmission count they should expect. This can be ensured, for example, by providing corresponding information in the scheduling assignment or by the eNodeB broadcasting information within the cell.

[0227] One exemplary implementation involves using incremental redundancy as known in 3GPP. Specifically, in HARQ operation, the eNB can transmit different coded versions of the original transport block (i.e., the data to be transmitted) in retransmissions, allowing the UE to utilize incremental redundancy (IR) combination to gain additional coded gain via combination gain. Similarly, V2X transmissions via sidelink interfaces can use incremental redundancy for retransmissions, allowing different redundant versions of the same data to be transmitted, for example, following a predetermined order of redundancy versions (such as 0, 2, 3, 1, as defined for HARQ synchronous non-adaptive retransmissions). Therefore, when describing the first transmission and retransmission of the same data (e.g., a transport block), it should not be interpreted as meaning that it is exactly the same data, but rather that it should also cover the cases where different redundant versions of the same data are transmitted.

[0228] In summary, it is assumed that the vehicle UE continuously performs a radio resource sensing process to obtain information about future radio resources (whether it be reservation and / or RSSI prediction, or other information). The vehicle UE should also be able to transmit periodic (and non-periodic) data, and a Mode 2 resource allocation process (UE autonomous) should be performed in the connection to select radio resources within a transmission window to be used for data transmission (which may also include the determination of other transmission parameters such as MCS). The information obtained through the resource sensing process is applied to the resource allocation process to improve it.

[0229] Different variations of the first embodiment will be described below. The first embodiment provides an improved transmission process for data transmission performed via the PC5 sidelink interface. The first embodiment improves the reliability of the initial transmission by prioritizing one of the data transmissions (e.g., the initial data transmission) by fully utilizing the radio resource sensing results used for resource allocation. On the other hand, resource allocation is less flexible for (re)transmission of remaining data, which therefore will not benefit from the resource sensing process in the same way as the initial transmission, but allows for reduced signaling overhead. When incremental redundancy is used, the first transmission is the most important transmission because it is the first transmission received by the receiving entity, and because it is self-decoding, which may not be the case for other redundancy versions.

[0230] When data becomes available for transmission, the vehicle UE should perform a UE-autonomous radio resource allocation procedure to obtain the necessary transmission parameters, including the selection of time-frequency radio resources within the transmission window, in order to perform the first transmission of the data to be processed. When determining the radio resources to be used for the initial transmission of data, the resource allocation procedure should be performed within the sensing window prior to the arrival of the data (see [link to documentation]). Figure 9 The results obtained from the sensing process are acquired during the sensing window. For example, radio resources that should be avoided can be selected from a variety of candidates ranked based on energy measurements performed during the sensing window.

[0231] To determine how to perform data retransmission, the transmitting device should determine a suitable data transmission timing pattern (such as a T-RPT known from the background section), which defines the timing pattern for one or more data transmissions. A T-RPT is typically a bitmap of several bits (e.g., 8 bits) in length, with each bit associated with a possible transmission timing of the data (e.g., a subframe). Multiple T-RPTs can be defined. For example, T-RPTs can have different numbers of transmissions, where an 8-bit T-RPT can indicate 1 to 8 transmissions. Furthermore, the location of transmissions can vary within the T-RPTs, where, for example, there can be 8 different T-RPTs indicating a single transmission. How many and which T-RPTs are defined in the transmitting device can be predetermined (e.g., by standards or network operators) or can be configurable (e.g., by controlling the eNodeB of the vehicle UE). As an example, T-RPTs already defined for D2D communication in 3GPP Releases 12 and 13 can be reused. In any case, the vehicle UE should select a suitable T-RPT to determine the timing for performing data retransmission. The T-RPT and the data transmission indicated therefrom are therefore positioned within the transmission window using the first transmission as a reference. For example, the selected T-RPT may immediately follow the first data transmission, or it may include the first data transmission as part of the T-RPT.

[0232] Accordingly, the vehicle UE will perform the first data transmission according to the selected time-frequency radio resources, and subsequently perform data retransmission with the transmission timing defined by the selected T-RPT. In addition, the retransmission performed by the vehicle UE may use the same frequency (i.e., PRB) used for the initial transmission, or may use a frequency derived from the frequency of the initial transmission based on the frequency hopping mode (e.g., as known from the prior art).

[0233] The first embodiment therefore provides a solution that combines improved first data transmission based on sensing results with a simple transmission mode to coordinate data retransmissions referenced to the first transmission. Accordingly, the information to be provided to the receiving entity is therefore quite limited and does not result in high signaling overhead. Specifically, a scheduling assignment for data transmission transmitted by the vehicle UE indicates the time-frequency radio resources used for the first transmission and the selected T-RPT, enabling the receiving entity to receive both the first data transmission and data retransmissions. Optionally, the scheduling assignment may also include information about whether a frequency hopping mode is used for the frequency resources used for data retransmissions.

[0234] Figure 10This is a sequence diagram illustrating the UE behavior according to the exemplary implementation of the first embodiment described above. It can be clearly seen from the diagram that the resource sensing process and the steps the UE will perform to transmit the data to be transmitted are illustrated separately. This is achieved using dashed lines. Figure 10 The illustration shows how information provided by the resource sensing process (such as radio resource reservations or energy predictions performed during the sensing window) can be used as inputs at various steps of the process. For example, UE autonomous radio resource allocation can exclude reserved radio resources from the selection to avoid interference. Additionally, as will be explained in more detail with reference to other implementations of the embodiments, the selection of an appropriate T-RPT can also be based on information obtained through the sensing process.

[0235] Combining Figure 11 and Figure 12 This describes a first detailed implementation of the general first embodiment discussed above. Figure 11 and Figure 12 The illustrations depict the sequence of subframes within a transmission window and the corresponding timing of data transmission, including the initial transmission and three data retransmissions. In the exemplary illustrations, the transmission window is depicted as including subframe P, where data becomes available, and subframe L, which is considered the latest subframe, while still meeting data latency requirements. The transmission window can also be defined differently, for example, excluding subframe 10 or even additional subsequent subframes 11, ..., to take processing time into account.

[0236] In both figures, it is assumed that the vehicle UE determines that the time-frequency radio resources in subframe 12 are optimal for the first data transmission. The corresponding indication will be included in the corresponding scheduling assignment, enabling the receiving entity to receive the data. As assumed so far, a total of four transmissions (e.g., one transport block) will be performed to improve transmission reliability. In this implementation, the vehicle UE will therefore select the T-RPT based on the total number of transmissions to be performed. Figure 11 and Figure 12 Two variations are described to distinguish whether T-RPT includes or excludes initial data transmission. Figure 11 In the variant shown, the vehicle UE will therefore select the T-RPT from the four total transmissions in the T-RPT; Figure 11 An exemplary T-RPT that can be selected by the vehicle UE is shown. On the other hand, in Figure 12 In the variant shown, since the T-RPT does not include the first transmission, the vehicle UE will therefore select the T-RPT from the T-RPT which has a total of three transmissions.

[0237] Figure 12In the variant, T-RPT, exemplarily, begins immediately after the subframe in which the initial transmission is performed. Alternatively, while still using subframe 12 (i.e., the timing of the first data transmission) as a reference for the start of T-RPT (and therefore the retransmission timing), a different timing offset from the timing of the first data transmission can be used. For example, T-RPT may begin at a distance from one or more subframes in which the first data transmission occurred. The timing offset may be configurable (e.g., by the vehicle UE or eNodeB) or predetermined, but needs to be known to the receiving entity.

[0238] In addition, in various subframes ( Figure 11 Subframes 14, 15, and 19 in the variant, or Figure 12 The retransmission performed at subframes 15, 16, and 20 in the variant can use the same frequency as that used for the first data transmission, or it can use a “hop” frequency derived from the frequency used for the first data transmission (based on a known frequency hopping pattern).

[0239] As mentioned above, the selection of T-RPT is affected by the total number of transmissions (see [link]). Figure 11 ) or number of retransmissions (see Figure 12 In addition to the aforementioned limitations, in one exemplary variant, the vehicle UE can randomly determine the T-RPT (with the necessary number of retransmissions) from all those T-RPTs. While this would be a simple implementation, it may have the following drawbacks: the randomly selected timing pattern may produce retransmission timing (subframes), which will cause serious interference to the transmission of other devices; as mentioned above, the frequency resources are fixed by the frequency resources selected for the initial data transmission, or the same frequency resources, or follow their frequency hopping pattern.

[0240] Alternatively, instead of randomly determining the T-RPT, the vehicle UE can take into account the results of the sensing process as much as possible. Specifically, the same physical resource block reserved in one subframe may be available in another subframe, allowing the vehicle UE to minimize interference with transmissions from other UEs by appropriately selecting the T-RPT based on the sensed information.

[0241] Similarly, whether to use frequency hopping for frequency domain resources can also be based on the results of the sensing process, allowing the vehicle UE to choose whether to use frequency hopping or not for the frequency domain, depending on, for example, which frequency resources will cause the least interference.

[0242] The determination of the timing pattern and the use of frequency hopping are interrelated, as different frequencies at different subframes will lead to different collisions and interferences. Accordingly, the appropriate T-RPT and the use of frequency hopping can be determined together to combine the benefits of selecting the optimal T-RPT and the optimal PRB.

[0243] As described above, the scheduling assignment for the entire data transmission needs to indicate the time-frequency resources used for the initial data transmission and the selected T-RPT. This is the primary information regarding the timing of the first transmission of data derived by the receiving entity and the remaining retransmissions of the data. Optionally, the scheduling assignment may also include information about whether frequency hopping is used for the initial transmission. Accordingly, the scheduling assignment is compact and does not result in high signaling overhead.

[0244] Data retransmission will therefore be completed within the time period given by the determined T-RPT, which in the exemplary case is 7 (see [reference]). Figure 11 ) or 8 (see Figure 12 The retransmission is completed within a subframe. In other words, especially compared to the exemplary delay requirement of 100ms, retransmissions must be performed within a relatively short time window. This reduces the flexibility of vehicle UE transmission retransmissions. Although one variant also takes the sensing results into account, the probability of data transmission conflicts with other UEs remains high and may be difficult to avoid, due to the very limited flexibility of the variant in question, as only a few different T-RPTs exist within a very short time frame.

[0245] The following provides alternative implementations of the first embodiment to improve upon the above-described variations of the first embodiment. (As will be combined with...) Figure 13 and Figure 14 As explained, instead of limiting retransmission to a specific time frame given by the length of the timing pattern (e.g., Figure 11 and Figure 12 As shown in the diagram, another exemplary implementation of the first embodiment extends the retransmission possibility throughout the remaining transmission window. Specifically, in conjunction with the above... Figure 11 and Figure 12 In the same manner described, the vehicle UE should perform a radio resource allocation to determine the optimal radio resources for the first data transmission based on information obtained from the resource sensing process. In this example, it is assumed that the vehicle UE determines the optimal time-frequency radio resources in subframe 14, such that the initial transmission is performed in those determined frequencies of subframe 14.

[0246] On the other hand, the data transmission timing pattern selected by the vehicle UE includes only one transmission, i.e., only one transmission for the entire T-RPT. However, the first transmission T-RPT is subsequently repeated throughout the remaining transmission window after the first transmission and has the first data transmission timing as a reference, so as to define several data retransmission candidates. For example, as Figure 14 As shown, repeated T-RPTs can begin in the next subframe after the first data transmission timing (as combined with the above). Figure 12The discussion could also extend to other timings offset from the first data transmission timing. Alternatively, such as... Figure 13 As shown, the repeating T-RPT begins, making the first repeating T-RPT (more precisely, the "1" in the first T-RPT bitmap) consistent with the timing of the first data retransmission.

[0247] By positioning repeated T-RPTs after the first data transmission sequence in this way, each T-RPT defines a data retransmission candidate at those subframes where the repeated T-RPT indicates a transmission. The data retransmission candidates are thus (e.g., after the first data transmission sequence) distributed throughout the remaining transmission window and spaced equidistantly from each other according to the length of the T-RPT. For example, in Figure 13 In the exemplary implementation given, the first data transmission is defined to occur in subframe 14, such that data retransmission candidates will be in subframes 22, 30, 38, 46...110 (each having a distance between 8 subframes, the distance being consistent with the length of T-RPT).

[0248] Assuming the transmission window is 100ms and the transmission mode is 8 bits, then there can be 12 (e.g., for...). Figure 14 ) and a maximum of 14 (e.g., for Figure 13 The maximum value among different data retransmission candidates (also depending on the actual implementation used). The final T-RPT can be truncated, and therefore, depending on the location of the "1" data transmission within the (truncated) T-RPT, another data retransmission opportunity may or may not be generated.

[0249] The vehicle UE can then select a data retransmission candidate from those defined thus to ensure data retransmission. Of course, this selection also depends on the total number of transmissions (i.e., the total number of retransmissions). Figure 13 In the hypothetical exemplary scenario, it is assumed that only two total transmissions are performed, meaning only one retransmission is required, forcing the vehicle UE to select only one available data retransmission candidate. Figure 13 In the exemplary scenario shown, assume the vehicle UE decides to transmit a single data retransmission at subframe 30, which is associated with the third in the T-RPT sequence. Figure 14 In the exemplary scenario shown, it is assumed that the vehicle UE will perform three total data transmissions, and therefore the vehicle UE must select two retransmission candidates; assuming that in subframes 22 and 38, that is, the first and third in the same repeated T-RPT.

[0250] To inform the receiving entity where the vehicle UE will perform the first transmission and retransmission, the scheduling assignment should not only indicate the time-frequency radio resources (as previously discussed) used for the first transmission and the selected T-RPT, but also information about the data retransmission candidates that the vehicle UE will actually use for data (re)transmission. One possible option for indicating the data retransmission candidate used among all candidates is to provide a bitmap (e.g., called a T-RPT selection bitmap) in the scheduling assignment, where bits of the T-RPT selection bitmap are associated with repeated T-RPTs, thereby uniquely identifying one of the repeated T-RPTs. Figure 13 and Figure 14 As shown, depending on the implementation, the T-RPT selection bitmap can have different lengths and should have a length to allow for flexible indication of all data retransmission candidates. As is evident from the diagram, a "1" in the T-RPT selection bitmap points to the T-RPT actually used by the vehicle UE to perform a retransmission. The T-RPT selection bitmap will be included in the scheduling assignment, which, while slightly increasing signaling overhead, provides the benefit of significantly increased flexibility in performing retransmissions.

[0251] To improve retransmission reliability and reduce potential conflicts with other data transmissions, the vehicle UE can determine the primary transmission time-retransmission point (T-RPT) and the data retransmission candidates to be actually used for retransmission based on the results obtained from the sensing process. Specifically, there are up to eight different primary transmission T-RPTs (assuming an 8-bit T-RPT), each defining different data retransmission candidates within the entire transmission window. Furthermore, among these defined data retransmission candidates (e.g., 13 candidates), there are several different combinations of candidates to perform data retransmission. In general, depending on the primary transmission T-RPT and the resulting options for performing data retransmission, the vehicle UE should select the combination of T-RPT and data retransmission candidates that will produce, for example, minimal interference based on predictions obtained from the sensing process.

[0252] Furthermore, the vehicle UE can use the same frequency used for the initial data transmission, or it can use a frequency derived from the frequency used for the first data transmission based on a frequency hopping pattern. As previously mentioned, this decision can also be based on the results of the sensing process, for example, considering that radio resource reservations can vary within a single subframe due to different PRBs. Therefore, three different degrees of freedom can exist for the vehicle UE to optimize data retransmission reliability: one transmission T-RPT, the retransmission candidate actually used among all retransmission candidates, and whether the frequency resource is based on frequency hopping. These three degrees of freedom are interrelated and can be selected together based on sensing results obtained prior to the sensing window to benefit as much as possible from the sensing results while allowing for a simple (re)transmission process.

[0253] According to another implementation, the combination is further improved by selecting one of the data retransmission resources based on the sensing results. Figure 13 and Figure 14 The solutions presented and discussed. Specifically, Figure 15 The diagram illustrates data that can be used by the UE to transmit data, similar to what has been discussed above. Figure 14 The sequence of subframes within the transmission window. Combined with... Figure 13 and Figure 14 In the same manner as the presented solution, the vehicle UE should perform a radio resource allocation process to determine the optimal radio resources for the first data transmission based on information obtained from the resource sensing process. Furthermore, the vehicle UE will select a single transmission time-retransmission point (T-RPT), which is repeatedly positioned throughout the remaining transmission window with the first data transmission as a reference. Unlike previous solutions, to determine the T-RPT, the vehicle UE should first determine the optimal retransmission candidate within the remaining transmission window (i.e., after the first data transmission) based on the sensing results. Based on the sensing results, the vehicle UE can freely select frequency and time resources for the preferred retransmission candidate, thereby avoiding transmission conflicts with other UEs.

[0254] Subsequently, the vehicle UE uses the selected preferred retransmission candidate's time position to determine the T-RPT. This will combine... Figure 15 This will be explained. For example, assume that a preferred retransmission candidate is found in subframe 26 (e.g., it is the second-highest ranked candidate, and the UE selects the highest-ranked candidate for the first data transmission). For example, assume that the positioning of the 8-bit repeated T-RPT begins immediately after the first data transmission (see [link to documentation]). Figure 15 The vehicle UE will therefore select T-RPT 00010000, such that one of the "1"s in the repeated T-RPT matches the previously selected preferred data retransmission candidate (see subframe 26). Accordingly, one of the data retransmissions performed by the vehicle UE should occur at subframe 26 at a frequency selected during the resource allocation process based on the sensing results (i.e., the frequency used at subframe 26 may be different from those frequencies used for the initial data transmission in subframe 14). For example, in Figure 15 In this context, it is assumed that a first data retransmission is performed at the preferred data retransmission candidate, while a second retransmission is performed at subframe 34 with the next retransmission possibility. The previously mentioned T-RPT selection bitmap must indicate these retransmissions, and therefore the second and third T-RPTs are indicated as being used by the vehicle UE for data retransmission.

[0255] As explained in the previous implementation, the vehicle UE may have to select another data retransmission candidate from the remaining data retransmission candidates. This can be done, for example, by using the results of the sensing process, in order to avoid transmission conflicts with other UEs.

[0256] Figure 15 This improved solution results in a reduced collision rate and thus increases data transmission reliability by freely selecting additional time and frequency resources for a data retransmission based on previously obtained sensing results. However, the solution slightly increases signaling overhead. As previously stated... Figure 13 and Figure 14 The implementation discussed herein indicates that the vehicle UE, for the data candidate transmission, specifies the time-frequency radio resources used for the first data transmission, along with the selected T-RPT and T-RPT selection bitmap, in the scheduling assignment for the data candidate transmission. When the T-RPT is combined with the T-RPT selection bitmap and the timing of the first data transmission is taken into account, to uniquely identify the timing of all remaining data retransmissions, the receiving entity needs to know the frequency used by the vehicle UE to transmit the data retransmission at the preferred radio resources (see, for example, subframe 26 above), because the frequency is freely chosen based on sensing results and therefore will not coincide with (or adhere to) the frequency already indicated in the scheduling assignment for the first data transmission. Therefore, one solution is to include information about other frequencies used for said one retransmission at subframe 26; this can be done either by explicitly identifying the frequencies or by including a frequency offset from the frequency used for the first data transmission. The receiving entity can use the frequency offset to determine the frequency used for said one data retransmission at subframe 26.

[0257] Furthermore, the same frequency used for the first data retransmission or a preferred data retransmission can also be used for transmitting the remaining data retransmissions. Alternatively, the frequency hopping pattern used for the first data transmission or preferred data retransmission can be used for the remaining data retransmissions. In this respect, the corresponding frequency hopping indication in the scheduling assignment appropriately notifies the receiving entity.

[0258] The following describes further improvements to the radio resource allocation performed on initial data transmission and data retransmission. According to exemplary implementations, these include... Figure 9 The data resource pool of multiple time-frequency radio resources, illustrated in a simplified manner, is divided into time-frequency radio resources that can only be used for performing the first data transmission, while the remaining time-frequency radio resources in the data resource pool can only be used for performing data retransmission. Alternatively, two different data resource pools can be provided, one for initial data transmission and the other for data retransmission. In any case, during the resource allocation process, the vehicle UE uses different resources for initial transmission and data retransmission. Data resource pool isolation should apply, for example, to all vehicle UEs in the corresponding cell. Therefore, by isolating the available resources for data transmission between initial data transmission and data retransmission, the initial transmission can be further protected, as it is theoretically impossible to conflict with retransmission.

[0259] The isolation of available time-frequency resources can be accomplished in various ways. For example, a corresponding formula can be provided, which is then used by the vehicle UE and other UEs to determine which time-frequency radio resources will be used for initial data transmission and which will be used for data retransmission. Simple formulas can be based on, for example, modular arithmetic. Furthermore, different data resource pools for initial data transmission and data retransmission can be configured by the eNodeB through appropriate broadcast system information.

[0260] In one particular exemplary variant, isolation is performed in the time domain, such that subframes are used for initial transmission or retransmission.

[0261] This improvement could, for example, be applied to combination. Figure 9 The discussed implementation involves the vehicle UE performing a radio resource allocation process for each (re)transmission. Furthermore, the improvements can also be applied to combinations as described above. Figures 11-15 The discussion covers implementation methods. For example, regarding... Figure 11 and Figure 12 The solution presented herein, in an improved version, performs radio resource selection for the first transmission from the time-frequency resources available only for the initial transmission. Subsequently, the selected T-RPT mode (random selection or selection based on sensing results) will only indicate subframes that are actually available in the data resource pool pointing to data retransmission. Figure 16 An exemplary illustration shows an implementation where subframes unavailable for retransmission are crossed out. For example, assume that only the third subframe is available for retransmission at a time, specifically subframes 14, 17, 20, 23, 26, 29, etc. It is evident that (except for the first bit of the T-RPT in the aforementioned variant, which is assumed to indicate the first transmission) the bits of the T-RPT bitmap correspond only to the subframes that are indeed available for retransmission. Therefore, by using the... Figure 11 In the exemplary scenario of (10110001), with the same T-RPT bitmap, the vehicle UE will perform retransmissions at subframes 17, 20, and 32.

[0262] Similarly, targeting according to Figure 13 , 14 And in the implementation of 15, the repeated T-RPT mode will be repeated throughout the entire subframe of the transmission window belonging to the data resource pool with retransmission restrictions. Regarding... Figure 15 The solution in the text specifically performs radio resource allocation for a preferred data retransmission (in subframe 26), selecting resources within the data resource pool that are subject to retransmission restrictions.

[0263] Other embodiments

[0264] According to a first aspect, a transmitting device is provided for transmitting data to one or more receiving devices via a sidelink interface. The data transmission includes a first transmission of the data and one or more retransmissions of the data following the first data transmission. A receiving unit and a processor of the transmitting device perform a resource sensing process to acquire information about radio resources available for the transmitting device to transmit data at a later time. After the data becomes available for transmission, the processor performs autonomous radio resource allocation based on information acquired by the resource sensing process during a sensing window before the data becomes available for transmission, to select time-frequency radio resources within the transmission window to be used for performing the first data transmission. The processor determines a data transmission timing pattern among a plurality of data transmission timing patterns, each data transmission timing pattern indicating a transmission timing sequence for performing one or more data transmissions. The transmitting unit of the transmitting device performs the first data transmission using the selected time-frequency radio resources and performs one or more data retransmissions with a transmission timing sequence defined by the determined data transmission timing pattern relative to the first data transmission.

[0265] According to the second aspect provided in addition to the first aspect, the plurality of data transmission timing patterns indicate different numbers of data transmissions. The processor determines a data transmission timing pattern from among the data transmission timing patterns corresponding to the total number of transmissions to be performed on the data; in an optional implementation, the total number of transmissions to be performed on the data is determined by the processor or pre-configured. According to an option, the one or more data retransmissions are performed within a time span defined by the length of the determined data transmission timing pattern. The data transmission timing pattern is determined by the processor randomly or based on information acquired by a resource sensing process during a sensing window.

[0266] According to a third aspect provided in addition to one of the first to second aspects, the transmitting unit transmits a scheduling assignment that indicates a selected time-frequency radio resource for the first data transmission and identifies the determined data transmission timing pattern.

[0267] According to the fourth aspect in addition to the first aspect, the determined data transmission timing pattern indicates only one data transmission. The processor determines data retransmission candidates for performing the one or more data retransmissions within the transmission window by repeatedly determining the data transmission timing pattern relative to the timing of the first data transmission within the transmission window, and subsequently by identifying the timing position given by an indicated data transmission in each repeated data transmission timing pattern. The processor determines which data retransmission candidates will be used to perform the one or more data retransmissions, which can optionally be done based on the total number of transmissions to be performed on the data, wherein the total number of data transmissions can be determined by the processor or pre-configured. According to one option, the processor determines the data transmission timing pattern to be used for the data retransmission and the data retransmission candidates based on information acquired by a resource sensing process during the sensing window.

[0268] According to a fifth aspect other than one of the first to fourth aspects, one or more data retransmissions are performed using the same frequency radio resources as those used for the first data transmission or using frequency radio resources determined by the processor from the frequency radio resources used for the first data transmission based on a frequency hopping mode. According to one option, the processor determines whether the one or more data retransmissions use the same frequency radio resources as the first data transmission or use frequency radio resources following a frequency hopping mode based on information acquired by the resource sensing process during a sensing window. According to another option, the scheduling assignment further instructs the transmitting device whether to use a frequency hopping mode to determine the frequency radio resources used for transmitting the one or more data retransmissions.

[0269] According to the sixth aspect in addition to the first aspect, the determined data transmission timing pattern indicates only one transmission. After the first data transmission timing, the processor determines a preferred transmission timing for one of the one or more data retransmissions based on the information acquired by the resource sensing process during the sensing window. The processor determines the data transmission timing pattern such that when the data transmission timing pattern is repeated multiple times within the transmission window relative to the timing of the first data transmission, a data transmission indicated by the data transmission timing pattern is consistent with the determined preferred transmission timing. Data retransmission candidates for performing one or more data retransmissions are defined within the transmission window by repeating the data transmission timing pattern and subsequently by identifying the timing position given by a data transmission indicated by each repeated data transmission timing pattern. The processor determines which data retransmission candidates will be used to perform the remaining data retransmissions, which may optionally be done based on information acquired by the resource sensing process during the sensing window and depending on the total number of transmissions to be performed on the data. The total number of data transmissions may be determined by the processor or pre-configured, with the transmitting unit transmitting one data retransmission at the determined preferred transmission timing and transmitting the remaining data retransmissions at the determined retransmission candidates to be used.

[0270] According to a seventh aspect, in addition to the sixth aspect, the scheduling assignment transmitted by the transmitting unit indicates frequency radio resources for data retransmission in a preferred transmission sequence. For example, the indication of frequency resources for data retransmission in a preferred transmission sequence may be an offset relative to the frequency radio resources used for the first data transmission. According to one option, the remaining data retransmissions are performed using either the same frequency radio resources used for the first data transmission or the same frequency radio resources used for data retransmission in a preferred transmission sequence. Alternatively, the remaining data retransmissions are performed using frequency radio resources determined by the processor based on a frequency hopping mode from the frequency radio resources used for the first data transmission or from the frequency radio resources used for data retransmission in a preferred transmission sequence. Accordingly, the scheduling assignment also instructs the transmitting device whether to use a frequency hopping mode to determine the frequency radio resources used for transmitting the one or more data retransmissions.

[0271] According to an eighth aspect (excluding the fourth to seventh aspects), the transmitting unit transmits a scheduling assignment indicating selected time-frequency radio resources for the first data transmission and identifying a determined data transmission timing pattern. The scheduling assignment also indicates which of a plurality of repeating data transmission timing patterns defines the transmission timing for performing the one or more data retransmissions. Optionally, the data transmission timing pattern indication is encoded as a bitmap, wherein the bits of the bitmap are associated with one of the plurality of repeating data transmission timing patterns.

[0272] According to a ninth aspect other than one of the first through eighth aspects, the data transmission timing pattern has a length of multiple bits. Each bit of the data transmission timing pattern indicates whether data transmission will be performed with a transmission timing associated with the position of the corresponding bit. Optionally, the data transmission timing pattern is located within the timing window relative to the first data transmission so as to also indicate or not indicate the first data transmission.

[0273] According to a tenth aspect, excluding any one of the first to ninth aspects, the data resource pool includes a plurality of time-frequency radio resources available for the transmitting device to perform data transmission. The data resource pool is divided into time-frequency radio resources available for performing the first data transmission and time-frequency radio resources available for performing data retransmission. Subsequently, during autonomous radio resource allocation, the processor selects a time-frequency radio resource from the available time-frequency radio resources for performing the first data transmission. Optionally, the plurality of time-frequency radio resources in the data resource pool are divided in the time domain between time-frequency radio resources for the first data transmission and time-frequency radio resources for data retransmission. Alternatively, the division of the data resource pool is pre-configured or configured by a radio base station controlling the transmitting device.

[0274] According to the eleventh aspect, excluding any one of aspects seven through ten, the resource sensing process includes:

[0275] To determine radio resources reserved by other transmitting devices, the receiving unit and the processor monitor scheduling assignments transmitted by the other transmitting devices, which indicate radio resources reserved by the other transmitting devices at a later time point.

[0276] • Optionally, the received signal energy in the radio resources can be measured to identify radio resources used for transmission by other transmitting devices.

[0277] Optionally, the autonomous radio resource allocation includes excluding radio resources reserved by other transmitting devices from the plurality of transmit radio resources.

[0278] According to a twelfth aspect, a method is provided for a transmitting device to transmit data to one or more receiving devices via a sidelink interface. The transmission of the data includes a first transmission of the data and one or more retransmissions of the data following the first data transmission. The method includes the following steps performed by the transmitting device: Performing a resource sensing process to acquire information about radio resources available for the transmitting device to transmit data at a later time. After the data becomes available for transmission, performing an autonomous radio resource allocation based on the information acquired by the resource sensing process during a sensing window before the data becomes available for transmission, to select time-frequency radio resources within the transmission window to be used for performing the first transmission of data. The transmitting device determines a data transmission timing pattern among a plurality of data transmission timing patterns, each data transmission timing pattern indicating a transmission timing sequence for performing one or more data transmissions. The transmitting device uses the selected time-frequency radio resources to perform the first data transmission and performs one or more data retransmissions with a transmission timing sequence defined by the determined data transmission timing pattern relative to the first data transmission.

[0279] According to the thirteenth aspect provided in addition to the twelfth aspect, the plurality of data transmission timing patterns indicate different numbers of data transmissions. The method includes determining a data transmission timing pattern from among data transmission timing patterns corresponding to the total number of transmissions to be performed on the data. Optionally, the total number of transmissions to be performed on the data is determined by the transmitting device or pre-configured. Optionally, the one or more data retransmissions are performed within a time span defined by the length of the determined data transmission timing pattern. Optionally, the data transmission timing pattern is determined by the transmitting device randomly or based on information acquired by a resource sensing process during a sensing window.

[0280] According to the fourteenth aspect provided in addition to the twelfth or thirteenth aspect, the method further includes the steps of: sending a scheduling assignment indicating selected time-frequency radio resources for the first data transmission, and identifying the determined data transmission timing pattern.

[0281] According to the fifteenth aspect provided in addition to the twelfth aspect, the determined data transmission timing pattern indicates only one data transmission. The method includes the steps of: determining a data transmission timing pattern determined by repeated timing relative to a first data transmission within the transmission window, and subsequently determining data retransmission candidates for performing the one or more data retransmissions within the transmission window by identifying a timing position given by an indicated data transmission in each repeated data transmission timing pattern. The method includes the step of: determining which data retransmission candidates will be used to perform the one or more data retransmissions, which may optionally be based on the total number of transmissions to be performed on the data, wherein the total number of data transmissions is determined by the processor or pre-configured. Optionally, the method includes the step of: determining the data transmission timing pattern to be used for the data retransmission and the data retransmission candidates based on information acquired by a resource sensing process during a sensing window.

[0282] According to the sixteenth aspect, provided in addition to any one of aspects 12 to 15, one or more data retransmissions are performed using the same frequency radio resources as those used for the first data transmission or using frequency radio resources determined from the frequency radio resources used for the first data transmission based on a frequency hopping mode. Optionally, the method includes the step of determining, based on information acquired by the resource sensing process during a sensing window, whether the one or more data retransmissions use the same frequency radio resources as the first data transmission or use frequency radio resources following a frequency hopping mode. Optionally, the scheduling assignment further instructs the transmitting device whether to use a frequency hopping mode to determine the frequency radio resources used for transmitting the one or more data retransmissions.

[0283] According to the seventeenth aspect provided in addition to the twelfth aspect, the determined data transmission timing pattern indicates only one data transmission. The method includes the step of: after the first data transmission timing, determining a preferred transmission timing for one of the one or more data retransmissions based on information acquired by the resource sensing process during the sensing window. The method includes the step of: determining the data transmission timing pattern such that when the data transmission timing pattern is repeated multiple times within the transmission window relative to the timing of the first data transmission, a data transmission indicated by the data transmission timing pattern coincides with the determined preferred transmission timing. Data retransmission candidates for performing one or more data retransmissions are defined within the transmission window by repeating the data transmission timing pattern and subsequently by identifying the timing position given by a data transmission indicated by each repeated data transmission timing pattern. The method includes the step of: determining which data retransmission candidates will be used to perform the remaining data retransmissions, which may optionally be based on information acquired by the resource sensing process during the sensing window and depend on the total number of transmissions to be performed on the data, wherein the total number of data transmissions is determined by the transmitting device or pre-configured. The method includes the following steps: transmitting a data retransmission at a determined preferred transmission timing, and transmitting the remaining data retransmissions at a determined retransmission candidate.

[0284] According to the eighteenth aspect, in addition to the seventeenth aspect, the scheduling assignment transmitted by the transmitting unit indicates frequency radio resources for data retransmission in a preferred transmission sequence, optionally as an offset relative to the frequency radio resources used for the first data transmission. Optionally, the remaining data retransmissions may be performed using the same frequency radio resources used for the first data transmission or the same frequency radio resources used for data retransmission in a preferred transmission sequence. Alternatively, the remaining data retransmissions may be performed using frequency radio resources determined by the processor based on a frequency hopping mode from the frequency radio resources used for the first data transmission or from the frequency radio resources used for data retransmission in a preferred transmission sequence. The scheduling assignment also indicates whether the transmitting device uses a frequency hopping mode to determine the frequency radio resources used for transmitting the one or more data retransmissions.

[0285] According to a nineteenth aspect provided in addition to one of aspects fifteen through eighteen, the method further includes the steps of: sending a scheduling assignment indicating selected time-frequency radio resources for the first data transmission, and identifying a determined data transmission timing pattern. The scheduling assignment further indicates which of a plurality of repeating data transmission timing patterns defines the transmission timing for performing the one or more data retransmissions. Optionally, the data transmission timing pattern indication is encoded as a bitmap, wherein the bits of the bitmap are associated with one of the plurality of repeating data transmission timing patterns.

[0286] According to a twentieth aspect provided in addition to one of aspects twelfth to nineteenth, the data transmission timing pattern has a length of multiple bits, and each bit of the data transmission timing pattern indicates whether data transmission will be performed with a transmission timing associated with the position of the corresponding bit. Optionally, the data transmission timing pattern is located in the timing window relative to the first data transmission so as to also indicate or not indicate the first data transmission.

[0287] According to a 21st aspect provided in addition to one of aspects 12 to 20, the data resource pool includes a plurality of time-frequency radio resources available for the transmitting device to perform data transmission. The data resource pool is divided into time-frequency radio resources available for performing a first data transmission and time-frequency radio resources available for performing data retransmission. The method includes the step of selecting, during autonomous radio resource allocation, time-frequency radio resources for performing the first data transmission from among the time-frequency radio resources available for performing the first data transmission. Optionally, the plurality of time-frequency radio resources in the data resource pool are divided in the time domain between time-frequency radio resources for performing the first data transmission and time-frequency radio resources for performing data retransmission. Optionally, the division of the data resource pool is pre-configured or configured by a radio base station controlling the transmitting device.

[0288] According to one aspect of the invention, a transmitting device for transmitting data to one or more receiving devices via a sidelink interface, wherein the transmission of data includes a first transmission of the data and one or more retransmissions of the data after the first transmission, the transmitting device comprising: a receiving unit and a processor, the processor performing a resource sensing process to acquire information about radio resources available for the transmitting device to transmit data at a later time point, the processor performing autonomous radio resource allocation based on the information acquired by the resource sensing process during a sensing window prior to the data becoming available for transmission, to select time-frequency radio resources within the transmission window to be used for performing the first transmission of the data, and the processor determining a data transmission timing mode among a plurality of data transmission timing modes, each data transmission timing mode indicating a transmission timing for performing one or more data transmissions, and a transmitting unit performing the first data transmission using the selected time-frequency radio resources, and performing the one or more data retransmissions with the transmission timing defined by the determined data transmission timing mode relative to the first data transmission.

[0289] According to the aforementioned transmitting device, wherein the plurality of data transmission timing patterns indicate different numbers of data transmissions, and the processor determines a data transmission timing pattern from among the data transmission timing patterns corresponding to the total number of transmissions to be performed on the data, wherein the total number of transmissions to be performed on the data is determined by the processor or pre-configured, wherein the one or more data retransmissions are performed within a time span defined by the length of the determined data transmission timing pattern, wherein the data transmission timing pattern is determined by the processor randomly or based on the information acquired by the resource sensing process during the sensing window.

[0290] According to the aforementioned transmitting device, wherein the transmitting unit transmits a scheduling assignment, the scheduling assignment indicating the selected time-frequency radio resources for the first data transmission, and identifies the determined data transmission timing pattern.

[0291] According to the aforementioned transmitting device, wherein the determined data transmission timing pattern indicates only one data transmission, wherein the processor determines the determined data transmission timing pattern by repeating the timing relative to the first data transmission multiple times within the transmission window and subsequently by identifying the timing position given by the indicated one data transmission in each repeated data transmission timing pattern to determine data retransmission candidates for performing the one or more data retransmissions within the transmission window, and wherein the processor determines which data retransmission candidates will be used to perform the one or more data retransmissions based on the total number of transmissions to be performed on the data, the total number of data transmissions being determined by the processor or pre-configured, wherein the processor determines the data transmission timing pattern to be used for the data retransmission and the data retransmission candidates based on the information acquired by the resource sensing process during the sensing window.

[0292] According to the aforementioned transmitting device, the one or more data retransmissions are performed using the same frequency radio resources as those used for the first data transmission or using frequency radio resources determined by the processor from the frequency radio resources used for the first data transmission based on a frequency hopping mode. The processor determines whether the one or more data retransmissions use the same frequency radio resources as those used for the first data transmission or use frequency radio resources following the frequency hopping mode based on information acquired by the resource sensing process during the sensing window. The scheduling assignment further instructs the transmitting device whether to use a frequency hopping mode to determine the frequency radio resources used for transmitting the one or more data retransmissions.

[0293] According to the aforementioned transmitting device, wherein the determined data transmission timing pattern indicates only one transmission, wherein the processor, after the first data transmission timing, determines a preferred transmission timing for one of the one or more data retransmissions based on the information acquired by the resource sensing process during the sensing window, and wherein the processor determines the data transmission timing pattern such that when the data transmission timing pattern is repeated multiple times relative to the timing of the first data transmission within the transmission window, the data transmission indicated by the data transmission timing pattern is consistent with the determined preferred transmission timing, wherein this is achieved by repeating the data transmission timing pattern and subsequently by recognizing... The processor defines data retransmission candidates for performing one or more data retransmissions within the transmission window, based on the timing position of a data transmission indicated by each repeated data transmission timing pattern, and determines which data retransmission candidates will be used to perform the remaining data retransmissions. This is based on the information acquired by the resource sensing process during the sensing window and depends on the total number of transmissions to be performed on the data, which is determined by the processor or pre-configured. The transmitting unit transmits one data retransmission at the determined preferred transmission timing and transmits the remaining data retransmissions at the determined retransmission candidates to be used.

[0294] According to the aforementioned transmitting device, the scheduling assignment transmitted by the transmitting unit indicates the frequency radio resources for data retransmission in the preferred transmission timing, as an offset relative to the frequency radio resources used for the first data transmission, and wherein the remaining data retransmission is performed using the same frequency radio resources used for the first data transmission or the same frequency radio resources used for data retransmission in the preferred transmission timing, or wherein the remaining data retransmission is performed using frequency radio resources determined by the processor based on a frequency hopping mode from the frequency radio resources used for the first data transmission or from the frequency radio resources used for data retransmission in the preferred transmission timing, and wherein the scheduling assignment further indicates whether the transmitting device uses a frequency hopping mode to determine the frequency radio resources used for transmitting the one or more data retransmissions.

[0295] According to the aforementioned transmitting device, wherein the transmitting unit transmits a scheduling assignment, the scheduling assignment indicating a selected time-frequency radio resource for the first data transmission, and identifies a determined data transmission timing pattern, wherein the scheduling assignment further indicates which of the plurality of repeated data transmission timing patterns defines the transmission timing for performing the one or more data retransmissions, wherein the data transmission timing pattern indication is encoded as a bitmap, wherein the bits of the bitmap are respectively associated with one of the plurality of repeated data transmission timing patterns.

[0296] According to the aforementioned transmitting device, the data resource pool includes a plurality of time-frequency radio resources available for the transmitting device to perform data transmission. The data resource pool is divided into time-frequency radio resources available for performing a first data transmission and time-frequency radio resources available for performing data retransmission. The processor selects a time-frequency radio resource available for performing the first data transmission among the time-frequency radio resources available for performing the first data transmission during the autonomous radio resource allocation. The plurality of time-frequency radio resources in the data resource pool are divided in the time domain between the time-frequency radio resources for the first data transmission and the time-frequency radio resources for data retransmission. The division of the data resource pool is pre-configured or configured by a radio base station controlling the transmitting device.

[0297] According to one aspect of the invention, a method for a transmitting device to transmit data to one or more receiving devices via a sidelink interface, wherein the transmission of data includes a first transmission of the data and one or more retransmissions of the data after the first transmission, the method comprising the steps performed by the transmitting device: performing a resource sensing process to acquire information about radio resources available for the transmitting device to transmit data at a later time point; performing autonomous radio resource allocation based on the information acquired by the resource sensing process during a sensing window before the data becomes available for transmission, to select time-frequency radio resources within the transmission window to be used for performing the first transmission of the data; determining a data transmission timing pattern among a plurality of data transmission timing patterns, each data transmission timing pattern indicating a transmission timing for performing one or more transmissions of data; performing the first transmission using the selected time-frequency radio resources; and performing the one or more data retransmissions with the transmission timing defined by the determined data transmission timing pattern relative to the first transmission.

[0298] According to the aforementioned method, wherein the plurality of data transmission timing patterns indicate different numbers of data transmissions, and the method includes determining a data transmission timing pattern from among the data transmission timing patterns corresponding to the total number of transmissions to be performed on the data, wherein the total number of transmissions to be performed on the data is determined by the transmitting device or pre-configured, wherein the one or more data retransmissions are performed within a time span defined by the length of the determined data transmission timing pattern, wherein the data transmission timing pattern is determined by the transmitting device randomly or based on the information acquired by the resource sensing process during the sensing window.

[0299] According to the aforementioned method, wherein the determined data transmission timing pattern indicates only one data transmission, and the method includes the following steps: determining data retransmission candidates for performing the one or more data retransmissions within the transmission window by repeatedly reproducing the determined data transmission timing pattern relative to the timing of the first data transmission within the transmission window and subsequently by identifying the timing position given by the indicated one data transmission in each repeated data transmission timing pattern; and determining which data retransmission candidates will be used to perform the one or more data retransmissions, based on the total number of transmissions to be performed on the data, the total number of data transmissions being determined by the processor or pre-configured, wherein the method includes the following step: determining the data transmission timing pattern to be used for the data retransmission and the data retransmission candidates based on the information acquired by the resource sensing process during the sensing window.

[0300] According to the aforementioned method, wherein the determined data transmission timing pattern indicates only one transmission, wherein the method includes the following steps: after the first data transmission timing, determining a preferred transmission timing for one of the one or more data retransmissions based on the information acquired by the resource sensing process during the sensing window, and determining the data transmission timing pattern such that when the data transmission timing pattern is repeated multiple times relative to the timing of the first data transmission within the transmission window, the data transmission indicated by the data transmission timing pattern is consistent with the determined preferred transmission timing, wherein the data transmission timing pattern is repeated... Then, within the transmission window, data retransmission candidates for performing one or more data retransmissions are defined by identifying the timing position given by a data transmission indicated by each repeated data transmission timing pattern. It is determined which data retransmission candidates will be used to perform the remaining data retransmissions, based on the information acquired by the resource sensing process during the sensing window and depending on the total number of transmissions to be performed on the data, which is determined by the transmitting device or pre-configured, and that a data retransmission is transmitted at the determined preferred transmission timing, and the remaining data retransmissions are transmitted at the determined retransmission candidates to be used.

[0301] According to the aforementioned method, the method further includes the following steps: sending a scheduling assignment, the scheduling assignment indicating a selected time-frequency radio resource for the first data transmission, and identifying a determined data transmission timing pattern, wherein the scheduling assignment further indicates which of the plurality of repeated data transmission timing patterns defines the transmission timing for performing the one or more data retransmissions, wherein the data transmission timing pattern indication is encoded as a bitmap, wherein the bits of the bitmap are respectively associated with one of the plurality of repeated data transmission timing patterns.

[0302] According to the aforementioned method, the data resource pool includes a plurality of time-frequency radio resources available for the transmitting device to perform data transmission. The data resource pool is divided into time-frequency radio resources available for performing a first data transmission and into time-frequency radio resources available for performing data retransmission. The method includes the step of selecting, during the autonomous radio resource allocation, time-frequency radio resources for performing the first data transmission among the time-frequency radio resources available for performing the first data transmission. The plurality of time-frequency radio resources in the data resource pool are divided in the time domain between time-frequency radio resources for performing the first data transmission and time-frequency radio resources for performing data retransmission. The division of the data resource pool is pre-configured or configured by a radio base station controlling the transmitting device.

[0303] The hardware and software implementation methods disclosed herein

[0304] Other exemplary embodiments relate to implementing the various embodiments described above using hardware, software, or a combination of software and hardware. In this regard, a user terminal (mobile terminal) is provided. The user terminal is adapted to perform the methods described herein, including corresponding entities to appropriately participate in the methods, such as a receiving unit, a transmitting unit, and a processor.

[0305] It is further recognized that various embodiments can be implemented or executed using computing devices (processors). Computing devices or processors can be, for example, general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices. Various embodiments can also be executed or implemented using combinations of these devices. Specifically, each functional block used in the description of each of the above embodiments can be implemented as an integrated circuit using an LSI. They can be formed individually as chips, or they can be formed as a single chip to include some or all of the functional blocks. They can include data inputs and outputs coupled thereto. The LSIs described herein may be referred to as ICs, system LSIs, super LSIs, or ultra-LSIs depending on their level of integration. However, the techniques for implementing integrated circuits are not limited to LSIs and can be implemented using dedicated circuits or general-purpose processors. Furthermore, FPGAs (Field-Programmable Gate Arrays) that can be programmed after the LSI is manufactured, or reconfigurable processors in which the connections and settings of the circuitry cells disposed within the LSI can be reconfigured, can be used.

[0306] Furthermore, various embodiments can also be implemented using software modules, which are executed by a processor or directly in hardware. Combinations of software modules and hardware implementations are also possible. Software modules can be stored on any type of computer-readable storage medium, such as RAM, EPROM, EEPROM, flash memory, registers, hard disks, CD-ROMs, DVDs, etc. It should also be noted that various features of different embodiments can be used individually or in any combination as the subject matter of another embodiment.

[0307] Those skilled in the art will understand that many variations and / or modifications can be made to the present disclosure shown in the specific embodiments. Therefore, this embodiment is to be regarded as illustrative in all respects and not restrictive.

Claims

1. A transmitting device for transmitting data to one or more receiving devices via a sidelink interface, wherein the transmission of data includes a first data transmission and one or more data retransmissions following the first data transmission, the transmitting device comprising: Processor, which: A resource sensing process is performed to select radio resources that can be used by the transmitting device to transmit data at a later time. Based on the results of the resource sensing process during the sensing window, autonomous radio resource allocation is performed to select time-frequency radio resources within the transmission window to be used for performing the first data transmission. A data transmission timing pattern is determined among multiple data transmission timing patterns, each data transmission timing pattern indicating the transmission timing for performing one or more data transmissions; and The sending unit: The first data transmission is performed using the selected time-frequency radio resources. The retransmission timing for performing the one or more data retransmissions is determined based on the transmission timing indicated by the determined data transmission timing pattern and the time interval between the first data transmission and the one or more data retransmissions. The one or more data retransmissions are performed according to the retransmission timing. The time interval is configurable, independent of the determined data transmission timing pattern, and is known to the one or more receiving devices. The one or more data retransmissions are performed within a time span defined by the length of the determined data transmission timing pattern.

2. The transmitting device according to claim 1, wherein the plurality of data transmission timing patterns indicate different numbers of data transmissions, and the processor determines a data transmission timing pattern from the data transmission timing patterns corresponding to the total number of transmissions to be performed on the data, wherein, The total number of data transfers to be performed is determined by the processor or pre-configured. The data transmission timing pattern is determined by the processor randomly or based on information acquired by the resource sensing process during the sensing window.

3. The transmitting device according to claim 1 or 2, wherein the transmitting unit transmits a scheduling assignment, the scheduling assignment indicating a selected time-frequency radio resource for the first data transmission, and identifying a determined data transmission timing pattern.

4. The transmitting device of claim 1, wherein the determined data transmission timing pattern indicates only one data transmission, wherein the processor determines a data retransmission candidate for performing the one or more data retransmissions within the transmission window by repeatedly reproducing the determined data transmission timing pattern relative to the timing of the first data transmission within the transmission window and subsequently by identifying a timing position given by the indicated single data transmission in each repeated data transmission timing pattern, and in, The processor determines which data retransmission candidates will be used to perform the one or more data retransmissions based on the total number of data transmissions to be performed on the data. The total number of data transmissions is determined by the processor or pre-configured. The processor determines the data retransmission candidates to be used for the data retransmission based on information acquired by the resource sensing process during the sensing window.

5. The transmitting apparatus of claim 3, wherein the one or more data retransmissions are performed using the same frequency radio resources as those used for the first data transmission or using frequency radio resources determined by the processor from the frequency radio resources used for the first data transmission based on a frequency hopping mode. in, The processor determines, based on information acquired by the resource sensing process during the sensing window, whether the one or more data retransmissions use the same frequency radio resources as the first data transmission or use frequency radio resources following the frequency hopping pattern. The scheduling assignment further instructs the transmitting device whether to use frequency hopping mode to determine the frequency radio resources used for transmitting the one or more data retransmissions.

6. The transmitting device of claim 1, wherein the determined data transmission timing pattern indicates only one transmission, wherein the processor, after the first data transmission timing, determines a preferred transmission timing for one of the one or more data retransmissions based on information acquired by the resource sensing process during the sensing window, and wherein the processor determines the data transmission timing pattern such that when the data transmission timing pattern is repeated multiple times within the transmission window relative to the timing of the first data transmission, the data transmission indicated by the data transmission timing pattern is consistent with the determined preferred transmission timing. This involves defining data retransmission candidates for performing one or more data retransmissions within the transmission window by repeating the data transmission timing pattern and subsequently identifying the timing position given by the indicated data transmission in each repeated data transmission timing pattern. The processor determines which data retransmission candidates will be used to perform the remaining data retransmissions, based on the information acquired by the resource sensing process during the sensing window and depending on the total number of data transmissions to be performed, which is determined by the processor or pre-configured. in, The transmitting unit transmits a data retransmission once at the determined preferred transmission timing, and transmits the remaining data retransmissions at the determined retransmission candidate.

7. The transmitting apparatus of claim 6, wherein the scheduling assignment instruction transmitted by the transmitting unit is for frequency radio resources used for retransmitting the data in a preferred transmission timing, as an offset relative to the frequency radio resources used for the first data transmission, and in, The remaining data retransmissions are performed using the same frequency radio resources used for the first data transmission or the same frequency radio resources used for the data retransmissions in the preferred transmission timing, or wherein the remaining data retransmissions are performed using frequency radio resources determined by the processor based on a frequency hopping mode from the frequency radio resources used for the first data transmission or from the frequency radio resources used for the data retransmissions in the preferred transmission timing, and wherein the scheduling assignment further instructs the transmitting device whether to use a frequency hopping mode to determine the frequency radio resources used for transmitting the one or more data retransmissions.

8. The transmitting apparatus according to any one of claims 4 to 7, wherein the transmitting unit transmits a scheduling assignment, the scheduling assignment indicating selected time-frequency radio resources for the first data transmission, and identifying a determined data transmission timing pattern. in, The scheduling assignment further indicates which of the plurality of repeated data transmission timing patterns defines the retransmission timing for performing the one or more data retransmissions, wherein the data transmission timing pattern indication is encoded as a bitmap, wherein the bits of the bitmap are associated with one of the plurality of repeated data transmission timing patterns.

9. The transmitting apparatus according to any one of claims 1 to 2 and 4 to 7, wherein the data resource pool includes a plurality of time-frequency radio resources available for the transmitting apparatus to perform data transmission, the data resource pool being divided into time-frequency radio resources available for performing a first data transmission and into time-frequency radio resources available for performing data retransmission, and... in, During the autonomous radio resource allocation, the processor selects a time-frequency radio resource from the available time-frequency radio resources for performing the first data transmission. In this context, the multiple time-frequency radio resources of the data resource pool are divided in the time domain between time-frequency radio resources used for the first data transmission and time-frequency radio resources used for data retransmission. The division of the data resource pool is pre-configured or configured by the radio base station controlling the transmitting device.

10. A method for a transmitting device, the transmitting device being configured to transmit data to one or more receiving devices via a sidelink interface, wherein the transmission of the data includes a first data transmission and one or more data retransmissions following the first data transmission, the method comprising the following steps performed by the transmitting device: A resource sensing process is performed to select radio resources that can be used by the transmitting device to transmit data at a later time. Based on the results of the resource sensing process during the sensing window, autonomous radio resource allocation is performed to select the time-frequency radio resources within the transmission window to be used for performing the first data transmission. A data transmission timing pattern is determined among multiple data transmission timing patterns, each indicating the transmission timing for performing one or more data transmissions. The first data transmission is performed using the selected time-frequency radio resources. The retransmission timing for performing the one or more data retransmissions is determined based on the transmission timing indicated by the determined data transmission timing pattern and the time interval between the first data transmission and the one or more data retransmissions. The one or more data retransmissions are performed according to the retransmission timing. in, The time interval is configurable, independent of the determined data transmission timing pattern, and is known to the one or more receiving devices. The one or more data retransmissions are performed within a time span defined by the length of the determined data transmission timing pattern.

11. The method according to claim 10, wherein, The plurality of data transmission timing patterns indicate different numbers of data transmissions, and the method includes determining a data transmission timing pattern from among the data transmission timing patterns corresponding to the total number of transmissions to be performed on the data, wherein the total number of transmissions to be performed on the data is determined by the transmitting device or pre-configured. The data transmission timing pattern is determined by the transmitting device randomly or based on information acquired by the resource sensing process during the sensing window.

12. The method according to claim 10, wherein, The determined data transmission timing pattern indicates only one data transmission, and the method includes the following steps: Data retransmission candidates for performing the one or more data retransmissions are determined by repeatedly defining a data transmission timing pattern relative to the timing of the first data transmission within the transmission window, and subsequently by identifying the timing position given by an indicated data transmission within each repeated data transmission timing pattern. The candidate data retransmissions for the one or more data retransmissions will be determined based on the total number of data transmissions to be performed on the data. This total number of data transmissions is determined by the sending device or pre-configured. The method includes the following steps: determining the data retransmission candidates to be used for the data retransmission based on information acquired by the resource sensing process during the sensing window.

13. The method according to claim 10, wherein, The determined data transmission timing pattern indicates only one transmission, wherein the method includes the following steps: Following the first data transmission timing, a preferred transmission timing is determined for one of the one or more data retransmissions based on information acquired by the resource sensing process during the sensing window. The data transmission timing pattern is determined such that when the data transmission timing pattern is repeated multiple times within the transmission window relative to the timing of the first data transmission, the data transmission indicated by the data transmission timing pattern is consistent with the determined preferred transmission timing. This involves defining data retransmission candidates within the transmission window for performing one or more data retransmissions by repeating the data transmission timing pattern and subsequently identifying the timing position given by the indicated data transmission in each repeated data transmission timing pattern. Determining which data retransmission candidates will be used to perform the remaining data retransmissions is based on the information acquired by the resource sensing process during the sensing window and depends on the total number of data transmissions to be performed, which is determined by the transmitting device or pre-configured. A data retransmission is transmitted once in the determined preferred transmission timing, and the remaining data retransmissions are transmitted at the determined retransmission candidate.

14. The method according to any one of claims 12 to 13, further comprising the step of: A scheduling assignment is sent, indicating the selected time-frequency radio resources for the first data transmission and identifying the determined data transmission timing pattern. The scheduling assignment further indicates which of the plurality of repeated data transmission timing patterns defines the retransmission timing for performing the one or more data retransmissions, wherein the data transmission timing pattern indication is encoded as a bitmap, wherein the bits of the bitmap are associated with one of the plurality of repeated data transmission timing patterns.

15. The method according to any one of claims 10 to 13, wherein, The data resource pool includes multiple time-frequency radio resources that can be used by the transmitting device to perform data transmission. The data resource pool is divided into time-frequency radio resources that can be used to perform a first data transmission, and into time-frequency radio resources that can be used to perform data retransmission. The method includes the following steps: during the autonomous radio resource allocation, selecting time-frequency radio resources for performing the first data transmission among the time-frequency radio resources available for performing the first data transmission. In this context, the multiple time-frequency radio resources of the data resource pool are divided in the time domain between time-frequency radio resources used for the first data transmission and time-frequency radio resources used for data retransmission. The division of the data resource pool is pre-configured or configured by the radio base station controlling the transmitting device.

16. An integrated circuit that controls processing of a transmitting device for transmitting data to one or more receiving devices via a sidelink interface, wherein the data transmission includes a first data transmission and one or more data retransmissions following the first data transmission, the processing including: A resource sensing process is performed to select radio resources that can be used by the transmitting device to transmit data at a later time. Autonomous radio resource allocation is performed based on the results of the resource sensing process during the sensing window to select time-frequency radio resources within the transmission window to be used for performing the first data transmission. A data transmission timing pattern is determined among multiple data transmission timing patterns, each indicating the transmission timing for performing one or more data transmissions. The first data transmission is performed using the selected time-frequency radio resources. The retransmission timing for performing the one or more data retransmissions is determined based on the transmission timing indicated by the determined data transmission timing pattern and the time interval between the first data transmission and the one or more data retransmissions. The one or more data retransmissions are performed according to the retransmission timing. The time interval is configurable, independent of the determined data transmission timing pattern, and is known to the one or more receiving devices. The one or more data retransmissions are performed within a time span defined by the length of the determined data transmission timing pattern.

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