JP7432553B2 - System, wireless terminal device, vehicle, base station, method, and program for HARQ retransmission control in data transmission via direct communication between terminals - Google Patents

Description

The present invention relates to HARQ retransmission control in data transmission via direct communication between a plurality of wireless terminal devices that can communicate via a base station of a mobile communication network.

Conventionally, communication between short-distance devices (D2D: Device-to- A communication method is known in which direct wireless communication is performed using a device. In particular, V2X using cellular communication technology for mobile communication systems is also called "cellular V2X."

In the 3GPP (3rd Generation Partnership Project) LTE (Long Term Evolution) and Next Generation (NR) specifications, communication between short-range devices such as V2V, V2I, V2P, and V2X is possible without going through a mobile communication network (core network). Standard specifications for a Sidelink communication method for direct wireless communication using an interface called PC5 have been established in D2D (for example, see Non-Patent Documents 1, 2, 3, and 4).

The radio resource allocation control modes in the Sidelink communication system include a mode SL Mode-1 (hereinafter referred to as "first mode") in which the base station allocates Sidelink radio resources, and a mode in which the wireless terminal device itself allocates Sidelink radio resources. SL Mode-2 (hereinafter also referred to as "second mode") is known (see, for example, Patent Document 1 and Non-Patent Document 1). In addition, in order to improve the reliability of user data transmission (hereinafter referred to as "SL transmission") using the Sidelink communication method, SL HARQ (Hybrid Automatic Repeat Request), which is fed back from the receiving terminal through PSFCH (Physical Sidelink Feedback Channel), is used. HARQ retransmission control based on ACK/NACK is known (Patent Document 2, Non-Patent Document 5).

European Patent No. 3136811 US Patent Application Publication No. 2020/0314959

Pavel Mach, Zdenek Becavar, and Tomas Vanek, "In-Band Device-to-Device Communication in OFDMA Cellular Networks: A Survey and Challenges," IEEE Communication Surveys & Tutorials, vol.17, no.4, pp.1885-1922 , June 2015. 3GPP TR22.886 V16.2.0, "Study on enhancement of 3GPP support for 5G V2X services (Release 16)," Dec. 2018. 3GPP TR37.985 V16.0.0, "Overall description of Radio Access Network (RAN) aspects for Vehicle-to-everything (V2X) based on LTE and NR (Release 16)," June 2020. 3GPP TR38.885 V16.0.0, "Study on NR Vehicle-to-Everything (V2X) (Release 16)," March 2019. Shao-Yu Lien, Der-Jiunn Deng, Chun-Cheng Lin, Hua-Lung Tsai, Tao Chen, Chao Guo, And Shin-Ming Cheng, "3GPP NR Sidelink Transmissions Toward 5G V2X," IEEE Access, vol.8, pp .35368-35382, February 2020 (DOI: 10.1109/ACCESS.2020.2973706).

In the first mode in which the base station allocates Sidelink radio resources, dynamic radio resources for SL transmission are first allocated for SL transmission via the uplink control channel PUCCH, etc., regardless of initial transmission and HARQ retransmission. The base station requests a radio resource allocation request (SR: Scheduling Request) for This is ensured by notifying the terminal side.

However, in the first mode operation, not only in the initial transmission but also in HARQ retransmission, the L1 Since L2 signaling is performed, there is a problem that the HARQ retransmission delay during the first mode operation increases.

A base station according to a first aspect of the present invention has a function of communicating with a plurality of wireless terminal devices that perform direct terminal-to-terminal communication, and is a mobile communication network capable of controlling radio resources used for the direct terminal-to-terminal communication. It is a base station. The base station includes means for monitoring a feedback channel from a receiving wireless terminal device to a transmitting wireless terminal device in data transmission via the terminal-to-terminal direct communication, and decoding the feedback channel; means for notifying the transmitting wireless terminal device of a permission message including information on radio resources for HARQ retransmission when the decoding result of the communication channel includes a HARQ negative response from the receiving wireless terminal device; Equipped with.

The wireless terminal device according to the first aspect is a wireless terminal device that has a function of performing communication via a base station of a mobile communication network and a function of performing direct terminal-to-terminal communication with nearby wireless terminal devices. When this wireless terminal device performs data transmission to the peripheral wireless terminal device via the terminal-to-terminal direct communication, the wireless terminal device transmits data from the base station without receiving an HARQ negative response from the peripheral wireless terminal device. means for receiving a grant message including information on radio resources for HARQ retransmission; and means for performing HARQ retransmission of the data transmission to the wireless terminal device.

A system according to a first aspect includes the base station according to the first aspect and the wireless terminal device.

The method according to the first aspect is a method of performing HARQ retransmission control in data transmission via direct communication between terminals. This method includes monitoring a feedback channel from a receiving wireless terminal device to a transmitting wireless terminal device in data transmission via the terminal-to-terminal direct communication, decoding the feedback channel, and decoding the feedback channel. when the channel decoding result includes a HARQ negative response from the receiving side wireless terminal device, notifying the transmitting side wireless terminal device of a permission message including information on radio resources for HARQ retransmission; include.

A program in a base station according to the first aspect is a base station of a mobile communication network that has a function of communicating with a plurality of wireless terminal devices that perform direct communication between terminals and is capable of controlling radio resources used for direct communication between the terminals. It is a program executed on a computer or processor provided at the station. This program includes a program code for monitoring a feedback channel from a receiving wireless terminal device to a transmitting wireless terminal device in data transmission via the terminal-to-terminal direct communication, and decoding the feedback channel; When the decoding result of the feedback channel includes a HARQ negative response from the receiving side wireless terminal device, for notifying the transmitting side wireless terminal device of a permission message including information on radio resources for HARQ retransmission. and program code.

The program in the wireless terminal device according to the first aspect is a computer or a processor included in the wireless terminal device that has a function of communicating via a base station of a mobile communication network and a function of directly communicating between terminals with peripheral wireless terminal devices. This is a program executed in . This program enables HARQ retransmission from the base station without receiving an HARQ negative response from the peripheral wireless terminal device when data is transmitted to the peripheral wireless terminal device via the terminal-to-terminal direct communication. a program code for receiving a grant message containing information of radio resources for a wireless terminal; and a program code for performing HARQ retransmission of the data transmission to the wireless terminal device.

A base station according to a second aspect of the present invention has a function of communicating with a plurality of wireless terminal devices that perform direct communication between terminals, and is a base of a mobile communication network that can control radio resources used for the direct communication between terminals. It is a station. The base station includes means for receiving a feedback message including an HARQ negative response and a radio resource allocation request from a wireless terminal device on the receiving side of data transmission via the terminal-to-terminal direct communication; and means for transmitting a permission message including a HARQ negative response and information on radio resources for HARQ retransmission to a wireless terminal device on the receiving side of the data transmission.

The first wireless terminal device according to the second aspect is a wireless terminal device that has a function of performing communication via a base station of a mobile communication network and a function of performing direct terminal-to-terminal communication with peripheral wireless terminal devices. The wireless terminal device includes means for receiving data transmission from the peripheral wireless terminal device via the terminal-to-terminal direct communication, and transmitting a feedback message including a HARQ negative response and a wireless resource allocation request to the base station in response to the data transmission. and a means to do so.

The second wireless terminal device according to the second aspect is a wireless terminal device that has a function of performing communication via a base station of a mobile communication network and a function of performing direct terminal-to-terminal communication with peripheral wireless terminal devices. When this wireless terminal device performs data transmission to the peripheral wireless terminal device via the terminal-to-terminal direct communication, the wireless terminal device transmits data from the base station without receiving an HARQ negative response from the peripheral wireless terminal device. means for receiving a grant message including a HARQ negative response and information on radio resources for HARQ retransmission; and in response to the grant message received from the base station without receiving a HARQ negative response from the surrounding wireless terminal device. and means for performing HARQ retransmission of the data transmission to the surrounding wireless terminal devices.

A system according to a second aspect includes the base station, the first wireless terminal device, and the second wireless terminal device according to the second aspect.

The method according to the second aspect is a method of performing HARQ retransmission control in data transmission via direct communication between terminals. This method includes receiving a feedback message including an HARQ negative response and a radio resource allocation request from a wireless terminal device on the receiving side of data transmission via the terminal-to-terminal direct communication; transmitting a grant message including a negative response and information on radio resources for HARQ retransmission to a wireless terminal device on the receiving side of the data transmission.

A program in a base station according to a second aspect is a base station of a mobile communication network that has a function of communicating with a plurality of wireless terminal devices that perform direct communication between terminals and is capable of controlling radio resources used for direct communication between the terminals. It is a program executed on a computer or processor provided in a station. This program includes a program code for receiving a feedback message including an HARQ negative response and a radio resource allocation request from a wireless terminal device on the receiving side of data transmission via the terminal-to-terminal direct communication, and a program code for receiving a feedback message including a HARQ negative response and a radio resource allocation request, and , program code for transmitting a grant message including the HARQ negative response and information on radio resources for HARQ retransmission to a wireless terminal device on the receiving side of the data transmission.

The program in the first wireless terminal device according to the second aspect is a wireless terminal device having a function of performing communication via a base station of a mobile communication network and a function of performing direct terminal-to-terminal communication with peripheral wireless terminal devices. It is a program executed on a computer or processor provided with the computer or processor. This program sends a feedback message to the base station including a program code for receiving data transmission from the peripheral wireless terminal device via the terminal-to-terminal direct communication, and a HARQ negative response to the data transmission and a wireless resource allocation request. and a program code for sending to.

The program in the second wireless terminal device according to the second aspect is adapted to a wireless terminal device having a function of communicating via a base station of a mobile communication network and a function of directly communicating between terminals with peripheral wireless terminal devices. It is a program executed on a computer or processor provided with the computer or processor. This program is configured such that when data is transmitted to the peripheral wireless terminal device via the terminal-to-terminal direct communication, the HARQ negative response is sent from the base station without receiving an HARQ negative response from the peripheral wireless terminal device. A program code for receiving a grant message including a response and information on radio resources for HARQ retransmission; and a program code for receiving a grant message from the base station without receiving a HARQ negative response from the peripheral wireless terminal device. Accordingly, a program code for performing HARQ retransmission of the data transmission to the peripheral wireless terminal device is included.

A vehicle according to another aspect of the present invention is a vehicle that travels on a travel route. This vehicle is equipped with any of the wireless terminal devices described above.

According to the present invention, it is possible to reduce HARQ retransmission delay during operation of an allocation control mode in which a base station allocates radio resources for direct communication between terminals.

1 is a schematic configuration diagram showing an example of the overall configuration of a communication system according to an embodiment. FIG. 2 is an explanatory diagram showing an example of a radio frame of downlink (DL) and uplink (UL) of Uu communication and sidelink communication (SL) in the communication system according to the embodiment. FIG. 7 is an explanatory diagram showing other examples of radio frames for downlink (DL) and uplink (UL) of Uu communication and sidelink communication (SL) in the communication system according to the embodiment. FIG. 7 is an explanatory diagram showing still another example of radio frames for downlink (DL) and uplink (UL) of Uu communication and sidelink communication (SL) in the communication system according to the embodiment. (a) and (b) are explanatory diagrams showing an example of a configuration example of radio resources (RE) of a time slot 431 at the time of initial transmission and at the time of HARQ retransmission of SL data transmission according to the reference example, respectively. FIG. 7 is a sequence diagram showing an example of initial transmission and HARQ retransmission of SL data transmission during SL Mode-1 operation according to a reference example. FIG. 2 is a sequence diagram showing an example of initial transmission of SL data transmission and HARQ retransmission during SL Mode-1 operation in the communication system according to the embodiment. FIG. 8 is an explanatory diagram showing an example of a radio frame of downlink (DL) and uplink (UL) of Uu communication and sidelink communication (SL) in the data transmission of FIG. 7; FIG. 7 is a sequence diagram showing another example of initial transmission of SL data transmission and HARQ retransmission during SL Mode-1 operation in the communication system according to the embodiment.

Embodiments of the present invention will be described below with reference to the drawings.
The system according to the embodiment described in this document uses SL Mode in which a base station of a mobile communication network allocates radio resources when a plurality of wireless terminal devices mounted on a plurality of vehicles perform direct inter-terminal communication using the Sidelink communication method. This is a system that can reduce HARQ ( Hybrid Automatic Repeat Request) retransmission delay during -1 (first mode) operation.

Here, this book is based on the assumption that it will be applied to LTE (Long Term Evolution)/LTE-Advanced mobile communication systems (hereinafter referred to as "LTE systems") and fifth generation mobile communication systems (hereinafter referred to as "5G systems"). Although embodiments of the invention will be described, the concept of the invention is applicable to any system that uses similar cell configurations and physical channel configurations. In addition, the reference signal sequence used for propagation path estimation and the encoding method used for error correction are not limited to those defined in the LTE system or 5G system, but may be any suitable for these applications. , it doesn't matter what type it is. Embodiments of the present invention may be applied to next-generation mobile communication systems (also referred to as "NR systems") after the fifth generation.

FIG. 1 is a schematic configuration diagram showing an example of the overall configuration of a communication system according to an embodiment of the present invention. In FIG. 1, the communication system according to the present embodiment is an example of a 5G system, and includes a base station 10 with a two-cell configuration connected to a core network (for example, EPC, 5GC, or NGC) 15 of a mobile communication network. Be prepared. Note that although the example in FIG. 1 shows an example including one base station 10, the number of base stations may be plural. Further, the cell formed by the base station 10 may be a single cell or may be three or more cells.

The core network 15 is, for example, an IP (Internet Protocol)-based EPC (Evolved Packet Core) defined by 3GPP (3rd Generation Partnership Project). The core network 15 may be a core network dedicated to the 5G system, or a core network used for both the 5G system and the LTE system. The core network device (EPC device or 5GC device) is a logical node SCEF (Service Capability Exposure Function), NEF (Network Exposure Function), UPF (User Plane Function) that processes user data, and the like. The core network device (EPC device or 5GC device) may be a VAE (V2X Application Enabler) that enables coordination of multiple V2X (Vehicle-to-Everything) services. Note that the base station 10 may have some of the functions of the core network device (for example, the functions of the UPF or the functions of a logical node other than the UPF) as in this embodiment.

The base station 10 is, for example, a gNodeB (gNB) or en-gNodeB (en-gNB) of a 5G system, and communicates with communication terminals located in a cell, which is a wireless communication area formed by the base station, via antennas 101 and 102. It is possible to wirelessly communicate with a device (also referred to as a "terminal", "user terminal", "user equipment", "UE", "mobile station", "mobile device", etc., hereinafter referred to as "UE") 20.

The base station 10 includes, for example, a base station device 100 provided inside a building or the like, and a plurality of antennas 101 and 102 corresponding to two cells forming a cell formed by the base station 10. Each of the plurality of antennas 101 and 102 is provided at the top of a building, pillar, steel tower, or the like. The antennas 101 and 102 may be omnidirectional antennas, or may be antennas consisting of a plurality of antenna elements capable of forming one or more beams in a predetermined direction (for example, antennas consisting of a plurality of antenna elements arranged two-dimensionally or three-dimensionally). It may also be a Massive MIMO antenna (Massive MIMO antenna) consisting of an array antenna arranged in an array. Note that although the illustrated example includes two antennas 101 and 102, the number of antennas may be singular or three or more.

The base station device 100 includes, for example, a DU (distribution unit) 110, a CU (aggregation unit) 120, a CNE (core network device) 130, and an MEC (Multi-access Edge Computing) device 140. Note that in the illustrated example, the CNE 130 is a 5G core, but in a Non-Stand Alone (NSA) configuration in which 5G layer 3 (L3) control is performed using LTE, it may be an EPC. Further, the MEC device 140 may be provided at a node between the base station 10 and the core network 15, or may be provided outside the core network.

The DU 110 includes, for example, an RFU (radio unit) 111 and an RFU 112. The RFU 111 and the RFU 112 include, for example, an amplification section, a frequency conversion section, a transmission/reception switching section (DUP), an orthogonal modulation/demodulation section, and the like. The DU 110 may have some functions of a BBU (baseband unit) described below. Note that in the illustrated example, two cells are configured per base station, so two RFUs 111 and 112 are provided, but the number of RFUs may be single or may be three or more.

The CU 120 includes, for example, a BBU (baseband unit) 121 and a CU controller 122 that controls each part of the CU 120. The BBU 121 converts (modulates and demodulates) control information and user data (IP packets) to be transmitted and received, and baseband signals such as OFDM signals that are transmitted and received via a wireless transmission path, for example. As the modulation method, for example, QPSK, 16QAM, 64QAM, etc. can be used. Baseband signals are sent to and received from the DU 110. The CU controller 122 is composed of, for example, a CPU and a memory, and controls each part of the CU 120 by executing a program installed in advance.

CU 120 may be connected to multiple DUs. Further, the CU 120 may be connected to a DU of a remotely installed slave station via a high-speed communication line such as an optical communication line using an optical fiber. Alternatively, a plurality of BBUs 121 may be provided in the CU 120 and connected to each RFU. For example, the BBU 121 is configured with a plurality of BBU#1 and BBU#2, a plurality of external connection sections 121a are provided connected to each BBU#1 and BBU#2, and an optical communication line is connected to the plurality of external connection sections 121a. A plurality of remotely located external RFU#1 and RFU#2 may be configured to be remotely connected via a high-speed communication line such as.

The CNE 130 has the above-described UPF function and communicates with various nodes on the core network 15 using a predetermined communication interface and protocol. The CNE 130 relays various data such as user data between the core network 15 and CU 120, and relays various data such as user data between the core network 15 and CU 120 and the MEC device 140.

The MEC device 140 is composed of, for example, a CPU and a memory, and transmits and receives data to and from the UE 20 located in the cell of the base station 10 by executing a program installed in advance or a program downloaded via a communication network. It is possible to process various types of data sent to the base station 10, and to execute various types of control over the UE 20 located in the cell of the base station 10. Furthermore, by executing a predetermined program, the MEC device 140 can also function as various means for selecting and controlling a radio resource allocation control mode, which will be described later.

Note that the selection control of the radio resource allocation control mode, which will be described later, may be performed by the above-mentioned CU 120 instead of the MEC device 140. For example, by executing a predetermined program, the CU controller of the CU 120 may also function as various means for selecting and controlling a radio resource allocation control mode, which will be described later. Further, the CU 120 and the MEC device 140 may cooperate with each other to perform selection control of a radio resource allocation control mode, which will be described later.

The UEs 20(1) to 20(3) are vehicles (trucks in the illustrated example) 30(1) to 30(3) that move on a road 90 as a travel route located in a cell formed by the base station 10. It is installed in. Vehicles 30(1) to 30(3) equipped with UEs 20(1) to 20(3) form preset groups, cooperate with each other, form a vehicle group, and move.

In addition, the illustrated example shows a case where three UEs 20 (1) to 20 (3) mounted on three vehicles 30 (1) to 30 (3) are located in the cell of the base station 10. However, a plurality of UEs 20 mounted on two or four or more vehicles 30 may be in the area. In addition, the illustrated example shows a case where three vehicles 30(1) to (3) form a group of vehicles in a platoon (in the front and rear directions of each other) and travel in a group, that is, in a platoon. However, the relative positional relationship between the vehicles 30 is not limited as long as the UEs 20 mounted on the plurality of vehicles 30 are in a positional relationship that allows direct communication with each other. Furthermore, the vehicle 30 may be a moving object such as a car, truck, bus, or motorcycle that moves on a road 90 that is a moving route on the ground, or a moving body that can move by flying on a moving route in space such as the sky. It may be a body, or it may be a moving body that can move along a movement route underground, on water (for example, on the sea), underwater (for example, under the sea), or the like.

In addition, in the following explanation, when describing a configuration, function, etc. that is common to multiple UEs 20(1) to 20(3), it will be written as UE20 etc. without parentheses, and if multiple vehicles 30(1) to 30 When describing the configuration, functions, etc. common to (3), the term vehicle 30 etc. will be written without parentheses. In direct communication between terminals, the UE that is the source of data is also referred to as the transmitter UE 20T, and the UE that is the destination of the data is also referred to as the receiver UE 20R.

The UE 20 of the vehicle 30 connects to the base station 10 of the mobile communication network (cellular network) using a base station-mediated communication method (for example, a next-generation NR method such as 3G, LTE, or 5G), which is a first communication method. (hereinafter, communication using the base station communication method is also referred to as "Uu communication"). 5G Uu communication uses URLLC (Ultra Reliable & Low Latency Communication) for ultra-reliable and low-latency communication, eMBB (Enhanced Mobile Broadband) for high-speed and large-capacity communication, and simultaneous connection of a large number of low-cost and low-power consumption terminals. Communication types such as mMTC (Massive Machine Type Communication) can be used. In particular, ultra-high Reliable, low-latency communication URLLC is suitable.

For example, in the following vehicle self-driving truck platoon driving in Figure 1, the first vehicle (hereinafter also referred to as "leader vehicle") 30 (1) is manually operated by a manned driver, and the following vehicle (hereinafter also referred to as "member vehicle") .) 30(2) and 30(3) are unmanned automatic driving. In the following vehicle self-driving truck platooning, remote operation between the vehicles 30(1) to 30(3) and the UEs 20(1) to 20(3) on the network side via the base station 10 and the core network 15 of the mobile communication network. Performs Uu communication with the monitoring center. For example, the remote operation monitoring center can receive monitoring monitor images (still images, videos) and sensor information of each vehicle 30(1) to 30(3) through uplink Uu communication. Furthermore, the remote operation monitoring center can transmit control signals such as emergency stop signals to each of the vehicles 30(1) to 30(3) through downlink Uu communication. UU communication between this vehicle and the remote operation monitoring center on the network side enables centralized remote management and remote operation of multiple vehicles 30(1) to 30(3), reducing the burden on drivers and improving safety. Can be done.

The UE 20 includes, for example, an antenna 21, a transmission/reception switching unit (DUP), a reception unit, a CP removal unit, an FFT unit, a signal separation unit, a propagation path compensation unit, a demodulation unit, a decoding unit, a DMRS propagation path (channel) estimation unit, and a signal It includes a multiplexing section, an IFFT section, a CP insertion section, a transmitting section, and a control section. The antenna 21 can be used for both Uu communication and Sidelink communication. The DMRS propagation path (channel) estimation unit estimates a radio propagation path (equivalent propagation path) based on the reception result of a known demodulation reference signal (DMRS) transmitted from the base station 10, for example. The demodulator demodulates and decodes the data signal included in the transmission signal based on the estimation result of the radio propagation path (equivalent propagation path). Since the constituent parts of the other parts have the same functions as conventional ones, their explanations will be omitted.

In addition, the UE 20 of the vehicle 30 performs wireless communication with other vehicles (hereinafter also referred to as "direct communication between terminals") with each vehicle using a second communication method that does not go through a base station of a mobile communication network (cellular network). This can be done through direct communication between terminals installed on the device. The wireless links between terminals in direct communication between terminals are the downlink (DL), which is a radio link from the base station side to the terminal side in communication via a base station, and the uplink, which is a radio link from the terminal side to the base station side. (UL), it is also called a side link (Sidelink). The second communication method is, for example, a Sidelink communication method using a wireless interface between terminals called PC5. The PC5 interface is a D2D (Device to Device) interface that allows direct communication between UEs, between UEs and other devices (e.g. vehicles), between vehicles, or between vehicles and other devices without going through a base station. Yes, it has been standardized in 3GPP Release 12 and later for LTE and in Release 16 and later for 5G.

Autonomous truck platooning (see Figure 1), autonomous driving/platooning BRT (Bus Rapid Transit), or on track tracks, which electronically connects multiple vehicles running on the road through terminal-to-terminal communication. The Sidelink communication method, in which the terminals installed on each vehicle directly communicate with each other, is used for transmitting control messages between each vehicle in electronic connection between railway vehicles, and for transmitting surrounding monitoring video from the following vehicle to the leading vehicle. Suitable.

For example, in the following vehicle self-driving truck platoon driving in Figure 1, vehicle control messages (e.g. speed, acceleration, Control information such as inter-vehicle distance and steering), monitoring monitor images (still images and videos) and sensor information can be transmitted. Sidelink (FL) in the figure is vehicle-to-vehicle communication from the preceding vehicle to the following vehicle, and Sidelink (BL) is vehicle-to-vehicle communication from the following vehicle to the preceding vehicle. By using this vehicle-to-vehicle communication (direct communication between terminals) to run in a platoon of self-driving trucks, it is possible to solve the driver shortage and improve the working environment. Furthermore, by applying 5G's ultra-low latency and highly reliable communication in vehicle-to-vehicle communication (direct communication between terminals), it is possible to shorten the distance between vehicles when driving in a platoon, improve fuel consumption efficiency by reducing air resistance in a group of vehicles, In addition, it is possible to reduce CO ₂ emissions and alleviate congestion by increasing road capacity.

In the Sidelink communication method, a single direct communication between terminals (hereinafter referred to as "single-hop communication") may be performed with the UE of the data transmission destination vehicle without going through the UE of another vehicle. Alternatively, multi-hop communication involving direct communication between multiple terminals via UEs of multiple other vehicles may be performed.

In the Sidelink communication method, a Layer-2 ID is a communication identifier (frame identifier) that identifies a frame (also called a "MAC packet") which is a data processing unit in the data link layer (Layer-2) of a layered communication model. is defined.

In the layered communication model in the UE 20, for example, from the lowest level to the highest level, layer 1 (L1) consisting of a physical layer, a MAC (media access control) layer, an RLC (radio link control) layer, and a PDCP (packet data convergence) layer. Layer 2 (L2), which processes data in units of frames, a network layer, which processes data in units of packets using various protocols (e.g., IP, Non-IP, ARP), and an application layer. . Data in the application layer is also called a "message".

For example, the UE 20 specifies a Destination L2ID (Dst.L2ID), which is a frame identifier as a communication identifier of a transmission destination (communication destination) in layer 2 (L2), using a part of uplink radio resources of mobile communication. data (message) in frames. The UE 20 of the receiving vehicle 30 determines whether the destination frame identifier (Dst.L2ID) included in the header of the received frame matches the frame identifier (L2ID) assigned to its own device. .

If the UE 20 of the vehicle 30 determines that the destination frame identifier (Dst.L2ID) included in the header of the received frame matches the frame identifier (L2ID) assigned to its own device, the UE 20 of the vehicle 30 transmits the received frame. By processing packets containing data (messages) in such a way that they are sent to an upper layer, the data can be used for applications. On the other hand, if the UE 20 of the vehicle 30 determines that the destination frame identifier (Dst.L2ID) included in the header of the received frame does not match the frame identifier (L2ID) assigned to its own device, the UE 20 receives the received frame. By processing packets containing frame data (messages) so that they are not sent to the upper layer, the data can be made unusable by applications.

In the example of FIG. 1, the UEs 20(1) to 20(3) of the plurality of vehicles 30(1) to 30(3) may be located in the same cell, or may be located in different cells. You can. In addition, the UEs 20(1) to 20(3) of the vehicles 30(1) to 30(3) selectively or simultaneously perform direct communication between terminals using the Sidelink communication method and Uu communication using the base station communication method. It may be.

FIG. 2 is an explanatory diagram showing an example of a radio frame of downlink (DL) and uplink (UL) of Uu communication and sidelink communication (SL) in the communication system according to the present embodiment. In FIG. 2, different frequency bands are used in the downlink of Uu communication (hereinafter referred to as "DL"), the uplink of Uu communication (hereinafter referred to as "UL"), and the sidelink communication (hereinafter referred to as "SL"). .

In FIG. 2, DL and UL radio frames 401 and 402 each have a predetermined subcarrier interval (15 kHz in the illustrated example) and a predetermined number (10 in the illustrated example) of time slots (“subframes”). ) has a predetermined time length (10 ms in the illustrated example).

The first time slot 401a in the DL radio frame 401 contains a block (SSB) consisting of a downlink SS (synchronization signal) and a PBCH (physical broadcast channel), and a PBCH_DMRS (PBCH demodulation reference block) for demodulating PBCH information. signal). The second and subsequent DL time slots 401b include a PDCCH (Physical Downlink Control Channel) for downlink control, a PDSCH (Physical Downlink Shared Channel) for data transmission, and a channel for demodulating PDCCH and PDSCH data. OFDM (orthogonal frequency division multiplexing) symbols used for each DMRS (data demodulation reference signal) can be assigned.

The first time slot 402a in the UL radio frame 402 is a special time slot that includes an uplink PRACH (Physical Random Access Channel). The UL second and subsequent time slots 402b include a PUCCH (Physical Uplink Control Channel) for uplink control, a PUSCH (Physical Uplink Shared Channel) for data transmission, and a channel for demodulating PUCCH and PUSCH data. OFDM symbols used for each DMRS (data demodulation reference signal) can be assigned. Note that in a time slot in which resources are allocated to the PUSCH, control information to be transmitted on the PUCCH may be multiplexed onto the PUSCH without using the PUCCH.

In FIG. 2, an SL radio frame 403 has a predetermined subcarrier interval (in the illustrated example, 60 kHz, which is wider than the DL/UL), and a predetermined number of subcarriers (40, which is larger than the DL/UL in the illustrated example). It has a predetermined time length (10 ms in the illustrated example) consisting of time slots.

The first time slot 403a in the SL radio frame 403 is used for Sidelink Primary Synchronization Signal (S-PSS) and Sidelink Secondary Synchronization Signal used for synchronizing Sidelink communication. SLSS (Sidelink synchronization signal) consisting of l (S-SSS) and PSBCH (physical Sidelink broadcast channel) and PSBCH_DMRS (PSBCH demodulation reference signal) for demodulating PSBCH information. SLSS, PSBCH, and PSBCH_DMRS are transmitted, for example, by any one of the plurality of UEs 20 (hereinafter also referred to as "leader UE" or "master UE") 20(1) outside the cell range of the base station 10. It can be used for sidelink communication synchronization processing and connection establishment processing performed with other UEs (hereinafter also referred to as "member UEs") 20(2) and 20(3).

Note that whether or not each UE is a leader UE may be specified from the mobile communication network side (for example, an MEC device), or may be specified by a storage medium built into the UE (for example, a SIM (Subscriber It may be determined based on information written in the Identity Module Card).

Other time slots 403b in the SL radio frame 403 include a PSCCH (Physical Sidelink Control Channel) for L1/L2 control of Sidelink communication, and a PSFCH (Physical Sidelink Feedback Channel) for data retransmission (HARQ-ACK/NACK feedback). , a PSSCH (Physical Sidelink Shared Channel) for data transmission, and an OFDM (Orthogonal Frequency Division Multiplexing) symbol to be used for each of the DMRS for demodulating the data of the PSCCH, PSFCH, and PSSCH. For example, within the range of the cell of the base station 10, the PSCCH is transmitted mainly by one of the plurality of UEs 20 (leader UE, master UE) 20(1) to other member UEs 20(2), 20(3). ) can be used for sidelink communication synchronization processing and connection establishment processing.

FIG. 3 is an explanatory diagram showing another example of radio frames for downlink (DL) and uplink (UL) of Uu communication and sidelink communication (SL) in the communication system according to the present embodiment. In the example of FIG. 3, DL and UL are operated using TDD (time division multiplexing) in the same frequency band, and SL is operated in an independent frequency band different from DL and UL.

In FIG. 3, a radio frame 411 shared by DL and UL has a predetermined subcarrier interval (15 kHz in the illustrated example) and a predetermined time length consisting of a predetermined number (20 in the illustrated example) of time slots. (10 ms in the illustrated example).

The first time slot 411a in the shared radio frame 411 is a special time slot that includes a block (SSB) consisting of a downlink SS and PBCH, and a PBCH_DMRS. OFDM symbols used for downlink PDCCH, PDSCH, and DMRS can be allocated to a plurality of time slots 411c marked with "D" in the figure. The two time slots 411b marked with "S" in the figure are special time slots that include uplink GP (guard period), PRACH, and SRS (sounding reference signal), respectively. 411d can allocate OFDM symbols used for uplink PUCCH, PUSCH, and DMRS to a plurality of time slots marked with "U" in the figure. Note that in a time slot in which resources are allocated to the PUSCH, control information to be transmitted on the PUCCH may be multiplexed onto the PUSCH without using the PUCCH.

In FIG. 3, an SL radio frame 412 has a predetermined subcarrier interval (60 kHz in the illustrated example) and a predetermined time length (in the illustrated example) consisting of a predetermined number (40 in the illustrated example) of time slots. 10ms).

The first time slot 412a in the SL radio frame 412 is a special time slot that includes the SLSS, PSBCH, and PSBCH_DMRS used for synchronizing Sidelink communication. The other time slots 412b can be assigned OFDM symbols used for the PSCCH, the PSFCH as a feedback channel, the PSSCH, and the DMRS.

FIG. 4 is an explanatory diagram showing still another example of radio frames for downlink (DL) and uplink (UL) of Uu communication and sidelink communication (SL) in the communication system according to the present embodiment. In the example of FIG. 4, DL, UL, and SL are operated using TDD (time division multiplexing) in the same frequency band.

In FIG. 4, a radio frame 421 shared by DL, UL, and SL has a predetermined subcarrier interval (60 kHz in the illustrated example) and a predetermined number of time slots (40 in the illustrated example). It has a time length (10 ms in the illustrated example). The first time slot 421a is a special time slot that includes an uplink PRACH, a downlink block (SSB) consisting of SS and PBCH, and PBCH_DMRS. The second time slot 421b from the beginning is a special time slot that includes SS and PBCH blocks used for synchronizing Sidelink communication.

The other multiple time slots of the shared radio frame 421 are a DL time slot 421c(1), a UL time slot 421c(2), and an SL time slot 421c(3) separated by a GP (guard period). and has. OFDM symbols used for downlink PDCCH and PDSCH can be allocated to DL time slot 421c(1). OFDM symbols used for uplink PUCCH and PUSCH can be allocated to the UL time slot 421c(2). Note that in a time slot in which resources are allocated to the PUSCH, control information to be transmitted on the PUCCH may be multiplexed onto the PUSCH without using the PUCCH. OFDM symbols used for PSCCH and PSSCH can be allocated to the SL time slot 421c(3).

Note that, as an example of other radio resources, a part of the UL resources, which are also standardized in LTE D2D, etc., may be used as the SL resources.

The UEs 20(1) to 20(3) of the vehicles 30(1) to 30(3) use an inter-terminal synchronization method that determines and sets the transmission/reception timing of radio frames when performing direct communication between terminals using the Sidelink communication method. For example, it is possible to select from the Uu synchronization method as the first synchronization method and the SLSS synchronization method as the second synchronization method. Further, as another synchronization method, a GNSS synchronization method may be used.

The Uu synchronization method includes Primary Synchronization Signal (PSS), Secondary Synchronization Signal (SSS), etc., which are periodically transmitted by the base station 10 of a mobile communication network (cellular network) for cell search on the terminal side and establishment of DL synchronization. This is a method that uses the common signal of 1 as a reference for synchronization between terminals. The SL synchronization method uses SLSS to achieve synchronization between terminals, and is used when other synchronization references cannot be used, such as inside a tunnel or in an area outside the coverage area of a base station. On the other hand, the GNSS synchronization method is a method in which a GNSS (Global Navigation Satellite System) receiver installed in the UE 20 as a current position acquisition means uses a time reference obtained by receiving radio waves from a GNSS satellite as a reference for synchronization between terminals. Yes, the time reference signal source is the GNSS receiver within the own device.

For example, the UE 20 of the vehicle 30 uses the Uu synchronization method to determine the transmission/reception timing of radio frames of the Sidelink communication method within the range of the cell of the base station 10, and uses the common signal from the base station when outside the cell of the base station 10. Since it is not possible to use other reference signal sources for synchronization such as SLSS synchronization, the transmission and reception timing of radio frames in the Sidelink communication method is determined using the SLSS synchronization method.

In the radio communication system having the above configuration, as a radio resource (time slot) allocation control mode in the Sidelink communication method illustrated in FIGS. , also referred to as "Mode-1" for short), and SL Mode-2 (hereinafter also referred to as "Mode-2" for short) as a second mode in which each UE 20 autonomously selects SL radio resources. be. These Mode-1 and Mode-2 can be selected and applied to each group (group) made up of UEs 20 of a plurality of vehicles 30. A group may be fixedly formed by a plurality of preset UEs, or may be formed ad hoc by a plurality of UEs located close to each other.

FIGS. 5A and 5B are explanatory diagrams illustrating an example of the configuration of radio resources (RE) of the time slot 431 at the time of initial transmission of SL data transmission and at the time of HARQ retransmission, respectively, according to the reference example. AGC (automatic gain control), PSCCH, PSSCH, DMRS, and Guard (guard period) are assigned to the beginning of the time slot 431 for SL data transmission. AGC is information for controlling the gain of the receiving amplifier so that the receiving amplifier of the receiving side UE does not become saturated. At the time of initial transmission of SL data transmission in FIG . During HARQ retransmission of SL data transmission in FIG. 5(b), HARQ retransmission includes a PSFCH for returning a HARQ response message (HARQ-ACK or HARQ-NACK), and Guard and AGC for the PSFCH. Since the radio resource group 431a for SL is inserted, radio resources that cannot be used for SL data transmission occur.

FIG. 6 is a sequence diagram illustrating an example of initial transmission of SL data transmission and HARQ retransmission during SL Mode-1 operation according to the reference example. In FIG. 6, the transmitting side UE 20T executes an RRC connection reconfiguration procedure (RRC Reconfiguration Procedure) with the base station 10, and performs negotiation for transmitting and receiving a scheduling request message in data transmission in SL Mode-1 (S101). ).

When the RRC connection reconfiguration with the base station 10 is completed, the transmitting side UE 20T transmits a scheduling request message requesting radio resource allocation for initial transmission of SL data transmission to the base station 10 on the PUCCH. (S102), When a grant message including information on the radio resource allocated to the initial transmission is received from the base station 10 on the PDCCH (S103), the initial transmission data is received using the PSSCH set for the radio resource. It is transmitted to the side UE 20R (S104).

When the receiving side UE 20R fails to receive the initial transmission data, the receiving side UE 20R uses the PSFCH set in a part of the radio resources allocated to the initial transmission of SL (for example, the radio resource group 431a in FIG. 5(b)) to perform HARQ- A HARQ retransmission request including a NACK (negative response) is returned to the transmitting side UE 20T (S105). The transmitting side UE 20T that has received the HARQ-NACK sends back a scheduling request message requesting radio resource allocation for SL HARQ retransmission to the base station 10 on the PUCCH (S106), and includes information on the allocated radio resource. When a grant message is received from the base station 10 on the PDCCH (S107), HARQ retransmission data is transmitted to the receiving side UE 20R using the PSSCH set for the radio resource (S108). When the receiving side UE 20R successfully receives the HARQ retransmission data, the receiving side UE 20R uses the PSFCH set in a part of the radio resources allocated for SL HARQ retransmission (for example, the radio resource group 431a in FIG. 5(b)) to perform HARQ-retransmission data. An ACK (acknowledgement) is returned to the transmitting side UE 20T (S109).

In the reference example of FIG. 6, when the receiving side UE 20R fails to receive the first transmission data of SL, a HARQ retransmission request including HARQ-NACK is received before the sending side UE 20T sends HARQ retransmission data to the receiving side UE 20R. (S105), feedback transmission of a scheduling request message (S106), and reception of a grant message (S107), which require intermediate signaling processing in three stages, increasing HARQ retransmission delay.

Therefore, in this embodiment, as shown below, when the receiving side UE 20R fails to receive the initial transmission data of SL, the intermediate signaling process until the sending side UE 20T transmits HARQ retransmission data to the receiving side UE 20R is performed as follows. By doing so in stages, HARQ retransmission delay is reduced.

FIG. 7 is a sequence diagram illustrating an example of initial transmission and HARQ retransmission of SL data transmission during SL Mode-1 operation in the communication system according to the embodiment. FIG. 8 is an explanatory diagram showing an example of a radio frame of downlink (DL) and uplink (UL) of Uu communication and sidelink communication (SL) in the data transmission of FIG. 7. Note that in FIG. 7, descriptions of processes common to those in FIG. 6 described above will be omitted.

In FIG. 7, when negotiating between the transmitting side UE 20T and the base station 10 for sending and receiving a scheduling request message in data transmission in SL Mode-1 (S201), the receiving side UE 20R and the base station 10 RRC connection reconfiguration is executed, and negotiation for transmission and reception of a scheduling request message is performed when direct feedback (FB) transmission of an HARQ retransmission request is performed from the receiving side UE 20R to the base station 10 (S202).

When the receiving side UE 20R fails to receive the initial transmission data, the receiving side UE 20R receives a portion of the UL/SL shared radio frame allocated to the initial transmission of SL (for example, the fifth slot 442c(2) of the radio frame 442 in FIG. 8). A HARQ retransmission request including a HARQ-NACK (negative acknowledgment) is returned to the transmitting side UE 20T using the PSFCH set in the SL required radio resource group 431a) (S206).

In addition, in the AGC (for PSFCH) section (see FIG. 8) that is transmitted from the receiving side UE 20R prior to the PSFCH of the HARQ retransmission request, the base station 10 receives the P SFCH without using Timing Advance and demodulation reference signal. In order to make this possible, predetermined signal sequences whose reception timing at the base station 10 can be detected (reception timing can be estimated) are multiplexed and transmitted. As this signal sequence, for example, a CAZAC (Constant Amplitude and Zero Auto-correlation Code) sequence such as a ZC (Zadoff-Chu) sequence, which is also used in RACH (Random Access CHannel), etc. is used. I can.

The base station 10 monitors the PSFCH in the UL/SL shared radio frame transmitted from the receiving side UE 20R and addressed to the sending side UE 20T. When the base station 10 decodes the PSFCH and confirms the HARQ retransmission request including HARQ-NACK (negative acknowledgment) (S207), the base station 10 sends the SL HARQ retransmission request without waiting for the scheduling request (SR) message from the transmitting side UE 20T. A grant message including information on the radio resources allocated to the UE 20T is transmitted to the transmitting side UE 20T on the PDCCH (S208).

The transmitting side UE 20T transmits HARQ retransmission data to the receiving side UE 20R using the PSSCH set in the allocated radio resource (S209). When the receiving side UE 20R successfully receives the HARQ retransmission data, it returns a HARQ-ACK (acknowledgement) to the transmitting side UE 20T using the PSFCH set as part of the radio resources allocated for SL HARQ retransmission ( S210).

According to the example of FIG. 7, when the receiving side UE 20R fails to receive the first transmission data of SL, the transmission from the receiving side UE 20R to the transmitting side UE 20T takes place before the sending side UE 20T sends HARQ retransmission data to the receiving side UE 20R . Since only two stages of intermediate signaling processing are required: sending and receiving messages to and from the base station 10 (S206) and sending and receiving messages from the base station 10 to the transmitting UE 20T (S208), HARQ retransmission delays can be reduced.

Further, according to the example of FIG. 7, a scheduling request (SR) for HARQ retransmission from the transmitting side UE 20T to the base station 10 is unnecessary, and control overhead between the transmitting side UE 20T and the base station 10 is reduced. be able to.

FIG. 9 is a sequence diagram showing another example of initial transmission of SL data transmission and HARQ retransmission during SL Mode-1 operation in the communication system according to the embodiment. Note that in FIG. 9, descriptions of processes common to those in FIG. 6 described above will be omitted.

In the example of FIG. 9, for example, the radio frames illustrated in FIGS. 2 to 4 described above can be used as the downlink (DL) and uplink (UL) of Uu communication and the radio frames of Sidelink communication (SL). .

In FIG. 9, when negotiation is performed between the transmitting side UE 20T and the base station 10 for sending and receiving a scheduling request message in data transmission in SL Mode-1 (S301), between the receiving side UE 20R and the base station 10. RRC connection reconfiguration is executed, and negotiation is performed for transmitting and receiving a scheduling request message when directly transmitting an HARQ retransmission request from the receiving side UE 20R to the base station 10 (S302).

When the receiving side UE 20R fails to receive the first transmission data, it sets a HARQ retransmission request (feedback message) including an SL HARQ-NACK (negative acknowledgment) and a HARQ retransmission scheduling request message as part of the UL radio frame. PUCCH or PUSCH is multiplexed and feedback is transmitted directly to base station 10 (S306).

When the base station 10 receives the HARQ retransmission request including the SL HARQ-NACK (negative acknowledgment) and the HARQ retransmission scheduling request message from the receiving side UE 20R, the base station 10 assigns the SL HARQ-NACK (negative acknowledgment) and the HARQ retransmission scheduling request message. A grant message including radio resource information is transmitted to the transmitting side UE 20T on the PDCCH (S307). The transmitting side UE 20T can obtain SL HARQ-NACK information via the base station 10 without using the PSFCH.

The transmitting side UE 20T transmits HARQ retransmission data to the receiving side UE 20R using the PSSCH set in the allocated radio resource (S308). When the receiving side UE 20R successfully receives the HARQ retransmission data, it returns a HARQ-ACK (acknowledgement) to the transmitting side UE 20T using the PSFCH set as part of the radio resources allocated for SL HARQ retransmission ( S309).

According to the example in FIG. 9, when the receiving side UE 20R fails to receive the first transmission data of SL, the feedback from the receiving side UE 20R to the base station is not reached until the sending side UE 20T sends HARQ retransmission data to the receiving side UE 20R. Since only two stages of intermediate signaling processing are required: direct message transmission/reception (S306) and message transmission/reception from the base station 10 to the transmitting side UE 20T (S307), HARQ retransmission delays can be reduced.

Moreover, according to the example of FIG. 9, since there is no message transmission/reception for HARQ retransmission using PSFCH from the receiving side UE 20R to the sending side UE 20T, the overhead associated with the PSFCH can be reduced. Furthermore, radio resources for AGC and Guard sections of PSFCH can also be reduced.

As described above, according to the present embodiment, it is possible to reduce the SL HARQ retransmission delay during the operation of the allocation control mode in which the base station 10 allocates radio resources for SL communication between terminals existing within the range of the base station.

In addition, the processing steps described in this specification, wireless communication systems, mobile communication systems, control devices, MEC devices, base stations, and wireless terminal devices (terminals, terminal devices, user equipment (UE), mobile stations, mobile devices) The components of can be implemented by various means. For example, these steps and components may be implemented in hardware, firmware, software, or a combination thereof.

Regarding hardware implementation, processing units, etc. used to realize the above steps and components in entities (e.g., various wireless communication devices, Node B, eNodeB, gNodeB, terminal, hard disk drive device, or optical disk drive device) The means includes one or more of an application specific integrated circuit (ASIC), a digital signal processor (DSP), a digital signal processor (DSPD), a programmable logic device (PLD), a field programmable gate array ( FPGA), processor, controller, microcontroller, microprocessor, electronic device, other electronic unit designed to perform the functions described herein, computer, or combinations thereof. Good too.

Additionally, for firmware and/or software implementations, the means used to implement the components described above, such as processing units, may include programs (e.g., procedures, functions, modules, instructions) that perform the functions described herein. , etc.). In general, any computer/processor readable medium tangibly embodying firmware and/or software code, such as a processing unit, may be used to implement the above steps and components described herein. may be used for implementation. For example, the firmware and/or software code may be stored in memory and executed by a computer or processor, eg, in a controller. The memory may be implemented within the computer or processor, or external to the processor. The firmware and/or software code may also be stored in, for example, random access memory (RAM), read-only memory (ROM), non-volatile random access memory (NVRAM), programmable read-only memory (PROM), electrically erasable PROM (EEPROM), etc. ), flash memory, floppy disks, compact disks (CDs), digital versatile disks (DVDs), magnetic or optical data storage devices, etc. good. The code may be executed by one or more computers or processors and may cause the computers or processors to perform certain aspects of the functionality described herein.

Further, the medium may be a non-temporary recording medium. Further, the code of the program may be read and executed by a computer, processor, or other device or apparatus, and its format is not limited to a specific format. For example, the code of the program may be a source code, an object code, or a binary code, or may be a mixture of two or more of these codes.

The description of the embodiments disclosed herein is also provided to enable any person skilled in the art to make or use the present disclosure. Various modifications to this disclosure will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other variations without departing from the spirit or scope of this disclosure. Therefore, this disclosure is not to be limited to the examples and designs described herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

10: Base station 10A: Cell 14: MEC device 15: Core network 20: UE (wireless terminal device)
21: Antenna 30: Vehicle 90: Road 100: Base station device 101: Antenna 102: Antenna 122: CU controller 140: MEC device

Claims (4)

A base station of a mobile communication network that has a function of communicating with a plurality of wireless terminal devices that perform direct terminal-to-terminal communication and is capable of controlling radio resources used for the direct terminal-to-terminal communication,
Monitoring a feedback channel included in a radio resource allocated for direct communication between terminals in a radio frame from a wireless terminal device on a receiving side to a wireless terminal device on a transmitting side of data transmission via the terminal-to-terminal direct communication. , means for decoding the feedback channel;
When confirming a HARQ retransmission request in which the decoding result of the feedback channel includes an HARQ negative response from the receiving wireless terminal device, means for notifying the transmitting wireless terminal device of a permission message including information on radio resources for HARQ retransmission for permitting retransmission of data through direct terminal-to-terminal communication;
A base station characterized by comprising : A system comprising the base station according to claim 1, a wireless terminal device on the receiving side of data transmission via the direct communication between terminals, and a wireless terminal device on the transmitting side of data transmission via the direct communication between terminals . A method for performing HARQ retransmission control in data transmission via direct communication between terminals , the method comprising:
A base station of a mobile communication network that has a function of communicating with a plurality of wireless terminal devices that perform direct terminal-to-terminal communication and is capable of controlling radio resources used for the direct terminal-to-terminal communication transmits data via the direct terminal-to-terminal communication. Monitoring a feedback channel included in a radio resource allocated for direct communication between terminals in a radio frame from a wireless terminal device on the receiving side of transmission to a wireless terminal device on the transmitting side, and decoding the feedback channel. and,
When the base station confirms an HARQ retransmission request in which the decoding result of the feedback channel includes an HARQ negative response from the receiving wireless terminal device, the base station transmits an HARQ retransmission request from the transmitting wireless terminal device to the receiving wireless terminal device. Notifying the transmitting side wireless terminal device of a permission message including information on radio resources for HARQ retransmission for permitting retransmission of data to the terminal device through direct terminal-to-terminal communication;
A method characterized by comprising: A program executed on a computer or processor provided in a base station of a mobile communication network that has the function of communicating with a plurality of wireless terminal devices that perform direct terminal-to-terminal communication and can control radio resources used for direct terminal-to-terminal communication. There it is,
Monitoring a feedback channel included in a radio resource allocated for direct communication between terminals in a radio frame from a wireless terminal device on a receiving side to a wireless terminal device on a transmitting side of data transmission via the terminal-to-terminal direct communication. , a program code for decoding the feedback channel;
When confirming a HARQ retransmission request in which the decoding result of the feedback channel includes an HARQ negative response from the receiving wireless terminal device, a program code for notifying the transmitting wireless terminal device of a permission message including information on radio resources for HARQ retransmission to permit retransmission of data through direct terminal-to-terminal communication;
A program characterized by including.

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