KR102740322B1 - Operation method of communication node supporting direct communication in network - Google Patents

Abstract

An operating method of a communication node supporting direct communication in a network is disclosed. The operating method of a first UE includes a step of obtaining scheduling information set for the direct communication from a first base station to which the first UE belongs, a step of checking MCS information and radio resource information included in the scheduling information, and a step of transmitting a first message to which an MCS indicated by the MCS information is applied to a second UE via a radio resource indicated by the radio resource information. Accordingly, the performance of the communication network can be improved.

Description

{OPERATION METHOD OF COMMUNICATION NODE SUPPORTING DIRECT COMMUNICATION IN NETWORK}

The present invention relates to direct communication technology, and more specifically, to an operating method of a communication node supporting vehicle communication based on a cellular system.

WAVE (wireless access for vehicular environments) protocol is a protocol that supports vehicle communication and can support V2X (vehicle to everything) communication. V2X communication can include V2V (vehicle to vehicle) communication, V2I (vehicle to infrastructure) communication, V2P (vehicle to pedestrian) communication, IVN (in-vehicle networking) communication, etc.

According to the WAVE protocol, seven channels can be supported in the 5.85 to 5.925 GHz frequency band (i.e., 75 MHz bandwidth). The seven channels can be used for V2X communication. One of the seven channels can be used for transmitting and receiving control information and can be referred to as a control channel (CCH). The remaining six channels of the seven channels can be used for traffic safety-related services, general commercial services, etc. and can be referred to as service channels (SCH).

In a vehicular communication environment, the coverage (e.g., communication range) of a roadside unit (RSU) may overlap with the coverage of an adjacent RSU to ensure service continuity. The frequency used by the RSU may be different from the frequency used by the adjacent RSU. In this case, if services between an RSU and an onboard unit (OBU) and services between OBUs belonging to different coverages are provided simultaneously, frequency interference may occur in one physical layer.

Meanwhile, the technology that serves as the background for the invention was written to promote understanding of the background for the invention, and may include content that is not a prior art already known to a person with ordinary knowledge in the field to which the technology belongs.

The purpose of the present invention to solve the above problems is to provide an operating method of a communication node that supports vehicle communication based on a cellular system.

According to one embodiment of the present invention for achieving the above object, a method for operating a first UE supporting direct communication in a communication network includes the steps of: acquiring scheduling information set for the direct communication from a first base station to which the first UE belongs; checking MCS information and radio resource information included in the scheduling information; and transmitting a first message to which an MCS indicated by the MCS information is applied to a second UE through a radio resource indicated by the radio resource information.

Here, the state of the first UE may be an RRC connected state or an RRC idle state.

Here, the scheduling information can be shared between the first base station and the second base station to which the second UE belongs.

Here, the wireless resource indicated by the wireless resource information can be set based on the speed of the vehicle in which the first UE is located, the density of vehicles in the zone to which the first UE belongs, or the service coverage of the direct communication.

Here, when the mode 1 method is used, the radio resource information can indicate a radio resource selected by the first base station from among the direct communication resource pool, and when the mode 2 method is used, the radio resource information can indicate a direct communication resource pool.

Here, the MCS information may indicate an MCS index or MCS range set by the first base station.

Here, the MCS indicated by the MCS information can be set based on the speed of the vehicle in which the first UE is located, the density of vehicles in the zone to which the first UE belongs, or the service coverage of the direct communication.

Here, the communication between the first base station and the first UE can be performed via a Uu interface, and the direct communication between the first UE and the second UE can be performed via a PC5 interface.

Here, the first base station may be a first RSU belonging to a vehicular communication network, the first UE may be a first OBU belonging to the vehicular communication network, and the second UE may be a second OBU belonging to the vehicular communication network.

Here, the operation method of the first UE may further include a step of acquiring a direct communication resource pool from the first base station, a step of performing a monitoring operation on radio resources belonging to the direct communication resource pool, and a step of receiving a second message from the second UE based on the monitoring operation.

Here, the operating method of the first UE may further include the steps of requesting the first base station to allocate additional radio resources for the direct communication when the radio resources cannot be used, the step of obtaining additional radio resource information from the first base station, and the step of transmitting a third message to the second UE through the additional radio resources indicated by the additional radio resource information.

Here, the first UE can request allocation of the additional radio resources to the first base station based on a random access procedure, a PUCCH scheduling request procedure or a BSR procedure.

Here, the additional wireless resource may be selected from among wireless resources excluding the wireless resource used for transmission of the first message from the direct communication resource pool.

According to another embodiment of the present invention for achieving the above object, a method for operating a first UE supporting direct communication in a communication network includes the steps of: transmitting a first message requesting termination of the direct communication to a first base station to which the first UE belongs when the direct communication between the first UE and the second UE is terminated; and performing a release operation of radio resources or a release operation of an RRC connection with the first base station for termination of the direct communication, wherein when the release operation of the radio resources is performed, the first UE operates in an RRC connected state, and when the release operation of the RRC connection is performed, the first UE operates in an RRC idle state.

Here, the operation method of the first UE may further include a step of requesting allocation of radio resources for the direct communication to the first base station when the direct communication between the first UE and the second UE in an RRC connection state is requested, a step of obtaining radio resource information from the first base station, and a step of transmitting a second message to the second UE through the radio resources indicated by the radio resource information.

Here, the operation method of the first UE may further include a step of selecting a radio resource from a direct communication resource pool acquired from the base station when the direct communication between the first UE and the second UE in an RRC idle state is requested, and a step of transmitting a third message to the second UE through the selected radio resource.

Here, the direct communication resource pool can be set based on the speed of the vehicle where the first UE is located, the density of vehicles in the zone to which the first UE belongs, or the service coverage of the direct communication.

Here, the direct communication radio resource pool can be shared between the first base station and the second base station to which the second UE belongs.

Here, the MCS applied to the third message can be set based on the speed of the vehicle where the first UE is located, the density of vehicles in the zone to which the first UE belongs, or the service coverage of the direct communication.

Here, the first base station may be a first RSU belonging to a vehicular communication network, the first UE may be a first OBU belonging to the vehicular communication network, and the second UE may be a second OBU belonging to the vehicular communication network.

According to the present invention, vehicle communication (e.g., V2V communication, V2I communication, V2P communication, INV communication, etc.) can be supported based on a cellular system. In addition, an autonomous driving system, an ITS (intelligent transportation system), etc. can be efficiently constructed. Accordingly, the performance of the communication system can be improved.

Figure 1 is a conceptual diagram illustrating one embodiment of a wireless communications network.
FIG. 2 is a block diagram illustrating one embodiment of a communication node constituting a wireless communication network.
Figure 3 is a conceptual diagram illustrating the first scenario of D2D communication.
Figure 4 is a conceptual diagram illustrating a second scenario of D2D communication.
Figure 5 is a conceptual diagram illustrating a third scenario of D2D communication.
Figure 6 is a conceptual diagram illustrating the fourth scenario of D2D communication.
Figure 7 is a flowchart illustrating a method of transmitting a periodic message performed at a communication node.
Figure 8 is a conceptual diagram illustrating an embodiment of a vehicle communication network.
Figure 9 is a conceptual diagram illustrating a deployment scenario of a cellular communication network.
Figure 10 is a conceptual diagram illustrating a deployment scenario of a vehicle communication network.
FIG. 11 is a flowchart illustrating an embodiment of a communication method performed by a communication node in a vehicular communication network.
Fig. 12 is a flowchart illustrating an embodiment of a communication method based on line-of-sight communication in a vehicular communication network.
Figure 13 is a timing diagram illustrating an embodiment of a method for transmitting a message via PRB.
Figure 14 is a timing diagram illustrating an embodiment of a method for repeatedly transmitting data.

The present invention can be modified in various ways and has various embodiments, and thus specific embodiments will be illustrated and described in detail. However, this is not intended to limit the present invention to specific embodiments, but should be understood to include all modifications, equivalents, or substitutes included in the spirit and technical scope of the present invention.

The terms first, second, etc. may be used to describe various components, but the components should not be limited by the terms. The terms are only used to distinguish one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as the second component, and similarly, the second component may also be referred to as the first component. The term and/or includes a combination of a plurality of related described items or any one of a plurality of related described items.

When it is said that a component is "connected" or "connected" to another component, it should be understood that it may be directly connected or connected to that other component, but that there may be other components in between. On the other hand, when it is said that a component is "directly connected" or "directly connected" to another component, it should be understood that there are no other components in between.

The terminology used in this application is only used to describe specific embodiments and is not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this application, it should be understood that the terms "comprises" or "has" and the like are intended to specify the presence of a feature, number, step, operation, component, part or combination thereof described in the specification, but do not exclude in advance the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts or combinations thereof.

Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms defined in commonly used dictionaries, such as those defined in common dictionaries, should be interpreted as having a meaning consistent with the meaning they have in the context of the relevant art, and will not be interpreted in an idealized or overly formal sense unless expressly defined in this application.

Hereinafter, with reference to the attached drawings, a preferred embodiment of the present invention will be described in more detail. In order to facilitate an overall understanding in describing the present invention, the same reference numerals are used for the same components in the drawings, and redundant descriptions of the same components are omitted.

A wireless communication network to which embodiments according to the present invention are applied will be described. The wireless communication network to which embodiments according to the present invention are applied is not limited to the contents described below, and the embodiments according to the present invention can be applied to various wireless communication networks. Here, the wireless communication network can be used in the same meaning as the wireless communication system.

Figure 1 is a conceptual diagram illustrating one embodiment of a wireless communications network.

Referring to FIG. 1, a wireless communication network (100) may include a plurality of communication nodes (110-1, 110-2, 110-3, 120-1, 120-2, 130-1, 130-2, 130-3, 130-4, 130-5, 130-6). Each of the plurality of communication nodes may support at least one communication protocol. For example, each of the plurality of communication nodes may support a communication protocol based on CDMA (code division multiple access), a communication protocol based on WCDMA (wideband CDMA), a communication protocol based on TDMA (time division multiple access), a communication protocol based on FDMA (frequency division multiple access), a communication protocol based on OFDM (orthogonal frequency division multiplexing), a communication protocol based on OFDMA (orthogonal frequency division multiple access), a communication protocol based on SC (single carrier)-FDMA, a communication protocol based on NOMA (non-orthogonal multiple access), a communication protocol based on SDMA (space division multiple access), a communication protocol based on radio access technology (RAT) that supports multiple access based on beamforming technology using a massive antenna, etc. Each of the plurality of communication nodes may have the following structure.

FIG. 2 is a block diagram illustrating one embodiment of a communication node constituting a wireless communication network.

Referring to FIG. 2, a communication node (200) may include at least one processor (210), a memory (220), and a transceiver device (230) that is connected to a network and performs communication. In addition, the communication node (200) may further include an input interface device (240), an output interface device (250), a storage device (260), etc. Each component included in the communication node (200) may be connected by a bus (270) and may communicate with each other.

The processor (210) can execute a program command stored in at least one of the memory (220) and the storage device (260). The processor (210) may mean a central processing unit (CPU), a graphics processing unit (GPU), or a dedicated processor in which methods according to embodiments of the present invention are performed. Each of the memory (220) and the storage device (260) may be configured with at least one of a volatile storage medium and a nonvolatile storage medium. For example, the memory (220) may be configured with at least one of a read only memory (ROM) and a random access memory (RAM).

Referring back to FIG. 1, each of the plurality of communication nodes may be a base station or a user equipment (UE). Each of the first base station (110-1), the second base station (110-2), and the third base station (110-3) may form a macro cell. Each of the fourth base station (120-1) and the fifth base station (120-2) may form a small cell. The fourth base station (120-1), UE3 (130-3), and UE4 (130-4) may be within the coverage of the first base station (110-1). UE2 (130-2), UE4 (130-4), and UE5 (130-5) may be within the coverage of the second base station (110-2). The fifth base station (120-2), UE4 (130-4), UE5 (130-5), and UE6 (130-6) may be within the coverage of the third base station (110-3). UE1 (130-1) may be within the coverage of the fourth base station (120-1). UE6 (130-6) may be within the coverage of the fifth base station (120-2).

Here, each of the plurality of base stations (110-1, 110-2, 110-3, 120-1, 120-2) may be referred to as a NodeB, an evolved NodeB, a base transceiver station (BTS), a radio base station, a radio transceiver, an access point, an access node, a road side unit (RSU), a radio remote head (RRH), a transmission point (TP), a transmission and reception point (TRP), a relay, etc. Each of the plurality of UEs (130-1, 130-2, 130-3, 130-4, 130-5, 130-6) may be referred to as a terminal, an access terminal, a mobile terminal, a station, a subscriber station, a mobile station, a portable subscriber station, a node, a device, an OBU (on board unit), etc.

Each of the plurality of communication nodes (110-1, 110-2, 110-3, 120-1, 120-2, 130-1, 130-2, 130-3, 130-4, 130-5, 130-6) can support cellular communication (e.g., long term evolution (LTE), advanced (LTE-A) specified in the 3rd generation partnership project (3GPP) standard, etc.). Each of the plurality of base stations (110-1, 110-2, 110-3, 120-1, 120-2) can operate in a different frequency band or can operate in the same frequency band. Each of the plurality of base stations (110-1, 110-2, 110-3, 120-1, 120-2) can be connected to each other via an ideal backhaul link or a non-ideal backhaul link, and can exchange information with each other via the ideal backhaul link or the non-ideal backhaul link. Each of the plurality of base stations (110-1, 110-2, 110-3, 120-1, 120-2) can be connected to a core network (not shown) via the ideal backhaul link or the non-ideal backhaul link. Each of the plurality of base stations (110-1, 110-2, 110-3, 120-1, 120-2) can transmit a signal received from the core network to a specific UE (130-1, 130-2, 130-3, 130-4, 130-5, 130-6) and can transmit a signal received from a specific UE (130-1, 130-2, 130-3, 130-4, 130-5, 130-6) to the core network.

Each of the plurality of base stations (110-1, 110-2, 110-3, 120-1, 120-2) can support OFDMA-based downlink transmission and SC-FDMA-based uplink transmission. In addition, each of the plurality of base stations (110-1, 110-2, 110-3, 120-1, 120-2) can support MIMO (multiple input multiple output) transmission (e.g., SU (single user)-MIMO, MU (multi user)-MIMO, massive MIMO, etc.), CoMP (coordinated multipoint) transmission, CA (carrier aggregation) transmission, unlicensed band transmission, device to device communication (D2D) communication (e.g., ProSe (proximity service)), etc. Here, each of the plurality of UEs (130-1, 130-2, 130-3, 130-4, 130-5, 130-6) can perform an operation corresponding to the base station (110-1, 110-2, 110-3, 120-1, 120-2), an operation supported by the base station (110-1, 110-2, 110-3, 120-1, 120-2).

For example, the second base station (110-2) can transmit a signal to UE4 (130-4) based on the SU-MIMO scheme, and UE4 (130-4) can receive a signal from the second base station (110-2) by the SU-MIMO scheme. Alternatively, the second base station (110-2) can transmit a signal to UE4 (130-4) and UE5 (130-5) based on the MU-MIMO scheme, and each of UE4 (130-4) and UE5 (130-5) can receive a signal from the second base station (110-2) by the MU-MIMO scheme. Each of the first base station (110-1), the second base station (110-2), and the third base station (110-3) can transmit a signal to UE4 (130-4) based on the CoMP scheme, and UE4 (130-4) can receive a signal from the first base station (110-1), the second base station (110-2), and the third base station (110-3) based on the CoMP scheme. Each of the plurality of base stations (110-1, 110-2, 110-3, 120-1, 120-2) can transmit and receive a signal with UEs (130-1, 130-2, 130-3, 130-4, 130-5, 130-6) within its coverage based on the CA scheme. Each of the first base station (110-1), the second base station (110-2), and the third base station (110-3) can coordinate D2D communication between UE4 (130-4) and UE5 (130-5), and each of UE4 (130-4) and UE5 (130-5) can perform D2D communication through coordination of the second base station (110-2) and the third base station (110-3), respectively.

Next, the operation methods of communication nodes in a wireless communication network will be described. Even if a method (e.g., transmitting or receiving a signal) performed by a first communication node among the communication nodes is described, a second communication node corresponding thereto can perform a method (e.g., receiving or transmitting a signal) corresponding to the method performed by the first communication node. That is, when the operation of a UE is described, a base station corresponding thereto can perform an operation corresponding to the operation of the UE. Conversely, when the operation of a base station is described, a UE corresponding thereto can perform an operation corresponding to the operation of the base station.

Meanwhile, public safety communication technologies (e.g., disaster communication technologies) based on the LTE/LTE-A system may include ETWS (earthquake and tsunami warning system), PWS (public warning system), D2D communication (e.g., ProSe), GCSE (group communication service), etc. Here, in D2D communication and GCSE, communication can be performed through a wireless channel between UEs without going through a base station. The functions of D2D communication can be classified into functions of commercial services, functions of public safety, etc. The scenarios of D2D communication can be as follows.

Figure 3 is a conceptual diagram illustrating the first scenario of D2D communication.

Referring to FIG. 3, each of UE1 (310) and UE2 (410) may be located outside the coverage of the base station. For example, if there is a message to be transmitted to UE2 (410), UE1 (310) may directly transmit the message to UE2 (410). In addition, UE1 (310) may directly receive the message from UE2 (410). That is, UE1 (310) and UE2 (410) may transmit and receive messages based on D2D communication. The resource allocation operation and control signaling operation for D2D communication may be basically performed based on a distributed control method.

Figure 4 is a conceptual diagram illustrating a second scenario of D2D communication.

Referring to FIG. 4, UE1 (310) may be located within the coverage of the first base station (300), and the second terminal (210) may be located outside the coverage of the first base station (300). This case may be referred to as a "partial coverage scenario." For example, if there is a message to be transmitted to UE2 (410), UE1 (310) may directly transmit the message to UE2 (410). In addition, UE1 (310) may directly receive the message from UE2 (410). That is, UE1 (310) and UE2 (410) may transmit and receive messages based on D2D communication. The resource allocation operation and the control signaling operation for D2D communication may be performed based on a distributed control method or a base station control method (or a network control method).

Figure 5 is a conceptual diagram illustrating a third scenario of D2D communication.

Referring to FIG. 5, each of UE1 (310) and UE2 (410) may be located within the coverage of the first base station (300). For example, if there is a message to be transmitted to UE2 (410), UE1 (310) may directly transmit the message to UE2 (410). In addition, UE1 (310) may directly receive the message from UE2 (410). That is, UE1 (310) and UE2 (410) may transmit and receive messages based on D2D communication. When UEs (310, 410) are located within the coverage of the first base station (300), resource allocation operations and control signaling operations for D2D communication may be basically performed based on a base station control method (or a network control method).

Figure 6 is a conceptual diagram illustrating the fourth scenario of D2D communication.

Referring to FIG. 6, UE1 (310) may be located within the coverage of the first base station (300), and UE2 (410) may be located within the coverage of the second base station (400). For example, if there is a message to be transmitted to UE2 (410), UE1 (310) may directly transmit the message to UE2 (410). In addition, UE1 (310) may directly receive the message from UE2 (410). That is, UE1 (310) and UE2 (410) may transmit and receive messages based on D2D communication. When UEs (310, 410) are located within the coverage of base stations (300, 400), resource allocation operations and control signaling operations for D2D communication may be basically performed based on a base station control method (or a network control method).

Meanwhile, in the LTE/LTE-A system, D2D communication can support voice service and can support voice service based on one QoS (quality of service). A UE supporting D2D communication can transmit data using a broadcast method or a multicast method instead of a unicast method. When the UE is located within the coverage of a base station, D2D communication can be performed based on mode 1. When mode 1 is used in D2D communication, the base station can inform the UE of resource information (e.g., radio resource information) used for D2D communication. For example, the base station can allocate available resources (e.g., available radio resources) from a D2D communication resource pool to the UE. The UE can perform D2D communication using the resources (e.g., allocated radio resources) allocated by the base station. Therefore, D2D communication can be performed without collision between UEs.

When the UE is located outside the coverage of the base station, D2D communication can be performed based on Mode 2. When Mode 2 is used in D2D communication, the UE can randomly select a resource (e.g., a radio resource) from a D2D communication resource pool set by the communication system, and perform D2D communication using the selected resource (e.g., the selected radio resource). Since the resource (e.g., a radio resource) used for D2D communication is randomly selected, collisions between UEs may occur.

In a partial coverage scenario, D2D communication can be performed based on Mode 1 or Mode 2. The criteria for selecting the mode can be preset, and the UE can select Mode 1 or Mode 2 based on the preset criteria, and perform D2D communication using resources determined by the selected mode (e.g., determined radio resources).

Direct communication can be performed based on the D2D communication technology described above. Direct communication can include D2D communication, vehicle communication, MTC (machine type communication), M2M (machine to machine)-based communication, IoT (internet of things)-based communication, etc. Vehicle communication can be V2X (vehicle to everything) communication. V2X communication can include V2V (vehicle to vehicle) communication, V2I (vehicle to infrastructure) communication, V2P (vehicle to pedestrian) communication, IVN (in-vehicle networking) communication, etc. Communication between OBUs, communication between OBUs and RSUs, and communication between RSUs can be performed based on D2D communication technology. Based on vehicle communication, discovery service and communication service between communication nodes can be provided.

In the embodiments described below, the RSU may be a communication system, a base station, etc., and the OBU may be a UE, etc. The UE may be a UE owned by a pedestrian, a UE owned by a person using a means of transportation (e.g., a vehicle, a motorcycle, a bicycle, a wheelchair, a baby carriage, etc.), etc. User information (e.g., information indicating whether the owner of the UE is a pedestrian, information indicating whether the owner of the UE is a user of the means of transportation, etc.) may be automatically set based on a sensor included in the UE (e.g., a gyro sensor, etc.) or a measurement function of the UE (e.g., a function for measuring a distance moved per unit time, a function for measuring a change in the strength of a received signal, etc.). Alternatively, the user information may be set according to an input of a user of the UE.

When Mode 1 is used, vehicular communication can be performed using resources scheduled by a base station (e.g., a communication system, RSU). When Mode 2 is used, vehicular communication can be performed using resources randomly selected from a vehicular communication resource pool set by the base station. The vehicular communication resource pool can be the same as or different from the D2D communication resource pool described above.

When mode 1 is used, the OBU (or UE) can operate in an RRC (radio resource control) connected state, and the base station can control the management and allocation of resources. For example, the base station can directly set the mode of vehicular communication (e.g., mode 1 or mode 2). The OBU in the RRC idle state can operate in the RRC connected state when there is data to be transmitted. That is, the state of the OBU can transition from the RRC idle state to the RRC connected state. The OBU in the RRC connected state can request the base station to allocate resources for vehicular communication. If necessary, the OBU in the RRC connected state can transmit a BSR (buffer status report) to the base station. When the OBU requests resource allocation for vehicular communication, the base station can allocate available resources from the vehicular communication resource pool to the OBU. The OBU can transmit data using the resources allocated by the base station. Additionally, the base station can allocate resources for OBUs in the RRC idle state based on the SPS (semi-persistence scheduling) method. In this case, the OBUs in the RRC idle state can transmit data without collision by using the resources allocated by the base station.

When Mode 2 is used, regardless of the state of the OBU (or UE) (e.g., RRC connected state or RRC idle state), the OBU can randomly select a resource from a vehicular communication resource pool configured by the base station, and transmit data using the selected resource. Meanwhile, the OBU can receive a synchronization signal from another communication node (e.g., a base station, an RSU, an OBU, a UE, etc.), and transmit data using the resource selected from the vehicular communication resource pool after synchronization based on the synchronization signal. The synchronization signal can be transmitted in a broadcast manner from any communication node (e.g., a base station, an RSU, an OBU, a UE, etc.) through resources configured for transmission of the synchronization signal. If the synchronization signal is not detected, the OBU can transmit the synchronization signal directly. That is, the OBU can act as a synchronization source.

Below, a manner in which resources for direct communication (e.g., D2D communication, vehicular communication, etc.) are allocated by a base station may be referred to as a "mode 1 manner". Resources allocated by the mode 1 manner may be referred to as "mode 1 resources". A manner in which resources for direct communication (e.g., D2D communication, vehicular communication, etc.) are randomly selected by an OBU from a preset vehicular communication resource pool may be referred to as a "mode 2 manner". Resources selected by the mode 2 manner may be referred to as "mode 2 resources".

Meanwhile, a message generated periodically in vehicle communication (hereinafter referred to as a "periodic message") can be transmitted using Mode 1 resources regardless of the state of the OBU (e.g., RRC connection state or RRC idle state). A message generated by the occurrence of a specific event (hereinafter referred to as a "aperiodic message") can be transmitted using Mode 2 resources. Aperiodic messages can be transmitted using Mode 1 resources depending on properties such as required reliability, service coverage, and latency.

An OBU may include an AS layer block supporting functions of a protocol layer for wireless access (e.g., an access stratum (AS) layer) and an NAS layer block supporting functions of a higher layer (e.g., a non-access stratum (NAS) layer or an application layer). The AS layer may be a physical layer (e.g., layer 1), a medium access control (MAC) layer (e.g., layer 2), or a radio resource control (RRC) layer.

An OBU may cancel or skip transmission of a periodic message. For example, if radio resources for transmission of a periodic message are not allocated, if radio resources for transmission of a periodic message are not selected, or if there is an upper layer instruction (e.g., a configuration condition) requesting cancellation or skipping of periodic message transmission, the transmission of a periodic message may be canceled or skipped. If transmission of a periodic message is canceled, skipped, or fails for any other reason, the OBU may transmit the periodic message in an aperiodic manner, or transmit an updated periodic message at the next transmission cycle (or transmission point).

Specifically, the AS layer block can obtain a periodic message from the NAS layer block, and transmit the periodic message according to a preset period. If the periodic message is not transmitted, the AS layer block (e.g., a physical layer block, a MAC layer block, or an RRC layer block included in the AS layer block) can transmit a signaling parameter (or a primitive message between layer blocks included in an OBU) or a separate control message indicating a transmission failure (or cancellation, omission) of the periodic message to the NAS layer block (e.g., a block supporting a control function). In addition, the reason for the transmission failure (or cancellation, omission) of the periodic message can also be reported to the NAS layer block.

The NAS layer block can detect a failure (or cancellation, omission) of transmission of a periodic message by receiving a signaling parameter or a separate control message from the AS layer block. Alternatively, the NAS layer block can detect a failure (or cancellation, omission) of transmission of the periodic message by another method. In this case, the NAS layer block can instruct the AS layer block to transmit the periodic message in an aperiodic manner (e.g., triggering the AS layer block). Alternatively, the NAS layer block can instruct the AS layer block to transmit an updated periodic message at the next transmission period (or the next transmission time) (e.g., triggering the AS layer block). Alternatively, the NAS layer block can instruct the AS layer block to omit transmission of the periodic message (e.g., triggering the AS layer block).

Meanwhile, the NAS layer block can control the occurrence frequency (or transmission cycle) of the periodic message. In addition, the NAS layer block can maintain and manage the updated latest information, and control the transmission of the updated latest information at the next transmission cycle (or the next transmission time). The NAS layer block can transmit the occurrence frequency (or transmission cycle) information of the periodic message, and the control information related to the maintenance/management/transmission of the updated latest information to the AS layer block through a signaling parameter (or a primitive message between layer blocks included in the OBU) or a separate control message.

The NAS layer block can adjust the occurrence frequency (or transmission cycle) of the periodic message based on the movement speed of the OBU (or UE), the wireless channel environment, the reason for failure (or cancellation, omission) of the periodic message transmission, etc. that have been acquired in advance. Alternatively, the NAS layer block can transmit a signaling parameter (or a primitive message between layer blocks included in the OBU) or a separate control message requesting a report on the movement speed of the OBU, the wireless channel environment, the reason for failure (or cancellation, omission) of the periodic message transmission, etc., to the AS layer block, and adjust the occurrence frequency (or transmission cycle) of the periodic message based on the movement speed of the OBU, the wireless channel environment, the reason for failure (or cancellation, omission) of the periodic message transmission, etc. reported from the AS layer block.

The AS layer block can obtain information on the occurrence frequency (or transmission cycle) of a periodic message and control information related to the maintenance/management/transmission of updated latest information from the NAS layer block. The AS layer block can transmit a periodic message according to the occurrence frequency (or transmission cycle). The AS layer block can maintain/manage/transmit the updated latest information based on the control information. The AS layer block can transmit the transmission result of the periodic message and the maintenance/management/transmission result of the updated latest information to the NAS layer block. In addition, the AS layer block can report the moving speed of the OBU, the wireless channel environment, the reason for failure (or cancellation, omission) of periodic message transmission, etc. to the NAS layer block at the request of the NAS layer block.

Meanwhile, the operation for adjusting the occurrence frequency (or transmission cycle) of the periodic message as described above and the operation related to maintenance/management/transmission of the updated latest information may be performed in the RRC layer block belonging to the AS layer block instead of the NAS layer block. In this case, the NAS layer block may transmit control information related to adjusting the occurrence frequency (or transmission cycle) of the periodic message and control information related to maintaining/managing/transmitting the updated latest information to the RRC layer block. The RRC layer block may adjust the occurrence frequency (or transmission cycle) of the periodic message and perform the operation related to maintaining/managing/transmitting the updated latest information using the control information acquired from the NAS layer block. For example, the RRC layer block may transmit a signaling parameter (or a primitive message between layer blocks included in the OBU) or a separate control message requesting an operation based on the adjusted occurrence frequency (or transmission cycle) of the periodic message to the MAC layer block and the physical layer block. In addition, the RRC layer block can transmit a signaling parameter (or a primitive message between layer blocks included in the OBU) or a separate control message requesting to perform an operation related to maintaining/managing/transmitting the updated latest information, to the MAC layer block and the physical layer block. When a signaling parameter (or a primitive message between layer blocks included in the OBU) or a separate control message is received from the RRC layer block, the MAC layer block and the physical layer block can adjust the occurrence frequency (or transmission cycle) of the periodic message based on the request of the RRC layer block and perform an operation related to maintaining/managing/transmitting the updated latest information.

Meanwhile, conditions for adjusting the occurrence frequency (or transmission cycle) of periodic messages, conditions for canceling (or omitting) transmission of periodic messages, etc. can be preset based on control information of the NAS layer or an RRC control message (e.g., control information of the RRC layer). When the current state satisfies the preset conditions, an AS layer block (e.g., an RRC layer block, a MAC layer block, a physical layer block) can adjust the occurrence frequency (or transmission cycle) of periodic messages, and cancel (or omit) transmission of the periodic messages. In this case, the AS layer block can report the result of adjusting the occurrence frequency (or transmission cycle) of the periodic messages, and the result of canceling (or omitting) transmission of the periodic messages to the NAS layer block.

Next, a transmission method of a periodic message performed in a communication node (e.g., OBU, UE) will be described. If a mode 1 resource is not allocated, a mode 2 resource is not selected, or transmission of a periodic message fails (or is canceled, omitted), the following transmission method may be used.

Figure 7 is a flowchart illustrating a method of transmitting a periodic message performed at a communication node.

Referring to FIG. 7, the OBU (or UE) can compare the transmission delay time of the periodic message with the preset transmission delay time, or compare the number of transmission failures of the periodic message with the preset number of transmission failures (S700). The preset transmission delay time and the preset number of transmission failures can be set based on the properties, priority, etc. of the periodic message. The OBU can obtain the preset transmission delay time and the preset number of transmission failures through system information (or a separate control message).

If the transmission delay time of the periodic message is greater than or equal to a preset transmission delay time (or, if the number of transmission failures of the periodic message is greater than or equal to a preset number of transmission failures), aperiodic transmission may be triggered. If aperiodic transmission is triggered, the OBU may set resources for aperiodic transmission (S710). For example, the OBU may acquire mode 1 resources allocated by the base station. The mode 1 resources may be allocated based on the mode 1 method described above. In addition, the OBU may report the latest information of the periodic message, the transmission delay time, the number of transmission failures, the reason for transmission failure, etc. to the base station in the allocation procedure of the mode 1 resources.

Alternatively, the OBU may select a Mode 2 resource. The Mode 2 resource may be selected based on the Mode 2 method described above. In addition, the OBU (or UE) may report the latest information of the periodic message, transmission delay time, number of transmission failures, transmission failure reasons, etc. to the base station in the Mode 2 resource selection procedure. Alternatively, the OBU may acquire an uplink resource allocated by the base station. For example, the OBU may acquire an uplink resource by performing an uplink resource request procedure (e.g., a scheduling request procedure) or an access procedure.

The OBU can determine whether mode 1 resources or mode 2 resources are available (S720). If mode 1 resources are available, the OBU can transmit a periodic message using mode 1 resources, or if mode 2 resources are available, the OBU can transmit a periodic message using mode 2 resources (S730). On the other hand, if both mode 1 resources and mode 2 resources are unavailable, the periodic message can be transmitted through the base station (S740). For example, the OBU can report the latest information of the periodic message, transmission delay time, number of transmission failures, reason for transmission failure, etc. to the base station using uplink resources. If the latest information of the periodic message, etc. is received from the OBU, the base station can transmit the periodic message including the latest information to other communication nodes (e.g., OBU, UE, RSU, base station). In this case, the base station can transmit the periodic message in a broadcast manner, a multicast manner, or a unicast manner through downlink resources. Alternatively, the base station can transmit the periodic message using a PC5 interface for vehicular communication.

Figure 8 is a conceptual diagram illustrating an embodiment of a vehicle communication network.

Referring to FIG. 8, MME1 (mobility management entity 1)/GW1 (gateway 1) (811), MME2/GW2 (812), base station 1 (821), base station 2 (822), RSU1 (831), RSU2 (832), UE1 (841), UE2 (842), OBU1 (851), OBU2 (852), etc. can support direct communication (e.g., D2D communication, vehicle communication, etc.). Each of base station 1 (821) and base station 2 (822) can be connected to MME1/GW1 (811), MME2/GW2 (812), etc. via the S1 interface. Base station 1 (821) and base station 2 (822) can each transmit and receive control information to and from MME1/GW1 (811), MME2/GW2 (812), etc. via the control plane, and can transmit and receive data to and from MME1/GW1 (811), MME2/GW2 (812), etc. via the user plane. Base station 1 (821) can be connected to base station 2 (822) via the X2 interface.

RSU1 (831) can be connected to base station 1 (821) through an X2 interface if it supports a base station function, and can be connected to MME1/GW1 (811) through an S1 interface. RSU1 (831) can perform transmission and reception operations of control information/data through the X2 interface and the S1 interface. Here, the S1 interface can be a logical interface, and RSU1 (831) can be physically connected to MME1/GW1 (811) via base station 1 (821). Alternatively, RSU1 (831) can be connected to base station 1 (821) through an Un interface if it supports a relay function (e.g., L3/L2 relay function), and can perform transmission and reception operations of control information/data through the Un interface. Alternatively, RSU1 (831) may be connected to base station1 (821) via a Uu interface if it supports a UE (or OBU) function, and may perform transmission and reception operations of control information/data via the Uu interface.

RSU2 (832) can be connected to base station 2 (822) via a Un interface if it supports a relay function (e.g., L3/L2 relay function) and can perform transmission and reception operations of control information/data via the Un interface. Alternatively, RSU2 (832) can be connected to base station 2 (822) via a Uu interface if it supports a UE (or, OBU) function and can perform transmission and reception operations of control information/data via the Uu interface. RSU1 (831) can be connected to RSU2 (832) via a PC5 interface or a Uu interface. Transmission and reception operations of control information/data between RSU1 (831) and RSU2 (832) can be performed via the PC5 interface or the Uu interface.

UE1 (841) can be connected to base station 1 (821) via the Uu interface, and can be connected to OBU1 (851) via the PC5 interface. UE1 (841) can perform transmission and reception operations of control information/data via the Uu interface and the PC5 interface. UE2 (842) can be connected to base station 2 (822) via the Uu interface, and can be connected to OBU2 (852) via the PC5 interface. UE2 (842) can perform transmission and reception operations of control information/data via the Uu interface and the PC5 interface.

OBU1 (851) can be connected to RSU1 (831) supporting a base station function (or relay function) through a Uu interface, can be connected to UE1 (841) through a PC5 interface, and can be connected to OBU2 (852) through a PC5 interface. OBU1 (851) can perform transmission and reception operations of control information/data through the Uu interface and the PC5 interface. OBU2 (852) can be connected to base station2 (822) through a Uu interface, can be connected to RSU2 (832) supporting a UE function (or OBU function) through a PC5 interface, can be connected to UE2 (842) through a PC5 interface, and can be connected to OBU1 (851) through the PC5 interface. OBU2 (852) can perform transmission and reception operations of control information/data through the Uu interface and the PC5 interface.

Here, the PC5 interface may be a PC5 interface for D2D communication in an LTE/LTE-A system, or may be a wireless interface for direct communication between communication nodes (e.g., RSU, OBU, UE, etc.) in a vehicular communication network (e.g., a PC5 interface for vehicular communication).

Figure 9 is a conceptual diagram illustrating a deployment scenario of a cellular communication network.

Referring to FIG. 9, a base station can manage multiple cells (e.g., three cells). Each of the multiple base stations can be operated by the same operator or different operators. In addition, the cellular communication network can be divided into multiple zones. Multiple cells can be located in each zone, and a base station can be located. Or, a base station may not be located in each zone. Here, the zone can be the same as a zone in the vehicular communication network described below.

Figure 10 is a conceptual diagram illustrating a deployment scenario of a vehicle communication network.

Referring to FIG. 10, the vehicular communication network may include a base station, an RSU, an OBU, a UE, etc. The RSU may be located in a traffic light, a traffic sign, a structure on the road, a structure around the road (e.g., a street light, a utility pole, a street tree, etc.), a building around the road, a center line of the road, etc. The RSU may perform a base station function, a relay function, or a UE function (or, an OBU function). The OBU may be located in a vehicle. The UE may be a UE owned by a pedestrian, a UE owned by a person using a vehicle, etc.

A zone may include at least one RSU, at least one OBU, at least one UE, etc. A zone may be set in consideration of a moving speed, density, moving path, etc. of a vehicle (or, OBU, UE). In order for direct communication (e.g., D2D communication, vehicular communication, etc.) to be efficiently performed in one zone, frequency information (e.g., bandwidth, center frequency, etc.), configuration information of a physical layer (e.g., configuration information of a synchronization signal, a reference signal, a pilot signal, etc.), configuration/arrangement information of a resource element (or a resource block) in a radio frame (or a subframe), configuration/mapping information of a direct communication resource pool, etc. may be exchanged in advance between cells, and thus cells in one zone may be operated identically. Here, the direct communication resource pool may be a D2D communication resource pool, a vehicular communication resource pool, etc. In addition, the direct communication resource pool may include a resource pool for a discovery operation, a resource pool for data communication, etc.

Even if each of the cells in a zone or neighboring zones has a different operator (e.g., inter-PLMN (inter-public land mobile network)), each of the OBUs (or UEs) has a different subscribed operator, or each of the vehicles has a different manufacturer, the information described above (e.g., frequency information, physical layer configuration information, configuration/arrangement information of resource elements (or resource blocks) within a radio frame (or subframe), configuration/mapping information of a direct communication resource pool, etc.) can be used identically to enable vehicle communication. In addition, transmission and reception operations of control information/data can be performed based on the same access procedure.

Meanwhile, resources for direct communication in a vehicular communication network (e.g., a vehicular communication resource pool) can be set based on the Mode 1 method or the Mode 2 method described above. In a vehicular communication network, an end node (e.g., a base station, a cell, an access point, an RSU, etc.) can set a vehicular communication resource pool based on at least one of the parameters below. Here, the vehicular communication resource pool can be set per vehicle (or, OBU, UE) or per zone.

- Road-related parameters (e.g., lane width, number of lanes, number of intersections, shape of intersections, road type (e.g., city road, main road, secondary road, exclusive car road, expressway, etc.), road condition (e.g., icing, flooding, etc.), accident situation, etc.)

- Vehicle-related parameters (e.g., number of vehicles (or OBUs, UEs), density of vehicles (or OBUs, UEs) (e.g., number of vehicles (or OBUs, UEs) per unit area), moving speed of vehicles (or OBUs, UEs) (e.g., average moving speed), moving path of vehicles (or OBUs, UEs), etc.)

- Service-related parameters (e.g., service-specific coverage (e.g., service-specific reach), transmission reliability, etc.)

- Message-related parameters (e.g., how the message is transmitted (e.g., periodic, aperiodic (or event-based), etc.), characteristics of the data included in the message (e.g., priority, size, type, etc.))

- Parameters related to operating hours (e.g., start time, end time, weekdays, weekends, etc.)

For example, if it is predicted that there will be relatively many vehicles (or OBUs, UEs) based on road-related parameters, the vehicular communication resource pool can be set to include relatively many resources. Conversely, if it is predicted that there will be relatively few vehicles (or OBUs, UEs) based on road-related parameters, the vehicular communication resource pool can be set to include relatively few resources.

If it is determined that there are relatively many vehicles (or OBUs, UEs) based on vehicle-related parameters, the vehicle communication resource pool can be set to include relatively many resources. Conversely, if it is determined that there are relatively few vehicles (or OBUs, UEs) based on vehicle-related parameters, the vehicle communication resource pool can be set to include relatively few resources. In addition, if the speed of the vehicle is below a preset threshold (or if the density of the vehicles exceeds a preset threshold), the vehicle communication resource pool can be set to include relatively many resources. Conversely, if the speed of the vehicle exceeds a preset threshold (or if the density of the vehicles is below a preset threshold), the vehicle communication resource pool can be set to include relatively few resources.

Here, the OBU (or UE) can report vehicle-related parameters to the base station (or RSU). Or, the server connected to the OBU can estimate vehicle-related parameters based on information acquired from the vehicle's navigation system and report the estimated vehicle-related parameters to the base station. Or, if the base station is equipped with sensors, video devices (e.g., closed circuit television (CCTV), cameras, etc.), the base station can estimate vehicle-related parameters using the sensors, video devices, etc.

If the coverage of the service is determined to be relatively wide based on service-related parameters, the vehicle communication resource pool may be set to include relatively more resources. Conversely, if the coverage of the service is determined to be relatively narrow based on service-related parameters, the vehicle communication resource pool may be set to include relatively fewer resources.

If it is determined that the data to be transmitted is relatively large based on message-related parameters, the vehicle communication resource pool may be set to include relatively large resources. Conversely, if it is determined that the data to be transmitted is relatively small based on message-related parameters, the vehicle communication resource pool may be set to include relatively small resources.

If it is predicted that there will be relatively many vehicles (or OBUs, UEs) based on the operation time-related parameters, the vehicular communication resource pool can be set to include relatively many resources. Conversely, if it is predicted that there will be relatively few vehicles (or OBUs, UEs) based on the operation time-related parameters, the vehicular communication resource pool can be set to include relatively few resources.

In addition, the base station can set up a vehicular communication resource pool to enable reuse of resources. For example, the base station can set up a vehicular communication resource pool so that different resources are allocated to each of the contiguous zones to reduce interference in vehicular communication. The base station can set up a vehicular communication resource pool so that the same resources are allocated to each of the separated zones (i.e., non-contiguous zones).

The base station can transmit configuration information of the vehicular communication resource pool to the OBU via system information or a dedicated control message. The configuration information of the vehicular communication resource pool can include at least one of a system bandwidth, a transmission bandwidth, frequency resource information (e.g., a subcarrier index, etc.), time resource information (e.g., a subframe index, a slot index, a symbol index, etc.), a resource allocation period, resource usage permission information (e.g., a priority), channel configuration information of a physical layer, a valid time of the configuration information of the vehicular communication resource pool, a valid service area of the configuration information of the vehicular communication resource pool (e.g., a cell identifier, a tracking area identifier, a zone identifier, etc.), and an allocation method (mode 1, mode 2) of the vehicular communication resource pool.

The OBU can receive configuration information of a vehicle communication resource pool from a base station, and can identify resources used for vehicle communication based on the configuration information of the vehicle communication resource pool. Therefore, the OBU can perform vehicle communication using resources included in the vehicle communication resource pool.

Meanwhile, in vehicular communication, a modulation and coding scheme (MCS) can be set by a base station (or RSU) or an OBU (or UE). The base station can set the MCS using at least one of the road-related parameters, vehicle-related parameters, service-related parameters, message-related parameters, and operating time-related parameters described above. The base station can set a specific MCS index (e.g., MCS level) or an available MCS range. The MCS index (or MCS range) can be set per vehicle (or OBU, UE) or per zone. For example, if the MCS index (or MCS range) is set per zone, OBUs belonging to the zone can use the same MCS index (or MCS range).

The base station can transmit the configured MCS information (e.g., MCS index, MCS range) to the OBU via system information or a dedicated control message. The OBU can receive the MCS information from the base station. If the MCS index is received, the OBU can perform vehicle communication using the MCS indicated by the MCS index. If the MCS range is received, the OBU can select an MCS within the MCS range and perform vehicle communication using the selected MCS.

Meanwhile, a fixed MCS may be used in the base station and the OBU. For example, a fixed MCS may be used according to the characteristics of data included in the message (e.g., priority, size, type, etc.). Or, a fixed MCS may be used by zone (or by road). When a fixed MCS is used, control information (e.g., sidelink control (SC) information in LTE/LTE-A-based D2D communication) including scheduling information for resources used for data transmission to which the fixed MCS is applied may not be transmitted. For example, a periodic message transmitted in a broadcast manner or a message including data within a preset size range may be transmitted using a fixed MCS without separate scheduling information. In particular, when resources for vehicle communication are allocated in the SPS manner, the fixed MCS may be usefully used. In addition, a message to which the fixed MCS is applied may be transmitted through a resource other than a resource to which a message to which the MCS set by the base station or the OBU is applied is transmitted.

Meanwhile, the OBU can set the MCS by using at least one of the road-related parameters, vehicle-related parameters, service-related parameters, message-related parameters, and operating time-related parameters described above. Here, the preset threshold used for judging each parameter (e.g., the road-related parameters, the vehicle-related parameters, the service-related parameters, the message-related parameters, the operating time-related parameters, etc.) can be transmitted to the OBU through signaling of the base station, or can be stored in advance in the OBU. The criterion for determining the MCS (e.g., high-efficiency MCS, low-efficiency MCS) (e.g., the mapping relationship between each parameter and the MCS) can be transmitted to the OBU through signaling of the base station, or can be stored in advance in the OBU.

For example, when the speed of the vehicle (or, OBU, UE) is higher than a preset threshold (for example, when the speed of the vehicle (or, OBU, UE) is high), the OBU can use a high-efficiency MCS (for example, a high order modulation scheme (for example, 16QAM (quadrature amplitude modulation), 64QAM, etc.) and a high coding rate (for example, 1/2, 2/3, 4/5, etc.)). When the speed of the vehicle (or, OBU, UE) is lower than a preset threshold (for example, when the speed of the vehicle (or, OBU, UE) is low), the OBU can use a low-efficiency MCS (for example, a low order modulation scheme (for example, BPSK (binary phase shift keying), QPSK (quadrature phase shift keying)), and a low coding rate (for example, 1/12, 1/6, 1/3, etc.)). The preset threshold used to determine the speed of the vehicle (or, OBU, UE) can be transmitted to the OBU via signaling from the base station, or can be stored in advance in the OBU. The criterion for determining the MCS (e.g., high-efficiency MCS, low-efficiency MCS) (e.g., the mapping relationship between the speed of the vehicle and the MCS) can be transmitted to the OBU via signaling from the base station, or can be stored in advance in the OBU.

Also, when the density of the vehicle (or, OBU, UE) (or, data size) is higher than a preset threshold, the OBU can use a high-efficiency MCS (e.g., a high-order modulation scheme (e.g., 16QAM, 64QAM, etc.) and a high coding rate (e.g., 1/2, 2/3, 4/5, etc.)). When the density of the vehicle (or, OBU, UE) (or, data size) is lower than the preset threshold, the OBU can use a low-efficiency MCS (e.g., a low-order modulation scheme (e.g., BPSK, QPSK, etc.) and a low coding rate (e.g., 1/12, 1/6, 1/3, etc.)). The preset threshold used to determine the density of the vehicle (or, OBU, UE) (or, data size) can be transmitted to the OBU via signaling of the base station, or can be stored in advance in the OBU. The criteria for determining MCS (e.g., high-efficiency MCS, low-efficiency MCS) (e.g., mapping relationship between vehicle density (or data size) and MCS) can be transmitted to the OBU through signaling of the base station, or can be stored in advance in the OBU.

In addition, if the coverage of the service (e.g., the reach of the service) is more than a preset threshold value (e.g., 500 m or 1 km), the OBU may use a low-efficiency MCS (e.g., a low-order modulation scheme (e.g., BPSK, QPSK, etc.) and a low coding rate (e.g., 1/12, 1/6, 1/3, etc.)). If the coverage of the service (e.g., the reach of the service) is less than a preset threshold value (e.g., 200 m or 300 m), the OBU may use a high-efficiency MCS (e.g., a high-order modulation scheme (e.g., 16QAM, 64QAM, etc.) and a high coding rate (e.g., 1/2, 2/3, 4/5, etc.)). The preset threshold value used to determine the coverage of the service (e.g., the reach of the service) may be transmitted to the OBU via signaling of the base station, or may be stored in advance in the OBU. The criteria for determining MCS (e.g., high-efficiency MCS, low-efficiency MCS) (e.g., mapping relationship between coverage of service (e.g., service reach) and MCS) can be transmitted to the OBU through signaling of the base station, or can be stored in advance in the OBU.

Next, a method for supporting autonomous driving in a vehicle communication network (e.g., a vehicle communication network illustrated in FIG. 10) will be described. An RSU supporting autonomous driving may be an RSU installed on a traffic light at an intersection (or a crosswalk), an RSU linked to a traffic light at an intersection (or a crosswalk), or an RSU installed on a structure (or a building) around a road. In addition, the RSU may support a base station function or a relay function. In this case, the RSU may directly set up a communication resource pool and support a connection function between an infrastructure network and an OBU.

The RSU can control traffic signals (e.g., control the timing of traffic signals, stop operation of specific traffic signals, etc.) by exchanging information with a traffic control center (e.g., an intelligent transportation system (ITS) etc.) (or, without exchanging information). The RSU can transmit and receive control information/data to and from the OBU using resources for direct communication (e.g., D2D communication, vehicular communication) (e.g., a radio interface between a base station and a UE (e.g., a Uu interface)).

The RSU can obtain vehicle-related parameters from the OBU, or estimate vehicle-related parameters using separate sensors, video devices, etc. In addition, the RSU can obtain vehicle-related parameters from another RSU installed or linked to a traffic light at an adjacent intersection (or crosswalk). The RSU can control traffic signals by considering the vehicle-related parameters.

The RSU can transmit a control message to the OBU to instruct deceleration, acceleration stop, stop, etc. before the stop signal of the traffic light turns on (for example, before a preset reference time). In addition, the RSU can transmit a control message to the OBU to instruct the operating time of the stop signal of the traffic light. Here, the operating time can be the remaining time until the stop signal turns on or the exact time when the stop signal operates. When the stop signal related control message is received, the OBU can control the vehicle to decelerate or stop based on the speed of the vehicle, road conditions (for example, road related parameters), the distance from the preceding vehicle, etc. In particular, a vehicle supporting autonomous driving can efficiently perform an autonomous driving function based on information acquired through direct communication with the RSU instead of information collected from sensors used for autonomous driving. For example, the RSU can improve the efficiency of the autonomous driving function by transmitting a control signal to the OBU that supports the autonomous driving function to notify the operation (or end of operation) of a traffic light indicating start, stop, go straight, turn left, or turn right, or the operation (or end of operation) of a traffic light installed at a crosswalk for pedestrians.

The RSU can obtain user information (i.e., user information of the UE) from a UE located on a road (e.g., a sidewalk) by using resources (e.g., a wireless interface (e.g., a Uu interface) between a base station and a UE) for direct communication (e.g., D2D communication, vehicular communication), and transmit the obtained user information to an OBU located on the road. The user information can be safety-related information (e.g., information for preventing vehicle accidents). For example, the user information can be the location, speed, type (e.g., disabled person, child, etc.) of a user (e.g., pedestrian), walking assistance device, transportation means (e.g., bicycle), etc.

Alternatively, the RSU may acquire user information through a method other than direct communication, and transmit the acquired user information to the OBU located on the road. For example, the RSU may acquire user information based on image information acquired from an image device (e.g., CCTV, camera, etc.), or may acquire user information through line-of-sight communication. Here, the line-of-sight communication may be point-to-point direct communication that acquires information from a counterpart communication node by transmitting a radio wave (or beam) having strong straightness to the counterpart communication node. According to line-of-sight communication, communication with a counterpart communication node can be performed even when the identifier information of the counterpart communication node (e.g., phone number, source ID, destination ID, etc.) is not known.

The RSU can obtain vehicle information (i.e., vehicle information on which the OBU is installed) from an OBU located on the road, and transmit the obtained vehicle information to a UE located on the road (e.g., a sidewalk). By this operation, vehicle accidents can be prevented. Here, the vehicle information can be the vehicle's speed, moving path, type, etc.

Meanwhile, if the presence of a pedestrian is confirmed through a separate sensor, video device (e.g., CCTV, camera, etc.), the RSU can transmit the confirmed pedestrian-related information (e.g., user information) to the OBU in a broadcast manner using resources for direct communication. Or, if the presence of a pedestrian is confirmed, the RSU can request user information from the pedestrian's UE and obtain user information from the UE in response to the request. Regardless of the request for user information, the UE can transmit user information to the RSU if the presence of the RSU is confirmed. The RSU can generate an alarm message for preventing a vehicle accident by considering the acquired user information, and transmit the generated alarm message to the OBU located on the road.

Meanwhile, the user information (or vehicle information) described above can be transmitted to an RSU that performs monitoring of road-related parameters and an RSU that supports relay function outside the coverage of the communication network.

Next, a communication method performed by a communication node in a vehicular communication network will be described.

FIG. 11 is a flowchart illustrating an embodiment of a communication method performed by a communication node in a vehicular communication network.

Referring to FIG. 11, each of base station 1 and base station 2 may be a base station (821, 822) or an RSU (831, 832) illustrated in FIG. 8. Each of OBU1 and OBU2 may be a UE (841, 842) or an OBU (851, 852) illustrated in FIG. 8. For example, transmission and reception of control information/data between the base station and the OBU may be performed via a Uu interface. Transmission and reception of control information/data between the OBUs may be performed via a PC5 interface. Each of base station 1, base station 2, OBU1, and OBU2 may have a structure identical to or similar to the communication node (200) illustrated in FIG. 2. The operator of base station 1 may be identical to or different from the operator of base station 2. The operator to which OBU1 is subscribed may be identical to or different from the operator to which OBU2 is subscribed.

Meanwhile, in order to perform direct communication regardless of the state of OBUs (e.g., RRC connection state, RRC idle state), base stations can negotiate a direct communication resource pool in advance. The configuration information of the direct communication resource pool can include system bandwidth, center frequency, frequency resource information, time resource information, resource cycle (or interval), etc. The direct communication resource pool can be classified into a transmission resource pool, a reception resource pool, etc. In addition, the direct communication resource pool can be classified into a resource pool for discovery operation, a resource pool for data communication, etc.

A connection (e.g., bearer) establishment operation between base station 1 and OBU1 can be performed (S1100). When the connection establishment operation is completed, OBU1 can operate in an RRC connection state. In step S1100, base station 1 can allocate resources for direct communication to OBU1 based on a mode 1 scheme. For example, base station 1 can select resources for direct communication from a direct communication resource pool (e.g., a direct communication resource pool agreed upon in advance by base stations) and transmit selected resource information to OBU1. OBU1 can obtain resource information from base station 1 and confirm resources for direct communication based on the obtained resource information.

OBU2 can operate in an RRC idle state without establishing a connection with base station 2. For example, OBU2 can operate in a state of being camped at base station 2. Resources for direct communication of OBU2 can be set based on a mode 2 method. For example, base station 2 can transmit system information including configuration information of a direct communication resource pool (for example, a direct communication resource pool agreed upon in advance by base stations) (S1101). OBU2 can obtain system information from base station 2 and confirm configuration information of the direct communication resource pool from the system information. Here, step S1101 is described as being performed after step S1100, but the execution order of step S1101 may not be limited to the content described above. For example, step S1101 may be performed simultaneously with step S1100 or before step S1100.

Afterwards, OBU1 can transmit control information (or data) to OBU2 using direct communication (S1102). Even if the state of OBU1 (e.g., RRC connection state) is different from the state of OBU2 (e.g., RRC idle state), the transmission and reception operation of the control information (or data) can be performed. For example, OBU1 can transmit scheduling information of the control information (or data) using a separate physical layer control channel for direct communication (e.g., a resource for transmitting scheduling information). The scheduling information can include resource allocation information (e.g., frequency resource information, time resource information), MCS information, etc. Here, the MCS information can be set based on at least one of the road-related parameters, vehicle-related parameters, service-related parameters, message-related parameters, and operating time-related parameters described above.

After the scheduling information is transmitted, OBU1 can transmit control information (or data) to which the MCS indicated by the scheduling information is applied through the resources indicated by the scheduling information. Meanwhile, OBU2 can obtain the scheduling information from OBU1 by monitoring resources belonging to the direct communication resource pool. OBU2 can obtain the control information (or data) from OBU1 through the resources indicated by the scheduling information, and perform a demodulation/decoding operation on the control information (or data) based on the MCS indicated by the scheduling information.

OBU2 can randomly select a resource from the direct communication resource pool acquired in step S1101, and transmit control information (or data) to OBU1 using the selected resource (S1103). OBU1 can confirm configuration information of the direct communication resource pool (e.g., a direct communication resource pool agreed upon in advance by base stations) from system information transmitted from base station 1 or a separate control message. OBU1 can receive control information (or data) from OBU2 by performing monitoring on resources belonging to the confirmed direct communication resource pool. In addition, OBU1 can obtain scheduling information from an adjacent communication node, and receive control information (or data) from OBU2 through a resource indicated by the scheduling information.

Meanwhile, if there is no resource to be used for transmitting control information (or data) (for example, if the resource allocated in step S1100 cannot be used), OBU1 may request resource allocation to base station 1 (for example, transmit a control message requesting resource allocation) (S1104). For example, OBU1 may request resource allocation to base station 1 based on a random access procedure, a scheduling request procedure of a physical uplink control channel (PUCCH), or a BSR procedure. In order to minimize the impact on other communication nodes receiving services from base station 1, a separate resource for OBU1 (for example, a resource allocated based on a random access procedure, a PUCCH, a resource allocated based on a BSR procedure, etc.) may be set. In particular, a separate PUCCH for direct communication may be set.

When base station 1 receives a request for resource allocation from OBU1, base station 1 may allocate resources for direct communication (S1105). For example, base station 1 may select resources for direct communication from a direct communication resource pool (e.g., a direct communication resource pool agreed upon in advance by base stations) and transmit information on the selected resources to OBU1. The resources for direct communication allocated in step S1105 may be different from the resources for direct communication allocated in step S1100. When resources for direct communication are allocated, OBU1 may transmit control information (or data) to another communication node (e.g., OBU2) using the allocated resources (S1106). Alternatively, when the request procedure for resource allocation (i.e., steps S1104 and S1105) is not performed, OBU1 may randomly select resources from a direct communication resource pool acquired through system information or a separate request message, and transmit control information (or data) to another communication node (e.g., OBU2) using the selected resources. OBU2 can receive control information (or data) from OBU1 by performing monitoring on resources belonging to the direct communication resource pool acquired in step S1101.

Meanwhile, OBU2 in the RRC idle state can perform a connection setup operation with base station 2 if necessary (S1107). When the connection setup operation is completed, OBU2 can operate in the RRC connected state. In step S1107, base station 2 can allocate resources for direct communication to OBU2 based on the mode 1 scheme. For example, base station 2 can select resources for direct communication from a direct communication resource pool (e.g., a direct communication resource pool agreed upon in advance by base stations) and transmit the selected resource information to OBU2. OBU2 can obtain resource information from base station 2 and confirm resources for direct communication based on the obtained resource information. Thereafter, OBU2 can transmit control information (or data) to OBU1 using the resources allocated from base station 2 (S1108). OBU1 can receive control information (or data) from OBU2 by monitoring resources belonging to the direct communication resource pool obtained through system information or a separate control message.

Meanwhile, when the direct communication service based on the mode 1 method is terminated, OBU1 can transmit a message indicating termination of the direct communication service based on the mode 1 method to base station 1 (S1109). When the message indicating termination of the direct communication service based on the mode 1 method is received, base station 1 can perform a resource release operation or a connection release operation of direct communication (S1110). When the resource release operation is performed, base station 1 can release resources set for direct communication of OBU1. In this case, OBU1 may not perform a direct communication function and may operate in an RRC connection state. When the connection release operation is performed, base station 1 can release resources set for direct communication of OBU1 and release the connection with OBU1. In this case, base station 1 can transmit a reconfiguration message notifying the release of the connection to OBU1. The reconfiguration message may include configuration information of a direct communication resource pool according to the mode 2 method (for example, a direct communication resource pool agreed upon in advance by base stations). Here, OBU1 can operate in the RRC idle state and can directly check the configuration information of the communication resource pool by receiving a reset message from base station 1.

Thereafter, when control information (or data) to be transmitted via direct communication is generated, OBU1 can randomly select a resource from the system information or the direct communication resource pool acquired through step S1110, and transmit the control information (or data) to OBU2 using the selected resource (S1111). OBU2 can receive control information (or data) from OBU1 by performing monitoring on resources belonging to the direct communication resource pool acquired through step S1101.

Meanwhile, if there is no resource to be used for transmitting control information (or data) (for example, if the resource allocated in step S1107 cannot be used), OBU2 may request resource allocation to base station 2 (for example, transmit a control message requesting resource allocation) (S1112). Here, step S1112 may be identical to or similar to step S1104 described above. OBU2 may acquire resources for direct communication from base station 2 in response to the request for resource allocation, and may transmit control information (or data) using the acquired resources.

The steps S1100 to S1112 described above may not be performed sequentially. In order to provide a direct communication service, some steps (e.g., steps for connection establishment operation (S1100, S1107), steps for resource allocation request (S1104, S1105, S1112), steps for control information/data transmission (S1102, S1103, S1106, S1108, S1111), steps for terminating direct communication (S1109, S1110), etc.) may be selectively performed.

Next, a communication method based on line-of-sight communication (or image information) in a vehicular communication network will be described.

Fig. 12 is a flowchart illustrating an embodiment of a communication method based on line-of-sight communication in a vehicular communication network.

Referring to FIG. 12, the vehicle communication network may include a preceding vehicle, a following vehicle, etc. Each of the preceding vehicle and the following vehicle may include an OBU (851, 852) or a UE (841, 842) illustrated in FIG. 8. Each of the preceding vehicle and the following vehicle may include an imaging device. The following vehicle may obtain an image of the preceding vehicle using the imaging device, and may estimate information of the preceding vehicle (e.g., vehicle type, number, etc.) by analyzing the obtained image (S1200).

The following vehicle can transmit a message including information of the preceding vehicle, information of the following vehicle (e.g., vehicle type, number, etc.), an identifier of the following vehicle, etc., to the preceding vehicle (S1201). In this case, the following vehicle can transmit a message including information of the preceding vehicle, information of the following vehicle, an identifier of the following vehicle, etc., to the preceding vehicle using direct communication or line-of-sight communication. If direct communication is used, the message can be transmitted in a broadcast manner or a multicast manner. If line-of-sight communication is used, the message can be transmitted via radio waves (or beams) having strong straightness.

The preceding vehicle can receive a message from the following vehicle, and can check the preceding vehicle information, the following vehicle information, the following vehicle identifier, etc. included in the message. If the reliability of the message (or the information included in the message) received from the following vehicle meets a preset standard (or if necessary), the preceding vehicle can transmit a message including its identifier to the following vehicle (S1202). If steps S1201 and S1202 are performed, operations related to joining/leaving the group, operations for reporting the status of each vehicle (for example, abnormal status, etc.), etc. can be performed.

In steps S1200 to S1202 described above, the preceding vehicle may perform the role of the following vehicle, and the following vehicle may perform the role of the preceding vehicle. For example, steps S1200 and S1201 may be performed by the preceding vehicle, and step S1202 may be performed by the following vehicle.

Afterwards, direct communication (e.g., point-to-point direct communication) between the preceding vehicle and the following vehicle can be performed (S1203). When direct communication is performed, group joint/withdrawal related operations, operations for reporting the status of each vehicle (e.g., abnormal status, etc.), etc. can be performed.

Meanwhile, in order to support vehicular communication, the base station (or RSU) can perform downlink transmission in a broadcast manner or a multicast manner. For example, the base station can transmit information acquired from an OBU (or UE) or a communication node belonging to a network (e.g., a communication node belonging to a higher layer) through a broadcast resource (or a multicast resource) of the downlink. When the broadcast manner is used, the base station can transmit information acquired from the OBU or the network through a resource set for MBSFN (MBMS (multimedia broadcast/multicast service) single-frequency network) transmission (hereinafter, referred to as "MBSFN resource").

The base station can transmit control information/data related to vehicle communication in a broadcast manner using MBSFN resources according to the MBMS procedure. In this case, the base station can set a separate MBSFN subframe supporting vehicle communication, and transmit control information/data related to vehicle communication using the separate MBSFN subframe. In addition, the base station can transmit information acquired from the OBU to a communication node belonging to the network (e.g., a server supporting vehicle communication, an MCE (MBMS coordination entity), etc.). The base station can transmit control information/data related to vehicle communication in a broadcast manner using the MBSFN subframe under the control of a communication node belonging to the network (e.g., a server supporting vehicle communication, an MCE, etc.).

Meanwhile, when the multicast method is used, the base station can transmit control information of the physical layer using a separate group scheduling identifier (e.g., V2X-RNTI (radio network temporary identifier)) set for vehicular communication, and can transmit information using a physical downlink shared channel (PDSCH) indicated (e.g., addressed) by the control information of the physical layer. In particular, the base station can simultaneously perform an operation of transmitting information acquired from an OBU belonging to a specific group to a communication node belonging to a network (e.g., a server supporting vehicular communication, an MCE, etc.) and an operation of transmitting information acquired from an OBU belonging to a specific group to a specific group in a multicast manner using a specific group scheduling identifier.

Here, if the vehicle communication-related control information/data is received from the OBU through a resource included in the vehicle communication resource pool or an uplink resource, the base station can identify the group to which the OBU that transmitted the vehicle communication-related control information/data belongs. In this case, the base station can decide to transmit the acquired vehicle communication-related control information/data to the OBUs belonging to the identified group, regardless of whether the acquired vehicle communication-related control information/data is transmitted from the OBU to a communication node belonging to the network. For example, the base station can transmit the vehicle communication-related control information/data to the OBUs belonging to the corresponding group by using a group identifier (e.g., a destination identifier/address for vehicle communication) or a group scheduling identifier (e.g., V2X-RNTI). In this case, the vehicle communication-related control information/data can be transmitted in a multicast manner through a downlink resource.

In the transmission procedure of vehicle communication-related control information/data described above, the OBU can transmit vehicle communication-related control information/data using a PC5 interface or a Uu interface, and the base station can transmit vehicle communication-related control information/data using a Uu interface.

Meanwhile, in order to support D2D communication, vehicle communication, MTC, M2M-based communication, IoT-based communication, etc. in the LTE/LTE-A system, message transmission can be performed in units of PRB (physical resource block). Here, the message can include control information, data, etc. for direct communication. Message transmission through PRB can be performed as follows.

Figure 13 is a timing diagram illustrating an embodiment of a method for transmitting a message via PRB.

Referring to FIG. 13, the control channel may be a physical downlink control channel (PDCCH), a physical sidelink control channel (PSCCH), etc., and the data channel may be a physical sidelink shared channel (PDSCH), a PSSCH, etc. The PRB may be set according to a scheduling period. In addition, the PRB may be set based on a frequency hopping method. A base station (e.g., a block supporting a scheduling function included in the base station) may generate scheduling information including PRB allocation information, MCS information, etc. The base station may transmit the scheduling information through a control channel. An OBU may receive scheduling information from a base station through the control channel, and may transmit data to which an MCS indicated by the scheduling information is applied through a PRB indicated by the scheduling information.

Alternatively, the OBU may randomly select a PRB from a direct communication resource pool acquired in advance from the base station, and transmit data through the selected PRB. In this case, the base station may not transmit scheduling information, and may control the OBU to randomly select a PRB from the direct communication resource pool. In addition, the base station may control a preset OBU (or UE, group) to select a PRB based on a scheduling pattern.

Next, a method for repeatedly transmitting data in direct communication will be described. Here, the repeated transmission may include retransmission, transmission based on hybrid automatic repeat request (HARQ), etc. The data channel of the physical layer for direct communication may be a PUSCH, a PSSCH of an LTE/LTE-A system, a separate data channel set for direct communication, etc. The control channel of the physical layer for direct communication may be a PDCCH, an enhanced PDCCH (ePDCCH), a PUCCH, a PSCCH of an LTE/LTE-A system, a separate control channel set for direct communication, etc.

In order to extend service coverage, improve transmission reliability, etc. in direct communication, a message may be repeatedly transmitted through PRBs (e.g., PRBs allocated by a base station, PRBs selected by an OBU) continuously or discretely in a transmission period (or, transmission duration, transmission window). Here, the message may include control information, data, etc. for direct communication. The transmission period may be a time period set on the time axis, and may be set separately for direct communication. The transmission period may be signaled to the OBU via a separate control message. For example, the transmission period may be the transmission period illustrated in FIG. 13.

Control information for repeated transmission of data may include the number of repeated transmissions, RV (redundancy version), MCS information, repeated transmission time, resource allocation information (e.g., system bandwidth, frequency resource information (e.g., subcarrier index, etc.), time resource information (e.g., subframe index, slot index, symbol index, etc.)), etc. Control information for repeated transmission may be transmitted in an explicit signaling manner or an implicit manner. Alternatively, control information for repeated transmission may be set by a communication node that performs repeated transmission of data. Here, the communication node may be a base station, a UE, an RSU, an OBU, etc.

Explicit Signaling Method of repeated transmission of data based on method

A transmitting communication node can transmit control information for repeated transmission to a receiving communication node. Alternatively, the control information for repeated transmission can be preset in the transmitting communication node and the receiving communication node. Accordingly, the transmitting communication node can perform repeated transmission of data based on the control information for repeated transmission. The receiving communication node can receive repeatedly transmitted data based on the control information for repeated transmission, and perform a demodulation/decoding operation on the received data. In addition, the receiving communication node can transmit a feedback message (e.g., an ACK (acknowledgement) message) indicating that the data has been successfully received to the transmitting communication node.

implicit Signaling Method of repeated transmission of data based on method

The number of times data is repeatedly transmitted can be set based on the capability of the communication node, the location of the communication node, MCS information, resource allocation information, the properties of the service (e.g., whether periodic data occurs, whether data is transmitted in segments, how data is transmitted, etc.), the coverage of the service (e.g., reach), the area of the service, the size of the data, etc. In other words, the mapping relationship between the number of times data is repeatedly transmitted and other information can be set in advance in the network, or can be transmitted to the communication node through separate control signaling.

For example, MCS index 1 can be mapped to repetition number 2, MCS index 2 can be mapped to repetition number 4, and MCS index 3 can be mapped to repetition number 6. Accordingly, a transmitting communication node can select a repetition number of transmissions mapped to an MCS index, and repeatedly transmit data according to the selected repetition number of transmissions. A receiving communication node can check the repetition number of transmissions mapped to an MCS index, and receive repeatedly transmitted data according to the checked repetition number of transmissions.

In addition, when the data transmission method is classified into a transmission method via a path (or logical channel) of the user plane and a transmission method via a path of the control plane, the number of repeated transmissions mapped to the transmission method via the path of the user plane may be different from the number of repeated transmissions mapped to the transmission method via the path of the control plane. Alternatively, the number of repeated transmissions may be set differently depending on whether piggyback transmission is performed.

In addition, a mapping relationship between the size range of data and the number of repeated transmissions can be preset, and the number of repeated transmissions can be set according to the size range of data to which the current data belongs.

Method of repeated transmission of data based on the settings of the communication node

The minimum number of repeated transmissions and the maximum number of repeated transmissions can be preset in the network, or can be transmitted to the communication node through separate control signaling. The transmitting communication node can set the number of repeated transmissions to a multiple of the minimum number of repeated transmissions. Here, the set number of repeated transmissions can be less than or equal to the maximum number of repeated transmissions. In addition, the number of repeated transmissions can be variably set according to the capability of the communication node, the location of the communication node, MCS information, resource allocation information, the property of the service, the coverage of the service, the area of the service, the size of the data, etc.

Figure 14 is a timing diagram illustrating an embodiment of a method for repeatedly transmitting data.

Referring to FIG. 14, each of the transmitting communication node and the receiving communication node may be the base station, RSU, UE, OBU, etc. described above. T1 may indicate data to be transmitted initially, T2 may indicate data to be transmitted twice repeatedly, T3 may indicate data to be transmitted three times repeatedly, T4 may indicate data to be transmitted four times repeatedly, T5 may indicate data to be transmitted five times repeatedly, and T6 may indicate data to be transmitted six times repeatedly. Scheduling information of T1 (e.g., resource allocation information, MCS information, etc.) may be set by the communication node, or may be signaled to the communication node via a separate control message. When the scheduling information of T1 is determined, scheduling information of T2 (or, T3, T4, T5, T6, etc.) subsequent to T1 may be determined based on the scheduling information of T1.

The number of times data is repeatedly transmitted can be determined based on the method described above. The mapping relationship between the number of times of repeated transmission and other information, the transmission period of data, the initial transmission time, the time point of repeated transmission, the minimum number of times of repeated transmission, the maximum number of times of repeated transmission, the criteria for changing the number of times of repeated transmission (or, conditions, rules), the repeated transmission method, scheduling information, etc. can be defined as common parameters in the network, and can be set per specific service area (e.g., service area, cell, coverage, etc.), per group of communication nodes, or per communication node, and can be signaled to the communication node through system information, a dedicated control message, a MAC control PDU (protocol data unit), or a control field of a physical layer.

A transmitting communication node can repeatedly transmit data according to the number of repeated transmissions in a transmission period. A receiving communication node can receive data from the transmitting communication node, and perform demodulation/decoding on the received data by performing soft combining based on the minimum number of repeated transmissions in a transmission period. Meanwhile, even if the receiving communication node does not know the number of repeated transmissions, it can perform demodulation/decoding on the data by using a repeated reception technique. Here, the soft combining technique may include a chase combining technique, an IR (incremental redundancy) technique, etc. In addition, a technique for combining repeatedly transmitted data (or bits, symbols) (for example, a technique for transmitting a pattern of different parity bits or an RV of a CRC (cyclic redundancy check)) may be used to improve reception performance.

In Case 1, the data transmission method can be as follows:

In Case 1, the number of repetition transmissions can be 6. The transmitting communication node can repeatedly transmit data (T1, T2, T3, T4, T5, T6) 6 times in a transmission cycle. The receiving communication node can receive data (T1, T2, T3, T4, T5, T6) from the transmitting communication node, and perform demodulation/decoding on the received data (T1, T2, T3, T4, T5, T6) by performing soft combining based on the minimum number of repetition transmissions.

When the minimum number of repeated transmissions is 2, the receiving communication node can perform soft combining of two data units. The receiving communication node can check the CRC by performing soft combining for each of "T1, T2", "T3, T4", and "T5, T6". If the CRC result for the two data is "check good" (for example, if the channel state satisfies a preset criterion), the data can be transmitted to the upper layer.

On the other hand, if the CRC results for the two data are not "check good" (for example, if the channel status does not satisfy the preset criterion), the receiving communication node can perform soft combining on the soft combining results of "T1, T2" and "T3, T4", and can perform soft combining on the soft combining results of "T3, T4" and "T5, T6". If the CRC results for the four data are "check good", the data can be transmitted to the upper layer.

On the other hand, if the CRC results for the four data are not "check good", the receiving communication node can perform soft combining on the soft combining results of "T1, T2", the soft combining results of "T3, T4", and the soft combining results of "T5, T6". If the CRC results for the six data are "check good", the data can be transmitted to the upper layer. On the other hand, if the CRC results for the six data are not "check good", a message indicating a reception failure can be transmitted to the upper layer.

In cases 2 and 6, the data transmission method can be as follows:

In cases 2 and 6, the number of repetition transmissions can be 4. The transmitting communication node can transmit data (T1, T2, T3, T4) repeatedly 4 times in a transmission cycle. The receiving communication node can receive data (T1, T2, T3, T4) from the transmitting communication node, and perform demodulation/decoding on the received data (T1, T2, T3, T4) by performing soft combining based on the minimum number of repetition transmissions.

When the minimum number of repeated transmissions is 2, the receiving communication node can perform soft combining on two data units. The receiving communication node can check the CRC by performing soft combining on "T1, T2" and "T3, T4" respectively. If the CRC result for the two data is "check good", the data can be transmitted to the upper layer.

On the other hand, if the CRC results for two data are not "check good", the receiving communication node can perform soft combining on the soft combining results of "T1, T2" and the soft combining results of "T3, T4". If the CRC results for four data are "check good", the data can be transmitted to the upper layer. On the other hand, if the CRC results for four data are not "check good", a message indicating reception failure can be transmitted to the upper layer.

In cases 3, 4 and 5, the data transmission method can be as follows:

In cases 3, 4, and 5, the number of repetition transmissions can be 2. The transmitting communication node can transmit data (T1, T2) twice repeatedly in a transmission cycle. The receiving communication node can receive data (T1, T2) from the transmitting communication node, and perform demodulation/decoding on the received data (T1, T2) by performing soft combining based on the minimum number of repetition transmissions. When the minimum number of repetition transmissions is 2, the receiving communication node can perform soft combining in units of two data. The receiving communication node can check the CRC by performing soft combining on "T1, T2". If the CRC result for the two data is "check good", the data can be transmitted to the upper layer. On the other hand, if the CRC result for the two data is not "check good", a message indicating a reception failure can be transmitted to the upper layer.

The methods according to the present invention may be implemented in the form of program commands that can be executed through various computer means and recorded on a computer-readable medium. The computer-readable medium may include program commands, data files, data structures, etc., alone or in combination. The program commands recorded on the computer-readable medium may be those specially designed and configured for the present invention or may be known and available to those skilled in the art of computer software.

Examples of computer-readable media include hardware devices specifically configured to store and execute program instructions, such as ROM, RAM, and flash memory. Examples of program instructions include not only machine language codes generated by a compiler, but also high-level language codes that can be executed by a computer using an interpreter, etc. The above-described hardware devices can be configured to operate with at least one software module to perform the operations of the present invention, and vice versa.

Although the present invention has been described with reference to the above embodiments, it will be understood by those skilled in the art that various modifications and changes can be made to the present invention without departing from the spirit and scope of the present invention as set forth in the claims below.

Claims (20)

As an operation method of UE (user equipment) in a communication system,
A step of receiving a signaling message from a base station indicating a speed threshold, a first MCS (modulation and coding scheme) range to be used when the speed of the UE is above the speed threshold, and a second MCS range to be used when the speed of the UE is below the speed threshold;
A step of determining an MCS value within the first MCS range or the second MCS range based on the speed of the UE; and
A step of performing a transmission procedure using the determined MCS value is included.
A method of operating a UE, wherein each of the first MCS range and the second MCS range indicates minimum and maximum MCS values. delete In claim 1,
A method of operation of a UE, wherein the above transmission procedure is performed without scheduling of the base station. In claim 1,
A method of operation of a UE, wherein the signaling message further indicates a resource pool, and the transmission procedure is performed using the first MCS range or the second MCS range in the resource pool. In claim 4,
The steps for performing the above transmission procedure are:
a step of determining resources within the above resource pool; and
A method of operating a UE, comprising the step of performing the transmission procedure using the determined MCS value in the determined resources. In claim 4,
A method of operating a UE, wherein the above resource pool is used for the transmission procedure in a zone including one or more cells. As a method of operating a base station in a communication system,
Step of determining the speed threshold;
A step of determining a first MCS (modulation and coding scheme) range used when the speed of the UE (user equipment) is above the speed threshold and a second MCS range used when the speed of the UE is below the speed threshold;
generating a signaling message indicating the speed threshold, the first MCS range, and the second MCS range; and
Comprising the step of transmitting the signaling message to the UE,
A method of operating a base station, wherein each of the first MCS range and the second MCS range indicates minimum and maximum MCS values. delete In claim 7,
A method of operating a base station, wherein the signaling message further indicates a resource pool, and a transmission procedure is performed using the first MCS range or the second MCS range in the resource pool. In claim 9,
A method of operating a base station, wherein the above resource pool is used for the transmission procedure in a zone including one or more cells. In claim 9,
A method of operating a base station, wherein the above resource pool is set based on the speed of the UE. delete delete delete delete delete delete delete delete delete

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