WO2018084590A1

WO2018084590A1 - Method and device for transmitting sidelink channel busy ratio in wireless communication system

Info

Publication number: WO2018084590A1
Application number: PCT/KR2017/012314
Authority: WO
Inventors: 이영대; 이재욱
Original assignee: 엘지전자 주식회사
Priority date: 2016-11-03
Filing date: 2017-11-02
Publication date: 2018-05-11

Abstract

As a channel busy ratio (CBR) is defined to measure the congestion of a PC5 interface in order to support an effective vehicle-to-everything (V2X) communication, an eNodeB (eNB) transmits CBR information of a sidelink channel to a user equipment (UE) for each resource pool used for V2X communication. The user equipment which has received the CBR information determines if there is a usable CBR and, if it is determined that there is no usable CBR, can use the received CBR information.

Description

Method and apparatus for transmitting sidelink channel congestion rate in wireless communication system

The present invention relates to wireless communication, and more particularly, to a method and apparatus for transmitting a sidelink channel busy ratio (CBR) in a wireless communication system.

3rd generation partnership project (3GPP) long-term evolution (LTE) is a technology for enabling high-speed packet communication. Many approaches have been proposed to reduce the cost, improve service quality, expand coverage, and increase system capacity for LTE targets. 3GPP LTE is a high level requirement that requires cost per bit, improved service usability, flexible use of frequency bands, simple structure, open interface and proper power consumption of terminals.

LTE-based vehicle-to-everything (V2X) is urgently needed from the market, because the widespread LTE-based network offers the opportunity for the automotive industry to realize the concept of a "connected car." In particular, the market for vehicle-to-vehicle (V2V) communications is expected to have ongoing or initiated related activities, such as research projects, field testing and regulatory work, in some countries or regions, such as the United States, Europe, Japan, Korea, and China. do.

In response to this situation, 3GPP is actively researching and specification of LTE-based V2X. Among the LTE-based V2X, the discussion about PC5-based V2V is the top priority. It is possible to support V2V services based on LTE's PC5 interface with improvements in LTE sidelink (SL) resource allocation, physical hierarchy and synchronization.

In order to support effective V2X communication, a channel busy ratio (CBR) may be defined for congestion measurements on the PC5 interface. Various aspects are discussed in relation to CBR.

The present invention provides a method and apparatus for transmitting a sidelink channel busy ratio (CBR) in a wireless communication system. The present invention provides a method for a network to broadcast CBR information to all terminals in a cell. The present invention provides a method of using CBR information broadcasted from a network when a UE (UE) does not have CBR available.

In one aspect, a method for transmitting channel busy ratio (CBR) information by an eNB (eNodeB) in a wireless communication system is provided. The method includes transmitting CBR information of a sidelink channel to a user equipment (UE) for each resource pool used for vehicle-to-everything (V2X) communication.

In another aspect, a method of using channel busy ratio (CBR) information by a user equipment (UE) in a wireless communication system is provided. The method receives CBR information of a sidelink channel from an eNB (eNodeB) for each resource pool used for vehicle-to-everything (V2X) communication, determines whether there is an available CBR, and no CBR is available. If it is determined that includes the use of the received CBR information.

In another aspect, a user equipment (UE) in a wireless communication system is provided. The terminal includes a memory, a transceiver, and a processor connected to the memory and the transceiver. The processor controls the transceiver to receive channel busy ratio (CBR) information of a sidelink channel from an eNB (eNodeB) for each resource pool used for vehicle-to-everything (V2X) communication. It is determined whether there is a CBR, and if it is determined that there is no CBR available, the received CBR information is used.

By allowing all UEs in the cell to use CBR information, V2X transmission patterns / parameters can be effectively adjusted.

1 shows a structure of a 3GPP LTE system.

2 is a block diagram of a user plane protocol stack of an LTE system.

3 is a block diagram of a control plane protocol stack of an LTE system.

4 illustrates a method of transmitting CBR information by an eNB according to an embodiment of the present invention.

5 illustrates a method in which a UE uses CBR information according to an embodiment of the present invention.

6 illustrates a wireless communication system in which an embodiment of the present invention is implemented.

1 shows a structure of a 3GPP LTE system. Referring to FIG. 1, a 3GPP long-term evolution (LTE) system structure includes one or more user equipment (UE) 10, an evolved-UMTS terrestrial radio access network (E-UTRAN), and an evolved packet core (EPC). Include. The UE 10 is a communication device moved by a user. The UE 10 may be fixed or mobile and may be referred to by other terms such as a mobile station (MS), a user terminal (UT), a subscriber station (SS), and a wireless device.

The E-UTRAN includes one or more evolved NodeBs (eNBs) 20, and a plurality of UEs may exist in one cell. The eNB 20 provides an end point of a control plane and a user plane to the UE 10. The eNB 20 generally refers to a fixed station that communicates with the UE 10 and may be referred to in other terms, such as a base station (BS), an access point, and the like. One eNB 20 may be arranged per cell.

Hereinafter, downlink (DL) means communication from the eNB 20 to the UE 10. Uplink (UL) means communication from the UE 10 to the eNB 20. Sidelink (SL) means communication between the UE (10). In the DL, the transmitter may be part of the eNB 20 and the receiver may be part of the UE 10. In the UL, the transmitter may be part of the UE 10 and the receiver may be part of the eNB 20. In the SL, the transmitter and the receiver may be part of the UE 10.

The EPC includes a mobility management entity (MME) and a serving gateway (S-GW). The MME / S-GW 30 is located at the end of the network. The MME / S-GW 30 provides an end point of session and mobility management functionality for the UE 10. For convenience of description, the MME / S-GW 30 is simply expressed as a "gateway", which may include both the MME and the S-GW. A packet dana network (PDN) gateway (P-GW) may be connected to an external network.

The MME includes non-access stratum (NAS) signaling to the eNB 20, NAS signaling security, access stratum (AS) security control, inter CN (node network) signaling for mobility between 3GPP access networks, idle mode terminal reachability ( Control and execution of paging retransmission), tracking area list management (for UEs in idle mode and activation mode), P-GW and S-GW selection, MME selection for handover with MME change, 2G or 3G 3GPP access Bearer management features, including roaming, authentication, and dedicated bearer setup, selection of a serving GPRS support node (SGSN) for handover to the network, public warning system (ETWS) and earthquake and tsunami warning system (CMAS) It provides various functions such as message transmission support. S-GW hosts can be based on per-user packet filtering (eg, through deep packet inspection), legal blocking, terminal IP (Internet protocol) address assignment, transport level packing marking in DL, UL / DL service level charging, gating and It provides various functions of class enforcement, DL class enforcement based on APN-AMBR (access point name aggregate maximum bit rate).

An interface for user traffic transmission or control traffic transmission may be used. The UE 10 and the eNB 20 are connected by a Uu interface. The UEs 10 are connected by a PC5 interface. The eNBs 20 are connected by an X2 interface. The neighboring eNB 20 may have a mesh network structure by the X2 interface. The eNB 20 and the gateway 30 are connected through an S1 interface.

2 is a block diagram of a user plane protocol stack of an LTE system. 3 is a block diagram of a control plane protocol stack of an LTE system. The layer of the air interface protocol between the UE and the E-UTRAN is based on the lower three layers of the open system interconnection (OSI) model, which is well known in communication systems. Hierarchical).

The physical layer (PHY) belongs to L1. The physical layer provides an information transmission service to a higher layer through a physical channel. The physical layer is connected to a higher layer of a media access control (MAC) layer through a transport channel. Physical channels are mapped to transport channels. Data is transmitted between the MAC layer and the physical layer through a transport channel. Data is transmitted over a physical channel between different physical layers, that is, between a physical layer of a transmitter and a physical layer of a receiver.

The MAC layer, radio link control (RLC) layer, and packet data convergence protocol (PDCP) layer belong to L2. The MAC layer provides a service to an RLC layer, which is a higher layer, through a logical channel. The MAC layer provides data transfer services on logical channels. The RLC layer supports reliable data transmission. Meanwhile, the function of the RLC layer may be implemented as a functional block inside the MAC layer, in which case the RLC layer may not exist. The PDCP layer introduces an IP packet, such as IPv4 or IPv6, over a relatively low bandwidth air interface to provide header compression that reduces unnecessary control information so that the transmitted data is transmitted efficiently.

The radio resource control (RRC) layer belongs to L3. The RRC layer at the bottom of L3 is defined only in the control plane. The RRC layer is responsible for the control of logical channels, transport channels, and physical channels in connection with configuration, re-configuration, and release of radio bearers (RBs). RB means a service provided by L2 for data transmission between the UE and the E-UTRAN.

Referring to FIG. 2, the RLC and MAC layers (end at the eNB at the network side) may perform functions such as scheduling, ARQ, and hybrid automatic repeat request (HARQ). The PDCP layer (terminating at the eNB at the network side) may perform user plane functions such as header compression, integrity protection and encryption.

Referring to FIG. 3, the RLC / MAC layer (end at eNB at network side) may perform the same functions for the control plane. The RRC layer (terminated at the eNB at the network side) may perform functions such as broadcast, paging, RRC connection management, RB control, mobility functionality, and UE measurement reporting and control. The NAS control protocol (terminated at the gateway's MME at the network side) may perform functions such as SAE bearer management, authentication, LTE_IDLE mobility management, paging start in LTE_IDLE, and security control for signaling between the gateway and the UE.

The physical channel transmits signaling and data between the physical layer of the UE and the physical layer of the eNB through radio resources. The physical channel is composed of a plurality of subframes in the time domain and a plurality of subcarriers in the frequency domain. One subframe of 1ms consists of a plurality of symbols in the time domain. A specific symbol of the corresponding subframe, for example, the first symbol of the subframe may be used for the PDCCH. The PDCCH may carry dynamically allocated resources, such as a physical resource block (PRB) and modulation and coding schemes (MCS).

The DL transport channel is a broadcast channel (BCH) used for transmitting system information, a paging channel (PCH) used for paging a UE, and a downlink shared channel (DL-SCH) used for transmitting user traffic or control signals. , Multicast channel (MCH) used for multicast or broadcast service transmission. The DL-SCH supports dynamic link adaptation and dynamic / semi-static resource allocation by varying HARQ, modulation, coding and transmit power. In addition, the DL-SCH may enable the use of broadcast and beamforming throughout the cell.

The UL transport channel generally includes a random access channel (RACH) used for initial access to a cell, an uplink shared channel (UL-SCH) used for transmitting user traffic or control signals. The UL-SCH supports dynamic link adaptation with HARQ and transmit power and potential changes in modulation and coding. In addition, the UL-SCH may enable the use of beamforming.

Logical channels are classified into control channels for information transmission in the control plane and traffic channels for information transmission in the user plane according to the type of information to be transmitted. That is, a set of logical channel types is defined for different data transfer services provided by the MAC layer.

The control channel is used only for conveying information in the control plane. The control channel provided by the MAC layer includes a broadcast control channel (BCCH), a paging control channel (PCCH), a common control channel (CCCH), a multicast control channel (MCCH), and a dedicated control channel (DCCH). BCCH is a DL channel for broadcasting system control information. PCCH is a DL channel for the transmission of paging information, and is used when the network does not know the location of the cell unit of the UE. CCCH is used by the UE when it does not have an RRC connection with the network. The MCCH is a one-to-many DL channel used for transmitting multimedia broadcast multicast services (MBMS) control information from the network to the UE. DCCH is a one-to-one bidirectional channel used by a UE having an RRC connection for transmission of dedicated control information between the UE and the network.

The traffic channel is used only for conveying information in the user plane. The traffic channel provided by the MAC layer includes a dedicated traffic channel (DTCH) and a multicast traffic channel (MTCH). DTCH is used for transmission of user information of one UE on a one-to-one channel and may exist in both UL and DL. MTCH is a one-to-many DL channel for transmitting traffic data from the network to the UE.

The UL connection between the logical channel and the transport channel includes a DCCH that can be mapped to the UL-SCH, a DTCH that can be mapped to the UL-SCH, and a CCCH that can be mapped to the UL-SCH. The DL connection between logical channel and transport channel is BCCH which can be mapped to BCH or DL-SCH, PCCH which can be mapped to PCH, DCCH which can be mapped to DL-SCH, DTCH which can be mapped to DL-SCH, MCH MCCH that can be mapped to and MTCH that can be mapped to MCH.

The RRC state indicates whether the RRC layer of the UE is logically connected with the RRC layer of the E-UTRAN. The RRC state may be divided into two types, such as an RRC connected state (RRC_CONNECTED) and an RRC idle state (RRC_IDLE). In RRC_IDLE, while the UE designates a discontinuous reception (DRX) set by the NAS, the UE may receive a broadcast of system information and paging information. In addition, the UE may be assigned an ID for uniquely designating the UE in the tracking area, and perform public land mobile network (PLMN) selection and cell reselection. Also in RRC_IDLE, no RRC context is stored at the eNB.

In RRC_CONNECTED, it is possible for the UE to have an E-UTRAN RRC connection and context in the E-UTRAN to send data to the eNB and / or receive data from the eNB. In addition, the UE may report channel quality information and feedback information to the eNB. In RRC_CONNECTED, the E-UTRAN may know the cell to which the UE belongs. Therefore, the network may transmit data to and / or receive data from the UE, and the network may inter-RAT with a GSM EDGE radio access network (GERAN) through the UE's mobility (handover and network assisted cell change (NACC). radio access technology (cell change indication), and the network may perform cell measurement for a neighboring cell.

In RRC_IDLE, the UE specifies a paging DRX cycle. Specifically, the UE monitors a paging signal at a specific paging occasion for each UE specific paging DRX cycle. Paging opportunity is the time period during which the paging signal is transmitted. The UE has its own paging opportunity. The paging message is transmitted on all cells belonging to the same tracking area (TA). When a UE moves from one TA to another TA, the UE may send a tracking area update (TAU) message to the network to update its location.

Sidelinks are described. Sidelink is an interface between UEs for sidelink communication and sidelink discovery. Sidelinks correspond to PC5 interfaces. Sidelink communication is an AS feature that enables two or more neighboring UEs to directly communicate Proximity-based services (ProSe) using E-UTRA technology without going through any network node. Sidelink discovery is an AS feature that allows two or more neighboring UEs to directly discover ProSe using E-UTRA technology without going through any network node.

The sidelink physical channel includes a physical sidelink broadcast channel (PSBCH) for transmitting system and synchronization related information transmitted from the UE, a physical sidelink discovery channel (PSCH) for transmitting a sidelink discovery message transmitted from the UE, and a side transmitted from the UE. A physical sidelink control channel (PSCCH) for transmitting a control signal for link communication and a physical sidelink shared channel (PSSCH) for transmitting data for sidelink communication transmitted from a UE. Sidelink physical channels are mapped to sidelink transport channels. PSBCH is mapped to a sidelink broadcast channel (SL-BCH). The PSDCH is mapped to a sidelink discovery channel (SL-DCH). PSSCH is mapped to a sidelink shared channel (SL-SCH).

In sidelinks, logical channels are classified into control channels for information transmission in the control plane and traffic channels for information transmission in the user plane. The sidelink control channel includes a sidelink broadcast control channel (SBCCH), which is a sidelink channel for broadcasting sidelink system information from one UE to another UE. SBCCH is mapped to SL-BCH. The sidelink traffic channel includes a sidelink traffic channel (STCH), which is a point-to-multipoint channel for the transmission of user information from one UE to another. STCH is mapped to SL-SCH. This channel can only be used by UEs capable of sidelink communication.

Sidelink communication is a communication mode in which a UE can communicate directly via a PC5 interface. This communication mode is supported when the UE is served by the E-UTRAN and when the UE is outside of E-UTRA coverage. Only UEs authorized to be used for public safety tasks can perform sidelink communication.

The UE supporting sidelink communication may operate in the following two modes for resource allocation. The first mode is scheduled resource allocation. Scheduled resource allocation may be called mode 1. In mode 1, the UE needs to be in RRC_CONNECTED to send data. The UE requests a transmission resource from the eNB. The eNB schedules transmission resources for the transmission of sidelink control information (SCI) and data. The UE transmits a scheduling request (dedicated scheduling request (D-SR) or random access) to the eNB and then sends a sidelink buffer status report (BSR). Based on the sidelink BSR, the eNB can determine that the UE has data for sidelink communication transmission and can estimate the resources required for transmission. The eNB may schedule transmission resources for sidelink communication using the configured sidelink radio network temporary identity (SL-RNTI).

The second mode is UE autonomous resource selection. UE autonomous resource selection may be referred to as mode 2. In mode 2, the UE itself selects a resource from a resource pool, and selects a transmission format for transmitting sidelink control information and data. There may be up to eight resource pools preconfigured for out of coverage operations or provided by RRC signaling for in-coverage operations. Each resource pool may be associated with one or more ProSe per-packet priorities (PPPPs). For transmission of a MAC protocol data unit (PDU), the UE selects a resource pool that has one of the same PPPPs as that of the logical channel having the highest PPPP among the logical channels identified in the MAC PDU. Sidelink control pools and sidelink data pools are associated one-to-one. If a resource pool is selected, the selection is valid for the entire sidelink control period. After the sidelink control period ends, the UE may select the resource pool again.

The UE is considered to be in coverage for sidelink communication whenever it detects a cell on a public safety ProSe carrier. If the UE is out of coverage for sidelink communication, the UE may only use mode 2. If the UE is in coverage for sidelink communication, mode 1 or mode 2 may be used depending on the eNB configuration. If the UE is in coverage for sidelink communication, the UE should only use mode 1 indicated by the eNB configuration, unless one of the exceptional cases occurs. If an exception occurs, the UE may temporarily use mode 2, even if it is configured to use mode 1. The resource pool to be used in exceptional cases may be provided by the eNB.

The cell of the public safety ProSe carrier may select one of the following two options. First, a cell of a public safety ProSe carrier may provide a transmission resource pool for mode 2 in SIB18. A UE that is allowed side link communication may use this resource for side link communication in RRC_IDLE in a cell of the same carrier (ie, public safety ProSe carrier). A UE authorized for sidelink communication may use this resource for sidelink communication in RRC_IDLE or RRC_CONNECTED in a cell of another carrier.

Alternatively, the cell of the public safety ProSe carrier may indicate that the SIB18 supports sidelink communication but does not provide a transmission resource. The UE needs to enter RRC_CONNECTED to perform sidelink communication transmission. In this case, the cell of the public safety ProSe carrier may provide an exceptional transmission resource pool for mode 2 to be used by the UE as a broadcast signal in exceptional cases. The UE of RRC_CONNECTED authorized to perform sidelink communication transmission instructs the serving eNB that it wants to perform sidelink communication transmission. The eNB uses the UE context received from the MME to verify whether the UE is authorized for side link communication transmission. The eNB may configure the UE by dedicated signaling with a transmission resource pool for mode two. This resource can be used without limitation while the UE is in RRC_CONNECTED. Alternatively, the eNB may configure the UE to use the exceptional transmission resource pool for mode 2 which the UE is allowed to use only in exceptional cases, otherwise it depends on mode 1.

When the UE is out of coverage for sidelink communication, the set of transmit and receive resource pools for sidelink control information is preconfigured in the UE. When the UE is in coverage for sidelink communication, the resource pool for sidelink control information is configured as follows. The resource pool used for reception is configured by the eNB via RRC in broadcast signaling. The resource pool used for transmission is configured by the eNB via RRC in dedicated or broadcast signaling when mode 2 is used and by the eNB via RRC in dedicated signaling when mode 1 is used. The eNB schedules a specific resource for sidelink control information transmission in the configured reception pool.

When the UE is out of coverage for sidelink communication, the set of transmit and receive resource pools for sidelink data is preconfigured in the UE. When the UE is in coverage for sidelink communication, the resource pool for sidelink data is configured as follows. When mode 2 is used, the resource pool used for transmission and reception is configured by the eNB via RRC in dedicated or broadcast signaling. If mode 1 is configured, there is no resource pool for transmission and reception.

Sidelink discovery is defined as the procedure used by a UE that supports sidelink discovery to discover other UEs in proximity using E-UTRA direct radio signals over PC5. Sidelink discovery is supported both when the UE is served by the E-UTRAN and when the UE is out of E-UTRA coverage. Outside the E-UTRA range, only ProSe-enabled public safety UEs can perform sidelink discovery. For public safety sidelink discovery, the allowed frequencies are preconfigured at the UE and are used even if the UE is out of range of E-UTRA at that frequency. The preconfigured frequency is the same frequency as the public safety ProSe carrier.

There are two types of resource allocation in discovery message notifications. The first is UE autonomous resource selection, which is a resource allocation procedure in which resources for advertising discovery messages are allocated on a non-UE specific basis. UE autonomous resource selection may be referred to as type 1. In type 1, the eNB provides the UE with a resource pool configuration used for the announcement of the discovery message. The configuration may be signaled by broadcast or dedicated signaling. The UE autonomously selects a radio resource from the indicated resource pool and announces a discovery message. The UE may announce a discovery message on a randomly selected discovery resource during each discovery period.

The second is scheduled resource allocation, which is a resource allocation procedure in which resources for advertising discovery messages are allocated on a UE specific basis. Scheduled resource allocation may be referred to as type 2. In type 2, a UE of RRC_CONNECTED may require a resource to announce a discovery message from an eNB via RRC. The eNB allocates resources via RRC. Resources are allocated within resource pools configured in the UE for notification.

For the UE in RRC_IDLE, the eNB may select one of the following options. The eNB may provide a resource pool for type 1 based discovery message notification in SIB19. UE authorized for sidelink discovery uses this resource to announce a discovery message in RRC_IDLE. Or, the eNB may indicate that it supports sidelink discovery in SIB19 but does not provide resources for discovery message notification. The UE needs to enter RRC_CONNECTED to request resources for discovery message notification.

For a UE in RRC_CONNECTED, the UE authorized to perform sidelink discovery announcement instructs the eNB that it wants to perform sidelink discovery announcement. The UE may also inform the eNB of the desired frequency for sidelink discovery announcement. The eNB uses the UE context received from the MME to verify whether the UE is authorized for sidelink discovery announcement. The eNB may configure a type 1 resource pool for discovery message notification in the UE through dedicated signaling. The eNB may configure a resource pool in the form of time and frequency index with dedicated resources through dedicated RRC signaling for discovery message notification. Resources allocated by the eNB via dedicated signaling are valid until the eNB reconfigures the resources by RRC signaling or the UE enters RRC_IDLE.

Authorized receiving UEs in RRC_IDLE and RRC_CONNECTED monitor the type 1 resource pool and the type 2 resource pool. The eNB provides a resource pool configuration used for monitoring in-band, inter-frequency discovery message of the same or another PLMN cell in RRC signaling (SIB19). RRC signaling (SIB19 or dedicated) may include a detailed sidelink discovery configuration used for the announcement of sidelink discovery in a cell within frequency, between frequencies of the same or different PLMNs.

Describes vehicle-to-everything (V2X) communication. There are four types of V2X communications: vehicle-to-vehicle (V2V) communications, vehicle-to-infrastructure (V2I) communications, vehicle-to-network (V2N), and vehicle-to-pedestrian (V2P) communications. These four types of V2X can use "collaboration consciousness" to provide more intelligent services for end users. This allows vehicle, road side unit (RSU) and transportation entities such as pedestrians to collect knowledge about their local environment (for example, information received from other vehicles or sensor equipment in close proximity), and can be used for collaborative collision alerts or autonomous driving. This means that knowledge can be processed and shared to provide intelligent services.

V2X service is a type of communication service that includes a transmitting or receiving UE using a V2V application over 3GPP transmission. The V2X service may be divided into a V2V service, a V2I service, a V2P service, and a V2N service according to the counterparticipant in the communication. V2V service is a type of V2X service that is a UE that uses V2V applications on both sides of the communication. A V2I service is a type of V2X service that uses a V2I application, with one side of communication being a UE and the other side being an RSU. The RSU is an entity supporting a V2I service that can transmit / receive with a UE using a V2I application. RSU is implemented in an eNB or a fixed UE. V2P service is a type of V2X service that is a UE that uses V2P applications on both sides of the communication. A V2N service is a type of V2X service in which one side of communication is a UE and the other is a serving entity, all using V2N applications and communicating with each other via an LTE network entity.

In V2V, the E-UTRAN allows UEs in close proximity to each other to exchange V2V related information using E-UTRA (N) when permit, authorization and proximity criteria are met. Proximity criteria may be configured by a mobile network operator (MNO). However, the UE supporting the V2V service may exchange such information when it is provided or not provided by the E-UTRAN supporting the V2X service. The UE supporting the V2V application sends application layer information (eg, about its location, dynamics and attributes as part of the V2V service). The V2V payload must be flexible to accommodate different content, and information can be sent periodically depending on the configuration provided by the MNO. V2V is mainly broadcast based. V2V includes the direct exchange of V2V related application information between different UEs, and / or due to the limited direct communication range of V2V, V2V is an infrastructure supporting V2X service for V2V related application information between different UEs (eg For example, the exchange through the RSU, application server, etc.).

In V2I, the UE supporting the V2I application transmits application layer information to the RSU. The RSU transmits application layer information to the UE supporting the UE group or the V2I application.

In V2P, the E-UTRAN allows UEs in close proximity to each other to exchange V2P related information using the E-UTRAN when permit, authorization and proximity criteria are met. Proximity criteria may be constructed by the MNO. However, the UE supporting the V2P service may exchange this information even when not serviced by the E-UTRAN supporting the V2X service. The UE supporting the V2P application transmits application layer information. Such information may be broadcast by vehicle UEs (eg, alerting pedestrians) that support V2X services and / or pedestrian UEs (eg, alerting vehicles) that support V2X services. V2P involves exchanging V2V related application information directly between different UEs (one vehicle, another pedestrian), and / or due to the limited direct communication range of V2P, V2P is a V2P related application between different UEs. This involves exchanging information through infrastructures that support V2X services (eg, RSUs, application servers, etc.).

In V2X communication, messages such as common awareness messages (CAM), decentralized environmental notification messages (DENM), or basic safety messages (BSM) may be transmitted. The CAM includes information such as the type, location, speed, and direction of the vehicle, and can be broadcast periodically by all vehicles. The DENM includes information on a type of a specific event, a region in which a specific event occurs, and may be broadcast by an RSU or a vehicle. The BSM is included in the US J2735 safety message and has similar characteristics to CAM. BSM can provide emergency brake warnings, forward collision warnings, intersection safety assistance, blind spot and lane change warnings, overtaking warnings, and out of control warnings.

Support for V2X services over the PC5 interface is provided by V2X sidelink communication, a communication mode in which the UE can communicate directly over the PC5 interface. This communication mode is supported when the UE is served by the E-UTRAN and when the UE is outside of E-UTRA coverage. Only UEs authorized for V2X service can perform V2X sidelink communication.

User plane protocol stacks and functions for sidelink communication are also used for V2X sidelink communication. In the case of V2X sidelink communication, the STCH for sidelink communication is also used for V2X sidelink communication. Also, non-V2X (eg, public safety) data is not multiplexed with V2X data transmitted on resources configured for V2X sidelink communication. Control plane protocol stacks and functionality for SBCCH for sidelink communication are also used for V2X sidelink communication.

UE supporting V2X sidelink communication may operate in two modes for resource allocation. The first mode is scheduled resource allocation. Scheduled resource allocation for V2X sidelink communication may be referred to as mode 3. The UE needs to be in RRC_CONNECTED to send data. The UE requests a transmission resource from the eNB. The eNB schedules transmission resources for transmission of side link control information and data. The second mode is UE autonomous resource selection. UE autonomous resource selection for V2X sidelink communication may be referred to as mode 4. In order to transmit the sidelink control information and data, the UE selects a resource from a resource pool by itself and performs a transmission format selection. When the mapping between the zone and the V2X sidelink transmission resource pool is configured, the UE selects the V2X sidelink resource pool based on the region where the UE is located.

The UE performs sensing for (re) selection of sidelink resources. Based on the detection result, the UE (re) selects a particular sidelink resource and reserves a plurality of sidelink resources. Up to two parallel and independent resource reservation processes are allowed to be performed by the UE. The UE is also allowed to perform a single resource selection for V2X sidelink transmission. The geographic area may be configured or preconfigured by the eNB. Once the region is constructed, the world is divided into geographical regions using a single fixed reference point (ie, geographic coordinates (0, 0)), length, and width. The UE determines the region ID by the length and width of each region, the number of regions by length and width, and a modulo operation using a single fixed reference point. The length and width of each area, the number of areas by length and width, are provided by the eNB when the UE is in coverage, and preconfigured when the UE is out of coverage. The area is configurable for both UEs in coverage and UEs out of coverage. For a UE in coverage, when the UE uses UE autonomous resource selection (ie mode 4), the eNB may provide a mapping between the region and the V2X sidelink transmission resource pool in SIB21. For a UE that is out of coverage, the mapping between the region and the V2X sidelink transmission resource pool may be preconfigured. If the mapping between the region and the V2X sidelink transmission resource pool is (pre) configured, the UE selects the sidelink transmission resource from the resource pool corresponding to the region where it is currently located. The realm concept does not apply to receive pools, but also to exceptional V2X sidelink transport pools. Resource pools for V2X sidelink communication are not configured based on priority.

For V2X sidelink transmission, a transmission resource pool configuration including an exceptional transmission resource pool for the target cell may be signaled via a handover command to reduce transmission interruption during handover. Accordingly, as long as synchronization with the target cell is performed, the UE may use the sidelink transmission resource pool of the target cell before handover is completed. If an exceptional transmission resource pool is included in the handover command, the UE starts using the resource randomly selected from the exceptional transmission resource pool starting from the receipt of the handover command. If the UE is configured with scheduled resource allocation in the handover command (ie mode 3), the UE continues to use the exceptional transmission resource pool while the timer associated with the handover is running. If the UE is configured for UE autonomous resource selection (ie mode 4) in the target cell, the UE continues to use the exceptional transmission resource pool until the initial detection of the transmission resource pool for UE autonomous resource selection is completed. In exceptional cases (e.g. during a radio link failur (RLF), during a transition from RRC_IDLE to RRC_CONNECTED, or during a change of the dedicated sidelink resource pool in the cell), the UE provides an exception provided in SIB21 of the serving cell based on the detection You can select a resource from the transport resource pool and use it temporarily. In order to avoid an interruption time of V2X message reception due to a delay in acquiring the broadcast reception pool from the target cell, the synchronization configuration for the target cell and the reception resource pool configuration may be signaled to the UE of RRC_CONNECTED in the handover command. For the UE of RRC_IDLE, it is up to the UE implementation to minimize the sidelink transmit / receive downtime associated with SIB21 acquisition of the target cell. Whenever a UE detects a cell on a carrier used for V2X sidelink communication, the UE is considered to be in coverage on that carrier. If a UE authorized for V2X sidelink communication is in coverage for V2X sidelink communication, the UE may use scheduled resource allocation (ie mode 3) or UE autonomous resource selection (ie mode 4) depending on the eNB configuration. have. When the UE is out of coverage for V2X sidelink communication, the set of transmit and receive resource pools for data is preconfigured at the UE. V2X sidelink communication resources are not shared with other non-V2X applications that are sent over the sidelink.

The UE of RRC_CONNECTED may transmit a sidelink UE information message to the serving cell if it is interested in V2X communication transmission to request sidelink resources. If the UE is configured by a higher layer to receive V2X communication and PC5 resources are provided, the UE receives the configured resources.

The serving cell may provide a synchronization configuration for half-carriers used for V2X sidelink communication. In this case, the UE follows the synchronization configuration received from the serving cell. If no cell is detected on the carrier used for V2X sidelink communication and the UE does not receive the synchronization configuration from the serving cell, the UE follows the preconfigured synchronization configuration. There are three types of synchronization criteria: eNB, UE, and global navigation satellite system (GNSS). When the GNSS is configured as a synchronization source, the UE uses coordinated universal time (UTC) time to calculate the direct frame number and subframe number. When eNB timing is configured as a synchronization criterion for a UE for a dedicated carrier for V2X, the UE follows the PCell (RRC_CONNECTED) / Serving Cell (RRC_IDLE) for synchronization and DL measurement.

In order to support effective V2X sidelink communication, a channel busy ratio (CBR) can be defined for congestion measurements on PC5. The CBR may be defined as the ratio of the portion of the subchannel where the sidelink received signal strength indicator (S-RSSI) observed during a particular time period (eg, 100 ms) exceeds a (pre) configured threshold. Only subchannels included in the resource pool can be used for CBR measurement. For the UE in mode 3, the eNB may indicate the set of resources for the UE to perform CBR measurement. For a UE of mode 4, CBR measurement may be performed resource-specifically. The UE may perform CBR measurements on at least the current transmission resource pool, that is, the transmission resource pool used to perform the current V2X sidelink communication. Whether the UE will perform CBR measurement on a transmission resource pool other than the current transmission resource pool is under discussion. In addition, the UE may report the result of the CBR measurement to the eNB.

Hereinafter, various operations of the UE or the network in relation to the CBR according to various embodiments of the present invention are proposed.

1. CBR Information Broadcast

There may be a situation in which the UE cannot use CBR information on the current transmission resource pool as follows.

1) When the UE performs CBR measurement only on the current transmission resource pool and the transmission resource pool changes as the UE moves

2) When the UE changes the serving cell and does not perform CBR measurement before changing the serving cell

3) For pedestrian UEs (P-UEs) without detection capability

If the UE cannot use the CBR information for the current transmission resource pool, the transmission pattern and / or parameters for the V2X communication may not be adjusted. As a result, a UE with available CBR information may not be preferred over a UE with low priority traffic and no available CBR information. Therefore, in order to apply the adjustment of transmission pattern / parameters for V2X communication to all UEs fairly, it is necessary to make CBR information available to all UEs in a cell.

4 illustrates a method of transmitting CBR information by an eNB according to an embodiment of the present invention. In step S100, the eNB broadcasts the CBR information of the sidelink channel to the UE in the cell for each resource pool used for V2X communication. The CBR information may include a CBR value expressed as a percentage between 0 and 100. The CBR value may have a value in x units from 0 to 100. For example, when x = 10, the CBR value may be any one of {0, 10, 20 ... 100}. In addition, the CBR information may include associated resource pool ID information.

The CBR information may be broadcasted through a system information block type (SIB) 21 for V2X sidelink communication. Or, if the update frequency of the CBR information is different from the existing information included in the SIB21, it may be broadcasted through the new SIB.

5 illustrates a method in which a UE uses CBR information according to an embodiment of the present invention. In step S200, the UE receives the CBR information of the sidelink channel from the eNB for each resource pool used for V2X communication. In step S210, the UE determines whether there is an available CBR. If it is determined that there is no CBR available, in step S220, the UE uses the received CBR information. If it is determined that there is available CBR, the UE may ignore the received CBR information.

The CBR information may include a CBR value expressed as a percentage between 0 and 100. The CBR value may have a value in x units from 0 to 100. For example, when x = 10, the CBR value may be any one of {0, 10, 20 ... 100}. In addition, the CBR information may include associated resource pool ID information. In addition, the CBR information may be received through SIB 21 for V2X sidelink communication. Alternatively, if the update frequency of the CBR information is different from the existing information included in SIB21, it may be received through a new SIB.

2. Configure and report CBR reporting

Step 1: The network configures the CBR reporting configuration. The CBR reporting configuration may include information about a measurement target. The information on the measurement target may be a resource pool ID including an exceptional resource pool.

The CBR reporting configuration may be configured for each UE, for each resource pool, or for each priority. CBR reporting may be triggered by an event and reported, or may be reported periodically. The trigger type of such CBR reporting may be configured for each resource pool or for each priority.

When CBR reporting is triggered by an event, the following event can be defined.

Event 1: The CBR of the current resource pool is above the provided CBR level + offset.

Event 2: The CBR of the current resource pool is above the provided CBR level-offset.

Event 3: The CBR of the current resource pool is higher or lower than the last reported CBR value for that resource pool.

The CBR level may be provided in dedicated signaling or broadcast signaling. The provided CBR level may be the CBR level of the current resource pool. If the CBR level is not provided in dedicated signaling, the UE may use the CBR information provided through broadcast signaling. The offset may also be provided via dedicated signaling or broadcast signaling. In addition, the CBR level may be provided through broadcast signaling, and the offset may be configured through dedicated signaling.

In addition, when CBR reporting is triggered by an event, the CBR reporting configuration may include information on a time to trigger (TTT). This indicates the time interval that a particular criterion for the event that triggers the CBR report should be satisfied. The trigger time may be configured for each UE, for each resource pool, or for each priority.

If CBR reporting is reported periodically, a periodic reporting timer may be configured for each UE, for each resource pool, or for each priority. When the timer value is configured for each resource pool or priority, different timers may be executed for each resource pool or priority.

In the above description, the priority may be ProSe per-packet-priority (PPPP).

(2) Step 2: The UE performs CBR measurement on the measurement target configured using the relevant parameter (eg, TTT). The UE triggers a measurement report when an event for a resource pool or priority is met or a periodic timer expires.

3. CBR-based path switching

If the congestion of the sidelinks is high, it may not be possible to adjust the transmission pattern. In this case, it may be desirable to switch traffic transmission from sidelink (ie, PC5 interface) to uplink (Uu interface). For the UE of RRC_CONNECTED, the network may control the path of the UE based on the reported CBR information. If the network determines that the sidelink is highly overloaded, the network may release dedicated sidelink resources configured to allow the UE to transmit traffic on the uplink.

On the other hand, for the UE of RRC_IDLE, there should be a clear criterion for switching between sidelink and uplink. Otherwise, the UE will not impose a penalty on itself to mitigate congestion. The UE will not change the transmission pattern, thus congestion may not be improved. To avoid this phenomenon, it is necessary for the network to provide an explicit criterion for the UE of RRC_IDLE to switch from sidelink to uplink.

The detailed method of performing CBR-based path switching is as follows. It is assumed here that the UE is currently using sidelinks.

(1) Step 1: The UE performs CBR measurement on the current transmission resource pool and / or the resource pool provided by broadcast / dedicated signaling. The UE may start performing CBR measurement after receiving resource pool information to be measured in step 2 to be described later.

(2) Step 2: The network provides CBR level information through broadcast / dedicated signaling. The CBR level information includes at least one of the following information.

CBR value to allow UE to switch to uplink

-Allowed interface (sidelink, uplink or both) and CBR range information for transmission / reception;

A resource pool identity associated with the CBR value or the CBR range information

If the resource pool information is provided and the UE uses the resource pool, the UE may apply the relevant CBR value or CBR range for the resource pool.

(3) Step 3: If the CBR measurement result of the UE is equal to or greater than the CBR value, the UE triggers establishment of an RRC connection. Specifically, the AS layer of the UE may inform the upper layer (eg, the NAS layer) of the need for switching to uplink, and the NAS layer of the UE may trigger establishment of an RRC connection. If the CBR of the current transmission resource pool is within one CBR range, the AS layer of the UE may inform the upper layer of the allowed interface and the upper layer may determine a path. As a result, the path may be switched to uplink for transmission / reception.

The eNB 800 includes a processor 810, a memory 820, and a transceiver 830. Processor 810 may be configured to implement the functions, processes, and / or methods described herein. Layers of the air interface protocol may be implemented by the processor 810. The memory 820 is connected to the processor 810 and stores various information for driving the processor 810. The transceiver 830 is connected to the processor 810 to transmit and / or receive a radio signal.

The UE 900 includes a processor 910, a memory 920, and a transceiver 930. Processor 910 may be configured to implement the functions, processes, and / or methods described herein. Layers of the air interface protocol may be implemented by the processor 910. The memory 920 is connected to the processor 910 and stores various information for driving the processor 910. The transceiver 930 is connected to the processor 910 to transmit and / or receive a radio signal.

Processors

810 and 910 may include application-specific integrated circuits (ASICs), other chipsets, logic circuits, and / or data processing devices. The

memories

820 and 920 may include read-only memory (ROM), random access memory (RAM), flash memory, memory cards, storage media and / or other storage devices. The

transceivers

830 and 930 may include a baseband circuit for processing radio frequency signals. When the embodiment is implemented in software, the above-described technique may be implemented as a module (process, function, etc.) for performing the above-described function. The module may be stored in the

memory

820, 920 and executed by the

processor

810, 910. The

memories

820 and 920 may be inside or outside the

processors

810 and 910, and may be connected to the

processors

810 and 910 by various well-known means.

In the exemplary system described above, methods that may be implemented in accordance with the above-described features of the present invention have been described based on a flowchart. For convenience, the methods have been described as a series of steps or blocks, but the claimed features of the present invention are not limited to the order of steps or blocks, and certain steps may occur in the same order as other steps and in a different order than described above. In addition, those skilled in the art will appreciate that the steps shown in the flowcharts are not exclusive and that other steps may be included or one or more steps in the flowcharts may be deleted without affecting the scope of the present invention.

Claims

In the method for transmitting channel busy ratio (CBR) information by the eNB (eNodeB) in a wireless communication system,

A method comprising transmitting CBR information of a sidelink channel to a user equipment (UE) for each resource pool used for vehicle-to-everything (V2X) communication.
The method of claim 1,

The CBR information includes a CBR value expressed as a percentage between 0 and 100.
The method of claim 2,

The CBR value is a ratio of a portion of a subchannel in which a sidelink received signal strength indicator (S-RSSI) exceeds a threshold for a specific time interval.
The method of claim 1,

The CBR information includes information about an identity of the resource pool.
The method of claim 1,

The CBR information is broadcast and transmitted to all terminals in the cell through a system information block type (SIB) 21 for the V2X communication.
In a method of using channel busy ratio (CBR) information by a user equipment (UE) in a wireless communication system,

Receiving CBR information of a sidelink channel from an eNB (eNodeB) for each resource pool used for vehicle-to-everything (V2X) communication;

Determine whether there is CBR available; And

If it is determined that no CBR is available, using the received CBR information.
The method of claim 6,

And if it is determined that there is available CBR, the received CBR information is ignored.
The method of claim 6,

The CBR information includes a CBR value expressed as a percentage between 0 and 100.
The method of claim 8,

The CBR value is a ratio of a portion of a subchannel in which a sidelink received signal strength indicator (S-RSSI) exceeds a threshold for a specific time interval.
The method of claim 6,

The CBR information includes information about an identity of the resource pool.
The method of claim 6,

The CBR information is received through a system information block type (SIB) 21 for the V2X communication.
In a user equipment (UE) in a wireless communication system,

Memory;

A transceiver; And

A processor connected to the memory and the transceiver;

The processor,

Controlling the transceiver to receive channel busy ratio (CBR) information of a sidelink channel from an eNB (eNodeB) for each resource pool used for vehicle-to-everything (V2X) communication;

Determine whether there is CBR available, and

If it is determined that there is no CBR available, the terminal characterized by using the received CBR information.