WO2016018009A1 - Method and device for controlling transmission power of terminal in d2d communication - Google Patents

Abstract

The present invention relates to a method for controlling the power of a terminal in device-to-device (D2D) communication and, particularly, to a device and a method for supporting Type 1 discovery or Mode 2 D2D communication. The present invention relates to a method for controlling the transmission power of a terminal performing D2D communication, and the terminal, the method comprising the steps of: selecting an arbitrary resource in a discovery period for D2D resource selection; determining whether the selected resource satisfies a preset transmission power control condition; and transmitting information for the D2D communication through the selected resource, by using the power determined according to the determination result. The present disclosure relates to a communication scheme for fusing IoT technology with a 5G communication system for supporting a data rate higher than that of a 4G system and subsequent systems thereafter. The present disclosure can be applied to intelligent services (for example, a smart home, a smart building, a smart city, a smart or connected car, healthcare, digital education, retail business, security and safety related services, and the like) on the basis of the 5G communication technology and IoT related technology.

Description

Method and apparatus for controlling transmission power of terminal in D2D communication

The present invention relates to a transmission power control method of a terminal in D2D communication, and more particularly, to an apparatus and method for supporting Type 1 discovery or Mode 2 D2D communication.

Recently, as the usage of smartphones increases rapidly, various application services and contents using smartphones are activated, and this aspect is expected to be accelerated further in the future. Accordingly, various techniques are emerging to effectively prevent data congestion due to these various application services in cellular systems.

In order to meet the increasing demand for wireless data traffic since the commercialization of 4G communication systems, efforts are being made to develop improved 5G communication systems or pre-5G communication systems. For this reason, a 5G communication system or a pre-5G communication system is called a system after a 4G network (Beyond 4G Network) or a system after an LTE system (Post LTE). In order to achieve high data rates, 5G communication systems are being considered for implementation in the ultra-high frequency (mmWave) band (eg, such as the 60 Gigabit (60 GHz) band). In order to mitigate the path loss of radio waves in the ultra-high frequency band and increase the propagation distance of radio waves, beamforming, massive array multiple input / output (FD-MIMO), and FD-MIMO are used in 5G communication systems. Array antenna, analog beam-forming, and large scale antenna techniques are discussed. In addition, in order to improve the network of the system, 5G communication systems have advanced small cells, advanced small cells, cloud radio access network (cloud RAN), ultra-dense network (ultra-dense network) , Device to Device communication (D2D), wireless backhaul, moving network, cooperative communication, Coordinated Multi-Points (CoMP), and interference cancellation The development of such technology is being done. In addition, in 5G systems, Hybrid FSK and QAM Modulation (FQAM) and Slide Window Superposition Coding (SWSC), Advanced Coding Modulation (ACM), and FBMC (Filter Bank Multi Carrier) and NOMA are advanced access technologies. (non orthogonal multiple access), and sparse code multiple access (SCMA) are being developed.

Meanwhile, the Internet is evolving from a human-centered connection network in which humans create and consume information, and an Internet of Things (IoT) network that exchanges and processes information between distributed components such as things. The Internet of Everything (IoE) technology, which combines big data processing technology through connection with cloud servers and the like, is emerging. In order to implement the IoT, technical elements such as sensing technology, wired / wireless communication and network infrastructure, service interface technology, and security technology are required, and recently, a sensor network for connection between things, a machine to machine , M2M), Machine Type Communication (MTC), etc. are being studied. In an IoT environment, intelligent Internet technology (IT) services can be provided that collect and analyze data generated from connected objects to create new value in human life. IoT is a field of smart home, smart building, smart city, smart car or connected car, smart grid, health care, smart home appliances, advanced medical services, etc. through convergence and complex of existing information technology (IT) technology and various industries. It can be applied to.

Accordingly, various attempts have been made to apply the 5G communication system to the IoT network. For example, technologies such as sensor network, machine to machine (M2M), machine type communication (MTC), and the like, are implemented by techniques such as beamforming, MIMO, and array antennas. It is. Application of cloud radio access network (cloud RAN) as the big data processing technology described above may be an example of convergence of 5G technology and IoT technology.

In particular, device-to-device communication (D2D) (or device-to-device direct communication) for efficiently distributing the load of a base station as a large amount of mobile content is recently used using the proximity of a mobile communication terminal. Communication). D2D is currently adopted as a study item in 3GPP LTE release 12, and standardization began in RAN1 in January 2013. Meanwhile, RAN Plenary decided to end D2D study items in February 2014 and start work item standardization on D2D from March 2014.

LTE-based D2D communication technology may be classified into discovery between devices and communication between devices.

Inter-device discovery is one terminal identifying the identity (or identifier) or interest of other terminals in its proximity, or another terminal located in close proximity of its identity or interest It means a series of processes to inform people. At this time, the identity and interest may be an identifier (ID), an application identifier, or a service identifier of the terminal, and may be variously configured according to a D2D service and an operation scenario.

The hierarchical structure of the terminal is assumed to be a D2D application layer, a D2D management layer, and a D2D transport layer. The D2D application layer refers to a D2D service application running on a terminal operating system (Operating System), the D2D management layer is responsible for converting the navigation information generated in the D2D application into a format suitable for the transport layer, the transport layer PHY / MAC layer of the LTE or WiFi wireless communication standard. At this time, the discovery between terminals may have the following procedure. When the user executes the D2D application program, information for discovery is generated in the application layer and transferred to the D2D management layer. The management layer converts the navigation information received from the application layer into a management layer message. The management layer message is transmitted through the transmission layer of the terminal, and the receiving terminals perform the receiving operation in the reverse order of the transmission process.

On the other hand, the communication between terminals is a communication method for directly transmitting traffic between terminals without going through an infrastructure such as a base station or an access point (AP). In this case, the terminal-to-terminal communication may perform a terminal-to-terminal search process, and then perform communication (ie, with the discovered terminals) based on the result, or perform terminal-to-terminal communication without going through the terminal-to-terminal discovery process. Prior to terminal-to-terminal communication, whether a terminal-to-device discovery process is required may vary depending on the D2D service and operation scenario.

D2D service scenarios can be broadly classified into commercial services (non-public safety services) and public safety services (public safety services). Each service can include a myriad of use cases, but examples include advertising, social network services, games, public safety, and public safety services.

1. Advertisement: Stores, cafes, cinemas, restaurants, etc., pre-registered to network operators supporting D2D, will use end-to-end navigation or end-to-end communication to advertise their identity to D2D users in close proximity. Can be. At this time, the interest may be promotions, event information or discount coupons of the advertisers. If the identity matches the user's interests, the user can visit the store to obtain more information using existing cellular networks or terminal-to-device communications. As another example, an individual user may search for a taxi located near the user through a search between terminals, and may exchange data about his or her destination or fare information through existing cellular communication or communication between terminals.

2. Social network service (SNS): A user can send his or her application and interests to that application to other users in the immediate vicinity. At this time, the identity or interest used in the search between the terminals may be a friend list or an application identifier of the application. After the user searches through the terminals, the user may share the contents such as photos and videos owned by the terminals with the neighboring users through the communication between the terminals.

3. Game: A user searches for users and a game application through a terminal-to-device search process in order to enjoy a mobile game with users in close proximity, and performs communication between terminals for transmission of data necessary for a game. can do

4. Public safety and public safety services: Police officers and firefighters may use D2D communication technology for public safety purposes. In other words, when an existing situation such as an earthquake, volcanic eruption, tsunami, or other existing cellular network is damaged due to an emergency such as fire or landslide, cellular communication is impossible, police officers and firefighters can use D2D communication technology to find an adjacent colleague, Each emergency information can be shared among neighboring users.

Currently, 3GPP LTE D2D standardization is performed for both inter-device discovery and inter-device communication, but the standardization range is different. The search between terminals is intended for commercial use and should be designed to operate only in the coverage of the base station. That is, the search between terminals does not support the search between the terminals in a situation where there is no base station (or out of coverage of the base station). The terminal-to-device communication is intended for public safety and disaster network services, not for commercial use, and includes in-network coverage of the base station, out-of-network coverage of the base station, and partial network coverage of the base station. Some terminals exist in the coverage of the base station and some terminals must be able to support all of the communication in the situation that exists outside the coverage of the base station. Therefore, in public safety and disaster network service, communication between terminals should be performed without support of inter-device discovery.

The inter-device discovery and the inter-device communication are both characterized in an uplink subframe of LTE. That is, the D2D transmitter transmits a D2D discovery signal and data for D2D communication in an uplink subframe, and the D2D receiver receives it in an uplink subframe.

In the current LTE system, since the terminal receives data and control information from the base station through downlink and the terminal transmits data and control information through the uplink to the base station, the operation of the current D2D transmitter / receiver is different from the existing LTE. For example, a terminal not supporting the D2D function is equipped with an orthogonal frequency division multiplexing (OFDM) based receiver to receive downlink data and control information from the base station, and transmits uplink data and control information to the base station. In order to do this, a single carrier-frequency division multiplexing (SC-FDM) based transmitter is required. However, since the D2D user equipment must support both the cellular mode and the D2D mode, a separate SC-FDM receiver is installed to receive the D2D data and control information through the uplink along with the OFDM-based receiver and the SC-FDM-based transmitter. Should be.

Currently, LTE D2D defines two types of search methods between terminals according to resource allocation methods.

1. Type 1 discovery: The base station transmits to the D2D UEs all D2D UEs in a cell that manages an uplink resource pool available for D2D discovery through a system information block (SIB). Broadcast. In this case, the base station may inform the size (eg, x consecutive subframes) of the resources available for the D2D user equipment and the period of the resources (for example, repeat every y seconds). Upon receiving this, the D2D transmitting terminals transmit a D2D discovery signal by selecting resources to be used by them. Meanwhile, the D2D receiving terminals should receive all D2D discovery signals transmitted in the resource region included in the SIB information.

2. Type 2 discovery: The base station informs the area of the discovery signal resource that the D2D receiving terminals should receive through the SIB. Meanwhile, the base station schedules discovery signal resources for D2D transmitting terminals. In this case, scheduling of the base station may be performed through a semi-persistent method or a dynamic method.

The communication method between terminals may be classified into two types according to resource allocation as in the discovery method between terminals.

Mode 1: The base station directly informs the data transmission resource for D2D communication used by the D2D transmitter.

2. Mode 2: The base station informs the area of the resource that can be used by the D2D transmitter, and the terminals within the resource area transmit data by selecting resources in a distributed manner.

Meanwhile, LTE D2D standardization considers frequency division multiplexing (FDM) between D2D UEs and also uses a PUCCH (Physical Uplink Control Channel), which is an uplink feedback channel of an existing cellular terminal, even within a subframe allocated for D2D use. And PUSCH (Physical Uplink Shared Channel), which are used for D2D discovery and communication, were determined to be used for frequency multiplexing. In addition, in LTE D2D standardization, maximum power transmission is assumed to increase coverage of D2D discovery and D2D communication.

In Type 1 discovery and Mode 2 communication, the base station allocates D2D resources through a system information block (SIB) transmitted in a downlink subframe. For example, the base station scrambles the resource allocation information for the D2D discovery signal and D2D communication (data transmission) with a system information-radio network temporary identifier (SI-RNTI) or a D2D-RNTI (Physical Downlink Control Channel). To send). All UEs in the cell know the SI-RNTI in advance, and use this to obtain allocation information included in the SIB from the PDCCH. SIB is transmitted through the Physical Downlink Shared Channel (PDSCH). That is, the UE obtains resource allocation information of the SIB allocated to the PDSCH from the PDCCH, and finally obtains resource allocation information for transmitting the D2D discovery signal after decoding the SIB.

When resources for D2D discovery signal transmission or D2D data transmission are allocated through such resource allocation, UEs desiring D2D discovery signal or D2D data transmission are distributed in D2D discovery signal or D2D data in the allocated resources. Select (RB: resource block). The distributed resource selection method of the UE can be largely classified into a random resource selection method and an energy sensing-based resource selection method.

Random resource selection

(1) The terminal randomly selects and transmits a resource in a D2D resource pool allocated from the base station.

2. Energy sensing-based resource selection

(1) The UE measures energy levels of all radio resources (RBs) in the interval during the predefined interval. In this case, the predefined interval becomes a subset of the D2D resource region.

(2) The terminal selects the RB having the lowest energy level and transmits peer discovery information or data in that RB, or the energy level is below a certain threshold (i.e., within the lower x%, for example within 5%). Randomly selects one of the RBs and transmits discovery information or data from the RB.

According to the above-described prior art, in order to ensure D2D coverage, the D2D transmitter transmits discovery signals and data in a frequency-time resource (RB) allocated for D2D communication at maximum transmission power. The use of this maximum transmit power may be easy to ensure the search performance and data coverage of the D2D transmitter, but may cause interference for other uplink signals using adjacent frequencies. That is, the maximum transmission power usage of the D2D transmitter may cause in-band emission according to the dynamic range limitation of the automatic gain control (AGC) mounted in the base station receiver or the D2D receiver.

For example, when the D2D transmitter located near the base station transmits a signal to the D2D PUSCH using the maximum transmission power, for the PUCCH transmitted to the base station for feedback of the cellular terminal and separately transmitted on the D2D PUSCH and the frequency, D2D PUSCH may cause interference due to in-band radiation.

Also, if D2D transmitter A located close to the D2D receiver transmits the D2D signal at PUSCH RB A using the maximum transmit power, the D2D transmitter B far from the D2D receiver transmits the D2D signal at PUSCH RB B using the maximum transmit power. (Where RB A and RB B are orthogonal resources on the frequency axis), due to the limitations of the dynamic range of the D2D receiver AGC, the signal transmitted by D2D transmitter B may cause interference due to in-band radiation of the signal transmitted by D2D transmitter A. Cannot be correctly received by the D2D receiver.

Therefore, when the PUSCH used by the D2D UE and the PUCCH used for the feedback of the existing cellular terminal are frequency-divided and transmitted in the same subframe, the D2D signal should be received by the base station due to the maximum transmission power usage of the D2D UE. There is a need for a method that can solve this problem because it can cause in-band radiation on the PUCCH. In addition, a technique for solving the interference problem between the D2D transmitter caused by the use of the maximum transmission power between the D2D terminals is required.

In order to solve the above problems, the present invention provides a method and apparatus for increasing the reliability of the D2D search signal and the D2D data signal.

Specifically, the present invention provides a method and apparatus for reducing problems due to in-band radiation generated from the base station and the D2D receiver through power control of the D2D terminals.

Accordingly, the method for controlling transmission power of a terminal performing device to device communication according to the present invention includes selecting an arbitrary resource in a discovery period for selecting a D2D resource, and controlling the transmission power in which the selected resource is preset. Determining whether the condition is satisfied, and transmitting information for the D2D communication through the selected resource at a transmission power determined according to the determination result.

In addition, the terminal performing device to device communication according to the present invention, the communication unit for transmitting and receiving information for the D2D communication and in the discovery period for the D2D resource selection, selects any resource, the selected resource is And a controller for determining whether a set transmission power control condition is satisfied and transmitting information for the D2D communication through the selected resource at the transmission power determined according to the determination result.

The power control method according to the present invention is directed to an in-band radiation problem occurring between D2D transmitting terminals existing in a hot spot area and an in-band radiation problem caused by the D2D transmitting terminal to a base station receiving terminal or a D2D receiving terminal. Make it work.

In addition, the power control method according to the present invention, it is possible to minimize the effect of the D2D communication to the existing cellular system, and to increase the reception reliability of the D2D discovery signal or D2D data signal.

1 is a diagram for explaining D2D resource allocation in a wireless communication system.

2A and 2B are diagrams for explaining in-band radiation occurring in a wireless communication system.

3 is a diagram for describing in-band radiation for a D2D receiving terminal.

4 is a diagram for describing in-band radiation for a base station.

5 is a diagram for describing in-band radiation between D2D transmitting terminals.

6 is a diagram illustrating a D2D resource structure according to an embodiment of the present invention.

FIG. 7 is a diagram illustrating another embodiment of a D2D resource structure, and illustrates an example of operating a plurality of discovery resource pools.

FIG. 8 is a diagram illustrating another embodiment of a D2D resource structure and illustrates an example having different discovery periods and discovery intervals among a plurality of discovery resource pools.

FIG. 9 is a diagram illustrating another embodiment of a D2D resource structure, and illustrates an operation of operating multiple discovery resource pools by Time Division Multiplexing (TDM) and Frequency Division Mutliplexing (FDM).

10 is a flowchart illustrating a power control method of a D2D transmitting terminal according to an embodiment of the present invention.

11 is a flowchart illustrating a power control method of a D2D transmitting terminal according to another embodiment of the present invention.

12 is a diagram illustrating an example in which preset transmission power values are tabulated in another embodiment of the present invention.

13 is a flowchart illustrating a power control method of a D2D transmitting terminal according to another embodiment of the present invention.

14 is a block diagram showing the structure of a D2D user equipment according to the present invention.

The present invention is a terminal supporting D2D communication, and includes a smart phone, a portable terminal, a mobile terminal, a cellular telephone, a personal digital assistant (PDA), and a portable multimedia (PMP). Player) It can be applied for all devices or services supporting D2D communication, as well as general electronic terminals such as terminals, handheld devices, notebook computers, Wibro terminals, smart TVs, and smart refrigerators.

Embodiments according to the present invention are described as being a terminal supporting D2D communication in connection with a D2D transmitting apparatus and a D2D receiving apparatus. The transmitting device and the receiving device are referred to as a system, subscriber unit, subscriber station, mobile station, mobile, remote station, remote terminal, mobile device, user terminal, terminal, D2D terminal, wireless communication device, user agent, user device, or user equipment. Can be. The D2D transmitter may be referred to as a D2D transmitter, a transmitter, a D2D transmitter, a transmitter, a transmitter, a transmitter, and the like, and the D2D receiver may be referred to as a D2D receiver, a receiver, a D2D receiver, a receiver, a receiver, a receiver, or the like. Can be. A terminal supporting one D2D communication may operate as a transmitting device or a receiving device according to an operation mode.

The D2D terminal performs data communication according to any one type of D2D discovery and D2D communication. The D2D UE performs D2D discovery according to a Type 1 discovery or Type 2 discovery method. Type 1 discovery is a method for selecting a resource to be distributed to a plurality of D2D UEs in a resource area allocated from the base station, hereinafter, Type 1, Type 1 discovery, the first discovery resource allocation method (method), distributed discovery resources May be named such as an assignment. Type 2 discovery is a method in which a base station directly allocates discovery resources for use by each D2D user equipment, which may be referred to as type 2, type 2 discovery, second discovery resource allocation method (method), and explicit discovery resource allocation. Meanwhile, the D2D user equipment performs D2D communication according to Mode 1 communication or Mode 2 communication method. Mode 1 communication is a method in which a base station directly allocates resources for D2D communication to be used by each D2D terminal. Hereinafter, Mode 1 communication may be referred to as Mode 1, a first communication resource allocation method (method), or explicit communication resource allocation. Mode 2 communication is a method of selecting resources to be distributed by a plurality of D2D UEs in a resource area allocated from a base station. Hereinafter, Mode 2 communication may be referred to as Mode 2, a second communication resource allocation method, distributed communication resource allocation, or the like. Embodiments according to the present invention may be more effectively applied to Type 1 discovery and Mode 2 communication among the above-described D2D discovery methods and D2D communication methods, but are not limited thereto. It is apparent that the present invention can be applied to various types of D2D discovery methods and D2D communication methods including the above-described method without changing the technical spirit of the present invention.

It is to be noted that the technical terms used herein are merely used to describe particular embodiments and are not intended to limit the spirit of the present invention. In addition, technical terms used herein should be interpreted as meanings generally understood by those of ordinary skill in the art to which the present invention belongs, unless specifically defined otherwise in the present specification, and excessively comprehensive It should not be construed in meaning or in excessively reduced sense.

Also, the singular forms used herein include the plural forms unless the context clearly indicates otherwise. In this specification, "configured." Or "includes." And the like should not be construed as including all of the various elements or steps described in the specification.

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings. In the following description of the present invention, detailed descriptions of related well-known functions or configurations will be omitted if it is determined that the detailed description of the present invention may unnecessarily obscure the subject matter of the present invention. In addition, terms to be described below are terms defined in consideration of functions in the present invention, which may vary according to intention or custom of a user or an operator. Therefore, the definition should be made based on the contents throughout the specification.

1 is a diagram for explaining D2D resource allocation according to an embodiment of the present invention. Specifically, FIG. 1 is a diagram illustrating a method of allocating D2D resources in a wireless communication system (for example, an LTE system) according to an embodiment of the present invention. The resource allocation method illustrated in FIG. 1 may correspond to an example of resource allocation for Type 1 discovery and Mode 2 communication.

In FIG. 1, a system to which an embodiment of the present invention is applied illustrates a frequency division duplexing (FDD) system. However, the system in which the embodiments operate according to the present invention is not limited to the FDD system.

Referring to FIG. 1, downlink (DL) and uplink (UL) uplink (UL) use different frequency bands in an FDD system. Each frequency band consists of one radio frame 101 comprising ten subframes 103. One subframe consists of two slots 105, and one slot consists of six or seven symbols. One subframe 103 is composed of control channel regions 107a and 107b and data channel regions 109a and 109b for transmitting a control channel and a data channel to the terminal, respectively. Are separated by frequency.

In the first two frames of the first subframe (subframe 0) and the sixth subframe (subframe 5) of the DL frame, the last two symbols have a primary synchronization signal (PSS) 111 and a secondary synchronization signal (SSS) 113. Is assigned. The PSS 111 and the SSS 113 are used for synchronization between the terminal and the base station.

A physical broadcast channel (PBCH) 115 is allocated to the second slot of the first subframe (subframe 0) of the DL frame, and the UE acquires system information through the PBCH 115.

In the wireless communication system according to the present invention, resource allocation information for D2D is transmitted through a system information block (SIB) 117, and a transmission period of the SIB may be designed to be 40ms to 640ms or more.

D2D UEs synchronize downlink synchronization with a system and a synchronization signal (PSS 111 and SSS 113) and receive information of a cell to which they are connected by using a master information block (MIB) transmitted to the PBCH 115. do. For example, the MIB may include essential parameter information such as a DL system bandwidth, a system frame number, a physical hybrid-ARQ indication channel (PHICH), and the like. Terminals receiving the MIB may receive a physical downlink control channel (PDCCH) transmitted from the base station every subframe. Basically, the PDCCH transmits DL / UL resource allocation information. Each terminal decodes allocation information of SIB 117 resources existing in the PDCCH using a known system information-radio network temporary identifier (SI-RNTI) or D2D-RNTI. That is, the UE knows information on the frequency-time domain in which the SIB 117 is located by decoding the PDCCH using SI-RNTI, and decodes the SIB 117 through decoding of the frequency-time domain.

The UEs that successfully decode the SIB 117 transmit information on D2D resource allocation (uplink subframe information used for D2D) included in the SIB (information on a resource region for D2D in Type 1 discovery or Mode 2 communication). By acquiring), it is possible to know how many subframes or consecutive subframes in the corresponding frame are subframes for D2D use and information on the period of the D2D subframe.

If there is a change in the position of the D2D subframe within the frame (for example, the D2D subframe is changed from subframe 3 to 5, or the amount of D2D subframe is 3 to 2 subframes). When increasing to a subframe, etc.), the base station may inform the UE of the change in the D2D resource through the SIB or the paging channel.

In Type 1 discovery or Mode 2 communication, a UE transmitting D2D information (D2D signal, D2D data) selects a D2D resource to be used for its own transmission in subframe (s) for D2D allocated through SIB. The UE transmitting the D2D information and receiving the D2D information receives and decodes the D2D subframe (s) allocated through the SIB.

2A and 2B are diagrams for describing in-band emission generated in a wireless communication system. For convenience of description, FIGS. 2A and 2B illustrate a case in which 50 resource blocks (RBs) are used in a 10 MHz bandwidth.

FIG. 2A illustrates a case where a D2D transmitting terminal uses a 12th RB (using one RB), and FIG. 2B illustrates a case where a D2D transmitting terminal uses a 12th to 17th RB (using 6 RBs).

In FIG. 2A, the relative transmit power of the D2D transmitting terminal using the 12th RB is 0 dB. That is, when the transmission power of the D2D transmitting terminal is X dBm in the 12th RB, the relative transmission power is 0 dB in the 12th RB. If there is no in-band radiation, the transmit power should exist only in the 12th RB. In the actual communication environment, the in-band radiation exists. Therefore, as shown in FIG. In RBs there is leakage power due to in-band radiation. Therefore, even though the D2D transmitting terminal uses only the 12th RB, it causes interference in adjacent RBs. On the other hand, when the amount of resources used by the D2D transmitting terminal increases, as shown in Figure 2b the effect of the interference becomes more serious.

3 is a diagram for describing in-band radiation for a D2D receiving terminal. Specifically, FIG. 3 illustrates an interference problem that the D2D receiving terminal (D2D receiver) receives due to in-band radiation of the D2D transmitting terminal (D2D transmitter).

Referring to FIG. 3, in a wireless communication system, a D2D transmitter (D2D UE-1, D2D UE-2) far away from the D2D receiver with respect to the D2D receiver and a D2D transmitter (D2D UE-3) D2D UE-4) is present. Each D2D transmitter transmits a D2D discovery signal or D2D data at maximum power in a D2D resource allocated by a base station or selected by a base station, that is, a PUSCH.

At this time, even if all the D2D transmitters of FIG. 3 use frequency resources (RB) orthogonal to each other, due to the limitation of the AGC dynamic range of the D2D receiver, in the D2D receiver, the PUSCH occupied by D2D UE-3 or D2D UE-4 The RB received power may cause interference 301 and 303 in the received power of the PUSCH RB occupied by the D2D UE-1 and the D2D UE-2.

4 is a diagram for describing in-band radiation for a base station. Specifically, FIG. 4 illustrates an interference problem received by an enhanced node B (eNB) receiver due to in-band radiation of a D2D transmitting terminal (D2D transmitter).

Referring to FIG. 4, in a wireless communication system, there are a cellular terminal UE-1 that is located near a base station receiver based on a base station receiver and a cellular terminal UE-2 that is far away from the base station receiver. Also within the wireless communication system are D2D transmitters (D2D UE-3, D2D UE-4) located close to the base station receiver.

It is assumed that cellular terminals are transmitting feedback such as HARQ ACK / NACK and CQI to the base station through the PUCCH. In this case, the base station performs transmission power control of the cellular terminals UE-1 and UE-2 transmitting the PUCCH in order to receive the PUCCH at a constant reception power. For example, the base station transmits the UEC located far from the base station to transmit the PUCCH at high transmission power, and the UE-1 located close to the base station transmits the PUCCH at low transmission power. 2) to control.

On the other hand, it is assumed that the D2D transmitters UE-3 and UE-4 operating close to the base station perform D2D discovery or D2D communication with each other in a D2D resource allocated by the base station or selected by the base station, that is, a PUSCH.

In this case, even if the PUCCH used by the cellular terminals UE-1 and UE-2 and the PUSCH used by the D2D terminal are allocated to different resources on the frequency axis, the D2D transmitter does not perform power control (that is, at maximum power). If transmitting the D2D discovery signal or D2D data), the PUCCH of the cellular terminal received by the base station is subject to interference (401, 403) due to in-band radiation of the PUSCH of the D2D terminal.

As another example, the cellular resource used by the cellular terminals UE-1 and UE-2 for uplink data transmission and the D2D resource used by the D2D terminals UE-3 and UE-4 are in the same subframe. In frequency division multiplexing (FDM) can be used. The PUSCH used by the cellular terminals UE-1 and UE-2 performs transmission power control similarly to the PUCCH. That is, UE-1 transmits cellular PUSCH at low transmit power and UE-2 transmits cellular PUSCH at high transmit power. At this time, if the D2D transmitter does not perform power control, the PUSCH of the cellular terminal received by the base station is subject to interference due to in-band radiation of the PUSCH transmitted by the D2D terminal.

5 is a diagram for describing in-band radiation between D2D transmitting terminals. Specifically, FIG. 5 is a diagram illustrating interference received by a D2D receiver due to in-band radiation between D2D transmitters in a congested environment of a network.

Referring to FIG. 5, in a wireless communication system, D2D transmitters UE-1 and UE-2 located close to each other based on a D2D receiver and D2D transmitters UE-3 and UE-4 located far away exist. . In a congested environment, numerous terminals exist around UE-1 and UE-2. This situation can occur frequently in hot-spots such as department stores, airports and shopping malls.

D2D transmitters transmit D2D discovery signals or D2D data at full power. In this case, the in-band radiation of the D2D transmitters UE-1 and UE-2 that are close to the D2D receiver may correspond to the D2D discovery signal or D2D data of the D2D transmitters UE-3 and UE-4 that are far away from the D2D receiver. It causes interference, and therefore, the D2D receiver cannot correctly receive the signals of the D2D transmitters UE-3 and UE-4 which exist at a long distance.

The purpose of D2D discovery is to discover as many surrounding D2D terminals as possible at a given time. In addition, the purpose of D2D communication is to broadcast its data to as many peripheral terminals as possible. Therefore, in order to meet these requirements, the problem of in-band emission must be solved. In other words, in a congestion environment as shown in FIG. 5, a D2D signal transmitted by terminals existing in close proximity, such as UE-1 and UE-2, is applied to a signal transmitted by terminals existing in a long distance such as UE-3 and UE-4. This can cause radiation problems in the band. Therefore, there is a need for a solution to this.

6 shows a D2D resource structure according to an embodiment of the present invention.

The D2D user equipment performs D2D discovery to search for and select a resource for D2D discovery or D2D communication. As used herein, the D2D discovery may be used as the same or different meaning as the D2D discovery for searching for a neighboring terminal of interest as a type of D2D communication.

The base station transmits information about one discovery period consisting of N transmission time intervals (TTIs) for D2D discovery through the SIB to all D2D terminals existing in the cell. Information about one search period broadcasts the size (TTI number) of the search period and the length (time) of the search period.

In an embodiment of the present invention, within one discovery period, the D2D transmitting terminal may be referred to as a resource region 601 (Max. Region, maximum transmission power region, uncontrolled region, maximum region, etc.). And a resource region 603 (which can be named Ctrl. Region, control region, non-maximum region, etc.) capable of transmitting with a transmission power smaller than the maximum transmission power. Max. Area 601 and Ctrl. The area 603 may be an area divided based on the maximum transmittable power, whether to transmit at the maximum power, or whether a power control is required. In various embodiments of the present disclosure, the length of one search period, Max. Area 601 and Ctrl. There is no particular limitation on the number, location, and the like of the region 603.

Information about such a resource region may also be transmitted from the base station to the D2D terminals through the SIB. According to various embodiments of the present disclosure, information on the D2D resource region (information on the type of D2D resource region, the number of arbitrary resource regions, the position, etc.) may be transmitted through various message formats other than the SIB, and there is no particular limitation. For example, the information on the D2D resource region may be transmitted to the D2D terminal through higher signaling such as RRC signaling. The D2D terminal according to the present invention controls power for transmitting D2D information (D2D discovery signal or D2D data) according to the type of resource region and whether the network is congested according to the above-described embodiment of the present invention. Upon receiving the SIB, the D2D terminal obtains information about a discovery period and information about a D2D resource region. In addition, the D2D terminal may determine the current network congestion state based on the total power strength of the received signals. Accordingly, the terminal may control the power to transmit the corresponding D2D information based on the type of the D2D resource region to which the D2D resource to be used belongs and the current network congestion state.

In the above-described embodiment of the present invention, the D2D terminal may operate differently depending on whether the D2D terminal operates as a terminal (D2D transmitting terminal) transmitting D2D information or a terminal (D2D receiving terminal) receiving D2D information. Can be. In addition, when the D2D terminal operates as a D2D transmitting terminal, the operation may vary depending on a method of selecting a D2D resource for transmitting D2D information. The operation of each D2D user equipment will be described as follows.

Random resource selection

(1) operation of the transmitting terminal

1) Randomly select a resource to be used within one discovery period.

2) The type of resource area that contains the resource you selected is Max. Ctrl or Area. Determine if it is an area.

3) Select the resource area Ctrl. In case of realm, it is determined whether there is congestion in resource usage. In this case, the transmitting terminal may determine whether the network is congested in various ways. For example, when operating as a receiving terminal, the transmitting terminal may measure power for resources within a discovery period, and determine that the power is in a congestion state if the power is greater than or equal to (or greater than) a preset threshold. Or, for example, the transmitting terminal may perform a cyclic redundancy check (CRC) on a resource within the discovery period, and determine that the terminal is congested if the success rate of the CRC execution result is less than or equal to (or less than) the preset threshold. Can be. Or, for example, if the success rate of the CRC execution result is greater than or equal to (or greater than) the predetermined threshold value, the transmitting terminal may determine that the congestion state is not congested. The threshold value may be preset and stored according to an instruction of the base station or at the time of manufacture of the terminal.

4) Select the resource area Ctrl. Area, and if the current network condition is determined to be congested, transmit D2D information at a predefined transmit power instead of the maximum transmit power. The preset transmission power may be preset and stored according to the instructions of the base station or at the time of manufacture of the terminal. The preset transmission power may be configured to be mapped according to the congestion level (congestion level) of the network. According to an embodiment, the preset transmission power may be a value that maps network congestion into two levels and is mapped to each level, wherein the transmission power corresponds to an arbitrary value and 0, that is, transmission on / off corresponding to each level. can be set to off. In this case, it is obvious that the transmission power can be set to 0 (off) (that is, no D2D information is transmitted) for the high level of congestion.

5) In all other cases, transmit at the maximum transmit power value.

(2) operation of the receiving terminal

1) The decoding is performed on all resources within the discovery period except for the subframe including the resources transmitted by the terminal.

2) After decoding, calculate and save CRC success rate. This may then be used to determine whether the network is congested when the receiving terminal operates as the transmitting terminal.

3) Alternatively, measure power for all resources within the discovery period except for subframes containing the resources they transmit. The measured power may then be used to determine whether the network is congested when the receiving terminal operates as the transmitting terminal.

2. Energy sensing-based resource selection

(1) operation of the transmitting terminal

A. Max. During 1 search cycle for resource selection. Perform energy scanning (sensing) on the area. In this case, the energy scanning may be expressed as measuring an energy level, and the energy level may be calculated by averaging the reference signal received power (RSRP) with time.

B. Select resources based on the results of scanning. For example, the terminal may select one resource whose sensed energy is equal to or less than a predetermined threshold energy level, or randomly select one of the resources whose energy level is the lower z% after sorting the energy levels of all resources.

C. The type of resource zone that contains the resource you selected is Max. Ctrl or Area. Determine if it is an area.

D. Selected resource area is Ctrl. In case of realm, it is judged whether it is congested or not. In this case, the transmitting terminal may determine whether the network is congested in various ways. For example, the transmitting terminal may determine whether the network is congested based on energy values for resources within a predetermined discovery period in the process of performing energy sensing. In this case, the transmitting terminal may determine that the network state is congested when the number of RBs having an energy equal to or greater than a predetermined threshold energy level (for example, a dBm) is less than x%. Alternatively, the transmitting terminal may determine that the network condition is not congested when the number of RBs having energy equal to or less than a predetermined threshold energy level (for example, b dBm) is y% or more.

Or, for example, the transmitting terminal may perform a cyclic redundancy check (CRC) on a resource within the discovery period, and determine that the terminal is congested if the success rate of the CRC execution result is less than or equal to (or less than) the preset threshold. Can be. Or, for example, if the success rate of the CRC execution result is greater than or equal to (or greater than) the predetermined threshold value, the transmitting terminal may determine that the congestion state is not congested. The threshold value may be preset and stored according to an instruction of the base station or at the time of manufacture of the terminal.

E. Selected resource area is Ctrl. Area, and if the current network state is determined to be congestion, transmit D2D information at a predefined transmit power, not a maximum transmit power. The preset transmission power may be preset and stored according to the instructions of the base station or at the time of manufacture of the terminal. The preset transmission power may be configured to be mapped according to the congestion level (congestion level) of the network. According to an embodiment, the preset transmission power may be a value that maps network congestion into two levels and is mapped to each level, wherein the transmission power corresponds to an arbitrary value and 0, that is, transmission on / off corresponding to each level. can be set to off. In this case, it is obvious that the transmission power can be set to 0 (off) (that is, no D2D information is transmitted) for the high level of congestion.

F. In all other cases, transmit at the maximum transmit power value.

(2) operation of the receiving terminal

The decoding is performed on all resources within the discovery period except for the subframe including the resources that are transmitted.

In another embodiment of the present invention, the base station may statistically collect the number of UEs used in the D2D service in a cell through a D2D capability negotiation process when the D2D UE is initially connected. Based on this, it is possible to control the resource access of the D2D terminal by determining the degree of congestion occurring when the resource access (or resource occupation) of the D2D terminal is performed. For example, when the number of D2D UEs in a cell is statistically large, the base station may increase the amount of D2D resources that can be used by the D2D UEs. On the contrary, when the number of D2D terminals in the cell is statistically small, the base station may reduce the amount of D2D resources available to the D2D terminals. Through this, D2D UEs can prevent resource collisions that may occur when random resources are selected or energy level-based resources are selected. The D2D resource information (for example, the position of the time axis and the frequency axis of the D2D resource and the period and interval of the D2D resource, etc.) transmitted to the D2D UE in the cell through SIB or RRC signaling may be changed by a specific time or a specific event. have. In residential areas, for example, frequent D2D use is expected from after work to 1-2 am, while in business areas (where companies are concentrated), resources can increase from work to work. . In addition, in a stadium such as a baseball field or a soccer field, frequent D2D usage may be expected on the day when a baseball or soccer game is planned, and when such an event occurs, the base station may increase the amount of resources available to the D2D terminal in the cell. Can be. In addition, when there is no change in the amount of resources, the base station may inform the terminal only whether or not there is a change in the resource information and power control parameters, including the amount of resources. Terminals that are not initially connected may not receive resource information and power control parameters that are transmitted later when there is no change in resource information and power control parameters through such signaling.

As another example, the base station can detect the congestion level without adjusting the amount of resources and can prevent resource collisions occurring when selecting resources of the D2D UEs. Specifically, when the number of D2D UEs in a cell increases, the base station increases the resource access control probability p of the D2D UEs, and when the number of D2D UEs in the cell decreases, the base station decreases the resource access control probability p of the D2D UEs. . The resource access control probability p of the D2D terminal is transmitted from the base station to the D2D terminal through SIB or RRC signaling. For example, assuming that p = {0, 0.2, 0.4, 0.8, 1}, and if the base station configures p = 1, the terminal is configured in one of the discovery resources in every discovery period when the total discovery period is configured to L Random selection or energy level based resource selection may be performed. On the contrary, when one of the values other than p is 1 is configured by the base station, the terminal performs resource access every p * L periods (for example, assuming that L = 10 and p = 0.5, p * L = 5, a resource may be selected randomly or on an energy basis every five discovery periods (if p * L is not an integer, it may be rounded up or down). As another example, the probability that the terminal can access the resource may be applied within the discovery period. That is, a resource is randomly selected based on the probability of p within one discovery period or based on energy, and the resource connection is performed with the probability of p within every discovery period while the base station does not change the configuration of the p value.

As another example, the resource access control may be a combination of the congestion prediction (obtained through the D2D capability negotiation process, etc.) of the base station and the congestion prediction through CRC check in the terminal. Specifically, when assuming the resource occupancy probability of the terminal according to the congestion degree predicted by the base station as p1, and the terminal assumes the resource access probability according to the congestion determination through CRC check, etc. as p2, the terminals are actually connected to resources in the cell. The probability of access can be determined by various combinations of p1 and p2. For example, there may be a weighted sum of p1 and p2. That is, the resource access probability of the terminal may be determined by c * p1 + (1−c) * p2. In this case, the value c is a value transmitted by the base station to the terminal through SIB or RRC signaling and has a value between 0 and 1. Whether the probability p1 and p2 are used to determine the congestion of the terminal may be transmitted to the terminal through SIB or RRC signaling. For example, in the case of p2 = off, whether congestion is determined using only p1 received from the base station. FIG. 7 illustrates another embodiment of a D2D resource structure. In the case of FIG. 6, within one discovery period corresponding to N TTIs (N subframes), a resource region Max using maximum transmission power and a resource region Ctrl performing transmission power control are divided. . In FIG. 7, unlike FIG. 6, the same transmission power is used within one discovery period including N TTIs. That is, the maximum transmission power may be used within one discovery period, and the transmission power control may be performed within another discovery period. In addition, it is illustrated that different transmission powers may be used for each discovery period when performing transmission power. In this case, what transmission power to use in each discovery period may be determined by i) the base station, ii) the terminal with the help of the base station, or iii) the terminal itself without the help of the base station.

i) When the base station determines: SIB or RRC signaling transmit power value associated with each discovery period together with the discovery resource information (discovery period is composed of N TTI, has an interval consisting of M TTI, etc.) It can be transmitted to the D2D terminals in the cell through. That is, it may be informed that the maximum transmission power usage is used for the discovery period K, the P1 transmission power usage is used for the discovery period K + 1, and the P2 transmission power usage is used for the discovery period K + 2. This transmission power value is implicitly mapped to each discovery period (that is, in this case, only resource information is transmitted through SIB or RRC signaling, and the transmission power value does not need to be transmitted to the terminal through SIB or RRC signaling. ), It may explicitly inform the transmission power value (ie, in this case, the transmission power value that can be used in each discovery period together with the resource information is also transmitted to the UE through SIB or RRC signaling). The operation of the terminal for the case where the base station determines the transmission power value is the same as mentioned in FIG.

ii) When the UE determines with the help of the base station: The base station does not inform the transmit power value that the terminals can transmit, but may provide only a transmit power parameter for the terminal to determine the transmit power. For example, the transmission power control of the LTE cellular system is as shown in Equation 1 below.

Wow

The value exists.

[Equation 1]

Equation 1 is a transmission power of a Physical Uplink Shared CHannel (PUSCH), which is a physical channel for uplink data transmission in an i- th subframe of a terminal,

It is shown.

At this time,

Is

+

This parameter is configured to be a value informed by the base station to the terminal through higher layer signaling. Especially,

Is a cell-specific value composed of 8-bit information and has a range of [-126, 24] dB. Also

Is a UE-specific value composed of 4-bit information and has a range of [-8, 7] dB. The cell-specific value is transmitted by the base station through the SIB, and the UE-specific value is transmitted by the base station to the terminal through dedicated RRC signaling. Meanwhile,

Is a value for compensating for path-loss, and is a cell-specific value in which one of {0, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1} is informed by the base station through 3-bit information. Value.

Such

Wow

When the base station transmits the value to the terminal, the terminal may calculate a transmission power value based on the value. That is, the base station can be used in the discovery period K transmitted to the terminal through the SIB or RRC signaling

,

Values, which can be used in the discovery period K + 1

,

The values can be different. Upon receiving this, the UE may calculate its transmission power value based on parameter values corresponding to the resource region selected by the UE and the path loss value measured by the UE.

Meanwhile, in order to apply values currently used in the LTE cellular system to the D2D system, it may be necessary to change parameter values. For example, UE-specific parameter in D2D discovery that supports transmission of RRC_Idle UEs

May be unnecessary. This is because the UE in the RRC_Idle state cannot receive the dedicated RRC signal from the base station.

In addition, cell-specific values to support discovery in public service (public safety and disaster) applications

The range of needs to be extended from [-126, 24] dB to [-126, 31] dB. This is because the class of the terminal used in the public service is higher than the class of the general commercial terminal, so that the maximum transmission power (31 dB) higher than the maximum transmission power (23 dB) used by the general commercial terminal can be used. Operations of the D2D transmitting terminal and the D2D receiving terminal in the case where the terminal determines the transmission power with the help of the base station are as follows.

Random resource selection

(1) operation of the transmitting terminal

A. Information about discovery resource pools (purpose of resource pool, time and frequency axis constituting resource pool, amount of resources, etc.), probability of resource connection, transmission power control parameter for each resource pool (P _{0_ PUSCH} And α value).

B. The UE randomly selects a resource within a discovery period in one or more resource pools allowed by the base station among a plurality of resource pools.

C. When a base station instructs a specific D2D transmitting terminal to use maximum transmit power through separate dedicated RRC signaling, or commands a maximum transmit power of a specific terminal through D2D DCI, or all in the cell through SIB or RRC signaling. When instructing the D2D user equipment to use the maximum transmission power in a specific resource pool, the transmission power control parameter previously received through SIB or RRC signaling is ignored, and the maximum transmission power is used according to the command of the base station. If there is no such command, the D2D transmitting terminal performs the following operation.

D. Calculate the transmit power using the path reduction value predicted from the RSRP (Reference Signal Received Power) with the base station, the information on the resource pool received from the base station, and the transmit power control parameter (in this case, the UE in the cellular DRX mode In order to measure RSRP for power control of D2D transmission, RSRP is measured by exiting DRX mode and using a CRS (Cell-specific Reference Signal) existing in a downlink subframe. Downlink synchronization may be received with the base station through a link synchronization signal (PSS / SSS: Primary Synchronization Signal / Secondary Synchronization Signal).

E. Whether to transmit on a selected resource within a discovery period according to a parameter determining whether congestion occurs in resource use. In this case, the parameter for determining whether the congestion is received from the base station, or may be a value determined through the CRC check when the transmitting D2D terminal is operating in the reception mode. It may also be a method by a combination of the two methods.

F. Transmit the discovery signal with the given resource access probability using the transmit power value calculated from the selected resource.

(2) operation of the receiving terminal

A. Receive resource pool information for receiving D2D from the base station (for example, resource pool information, configuration information of resources on a time axis and a frequency axis constituting the resource pool, and the like).

B. The base station decodes all resources in the discovery period except for a subframe including resources transmitted by the base station in at least one resource pool designated for reception.

C. Whether the base station controls the resource access probability (p2) according to the congestion measured by the D2D terminal or the base station controls the resource access probability (p1) according to the congestion predicted through the negotiation process of the D2D capability, or p1 It is determined whether the resource connection is controlled by the probability of a combination of and p2 (receive information p1 = on / off or p2 = on / off through SIB or RRC signaling. If p1 = on and p2 = on, c value that determines c * p1 + (1-c) * p2 also received via SIB or RRC signaling).

D. If p1 = off and p2 = on or p1 = on and p2 = on, after decoding, CRC success rate is calculated and stored. The CRC success rate may be used to determine whether resource usage is congested when the receiving terminal operates as the transmitting terminal. Otherwise, if p1 = off and p2 = off or p1 = on and p2 = off, only decoding is performed and the CRC success rate is not calculated.

2. Energy sensing-based resource selection

(1) operation of the transmitting terminal

A. Receive information on a discovery resource pool, a probability of resource access, and a transmission power control parameter for each resource pool in the same manner as the procedure A in random resource selection.

B. Similarly to the procedure B in random resource selection, the UE performs scanning of resources within a discovery period in one or more resource pools allowed by the base station among a plurality of resource pools.

C. Select a resource based on the scanned result. For example, the terminal may select one resource whose sensed energy is equal to or less than a predetermined threshold energy level, or randomly select one of the resources whose energy level is the lower z% after sorting the energy levels of all resources.

D. Same as C procedure for random resource selection

E. Same as procedure D in random resource selection

F. It is possible to determine whether to transmit on a selected resource within a discovery period according to a parameter determining whether congestion occurs in resource use. In this case, the parameter for determining whether the congestion is received from the base station, or when the transmitting D2D terminal operates in the reception mode, it may be a value determined through energy sensing. It may also be a method by a combination of the two methods. In particular, when determining congestion of resource usage through energy sensing, when the number of RBs having energy above a predetermined threshold energy level (for example, a dBm) compared to the total number of RBs is less than x%, the network state is congested. It can be judged that. Alternatively, the transmitting terminal may determine that the network condition is not congested when the number of RBs having energy equal to or less than a predetermined threshold energy level (for example, b dBm) is y% or more.

G. Selected resource area is Ctrl. In the case of a realm, it is determined whether the resource is congested. In this case, the transmitting terminal may determine whether the network is congested in various ways. For example, the transmitting terminal may determine whether the network is congested based on energy values for resources within a predetermined discovery period in the process of performing energy sensing. In this case, the transmitting terminal may determine that the network state is congested when the number of RBs having an energy equal to or greater than a predetermined threshold energy level (for example, a dBm) is less than x%. Alternatively, the transmitting terminal may determine that the network condition is not congested when the number of RBs having energy equal to or less than a predetermined threshold energy level (for example, b dBm) is y% or more.

H. The discovery signal is transmitted at the given resource access probability using the transmit power value calculated from the selected resource.

(2) operation of the receiving terminal

A. Receive resource pool information for receiving D2D from the base station (for example, resource pool information, configuration information of resources on a time axis and a frequency axis constituting the resource pool, and the like).

B. The base station performs decoding on all resources within the discovery period except for a subframe including resources transmitted by the base station in at least one resource pool designated for reception.

C. Whether the base station controls the resource access probability (p2) according to the congestion measured by the D2D terminal or the base station controls the resource access probability (p1) according to the congestion predicted through the negotiation process of the D2D capability, or p1 It is determined whether the resource connection is controlled by the probability of a combination of and p2 (receive information p1 = on / off or p2 = on / off through SIB or RRC signaling. If p1 = on and p2 = on, c value that determines c * p1 + (1-c) * p2 also received via SIB or RRC signaling).

D. In the case of p1 = off and p2 = on or p1 = on and p2 = on, power is measured and stored for all resources within the discovery period except for the subframe including the resources transmitted by itself. The power level of such a resource may then be used to determine whether resource usage is congested when the receiving terminal operates as the transmitting terminal. Otherwise, when p1 = off and p2 = off or p1 = on and p2 = off, only decoding is performed and the measured power value for the resource is not stored.

iii) If the terminal decides itself without the help of the base station: In a disaster situation such as a fire or earthquake, or in a disaster and public safety situation such as terrorism and the collapse of a building, the base station may not be able to communicate with the terminal due to the collapse of the base station. In such a situation, transmission power control may be performed using information on transmission power parameters and resources pre-built in the terminal. In other words, the resource region K may be operated with P1 transmission power, and resource region K + 1 with P2 transmission power. In this case, P1 and P2 may be maximum transmission power.

8 shows another embodiment of a D2D resource structure. Unlike FIG. 6 and FIG. 7, FIG. 8 illustrates an example in which there are a plurality of discovery resources. That is, in FIG. 6 and FIG. 7, a discovery period consisting of N TTIs is repeated every M TTI intervals. However, in FIG. 8, a discovery period consisting of N1 TTIs is repeated every M1 TTI intervals, and at the same time, another discovery period consisting of N2 TTIs is repeated every M2 TTI intervals. At this time, there is a resource region using different transmission powers within one discovery period composed of N1 or N2 TTIs as shown in FIG. 6, or the same transmission power is used within one discovery period as shown in FIG. The discovery period may be operated to use different transmission powers. For this operation, the base station uses the purpose of each discovery resource pool (e.g., commercial / public safety use, Type 1 discovery / Type 2B discovery, or short / medium / long range classes), and time base resource information (eg, discovery resource pool). For example, search period, search interval, etc.), and frequency axis resource information of the search resource pool (e.g., start point on the frequency axis of the search resource pool and end point on the frequency axis, etc.), and transmission for each resource pool The power control parameter is transmitted to the terminal through SIB or RRC signaling. In this case, as mentioned in FIG. 7, according to the type of transmission power control parameter, the base station determines the transmission power, the terminal determines by itself with the help of the base station, or the terminal may determine itself.

9 shows another embodiment of a D2D resource structure. The difference from FIG. 8 indicates that multiple search resource pools may exist on the frequency axis. Specifically, two or more different resource pools that may have different transmission power control parameters may exist in a discovery resource pool consisting of N1 TTIs and having M1 discovery intervals. At the same time, there may be another discovery resource pool composed of N2 TTIs and M2 discovery intervals. As mentioned in FIG. 8, the base station transmits time and frequency resource information of the discovery resource pool and transmission power control parameters available in each resource pool to the terminal through SIB or RRC signaling. Although not illustrated in FIG. 9, two or more different resource pools within one discovery period may include physical uplink shared channel (PUSCH) and frequency division multiplexing (WSCH) for cellular (WAN) uplink transmission. Frequency Division Multiplexing (FDM) may operate.

10 is a flowchart illustrating a power control method of a D2D transmitting terminal according to an embodiment of the present invention.

Referring to FIG. 10, a transmitting terminal receives a D2D power control parameter (1001). The transmitting terminal receives information for D2D power control through the SIB from the base station. The information for D2D power control may be configured to include information for D2D discovery, information for D2D resource selection, and the like. For example, the information for D2D power control includes information about a resource region allocated for D2D, information about a discovery period, information about a type of the D2D resource region, and information about a preset transmission power. can do. The D2D power control parameter may be received via the SIB, but there is no particular limitation on this.

The transmitting terminal selects the D2D resource to be used by the transmitting terminal through a random resource selection method or an energy sensing based resource selection method (1003).

The transmitting terminal determines whether the selected D2D resource satisfies a preset condition, that is, a condition for controlling the transmission power (1005). That is, the transmitting terminal has the selected D2D resource Ctrl. It may be determined whether a condition is satisfied that the area and the current network state are congested.

Specifically, the transmitting terminal determines the type and congestion of the resource region to which the selected D2D resource belongs. The transmitting terminal selects Max. Area or Ctrl. It may be determined whether or not the area. Also, the transmitting terminal may determine whether congestion is based on at least one of a power or energy level measured in the selected D2D resource and a CRC result performed in the selected D2D resource.

If the selected D2D resource satisfies the condition to control the transmission power, the transmitting terminal transmits a D2D discovery signal or D2D communication data by controlling power based on the D2D power control parameter (1007).

On the contrary, if the selected D2D resource does not satisfy the condition to control the transmission power, the transmitting terminal transmits the D2D discovery signal or the D2D communication data selected by the maximum transmission power (1009).

11 is a flowchart illustrating a power control method of a D2D transmitting terminal according to another embodiment of the present invention.

Although the embodiment of FIG. 10 only considers power control for solving in-band radiation problems between D2D terminals, the embodiment of FIG. 11 considers interworking with power control for solving in-band radiation problems caused by a base station. .

Power control for solving the in-band radiation problem between the D2D terminals is power control considering the D2D receiver, while power control for solving the in-band radiation problem caused by the base station is power control considering the base station receiver. Therefore, simultaneous interlocking of different power control schemes operated under different conditions is required, and the embodiment of FIG. 8 proposes a power control method considering this.

In order to solve the in-band radiation problem caused by the base station, the D2D transmitting terminal located near the base station should perform power control so as not to cause in-band radiation on the PUCCH received by the base station. In addition, if the D2D transmitting terminal located near the base station causes in-band radiation to the D2D receiving terminal, the D2D transmitting terminal should perform power control to solve the in-band radiation caused by the D2D receiving terminal.

Referring to FIG. 11, a D2D transmitting terminal receives a power control parameter from a base station via SIB (1101). In this case, the power control parameter may include a transmit power value P _eNB for solving in-band radiation caused by the base station and a transmit power value P _D2D for solving in-band radiation generated at the D2D receiver. Although an exemplary embodiment of the present invention illustrates one transmission power value for each of two power controls, the transmission power values may be tabled at a plurality of levels and transmitted from the base station to the terminal through the SIB. In this case, as shown in FIG. 12, the transmit power values may be tabled as a plurality of values according to whether the transmitting terminal interferes with the PUCCH of the base station and whether the network is congested, and may be transmitted to the terminal.

Upon receiving the power control parameter, the D2D transmitting terminal measures downlink quality with the base station in order to predict the distance from the base station (1103). In this case, the downlink quality may be measured using various kinds of reference signals transmitted to the terminal through downlink, such as a cell-specific reference signal (CRS) and a demodulation reference signal (DM-RS) transmitted by the base station. The downlink quality measurement may be performed before transmission resource selection or after transmission resource selection.

Thereafter, the transmitting terminal selects the D2D resource to be used by the transmitting terminal through the random resource selection method or the energy sensing based resource selection method described above (1105).

When transmitting at the maximum transmission power in the selected D2D resource, the transmitting terminal determines whether it can affect the PUCCH reception of the base station and whether the current network is congested (1107).

The transmitting terminal may determine whether it affects the PUCCH reception of the base station according to a result of comparing the downlink quality measurement value with the P _eNB value received through the SIB. This may be determined based on whether the distance of the transmitting terminal is close to the base station and whether the PUCCH is allocated to a frequency adjacent to a resource selected by the transmitting terminal.

In addition, the transmitting terminal may determine whether congestion is based on at least one of a power or energy level measured in the selected D2D resource and a CRC result performed in the selected D2D resource.

When the determination result affects the PUCCH reception of the base station or the network is congested, the transmitting terminal transmits a D2D discovery signal or D2D communication data by controlling power based on the received D2D power control parameter. For example, if the determination result affects the PUCCH reception of the base station, the transmitting terminal transmits the D2D information to the P _eNB , and if the network is congested as a result of the determination, the transmitting terminal transmits the D2D information to the P _D2D .

On the contrary, when the determination result does not affect the PUCCH reception of the base station and the network is not congested, the transmitting terminal transmits the D2D discovery signal or the D2D communication data at the maximum transmission power (1111).

When the event _to be transmitted to P _D2D and the event _to be transmitted to P _eNB occur simultaneously in the D2D resource selected by the user, that is, when the network is congested while affecting the PUCCH reception, the transmitting terminal transmits the transmit power to the minimum of the two values. Can be adjusted (ie min {P _eNB , P _D2D }). If it belongs only to one of the two events, as described above, the transmitting terminal performs the D2D transmission at the transmission power corresponding to the event. If no event occurs, the transmitting terminal transmits the D2D discovery signal or data at the maximum transmission power as described above.

13 is a flowchart illustrating a power control method of a D2D transmitting terminal according to another embodiment of the present invention.

In the embodiment of FIG. 12, unlike in the embodiment of FIG. 11, in order to guarantee D2D performance, a minimum value (P _TH ) of D2D transmission power is operated to include min {P _eNB , P _D2D } P _TH It becomes smaller, so that when the D2D transmission becomes meaningless, the D2D transmitting terminal requests the base station for resource change.

In FIG. 13, steps 1301 to 1309 are the same as those described with reference to FIG. 11.

Referring to FIG. 13, the transmitting terminal determines whether the transmission power determined according to whether the power is smaller than the minimum threshold power (1311).

If the transmission power is not less than the minimum threshold power, the transmitting terminal transmits the D2D information at the finally determined transmission power as in the embodiment of FIG. 11 (1315).

If the transmit power is less than the minimum threshold power, the transmitting terminal requests the base station to change resources (1313).

In the case of D2D discovery, the transmit power value to be transmitted by the terminal operating in Type 1 is P _TH If smaller, the transmitting terminal requests the base station to switch the search method to Type 2. In the case of D2D communication, the transmit power value to be transmitted by the terminal operating in Mode 2 is P _TH. If smaller, the transmitting terminal requests the base station to switch the communication method to Mode 1.

When the terminal to switch to Type 2 / Mode 1 is in the RRC_Idle state, the transmitting terminal performs a random access to receive the resource for transmitting the resource request. When the terminal to switch to Type 2 / Mode 1 is in the RRC_Connected state, the transmitting terminal performs random access even when there is no resource for transmitting the resource request. In the RRC_Connected state, when a resource for transmitting a resource request is allocated (that is, when a resource for cellular PUSCH transmission is allocated, piggybacking the cellular data and the resource for transmitting the resource request) is performed. Send a resource request from a resource. The base station receiving the resource request from the D2D transmitting terminals may allow the resource request and may inform the terminal of information on a resource in which a time / frequency resource used by the requesting terminal is changed into a physical downlink control channel (PDCCH).

Meanwhile, the terminals that have performed the D2D transmission power control may report to the base station that they have performed the transmission power control. After receiving this report, the base station monitors for a certain time and then press Ctrl. Determine whether to increase or decrease the proportion of the area. Ctrl. If a change in the ratio of the region occurs, the base station transmits it to all D2D terminals in the cell through the SIB.

14 is a block diagram showing the structure of a D2D user equipment according to the present invention.

Referring to FIG. 14, the D2D terminal 1400 according to the present invention includes a communication unit 1401, a controller 1403, and a storage unit 1405. The D2D terminal 1400 may operate as a transmitting terminal or a receiving terminal according to an embodiment of the present invention.

The communication unit 1401 may transmit data to or receive data from another terminal. To this end, the communication unit 1401 may include at least one communication module and an antenna.

The controller 1403 may control each component of the terminal 1400 for power control according to the present invention. The detailed operation of the controller 1403 is as described above.

The storage unit 1405 may store various parameters for performing an operation according to the present invention.

Those skilled in the art will appreciate that various modifications and variations can be made without departing from the essential features of the present invention. Therefore, the embodiments disclosed in the present invention are not intended to limit the technical idea of the present invention but to describe the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The protection scope of the present invention should be interpreted by the following claims, and all technical ideas within the equivalent scope should be interpreted as being included in the scope of the present invention.

Claims (15)

1. A transmission power control method of a terminal performing device to device communication,

   Selecting a resource in a search period for selecting a D2D resource;

   Determining whether the selected resource satisfies a preset transmission power control condition; And

   And transmitting information for the D2D communication through the selected resource at a transmission power determined according to the determination result.
2. The method of claim 1, wherein the search period,

   At least one uncontrolled region capable of transmitting information for the D2D communication at a maximum transmit power, and at least one control region capable of transmitting information for the D2D communication at a power lower than the maximum transmit power,

   The preset transmission power control condition is,

   And a condition in which the selected resource is the control region.
3. The method of claim 1,

   Determining whether the network is congested;

   The preset transmission power control condition is,

   And a condition that the network is in a congested state.
4. The method of claim 4, wherein the determining of the congestion comprises:

   Measuring power for a resource within the discovery period; And

   And determining whether the congestion is based on a result of the power measurement.
5. The method of claim 4, wherein the determining of the congestion comprises:

   Performing a cyclic redundancy check (CRC) on resources within the discovery period; And

   And determining whether the congestion is based on a success rate of performing the CRC.
6. The method of claim 1, wherein the transmitting step,

   If the preset transmission power control condition is satisfied, the information for the D2D communication is transmitted through the selected resource at a preset transmission power. If the preset transmission power control condition is not satisfied, the selected resource is at the maximum transmission power. Transmitting power information for the D2D communication through the transmission power control method.
7. The method of claim 1, further comprising: determining whether uplink interference between the selected resource and an adjacent cellular terminal is detected.

   The transmitting step,

   Transmitting information for the D2D communication via the selected resource at a transmission power determined based on at least one of a determination result of whether the preset transmission power control condition is satisfied and the determination result of the interference. Transmission power control method, characterized in that.
8. The method of claim 1,

   If the determined transmission power is lower than a preset threshold, requesting a base station to switch resource allocation mode for the D2D communication.
9. As a terminal performing device to device communication,

   Communication unit for transmitting and receiving information for the D2D communication; And

   In a search period for selecting a D2D resource, an arbitrary resource is selected, it is determined whether the selected resource satisfies a preset transmission power control condition, and the D2D is transmitted through the selected resource with the transmission power determined according to the determination result. And a control unit for transmitting information for communication.
10. The method of claim 9, wherein the search period,

    At least one uncontrolled region capable of transmitting information for the D2D communication at a maximum transmit power, and at least one control region capable of transmitting information for the D2D communication at a power lower than the maximum transmit power,

    The preset transmission power control condition is,

    And the condition that the selected resource is the control area.
11. The method of claim 9, wherein the control unit,

    To determine if the network is congested,

    The preset transmission power control condition is,

    And a condition in which the network is congested.
12. The method of claim 11, wherein the control unit,

    And measuring power for resources within the discovery period and determining whether the congestion is based on a result of the power measurement.
13. The method of claim 11, wherein the control unit,

    And performing a cyclic redundancy check (CRC) on a resource within the discovery period, and determining whether the congestion is based on a success rate of performing the CRC.
14. The method of claim 9, wherein the control unit,

    If the preset transmission power control condition is satisfied, the information for the D2D communication is transmitted through the selected resource at a preset transmission power. If the preset transmission power control condition is not satisfied, the selected resource is at the maximum transmission power. Transmits information for the D2D communication through

    And when the determined transmission power is lower than a preset threshold, requesting a base station to switch a resource allocation mode for the D2D communication.
15. The method of claim 9, wherein the controller is further configured to determine whether the selected resource is adjacent to the uplink interference of the cellular terminal and to determine whether the preset transmission power control condition is satisfied or not. The terminal characterized in that for transmitting the information for the D2D communication via the selected resource at a transmission power determined based on at least one.

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