KR101388701B1 - Method for optimizing the device to device communication based on lte-advanced and apparatus performing the same - Google Patents

Abstract

Disclosed are a method of optimizing a device-to-device (D2D) communication based on LTE-advanced and an apparatus performing the same. The method of optimizing D2D communication based on LTE-advanced comprises the steps of: receiving the state information of a channel from a base station; determining a transmission power based on the state information of the received channel; and transmitting the determined transmission power to a relay after decode and forward (DF). Therefore, the present invention can minimize the waste of unnecessary power and improve the reliability of the D2D communication.

Description

METHOD FOR OPTIMIZING THE DEVICE TO DEVICE COMMUNICATION BASED ON LTE-ADVANCED AND APPARATUS PERFORMING THE SAME}

The present invention relates to direct communication between devices (device-to-device communication, hereinafter referred to as D2D communication), and more specifically, to an LTE-Advanced based D2D communication optimization method capable of optimizing D2D communication and performing the same. Relates to a device.

Recently, as the use of applications for transmitting or receiving a large amount of data through radio is increased, a frequency of overloading of a mobile communication network is increasing rapidly while using a smart phone, and a network failure due to a surge of an overload frequency of a mobile communication network And degradation of service quality are becoming serious problems.

Accordingly, as one solution to solve the above-described problems, there is a solution to the problem of direct-wireless communication (hereinafter referred to as " D2D communication ") between adjacent devices within a radius of 1 to 2 Km located in the same or nearby cells in a mobile communication system ) Is being studied.

Herein, D2D communication is a technology for establishing a D2D radio link through a mobile communication air interface using a mobile communication frequency band between adjacent devices, and then performing direct data transmission / reception between devices via a D2D wireless link without passing through a base station.

On the other hand, the existing D2D communication used a frequency band that does not require a license. Thus, unlike cellular services, there is an advantage of free accessibility, but it is relatively difficult to control the influence of interference generated between D2D terminals, and has a disadvantage in that it does not provide a convenient user experience.

3GPP LTE-Advanced proposed a D2D communication model provided by an operator unlike the existing D2D communication to overcome the above disadvantages, but since the cellular terminal and the D2D terminal share frequency resources, interference between the cellular terminal and the D2D terminal occurs. Was done. Therefore, recently, studies for solving the interference problem between the cellular terminal and the D2D terminal have been continued.

An object of the present invention is to provide an optimization method of LTE-Advanced based D2D communication that can mitigate interference by determining the optimal transmission power.

In addition, another object of the present invention is to provide an apparatus for performing the optimization method of the LTE-Advanced based D2D communication.

According to the optimization method of LTE-Advanced based D2D communication according to an embodiment of the present invention for achieving the above object, receiving the state information of the channel from the base station, and the transmission power based on the received state information of the channel Determining and transmitting to a Decode-and-Forward (DF) relay at the determined transmit power.

Here, the determining of the transmission power based on the state information of the received channel may include a Lagrangian multiplier based on convexity of capacity and Karush-Kuhn-Tucker (KKT) condition. A multiplier may be applied to determine the transmission power for maximizing the Ergodic capacity.

Here, the optimization method of LTE-Advanced based D2D communication may be performed within a range of average interference constraint set by the base station.

In addition, according to the optimization method of LTE-Advanced based D2D communication according to an embodiment of the present invention for achieving another object of the present invention, in the optimization method of D2D communication performed in the transmission relay after decoding, data from the D2D terminal If it is determined that the signal is received, receiving the status information of the channel from the base station, determining the transmission power based on the status information of the received channel, and decoding the data signal to the other D2D through the determined transmission power And transmitting to the terminal.

Here, the determining of the transmission power based on the state information of the received channel may include a Lagrangian multiplier based on convexity of capacity and Karush-Kuhn-Tucker (KKT) condition. A multiplier may be applied to determine the transmission power for maximizing the Ergodic capacity.

In addition, according to the D2D terminal according to an embodiment of the present invention for achieving another object of the present invention, by determining the transmission power based on the communication unit and the state information of the channel received from the base station through the communication unit, the determined transmission It includes a processor for transmitting a data signal to a decode-and-forward (DF) relay on power.

Herein, the processor may apply a Lagrangian multiplier based on the convexity of the capacity and the Karush-Kuhn-Tucker (KKT) condition to maximize the Ergodic capacity. It is possible to determine the transmission power to.

Here, the processor may be performed within a range of average interference constraint set by the base station.

In addition, according to the after-decoding transmission terminal according to an embodiment of the present invention for achieving another object of the present invention, if it is determined that the data signal is received from the D2D terminal through the transceiver and the transceiver, the base station of the channel And receiving a state information, determining a transmission power based on the received state information of the channel, and decoding the data signal and transmitting the decoded data signal to another D2D terminal through the determined transmission power.

Herein, the controller is configured to apply a Lagrangian multiplier based on the convexity of the capacity and the Karush-Kuhn-Tucker (KKT) condition to maximize the Ergodic capacity. It is possible to determine the transmission power to.

According to the optimization method of LTE-Advanced based D2D communication and the apparatus for performing the same according to an embodiment of the present invention as described above, the transmission power is determined based on the channel state information received from the base station, and another D2D using a relay The signal may be transmitted at the transmission power determined by the terminal. In addition, a signal may be transmitted to another D2D terminal at a transmission power determined again through a relay using a post-decoding transmission method.

Therefore, the D2D transmission power can be determined flexibly according to the channel state, and by arranging relays between the D2D terminals, it is possible to improve the reliability of the D2D communication by reducing the outage probability even under the condition that the transmission power is limited. have.

1 is a conceptual diagram illustrating a communication and interference channel model between a cellular terminal and a D2D terminal in an LTE-Advanced Network.
2 is a conceptual diagram illustrating an operating environment in which an optimization method for LTE-Advanced based D2D communication according to an embodiment of the present invention is implemented.
3 is a flowchart illustrating an optimization process of LTE-Advanced based D2D communication performed in a D2D terminal according to an embodiment of the present invention.
4 is a flowchart illustrating an optimization process of LTE-Advanced based D2D communication performed in a transmission relay after decoding according to an embodiment of the present invention.
5 is a block diagram illustrating a configuration of a D2D user equipment that performs an optimization method of LTE-Advanced based D2D communication according to an embodiment of the present invention.
6 is a block diagram illustrating a configuration of a post-decoding transmission relay that performs an optimization method of LTE-Advanced based D2D communication according to an embodiment of the present invention.
7 is an outage probability-cellular terminal power graph for explaining reliability of D2D communication according to an embodiment of the present invention.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail.

It should be understood, however, that the invention is not intended to be limited to the particular embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

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

When a component is referred to as being "connected" or "connected" to another component, it may be directly connected to or connected to that other component, but it may be understood that other components may be present in between. Should be. On the other hand, when an element is referred to as being "directly connected" or "directly connected" to another element, it should be understood that there are no other elements in between.

The terminology used in this application is used only to describe a specific embodiment and is not intended to limit the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, the terms "comprise" or "have" are intended to indicate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, and one or more other features. It is to be understood that the present invention does not exclude the possibility of the presence or the addition of numbers, steps, operations, components, components, or a combination thereof.

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

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In order to facilitate the understanding of the present invention, the same reference numerals are used for the same constituent elements in the drawings and redundant explanations for the same constituent elements are omitted.

In the present specification, embodiments of the present invention focus on D2D terminals and relays, and the base station may be a terminal node of a network that directly communicates with a cellular terminal and a D2D terminal.

In the present specification, the base station may be replaced with terms such as a fixed station, a Node B, an eNode B (eNB), an access point, and the like, and the D2D terminal or the cellular terminal may be a mobile station (MS), It may be replaced with terms such as a user equipment (UE), a subscriber station (SS), a mobile subscriber station (MSS), and a mobile terminal. The mobile terminal includes various devices such as a PDA (Personal Digital Assistant), a cellular phone, a Personal Communication Service (PCS) phone, a Global System for Mobile (GSM) phone, a Wideband CDMA (WCDMA) phone, and a Mobile Broadband System (MBS) phone. Can be.

In addition, the application type (Machine Application Type) of the D2D terminal is increasing, and the types of application of the device are security, public safety, tracking and tracing, payment, payment, Fleet Management in Healthcare, Remote Maintenance and Control, Metering, Consumer Device, Point of Sales and Security-Related Applications ), Device-to-device communication in vending machines, remote monitoring of machines and installations, smart metering to automatically measure heat and electricity usage and measurement of operating time on construction machinery, and surveillance video from surveillance cameras ( Surveillance Video) communication, but the present invention is not limited thereto, and the D2D terminal may be various devices performing types other than the above-described application type.

Meanwhile, embodiments of the present invention may be implemented by various means such as hardware, firmware, software, or a combination thereof. In the case of a hardware implementation, at least one Application Specific Integrated Circuits (ASICs), Digital Signal Processors (DSPs), Digital Signal Processing Devices (DSPDs), Programmable Logic Devices (PLDs), Field Programmable Gate Arrays (FPGAs), Processors, It may be implemented through a controller, a microcontroller, a microprocessor, or the like.

In the case of an implementation by firmware or software, it may be implemented in the form of a module, procedure, or function that performs a function or an operation, and the software code may be executed by a processor stored in a memory device, and the memory device may be internal to the processor or It may be located outside to transmit and receive data with the processor by various means.

1 is a conceptual diagram illustrating a communication and interference channel model between a cellular terminal and a D2D terminal in an LTE-Advanced Network.

Referring to FIG. 1, the cellular terminal 100, the base station 200, the D2D terminal 300, and the D2D terminal 400 share frequency resources within the same cellular network.

Here, the cellular terminal 100 and the D2D terminals 300 and 400 may use a single antenna, and the base station 200 may use multiple antennas.

As shown in FIG. 1, in 3GPP LTE-Advanced, a D2D communication model by a cellular operator has been proposed, and thus, interference between D2D terminals can be efficiently controlled.

However, since the D2D terminals 300 and 400 share frequency resources with the cellular terminal 100, interference between the cellular terminal 100 and the D2D terminals 300 and 400 may occur. Accordingly, various methods for solving the interference problem between the cellular terminal 100 and the D2D terminals 300 and 400 have been proposed.

The first is a method of controlling the transmission power of the D2D terminal. That is, since the priority of the service is in the cellular terminal 100 on the cellular network, the influence of the interference on the cellular terminal 100 is minimized by proposing a transmission power of the D2D device.

In particular, the base station 200 sets a maximum allowable amount of interference that may be received from the D2D terminals 300 and 400, so that a signal-to-interference plus noise ratio (SINR) of the cellular terminal 100 is specified. Hereinafter, there was a method of proposing a transmission power of the D2D terminals 300 and 400 in a fixed size so that communication can be made.

The second is a method of exclusively separating the resource occupancy of the cellular terminal 100 and the D2D terminal (300, 400) in the space or frequency domain. This can be implemented using the existing proposed time division multiplexing (TDD) or frequency division multiplexing (FDD) technique.

Alternatively, a method of reducing the influence of interference by allocating different frequency bands to the cellular terminal 100 and the D2D terminals 300 and 400 distributed in a space capable of affecting each other has also been proposed.

As another method, a method of using an interference cancellation technique has been proposed by transmitting a signal of the cellular terminal 100 to the D2D terminals 300 and 400.

However, the first method cannot guarantee the reliability of the D2D communication service provided by the same operator because the priority is tailored to the cellular terminal 100.

In addition, in the second method, information to be handled by the base station 200 becomes excessive, and communication efficiency is lower than that of the case where the cellular terminal 100 and the D2D terminals 300 and 400 simultaneously use the same frequency band.

In addition, when the base station 200 participates in the IC process, since the signal from the base station 200 must wait, the advantage of the D2D called direct communication between the D2D terminals 300 and 400 disappears.

Accordingly, a method for solving the interference problem between the cellular terminal 100 and the D2D terminals 300 and 400 according to an embodiment of the present invention will be described below.

2 is a conceptual diagram illustrating an operating environment in which an optimization method for LTE-Advanced based D2D communication according to an embodiment of the present invention is implemented.

Hereinafter, it is assumed that the base station 200 grasps channel information between terminals within a control range through open loop feedback.

Referring to FIG. 2, an operating environment in which an optimization method of LTE-Advanced based D2D communication is implemented according to an embodiment of the present invention includes a cellular terminal 100, a base station 200, and a D2D terminal 300 within one cell coverage. , 400), and a decode-to-forward (DF) relay 500.

The cellular terminal 100 communicates with the base station 200 using an existing communication protocol.

In addition, the D2D terminal 300 determines transmission power by using channel state information received from the base station 200 through closed loop feedback, and decodes the determined transmission power to transmit data to the transmission relay 500. Send a signal.

After decoding, when the data relay is received from the D2D terminal 300, the transmission relay 500 determines transmission power to be used for data transmission to another D2D terminal 400 by using channel state information received from the base station.

In addition, after decoding, the transmission relay 500 decodes the received data signal and transmits the data signal decoded with the determined transmission power to another D2D terminal 400.

Here, since the D2D terminal 300 and the post-decoding transmission relay 500 determine their transmission power using the channel state information received from the base station 200, the transmission power is expressed as a function of the channel, and the channel According to the state of the transmission power can be determined flexibly.

D2D communication according to an embodiment of the present invention transmits a signal using a decode-and-Froward (DF) technique among cooperative communication techniques in order to increase reliability. That is, the D2D terminal 300 transmits a data signal to another D2D terminal 400 through the transmission relay 500 after decoding in order to increase the reliability of the D2D communication.

Accordingly, as described above, since the D2D communication according to an embodiment of the present invention transmits a data signal using a dual-hop decoding method, a total of two exclusive slots for transmitting the data signal are provided. Since this is necessary, time division multiplex is used.

In addition, since the channel state may change for each hop, the optimum transmission power is determined again using the new channel state information fed back from the base station 200.

3 is a flowchart illustrating an optimization process of LTE-Advanced based D2D communication performed in a D2D terminal according to an embodiment of the present invention.

Referring to FIG. 3, the D2D terminal 300 (refer to FIG. 2) receives the state information of the channel from the base station 200 (S310).

Here, the state information of the channel may include a gain of a D2D communication channel, a gain of an interference channel, a transmission power from a node to another node, and the like.

Thereafter, the D2D terminal 300 determines an optimal transmission power based on the channel state information received through step 310 (S320). Here, the optimal transmission power may be determined through the following process.

First, an average interference constraint to be considered when the D2D terminal 300 transmits a data signal is defined as in Equation 1 below.

는 i노드와 j노드 사이의 채널 이득이고,

는 통계적 평균이고,

는 i노드에서 j노드로의 전송 파워이고,

는 기지국(200)에서의 D2D 단말(300, 400)에 의한 평균 간섭의 최대치이다.In Equation 1, 1 is a D2D terminal 300, 2 is a post-decoding transmission relay 500, 3 is a D2D terminal 400, C is a cellular terminal, B is a base station (eNB),

Is the channel gain between node i and node j ,

Is the statistical mean,

Is the transmit power from node i to node j ,

Is the maximum value of the average interference by the D2D terminals 300 and 400 in the base station 200.

The D2D terminal 300 transmits a signal with an optimal transmission power for maximizing the Ergodic capacity based on the average interference constraint of Equation 1.

Here, the addiction capacity may be expressed as Equation 2 below.

은 노이즈 베리언스(noise variance)이고,

는 셀룰러 단말의 전송파워이고,

는 i노드와 j노드 사이의 채널 이득이고,

는 i노드에서 j노드로의 전송 파워이고,

는 셀룰러 단말과 j노드 사이의 채널 이득이다.In Equation 2, C is an addiction capacity,

Is the noise variance,

Is the transmission power of the cellular terminal,

Is the channel gain between node i and node j ,

Is the transmit power from node i to node j ,

Is the channel gain between the cellular terminal and the j node.

Here, the agadic capacity is defined as the prediction of Shannon channel capacity immediately under the assumption that the fading process is white. In addition, channel capacity is the upper bound on the amount of information that can be reliably transmitted over a communication channel. By means of the noisy-channel coding theorem, the channel capacity of a given channel is a limited proportion of information that can be derived individually with small error probabilities.

In addition, the D2D terminal 300 may determine the transmission power of the D2D terminal 300 to maximize the addiction capacity using the channel capacity and the average interference constraint.

The transmission power of the optimized D2D terminal 300 obtained by applying the Lagrangian multiplier based on the convexity of capacity and the Karush-Kuhn-Tucker (KKT) condition is represented by the following equation. It can be represented as 3.

는 최적화된 전송 파워이고,

은 노이즈 베리언스(noise variance)이고,

는 라그랑주 승수이고,

는 max(0,

)이다.In Equation 3,

Is the optimized transmission power,

Is the noise variance,

Is the Lagrange multiplier,

Max (0,

)to be.

Here, the determined optimized transmission power is proportional to the channel gain between the D2D terminals 300 and 400 and inversely proportional to the interference channel gain. In other words, if the D2D communication channel gain is large, allocate more transmission power to maximize performance.If the D2D communication channel gain is small or the interference channel gain is large, the reliability of the D2D communication cannot be guaranteed. Waste of transmission power can be prevented.

In addition, in the case of the Lagrange function, the optimal transmission power obtained through Equation 3 may be obtained by substituting the average interference constraint of Equation 1. If this is expressed mathematically, it may be expressed as Equation 4 below.

는 셀룰러 단말(C)와 D2D 통신에서의 j노드 (2 또는 3) 사이의 간섭잡음비(interference-to-noise ratio, INR,

)의 평균값의 역수이고,

는 익스포넨셜 인테그럴(Exponential Integral,

)이다.In Equation 4,

Is an interference-to-noise ratio (INR) between the cellular terminal C and the j node (2 or 3) in D2D communication.

Is the inverse of the mean of

Exponential Integral,

)to be.

Referring back to FIG. 3, the D2D terminal 300 transmits the data signal to the transmission relay 400 after decoding with the optimal transmission power determined in step 320 (S330).

Hereinafter, an optimization process of LTE-Advanced based D2D communication performed by the after-decoding transmission relay 500 performing post-decoding with reference to FIG. 4 will be described.

4 is a flowchart illustrating an optimization process of LTE-Advanced based D2D communication performed in a transmission relay after decoding according to an embodiment of the present invention.

Referring to FIG. 4, after decoding, the transmission relay 500 determines whether a data signal is received from the D2D terminal 300 (S410). If it is determined that the data signal is received, the transmission relay 500 receives the state information of the current channel from the base station 200. Receive (S420).

Thereafter, after decoding, the transmission relay 500 determines an optimal transmission power based on the state information of the channel received through step 420 (S430).

Here, the step 430 of determining the optimum transmit power is the same as the step 320 of FIG.

After decoding, the transmission relay 500 decodes the data signal received from the D2D terminal 300 when the optimal transmission power is determined through step 430, and then decodes the data signal decoded at the determined optimal transmission power to another D2D terminal 400. In step S440).

LTE-Advanced based D2D communication according to an embodiment of the present invention can increase the reliability of the D2D communication by transmitting a data signal using a transmission method after decoding during cooperative communication.

5 is a block diagram illustrating a configuration of a D2D user equipment that performs an optimization method of LTE-Advanced based D2D communication according to an embodiment of the present invention.

Referring to FIG. 5, a D2D terminal 300 performing an optimization method of LTE-Advanced based D2D communication according to an embodiment of the present invention may include a communication unit 310 and a processor 320.

First, the communication unit 310 may receive channel state information from the base station 200, provide the channel state information to the processor 320, and transmit the data signal to the transmission relay 500 after decoding based on the control of the processor 320.

Here, the communication unit 310 is the base station 200 and the post-decoding transmission relay 500 and the Wi-Fi, Bluetooth, Zigbee (UigB), Ultra Wide Band (UWB), Near Field Communication (NFC) Communication may be performed using various wireless communication technologies such as binary division multiple access (B-CDMA) and long term evolution (LTE).

The processor 320 receives channel state information from the base station 200 through the communication unit 310.

Here, the state information of the channel may include a gain of a D2D communication channel, a gain of an interference channel, a transmission power from a node to another node, and the like.

In addition, the processor 320 determines an optimal transmission power based on the received channel state information.

Here, since the processor 320 determines the optimal transmission power has already been described with reference to FIGS. 3 and 4, a detailed description thereof will be omitted to avoid duplication.

The optimized transmit power determined by the processor 320 is proportional to the channel gain between the D2D terminals 300 and 400 and inversely proportional to the interfering channel gain. In other words, if the D2D communication channel gain is large, allocate more transmission power to maximize performance.If the D2D communication channel gain is small or the interference channel gain is large, the reliability of the D2D communication cannot be guaranteed. Waste of transmission power can be prevented.

In addition, the processor 320 transmits the data signal to the transmission relay 400 after decoding through the communication unit 310 at the determined optimal transmission power.

The D2D terminal 300 according to an embodiment of the present invention may increase the reliability of the D2D communication by transmitting a data signal to another D2D terminal 400 through the transmission relay 500 after decoding.

6 is a block diagram illustrating a configuration of a post-decoding transmission relay that performs an optimization method of LTE-Advanced based D2D communication according to an embodiment of the present invention.

Referring to FIG. 6, the post-decoding transmission relay 500 that performs an optimization method of LTE-Advanced based D2D communication according to an embodiment of the present invention may include a transceiver 510 and a controller 520.

First, the transceiver 510 may receive channel state information from the base station 200, provide the channel state information to the controller 520, and transmit the decoded data signal to another D2D terminal 400 based on the control of the controller 520. have.

Here, the transceiver 310 is a base station 200 and other D2D terminal 400 and the Wi-Fi, Bluetooth, Zigbee (UigB), Ultra Wide Band (UWB), Near Field Communication (NFC: Near Field Communication) Communication may be performed using various wireless communication technologies such as binary division multiple access (B-CDMA) and long term evolution (LTE).

If it is determined that the data signal is received from the D2D terminal 300 through the transceiver 510, the controller 520 receives the state information of the current channel from the base station 200 (S420).

In addition, the controller 520 determines the optimal transmission power based on the state information of the channel received from the base station 200.

Here, since the method of determining the optimal transmission power is the same as the method described in FIG. 3, detailed description is omitted to avoid duplication.

The optimized transmission power determined by the controller 520 is proportional to the channel gain between the D2D terminals 300 and 400 and inversely proportional to the interference channel gain.

In addition, when the optimal transmission power is determined, the controller 520 decodes the data signal received from the D2D terminal 300, and then transmits the data signal decoded at the determined optimal transmission power to another D2D terminal 400.

According to an embodiment of the present invention, by transmitting a data signal by using a transmission method after decoding during cooperative communication in LTE-Advanced based D2D communication, reliability of D2D communication can be improved.

7 is an outage probability-cellular terminal power graph for explaining reliability of D2D communication according to an embodiment of the present invention.

Referring to FIG. 7, the smaller the transmission power of the cellular terminal 100 is, the lower the outage probability is, and when the relay transmission (N = 2,3) is more effective than the direct transmission (N = 1), Lower.

Here, in the outage probability-cellular terminal power graph (the maximum value of the average interference by the D2D terminal at the base station) is set to 10 (dB) and R (achievable speed) to 0.5 (nats / s / Hz).

According to an embodiment of the present invention, as shown in the graph of FIG. 7, the fading effect may be alleviated within the limited transmission power of the D2D terminals by using D2D communication through cooperative communication.

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined in the appended claims. It will be possible.

100: cellular terminal 200: base station
300, 400: D2D terminal 310: communication unit
320: processor 500: transmission relay after decoding
510: transceiver 520: controller

Claims (10)

In the D2D communication optimization method performed in the D2D terminal,
Receiving status information of a channel from a base station;
Determining a transmit power based on state information of the received channel; And
Transmitting a data signal to a relay at the determined transmission power,
Determining the transmission power,
Based on the convexity of the capacity and the Karush-Kuhn-Tucker (KKT) conditions, Lagrangian multiplier is applied to determine the transmission power to maximize the Ergodic capacity. LTE-Advanced based D2D communication optimization method. delete The method according to claim 1,
The optimization method of the LTE-Advanced based D2D communication,
The method for optimizing LTE-Advanced based D2D communication, characterized in that performed within the range of the average interference constraint (average interference constraint) set by the base station. In the method of optimizing D2D communication performed in the transmission relay after decoding,
If it is determined that a data signal is received from the D2D terminal, receiving state information of a channel from a base station;
Determining a transmit power based on state information of the received channel; And
Decoding the data signal and transmitting the data signal to another D2D terminal through the determined transmission power;
Determining the transmission power,
Based on the convexity of the capacity and the Karush-Kuhn-Tucker (KKT) conditions, Lagrangian multiplier is applied to determine the transmission power for maximizing the Ergodic capacity. LTE-Advanced based D2D communication optimization method. delete A communication unit; And
And a processor configured to determine a transmission power based on state information of a channel received from a base station through the communication unit, and to transmit a data signal to the relay at the determined transmission power.
The processor comprising:
Based on the convexity of the capacity and the Karush-Kuhn-Tucker (KKT) conditions, Lagrangian multiplier is applied to determine the transmission power to maximize the Ergodic capacity. D2D terminal. delete The method of claim 6,
The processor comprising:
D2D terminal, characterized in that performed within the range of the average interference constraint (average interference constraint) set by the base station. A transmission / reception unit; And
If it is determined that the data signal is received from the D2D terminal through the transceiver, the base station receives the state information of the channel, determines the transmission power based on the received state information of the channel, and then decodes the data signal to determine the transmission. Including a control unit for transmitting to another D2D terminal through power,
Wherein,
Based on the convexity of the capacity and the Karush-Kuhn-Tucker (KKT) conditions, Lagrangian multiplier is applied to determine the transmission power to maximize the Ergodic capacity. Relay after decryption. delete

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