KR102277257B1 - Apparatus and method of performing communication in a system supporting full-duplex communication and Half-duplex communication - Google Patents

Abstract

A method for a terminal to switch a communication method in a system supporting a full-duplex communication method and a half-duplex communication method includes: measuring an interference signal strength from another terminal; transmitting information on the measured interference signal strength from the other terminal to the base station; receiving information on a communication method selected based on information on the strength of the interference signal from the base station; and switching to the selected communication method, wherein the selected communication method may be the full-duplex communication method or the half-duplex communication method.

Description

A method for performing communication in a system supporting a full-duplex communication method and a half-duplex communication method, and an apparatus for the same

The present invention relates to wireless communication, and more particularly, to a method for performing communication in a system supporting a full-duplex communication scheme and a half-duplex communication scheme, and a method for supporting the same.

Full-duplex communication technology performs transmission and reception at the same time in one node, so that time resources or frequency resources are orthogonally divided and used, compared to the existing half-duplex communication, the capacity of the system. It is a technology that can theoretically improve the However, due to the characteristics of simultaneous transmission and reception in such a node, strong self-interference is experienced. In this situation, in order to improve the performance of full-duplex communication, methods for removing self-interference have been proposed and implemented through software and hardware.

The full-duplex communication method that has been implemented and tested as an actual circuit so far can be largely divided into a separated antenna method and a shared antenna method. The Separated antenna method is a technology that makes it possible to use the same frequency and time resources for transmission and reception by separating spatial resources using multiple antennas of each node. Therefore, in order to divide the space, the antennas of one node are divided into a transmitting antenna and a receiving antenna and used. The advantage of such a communication system is that it operates in a full-duplex communication method through separation of spatial resources using multiple antennas without separation of time or frequency resources for transmission and reception, which is a performance constraint factor that occurs in the existing half-duplex communication system during bi-directional communication. that the capacity can be increased. The shared antenna method is a full-duplex communication method that uses a circulator to transmit and receive simultaneously using the same antenna. Circulator is a circuit element that allows signals to flow only in a cyclically determined direction when there are inputs and outputs in multiple directions, thereby enabling full-duplex communication at the same time. Through this circuit, the signal generated at the transmitting end is sent to the antenna, and the signal entering the antenna can enter the receiving end at the same time, making full-duplex communication possible through the same antenna.

Even in the presence of magnetic interference in the shared antenna method, it was shown through actual circuit implementation that the full-duplex communication method is a technology that can effectively increase the capacity of the system by removing a significant amount of interference by applying the cancellation technology.

As a lot of research on full-duplex communication in a P2P situation has been conducted, full-duplex communication is becoming more and more realized based on studies on self-interference cancellation considered as the biggest problem. In order to increase the capacity of the system by utilizing this, research in the form of applying the full-duplex transmission technology to the cellular network began to emerge. When a base station using conventional half-duplex communication and multiple terminals communicate, since time resources or frequency resources are divided and transmitted, a terminal transmitting in an uplink and a terminal receiving in a downlink do not operate at the same time. Although this communication method does not cause interference between terminals, since resources are divided and used, overall frequency efficiency is lowered.

In order to overcome this limitation, a cellular system in which the base station operates in full-duplex communication and the terminals use half-duplex communication is considered in consideration of existing terminals. When full-duplex communication is applied to the base station, it is possible to overcome the damage caused by the resource division of half-duplex communication and obtain higher system performance. Problems arise. The present invention intends to propose a method for solving this problem.

An object of the present invention is to provide a method for a terminal to switch a communication method in a system supporting a full-duplex communication method and a half-duplex communication method.

Another technical problem to be achieved in the present invention is to provide a method for a base station to support switching of a communication method of a terminal in a system supporting a full-duplex communication method and a half-duplex communication method.

Another technical problem to be achieved in the present invention is to provide a terminal for switching a communication method in a system supporting a full-duplex communication method and a half-duplex communication method.

Another technical problem to be achieved in the present invention is to provide a base station that supports switching of a communication method of a terminal in a system supporting a full-duplex communication method and a half-duplex communication method.

The technical problems to be achieved in the present invention are not limited to the above technical problems, and other technical problems not mentioned will be clearly understood by those of ordinary skill in the art to which the present invention belongs from the following description.

In order to achieve the above technical problem, a method for a terminal to switch a communication method in a system supporting a full-duplex communication method and a half-duplex communication method, the interference signal strength from another terminal measuring; transmitting information on the measured interference signal strength from the other terminal to the base station; receiving information on a communication method selected based on information on the strength of the interference signal from the base station; and switching to the selected communication method, wherein the selected communication method may be the full-duplex communication method or the half-duplex communication method. The method, further comprising the step of receiving, from the base station, information indicating that selection of the communication method is performed in units of a predetermined resource block (RB), the interference of the other terminal in the unit of the predetermined RB strength can be measured. The measured interference strength of another UE may be an average value for the predetermined RB unit.

In order to achieve the above other technical problem, a method in which a base station supports communication method switching of a terminal in a system supporting a full-duplex communication method and a half-duplex communication method is at least one Receiving information about the interference signal strength from another terminal measured by the at least one terminal from the terminal; selecting a communication method for each of the at least one terminal based on the information on the interference signal strength; and transmitting information on the selected communication method to each of the at least one terminal, wherein the selected communication method is the full-duplex communication method or the half-duplex communication method. The communication method selection for each of the at least one terminal may be selected such that the channel capacity of the system is maximized based on the information on the interference signal strength. The method further comprises transmitting information indicating that selection of the communication method is performed in units of a predetermined resource block (RB) to the at least one terminal, wherein the received interference signal strength is The interference strength of the other terminal is measured in a predetermined RB unit. The measured interference strength of another UE is an average value for the predetermined RB unit. The measured interference strength of another terminal is the average interference strength of the entire system bandwidth.

In order to achieve the above another technical task, a terminal switching a communication method in a system supporting a full-duplex communication method and a half-duplex communication method is an interference signal strength from another terminal processor to measure; a transmitter for transmitting information on the measured strength of an interference signal from another terminal to a base station; and a receiver configured to receive information on a communication method selected based on the information on the interference signal strength from the base station, wherein the processor controls to switch to the selected communication method, wherein the selected communication method is the full-duplex communication method or the half-duplex communication method.

In order to achieve the above another technical task, a base station supporting communication method switching of a terminal in a system supporting a full-duplex communication method and a half-duplex communication method is at least one terminal a receiver for receiving information on the strength of an interference signal from another terminal measured by the at least one terminal; a processor for selecting a communication method for each of the at least one terminal based on the information on the interference signal strength; and a transmitter for transmitting information on the selected communication method to each of the at least one terminal, wherein the selected communication method may be the full-duplex communication method or the half-duplex communication method.

When the technique proposed in the present invention is used, compared to the technique of using one operation technique as a fixed method, full-duplex communication is used in a situation where inter-terminal interference is small and half-duplex communication is switched to a higher system sum-duplex communication in a situation where inter-terminal interference is large. rate can be obtained.

The effects obtainable in the present invention are not limited to the above-mentioned effects, and other effects not mentioned may be clearly understood by those of ordinary skill in the art to which the present invention belongs from the following description. will be.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are included as a part of the detailed description for better understanding of the present invention, provide embodiments of the present invention, and together with the detailed description, explain the technical spirit of the present invention.
1 is a block diagram illustrating the configuration of a base station 105 and a terminal 110 in a wireless communication system 100 .
2 is an exemplary diagram of a network supporting a full-duplex/half-duplex communication operation method of a terminal proposed in the present invention.
3 is a diagram exemplarily illustrating a procedure for selecting a full-duplex/half-duplex communication operation method of a terminal to be proposed in the present invention.
4 is a diagram illustrating an SRS transmission structure.
5 is a diagram illustrating the sum channel capacity when both terminals perform full-duplex communication while the second terminal is in the corresponding coordinates in a situation where the base station is located at the origin and terminal 1 is located 20 m away from the base station.
6 is a diagram illustrating a ratio of the sum channel capacity when both terminals perform full-duplex communication and when both terminals perform half-duplex communication.
FIG. 7 is a view showing which combination has the largest sum channel capacity at a corresponding location in consideration of all combinations of four operation states that two terminals can take in the same experimental environment as FIG. 6 .

Hereinafter, preferred embodiments according to the present invention will be described in detail with reference to the accompanying drawings. DETAILED DESCRIPTION The detailed description set forth below in conjunction with the appended drawings is intended to describe exemplary embodiments of the present invention and is not intended to represent the only embodiments in which the present invention may be practiced. The following detailed description includes specific details in order to provide a thorough understanding of the present invention. However, it will be apparent to one skilled in the art that the present invention may be practiced without these specific details. For example, the following detailed description will be described in detail on the assumption that the mobile communication system is a 3GPP LTE or LTE-A system, but except for the specific details of 3GPP LTE and LTE-A, it is also applied to any other mobile communication system. Applicable.

In some cases, well-known structures and devices may be omitted or shown in block diagram form focusing on core functions of each structure and device in order to avoid obscuring the concept of the present invention. In addition, the same reference numerals are used to describe the same components throughout the present specification.

In addition, in the following description, it is assumed that a terminal refers to a mobile or fixed user end device such as a user equipment (UE), a mobile station (MS), and an advanced mobile station (AMS). In addition, it is assumed that the base station collectively refers to an arbitrary node of a network end that communicates with the terminal, such as a Node B, an eNode B, a base station, and an access point (AP). Although this specification is described based on the IEEE 802.16 system, the contents of the present invention are applicable to various other communication systems.

In a mobile communication system, a terminal or user equipment may receive information from a base station through a downlink, and the terminal may also transmit information through an uplink. Information transmitted or received by the terminal includes data and various control information, and various physical channels exist depending on the type of information transmitted or received by the terminal and use.

The following technologies include code division multiple access (CDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), orthogonal frequency division multiple access (OFDMA), single carrier frequency division multiple access (SC-FDMA), etc. It can be used in various wireless access systems. CDMA may be implemented with a radio technology such as Universal Terrestrial Radio Access (UTRA) or CDMA2000. TDMA may be implemented with a radio technology such as Global System for Mobile communications (GSM)/General Packet Radio Service (GPRS)/Enhanced Data Rates for GSM Evolution (EDGE). OFDMA may be implemented with a radio technology such as IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802-20, Evolved UTRA (E-UTRA), and the like. UTRA is part of the Universal Mobile Telecommunications System (UMTS). 3GPP (3rd Generation Partnership Project) long term evolution (LTE) is a part of Evolved UMTS (E-UMTS) using E-UTRA, and employs OFDMA in downlink and SC-FDMA in uplink. LTE-A (Advanced) is an evolved version of 3GPP LTE.

In addition, specific terms used in the following description are provided to help the understanding of the present invention, and the use of these specific terms may be changed to other forms without departing from the technical spirit of the present invention.

1 is a block diagram illustrating the configuration of a base station 105 and a terminal 110 in a wireless communication system 100 .

Although one base station 105 and one terminal 110 (including a D2D terminal) are illustrated to simplify the wireless communication system 100, the wireless communication system 100 includes one or more base stations and/or one or more terminals. It may include a terminal.

Referring to FIG. 1 , a base station 105 includes a transmit (Tx) data processor 115 , a symbol modulator 120 , a transmitter 125 , a transmit/receive antenna 130 , a processor 180 , a memory 185 , and a receiver ( 190 ), a symbol demodulator 195 , and a receive data processor 197 . In addition, the terminal 110 includes a transmit (Tx) data processor 165 , a symbol modulator 170 , a transmitter 175 , a transmit/receive antenna 135 , a processor 155 , a memory 160 , a receiver 140 , and a symbol. It may include a demodulator 155 and a receive data processor 150 . Although the transmit/receive antennas 130 and 135 are shown as one in the base station 105 and the terminal 110, respectively, the base station 105 and the terminal 110 are provided with a plurality of transmit/receive antennas. Accordingly, the base station 105 and the terminal 110 according to the present invention support a multiple input multiple output (MIMO) system. In addition, the base station 105 according to the present invention can support both single user-MIMO (SU-MIMO) and multi-user-MIMO (MU-MIMO) schemes.

On the downlink, transmit data processor 115 receives traffic data, formats and codes the received traffic data, interleaves and modulates (or symbol maps) the coded traffic data, and generates modulation symbols (“data symbols"). A symbol modulator 120 receives and processes these data symbols and pilot symbols and provides a stream of symbols.

The symbol modulator 120 multiplexes the data and pilot symbols and transmits them to the transmitter 125 . In this case, each transmission symbol may be a data symbol, a pilot symbol, or a signal value of zero. In each symbol period, pilot symbols may be transmitted continuously. The pilot symbols may be frequency division multiplexing (FDM), orthogonal frequency division multiplexing (OFDM), time division multiplexing (TDM), or code division multiplexing (CDM) symbols.

Transmitter 125 receives a stream of symbols and converts them to one or more analog signals, and further modulates (eg, amplifies, filters, and frequency upconverts) the analog signals to create a wireless channel Generates a downlink signal suitable for transmission through the transmission antenna 130 then transmits the generated downlink signal to the terminal.

In the configuration of the terminal 110 , the reception antenna 135 receives a downlink signal from the base station and provides the received signal to the receiver 140 . Receiver 140 modulates (eg, filters, amplifies, and frequency downconverts) the received signal and digitizes the modulated signal to obtain samples. A symbol demodulator 145 demodulates the received pilot symbols and provides them to a processor 155 for channel estimation.

A symbol demodulator 145 also receives a frequency response estimate for the downlink from the processor 155, performs data demodulation on the received data symbols, and generates a data symbol estimate (which is an estimate of the transmitted data symbols). and provides the data symbol estimates to a receive (Rx) data processor 150 . A receive data processor 150 demodulates (ie, symbol de-maps) the data symbol estimates, deinterleaves, and decodes the data symbol estimates to recover the transmitted traffic data.

The processing by symbol demodulator 145 and receive data processor 150 is complementary to the processing by symbol modulator 120 and transmit data processor 115 at base station 105, respectively.

The terminal 110 processes the traffic data on the uplink, and the transmission data processor 165 provides data symbols. A symbol modulator 170 may receive and multiplex the data symbols, perform modulation, and provide a stream of symbols to a transmitter 175 . A transmitter 175 receives and processes the stream of symbols to generate an uplink signal. In addition, the transmit antenna 135 transmits the generated uplink signal to the base station 105 .

In the base station 105, an uplink signal is received from the terminal 110 through the reception antenna 130, and the receiver 190 processes the received uplink signal to obtain samples. A symbol demodulator 195 then processes these samples and provides received pilot symbols and data symbol estimates for the uplink. The receive data processor 197 processes the data symbol estimate to recover the traffic data transmitted from the terminal 110 .

The processors 155 and 180 of the terminal 110 and the base station 105 respectively instruct (eg, control, coordinate, manage, etc.) operations in the terminal 110 and the base station 105 , respectively. Each of the processors 155 and 180 may be connected to memory units 160 and 185 that store program codes and data. The memories 160 and 185 are connected to the processor 180 to store an operating system, applications, and general files.

The processors 155 and 180 may also be referred to as controllers, microcontrollers, microprocessors, microcomputers, or the like. Meanwhile, the processors 155 and 180 may be implemented by hardware, firmware, software, or a combination thereof. When implementing the embodiment of the present invention using hardware, ASICs (application specific integrated circuits) or DSPs (digital signal processors), DSPDs (digital signal processing devices), PLDs (programmable logic devices) configured to carry out the present invention , field programmable gate arrays (FPGAs), etc. may be provided in the processors 155 and 180 .

On the other hand, when the embodiments of the present invention are implemented using firmware or software, the firmware or software may be configured to include a module, procedure, or function that performs the functions or operations of the present invention, and Firmware or software configured so as to be provided in the processors 155 and 180 or stored in the memories 160 and 185 may be driven by the processors 155 and 180 .

The layers of the radio interface protocol between the terminal and the base station are the first layer (L1) and the second layer (L2) based on the lower three layers of the OSI (open system interconnection) model well known in the communication system. ), and a third layer L3. The physical layer belongs to the first layer and provides an information transmission service through a physical channel. The RRC (Radio Resource Control) layer belongs to the third layer and provides control radio resources between the UE and the network. The terminal and the base station may exchange RRC messages through the wireless communication network and the RRC layer.

In this specification, the processor 155 of the terminal and the processor 180 of the base station process signals and data except for the terminal 110 and the base station 105 receiving or transmitting a signal and a storage function, respectively. However, for convenience of description, the processors 155 and 180 are not specifically referred to below. Even if there is no mention of the processors 155 and 180 in particular, it can be said that a series of operations such as data processing, not a function of receiving or transmitting a signal and a storage function, are performed.

The research result of analyzing the theoretical system capacity using a multi-cell analysis model and stochastic geometry in an environment where terminals operating in half-duplex communication communicate with a cellular system with a base station operating in full-duplex communication have. Here, the effect of inter-terminal interference is also taken into consideration and the performance is analyzed, but only half-duplex communication is always operated without considering the operation selection technique that changes the operation method of the UE according to the inter-terminal interference. A system in which a base station operating in full-duplex communication and terminals operating in half-duplex communication perform communication operates as follows. First, terminals operating in half-duplex communication are classified into uplink terminals and downlink terminals. In addition, the assumption is made that the uplink terminal and the downlink terminal are geographically far apart so that inter-terminal interference does not occur. Based on this assumption, the existing multi-terminal multi-antenna (MU-MIMO) technique is used so that the interference inside the uplink terminal and the interference inside the downlink terminal do not occur.

In a system in which there are base stations operating in full-duplex communication and terminals operating in half-duplex communication, and inter-terminal interference is considered, the performance of the system is analyzed in an environment in which the operation methods of the base stations and terminals are fixed. As full-duplex communication becomes more and more realistic, research into the form applied to cellular networks has begun to develop. However, there is still a limitation that full-duplex communication is applied only to the base station. In order to solve the limitations of the prior art, both the base station and the terminal operate in full-duplex communication in an actual cellular environment to improve system performance. In addition, when both the base station and the terminal operate in full-duplex communication, it is essential to appropriately select a terminal operation method so that the performance of the entire system can be maximized in consideration of the interference between terminals that will be newly generated.

Accordingly, in the present invention, in order to improve the system channel capacity of a cellular system, a standard for a method for selecting an operation method of a full-duplex communication method capable of simultaneously supporting multiple terminals capable of full-duplex communication is proposed. In order to solve the problems of the prior art, the present invention proposes a method of selecting a full-duplex/half-duplex communication operation method of the terminal so that the sum channel capacity of the entire system is maximized.

2 is an exemplary diagram of a network supporting a full-duplex/half-duplex communication operation method of a terminal proposed in the present invention.

In FIG. 2 , it is assumed that the system uses a user equipment (UE) or a terminal capable of full-duplex communication with a full-duplex base station (BS). Conventional techniques for removing interference between terminals increase the amount of space resources used for interference cancellation as the number of terminals increases, resulting in loss of overall performance. Therefore, in the present invention, based on the information on the inter-terminal interference obtained from the UE, in order to maximize the performance of the entire system, the base station limits the operation of some UEs to half-duplex communication to propose a method of controlling inter-terminal interference. In more detail, the base station may instruct the terminals to operate in half-duplex communication in an environment where inter-terminal interference is severe, and to operate in full-duplex communication when inter-terminal interference is weak. When multiple antennas are applied in the process of selecting the terminal operation method of the base station (selecting whether to operate in the full-duplex communication method or the half-duplex communication method), the received signal is separated through beamforming and the signal strength is measured based on this. Measurement assumptions are used and reflected in the Signal to Interference plus Noise Ratio (SINR).

3 is a diagram exemplarily illustrating a procedure for selecting a full-duplex/half-duplex communication operation method of a terminal to be proposed in the present invention.

In order to help the base station select a terminal operation method (full-duplex communication method or half-duplex communication method), each terminal (eg, UE1, UE2) measures the intensity of interference from the other terminal, and reports it to the base station It can be done (S310). When the base station has information on the signal strength between each node, it can determine the operation method of the terminals based on the information (S320). The process of the base station determining the operation method of the terminals is as follows.

For example, the operation methods that two terminals can take are full-duplex communication (FD) and half-duplex communication (HD), and there are four combinations of possible terminals and operation methods ((UE1/UE2)= (FD/ FD, FD/HD, HD/FD, HD/HD)). In this case, the sum of the system channel capacity when each node can separate the received signal through beamforming for each operation method combination is as follows.

First, the sum of the system channel capacity when both terminals operate in full-duplex communication can be expressed as in Equation 1 below. In this case, all nodes operating in full-duplex communication consider residual self-interference remaining after undergoing cancellation during self-interference.

,

는 기지국이 보낸 신호를 각각 1번, 2번 단말이 수신한 파워를 나타내고,

,

는 각각 1번, 2번 단말이 보낸 신호를 기지국이 수신한 파워를 나타내고 있다.

는 1번 단말의 송신 신호가 2번 단말에게 수신되는 간섭 신호 파워를 나타내고,

는 2번 단말의 송신 신호가 1번 단말에게 수신되어 발생하는 간섭 신호 파워를 나타낸다.

는 각 노드에서의 자기 간섭 중 cancellation 후 남은 간섭을 나타내고

은 노이즈(잡음)을 나타낸다.here,

,

denotes the power received by the first and second terminals, respectively, of the signals sent by the base station,

,

denotes the power received by the base station for the signals sent by the first and second terminals, respectively.

represents the interference signal power received by the transmission signal of the first terminal by the second terminal,

denotes the interference signal power generated when the transmission signal of the second terminal is received by the first terminal.

represents the remaining interference after cancellation among self-interference in each node.

denotes noise (noise).

The first term in Equation 1 represents the channel capacity of UE 1 for a signal sent to the base station, the second term is the channel capacity of UE 2 with respect to the signal sent by the base station, and the third term is the channel capacity of UE 1 The channel capacity of the base station for the transmitted signal, the fourth term indicates the channel capacity of the base station for the signal sent by the second terminal. The base station sees that it is possible to separately receive an uplink signal from each terminal through beamforming. Considering the residual self-interference remaining after cancellation during self-interference due to full-duplex communication, for example, it is possible to measure the channel capacity in the form of SINR. have.

In addition, in the same manner, the sum of the system channel capacity in which both terminals operate in half-duplex communication can be expressed as in Equation 2 below.

In Equation 2, the first term of the equation expresses the channel capacity of UE 1 with respect to the signal sent to the base station, the second term is the channel capacity of UE 2 with respect to the signal sent by the base station, and the third term is 1 The channel capacity of the base station for the signal sent by the terminal No. 1, the fourth term expresses the channel capacity of the base station for the signal sent by the terminal No. 2 . When half-duplex communication is used, there is no inter-terminal interference in the terminal, but the time resource or frequency resource is divided in half and used, resulting in a pre-log term.

Next, the sum of the system channel capacity when UE 1 uses full-duplex communication and UE 2 uses half-duplex communication can be expressed as Equation 3 below.

In Equation 3, the communication between the base station and the first terminal is calculated as full-duplex communication. Since the second terminal operates in half-duplex communication, the case where the second terminal does not interfere with the first terminal because it operates in the downlink and the case where the second terminal does not interfere with the first terminal because the uplink operates in the uplink occurs. This situation can be expressed by the first term and the second term of the above equation, respectively. The third term in Equation 3 represents the performance that occurs while receiving the signal of the first terminal in the base station operating in full-duplex communication. On the other hand, the uplink and downlink between the base station and the second terminal are calculated as half-duplex communication, and when the signal transmitted from the base station is received by the second terminal, the transmitted signal of the first terminal is considered as interference. is reflected and the uplink sent by UE 2 to the base station is expressed in the form of the fifth term. In the same way, it is also possible to calculate for which terminal 1 uses half-duplex communication and terminal 2 uses full-duplex communication.

The base station may compare all four values calculated in this way and select the operation method of the terminal showing the best performance (S320). The base station may transmit a control signal to the terminal (S330) so that the terminal can operate in the determined operation method.

A process in which the base station obtains the information of the inter-node signal strength required for selecting the operation technique of the terminals from the terminal in S320 will be described in more detail as follows. In order to obtain information on a channel between the terminal and the base station, the signal strength between the terminal and the base station can be measured by using various reference signals (RS). In addition, the strength of the interference between the terminal and the terminal, that is, between terminals, is known by receiving a reference signal sent by the terminal to the base station from the counterpart terminal or by measuring the signal strength of the data transmitted from the terminal to the base station by the counterpart terminal.

The process of obtaining information on the signal strength between each node based on these signals is as follows. First, terminal 1 and terminal 2 respectively transmit their own reference signals or data signals while receiving a signal from the other terminal. All terminals operate in a full-duplex mode to transmit their own signals while receiving a signal from the other terminal, and use this to measure the strength of inter-terminal interference. If the interference signal received by one terminal from the neighboring base station and the interference signal received from the other terminal are orthogonal, the terminal can measure and calculate the strength of the interference signal from the neighboring base station and the interference signal strength from the other terminal. have.

At the same time, the base station obtains information on the signal strength between the base station and the first terminal and the signal strength between the base station and the second terminal, respectively, based on the signal transmitted from each terminal. Next, each terminal reports information on the inter-terminal interference strength obtained by the terminal to the base station (S310). When this process is completed, the base station obtains information on the signal strength between all nodes.

As an example, in order to support frequency selective scheduling in the 3GPP LTE system, a sounding reference signal (SRS), which is an LTE uplink reference signal used for the purpose of obtaining information on an uplink channel of a terminal, may be utilized. In SRS, each terminal uses 12 orthogonal signals through phase shifting so that information can be obtained even when SRSs of different terminals are simultaneously received by the base station. Through this, terminal 1 (UE1) and terminal 2 (UE2) ), it is possible to measure the strength of the inter-terminal interference between the terminal 1 and the terminal 2 by receiving the SRS. In addition, the SRS is transmitted using one symbol once in every subframe, so that information on signal strength can be obtained at 1 ms intervals, and channel information for the entire PUSCH frequency band can be obtained as shown in FIG. 4 .

4 is a diagram illustrating an SRS transmission structure.

When a Physical Uplink Shared CHannel (PUSCH) uses n resource blocks (RBs), one RB consists of 12 subcarriers. In the case of SRS, each two subcarriers are positioned once. Therefore, 6 are located per RB, and 6*n channel information is obtained when the entire frequency band is considered. Reporting all of the channel information for all frequencies obtained by the terminal to the base station may be inefficient because an overhead is generated by consuming a corresponding amount of resources. In consideration of this, a method of calculating an average value of channel information for the entire frequency band obtained and reporting information on one average value is used. If the base station wants to determine an operation technique for a specific RB unit, it can calculate an average value for the corresponding RB and report it to the base station. In order for the base station to determine an operation technique for a specific RB unit, information on an operation mode for a specific RB unit (eg, information related to the number of RBs (eg, RB index information preset according to the number of RBs)) , information on the RB frequency band, timing, conditions for triggering an operation method of a specific RB unit, etc.) need to be informed in advance. After receiving the information on the operation mode of the specific RB unit in advance, the UEs may perform the operation according to the operation technique of the specific RB unit if the base station desires. As an example, it is also possible to set and operate an operation method optimized for signal strength in each RB for each RB rather than the same operation method at all frequencies.

To verify the performance of the proposed method, a small cell with a radius of 50 m was set, and the base station transmit power was set to 30 dBm, the antenna gain to 5 dBm, the terminal transmit power to 20 dBm, and the noise to -104 dBm. In this case, it is assumed that each base station and the terminal operating in full-duplex communication can use full-duplex communication because self-interference is completely canceled through a self-interference cancellation technique.

5 is a diagram illustrating the sum channel capacity when both terminals perform full-duplex communication while the second terminal is in the corresponding coordinates in a situation where the base station is located at the origin and terminal 1 is located 20 m away from the base station.

When the second terminal is located near the location of the first terminal, interference between terminals is severe, and it can be seen that the total channel capacity of the entire system is severely reduced and appears in a dark color.

6 is a diagram illustrating a ratio of the sum channel capacity when both terminals perform full-duplex communication and when both terminals perform half-duplex communication.

In FIG. 6, the ratio value is smaller than 1 inside the red circle, which means that when both terminals use half-duplex communication, the sum channel capacity is greater than when both terminals use full-duplex communication. . Through this, both terminals use half-duplex communication in an environment where interference between terminals is severe because the locations of the two terminals are close, and on the contrary, when interference between terminals is weak, better performance can be obtained if both terminals perform full-duplex communication. Through this, it can be confirmed that it is necessary to select an appropriate terminal operation method according to the situation.

FIG. 7 is a view showing which combination has the largest sum channel capacity at a corresponding location in consideration of all combinations of four operation states that two terminals can take in the same experimental environment as FIG. 6 .

Referring to FIG. 7 , when the second terminal is located close to the first terminal, inter-terminal interference is strong, so that it is best for both terminals to use half-duplex communication. In addition, when the second terminal is far away from the first terminal and the inter-terminal interference is small, it was found that both terminals use full-duplex communication. Although the inter-terminal interference is relatively strong, if the signal strength between the base station and the terminal 1 and the signal strength difference between the base station and the terminal 2 are large, the terminal with the high signal strength between the base station and the terminal performs full-duplex communication between the base station and the terminal. A terminal with poor signal strength obtained good results by communicating with half-duplex communication. Since the best operation method varies according to the strength of the mutual signal between nodes, the proposed method shows better performance than the existing method that uses one operation method in a fixed manner.

In the present invention, a "terminal operation method selection method in a small cell network capable of full-duplex communication" structure that increases the sum-rate of a system by determining an operation method of a terminal based on information on inter-terminal interference in a multi-terminal full-duplex communication environment suggested. When the technique proposed in the present invention is used, compared to the technique of using one operation technique as a fixed method, full-duplex communication is used in a situation where inter-terminal interference is small and half-duplex communication is switched to a higher system sum-duplex communication in a situation where inter-terminal interference is large. rate can be obtained.

The embodiments described above are those in which elements and features of the present invention are combined in a predetermined form. Each component or feature should be considered optional unless explicitly stated otherwise. Each component or feature may be implemented in a form that is not combined with other components or features. It is also possible to configure embodiments of the present invention by combining some elements and/or features. The order of operations described in the embodiments of the present invention may be changed. Some features or features of one embodiment may be included in another embodiment, or may be replaced with corresponding features or features of another embodiment. It is obvious that claims that are not explicitly cited in the claims can be combined to form an embodiment or included as a new claim by amendment after filing.

It is apparent to those skilled in the art that the present invention may be embodied in other specific forms without departing from the spirit and essential characteristics of the present invention. Accordingly, the above detailed description should not be construed as restrictive in all respects but as exemplary. The scope of the present invention should be determined by a reasonable interpretation of the appended claims, and all modifications within the equivalent scope of the present invention are included in the scope of the present invention.

Claims (10)

In a method for a terminal to switch a communication method in a system supporting a full-duplex communication method and a half-duplex communication method,
measuring an interference signal strength from another terminal;
transmitting information on the measured interference signal strength from the other terminal to the base station;
Receiving from the base station information on the communication method selected by the base station based on the information on the interference signal strength, the signal strength information between the base station and the terminal, and the signal strength information between the base station and the other terminal ; and
Comprising the step of performing communication using the selected communication method,
The selected communication method is the full-duplex communication method or the half-duplex communication method;
The communication method is selected such that the sum of the system channel capacity calculated based on the information on the interference signal strength, the signal strength information between the base station and the terminal, and the signal strength information between the base station and the other terminal is the maximum, A method of performing communication of a terminal. The method of claim 1,
The method further comprising the step of receiving information indicating that selection of the communication method is performed in units of a predetermined resource block (RB) from the base station before measuring the interference signal strength from the other terminal,
A method of performing communication of a terminal for measuring the interference strength of the other terminal in the predetermined RB unit. 3. The method of claim 2,
The measured interference strength of another terminal is an average value for the predetermined RB unit. In a method for a base station to support communication method switching of a terminal in a system supporting a full-duplex communication method and a half-duplex communication method, the method comprising:
Receiving information about the interference signal strength from another terminal measured by the at least one terminal from at least one terminal;
obtaining information on signal strength between the base station and the at least one terminal;
Selecting a communication method for each of the at least one terminal such that the sum of system channel capacities calculated based on the information on the interference signal strength and the information on the signal strength between the base station and the at least one terminal becomes the maximum ; and
Comprising the step of transmitting information on the selected communication method to each of the at least one terminal,
The selected communication method is the full-duplex communication method or the half-duplex communication method, the base station supporting the communication method switching of the terminal. delete 5. The method of claim 4,
The method further comprising transmitting information indicating that selection of the communication method is performed in units of a predetermined resource block (RB) to the at least one terminal before receiving the information on the interference signal strength,
The received interference signal strength is that the interference strength of the other terminal is measured in the predetermined RB unit, the base station supporting the communication method switching of the terminal. 7. The method of claim 6,
The measured interference strength of the other terminal is an average value for the predetermined RB unit, the method of the base station supporting communication method switching of the terminal. 5. The method of claim 4,
The measured interference strength of the other terminal is the average interference strength of the entire system bandwidth, the base station supporting the communication method switching of the terminal. In a terminal for switching a communication method in a system supporting a full-duplex communication method and a half-duplex communication method,
a processor for measuring the strength of an interference signal from another terminal;
a transmitter for transmitting information on the measured strength of an interference signal from another terminal to a base station; and
Comprising a receiver for receiving information on the communication method selected by the base station,
The processor controls the communication to be performed in the selected communication method,
The selected communication method is the full-duplex communication method or the half-duplex communication method;
The communication method is provided to the base station so that the sum of the system channel capacity calculated based on the information on the interference signal strength, the signal strength information between the base station and the terminal, and the signal strength information between the base station and the other terminal becomes the maximum. selected by the terminal. In a base station supporting communication method switching of a terminal in a system supporting a full-duplex communication method and a half-duplex communication method,
a receiver for receiving information on interference signal strength from another terminal measured by the at least one terminal from at least one terminal;
The signal strength between the base station and the at least one terminal is measured, and the sum of the system channel capacity calculated based on the information on the interference signal strength and the measured signal strength between the base station and the at least one terminal is the maximum. a processor for selecting a communication method for each of the at least one terminal so as to become and
A transmitter for transmitting information on the selected communication method to each of the at least one terminal,
The selected communication method is the full-duplex communication method or the half-duplex communication method.

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