KR101802078B1 - Wireless communication system using variable full-duplex and method for improving communication performance using the same - Google Patents

Abstract

The present invention relates to a wireless communication system using a variable full-duplex method and a method for improving communication performance by using the same. According to the present invention, the method for improving the communication performance using the wireless communication system using the variable dull-duplex method comprises the steps of: a relay terminal, which relays a signal of a transmission terminal occupying a channel at a cell edge, detecting a first channel state between the relay terminal and the transmission terminal; detecting a second channel state between a transmission antenna and a receipt antenna included in the relay terminal; comparing the first channel state with the second channel state by each sub-carrier; in the case that the number of the sub-carriers where the first channel state is better than the second channel state is greater than a predetermined critical value, selecting the full-duplex method and in the case the number of the sub-carriers is equal to or less than the critical value, selecting a half-duplex method; and relaying the signal to a base station or a receipt terminal using the selected full-duplex or half-duplex method. The present invention uses the variable full-duplex communication considering the channel state in a relay node in the case of using cooperative communications additionally using the relay node in a wireless LAN, thereby increasing waiting time of the relay node to save power consumption.

Description

TECHNICAL FIELD [0001] The present invention relates to a wireless communication system using a variable full duplex method and a communication performance improving method using the same,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wireless communication system using a variable full duplex method and a communication performance improving method using the same, and more particularly to a wireless communication system capable of communication in a variable full duplex manner at a relay node, And a method for improving performance.

In recent years, computer and internet technologies have rapidly developed and the spread of portable computers has spread, and the field of computer communication technology has been rapidly increasing in the world. In order to guarantee such mobility, a wireless local area network (WLAN) technology, which applies wired / wireless communication technology to computer communication technology, has been applied and has become a representative wireless communication technology.

In a basic configuration of a wireless LAN, wireless communication is performed through a connection between a base station (BS) connected to a wireline and a user terminal which is guaranteed to be mobile. In order to perform such wireless communication, it is necessary to consider the battery capacity problem of the terminal in addition to the problems of transmission method of the BS and the terminals, signal interference, connection method, and the like.

Even if the terminal has good performance, if the capacity of the battery is insufficient or the consumption of the battery is large, the good performance can not be utilized. In the worst case, the basic communication becomes impossible and the terminal operation becomes difficult. One of the ways to use the battery of the terminal for a long time is to increase the capacity of the battery, and to save power in the transmission section.

However, in order to meet such demands, it is necessary to develop a low-power system that can reduce the power consumption of the battery.

The technology which is the background of the present invention is disclosed in Korean Patent No. 1218726 (published on Jan. 21, 2013).

The present invention relates to a wireless communication system using a variable full duplex scheme capable of reducing power consumption of a relay node when cooperative communication is further performed using a relay node in a wireless LAN network and a method for improving communication performance using the wireless communication system .

The present invention provides a method for improving communication performance using a wireless communication system using a variable full duplex method, the method comprising: detecting, by a relay terminal, a signal of a transmitting terminal occupying a channel outside a cell, Detecting a second channel state between a transmission antenna and a reception antenna included in the relay terminal, comparing the first channel state and the second channel state for each subcarrier, Selecting a full duplex scheme when the number of subcarriers whose channel state is better than the second channel state is greater than a preset threshold value and selecting a half duplex scheme when the number of subcarriers is less than the predetermined threshold value, Or to a receiving terminal by using the relay station.

Here, the step of comparing the first channel state with the second channel state may include comparing the first channel state with a second channel state to which a predetermined weight is assigned, for each subcarrier, It can have a positive value.

Further, the weight W _K can be set in a range of 0.01? W _K ? 0.02.

The comparing of the first channel state and the second channel state may further include calculating an Euclidean distance of the first channel state and an Euclidean distance of the second channel state for each subcarrier, Can be compared.

Also, the threshold value may correspond to half of the total number of subcarriers.

The present invention provides a wireless communication system using a variable full duplex scheme, comprising: a transmission terminal occupying a channel outside a cell of a base station; a transmission terminal having a transmission antenna and a reception antenna; Wherein the relay terminal comprises a channel state detector for detecting a first channel state between the transmitting terminal and a second channel state between the transmitting antenna and the receiving antenna, A channel state comparison unit for comparing the first channel state and the second channel state on a subcarrier basis; and a second state determiner for, if the first channel state is greater than a predetermined threshold, And selects a half-duplex mode when the selected value is lower than or equal to the threshold value, And a communication unit for relaying the signal to the base station or the reception terminal by using a full-duplex or half-duplex scheme.

According to the wireless communication system using the variable full duplex method and the communication performance improving method using the same according to the present invention, when the cooperative communication that further uses the relay node in the wireless LAN network is used, The duplex communication is advantageous in that power consumption can be reduced by increasing the waiting time of the relay node.

1 is a diagram showing a system model to which an embodiment of the present invention is applied.
2 is a diagram illustrating a power management operation of a general wireless LAN.
FIG. 3 is a flowchart illustrating an operation of a full-duplex communication used in a relay terminal according to an exemplary embodiment of the present invention.
4 is a diagram illustrating a configuration of a relay terminal according to an embodiment of the present invention.
5 is a diagram illustrating a communication performance improving method using FIG.
6 is a graph showing a transmission rate according to the number of nodes outside the coverage area of the base station.
7 is a graph showing the average power consumption per communication of 1 Mbyte.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention.

1 is a diagram showing a system model to which an embodiment of the present invention is applied. In FIG. 1, the entire cell area by the base station (BS) is divided into four groups according to the distance from the base station (BS). Specifically, group 1 (54Mbps) within 25m, group 2 (36Mbps) within 25 ~ 50m, group 3 (18Mbps) within 50 ~ 75m and group 4 (9Mbps) within 75 ~ 100m. The parentheses indicate the data rate of the group.

It can be seen from FIG. 1 that the transmission rate of a node (terminal) becomes lower toward the group 1 to 4, that is, toward the outer side of the cell. Of course, there may be various variations in the number of groups divided in the cell, the distance reference for dividing, and the transmission rate of each group in FIG.

In the embodiment of the present invention, a node belonging to group 4 is defined as a node outside the cell. When a node outside the cell belonging to group 4 (low-speed node) occupies the channel in the system, It is assumed that a node belonging to an adjacent group 3 supporting a high data rate is used as a relay terminal.

The relay node belonging to the group 3 receives the signal sent from the low-speed node (the transmitting node) belonging to the group 4 and performs the relay communication to transmit the signal to the base station or the receiving node again. At this time, the relay node uses full-duplex or half-duplex communication.

The full duplex scheme consumes only one time slot for receiving a signal from the transmitting node and sending the signal to the base station, and the half duplex scheme consumes two time slots. Considering the power consumption of the terminal in the position of the relay terminal, the full-duplex mode in which relay communication is performed only during one time slot is more advantageous than the half-duplex mode.

A power management operation of an existing wireless LAN will be described below to facilitate understanding of the present invention. 2 is a diagram illustrating a power management operation of a general wireless LAN.

Upon receiving the beacon frame signal broadcasted from the base station (BS), each of the nodes (nodes 1,2,3) in the cell checks whether there is data to be transmitted to the base station (BS) based on the received beacon frame signal . If data is present, the nodes connected to the base station (BS) transmit the PS-POLL to the base station (BS) to occupy the channel.

The base station BS schedules and broadcasts channel occupation time information for each node based on the PS-POLL signal received from each node. Each node operates in an awake mode for a time occupied by a channel based on its channel occupation time information, and communicates data. In a power saving state (PS) Mode.

In the case of FIG. 2, when node 1 occupies the channel, node 3 exists in PS state, and node 3 occupies the channel, then node 1 exists in PS state. In this way, the BS broadcasts expected channel occupancy time information for each node, and each node waits in the PS state for a time occupying the channel, thereby saving power consumption.

In the case of a relay node, when the signal is not relayed, it waits in the PS state to reduce power consumption. When a full-duplex system is used for relay communication, only one time slot is required. Therefore, the wake-up time is shorter than the half-duplex mode, and the power consumption is less because the wait time of the PS state is long. Therefore, it can be seen that the full-duplex communication having a relatively long waiting time consumes less power than the half-duplex communication.

FIG. 3 illustrates the operation of the full-duplex communication used in the relay terminal in the embodiment of the present invention. In FIG. 3, the transmitting node S means a terminal occupying a channel in a cell outside, and the relay node R serves to relay the signal of the transmitting node S to the receiving node D. At this time, the receiving node D may correspond to a base station or another terminal.

Hereinafter, for convenience of explanation, it is assumed that the transmitting node S is a transmitting terminal, the relay node R is a relay terminal, and the receiving node D is a base station. Generally, in full-duplex communication, reception and transmission of signals occur simultaneously during one time slot (Time slot 1). The relay terminal R using the full-duplex communication in the cooperative communication scheme of FIG. 3 also performs the operation of receiving a signal from the transmitting terminal S and sending a signal to the base station D in one time slot. Of course, when half duplex communication is used, the relay terminal R performs an operation of receiving a signal and a sending operation in individual time slots (Time slots 1 and 2).

In the full-duplex communication of the relay terminal R when the cooperative communication is used in the wireless LAN, the channel H _SR between the transmitting terminal S and the relay terminal R, the Tx antenna within the relay terminal R, A channel (H _RR ) (Self-interference) between Rx antennas is considered.

Since the distance between the transmitting antenna and the receiving antenna of the relay node R is much closer than the distance between the transmitting node S and the relay node R, Self-interference effect occurs largely. Of course, the influence of magnetic interference is not taken into consideration in half-duplex communication in which signal transmission and reception are performed in separate time slots.

Generally, when a terminal outside a cell of a base station occupies a communication channel, as shown in FIG. 1, a communication supporting a low transmission rate is used for communication reliability. In this case, when a cooperative communication using an additional relay terminal is used, But the power consumption of the relay terminal is increased.

In the embodiment of the present invention, a terminal occupying a channel in a cell outer area in a wireless LAN network communicates with a relay terminal in a better position to improve a transmission rate, and at the relay terminal, two channel states (H _SR , H _RR ) By using variable full-duplex communication in which the full-duplex or half-duplex mode is selected, power consumption can be reduced by increasing the waiting time of the relay terminal.

4 is a diagram illustrating a configuration of a relay terminal according to an embodiment of the present invention. The relay terminal R according to the embodiment of the present invention includes a channel status detection unit 1, a channel status comparison unit 2, a control unit 3, and a communication unit 4.

The channel state detection unit 1 detects a first channel state (H _SR ) between the relay terminal R and the transmission terminal S and detects a second channel state H (H) between a transmission antenna and a reception antenna in the relay terminal R _RR ). Techniques for estimating channel conditions are well known.

Here, the channel state is obtained for each subcarrier. The subcarrier means an object used for modulating each information signal in OFDM which is a multiplexing technique used in a wireless LAN.

If, the number of subcarriers used in the OFDM, if the 64 (N _K), the first channel state (H _SR) is a 64 channel state corresponding to the 64 sub-carriers is obtained, and the second channel state (H _RR) 64 channel states corresponding to 64 subcarriers are also obtained.

In addition, 64 channel states corresponding to 64 subcarriers can be obtained by exchanging known signals between the relay terminal R and the transmission terminal D in advance. 64 channel states can be obtained between the transmission antenna and the reception antenna in the relay terminal R in the same manner.

The channel state comparison unit 2 compares the first channel state (H _SR ) and the second channel state (H _RR ) for each subcarrier. That is, two channel states of subcarriers of the same index are compared with each other, and a comparison result is obtained by the number of subcarriers (ex, 64).

Here, the Euclidean distance can be utilized when comparing the channel states. That is, the Euclidean distance of the first channel state and the Euclidean distance of the second channel state are calculated and compared with each other for each subcarrier.

This is achieved by separately calculating the Euclidean distance corresponding to the channel state of each subcarrier, and then comparing the Euclidean distances between subcarriers of the same index with each other.

The channel state coefficient of each subcarrier may have a complex number form such as a + jb. The Euclidean distance corresponding to the channel state coefficient is the closest distance of the corresponding vector (a, b) at the origin (0, 0) , a ² and b ² can be added together and root (√) can be calculated. This represents the L2-norm of (a, b).

로 표현될 수 있고, 송신 안테나로부터 수신 안테나로의 제2 채널 상태(H_RR)의 유클리디안 거리는

로 표현될 수 있다. The Euclidean distance of the first channel state (H _SR ) between the transmitting terminal S and the relay terminal R considered for the kth subcarrier in the embodiment of the present invention is

And the Euclidean distance of the second channel state (H _RR ) from the transmit antenna to the receive antenna can be expressed as

. ≪ / RTI >

과

을 비교하면 된다. 여기서 물론, 서브 캐리어의 인덱스 k는 k = 1, 2, …, N_K로 정의된다.The relay terminal R is provided for each subcarrier

and

. Of course, the index k of the subcarriers is k = 1, 2, ... , N _K , respectively.

If the first channel state (H _SR ) is higher than the second channel state (H _RR ) and the number of subcarriers that are superior to the second channel state (H _RR ) is greater than a preset threshold value, the controller 3 selects the full- Select the half-duplex method. In the embodiment of the present invention, the threshold value may use N _K / 2 values corresponding to half of the total number of subcarriers (N _K ).

The communication unit 4 relays the signal of the transmitting terminal S to the base station or the receiving terminal by using the full duplex or half duplex manner adaptively selected by the control unit 3. [

If the full-duplex communication method is used in the relay terminal R, when detecting a signal received from the transmitting terminal S as compared with when the full-duplex communication is not used, the H _RR is considered as additional interference, . Therefore, in the proposed method, in order to reduce additional interference caused by the use of full-duplex communication when the relay terminal R detects a signal received from the transmitting terminal S, when the influence of the H _RR is not large compared to the H _SR Only full-duplex communication is used.

Embodiment of the present invention is larger the first channel state (H _SR) is the number of the second channel state superior subcarrier than (H _RR) N _K / is greater than the second value, the effect of H _RR preparation and H _SR Duplex communication is selected. On the contrary, if the value is less than or equal to the N _K / 2 value, it is determined that the influence of magnetic interference by the H _RR is large, and half-duplex communication which does not need to consider magnetic interference is selected.

According to the present embodiment, power consumption can be greatly reduced compared to when half duplex communication is used at all times, and full duplex communication is performed only when the influence of magnetic interference is small, thereby improving the reliability of the system.

Also, in the embodiment of the present invention, a weight value W _K is added to the second channel state (H _RR ) when the first channel state (H _SR ) and the second channel state (H _RR ) are compared. The weight (W _K ) is a positive value between 0 and 1.

The reason why the weight is smaller than 1 is that the distance between the transmitting antenna and the receiving antenna in the relay terminal R is much closer than the distance between the transmitting terminal S and the relay terminal R. [ That is, since the channel state is measured largely as the distance is closer, the weight for H _RR is set to a value smaller than 1.

과

을 비교할 때,

에는 1보다 작은 가중치(W_K)를 부여하여 비교를 한다. 본 발명의 실시예에서 가중치는 .01 ≤ W_K ≤ 0.02 범위에서 설정되는데 이는 모의 실험을 통해 결정된 값이다.therefore,

and

When compared,

(W _K ) smaller than 1 are given to perform comparison. In the embodiment of the present invention, the weight is set in a range of .01? W? _K ? 0.02, which is a value determined through simulation.

Equation (1) below shows a formula for comparing two channel states for all subcarriers in an embodiment of the present invention.

In Equation (1), n is a value that increases (accumulates) when the influence of H _RR is relatively small compared to H _SR in a specific subcarrier. As a result of performing all the N _K (ex, 64) subcarriers, the full duplex communication method is used only when the value of last updated n is larger than half (ex, 32) of the total number of subcarriers do.

5 is a diagram illustrating a communication performance improving method using FIG. A communication performance improving method according to an embodiment of the present invention will now be described.

The relay terminal R detects the first channel state (H _SR ) and the second channel state (H _RR ) respectively (S510). The first channel state (H _SR ) and the second channel state (H _RR ) are compared for each subcarrier (S520).

If later, the first channel state (H _SR) is said second channel state (H _RR) larger the number of excellent subcarriers rather than below the set compared with a threshold to (S530), the threshold value is selected for full-duplex, and (S540) , And if it is less than or equal to the threshold value, the half duplex mode is selected (S550).

Then, in step S560, a signal of the transmitting terminal S is relayed to the base station or the receiving terminal using the selected full-duplex or half-duplex method.

Hereinafter, a simulation result comparing the power saving effect of the present invention with the conventional technique will be described. In order to compare the performance, we compared the existing wireless LAN with existing cooperative communication method, always using full duplex communication at relay node, and the method of this embodiment using variable full duplex communication.

FIG. 6 is a graph showing a transmission rate according to the number of nodes outside the coverage area of a base station (BS), and FIG. 7 is a graph showing an average power consumption per communication of 1 Mbyte.

In Figure 6, transmission rate was obtained using a transmission rate and FER (frame error rate, F _e) of the occupied channels in a wireless local area network of a BS node units, each frame is assumed to have been configured with 100bit.

Equation (2) means a calculation formula of FER when cooperative communication is not used.

In Equation (2), B _e is the bit error rate (BER), and L is the length of the frame.

Equation (3) represents a calculation formula of FER when cooperative communication is used.

In Equation (3), B _e ^R is the BER at the relay node, and B _e ^D is the BER at the receiving node.

Equation (4) represents an equation for calculating a transmission rate.

E (·) in equation (4) refers to the expected value and, R _i is a transmission rate of the i-th group of nodes, (F _{e) i} is FER, P _i when the node of the i-th group have been occupied by the channel i And the probability that the node of the ith group will occupy the channel.

In the graph of FIG. 6, '○' indicates a Wi-Fi based on the existing Wi-Fi, '□' indicates a cooperative communication method using a single existing relay terminal, '+' indicates cooperation using a plurality of existing relay terminals Communication method, '◇' is a cooperative communication method that uses single relay terminal but always uses full duplex method.

The remaining graphs, that is, '◁', '▷', and '∘' are cooperative communications using a variable full duplex scheme according to an embodiment of the present invention, and the weights W _k are set to 0.01, 0.02, and 0.05, respectively. The graphs of '◁' and '▷' using the weights of 0.01 and 0.02, respectively, show that the transmission rate is superior to that of the conventional method.

As described above, the method according to the embodiment of the present invention improves the transmission rate compared to the conventional method, and it can be confirmed that the transmission rate is greatly improved as the number of nodes outside the coverage of the base station increases (nunber of user in group 4).

Table 1 shows the power consumption per second in the wireless LAN.

condition send reception AM waiting PS standby Power Consumption 1875mw 1300mW 1080mw 45mW

The average power consumption shown in FIG. 7 indicates the time required for all the nodes in the coverage of the base station to maintain transmission, reception, and standby states until transmission and reception of 1 Mbyte data are completed, and power consumption per second .

Referring to the graph of FIG. 7, the technique according to an embodiment of the present invention significantly reduces power consumption by reducing the time for nodes to maintain the transmission and reception state than the conventional method. As the number of nodes outside the coverage of the base station increases It can be confirmed that the power consumption is greatly improved.

According to the wireless communication system using the variable full duplex method and the communication performance improving method using the same according to the present invention, when the cooperative communication that further uses the relay node in the wireless LAN network is used, Or a variable full duplex communication in which a half-duplex scheme is adaptively selected, there is an advantage that power consumption can be reduced by increasing the waiting time of the relay node.

While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. Accordingly, the true scope of the present invention should be determined by the technical idea of the appended claims.

S: transmitting terminal R: relay terminal
1: channel state detecting unit 2: channel state comparing unit
3: control unit 4: communication unit

Claims (10)

A method for improving communication performance using a wireless communication system using a variable full duplex method,
Detecting a first channel state between the transmitting terminals by a relay terminal relaying a signal of a transmitting terminal occupying a channel at a cell outskirt;
Detecting a second channel state between a transmission antenna and a reception antenna included in the relay terminal;
Comparing the first channel state and the second channel state for each subcarrier;
Selecting a full duplex mode when the number of subcarriers whose first channel state is greater than a predetermined threshold value and selecting a half-duplex mode when the number of subcarriers is less than the predetermined threshold; And
And relaying the signal to a base station or a receiving terminal using the selected full duplex or half duplex scheme. The method according to claim 1,
Wherein the comparing the first channel state and the second channel state comprises:
Comparing the first channel state and a second channel state given a predetermined weight value for each subcarrier,
Wherein the weight has a positive value less than one. The method of claim 2,
Wherein the weight (W _K ) is set in a range of 0.01? W _K ? 0.02. The method of claim 2,
Wherein the comparing the first channel state and the second channel state comprises:
And calculating the Euclidean distance of the first channel state and the Euclidean distance of the second channel state for each subcarrier, and compares the calculated Euclidean distance and the Euclidean distance of the second channel state. The method according to claim 1,
Wherein the threshold corresponds to one half of the total number of subcarriers. In a wireless communication system using a variable full duplex scheme,
A transmitting terminal occupying a channel outside a cell of a base station; And
And a relay terminal having a transmitting antenna and a receiving antenna and relaying the signal of the transmitting terminal to the base station or the receiving terminal by using a half-duplex or full-
The relay terminal,
A channel state detector for detecting a first channel state between the transmitting terminals and detecting a second channel state between the transmitting antenna and the receiving antenna;
A channel state comparator for comparing the first channel state and the second channel state for each subcarrier;
Selecting a full duplex mode when the first channel state is greater than a preset threshold value and selecting a half duplex mode when the first channel state is less than the threshold value; And
And relaying the signal to the base station or the receiving terminal using the selected full-duplex or half-duplex mode. The method of claim 6,
Wherein the channel state comparison unit comprises:
Comparing the first channel state and a second channel state given a predetermined weight value for each subcarrier,
Wherein the weight has a positive value less than one. The method of claim 7,
Wherein the weight (W _K ) is set in a range of 0.01? W _K ? 0.02. The method of claim 7,
Wherein the channel state comparison unit comprises:
And calculates the Euclidean distance of the first channel state and the Euclidean distance of the second channel state for each subcarrier, and compares the calculated Euclidean distance and the Euclidean distance of the second channel state. The method of claim 6,
Wherein the threshold corresponds to half the total number of subcarriers.

Images