KR20100092618A - Apparatus and method for communication in wireless communication network - Google Patents

Abstract

PURPOSE: A communication apparatus in a wireless communication network and a method thereof are provided to measure quality of a transfer channel through a frame that a transmitting terminal or a receiving terminal transfers to simultaneously select a relay target terminal, thereby reducing overhead due to corroborative communication. CONSTITUTION: A relay control unit(140) includes an identification number of a relay target terminal in the first data frame transferred by a frame transceiver(110). If a request frame notifying the use of collaborative communication is received from the relay target terminal, the relay control unit transmits a relay frame notifying initiation of the collaborative communication to a receiving terminal. If a response frame is received from the receiving terminal, the relay control unit transmits the second data frame transmitted from the relay target terminal to the receiving terminal.

Description

Apparatus and method for communication in wireless communication network

The present invention relates to a communication apparatus and method in a wireless communication network, and more particularly, to an apparatus and method for receiving a data frame or a data frame transmitted by another transmitting terminal in a wireless communication network and transmitting the same to a receiving terminal. .

Data communication according to the IEEE 802.11a / b / g standard for a wireless LAN network supports high data rate communication in order to satisfy increasing user demand for transmission delay. In addition, according to the wireless communication environment, a plurality of transmission speeds are defined to maximize transmission efficiency. Receiver-based rate adaptation technology is a technique for utilizing these multiple transmission rates. The transmitting terminal transmits a request-to-send (RTS) frame and the receiving terminal transmits the RTS frame immediately before transmitting data. In the receiving process, the quality of the transmission channel is measured. Next, the receiving terminal determines the data transmission rate of the transmitting terminal and provides it to the transmitting terminal through a clear-to-send (CTS) frame.

At this time, if the transmission channel quality from the transmitting terminal to the receiving terminal is not good and a high transmission rate cannot be used, the relay terminal can use a high transmission rate because both the receiving channel quality from the transmitting terminal and the transmission channel quality to the receiving terminal are good. The data transmission method using the data is called cooperation communication.

Conventionally, when selecting a relay terminal for cooperative communication, a method of selecting a relay terminal immediately before the transmitting terminal collects information on a transmission speed and transmits data is used. However, there is a fear that the transmitting terminal may select the wrong relay terminal because the available transmission speed cannot be measured in real time according to the quality of the transmission channel. Accordingly, there is a problem in that, due to cooperative communication, transmission delay may be increased or additional overhead may be generated to cancel the selection of a wrong relay terminal.

In addition, in IEEE 802.11, a distributed coordination function (DCF) is used to prevent transmission collisions between a plurality of transmission terminals or to prevent a specific transmission terminal from monopolizing a transmission channel. The DCF is a method for sharing and using one channel in a network composed of a plurality of stations, that is, only transmitting terminals that can win data. Each transport terminal controls the use of the transport channel through a contention window and a backoff mechanism.

First, the transmitting terminal to transmit data checks whether the transmission channel is busy or idle. The use state refers to a state in which another transmitting terminal first transmits data by occupying a transmission channel, and the idle state refers to a state in which no transmission terminal using a transmission channel exists. If it is determined that the transmission channel is in the idle state, the state of the transmission channel is continuously checked during the DIFS (DCF interframe space), which is an interframe interval, and the data frame is transmitted if the transmission channel is in the idle state. As a result of the check, if the transport channel is in use, data transmission is delayed until it is idle. At this time, if there are a large number of transmission terminals waiting for the transport channel to be changed, the collision probability is highest at the end of the DIFS period. Therefore, IEEE 802.11 minimizes collisions between contention terminals through a backoff mechanism.

Each transmitting terminal has a contention window and a backoff timer, and when the data transmission attempt is made, a random value is selected in the contention window to determine the backoff timer. Each transmitting terminal detects the state of the transport channel through virtual carrier sensing, and maintains the value of the backoff timer if the channel is in use, and decreases the value of the backoff timer if the channel is idle. When the backoff timer value reaches 0, it attempts to transmit data. At this time, if a collision occurs in the transmission process, the contention window is doubled, and accordingly, the value of the backoff timer is determined again to retransmit.

At this time, in a network that can use cooperative communication, there is a transmitting terminal that transmits data to a receiving terminal through a relay terminal or directly to a receiving terminal without passing through a relay terminal. Therefore, when the cooperative communication is performed, a duration field of a frame transmitted by the transmitting terminal, the relay terminal, and the receiving terminal should be appropriately set for virtual carrier sensing.

The technical problem to be achieved by the present invention is a communication apparatus and method in a wireless communication network that can reduce the overhead caused by the wrong relay terminal by reflecting the environment and data transmission speed of the transmission channel that changes in real time in the wireless communication network To provide.

Another technical problem to be solved by the present invention is to provide a communication method in a wireless communication network that can reduce overhead caused by an incorrect relay terminal by reflecting the environment and data transmission speed of a transmission channel that changes in real time in a wireless communication network. The present invention provides a computer-readable recording medium that records a program for execution on a computer.

In order to achieve the above technical problem, a communication apparatus in a wireless communication network according to the present invention includes a frame transmitting and receiving unit for transmitting a frame to or receiving a frame from another terminal device constituting a wireless communication network; The transmission rate used in the transmission channel with the transmitting terminal transmitting the frame to the receiving terminal which is the destination of the frame to be transmitted, the transmission rate used in the transmission channel with the receiving terminal, and the transmission channel between the transmitting terminal and the receiving terminal. A transmission rate measuring unit for measuring a transmission rate; When the data is transmitted from the transmitting terminal to the receiving terminal by performing relay transmission by the first transmission delay and cooperative communication when data is directly transmitted from the transmitting terminal to the receiving terminal based on the measured transmission rate. A relay target terminal determining unit for calculating a second transmission delay and determining the transmission terminal as a relay target terminal for providing cooperative communication when the second transmission delay is less than the first transmission delay; And an identification number of the relay target terminal in a first data frame transmitted to the receiving terminal by the frame transceiver, and receiving a request frame informing the use of the cooperative communication from the relay target terminal. And a relay controller configured to transmit a relay frame notifying start of the transmission, and to transmit a second data frame transmitted from the relay target terminal to the receiving terminal when a response frame indicating that cooperative communication is available from the receiving terminal is received.

In order to achieve the above technical problem, a communication method in a wireless communication network according to the present invention includes a transmission rate used in a transmission channel with a transmission terminal for transmitting a frame to a reception terminal, which is a destination of a frame to be transmitted, and the reception. A transmission rate measuring step of measuring a transmission rate used in a transmission channel with a terminal and a transmission rate used in a transmission channel between the transmitting terminal and the receiving terminal; A first transmission delay when data is directly transmitted from the transmitting terminal to the receiving terminal based on the measured transmission rate, and relay transmission by cooperative communication, thereby performing data transmission from the transmitting terminal to the receiving terminal; A relay target terminal determining step of calculating a second transmission delay and determining the transmitting terminal as a relay target terminal for providing cooperative communication if the second transmission delay is less than the first transmission delay; And an identification number of the relay target terminal in the first data frame transmitted to the receiving terminal, and when the request frame notifying the use of the cooperative communication is received from the relay target terminal, the relay notifying the start of the cooperative communication to the receiving terminal. And a relay control step of allowing a frame to be transmitted and transmitting a second data frame transmitted from the relay target terminal to the receiving terminal when a response frame indicating that cooperative communication is available from the receiving terminal is received.

According to another aspect of the present invention, there is provided a communication apparatus in a wireless communication network, the frame transmitting and receiving unit for transmitting a frame to or receiving a frame from another terminal device constituting a wireless communication network; The transmission rate used in the transmission channel with the relay terminal providing cooperative communication so that the frame is relayed to the receiving terminal which is the destination of the frame to be transmitted, the transmission rate used in the transmission channel with the receiving terminal, and the relay terminal and the receiving terminal. A transmission rate measuring unit for measuring a transmission rate used in the transmission channel between the transmission rate measurement unit; When overhearing a frame indicating that cooperative communication provided by the relay terminal can be used, the first transmission delay when data is directly transmitted to the receiving terminal based on the measured transmission rate and the cooperative communication provided by the relay terminal Calculates a second transmission delay when the data is transmitted to the receiving terminal by performing relay transmission by the second transmission delay, and decides to use cooperative communication provided by the relay terminal if the second transmission delay is smaller than the first transmission delay. Cooperative communication decision unit; A control unit for transmitting a request frame for notifying the use of cooperative communication to the relay terminal and for transmitting a data frame to the relay terminal upon receiving a response frame indicating that cooperative communication is possible from the receiving terminal; And a contention window adjustment unit for increasing a contention window value for determining a waiting time for accessing a transmission channel to the reception terminal when the frame transceiver transmits a data frame to the relay terminal.

In another aspect of the present invention, there is provided a communication method in a wireless communication network according to an embodiment of the present invention in a transmission channel with a relay terminal for providing cooperative communication such that a frame is relayed to a receiving terminal which is a destination of a frame to be transmitted. A transmission rate measuring step of measuring a transmission rate used, a transmission rate used in a transmission channel between the receiving terminal, and a transmission rate used in a transmission channel between the transmitting terminal and the receiving terminal; When overhearing a frame indicating that cooperative communication provided by the relay terminal can be used, the first transmission delay when data is directly transmitted to the receiving terminal based on the measured transmission rate and the cooperative communication provided by the relay terminal Calculates a second transmission delay when the data is transmitted to the receiving terminal by performing relay transmission by the second transmission delay, and decides to use cooperative communication provided by the relay terminal if the second transmission delay is smaller than the first transmission delay. Determining cooperative communication; A control step of transmitting a request frame informing the use of the cooperative communication to the relay terminal and transmitting a data frame to the relay terminal upon receiving a response frame indicating that the cooperative communication is possible from the receiving terminal; And a contention window adjustment step of increasing a contention window value for determining a waiting time for accessing a transmission channel to the receiving terminal when a data frame is transmitted to the relay terminal.

According to a communication apparatus and method in a wireless communication network according to the present invention, the relay terminal measures the quality of a transmission channel through a frame transmitted by a transmitting terminal and a receiving terminal, and simultaneously selects a relay target terminal, It can reduce the overhead incurred. In addition, by controlling the cooperative communication in the relay terminal when there are a plurality of target terminals, it is possible to reduce the competition for the use of the transmission channel to improve the performance of the wireless communication network.

Hereinafter, exemplary embodiments of a communication apparatus and method in a wireless communication network according to the present invention will be described in detail with reference to the accompanying drawings.

Figure 1a is a block diagram showing the configuration of a preferred embodiment of a communication device in a wireless communication network according to the present invention.

Referring to FIG. 1A, a communication apparatus in a wireless communication network according to the present invention includes a frame transceiver 110, a transmission rate measurement unit 120, a relay target terminal determiner 130, and a relay controller 140. do. The communication apparatus in the wireless communication network illustrated in FIG. 1A is one of a plurality of transmitting terminals transmitting data to a receiving terminal of the wireless communication network, and may operate as a relay terminal for relaying and transmitting data of another transmitting terminal to the receiving terminal.

1B is a block diagram showing the configuration of another preferred embodiment of a communication apparatus in a wireless communication network according to the present invention.

Referring to FIG. 1B, a communication apparatus in a wireless communication network according to the present invention includes a frame transceiver 110, a transmission rate measuring unit 120, a cooperative communication determination unit 150, a contention window adjusting unit 160, and a controller. 170 is provided. The communication apparatus in the wireless communication network shown in FIG. 1B is a transmitting terminal that transmits data directly to a receiving terminal or by cooperative communication provided by a relay terminal. In addition, when the relay device is selected as a relay target terminal to receive cooperative communication, the communication device in the wireless communication network according to the present invention shown in FIG. 1B may operate as a relay target terminal. This will be described later in detail.

In this case, when the communication apparatus in the wireless communication network according to the present invention is used in a wireless communication network configured in an infrastructure mode, the access point is a transmitting terminal requiring cooperative communication provided by the relay terminal or Perform the function of the receiving terminal.

The frame transceiver 110 transmits a frame to or receives a frame from another terminal device constituting a wireless communication network. At this time, the relay controller 150 and the controller 170 determine whether the frame transceiver 110 transmits the frame or control the frame transmitted by the frame transceiver 110 based on the frame received by the frame transceiver 110. do. In addition, the transmission rate measuring unit 120 measures a transmission rate used in a transmission channel with another terminal device and a transmission rate used in a transmission channel between other terminal devices. Specifically, the transmission rate measuring unit 120 provided in the communication device of FIG. It measures the transmission rate used in the channel and the transmission rate used in the transmission channel between the transmitting terminal and the receiving terminal, and the transmission rate measuring unit 120 provided in the communication device of FIG. Measures the transmission rate used in the transmission channel with the relay terminal providing cooperative communication so that the frame is relayed, the transmission rate used in the transmission channel with the receiving terminal, and the transmission rate used in the transmission channel between the relay terminal and the receiving terminal. do.

2 is a diagram illustrating a wireless communication network including a plurality of transmitting terminals and a receiving terminal for receiving data from the transmitting terminals.

Referring to FIG. 2, terminal A is a receiving terminal for receiving data from other transmitting terminals, and terminals B to F are transmitting terminals. Among the transmitting terminals, terminal B and terminal C may transmit data with the shortest transmission delay when transmitting data directly to terminal A than when using cooperative communication provided by another neighboring terminal because the quality of the transmission channel to terminal A is good. Corresponds to the terminal. Therefore, the terminal B and the terminal C can operate as a relay terminal for providing cooperative communication to other transmitting terminals. In addition, the terminal D to the terminal F correspond to a terminal capable of transmitting data with a small transmission delay when the cooperative communication using the terminal B or the terminal C as a relay terminal due to the poor quality of the transmission channel to the terminal A. Accordingly, the terminal D to the terminal F may be selected as relay target terminals by terminal B and terminal C which are relay terminals.

If the transmission channel from the terminal B to the terminal A is represented by the channel BA, and the maximum transmission rate available in the channel BA is R _BA , the relationship between the maximum transmission rates available in the transmission channel between the terminal B to the terminal F and the terminal A is as follows. Is the same as

The transmitting and receiving terminals constituting the wireless communication network exchange RTS frames and CTS frames as control frames before transmitting data frames, and adjacent terminals of the transmitting terminals overhear the exchanged frames. The transmission rate measurement unit 120 may measure the maximum transmission rate used in the transmission channel by overhearing the RTS frame transmitted by the transmitting terminal and the CTS frame transmitted by the receiving terminal, and the data transmitted by the transmitting terminal to the receiving terminal through direct communication. It may be measured by interpreting a physical layer convergence protocol (PLCP) header of a frame. More specifically, the transmission rate measuring unit 120 measures a signal-to-noise ratio (SNR) when receiving or overhearing the RTS frame transmitted by the transmitting terminal and the CTS frame transmitted by the receiving terminal. The maximum transmission rate is determined by comparing the measured SNR with a threshold of a predefined SNR for each transmission rate. That is, when the transmitting terminal transmits a data frame at a specific transmission rate, the receiving terminal successfully receives the data frame when the SNR value measured when the receiving terminal receives a control frame is greater than the predefined SNR threshold value for that transmission rate. can do.

In a wireless communication network in which a communication apparatus in a wireless communication network according to the present invention is used, since all terminals use the same frequency band for transmission and reception, a transmission channel between a transmitting terminal and a receiving terminal is considered to be a symmetry channel. Can be. Therefore, the maximum transmission rate measured by receiving or overhearing the control frame of the adjacent terminal can be used in the data transmission process to the corresponding terminal. For example, the maximum data rate available on channel B-A is the same as the maximum data rate available on channel A-B.

In the wireless communication network illustrated in FIG. 1A, the relay target terminal determiner 130 provided in the relay terminal may transmit data from the transmitting terminal to the receiving terminal using the transmission rate measured by the transmission rate measuring unit 120. First transmission delay, which is a transmission delay in case of direct transmission, and relay transmission by cooperative communication, to calculate a second transmission delay, which is a transmission delay when data is transmitted from a transmitting terminal to a receiving terminal, and the second transmission delay If it is less than the first transmission delay, the corresponding transmission terminal is determined as a relay target terminal to provide cooperative communication. Hereinafter, a communication apparatus in the wireless communication network shown in FIG. 1B is defined as a relay target terminal.

When the maximum transmission rate that can be used in each transmission channel is measured by the transmission rate measuring unit 120, information about a transmission delay when transmitting data through each transmission channel can be obtained. When data is transmitted from a transmitting terminal to a receiving terminal, it is recognized that there is an advantage to provide cooperative communication only when the transmission delay in case of using cooperative communication is smaller than the transmission delay in case of direct communication. Accordingly, the relay target terminal determiner 130 sets the transmission delay in case of direct communication as the first transmission delay and the transmission delay in case of using cooperative communication as the second transmission delay, and the second transmission delay is the first transmission delay. Only the transmitting terminal that becomes smaller is identified and the terminal to be relayed is determined.

In addition, the relay terminal is also one of a plurality of transmitting terminals for transmitting data to the receiving terminal, and may sometimes determine a relay target terminal for providing cooperative communication while transmitting its data frame to the receiving terminal. In this case, the relay controller 140 includes the identification number of the relay target terminal and the number of frame retransmissions of the relay terminal in the header of the first data frame transmitted by the relay terminal to the receiving terminal. The receiving terminal receiving the data frame transmits to the relay terminal an acknowledgment frame, for example, an acknowledgment character (ACK) frame indicating that the data frame was successfully received. The ACK frame includes identification numbers of the relay target terminal, the relay terminal and the receiving terminal, and information on the number of times of frame retransmission of the relay terminal. Accordingly, the relay target terminal can recognize that it is determined as the relay target terminal by overhearing the data frame.

The transmission rate measuring unit 120 of the relay target terminal may include a transmission rate used in a transmission channel with a relay terminal, a transmission rate used in a transmission channel with a receiving terminal, and a transmission rate used in a transmission channel between the relay terminal and a receiving terminal. Measure At this time, when the frame including the identification number of the relay target terminal is transmitted between the relay terminal and the receiving terminal as described above, the coherent communication determining unit 150 directly transmits the data to the receiving terminal based on the measured transmission rate. Performing a relay transmission by the first transmission delay in case of transmission and cooperative communication provided by the relay terminal, calculating a second transmission delay when data is transmitted to the receiving terminal, and the second transmission delay is smaller than the first transmission delay. If so, it decides to use cooperative communication provided by the relay terminal.

Alternatively, the relay target terminal may be determined while the relay terminal has already relayed the data frame by the cooperative communication request of another transmitting terminal. The other transmitting terminal (hereinafter referred to as the transmitting terminal) collects information on the maximum transmission rate that can be used in the transmission channel from the transmitting terminal to the receiving terminal, the transmission channel from the transmitting terminal to the relay terminal, and the transmission channel from the relay terminal to the receiving terminal. do. Next, if it is determined that the cooperative communication of the relay terminal can transmit the data frame to the receiving terminal with a smaller transmission delay than when the data is transmitted to the receiving terminal by direct communication, a flag value indicating whether cooperative communication is possible in the relay terminal is displayed. Send an RTS frame set to true. The RTS frame with the flag set to TRUE contains the identification numbers of the transmitting and receiving terminals, the receiving and receiving terminals, the maximum transmission rate available in the transmitting channel from the transmitting and receiving terminals and the transmitting channel from the relay terminal to the receiving terminal. Information about the maximum baud rate is included. In addition, the duration field of the RTS frame used for virtual carrier sensing to determine the state of the transport channel is the maximum transmission speed available in the transport channel from the transmitter-to-relay terminal and the maximum available in the transport channel from the relay-to-receiver terminal. It is determined by the transmission speed and the size of the data frame to be transmitted.

When the frame transceiver 110 receives an RTS frame from which the flag value is set to true, the frame transceiver 110 transmits a partner clear-to-send (PCTS) frame, and then transmits a CTS frame indicating that the receiving terminal is capable of cooperative communication. Cooperative communication is started. Therefore, the transmitter terminal transmits the data frame to the relay terminal, and the relay terminal relays the data frame of the transmitter terminal to the receiver terminal.

When the relay terminal does not have a data frame to be transmitted to the receiving terminal in the process of relaying the data frame of the transmitter terminal, the relay target terminal determiner 130 may determine the relay target terminal. When the new relay target terminal is determined while relaying the data frame of the transmitter terminal, the header of the data frame to be relayed includes the identification number of the relay target terminal and the number of times of frame retransmission of the transmitter terminal. Accordingly, the ACK frame transmitted by the receiving terminal includes information on the identification number of the relay target terminal, the relay terminal and the receiving terminal, and the number of times of frame retransmission of the transmitter / receiver terminal.

As mentioned above, in order for the transmitting terminal to transmit data, a process of exchanging RTS and CTS control frames with the receiving terminal must be preceded. However, in case of data transmission by cooperative communication rather than direct communication, a transmitting terminal, a relay terminal and a receiving terminal are involved. Therefore, the process of exchanging control frames is also different from that of direct communication. First, a transmitting terminal to transmit data transmits an RTS frame to a relay terminal and a receiving terminal. After receiving the RTS frame, the relay terminal transmits a PCTS frame, which is a relay frame, to indicate the start of the cooperative communication to the receiving terminal, and finally the receiving terminal transmits a CTS frame, which is a response frame indicating that cooperative communication is possible, so that the transmitting terminal can transmit data. Announce that there is. The control frame transmitted as described above is transmitted at the basic transmission rate instead of the maximum transmission rate of the transmission channel. When one terminal transmits the control frame, both terminals except the corresponding terminal receive the transmitted control frame.

After the relay target terminal decides to use the cooperative communication, it transmits a request frame indicating the use of the collaborative communication, for example, an RTS frame, wherein the backoff timer value of the relay target terminal is smaller than the maximum contention window value defined in the IEEE 802.11 standard. If it is, the RTS frame is transmitted regardless of the current backoff timer value. Otherwise, the RTS frame is transmitted according to the IEEE 802.11 standard, ignoring the ACK frame transmitted from the receiving terminal. The transmitted RTS frame includes the identification number of the relay target terminal, the relay terminal and the receiving terminal, the maximum transmission rate available in the transmission channel from the relay target terminal to the relay terminal, and the maximum transmission rate available in the transmission channel from the relay terminal to the receiving terminal. Contains information about this. In addition, the duration field of the RTS frame used for sensing the state of the transport channel is determined by the information on the transmission rate measured by the relay target terminal.

Next, when receiving the RTS frame from the relay target terminal, the frame transmitting / receiving unit 110 of the relay terminal transmits a relay frame indicating a start of cooperative communication, for example, a PCTS frame to the receiving terminal. Information on the number and transmission rate measured when receiving the RTS frame is included. In addition, the duration field of the PCTS frame for virtual carrier sensing is determined by the duration field value of the RTS frame, the transmission rate measured by the relay terminal, and the information about the transmission rate included in the RTS frame. In this case, when the RTS frame is received, the frame transceiver 110 may transmit a PCTS frame unconditionally, but the relay controller 140 may use the transmission channel from the relay target terminal to the relay terminal measured when the RTS frame is received as the relay terminal. The frame transceiver 110 may transmit the PCTS frame only when the maximum transmission rate is greater than or equal to the maximum transmission rate available in the transmission channel from the relay target terminal included in the RTS frame to the relay terminal. Since the maximum transmission speed used in the transmission channel is changed in real time, the transmission speed when the relay terminal receives the RTS frame from the relay target terminal is measured by the relay target terminal and is larger than the transmission speed included in the RTS frame. This is because it can only be seen as a benefit of cooperative communication.

The receiving terminal that receives the RTS frame transmitted from the relay target terminal and the PCTS frame transmitted from the relay terminal measures the maximum transmission rate that can be used in the transmission channel from the relay target terminal to the receiving terminal and the transmission channel from the relay terminal to the receiving terminal. The receiving terminal transmits a response frame, for example, a CTS frame, indicating that cooperative communication is possible according to the measurement result. In this case, the CTS frame may include a flag indicating whether cooperative communication is available. The flag included in the CTS frame has a value of true or false. In order for the flag value to be set to true, 1) the receiving terminal receives a PCTS frame from the relay terminal within a preset time, and 2) the transmission rate of the transmission channel measured when the PCTS frame is received from the relay terminal included in the RTS frame. 3) The transmission delay when the cooperative communication is performed according to the transmission rate included in the PCTS frame and the transmission rate measured by the receiving terminal, that is, the second transmission delay. It should appear that the transmission delay of this direct communication, i.e., less than the first transmission delay. If the above three conditions are not satisfied, the receiving terminal transmits by setting the flag value of the CTS frame to false.

First, in the CTS frame where the flag value is set to true, the maximum transmission rate available in the transmission channel from the relay target terminal included in the PCTS frame to the relay terminal, and the transmission channel from the relay terminal to the receiving terminal measured when the receiving terminal receives the PCTS frame Includes the maximum baud rate available at. In addition, the duration field of the CTS frame for the virtual carrier sensing is determined by the duration field value of the RTS frame, information on the transmission rate included in the PCTS frame, and the transmission rate measured by the receiving terminal.

As described above, when the CTS frame having the flag value set to true is received from the receiving terminal, the frame transmitting / receiving unit 110 receives a second data frame to be transmitted from the receiving terminal to the receiving terminal. Relay transmission. That is, the relay target terminal transmits the data frame to the relay terminal at the maximum transmission speed available in the transmission channel from the relay target terminal included in the CTS frame to the relay terminal, and the relay terminal from the relay terminal specified in the CTS frame to the receiving terminal. The data frame is transmitted to the receiving terminal at the maximum data rate available in the transmission channel. Since the transmission speed of the transmission channel included in the CTS frame is the most recently measured transmission speed, the relay apparatus of the wireless communication network according to the present invention can perform cooperative communication by reflecting the transmission speed of the transmission channel that changes in real time. .

On the other hand, the CTS frame in which the flag value is set to false includes the maximum transmission rate that can be used in the transmission channel from the relay target terminal to the receiving terminal measured when the receiving terminal receives the RTS frame. In addition, the duration field of the CTS frame for the virtual carrier sensing is determined by the duration field value of the RTS frame and the transmission rate measured by the receiving terminal while receiving the RTS frame.

In addition, the relay target terminal means that the cooperative communication cannot be used when receiving the CTS frame with the flag value set to false. Therefore, the relay target terminal must perform direct communication with the receiving terminal. That is, the relay target terminal transmits the data frame to the receiving terminal at the maximum transmission rate included in the CTS frame than the estimated transmission time when the RTS frame is transmitted, and if the time required for receiving the ACK frame transmitted by the receiving terminal is greater, Transmits a data frame to the receiving terminal at the maximum transmission rate available in the transmission channel from the relay target terminal included in the frame to the receiving terminal, and transmits a control frame in which the duration field value is set to the time required for the receiving terminal to transmit the ACK frame. . Otherwise, the data frame is transmitted to the receiving terminal at the maximum transmission rate available in the transmission channel from the relay target terminal included in the CTS frame to the receiving terminal without additional control frame transmission.

The communication apparatus in the wireless communication network according to the present invention may determine another transmitting terminal as the second relay target terminal in the process of relaying the data frame of the relay target terminal to the receiving terminal. In this case, the relay controller 140 includes the identification number of the second relay target terminal and the number of frame retransmissions in the header of the data frame of the relay target terminal for relay transmission. The receiving terminal receiving the data frame transmits the ACK frame including the identification number of the second relay target terminal, the relay terminal and the receiving terminal, and information on the number of times of retransmission of the frame by the relay terminal to the relay target terminal. Subsequent processes are performed in the same manner as the control frame transmission and the data frame transmission between the relay target terminal, the relay terminal, and the receiving terminal. However, when the relay terminal determines the relay target terminal during the relay transmission of the data frame of the transmitter terminal, the number of frame retransmissions follows the number of frame retransmissions of the transmitter terminal.

As such, the relay target terminal transmits the data frame to the receiving terminal by cooperative communication provided by the relay terminal performed by receiving the CTS frame with the flag value set to true or direct communication performed by receiving the CTS frame with the flag value set to false. do. Subsequently, the contention window adjusting unit 160 of the relay target terminal sets the number of retransmissions of its own frame to be equal to the number of frame retransmissions of the relay terminal regardless of whether an ACK frame indicating that the data frame has been successfully received from the receiving terminal is received. It also increases the contention window for determining the backoff timer. At this time, it is preferable to increase the value of the contention window to double. If the increased contention window value is larger than the maximum contention window value defined in the IEEE 802.11 standard, the contention window value is adjusted to be equal to the maximum contention window value. The new backoff timer value is determined using the adjusted contention window value, which is added to the currently set backoff timer value.

 The relay controller 140 may include the identification numbers of the relay target terminals in the header of the data frame transmitted to the receiving terminal in a round-robin manner when there are a plurality of transmission terminals determined as the relay target terminals. This is to give equal opportunities to use cooperative communication in each relay target terminal. If the RTS frame notifying that the relay target terminal will be used after receiving the identification number of each relay target terminal is included in the header of the data frame transmitted from the relay terminal to the receiving terminal at least once, the corresponding relay target terminal needs the cooperative communication. Are classified as terminals that do not.

Hereinafter, a specific embodiment to which a communication apparatus in a wireless communication network according to the present invention is applied using terminals A to F shown in FIG. 2 will be described in detail with reference to the accompanying drawings.

3 illustrates an embodiment in which a communication apparatus in a wireless communication network according to the present invention is applied when a relay terminal (terminal B) transmits a data frame to a receiving terminal (terminal A) before the relay target terminal (terminal D). Figure is a diagram.

Referring to FIG. 3, UE B transmits an RTS frame 311 to transmit data frame 313 to UE A, and UE A responds to CTS frame 312 after a short interframe space (SIFS). SIFS is an interframe space used for transmission of control frames having the highest priority such as RTS, CTS, and ACK frames, and thus has the shortest interval so that transmission rights can be obtained earlier than other frames. The CTS frame 312 includes the R _BA measured by the terminal A while receiving the RTS frame 311. If there is a transmitting terminal capable of providing cooperative communication with the terminal B before transmitting the data frame 313, the terminal B selects one of the terminal D as a relay target terminal and a header of the data frame 313. ) Includes the identification number (ID) of the terminal D and the number of frame retransmissions of the terminal B. Terminal B receives CTS frame 312 and transmits data frame 313 after SIFS passes.

Terminal A, which has successfully received data frame 313, transmits an ACK frame 314 after SIFS to inform terminal B of receipt of a successful data frame. When the data frame 313 received by the terminal A includes the identification number (ID) of the terminal D, which is a relay target terminal, the ACK frame 314 is an identifier of the terminal D, the terminal B and the terminal A, and the frame of the terminal B. Including the number of retransmissions, the terminal D notifies the terminal A of data transmission through the cooperative communication with the terminal B. The higher the transmission rate is, the smaller the transmission radius of the data frame is, so that the terminal D may not successfully overhear the data frame 313 transmitted from the terminal B to the terminal A. By using the ACK frame transmitted to the UE D again informs the terminal A through the cooperative communication with the terminal B can transmit data.

The terminal D determined by the terminal B as a relay target terminal is R _DB , R _BA and R while overhearing the RTS frame 311 and the data frame 313 transmitted by the terminal B and the CTS frame 312 transmitted by the terminal A. Measure _DA . Therefore, when overhearing the ACK frame 314, it is possible to estimate the transmission delay when using cooperative communication using R _DB and R _BA , and the transmission delay when using direct communication using R _DA . . If the transmission delay of the cooperative communication is smaller than the transmission delay of the direct communication and the backoff timer value of the terminal D is smaller than the maximum contention window value defined in the IEEE 802.11 standard, the terminal D correlates to the value of the current backoff timer. ACK frame 314 without overhearing and transmits the RTS frame 321 for cooperative communication after SIFS.

Since the information about the transmission rate collected by the terminal B does not reflect the change in the transmission channel quality in real time, the transmission of the terminal D through the relay transmission of the terminal B may cause a loss in transmission delay compared to the direct communication. . However, the UE D determines whether to use cooperative communication according to the transmission rates R _DB , R _BA , and R _DA measured just before transmitting the RTS frame 321. Since abandoning the use of cooperative communication without incurring any overhead, the communication apparatus in the wireless communication network according to the present invention can effectively cope with the situation of a dynamically changing transport channel.

The RTS frame 321 transmitted by the terminal D for cooperative communication includes an identifier (ID) of the terminal D, the terminal B, and the terminal A, and R _DB , R _BA , and R _DA collected by the terminal D, and performs virtual carrier sensing. The duration field value of the RTS frame 321 is expressed by Equation 1 below.

Here, DUR _RTS is the duration field value of the RTS frame 321 transmitted by the terminal D, T _PCTS , T _CTS and T _ACK is the time required for transmitting the PCTS frame, CTS frame, ACK frame, respectively, L is the terminal D The size of the data frame to be transmitted, R _DB is the maximum speed available in the transmission channel from the terminal D to the terminal B, and R _BA is the maximum speed available in the transmission channel from the terminal B to the terminal A.

The terminal B measures the R _DB in the process of receiving the RTS frame 321, and transmits the PCTS frame 322 only when the measured R _DB is greater than or equal to the R _DB included in the RTS frame 321. PCTS frame 322 includes an identification number (ID) of the terminal A and the R _DB measured by the terminal B. The duration field value of the PCTS frame 322 for virtual carrier sensing is represented by Equation 2 below.

Here, DUR _PCTS is a duration field value of a PCTS frame, T _CTS and T _ACK are times required for transmitting a CTS frame and an ACK frame, respectively, L is a size of a data frame to be transmitted by UE D, and RR _DB is UE B. The measured R _DB and RT _BA are R _BA included in the RTS frame 321. When the RT _DB is an RT _DB included in the RTS frame 321, L may be calculated using DUR _RTS , RT _DB, and RT _BA represented by Equation 1.

UE A measures R _DA in the process of receiving the RTS frame 321, and measures R _BA in the process of receiving the PCTS frame 322. Terminal A 1) receiving the PCTS frame 322 in time for the two SIFS after receiving the RTS frame 321, and 2) the measured R _BA is than the R _BA contained in the RTS frame 321 is greater Or 3) If the R _DA and R _BA measured by the terminal A and the R _DB included in the PCTS frame 322 satisfy the condition shown in Equation 3 below, the flag value indicating whether cooperative communication is possible is true. The CTS frame 323 set as is transmitted. Otherwise, the CTS frame 323 is set with the flag set to false.

That is, the terminal A compares the transmission delay of the cooperative communication with the transmission delay of the direct communication to determine whether to use the cooperative communication, and informs the terminal D and the terminal B of the information through the CTS frame 323.

The CTS frame 323 in which a flag value indicating whether cooperative communication is set to true includes an R _DB specified in the PCTS frame 322 and an R _BA measured by the terminal A, and the CTS frame 323 for virtual carrier sensing. The duration field value of) is determined as in Equation 4 below.

Here, DUR _CTS is the duration field value of the CTS frame 323, T _ACK is the time required to transmit the ACK frame, L is the size of the data frame to be transmitted by the terminal D, RR _DB is included in the PCTS frame 322 R _DB , RR _BA is the R _BA measured by UE A. Let RT _DB and RT _{BA be} R _DB and R _BA specified in RTS frame 321, respectively, and L can be calculated using DUR _RTS , RT _DB and RT _BA .

In the same manner as described above, the terminal B and the terminal A re-measure the quality of each transport channel when receiving the RTS frame 321 and the PCTS frame 322 in the handshake process for the data transmission of the terminal D, the current transport channel If the situation is that the cooperative communication cannot be performed at the transmission rate specified in the RTS frame 321, the use of the cooperative communication is canceled through the CTS frame 323, and the terminal D directly transmits the data frame to the terminal A. .

The terminal D receives the CTS frame 323 with a flag value indicating whether the cooperative communication is set to true and after the SIFS passes, the data frame 324 to the terminal B at the transmission rate of the R _DB specified in the CTS frame 323. Send it. The terminal B receives the data frame 324 and relays the data frame 325 of the terminal D to the terminal A at the transmission rate of R _BA specified in the CTS frame 323 after the SIFS passes. After successfully receiving the data frame 325, the terminal A transmits an ACK frame 326 to the terminal D after the SIFS has elapsed, indicating that the data has been successfully received.

When there are other transmitting terminals capable of providing cooperative communication, the terminal B selects the second relay target terminal E, and relays it before relaying the data frame 325 of the terminal D. The identification number (ID) of the terminal E and the number of times of frame retransmission of the terminal B are included in the header of the data frame 325. If the data frame 325 received by the terminal A includes the identification number of the terminal E, which is the second relay target terminal for the terminal B to provide cooperative communication, the terminal A is the terminal ACK, the terminal B, and the ACK frame 326. By including the identification number of the terminal A and the number of frame retransmissions of the terminal B to inform that the terminal E can transmit data to the terminal A through the cooperative communication with the terminal B. The terminal E selected by the terminal B is overhearing the PCTS frame 322 transmitted by the terminal B, the data frame 325 transmitted by the terminal B, and the CTS frame 323 transmitted by the terminal A, and R _EB , R _BA. Since the _REA is measured, the transmission delay in cooperative communication can be predicted using R _EB and R _BA when overhearing the ACK frame 326, and the transmission delay in direct communication can be predicted using R _EA . . If the transmission delay of the cooperative communication is smaller than the transmission delay of the direct communication, the terminal E overhears the ACK frame 326, and then the terminal B and the terminal A and the RTS frame 331, the PCTS frame 332, and the CTS frame 333. ), Data frames 334 and 335 and ACK frames 336 are exchanged to transmit the data frames through cooperative communication in the same manner as in the case of the terminal D.

When the terminal B relays the data frame 335 of the terminal E, the terminal B selects the third relay target terminal F as the terminal to be supported for the relay transmission of the terminal B and cooperates with the terminal F in the same manner as the cooperative communication of the terminal E. Communication can be made. In this way, the communication apparatus in the wireless communication network according to the present invention can continuously perform the cooperative communication of all terminals capable of providing cooperative communication with the terminal B without incurring any overhead for access to the transmission channel. Can be. Terminal B selects the relay target terminals in a round-robin manner to provide cooperative communication, and guarantees fair use of the transport channel between the relay terminal terminal B and the relay target terminal terminals D, E and F. To this end, the terminal B selects the terminal D, the terminal E, and the terminal F at most once after transmitting the RTS frame 311. In addition, when the terminal D selected by the terminal B does not transmit the RTS frame for the cooperative communication, the terminal B identifies the terminal D as a terminal that does not require coordination so that subsequent cooperative communication may not be interrupted.

Since the terminal D, the terminal E, and the terminal F transmit data frames through the cooperative communication regardless of the backoff timer value, the transmission channel is used again when the backoff timer expires after the cooperative communication. This causes a problem that the terminal D, the terminal E, and the terminal F use the transport channel more frequently than the terminal B which is the relay terminal. In order to solve this problem, the terminal D, the terminal E, and the terminal F, which have transmitted data by the selection of the terminal B, currently have a backoff timer value newly selected immediately after the data is transmitted regardless of whether the data transmission is successful or not. In addition to the off timer value, the transport channel is used in the same period as when the use of the transport channel is allowed only by the expiration of the back off timer.

In the channel usage according to the IEEE 802.11 standard, the terminal whose backoff timer expires waits for the channel idle time as much as DIFS, while the terminal selected by the terminal B, which is a relay terminal using a communication device in the wireless communication network according to the present invention, After receiving the ACK frame (314, 326, 336) and waits for the channel idle time as much as SIFS and transmits the RTS frame (321, 331) for cooperative communication. Therefore, when considering a wireless communication network in which a hidden node problem does not occur, the RTS frames 321 and 331 for cooperative communication are transmitted without collision with other frames, which causes the terminal B, which is a relay terminal, and the terminal D, which is a relay target terminal. , UE E and UE F experience collision rates of different RTS frames.

In a wireless communication network using DCF according to the IEEE 802.11 standard, each terminal doubles the value of the contention window each time a collision occurs, so that terminal D and terminal supported cooperative communication of terminal B compared to terminal B, which is a relay terminal. The problem arises that the E and the terminal F use the channel more frequently. In order to solve this problem, the ACK frames 314, 326, and 336 of the terminal A informing the terminal selected by the terminal B include the number of frame retransmissions of the terminal B, the terminal D transmitting data by the selection of the terminal B, The terminal E and the terminal F increase the number of frame retransmissions by the number of frame retransmissions of the terminal B immediately after the data transmission, regardless of whether the data transmission is successful or not, and increase the contention window by two times. If the adjusted contention window of terminal D, terminal E, or terminal F is larger than the maximum contention window value defined in the IEEE 802.11 standard, the contention window is readjusted to the maximum contention window value and the new content of the backoff timer is adjusted using the adjusted contention window value. Determine the value.

4 illustrates another embodiment in which a communication apparatus in a wireless communication network according to the present invention is applied when a relay terminal (terminal B) transmits a data frame to a receiving terminal (terminal A) before the relay target terminal (terminal D). Figure is a diagram.

Referring to FIG. 4, after the terminal B transmits the RTS frame 411 and the terminal A responds with the CTS frame 412 to transmit the data frame of the terminal B, the terminal B transmits the data frame 413. Terminal A responds with an ACK frame 414. The terminal B selects the terminal D as a relay target terminal to provide the cooperative communication, and includes the terminal D in the header of the data frame 413 transmitted to the terminal A. The terminal A may use the cooperative communication through the ACK frame. Inform.

The terminal D transmits the RTS frame 421 for cooperative communication, and the terminal B measures the R _DB in the process of receiving the RTS frame 421. When the measured R _DB is less than the R _DB included in the RTS frame 421, the terminal B does not transmit the PCTS frame, the terminal A does not receive a PCTS frame for a time corresponding to two SIFS available for cooperative communication By transmitting a CTS frame 422 having a flag value indicating false, the terminal D transmits a data frame to the terminal A by direct communication.

The CTS frame 422 in which the flag value indicating whether the cooperative communication is set to false includes the R _DA measured by the terminal A, and the duration field value of the CTS frame 422 for virtual carrier sensing is represented by the following equation. It is expressed as 5.

Here, DUR _CTS is the duration field value of the CTS frame 422, T _ACK is the time required to transmit the ACK frame, L is the size of the data frame to be transmitted by the terminal D, and RR _DA is R measured by the terminal A the _DA. If DUR _RTS is the duration field value, RT _DB and RT _BA of the RTS frame 421, respectively, R _DB and R _BA included in the RTS frame 421, L denotes DUR _RTS , RT _{D, B} and RT _BA . Can be calculated. In addition, the DUR _RTS is equal to the duration field value of the RTS frame 321 shown in Equation (1).

The terminal D receiving the CTS frame 422 having the flag value indicating whether the cooperative communication is set to false limits the elapsed time after transmitting the RTS frame 421. The duration field value of the RTS frame 421 is CTS. If it is less than the transmission delay when transmitting the data frame 424 at the transmission rate of R _DA specified in the frame 422, the control frame 423 receiving the CTS frame 422 and notifying the increased transmission delay after the SIFS time elapses. By transmitting, neighboring terminals can successfully perform virtual carrier sensing. At this time, the duration field value of the control frame 423 is expressed by the following equation (6).

Here, DUR is the duration field value of the control frame 423, T _ACK is the time required to transmit the ACK frame, L is the size of the data frame to be transmitted by the terminal D, and RR _DA is included in the CTS frame 422 Is R _DA .

The terminal D transmits the data frame 424 to the terminal A at the transmission rate of the R _DA included in the CTS frame 422 after the SIFS has elapsed. Terminal A, which has successfully received data frame 424, sends ACK frame 425 to terminal D.

5 shows another embodiment in which a communication device in a wireless communication network according to the present invention is applied when a relay terminal (terminal B) transmits a data frame to a receiving terminal (terminal A) before the relay target terminal (terminal D). An example is shown.

Referring to FIG. 5, after the terminal B transmits the RTS frame 511 and the terminal A responds with the CTS frame 512 to transmit the data frame of the terminal B, the terminal B transmits the data frame 513. Terminal A responds with an ACK frame 514. The terminal B selects the terminal D as a relay target terminal to provide cooperative communication and includes it in the header of the data frame 513 transmitted to the terminal A. The terminal A may use the cooperative communication through the ACK frame 514. Announce that there is.

The terminal D transmits the RTS frame 521 to use the cooperative communication, and the terminal B transmits the PCTS frame 522 after the SIFS passes. UE A measures R _DA in the process of receiving the RTS frame 521, and measures R _BA in the process of receiving the PCTS frame 522. UE A is the measured R _BA is set forth in the RTS frame (521), R _BA is less than or R _DA, R _BA and PCTS frame 522, a terminal A is measured than with the R _DB is the condition shown in the following equation (7) If satisfactory, the CTS frame 523 is set to false by setting a flag value indicating whether the cooperative communication is available, so that the terminal D transmits the data frame 525 at the transmission rate of the R _DA included in the CTS frame 523 by direct communication. ) Is transmitted to terminal A.

6 illustrates a communication apparatus in a wireless communication network according to the present invention when a relay target terminal (terminal D) transmits a day frame to a receiving terminal (terminal A) using a transmission channel before the relay terminal (terminal B). 1 is a diagram illustrating an embodiment to be applied.

Referring to FIG. 6, the terminal D selects, as a relay terminal, a terminal B, which is one of the terminals enabling the cooperative communication with the shortest transmission delay, among the terminals that can be provided with the cooperative communication, and whether to use the cooperative communication. The RTS frame 611 having a flag value indicating true is transmitted. The RTS frame 611 in which the flag value indicating whether the cooperative communication is used is set to true is the identification number (ID) of the terminal D, the terminal B and the terminal A, and information about the R _DB and the R _BA most recently measured by the terminal D. It includes. In addition, the duration field value of the RTS frame 611 for virtual carrier sensing may be expressed by Equation 8 below.

Here, DUR _RTS is a duration field value of the RTS frame 611, T _PCTS , T _CTS and T _ACK are times required for transmitting a PCTS frame, a CTS frame and an ACK frame, respectively, and L is data to be transmitted by the terminal D. The size of the frame.

The process after the terminal D transmits the RTS frame 611 in which a flag value indicating whether to use cooperative communication is set to true is the same as the process in which the terminal D selected by the terminal B transmits data to the terminal A as described above. Is performed.

Upon receiving the CTS frame 613 in which a flag value indicating whether to use cooperative communication is set to true, the terminal D includes the number of frame retransmissions of the terminal D in the header of the data frame 614 transmitted to the terminal B. When the terminal B selects the terminal E as the second relay target terminal to provide cooperative communication in the process of relaying the data frame 615 of the terminal D, the data frame 615 for relay transmission includes the identification number of the terminal E ( ID) and the number of frame retransmissions of the terminal D so that the terminal E adjusts the contention window according to the number of frame retransmissions of the terminal D accessing the channel.

When the terminal D uses the transport channel before the terminal B, the cooperative communication (620, 630) of the terminal E and the terminal F which is continuous through the data frame 615 relayed by the terminal B excludes only the terminal B which is the relay terminal. Because of transmitting the data frame of the terminal causes an unfair use of the transmission channel between the terminal. Therefore, when the terminal B does not have a data frame to be transmitted to the terminal A other than the data frame 615 to be relayed, the terminal D selects a second or third relay target terminal to support the relay transmission, and thus the cooperative communication of the terminal D is performed. To the cooperative communication (620, 630) of the terminal E, terminal F. This method enables continuous cooperative communication through terminal B without overhead for channel access even when terminal D, terminal E, and terminal F generate data frames more frequently than terminal B, which is a relay terminal.

When the terminal D transmits data to the terminal A through the relay transmission of the terminal B, the CTS frame transmitted by the terminal A includes the R _DB and the R _BA , and the terminal A transmits when the terminal D transmits the data directly to the terminal A. The CTS frame includes R _DA . Among the transmitting terminals shown in FIG. 2, another transmitting terminal C, which may be a relay terminal, measures R _DC when overhearing the RTS frame of the terminal D, and R _CA when overhearing the CTS frame of the terminal A. Measure

When the terminal D satisfies the following Equation 9 when the cooperative communication is used or when the terminal D satisfies the following Equation 10 when the terminal D uses the direct communication, the terminal C may provide the cooperative communication with the smaller transmission delay to the terminal D. For this reason, the terminal C selects the terminal D as the terminal to receive the cooperative communication of the terminal C, or deletes the information of the terminal D from the information of the terminals requiring the cooperative communication. In this way, the terminal D, the terminal E, and the terminal F are supported by the relay transmission only by the relay terminals that enable the cooperative communication with the shortest transmission delay.

7 is a flowchart illustrating a process of performing an embodiment of a communication method in a wireless communication network according to the present invention.

Referring to FIG. 7, first, the transmission rate measuring unit 120 transmits a transmission rate used in a transmission channel with a transmission terminal for transmitting a frame to a reception terminal, which is a destination of a frame to be transmitted, and a transmission channel used with a reception terminal. The speed and the transmission speed used in the transmission channel between the transmitting terminal and the receiving terminal are measured (S710). Next, the relay target terminal determiner 130 transmits the data to the receiving terminal by cooperative communication from the first transmission delay and the transmitting terminal when the data is directly transmitted from the transmitting terminal to the receiving terminal based on the measured transmission speed. If the second transmission delay is less than the first transmission delay, and if the second transmission delay is smaller than the first transmission delay, the transmission terminal is determined as a relay target terminal to provide cooperative communication (S720). The relay controller 140 includes the identification number of the relay target terminal in the first data frame transmitted by the frame transmitter / receiver 110 to the receiving terminal (S730), and determines that the relay target terminal uses cooperative communication to inform the request frame. As a result of the process of transmitting the received CTS frame is set to the flag value indicating whether the cooperative communication is possible from the receiving terminal (S740) and transmits the second data frame transmitted from the relay target terminal to the receiving terminal (S750).

8 is a flowchart illustrating a process of determining a second relay target terminal in the process of providing a cooperative communication by the relay terminal determining the relay target terminal.

Referring to FIG. 8, the relay terminal determines whether a request for cooperative communication is provided by including an identification number (ID) of the relay terminal in an RTS frame transmitted by the relay target terminal (S810) and the relay measured while receiving the RTS frame. By comparing the maximum rate available in the channel from the target terminal to the relay terminal and the transmission rate included in the RTS frame, the relay terminal can successfully receive the data frame transmitted at the transmission rate included in the RTS frame. It is determined whether there is (S820). When it is possible to provide the cooperative communication required by the relay target terminal, it transmits a PCTS frame (S830), receives a CTS frame in which a flag value indicating whether the cooperative communication is available from the receiving terminal is set to true (S840), The data frame received from the relay target terminal is relayed and transmitted (S850). The relay terminal determines whether there is a second relay target terminal which is another transmitting terminal for providing cooperative communication (S860), and if present, adds the identification number of the second relay target terminal to the header of the data frame to be relayed. (S870).

9 is a flowchart illustrating a process of performing another preferred embodiment of a communication method in a wireless communication network according to the present invention. That is, Fig. 9 shows the operation of the transmitting terminal determined as the relay target terminal by the relay terminal.

Referring to FIG. 9, the relay target terminal determines whether the receiving terminal is determined as a relay target terminal by the relay terminal by overhearing an ACK frame transmitted to the relay terminal (S910). Next, in the case of having a data frame to be transmitted to the receiving terminal that transmits the ACK frame (S915), the number of times of frame retransmission of the relay terminal in exchange for transmitting the RTS frame at a lower collision rate than the relay terminal before proceeding with the data transmission process. The competition window is adjusted according to (S920). The relay target terminal determines whether to use cooperative communication by using information about the transmission speed collected while overhearing the frames of the relay terminal and the receiving terminal (S925), and accordingly, the identification number of the relay terminal for the cooperative communication. The RTS frame including the ID is transmitted (S930) or the RTS frame for direct communication is transmitted (S935). The relay target terminal receives the CTS frame from the receiving terminal (S940), and transmits the data frame to the relay terminal for relay transmission according to a setting value of a flag indicating whether cooperative communication of the CTS frame is available (S945). (S965), it transmits directly to the receiving terminal. When the relay target terminal needs to use direct communication and needs more time than the duration field value set in the RTS frame for data transmission (S950), the transmission channel reservation time is extended through the control frame (S955). The frame is directly transmitted to the receiving terminal (S960). The relay target terminal checks whether the data transmission is successful through the ACK frame transmitted from the receiving terminal (S970), and adds the newly selected backoff timer to the currently remaining backoff timer in exchange for additional transmission channel usage (S980). ). If the transmitting terminal fails to transmit data, the contention window is adjusted according to the IEEE802.11 standard (S975).

10 is a flowchart illustrating a process in which a relay target terminal directly selects a relay terminal and transmits a data frame by cooperative communication.

Referring to FIG. 10, if there is a relay terminal capable of providing cooperative communication (S1010), the relay target terminal transmits an RTS frame including an identification number (ID) of the relay terminal (S1015). The RTS frame for communication is transmitted (S1020). The relay target terminal receives the CTS frame from the receiving terminal (S1025), and transmits the data frame to the relay terminal according to a setting value of a flag indicating whether cooperative communication of the CTS frame is available (S1030) or the relay transmission is performed. In operation S 1035, the data frame is directly transmitted to the receiving terminal in operation S 1050. If the relay target terminal needs to use direct communication and needs more time than the duration field value set in the RTS frame for data transmission (S1040), the transmission channel reservation time is extended through the control frame (S1045), The data frame is directly transmitted to the receiving terminal (S1050). The relay target terminal checks whether the data transmission is successful through the ACK frame transmitted from the receiving terminal (S1055), and when the relay target terminal fails to transmit the data, adjusts the contention window according to the IEEE 802.11 standard (S1060).

11 is a flowchart illustrating an operation in a data transmission process by cooperative communication of a receiving terminal receiving a data frame.

Referring to FIG. 11, when receiving a RTS frame (S1110), the receiving terminal determines whether the relay target terminal requires cooperative communication based on the information included in the RTS frame (S1115). When receiving the RTS frame for the cooperative communication, the receiving terminal waits for the PCTS frame transmitted from the relay terminal (S1120), and the cooperative communication included in the RTS frame based on the transmission rate measured in the process of receiving the RTS frame and the PCTS frame. It is determined whether this is possible (S1125), and if possible, transmits a CTS frame for cooperative communication (S1130). The receiving terminal transmits the CTS frame for direct communication when the relay target terminal does not want to use the cooperative communication or the cooperative communication included in the RTS frame is impossible in the current transmission channel situation (S1135). When the receiving terminal receives the data frame (S1140), it is determined whether the information on the next cooperative communication is included in the header of the data frame (S1145), and if so, the corresponding information is added to the ACK frame (S1150). In operation S1155, an ACK frame is transmitted.

The invention can also be embodied as computer readable code on a computer readable recording medium. Computer-readable recording media include all types of recording devices that store data that can be read by a computer system. Examples of the computer-readable recording medium include a ROM, a RAM, a CD-ROM, a magnetic tape, a floppy disk, an optical data storage device, and the like, and may be implemented in the form of a carrier wave (for example, transmission via the Internet) . The computer readable recording medium can also be distributed over network coupled computer systems so that the computer readable code is stored and executed in a distributed fashion.

Although the preferred embodiments of the present invention have been shown and described above, the present invention is not limited to the specific preferred embodiments described above, and the present invention belongs to the present invention without departing from the gist of the present invention as claimed in the claims. Various modifications can be made by those skilled in the art, and such changes are within the scope of the claims.

Figure 1a is a block diagram showing the configuration of a preferred embodiment of a communication device in a wireless communication network according to the present invention,

1B is a block diagram showing the configuration of another preferred embodiment of a communication apparatus in a wireless communication network according to the present invention;

2 illustrates a wireless communication network including a plurality of transmitting terminals and a receiving terminal for receiving data from the transmitting terminals;

3 illustrates an embodiment in which a communication apparatus in a wireless communication network according to the present invention is applied when a relay terminal (terminal B) transmits a data frame to a receiving terminal (terminal A) before the relay target terminal (terminal D). Drawing,

4 illustrates another embodiment in which a communication apparatus in a wireless communication network according to the present invention is applied when a relay terminal (terminal B) transmits a data frame to a receiving terminal (terminal A) before the relay target terminal (terminal D). Drawing,

5 shows another embodiment in which a communication apparatus in a wireless communication network according to the present invention is applied when a relay terminal (terminal B) transmits a data frame to a receiving terminal (terminal A) before the relay target terminal (terminal D). Drawing showing an example,

6 shows a communication apparatus in a wireless communication network according to the present invention when a relay target terminal (terminal D) transmits a day frame to a receiving terminal (terminal A) using a transmission channel before the relay terminal (terminal B). Figure showing an embodiment applied,

7 is a flowchart illustrating a process of performing an embodiment of a communication method in a wireless communication network according to the present invention;

8 is a flowchart illustrating a process of determining a second relay target terminal in a process of providing a cooperative communication by determining a relay target terminal by the relay terminal;

9 is a flowchart illustrating a process of performing another preferred embodiment of a communication method in a wireless communication network according to the present invention;

10 is a flowchart illustrating a process in which a relay target terminal directly selects a relay terminal and transmits a data frame by cooperative communication;

11 is a flowchart illustrating an operation in a data transmission process by cooperative communication of a receiving terminal receiving a data frame.

Claims (17)

A frame transmission / reception unit configured to transmit a frame to or receive a frame from another terminal device constituting a wireless communication network; The transmission rate used in the transmission channel with the transmitting terminal transmitting the frame to the receiving terminal which is the destination of the frame to be transmitted, the transmission rate used in the transmission channel with the receiving terminal, and the transmission channel between the transmitting terminal and the receiving terminal. A transmission rate measuring unit for measuring a transmission rate; A first transmission delay when data is directly transmitted from the transmitting terminal to the receiving terminal based on the measured transmission rate, and relay transmission by cooperative communication, thereby performing data transmission from the transmitting terminal to the receiving terminal; A relay target terminal determining unit for calculating a transmission delay and determining the transmission terminal as a relay target terminal for providing cooperative communication when the second transmission delay is less than the first transmission delay; And Including the identification number of the relay target terminal in the first data frame transmitted to the receiving terminal by the frame transmitting and receiving unit, if the request frame to inform the use of the cooperative communication from the relay target terminal to start the cooperative communication to the receiving terminal A relay controller configured to transmit a relay frame for notifying the controller and to transmit a second data frame transmitted from the relay target terminal to the receiving terminal when a response frame indicating that cooperative communication is available from the receiving terminal is received. Communication apparatus in a wireless communication network. The method of claim 1, The request frame received from the relay target terminal includes identification numbers of the transmitting terminal and the receiving terminal, a maximum transmission rate used in a transmission channel with the relay target terminal, and a maximum transmission rate used in a transmission channel with the receiving terminal. Communication device in a wireless communication network, characterized in that it comprises information. The method according to claim 1 or 2, And a flag value indicating whether the cooperative communication is possible is set to true in the response frame indicating that the cooperative communication is possible. 3. The method of claim 2, The relay control unit is a maximum transmission rate used in the transmission channel with the relay target terminal measured when receiving the request frame is greater than the maximum transmission rate used in the transmission channel with the relay target terminal included in the request frame. And the frame transceiver transmits the relay frame. The method according to claim 1 or 2, The transmission rate measuring unit overhears the control frame transmitted between the relay target terminal and the receiving terminal, and analyzes and transmits a physical layer convergence protocol (PLCP) header of a data frame transmitted directly by the relay target terminal to the receiving terminal. Communication device in a wireless communication network, characterized in that for measuring the speed. The method according to claim 1 or 2, When the plurality of relay target terminals are determined by the relay target terminal determiner, the relay control unit includes the identification numbers of the relay target terminals in a header of the first data frame transmitted to the receiving terminal in a round-robin manner. A communication device in a wireless communication network, characterized in that the. The transmission rate used in the transmission channel with the transmitting terminal transmitting the frame to the receiving terminal which is the destination of the frame to be transmitted, the transmission rate used in the transmission channel with the receiving terminal, and the transmission channel between the transmitting terminal and the receiving terminal. A transmission rate measuring step of measuring a transmission rate; A first transmission delay when data is directly transmitted from the transmitting terminal to the receiving terminal based on the measured transmission rate, and relay transmission by cooperative communication, thereby performing data transmission from the transmitting terminal to the receiving terminal; A relay target terminal determining step of calculating a second transmission delay and determining the transmitting terminal as a relay target terminal for providing cooperative communication if the second transmission delay is less than the first transmission delay; And The relay frame informing the start of the cooperative communication is transmitted to the receiving terminal when the request frame indicating the use of the cooperative communication is received from the relay target terminal and includes the identification number of the relay target terminal in the first data frame transmitted to the receiving terminal. And a second control frame for transmitting a second data frame transmitted from the relay target terminal to the receiving terminal when a response frame indicating that cooperative communication is possible from the receiving terminal is received. Communication method in The method of claim 7, wherein The request frame received from the relay target terminal includes identification numbers of the transmitting terminal and the receiving terminal, a maximum transmission rate used in a transmission channel with the relay target terminal, and a maximum transmission rate used in a transmission channel with the receiving terminal. A communication method in a wireless communication network, characterized in that information is included. The method according to claim 7 or 8, And a flag value indicating whether the cooperative communication is possible is set to true in the response frame indicating that the cooperative communication is possible. The method of claim 8, In the relay control step, the maximum transmission rate used in the transmission channel with the relay target terminal measured when receiving the request frame is the maximum transmission rate used in the transmission channel with the relay target terminal included in the request frame. The communication method in a wireless communication network, characterized in that for transmitting the relay frame if it is abnormal. The method according to claim 7 or 8, In the transmission rate measuring step, overhearing a control frame transmitted between the relay target terminal and the receiving terminal, and interprets a physical layer convergence protocol (PLCP) header of a data frame transmitted by the relay target terminal to the receiving terminal. A communication method in a wireless communication network, characterized by measuring the transmission speed. The method according to claim 7 or 8, In the relay control step, when a plurality of relay target terminals are determined in the relay target terminal determination step, identification numbers of the relay target terminals are included in a header of a first data frame transmitted to the receiving terminal in a round-robin manner. Communication method in a wireless communication network, characterized in that it comprises a. A frame transmission / reception unit configured to transmit a frame to or receive a frame from another terminal device constituting a wireless communication network; The transmission rate used in the transmission channel with the relay terminal providing cooperative communication so that the frame is relayed to the receiving terminal which is the destination of the frame to be transmitted, the transmission rate used in the transmission channel with the receiving terminal, and the relay terminal and the receiving terminal. A transmission rate measuring unit for measuring a transmission rate used in the transmission channel between the transmission rate measurement unit; When overhearing a frame indicating that cooperative communication provided by the relay terminal can be used, the first transmission delay when data is directly transmitted to the receiving terminal based on the measured transmission rate and the cooperative communication provided by the relay terminal Calculates a second transmission delay when the data is transmitted to the receiving terminal by performing relay transmission by the second transmission delay, and decides to use cooperative communication provided by the relay terminal if the second transmission delay is smaller than the first transmission delay. Cooperative communication decision unit; A control unit for transmitting a request frame for notifying the use of cooperative communication to the relay terminal and for transmitting a data frame to the relay terminal upon receiving a response frame indicating that cooperative communication is possible from the receiving terminal; And And a contention window adjusting unit configured to increase a contention window value for determining a waiting time for accessing a transmission channel to the receiving terminal when the frame transceiver transmits a data frame to the relay terminal. Communication device. The method according to claim 13, And the contention window adjustment unit doubles the contention window value. The transmission rate used in the transmission channel with the relay terminal providing cooperative communication so that the frame is relayed to the receiving terminal which is the destination of the frame to be transmitted, the transmission rate used in the transmission channel with the receiving terminal, and the transmitting terminal and the receiving terminal. A transmission rate measuring step of measuring a transmission rate used in a transmission channel between the frames; When overhearing a frame indicating that cooperative communication provided by the relay terminal can be used, the first transmission delay when data is directly transmitted to the receiving terminal based on the measured transmission rate and the cooperative communication provided by the relay terminal Calculates a second transmission delay when the data is transmitted to the receiving terminal by performing relay transmission by the second transmission delay, and decides to use cooperative communication provided by the relay terminal if the second transmission delay is smaller than the first transmission delay. Determining cooperative communication; A control step of transmitting a request frame informing the use of the cooperative communication to the relay terminal and transmitting a data frame to the relay terminal upon receiving a response frame indicating that the cooperative communication is possible from the receiving terminal; And And a contention window adjustment step of increasing a contention window value for determining a waiting time for accessing a transmission channel to the receiving terminal when a data frame is transmitted to the relay terminal. The method of claim 15, In the contention window adjustment step, doubling the contention window value. A computer-readable recording medium having recorded thereon a program for executing a communication method in a wireless communication network according to any one of claims 7, 8, 10, 15, and 16 on a computer.

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