KR101064440B1 - Method for cooperative communication for ieee 802.11 wireless lans - Google Patents

Abstract

Disclosed is a cooperative communication method of an IEEE 802.11 wireless LAN, which can improve a throughput of a wireless LAN and can guarantee fairness for a throughput of each device. First, if there is data to be transmitted, the relay device determines whether to cooperate with each other based on the cooperative communication decision information provided from the receiving device. After selecting the transmitting apparatus, the relay apparatus receives the relay data transmitted from the selected transmitting apparatus and transmits the received relay data to the receiving apparatus. Therefore, the overall throughput of the IEEE 802.11 WLAN can be improved, and the fairness of the throughput of each device can be guaranteed.

IEEE 802.11, WLAN, Throughput, Collaboration, Relay, Fairness

Description

Cooperative communication method of IEEE 802.11 wireless LAN {METHOD FOR COOPERATIVE COMMUNICATION FOR IEEE 802.11 WIRELESS LANS}

The present invention relates to a wireless LAN communication method, and more particularly, to a cooperative communication method of an IEEE 802.11 wireless LAN capable of guaranteeing throughput improvement and fairness in an IEEE 802.11 wireless LAN supporting multiple data rates.

The IEEE 802.11 series wireless local area network (WLAN) technology has improved data throughput in response to increasing quality of service (QoS) of user applications. IEEE 802.11 wireless LAN using the Industrial, Scientific and Medical (ISM) frequency band provides a data communication service by sharing a wireless channel with a plurality of terminals.

The IEEE 802.11 WLAN provides a contention-based Distributed Coordinate Function (DCF) function in a medium access control (MAC) layer to guarantee fair transmission opportunities of all terminals in a basic service set (BSS). DCF is a method of allowing each terminal to be distributed by a binary exponential backoff algorithm based on carrier sense multiple access / collision avoidance (CSMA / CA) to prevent collisions in data transmission between terminals.

In addition, each terminal of the IEEE 802.11 WLAN receives different transmission rates from the AP (Access Point) according to channel conditions, and a set of terminals having the same transmission rate is divided into one group.

IEEE 802.11 series wireless LAN standards that support multiple data rates are representative of IEEE 802.11a, IEEE 802.11b, and IEEE 802.11g. Groups of terminals are determined according to the range of data rates supported by each standard. For example, for IEEE 802.11b, there are four supported data rates: 1, 2, 5.5, and 11 Mbps.

In the case of the MAC protocol of the IEEE 802.11 standard, since each terminal operates based on DCF, all terminals are guaranteed an equal transmission opportunity regardless of the transmission rate of the terminal. However, in a wireless LAN system sharing one wireless channel, a low speed terminal having the lowest data rate transmits data longer than a high speed terminal, and the channel occupancy time of the high speed terminal decreases, thereby reducing the overall network. The degradation of throughput occurs, which is called performance anomaly.

1 illustrates an operation of a general IEEE 802.11 MAC protocol.

Referring to FIG. 1, in the IEEE 802.11 WLAN, in order to solve a hidden node problem, the operation is performed in Request To Send (RTS) / Clear To Send (CTS) mode, which is a binary exponential backoff operation of DCF. Thereafter, the RTS / CTS control frame is exchanged between the transmitting terminal and the receiving terminal.

Specifically, the source terminal (Source) detects the use of the channel during the DIFS (DCF InterFrame Space) time to occupy the channel and sets the backoff window value through a binary exponential backoff algorithm.

Then, when the backoff window value is 0, the transmitting terminal (Source) immediately transmits the RTS control frame to the receiving terminal (AP) to inform the channel usage. In this case, when there is no other terminal having the same backoff window value, the RTS control frame transmitted by the transmitting terminal (Source) is transmitted to the receiving terminal (AP) without collision, and the receiving terminal (AP) is a SIFS (Short InterFrame). After the Space time, the CTS control frame is transmitted to the transmitting terminal.

The transmitting terminal (Source) receiving the CTS control frame transmits the data frame to the receiving terminal (AP) after SIFS through the occupied channel, and the receiving terminal (AP) receiving the CTS control frame transmits to the transmitting terminal (Source). Notify sends an ACK control frame after SIFS.

Thereafter, another transmitting terminal (2nd Source) transmits data to the receiving terminal (AP) through the same process as described above.

As shown in FIG. 1, in the general IEEE 802.11-based MAC protocol, the channel access probability of all UEs is the same due to the characteristics of CSMA / CA, which gives a fair transmission opportunity to all UEs. In this case, the channel occupancy time is increased more than when the fast terminal accesses the channel. Therefore, as the number of low-speed terminals accessing the channel increases, a performance anomaly problem occurs that the overall throughput of the network is further reduced.

Method for reducing channel occupancy time of low speed terminal by adjusting initial backoff window value of low speed terminal or reducing size of maximum transmittable data frame of low speed terminal in binary exponential backoff algorithm Although this has been proposed, such methods may cause an unfair problem that the throughput of the low speed terminals in the network is reduced.

In addition, recently, methods for improving performance abnormality have been proposed by reducing data transmission time of a low speed terminal by performing cooperative communication using a relay terminal in a wireless LAN environment. However, even in the case of performing cooperative communication using a relay terminal, there is a disadvantage that a problem of performance or higher may not be completely solved due to a low speed terminal that does not perform cooperative communication with the relay terminal. In addition, the performance of the cooperative communication by the request of the low speed terminal has a problem that can act as a large overhead in the relay terminal.

An object of the present invention for solving the above problems is to provide a cooperative communication method of the IEEE 802.11 WLAN that can improve the throughput of the wireless LAN, and can guarantee the fairness of the throughput of each device.

The cooperative communication method of the IEEE 802.11 WLAN according to an aspect of the present invention for achieving the above object of the present invention, whether or not the cooperative communication based on the cooperative communication determination information provided from the receiving device when the relay device has data to transmit Selecting a transmitting device to be relayed based on signal strength of each of at least one transmitting device when the determining step and the relay device determine to perform cooperative communication; And receiving the relayed data and transmitting the relayed data to the receiving device. The cooperative communication method of the IEEE 802.11 WLAN may further include transmitting, by the relay device, data of the relay device to the receiving device after the transmission of the relay data is successful. Determining whether the relay device has a cooperative communication based on the cooperative communication determination information provided from the receiving device when the relay device has data to be transmitted, may be performed based on a beacon signal provided from the receiving device when the relay device has data to transmit. Obtaining cooperative communication determination information, generating a predetermined comparison reference value based on a source device information table managed by the relay device, and the relay device comparing the cooperative communication determination information with the predetermined reference value And determining whether to cooperate with each other based on the compared result. The source device information table may store the MAC address and signal strength of each of at least one transmitting device belonging to a group having a lower speed than the group to which the relay device belongs. If it is determined that the relay device performs cooperative communication, selecting a transmitting device to relay based on signal strength of each of the at least one transmitting device, the relay device selects the highest signal strength in the source device information table. It is possible to select a transmitter as the transmitter to be relayed. The source device information table may be configured by overhearing a control frame exchanged between the at least one transmitting device and the receiving device by measuring the signal strength of the control frame. The relay device may perform relaying of a transmission device belonging to a group having the lowest transmission rate among a plurality of groups divided according to transmission rates defined in the IEEE 802.11 standard. Receiving the relay data transmitted from the transmission device selected by the relay device and transmitting the received relay data to the reception device, the relay device asks the selected transmission device to participate in cooperative communication; Transmitting a second control frame indicating that the relay device participates in cooperative communication from the transmitting device, and wherein the relay device notifies the receiving device that the cooperative communication is performed. Transmitting a second control frame which is a response signal to the third control signal from the receiving device, and the relay device receiving the relay data transmitted from the transmitting device. And transmitting to the. In the cooperative communication method of the IEEE 802.11 WLAN, a source device information table managed by each of at least one transmitting device other than the relay device that overhears a second control frame indicating that the transmitting device participates in cooperative communication. May delete the information of the transmitting apparatus. The relay device may transmit the relay data transmitted from the transmitting device to the receiving device after the relay device overhears a first response frame indicating successful reception of the relay data from the receiving device. And transmitting the data of the relay device to the receiving device.

In addition, in the cooperative communication method of the IEEE 802.11 wireless LAN according to another aspect of the present invention, the receiving device to set the cooperative communication determination value based on the transmission status of the traffic transmitted from at least one transmitting device and the receiving device And including the set cooperative communication decision value in a beacon signal and transmitting the same. The setting of the cooperative communication determination value based on the transmission state of the traffic transmitted from the at least one transmitting device by the receiving device includes: determining the amount of traffic transmitted by the receiving device at a transmission rate equal to or less than a preset speed; And setting the cooperative communication determination value instructing cooperative communication when the amount of traffic transmitted at a transmission rate less than or equal to a preset speed is greater than a preset reference amount.

In addition, the cooperative communication method of the IEEE 802.11 WLAN according to another aspect of the present invention, the transmitting device receives a first control frame from the relay device to ask the intention to participate in the cooperative communication from the relay device, the transmission device is Transmitting a second control frame indicating participation in the cooperative communication to the relay device, and scheduling traffic to be transmitted by the transmitting device using two queues based on a delay sensitivity of the traffic. . The transmitting device may schedule traffic to be transmitted using two queues, and the transmitting device may schedule non-real-time traffic using a first queue and schedule real-time traffic through a second queue.

According to the cooperative communication method of the IEEE 802.11 WLAN as described above, if there is data to be transmitted by the relay device, whether or not the cooperative communication is determined on the basis of a beacon signal provided to the receiving device (for example, the AP) and managed by the relay device. After selecting the transmitting device having the highest signal strength as the relay target device in the source device information table, the data transmitted from the relay target device is relayed to the receiving device and then its data is transmitted to the receiving device.

Therefore, the overall throughput of the IEEE 802.11 WLAN can be improved, and the fairness of the throughput of each device can be guaranteed.

As the invention allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the written description. However, this is not intended to limit the present invention to specific embodiments, it should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention. Like reference numerals are used for like elements in describing each drawing.

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

It is to be understood that when an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, . On the other hand, when a component is referred to as being "directly connected" or "directly connected" to another component, it should be understood that there is no other component in between.

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

Hereinafter, with reference to the accompanying drawings, it will be described in detail a preferred embodiment of the present invention. Hereinafter, the same reference numerals are used for the same components in the drawings, and duplicate descriptions of the same components are omitted.

2 is a conceptual diagram illustrating a cooperative communication method of a wireless LAN according to an embodiment of the present invention, and FIG. 3 shows information stored in each relay device in the cooperative communication method of a wireless LAN according to an embodiment of the present invention. 2 illustrates an example of an IEEE 802.11b-based wireless LAN.

2 and 3, the wireless LAN is I according to the transmission rate defined in the IEEE 802.11 standard, where I is a natural number of 1 or more, and means the total number of transmission rates that the standard can support according to modulation and demodulation technology. And each device has a transmission rate R _i corresponding to the group i to which it belongs (where i is in the range of 1 to I).

As illustrated in FIG. 2, in an IEEE 802.11b-based WLAN environment, four (ie, I = 4) groups are classified according to the maximum data rate supported, and group i becomes any one of 1 to 4. FIG.

Specifically, the maximum transmission rate (R ₁₎ is 11Mbps, the maximum transmission rate (R ₄₎ of the maximum transmission rate (R ₃₎ of the maximum transmission rate (R ₂₎ of the group 2 is 5.5Mbps, 2Mbps Group 3, Group 4, Group 1 1 Mbps.

In a cooperative communication method of a wireless LAN according to an embodiment of the present invention, a relay device belongs only to group I-1, and a relay terminal selects a device having the highest signal strength among the low speed devices belonging to group I and then selects Relay data transmission.

For example, as shown in FIG. 2, in an IEEE 802.11b environment, a relay terminal belongs to group 3, selects a low speed device having the highest signal strength among neighboring devices belonging to group 4, and transmits data of the selected low speed device. Relays As described above, the relay device manages information necessary for selecting a low speed terminal to perform relaying through a source device information table (SIT: hereinafter abbreviated as 'SIT').

Specifically, each relay device overhears a control frame transmitted and received between devices belonging to a subgroup of a group to which it belongs and a receiving device (for example, an AP), and then measures signal strength of the control frame. Corresponds to the MAC address of the device and stores it in the SIT.

As shown in FIG. 3, the SIT stores the MAC address of the transmitting apparatus and the signal strength information of the corresponding transmitting apparatus measured by the relay apparatus, and the relay apparatus includes the MAC header of the control frame exchanged during the transmission of the data frame of the slow transmitting apparatus. And / or obtains the MAC address of the corresponding transmission apparatus through physical layer convergence procedure (PLCP) header information, and stores the signal strength measured through the eavesdropping control frame in correspondence with the obtained MAC address. The transmitting devices stored in the SIT are candidate stations to which data transmission is to be relayed by the relay device and are located in a range where cooperative communication is possible at the location of the relay device and belong to a group having a lower transmission rate than the group to which the relay device belongs. It consists of The relay device continuously manages the SIT in order of the devices having the highest measured signal strength, and updates corresponding information of the SIT in accordance with the control frame transmission of the transmitting device.

Hereinafter, as shown in FIG. 2, a cooperative communication method of a wireless LAN in which a relay device belonging to a group I-1 relays an adjacent device belonging to a group I is described as RM-CMAC (Relay-volunteered Multi-rate-Coorperative MAC: RM- CMAC) protocol.

4 is a conceptual diagram illustrating a cooperative communication method of a wireless LAN according to another embodiment of the present invention, illustrating an IEEE 802.11b-based wireless LAN environment as an example.

Referring to FIG. 4, in the cooperative communication method of a wireless LAN according to another embodiment of the present invention, devices belonging to all groups except the low speed devices belonging to the lowest group, Group I, may serve as relay devices. The relay device belonging to i may perform relaying of devices belonging to the i + 1 group.

For example, as illustrated in FIG. 4, a relay device belonging to group 1 may perform relaying for a selected device among groups belonging to group 2, and a relay device belonging to group 3 may be relayed among devices belonging to group 4. Relaying to the selected device can be performed.

In addition, each relay device manages the SIT for devices belonging to a group (i + 1) that is slower than the group (i) to which it belongs and is shown in FIG. 2 and FIG. Relays may be performed by selecting a device having the highest signal strength at.

Hereinafter, a wireless LAN in which a device belonging to a group (i), which is not the slowest group (i.e., group I) as shown in FIG. 4, relays to a device belonging to a group (i + 1) that is slower than itself. The cooperative communication method of the ERM-CMAC (Extended RM-CMAC) protocol.

The RM-CMAC protocol and the ERM-CMAC protocol may be classified according to the group in which the devices capable of performing the role of the relay device are deployed, and the frame exchange process for the cooperative communication between the relay device and the transmitting device is the same.

In the embodiment of the present invention shown in Figs. 2 to 4, the relay device is selected to perform the relay by selecting the device having the highest signal strength among the devices included in the SIT, for example, but another embodiment of the present invention In an embodiment, the relay device may be configured to perform relaying by selecting a device having the lowest signal strength among the devices included in the SIT.

5 shows a cooperative communication method of a wireless LAN according to an embodiment of the present invention.

Referring to FIG. 5, when there is data to be transmitted by a relay device belonging to group i-1, the relay device performs a backoff operation, and when the backoff window value is 0, cooperation provided from a receiving device (eg, an AP) is performed. Based on the communication determination value (Cooperation Window Probability (Pcw)), it is determined whether or not cooperative communication.

The cooperative communication determination value Pcw may be transmitted from the receiving device through a beacon frame, and may have a real value between 0 and 1. In addition, the receiving device may set the cooperative communication decision value based on the transmission status of the traffic transmitted on the uplink from the low speed devices. For example, the receiving apparatus may set the cooperative communication determination value Pcw to a predetermined value indicating the cooperative communication when the amount of traffic transmitted at a transmission rate equal to or less than a preset transmission rate is greater than a preset reference amount. When the amount of traffic transmitted from the network is less than a predetermined reference amount, the cooperative communication determination value Pcw may be set to a predetermined value indicating direct communication. As described above, the receiving device may actively adjust the cooperative communication participation rate of the relay device by adjusting the cooperative communication determination value Pcw according to the traffic transmission state of the low speed device.

In addition, the relay device generates a reference comparison value that is a real value between 0 and 1 based on the SIT managed by the relay device, and then relays if the reference comparison value generated is smaller than or equal to the cooperative communication determination value Pcw. Perform cooperative communication, and if the generated reference comparison value is larger than the cooperative communication determination value Pcw, transmission is performed based on the MAC protocol defined in the existing IEEE 802.11 without performing relaying. Here, the relay device may generate the reference comparison value according to the number of devices included in the SIT managed by the relay device or the signal strength of each device included in the SIT. For example, the relay device may generate the reference comparison value based on the presence or absence of the relay device having a signal strength smaller than (or greater than) the predetermined reference signal strength.

When the relay device performs cooperative communication through the above-described determination process, the relay device searches for the SIT, selects the device having the highest signal strength as the transmission device to relay, and transmits a HELLO frame to the selected transmission device. .

The transmitting device that receives the HELLO frame transmits a willingness to participate in the cooperative communication to the relay device through the HELLO C-ACK frame, and the relay device transmits the C-RTS frame to the receiving device to the receiving device and the selected transmitting device. Inform that it is performed.

The receiving device receiving the C-RTS frame transmits the C-CTS frame to the relay device and the transmitting device, and the transmitting device receiving the C-CTS frame from the receiving device transmits an MPDU (MAC Protocol Data Unit) to the relay device. . In this case, since the relay device (group i-1) and the transmitter device (group i) belong to groups adjacent to each other, the relay device (group i-1) and the transmitter device (group i-1) are less affected by path-loss due to distance. Therefore, MPDU transmission can be performed at the highest data rate supported by the WLAN system.

The relay apparatus checks the frame check sequence (FCS) of the MPDU received from the transmitting apparatus and delivers the MPDU of the transmitting apparatus to the receiving apparatus.

The receiving device notifies the successful reception of the MPDU by receiving the MPDU of the relaying device from the relay device and then transmitting the source data C-ACK frame to the transmitting device.

The relay device overhears the source data C-ACK frame and transmits the MPDU to be transmitted to the receiving device, and the receiving device transmits the relay data C-ACK frame to the relay device after receiving the MPDU transmitted from the relay device. Indicate that the MPDU sent by the relay has been successfully received. Thereafter, the relay device and the transmitting device compete for the next transmission opportunity.

In the case of performing cooperative communication through the relay device as described above, the transmission device schedules traffic using a dual queue. Transmission devices, which are limited in transmission opportunities due to low communication speeds, are limited in receiving real-time service of delay-sensitive multimedia traffic.

 Therefore, according to the embodiment of the present invention, the transmission apparatus basically follows the transmission queue structure of the IEEE 802.11 standard, and additionally includes a separate queue for processing traffic through cooperative communication, and is preset in the case of performing cooperative communication. According to the criteria, traffic may be scheduled using a double queue.

For example, when the criterion is set to delay sensitivity, the transmitting device may classify traffic into real-time traffic and non-real-time traffic according to delay sensitivity when performing cooperative communication, and schedule each traffic using a different queue. .

In the case of transmission through cooperative communication, a low-speed transmitting device can transmit data through a relay device having a higher speed than itself, so that it can handle traffic requiring high quality of service (QoS), Service quality can be satisfied by scheduling real-time traffic requiring service quality through a separate queue.

6 shows a structure of a control frame used in the cooperative communication method of the wireless LAN shown in FIG.

FIG. 6 (a) shows a HELLO control frame transmitted by the relay device to confirm the cooperative communication intention to the selected transmission device. The address of the transmitting device (Receiver Address: Source STA) and the address of the relay device (Transmitter Address: Relay STA).

FIG. 6 (b) shows a C-RTS control frame for channel occupancy at the same time that the relay device notifies the receiving device that cooperative communication is performed, and in accordance with the RTS control frame of IEEE 802.11 in that it performs a channel occupancy function. It performs a similar function. The C-RTS control frame includes a Receiver Address (AP), a Relay Address (Relay STA), and an Optional Address (Source STA).

6 (c) shows a C-CTS control frame that responds to a relay device and a transmitter that the receiving device has completed channel occupancy for cooperative communication, and includes an address (Receiver1 Address: Relay STA) and a transmitter of the relay device. It includes the address (Receiver2 Address: Source STA).

6 (d) shows a C-ACK control frame for cooperative communication, wherein the C-ACK control frame includes a type field indicating a type of the C-ACK control frame, and includes an address of a relay device or a transmitting device. It includes.

The C-ACK control frame is divided into four types: HELLO C-ACK, negative C-ACK, source data C-ACK, and relay data C-ACK. The information on the type of C-ACK control frame is 1 byte in size. It is included in the type field having type.

The HELLO C-ACK control frame is a frame indicating that there is a data frame to be transmitted through cooperative communication in response to the transmitting device to the HELLO control frame transmitted by the relay device. The negative C-ACK is a frame used when the transmitting device that receives the HELLO frame from the relay device notifies the relay device that there is no data frame to transmit through the cooperative communication.

In addition, when there are a plurality of relay devices in a cooperative communication method of a wireless LAN according to an embodiment of the present invention, two or more relay devices may select the same transmission device with reference to each SIT. In this case, each relay device that selects the same transmission device performs a cooperative communication between the relay devices that first obtain a transmission opportunity through a backoff competition, and transmits a HELLO frame to the selected transmission device, and the corresponding transmission device responds thereto. When the HELLO C-ACK control frame is transmitted, the other relay devices overhearing the HELLO C-ACK control frame delete the information of the corresponding transmitting device from their SIT and set the priority of the transmitting devices registered in the SIT. The update prevents duplicate selection of the transmitting apparatus.

7 shows a topology of a wireless LAN for evaluating the performance of a cooperative communication method according to an embodiment of the present invention, and FIG. 8 shows a parameter value used in the performance evaluation process of the cooperative communication method according to an embodiment of the present invention. .

7 and 8, a wireless LAN standard for performance evaluation of a cooperative communication method according to an embodiment of the present invention is IEEE 802.11b, and controls except for a newly defined control frame as shown in FIGS. 6 and 8. The size of the frame follows the standard of IEEE 802.11b. In addition, it is assumed that each device always has a saturation traffic condition with a data frame to transmit.

In addition, performance was measured while changing the total number of devices in the WLAN from 4 to 30, and the number of devices in each group was simulated to be randomly developed.

를 기반으로 공평성을 측정하였다. 공평성 F는 수학식 1과 같이 Jain의 공평성 지표(Index)를 사용하여 계산하였다.Performance evaluation was measured by three factors: throughput, fairness and MAC latency. Throughput is a performance analysis factor to check whether the RM-CMAC protocol improves the performance abnormality, and the average number of successful transmissions by a predetermined device belonging to group i to confirm fairness accordingly.

The fairness was measured based on. The fairness F was calculated using Jain's fairness index as shown in Equation 1.

In Equation 1, I denotes the total number of groups.

The MAC delay time refers to the time taken for a certain device to successfully transmit one frame, and averages from the backoff process to receiving a C-ACK frame or an ACK frame to a receiving device (eg, an AP). The time required is measured. MAC latency can be used as a measure of the transmission opportunities of each device with fairness.

FIG. 9 is a graph illustrating a result of comparing an average throughput for a cooperative communication method of a wireless LAN according to an embodiment of the present invention with existing IEEE 802.11b, and FIG. 10 is a cooperative communication of a wireless LAN according to an embodiment of the present invention. Fig. 11 is a graph showing a result of comparing the fairness of the method with the conventional IEEE 802.11b, Figure 11 is a result of comparing the MAC delay time for the cooperative communication method of the wireless LAN according to an embodiment of the present invention and the existing IEEE 802.11b A graph representing.

9 to 11 compare the performance of the RM-CMAC protocol and ERM-CMAC protocol and the existing IEEE 802.11b according to an embodiment of the present invention while adjusting the initial backoff window value (W _4,0 ) of the low speed device Shown.

Referring to FIG. 9, the RM-CMAC protocol and the ERM-CMAC protocol according to the embodiment of the present invention exhibit similar performance as the initial backoff window value of the IEEE 802.11b based low speed device is increased to 512. It can be seen that it shows a higher throughput compared to the existing IEEE 802.11b RTS / CTS mode of less than 512.

When the initial backoff window value is adjusted to 512, although the conventional IEEE 802.11b RTS / CTS mode shows higher throughput, referring to FIG. 10, the existing IEEE 802.11b RTS / CTS mode is the best in terms of fairness. It can be seen that the result is not. This is due to the fact that it did not provide adequate compensation while limiting the transmission opportunities of low speed devices.

However, it can be seen from FIGS. 9 and 10 that the RM-CMAC protocol and the ERM-CMAC protocol according to the embodiment of the present invention guarantee the fairness while increasing the overall average throughput of the WLAN.

In addition, referring to FIG. 11, the MAC delay time of the conventional IEEE 802.11b RTS / CTS mode has a larger delay time as the initial backoff window value increases, but according to the embodiment of the present invention, the RM-CMAC protocol and The ERM-CMAC protocol shows that the average MAC latency of the entire network is reduced by reducing the latency of the low speed device through cooperative communication.

Although described with reference to the embodiments above, those skilled in the art will understand that the present invention can be variously modified and changed without departing from the spirit and scope of the invention as set forth in the claims below. Could be.

1 illustrates an operation of a general IEEE 802.11 MAC protocol.

2 is a conceptual diagram illustrating a cooperative communication method of a wireless LAN according to an embodiment of the present invention.

3 illustrates information stored in each relay device in a cooperative communication method of a wireless LAN according to an embodiment of the present invention.

4 is a conceptual diagram illustrating a cooperative communication method of a wireless LAN according to another embodiment of the present invention.

5 shows a cooperative communication method of a wireless LAN according to an embodiment of the present invention.

6 shows a structure of a control frame used in the cooperative communication method of the wireless LAN shown in FIG.

7 shows a topology of a wireless LAN for evaluating the performance of a cooperative communication method according to an embodiment of the present invention.

8 illustrates parameter values used in a performance evaluation process of a cooperative communication method according to an embodiment of the present invention.

9 is a graph showing a result of comparing the average throughput for the cooperative communication method of the wireless LAN according to an embodiment of the present invention with the conventional IEEE 802.11b.

10 is a graph showing a result of comparing the fairness of the cooperative communication method of the wireless LAN according to an embodiment of the present invention with the existing IEEE 802.11b.

11 is a graph showing a result of comparing the MAC delay time for a cooperative communication method of a wireless LAN according to an embodiment of the present invention with the existing IEEE 802.11b.

Claims (14)

In the cooperative communication method of the IEEE 802.11 WLAN, Obtaining cooperative communication determination information from a signal provided from a receiving device when the relay device has data to transmit; Generating a predetermined comparison reference value based on a source device information table managed by the relay device; Comparing, by the relay device, the cooperative communication determination information with the predetermined reference value and determining whether to cooperate with the cooperative communication based on a result of the comparison; When the relay device determines to perform cooperative communication, selecting a transmission device to be relayed based on signal strength of each of at least one transmission device; And And receiving the relay data transmitted from the transmitting device selected by the relay device and transmitting the relayed data to the receiving device. delete delete The method of claim 1, wherein the source device information table is And wherein the relay device associates and stores the MAC address and signal strength of each of at least one transmitting device belonging to a lower speed group than the group to which the relay device belongs. The method of claim 4, wherein when the relay device determines to perform cooperative communication, selecting a transmitting device to be relayed based on signal strength of each of the at least one transmitting device, And wherein the relay device selects a transmitter having the highest signal strength as the transmitter to be relayed from the source device information table. The method of claim 1, wherein the source device information table, The relay device overhears the control frame exchanged between the at least one transmitting device and the receiving device, and measures and measures the signal strength of the tampering control frame. Way. According to claim 1, The relay device, A method of cooperative communication in an IEEE 802.11 WLAN, characterized in that for relaying a transmission device belonging to a group having the lowest transmission rate among a plurality of groups classified according to the transmission rate defined in the IEEE 802.11 standard. The method of claim 1, wherein the relay device receives the relay data transmitted from the selected transmission device and transmits the received relay data to the reception device. Transmitting, by the relay device, a first control frame to the selected transmitting device asking the intention of participating in cooperative communication; Receiving a second control frame indicating that the relay device participates in cooperative communication from the transmitting device; Transmitting, by the relay device, a third control frame informing the receiving device that cooperative communication is performed; Receiving, by the relay device, a fourth control frame that is a response signal to the third control signal from the receiving device; And And transmitting, by the relay device, the relay data transmitted from the transmitting device to the receiving device. According to claim 8, The cooperative communication method of the IEEE 802.11 WLAN, At least one transmitting device other than the relay device that reads the second control frame instructing the cooperative communication from the transmitting device deletes the information of the transmitting device from the source device information table managed by the transmitting device. A cooperative communication method of IEEE 802.11 WLAN. The method of claim 8, wherein the relay device transmits relay data transmitted from the transmitting device to the receiving device. IEEE overhearing a first response frame indicating that the relay device has successfully received the relay data from the receiving device, and then transmitting the data of the relay device to the receiving device. 802.11 cooperative communication method of WLAN. In the cooperative communication method of the IEEE 802.11 WLAN, Determining, by the receiving device, the amount of traffic transmitted at a rate lower than or equal to a preset rate; Setting, by the receiving apparatus, a cooperative communication determination value for instructing cooperative communication when the amount of traffic transmitted at a transmission rate less than or equal to a preset speed is greater than a preset reference amount; And And receiving, by the receiving device, the set cooperative communication decision value in a beacon signal and transmitting the beacon signal. delete In the cooperative communication method of the IEEE 802.11 WLAN, Receiving, from the relay device, a first control frame from the relay device asking the intention of participating in the cooperative communication; Transmitting a second control frame to the relay device indicating that the transmitting device participates in cooperative communication; And And scheduling the traffic to be transmitted by the transmitting device using two queues based on delay sensitivity of the traffic. The method of claim 13, wherein the transmitting apparatus schedules the traffic to be transmitted using two queues, And the transmission apparatus schedules the non-real time traffic using the first queue, and schedules the real time traffic through the second queue.

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