WO2014017735A1 - Method for transmitting data by using reverse order implied information obtained by competition by means of distributed coordination function in wireless lan, and wireless communication device for transmitting data by using same - Google Patents

Abstract

According to the present invention, collision with a back-off slot in a competition by means of a DCF can be significantly reduced, and a throughput higher than existing DCFs can be provided. Also, overhead due to additional control messages is eliminated by reverse order implied information operating in a distributed manner in terminals, and communication with existing terminals is enabled even in a wireless network using APs or the DCF.

Description

Data transmission method using backward order implied information obtained through competition by distributed coordination function of wireless LAN and wireless communication device transmitting data using same

The present invention relates to data transmission using a wireless LAN, and in particular, by assigning a specific function to a distributed coordination function, which is a medium access elimination technique basically used in an IEEE 802.11 WLAN, a higher throughput can be achieved than a distributed coordination function. The present invention relates to a data transmission method using reverse order implied information obtained through competition by a distributed coordination function, and a wireless communication device transmitting data using the same.

In recent years, IEEE 802.11 WLANs have been widely used for wireless Internet access due to the simplicity of installation and low cost. Currently, IEEE 802.11 WLANs define two different media access control schemes.

The basic approach uses a distributed coordination function (hereinafter referred to as "DCF"), which is a common carrier sense multiple access / collision avoidance technique, which is a rule applied when accessing a wireless medium based on competition. It can be used in both ad-hoc and infrastructure network environments.

In addition, a media access control technique called a polling based point coordination function (hereinafter referred to as "PCF") may be selectively used.

Wireless has a characteristic of broadcasting and when two channels are used in the same band, two terminals cannot transmit at the same time. If two or more terminals transmit at the same time, collision occurs and all transmissions may fail.

In the conventional distributed coordination function (DCF), three inter-frame spaces (IFS, Short Interframe Space), PIFS (PCF Interframe Space), and DIFS are used to implement the IEEE 802.11 media access control scheme. (DCF Interframe Space) is included.

Inter Frame Space (IFS) means the minimum waiting time after transmitting one frame and before performing the next frame transmission operation. The time interval is SIFS <PIFS <DIFS. It is longer and SIFS is used for the communication with the highest priority because it has the shortest time interval.

Hereinafter, a general method of probabilistically avoiding collisions occurring in a wireless environment by a distributed coordination function (DCF) will be described.

The distributed coordination function (DCF) uses a binary exponential back-off method to avoid collision between transmitting terminals and to prevent continuous channel occupancy of a specific terminal. In the Binary Exponential Back-off method, if a data transmission signal on a transmission medium collides in a wireless LAN, the probability of continuous collision is lowered by giving a delay time before attempting transmission again.

Before transmitting data, all terminals check whether the transmission medium is occupied by another terminal. At this time, if the transmission medium is not used during DIFS time, it is considered as idle and immediate transmission. The terminal receiving the data notifies the success of the transmission by sending an ACK frame immediately after a predetermined time SIFS. Regardless of whether there is still data to be transmitted, the terminal which has successfully transmitted first selects the back off number as an arbitrary value smaller than the contention window and then starts back off. .

SIFS is smaller than DIFS so that the transmission of other terminals does not interfere with the transmission of the ACK frame. If no ACK frame is received, the transmission is considered failed and the transmission window is doubled. The initial contention window value is set to CWmin , and the maximum size of the transmission window is CWmax . If the transfer is successful, the transfer window is initialized with the CWmin value.

If the medium is busy by another terminal, the terminal selects the back off number as an arbitrary value smaller than the contention window. At this time, if the transmission medium is not used during the DIFS time, it is regarded as idle and starts back off.

If transmission of another UE does not occur during a slot time of a predetermined time, the back off number is reduced by one, and when the back off number is 0, data is transmitted. When the other terminal recognizes the transmission, the back off is stopped, and when the transmission medium is idle again during DIFS, the back off is resumed.

Thereafter, if the back off number is zero and the transmission medium is idle, transmission starts.

However, although the conventional distributed coordination function (DCF) is essentially adopted as a media access control scheme of the IEEE 802.11 WLAN, it generally shows low performance. In particular, as the number of terminals increases, frequent collisions occur and backoff is not used. off) resulting in bandwidth wastage due to slots, resulting in low transmission rates.

On the other hand, various conventional techniques have been proposed to improve the above problems, but in a general contention-based distributed media access control scheme, collision and unused back off are one of the equivalent trade-off relationships. This approach has been limited in achieving the desired performance gains because attempting to reduce the number increases the other.

The technical problem to be solved by the present invention is to compete with the distributed coordination function (DCF) of the WLAN, to improve the inefficiency of the distributed coordination function (DCF), which is a medium access elimination technique basically used in IEEE 802.11 WLAN It is to provide a data transmission method using the reverse order implied information obtained through.

Another technical problem to be solved by the present invention is to provide a wireless communication device for transmitting data using a data transmission method using the reverse order implied information obtained through the competition by the distributed coordination function (DCF) of the wireless LAN. will be.

In the data transmission method using the reverse order implied information obtained through the competition by the distributed coordination function (DCF) of the wireless LAN according to the present invention for achieving the technical problem, the first terminal competes by the distributed coordination function of the WLAN Step of successful data transmission through the step 2 The second terminal recognizes the first terminal successful data transmission The data transmission is successful from the moment when the terminal competes after the distributed coordination function interval (DIFS) for transmission When one transmission round is called until the transmission medium starts idle as much as DIFS for the next competition, after the first terminal succeeds in data transmission in the one transmission round, the second terminal in a subsequent transmission round. Successful data transmission through competition by the distributed adjustment function; and the second terminal expands the first terminal to a senior terminal. If the first terminal succeeds in data transmission through competition by the dispersion adjustment function, the second terminal includes transmitting data without contention by the dispersion adjustment function.

When the second terminal identifies the first terminal as the senior terminal, it is preferable that the second terminal cannot participate in the competition by the dispersion adjustment function. In addition, when the second terminal identifies the first terminal as a senior terminal, the second terminal doubles the back-off of the second terminal by doubling the minimum contention window value CWmin and the minimum contention window and subtracts 1 from the second terminal. It is preferable to select a value between one value (2 CWmin-1). It is also preferable that terminals having a senior terminal are given only one transmission opportunity in the one transmission round. In addition, when the RTS / CTS option is activated and used together, the terminal that successfully transmits data through the RTS / CTS is preferably treated the same as the terminal that successfully transmits data through contention by the distributed coordination function. .

The wireless communication device for transmitting data using the data transmission method using the reverse order implied information obtained through the competition by the distributed coordination function (DCF) of the wireless LAN according to the present invention for achieving the technical problem, A senior terminal detector for detecting a first terminal that succeeds in data transmission by participating in a competition by a dispersion coordination function, and in a continuous transmission round after data transmission success of the first terminal. Re-joining the competition by the coordination function to acquire the channel right and succeeding in data transmission, the senior terminal confirming unit for confirming the detected first terminal to the senior terminal and the identified senior terminal competition by the distributed coordination function Unsuccessful data transmission that transmits data without contention by distributed coordination function A comprise.

According to the data transmission method using the reverse order implied information obtained through the competition by the distributed coordination function (DCF) of the wireless LAN according to the present invention and a wireless communication device transmitting data using the same, the conventional distributed coordination function (DCF) By using (), back off slots and collisions can be greatly reduced, and throughput can be realized higher than that of DCF.

In addition, according to the present invention, since there is no overhead due to the additional control message because the order suggestion can be distributed in the terminal, it is already widely installed because it adds a simple function in the IEEE 802.11 DCF already defined as a standard. A wireless network using an access point (AP) or IEEE 802.11 DCF provides compatibility with existing terminals.

FIG. 1 is a flowchart illustrating a data transmission method using reverse order implied information obtained through competition by a distributed coordination function (DCF) of a wireless LAN according to the present invention.

2 illustrates an embodiment of a data transmission method using backward order implied information obtained through competition by a distributed coordination function (DCF) of a wireless LAN according to the present invention.

3 is a diagram illustrating an embodiment of a configuration of a wireless communication device transmitting data using a data transmission method using backward order implied information obtained through competition by a distributed coordination function (DCF) of a wireless LAN according to the present invention. It is shown.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, the embodiments described herein and the configurations shown in the drawings are merely exemplary embodiments of the present invention, and the present invention. It is not intended to represent all of the technical spirit of the present invention, it should be understood that there may be various equivalents and modifications that can replace them at the time of the present application.

In the present invention, all terminals compete through IEEE 802.11 DCF for data transmission as before. At this time, due to the nature of the wireless communication, all the terminals can be aware of the transmissions in progress. All the awake terminals, i.e., terminals not in power saving mode provided by IEEE 802.11 in order to intentionally reduce energy consumption, are being transmitted. To determine if the data is intended for itself, it receives the frame being transmitted and decodes a Medium Access Control (MAC) header among them, and if the destination described in the header is itself, Receive and raise to a higher layer, or discard. The present invention starts from the fact that all the terminals can now know the ongoing transmissions.

In order to reduce waste due to excessive idle slots and collisions and waste due to competition, each terminal needs to know when it should send data. For example, terminal B always sends after terminal A, and then reserves the right to occupy the medium after successful transmission of each terminal, such as terminal C.

However, such reservations have conventionally used control messages that cause excessive overhead, or have made assumptions that are unacceptable in the real world. The present invention implies reverse order for transmission reservations without any additional overhead. (Implicit Backward Ordering) information is used. To this end, competition for acquiring a transmission medium use authority using IEEE 802.11 DCF is performed, and when transmitting data, only one terminal can be normally transmitted at any one time due to the characteristics of wireless communication. That is, the order of the terminal which attempts the transmission and succeeds is determined, but this order information is used by this invention.

In the present invention, there is no excessive idle slots or collisions, and the implicit backward ordering information for reserving a transmission order without any overhead is defined as a process of identifying an immediate predecessor.

FIG. 1 is a flowchart illustrating a data transmission method using reverse order implied information obtained through competition by a distributed coordination function (DCF) of a wireless LAN according to the present invention.

FIG. 2 illustrates an embodiment of a data transmission method using reverse order implied information obtained through contention by a distributed coordination function (DCF) of a wireless LAN according to the present invention.

With reference to Figures 1 and 2 will be described a data transmission method using the reverse order implied information obtained through the competition by the distributed coordination function (DCF) of the wireless LAN according to the present invention and its embodiment will be described.

First, the first terminal succeeds in data transmission through contention by the distributed coordination function of the wireless LAN (step S100). The second terminal recognizes the first terminal that successfully transmits the data (step S110).

When one UE makes a round of transmission from the moment when the UE competes after the DIFS frame for transmission, until the transmission medium starts idle as much as DIFS for the next competition after successful data transmission. After the first terminal succeeds in data transmission in the one transmission round, the second terminal succeeds in data transmission through competition by the dispersion adjustment function in successive transmission rounds (step S120). The first terminal is confirmed as a senior terminal (step S130).

The steps S100 to S130 will be described in more detail with reference to FIG. 2. When the first terminal is referred to as the terminal A and the second terminal is referred to as the terminal B, the terminal A succeeds in transmission through the DCF. After that, the terminal B successfully transmits data through contention. In more detail, after the terminal A waits as much as Backoff 4 after DIFS, the terminal A acquires the channel right 200 and transmits data, and receives the ACK frame 202 after SIFS, thereby successfully transmitting. . At this time, the terminal B is in the "BUSY MEDIUM" state 206 while the terminal A is acquiring the channel right 200, and if the DIFS has elapsed after the terminal A succeeds in transmission, decreases the number of backoffs and then goes back to Backoff ( If the channel continues to be empty until the time started by 7) elapses and the number of the backoff becomes 0, the terminal B acquires the channel right 208 and starts data transmission. Then, upon receiving the ACK frame 210, data transmission is successfully completed. On the other hand, channel A is in the "BUSY MEDIUM" state 204 until channel B acquires the channel right 208, receives the ACK frame 210, and transmits data.

At this time, the terminal B can recognize the terminal A that succeeded in data transmission just before its data success. In this case, the terminal B identifies the terminal A as its immediate predecessor (230).

In this way, after the first terminal is identified as the senior terminal of the second terminal, the first terminal participates in the competition by the distributed coordination function to transmit data again, acquires channel usage rights, and succeeds in data transmission. In this case, since the first terminal is a senior terminal, the second terminal transmits data without contention by the dispersion coordination function by implicit backward ordering (step S140). In this case, the second terminal transmits the first terminal. If confirmed by the senior terminal, it is desirable to prevent participation in the competition by the distributed adjustment function. In addition, when the second terminal identifies the first terminal as a senior terminal, the back-off of the second terminal is doubled by a minimum contention window value (CWmin) and the minimum contention window, and then subtracted one. It is preferable to select a value between the values (2 CWmin-1). In addition, it is preferable that terminals having a senior terminal are given only one transmission opportunity in the one transmission round. In addition, when the RTS / CTS option is activated and used together, the terminal that successfully transmits data through the RTS / CTS is preferably treated the same as the terminal that successfully transmits data through contention by the distributed coordination function. .

The step S140 will be described in detail with reference to FIG. 2. When UE A corresponding to the first terminal succeeds in data transmission through DCF contention, UE B corresponding to the second terminal receives implicit order information. Through this, there is an additional transmission opportunity without contention by the DCF.

In more detail, after the terminal B confirms the terminal A as a senior terminal, the terminal A waits until the backoff number becomes 0 when DIFS ends again after a time elapses. Referring to FIG. If the channel is empty until terminal A goes from backoff (4) to backoff (0), that is, until the number of backoffs decreases from 4 to 0, terminal A obtains channel license 250 and transmits data. Receive an ACK frame 252 to complete the transmission successfully.

On the other hand, the terminal B is in the BUSY MEDIUM state (256) until the terminal A obtains the channel license 250 and completes the transmission, and if the terminal A confirmed as a senior terminal succeeds in transmitting the data, the channel immediately after the SIFS without DCF competition It acquires the right of use 258 to transmit data and receives the ACK frame 260 to complete successful data transmission.

It is important to note that this series of procedures does not require any additional functionality and no additional control messages.

In this process, in principle, terminals having their own senior terminals cannot participate in the DCF competition. However, if their senior terminals no longer send and participate in the DCF competition, the subsequent terminals may not be able to transmit data forever. In order to prevent this case, the UEs identifying their senior terminals select a backoff from [CWmin, 2CWmin-1]. In case of successful data transmission without competition due to his senior terminal, he chooses his next backoff as above. In this way, even if his senior terminal no longer participates in the DCF race because there is no more data to send, he does not miss the opportunity of transmission forever.

Another exceptional situation occurs when two terminals always have something to send and identify each other as their own senior terminal. In this case, the transmission medium will always be occupied by these two terminals and the other terminals will not even be able to participate in the competition.

To prevent this from happening, we define a logical round of transmission. The transmission round refers to two consecutive DIFS intervals. In FIG. 2, the first terminal A competes after DIFS for transmission, and after data transmission is successfully completed, until one transmission medium starts idle as much as DIFS for another competition. At this time, all terminals having a senior terminal may have only one transmission opportunity in one round. If he has more than one transmission opportunity, his senior terminal does not pursue anymore.

The present invention can be used together with the RTS / CTS without any problem. According to the IEEE 802.11 standard, it is recommended to use RTS / CTS as a way to solve the hidden terminal problem. That is, when the present invention and the RTS / CTS are used together when the RTS / CTS option is activated, a terminal that successfully transmits data through the RTS / CTS may be treated the same as a terminal that successfully transmits data through the DCF. .

Meanwhile, FIG. 3 illustrates an example of a configuration of a wireless communication device that transmits data using a data transmission method using reverse order implied information obtained through competition by a distributed coordination function (DCF) of a wireless LAN according to the present invention. It is shown.

The wireless communication device according to the present invention includes a senior terminal detection unit 300, a senior terminal confirmation unit 320 and the contention-free data transmission unit 340.

The senior terminal detection unit 300 participates in the competition by the DCF of the WLAN, and detects the first terminal that succeeds in data transmission through the competition by the DCF.

The senior terminal confirming unit 320 participates in the competition by the DCF in a continuous transmission round after the successful transmission of the data of the first terminal, and acquires the channel use right by the DCF competition and succeeds in transmitting the data. Confirm the terminal as a senior terminal.

The contention-free data transmission unit 340 transmits data following the first terminal without competition by the DCF when the senior terminal identified by the senior terminal identification unit 320 succeeds in data transmission through the competition by the DCF. do.

At this time, if the first terminal is confirmed as the senior terminal, it is preferable that the terminal having the senior terminal can not participate in the competition by the DCF. In addition, when the senior terminal confirming unit 320 confirms the first terminal as the senior terminal, the back-off is doubled by the minimum contention window value CWmin and the minimum contention window, and then subtracted 1. It is preferable to select a value between (2CWmin-1). Also, it is preferable that terminals having a senior terminal are given only one transmission opportunity in the one transmission round. In addition, when the RTS / CTS option is activated and used together In the case of a terminal that successfully transmits data through the RTS / CTS, it is preferable to treat the same as a terminal that successfully transmits data through contention by the distributed coordination function.

The wireless communication device includes any communication device for performing wireless communication, and may include a mobile communication device including a smart phone.

The present invention can be embodied as code that can be read by a computer (including all devices having an information processing function) in a computer-readable recording medium. The computer-readable recording medium includes all kinds of recording devices in which data that can be read by a computer system is stored. Examples of computer-readable recording devices include ROM, RAM, CD-ROM, magnetic tape, floppy disks, optical data storage devices, and the like.

In the above description, the technical idea of the present invention has been described with the accompanying drawings, which illustrate exemplary embodiments of the present invention by way of example and do not limit the present invention. In addition, it is apparent that any person having ordinary knowledge in the technical field to which the present invention belongs may make various modifications and imitations without departing from the scope of the technical idea of the present invention.

Claims (10)

1. The first terminal succeeding in data transmission through contention by the distributed coordination function of the wireless LAN;

   Recognizing, by the second terminal, the first terminal that has successfully transmitted data;

   When one UE makes a round of transmission from the moment when the UE competes after the DIFS frame for transmission, until the transmission medium starts idle as much as DIFS for the next competition after successful data transmission. After the first terminal successfully transmits data in the one transmission round, the second terminal succeeds in data transmission through competition by the dispersion adjustment function in successive transmission rounds;

   Confirming, by the second terminal, the first terminal as a senior terminal; And

   If the first terminal succeeds in data transmission through competition by the distributed coordination function, the second terminal transmits data without contention by the distributed coordination function; A data transmission method using backward order implied information obtained through contention by a coordination function.
2. The method of claim 1, wherein the second terminal,

   And identifying the first terminal as a senior terminal, cannot participate in the competition by the distributed coordination function. The data transmission method using the reverse order implied information obtained through the competition by the distributed coordination function of the WLAN.
3. The method of claim 1, wherein the second terminal

   When the first terminal is identified as the senior terminal, the back-off of the second terminal is doubled by the minimum contention window value CWmin and the minimum contention window and then subtracted by 1 (2CWmin-1). The data transmission method using the reverse order implied information obtained through the competition by the distributed coordination function of the wireless LAN, characterized in that selected by the value between.
4. The method of claim 1,

   Terminals having a senior terminal is a data transmission method using the reverse order implied information obtained through the competition by the distributed coordination function of the wireless LAN, characterized in that only one transmission opportunity is given to the one transmission round.
5. The method of claim 1,

   When the RTS / CTS option is activated and used together, the terminal that successfully transmits data through the RTS / CTS is treated the same as a terminal that successfully transmits data through contention by the distributed coordination function. A data transmission method using backward order implied information obtained through competition by a distributed coordination function of a WLAN.
6. A senior terminal detecting unit which participates in a competition by the distributed coordination function of the WLAN and detects a first terminal that succeeds in data transmission through the competition by the distributed coordination function;

   In the subsequent transmission round after the successful transmission of the data of the first terminal, re-join the competition by the distributed coordination function to obtain channel use rights and if the data transmission is successful, the senior terminal to confirm the detected first terminal to the senior terminal Terminal identification unit; And

   And a contention-free data transmitter for transmitting the data without contention by the distributed adjustment function when the identified senior terminal succeeds in data transmission through the contention by the dispersion adjustment function.
7. The method of claim 6,

   And confirming the first terminal as the senior terminal, the terminal having the senior terminal cannot participate in the competition by the distributed coordination function.
8. The method of claim 6,

   When the senior terminal confirming unit confirms the first terminal as the senior terminal, a back-off value is obtained by subtracting 1 after doubling the minimum contention window value CWmin and the minimum contention window (2CWmin-1). Wireless communication device characterized in that the selection between.
9. The method of claim 6,

   A terminal having a senior terminal is provided with only one transmission opportunity in the one transmission round.
10. The method of claim 6,

    When the RTS / CTS option is activated and used together, the terminal that successfully transmits data through the RTS / CTS is treated the same as a terminal that successfully transmits data through contention by the distributed coordination function. Wireless communication device.

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