KR101151816B1 - Method of data transmission using media access control protocol in a wireless network - Google Patents

Abstract

The present invention relates to a data transmission method using a medium access protocol in a wireless communication network, and more particularly, to a data transmission method using a medium access protocol in a wireless communication network in a wireless LAN system.

The present invention provides a data transmission method capable of increasing a data transmission rate, reducing a collision rate of data, and efficiently using frequency resources.

A data transmission method according to an embodiment of the present invention is a data transmission method in a wireless communication system in which a predetermined transmission period exists and a signal indicating the start of a transmission period exists, Calculating a time value for controlling the transmission idle period if the transmission idle period is in operation; and transmitting a predetermined data set if the transmission idle period does not operate Determining whether to transmit the predetermined data set according to a predetermined criterion using the calculated time value, and determining a new data set when the predetermined data set can not be transmitted.

Wireless LAN, medium access control, frame transmission, backoff, transmission pause period, dynamic frequency selection

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a data transmission method using a medium access control protocol in a wireless communication network,

The present invention relates to a data transmission method using a medium access protocol in a wireless communication network, and more particularly, to a data transmission method using a medium access protocol in a wireless communication network in a wireless LAN system.

This study was conducted as part of the Ministry of Knowledge Economy's IT Growth Driving Project. [Project Number: 2006-S-014-03, Title: Development of 200Mbps IEEE 802.11n Modem and RF Chipset].

The initial Internet network is developing on the basis of exponential demand from the low-speed wired network to the recent high-speed Internet network. In addition, many technologies for providing Internet service while ensuring human mobility as well as high-speed transmission have been developed. As a representative example, a method of providing a data service by providing an extra band to a mobile communication network developed based on an existing voice service. However, due to limited frequency and channel resources, this method has many difficulties in servicing the current high capacity multimedia packet.

Thus, new networks have been developed to provide wireless packet services. Wireless LAN technology has been studied and commercialized at a high speed in a short distance, and networks for servicing a wide area such as Wibro (Wireless Broadband) have been developed and commercialized.

Of the technologies for servicing these data packets, the wireless LAN technology is the most widely used wireless network technology. The most representative example of the wireless LAN standard is IEEE 802.11, and the MAC of the IEEE 802.11 is an indispensable function and defines a DCF (Distributed Coordination Function) and a PCF (Point Coordination Function) as an optional function. Among them, the DCF protocol uses a collision avoidance (CA) technique that can reduce the probability of collision of wireless terminals to perform carrier sensing multiple access / collision avoidance : Hereinafter referred to as 'CSMA / CA') method. In IEEE 802.11, IFS (Inter-Frame Space) is used to give priority among various frames. IFS means time interval from the end of frame to the transmission of next frame. In DCF, a short inter-frame space (SIFS) having the shortest length and a distributed inter-frame space (DIFS) used for data transmission are used.

A wireless terminal having data to be transmitted performs carrier sensing to check a current wireless channel state and checks the state of a channel for a DIFS time if the channel is in an idle state. If the channel is idle during the DIFS time, it waits for a random backoff time and then transmits the data. At this time, if the use of the channel by another node is confirmed, the backoff counter stops counting and stores the remaining backoff time, and uses the backoff time as the next backoff time.

The above-described wireless LAN structure basically consists of an access point (AP) and a terminal. The AP periodically transmits a beacon frame including an SSID (Service Set Identifier) and the MAC address of the AP ). The wireless terminal acquires available AP information from the beacon frame transmitted from the AP and performs an association procedure defined in the 802.11 MAC standard. Even in an independent Basic Service Set (IBSS) composed of terminals without a base station, a combining procedure between a terminal and a terminal is performed using a beacon frame transmitted from each terminal.

1 is a schematic diagram illustrating a backoff transmission operation of a beacon frame and a data frame in an IEEE 802.11 wireless LAN system. Generally, the beacon frame 110 is transmitted according to a constant transmission interval (Beacon Interval) 140. If a channel attempts to transmit a beacon frame at the AP but the channel is BUSY, that is, if the medium is in use, the beacon that is waiting for transmission is transmitted only when the channel becomes IDLE, that is, the medium is available. After the beacon frame 110 is transmitted, the frames 110 and 120 that have acquired the channel first transmit data. The transmission protocol of the beacon frame and the data frame defined in the DCF protocol may be any value selected in the contention window (hereinafter referred to as "CW ") range after the DIFS time, And transmits the data through the backoff process. If a beacon frame is transmitted at the time of acquiring a wireless channel to transmit data, a beacon frame having a higher priority than general data is transmitted first, and data is transmitted at a transmission time through a backoff process.

However, DCF in IEEE 802.11 does not support user defined QoS. Thus, what is developed is Enhanced Distributed Channel Access (EDCA) protocol of IEEE 802.11e. This transport protocol has eight user priorities (hereinafter referred to as " UP ") based on the DCF protocol and classifies the UPs into four queues (Access Classes) , And the corresponding data can be distributed and transmitted. The transmission queue for each AC having different priorities can be arbitrarily determined based on the DIFS of the DCF protocol according to the priorities and the values of arbitrary IFS (Arbitration Interframe Space, hereinafter referred to as "AIFS &Quot; CW ") value, and a transmission opportunity can be obtained through a backoff process defined in the DCF protocol. A sender who has obtained a transmission opportunity performs transmission of data stored in each transmission queue for a certain period of time, called a transmission opportunity (hereinafter referred to as "TXOP") defined in the specification.

Since the MAC protocol of IEEE 802.11 and IEEE 802.11e is based on the DCF transmission method using CSMA / CA in accessing the wireless medium, the basic backoff transmission method of the DCF protocol in the EDCA protocol defined in IEEE 802.11e is efficiently , It is possible to realize wireless data service considering QoS and it can be expected to have some improved performance because it is based on TXOP transmission protocol.

In addition, the wireless LAN system uses a 2.4GHz ISM (Industrial, Scientific, Medical) band represented by 802.11b and 802.11g and a 5GHz band represented by 802.11b. In the case of a wireless LAN system operating in the 5 GHz band, the same band as the radar may cause interference to each other's systems. Therefore, in order to provide a more efficient quality of service (hereinafter referred to as "QoS") and to support high-speed performance in the case of using the 5 GHz band method, the IEEE 802.11 work group 'h' (Hereinafter referred to as "DFS ") scheme. For this purpose, the IEEE 802.11 wireless media protocol resets the transmission through the backoff process defined by the DCF after the transmission idle period ends after the transmission is stopped by setting the transmission idle period (Quiet Period) do. The transmission idle period is determined by a starting point and a transmission idle duration determined by a beacon frame.

Each terminal of the wireless LAN system performs a transmission idle period and a backoff operation according to a timer operating on the basis of the received beacon frame. Since the transmission idle period of the channel is a idle state in which transmission of the same wireless channel is not performed in order to observe the wireless environment, the wireless media protocol defines the state of the channel to which the transmission idle period belongs as a quiet channel, (BUSY state) in which the wireless channel is used.

FIG. 2 is a schematic diagram illustrating a transmission idle period and a data transmission process in one interval among the beacon transmission intervals shown in FIG. 1. FIG. FIG. 2A shows a process of operating in a beacon interval 220 of one interval. After the periodically repeated beacon frame 210 is transmitted, the wireless environment is measured using the Quiet Offset 230 and the Quiet Duration 240, which are transmission idle periods. The UEs and APs wishing to use the channel resume transmission through the backoff process defined by the DCF after the transmission idle period ends. That is, after waiting for a certain IFS 250, the data 270 and 280 are transmitted after a backoff 260 process.

3 is a structural diagram showing information of a transmission pause period.

In FIG. 3, an Element ID 310, a Length 320, a Quiet Count 330, a Quiet Period 340, a Quiet Duration 350, and a Quiet Offset 360 are used to indicate information on a transmission pause period. The Quiet Offset 360 and the Quiet Duration 350 indicating the start time of the transmission idle period in the same BSS maintain the same value through the value in the Beacon frame and the information for the transmission idle period Is the information of the transmission idle period of the general IEEE 802.11h.

Since the transmission idle channel operates arbitrarily, there is a delay in data transmission in which the service is already started, or a collision occurs between the transmission idle period and the data transmission channel, which may degrade performance and ultimately deteriorate network performance . Therefore, it is necessary to study the wireless media access control method with efficient backoff processing method.

Accordingly, the present invention provides a backoff method of a wireless medium access control protocol that can increase a data transmission rate.

Also, the present invention provides a backoff method of a wireless medium access control protocol capable of reducing a collision rate of data.

Also, the present invention provides a backoff method of a radio medium access control protocol that can efficiently use frequency resources.

A data transmission method according to an embodiment of the present invention is a data transmission method in a wireless communication system in which a predetermined transmission period exists and a signal indicating the start of a transmission period exists, Calculating a time value for controlling the transmission idle period if the transmission idle period is in operation, transmitting a predetermined data set if the transmission idle period does not operate, Determining whether to transmit the predetermined data set using the calculated time value based on a predetermined criterion, and determining a new data set if the predetermined data set can not be transmitted.

According to the wireless medium access control protocol of the present invention, it is possible to reduce data delay and support QoS. High-speed data processing is possible, and the performance of the wireless data network can be improved.

In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail. Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Hereinafter, the present invention will be described with reference to the accompanying drawings.

In a basic backoff scheme defined by a Distributed Coordination Function (DCF) of the IEEE 802.11 wireless media access control protocol, the present invention effectively controls the transmission process of a data service in which transmission is performed during a period for measuring a radio environment, (Access Classes), which are QoS-aware, and are independent of each other. Therefore, it is possible to reduce the service delay caused by the wireless medium access control protocol Performance.

FIG. 4 is a schematic diagram showing an embodiment of a process of transmitting data within a time period for waiting for a transmission pause in a wireless channel according to an embodiment of the present invention.

After the beacon frame 400 is transmitted, a transmission idle period for measuring the state of the wireless medium defined in 802.11h, i.e., a Quiet Offset 430 and a idle period 440, is performed. The dormancy offset 430 and the idle period 440 are the same as in the normal operation. In the present invention, when an arbitrary terminal requests transmission of data at an arbitrary time (Tn) 420 based on a time point (T0) 450 at which an IFS starts after a beacon frame 400 is transmitted, a channel BUSY ends The IFS time has already passed and backoff 460 is performed. In a Quiet Remaining Time (Quiet Offset) 430, when the transmission completion time of the data to be transmitted after the back-off, that is, the time when all the data is transmitted, (TO) 420, the data frames 470 and 480 are transmitted.

5 is a conceptual diagram illustrating a transmission process of a wireless LAN system for controlling transmission pause channels for four ACs defined by the EDCA protocol.

In step 510 of FIG. 5, when the AP receives a data transmission request, the AP determines whether a channel using a transmission idle period is applied. If the terminal does not apply the transmission idle period, it transmits data on the AC determined in step 550. [ In step 530, the AP calculates a time value for performing a quiet channel operation if a transmission idle period is applied.

The AC including the data to be transmitted is an AC that acquires the channel from the internal contention of the EDCA protocol. The current AC from the internal competition is called ACn, and since there are four ACs, the value of n ranges from 0 to 3. The transmission time of the data for the determined ACn is also referred to as TMPDU. TMPDU includes a backoff time (TBackoff) for determining a transmission time point and a transmission time (MPDU_RESP_TX_TIME) of the MPDU. The transmission time of MPDU includes both MPDU data, SIFS (Short IFS) time, and response transmission time to MPDU.

The time remaining for the start of the transmission idle period is called Qremain. Qremain represents the time remaining after subtracting Tn, which is the time at which a data transmission request occurs in the Qoffset. The calculated time values are shown in Table 1.

3)Accss Category N (0

3) ACn Time to Transmit a MPDU TMPDU Quiet Offset Qoffset Quiet Past Time Tn Quiet Remain Time

Time to Backoff TBackoff Time to transmit a MPDU

In step 540, if the transmission idle period is applied, it is determined whether the transmission time (TMPDU) for ACn is longer than the Qremain time. In step 560, if the TMPDU is longer than the Qremain time, the transmission is not started but the channel (quiet channel) for the ACn is set to BUSY, and then the transmission of data is suspended until the transmission idle period ends. In step 570, internal competition is performed again between the remaining ACs except for the AC determined in step 540. If the TMPDU is not longer than the Qremain time, the MPDU transmission for ACn is possible in step 550, so that data for the determined AC is transmitted.

If it is determined in step 580 that there is an AC to transmit as a result of internal competition between ACs other than the AC that can not be transmitted, if there is an AC to be transmitted, TMPDU compares Qremain with the newly determined ACn And if it is determined that there is no AC to transmit, step 590 is performed.

The present invention relates to a wireless LAN system capable of dynamically selecting a frequency according to a wireless environment, and is capable of efficiently performing a backoff process for each of four access category (AC) data transmitted during a pause period for observing a wireless environment And provides a method for efficiently processing the backoff process by controlling the basic channel state defined by the DCF of IEEE 802.11 with more detailed conditions.

1 is a schematic diagram showing a back-off transmission operation of a beacon frame and a data frame in an IEEE 802.11 wireless LAN system,

FIG. 2 is a schematic diagram illustrating a transmission idle period and a data transmission process in one interval among the beacon transmission intervals shown in FIG. 1;

3 is a structure diagram showing information of a transmission pause period;

FIG. 4 is a schematic diagram showing an embodiment of a process of transmitting data within a time period for waiting for a transmission pause in a wireless channel according to an embodiment of the present invention;

5 is a conceptual diagram illustrating a transmission process of a WLAN system that controls transmission pause channels for four ACs defined by the EDCA protocol.

Claims (6)

A data transmission method in a wireless communication system in which a predetermined transmission period exists and a signal indicating the start of a transmission period exists, Receiving a transmission request for data to be transmitted and determining whether to apply a transmission idle period; Calculating a time value for controlling the transmission idle period if the transmission idle period is in operation; Transmitting a predetermined data set if the transmission idle period does not operate; Determining a new data set if transmission of the predetermined data set ACn is not possible; Wherein the step of determining based on the predetermined criteria comprises: (TMPDU) for the predetermined data set (ACn) and a remaining time (Qremain) for the start of the transmission idle period to compare the data transmission time (TMPDU) for the predetermined data set ) Is less than a remaining time (Qremain) for starting the transmission idle period, transmitting the predetermined data set. 2. The method of claim 1, And transmitting data on AC determined through an internal contention process of the EDCA using an existing WLAN transmission method.  2. The method of claim 1, wherein the time value for controlling the transmission idle period comprises: Calculating a data transmission time (TMPDU) for the predetermined data set (ACn) And calculating a remaining time (Qremain) for starting the transmission idle period. 4. The method of claim 3, wherein calculating the remaining time (Qremain) for the start of the transmission idle period comprises: Determining a value of a predetermined dwell offset (Qoffset) And calculating a time remaining after subtracting a time point (Tn) at which the data transmission request is generated from a time point of the dormant offset (Qoffset). 2. The method of claim 1, wherein the step of determining based on the predetermined criteria comprises: (TMPDU) of the data for the predetermined data set (ACn) and a remaining time (Qremain) for the start of the transmission idle period to compare the data transmission time (TMPDU) for the predetermined data set ) Is greater than a remaining time (Qremain) for the start of the transmission idle period, stopping the transmission of the predetermined data set. 2. The method of claim 1, wherein determining a new data set comprises: Performing EDCA internal competition for data sets other than the predetermined data set; Determining a new data set through the internal competition; And if the new data set exists, determining whether to transmit the data according to the predetermined criterion.

Images