KR20070042753A - System and method for data flow control in a wireless communication system - Google Patents

Abstract

The present invention relates to data flow control of a base station in a wireless communication system including a plurality of terminals, a base station communicating with the terminals, and a base station controller managing a plurality of base stations including the base station. When the data received from the base station controller is transmitted to the terminals, the data transmission amount to be transmitted to the terminals is measured, the data transmission amount is compared with a predetermined threshold value, and the data transmission amount is a predetermined threshold value. If exceeded, a flow control message for controlling the data flow received from the base station controller is transmitted to the base station controller.

Base station, base station controller, flow control message, data flow control

Description

SYSTEM AND METHOD FOR DATA FLOW CONTROL IN A WIRELESS COMMUNICATION SYSTEM}

1 is a diagram schematically illustrating data flow control in a general wireless communication system.

2 is a diagram schematically illustrating data flow control in a wireless communication system according to a first embodiment of the present invention.

3 is a diagram schematically illustrating data flow control in a wireless communication system according to a second embodiment of the present invention.

4 is a diagram schematically illustrating data flow control in a wireless communication system according to a third embodiment of the present invention.

5 is a flowchart schematically illustrating a method of operating a base station for data flow control in a wireless communication system according to an embodiment of the present invention.

6 is a flowchart schematically illustrating a method of operating a base station for data flow control in a wireless communication system according to a second embodiment and a third embodiment of the present invention;

7 is a flowchart schematically illustrating an operation process of setting a threshold in a base station according to a third embodiment of the present invention.

The present invention relates to a wireless communication system, and more particularly, to a system and method for data flow control in a broadband wireless communication system.

Digital cellular wireless communication system, which improves the channel capacity and voice quality of analog cellular wireless communication, provides voice and low-speed data services. Therefore, there are limitations in providing various multimedia services. However, according to the development of communication technology, a wireless communication system, that is, an international mobile telecommunication (IMT)-that allows access to a fixed network service such as an existing telephone or an integrated service digital network (ISDN) using one or more wireless links. 2000 A communication system has emerged. The IMT-2000 communication system is a communication system that can transmit and receive various information at high speed anywhere in the world by overcoming the limitations of the mobility of the terminal and the limitation of the transmission speed. Accordingly, the IMT-2000 communication system has been developed to provide a multimedia service such as a high speed data service and a video service including the Internet as well as a voice service.

However, with the recent increase in various multimedia services using the Internet, attempts to interwork multimedia services provided by the wired Internet have been increasing in the wireless communication system. In addition, researches are being actively conducted on broadband wireless communication systems that can provide high-speed, high-quality multimedia services that were not provided by conventional narrowband wireless communication systems.

Among these broadband wireless communication systems, there is a high-speed portable Internet system (Wibro: hereinafter referred to as WiBro) system, and the WiBro communication system is referred to as a local area network (LAN). It is a system that has a larger cell size, supports mobility, and provides seamless services.

Accordingly, the WiBro system will be described as an example of the broadband wireless communication system. The WiBro system is expected to develop various application services by integrating wired and wireless networks, increasing personal mobility, and increasing the speed and capacity of transmission data. In addition, because video-related services, Internet broadcasting services, or services requiring large database access technology (DB) are predicted, next-generation mobile communication systems will use ultra-high speeds of up to several hundred Mbps using the 2 ~ 60GHz band. It will be possible to send and receive data.

The WiBro system can provide a high speed communication service in a wireless communication environment by using various types of portable terminals such as a notebook, PDA, and handheld PC. The WiBro system includes information providing services such as internet access, e-mail, and data retrieval, entertainment services such as photo transmission, video on demand (VoD), and games, and remote payment, Provides services such as business services such as e-commerce.

The WiBro system includes a portable subscriber station (PSS), a radio access station (RAS), and an access control router (ACR).

First, the base station controller is located between a core network (CN) and a base station, and performs a Convergence Sublayer (CS) function, an Automatically Request (ARQ) processing function, and handoff. Perform control functions. It also provides an interface with the core network.

The base station is located between the base station controller and the terminal, and provides a wireless access interface that conforms to the Institute of Electrical and Electronics Engineers (IEEE) 802.16 standard.

The terminal also communicates with a base station according to a radio access standard as an end point of a radio channel.

A data flow control method currently provided between a base station and a base station controller to provide a data service in the WiBro system configured as described above will be described with reference to FIG. 1 below.

1 is a diagram schematically illustrating data flow control in a general wireless communication system.

Referring to FIG. 1, the data flow control between the base station controller 110 and the base station 150 is illustrated, and the control flow operation is performed by the flow control message, that is, the base station 150 from the base station controller 110 to the base station 150. The data flow is controlled using the Q_State_IE REQ message requesting the information on the buffer state of 150 and the Q_State_IE message reporting the buffer state information from the base station 150 to the base station controller 110 in correspondence with the Q_State_IE REQ message.

The data flow control is performed between the transmitter and the receiver, that is, the base station controller 110 and the base station 150. If the transmitter transmits data more than the capacity of data processed by the receiver, an overflow occurs in the receiver, and the transmitter transmits data less than the capacity of data processed by the receiver. Underflow occurs. The data flow control is to prevent the above overflow and underflow between the transceivers.

The base station controller 110 requests the buffer status information from the base station 150 and receives the buffer status information from the base station 150 according to the request for the buffer status information to perform data flow control. In the case of using the data flow control method as described above, data cannot be transmitted in a transmission / reception section of the Q_State_IE REQ message and the Q_State_IE REQ message, and thus an underflow occurs in the section. Therefore, when the flow control method is used as described above, there is a problem that a decrease in data throughput occurs due to underflow occurring in the receiver, that is, the base station 150.

In addition, when the flow control message is transmitted and received through the above method, that is, the message for requesting buffer status information and the message for transmitting buffer status information in response to the message for requesting buffer status information are transmitted and received for data flow control. There was a problem that messages acted as overhead in the system.

Accordingly, there is a need for efficient data flow control in a wireless communication system.

Accordingly, an object of the present invention is to provide a system and method for efficiently performing data flow control in a wireless communication system.

Another object of the present invention is to provide a data flow control system and method in which a decrease in data throughput does not occur in a wireless communication system.

Another object of the present invention is to provide a system and method for efficiently transmitting a message for data flow control in a wireless communication system.

The method of the present invention for achieving the above objects; A method of controlling a data flow of a base station in a wireless communication system comprising a plurality of terminals, a base station communicating with the terminals, and a base station controller managing a plurality of base stations including the base station, the method comprising: receiving data received from a base station controller; When transmitting to the terminal, the process of measuring the amount of data transmission to the terminal, the process of comparing the data transmission amount and a predetermined threshold value, and the amount of data transmission exceeds a predetermined threshold value And transmitting a flow control message for controlling the data flow received from the base station controller to the base station controller.

The system of the present invention for achieving the above objects; A data flow control system in a wireless communication system including a plurality of terminals, a base station communicating with the terminals, and a base station controller managing a plurality of base stations including the base station, the data flow control system comprising: terminals receiving data received from a base station controller; In the case of transmitting to the mobile station, the flow rate for measuring the data transmission amount to be transmitted to the terminals and comparing it with a predetermined threshold value, and controlling the data flow received from the base station controller when the data transmission amount exceeds the threshold value And a base station controller for transmitting a message to the base station controller, and controlling a flow of data transmitted to the base station by receiving a flow control message from the base station.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that in the following description, only parts necessary for understanding the operation according to the present invention will be described, and descriptions of other parts will be omitted so as not to distract from the gist of the present invention.

The present invention will be described for performing data flow control of a wireless broadband system (Wibro: hereinafter referred to as WiBro) system among wireless communication systems as an example, and a base station controller (ACR) of the Wibro communication system. As an example, data flow control between an access control router (RAS) and a base station (RAS) is illustrated, and the base station checks the buffer status of the base station at a predetermined time interval and transmits information on the buffer status. It transmits to the base station controller through the control of the flow of data. Alternatively, when the buffer size of the base station is set to a threshold value and the threshold value is exceeded, a flow control message is transmitted to the base station to perform data flow control. Or setting a threshold value in consideration of downlink channel quality of the base station and a portable subscriber station (PSS) hereinafter and a buffer size of the base station and exceeding the threshold value. The flow control message is transmitted to the base station to control the flow of data.

2 is a diagram schematically illustrating data flow control in a wireless communication system according to a first embodiment of the present invention.

Referring to FIG. 2, the base station 250 transmits a flow control message, that is, a Q_State_IE message, to the base station controller 210 at predetermined time intervals. The base station controller 210 controls the amount of data transmitted to the base station controller using the Q_State_IE message transmitted from the base station 250. Here, the Q_State_IE message including the information on the buffer state is transmitted at a predetermined time interval from the base station 250 without using the message requesting the buffer state of the existing base station 250, that is, the Q_State_IE REQ message. Thus, the flow control message is transmitted at the predetermined time, for example T1 interval as shown.

Thus, it is possible to control the data flow by transmitting Q_State_IE at regular intervals without using the Q_State_IE REQ message as shown in FIG. 1, and control the flow of data using only the flow control message, that is, the Q_State_IE message. can do.

Here, the Q_State_IE message may be, for example, a specified connection ID of a downlink buffer according to the state information report, a bit or byte value of a transmission buffer size, and a transmission buffer. A sequence number of a tail and a sequence number of a transmission buffer head. In addition, when the base station controller 210 and the base station 250 are an Automatic Repeat ReQuest (ARQ) connection, the Q_State_IE message may include a bit or byte value of a retransmission buffer size and a retransmission buffer tail. And the sequence number of the retransmission buffer head.

Data flow control as described in FIG. 2 is operated in a proactive manner at predetermined time intervals. Accordingly, the data flow is not controlled using the Q_State_IE REQ message requesting the buffer state information and the Q_State_IE message reporting the buffer state information as described with reference to FIG. 1. In addition, by transmitting the Q_State_IE message reporting the buffer state information at the predetermined time interval, the overhead due to the transmission of the flow control message is reduced by not transmitting the Q_State_IE REQ message, and the Q_State_IE REQ and Q_State_IE message There is also no data transfer delay.

However, when the above-described method is used, the flow is more than necessary even when there is no data received by the base station 250 or the amount of data received due to the periodic transmission of the flow control message, that is, the Q_State_IE message. Waste of resources may occur due to the transmission of control messages. Accordingly, the data flow control method according to another embodiment of reducing the system load due to message processing generated by using the method as shown in FIG. 2 and using the bandwidth of the network more efficiently is described below. This will be explained in.

3 is a diagram schematically illustrating data flow control in a wireless communication system according to a second embodiment of the present invention.

Referring to FIG. 3, when the size of data transmitted from the base station controller 310 to the base station 350, that is, the amount of data transmission exceeds the preset threshold at the base station 350, transmits a flow control message, that is, a Q_State_IE message. do.

The base station 350 receives the data transmitted from the base station controller 310, and transmits the received data to each terminal (not shown). At this time, the base station 350 has a buffer for each service flow of the terminal. The base station 350 sets a randomly selected value among the maximum buffer sizes according to the service flow provided to the terminal as the threshold value Tc.

The threshold determined at this time should be smaller than the maximum buffer size of each service flow. If the threshold value is equal to the maximum buffer size, the threshold value is set to each service because underflow occurs in the base station 350 during the time that the flow control message is transmitted from the base station 350 to the base station controller 310. It must be smaller than the maximum buffer size of the flow. Accordingly, the threshold has a fixed value in consideration of the maximum throughput of the terminals.

The base station 350 measures a transmission amount of data transmitted to the terminal using a preset threshold value and compares it with the threshold value. Thus, the base station 350 transmits the flow control message, that is, the Q_State_IE message to the base station controller 310 when the amount of data transmitted to the terminal exceeds the threshold. Thus, when the transmission time of the flow control message is determined, the transmission time of the flow control message is determined using the size of data to be transmitted to the terminal, that is, the amount of data transmission. The Q_State_IE includes the information as described above with reference to FIG. 2, and the information included in the Q_State_IE has been described in detail with reference to FIG. 2, and thus a detailed description thereof will be omitted.

Using the scheme as shown in FIG. 3, the transmission of the flow control message, that is, the Q_State_IE message, does not take into account the radio conditions of the base station 350 and the terminals. Accordingly, when the channel quality between the base station 350 and the terminals is good, the base station 350 transmits data to each terminal with a high throughput. Accordingly, the flow control message may also be transmitted frequently. Frequent transmission of flow control messages also acts as an overhead when the flow control message is processed by the base station controller 310. Accordingly, a data flow method according to another embodiment considering the transmission of a frequent flow control message generated by using the method as shown in FIG. 3 will be described below.

4 is a diagram schematically illustrating data flow control in a wireless communication system according to a third embodiment of the present invention.

Referring to FIG. 4, the threshold value is determined in advance in consideration of not only the size of data transmitted from the base station controller 310 to the base station 350, that is, the amount of data transmission but also the radio conditions of the base station 350 and the terminal. If the threshold value is exceeded, a flow control message, that is, a Q_State IE message is transmitted.

The base station 450 receives data transmitted from the base station controller 410 and transmits the received data to each terminal (not shown). In this case, as described above, the base station 450 has a buffer for each service flow of the terminal. The threshold value Tv is set by applying a function value considering the wireless situation of the base station 350 and the terminal, that is, the channel quality, to the size of the buffer according to the service flow. Accordingly, the threshold value is shown in Equation 1 below.

Tv = F (x) * SvcFlowBuffSize

In Equation 1, Tv is a threshold value, F (x) is a function value considering channel quality, and SvcFlowBuffSize is a buffer size according to a service flow. In this case, x of the F (x) is, for example, a level of modulation and coding scheme (MCS: Modulation and Coding Scheme (MCS) hereinafter) between the base station 450 and the terminal. it means. Accordingly, the F (x) value increases when the channel quality of the downlink between the base station 450 and the terminal is high and the MCS level increases, and when the MCS level decreases due to poor downlink channel quality, the F (x) value increases. Is lowered. When the threshold value is set using the F (x) value as described above, the threshold value is dynamically changed according to the wireless situation of the PSS, and the transmission time of the Q_State_IE message is variably adjusted to reduce overhead due to message processing. It is possible to do

The base station 450 measures a transmission amount of data transmitted to the terminals using the threshold value that is variably set as described above and compares the threshold value. Thus, the base station 450 transmits the flow control message, that is, the Q_State_IE message, to the base station controller 410 when the amount of data transmitted to each terminal exceeds the threshold. In this case, the transmission time of the flow control message is determined using the size of data to be transmitted to the terminals, that is, the amount of data transmission.

When the channel quality of the downlink is good, the threshold value increases when the F (x) value increases according to the MCS level, and when the channel quality of the downlink decreases, the F (x) value decreases. In this case, the threshold value is lowered.

For example, in the region 401, when the channel quality between the base station 450 and the terminals is good, the F (x) value has a high value, and thus the threshold value is set high to receive a large amount of data. Do. However, if the channel quality between the base station 450 and the terminals at 405 is lower than when receiving data in the 405 area, the value of F (x) is lowered, which reduces the amount of data transmitted to each terminal. In this case, the transmission of the flow control message is determined, and accordingly, the flow control message is transmitted to the base station controller 410. Then, the amount of data transmitted from the base station controller is controlled to perform flow control in the region 403 than the region 401 to transmit the reduced amount of data to the base station.

The Q_State_IE described above with reference to FIG. 4 also includes information as described with reference to FIG. 2, and a detailed description thereof has been described above with reference to FIG. 2, and thus a detailed description thereof will be omitted. As described above, the transmission time of the flow control message transmitted from the base station 450 to the base station controller 410 for the flow control of the data is determined by the amount of data transmission according to the downlink threshold.

5 is a flowchart schematically illustrating a method of operating a base station for data flow control in a wireless communication system according to an embodiment of the present invention.

Referring to FIG. 5, in step 501, the base station receives data to be transmitted to each terminal from the base station controller and proceeds to step 502. In step 503, the base station transmits the data received from the base station controller to each terminal, and proceeds to step 505.

In step 505, the base station determines whether the flow control message, that is, Q_State_IE, has been transmitted to the base station controller for a predetermined time. At this time, if a certain period, i.e., a predetermined time has not passed, the flow proceeds to step 501. However, if a certain time has passed since the flow control message is transmitted, the process proceeds to step 507.

In step 507, the base station transmits a flow control message to the base station controller because a predetermined time has elapsed since the flow control message was transmitted.

5 illustrates the operation of the base station for the operation of periodically transmitting a flow control message, that is, Q_State_IE, from the base station to the base station controller according to the first embodiment.

6 is a flowchart schematically illustrating a method of operating a base station for data flow control in a wireless communication system according to a second embodiment and a third embodiment of the present invention.

Referring to FIG. 6, in step 601, the base station receives data to be transmitted to each terminal from the base station controller and proceeds to step 602. In step 603, the base station transmits data received from the base station controller to each terminal. At this time, the base station measures the amount of data transmission to each terminal and proceeds to step 605.

In step 605, the base station measures the amount of data transmission to each terminal to determine whether the amount of data transmission exceeds a preset threshold. In this case, if the data transmission amount does not exceed the preset threshold as a result of the determination, step 601 is performed. However, if the data transmission amount exceeds the preset threshold as a result of the determination, step 607 is performed. In the determination of the threshold value, a randomly selected value among the maximum buffer sizes according to the service flow provided by the base station to each terminal is set as the threshold value. In addition, the threshold set at this time must be smaller than the maximum buffer size according to each service flow, in order to prevent underflow that occurs when the flow control message is transmitted.

In step 607, the base station transmits a flow control message, that is, a Q_State_IE message, to the base station controller.

In another method of determining the threshold value, the base station sets the threshold value in consideration of channel quality information of each terminal providing a service and a buffer size according to a service flow. In this case, a method of setting a threshold value in consideration of the channel quality information and the size of the buffer according to the service flow will be described in detail with reference to FIG. 7.

7 is a flowchart schematically illustrating an operation of setting a threshold value in a base station according to the third embodiment of the present invention.

Referring to FIG. 7, in step 701, the base station reports channel quality from each terminal that the base station provides a service, and proceeds to step 703. In this case, the channel quality received by the base station from the terminals may be a downlink MCS level. In this case, the MCS level received from the terminal is used to apply the channel quality, but it is also possible to apply another value for measuring the channel quality, that is, the channel state of the downlink of the base station and the terminal.

In step 703, the base station calculates a function value in consideration of the received channel quality and proceeds to step 705.

In step 705, the base station sets a threshold by applying the function value in consideration of the channel quality to a buffer size according to the service flow provided from the base station to the terminals by the function value in consideration of the received channel quality. Thus, setting the threshold value is shown in Equation (1).

A method of controlling the data flow as described above has been described with reference to the operation between the base station controller and the base station in the Wibro communication system, but the above-described data flow control is performed in a system including the base station controller and the devices having the functions of the base station. It is also possible to extend the method.

Such data flow control is performed between the base station controller and the respective medium access control (MAC) of the base station (hereinafter referred to as 'MAC'). In this case, the MAC for transmitting the flow control message by determining the transmission time of the flow control message like the base station is referred to as a high MAC, and the MAC for receiving the flow control message and controlling the data transmission amount as the lower MAC (such as the base station controller). Low MAC), it is also possible to extend and apply the data flow control scheme as described above through the relationship between the upper MAC and the lower MAC.

Meanwhile, in the detailed description of the present invention, specific embodiments have been described, but various modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined not only by the scope of the following claims, but also by the equivalents of the claims.

The present invention as described above has the advantage of performing data flow control by reducing the message used for data flow control by generating a message for data flow control in the base station of the wireless communication system and transmitting it to the base station controller, By simplifying the flow control message transmission, there is an advantage that underflow does not occur. In addition, in the wireless communication system, various message transmission methods are proposed between the base station controller and the base station, which has the advantage of efficiently transmitting the flow control message without degrading the data throughput.

Claims (14)

A method of controlling a data flow of a base station in a wireless communication system including a plurality of terminals, a base station communicating with the terminals, and a base station controller managing a plurality of base stations including the base station, When transmitting data received from the base station controller to the terminals, measuring the amount of data transmission to the terminals; Comparing the data transmission amount with a predetermined threshold value; And transmitting a flow control message to the base station controller for controlling a data flow received from the base station controller when the data transmission amount exceeds a predetermined threshold. The method of claim 1, And the data flow control is performed between the medium access control of the base station controller and the medium access control of the base station. The method of claim 1, The threshold value is set using a buffer size according to a service flow assigned to the terminals. The method of claim 4, wherein The threshold value is set to less than the maximum buffer size according to the service flow. The method of claim 1, The threshold value is set using the channel quality between the base station and the terminals and the buffer size of the base station. The method of claim 5, The setting of the threshold value includes a process of setting a function value in consideration of the channel quality by receiving and receiving the channel quality of the terminals; And setting the threshold by applying the function value to a buffer size according to the service flow of the base station. The method of claim 5, The channel quality is a data flow control method, characterized in that using the modulation and coding scheme level of the downlink received from the terminal. A data flow control system in a wireless communication system including a plurality of terminals, a base station communicating with the terminals, and a base station controller managing a plurality of base stations including the base station, In case of transmitting data received from the base station controller to the terminals, the amount of data transmission to the terminals is measured and compared with a predetermined threshold value, and received from the base station controller when the data transmission amount exceeds the threshold value. A base station transmitting a flow control message for controlling a data flow to the base station controller; And a base station controller for controlling a flow of data transmitted to the base station by receiving a flow control message from the base station. The method of claim 8, And the data flow control is performed between the medium access control of the base station controller and the medium access control of the base station. The method of claim 8, And the base station sets a threshold using a buffer size according to service flows assigned to the terminals. The method of claim 10, The threshold value is set to less than the maximum buffer size according to the service flow. The method of claim 8, And the base station sets a threshold using channel quality with the terminals and a buffer size of the base station. The method of claim 12, The threshold value is a data flow control system, characterized in that for receiving the channel quality of the terminal to set the function value in consideration of the channel quality, and applying the function value to the buffer size according to the service flow of the base station. The method of claim 12, And the channel quality uses a downlink modulation and coding scheme level received from the terminal.

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