KR20060066298A - Method and system for controlling data rate in wireless communication system using ofdma - Google Patents

Abstract

The present invention relates to a method and system for providing information on a wireless channel environment in a wireless communication system, and more particularly, to provide information on a wireless channel environment to a base station by a subscriber station in a wireless communication system using an orthogonal frequency multiple access method. It relates to a method and a system.

When the subscriber station requests the base station to change the data rate based on the information on the radio channel environment, piggybacks the ARQ feedback message without transmitting the existing signaling message, thereby saving radio channel resources. can do.

IEEE 802.16d / e, ARQ Feedback, CINR

Description

TECHNICAL AND SYSTEM FOR CONTROLLING DATA RATE IN WIRELESS COMMUNICATION SYSTEM USING OFDMA             

1 is a view schematically showing the structure of a broadband wireless access communication system using a conventional orthogonal frequency division multiplexing / orthogonal frequency division multiple access scheme;

2 is a diagram illustrating a data transmission control method between a subscriber station and a base station according to the prior art;

3 is a diagram illustrating a data transmission control method between a subscriber station 300 and a base station 302 according to an exemplary embodiment of the present invention.

The present invention relates to a method and system for providing information on a radio channel environment in a wireless communication system, and more particularly, to a method and system for providing information on a radio channel environment in a wireless communication system of an orthogonal frequency multiple access method. will be.

Typically, a typical mobile communication system is a mobile communication system using a cellular communication scheme. Such a mobile communication system uses a multiple access scheme to simultaneously communicate with multiple users. As such, the multiple access method used in the mobile communication system includes a time division multiple access (TDMA) method and a code division multiple access (CDMA) method. It is typically used. The code division multiple access system has been developed in a form capable of transmitting high-speed packet data in a system mainly providing voice communication according to the rapid development of technology.

However, in the code division multiple access scheme, it is difficult to transmit more multimedia data while reaching the usage limit of the resource code. Accordingly, there is a demand for a multiple access method that can distinguish more users and transmit more data to each divided user. A multiple access scheme that is emerging to accommodate such a request is an Orthogonal Frequency Division Multiple Access (hereinafter, referred to as "OFDMA") scheme. The orthogonal frequency division multiple access method is a method of classifying users using subchannels maintaining a plurality of orthogonalities and transmitting data through them.

As described above, a cellular system using an OFDMA scheme has been proposed to transmit high-speed data in a cellular system. The OFDMA method has been researched and tried to provide high-speed wireless Internet service at the Institute of Electrical and Electronics Engineers (IEEE) 802.16d standardization conference. The 802.16 system is a system for supporting high-speed services beyond the speed provided by the third generation (3G) mobile communication system, and as described above, in addition to the various physical layer technologies used in the third generation mobile communication system, orthogonal High-speed services are implemented using transmission methods such as Frequency Division Multiplexing, multiple input / output ("MIMO") antenna methods, and advanced antenna techniques such as smart antennas.

Currently, the 3rd generation communication system generally supports a transmission rate of about 384 Kbps in an outdoor channel environment having a relatively poor channel environment, and a transmission rate of up to 2 Mbps even in an indoor channel environment having a relatively good channel environment. Meanwhile, a wireless local area network (LAN) system and a wireless metropolitan area network (MAN) system are generally 20Mbps ~ 20Mbps. It supports a transfer rate of 50Mbps. Therefore, in the current 4th generation (4G) communication system, a new communication system is developed in the form of guaranteeing mobility and QoS in a wireless LAN system and a wireless MAN system that guarantee a relatively high transmission speed, and to be provided in the 4G communication system. Researches to support high speed services are being actively conducted.

However, the wireless MAN system is suitable for high-speed communication service support because of its wide coverage and high transmission speed, but does not consider mobility of a user, that is, a subscriber station (SS) at all. Because of the system, handover due to the fast movement of the subscriber station is not considered at all. In addition, the communication system considered in IEEE 802.16a is a system for performing a ranging operation between a subscriber station and a base station (BS). Next, a communication system structure considered in the IEEE 802.16a according to the prior art will be described with reference to FIG. 1.

1 is a diagram schematically illustrating a structure of a broadband wireless access communication system using a conventional orthogonal frequency division multiplexing / orthogonal frequency division multiple access scheme, and particularly a structure of an IEEE 802.16a communication system. .

Before explaining FIG. 1, the wireless MAN system is a broadband wireless access (BWA) communication system, which has a wider service area and supports a higher transmission speed than the wireless LAN system. In order to support a broadband transmission network to a physical channel of the wireless MAN system, an orthogonal frequency division multiple access (OFDM) scheme and an orthogonal frequency division multiple access (OFDMA) scheme are applied to a system that supports the IEEE 802.16a communication system. to be. The IEEE 802.16a communication system is a broadband wireless access communication system using an OFDM / OFDMA scheme. Since the IEEE 802.16a communication system applies the OFDM / OFDMA scheme to the wireless MAN system, high-speed data transmission is possible by transmitting a physical channel signal using a plurality of sub-carriers. In addition, the IEEE 802.16e communication system is a system that considers the mobility of a subscriber station in the IEEE 802.16a communication system.

The IEEE 802.d / e standard describes an air interface for point-to-multiplex bandwidth that provides multiple services in a broadband wireless network, and the frequency band of the application service (10-66 Ghz or 11 Ghz frequency). Band transmission method is used. Currently developed broadband wireless system uses TDD (Time Division Duplex) OFDMA transmission technology that provides portable Internet service in 2 ~ 6GHz frequency band. The system transmits high speed data of up to 30 to 50 Mbps per sector, can cover a wider range (1km / urban, 5km / rural) and provides mobility (60km / hour) compared to conventional wireless LAN systems. .

As a result, both the IEEE 802.16a communication system and the IEEE 802.16e communication system are broadband wireless access communication systems using the OFDM / OFDMA scheme. For convenience of description, the IEEE 802.16a communication system will be described as an example.

The OFDMA transmission scheme provides each user with a portion of a subcarrier (Sub carrier) available for transmitting high-speed data to multiple users to realize multiple access. In this case, more efficient high-speed data can be provided by changing the number of subcarriers allocated according to a transmission rate required by each user. OFDMA ensures orthogonality between users by eliminating intra-cell interference by assigning different subcarriers to each user. Therefore, it is possible to transmit data to a large number of users at a specific time, thereby increasing system capacity.

Referring to FIG. 1, the IEEE 802.16a communication system has a single cell structure, and a plurality of subscriber stations 110, 120 managed by the base station 100 and the base station 100, It consists of 130. Signal transmission and reception between the base station 100 and the subscriber stations (110, 120, 130) is performed using the OFDM / OFDMA method.

In a broadband wireless communication system using an OFDMA scheme, a subscriber station must acquire down-link parameters for communication with a base station and search for a serviceable branch station. First, the base station and the subscriber station must be synchronized with each other in order to perform communication with each other, which is possible by the subscriber station receives a DL-MAP (DL-MAP) message transmitted by the base station.

In addition, for acquiring downlink parameters and searching for a base station, the base station periodically includes a downlink channel profile (DownLink Channel Descriptor) (hereinafter referred to as "DCD") to all subscriber stations located in the corresponding jurisdiction. Create and send messages.

The DCD message is sent by the base station periodically to define the characteristics of the downlink physical channel. The DCD message is broadcasted by the base station at regular intervals (DCD Interval).

If the subscriber station does not receive a valid DCD message, it cannot perform a procedure for receiving a service provided by the base station. Therefore, all subscriber stations should always receive the DCD message from the base station within the relevant jurisdiction.                         

 2 is a diagram illustrating a data transmission control method between a subscriber station and a base station according to the prior art, which will be described below.

FIG. 2 is a signal flowchart illustrating a method of controlling data transmission / reception between a base station 302 and a subscriber station 300 in a broadband wireless access communication system using a conventional OFDM / OFDMA scheme.

In step 204, the base station 202 transmits data to the subscriber station 200 using an existing downlink interval usage code (DIUC). In step 206, the subscriber station 200 measures a carrier to interference noise ratio (hereinafter referred to as "CINR") to measure the environment of the wireless channel.

In step 208, the subscriber station 200 needs to change information on a wireless channel such as data rate, modulation rate, and forward error control for correcting an error for a transmitted packet based on the CINR information. Check if there is a need. If the information on the radio channel needs to be changed in step 208, the subscriber station 200 informs the base station 202 of the downlink burst profile in step 210 to downlink Burst Profile change. Burst Profile Change (hereinafter referred to as "DBPC")-Request (REQuest) message is transmitted to the base station 202.

In step 212, the base station 202 checks whether the radio channel environment for data transmission / reception with the subscriber station 200 is changed based on the received DBPC-REQ message. In step 214, the base station 202 transmits a DBPC-RSP (Response) message, which is a response message to the channel environment change requested by the subscriber station 200, to the subscriber station 200. Thereafter, the base station 202 transmits data to the subscriber station 200 by DIUC according to the changed channel environment.

As shown in FIG. 2, in the conventional 802.16d / e broadband wireless communication system, the subscriber station 200 measures information such as CINR, and whenever a change in the wireless channel environment is recognized, a DBPC-REQ message. By transmitting the to the base station 202, a lot of resources are wasted by allocating a separate radio channel. In addition, whenever the subscriber station 200 receives the requested DBPC-REQ message, the load is increased on the base station 202 by transmitting the DBPC-RSP message, which is a response message thereto.

Accordingly, an object of the present invention is to provide a method and system for controlling a data rate in a broadband wireless communication system.

Another object of the present invention is to provide a method and system for transmitting information on data rate control based on a wireless channel environment measured by a subscriber station to a base station in a broadband wireless communication system.

According to an aspect of the present invention, there is provided a method of controlling a data rate in a wireless communication system including a subscriber station and an active base station to which the subscriber station is currently being serviced. Measuring the radio channel environment with the base station; if the radio channel environment is changed, piggybacking the data transmission change request information in an automatic repeat request (ARQ) feedback message; and transmitting the received ARQ. And checking whether there is change request information in the radio channel environment included in the information element of the feedback message, and determining whether to transmit data based on the presence or absence of a change in data transmission.

The system of the present invention for achieving the above object, in a system for controlling the data rate in the subscriber station and the base station that the subscriber terminal is currently being serviced, measuring radio channel information with the base station, A subscriber station for piggybacking and transmitting a desired data rate change request and the radio channel information to the base station in an ARQ feedback message when radio channel information is changed; and in the ARQ feedback message transmitted by the subscriber station. And the base station inspecting whether to determine a change in a transmission rate of data to be transmitted to the subscriber station based on the data rate and the radio channel information.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

In general, when a subscriber station receives data from a base station, the subscriber station transmits an automatic retransmission request (hereinafter referred to as "ARQ") feedback message in response. In an embodiment of the present invention, the data transmission rate between the base station 302 and the subscriber station 300 is controlled using the ARQ feedback message. The configuration of the ARQ feedback message will be described later with reference to Table 1 below.

3 is a diagram illustrating a data transmission control method between a subscriber station 300 and a base station 302 according to an exemplary embodiment of the present invention, which will be described below.

The IEEE 802.16 d / e standardization group generally uses the ARQ scheme to preserve packet loss in the Medium Access Control (MAC) layer for data transmission. In the present invention, the ARQ feedback information is used. By transmitting the data burst profile (Data Burst Profile) required by the subscriber station 300 to reflect the instantaneous radio channel environment. Here, the radio channel environment refers to information such as a modulation scheme, a data rate, and an FEC scheme for a radio channel between the base station and the subscriber station.

First, in step 304, the base station 302 transmits data to the subscriber station 300 using an existing downlink interval usage code (DIUC). In step 306, the subscriber station 300 measures a carrier to interference noise ratio (hereinafter referred to as "CINR") to measure the environment of the radio channel between the base station 302.                     

If the wireless channel environment is changed in step 308, the subscriber station 300 proceeds to step 310 and adds the measured CINR value and DIUC to the ARQ feedback message to be transmitted to the base station 302.

In step 312, the subscriber station 300 transmits the ARQ feedback message added with the CINR and the DIUC to the base station 302. In step 314, the base station 302 transmits the CINR value and the DIUC of the received ARQ feedback message. Check the value.

In step 316, the base station 302 determines whether to change the wireless channel environment with the subscriber station 300 based on the received ARQ feedback message. In step 316, if the base station 302 does not change the radio channel environment, the subscriber station 300 transmits data of the next frame using a DIUC value before requesting a new change. On the other hand, if the base station 302 wants to change the radio channel environment in step 316, the base station 302 inputs the DIUC value requested by the subscriber station 300 in the DIUC field of the ARQ feedback message and transmits it. Thereafter, in step 320, the base station 302 transmits data according to the changed DIUC value from the next frame.

Although not shown in FIG. 3, the base station 302 includes whether to allocate the DIUC value requested by the subscriber station 300 in a DL-MAP message that is broadcast to the subscriber station 300 periodically. It is delivered through an information element (hereinafter referred to as "IE").

In the following Table 1, the subscriber station 300 measures the CINR value and transmits it to the base station 302 or the information element of the ARQ feedback message transmitted by the base station 302 to the subscriber station 300 ( IE).

Syntax Size ARQ_Feedback_Message Format () { DIUC 4bit ARQ_Feedback_Payload variable }

As shown in Table 1, the ARQ feedback message includes a plurality of IEs, that is, a DIUC field indicating a DIUC value requested by the subscriber station 300, and an ARQ_Feedback_Payload in which data of an ARQ feedback message is stored.

In the DIUC field, according to an embodiment of the present invention, the subscriber station 300 measures a CINR value and sets a DIUC value corresponding to the value.

That is, in the present invention, as shown in Table 1, a method of piggybacking and transmitting information on downlink channel state to an ARQ feedback message is used.

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 determined not only by the scope of the following claims, but also by the equivalents of the claims.

 As described above, the present invention does not transmit a separate signaling message by checking the reception state of the data received by the subscriber station, improves the traffic transmission efficiency by using the ARQ feedback message, and quickly transmits channel information to the base station. It can improve performance by preventing data loss caused by not following channel changes.

Claims (7)

A method of controlling data rate in a wireless communication system comprising a subscriber station and an active base station to which the subscriber station is currently receiving service, Measuring, by the subscriber station, a wireless channel environment with the base station; If the wireless channel environment is changed, piggybacking the data transmission change request information in an ARQ feedback message; Checking, by the base station, whether there is change request information of the radio channel environment included in the information element of the received ARQ feedback message; And including change information in an ARQ feedback message transmitted on the downlink based on the presence or absence of a data transmission change. 10. A method of controlling a data rate in an orthogonal frequency division multiple access wireless communication system. The method of claim 1, wherein the wireless channel information includes a carrier-to-noise interference ratio (CINR) measured by the subscriber station. 4. The orthogonal frequency division multiplexing according to claim 1, wherein the data transmission change request information piggybacked on an information element of the ARQ feedback message includes the carrier-to-noise interference ratio and a downlink interval indication code (DIUC). A transmission rate control method in an access wireless communication system. The method of claim 1, wherein the ARQ message sent on the downlink, And a modified downlink interval indication code (DIUC) value of data to be transmitted by the base station on the downlink. A system for controlling a data rate at a subscriber station and a base station to which the subscriber station is currently receiving service, The subscriber station measuring radio channel information with the base station and piggybacking and transmitting a desired data rate change request and the radio channel information to the base station in an ARQ feedback message when the radio channel information is changed; , Orthogonal frequency division multiple access, comprising: determining whether to determine a change in a transmission rate of data to be transmitted to the subscriber station based on data rate and radio channel information in the ARQ feedback message transmitted by the subscriber station; Rate control system in wireless communication system of the scheme. 6. The rate control system of claim 5, wherein the wireless channel environment information measured by the subscriber station includes a carrier-to-noise interference ratio (CINR). The method of claim 5, wherein the base station, A rate control system in an orthogonal frequency division multiple access wireless communication system characterized by including a downlink interval indication code (DIUC) value according to a change in a wireless channel environment in an ARQ feedback message transmitted on a downlink. .

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