KR101250930B1 - Apparatus and method for transmitting control information in broadband wireless access communication system - Google Patents

Abstract

The present invention relates to an apparatus and method for transmitting control information in a broadband wireless access communication system. According to an aspect of the present invention, there is provided a transmission apparatus comprising: an encoder for generating code symbols by encoding control information to be transmitted at a predetermined code rate, a modulator for generating modulation symbols by modulating code symbols from the encoder in a predetermined modulation scheme, and terminals. And a repeater for determining the number of repetitions of the control information using the channel information fed back from the repetition unit, and a repeater for repeatedly outputting the modulation symbols from the modulator according to the determined number of repetitions.

Frame, MAP, Repeat Count, Coding, CQI

Description

Apparatus and method for transmitting control information in a broadband wireless access communication system {APPARATUS AND METHOD FOR TRANSMITTING CONTROL INFORMATION IN BROADBAND WIRELESS ACCESS COMMUNICATION SYSTEM}

1 is a view showing a frame structure in a broadband wireless access communication system according to an embodiment of the present invention.

2 illustrates an apparatus for transmitting a MAP in a broadband wireless access communication system in accordance with an embodiment of the present invention.

3 is a diagram illustrating a procedure for transmitting a MAP in a broadband wireless access communication system according to an embodiment of the present invention.

The present invention relates to an apparatus and method for transmitting control information in a broadband wireless access communication system, and more particularly to transmitting map (MAP) information in an orthogonal frequency division multiple access (OFDMA) communication system. An apparatus and method are provided.

The OFDMA technology is a multi-access wireless communication technique using multiple carriers, and has emerged as a core technology of the next generation communication system with higher frequency efficiency and transmission rate than a conventional communication system using a single carrier.

When using the OFDMA technique, the receiver needs MAP information located in the first half of the OFDMA frame in order to identify an allocation position (or resource) of a data burst carrying actual traffic. In addition, the position of this MAP is confirmed by 24-bit information called a frame control header (FCH). That is, the receiver first decodes the FCH to find out the location of the MAP, decodes the MAP of the corresponding location, and then extracts the data burst.

Table 1 below shows field configurations of an FCH message used in an IEEE 802.16 based system.

Syntax Size Notes Frame_Control_Header () { Used Subchannel bitmap 6bits Bit0: Group0 (subch 0 to 5)
Bit1: Group1 (subch 6-9)
Bit0: Group0 (subch 10 to 15)
Bit1: Group1 (subch 16 to 19)
Bit0: Group0 (subch 20-25)
Bit1: Group1 (subch 26 to 29) Ranging_Change_Indication 1 bit Repetition_Coding_Indication 2 bits Repetition coding on DL-MAP
00-No Repetition
01-Repetition coding of 2
10-Repetition coding of 4
11-Repetition coding of 6 Coding_Indication 3bits 0b000-CC
0b001-BTC
0b010-CTC
0b011-ZT CC
0b100 to 0b111-Reserved DL_Map_Length 8bits Number of subchannels for DL_MAP DL_Map_length 4bits Shall be set to zero }

As shown in Table 1, the FCH message includes usable subchannel bitmap information, ranging_change_indication information, repetition_coding_indication information of the DL-MAP, and DL-. Encoding information (coding_indication) of the MAP and DL-MAP length (DL-MAP length) information. As such, the FCH message then contains the information needed to decode the MAP information.

In general, in the downlink frame in the IEEE 802.16 based system, the first preamble signal for the terminal synchronization is located, followed by the DL / UL MAP including resource allocation information (data burst position, modulation level, etc.) . According to the prior art, since the DL / UL MAP is information that all the terminals need to receive, that is, all the terminals at the cell boundary must also be received, the most robust modulation scheme (QPSK, R = 1 / 2, Repetition = 6). That is, according to the prior art, the repetition coding indication field in the FCH message is always set to "11".

In the IEEE 802.16 based system, as shown in FIG. 1, the minimum burst can be configured by one subchannel and one symbol, thereby maximizing the degree of freedom of frame configuration. However, as the degree of freedom increases, the number of control information to be transmitted also increases, and when data of several users are mixed in a frame, information to inform the user through DL-MAP and UL-MAP acts as a significant overhead. Furthermore, if such MAP information is always coded with the maximum number of repetitions (eg, six times), the size is a significant burden. In the worst case, the resource that can be allocated to the actual user in the frame is small, the throughput of the system is reduced. For example, when users are all distributed in a good channel condition, it is inefficient to transmit MAP information in the most robust manner (QPSK, R = / 2, Repetition = 6).

Accordingly, an object of the present invention is to provide an apparatus and method for reducing the size of control information in a broadband wireless access communication system.

Another object of the present invention is to provide an apparatus and method for adaptively adjusting the coding degree of a map including control information in a broadband wireless access communication system.

Another object of the present invention is to provide an apparatus and method for adaptively adjusting the number of repetitive coding of a map including control information using information fed back from a terminal in a broadband wireless access communication system.

According to an aspect of the present invention for achieving the above object, an apparatus for transmitting control information in a broadband wireless access communication system, comprising: an encoder for generating code symbols by encoding control information to be transmitted at a predetermined code rate; A modulator for generating modulation symbols by modulating code symbols from an encoder with a predetermined modulation scheme, a determiner for determining the number of repetitions of the control information using channel information fed back from terminals, and modulating the modulation symbols from the modulator. It characterized in that it comprises a repeater for repeatedly outputting according to the determined number of repetitions.

According to another aspect of the present invention, a method for transmitting control information in a broadband wireless access communication system, the method for determining the number of repetition of the control information using the channel information fed back from the terminal, and the control information to be transmitted Generating code symbols by encoding at a predetermined code rate, generating modulated symbols by modulating the code symbols by a predetermined modulation method, and repeating the modulated symbols according to the determined repetition number of times; It is done.

Hereinafter, the operation principle of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, detailed descriptions of well-known functions or configurations will be omitted when it is determined that the detailed description of the present invention may unnecessarily obscure the subject matter of the present invention. The following terms are defined in consideration of the functions of the present invention, and may be changed according to the intentions or customs of the user, the operator, and the like. Therefore, the definition should be based on the contents throughout this specification.

Hereinafter, a method for reducing the size of a map including control information in a broadband wireless access communication system will be described.

1 illustrates a frame structure in an OFDMA-based broadband wireless access communication system according to an embodiment of the present invention.

As shown, in the OFDMA standard, data transmission units in a conceptual frequency and time domain are represented by subchannels and symbols, respectively. The minimum data unit that can be sent to one user (terminal) consists of one subchannel and one symbol. The vertical axis represents the index of the subchannel, which is a frequency resource allocation unit, and one frame includes L + 1 subchannels from the sth to the (s + L) th. The horizontal axis represents the index of the OFDM symbol which is a time resource allocation unit, and one frame includes downlink OFDM symbols from the kth to (k + M) th and (k + M + 1) th to (k +). Uplink OFDM symbols up to M + N). A TTG (Transmit / receive Transition Gap), which is a guard region, exists between the downlink and the uplink.

Preamble, Frame Control Header (FCH), DL-MAP, UL-MAP, Downlink Burst (DL-Burst) are configured in the downlink section in the frame, and the ranging subchannel in the uplink section. A CQI channel, an ARQ channel (ACK), and an uplink burst (UL-Burst) are configured. The preamble is used to provide time and frequency synchronization and cell information to users, the FCH contains information for decoding the MAP, and the DL-MAP is the downlink bursts transmitted from the base station. It contains information that indicates whether or not it is located in the frame. Meanwhile, the UL-MAP includes information on uplink bursts transmitted by users (terminals).

The present invention is characterized by flexibly adjusting the area (or size) occupied by the DL / UL MAP as shown.

2 illustrates an apparatus for transmitting a MAP in a broadband wireless access communication system according to an embodiment of the present invention.

As shown, the MAP transmission apparatus according to the present invention, MAP information generator 200, encoder 202, modulator 204, repeater 206, subcarrier mapper 208, OFDM modulator 210, RF The processor 212, the scheduler 214, and the iteration count determiner 216 is configured.

Referring to FIG. 2, first, the scheduler 214 performs resource scheduling using channel information (CQI information) for each terminal fed back through a feedback channel (eg, CQI channel), and performs the scheduling result (resource allocation information, etc.). ) Is provided to the MAP information generator 200. In addition, the scheduler 214 controls the modulation level and subcarrier mapping (or resource mapping) of the transmission burst according to the scheduling result. Here, the scheduling algorithm includes a proportional fairness algorithm, a round robin algorithm, and the like.

In addition, according to the present invention, the scheduler 214 determines whether a broadcast message exists in the MAP information to be transmitted, and indicates whether the broadcast message exists or not and the channel information of the channel information of the users who will provide the service in this frame. The channel information having a low value is provided to the repetition number determiner 216.

The repetition number determiner 216 determines whether a broadcast message exists based on the information provided from the scheduler 214. If the broadcast message is present, the number of repetitions of the MAP information is determined as the maximum value (for example, six times). If the broadcast message does not exist, the repetition frequency of the MAP information is the channel having the lowest value. The information is determined based on the information provided to the repeater 206. In addition, although not shown, the number of repetitions determined in this manner is set in the repetition coding instruction field of the FCH message and broadcasted.

For example, the number of repetitions of MAP information according to the CQI information may be determined as shown in Table 2 below.

CQI CINR (dB) Repetition Coding Indication 0 CINR≤3 Repetition 6 One -1 <CINR≤0 Repetition 4 2 0 <CINR≤2 Repetition 2 3 2 <CINR≤4 No repetition

In Table 2, the CINR level may be changed according to an optimization situation as an example. That is, the repeat count determiner 216 determines the repeat count based on the memory table shown in Table 2.

The MAP information generator 200 generates MAP information according to the scheduling result received from the scheduler 214. The MAP information may include location information and a modulation level (MCS level) information about the burst. The encoder 202 encodes the information bit stream from the MAP information generator 200 to generate code symbols. For example, the encoder 202 uses an encoder using a convolutional code (CC), an encoder using a block turbo code (BTC), and a convolutional turbo code (CTC). And an encoder using a zero tailing convolutional code (ZT-CC). In the embodiment of the present invention, it is assumed that a convolutional turbo encoder is used and the code rate is 1/2.

The modulator 204 modulates the code symbols from the encoder 202 in a predetermined modulation scheme to generate modulation symbols. Here, it is assumed that the modulator 408 uses a Quadrature Phase Shift Keying (QPSK) modulation scheme. The iterator 206 repeatedly outputs the modulation symbols from the modulator 204 according to the number of iterations from the iteration determiner 216. Here, the repetition frequency may be the largest value or a value determined by the feedback channel information depending on the presence of a broadcast message.

The subcarrier mapper 208 maps the modulation symbols output from the repeater 206 to subcarriers corresponding to a predetermined time-frequency domain. The OFDM modulator 210 performs inverse fast fourier transform (IFFT) operation on subcarrier mapped data from the subcarrier mapper 208 and adds a guard interval (eg, Cyclic Prefix) to the IFFT calculated data (sample data). To print. A radio frequency (RF) processor 212 converts sample data from the OFDM modulator 210 into an analog signal, converts the analog signal into an RF signal that can be actually transmitted, and transmits the same through an antenna.

3 illustrates a procedure for transmitting a MAP in a broadband wireless access communication system according to an embodiment of the present invention.

Referring to FIG. 3, the base station first receives channel information (CQI information) from users (terminals) in step 301. In step 303, the base station performs resource scheduling using the received channel information to select users to be served in this frame.

After selecting the users to service, the base station checks whether there is a broadcasting message in the MAP information in step 305. Here, the broadcasting message is a message that must be received by all terminals in the cell. For example, the broadcasting message may be a ranging channel allocation message or a feedback channel (CQI channel, ARQ channel, etc.) allocation message.

If the MAP information does not include a broadcast message, the base station proceeds to step 307 to select channel information having the smallest value among channel information of the selected users, and based on the selected channel information. After determining the number of repetitions of the information, go to step 311. If the MAP information includes a broadcasting message, the base station proceeds to step 309 and determines the number of repetitions of the MAP information as the largest value (for example, six times) and then proceeds to step 311.

The base station modulates MAP information generated with the scheduling result in a predetermined manner in step 311. For example, the MAP information is encoded by a convolutional code (CTC) having a code rate of 1/2, the coded data is modulated by a QPSK scheme, and the modulated data is repeated according to the determined number of repetitions.

In step 313, the base station generates a downlink frame including the processed MAP information and transmits the generated downlink frame to the terminal.

While the present invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiments, but is capable of various modifications within the scope of the 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 those equivalent to the scope of the claims.

As described above, the present invention determines the modulation method of the control information (MAP) on the basis of the smallest value of the channel information of the terminals to provide a service, the existing technology to use the most robust modulation method fixed Compared with this, there is an advantage that can improve the system throughput. In other words, the actual traffic transmission efficiency can be increased by reducing the size occupied by the limited intra frame control information.

Claims (17)

An apparatus for transmitting control information in a broadband wireless access communication system, An encoder which includes position information on the burst and information on modulation level, and generates code symbols by encoding control information which should be received by a plurality of terminals; A modulator for modulating code symbols from the coder to generate modulation symbols; A determiner for determining a repetition number of the control information by using channel information fed back from the plurality of terminals; And an iterator for repeatedly outputting modulation symbols from the modulator according to the determined number of repetitions. The method of claim 1, The control information device characterized in that the map (MAP) information. The method of claim 1, The encoder is an encoder using a convolutional code (CC), an encoder using a block turbo code (BTC), an encoder using a convolutional turbo code (CTC), a zero tailing convolutional code Device characterized in that one of the encoder using (ZT-CC: Zero Tailing Convolutional Code). The method of claim 1, And the code rate of the encoder is 1/2. The method of claim 1, And the determiner determines the repetition frequency based on the smallest value among channel information of users who provide a service. The method of claim 1, And the determiner comprises a memory table that stores a mapping relationship between channel information and the number of repetitions. The method of claim 1, The determiner, if the control information includes a broadcasting message, characterized in that for determining the repetition frequency as the largest value. The method of claim 1, An OFDM modulator for modulating orthogonal frequency division multiplexing (OFDM) modulation symbols from the repeater; And an RF processor for transmitting the OFDM modulated data by RF processing. The method of claim 1, And the determined repetition frequency information is set and broadcast in a frame control header (FCH) message. A method for transmitting control information in a broadband wireless access communication system, Determining a repetition frequency of the control information by using channel information fed back from a plurality of terminals, and the control information includes position information and a modulation level information about a burst, and is information to be received by the plurality of terminals. , Generating code symbols by encoding the control information; Generating modulation symbols by modulating the code symbols; Repeating the modulation symbols according to the determined number of repetitions. The method of claim 10, The control information is characterized in that the map (MAP) information. The method of claim 10, The coding scheme is one of a convolutional code (CC), a block turbo code (BTC), a convolutional turbo code (CTC), and a zero tailing convolutional code (ZT CC). Method characterized in that. The method of claim 10, And the control information is encoded at a code rate of 1/2. The method of claim 10, wherein the determining process, Determining whether a broadcasting message is included in the control information; When the broadcasting message is not included, selecting channel information having the smallest value among channel information of users to provide a service; And determining the repetition frequency based on the selected channel information. The method of claim 14, And if the broadcasting message is included, determining the repetition number as the largest value. The method of claim 10, Orthogonal frequency division multiplexing (OFDM) modulation of the repeated modulation symbols; And transmitting the OFDM-modulated data by RF (Radio Frequency) processing. The method of claim 10, And broadcasting a frame control header (FCH) message including the determined number of repetition information.

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