KR100705500B1 - Methods for transmitting and receiving of an adaptive Modulation and Coding Scheme information for a burst mode OFDM/TDD system and apparatuses thereof - Google Patents

Abstract

The present invention relates to a method and apparatus for transmitting and receiving information on a modulation and coding scheme (MCS) for a subchannel group in a burst mode orthogonal frequency division multiplexing (OFDM) / time division multiplexing (TDD) mobile communication system.

In the present invention, a method for transmitting MCS level information includes receiving channel information corresponding to a subchannel group corresponding to a burst; Determining MCS information corresponding to the channel information and mapping, by an MCS level coding unit, the MCS information for the subchannel group to one of a plurality of preset codes; Generating a WH code for a subchannel in the subchannel group corresponding to the mapped MCS level code by a Walsh-Adamar (WH) code generating unit in the MCS level coding unit; Processing previously known pattern data of a sub-channel group by using the generated WH code; And e) mapping the processed pattern data signal to a subchannel belonging to the subchannel group, and then including the preamble symbol in one preamble symbol and transmitting the same.

Therefore, separate control channels can be saved by using one preamble to convey information on the adaptive modulation / code scheme.

Modulation / Code, MCS, Adaptive Modulation, Preamble, OFDM, TDD

Description

Methods and transmitting and receiving information on an adaptive modulation and coding scheme of a burst mode OMD / TD system, and an adaptive modulation and coding scheme for information for a burst mode OFDM / TDD system and apparatuses

1 is a block diagram of a burst mode OFDM / TDD mobile communication system according to an embodiment of the present invention.

2 is a diagram illustrating a burst mode frame structure according to an embodiment of the present invention.

3 is a diagram illustrating a structure in a frequency domain and a time domain for a preamble according to an embodiment of the present invention.

4 is a diagram illustrating a mapping relationship between codes and MCS levels in a transmitter according to an embodiment of the present invention.

FIG. 5 is a diagram illustrating a process of generating preamble data using a corresponding MCS level code for a subchannel group 0 in a transmitter according to an embodiment of the present invention.

6 is a diagram illustrating a process of obtaining a MCS level of a corresponding subchannel group by using preamble data for subchannel 0 in a receiver according to an embodiment of the present invention.

7 is a flowchart illustrating a method of transmitting and receiving MCS information according to an embodiment of the present invention.

The present invention relates to a method for transmitting and receiving information on an adaptive modulation and coding scheme of a burst mode OFDM / TDD system. More specifically, the burst mode orthogonal frequency division multiplexing (OFDM) / The present invention relates to a method and apparatus for transmitting and receiving information on a modulation and coding scheme (MCS) for a subchannel group in a time division duplex (TDD) mobile communication system.

In general, in a burst mode OFDM / TDD communication system, when data is transmitted using an adaptive modulation method, the transmitter may determine to the receiver what modulation and coding scheme (MCS) is used for each subchannel group in the OFDM symbol. Notify via control channel.

On the other hand, as a prior art, Korean Patent Application No. 2001-33186 (filed date: June 13, 2001) discloses an invention named "Orthogonal Frequency Division Multiple Modulation Demodulation Circuit".

Specifically, the foregoing invention divides a plurality of subcarriers into a plurality of groups in an OFDM system that communicates using a plurality of subcarriers, transmits and receives a plurality of communication channels, and divides the subcarrier groups into a plurality of communication channels, respectively. By assigning to, it is possible to multiplex signals having different bit rates and QoS and transmit signals through one OFDM line.

On the other hand, as a prior art, in January 2003 IEICE Trans. Comm. E86-B, Volume 1, pages 257 to 265, published a paper entitled "Proposal of grouping adaptive modulation method for burst mode OFDM transmission system."

Specifically, the preceding paper uses frame presynchronization, frequency synchronization, channel response, and noise power by using two preamble symbols in order to reduce AMI (Adaptive Modulation Information) bits required for the demodulation process of the receiver. The AMI bit information can be transmitted.

However, according to the related art, in order to inform the receiver of information on the modulation / code scheme applied to each subchannel group, one preamble subchannel has one pilot subchannel in two preamble symbols, and the remaining subchannels except for the pilot subchannel. Maps Walsh-hadamard (WH) codes to each MCS level and transmits them in a fixed Quadrature Phase Shift Keying (QPSK) modulation scheme, which causes a large amount of overhead in the system. There is this.

In order to solve the above problem, the present invention provides a single preamble without using a separate control channel for transmitting adaptive modulation / code information (MCS) of each subchannel group in a burst mode OFDM / TDD communication system. Provided are a method and apparatus for transmitting and receiving information on an adaptive modulation and coding scheme capable of transmitting information on modulation / code schemes of all subchannel groups by using the same.

As a means for achieving the above object, an information transmission method for an adaptive modulation and coding scheme according to the present invention comprises the steps of: a) receiving channel information corresponding to a subchannel group corresponding to a burst; b) determining, by the MCS level coding unit, the MCS information corresponding to the channel information and mapping the MCS information for the subchannel group with one of a plurality of preset codes; c) a Walsh-Hadamard (WH) code generator in the MCS level coding section generating a WH code for a subchannel in the subchannel group corresponding to the mapped MCS level code; d) processing previously known pattern data (Known pattern) of the subchannel group using the generated WH code; And e) mapping the processed pattern data signal to a subchannel belonging to the subchannel group, and then including the preamble symbol in one preamble symbol and transmitting the same.

In addition, the method for receiving information about the adaptive modulation and coeld scheme according to the present invention comprises the steps of: a) receiving demodulation data output from one preamble symbol including MCS level information for a subchannel group; b) an MCS level decoding unit multiplying the corresponding code with each of the demodulation data among a set of Walsh-Hadamard (WH) codes; c) performing maximum ratio combining (MRC) on each of the products of the corresponding WH code and the demodulation data; And d) selecting a WH code that outputs the maximum MRC among the MRCs, and selecting an MCS level code corresponding to the selected WH code as MCS level information for the subchannel group.

Hereinafter, an information transmission and reception method and apparatus for an adaptive modulation and coding scheme of a burst mode OFDM / TDD system according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

An embodiment of the present invention is a method of delivering Modulation and Coding Scheme (MCS) level information for each subchannel group using a preamble signal instead of using a fixed control channel for feedback information related to Adaptive Modulation and Coding (AMC) As an example, a method and apparatus for transmitting and receiving MCS level information of a subchannel group using one preamble instead of using two preambles will be described.

1 is a block diagram of a burst mode OFDM / TDD mobile communication system according to an embodiment of the present invention.

As shown in FIG. 1, the OFDM / TDD mobile communication system according to the present invention may be largely divided into a transmitter 100 and a receiver 200, wherein the transmitter 100 and the receiver 200 are connected to a transmitter of a base station. In the case of the receiver, the transmitter 100 transmits the user's transmission data in a burst frame to the user terminal, and the receiver 200 detects data transmitted from the user terminal. In this case, since the structure of the user terminal may be applied in the same manner as the structure of the transmitter and receiver of the base station, reference will be made to the structure of the base station transmitter and receiver.

Specifically, the transmitter 100 includes a user data selector 101, a serial / parallel converter (S / P) 102, an adaptive modulator 103, an IFFT unit 104, and a guard interval insertion unit 105. ), Parallel / serial converter (P / S: 106), multiplexer (MUX: 107), digital / analog converter (DAC: 108), carrier modulator 109, MCS level coding unit 150, preamble The inserter 111 and the packet scheduler 112 are included.

In addition, the receiver 200 includes a carrier demodulator 201, an analog / digital converter (ADC: 202), a demultiplexer (DEMUX: 203), a serial / parallel converter (S / P: 204), and a protection interval. Remover 205, FFT 206, Adaptive Demodulator 207, Parallel / Serial Transformation (P / S) 208, Channel Estimator 209, Channel Compensator 210 and MCS Level Decoding The unit 250 is included.

First, a method of generating and transmitting a burst frame by the transmitter 100 will be described below.

The channel information for each subchannel group is transmitted from the channel estimator 209 of the receiver 200 to the packet scheduler 112 and the MCS level coding unit 150.

When the packet scheduler 112 selects a user to use the current burst frame by using channel information of each subchannel group, the adaptive modulator 103 applies a modulation / code scheme (MCS) to be applied to each subchannel group. Adaptive modulation of the data is performed according to each mode by using.

The modulated data is multiplexed with the preamble of the burst frame via the IFFT unit 104, the guard interval insertion unit 105, and the P / S converter 106. That is, the modulated data is converted into an RF signal by a baseband signal through a fast inverse fast Fourier transform unit (IFFT) 104, and a guard period is inserted into the baseband signal by the guard interval inserting unit 105. Thereafter, the signal in which the protection interval is inserted through the protection interval insertion unit 105 is converted into a serial signal through the P / S conversion unit 106, and then the preamble insertion unit (the multiplexing unit 107) is used. Multiplexed with the preamble inserted at 111;

In addition, the MCS level of each subchannel group is determined by the MCS level coding unit 150 using the channel information of each subchannel group, and at this time, the WH code according to the corresponding channel information is selected. After the corresponding code is selected, the WH code is modulated using a modulation scheme for each subchannel group.

The given pilot pattern and the modulated WH code are then multiplexed with the data to be transmitted, so that a burst frame is generated.

Accordingly, the burst frame is transmitted through an antenna via the DAC 108 and the carrier modulator 109.

Meanwhile, a method of receiving the burst frame by the receiver 200 will be described below.

For example, the RF signal received from the user terminal may include a carrier demodulator 201, an analog / digital converter (ADC) 202, a demultiplexer 203, and a serial / parallel converter (S / P: 204). The guard period is converted into a baseband signal, and the guard interval inserted into the baseband signal is removed through the guard interval remover 220.

Thereafter, the signal from which the guard interval is removed is Fourier transformed through a fast Fourier transform unit (FFT) 206, and then demodulation for each subchannel group is performed through the adaptive demodulator 207.

In addition, after the channel is estimated through the channel estimating unit 209 using the pilot signal passed through the FFT unit 206, the packet scheduler 112 of the above-described transmitting unit 100 is transmitted to each user of the corresponding unit. Channel status for the channel group is reported.

Subsequently, after the SNR of the channel is measured using the pilot signal of each subchannel group, the demodulation method of the WH code of the corresponding subchannel group is determined using the measured value.

That is, after the channel compensator 210 compensates the modulated WH code symbol by using the channel information estimated by the channel estimator 209, the MCS level decoding unit 250 performs MRC (Maximal). A MCS level value corresponding to the largest value of the WH code values is found by using a ratio combining method. In other words, the MCS level value corresponding to the maximum WH code value becomes MCS level information to be obtained according to an embodiment of the present invention.

The transmission apparatus shown in FIG. 1 will be described in detail below with respect to the MCS coding unit and the MCS decoding unit used in the reception apparatus.

2 is a diagram illustrating a burst mode frame structure according to an embodiment of the present invention.

Referring to FIG. 2, a burst mode frame, that is, a burst frame according to an embodiment of the present invention includes one OFDM preamble symbol and L data symbols. In an OFDM system, the preamble consists of a guard interval (GI) and a preamble OFDM symbol, and the L data symbols each consist of a GI and a data OFDM symbol.

Therefore, as the packet scheduler of FIG. 1 described above broadcasts user information on the corresponding burst currently scheduled through broadcast information, users may receive data in the burst mode.

3 is a diagram illustrating a structure in a frequency domain and a time domain for a preamble according to an embodiment of the present invention.

Referring to FIG. 3, in an embodiment of the present invention, a preamble OFDM symbol is composed of N subchannels, and each of the eight subchannels forms one subchannel group. In addition, each subchannel group may be composed of ㅁ X ₀ , ㅁ X ₁ , ㅁ X ₂ and ㅁ X ₃ , which are different known pattern data according to one pilot and three subchannel positions.

Here, the length T _S of the preamble OFDM symbol has a structure of two 1/2 OFDM symbols each having a length T _S / 2, and at this time, the 1/2 OFDM symbol may be copied.

As a result, only one preamble OFDM symbol is used in the information transmission and reception method for the adaptive modulation and coding scheme of the burst mode OFDM / TDD system according to an embodiment of the present invention. Therefore, overhead can be reduced compared to using two preamble OFDM symbols.

4 is a diagram illustrating a mapping relationship between codes and MCS levels in a transmitter according to an exemplary embodiment of the present invention.

Referring to FIG. 4, information (MCS) for the adaptive modulation and coding scheme of a burst mode OFDM / TDD system according to an embodiment of the present invention may be, for example, eight MCS levels, three types of modulation schemes, and three. It has a kind of code rate. That is, corresponding to eight codes of 000, 001, 010, 011, 100, 101, 110, and 111, NULL, QPSK 1/2, QPSK 3/4, 16QAM 1/3, 16QAM 1/2, 16QAM 3 / It has MCS levels of 4, 64QAM 1/2 and 64QAM 3/4, with code rates of QPSK, 16QAM and 64QAM.

5 is a diagram illustrating a process of generating preamble data using a corresponding MCS level code for a subchannel group 0 in a transmitter according to an embodiment of the present invention.

The MCS level coding unit 150 shown in FIG. 5 includes an MCS level information determination unit 140, an MCS level code table 151, and a WH code generation unit 152.

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Referring to FIG. 5, after receiving channel information about subchannel group 0 from a preamble OFDM symbol according to an embodiment of the present invention, a user selects one of eight codes 151. That is, the MCS level coding unit 150 searches for and maps a code corresponding to the MCS level determined by the MCS information determination unit 140 for subchannel group 0 from the MCS level code table 151. At this time, the Walsh-Hadamard (WH) code generation unit 152 determines the modulation bits, [b ₀ b ₁ ] for the sub-channels in the sub-channel group, according to the code type using the input code.

For example, if QPSK 1/2 is applied to a corresponding subchannel group, X ₀ with a value of [b ₀ b ₁ ] is A {-X ₀ -X ₀ X ₀ } value that maps to each subchannel. In this case, b _{0 and} b ₁ are 2-bit inputs for modulating QPSK on one subchannel.

Accordingly, the known pattern data signal is input to each subchannel constituting the subchannel group 0 to transmit one preamble OFDM symbol. That is, modulated signals are input to the three subchannels constituting the subchannel group 0 and transferred to the receiver of the user. Here, reference numeral 160 denotes a preamble OFDM symbol transmitted to the receiver of the user.

In the exemplary embodiment of the present invention, a general shape of the WH code is used, but it is apparent to those skilled in the art that various codes can be used due to the characteristics of the WH code.

6 is a diagram illustrating a process of obtaining a MCS level of a corresponding subchannel group by using preamble data for subchannel 0 in a receiver according to an embodiment of the present invention.

The MCS level decoding unit 250 illustrated in FIG. 6 includes a WH code table 251, a multiplier 252, an MRC calculator 253, an MRC selector 254, and an MCS code table 255.

Referring to FIG. 6, the MCS level decoding unit 250 in the user's receiving unit according to an embodiment of the present invention may decode the MCS level for subchannel group 0 from the preamble OFDM symbol 240 output from the output of the FFT unit. After multiplying the demodulated data and the corresponding code in the WH code table 251, MRC is performed. Here, reference numeral 252 denotes a multiplier for multiplying a corresponding code among a set of demodulation data and a WH code.

If the output of the FFT unit is {-X ₀ -X ₀ -X ₀ }, the MRC operation unit 253 corresponding to the eight code combinations calculates the multiplication and the MRC selection unit 254 calculates the MRC value that is maximum. Find. In this case, the code has a maximum MRC output value at 000.

Therefore, the code mapped to the maximum MRC output value is selected as MCS level information 26 for the subchannel group 0 in the MCS code table 255.

As a result, according to an embodiment of the present invention, in a burst mode OFDM / TDD communication system, information about an adaptive modulation / code scheme (MCS) of a downlink can be transmitted and received using one preamble.

7 is a flowchart illustrating a method of transmitting and receiving MCS information according to an embodiment of the present invention.

In step S100, the transmitter receives channel information corresponding to the subchannel group corresponding to the burst. The channel information includes signal to noise ratio or signal to interference noise ratio as information on channel quality.

Based on the channel information, one of the MCS levels for adaptive modulation and encoding is determined, and the MCS level coding unit sequentially maps the corresponding subchannel groups by using codes assigned to the determined MCS levels (S110 and 120). .

 The WH code generator determines a bit modulated for the subchannel in the subchannel group according to the code type using the input code to generate a WH code (S130).

The generated WH code is pre-known pattern data allocated to preambles of some sub-channels in the sub-channel group, and the pre-known pattern data is processed according to the WH code (S140).

The processed pattern data is mapped to a preamble in a group of subchannels, multiplexed with data symbols, and transmitted to the receiver (S150).

Meanwhile, when the receiver receives the multiplexed frame, the receiver performs channel estimation and compensation using the measured signal-to-noise ratio to demodulate the WH code from the pattern included in the preamble (S200).

When the WH code for a specific subchannel group is demodulated, an MRC operation for multiplying the demodulated WH code with respect to the WH codes corresponding to all MCS levels is performed (S210).

In the MRC operation, the maximum value is output for the same WH code as the characteristics of the WH code, and the MCS level decoding unit determines the MCS level corresponding to the WH code corresponding to the maximum value (S220).

When the MCS level is determined, demodulation and decoding are performed on the data symbols included in the subchannel group on which the MCS level decoding is performed (S230).

According to the above-described configuration, in the adaptive modulation and coding scheme, the MCS level information on the burst may be determined using pattern data included in the preamble of the subchannel group without using a separate channel.

 While the invention has been described above based on the preferred embodiments thereof, these embodiments are intended to illustrate rather than limit the invention. It will be apparent to those skilled in the art that various changes, modifications, or adjustments to the above embodiments can be made without departing from the spirit of the invention. Therefore, the protection scope of the present invention will be limited only by the appended claims, and should be construed as including all such changes, modifications or adjustments.

According to the present invention, in a burst mode OFDM / TDD communication system, it is not necessary to use a separate control channel by using one preamble to convey information about the adaptive modulation / code scheme (MCS) of the downlink. In addition, according to the present invention, by synchronizing time synchronization and frequency synchronization using one preamble signal, overhead of the system side can be reduced accordingly.

Claims (11)

In the information transmission method for an adaptive modulation and coding scheme (MCS), a) receiving channel information corresponding to a subchannel group corresponding to a burst; b) determining, by the MCS level coding unit, the MCS information corresponding to the channel information and mapping the MCS information for the subchannel group with one of a plurality of preset codes; c) a Walsh-Hadamard (WH) code generator in the MCS level coding section generating a WH code for a subchannel in the subchannel group corresponding to the mapped MCS level code; d) processing previously known pattern data (Known pattern) of the subchannel group using the generated WH code; And e) mapping the processed pattern data signal to a subchannel belonging to the subchannel group, and then including the preamble symbol in one preamble symbol and transmitting the same Information transmission method for an adaptive modulation and coding scheme comprising a. The method of claim 1, The preamble of step a) is included in the OFDM symbol of the non-dedicated channel information transmission method for the adaptive modulation and coding scheme. The method of claim 2, The information transmission method for the adaptive modulation and coding scheme, characterized in that the known pattern included in the preamble is assigned to each subchannel group. The method of claim 3, And a preamble including the processed pattern data is burst framed with the data symbols of the corresponding subchannel group. The method of claim 1, The channel information of the subchannel group of step a) is determined by periodically receiving a signal-to-noise ratio (SNR) signal for the subchannel group, information transmission method for the adaptive modulation and coding scheme. In the information receiving method for the adaptive modulation and coding scheme (MCS), a) receiving demodulation data output from one preamble symbol including MCS level information for a subchannel group; b) an MCS level decoding unit multiplying the corresponding code with each of the demodulation data among a set of Walsh-Hadamard (WH) codes; c) performing maximum ratio combining (MRC) on each of the products of the corresponding WH code and the demodulation data; And d) selecting a WH code that outputs the maximum MRC among the MRC and selecting an MCS level code corresponding to the selected WH code as MCS level information for the subchannel group; Information receiving method for an adaptive modulation and coding scheme comprising a. The method of claim 6, The base station measures the signal-to-noise ratio (SNR) of the channel using the pilot signal of each subchannel group, and then uses the measurement to determine the demodulation method of the WH code of the subchannel group. Method of receiving information about modulation and coding scheme. In the transmission apparatus using an adaptive modulation and coding scheme (MCS), An MCS level information determiner that determines an MCS level for a group of subchannels from channel information; An MCS level code table storing codes corresponding to MCS level information determined by the MCS level information determination unit; And An MCS level coding unit including a WH code generation unit generating a Walsh-Hadamard (WH) code by using a code corresponding to the MCS level information and known pattern data included in the subchannel group; Preamble inserter for inserting the preamble including the pattern data processed by the WH code into the frame Transmission device comprising a. The method of claim 8, And an adaptive modulator for modulating data at the MCS level determined by the MCS level coding unit. In a receiving apparatus using an adaptive modulation and coding scheme (MCS), A WH code table storing Walsh-Hadamard (WH) codes corresponding to respective MCS levels for a subchannel group; An MRC operation unit performing multiplication with all WH codes and demodulated WH codes included in the WH code table; An MRC selector for selecting a WH code for calculating a maximum value by the MRC operation; And And an MCS level decoding unit including an MCS code table for storing MCS level information for a WH code corresponding to the maximum value. The method of claim 10, A channel estimator for estimating a channel using a signal-to-noise ratio to demodulate a WH code of a subchannel group; And an adaptive demodulator for demodulating data using MCS level information for a WH code corresponding to the maximum value.

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