KR20070059396A - Apparatus and method for transmitting data using a plurality of carriers - Google Patents

Abstract

An apparatus and a method for transmitting data using a plurality of carriers are provided to increase band efficiency of an existing system by generating additional data channels. An apparatus for transmitting data using a plurality of carriers includes a macro-constellation mapping module(210). The macro-constellation mapping module(210) performs constellation mapping of user data bits. A macro-constellation mapping module(220) performs the constellation mapping of pilot bits. A micro-constellation mapping module(230) performs the constellation mapping of additional data bits transmitted together with the pilot bits. A serial/parallel converting unit(240) converts constellation mapping performed transmission symbols to parallel signals. A multiplexing device(250) allocates the parallel signals to sub carriers by predetermined rules. An N point IFFT module(260) converts signals allocated to the sub carriers from a frequency region to a time region. A parallel/serial converter(270) converts the parallel signals to serial signals and transmits the serial signals to an RF(Radio Frequency) stage.

Description

Apparatus and method for transmitting data using a plurality of carriers}

1 is a diagram illustrating a transmitting side for transmitting an OFDM signal according to the prior art.

2 is a diagram illustrating an example of a transmitter in which additional data is included in a pilot signal and transmitted according to an embodiment of the present invention.

3 is a diagram illustrating an example of a transmitter in which additional data is included in a data signal and transmitted according to an embodiment of the present invention.

4 is a diagram illustrating a structure of a receiver for receiving a reception signal including the additional data signal according to an embodiment of the present invention.

FIG. 5 is a diagram illustrating a constellation map of data in which giant constellation mapping is performed by BPSK and fine constellation mapping is performed.

FIG. 6A illustrates a range of phases that fine constellation coordinates may have when the giant constellation mapping method is BPSK.

6B illustrates a range of values that fine constellation coordinates may have when the large constellation mapping method is M-ary QAM.

FIG. 7 is a diagram illustrating a result of generating fine constellation coordinates when the giant constellation mapping method is BPSK.

8 is a diagram illustrating a result of generating fine constellation coordinates when the giant constellation mapping method is M-ary QAM.

9 illustrates a concept of a method for including and transmitting additional data according to an embodiment of the present invention.

10 illustrates a maximum value of additional data included in a pilot signal and transmitted according to an embodiment of the present invention.

11 is a diagram illustrating an error rate for additional data when additional data is included in a pilot signal and transmitted according to an embodiment of the present invention.

FIG. 12 is a diagram illustrating an error rate of phase estimation for a fine constellation signal when additional data is included and transmitted in a pilot signal according to an embodiment of the present invention.

FIG. 13 is a diagram illustrating an error rate for additional data when additional data is included in a data signal and transmitted according to an embodiment of the present invention.

FIG. 14 is a diagram illustrating an error rate of phase estimation for a fine constellation signal when additional data is included and transmitted according to an embodiment of the present invention.

The present invention relates to a data transmission / reception method in a communication system, and more particularly, to a data transmission / reception method for transmitting additional data in an orthogonal frequency division multiplexing (OFDM) based communication system. It is about.

Recently, the demand for high-speed data transmission is increasing, and OFDM is a suitable method for such a high-speed transmission, and has been recently adopted as a transmission method of various high-speed communication systems. Hereinafter, OFDM will be described. The basic principle of OFDM is to divide a high-rate data stream into a large number of low-rate data streams, which are transmitted simultaneously using multiple carriers. Each of the plurality of carriers is called a subcarrier. Since orthogonality exists between the multiple carriers of the OFDM, the frequency components of the carriers can be detected at the receiving end even if they overlap each other. The high data rate data stream is converted into a plurality of low data rate data streams through a serial to parallel converter, and each subcarrier is included in the parallel data streams. After multiplying, the respective data strings are summed and sent to the receiving end. OFDMA is a multiple access method for allocating subcarriers according to a transmission rate required by multiple users in the OFDM.

The above-described OFDM communication method is used in various systems (IEEE 802.11a / g, HiperLAN, IEEE 802.16, DSL, DAB, DVB, etc.), and is effective when the communication channel exhibits selective fading. to be. The OFDM scheme uses a plurality of sub-carriers, so that the selective attenuation may appear to be flat-fading, and the technique for compensating for the attenuation in the entire system may be simplified. In order to easily estimate the simplified channel, pilot subcarriers information is used. Since the position and value of the pilot are known in advance by both the transmitter and the receiver, the receiver can obtain the result simply by performing division (or equivalent) to estimate the channel. The phase difference of different OFDM symbols is determined for synchronization, which is obtained by comparing and analyzing only phases of pilot signal parts in different OFDM signals. These pilots can be used for various purposes in addition to these two purposes, and may be used in a coded pilot form or a technique for reducing peak-to-average power ratio (PAPR).

1 is a diagram illustrating a transmitting side for transmitting an OFDM signal according to the prior art. As shown, data bits and pilot bits are mapped to specific data symbols through constellation mapping, and the data symbols are converted through S / P convert. After being converted into a parallel signal (transmission symbol transmitted to the receiver), it is mapped to an arbitrary subcarrier, and the IFFT operation is performed and then transmitted to the receiver through parallel / serial conversion. The data bits represent a bit stream representing user data excluding the pilot.

는 다음 식과 같이 주어진다.The above operation is summarized using a formula as follows. Conventional OFDM transmission scheme, that when using N subcarriers (subcarrier), assigned to the N _p of pilot sub-carriers in the dual, and is assigned to data or a guard band (guard band) to rest. For convenience of explanation, data (user data and pilot data) excluding guard bands will be described below. The number of subcarriers to which the data is allocated is N _d , and a relationship of N = N _p + N _d is established. Transmission symbol vector with user data plus pilot signal

Is given by

와

는 각각 사용자 데이터와 파일럿 부 반송파에 의해 전송되는 심볼 벡터로, 각각의 길이가 N_d와 N_p인 벡터이다. 주파수 영역에서의 전송 심볼 벡터

는 다음 식과 같이 역 푸리에 변환을 거치게 된다.In the above equation, P _d and P _p are matrices for reordering user data and pilot to subcarrier positions that are already assigned,

Wow

Are symbol vectors transmitted by user data and pilot subcarriers, respectively, and are vectors of lengths N _d and N _p , respectively. Transmission symbol vector in frequency domain

Will undergo an Inverse Fourier Transform as

는 푸리에 변환 행렬이다. 벡터

는 반송주파수로 다시 변조된 다음 안테나를 통해서 전송되고 수신 측에서는

과 같이 신호를 수신하게 된다. 여기에서

는 채널의 응답 벡터이고

는 수신잡음에 해당한다. 수신 측에서 수신 신호를 나타내는 벡터

을 복조하기 위해서 먼저 푸리에 변환을 수행한다. 그러면 하기 수학식 3과 같이 표현된다.From here

Is a Fourier transform matrix. vector

Is modulated back to the carrier frequency and then transmitted through the antenna.

Receive the signal as follows. From here

Is the response vector of the channel

Corresponds to the reception noise. A vector representing the received signal at the receiving end

In order to demodulate, we first perform a Fourier transform. Then it is expressed as Equation 3 below.

는 원래 데이터를 나타낸다. 만약, 채널이 추정되어 있다면 추정된 채널 값에 따라 하기 수학 식과 같이 전송 신호가 복조된다.H represents the channel response in the frequency domain

Represents the original data. If the channel is estimated, the transmission signal is demodulated according to the estimated channel value according to the following equation.

는 상기

를 추정한 값이다. OFDM을 전송하는 종래의 방법은 위와 동일하거나, 위에 상응하는 과정 등을 통해 이루어진다.

Above

Is an estimated value. The conventional method of transmitting OFDM is the same as above or through a corresponding process.

The present invention has been proposed to improve the above-described prior art, and the present invention provides a method for transmitting and receiving an OFDM signal capable of generating a new data communication channel.

Summary of the Invention

A transmission and reception method according to the present invention includes a first mapping step of mapping an input bit string to at least one transmission symbol; A second mapping step of changing any one of a magnitude and a phase of the transmission symbols transmitted by a specific subcarrier group consisting of a plurality of subcarriers, using constellation modification information indicating specific additional data; And transmitting the transmitted symbols on which the second mapping is performed to a receiving side by OFDM transmission data processing, wherein the constellation modification information is different from each other with respect to the transmitted symbols transmitted by the specific subcarrier group. It is characterized by the same.

According to another aspect of the present invention, there is provided an apparatus for transmitting an OFDM symbol using a plurality of subcarriers, the apparatus comprising: a first mapping module for mapping an input bit string to at least one transmission symbol; And changing the size and phase of the transmission symbols transmitted by a specific subcarrier group consisting of a plurality of subcarriers by using constellation modification information indicating specific additional data, and transmitting by the specific subcarrier group. And a second mapping module for changing the transmitted symbols by using the same constellation deformation information.

In another method of transmitting and receiving according to the present invention, in the method for receiving OFDM signals transmitted by a plurality of subcarriers, calculating any one of the size and phase of the received symbols received by the plurality of subcarriers, Calculating any one of the changed magnitude and phase from the set magnitude and phase; Acquiring additional data indicated by any one of the calculated magnitude and phase; Restoring the magnitude or phase of the received symbols by using any one of the calculated magnitude and phase; And acquiring data included in the reconstructed received symbol.

In addition, another communication apparatus according to the present invention, in an OFDM receiver for receiving OFDM signals transmitted by a plurality of subcarriers, calculating any one of the magnitude and phase of the received symbols received by the plurality of subcarriers A first demodulation module configured to calculate any one of a changed magnitude and a phase from a preset magnitude and phase, and obtain additional data indicated by any one of the calculated magnitude and phase; And a second demodulation module for reconstructing the magnitude or phase of the received symbols by using any one of the calculated magnitude and phase, and acquiring data included in the reconstructed received symbol.

Work of the present invention Example

The present invention proposes a method of including additional data by separate constellation mapping in a pilot signal or user data signal transmitted by a specific subcarrier in a communication system. The constellation mapping method is distinguished from a constellation mapping method applied to a pilot signal or a data signal included in an OFDM symbol. The present invention may form a separate additional channel through the separate constellation mapping. The present invention transmits the additional data through the separate constellation mapping, and there is no need to separately notify the receiving side of control information for restoring the additional data.

The construction, operation and effects of the present invention will be embodied according to one embodiment of the present invention described below.

According to an embodiment of the present invention, additional control information for transmitting data by overlaying a separate constellation signal for transmission of additional data to a group of subcarriers in an OFDM system and correctly restoring the overlaid constellation signal at a receiving end Do not send. An embodiment of the present invention provides a method of transmitting and receiving the additional data in a user data signal included in an OFDM symbol, and a method of transmitting and receiving the additional data in a pilot signal included in an OFDM symbol. The method of transmitting and receiving the additional data in the user data signal includes a method of transmitting and receiving the same additional data in all user data signals included in one OFDM symbol and a data signal included in one OFDM symbol. They are divided into a method of grouping the two data and transmitting and receiving different additional data in each group.

2 is a diagram illustrating an example of a transmitter in which additional data is included in a pilot signal and transmitted according to an embodiment of the present invention. 3 is a diagram illustrating an example of a transmitter in which additional data is included in a data signal and transmitted according to an embodiment of the present invention. Hereinafter, a data transmission method according to an embodiment of the present invention will be described with reference to FIGS. 2 and 3.

The transmitter of FIG. 2 includes a macro-constellation mapping module 210 that performs constellation mapping of user data bits, and a macro-constellation mapping module 220 that performs constellation mapping of pilot bits. ), A micro-constellation mapping module 230 for performing constellation mapping of the additional data bits transmitted together with the pilot bits, and a serial / conversion for converting the transmitted symbols on which the constellation mapping has been performed into parallel signals. A parallel conversion unit (240), and a multiplexing (MUX) device (250) for allocating the parallel signal to subcarriers according to a predetermined rule. An N point IFFT module 260 converts a signal allocated to the subcarrier from a frequency domain to a time domain, and a parallel / serial converter 270 that converts a parallel signal into a serial signal and transmits the serial signal to an RF terminal.

The transmitter of FIG. 3 includes a macro-constellation mapping module 310 for performing constellation mapping of user data bits, and fine constellation mapping for performing constellation mapping of additional data bits transmitted together with the user data bits. (Micro-constellation mapping) module 320, a macro-constellation mapping module 330 that performs constellation mapping of pilot bits, and a symbol that converts the transmitted symbols on which constellation mapping is performed into parallel signals. And a parallel conversion unit (340), and a multiplexing (MUX) device 350 for allocating the parallel signal to subcarriers according to a predetermined rule. The N point IFFT module 360 converts a signal allocated to the subcarrier from a frequency domain to a time domain, and a parallel / serial converter 370 converting a parallel signal into a serial signal and transmitting the same to an RF terminal.

The user data bit refers to a bit representing the user data signals transmitted by the OFDM scheme, the pilot bit refers to a bit representing the pilot signal that is already known from the transmitting and receiving side, and the additional data bit according to the present invention. The additional data signal additionally transmitted is shown. The giant constellation mapping refers to a constellation mapping method for the user data signal and the pilot signals except for the additional data signal. Therefore, the giant constellation mapping may be BPSK, QPSK, M-ary PSK, M-ary QAM, and the like, and the type is not limited. The fine constellation mapping refers to a separate constellation mapping method for the additional data signal.

As described above, according to the present embodiment, the additional data signal is included and transmitted in various ways. Hereinafter, a method of including and transmitting the additional data signal in a pilot signal will be described.

와

는 상기 파일럿 신호에 공통으로 포함되어 전송되는 값으로, 각각 크기(amplitude)와 위상(phase) 값을 나타낸다. 즉, 상기

는, 상기 부가 데이터 비트를 상기 미세 성상 매핑 방법에 의해 변환한 부가 데이터 심볼을 나타낸다. 상기 수학식 5은 수학식 2를 통해서 시간 영역신호로 변환되어 수신단으로 전달될 수 있다. 상기 부가 데이터 신호와 상기 파일럿 신호 및 사용자 데이터 신호가 포함된 신호는 서로 직교하는 다수의 부 반송파에 의해 전송된다. 본 실시예에 따라, 적어도 둘 이상의 성상 매핑 방법이 적용된 전송 심볼은, 상술한 바와 같이 서로 직교하는 다수의 부 반송파에 의해 전송되는 것이 바람직한바, 다양한 방법으로 상기 전송 심볼을 전송할 수 있다. 이하 설명의 편의를 위하여, 성상 매핑이 수행된 데이터 심볼을, 종래 기술에 따라 특정한 부 반송파에 매핑하고 RF 단을 통하여 수신 측으로 전송하는 일련의 절차를 OFDM 송신 데이터 처리라 칭한다. 도 2에서 상기 OFDM 송신 데이터 처리 단계는, 직/병렬 변 환부(240) 이하 단에서 처리되는 데이터 처리 단계를 포함하는바, 상기 OFDM 송신 데이터 처리 단계는 송신 품질 향상을 위한 다른 통신 장치가 포함될 수 있음은 통상의 당업자에게 자명하다. In the above formula,

Wow

Is a value that is commonly included in the pilot signal and transmitted, and denotes amplitude and phase values, respectively. That is

Denotes additional data symbols obtained by converting the additional data bits by the fine constellation mapping method. Equation 5 may be converted into a time domain signal through Equation 2 and transmitted to the receiving end. The additional data signal and the signal including the pilot signal and the user data signal are transmitted by a plurality of subcarriers orthogonal to each other. According to the present embodiment, the transmission symbols to which at least two constellation mapping methods are applied are preferably transmitted by a plurality of subcarriers orthogonal to each other as described above, so that the transmission symbols can be transmitted in various ways. For convenience of description below, a series of procedures for mapping data symbols on which constellation mapping has been performed to specific subcarriers and transmitting them to a receiver through an RF terminal according to the prior art is called OFDM transmission data processing. In FIG. 2, the OFDM transmission data processing step includes a data processing step processed at a lower stage of the serial / parallel converter 240, and the OFDM transmission data processing step may include another communication device for improving transmission quality. It will be apparent to those skilled in the art.

Hereinafter, a method of transmitting the additional data signal in common with the user data signal according to an embodiment of the present invention will be described.

와

는 상기 파일럿 신호에 공통으로 포함되어 전송되는 값으로, 각각 크기(amplitude)와 위상(phase) 값을 나타낸다. 상기 수학식 6과 같이 부가 데이터 신호를 상기 사용자 데이터 신호에 포함시키는 경우에는 다음과 같은 유리한 점이 있다. 파일럿 신호의 경우에는, 파일럿 신호의 개수에 제한이 있으며, 파일럿 신호는 수신 측에서의 등화(equalization) 내지 채널 추정(channel estimation) 등에 사용되고 있다. 수학식 5를 이용하여 상기 부가 데이터 신호를 상기 파일럿 신호에 포함시키는 경우. 상기 등화 내지 채널 추정에 어려움이 발생할 수 있다. 따라서, 파일럿 신호 대신 사용자 데이터 신호에 상기 부가 데이터 신호를 포함시키는 경우 이러한 수신 측에서 문제를 해결할 수 있다. 상기 수학식 6의 결과, 즉 적어도 둘 이상의 성상 매핑 방법이 적용된 전송 심볼은, 상술한 바와 같이 서로 직교하는 다수의 부 반송파에 의해 전송되는 것이 바람직한바, 상기 OFDM 송신 데이터 처리에 의하여 수신 측으로 전송된다. In the above formula,

Wow

Is a value that is commonly included in the pilot signal and transmitted, and denotes amplitude and phase values, respectively. When the additional data signal is included in the user data signal as shown in Equation 6, there are advantages as follows. In the case of pilot signals, the number of pilot signals is limited, and the pilot signals are used for equalization, channel estimation, and the like on the receiving side. When the additional data signal is included in the pilot signal using Equation 5. Difficulty may occur in the equalization or channel estimation. Therefore, when the additional data signal is included in the user data signal instead of the pilot signal, the problem may be solved at the receiving side. As a result of Equation 6, that is, the transmission symbols to which at least two constellation mapping methods are applied are preferably transmitted by a plurality of subcarriers orthogonal to each other, as described above. .

As described above, the present embodiment includes and transmits additional data signals in various ways. Hereinafter, a method of including and transmitting a plurality of additional data signals in the data signal will be described.

내지

은 상기 그룹에 각각 포함되어 전송되는 부가 데이터 신호를 나타낸다. 즉,

은 각 사용자 데이터 심볼에 할당된 부 반송파에 각각의 위상과 크기가 적용되는 방법을 나타낸다. 여기에서 상기

와

(단,

는 1 내지 N_d의 정수)는 같은 부가 데이터 신호를 전송하는 부 반송파 그룹에 속하는 부 반송파들에 대하여 동일한 값을 갖는다. 또한, 상술한 바와 같이 상기 부가 데이터 신호는 상기 미세 성상 매핑에 의해 특정한 부가 데이터 심볼로 매핑된 것이다. 상기 diag{} 연산은, 임의의 벡터를 행렬로 변환하는 연산으로, 상기 행렬은 상기 벡터 성분을 대각(diagonal) 성분으로 갖는다. 만약, 수신 측에 보내야할 부가 데이터 신호의 양이 많은 경우 상기 수학식 7과 같은 방법으로 사용자 데이터 심볼의 각 그룹마다 서로 다른 부가 데이 터 신호를 포함시키는 것이 바람직하다.Unlike the above Equation 5 or 6, the equation indicates a method of transmitting user data symbols included in one OFDM symbol to transmit different additional data signals for each group. N _d represents the number of groups, and

To

Represents additional data signals included in each of the groups and transmitted. In other words,

Shows how each phase and magnitude is applied to a subcarrier assigned to each user data symbol. Remind Here

Wow

(only,

Is an integer of 1 to N _d ) has the same value for subcarriers belonging to a subcarrier group transmitting the same additional data signal. As described above, the additional data signal is mapped to a specific additional data symbol by the fine constellation mapping. The diag {} operation is an operation of converting an arbitrary vector into a matrix, and the matrix has the vector component as a diagonal component. If the amount of additional data signals to be sent to the receiving side is large, it is preferable to include different additional data signals for each group of user data symbols in the same manner as in Equation (7).

In conclusion, a new additional channel may be provided between the transmitting and receiving sides through the method of transmitting and including the additional data signal as described above. In addition, the present embodiment uses constellation deformation information for modifying the magnitude or phase of constellation coordinates on a constellation map to include and transmit the additional data.

The transmitter according to an embodiment of the present invention is characterized in that it does not transmit control information on a phase or magnitude changed according to the fine constellation mapping to the receiving side. Accordingly, the receiver receives a signal from the transmitter, estimates the fine constellation mapping, removes the fine constellation mapping, and restores the data signal on which the giant constellation mapping is performed. The operation in the receiver will be described below.

4 is a diagram illustrating a structure of a receiver for receiving a reception signal including the additional data signal according to an embodiment of the present invention. The receiver according to the present embodiment includes a serial / parallel converter 480 for converting a serial input into a parallel output, an N-point FFT 470 for performing a Fourier transform for converting from a frequency domain to a time domain, and a transmitting side. In order to estimate the channel using the demultiplexing module (deMUX) 460 and the pilot, which distinguishes the mixed data and the pilot according to a predetermined rule, the constellation coordinates of the constellation map of the data are estimated through the estimated channel. A channel estimator and equalizer 450 to recover, a parallel / serial converter 440 for converting parallel inputs to serial outputs, and a fine constellation that generates constellation groups from equalized data signals and finds fine constellation signals therefrom Module 430 for estimating constellation mapping, reconstruction module 420 for acquiring additional data by reconstructing fine constellation mapping that finds data transmitted from fine constellation signals, and large constellations By restoring the mapping comprises a recovery module (410) for obtaining the user data.

The OFDM signal received through the channel is first converted into a signal in the frequency domain through the serial / parallel conversion and the FFT block. The transformed signal estimates a channel through a pilot and the data signal portion undergoes equalization. If the pilot signals are collected and the maximum likelihood channel estimation is performed, the following estimation values can be obtained.

or

을 나타내면, F는 푸리어 변환 행렬을 나타내고, V_P는 대각 행렬로써, 송신단에서 송신한 파일럿 부분만을 골라서 길이 N의 벡터로 표시했을 때(파일럿의 위치가 아닌 곳은 0으로 채움), 상기 길이 N의 벡터는 Vp의 대각원소가 된다.

은 수신 신호 벡터

에서 파일럿 부분을 나타낸다. 수학식 8에서 첫 번째 값은 파일럿 신호에 상기 부가 데이터 신호가 포함되어 전송되는 경 우 추정 값이고, 두 번째 값은 데이터 신호에 상기 부가 데이터 신호가 포함되어 전송되는 경우, 즉 상기 부가 데이터 신호가 파일럿에 포함되어 전송되지 않는 경우를 나타내는 추정 값이다. 추정된 상기 채널 응답을 주파수 영역으로 변환하여 하기 수학식 9와 같이 각 데이터 심볼의 부 반송파 위치에 대한 채널 값을 알아낸다. A is

F denotes a Fourier transform matrix, and V _P denotes a diagonal matrix, in which only the pilot portion transmitted from the transmitting end is selected and represented as a vector of length N (filled with a non-pilot position filled with 0). The vector of N becomes the diagonal element of Vp.

Silver received signal vector

Denotes the pilot part. In Equation 8, a first value is an estimated value when the additional data signal is included in a pilot signal and transmitted, and a second value is transmitted when the additional data signal is included in the data signal. It is an estimated value indicating a case in which the pilot is not transmitted. The estimated channel response is converted into a frequency domain to find a channel value for the subcarrier position of each data symbol as shown in Equation 9 below.

Equalizing the signals of the subcarrier position for transmitting the data symbol through the estimated channel as described above is expressed by Equation 10 below. Equation 10 is an example of a case in which the additional data signal is transmitted in a pilot signal.

이고,

는 수신 신호 벡터

중에 데이터 부분만 모아놓은 벡터이다. 그리고 데이터부분에 부가데이터를 실어서 보내는 경우, 상기 수학식 10과 달리 수학식 11과 같이 부가정보의 간단한 형태로 표현된다. In the above formula

ego,

Receive signal vector

This is a vector of only data parts. When the additional data is loaded on the data portion, the additional data is expressed in a simple form of the additional information as shown in Equation 11, unlike Equation 10 above.

The constellation of the data signal resulting from the equations (10) and (11) is rotated by a certain amount according to the added data. When the added data signal is also given to the magnitude, the generated constellation also changes in magnitude. FIG. 5 is a diagram illustrating a constellation map of data in which giant constellation mapping is performed by BPSK and fine constellation mapping is performed. FIG. 5 shows the result when the magnitude is 1 and the phase is applied by 30 degrees with respect to the additional data signal.

One embodiment of the present invention preferably performs channel estimation and equalization processes for correct demodulation of the receiver. An embodiment of the present invention provides a method of estimating and restoring a magnitude and phase corresponding to each data symbol (a user data signal, a pilot signal, and an additional data signal transmitted by a transmitter) received through each orthogonal subcarrier. Suggest. The data symbol received through each subcarrier is a data symbol received by a reception antenna and subjected to serial / parallel conversion and FFT conversion, and is referred to as a reception symbol for convenience of description below. As a result, the received symbol according to the present embodiment is a data symbol corresponding to a transmitted symbol obtained by performing two-phase constellation mapping in the transmitter, and performs two additional constellation demaps on the received symbol to perform the additional data. Signal and the user data signal can be restored.

와

에 관한 정보를 제공하지 않으며, 도 5를 통해서 알 수 있듯이 수신 측에서는 이미 알려진 BPSK 성상과는 다른 신호를 수신하게 되므로, 수신 측에서는 송신 측의 도움 없이 상기 미세 성상에 관한 정보(

와

)를 추정하여야 한다. 도 5와 같은 경우에는 크기(즉,

=1)에는 변화를 주지 않았으나 위상에 변화를 주었으므로 종래의 BPSK와 비교했을 때 회전된 모습을 보여주고 있으므로 이 회전된 양을 추정해야 한다. 하지만 이를 추정하기 위해서 각 데이터 심볼의 정확한 값을 알아야 하는 문제가 발생된다. 따라서 상기 미세 성상 매핑을 추정하는 모듈(430)에서 상기 각 수신 심볼의 정확한 값을 알아내기 위한 기법을 사용한다. 우선 각 데이터는 실제 어떤 신호인지 알지 못하므로 성상도(constellation map) 상의 성상 좌표가 뭉쳐있는 형태를 보고, 각각을 그룹을 지어놓고 이를 본래 데이터가 가지는 성상(거대 성상)으로 매핑하여 부가된 크기와 위상(미세 성상)을 알아내야 한다. 하나의 OFDM 심볼에는 다수의 데이터 심볼이 포함되므로, 다수의 수신 심볼에 대한 성상(즉, 수신 심볼 각각에 상응하는 크기와 위상)을 한꺼번에 획득할 수 있고, 이러한 다수의 성상을 이용하여 상기 거대 성상과 비교하여 미세 성상에 대한 정보를 추정할 수 있다. As described above, the transmitting end according to the present embodiment is directed to the receiving side.

Wow

It does not provide information about, and as shown in FIG. 5, since the receiving side receives a signal different from the known BPSK constellation, the receiving side does not provide information on the fine constellation without assistance of the transmitting side.

Wow

) Should be estimated. 5, the size (i.e.

= 1) is not changed, but the phase is changed, so the rotation amount is shown as compared with the conventional BPSK. Therefore, the amount of rotation should be estimated. However, in order to estimate this, a problem arises in that the exact value of each data symbol must be known. Therefore, the module 430 estimating the fine constellation mapping uses a technique for finding an accurate value of each received symbol. First of all, since each data does not know what kind of signal it is, the constellation coordinates on the constellation map are gathered together, and each group is grouped and mapped to the constellation (giant constellation) of the original data. Find out the phase. Since one OFDM symbol includes a plurality of data symbols, constellations (ie, magnitudes and phases corresponding to each of the received symbols) for a plurality of received symbols can be obtained at once, and the large constellations are used using the plurality of constellations. By comparing with, it is possible to estimate the information on the fine properties.

An example of an algorithm for estimating the magnitude and phase added by the fine constellation mapping will be described below.

1. Assign one sample to any group.

2. The centroids of the K groups are updated using the following equation. This is the process of calculating the center of gravity for each group.

는 j번째 그룹에 속해 있는 p번째 샘플이다.Where m _j is the center of the group, N _j is the number of samples in that group,

Is the pth sample in the jth group.

3. Determine the weight coefficient by considering the number of data in each group and update the K center points again. In other words, the center of gravity is updated to most closely resemble the shape of each constellation point.

는 성상 좌표간 각도 회전 값이다. 상기

는, 예를 들어, M-ary QAM은 90도, BPSK는 180도이다. In the above equation, X _k is the k-th largest constellation point (Macro-constellation point), w _k is the weight coefficient and is equal to N _j . And

Is the angular rotation value between constellation coordinates. remind

For example, M-ary QAM is 90 degrees, BPSK is 180 degrees.

4. If there are unassigned samples, select one of them and assign it to the nearest group among the K groups.

5. Repeat steps 2, 3 and 4 for the newly assigned sample.

The transmitter according to the present embodiment additionally transmits an additional data signal through fine constellation mapping, and another receiver according to the present embodiment estimates the fine constellation mapping information by itself and the additional data signal and the large constellation transmitted through fine constellation mapping. Restore the user data signal transmitted through the mapping. Hereinafter, a method of determining the constellation coordinates of the fine constellation mapping used in the transmitter / receiver will be described.

The coordinates of the microscopic constellations should be within a range capable of distinguishing the large constellation coordinates. FIG. 6A illustrates a range of phases that fine constellation coordinates may have when the giant constellation mapping method is BPSK. The illustrated 600 and 630 represent giant constellation coordinates mapped to giant constellations in a BPSK manner. In addition, 601 and 631 represent constellation coordinates in which the giant constellation coordinates are rotated by a fine constellation mapping method. The left part of FIG. 6A shows constellation coordinates rotated by the fine constellation. The transmitter according to the present embodiment rotates the constellation coordinates 600 and 630 for the original data not including the additional data signal, and the constellation coordinates 601 and 631 for the transmission signal including the additional data signal are As shown. 6A illustrates a concept of restoring constellation coordinates in a receiver. The constellation coordinates 601 and 631 for the transmission signal including the additional data signal are used to identify the additional data signal, and the fine constellation mapping. The rotational component by the method is removed to restore the constellation coordinates 600 and 630 by the original giant constellation mapping method. If the direction of restoring constellations in the receiver is fixed clockwise or counterclockwise, if the constellation mapping method is BPSK, the receiver can correctly restore the phase even if the phase is rotated from 0 to 180 degrees. Do.

6B illustrates a range of values that fine constellation coordinates may have when the large constellation mapping method is M-ary QAM. The illustrated 640 represents one of the giant constellation coordinates mapped to the giant constellation in the M-ary QAM method, and the illustrated 641 represents the constellation coordinates in which the giant constellation coordinates 640 are rotated by a fine constellation mapping method. As shown in the left part of FIG. 6B, when the giant constellation coordinates of the general M-ary QAM method are rotated from 0 degrees to 90 degrees, the reception side can correctly receive the data without additional control information. In the receiver, the constellation coordinates of which the phase is rotated can be identified and reconstructed to general giant constellation coordinates by a fine constellation mapping method. That is, if the direction of restoring the constellation coordinates in the receiver is fixed clockwise or counterclockwise, when the macro-stellar mapping method is M-ary QAM, the receiver side may be rotated 0 to 90 degrees by the fine constellation mapping method. Correct restoration is possible.

In conclusion, when the macroconstellation mapping method is BPSK, the phase change according to the fine constellation mapping method should be 0 to 180 degrees. In addition, when the large constellation mapping method is M-ary QAM, the phase change according to the fine constellation mapping method should be 0 to 90 degrees.

As described above, the width of the phase change according to the fine constellation mapping method is constantly limited. The method of mapping the fine constellation within the width of the phase change may be determined in various ways. As the fine constellation mapping method is different, a conversion relationship between the additional data bit and the corresponding data symbol is determined. Such fine constellation mapping method is preferably determined by a communication environment such as an allowable error rate.

FIG. 7 is a diagram illustrating a result of generating fine constellation coordinates when the giant constellation mapping method is BPSK. 7 (a) is an example of using micro-BPSK as a fine constellation mapping method when the giant constellation mapping method is BPSK, and FIG. 7 (b) is a microconvex mapping method when the constellation mapping method is BPSK. -QPSK is an example, and FIG. 7 (c) shows an example of using the micro-8 PSK as the fine constellation mapping method when the large constellation mapping method is BPSK. As described above, when the giant constellation mapping method is BPSK, phase rotation due to fine constellation mapping is limited to 0 to 180 degrees. The μ-BPSK refers to a method of transmitting the additional data by selecting two phase values, for example, 45 degrees and 135 degrees between 0 and 180 degrees. The constellation coordinates according to the giant constellation mapping is equal to 700. If the phase rotation of 45 degrees is applied, the constellation coordinates are equal to 701. If the phase rotation of 135 degrees is applied, the constellation coordinates are equal to 702. If it is determined that the μ-BPSK is to be used as a method of mapping between the transmission and reception sides, the transmitter per group to which the fine constellation coordinates are applied may provide one bit of additional data bits by the fine constellation mapping method. The μ-QPSK refers to a method of transmitting the additional data by selecting four phase values between 0 and 180 degrees. In FIG. 7B, which shows an example of μ-QPSK, 730 is constellation coordinates by giant constellation mapping, and 731, 732, 733, and 734 are fine constellation coordinates by phase rotation. In addition, the μ-8PSK refers to a method of transmitting the additional data by selecting eight phase values between 0 and 180 degrees. In FIG. 7C showing an example of the μ-8 PSK, 760 is constellation coordinates by giant constellation mapping, and 761, 762, 763, 764, 765, 766, 767, and 768 are fine constellation coordinates by phase rotation. The above-described fine constellation mapping method is only a preferable example of the fine constellation mapping method according to the present invention, and various constellation mapping may be performed using a phase transformation or a size transformation according to the fine constellation.

8 is a diagram illustrating a result of generating fine constellation coordinates when the giant constellation mapping method is M-ary QAM. FIG. 8 (a) shows an example of using micro-BPSK as a fine constellation mapping method when the large constellation mapping method is M-ary QAM, and FIG. 8 (b) shows the case where the large constellation mapping method is M-ary QAM. In the case of using micro-QPSK as a fine constellation mapping method, FIG. 8 (c) illustrates an example of using the μ-8 PSK as a fine constellation mapping method when the large constellation mapping method is M-ary QAM. As described above, when the large constellation mapping method is M-ary QAM, phase rotation due to fine constellation mapping is limited to 0 to 90 degrees. The μ-BPSK refers to a method of transmitting the additional data by selecting two phase values, for example, 30 degrees and 60 degrees between 0 and 90 degrees. The constellation coordinates according to the giant constellation mapping is equal to 800. If a phase rotation of 30 degrees is applied, the constellation coordinates are equal to 801. If a phase rotation of 60 degrees is applied, the constellation coordinates are equal to 802. If it is determined that the μ-BPSK is to be used as a method of mapping between the transmission and reception sides, the transmitter per group to which the fine constellation coordinates are applied may provide one bit of additional data bits by the fine constellation mapping method. The μ-QPSK refers to a method of transmitting the additional data by selecting four phase values between 0 and 90 degrees. In FIG. 8B showing an example of? -QPSK, 830 is constellation coordinates by giant constellation mapping, and 831, 832, 833, and 834 are fine constellation coordinates by phase rotation. In addition, the μ-8 PSK refers to a method of transmitting the additional data by selecting eight phase values between 0 and 90 degrees. In FIG. 8 (c) showing an example of the μ-8 PSK, 860 is constellation coordinates by giant constellation mapping, and 861, 862, 863, 864, 865, 866, 867, and 868 are fine constellation coordinates by phase rotation.

9 illustrates a concept of a method for including and transmitting additional data according to an embodiment of the present invention. As shown in FIG. 9, the same additional data may be included in the conventional pilot signal and transmitted, and the same additional data may be included in the conventional data signal and transmitted. In addition, the additional data may be included in a specific subcarrier group differently and transmitted.

10 illustrates a maximum value of additional data included in a pilot signal and transmitted according to an embodiment of the present invention. In the case of transmitting an OFDM symbol on 1024 subcarriers, the amount of additional data that can be transmitted according to a channel environment is shown.

11 is a diagram illustrating an error rate for additional data when additional data is included in a pilot signal and transmitted according to an embodiment of the present invention. In case of transmitting OFDM symbols through 1024 subcarriers, BER according to channel environment is illustrated.

FIG. 12 is a diagram illustrating an error rate of phase estimation for a fine constellation signal when additional data is included and transmitted in a pilot signal according to an embodiment of the present invention. In case of transmitting an OFDM symbol through 1024 subcarriers, an error rate of phase estimation for a fine constellation signal according to a channel environment is shown.

FIG. 13 is a diagram illustrating an error rate for additional data when additional data is included in a data signal and transmitted according to an embodiment of the present invention. In case of transmitting OFDM symbols through 1024 subcarriers, BER according to channel environment is illustrated.

FIG. 14 is a diagram illustrating an error rate of phase estimation for a fine constellation signal when additional data is included and transmitted according to an embodiment of the present invention. In case of transmitting an OFDM symbol through 1024 subcarriers, an error rate of phase estimation for a fine constellation signal according to a channel environment is shown.

Those skilled in the art through the above description can be seen that various changes and modifications can be made without departing from the spirit of the present invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification but should be defined by the claims.

The effect obtained by the present invention is as follows.

According to the present invention, an additional data channel is further generated in addition to the conventional data channel, thereby increasing the bandwidth efficiency of the existing system.

Claims (17)

A first mapping step of mapping an input bit string to at least one transmission symbol; A second mapping step of changing at least one of a magnitude and a phase of the transmission symbols transmitted by a specific subcarrier group consisting of a plurality of subcarriers using constellation modification information indicating specific additional data; And And transmitting the transmitted symbols on which the second mapping is performed to a receiver by OFDM transmission data processing. The constellation modification information is identical to each other for the transmission symbols transmitted by the specific subcarrier group. An OFDM signal transmission method characterized by the above-mentioned. The method of claim 1, wherein the second mapping step, Modulating the transmission symbols transmitted by the subcarrier group according to the constellation modification information value. An OFDM signal transmission method characterized by the above-mentioned. The method of claim 1, The constellation deformation information may have different magnitudes or phases according to the additional data. An OFDM signal transmission method characterized by the above-mentioned. The method of claim 1, wherein the first mapping step is performed by an M-ary QAM mapping method. The constellation deformation information has a phase from 0 degrees to 90 degrees An OFDM signal transmission method characterized by the above-mentioned. The method of claim 1, wherein the first mapping step is performed by the M-ary PSK mapping method. The constellation deformation information is at 0 degrees

Having a phase up to An OFDM signal transmission method characterized by the above-mentioned. The method of claim 1, The subcarrier group includes a plurality of subcarriers for transmitting a pilot signal. An OFDM signal transmission method characterized by the above-mentioned. The method of claim 1, The subcarrier group includes a plurality of subcarriers for transmitting user data signals. An OFDM signal transmission method characterized by the above-mentioned. An OFDM transmitter for transmitting a data symbol to a receiver using a plurality of subcarriers, A first mapping module for mapping an input bit string to at least one transmission symbol; And At least one of the size and phase of the transmission symbols transmitted by a specific subcarrier group consisting of a plurality of subcarriers is changed by using constellation modification information indicating specific additional data, A second mapping module for modifying the transmission symbols transmitted by the specific subcarrier group by using the same constellation modification information with respect to each other; An apparatus for transmitting an OFDM signal, further comprising. In the method for receiving an OFDM signal transmitted by a plurality of subcarriers, Calculating at least one of a magnitude and a phase of received symbols received by the plurality of subcarriers, and calculating at least one of a magnitude and a phase changed from a preset magnitude and phase; Acquiring additional data indicated by at least one of the calculated magnitude and phase; Restoring the magnitude or phase of the received symbols using at least one of the calculated magnitude and phase; And Acquiring data included in the recovered received symbol; OFDM signal receiving method comprising a. An OFDM receiver for receiving OFDM signals transmitted by multiple subcarriers, Compute at least one of the magnitude and phase of the received symbols received by the plurality of subcarriers, at least one of the magnitude and phase changed from a preset magnitude and phase, and at least any of the calculated magnitude and phase A first demodulation module for acquiring additional data indicated by one; And And a second demodulation module for reconstructing the magnitude or phase of the received symbols by using at least one of the calculated magnitude and phase, and obtaining data included in the reconstructed received symbol. Receiver. A transmission method for converting an input bit string corresponding to data to be transmitted to a receiver into at least one or more transmission symbols and transmitting using a plurality of subcarriers, The method may further include performing a fine constellation conversion step of changing at least one of a magnitude and a phase of the transmission symbols transmitted by a specific subcarrier group by using constellation deformation information indicating specific additional data. The constellation modification information is identical to each other for the transmission symbols transmitted by the specific subcarrier group. An OFDM signal transmission method characterized by the above-mentioned. The method of claim 11, wherein the step of converting the fine constellation, Modulating the transmission symbols transmitted by the subcarrier group according to the constellation modification information value. An OFDM signal transmission method characterized by the above-mentioned. The method of claim 11, The constellation deformation information may have different magnitudes or phases according to the additional data. An OFDM signal transmission method characterized by the above-mentioned. The method of claim 11, wherein the transmission symbol is generated by an M-ary QAM mapping method. The constellation deformation information has a phase from 0 degrees to 90 degrees An OFDM signal transmission method characterized by the above-mentioned. The method of claim 11, wherein the transmission symbol is generated by an M-ary PSK mapping method. The constellation deformation information is at 0 degrees

Having a phase up to An OFDM signal transmission method characterized by the above-mentioned. The method of claim 11, The subcarrier group includes a plurality of subcarriers for transmitting a pilot signal. An OFDM signal transmission method characterized by the above-mentioned. The method of claim 11, The subcarrier group includes a plurality of subcarriers for transmitting user data signals. An OFDM signal transmission method characterized by the above-mentioned.

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