KR20090018255A - Apparatus and method for detecting signal with hidden pilots in broadband wireless communication system - Google Patents

Abstract

An apparatus and a method for detecting signal with hidden pilots are provided to improve channel estimation accuracy by using a detected signal in broadband wireless telecommunications system. An estimator(112) estimates a channel value at an n-th repetition step using a hidden pilot signal and a transmission symbol block which is detected at an(n-1)th repetition step. A detector(110) detects a transmission symbol block from the received signal by using the channel value of the n-th repetition step and provides the transmission symbol block, which is detected based on a channel value estimation at a(n+1)th repetition step, to the estimator.

Description

Apparatus and method for detecting signals using hidden pilot in broadband wireless communication system {APPARATUS AND METHOD FOR DETECTING SIGNAL WITH HIDDEN PILOTS IN BROADBAND WIRELESS COMMUNICATION SYSTEM}

The present invention relates to a broadband wireless communication system, and more particularly, to an apparatus and method for detecting a signal using a hidden pilot signal in a broadband wireless communication system.

The 4th Generation (hereinafter referred to as '4G') communication system provides users with services of various quality of service (QoS) using a transmission rate of about 100 Mbps. There is active research going on. Particularly, in 4G communication systems, studies are being actively conducted to support high-speed services in a form of guaranteeing mobility and QoS in a broadband wireless access (BWA) communication system such as a wireless local area network system and a wireless urban area network system. Is going on. In addition, the representative communication system is the Institute of Electrical and Electronics Engineers (IEEE) 802.16 communication system.

The IEEE 802.16 communication system uses orthogonal frequency division multiplexing (OFDM) / orthogonal frequency division to support a broadband transmission network on a physical channel of the wireless communication system. A communication system employing an Orthogonal Frequency Division Multiple Access (hereinafter referred to as 'OFDMA') scheme.

In an OFDMA system such as the IEEE 802.16 system, preamble and pilot signals are periodically transmitted for channel estimation of a user. The preamble and the pilot signal are transmitted using a bandwidth for data transmission. Therefore, the loss of radio resources due to the use of the preamble and the pilot signal is inevitable. In order to solve this problem, an alternative using a hidden pilot signal has been proposed. The hidden pilot signal means a pilot signal transmitted through the same radio resource as the data signal. However, since the hidden pilot signal method is basically a mixture of the data signal and the pilot signal, the interference should be effectively eliminated.

Alternatives have been proposed to effectively cancel mutual interference in the hidden pilot scheme, but still, perfect interference cancellation is not possible. Therefore, there is a need for an alternative for effectively canceling mutual interference and detecting signals in the hidden pilot scheme.

Accordingly, an object of the present invention is to provide a signal detection apparatus and method in a broadband wireless communication system.

Another object of the present invention is to provide an apparatus and method for channel estimation and signal detection using a hidden pilot signal in a broadband wireless communication system.

Another object of the present invention is to provide an iteration signal detection apparatus and method for improving channel estimation accuracy using a signal detected in a broadband wireless communication system, and detecting a signal again using an improved channel value. have.

According to a first aspect of the present invention for achieving the above object, the receiving end device for detecting the transmission signal of the user k in the broadband wireless communication system, the transmission symbol block and the hidden pilot (n-1) iteration detected in the iteration step ( an estimator for estimating a channel value of the (n) -th repetition step using a hidden pilot) signal, and detecting a transmission symbol block from the received signal using the channel value of the (n) -th repetition step, and (n + 1) And a detector for providing the estimated transmission symbol block to the estimator for the channel value estimation of the second iteration step.

According to a second aspect of the present invention for achieving the above object, a transmission signal detection method of user k in a broadband wireless communication system uses a transmission symbol block and a hidden pilot signal detected in the (n-1) -th iteration step. Estimating a channel value of the (n) -th repetition step, and detecting a transmission symbol block from the received signal using the channel value of the (n) -th repetition step.

In the broadband wireless communication system, interference generated in the hidden pilot signal method is used by using an iteration detection technique using the channel estimation result through the hidden pilot signal for signal detection and using the signal detection result for the channel estimation. Can be effectively removed, and the system transmission rate can be improved.

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

Hereinafter, an iteration signal detection technique using a hidden pilot signal in a broadband wireless communication system will be described. The present invention describes an orthogonal frequency division multiplexing (hereinafter referred to as "OFDM") wireless communication system as an example, and may be equally applicable to other wireless communication systems.

를 구성하고,

를 N×M 크기의 사전 부호화기

와 곱한다. 그리고, 송신노드는 사전 부호화기

와 곱해진 i번째 심벌 블록

에 N×1 크기의 은닉 파일럿 신호

를 합하고, 사용자k에게 할당된 부반송파에 최종 송신심벌 블록을 매핑(mapping)한다. 상기 매핑된 사용자k의 최종 송신심벌 블록은 다른 사용자들의 송신심벌 블록과 함께 IFFT(Inverse Fast Fourier Transform) 연산되어 OFDM 심벌로 변환되고, CP(Cyclic Prefix) 추가된다. 여기서, 상기 송신노드가 단말이라면, 상기 다른 사용자들의 송신심벌은 널(null)이 된다. 이를 수식으로 표현하면 하기 <수학식 1>과 같다.The transmitting node modulates the transmission bits to the user k by M-ary phase shift keying (PSK) and includes an i-th symbol block of size M × 1 including M symbols.

Configure

N × M sized pre-encoder

Multiply by And the transmitting node is a pre-encoder

I symbol block multiplied by

N × 1 magnitude hidden pilot signal

Sums and maps the final transmission symbol block to the subcarrier allocated to user k. The final transmission symbol block of the mapped user k is transformed into an OFDM symbol by performing an Inverse Fast Fourier Transform (IFFT) operation together with transmission symbol blocks of other users, and added a CP (cyclic prefix). Here, if the transmitting node is a terminal, the transmission symbols of the other users are null. If this is expressed as an equation, Equation 1 is obtained.

는 모든 사용자들의 송신심벌을 포함하는 i번째 OFDM 심벌, 상기

는 사용자k의 i번째 OFDM 심벌, 상기

는 FFT 행렬, 상기

는 사용자k의 부반송파 할당 행렬, 상기

는 사용자k의 사전 부호화기, 상기

는 사용자k의 i번째 송신심벌 블록, 상기

는 사용자k의 은닉 파일럿 신호, 상기

는 사용자k'의 IFFT 행렬, 부반송파 할당 행렬, 사전 부호화 행렬의 곱, 상기

는 사용자k'의 IFFT 행렬, 부반송파 할당 행렬, 은닉 파일럿 신호의 곱, 상기

는 OFDM 심벌, 상기

는 CP 삽입 행렬, 상기

은 CP의 길이, 상기

은 CP 추가된 OFDM 심벌의 길이를 의미한다.In Equation 1,

I i OFDM symbol containing the transmission symbols of all users, the

Is the i th OFDM symbol of user k,

Is the FFT matrix,

Is the subcarrier allocation matrix of user k,

Is the user's pre-encoder,

Is the i th transmit symbol block of user k,

Is the hidden pilot signal of user k,

Is the product of the kFT's IFFT matrix, the subcarrier allocation matrix, and the precoding matrix,

Is the product of the kFT's IFFT matrix, the subcarrier allocation matrix, the hidden pilot signal,

Is an OFDM symbol,

CP insertion matrix, the

Is the length of CP, said

Denotes the length of the CP-added OFDM symbol.

로 디지털-아날로그 변환(digital-to-analog convert)되어 안테나를 통해 송신된다.The CP-added OFDM symbol is a sampling frequency

It is digital-to-analog converted and transmitted through the antenna.

로 아날로그-디지털 변환(analog-to-digital convert)되고 CP 제거되면 하기 <수학식 2>와 같다.In addition, after the signal transmitted from the transmitting node is received by the receiving node through the channel, the sampling frequency

After analog-to-digital convert and CP removal, Equation 2 is obtained.

는 사용자k'의 CP 제거된 i번째 시간영역 OFDM 심벌, 상기

는 첫째 열(column)이

인 N×N 크기의 순환 행렬(circulant matrix), 상기

는 사용자k'의 채널벡터, 상기

는 모든 사용자들의 송신심벌을 포함하는 i번째 OFDM 심벌, 상기

는 사용자k의 i번째 OFDM 심벌, 상기

는 백색잡음을 의미한다.In Equation 2,

Is an i-th time-domain OFDM symbol of CP removed by user k ',

Is the first column

Circulant matrix of size N × N,

Is the channel vector of user k ',

I i OFDM symbol containing the transmission symbols of all users, the

Is the i th OFDM symbol of user k,

Means white noise.

If Equation 2 is summarized using Equation 1, Equation 3 is obtained.

는 사용자k'의 CP 제거된 i번째 시간영역 OFDM 심벌, 상기

는 첫째 열이

인 N×N 크기의 순환 행렬, 상기

는 사용자k의 i번째 OFDM 심벌, 상기

는 백색잡음, 상기

는 사용자 k'의 IFFT행렬, 부반송파 할당 행렬, 사전 부호화 행렬의 곱, 상기

는 사용자k의 i번째 송신심벌 블록, 상기

는 사용자k'의 IFFT 행렬, 부반송파 할당 행렬, 은닉 파일럿 신호의 곱, 상기

는 사용자 k'의 첫째 열이

인 크기 N×(L+1)의 순환 행렬, 상기

는 사용자k'의 채널벡터를 의미한다.In Equation 3,

Is an i-th time-domain OFDM symbol of CP removed by user k ',

First fever

Circulating matrix of size N × N, where

Is the i th OFDM symbol of user k,

Is white noise, remind

Is a product of the IFFT matrix of the user k ', the subcarrier allocation matrix, and the precoding matrix,

Is the i th transmit symbol block of user k,

Is the product of the kFT's IFFT matrix, the subcarrier allocation matrix, the hidden pilot signal,

Is the first column of user k '

Circular matrix of size N × (L + 1),

Denotes a channel vector of user k '.

Channel estimation according to the present invention is performed in the time domain and uses the hidden pilot signal. However, since the hidden pilot signal is transmitted mixed with the data signal, the receiving node distinguishes the hidden learning signal, and the data signal of the detection target user, the data signal of another user, and the hidden learning signal serve as interference. Accordingly, the channel estimation according to the present invention applies an iteration technique to pre-eliminate interference from the received signal using the detected signal and redetect the signal, and reduces signal interference through preprocessing.

The line interference cancellation is performed as shown in Equation 4 below at the nth repetition time point for the user k 'received signal.

는 사용자k'의 (n)번째 반복 단계에서 선 간섭 제거된 i번째 시간영역 OFDM 심벌, 상기

는 사용자k'의 (n-1)번째 반복 단계에서 첫째 열이

인 N×N 크기의 순환 행렬, 상기

은 (n)번째 반복단계에서 추정된 사용자k'의 채널 벡터, 상기

는 사용자k'의 IFFT행렬, 부반송파 할당 행렬, 사전 부호화 행렬의 곱,

는 사용자k의 i번째 송신심벌 블록, 상기

은 사용자k'의 (n)번째 반복 단계에서 검출된 i번째 송신심벌 블록, 상기

는 사용자 k'의 첫째 열이

인 크기 N×(L+1)의 순환 행렬, 상기

는 사용자k'의 채널벡터, 상기

는 백색잡음을 의미한다.In Equation 4,

Is an i th time-domain OFDM symbol whose line interference has been removed in the (n) th iteration of user k ',

Is the first column in the (n-1) th iteration of user k '

Circulating matrix of size N × N, where

Is the channel vector of user k 'estimated in the (n) th iteration,

Is the product of k's IFFT matrix, subcarrier assignment matrix, precoding matrix,

Is the i th transmit symbol block of user k,

Is the i th transmit symbol block detected in the (n) th iteration of user k ',

Is the first column of user k '

Circular matrix of size N × (L + 1),

Is the channel vector of user k ',

Means white noise.

Then, preprocessing for the received signal of the user k 'is performed as shown in Equation 5 below.

는 사용자k'의 (n)번째 단계에서 전처리된 i번째 시간영역 OFDM 심벌, 상기

는 사용자k'의 첫째 열이

인 크기 N×(L+1)의 순환 행렬, 상기

는 사용자k'의 첫째 열이

인 N×N 크기 의 순환 행렬, 상기

는 사용자k'의 IFFT행렬, 부반송파 할당 행렬, 사전 부호화 행렬의 곱, 상기

는 사용자k'의 (n)번째 반복 단계에서 선 간섭 제거된 i번째 시간영역 OFDM 심벌,

는 사용자k의 i번째 송신심벌 블록, 상기

는 사용자k'의 (n)번째 반복 단계에서 첫째 열이

인 N×N 크기의 순환 행렬, 상기

은 사용자k'의 (n)번째 반복 단계에서 검출된 i번째 송신심벌 블록, 상기

는 백색잡음을 의미한다.In Equation 5,

Is the i-th time-domain OFDM symbol preprocessed in step (n) of user k ',

Is the first column of user k '

Circular matrix of size N × (L + 1),

Is the first column of user k '

Is a circulant matrix of size N × N, where

Is the product of the kFT's IFFT matrix, the subcarrier allocation matrix, and the pre-coding matrix,

Is an i th time-domain OFDM symbol whose line interference has been removed in the (n) th iteration of user k ',

Is the i th transmit symbol block of user k,

Is the first column in the (n) th iteration of

Circulating matrix of size N × N, where

Is the i th transmit symbol block detected in the (n) th iteration of user k ',

Means white noise.

가 0에 가까워져야 한다. 이와 같은 조건을 충족시키기 위해, 사전 부호화기와 은닉 파일럿은 하기 <수학식 6>과 같은 성질을 만족해야 한다.Here, for effective interference cancellation, the interference component due to the data signal of all other users preprocessed using the user's hidden learning signal

Should be close to zero. In order to satisfy this condition, the precoder and the hidden pilot must satisfy the following Equation (6).

는 사용자k'의 첫째 열이

인 크기 N×(L+1)의 순환 행렬, 상기

는 사용자k'의 IFFT 행렬, 부반송파 할당 행렬, 은닉 파일럿 신호의 곱, 상기

는 사용자k'의 IFFT행렬, 부반송파 할당 행렬, 사전 부호화 행렬의 곱의 i번째 열을 이용한 컬럼 와이즈(column-wise) 순환 행렬, 상기

는 사용자 인덱스를 의미한다.In Equation 6,

Is the first column of user k '

Circular matrix of size N × (L + 1),

Is the product of the kFT's IFFT matrix, the subcarrier allocation matrix, the hidden pilot signal,

Is a column-wise cyclic matrix using the i th column of the product of the IFFT matrix, the subcarrier allocation matrix, and the pre-coding matrix of the user k ',

Means user index.

In addition, interference components due to hidden pilot signals to other terminals should also be removed. To this end, the hidden pilot signal must satisfy the following properties.

는 사용자k'의 첫째 열이

인 크기 N×(L+1)의 순환 행렬, 상기

는 사용자k'의 IFFT 행렬, 부반송파 할당 행렬, 은닉 파일럿 신호의 곱, 상기

는 사용자 인덱스를 의미한다.In Equation 7,

Is the first column of user k '

Circular matrix of size N × (L + 1),

Is the product of the kFT's IFFT matrix, the subcarrier allocation matrix, the hidden pilot signal,

Means user index.

After the pre-coder and the concealment pilot satisfy the same properties as in Equations 6 and 7, and line interference cancellation is performed, channel estimation from the signal obtained through Equation 5 is performed as follows. Equation 8 is performed.

는 사용자k'의 채널벡터, 상기

는 사용자k'의 (n)번째 단계에서 전처리된 i번째 시간영역 OFDM 심벌, 상기

는 사용자 k'의 첫째 열이

인 크기 N×(L+1)의 순환 행렬을 의미한다.In Equation 8,

Is the channel vector of user k ',

Is the i-th time-domain OFDM symbol preprocessed in step (n) of user k ',

Is the first column of user k '

A cyclic matrix of phosphorus size N × (L + 1).

(=)인

-nary m-시퀀스(sequence)

을 생성한다. 여기서, 상기

는 소수(prime number)이며, 상기

은 1보다 큰 정수이다. 그리고,

개의 다상 수열(poly-phase sequence) 집합(set)

를 하기 <수학식 9>와 같이 생성한다.The design for ensuring that the pre-encoder and the hidden pilot signal satisfy the above-described properties is as follows. First, length

(= )sign

-nary m-sequence

Create Where

Is a prime number, and

Is an integer greater than one. And,

Sets of poly-phase sequences

It is generated as shown in <Equation 9>.

는 다상 수열 집합, 상기

은 설정되는

의 길이, 상기

는 설정되는 소수(prime number)를 의미한다.In Equation 9,

Is a multiphase sequence assembly,

Is set

The length of,

Means a prime number to be set.

를 이용하여 하기 <수학식 10>과 같이 사전 부호화기 및 은닉 파일럿 신호를 설계한다.Multi-Phase Sequence Set Generated by the Equation (9)

The precoder and the hidden pilot signal are designed by using Equation 10 below.

는 사용자k의 사전 부호화 행렬, 상기

사용자k의 은닉 파일럿 신호, 상기

는 사용자k의 부반송파 할당 행렬을 의미한다.In Equation 10,

Is the pre-coding matrix of user k,

User k's hidden pilot signal, said

Denotes a subcarrier allocation matrix of user k.

Transmission signal detection using channel estimation according to the present invention is performed as follows.

First, the signal of the user k received at the receiving node is processed as shown in Equation 11 through fast fourier transform (FFT) calculation and subcarrier demapping.

는 사용자k'의 i번째 수신신호, 상기

는 FFT 행렬, 상기

는 사용자k의 부반송파 할당 행렬, 상기

는 사용자k'의 CP 제거된 i번째 시간영역 OFDM 심벌, 상기

는 첫째 열이

인 N× N 크기의 순환 행렬, 상기

는 사용자k의 사전 부호화기, 상기

는 사용자k의 i번째 송신심벌 블록, 상기

는 사용자k의 은닉 파일럿 신호, 상기

는 백색잡음, 상기

는 사용자k의 채널 주파수 응답을 대각화한 행렬, 상기

는 부반송파 할당 행렬의 허미션(hermitian), FFT 행렬, 백색잡음의 곱을 의미한다. 여기서, 상기

는 하기 <수학식 12>와 같은 성질을 이용하여 생성된다.In Equation 11,

Is the i-th received signal of user k ',

Is the FFT matrix,

Is the subcarrier allocation matrix of user k,

Is an i-th time-domain OFDM symbol of CP removed by user k ',

First fever

Circulating matrix of size N × N, where

Is the user's pre-encoder,

Is the i th transmit symbol block of user k,

Is the hidden pilot signal of user k,

Is white noise, remind

Is a matrix obtained by diagonalizing the channel frequency response of user k,

Denotes the product of the hermitian, the FFT matrix, and the white noise of the subcarrier allocation matrix. Where

Is generated using the property shown in Equation 12 below.

는 사용자k의 부반송파 할당 행렬, 상기

는 사용자 인덱스를 의미한다.In Equation 12,

Is the subcarrier allocation matrix of user k,

Means user index.

Since the hidden pilot signal is not used when the transmission signal is detected in the signal of the user k processed as in Equation 11, the hidden pilot signal is removed using the channel information estimated through the nth iteration as shown in Equation 13 below.

는 사용자k의 (n)번째 반복 단계에서 은닉 파일럿 신호 성분이 제거된 i번째 수신신호, 상기

는 사용자k의 채널 주파 수 응답을 대각화한 행렬, 상기

는 사용자k의 n번째 반복에서 추정된 채널 주파수 응답을 대각화한 행렬, 상기

는 사용자k의 사전 부호화기, 상기

는 사용자k의 i번째 송신심벌 블록, 상기

는 사용자k의 은닉 파일럿 신호, 상기

는 부반송파 할당 행렬의 허미션, FFT 행렬, 백색잡음의 곱을 의미한다.In Equation 13,

Is the i th received signal from which the hidden pilot signal component has been removed in the (n) th iteration of user k,

Is a matrix obtained by diagonalizing the channel frequency response of user k,

Is a matrix of the channel frequency response estimated at the nth iteration of user k,

Is the user's pre-encoder,

Is the i th transmit symbol block of user k,

Is the hidden pilot signal of user k,

Denotes the product of the hermit, the FFT matrix, and the white noise of the subcarrier allocation matrix.

Thereafter, the receiving node detects a signal according to the corresponding detection scheme. For example, when using a minimum mean square error (MMSE) technique, the detected transmission signal may be represented by Equation 14 below.

은 사용자k의 (n)번째 반복 단계에서 검출된 i번째 송신심벌 블록, 상기

은 사용자k의 (n)번째 반복 단계에서 MMSE 검출 및 역 사전 부호화 행렬, 상기

는 사용자k의 (n)번째 반복 단계에서 은닉 파일럿 신호 성분이 제거된 i번째 수신신호, 상기

는 사용자k의 사전 부호화기, 상기

는 사용자 당 송신전력, 상기

은 심벌 블록에 포함된 심벌들의 개수, 상기

는 사용자k의 (n)번째 반복 단계에서 추정된 채널 주파수 응답을 대각화한 행렬, 상기

는 사용자k의 i번째 송신심벌 블록, 상기

는 사용자k의 은닉 파일럿 신호, 상기

는 부반송파 할당 행렬의 허미션, FFT 행렬, 백색잡음의 곱을 의미한다.In Equation 14,

Is the i th transmit symbol block detected in the (n) th iteration of user k,

Is the MMSE detection and inverse precoding matrix in the (n) th iteration of user k,

Is the i th received signal from which the hidden pilot signal component has been removed in the (n) th iteration of user k,

Is the user's pre-encoder,

Is the transmit power per user,

Is the number of symbols included in the symbol block,

Is a matrix of the channel frequency response estimated in the (n) th iteration of user k, wherein

Is the i th transmit symbol block of user k,

Is the hidden pilot signal of user k,

Denotes the product of the hermit, the FFT matrix, and the white noise of the subcarrier allocation matrix.

As shown in Equation 14, the cross correlation matrix of the error between the transmission signal of the user k and the actual transmission signal detected through the MMSE technique is expressed by Equation 15 below.

는 사용자k의 (n)번째 반복 단계에서 i번째 검출신호의 에러 상호 상관 행렬, 상기

은 사용자k의 (n)번째 반복 단계에서 실제 송신심벌 블록과 검출된 i번째 송신심벌 블록과의 차, 상기

는 사용자k의 사전 부호화기, 상기

는 사용자 당 송신전력, 상기

은 심벌 블록에 포함된 심벌들의 개수, 상기

는 사용자k의 (n)번째 반복 단계에서 추정된 채널 주파수 응답을 대각화한 행렬을 의미한다.In Equation 15,

Is an error cross-correlation matrix of the i th detection signal in the (n) th iteration of user k,

Is the difference between the actual transmission symbol block and the detected i-th transmission symbol block in the (n) th iteration of user k,

Is the user's pre-encoder,

Is the transmit power per user,

Is the number of symbols included in the symbol block,

Denotes a matrix obtained by diagonalizing the channel frequency response estimated in the (n) th iteration of user k.

가

이고,

가

이면,

는 대각화되고, 사용자k의 m번째 전송 신호의 에러분산 값들이 일정하게 유지된다는 것이다. 즉, 각 사용자의 전송 신호들이 주파수영역에서 고르게 확산되고, 이로 인해, 에러 값들이 주파수영역에서 평균화된다. 또한,

가

이면, 주파수영역으로 확산된 신호들이 다시 모이므로 주파수 다이버시티(diversity) 이득이 발생한다.The fact that we can know from Equation 15 is

end

ego,

end

If,

Is diagonalized and the error variance values of the mth transmission signal of user k are kept constant. That is, the transmission signals of each user are spread evenly in the frequency domain, whereby error values are averaged in the frequency domain. Also,

end

In this case, since the signals spread in the frequency domain are gathered again, a frequency diversity gain occurs.

Hereinafter, a configuration and an operation procedure of a receiver for performing channel estimation and transmission signal detection according to the above-described scheme will be described in detail with reference to the accompanying drawings. Here, when the receiving end is a base station, signal detection of the receiving end detects a transmission signal of one terminal among signals received from a plurality of terminals. On the other hand, when the receiving end is a terminal, signal detection of the receiving end is to detect a signal transmitted to itself among the signals received from the base station.

1 is a block diagram of a receiver in a broadband wireless communication system according to an exemplary embodiment of the present invention.

As shown in FIG. 1, the receiver includes an RF receiver 102, a CP remover 104, an FFT operator 106, a subcarrier mapper 108, a signal detector 110, and a channel estimator. 112, a decoder 114, and a demodulator 116.

인 디지털 신호로 변환한다. 상기 CP제거기(104)는 수신신호를 OFDM 심벌 단위로 분할하고, 상기 OFDM 심벌에서 CP를 제거한다. 예를 들어, 상기 CP 제거된 후의 수신신호는 상기 <수학식 2>와 같다.The RF receiver 102 down-converts an RF band signal received through an antenna to a baseband signal, and sampling frequency

To digital signal. The CP remover 104 divides the received signal into OFDM symbol units and removes a CP from the OFDM symbol. For example, the received signal after the CP is removed is expressed by Equation 2 above.

 The FFT operator 106 converts the time-domain OFDM symbol into frequency-domain signals through an FFT operation. That is, the FFT operator 106 recovers subcarrier symbols from the time-domain OFDM symbol. The subcarrier demapper 108 classifies the symbols for each subcarrier into symbols for each user. If the receiver is a terminal, the subcarrier demapper 108 extracts only symbols mapped to the subcarriers assigned thereto.

The signal detector 110 detects a transmission symbol block from the received signal by using a corresponding detection technique. For example, the signal detector 110 detects a transmission symbol using the MMSE technique as shown in Equation (14). At this time, the signal detector 110 removes the hidden pilot signal from the received signal using the channel value estimated by the channel estimator 112 prior to the transmission symbol detection. In addition, the signal detector 110 provides the detected transmission symbol to the channel estimator 112.

The channel estimator 112 estimates a channel and provides a channel estimate to the signal detector 110. In this case, the channel estimator 112 estimates a channel using the transmission symbol block detected by the signal detector 110, and a detailed function of the channel estimator 112 will be described with reference to FIG. 2.

The decoder 114 inverse pre-encodes the detected transmission symbol block. That is, the decoder 114 performs inverse pre-coding corresponding to the pre-coding performed by the transmitter to restore symbols before pre-coding. The demodulator 116 demodulates the inverse pre-coded symbols according to a corresponding scheme and converts them into bit strings.

2 is a block diagram of a channel estimator in a broadband wireless communication system according to an exemplary embodiment of the present invention.

As shown in FIG. 2, the channel estimator 112 includes an interference canceller 202, a preprocessor 204, a channel value calculator 206, and a domain converter 208.

The interference canceller 202 removes the interference in the received time-domain OFDM symbol using the detected transmission signal. Here, the interference refers to the data signal component of the user who wants to estimate the channel. For example, the interference cancellation of the interference canceller 202 may be performed by subtracting the product of the previous iteration step and the detected transmission symbol of the previous iteration step from the received time-domain OFDM symbol, as shown in Equation 4. Is performed.

The preprocessor 204 removes interference at the output of the interference canceller 202 using a hidden pilot signal. Here, the interference means a data signal component of a user who wants to estimate a channel, a data signal component of a user other than the user who wants to estimate a channel, and a hidden pilot signal component. For example, the interference cancellation of the preprocessor 204 is performed by multiplying a signal related to a hidden pilot signal by the interference canceled signal in the interference canceller 202 as shown in Equation 5 above. Here, the hidden pilot signal related term is a cyclic matrix whose element is the product of the IFFT matrix of the transmitter, the subcarrier assignment matrix of the transmitter, and the hidden pilot signal.

The channel value operator 206 estimates a channel value of the corresponding user by using the signal from which the preprocessor 204 has been canceled. For example, channel estimation of the channel value operator 206 is performed by dividing the signal from the preprocessor 204 by the square of the hidden pilot signal relation term, as shown in Equation (8). The domain converter 208 converts the channel value estimated by the channel value calculator 206 into a frequency domain and provides the signal to the signal detector 110.

Referring to FIG. 1 and FIG. 2, the transmission signal detection according to the present invention will be described below. First, the signal received through the antenna is converted into a time domain OFDM symbol from which the CP is removed through the RF receiver 102 and the CP controller 104. The time domain OFDM symbol is provided to the channel estimator 112.

Since there is no estimated transmission symbol block of the previous step in the case of the start step without the previous repetition step, in this case, the interference canceller 202 sets the estimated transmission symbol block value of the previous step to 0, that is, the time-domain OFDM provided. Bypass the symbol. In addition, the preprocessor 204 multiplies the time-domain OFDM symbol with the hidden pilot signal related term as shown in Equation 5, and the channel value operator 206 performs the preprocessing as shown in Equation 8. The channel value is estimated by dividing the value from processor 204 by the square of the hidden pilot signal relation term. The domain converter 208 converts the estimated channel value into a frequency domain and provides the signal to the signal detector 110.

The time domain OFDM symbol output from the CP remover 104 is converted into frequency domain signals via the FFT operator 106, and the subcarrier demapping unit 108 extracts symbols of subcarriers of user k. . The signal detector 110 removes the hidden pilot signal component from the subcarrier symbols of the user k using the estimated channel value as shown in Equation 13, and detects a transmission symbol according to the corresponding scheme. In this case, the signal detector 110 determines whether to proceed with the repetition step. That is, the signal detector 110 re-estimates a channel again using the detected transmission symbol block, and determines whether to redetect the transmission symbol block using the reestimated channel. For example, the signal detector 110 performs the repetition step until the maximum number of repetitions is satisfied, or the signal detector 110 performs the repetition step until the error rate is lowered below the threshold value. If it is determined to proceed with the repetition step, the signal detector 110 provides the detected transmission symbol block to the channel estimator 112, and if it is determined not to proceed with the repetition step, the signal detector 110 detects it. The decoded transmission symbol block to the decoder 114. The inverse encoder 114 inverse pre-codes the detected transmission symbol block, and the demodulator 116 demodulates the symbols according to a corresponding modulation scheme to restore the bit string.

3 is a flowchart illustrating a transmission signal detection procedure of a receiver in a broadband wireless communication system according to an exemplary embodiment of the present invention. In the following description, it is assumed that the transmission symbol detection target is user k.

Referring to FIG. 3, the receiver checks whether a signal is received from the transmitter in step 301.

인 디지털 신호로 변환한다. 그리고, 상기 수신단은 수신신호를 OFDM 심벌 단위로 분류하고, CP를 제거한다.When the signal is received, the receiver proceeds to step 303 and downconverts the received signal to a baseband signal, and the sampling frequency.

To digital signal. The receiver classifies the received signal into OFDM symbol units and removes the CP.

In step 305, the receiving end removes interference in the time-domain OFDM symbol by using a hidden pilot signal. Here, the interference means a data signal component of user k, a data signal of a user other than user k, and a hidden pilot signal component. For example, the interference cancellation in step 305 is performed by multiplying a received signal with a hidden pilot signal related term as in Equation 5 above. The term related to the hidden pilot signal is a cyclic matrix whose element is the product of the IFFT matrix of the transmitter, the subcarrier assignment matrix of the transmitter, and the hidden pilot signal of the user k.

After removing the interference, the receiver proceeds to step 307 to calculate the channel value of the user k, that is, estimate the channel value. For example, as shown in Equation 8, the receiving end is performed by dividing the interference canceled signal by the square of the hidden pilot signal related term in step 305.

After estimating the channel value, the receiver proceeds to step 309 and converts the estimated channel value into a frequency domain value.

In step 311, the receiving end converts the time-domain OFDM symbol into frequency-domain signals through an FFT operation and demaps the frequency-domain signals. In other words, the receiver recovers subcarrier symbols from the time-domain OFDM symbol and classifies signals of user k.

After classifying the signals of the user k, the receiver proceeds to step 313 to remove the hidden pilot signal from the received signal using the estimated channel value. For example, the receiver removes the hidden pilot signal component from the received signal as shown in Equation (13).

After removing the hidden pilot signal component, the receiver proceeds to step 315 to detect a transmission symbol block from the received signal using a corresponding detection technique. For example, the receiver detects a transmission symbol using the MMSE technique as shown in Equation (14).

After detecting the transmission symbol block, the receiver determines in step 317 whether to proceed with the repetition step. That is, the receiving end re-estimates the channel using the detected transmission symbol block, and determines whether to redetect the transmission symbol block using the re-estimated channel. For example, the receiving end performs the repeating step until the maximum number of repetitions is satisfied, or the repeating step is performed until the error rate is measured and lowered below the threshold.

If it is determined to proceed with the repetition step, the receiver proceeds to step 319 to remove the interference in the time-domain OFDM symbol by using the detected transmission symbol, and then returns to step 305. Here, the interference refers to the data signal component of user k. For example, the interference cancellation in step 319 is performed by subtracting the product of the previous repetition step and the detected transmission symbol of the previous repetition step from the received time-domain OFDM symbol.

On the other hand, if it is determined not to proceed with the repetition step, the receiver proceeds to step 321 to perform inverse pre-coding and demodulation to restore the bit string.

4 illustrates the performance of a detection technique in accordance with the present invention. 4 shows a graph of simulation results of measuring bit error rates (BERs) of a system for performing signal detection and a system not according to the present invention. In the simulation, the system parameters of the system according to the present invention and the conventional system not according to the present invention are shown in Table 1 below.

 System of the Invention  Conventional system Modulation method QPSK QPSK Number of data symbols per user 126 127 Number of data subcarriers per user 127 115 Pilot subcarriers per user 128 12 Null Subcarriers Per User One One Number of subcarriers used per user 128 128 Number of users 2 2 Channel characteristics i.i.d. 12-tap Exp. i.i.d. 12-tap Exp. CP length 12 12 Channel estimation Proposed method LS (Least Square) Detection method MMSE Maximum Likelihood (ML)

In FIG. 4, the horizontal axis represents bit energy to noise power (Eb / No), and the vertical axis represents a normalized transmission efficiency (NTE). And, in Figure 4, (a) and (c) is not performed the repetition step, (b) and (d) is a case of performing two repetitions, (a) and (b) is a pilot signal and When the power ratio of the data signal is 3: 7, (c) and (d) are cases where the power ratio of the pilot signal and the data signal is 7: 3. In the legend of each graph, the present invention / channel information and the conventional / channel information are assumed to know channel state information (CSI) accurately.

As shown in FIG. 4, the system to which the detection scheme according to the present invention is applied exhibits a higher data rate than the conventional system. In addition, it is confirmed that as the repetition step is performed, the increase rate of the transmission rate becomes larger.

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

1 is a block diagram of a receiving end in a broadband wireless communication system according to an embodiment of the present invention;

2 is a block diagram of a channel estimator in a broadband wireless communication system according to an embodiment of the present invention;

3 is a diagram illustrating a transmission signal detection procedure of a receiver in a broadband wireless communication system according to an embodiment of the present invention;

4 illustrates the performance of a detection technique in accordance with the present invention.

Claims (27)

A receiving end device for detecting a transmission signal of user k in a broadband wireless communication system, an estimator for estimating a channel value of the (n) -th repetition step by using the transmission symbol block and the hidden pilot signal detected in the (n-1) -th repetition step, A detector for detecting a transmission symbol block from the received signal using the channel value of the (n) th repetition step and providing the detected transmission symbol block to the estimator for the channel value of the (n + 1) th repetition step Apparatus comprising a. The method of claim 1, And the detector removes a hidden pilot signal component from a received signal using the channel value. The method of claim 2, The detector is characterized in that for removing the hidden pilot signal from the received signal as shown in the following equation,

Where

Is the i th received signal from which the hidden pilot signal component has been removed in the (n) th iteration of user k,

Is a matrix obtained by diagonalizing the channel frequency response of user k,

Is a matrix of the channel frequency response estimated at the nth iteration of user k,

Is the user's pre-encoder,

Is the i th transmit symbol block of user k,

Is the hidden pilot signal of user k,

Denotes the product of the hermitian, the fast fourier transform (FFT) matrix, and the white noise of the subcarrier allocation matrix. The method of claim 1, The estimator, A canceller for removing the data signal component of user k from the received signal using the transmission symbol block detected in the (n-1) th iteration step; A processor which removes the data signal component and the hidden pilot signal component of the user other than the user k from the output from the canceler using the hidden pilot signal; And an operator for estimating a channel value using the output from said processor. The method of claim 4, wherein The eliminator is characterized in that for removing the data signal component of the user k as shown in the following equation,

Where

Is an i th time-domain OFDM symbol whose line interference has been removed in the (n) th iteration of user k ',

Is the first column in the (n) th iteration of

Circulating matrix of size N × N, where

Is the product of k's IFFT matrix, subcarrier assignment matrix, precoding matrix,

Is the i th transmit symbol block of user k,

Is the i th transmit symbol block detected in the (n) th iteration of user k ',

Is the first column of user k '

Circular matrix of size N × (L + 1),

Is the channel vector of user k ',

Means white noise. The method of claim 4, wherein The processor is characterized in that for removing the data signal components and hidden pilot signal components of the user other than the user k, as shown in the following equation,

Where

Is the i-th time-domain OFDM symbol preprocessed in step (n) of user k ',

Is the first column of user k '

Circular matrix of size N × (L + 1),

Is the first column of user k '

Circulating matrix of size N × N, where

Is the product of the kFT's IFFT matrix, the subcarrier allocation matrix, and the pre-coding matrix,

Is the i-th time-domain OFDM symbol whose line interference has been removed in the (n) th iteration of user k ', i.e.

Is the i th transmit symbol block of user k,

Is the first column in the (n) th iteration of

Circulating matrix of size N × N, where

Is the i th transmit symbol block detected in the (n) th iteration of user k ',

Means white noise. The method of claim 6, remind

Is an apparatus characterized by satisfying the conditions as follows:

Where

Is the first column of user k '

Circular matrix of size N × (L + 1),

Is the product of the kFT's IFFT matrix, the subcarrier allocation matrix, the hidden pilot signal,

Is a column-wise cyclic matrix using the i th column of the product of the IFFT matrix, the subcarrier allocation matrix, and the pre-coding matrix of the user k ',

Means user index. The method of claim 4, wherein The calculator, characterized in that for estimating the channel value as shown in the following equation,

Where

Is the channel vector of user k ',

Is the i-th time-domain OFDM symbol preprocessed in step (n) of user k ', that is, the output of the processor,

Is the first column of user k '

A cyclic matrix of phosphorus size N × (L + 1). The method of claim 1, The detector is characterized in that for detecting the transmission symbol block according to the MMSE (Miminum Mean Square Error) technique. The method of claim 9, The detector is characterized in that for pre-decoding the transmission symbol block in a manner corresponding to the pre-coding of the detection and transmitting end, as shown in the following equation,

Where

Is the i th transmit symbol block detected in the (n) th iteration of user k,

Is the MMSE detection and inverse precoding matrix in the (n) th iteration of user k,

Is the i th received signal from which the hidden pilot signal component has been removed in the (n) th iteration of user k,

Is the user's pre-encoder,

Is the transmit power per user,

Is the number of symbols included in the symbol block,

Is a matrix of the channel frequency response estimated in the (n) th iteration of user k, wherein

Is the i th transmit symbol block of user k,

Is the hidden pilot signal of user k,

Denotes the product of the hermit of the subcarrier allocation matrix, the FFT matrix, and the white noise. The method of claim 10, The detector determines the progress of the repetition step and, if it is determined to proceed with the repetition step, provides the detected transmission symbol block to the estimator. Apparatus characterized in that provided by. The method of claim 11, The repeating step, characterized in that proceeds until the maximum number of repetitions is satisfied. The method of claim 1, A radio frequency (RF) receiver for sampling a signal received through an antenna and converting the signal into a digital signal; A CP canceller for classifying the digital signal into orthogonal frequency division multiplexing (OFDM) symbol units to remove a cyclic prefix (CP) and providing the estimator and the FFT operator; And an FFT operator for converting time-domain OFDM symbols into frequency-domain signals through an FFT operation. A transmission signal detection method of user k in a broadband wireless communication system, estimating a channel value of the (n) th repetition step by using the transmission symbol block and the hidden pilot signal detected in the (n-1) th repetition step, And detecting a transmission symbol block from the received signal using the channel value of the (n) -th iteration step. The method of claim 14, And removing the hidden pilot signal component from the received signal using the channel value. The method of claim 15, Removing the hidden pilot signal from the received signal, characterized in that the method is performed as follows:

Where

Is the i th received signal from which the hidden pilot signal component has been removed in the (n) th iteration of user k,

Is a matrix obtained by diagonalizing the channel frequency response of user k,

Is a matrix of the channel frequency response estimated at the nth iteration of user k,

Is the user's pre-encoder,

Is the i th transmit symbol block of user k,

Is the hidden pilot signal of user k,

Denotes the product of the hermitian, the fast fourier transform (FFT) matrix, and the white noise of the subcarrier allocation matrix. The method of claim 14, Estimating the channel value, Removing the data signal component of user k from the received signal by using the transmission symbol block detected in the (n-1) th iteration; Removing the data signal component and the hidden pilot signal component of the user other than the user k from the signal from which the data signal component of the user k is removed using the hidden pilot signal; Estimating a channel value using the received signal from which the user k data signal component, the user k other than the user k data signal component, and the hidden pilot signal component are removed. The method of claim 17, The method of removing the data signal component of the user k is performed as follows.

Where

Is an i th time-domain OFDM symbol whose line interference has been removed in the (n) th iteration of user k ',

Is the first column in the (n) th iteration of

Circulating matrix of size N × N, where

Is the product of k's IFFT matrix, subcarrier assignment matrix, precoding matrix,

Is the i th transmit symbol block of user k,

Is the i th transmit symbol block detected in the (n) th iteration of user k ',

Is the first column of user k '

Circular matrix of size N × (L + 1),

Is the channel vector of user k ',

Means white noise. The method of claim 17, Removing the data signal component and the hidden pilot signal component of the user other than the user k, characterized in that performed as follows:

Where

Is the i-th time-domain OFDM symbol preprocessed in step (n) of user k ',

Is the first column of user k '

Circular matrix of size N × (L + 1),

Is the first column of user k '

Circulating matrix of size N × N, where

Is the product of the kFT's IFFT matrix, the subcarrier allocation matrix, and the pre-coding matrix,

Is the i-th time-domain OFDM symbol whose line interference has been removed in the (n) th iteration of user k ', i.e.

Is the i th transmit symbol block of user k,

Is the first column in the (n) th iteration of

Circulating matrix of size N × N, where

Is the i th transmit symbol block detected in the (n) th iteration of user k ',

Means white noise. The method of claim 19, remind

Is characterized by satisfying the same conditions as the following formula,

Where

Is the first column of user k '

Circular matrix of size N × (L + 1),

Is the product of the kFT's IFFT matrix, the subcarrier allocation matrix, the hidden pilot signal,

Is a column-wise cyclic matrix using the i th column of the product of the IFFT matrix, the subcarrier allocation matrix, and the pre-coding matrix of the user k ',

Means user index. The method of claim 19, The channel value is estimated by the following formula,

Where

Is the channel vector of user k ',

Is the i-th time-domain OFDM symbol preprocessed in step (n) of user k ', that is, the output of the processor,

Is the first column of user k '

A cyclic matrix of phosphorus size N × (L + 1). The method of claim 14, The transmission symbol block detection is performed according to a MMSE technique. The method of claim 22, And inversely pre-coding the detected transmission symbol block in a manner corresponding to pre-coding at the transmitting end. The method of claim 23, wherein The transmission symbol block detection and inverse pre-coding are performed as follows.

Where

Is the i th transmit symbol block detected in the (n) th iteration of user k,

Is the MMSE detection and inverse precoding matrix in the (n) th iteration of user k,

Is the i th received signal from which the hidden pilot signal component has been removed in the (n) th iteration of user k,

Is the user's pre-encoder,

Is the transmit power per user,

Is the number of symbols included in the symbol block,

Is a matrix of the channel frequency response estimated in the (n) th iteration of user k, wherein

Is the i th transmit symbol block of user k,

Is the hidden pilot signal of user k,

Denotes the product of the hermit of the subcarrier allocation matrix, the FFT matrix, and the white noise. The method of claim 24, Determining the progress of the repetition step and re-estimating a channel value using the detected transmission symbol block if it is determined to proceed with the repetition step; If it is determined not to proceed with the repetition step, further comprising inversely pre-coding the detected transmission symbol block. The method of claim 25, The repeating step, characterized in that proceeds until the maximum number of repetitions is satisfied. The method of claim 14, Sampling the signal received through the antenna and converting the signal into a digital signal; Classifying the digital signal into orthogonal frequency division multiplexing (OFDM) symbol units to remove a cyclic prefix (CP); And converting the time-domain OFDM symbol into frequency-domain signals through an FFT operation.

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