KR101511257B1 - Spatial Modulation Method using Quaternary Quasi-Orthogonal Sequence for High Data Transmission - Google Patents

Abstract

The present invention provides a method for modulating a new quaternary quasi-orthogonal sequence space using a quaternary quasi-orthogonal sequence. According to an embodiment of the present invention, the method for modulating a new quaternary quasi-orthogonal sequence space includes increasing the number of bits used to select antennas by making use of quaternary quasi-orthogonal sequence. In this case, the transmission ratio may be increased by increasing the number of transmissible bits if the same transmission antenna and modulation are in use. In addition, lower differential modulation orders can be used when the same bits are transmitted on the same transmission antenna, which would lower the bit error rate and raise the overall performance.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spatial modulation method using Quaternary Quasi-Orthogonal Sequence,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to spatial modulation, and more particularly, to a spatial modulation method in which a data rate is increased for high capacity transmission.

2. Description of the Related Art In a wireless communication environment, a MIMO (Multiple-Input Multiple-Output) system that can increase a transmission rate by using a limited frequency resource and a transmission power has attracted great interest as the demand for high-speed data transmission increases. However, in the MIMO system, as the number of antennas increases, there is a disadvantage that the decoding complexity and the interference between the channels are drastically increased.

Recently, much research has been conducted on SM (Spatial Modulation) techniques that can reduce the complexity and inter-channel interference at the receiving end. The SM scheme divides the input data into a data signal and an antenna index signal. The data signal is symbol-modulated and transmitted through one antenna selected through an antenna index signal, thereby reducing interference between the demodulation complexity and the channel of the receiver.

A conventional SM scheme using N _t transmit antennas and using N _r receive antennas is shown in FIG.

인 입력 비트 벡터

를

개의 비트와

개의 비트로 분리한다. 여기서 M은 변조차수이며

는 전치 행렬이다. 분리된 비트 벡터 가운데 m-i개의 비트를 이용하여 N_t개의 송신안테나 중 전송할 안테나를 선택하고, i개의 비트는 심볼로 변조되어 앞에서 선택된 안테나로 변조된 심볼을 전송된다.In the conventional SM technique,

In input bit vector

To

Bit and

Lt; / RTI > bits. Where M is the modulation order

Is a transpose matrix. Among the N _t transmit antennas, the antenna to be transmitted is selected using mi bits among the separated bit vectors, i bits are modulated into symbols, and symbols modulated with the selected antenna are transmitted.

를 만족해야 한다. 이러한 SM 기법의 송신 신호 벡터는

로 표현할 수 있다. 여기서, j는 전송을 위해 선택된 송신 안테나 인덱스이고 q는 M-ary 성상의 q번째 심볼이며, 송신 신호 벡터

의 길이는 N_t 이다.Of course, each case of selecting a transmit antenna must be assigned to a bit

. The transmit signal vector of this SM scheme is

. Where j is the transmit antenna index selected for transmission, q is the qth symbol of the M-ary constellation, and the transmit signal vector

Lt; / RTI _> is _Nt .

를 통과하여 N_r개의 수신 안테나에 수신된다. 수신된 신호는 아래의 수학식 1과 같이 표현할 수 있다.Next, the transmission symbols generated through the SM scheme are transmitted through j (j = 1, 2, ..., N _t )

And is received by N _r receive antennas. The received signal can be expressed by Equation (1) below.

은 잡음 벡터로 수신기의 i.i.d AWGN(Additive White Gaussian Noise) 샘플값이며 실수부와 허수부가 각각 N₀/2의 양방향 전력밀도를 갖는다. 또한,

는 채널 백터로써 복소 페이딩값으로 실수부와 허수부가 각각 평균이 0이고 분산이 0.5인 i.i.d 가우시안(Gaussian) 분포를 갖는다.here,

Has a two-way power density and iid AWGN (Additive White Gaussian Noise) sample of the receiver as noise vector value a real part and an imaginary part N _0/2, respectively. Also,

Is a channel vector with a complex fading value with a real part and an imaginary part with an iid Gaussian distribution with an average of 0 and a variance of 0.5.

The equation (1), which is a signal received by the SM technique of FIG. 1, is expressed in a matrix form and expressed by the following equation (2).

Finally, demodulation uses the ML decoding method, which is shown in Equation 3 below.

,

이다. 그리고,

는

와

에 대한

의 조건부 PDF이고, h_j 는

의 j번째 열 벡터이며,

와

는 각각 프로베니우스 평균(Frobenius norm)과 허미션(Hermitian)이다.here,

,

to be. And,

The

Wow

For

, H _j is the conditional PDF of

Th row vector of < RTI ID = 0.0 >

Wow

Are the Frobenius norm and the Hermitian respectively.

In the conventional SM scheme, since only one selected antenna is used in view of the antenna index signal information without using all the transmit antennas, there is a disadvantage in terms of data rate, which will be further described with reference to FIG.

FIG. 2 is a diagram showing a spatial modulation matrix of a conventional spatial modulation technique. In the case of the existing spatial modulation scheme, the identity matrix is used as the spatial modulation matrix, and the column vector of the identity matrix is selected as the transmission antenna selection. Therefore, the number of column vectors of the unit matrix is the number of antennas that can be selected.

Since the number of rows and the number of columns are the same in the existing spatial modulation technique, the transmission rate does not change. The reception signal of the spatial modulation technique in which the unit matrix is connected can be expressed by Equation (4) below.

As described above, since the conventional SM scheme transmits the modulated symbols using only one transmission antenna without using all the transmission antennas, the transmission rate is relatively low.

In order to solve this problem, if the modulation order is increased in order to increase the transmission rate, the bit error rate becomes high and the performance degradation occurs. In order to increase the transmission rate without degrading performance, a method of increasing the number of transmission antennas can be assumed. However, due to demodulation complexity and physical limitations, increasing the number of transmit antennas is not practical.

In the band of several hundred Mbps to several Gbps, which is the frequency band used in the current wireless communication, there are many restrictions on increasing the number of transmitting antennas. Therefore, a search for a method of maximizing a transmission rate with a minimum number of antennas is sought.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-described problems and to provide a method and apparatus for improving a low transmission rate of a conventional SM scheme, in which a high capacity transmission is possible using a quaternary quasi-orthogonal sequence Modulation method.

According to an aspect of the present invention, there is provided a spatial modulation method including: modulating a signal; And transmitting a modulated signal in the modulation step using a transmission antenna selected as a spatial modulation matrix among a plurality of transmission antennas, wherein the number of rows constituting the spatial modulation matrix is determined by a number of transmission antennas , And the number of columns constituting the spatial modulation matrix is larger than the number of transmission antennas.

일 수 있다.And, the number of the transmission antennas is N _t, the number of columns

Lt; / RTI >

In addition, the columns of the spatial modulation matrix may be Orthogonal Sequences (Q-QOS).

The columns of the spatial modulation matrix may be Quasi-Orthogonal Sequences.

In addition, the columns of the spatial modulation matrix may be Quaternary Quasi-Orthogonal Sequences.

The size of the quaternary quasi-orthogonal sequence may be N, and the number of the quaternary quasi-orthogonal sequences may be N ² .

Also, the quaternary quasi-orthogonal sequence may be composed of a sequence using at least one of 1, -1, j, and -j.

Meanwhile, according to another embodiment of the present invention, a transmitter includes: a plurality of transmission antennas; A modulator for modulating the signal; And a spatial modulator for transmitting a modulated signal from the modulator using a transmit antenna selected as a spatial modulation matrix among the transmit antennas, wherein the number of rows constituting the spatial modulation matrix is determined by a number of transmit antennas , And the number of columns constituting the spatial modulation matrix is larger than the number of transmission antennas.

일 수 있다.And, the number of the transmission antennas is N _t, the number of columns

Lt; / RTI >

In addition, the columns of the spatial modulation matrix may be Quaternary Quasi-Orthogonal Sequences.

As described above, according to the embodiments of the present invention, it is possible to provide / analyze various types of SM-based techniques through the structural modification of the spatial modulation matrix in the spatial modulation scheme. In addition, the spatial modulation matrix form can be modified to control the transmission rate used for antenna selection.

In addition, according to embodiments of the present invention, the number of rows is N (N) using a Quaternary Quasi-Orthogonal Matrix (Q-QOM) composed of a Quaternary Quasi-Orthogonal Sequence so to create a N ² columns when clear up, and the number of N antenna selection for increased ^{to two} from the N. As a result, the transmission rate used for antenna selection is doubled.

FIG. 1 illustrates a conventional spatial modulation scheme,
2 is a diagram illustrating a conventional spatial modulation scheme using a spatial modulation matrix as an identity matrix,
FIG. 3 is a diagram illustrating a method of spatial modulation according to an embodiment of the present invention,
4 is a diagram illustrating a masking sequence,
5 is a diagram illustrating a Q-QOS configured when N _t = 4,
6 is a diagram illustrating a spatial modulation method capable of increasing a data rate using a quaternary quadrature sequence as a space modulation matrix.

Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 3 is a diagram provided for explanation of a spatial modulation method according to an embodiment of the present invention.

In the transmitter 100 shown in FIG. 3, the spatial modulator 120 space-modulates the signal modulated by the modulator 110. That is, the spatial modulator 120 is a means for selecting a transmission antenna to transmit the modulated signal. The transmit antenna selection is performed in a manner of selecting one of the columns constituting the spatial modulation matrix.

The signal received by the receiver 200 in FIG. 3 can be expressed by Equation (5) below.

만 만족하면 사용이 가능하다. 한편, 열의 개수에 따라 송신 안테나를 선택하는 부분의 비트 할당량을 조절하여 전송율을 높이거나 낮출 수 있다.The number of rows in the spatial modulation matrix is equal to the number of transmit antennas, but the number of columns depends on the matrix type

If you are satisfied, you can use it. On the other hand, it is possible to increase or decrease a transmission rate by adjusting a bit allocation amount of a portion for selecting a transmission antenna according to the number of columns.

The spatial modulation method according to an embodiment of the present invention constructs a spatial modulation matrix (SMM) using a Quaternary Quasi-Orthogonal Sequence (Q-QOS) to increase a transmission rate.

Accordingly, the spatial modulation matrix used in the spatial modulation method according to the embodiment of the present invention has more column vectors than the spatial modulation matrix used in the existing spatial modulation scheme, and thus, more bits are allocated to the antenna selection It is possible to increase the transmission rate.

의 성분으로 이루어진 시퀀스이며, 시퀀스의 크기가 N일 때 N²개의 시퀀스를 만들 수 있다. Q-QOS의 특징으로 각 시퀀스의 상관관계는

를 만족한다. 여기서,

는 Q-QOS의 u번째와 v번째 시퀀스를 나타내며,

는

시퀀스 간의 상관 관계이다.Q-QOS

, And N ² sequences can be generated when the size of the sequence is N. FIG. The Q-QOS is characterized by the correlation of each sequence

. here,

Denotes the u-th and v-th sequences of the Q-QOS,

The

Correlation between sequences.

In order to generate the Q-QOS, the Masking Sequence must first be found. A masking sequence usable in an embodiment of the present invention is illustrated in FIG.

All Q-QOS is composed of a set of N F _n, each set is made through the equation (6) below.

이며 c_l은 l번째 마스킹 시퀀스이다. 그리고, W_d는 크기가 d인 월시 코드(Walsh Code)이며,

는 덧셈 후 4로 나눈 나머지를 나타낸다.here,

And c _l is the lth masking sequence. W _d is a Walsh code having a size d,

Represents the remainder after division by 4.

로 바꿔주면 최종 Q-QOS가 된다. 여기서, e는 시퀀스 성분의 값이다. 이렇게, 최종적으로 만들어진 Q-QOS는 N_t=4일 경우, 도 5에 나타난 바와 같다.The components of each sequence calculated by Equation (6)

To Q-QOS. Here, e is the value of the sequence component. The final Q-QOS is as shown in FIG. 5 when N _t = 4.

In this way, if the size of the sequence is N, N ² Q-QOS can be created.

FIG. 6 illustrates a Quaternary Quasi-Orthogonal Sequence Spatial Modulation (Q-QOS-SM) method using a Q-QOM composed of Q-QOS as a spatial modulation matrix.

The existing SM scheme and spatial modulation matrix are different structures. In the case of the Q-QOS-SM method shown in FIG. 6, the received signal can be expressed by Equation (7) below.

The equation (7) can be expressed in a matrix form as shown in Equation (8) below.

를 사용하는 본 발명의 실시예에 따른 Q-QOS-SM 방법은 송신을 위해 사용하는 물리적인 안테나 개수는 기존의 SM 기법과 동일하지만 전송을 위해 사용되는 안테나를 결정하는 열의 개수가

으로 증가하여 논리적으로

개의 안테나를 갖는 것으로 해석할 수 있으며, 결론적으로 더 많은 안테나를 선택하는 방법을 통해 송신 안테나 선택에 더 많은 비트를 할당할 수 있게 된다.Quaternary quasi orthogonal matrix

The Q-QOS-SM method according to the embodiment of the present invention uses the same number of physical antennas used for transmission as in the conventional SM scheme, but the number of columns for determining the antennas used for transmission is

To logically

As a result, it is possible to allocate more bits to the transmission antenna selection by selecting more antennas.

의 비트를 할당할 수 있다.As a result, the transmission rate can be increased compared to the conventional SM technique. As compared with the increased transmission rate, the conventional SM scheme can allocate as many bits for selecting a transmission antenna, but the Q-QOS-SM scheme according to the embodiment of the present invention

Lt; / RTI >

비트를 전송할 수 있지만, 본 발명의 실시예에 따른 Q-QOS-SM 방법은

의 비트를 전송할 수 있다.That is, the bits allocated to the antenna selection can be allocated twice as much as the conventional SM scheme. As a result, the existing SM technique

Bit, but the Q-QOS-SM method according to an embodiment of the present invention

Lt; / RTI >

개에서 N_t개로 줄일 수 있으며, 동일한 안테나 수로 전송할 경우 변조 차수를 M에서 M/N_t로 줄일 수 있어 심볼 변조에 사용되는 비트의 에러율을 줄일 수 있으므로, 기존의 SM 기법과 비교하여 평균 에러율을 줄일 수 있는 효과적이다. Therefore, the Q-QOS-SM method according to the embodiment of the present invention can reduce the number of antennas required when transmitting the same data rate

To N _t , and the modulation order can be reduced from M to M / N _t when transmitting with the same number of antennas, thereby reducing the error rate of the bits used for symbol modulation. Therefore, the average error rate It is effective to reduce.

를 C라는 새로운 채널 행렬로 해석할 수 있으며, 아래의 수학식 9와 같이 표현할 수 있다.In the case of the Q-QOS-SM method according to the embodiment of the present invention, the received signal is expressed by the equation

Can be interpreted as a new channel matrix C, and can be expressed as Equation (9) below.

The ML decoding equation shown in Equation (3) can be equally applied to the Q-QOS-SM method according to the embodiment of the present invention, which can be summarized as Equation (10) below.

Up to now, the Q-QOS-SM method has been described in detail with a preferred embodiment.

The Q-QOS-SM method was a quaternary orthogonal sequence of columns of spatial modulation matrices. The technical idea of the present invention is that the QOS-SM method in which the columns of the spatial modulation matrix are quasi-orthogonal sequences, as well as the OS-SM method in which the columns of the spatial modulation matrix are orthogonal sequences Of course.

일 필요는 없다. 송신 안테나들의 개수(N_t) 보다 많은 것으로 족하다.In this case, the number of columns constituting the spatial modulation matrix is

. Is greater than the number of transmit antennas (N _t ).

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention.

100: Transmitter
110: modulator
120: spatial modulator
200: receiver

Claims (10)

Modulating the signal;
Transmitting a modulated signal in the modulation step using a transmission antenna selected as a space modulation matrix among a plurality of transmission antennas,
The number of rows constituting the spatial modulation matrix is equal to the number of transmission antennas,
Wherein the number of columns constituting the spatial modulation matrix is greater than the number of transmit antennas.
The method according to claim 1,
The number of the transmission antennas is N _t,
The number of columns

And the spatial modulation method.
The method according to claim 1,
The columns of the spatial modulation matrix,
Wherein the orthogonal sequences are orthogonal sequences.
The method of claim 3,
The columns of the spatial modulation matrix,
Wherein the quasi-orthogonal sequences are quasi-orthogonal sequences.
5. The method of claim 4,
The columns of the spatial modulation matrix,
Wherein the quadrature quasi-orthogonal sequences are quaternary quasi-orthogonal sequences.
6. The method of claim 5,
The size of the quaternary quasi-orthogonal sequence is N,
Wherein the number of the quaternary quasi-orthogonal sequences is N ² .
6. The method of claim 5,
Wherein the quaternary quasi-orthogonal sequence comprises a sequence using at least one of 1, -1, j, and -j.
A plurality of transmit antennas;
A modulator for modulating the signal; And
And a spatial modulator for transmitting a modulated signal from the modulator using a transmission antenna selected as a spatial modulation matrix among the transmission antennas,
The number of rows constituting the spatial modulation matrix is equal to the number of transmission antennas,
Wherein the number of columns constituting the spatial modulation matrix is greater than the number of transmit antennas.
9. The method of claim 8,
The number of the transmission antennas is N _t,
The number of columns

≪ / RTI >
9. The method of claim 8,
The columns of the spatial modulation matrix,
Wherein the quaternary quasi-orthogonal sequences are quaternary quasi-orthogonal sequences.

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