KR101066105B1 - Method and System for Transmitting Signal in Spatial Multiplexing System by Using Multidimensional Rotated Modulation - Google Patents

Abstract

The present invention relates to a method and system for transmitting a signal in a spatial multiplexing system using a multidimensional rotation modulation scheme.

A method for transmitting a signal in a spatial multiplexing system using a multidimensional rotation modulation scheme, the method comprising: (a) modulating an uncoded information bit; (b) storing the modulated complex symbol vector to produce a multidimensional integer component vector; (c) signal processing the multidimensional integer component vector to generate a complex symbol vector; And (d) modulating the complex symbol vector to transmit a signal. The present invention relates to a method and system for transmitting a signal in a spatial multiplexing system using a multi-dimensional rotation modulation scheme.

According to the present invention, it is possible to smoothly transmit signals using diversity of signal spaces and to guarantee various quality of service by only processing signals in a spatial multiplexing system. According to a preferred embodiment of the present invention, even if any component of the signal point undergoes severe fading in the process of space and time, it can be separated in the detection process, thereby making the signal point robust to the fading channel. It works. In addition, it is possible to ensure the quality of service according to the service level of the terminal without additional bandwidth and power consumption.

Spatial Multiplexing System, Multi-Dimensional Rotation Modulation, Multiple Antennas, QAM

Description

Method and System for Transmitting Signal in Spatial Multiplexing System by Using Multidimensional Rotated Modulation

1 is a block diagram schematically illustrating a system for transmitting a signal in a spatial multiplexing system using a multi-dimensional rotation modulation scheme according to a preferred embodiment of the present invention;

2 is a graph illustrating bit error rate performance of a system for transmitting signals in a spatial multiplexing system using a multi-dimensional rotation modulation scheme according to a preferred embodiment of the present invention,

3 is a graph illustrating bit error rate performance of a system for transmitting a signal in a spatial multiplexing system using a multi-dimensional rotation modulation scheme according to a preferred embodiment of the present invention compared to a scheme using two receiving antennas;

4 is a graph illustrating bit error rate performance of a system for transmitting signals in a spatial multiplexing system using a multi-dimensional rotation modulation scheme according to an orthogonal design based Alamouti scheme.

The present invention relates to a method and a system for transmitting a signal in a spatial multiplexing system using a multi-dimensional rotation modulation scheme, and more particularly, to information bits of a signal when transmitting a signal in a spatial multiplexing system using a transmitting antenna and a receiving antenna. By modulating the modulated complex vector, storing the modulated complex symbol vector to generate a multidimensional integer component vector, and processing the multidimensional integer component vector to generate a complex symbol vector, thereby minimizing the possibility of bilateral error (PEP). The present invention relates to a signal transmission method and system that can improve bandwidth efficiency without increasing the number.

Multiple-Input Multiple-Output (MIMO) systems have been recognized as one of the solutions to improve frequency efficiency and transmission quality in future broadband wireless access systems. For example, a transmission diversity scheme for improving transmission quality while using a plurality of antennas and a spatial multiplexing scheme capable of obtaining high spectral gain (bits / sec / Hz) are provided.

In the case of the transmit diversity method, although the transmission quality can be improved by increasing the diversity order, there is a problem that the transmission rate is basically limited to 1 symbol / sec / Hz. On the other hand, the spatial multiplexing method has a lower diversity order than the transmit diversity method, but can increase the transmission capacity in proportion to the number of antennas.

At present, as the demand for high data rate is rapidly increased in next generation wireless systems, spatial multiplexing methods such as V-BLAST (Vertical Bell-Labs Layered Space-Time) have been widely used. As described above, the spatial multiplexing method has an advantage that a high spectral gain can be obtained by increasing the number of transmitting antennas. In addition, to improve the transmission quality, the number of receiving antennas may be increased to obtain diversity gain or to obtain coding gain using channel coding. However, in reality, it is difficult to increase the number of receiving antennas in consideration of the size and power of the terminal. In addition, when using channel coding, there is a problem in that it is not easy to satisfy various code rates required in each channel environment.

On the other hand, in the conventional modulation diversity scheme, when a system using a single transmit / receive antenna takes a certain form of rotation on a symbol constellation and interleaves between components of a symbol, it shows excellent performance in a wireless channel.

Therefore, by considering the concept of modulation diversity in a spatial multiplexing system, there is a need for a method and system that can improve performance by only signal processing without depending on the number of antennas and without sacrificing additional power or bandwidth.

In order to solve the above problems, the present invention, when transmitting a signal in a spatial multiplexing system using a transmitting antenna and a receiving antenna, modulates the information bits of the signal, and stores the modulated complex symbol vector to generate a multidimensional integer component vector By generating a complex symbol vector by processing a multi-dimensional integer component vector, a signal transmission method and system that can improve bandwidth efficiency without increasing the number of antennas by minimizing the probability of pairwise error (PEP) It aims to provide.

In order to achieve the above object, the present invention provides a method for transmitting a signal in a spatial multiplexing system, comprising: (a) modulating an uncoded information bit; (b) storing the modulated complex symbol vector to produce a multidimensional integer component vector; (c) signal processing the multidimensional integer component vector to generate a complex symbol vector; And (d) modulating the complex symbol vector to transmit a signal.

In addition, according to another object of the present invention, a system for transmitting a signal in a spatial multiplexing system using a multi-dimensional rotation modulation scheme, comprising: a gray mapper block for modulating uncoded bits; A buffer for receiving and storing the modulated complex symbol vector from the gray mapper block to generate a multidimensional integer component vector; And a multidimensional rotation modulation block configured to receive and signal multidimensional integer component vectors from the buffer to generate a complex symbol vector, and to transmit a signal in a spatial multiplexing system using a multidimensional rotation modulation scheme. It features.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. First of all, in adding reference numerals to the components of each drawing, it should be noted that the same reference numerals have the same reference numerals as much as possible even if displayed on different drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

The present invention basically performs a symbol transmission process through a spatial multiplexing method using M _T transmit antennas and M _k receive antennas, and additionally combines multidimensional modulation schemes to increase spectral gain, even when channel conditions are not good. It is a way to provide a service.

1 is a block diagram schematically illustrating a system for transmitting a signal in a spatial multiplexing system using a multi-dimensional rotation modulation scheme according to an exemplary embodiment of the present invention.

As shown in FIG. 1, a system for transmitting signals in a spatial multiplexing system using a multi-dimensional rotation modulation scheme according to a preferred embodiment of the present invention includes a gray mapper block 100, a buffer 102, and a multi-dimensional system. And a multidimensional rotated QAM mapper block 104, a modulator 106, an antenna 108, and the like.

The gray mapper block 100 according to the preferred embodiment of the present invention performs a modulation process on uncoded bits, and the buffer 102 stores a modulated complex symbol vector received from the gray mapper block 100 to multi-dimensional integers. Create a component vector. The multi-dimensional rotation modulation mapper block 104 generates a complex symbol vector by processing the multi-dimensional integer component vector received from the buffer 102, and the modulator 106 receives the complex number received from the multi-dimensional rotation modulation mapper block 104. The symbol vector is modulated into a signal in a form that the antenna 108 can receive. On the other hand, the antenna 108 emits a signal received from the modulator 106 into the radio wave space.

In the gray mapper block 100 according to the preferred embodiment of the present invention, in order to obtain a signal vector of a multi-dimensional constellation rotated from the input signal, the input signal bits are 2 ^{M in} units of M bits. Gray mapping is performed on one of the quadrature amplitude modulation (QAM) symbols. A complex symbol vector of the form n / 2 × 1 is transformed into an n × 1 multidimensional symbol vector u in the buffer 102.

는 n × n 회전 행렬 M 을 u 에 취함으로써 얻어지고(즉,

= M·u), 수학식 1과 같이 실수부와 허수부로 구성된다.
Here, the dimension coefficient n represents a multiple of 2M _T , and u = [u ₁ , u ₂ , ..., u _n ] two-dimensional n / 2 (u _i + ju _{i + n / 2} ) in the ^T vector Represents a QAM symbol, and u _i represents a multidimensional integer component vector that is an integer component corresponding to the QAM symbol. On the other hand, the signal point of the rotated constellation

Is obtained by taking n × n rotation matrix M in u (i.e.

= M · u) and a real part and an imaginary part as shown in equation (1).

In addition, a complex signal vector x _t that is simultaneously transmitted at time t using M _T transmit antennas is defined as in Equation 2.

Where t = 1, 2, ..., n / 2M _T.

On the other hand, a transmission matrix X having a size M _T × (n / 2M _T ) obtained by aligning a transmitted signal sequence is defined as in Equation (3).

The symbols in the p th row of the transmission matrix X are generalized such that the average power of the symbols transmitted at each time is transmitted at the same time through the multiple antennas in each symbol period and is transmitted at each antenna. M _R × (n / 2M _T ) received signal matrix received by matching filtering and sampling for n / 2M _T time R = [ R ₁ | R ₂ | ... | R _{n / 2MT} ] may be expressed as Equation 4 in the form of a multidimensional vector.

Where D denotes diag ( H _i ) _{i = 1, 2, ..., n / 2MT} = diag ( H ₁ , H ₂ , ..., H _{n / 2MT} ) and w denotes [ w ₁ w ₂ ... w _{n / 2MT} ] ^T , r denotes vec ( R ) ¹ , x denotes vec ( X ), and E _S denotes the average energy per transmission symbol. In other words, E _S represents the average of the total energy transmitted at time t.

In the preferred embodiment of the present invention, since the fast fading channel model is assumed, the multiple input / output (MIMO) channel matrix H _t has a random and independent value for each t time. In addition, w _t is an additive complex white Gaussian noise vector.

에 가까운 확률을 나타내는 쌍방 에러 발생 가능성 P(x ->

) 는 수학식 5와 같이 근사화 된다.
On the other hand, assuming that the receiver is fully aware of the channel state information (CSI: Channel State Information), in the preferred embodiment of the present invention, the process of detecting the rotation matrix of x is performed using the reception vector r. Receive signal point r is the error signal point when transmit vector x is transmitted

Probability of two-sided error, indicating a probability close to P ( x- >

) Is approximated as in Equation 5.

사이의 해밍 디스턴스(Hamming Distance)를 나타낸다. Where L is u and

Hamming distance between them.

_k

_k, k = 1, 2, ... , n } | 에 의해 결정되므로, 에러율을 최소화하기 위해서는 먼저

에 대한 L 값을 최대화해야 된다. 따라서, 본 발명의 바람직한 실시예에 따른 다차원 회전 변조 방식은 시간과 공간에 대해서 성상도에 회전을 취해 줌으로써 모든 두 신호점 간에 해밍 디스턴스 L을 최대화하게 된다. 그러므로, 수학식 5에서 다차원 회전 변조 방식을 사용하여 신호점 집합에 있는 모든 가능한 두 신호점들에 전체 다이버시티 차수가 최대 다이버시티 차수를 가지도록 할 때, 비트 오류율(BER : Bit Error Rate) 성능 곡선의 기울기는 점진적으로 -L·(nM_R / M_T) 가 된다. 따라서, 동시에 n 값을 증가시킴에 따라 AWGN 채널에 근접한 성능을 얻게 된다. 또한, 충분한 다이버시티 차수가 보장됐을 때 성상도의 모든 두 신호점 간에 최소곱 거리(MPD : Minimum Product Distance)인 d_p,min =

을 최대화시켜야 하므로, 최적의 회전 행렬은 수학식 6과 같이 공식화된다.
In the fast fading channel, the following design conditions may be considered. When the signal-to-noise ratio value is high, the slope of the performance curve is Hamming Distance L = | {k |

_k

_k , k = 1, 2, ..., n} | Is determined by

We need to maximize the value of L for. Accordingly, the multi-dimensional rotation modulation scheme according to the preferred embodiment of the present invention maximizes the hamming distance L between all two signal points by rotating the constellation in time and space. Therefore, when the total diversity order has the maximum diversity order at all two possible signal points in the set of signal points using the multi-dimensional rotation modulation scheme in Equation 5, bit error rate (BER) performance The slope of the curve gradually becomes -L · (nM _R / M _T ). Thus, increasing the value of n at the same time yields performance close to the AWGN channel. In addition, d _{p, min} = the minimum product distance (MPD) between all two signal points in the constellation when sufficient diversity order is ensured.

Since it is necessary to maximize, the optimal rotation matrix is formulated as

Here, det (·) represents a determinant operation.

인 조건에 대해서는 주어진 회전 행렬에 대한 제약 조건의 수가 커지기 때문에 회전 행렬을 찾는 최적화 문제는 어려워진다. 또한, 다중 안테나를 사용하는 시스템의 경우 전송 신호 벡터의 차원 계수 n 이 4보다 크므로, 본 발명의 바람직한 실시예에서는 수학식 6을 만족하면서 더 나은 성능을 보이게 하는 수학식 7의 행렬을 고려한다.
In other words, in terms of modulation diversity, the optimal rotation matrix has the maximum diversity and is a matrix that maximizes d _{p, min} . However,

For the sine condition, the optimization problem of finding the rotation matrix becomes difficult because the number of constraints for a given rotation matrix increases. In addition, in the case of a system using multiple antennas, since the dimensional coefficient n of the transmission signal vector is larger than 4, in the preferred embodiment of the present invention, the matrix of Equation 7 that satisfies Equation 6 and shows better performance is considered. .

에 대해서 각 요소는 수학식 8과 같이 나타낼 수 있다.
here,

For each element can be expressed as Equation (8).

By using the optimal rotation matrix shown in Equation 7, diversity gain and coding gain can be obtained by simple signal processing by linear matrix transformation according to the dimension coefficient n, and various quality of service (QoS) requirements are required. It can be adaptively applied to the wireless fading channel environment.

FIG. 2 is a graph illustrating bit error rate performance of a system for transmitting a signal in a spatial multiplexing system using a multi-dimensional rotation modulation scheme according to a preferred embodiment of the present invention.

FIG. 2 compares the performance of the scheme according to the preferred embodiment of the present invention with the case where the spectral efficiencies are 4, 8, and 12 for dimensions n = 4 bits / sec / Hz and 8 bits / sec / Hz. Referring to FIG. 2, it can be seen that the bit error rate performance is improved as the size of the dimension increases with respect to the fixed signal-to-noise power ratio (SNR). Moreover, it can be seen that for high SNR, the scheme according to the preferred embodiment of the present invention has achieved a remarkable performance improvement over conventional spatial multiplexing systems. That is, when the dimension coefficient n is 8, the method according to the preferred embodiment of the present invention obtains a gain of almost 6 dB for the BER of 10 ^-4 compared to the conventional method, and gains of 8.5 dB when n = 12. It can be seen that.

3 is a graph illustrating bit error rate performance of a system for transmitting a signal in a spatial multiplexing system using a multi-dimensional rotation modulation scheme according to a preferred embodiment of the present invention compared with a scheme using two receiving antennas.

Referring to FIG. 3, it can be seen that when the number of receive antennas is one and n = 12, the gain obtained by the method according to the preferred embodiment of the present invention exceeds the receive diversity gain obtained by using two receive antennas.

4 is a graph illustrating bit error rate performance of a system for transmitting a signal in a spatial multiplexing system using a multi-dimensional rotation modulation scheme according to an orthogonal design-based Alamouti scheme according to a preferred embodiment of the present invention.

4 compares an Alamouti scheme based on Orthogonal Designs (OD) and a scheme according to a preferred embodiment of the present invention for one or two receive antennas. For a more accurate comparison, the data symbols of the scheme according to the preferred embodiment of the present invention have a constellation of 4-QAM, whereas the Alamouti scheme has a constellation of 16-QAM. When n is 8, for the same frequency efficiency (i.e., 4bit / sec / Hz), the Alamouti scheme shows a 2dB gain over the scheme according to the preferred embodiment of the present invention using one receive antenna. However, for a BER of 10 ^-5 Alamouti scheme it looks almost 3dB improved performance compared to the method according to an embodiment of the present invention using two receive antennas. Therefore, when there is sufficient antenna spacing in a Rich Scattered channel environment, the preferred embodiment of the present invention is a tradeoff between better transmission rate and performance than the Orthogonal Design (OD) scheme. Seems to provide.

While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. Accordingly, the embodiments disclosed herein are intended to be illustrative rather than limiting, and the spirit and scope of the present invention are not limited by these embodiments. It is intended that the scope of the invention be interpreted by the following claims, and that all techniques falling within their scope shall be construed as being included in the scope of the present invention.

As described above, according to the present invention, it is possible to smoothly transmit signals using diversity of signal spaces and to guarantee various quality of service by only processing signals in a spatial multiplexing system. According to a preferred embodiment of the present invention, even if any component of the signal point undergoes severe fading in the process of space and time, it can be separated in the detection process, thereby making the signal point robust to the fading channel. It works. In addition, it is possible to ensure the quality of service according to the service level of the terminal without additional bandwidth and power consumption.

Claims (6)

In the method for transmitting a signal in a spatial multiplexing system, (a) modulating uncoded information bits; (b) storing the modulated complex symbol vector to produce a multidimensional integer component vector; (c) signal processing the multidimensional integer component vector to generate a complex symbol vector; And (d) modulating the complex symbol vector to transmit a signal Method of transmitting a signal in a spatial multiplexing system comprising a. The method of claim 1, The complex symbol vector is spread in time and space to transmit a signal, characterized in that for transmitting in a spatial multiplexing system. The method of claim 1, And the spatial multiplexing system adjusts the signal transmission quality by changing a dimensional coefficient. In a system for transmitting a signal in a spatial multiplexing system using a multi-dimensional rotation modulation method, A gray mapper block that modulates uncoded bits; A buffer for receiving and storing the modulated complex symbol vector from the gray mapper block to generate a multidimensional integer component vector; And Multi-dimensional rotation modulation block generating complex symbol vectors by receiving and signaling multi-dimensional integer component vectors from the buffer System for transmitting a signal in a spatial multiplexing system using a multi-dimensional rotation modulation method comprising a. The method of claim 4, wherein The complex symbol vector is a system for transmitting a signal in a spatial multiplexing system using a multi-dimensional rotation modulation method characterized in that the spreading and transmitting in time and space. The method of claim 4, wherein The spatial multiplexing system transmits a signal in a spatial multiplexing system using a multi-dimensional rotation modulation scheme by changing a dimensional coefficient to adjust the signal transmission quality. .

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