阅读说明：本技术 一种基于星座旋转的等增益合并系统的工作方法 (Working method of equal gain combining system based on constellation rotation ) 是由 朱雪梅 吴瑾瑜 于 2020-06-19 设计创作，主要内容包括：一种基于星座旋转的等增益合并系统的工作方法,属于无线通信技术领域。首先使用了等增益合并接收方法,等增益合并接收方法不需要将加权系数按照各路信噪比进行自适应调整,因此设备简单,复杂度低,且不需要精确的信道估计；其次,引入了星座旋转,即通过星座图的旋转得到同相和正交分量,再将同相和正交分量分别通过不同天线发送以消除两路分量之间的相关性,使得发送后的信号独立地在各自的衰落信道上传输。本发明提出的方法对于基于等增益合并的调制系统性能有明显改善,且星座旋转的引入在获得调制分集增益的同时不会牺牲频带的带宽和功率,且由于不使用分量交织方式,因此不需要交织器和解交织器,可以降低系统实现的复杂度。(A working method of an equal gain combining system based on constellation rotation belongs to the technical field of wireless communication. Firstly, an equal gain combining and receiving method is used, and the equal gain combining and receiving method does not need to carry out self-adaptive adjustment on weighting coefficients according to signal-to-noise ratios of all paths, so that the equipment is simple, the complexity is low, and accurate channel estimation is not needed; secondly, constellation rotation is introduced, namely in-phase and quadrature components are obtained through rotation of a constellation diagram, and then the in-phase and quadrature components are respectively sent through different antennas to eliminate correlation between the two paths of components, so that the sent signals are independently transmitted on respective fading channels. The method provided by the invention has obvious improvement on the performance of a modulation system based on equal gain combination, does not sacrifice the bandwidth and power of a frequency band while obtaining modulation diversity gain due to the introduction of constellation rotation, does not need an interleaver and a deinterleaver due to the fact that a component interleaving mode is not used, and can reduce the complexity of system implementation.)

1. A working method of an equal gain combination system based on constellation rotation is characterized by comprising the following steps:

(1) firstly, input symbol stream is Gray mapped to complex frequency domain; let the transmitted signal vector be s ═ s₀,s₁,...,s_n,...,s_N-1]N is the length of the input symbol stream, where s_nRepresents the constellation point corresponding to the transmitted nth signal and has the value of s_n＝s_I,n+js_Q,nWherein s is_I,nAnd s_Q,nAre respectively s_nThe real and imaginary parts of (a) represent the in-phase and quadrature components of the constellation, respectively, and j represents the imaginary unit;

(2) rotating the signal constellation, and setting the transmitted signal vector after rotation as x ═ x₀,x₁,...,x_n,...,x_N-1]Wherein x is_nIs the constellation point corresponding to the rotated nth signal, and its value is x_n＝x_I,n+jx_Q,nLikewise, x_I,nAnd x_Q,nAre each x_nThe real part and the imaginary part of (a) respectively represent the rotated in-phase component and quadrature component of the constellation diagram, and j represents an imaginary unit; and x_I,nAnd x_Q,nAvailable of_I,nAnd s_Q,nIs represented by, i.e. x_I,n＝s_I,ncosθ+s_Q,nsinθ,x_Q,n＝-s_I,nsinθ+s_Q,ncos theta, theta is the rotation angle which makes the system error rate performance optimal, and the value range is [0, pi/2%]；

(3) In order to eliminate the correlation between the two components, the two components are subjected to independent fading, i.e. the in-phase component x is transmitted separately via different antennas_I＝[x_I,0,x_I,1,...,x_I,n,...,x_I,N-1]And an orthogonal component x_Q＝[x_Q,0,x_Q,1,...,x_Q,n,...,x_Q,N-1](ii) a Representing the transmitted signal by a matrix ofThe 1 st and 2 nd rows of the matrix represent two paths of sending signals, and preferably, the number of sending antennas is 2;

(4) the receiving end of the signal adopts the equal gain combination receiving mode, when the system is applied to the flat fading channel, the number of the receiving antennas is set as M_REach antenna receives in-phase and quadrature parts, which can be regarded as a pair, M_RAlso represents the number of diversity branches when the in-phase and quadrature components are respectively subjected to equal gain combination; the k-th pair of received signals may be represented as Y_k＝H_k·X+N_kWhereinLines 1 and 2 of (a) respectively represent the kth pair of received signals,lines 1 and 2 are independent identically distributed random variables under independent fading experienced by the kth pair of signals, respectivelyIs the additive white gaussian noise added to the k-th signal, where "·" denotes the dot product of the matrix; calculating weighting coefficients of kth pair of signalsWhere "+" denotes conjugation, the resulting normalized received signal vector is

(5) Finally, the output of the equal gain combiner is combinedSignalAnd judging by adopting a minimum Euclidean distance criterion, and obtaining a final output symbol stream, namely a recovered input symbol stream after judgment.

2. The method of claim 1, wherein in step (1), s is used for QPSK modulation and 8PSK modulation_I,nAnd s_Q,nThe respective value ranges are respectivelyAnd

3. the operating method of the constellation rotation-based equal gain combining system according to claim 1, wherein in step (2), the optimum rotation angle θ for QPSK modulation is 30.3 °, and the optimum rotation angle θ for 8PSK modulation is 9.5 °.

4. The method of claim 1, wherein in step (4), the flat fading channel comprises a flat rayleigh fading channel.

5. The method of claim 1, wherein in step (5), the error rate is obtained by comparing the final output symbol stream obtained after the decision with the input symbol stream, and the error rate at the optimal rotation angle θ is lower than the error rate without rotation.

6. The method of claim 1, wherein the Euclidean distance in step (5) is one of Euclidean distanceIs calculated by

Technical Field

The invention relates to a working method of an equal gain combining system based on constellation rotation, and belongs to the technical field of wireless communication.

Background

Signal Space Diversity (SSD) is an effective improvement scheme for dealing with fading, has the advantages of high Diversity gain and no need of occupying additional time and frequency band resources, can effectively improve the performance impact caused by fading, and has been widely used in wireless communication. Constellation rotation in combination with component interleaving is a key technique for SSD. The minimum number of distinguishable components in the multi-dimensional symbol set is defined by the diversity order, and the constellation rotation can maximize the diversity order between any two constellation points, so that the performance is improved. The component interleaving can eliminate the correlation among the components, so that the transmitted signals are independently transmitted on fading channels, and therefore, even if one path of components is subjected to severe fading, a receiver can restore the signals by only one component.

As is well known, in mobile communication, Equal Gain Combining (EGC) and maximum-ratio Combining (MRC) reception techniques are two of the most commonly used diversity Combining techniques. The performance of combining constellation rotation and Component interleaving in a maximal ratio combining system under the condition of single-input antenna and multiple-output antenna is studied by SunghoJeon in an article, Component-Interleaved received MRC with rotatedConnectionation for Signal Space Diversity, published in 2009. However, MRC combines the multiple signals in-phase with weighting determined by the snr corresponding to each branch, and the output snr of MRC is equal to the sum of the snrs of each branch. The EGC does not need to weight signals, signals of all branches are added by equal gains, compared with maximum ratio combination, the EGC does not need channel estimation, calculation of weighted values is simplified, a circuit is simple, realization is easy, and performance is slightly inferior to that of the maximum ratio combination. Therefore, a working method of an equal gain combining system based on constellation rotation under the condition of multiple input antennas and multiple output antennas is provided to improve the performance of the EGC, and no research is made in the aspect of searching documents.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides the working method of the constellation rotation-based equal gain combining system under the condition of multiple input antennas and multiple output antennas, which can save hardware resources, reduce the complexity of system implementation and obtain more excellent anti-fading performance compared with the constellation non-rotation equal gain combining system.

The technical scheme of the invention is as follows:

a working method of an equal gain combination system based on constellation rotation comprises the following steps:

(1) firstly, input symbol stream is Gray mapped to complex frequency domain; let the transmitted signal vector be s ═ s₀,s₁,...,s_n,...,s_N-1]N is the length of the input symbol stream, where s_nRepresents the constellation point corresponding to the transmitted nth signal and has the value of s_n＝s_I,n+js_Q,nWherein s is_I,nAnd s_Q,nAre respectively s_nThe real and imaginary parts of (a) represent the in-phase and quadrature components of the constellation, respectively, and j represents the imaginary unit;

(2) rotating the signal constellation, and setting the transmitted signal vector after rotation as x ═ x₀,x₁,...,x_n,...,x_N-1]Wherein x is_nIs the constellation point corresponding to the rotated nth signal, and its value is x_n＝x_I,n+jx_Q,nLikewise, x_I,nAnd x_Q,nAre each x_nThe real part and the imaginary part of (a) respectively represent the rotated in-phase component and quadrature component of the constellation diagram, and j represents an imaginary unit; and x_I,nAnd x_Q,nAvailable of_I,nAnd s_Q,nIs represented by, i.e. x_I,n＝s_I,ncosθ+s_Q,nsinθ,x_Q,n＝-s_I,nsinθ+s_Q,ncos theta, theta is the rotation angle which makes the system error rate performance optimal, and the value range is [0, pi/2%]；

(3) To remove the correlation between the two components, the two components can be subjected to independent fading, i.e. the in-phase component x is transmitted separately through different antennas_I＝[x_I,0,x_I,1,...,x_I,n,...,x_I,N-1]And an orthogonal component x_Q＝[x_Q,0,x_Q,1,...,x_Q,n,...,x_Q,N-1](ii) a For a more concise representation, the transmission signals are represented here by a matrix ofThe 1 st and 2 nd rows of the matrix represent two paths of sending signals, and obviously, the number of sending antennas is preferably 2;

(4) and a receiving end of the signal adopts a receiving mode of equal gain combination. When the system is applied to a flat fading channel, the number of receiving antennas is set to M_REach antenna receives in-phase and quadrature parts, which can be regarded as a pair, M_RAlso represents the number of diversity branches when the in-phase and quadrature components are respectively subjected to equal gain combination; the k-th pair of received signals may be represented as Y_k＝H_k·X+N_kWhereinLines 1 and 2 of (a) respectively represent the kth pair of received signals,

lines 1 and 2 are independent identically distributed random variables under independent fading experienced by the kth pair of signals, respectively

Is the additive white gaussian noise added to the k-th signal, where "·" denotes the dot product of the matrix; calculating weighting coefficients of kth pair of signalsWhere "+" denotes conjugation, the resulting normalized received signal vector isThen, the output signal of the equal gain combiner can be obtained as

(5) Finally, the output signals of the equal gain combiner are combined

The minimum Euclidean distance criterion is adopted to carry out judgment, and a final output symbol is obtained after judgmentThe stream of symbols, i.e., the stream of recovered input symbols.

Preferably, in step (1), s is used for QPSK modulation and 8PSK modulation_I,nAnd s_Q,nThe respective value ranges are respectively

And

preferably, in step (2), the optimum QPSK modulation rotation angle θ is equal to 30.3 °, and the optimum 8PSK modulation rotation angle θ is equal to 9.5 °.

Preferably, in step (4), the flat fading channel comprises a flat rayleigh fading channel.

Preferably, in step (5), the error rate can be obtained by comparing the final output symbol stream obtained after the decision with the input symbol stream, and the error rate at the optimal rotation angle θ should be lower than the error rate value when the symbol stream is not rotated.

Preferably, in step (5), the Euclidean distance is calculated byr_I,nAnd r_Q,nFor the received nth r_IAnd r_QA signal whereinh_k,I,nAnd h_k,Q,nRespectively represent the nth h_k,IAnd h_k,QValue ofAnd

respectively representing the horizontal and vertical coordinates of each constellation point after rotation.

The invention has the beneficial effects that:

the invention introduces constellation rotation in an equal gain combination system, namely in-phase (I path) and quadrature (Q path) components are obtained through rotation of a constellation diagram, and then the in-phase and quadrature components are respectively sent through different antennas to eliminate the correlation between the two paths of components, so that the sent signals are independently transmitted on respective fading channels. The method provided by the invention has obvious improvement on the performance of a modulation system based on equal gain combination, does not sacrifice the bandwidth and power of a frequency band while obtaining modulation diversity gain due to the introduction of constellation rotation, and does not need an interleaver and a deinterleaver because a component interleaving mode is not used for eliminating the correlation between two paths of components, thereby saving hardware resources and reducing the complexity of system realization. From the technical point of view, the invention has simple thought and easy implementation.

Drawings

Fig. 1 is a block diagram of an equal gain combining system based on constellation rotation according to the present invention.

Fig. 2 is a graph comparing bit error rates of gain combining systems such as QPSK modulation based on constellation rotation. In the 2 curves in fig. 2, from top to bottom, respectively, are the bit error rate curves of the QPSK modulation system in which (i) equal gain combining is adopted and the constellation is not rotated (θ ═ 0 °); and the error rate curve of the QPSK modulation system is combined by equal gain and constellation rotation (the optimal rotation angle theta is 30.3 degrees).

Fig. 3 is a graph comparing bit error rates of gain combining systems such as 8PSK modulation based on constellation rotation. In the 2 curves in fig. 3, from top to bottom, respectively, there are (i) error rate curves of an 8PSK modulation system that employs equal gain combining and constellation does not rotate (θ ═ 0 °); and the error rate curve of an 8PSK modulation system adopting equal gain combination and constellation rotation (the optimal rotation angle theta is 9.5 degrees).

Detailed Description

The present invention will be further described by way of examples, but not limited thereto, with reference to the accompanying drawings.