CN110011947A - An Interference Cancellation Modulation Method Based on Decomposition Matrix in Super-Nyquist Transmission System - Google Patents

Abstract

The invention relates to an interference elimination and modulation method based on decomposition matrix in a super-Nyquist transmission system, and belongs to the field of wireless mobile communication. The method includes: S1: adaptive adjustment: using the eigenvectors decomposed by the ISI matrix to generate an adaptive adjustment vector value; S2: FTN modulation: convoluting the signal to be transmitted with the pulse shaping function at a rate greater than the traditional Nyquist sampling rate S3: Matched filtering: Matched filtering is performed on the signal received at the receiving end, and then the output signal of the matched filtering is sampled at the super Nyquist sampling rate The processed signal is obtained; S4: Decomposition: multiply the decomposed vector value with the signal matrix output by the matched filter. The invention improves the transmission rate of the transmitted signal, completely eliminates the inter-symbol interference, and reduces the decoding complexity of the receiving end.

Description

Decomposition matrix-based interference cancellation modulation in a super-Nyquist transmission system method

technical field

The invention belongs to the field of wireless mobile communication, and relates to an interference elimination and modulation method based on decomposition matrix in a super-Nyquist transmission system.

Background technique

When the transmission rate of information symbols in the system is higher than the free transmission rate with Inter-Symbol Interference (ISI) stipulated by the Nyquist theorem, the system is called a super-Nyquist transmission system. The concept of Faster-Than-Nyquist (FTN) was first proposed by Mazo in the 1970s. In October 1975, Mazo showed in the article "Faster-Than-Nyquist Signaling" in System Technical Journal Compared with traditional Nyquist, FTN can carry more data with the same energy in the same bandwidth without losing its performance. The traditional Nyquist pulse criterion emphasizes the orthogonality of the signal to avoid inter-symbol interference. However, the introduction of ISI into the FTN system requires the sacrifice of bandwidth efficiency to ensure its orthogonality, but it also provides higher data transmission rates and Greater FTN signal capacity.

The patent document with publication number CN105634545 A discloses an interference cancellation method based on matrix decomposition in a super-Nyquist communication system, the main contribution of which is to avoid excessive computational complexity and interference cancellation caused by a trellis decoder. In this method, the ISI matrix is divided into upper and lower triangular matrices, and then on the basis of the serial interference elimination method, the ISI matrix, the transmitted signal sequence and the received signal are further divided into blocks, and then the interference elimination is obtained by demodulation. signal sequence. The patent document with publication number CN106302277 A discloses a super-Nyquist modulation system and method, the main contribution of which is to eliminate ISI by precoding the constellation points to be sent at the transmitting end, thereby improving the transmission performance of the system. These disclosed methods mainly solve the problems of inter-symbol interference in the super-Nyquist transmission system, but the above methods are all serial interference elimination, which makes the algorithm more complex and reduces at the same time. The efficiency of information transmission in the channel. In addition, the relationship between the increase of the receiver detection delay and the size of the ISI tap coefficient has not been considered, which leads to the still high complexity of the demodulation algorithm.

On this basis, the invention adds an adaptive adjustment module at the transmitting end to reduce inter-symbol interference, and adds a decomposition module at the receiving end to completely eliminate ISI.

SUMMARY OF THE INVENTION

In view of this, the purpose of the present invention is to provide an interference cancellation modulation method based on decomposition matrix in a super Nyquist transmission system, which also considers the relationship between detection delay and ISI tap coefficient size while improving information transmission efficiency. , thereby reducing the complexity of demodulation and improving the bit error rate performance and reliability of the system.

To achieve the above object, the present invention provides the following technical solutions:

An interference elimination and modulation method based on decomposition matrix in a super-Nyquist transmission system, the transmitted signal is processed through an adaptive adjustment module, an FTN modulation module at a transmitting end, and a matched filtering module and a decomposition module at the receiving end in turn, so as to eliminate the code Interference; the specific steps are:

S1: Adaptive adjustment module processing: use the eigenvectors decomposed by the ISI matrix to generate an adaptive adjustment vector value;

S2: FTN modulation module processing: convolve the signal to be transmitted with the pulse shaping function at a rate greater than the traditional Nyquist sampling rate, and then send the signal to be sent after the convolution through radio frequency;

S3: Matched filtering module processing: perform matched filtering on the signal received by the receiving end, and then sample the output signal of the matched filtering at a super Nyquist sampling rate to obtain a processed signal;

S4: Decomposition module processing: Multiply the decomposed vector value generated by the eigenvector decomposed by the ISI matrix and the signal matrix output by the matched filter to obtain a signal for eliminating ISI.

Further, the step S1 specifically includes: determining the ISI matrix H according to the parameters of the super-Nyquist transmission system, and performing eigendecomposition on the generated ISI matrix H to obtain H=pΛp ^H , where p and p ^H are the values of the eigenvectors. The formed matrix, Λ is a diagonal matrix; then the adaptive adjustment vector value is obtained according to the eigenvector matrix p.

Further, the parameters generated by the ISI matrix H include: the roll-off coefficient β of the pulse shaping function, the compression factor τ, the generated matrix dimension N and the length I of the signal sequence, where N≤I.

Further, the pulse shaping function consists of a root raised cosine filter.

Further, the step S3 specifically includes: the receiving end receives and transmits the signal through matched filtering, convolves the signal with the pulse shaping function at a sampling rate greater than the traditional Nyquist, and then convolves the convolved signal with a super-Nyquist sampling rate. sampling at the special sampling rate.

Further, in step S4, the method for obtaining the decomposed vector values includes: determining the ISI matrix H according to the parameters of the super-Nyquist transmission system, performing eigendecomposition on the generated ISI matrix H to obtain the eigenvector matrix p ^H , and then according to The eigenvector matrix p ^H yields the ISI-eliminating matrix in the decomposition module.

The beneficial effects of the present invention are: the present invention reduces the inter-symbol interference by passing the signal through the adaptive adjustment module at the transmitting end; the signal at the receiving end enters the decomposition module to eliminate the ISI of the signal. The present invention can greatly reduce the complexity of the modulation algorithm of the super-Nyquist communication system by applying the method of self-adaptive adjustment and decomposition of the matrix, and also reduces the complexity of the signal in the demodulation algorithm. The matrix-based calculation of the present invention makes the detection delay in the system independent of the size of the ISI tap group, reduces the detection delay of the receiver, and greatly reduces the decoding complexity of the receiver

Other advantages, objects, and features of the present invention will be set forth in the description that follows, and will be apparent to those skilled in the art based on a study of the following, to the extent that is taught in the practice of the present invention. The objectives and other advantages of the present invention may be realized and attained by the following description.

Description of drawings

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be preferably described in detail below with reference to the accompanying drawings, wherein:

1 is a schematic diagram of a module of a super-Nyquist modulation system in an embodiment of the present invention;

2 is a schematic diagram of a real system framework of a super-Nyquist modulation system in an embodiment of the present invention;

3 is a schematic diagram of a super-Nyquist modulation system model in an embodiment of the present invention;

FIG. 4 is a flowchart of the interference cancellation modulation method according to the present invention.

Detailed ways

The embodiments of the present invention are described below through specific specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the drawings provided in the following embodiments are only used to illustrate the basic idea of the present invention in a schematic manner, and the following embodiments and features in the embodiments can be combined with each other without conflict.

Please refer to FIG. 1 to FIG. 4. FIG. 1 is a schematic block diagram of the super-Nyquist modulation system adopted in the present invention. The super-Nyquist system model includes: an adaptive adjustment module at the transmitting end, an FTN modulation module, a channel, a receiving The matched filter module, decomposition module and demodulation module at the end. The model parameters of the system are the roll-off coefficient β of the pulse shaping function, the time compression factor τ and the dimension N of the signal transmission matrix.

Referring to Fig. 2 and Fig. 3, before the super Nyquist modulation system adopted in the present invention, the baseband signal to be transmitted linearly modulated is firstly generated at the transmitting end:

Among them, τ=T _F /T, τ∈(0,1] is the compression factor, when τ=1, the quadrature signal obeys the quadrature modulation, when τ<1 is the FTN signal, and T=1/(2B) is the traditional signal Nyquist symbol transmission time interval, B is the system bandwidth. The binary symbol sequence vector to be sent is a _i =[a ₁ ,a ₂ ,a ₃ ,...,a _I ] ^T , h(t) Shape the pulse for the root raised cosine with unit energy, i.e. The corresponding FTN transmission symbol rate is 1/(τT). Set all pulse normalization factors at the sender to Used to reduce the pulse energy and keep the power at the transmitter constant, i.e.

When the linearly modulated baseband signal to be transmitted is sent out through the transmitting antenna at the RF end, the signal received at the receiving end is expressed as:

r(t)=S(t)+w(t) (2)

Among them, it is assumed that w(t) is a colored noise with a mean value of 0 and a variance of δ ² in the transmission process.

Therefore, the signal sequence with the ISI matrix obtained by the modulation of the super-Nyquist transmission system at the receiving end is:

Substitute equations (1) and (2) into equation (3) to get the following:

in, represents the ISI tap group coefficients, represents the filtered noise samples.

Among them, the system parameters include the root raised cosine roll-off coefficient β, the time compression factor τ, and the signal sequence of the total length I of the signal pulse is divided into the transmission signal sequence of length N. Since there is ISI in the FTN system, the signal received by the receiving end is The ISI contained in the sequence can be expressed in matrix form as

which is

The transmission signal sequence length I is divided into sequences of each length N, so the ISI matrix order is expressed as N, and the matrix H is an ISI matrix.

After matched filtering as described above, the FTN signal is expressed in matrix form as:

The FTN signal has ISI after matched filtering, that is

The interference received by each symbol in the FTN modulated signal comes from the previous input symbol and the latter input symbol.

When the interference of the signal sequence is eliminated and then matched and filtered, there is no ISI in the signal at this time, that is, Therefore, the required sequence can be obtained by performing correlation calculation using the matrix, thereby realizing the elimination of inter-symbol interference.

Referring to Fig. 4, the interference cancellation modulation method of the present invention modulates and detects the super Nyquist system, and the specific steps are as follows:

In the first step, the interference matrix H obtained in the modulation of the FTN system is further eigendecomposed to obtain:

H=pΛp ^H (7)

Among them, p, p ^H are the matrix formed by the eigenvectors, and Λ=diag(λ _1,1 ,λ _2,2 ,λ _3,3 ,...,λ _n,n ) The diagonal matrix is formed by the eigenvalues of the H matrix . Therefore, the matrix vector u for reducing intersymbol interference produced by the adaptive adjustment module and the matrix u ^H for completely eliminating interference produced by the decomposition module are both composed of the eigenvectors obtained by eigendecomposition.

In the second step, take the binary symbol sequence vector A= _ai =[a ₁ ,a ₂ ,a ₃ ,...,a _I ] ^T to be sent, and obtain x(t)=A after the adaptive adjustment module ·u, where u·p is the unit matrix of dimension N, and the signal is transmitted in an independent and parallel manner in the channel, so after the signal at the transmitting end passes through the adaptive adjustment module, the intersymbol interference will be reduced and the signal transmission rate will be improved. .

The third step is to convolve the signal received by the receiver with the pulse shaping function at a rate greater than the traditional Nyquist sampling rate through the matched filter module, and then decompose the convolved signal sequence to obtain C=r(t )·u ^H , where u ^H ·p ^H is a unit matrix of dimension N, and finally the signal sequence A after the interference is eliminated is obtained.

In the first step, the vector value of the adaptive modulation and decomposition module is determined mainly according to the eigenvectors after the eigendecomposition of the interference matrix H generated by the FTN modulation. The second and third steps are both a simplified way of the interference matrix H, and finally a diagonal matrix Λ is obtained, and the interference is eliminated at this time. In addition, the transmission channel of the present invention can transmit the amount of information according to the diagonal matrix Λ after the eigendecomposition of the interference matrix H.

The fourth step is to demodulate the signal sequence after the ISI is eliminated at the receiving end. As mentioned above, the FTN modulated signal is represented in the form of a matrix. After the ISI is eliminated by correlation operations such as matrix decomposition, subsequent demodulation is performed in the receiving system to obtain an output signal sequence.

Among them, the present invention adopts the ISI elimination scheme using matrix decomposition and other related algorithms. Compared with the traditional ISI elimination scheme, because it is not based on grid decoding, the complexity of the receiving end will be reduced, and the system detection delay and tap will not be affected at the same time. the size of the coefficient.

The fifth step is to detect the decoded signal sequence. The decoded signal sequence and the source signal sequence are subjected to bit error analysis to further improve the FTN transmission and communication performance.

The present invention reduces the interference of the signal to be sent by using the adaptive adjustment vector value generated by the adaptive adjustment module at the transmitting end, thereby increasing the transmission rate of the transmitted signal; the decomposition module at the receiving end uses the generated decomposition vector value to eliminate intersymbol interference. The present invention can solve the problems of inter-symbol interference in the super-Nyquist transmission system. Compared with other interference elimination algorithm schemes, the present invention has the advantage that the matrix-based calculation makes the detection delay in the system irrelevant to the size of the ISI tap group. The receiver detection delay is reduced, thereby greatly reducing the decoding complexity at the receiver.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be Modifications or equivalent replacements, without departing from the spirit and scope of the technical solution, should all be included in the scope of the claims of the present invention.

Claims (5)

1. in a super-Nyquist transmission system, the interference cancellation and modulation method based on decomposition matrix is characterized in that, the method is to transmit signal successively by the self-adaptive adjustment module of transmitting end, super-Nyquist (Faster-Than- Nyquist, FTN) modulation module, and the matched filter module and decomposition module processing at the receiving end to eliminate inter-symbol interference; the specific steps are: S1: Adaptive adjustment module processing: using the eigenvectors decomposed by the Inter-Symbol Interference (ISI) matrix to generate an adaptive adjustment vector value; S2: FTN modulation module processing: convolve the signal to be transmitted with the pulse shaping function at a rate greater than the traditional Nyquist sampling rate, and then send the signal to be sent after the convolution through radio frequency; S3: Matched filtering module processing: perform matched filtering on the signal received by the receiving end, and then sample the output signal of the matched filtering at a super Nyquist sampling rate to obtain a processed signal; S4: Decomposition module processing: Multiply the decomposed vector value generated by the eigenvector decomposed by the ISI matrix and the signal matrix output by the matched filter to obtain the signal after the ISI is completely eliminated. 2. the interference cancellation modulation method based on decomposition matrix in a kind of super-Nyquist transmission system according to claim 1, it is characterized in that, described step S1 specifically comprises: determine according to the parameter of super-Nyquist transmission system ISI matrix H, and eigendecompose the generated ISI matrix H to obtain H=pΛp ^H , where p and p ^H are the matrix formed by the eigenvectors, and Λ is the diagonal matrix; then the adaptive adjustment is obtained according to the eigenvector matrix p vector value. 3. the interference cancellation modulation method based on decomposition matrix in a kind of super-Nyquist transmission system according to claim 2, is characterized in that, the parameter that described ISI matrix H generates comprises: the roll-off coefficient of pulse shaping function β, the compression factor τ, and the resulting matrix dimension N and the length I of the signal sequence, where N≤I. 4 . The interference cancellation modulation method based on decomposition matrix in a super-Nyquist transmission system according to claim 3 , wherein the pulse shaping function is composed of a root raised cosine filter. 5 . 5. The interference cancellation modulation method based on decomposition matrix in a kind of super-Nyquist transmission system according to claim 1, it is characterized in that, in step S4, described decomposition vector value acquisition mode comprises: according to super-Nyquist The parameters of the special transmission system determine the ISI matrix H, and the generated ISI matrix H is subjected to eigendecomposition to obtain the eigenvector matrix p ^H , and then the matrix for eliminating ISI in the decomposition module is obtained according to the eigenvector matrix p ^H .