CN109600332B - A CO-FBMC/OQAM modulation method and system - Google Patents

Abstract

The invention discloses a modulation method and a system of CO-FBMC/OQAM, which comprises an interference elimination pilot frequency module and a Kalman filtering compensation module; the interference elimination pilot frequency module comprises a first pilot frequency unit and a second pilot frequency unit which are respectively arranged at two ends of the symbol mapping module and used for removing inherent imaginary part interference at a pilot frequency position and ensuring that each CO-FBMC/OQAM symbol has a pilot frequency symbol to record phase noise superposed on the pilot frequency symbol; and the Kalman filtering compensation module extracts a test pilot frequency symbol of the receiving end, corrects the prediction process of the pilot frequency symbol to obtain a phase noise estimation value of the current moment, and then outputs the estimation value of a receiving end signal. The technical scheme has the capability of eliminating the inherent interference at the pilot frequency position, and meanwhile, the Kalman filtering processing module only needs to adopt one pilot frequency for operation, so that the technical scheme has the capabilities of reducing the calculated amount and reducing the judgment error.

Description

A CO-FBMC/OQAM modulation method and system

technical field

The invention belongs to the field of optical communication, and more particularly, relates to a modulation method and system of CO-FBMC/OQAM.

Background technique

Coherent Optical Filter Bank Multi-Carrier/Offset Quadrature Amplitude Modulation (CO-FBMC/OQAM: Coherent Optical-offset Quadrature Amplitude Modulation-based filter bank multicarrier) system in traditional optical communication although omit the cyclic prefix to some extent Better than CO-OFDM system, but because CO-FBMC/OQAM system has longer symbol length and high peak-to-average power ratio, and the phase noise mainly comes from laser linewidth and link nonlinearity, CO-FBMC/OQAM system The transmission performance of the receiver is easily affected by phase noise, resulting in the rotation and divergence of the QAM modulation constellation at the receiving end, which leads to an increase in the bit error rate. Therefore, how to efficiently monitor and compensate for phase noise is a key issue in CO-FBMC/OQAM systems, in which the inherent imaginary interference of the system has become a difficult problem to be solved by phase noise processing algorithms.

The existing solution to the estimation and compensation of system phase noise is the Kalman filter algorithm compensation scheme based on blind decision. This compensation scheme not only has high computational complexity, but also has inherent interference of the system superimposed on each symbol used for blind decision. When the phase noise of the laser is relatively large, it is very easy to make judgment errors, so the compensation range of this scheme is extremely limited.

SUMMARY OF THE INVENTION

Aiming at the defects of the prior art, the purpose of the present invention is to add a scrambling-removing pilot module at a fixed subcarrier position after the symbol mapping module at the transmitting end of the system, and add a pilot frequency corresponding to the optical domain-frequency domain conversion module at the receiving end of the system. The Kalman filter processing module is added to the position of the system, which aims to solve the estimation error from the inherent imaginary part of the system to the pilot band and the corresponding phase noise compensation problem at the receiving end.

In order to achieve the above object, on the one hand, the present invention provides a modulation method of CO-FBMC/OQAM, comprising:

(1) Convert the bit signal input by the CO-FBMC/OQAM system into a PAM data symbol;

(2) Access three columns of sub-carriers at one end of the PAM data symbol, place pilot symbols in odd-numbered bits of the middle column of sub-carriers, place zero symbols in even-numbered bits, and set the remaining two columns of sub-carriers to zero to complete the PAM data symbol and the first derivative access to the frequency unit;

(3) Access three columns of subcarriers at the other end of the PAM data symbols, place pilot symbols on the even bits of the subcarriers in the middle column, place zero symbols on odd bits, and set the remaining two columns of subcarriers to zeros to complete the PAM data symbols and the second column. access to the pilot unit;

(4) The first pilot unit and the second pilot unit receive the PAM data symbol, eliminate the inherent imaginary interference of the system, and record the phase information of the pilot position;

(5) The frequency domain-time domain conversion module receives the frequency domain signal processed by the pilot unit, modulates it after orthogonalization preprocessing, and completes the conversion from the frequency domain signal to the time domain signal;

(6) The acquired time-domain signal is subjected to IQ modulation after parallel-serial conversion and training sequence processing, so that the signal is transmitted to the system receiving end;

(7) The optical domain-frequency domain conversion module receives the baseband signal obtained after the received optical domain signal is balanced by coherent detection;

(8) demodulate the baseband signal through timing synchronization and serial-parallel conversion to obtain a frequency domain signal;

(9) extract the test pilot signal of the receiving end of the pilot position;

(10) Multiply the known pilot signal of the transmitting end and the estimated value of phase noise at the previous moment to obtain the predicted value of the receiving end pilot signal corresponding to the pilot signal of the transmitting end;

(11) The test pilot signal at the receiving end is subtracted from the predicted value of the pilot signal to obtain an error signal between the two;

(12) multiplying the error signal by the fixed Kalman gain to obtain the correction value of the phase noise;

(13) adding the value obtained by the multiplication to the estimated phase noise value at the previous moment to obtain the estimated phase noise value at the current moment;

(14) Conjugate the phase noise of the estimated value of the phase noise at the current moment;

(15) Multiply the conjugate value of the phase noise and the pilot symbol of the receiving end to obtain an estimated value after the phase noise compensation as a signal for phase noise compensation;

(16) recovering the bit signal after the phase-compensated output signal is demapped;

(17) The phase noise estimated value at the current time is subjected to delay processing as the phase noise estimated value at the previous time.

On the other hand, the present invention provides a CO-FBMC/OQAM system, including a symbol mapping module, an anti-scramble pilot module, a frequency domain-time domain conversion module, an IQ modulation module, an optical domain-frequency domain conversion module, a Kalman Filter compensation module and symbol demapping module;

The symbol mapping module is used to receive the bit data that has undergone serial-parallel conversion, and the output signal is converted to a real number through a complex number, and the real-valued signal is transmitted to the de-scrambling pilot module;

The interference-removing pilot module is used to receive the real-valued signal transmitted by the symbol mapping module, output a frequency domain signal that eliminates the inherent interference of the pilot, and at the same time add pilot signals at both ends of the symbol mapping module to record the Phase information to obtain the impact of phase noise on the system;

Preferably, the scrambling pilot module includes a first pilot unit and a second pilot unit; both the first pilot unit and the second pilot unit include 3 columns of subcarriers, and the subcarrier pilots located in the middle column The symbols and the zero-setting symbols are alternated, and the remaining two columns of sub-carriers are all set to zero, and the pilot symbols of the first pilot unit and the second pilot unit are respectively placed in the odd-numbered positions and even-numbered positions of the corresponding sub-carriers;

The frequency domain-time domain conversion module is used for receiving the frequency domain signal transmitted by the pilot module, and outputting the time domain signal;

The IQ modulation module is used for receiving time domain signals and outputting optical domain signals;

The optical domain-frequency domain conversion module is used for receiving optical domain signals and outputting frequency domain signals;

The Kalman filter compensation module is used to calculate the phase noise value at the position of the pilot symbol based on the state of the inherent interference of the pilot symbol eliminated by the interference-removing pilot module, so as to compensate the phase noise, and finally output the phase compensation. the frequency domain signal;

Preferably, the Kalman filter compensation module includes: a pilot frequency extraction unit, a subtractor, a first multiplier, an adder, a delay unit, a second multiplier, a conjugate processing unit, and a third multiplier;

The input end of the pilot frequency extraction unit is connected to the optical domain-frequency domain conversion module, and the output end is connected to the subtractor;

The input end of the subtractor is connected to the output end of the pilot frequency extraction unit and the output end of the second multiplier, and the output end is connected to the input end of the first multiplier;

The input end of the first multiplier is connected to the output end of the subtractor, and receives the fixed Kalman gain; the output end is connected to the input end of the adder;

The input end of the adder is connected to the output end of the first multiplier and the output end of the delay unit, and the output end is connected to the input end of the delay unit and the input end of the conjugate processing unit;

The input end of the delay unit is connected to the output end of the adder, and the output end is connected to the input end of the adder and the input end of the second multiplier;

the input end of the second multiplier is connected to the output end of the delay unit;

The input end of the conjugate processing unit is connected to the output end of the adder, and the output end is connected to the input end of the third multiplier;

The input end of the third multiplier is connected to the output end of the conjugate processing unit, and the output end is connected to the real-complex number conversion module;

The pilot frequency extraction unit is used to extract the pilot frequency signal from the pilot frequency of the receiving end;

The subtractor is used for subtracting the pilot signal at the receiving end and the predicted pilot signal to obtain an error signal therebetween;

the first multiplier is used to multiply the error signal by a fixed Kalman gain;

The adder is used to add the result obtained by the multiplier to the estimated phase noise value at the previous moment to obtain the estimated phase noise value at the current moment;

The delay unit is used to convert the estimated phase noise value at the current moment into the estimated phase noise value at the previous moment;

The second multiplier is used to multiply the transmit-end pilot signal by the estimated phase noise value at the last moment to obtain the received pilot value corresponding to the predicted pilot symbol;

The conjugate processing unit is used to obtain the conjugate value of the phase noise at the current moment;

The third multiplier is used to multiply the conjugate value of the phase noise at the current moment by the pilot symbol at the receiving end to obtain an estimated value after phase noise compensation;

The symbol demapping module is used for receiving the frequency domain signal converted from the real number to the complex number, and outputting bit data.

Through the above technical solutions conceived by the present invention, compared with the prior art, the following beneficial effects can be achieved:

(1) The invention adopts the interference-removing pilot module, so that the pilot symbols are not affected by the inherent imaginary interference in the CO-FBMC/OQAM system, thereby improving the accuracy of the phase noise estimation by the system.

(2) The interference suppression pilot frequency module adopted in the present invention can ensure that only one pilot frequency is used for each FBMC symbol to record the phase noise, which can avoid the need to perform calculation for each sub-carrier in the blind decision algorithm to solve its The disadvantages of the phase noise on the network can greatly reduce the computational complexity.

(3) The present invention adopts the Kalman filter algorithm based on pilot frequency to estimate the phase noise, which can avoid the decision process required in the blind estimation, thereby avoiding the introduction of decision errors.

Description of drawings

Fig. 1 is a structural design diagram of an interference suppression pilot module provided by an embodiment of the present invention;

2 is a structural diagram of a Kalman filter processing module provided by the present invention;

Fig. 3 is the CO-FBMC/OQAM system schematic diagram provided by the present invention;

4 is a schematic diagram of a CO-FBMC/OQAM system of 16QAM modulation provided by the present embodiment;

FIG. 5 is a simulation result provided by an embodiment of the present invention.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention.

The present invention provides a modulation method of a CO-FBMC/OQAM system, including:

S1: The symbol mapping module receives the serial-to-parallel converted binary input bit signal, and the output signal is converted into a PAM data symbol by converting a complex number to a real number;

S2: respectively access the first pilot unit and the second pilot unit of the scrambling pilot module at both ends of the PAM data symbol;

S3: The frequency domain-time domain conversion module receives the frequency domain signal processed by the pilot unit, modulates it after orthogonalization preprocessing, and completes the conversion from the frequency domain signal to the time domain signal;

S4: The acquired time domain signal is subjected to quadrature (IQ: in-phase and quadrature modulation) modulation after parallel-serial conversion and training sequence processing, so that the signal is transmitted to the system receiving end

S5: The optical domain-frequency domain conversion module converts the received optical domain signal into a frequency domain signal, and compensates the phase noise through the Kalman filter compensation module;

S6: recover the bit signal after passing the phase-compensated output signal through the symbol demapping module.

1 is the connection relationship between the interference suppression pilot module provided by the present invention and the pulse amplitude modulation (PAM: PulseAmplitudeModulation) data symbol. It can be seen from FIG. 1 that the step S2 specifically includes the following steps:

S2.1: Set three columns of carriers so that the odd-numbered bits of the sub-carriers in the middle column are placed with pilot symbols, the even-numbered bits are placed with zero symbols, and the remaining two columns of sub-carriers are all set to zero to complete the setting of the first pilot unit;

S2.2: Set three columns of carriers so that the odd-numbered bits of the sub-carriers in the middle column are placed with pilot symbols, the even-numbered bits are placed with zero symbols, and the remaining two columns of sub-carriers are all set to zero to complete the setting of the first pilot unit;

S2.3: The first pilot unit and the second pilot unit are respectively connected at both ends of the PAM data symbol.

FIG. 2 is a schematic structural diagram of the calculation of the Kalman filter compensation module provided by the present invention, and the step S5 according to the Kalman phase compensation method shown in FIG. 2 specifically includes the following steps:

S5.1: The pilot frequency extraction unit extracts the test pilot frequency signal at the receiving end of the pilot frequency position;

S5.2: Multiply the known pilot signal at the transmitting end by the estimated phase noise value at the previous moment to obtain the predicted value of the receiving end pilot signal corresponding to the pilot signal at the transmitting end;

S5.3: Subtract the test pilot signal at the receiving end and the predicted value of the pilot signal to obtain an error signal between the two.

S5.4: The error signal is multiplied by the fixed Kalman gain to obtain the correction value of the phase noise;

S5.5: The value obtained by the multiplication is added with the estimated phase noise value at the previous moment as the estimated value of phase noise at the current moment;

S5.6: Conjugate the phase noise of the estimated value of phase noise at the current moment;

S5.7: Multiply the conjugate value of the phase noise and the pilot symbol at the receiving end to obtain an estimated value after phase noise compensation as a signal for phase noise compensation;

S5.8: The phase noise estimation value at the current moment is subjected to delay processing as the phase noise estimation value at the previous moment.

FIG. 3 is a schematic diagram of the CO-FBMC/OQAM system provided by the present invention. It can be seen from FIG. 3 that the CO-FBMC/OQAM system transmitter includes a symbol mapping module, an interference suppression pilot module and a frequency domain-time domain conversion module, and the receiver It includes an optical domain-frequency domain conversion module, a Kalman filter compensation module and a symbol demapping module. The transmitter and receiver of the system are connected through an IQ modulation module, and the time domain signal at the transmitter is converted into an optical domain signal and transmitted to the receiver;

Preferably, the symbol mapping module is used to receive the bit data that has undergone serial-parallel conversion, and the output signal is converted to a real number through a complex number, and the real-valued signal is transmitted to the scrambling pilot module;

The interference-removing pilot module is used to receive the real-valued signal transmitted by the symbol mapping module, output a frequency-domain signal that eliminates the inherent interference of the pilot, and at the same time, is used to record the phase information in the pilot signal, so as to obtain the impact of phase noise on the system ;

The frequency domain-time domain conversion module is used for receiving the frequency domain signal transmitted by the pilot module, and outputting the time domain signal;

The IQ modulation module is used for receiving time domain signals and outputting optical domain signals;

The optical domain-frequency domain conversion module is used for receiving optical domain signals and outputting frequency domain signals;

The Kalman filter compensation module is used to calculate the phase noise value at the position of the pilot symbol based on the state of the inherent interference of the pilot symbol eliminated by the interference-removing pilot module, so as to compensate the phase noise, and finally output the phase compensation After the frequency domain signal;

The symbol demapping module is used for receiving the frequency domain signal converted from the real number to the complex number, and outputting bit data.

Preferably, the structure of the interference cancellation pilot module is shown in FIG. 1 , and the interference cancellation pilot module includes a first pilot unit and a second pilot unit;

Preferably, both the first pilot unit and the second pilot unit include three columns of sub-carriers, and the pilot symbols and zero-setting symbols located in the middle column of sub-carriers are alternated. The pilot symbols are placed in the odd and even positions of the corresponding subcarriers, and the remaining two columns of subcarriers are set to zero;

The scrambling pilot module can effectively remove the inherent imaginary interference at the pilot position, ensure that the value on the pilot is not affected by the inherent interference, and ensure that each CO-FBMC/OQAM symbol has a pilot symbol to record its value. Phase noise superimposed above.

The more specific working principle is as follows:

Considering the presence of phase noise and ASE noise, the demodulated signal at the receiving end of the CO-FBMC/OQAM system can be written as:

为ASE噪声，

代表泡利多相调制因子；Among them, m ₀ represents the m _0th sub-carrier, l ₀ is the 10th _FBMC /OQAM symbol, L _g =KM is the filter length, K is the overlap factor, M is the total number of sub-carriers, g(n) represents the time-domain response function of the filter, g _m,l represents the time-frequency offset formula of the filter,

is the ASE noise,

represents the Pauli polyphase modulation factor;

为系统自带的叠加在

的固有干扰，则上式可以简化为：make

Built-in overlay for the system

The inherent interference of , the above formula can be simplified as:

From the above formula, it can be found that the inherent interference will be superimposed on the received symbol, affecting the normal determination of the phase noise value, and the inherent interference is a value strongly correlated with the value of the signal itself, its size cannot be determined and must be eliminated.

时收发器的脉冲响应，由表1可知，导频位置的固有干扰主要来自于该导频所处子载波上与该导频间隔为奇数位置的符号，以及该导频相邻的两列子载波上的符号。因此本发明的消扰导频模块在虚部干扰大的位置置零的操作，可以极大的消除虚部干扰的影响。Table 1 transmits pilots in CO-FBMC/OQAM system

When the impulse response of the transceiver is shown in Table 1, the inherent interference of the pilot frequency mainly comes from the symbols on the subcarrier where the pilot frequency is located at odd positions with the pilot frequency, and the two adjacent columns of the pilot frequency on the subcarriers. symbol. Therefore, the operation of setting zero in the position where the interference of the imaginary part is large in the interference-removing pilot frequency module of the present invention can greatly eliminate the influence of the interference of the imaginary part.

Table 1

n-4 n-3 n-2 n-1 n n+1 n+2 n+3 n+4 m-1 0.0054 0.0429j -0.1250 -0.2058j 0.2393 0.2058j -0.1250 -0.0429j 0.0054 m 0 -0.0668 0.0002j 0.5644 1 0.5644 0.0002j -0.0668 0 m+1 0.0054 -0.0429j -0.1250 0.2058j 0.2393 -0.2058j -0.1250 0.0429j 0.0054

According to Table 1 and using the special pilot structure designed, equation (3) can be simplified to:

Preferably, the structure of the Kalman filter compensation module is shown in FIG. 2, including: a pilot frequency extraction unit 1, a subtractor 2, a first multiplier 3, an adder 4, a delay unit 5, a second multiplier 6, Conjugate processing unit 7, third multiplier 8.

The input end of the pilot frequency extraction unit 1 is connected to the input end of the optical domain-frequency domain conversion module, and the output end is connected to the subtractor 2;

The input end of the subtractor 2 is connected to the output end of the pilot frequency extraction unit 1 and the output end of the multiplier 6, and the output end is connected to the input end of the multiplier 3;

The input end of the first multiplier 3 is connected to the output end of the subtractor 2 to receive the fixed Kalman gain; the output end is connected to the input end of the adder 4;

The input end of the adder 4 is connected to the output end of the first multiplier 3 and the output end of the delay unit 5, and the output end is connected to the input end of the delay unit 5 and the input end of the conjugate processing unit 7;

The input end of the delay unit 5 is connected to the output end of the adder 4, and the output end is connected to the input end of the adder 4 and the input end of the multiplier 6;

The input end of the second multiplier 6 is connected to the output end of the delay unit 5;

The input end of the conjugate processing unit 7 is connected to the output end of the adder 4, and the output end is connected to the input end of the third multiplier 8;

The input end of the third multiplier 8 is connected to the output end of the conjugate processing unit 7, and the output end is connected to the real-complex number conversion module;

其中，z_n表示第n个CO-FBMC/OQAM符号，

表示第n个FBMC/OQAM符号中对应于导频位置p的符号值。Preferably, the pilot frequency extraction unit 1 is used to extract the pilot frequency signal in the frequency domain signal of the receiving end, that is, to complete:

where z _n represents the nth CO-FBMC/OQAM symbol,

Represents the symbol value corresponding to pilot position p in the nth FBMC/OQAM symbol.

与卡尔曼滤波算法中预测的收端导频符号值

作对比，得到预测误差信号e_n，即：The subtractor 2 is used to divide the pilot symbols actually received by the receiving end

and the value of the terminal pilot symbol predicted in the Kalman filter algorithm

For comparison, the prediction error signal e _n is obtained, namely:

The error signal contains unpredictable information, so the error signal is also called innovation. This innovation is mainly used to correct the predicted value of phase noise;

的修正值k_ne_n；、The first multiplier 3 is used to multiply the input innovation e _n by the Kalman gain k _n , that is, weight the innovation with an appropriate coefficient k _n to obtain the predicted value obtained by the measurement process and the prediction process.

The correction value k _n e _n of ;,

Preferably;

k_n为卡尔曼增益；R为测量过程协方差，可在前期通过训练序列得到，为一个固定值，k_n的计算值可根据新息的最小均方误差准则获取，即：in,

k _n is the Kalman gain; R is the covariance of the measurement process, which can be obtained through the training sequence in the early stage, and is a fixed value. The calculated value of k _n can be obtained according to the minimum mean square error criterion of innovation, namely:

相加，得到对相位噪声的基于卡尔曼滤波算法的最优估计值：The adder 4 is used to combine the correction value k _n e _n with the predicted value

Add up to get the optimal estimate of phase noise based on the Kalman filter algorithm:

进行一个时刻的延时，得到

根据预测方程(4)：

可知

最终得到上一时刻对该时刻的相位噪声的预测值

The delay unit 5 is used to convert the optimal estimated value based on the Kalman filter algorithm

After a time delay, we get

According to the prediction equation (4):

know

Finally, the predicted value of the phase noise at the last moment is obtained

与预测值

相乘得到收端导频信号的预测值

The second multiplier 6 is used to combine the known originating pilot signal

with the predicted value

Multiply to get the predicted value of the pilot signal at the receiving end

其中，j代表虚数；The conjugate processing unit 7 is used for the operation of conjugating the input phase noise:

Among them, j represents an imaginary number;

的共轭与FBMC/OQAM的频域信号相乘得到相位噪声补偿后的结果：

The third multiplier 8 is used to convert the input phase noise

The conjugate of is multiplied by the frequency domain signal of FBMC/OQAM to obtain the result after phase noise compensation:

In summary, the algorithm processing method of the Kalman filter compensation module is as follows:

First, the prediction and measurement equations required by the Kalman filter algorithm are established:

和其对应的发端导频符号

然后初始化相位噪声

预测误差协方差P(0)＝0。First, extract the pilot symbol in the receiving end symbol

and its corresponding originating pilot symbol

Then initialize the phase noise

The prediction error covariance P(0)=0.

For each FBMC/OQAM symbol, calculate its prediction process and measurement process in turn:

The equation for the prediction process is:

Among them, Q=2πΔvT is the prediction process covariance; Δv is the joint laser line width; T=T _s /M is the normalized FBMC/OQAM symbol period;

The equation for the measurement process is:

的相位噪声，根据

得到经过相位补偿后的信号。After the above iterations can be obtained corresponding to each

phase noise, according to

The signal after phase compensation is obtained.

As shown in FIG. 4 , a specific CO-FBMC/OQAM system provided in this embodiment is provided. The CO-FBMC/OQAM system in this embodiment has a total number of subcarriers of 256, an effective number of subcarriers of 250, and a symbol rate of 20GS/s, 16QAM modulation and carry pilot signal.

The originating working mechanism of the CO-FBMC/OQAM system is as follows:

The input binary information bits first pass through serial-to-parallel conversion, 16QAM mapping and complex number to real number processing to complete the preprocessing of OQAM to form 250 columns of parallel PAM data symbols, and then add the design of the present invention at both ends of the parallel data symbols. The muting pilot structure D1 unit and D2 unit, D1 unit and D2 unit mix 250 columns of parallel PAM data symbols together to form 256 columns of parallel data structures, and then go through the Pauli polyphase modulation module for systematic orthogonalization preprocessing, Entering the integrated filter bank module, each column of the 256 columns of parallel data is loaded on 256 columns of different subcarriers through IFFT conversion and integrated filter bank modulation, and the frequency domain to time domain conversion is completed. The upper training sequence forms the FBMC/OQAM baseband signal, and then realizes the frequency up-conversion from the electrical domain to the optical domain through IQ modulation to form a signal that can be transmitted in the optical fiber;

The working mechanism of the CO-FBMC/OQAM system is as follows:

The baseband signal obtained after modulating the FBMC/OQAM signal at the transmitting end in the optical domain is received by coherent detection and balance, firstly, after timing synchronization, serial-to-parallel conversion, analysis of the filter bank and channel estimation, the obtained frequency domain signal is sent to the filter compensation module. In this module, the pilot symbol at the receiving end is extracted through the extraction pilot unit 1, and then the predicted value of the pilot symbol at the receiving end obtained by multiplying the estimated value of phase noise at the previous moment processed by the delay unit 5 and the pilot symbol at the transmitting end is extracted, and then The test pilot symbol of the receiving end and the predicted value of the pilot symbol of the receiving end are subtracted in the subtractor 2 to obtain the error signal between the measured value and the predicted value, and the multiplier 3 receives the error value and multiplies the Kalman gain to obtain the measurement. The correction value of the process to the prediction process, the obtained correction value and the phase noise value of the previous moment are added in the adder 4 to obtain the estimated phase noise value obtained by the Kalman algorithm, and then processed by the conjugate processing unit 7 to finally obtain the phase noise. The signal output after phase compensation is obtained by multiplying the noise compensation value by the symbol at the receiving end. The output phase noise compensation signal passes through the real-to-complex conversion unit, the parallel-to-serial conversion unit and the 16QAM constellation demapping to obtain the restored bit signal output.

In this embodiment, performance simulation is performed on the signal processed by the CO-FBMC/OQAM system provided by this solution and the signal processed by the Kalman phase noise compensation device based on blind decision. The BER performance comparison chart of the system under the laser linewidth, among which, P-EKF is the CO-FBMC/OQAM system proposed by the present invention. The 6 subcarriers are used to place the pilot structure proposed by this scheme, and the B-EKF is a system of Kalman filtering algorithm structure based on blind decision for performance comparison. The total number of subcarriers is 256, and the number of effective subcarriers Number 256, the figure compares the performance of the two schemes under the condition of back-to-back transmission and after 400km of optical fiber transmission. It can be seen from the figure that under the two conditions, the phase noise tolerance of this scheme is improved by about 1000 kHz compared with the scheme based on blind decision, which greatly proves the superiority of this scheme.

Those skilled in the art can easily understand that the above are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention, etc., All should be included within the protection scope of the present invention.

Claims (7)

1. A modulation method of CO-FBMC/OQAM is characterized by comprising the following steps:

(1) converting an input bit signal into a PAM data symbol;

(2) eliminating inherent imaginary interference of pilot frequency at two ends of the PAM data symbol and recording phase information of the pilot frequency symbol;

(3) receiving the frequency domain signal processed by the pilot frequency unit, modulating the frequency domain signal after the orthogonalization pretreatment of the frequency domain signal, and completing the conversion from the frequency domain signal to the time domain signal;

(4) carrying out parallel-to-serial conversion and training sequence processing on the acquired time domain signal, and carrying out IQ modulation to transmit the optical domain signal to a system receiving end;

(5) converting the received optical domain signal into a frequency domain signal to perform Kalman filtering phase noise compensation;

(6) recovering a bit signal after demapping the output signal of the phase compensation;

wherein, the specific steps in the step (5) are as follows:

(5.1) receiving the optical domain signal through coherent detection balance to obtain a baseband signal;

(5.2) demodulating the baseband signal after timing synchronization and serial-parallel conversion to obtain a frequency domain signal;

(5.3) subtracting the predicted value of the test pilot signal and the receiving end pilot signal in the frequency domain signal to obtain an error signal;

(5.4) multiplying the received error signal by Kalman gain, and combining the phase noise estimation value at the previous moment to obtain the estimation value of the phase noise at the current moment;

and 5.5, acquiring a phase noise compensation signal according to the estimated value of the phase noise and the pilot frequency symbol.

2. The modulation method according to claim 1, wherein the specific steps in the step (2) are:

(2.1) accessing three rows of subcarriers at one end of the PAM data symbol, placing pilot symbols at odd-numbered positions, placing zero symbols at even-numbered positions and placing zero symbols at the other two rows of subcarriers at zero positions of the middle row of subcarriers, and completing the access of a first pilot unit and the PAM data symbol;

(2.2) accessing three rows of subcarriers at the other end of the PAM data symbol, placing pilot symbols at even positions, placing zero symbols at odd positions and placing zero symbols at the other two rows of subcarriers of the middle row of subcarriers, and completing the access of a second pilot unit and the PAM data symbol;

and (2.3) receiving the PAM data symbols by the first pilot frequency unit and the second pilot frequency unit, eliminating the inherent imaginary part interference of the system and recording the phase information of the pilot frequency position.

3. The modulation method according to claim 1, wherein the step (5.3) comprises the following steps:

(5.3.1) extracting a test pilot signal at the receiving end of the pilot position;

(5.3.2) multiplying the pilot signal known by the transmitting end by the phase noise estimation value at the previous moment to obtain the predicted value of the receiving end pilot signal corresponding to the transmitting end pilot signal;

and (5.3.3) subtracting the predicted values of the test pilot signal and the pilot signal at the receiving end to obtain an error signal between the test pilot signal and the pilot signal.

4. The modulation method according to claim 3, wherein the step (5.4) comprises the following steps:

(5.4.1) multiplying the error signal by a fixed Kalman gain to obtain a correction value of the phase noise;

(5.4.2) adding the multiplied value and the phase noise estimated value of the previous moment to obtain the phase noise estimated value of the current moment.

5. The modulation method according to claim 4, wherein the step (5.5) comprises the following steps:

(5.5.1) performing conjugation processing on the phase noise estimation value at the current moment;

(5.5.2) multiplying the conjugate value of the phase noise by the pilot frequency symbol of the receiving end to obtain an estimated value after the phase noise compensation, and taking the estimated value as a signal of the phase noise compensation;

(5.5.3) the phase noise estimate value at the current time is subjected to delay processing as the phase noise estimate value at the previous time.

6. A CO-FBMC/OQAM system is characterized by comprising a symbol mapping module, a disturbance elimination pilot frequency module, a frequency domain-time domain conversion module, an IQ modulation module, an optical domain-frequency domain conversion module, a Kalman filtering compensation module and a symbol de-mapping module;

the symbol mapping module is used for receiving the bit data after serial-parallel conversion, outputting a signal after the complex number is converted into a real number, and transmitting a real value signal to the interference elimination pilot frequency module;

the interference elimination pilot frequency module receives the real-value signal transmitted by the symbol mapping module, outputs a frequency domain signal for eliminating the inherent interference of the pilot frequency, is used for eliminating the inherent imaginary part interference at the position of the pilot frequency, and is simultaneously used for recording the phase information in the pilot frequency signal so as to acquire the influence of the phase noise on the system;

the frequency domain-time domain conversion module is used for receiving the frequency domain signal transmitted by the interference elimination pilot frequency module and outputting a time domain signal;

the IQ modulation module is used for receiving a time domain signal and outputting an optical domain signal;

the optical domain-frequency domain conversion module is used for receiving an optical domain signal of a time domain signal converted by the IQ modulator and outputting a frequency domain signal;

the Kalman filtering compensation module is used for calculating a phase noise value on a pilot frequency symbol position based on the state of eliminating the inherent interference of the pilot frequency symbol by the interference elimination pilot frequency module, so as to compensate the phase noise and finally output a frequency domain signal after phase compensation;

the symbol demapping module is used for receiving the frequency domain signal of the frequency domain signal after the real number is converted into the complex number, and outputting bit data;

wherein, the Kalman filtering compensation module comprises: the device comprises a pilot frequency extracting unit (1), a subtracter (2), a first multiplier (3), an adder (4), a delay unit (5), a second multiplier (6), a conjugate processing unit (7) and a third multiplier (8);

the input end of the pilot frequency extraction unit (1) is connected with the output end of the optical domain-frequency domain conversion module, and the output end of the pilot frequency extraction unit is connected with the subtracter (2);

the input end of the subtracter (2) is connected with the output end of the pilot frequency extraction unit (1) and the output end of the multiplier (6), and the output end of the subtracter is connected with the input end of the first multiplier (3);

the input end of the first multiplier (3) is connected with the output end of the subtracter (2), and the output end of the first multiplier is connected with the input end of the adder (4);

the input end of the adder (4) is connected with the output end of the first multiplier (3) and the output end of the delay unit (5), and the output end of the adder is connected with the input end of the delay unit (5) and the input end of the conjugate processing unit (7);

the input end of the delay unit (5) is connected with the output end of the adder (4), and the output end of the delay unit is connected with the input end of the adder (4) and the input end of the second multiplier (6);

the input end of the second multiplier (6) is connected with the output end of the delay unit (5);

the input end of the conjugate processing unit (7) is connected with the output end of the adder (4), and the output end of the conjugate processing unit is connected with the input end of the third multiplier (8);

the input end of the third multiplier (8) is connected with the output end of the conjugate processing unit (7), and the output end of the third multiplier is connected with the real complex number conversion module;

the pilot frequency extracting unit (1) is used for extracting a pilot frequency signal from a receiving end pilot frequency;

the subtracter (2) is used for subtracting the pilot signal at the receiving end from the predicted pilot signal to obtain an error signal between the pilot signal and the predicted pilot signal;

-said first multiplier (3) is adapted to multiply the error signal by a fixed kalman gain;

the adder (4) is used for adding the result obtained by the multiplier (3) and the phase noise estimation value at the previous moment to obtain the phase noise estimation value at the current moment;

the delay unit (5) is used for converting the phase noise estimation value of the current moment into the phase noise estimation value of the previous moment;

the second multiplier (6) is used for multiplying the sending pilot signal with the phase noise estimated value at the previous moment to obtain a receiving pilot value corresponding to the predicted pilot symbol;

the conjugation processing unit (7) is used for obtaining a conjugation value of the phase noise at the current moment;

and the third multiplier (8) is used for multiplying the conjugate value of the phase noise at the current moment by the pilot frequency symbol at the receiving end to obtain an estimated value after the phase noise compensation.

7. The CO-FBMC/OQAM system according to claim 6, wherein the interference cancellation pilot module comprises a first pilot unit and a second pilot unit;

the first pilot frequency unit and the second pilot frequency unit respectively comprise 3 rows of subcarriers, pilot frequency symbols of the subcarriers located in the middle row are alternated with zero setting symbols, the subcarriers in the other two rows are set to be zero, and the pilot frequency symbols of the first pilot frequency unit and the second pilot frequency unit are respectively arranged at the odd number position and the even number position of the corresponding subcarriers.

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