CN102195718B

CN102195718B - Method for demodulating chaotic pulse position modulated communication system

Info

Publication number: CN102195718B
Application number: CN 201110107110
Authority: CN
Inventors: 李辉; 恩德; 刘小磊; 张炜; 胡松华
Original assignee: Henan University of Technology
Current assignee: Henan University of Technology
Priority date: 2011-04-15
Filing date: 2011-04-15
Publication date: 2013-10-30
Anticipated expiration: 2031-04-15
Also published as: CN102195718A

Abstract

Aiming at the problem of relatively high bit error rate in the chaotic pulse position modulation communication system due to factors such as parameter mismatch and unsatisfactory synchronization characteristics between the receiver and the transmitter, the present invention proposes a chaotic pulse position modulation solution based on particle filter algorithm tune method. According to the mathematical model of the system, the demodulation end uses the particle filter to track the real modulated signal with the online separation method, and studies the performance of the proposed system by tracking the effect of the real signal and counting the bit error rate of the system. The simulation results show that: compared with the traditional chaotic pulse position modulation, the proposed method can track the real signal well, has good synchronization robustness, and can reduce the error propagation caused by the wrong judgment of the data, thus greatly reducing the error of the system. code rate.

Description

A Demodulation Method of Chaotic Pulse Position Modulation Communication System

技术领域technical field

本发明属于通信领域，尤其涉及一种混沌脉冲位置调制通信系统解调方法。The invention belongs to the field of communication, in particular to a demodulation method of a chaotic pulse position modulation communication system.

背景技术Background technique

近年来，由于良好的保密性和非周期性，混沌信号被广泛的应用到通信领域。考虑到实际通信条件，混沌信号对信道，滤波和通信噪声都要求苛刻。混沌脉冲位置调制系统利用相邻脉冲的间隔来携带信息，从而降低信道失真和滤波带来的消极影响，而且充分利用了混沌的保密性能，增强系统的可靠性。由于混沌脉冲位置调制系统是通过脉冲位置来解调系统的数字信息的，所以系统对发送端和接收端的同步有很高的要求，存在如下缺点：In recent years, chaotic signals have been widely used in the field of communication due to their good secrecy and aperiodicity. Considering the actual communication conditions, the chaotic signal has strict requirements on the channel, filtering and communication noise. The chaotic pulse position modulation system uses the interval between adjacent pulses to carry information, thereby reducing the negative effects of channel distortion and filtering, and fully utilizing the security performance of chaos to enhance the reliability of the system. Since the chaotic pulse position modulation system demodulates the digital information of the system through the pulse position, the system has high requirements on the synchronization of the sending end and the receiving end, and has the following disadvantages:

(1)实际系统受到扰动出现同步误差时，会导致数字信息错误判决，而由于延时环节在反馈环内，每一次混沌映射都包含所发送的序列信息，所以错误解调会导致误差传播；(1) When the actual system is disturbed and the synchronization error occurs, it will lead to wrong judgment of digital information, and because the delay link is in the feedback loop, each chaotic map contains the sequence information sent, so the wrong demodulation will lead to error propagation;

(2)实际系统的发送端和接收端总会存在参数失配现象，从而导致收发的同步误差，同步误差积累会产生大量误码。(2) There will always be a parameter mismatch between the sending end and the receiving end of the actual system, which will lead to synchronization errors in sending and receiving, and the accumulation of synchronization errors will generate a large number of bit errors.

粒子滤波算法是基于贝叶斯重要性抽样方法，在非线性的条件下利用最优估计来逼近真实值。算法主要利用粒子的随机游动性跟踪信号，并根据观测值确定每个粒子的权值，从而近似实际信号，并以样本的均值作为系统的估计值。由于混沌信号是一种典型的非线性信号，所以粒子滤波算法十分适合混沌信号处理。The particle filter algorithm is based on the Bayesian importance sampling method, which uses the optimal estimate to approach the true value under nonlinear conditions. The algorithm mainly uses the random walk of the particles to track the signal, and determines the weight of each particle according to the observed value, so as to approximate the actual signal, and uses the mean value of the sample as the estimated value of the system. Since the chaotic signal is a typical nonlinear signal, the particle filter algorithm is very suitable for chaotic signal processing.

发明内容Contents of the invention

本发明的目的是一种可以克服同步不理想带来高误码率的混沌脉冲位置调制通信系统解调方法。The object of the present invention is a demodulation method for a chaotic pulse position modulation communication system that can overcome the high error rate caused by unsatisfactory synchronization.

为实现上述目的，本发明采用以下技术方案，它包括如下步骤：To achieve the above object, the present invention adopts the following technical solutions, which may further comprise the steps:

步骤一，利用峰值检测器检测接收到的混沌脉冲位置调制信号，峰值检测器根据混沌脉冲位置调制信号的峰值设定检测器的阈值，判定高于该阈值的时刻收到一个混沌脉冲位置调制信号；Step 1, use the peak detector to detect the received chaotic pulse position modulation signal, the peak detector sets the threshold value of the detector according to the peak value of the chaotic pulse position modulation signal, and judges that a chaotic pulse position modulation signal is received at a time higher than the threshold ;

步骤二，利用计时器记录两个相邻的混沌脉冲位置调制信号之间的时间差；Step 2, using a timer to record the time difference between two adjacent chaotic pulse position modulation signals;

步骤三，将该时间差值送入粒子滤波器进行滤波，粒子滤波器将随机选取的粒子通过混沌映射后和随机选取的二进制信号进行组合，所得的值和观测值相比较计算当前粒子的权值；Step 3. Send the time difference to the particle filter for filtering. The particle filter combines the randomly selected particles with the randomly selected binary signal through the chaotic map, and compares the obtained value with the observed value to calculate the weight of the current particle. value;

步骤四，将滤波输出值和阈值比较器进行比较，阈值的设置值为由发送数据引起延时长度的一半。Step 4, compare the filtering output value with the threshold comparator, and the setting value of the threshold is half of the delay length caused by sending data.

采用上述技术方案的本发明，提出了一种混沌脉冲位置调制通信系统解调方法，可以解决现有混沌脉冲位置调制通信系统解调方法在同步不理想时带来高误码率的缺陷。The present invention adopting the above-mentioned technical solution proposes a demodulation method of a chaotic pulse position modulation communication system, which can solve the defect of high bit error rate caused by the existing chaotic pulse position modulation communication system demodulation method when the synchronization is not ideal.

附图说明Description of drawings

图1为粒子滤波混沌脉冲位置调制通信系统发射机原理图；Figure 1 is a schematic diagram of the transmitter of the particle filter chaotic pulse position modulation communication system;

图2为粒子滤波混沌脉冲位置调制通信系统接收机原理图；Fig. 2 is a schematic diagram of a particle filter chaotic pulse position modulation communication system receiver;

图3为粒子滤波混沌脉冲位置调制通信系统跟踪效果图；Figure 3 is a tracking effect diagram of the particle filter chaotic pulse position modulation communication system;

图4为存在同步差下粒子滤波方法和传统方法混沌脉冲位置调制通信系统误码率对比图。Figure 4 is a comparison chart of the bit error rate of the particle filter method and the traditional method chaotic pulse position modulation communication system in the presence of synchronization difference.

具体实施方式Detailed ways

本发明为一种基于粒子滤波的混沌脉冲位置调制通信系统解调方法，系统的工作原理如下所述：The present invention is a demodulation method of a chaotic pulse position modulation communication system based on particle filter. The working principle of the system is as follows:

混沌脉冲位置调制通信系统把待发送的二进制数字信息放到反馈环内，将原来的混沌映射结合数据信息转化成一个新的映射以实现调制。其系统动态方程数学模型为：The chaotic pulse position modulation communication system puts the binary digital information to be sent into the feedback loop, and converts the original chaotic map combined with the data information into a new map to realize modulation. The mathematical model of the system dynamic equation is:

T_n+1＝F(T_n)+S_n+1×d (1)T _n+1 ＝F(T _n )+S _n+1 ×d (1)

其中T_n是脉冲的间隔，F(T_n)是混沌映射函数，S_n是系统发送的二进制信息，为“0”或“1”，d是由发送数据引起的延时长度。Among them, T _n is the pulse interval, F(T _n ) is the chaotic mapping function, S _n is the binary information sent by the system, which is "0" or "1", and d is the delay length caused by sending data.

在发射机原理图1中，积分电路根据信号的延时量产生一个线性增长的电压，该电压和前一次经抽样保持电路和混沌映射F(·)产生的阈值进行比较。当超过该阈值时比较器会触发混沌时钟脉冲源，同时使数字信号源更新发送信息比特。因此，延迟的脉冲在t_n+1＝t_n+F(T_n)+d×S_n+1时刻产生。脉冲通过抽样保持电路首先更新阈值，然后对积分电路输出置零，最后通过脉冲信号发生器产生信道中发送的信号波形，即第n和第n+1个脉冲的时间间隔为T_n+1＝t_n+1-t_n＝F(T_n)+d×S_n+1。In the transmitter schematic diagram 1, the integrating circuit generates a linearly increasing voltage according to the delay of the signal, which is compared with the threshold generated by the previous sampling and holding circuit and the chaotic map F(·). When the threshold is exceeded, the comparator will trigger the chaotic clock pulse source, and at the same time make the digital signal source update the sending information bit. Therefore, a delayed pulse is generated at time t _n+1 =t _n +F(T _n )+d×S _n+1 . The pulse first updates the threshold through the sample-and-hold circuit, then sets the output of the integrating circuit to zero, and finally generates the signal waveform sent in the channel through the pulse signal generator, that is, the time interval between the nth and n+1th pulses is T _n+1 = t _n+1 −t _n =F(T _n )+d×S _n+1 .

在图2的接收机中，解调时首先使用峰值检测器检测接收到的信号，并利用计时器记下两个信号峰值之间的时间差。然后将该差值送入粒子滤波器进行滤波，最后滤波输出值和阈值比较器进行比较，大于阈值则判“1”输出，反之判“0”输出。In the receiver of Figure 2, the peak detector is used to detect the received signal during demodulation, and a timer is used to record the time difference between the two signal peaks. Then the difference is sent to the particle filter for filtering, and finally the filtered output value is compared with the threshold comparator. If it is greater than the threshold, it will be judged as "1" output, otherwise it will be judged as "0" output.

从前面的分析可知系统的观测方程为：From the previous analysis, we can see that the observation equation of the system is:

y_n＝T_n+ω_n (2)y _n =T _n +ω _n (2)

其中ω_n为高斯白噪声，用来表示由参数失配和随机扰动引起的同步误差，y_n为观测值。Among them, ω _n is Gaussian white noise, which is used to represent the synchronization error caused by parameter mismatch and random disturbance, and y _n is the observed value.

在利用粒子滤波进行跟踪解调时，采取了混沌信号在线分离办法。取y(1：n)∈{y(1)，…y(n)}，T(1：n)∈{T(1)，…T(n)}以及S(1：n)∈{S(1)，…S(n)}，其中y(1：n)∈{y(1)，…y(n)}为叠加同步误差后的观测信号，T(1：n)∈{T(1)，…T(n)}为源信号，S(1：n)∈{S(1)，…S(n)}为所发送的二进制信号。由于给定状态变量T(n)，S(n)，观测信号y(n)条件独立于边缘分布p(y(n)|T(n)，S(n))，由此可得到递推公式：When the particle filter is used for tracking and demodulation, the method of online separation of chaotic signals is adopted. Take y(1:n)∈{y(1),...y(n)}, T(1:n)∈{T(1),...T(n)} and S(1:n)∈{S (1),...S(n)}, where y(1:n)∈{y(1),...y(n)} is the observation signal after superimposing the synchronization error, T(1:n)∈{T( 1),...T(n)} is the source signal, S(1:n)∈{S(1),...S(n)} is the sent binary signal. Since the state variables T(n), S(n) are given, the observed signal y(n) is conditionally independent of the marginal distribution p(y(n)|T(n), S(n)), thus the recursion can be obtained formula:

$p p ((T T ((11 : : n no)))),, S S ((11 : : n no)) | | y the y ((11 : : n no)))) = = p p ((T T ((11 : : n no - - 11)),, S S ((11 : : n no - - 11)) | | y the y ((11 : : n no - - 11)))) \times \times$

$\frac{p p ((y the y ((n no)) | | T T ((n no)),, S S ((n no)))) \cdot \cdot p p ((T T ((n no)) | | T T ((n no - - 11)))) \cdot &Center Dot; p p ((S S ((n no)) | | S S ((n no - - 11))))}{p p ((y the y ((n no)) | | y the y ((11 : : n no - - 11))))} - - - - - - ((33))$

在上式中由于发送的二进制信号彼此间是相互独立的，所以p(S(n)|S(n-1))＝p(S(n))。从贝叶斯的观点看该模型的滤波问题即是利用带噪声的观测信号y(1：n)递推地估计联合后验概率密度函数p(T(1：n)，S(n)|y(1：n))及其边沿分布p(T(1：n)|y(1：n))和p(S(1：n)|y(1：n))。特别是得到p(T(1：n)|y(1：n))和p(S(1：n)|y(1：n))，由p(T(1：n)|y(1：n))和p(S(1：n)y(1：n))可以得到信号的状态分析。In the above formula, since the transmitted binary signals are independent of each other, p(S(n)|S(n-1))=p(S(n)). From the Bayesian point of view, the filtering problem of the model is to use the noisy observation signal y(1:n) to recursively estimate the joint posterior probability density function p(T(1:n), S(n)| y(1:n)) and its marginal distributions p(T(1:n)|y(1:n)) and p(S(1:n)|y(1:n)). In particular, p(T(1:n)|y(1:n)) and p(S(1:n)|y(1:n)) are obtained by p(T(1:n)|y(1 :n)) and p(S(1:n)y(1:n)) can get the state analysis of the signal.

基于粒子滤波的混沌脉冲位置调制通信系统解调方法的主要是思想是从先验分布函数U(t)(U(t)为均匀分布函数)中抽取随机粒子，二进制信息则服从离散等概分布，根据观测到的信息利用粒子滤波算法估计最优值来逼近真实值。通过峰值检测器检测出信号的时移长度，把得到的时移长度输入粒子滤波器进行解调。解调过程中，随机地选取粒子通过混沌映射后和随机的二进制信号进行组合，把得到的结果和观测值相比较计算当前粒子的权值。得出所有的粒子的权值后，如果粒子退化严重时，采用重采样减缓退化趋势。最后结合粒子的当前值和权重进行统计平均得出最优的结果。The main idea of the demodulation method of chaotic pulse position modulation communication system based on particle filter is to extract random particles from the prior distribution function U(t) (U(t) is a uniform distribution function), and the binary information obeys the discrete equiprobable distribution , according to the observed information, the particle filter algorithm is used to estimate the optimal value to approach the real value. The time shift length of the signal is detected by the peak detector, and the obtained time shift length is input into the particle filter for demodulation. During the demodulation process, randomly selected particles are combined with random binary signals through chaotic mapping, and the obtained result is compared with the observed value to calculate the weight of the current particle. After obtaining the weights of all particles, if the particle degrades seriously, resampling is used to slow down the degradation trend. Finally, the optimal result is obtained by combining the current value and weight of the particles for statistical averaging.

综上，解调端的粒子滤波算法基本流程如下：In summary, the basic flow of the particle filter algorithm at the demodulation end is as follows:

1)初始化：从先验分布中抽取初始状态

j＝1，…N；权重初始化

j＝1，…N。时刻n，对j＝1，…N执行下面的步骤1) Initialization: Extract the initial state from the prior distribution

j=1,...N; weight initialization

j=1, . . . N. At time n, execute the following steps for j=1,...N

2)一步预测2) One-step prediction

${y the y}_{n no}^{((j j))} = = {T T}_{n no}^{((j j))} + + {ω ω}_{n no}^{((j j))} - - - - - - ((44))$

3)计算权重3) Calculate the weight

4)重抽样4) Resampling

5)计算粒子滤波后的估计值

5) Calculate the estimated value after particle filtering

6)得到最优值后，根据系统方程和观测值进行解调6) After obtaining the optimal value, demodulate according to the system equation and the observed value

${p p}_{n no} = = {\overset{^^}{y the y}}_{n no} - - {y the y}_{n no} - - - - - - ((77))$

其中p_n为判决值。以d/2作为判决门限，大于d/2判决为“1”，反之为“0”。Where p _n is the judgment value. Take d/2 as the judgment threshold, if it is greater than d/2, the judgment is "1", otherwise it is "0".

7)n→n+1转到步骤2)。7) n→n+1 go to step 2).

为了显示基于粒子滤波算法的混沌脉冲位置调制系统的良好性能，通过仿真观察利用粒子滤波算法跟踪经过调制后的信号。仿真条件为：F(·)取带偏置的Tent映射，x_n+1＝1.4×|0.5-|0.5-(x_n-0.6)||+0.6+S_n+1×d，同步误差的方差取10^-3，采用100个粒子，仿真1000比特信号，发送信号“1”时的延时d＝0.4，截取500-600之间的100个比特，跟踪效果如图3所示。从图中可以看出，由于粒子滤波算法的随机游动性以及很好地处理非线性信号的优点，存在同步误差时其跟踪的效果良好，十分接近真实的发送信号。In order to show the good performance of the chaotic pulse position modulation system based on the particle filter algorithm, the modulated signal is tracked by the particle filter algorithm through simulation observation. The simulation conditions are: F(·) takes Tent mapping with bias, x _n+1 = 1.4×|0.5-|0.5-(x _n -0.6)||+0.6+S _n+1 ×d, the synchronization error The variance is 10 ^-3 , 100 particles are used, 1000-bit signal is simulated, the delay d=0.4 when the signal "1" is sent, and 100 bits between 500-600 are intercepted. The tracking effect is shown in Figure 3. It can be seen from the figure that due to the random walk of the particle filter algorithm and the advantages of dealing with nonlinear signals well, the tracking effect is good when there is a synchronization error, which is very close to the real sending signal.

下面对基于粒子滤波的混沌位置调制系统和传统的混沌位置调制系统的误码率进行比较。仿真中，同步误差方差取10^-2-10^-3之间的参数，采用1000个粒子和100000个比特信号，仿真结果如图4所示。从图中可以看出，相同的同步误差下由于基于粒子滤波的混沌脉冲位置调制系统能更好地跟踪调制后的信号，解调时其误码率明显要低于传统的混沌位置调制系统。The bit error rate of the chaotic position modulation system based on particle filter and the traditional chaotic position modulation system is compared below. In the simulation, the variance of the synchronization error takes parameters between 10 ^-2 -10 ^-3 , and 1000 particles and 100000 bit signals are used. The simulation results are shown in Figure 4. It can be seen from the figure that under the same synchronization error, the chaotic pulse position modulation system based on particle filter can better track the modulated signal, and its bit error rate during demodulation is obviously lower than that of the traditional chaotic position modulation system.

Claims

1. a kind of chaotic pulse position modulation communication system demodulation method is characterized in that, it comprises the steps:

Step 1, use the peak detector to detect the received chaotic pulse position modulation signal, the peak detector sets the threshold value of the detector according to the peak value of the chaotic pulse position modulation signal, and judges that a chaotic pulse position modulation signal is received at a time higher than the threshold ;

Step 2, using a timer to record the time difference between two adjacent chaotic pulse position modulation signals;

Step 3. Send the time difference to the particle filter for filtering. The particle filter combines the randomly selected particles with the randomly selected binary signal through the chaotic map, and compares the obtained value with the observed value to calculate the weight of the current particle. value;

Step 4, compare the filtering output value with the threshold comparator, and the setting value of the threshold is half of the delay length caused by sending data.