扩频组网突发通信中的同步问题研究

发布时间：2019-06-29 12:37

【摘要】：随着无线通信的发展,通信系统的抗干扰性能日益成为人们关注的重点,因此扩频技术应需而生并被广泛应用。在扩频通信系统中信号同步问题是影响系统性能的关键因素。在无线局域网中的突发通信模式使得在扩频组网突发通信中的同步问题更加成为人们研究的焦点。所以,本文对此类同步问题进行了相关的研究。首先,本文简要介绍了两种扩频技术的发展背景,以及突发通信的特点。在叙述了两种扩频系统的基本原理,并对直接序列扩频系统中的扩频伪码同步方法进行了系统的阐述之后,重点分析了跳频图案同步中的等待式同步法在军事通信中易于被敌人精确干扰的缺点,针对该缺点本文在组网通信的条件下,提出了一种新的同步方案,即离散频点同步法。与传统等待式同步方案在单一频率等待不同,新方案利用网络知识分别估计跳频图案中每一个频率的起始时刻,从而离散地解跳。如果某一个频率没有捕获到,接收机可以根据预期信息继续捕获下一个频率,因此,新方案中的整体同步过程并不会受影响。为仿真上述同步方法,本文在MATLAB/Simulink平台下搭建了三个系统模型,即基带直接序列扩频系统、基于直接序列扩频的预期帧检测系统和跳频通信系统。在上述系统中,扩频伪码的同步采用基于长序列相关的方法,跳频图案的同步则采用本文提出的离散频点同步方案。基于直接序列扩频的两个系统分别用于研究上述扩频伪码同步方法的抗噪声性能,以及该同步方法在具有一定网络知识的条件下的抗干扰性能。跳频通信系统用于研究新提出的离散频点同步方案的抗噪声性能、抗单频点干扰和抗特定频带干扰性能。最后,通过仿真本文得出如下结论:直接序列扩频的扩频伪码同步方法随着信噪比增加,同步的准确率提高,并在接近0dB处,准确率达到90%;预期帧检测系统随着信干比增加,检测的准确概率即同步准确概率也在提升,不同的预期帧格式,对应的同步性能不同;跳频系统的抗高斯噪声性能与一般非扩频通信系统相同,而采取离散频点同步方案的跳频系统比采取等待式同步方案的跳频系统的抗单频点干扰能力强,而对于特定频带干扰,信干比增加,系统误码率降低。不同的干扰因子对应着跳频系统不同的误比特率性能曲线,但对于采用新同步方案的跳频系统,在接近13dB处,误比特率都小于1e-3。
[Abstract]:With the development of wireless communication, the anti-interference performance of communication system has increasingly become the focus of attention, so spread spectrum technology should be born and widely used. Signal synchronization is the key factor affecting the performance of spread spectrum communication system. The burst communication mode in wireless local area network (WLAN) makes the synchronization problem in spread spectrum network burst communication more the focus of people's research. Therefore, this paper has carried on the related research to this kind of synchronization problem. First of all, this paper briefly introduces the development background of the two spread spectrum technologies and the characteristics of burst communication. After describing the basic principles of two kinds of spread spectrum systems and systematically expounding the synchronization method of spread spectrum pseudo codes in direct sequence spread spectrum systems, this paper focuses on the analysis of the shortcomings of waiting synchronization method in frequency hopping pattern synchronization, which is easy to be accurately interfered by the enemy in military communications. in view of this disadvantage, a new synchronization scheme, discrete frequency point synchronization method, is proposed in this paper under the condition of network communication. Different from the traditional waiting synchronization scheme at a single frequency, the new scheme uses network knowledge to estimate the starting time of each frequency in the frequency hopping pattern, so that the jump can be solved discretively. If a certain frequency is not captured, the receiver can continue to capture the next frequency according to the expected information, so the overall synchronization process in the new scheme will not be affected. In order to simulate the above synchronization method, three system models are built on MATLAB/Simulink platform, namely, baseband direct sequence spread spectrum system, expected frame detection system based on direct sequence spread spectrum and frequency hopping communication system. In the above system, the synchronization of spread spectrum pseudo-codes is based on long sequence correlation, and the synchronization of frequency hopping patterns is based on the discrete frequency point synchronization scheme proposed in this paper. Two systems based on direct sequence spread spectrum are used to study the anti-noise performance of the above spread spectrum pseudo-code synchronization method and the anti-interference performance of the synchronization method under certain network knowledge. The frequency hopping communication system is used to study the anti-noise performance, anti-single frequency point interference and anti-specific frequency band interference performance of the new discrete frequency point synchronization scheme. Finally, through simulation, the following conclusions are drawn: with the increase of signal-to-noise ratio (SNR), the accuracy of synchronization of spread spectrum pseudo-code synchronization method of direct sequence spread spectrum is improved, and the accuracy of synchronization is 90% when it is close to 0dB. With the increase of signal-to-interference ratio, the accurate probability of detection, that is, synchronization accuracy probability, is also improved, and the corresponding synchronization performance is different with different expected frame formats. The anti-Gaussian noise performance of frequency hopping system is the same as that of general non-spread spectrum communication system, but the frequency hopping system with discrete frequency point synchronization scheme has stronger anti-single frequency point interference ability than the frequency hopping system with waiting synchronization scheme, while for specific frequency band interference, the signal-to-interference ratio increases and the bit error rate of the system decreases. Different interference factors correspond to different bit error rate performance curves of frequency hopping system, but for frequency hopping system with new synchronization scheme, the bit error rate is less than 1e 鈮，

本文编号：2507825