【作者】 刘婷婷；

【导师】 刘顺兰；

【作者基本信息】 杭州电子科技大学 ， 通信与信息系统， 2009， 硕士

【摘要】 随着航空事业的发展,航空通信越来越受到人们的关注,也将在未来无线移动通信发展中发挥越来越重要的作用。在航空通信中,由于飞行器的快速运动,接收信号受到航空信道的严重的多径衰落的影响。因此,对于航空信道进行精确、有效、合理的建模具有重要意义。本文主要研究了航空信道的模型的建立及其应用,完成的工作如下:(1)对无线信道的特性进行研究,主要分析了通信环境中移动台的移动速度、电波频率以及信道的时间选择性和频率选择性衰落特性。并在此基础上,重点研究了航空信道的传播特性,根据飞行器状态的不同,将航空信道分为飞行场景、起飞和降落场景、陆地滑行场景和对流层散射场景等四类不同的航空信道场景,并分析了与之对应的大尺度衰落和小尺度衰落的特性,主要包括路径传播损耗、衰落深度、衰落速率、多普勒功率谱和延迟功率谱。(2)在航空通信系统条件下,根据信道在四种不同场景下的特性分别建立了相应的信道模型,并对所有建立的模型进行了仿真,通过对实验结果与理论分析的比较,可以得出两者是一致的,从而验证了模型建立的合理性和有效性。(3)研究了传统的SC-FDE系统在所建立的航空信道模型(四种场景)下的应用并对其进行了仿真,由于航空信道的恶劣特性,传统的SC-FDE系统传输性能很差,无法满足通信需要,本文建议了SC-FDE系统的改进方案即基于Turbo编码的SC-FDE系统,并将改进系统在四种不同场景下的信道模型上进行了仿真,并与传统的SC-FDE系统的误码率性能进行分析和比较,验证了改进系统的有效性,从而使得通信系统在比较复杂的航空信道上也可以得到比较好的传输性能(如在起飞和降落场景下,在信噪比较小的情况下系统的误码率BER可达到10?6甚至更小),从而满足信息传输的要求。(4)为进一步提高SC-FDE系统的传输质量,本文还研究了系统的定时同步方法,提出了一种新的定时同步算法,并在四种不同的航空信道中进行了仿真,仿真结果表明,在不同的航空信道中,原有的Schmidl&Cox算法有比较明显的平台效应,对于符号的定时同步很不准确:而本文中提出的新算法则很好地克服了原有的算法中峰值长度较大且不容易定位的问题,更能可靠地定位传输符号的起始位置。更多还原

【Abstract】 As the aviation enterprise develops, aeronautical communication attracts more and more attention and it will play a more important role in wireless mobile communication in the future. In the aeronautical communication, the rapid speed of the aircraft causes that the received signal suffers a lot from the multipath fading of the aeronautical channel. As a result, it is of great importance to build accurate, efficient and reasonable aeronautical channel models.This paper presents the simulation model of the aeronautical channel and its application. The main work in this paper is as follows:1. This paper studies the characters of the wireless channel, and mainly analyzes the speed of the mobile station in the communication environment, the frequency of the electric wave, the time selective fading character and the frequency selective fading character of the wireless channel. Based on this, the propagation characteristic of the aeronautical channel is specifically studied. According to the different state of the aircraft, the aeronautical channel consists of four different scenarios: en-route scenario, arrival and takeoff scenario, taxi scenario and troposcatter communication scenario, and the characters of large scale fading and small scale fading of each of the four scenarios were analyzed, such as the path loss, the fading depth, the fading rate, the Doppler power spectrum and the delay power spectrum.2. In the aeronautical communication, the channel models of the four different scenarios are separately built and simulated. The computer simulation result shows that the theory analysis agree with the experiment, and it proves the efficiency and rationality of the channel model.3. This paper studies the traditional SC-FDE system in the aeronautical channel models (four scenarios) and simulates it. Because of the bad transmission performance of the aeronautical channel, the traditional SC-FDE system has bad performance and can not satisfy the communication system. The improved SC-FDE system based on Turbo coding is proposed in this paper, and the simulation of the improved system in the four different scenario channels is analyzed and compared. The simulation result proves the efficiency of the improved system, and it has better transmission performance even in more complicated aeronautical channel and satisfies the communication, For example, in the channel of the arrival and takeoff scenario, the proposed improved SC-FDE system can achieve lower BER performance with 10?6 in the condition of low SNR.4. In order to further improve the transmission quality of the SC-FDE system, this paper studies the timing synchronization, and proposes a new timing synchronization method and simulated it in four different scenario channels. The results show that, in different aeronautical channels, the intrinsic Schmidl&Cox method has obviously plateau effect and it is not accurate for symbol timing synchronization. The new method in this paper can overcome the shortage in the Schmidl&Cox method in which the length of the peak value is large and it is difficult for symbol timing, and the new method can do better and more reliably in the symbol timing synchronization.更多还原