基于OFDM的新型AIS系统设计及关键技术研究

发布时间：2018-08-06 15:26

【摘要】：船舶自动识别系统(Automatic Identification System,AIS)是一种工作于甚高频段的船舶识别和导航系统。AIS主要用于船舶航行的数字化导航,实现船船和船岸间航行信息的自动交换。随着船舶用户数量急剧增加,航运业务的日益繁忙,AIS的频带资源严重不足,时隙冲突日益严重;AIS的信息传输速率为9.6kbps,只能传输简单的广播信息,不能传输图片、音频信息、视频信息,无法进行天气实时播报。基于此,本文提出了一种基于正交频分复用(Orthogonal Frequency Division Multiplexing,OFDM)的新型AIS系统;就该系统对符号定时偏差和载波频率偏差敏感的问题,提出了一种基于相关特性函数的盲同步估计算法;针对新型AIS系统峰均功率比(Peak to Average Power Ration,PAPR)较高的问题,提出了低复杂度(Selected Mapping,SLM)限幅级联算法。本文工作如下:(1)新型AIS系统设计主要包括系统参数设计、系统的帧结构设计、子载波起始位置设计、SO-TDMA协议设计。新型AIS系统的船舶容量提高了6倍,减轻了高负载下的时隙碰撞问题,信息传输速率达到了67.2kbps,远高于现有AIS系统的9.6 kbps。(2)提出了基于相关特性函数的符号定时偏差和载波频偏同步算法,该算法在未知多径信道长度的情况下,直接通过对接收信号做相关构造一个归一化的相关特性函数,通过此函数便可得到符号时延位置?和多径信道长度L,进而得到载波频率偏差。(3)根据傅里叶变换的性质提出了低复杂度SLM限幅级联算法,该算法的计算复杂度可降低35%左右。与此同时,在分组数M满足??128 M时,该算法最为合适。文中详细地分析了SLM限幅算法。仿真表明该算法使新型AIS系统的PAPR值优化了6.04dB,低复杂度的SLM限幅级联算法的PAPR性能比单一算法好,具有更低的计算复杂度。
[Abstract]:Automatic ship Identification system (Automatic Identification system AIS) is a kind of ship identification and navigation system working in VHF section. AIS is mainly used for the digitized navigation of ship navigation and realizes the automatic exchange of navigation information between ship and shore. With the rapid increase in the number of ship users, the increasingly busy shipping business is seriously short of the frequency band resources of AIS. The information transmission rate of AIS is 9.6kbps. it can only transmit simple broadcast information, not pictures and audio information. Video message, can not be broadcast in real time weather. In this paper, a novel AIS system based on orthogonal frequency division multiplexing (Orthogonal Frequency Division) is proposed, and a blind synchronization estimation algorithm based on correlation characteristic function is proposed to solve the problem that the system is sensitive to symbol timing deviation and carrier frequency offset. In order to solve the problem of high peak-to-average power (PAPR) of a new AIS system, a low complexity (Selected Mapping PAPR) concatenation algorithm is proposed. The main work of this paper is as follows: (1) the design of the new AIS system mainly includes the design of system parameters, the frame structure of the system, and the design of SO-TDMA protocol. The ship capacity of the new AIS system is increased by six times, and the time slot collision problem under high load is alleviated. The rate of information transmission is 67.2 kpss, which is much higher than that of existing AIS systems. (2) A symbol timing offset and carrier frequency offset synchronization algorithm based on correlation characteristic function is proposed. By correlating the received signal directly, a normalized correlation characteristic function is constructed, through which the symbol delay position can be obtained. (3) according to the nature of Fourier transform, a low complexity SLM amplitude limiting cascade algorithm is proposed, and the computational complexity of the algorithm can be reduced by about 35%. At the same time, when the number of blocks M satisfies 128m, the algorithm is most suitable. In this paper, the SLM limiting algorithm is analyzed in detail. The simulation results show that the PAPR value of the new AIS system is optimized by 6.04 dB, and the PAPR performance of the low complexity SLM limiter cascade algorithm is better than that of the single algorithm, and the computational complexity is lower.
【学位授予单位】：天津理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：U675.7;TN929.53

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