基于V-OFDM调制的卫星通信与导航一体化系统

发布时间：2018-01-30 11:24

  本文关键词： 向量正交频分复用 卫星通信 全球卫星导航系统 误码率 定位精度 稀疏信道 分集阶数　出处：《南京大学》2017年博士论文　论文类型：学位论文

【摘要】：卫星通信系统和卫星导航系统发展到今天给人们的生产生活带来了极大的便利,也同样面临着卫星频谱资源紧张、信道频率选择性衰落严重等许多亟待解决的问题。现阶段,尽管卫星通信和卫星导航面向不同的应用领域,但从技术层面来看两者之间存在密切联系。一方面,卫星通信的可靠性关系到接收机的抗干扰特性和导航电文的误码率,进而影响接收机的定位精度。另一方面,导航定位信号通过对传播时延的估计实现卫星通信系统的码元定时同步,而同步性能直接影响通信系统的可靠性。因此,在天地一体化信息网络背景下,建设卫星通信与导航一体化系统对于充分利用空间资源实现一星多用具有十分重要的意义。论文从通信和导航的基本性能指标误码率和定位精度出发,综合考虑频带利用率、峰均功率比和系统复杂度等因素,提出了基于向量正交频分复用(V-OFDM)调制的卫星通信和导航一体化系统,并对信道分配、导频设计、信道估计、信号检测、码元同步等关键技术进行了深入研究,取得了一系列创新性研究成果。首先,论文在比较单载波频域均衡(SC-FDE)和正交频分复用(OFDM)各自优缺点的基础上,综合得出V-OFDM调制模型,并指出V-OFDM是连接SC-FDE和OFDM的桥梁。V-OFDM调制的思想是将一个码间干扰信道划分为多个向量子信道,其中向量维数可以灵活设计。然而,V-OFDM调制在个别子载波传输信号无法获得分集增益,通过在发射端引入星座图旋转矩阵,能够使得所有子载波均能够获得全部的分集增益。设计了硬件上易于实现的并行旋转V-OFDM系统,通过优化星座图旋转角度,可在获得分集增益的同时,进一步提高编码增益。综合比较了宽带频率选择性衰落信道下接收机的误码率性能和解码复杂度,当信噪比较低时,可采用最小均方误差接收机;而当信噪比较高时,可采用球形解码。然后,论文研究了 V-OFDM卫星通信与导航一体化系统的可靠传输。针对卫星信道传播距离长的特点,建立了宽带稀疏频率选择性衰落卫星信道模型。揭示了稀疏信道的最大多径分集增益等于非零元素坐标对向量维数取模运算后余数集合的势,运用数学归纳法推导了随机信道分集阶数的分布律的闭合表达式。论文充分利用信道矩阵的稀疏性,提出了部分交集球形解码接收机,通过缩小搜索空间降低解码复杂度,并推导了球面半径极限定理。对于极端情况下候选发送符号向量集合为空集时,采用加权表决思想根据部分交集球形解码每次迭代过程中落入球面半径内的符号序列集合对发送信号作出判决,克服了部分交集球形解码在低信噪比条件下难以解码的缺点。为了适应卫星信道复杂快变的特点,采用基于加权表决的部分交集球形解码接收机能够在获得最大多径分集增益的同时,尽可能地降低接收机的解码复杂度,实现业务信号和导航电文的可靠传输。最后,论文研究了 V-OFDM卫星通信与导航一体化系统的精确定位。采用梳状导频结构不仅可以利用均匀分布的导频信道实现信道估计,并通过设计最优导频符号使得信道估计的均方误差达到最小,而且能够保证数据信号获得最大多径分集增益。深入研究了稀疏快速傅里叶变换运用散列合并实现降维过程,包括其中涉及的两个信号处理方法:置换和加窗滤波,揭示了理想/噪声环境信道估计与狭义/广义稀疏快速傅里叶逆变换之间的内在联系。利用导频信号实现码元同步通常包括捕获和跟踪两个阶段,通过调整接收机快速傅里叶变换滑动窗的起始点实现符号定时粗同步,随后动态调整传播时延估计实现精确同步。提出了基于牛顿迭代的多径时延最大似然估计方法,并推导了码跟踪精度的克拉美罗界。对于莱斯衰落卫星信道,设计了易于实现的超前/滞后延迟锁相环时延估计方法。全局最优的最大似然位置估计直接优化终端三维位置坐标,避免了因引入中间变量造成的误差累积,能够获得潜在的星座分集,实现地面终端的精确定位。论文在全面阐述V-OFDM调制的基础上,提出了宽带卫星通信和导航一体化系统,设计了具有误码率低、时延估计均方误差小的接收机。基于V-OFDM调制的卫星通信与导航一体化系统的提出为实现可靠传输和精确定位奠定了坚实的基础,进一步把天地一体化信息网络建设引向深入。
[Abstract]:The satellite communication system and satellite navigation system development today to people's production and life brought great convenience, is also facing the same satellite spectrum resource and serious problems including frequency selective fading channels. At this stage, although the satellite communications and satellite navigation for different application areas, but from the point of view of both the technical level there is a close relationship. On the one hand, related to the error rate of the receiver anti-jamming characteristic and the reliability of navigation satellite communication, thereby affecting the accuracy of the positioning receiver. On the other hand, positioning signals to realize symbol timing synchronization in satellite communication system by estimating the propagation delay, and the synchronization performance directly affects the reliability of communication system so, in the world of integrated information network under the background of the construction of satellite communication and navigation system to make full use of space resources To achieve a multi-purpose star has very important significance. This paper from the basic performance index of the bit error rate of communication and navigation and positioning accuracy of the comprehensive consideration of the utilization of bandwidth, peak to average power ratio and system complexity and other factors, proposed a vector based on orthogonal frequency division multiplexing (V-OFDM) modulation of satellite communication and navigation system, and the channel allocation, pilot design, channel estimation, signal detection, symbol synchronization technology conducted in-depth research, made a series of innovative research results. Firstly, the thesis is on the single carrier frequency domain equalization (SC-FDE) and orthogonal frequency division multiplexing (OFDM) based on their respective advantages and disadvantages, and concluded that the V-OFDM modulation model, and points out that V-OFDM is a bridge connecting the SC-FDE.V-OFDM modulation and OFDM is the idea of a intersymbol interference channel into multiple to the quantum channel, which can be a flexible vector dimension design. However, V-OFDM Modulation cannot obtain diversity gain in a sub carrier signal transmitted by the transmitter is introduced in the constellation rotation matrix, makes all subcarriers can obtain diversity gain. All the hardware design of V-OFDM system to realize the parallel rotation, by optimizing the constellation rotation angle, can achieve the diversity gain at the same time, to further improve the encoding gain. A comprehensive comparison of broadband frequency selective fading channel BER performance and decoding complexity of the receiver, when the SNR is low, the MMSE receiver; and when the SNR is high, the sphere decoding is studied in this paper. Then, the reliable transmission of V-OFDM satellite communication and navigation system according to the characteristics of satellite communication channel. The long distance, the establishment of a satellite broadband frequency selective fading channel model is sparse. The diameter of the sparse channel are revealed 鍒嗛泦澧炵泭绛変簬闈為浂鍏冪礌鍧愭爣瀵瑰悜閲忕淮鏁板彇妯¤繍绠楀悗浣欐暟闆嗗悎鐨勫娍,杩愮敤鏁板�﹀綊绾虫硶鎺ㄥ�间簡闅忔満淇￠亾鍒嗛泦闃舵暟鐨勫垎甯冨緥鐨勯棴鍚堣〃杈惧紡.璁烘枃鍏呭垎鍒╃敤淇￠亾鐭╅樀鐨勭█鐤忔，

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