车辆协作通信快变信道建模及联合同步与信道估计的研究

For wireless access in vehicular environments, the advantages of cooperative techniques become apparent here since the redundant links established in cooperation offer high stability and better coverage in such volatile and dynamic propagation conditions. On the basis of the research on channel modeling and synchronization under the fast fading channel, we will investigate the statitics of vehiclular fast fading channels, and a joint channel estimation and synchronization algorithm for high speed cooperative OFDM systems is proposed, which is grounded on the radio testing platform constructed by the Project of "Research on the Method of Current Model of RF Integrated Circuits" supported by the National Natural Science Foundation of China. Firstly, Birth-Death propagation of high-speed vehicular environments is studied, and the multipath fading channel characteristics under some specific communication scenarios are obtained in theory. Furthermore, closed form expressions of first and second order statistics of the underlying channels are desired, and stochastic reference and simulation models under various propagation conditions will be established, which will be used to analyse the overall system level performance. Secondly, the joint channel estimation and synchronization scheme is considered. In the first place, we will introduce Bjorck sequences as training sequences, for it has a better ambiguity function than CAZAC sequences which are found several appications in the LTE wireless standard, making them suitable for radar and communication applications in the presence of high Doppler shifts. To achieve a good tradeoff between computational complexity, a tile-structure based pilot is considered. Based on the above ideas, we focus on the low complexity and high efficiency channel estimation and multiple parameter syschronization algorithms suitable for vehicular cooperative communication systems, and the problems of sparse pilots and multiple synchronization parameters for multiple nodes are investigated.

在车载环境这种易变和高度动态的无线传播条件下，采用协作中继技术建立的冗余链接可提供较高的链路质量和覆盖范围。本项目拟在我们对信道建模和快变信道OFDM同步的前期研究基础上，结合国家自然科学基金项目"射频集成电路设计的电流模式方法学研究"已构建的射频测试平台，对车辆协作通信快变信道统计特性进行理论研究和建模，并提出一种快变信道条件下协作OFDM联合信道估计和同步方案。在信道建模方面，针对车辆协作通信高速移动环境多径生灭现象进行理论研究，探讨信道统计特性的闭合表示方法，建立各种传播条件下信道统计参考模型和仿真模型，并用于系统性能分析。在联合信道估计和同步方面，拟利用具有良好正交性的Bjorck序列来设计训练序列，研究适合车辆通信的导频结构，研究适合车辆协作通信的低复杂度信道估计方法和同步方法，解决现存车辆协作通信中低密度导频分布快变信道估计和目的节点多个同步参数估计的难题。

车辆通信日益受到工业界和学术界的广泛关注,作为车辆通信标准802.11p或DSRC，LTE-V是车辆通信的一个新的标准，可以提升道路安全、提高交通效率并提供丰富的交通在线信息和娱乐服务。这对车辆通信关键技术及挑战，我们展开了如下研究：（1）首先研究了车辆通信信道特性与建模，这是车辆通信与其他无线通信系统最本质的区别；（2）针对适合车辆通信最小二乘法（LS）和最小均方误差（MMSE）信道估计改进方法展开研究，提出了相关的改进算法；（3）信道估计算法一般认为已经很好的同步，没有考虑实际的同步误差，因此本课题提出了联合时间同步和信道估计的方法；（4）随着3GPP在LTE版本14启动基于移动网络的车辆通信LTEV（V2V），我们开始对未来移动通信系统适合车辆通信的调制方法和波形的峰均比PAPR展开研究，提出了联合数字预失真的方法来降低波形的峰均比。. 高效可靠的车辆通信可为人类社会带来前所未有的便利，如队列、无人驾驶、感知和地图共享等。车辆通信技术仍有很多技术问题需要解决，后续我们将继续对基于蜂窝的车辆通信技术展开研究，这也是未来车辆通信发展的一个可以预见的趋势。