Space-Time Coding for Wireless Communications

无线通信的空时编码michael P. Fitz和Urbashi mita提案9980616，俄亥俄州立大学这项研究将扩展天线通信系统中信道编码公式的最新状态。最近有研究表明，如果在发射机和接收机上同时使用多个天线，无线通信系统的容量可以大大增加。此外，实现这种增益的一种方法是在传输的数据序列中引入空间和时间上的可控冗余（编码），这是传统的方案。这一领域的研究还很新，有几个关键问题需要解决。例如，寻找空时编码的高效计算方法是必要的。通常，无线信道是时变的，并不总是能够很好地估计信道条件；因此，评价空时码的鲁棒性是有价值的。一个相关的项目是考虑空时编码和解码方法与用于估计信道和其他关键通信参数的算法的相互作用。Turbo码最近成为实现近香农容量的强大码，因此将研究这种码的时空泛化。最后，由于目前对空时编码的大部分研究都是针对窄带时分多址系统进行的，因此我们也应该考虑宽带时分多址系统的空时码设计和解码器设计。第一个研究重点将集中在开发和分析改进的时空网格码搜索技术。目前搜索空时格码距离谱的方法计算量很大。将探讨减少错误状态网格大小的方法以及降低网格搜索方案的复杂性。下一个重点是在实际信道条件下评估空时码的鲁棒性。此外，还将考虑参数信道的空时编码。因此，受限信道的不确定性将会存在，针对这种情况的编码设计将会被开发出来。第三个研究重点是将空时涡轮码作为一种方法来实现对各种信道条件的鲁棒性。turbo编码方案的随机结构有望减轻编码结构与信道特性之间可能的相互作用。第四部分将研究CDMA信道的空时码设计。CDMA信号具有较大的维数，因此其空时码设计与单用户系统不同。此外，多径信道中的CDMA信号会导致不同的最优码设计。最后的研究课题将考虑空时编码背景下的接收机设计。也就是说，将研究空时编码和调制的信道估计和同步。将设计利用空时码特性的算法。此外，还将分析对精确信道估计和同步的性能依赖。

Space-Time Coding for Wireless CommunicationsMichael P. Fitz and Urbashi MitraProposal 9980616,The Ohio State University This research will extend the state of the art in channel coding formulti-antenna communication systems. It has recently been shown thatthe capacity of a wireless communications system can be greatlyincreased if multiple antennae are used both at the transmitter and thereceiver. Furthermore, a method for achieving such gains is tointroduce controlled redundancy (coding) in the transmitted datasequence spatially as well as temporally, which is the conventionalscheme. This area of research is still quite new and several keyproblem areas need to be addressed. For example, computationallyefficient methods for finding space-time codes are necessary. Typically, the wireless channel is time-varying and it is not alwayspossible to achieve good estimates of the channel conditions; thusevaluating the robustness of space-time codes is of value. A relatedproject is to consider the interplay of space-time coding and decodingmethods with algorithms designed to estimate the channel and other keycommunication parameters. Turbo codes have recently emerged aspowerful codes for achieving near Shannon capacity, thus space-timegeneralizations of such codes will be studied. Finally, much of thecurrent work on space-time coding is for narrowband time divisionmultiple access systems, thus we shall consider space-time code designand decoder design for wideband code-division multiple-access systemsas well. The first research thrust will focus on the development and analysisof improved search techniques for space-time trellis codes. Current methods for searching the distance spectrum of space-time trellis codes can be computationally expensive. Methods for reducing the size of the error state trellis coupled with reduced complexity trellis search schemeswill be explored. The next focus is on evaluating the robustness of space-timecodes under realistic channel conditions. In addition, space-time coding for parametric channels will be considered. Thus, constrained channel uncertainty will exist and code designs for such scenarios will be developed.The third research focus will be on space-time turbo codes as one method to achieve robustness to a variety of channel conditions. The random--like structure of turbo coded schemes hold some promise of mitigating the possible interactions between the code structure and the channel characteristics.Space-time code designs for CDMA channels will be investigated in the fourth research thrust. CDMA signals have a larger dimensionality andthus the space-time code design is different from that for single-user systems. In addition, CDMA signals in a multipath channel will result in different optimal code designs. The final research topic will consider receiver designs in the context of space-time coding. That is, channel estimation and synchronization for space-time coding and modulation willbe investigated. Algorithms which exploit the properties of space-timecodes will be designed. In addition, the performance dependence on accuratechannel estimates and synchronization will be analyzed.