Space-Time Coding for Wireless Communications

俄亥俄州立大学Michael P.Fitz和Urbashi MitraProposal 9980616，这项研究将扩展多天线通信系统中信道编码的最新技术。最近的研究表明，如果在发射机和接收机上都使用多个天线，则无线通信系统的容量可以大大增加。此外，实现这种增益的方法是在空间上以及时间上在传输的数据序列中引入受控冗余(编码)，这是常规方案。这一研究领域仍然是相当新的，需要解决几个关键问题领域。例如，寻找空时码的计算效率很高的方法是必要的。通常，无线信道是时变的，并不总是可能实现对信道条件的良好估计，因此评估空时编码的稳健性是有价值的。一个相关的项目是考虑空时编码和解码方法与设计用于估计信道和其他关键通信参数的算法的相互作用。Turbo码是最近出现的一种能够获得接近香农容量的强大码，因此将研究这种码的空时推广。最后，目前空时编码的大部分工作是针对窄带时分多址系统的，因此我们还将考虑宽带码分多址系统的空时码设计和译码设计。第一个研究重点将集中在改进的空时格码搜索技术的发展和分析上。当前搜索空时格码的距离谱的方法在计算上可能是昂贵的。将探索结合降低复杂性的网格搜索方案来减小错误状态网格的大小的方法。下一个重点是评估空时码在现实信道条件下的稳健性。此外，还将考虑用于参数信道的空时编码。因此，受限的信道不确定性将会存在，并将开发针对此类场景的码设计。第三，研究重点将是空时Turbo码作为一种实现对各种信道条件的鲁棒性的方法。Turbo编码方案的类随机结构有望缓解码结构与信道特性之间可能存在的相互作用。第四个研究方向将研究码分多址信道中的空时码设计。由于码分多址信号的维度较大，因此空时编码的设计不同于单用户系统。此外，多径信道中的码分多址信号将导致不同的最优码设计。最后的研究主题将考虑在空时编码的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，还将分析性能对准确的信道估计和同步的依赖关系。

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.