Optimum Receivers Under Complexity Constraints for Radio CDMA Communications

9406069瓦拉纳西几种民用非定向通信应用，如移动无线电话和个人通信服务，都需要带宽效率高的多址无线电通信以及系统设计上的极大灵活性。码分多址(码分多址)的动态信道共享策略特别适合这种应用，它的可行性目前正在被积极研究。本课题将通过对这一广泛课题的多个方面的研究，为衰落多径无线信道中的码分多址通信提出复杂性约束下的最优接收机理论。为了简明地刻画多用户衰落信道中不可估量和可估量干扰的影响，定义了抗远近和抗衰落的渐近性能指标。针对慢衰落、时变但无记忆的多径衰落码分多址信道，提出了最优线性检测规则的设计与分析。对于具有记忆的动态时变多径衰落信道，将发展具有远近效应和抗衰落能力的线性自适应接收机。组检测的概念将在高斯和时变多径衰落的码分多址信道的背景下进行研究，以便解决在需要带宽高效通信的应用中弥合线性检测器和最佳检测器之间的性能差距的具有复杂性的策略的需求。通过设计签名波形，在带宽约束下优化衰落信道检测器的性能，也解决了接收机的最优化问题。这一研究工作的结果将产生在各种复杂性约束下的最优集中式码分多址接收机，这些接收机非常适合在基站上实现，并且将作为功能和性能的理想，由受更低复杂度约束的分散信号接收方案来仿真。***

9406069 Varanasi Several civilian nondirectional communication applications such as mobile radio telephony and personal communication services require bandwidth-efficient multiple-access radio communication as well as a tremendous flexibility in system design. The dynamic channel sharing strategy of Code-Division Multiple-Access (CDMA) is particularly well-suited and its feasibility for such applications and is currently being actively investigated. This project will advance the theory of optimum receivers under complexity constraints for CDMA communication in fading multipath radio channels through research on several aspects of this broad subject. The asymptotic performance measures of near-far resistance and fading resistance will be defined in order to succinctly characterize the effects of estimable and inestimable interference in multiuser fading channels. The design and analysis of optimum linear detection rules for slowly fading and time-varying but memoryless multipath fading CDMA channels is proposed. Linear adaptive receivers that are near-far and fading resistant will be developed for dynamically time-varying multipath fading channels with memory. The concept of group detection will be studied in the context of Gaussian as well as time-varying multipath fading CDMA channels in order to address the need for strategies with complexities ranging between those of linear and optimal detectors that bridge the wide gap in performance between them in applications requiring bandwidth efficient communication. Receiver optimality is also addressed through the design of signature waveforms that optimize the performance of fading channel detectors under bandwidth constraints. The results of this research effort will yield optimum centralized CDMA receivers under various complexity constraints that are well-suited for implementation at base stations and that will serve as ideals in both function and performance to be emulated by decentralized signal reception schemes constrained by even lower complexities. ***