ITR: Cooperative Wireless Networks

我们正处于一场新的无线革命中，这场革命是由消费者、军事、科学和其他应用采用无线网络所引发的。无线网络是能够使用无线接入方法向附近节点发送和接收信息的终端或节点的集合。无线信道的苛刻特性对无线网络节点之间的通信提出了根本的挑战。在无线链路上可靠通信的关键是利用分集，即在不同的衰落条件下观察相同的信息。虽然可以通过在不同的时间或频率传输相同的信号来利用分集，但从带宽的角度来看，隐含的冗余是昂贵的。然而，已经表明，在源和/或目的地引入额外的天线可以在不影响带宽效率的情况下实现分集增益。无线网络节点可以配备也可以不配备多天线。那么，他们如何确保在衰落的无线信道上进行可靠和高效的通信呢？在这项研究中，我们研究了一种新的策略，通过这种策略，节点可以协同发送和接收，从而可以利用原本无法利用的空间分集增益。从灵活性、可重构性和低管理成本的角度来看，无线网络中缺乏结构是有利的。然而，同样缺乏结构，使合作战略的实施具有挑战性。例如，可能很难知道哪些辅助节点已经正确地接收到该消息。事实上，可能很难知道哪些节点(如果有的话)可以被征募为帮助者。在这项研究中，我们通过分布式协作编码策略、巧妙的协议和复杂的信号处理技术相结合来解决这些问题。PI正在利用各自在空时编码和盲信号处理方面的专业知识，为无线网络中的协作通信设计实用的策略。此外，本研究还通过对信息论界限的研究，探讨了协作无线网络容量的基本极限。

We are in the midst of a new wireless revolution, brought on bythe adoption of wireless networks for consumer, military,scientific and other applications. Wireless networks are acollection of terminals, or nodes, that are capable oftransmitting and receiving information to nearby nodes usingwireless access methods. The harsh characteristics of the wireless channel provide thefundamental challenge for communication between wireless networknodes. The key to reliable communication over wireless links is theexploitation of diversity, i.e., observation of the sameinformation through different fading conditions. While it ispossible to harness diversity by transmitting the same signal atdifferent times or frequencies, the implied redundancy is costlyfrom a bandwidth perspective. It has been shown, however, thatintroducing additional antennas at the source and/ordestination enables diversity gain without compromise inbandwidth efficiency. Wireless network nodes may or may not be equipped with multipleantennas. How then, can they ensure reliable andefficient communication over the fading wireless channel? In this research, we investigatenovel strategies by which nodestransmit and receive cooperatively, allowingexploitation of spatial diversity gain that would otherwise beunavailable.The lack of structure in ``ad-hoc'' wireless networks isadvantageous from the viewpoint of flexibility,re-configurability, and low management cost. The same lack ofstructure, however, makes the implementation of cooperativestrategies challenging. It may be difficult, for example, to knowwhich of the helper nodes have correctly received the message. Infact, it may be difficult to know which, if any, of the nodes canbe enlisted as helpers. In this research, we solve these problemsthrough the combination of distributed cooperative codingstrategies, clever protocols, and sophisticated signalprocessing techniques. The PIs are leveraging their respective expertise inspace-time coding and blind signal processing to devisepractical strategies for cooperative communication inwireless networks. In addition, this research investigates thefundamental limits on the capacity of cooperative wirelessnetworks through a study of information-theoretic bounds.