Collaborative Research: Collaborative Quickest Detection in Ad hoc Networks with Application in Cognitive Radio

快速检测是监测随机过程中概率分布变化的一种重要技术。它被广泛应用于财务决策、环境监测和工业质量控制等问题。随着网络技术的快速发展，对基于多节点观测的快速检测和多节点决策提出了迫切的要求。基于这一需求，本研究研究了ad hoc网络中节点交换观测统计数据并对分布变化做出局部决策的协作最快检测。与现有的分散最快检测理论相比，协同最快检测不需要数据处理中心，从而避免了往返时间开销和可能的数据拥塞。此外，协作可以增强变更检测的敏捷性和健壮性。研究涉及统计信号处理（如检测规则）、信息论（如源编码）和网络（如调度或广播）等方面。协同快速检测技术在认知无线电系统中的一个重要应用是频谱感知。在这样的系统中，辅助节点需要监视主要用户的活动，一旦主要用户出现，辅助节点就应该退出该频段。这本质上是一个最快检测的问题，因为辅助节点需要尽可能快地检测更改。因此，本研究还涉及到认知无线电网络中协同最快检测的设计。跨学科的研究本质也有利于跨学科的教育。设计一学期的研究生水平课程，介绍快速检测、合作通信和认知无线电。该项目还希望吸引传统上代表性不足的群体。

Quickest detection is an important technique to detect the change of probability distribution in a random process being monitored. It is widely used in problems like financial decision making, environmental monitoring and industrial quality control. With the rapid development of networking techniques, there exist pressing demands to carry out quickest detection based on observations from many nodes and make decision at more than one node. Motivated by this demand, this research studies collaborative quickest detection in ad hoc networks, in which nodes exchange observation statistics and make local decisions about distribution change. In contrast to existing theory of decentralized quickest detection, the collaborative quickest detection does not need a data processing center, thus avoiding the round-trip time overhead and possible data congestion. Moreover, collaboration can enhance the agility and robustness of the detection of change. The research involves aspects of statistical signal processing (e.g. detection rule), information theory (e.g. source coding) and networking (e.g. scheduling or broadcast). An important application of collaborative quickest detection is spectrum sensing in cognitive radio systems. In such a system, secondary nodes need to monitor the activity of primary users and should quit the frequency band once primary users emerge. It is essentially a problem of quickest detection since the secondary nodes need to detect the change as quickly as possible. Therefore, this research also involves the design of collaborative quickest detection in cognitive radio networks. Inter-disciplinary essence of the research also lends itself to cross-disciplinary education. A one-semester graduate level course will be devised, which introduces quickest detection, cooperative communication and cognitive radio. This project also expects to attract traditionally underrepresented groups.