Dynamic Transmission Protocols and Advanced Signal Processing Techniques for Wireless Sensor Networks with Cooperative Diversity

无线传感器网络通常被定义为由小而低成本的传感器组成的密集无线网络，用于收集和传播数据。它们在各种领域都有应用，如系统维护、环境监测、交通、军事目的和在不适宜居住的地点收集信息。传感器网络的关键挑战之一是促进从远程位置更准确地监视和控制物理环境。回想一下，传感器网络的独特特征是节点移动性、频繁的链路故障、有限的链路容量以及有限的传感器设备的电池和计算资源，这给可靠的通信带来了巨大的挑战。下面的例子说明了这项提议的动机。动机的一个例子是：考虑一个场景，一排消防员冲进一座着火的建筑，准备执行救援任务。每个消防员都携带一台收发机，在大楼外与之通信并接受队长的命令。这种情况的一个基本要求是，每个消防员都被视为传感器，应该与船长或网络控制中心有稳定的连接。这样的传感器网络也可能需要支持实时视频流服务，因为消防员可能需要将他所看到的传输到外部进行安全评估。但现实情况是，由于室内环境中的多径衰落，无线链路并不稳定。为了满足这种多样化的服务质量，我们计划将协作分集这一以抗衰落能力著称的技术应用到传感器网络中。回想一下，通过使用协作分集，可以以低成本实现可靠的传输，并且易于实现，这是传感器网络应用的理想选择。该项目的目的是通过应用协作分集来提高无线传感器网络的系统吞吐量和传输健壮性。这项提议寻求的解决方案有两个方面。一是充分挖掘无线传播的动态特性，设计新的动态协作协议，为系统性能提供理论上的上界；第二步是从实际应用的角度出发，设计巧妙的数字信号处理算法，以实现协作协议所承诺的性能增益。显然，两者是密不可分的，这不仅是因为无线传感器网络可靠通信的最终目标只有在两者都完成的情况下才可能实现，而且因为两部分之间的交互是高效系统设计的关键。

Wireless sensor networks are typically defined as dense wireless networks of small and low-cost sensors which collect and disseminate data. They have applications in a variety of fields such as system maintenance, environmental monitoring, transportation, military purposes and gathering information in inhospitable locations. One of the key challenges for sensor networks is to facilitate monitoring and controlling of physical environments from remote locations with better accuracy. Recall that sensor networks are uniquely characterized by node mobility, frequent link failure, limited link capacity, and limited battery and computational resources of sensor devices, which pose significant challenges for reliable communications. The following example illustrates the motivation of this proposal. An example for the motivation: Consider a scenario where a platoon of firemen storm into a building burning for a rescue mission. Each fireman carries a transceiver with which he communicates and receives orders from the captain outside of the building. A basic demand of this scenario is that each fireman, viewed as a sensor, should have a stable connection with the captain, or a network controlling centre. And it is possible that such a sensor network also needs to support a real-time video stream service since a fireman might need to transmit what he sees to outside for safety evaluation. But the reality is that wireless links are not stable due to the multipath fading in the indoor environment. And the demand for high-speed high-quality real time service will make the task to satisfy the required quality of service more challenging.In order to meet such diversified quality of service, we plan to apply cooperative diversity, a technique well known for its ability to combat fading, to sensor networks in this proposal. Recall that, by using cooperative diversity, reliable transmission can be achieved at low cost and with easy implementation, which is ideal for the application of sensor networks. The aim of the project is to increase system throughput and transmission robustness of wireless sensor networks by applying cooperative diversity. The solution this proposal is seeking is two fold. One is to design new dynamic cooperative protocols by fully exploring the dynamic nature of radio propagation, which provides the theoretic upper bound of system performance. Then, the second step is from the practical aspect, where sophistic DSP algorithms shall be devised to realize the performance gain promised by the cooperative protocols. Obviously the two are inseparable not just because the ultimate goal of reliable communication for wireless sensor networks is only possible with the accomplishment of the both two parts, but also because the interaction between the two parts is the key for the efficient system design.