Clustering provides an effective method for prolonging the lifetime of a wireless sensor network. Current clustering algorithms usually utilize two techniques; selecting cluster heads with more residual energy, and rotating cluster heads periodically to distribute the energy consumption among nodes in each cluster and extend the network lifetime. However, they rarely consider the hot spot problem in multihop sensor networks. When cluster heads cooperate with each other to forward their data to the base station, the cluster heads closer to the base station are burdened with heavier relay traffic and tend to die much faster, leaving areas of the network uncovered and causing network partitions. To mitigate the hot spot problem, we propose an Unequal Cluster-based Routing (UCR) protocol. It groups the nodes into clusters of unequal sizes. Cluster heads closer to the base station have smaller cluster sizes than those farther from the base station, thus they can preserve some energy for the inter-cluster data forwarding. A greedy geographic and energy-aware routing protocol is designed for the inter-cluster communication, which considers the tradeoff between the energy cost of relay paths and the residual energy of relay nodes. Simulation results show that UCR mitigates the hot spot problem and achieves an obvious improvement on the network lifetime.

Data gathering is a common but critical operation in many applications of wireless sensor networks. Innovative techniques that improve energy efficiency to prolong the network lifetime are highly required. Clustering is an effective topology control approach in wireless sensor networks, which can increase network scalability and lifetime. In this paper, we propose a novel clustering schema EECS for wireless sensor networks, which better suits the periodical data gathering applications. Our approach elects cluster heads with more residual energy through local radio communication while achieving well cluster head distribution; further more, it introduces a novel method to balance the load among the cluster heads. Simulation results show that EECS outperforms LEACH significantly with prolonging the network lifetime over 35%.

在路由协议中利用分簇技术可以提高无线传感器网络的可扩展性.当簇首以多跳通信的方式将数据传输至数据汇聚点时,靠近汇聚点的簇首由于转发大量数据而负载过重,可能过早耗尽能量而失效,这将导致网络分割.该文提出一种新颖的基于非均匀分簇的无线传感器网络多跳路由协议.它的核心是一个用于组织网络拓扑的能量高效的非均匀分簇算法,其中候选簇首通过使用非均匀的竞争范围来构造大小不等的簇.靠近汇聚点的簇的规模小于远离汇聚点的簇,因此靠近汇聚点的簇首可以为簇间的数据转发预留能量.模拟实验结果表明,该路由协议有效地平衡了簇首的能量消耗,并显著地延长了网络的存活时间.

无线传感器和反应器网络（wireless sensor and actor network,WSAN）由三种具有不同级别能力和作用的节点构成,节点的异构性导致单纯使用一种安全模型将无法满足不同节点对性能和安全性的要求。为此,本文首次提出了一种复合式的安全模型,根据节点的能力和作用将WSAN网络分为两层,不同层通过应用不同的安全机制,实现不同级别的安全服务。另外,本模型通过多种方式降低系统开销,力求达到安全和性能的平衡。

Clustering provides an effective way for prolonging the lifetime of a wireless sensor network. Current clustering algorithms usually utilize two techniques, selecting cluster heads with more residual energy and rotating cluster heads periodically, to distribute the energy consumption among nodes in each cluster and extend the network lifetime. However, they rarely consider the hot spots problem in multihop wireless sensor networks. When cluster heads cooperate with each other to forward their data to the base station, the cluster heads closer to the base station are burdened with heavy relay traffic and tend to die early, leaving areas of the network uncovered and causing network partition. To address the problem, we propose an energy-efficient unequal clustering (EEUC) mechanism for periodical data gathering in wireless sensor networks. It partitions the nodes into clusters of unequal size, and clusters closer to the base station have smaller sizes than those farther away from the base station. Thus cluster heads closer to the base station can preserve some energy for the inter-cluster data forwarding. We also propose an energy-aware multihop routing protocol for the inter-cluster communication. Simulation results show that our unequal clustering mechanism balances the energy consumption well among all sensor nodes and achieves an obvious improvement on the network lifetime

Wireless Sensor and Actor Networks (WSANs) consist of three types of nodes with different capabilities and functions. Because of these heterogeneities, current network security mechanisms would be hard to satisfy the security/cost requirements of all types of nodes. In this paper, we propose an integrated security approach, which splits the WSAN network into two layers according to nodes' functionalities and capacities. Different security mechanisms are provided to achieve the security services at corresponding levels. Furthermore, several methods are also used to reduce the system costs.