Xianghua Xu

Distributed fault diagnosis of wireless sensor networks

In wireless sensor networks (WSN), faults occurring to sensor nodes are common due to the sensor device itself and the harsh deployment environment. In order to avoid degradation of service due to faults, it is necessary for the WSN to be able to detect faults early. In this paper we propose a localized fault diagnosis algorithm which executes in tree-like networks effectively. It is based on local comparisons of sensed data and dissemination of the test results to the remaining sensors. Furthermore, Times redundancy is used to diagnose the intermittent fault in sensing and communication. Simulation results show the proposed algorithm has high detection accuracy and low false alarm rate.

An Enhanced Routing Protocol for ZigBee/IEEE 802.15.4 Wireless Networks

ZigBee is a well accepted industrial standard for wireless sensor networks based on IEEE 802.15.4. Since aiming for the application of low data rate, low price and low power consumption, ZigBee networks have the limited resources such as computation complexity and storage space. So it is especially important to design an efficient and effective routing protocol to save the consuming energy and extend the lifetime for ZigBee networks. In this paper, we survey two kinds of routing methods of the existing ZigBee routing protocol, and then propose two improved algorithms respectively. Simulation results show that the proposed routing version is a more efficient routing protocol, which can reduce routing overhead and routing discovery delay.

A review of cluster formation mechanism for clustering routing protocols

Clustering routing protocols have prominent advantages over flat routing protocols in terms of scalability, which is very useful for wireless mesh network with dense nodes distribution. However, clustering schemes will add large extra overhead in order to select cluster-heads and collect neighbor nodes information during the phase of cluster construction. At present, there exist a lot of excellent clustering schemes, and in this paper, we propose different classification criteria according to clustering charateristics. Then, we present a comprehensive review of several representatives, and especially focus on cluster formation mechanism. At last, we sum up with three typical problems we have to seriously consider when analyzing or design a clustering routing protocol.

A Novel Fault Detection and Recovery Mechanism for Zigbee Sensor Networks

Wireless Sensor networks (WSN) are prone to cause failures due to the constraining factors of energy, memory and communication capability. This paper describes an efficient faulty detection and recovery mechanism for ZigBee network which is an industrial standard widely adopted for WSN. We propose a localized tree based method for detecting faults due to energy exhaustion of nodes and repair them after node failure. We design three types of failure mechanisms depending on the type of node in the tree network of ZigBee. In order to avoid much more exchange message and reduce the collision of re-joining network, we take an ¿elected new parent¿ strategy from the disconnected children, and make the disconnected node re-join network together with as many descendant nodes as possible. Simulation results show that our proposed method consumes less energy than the original ZigBee network, and prolong the lifetime of network efficiently.

An Efficient Self-Healing Scheme for Wireless Sensor Networks

The reliability of wireless sensor networks is affected by faults that may occur due to various reasons. In ZigBee sensor networks, ZigBee specification presents a self-healing process which relies on its tree topology. When a ZigBee node failed, all of the descendants of the fault node should rejoin the network. Instead, we present an efficient scheme for repair itself after node failure that just one or some of the descendants should rejoin the network. It allows a subnet of fault node rejoin the network with minimum message exchanges and, therefore, saves energy. Simulation results show that most of subnet rejoin the network in the first level of sub-tree, and confirm the efficiency of the proposed scheme.

System for temperature monitor in substation with ZigBee connectivity

Monitor substation equipment temperature is one of the most important factors for power systems to ensure safe transmission of electricity. Traditional methods for monitoring the substation temperature shows many disadvantages such as low accuracy, heavy workload, lack of real-time, etc. Therefore, a low cost, high accuracy and automatic method is needed for power system. This paper presents a temperature monitor system for substation with ZigBee connectivity. Node hardware, network protocol and software on PC were presented. Finally, the implementation performance shows the sensor nodes have an automatic, small size, low power consumption, and network stability.

A Gradient Reconfiguration Mechanism of Directed Diffusion in Wireless Sensor Networks

In Wireless Sensor networks (WSNs), most existing routing protocols do not consider a node mobility problem, because nodes in sensor network are generally assumed to be static.The network may get partitioned, due to the mobility of some nodes will cause other nodes to lose their connection with the network. Network partitioning poses significant challenges to the provisioning of continuous data streaming services in WSNs. In this paper, we propose a routing scheme which supports node Mobility and Energy-Efficient based on Directed Diffusion (MEDD) for WSNs. In MEDD, we design a gradient model which considers energy consumption balance and real-time requirement. Based on this, we mainly propose a mechanism which makes node be able to localize the gradient reconfiguration whenever its movement occurs. It ensures the robustness of network transmission. Simulation results show that our proposed method decreases the network overhead and prolongs the lifetime of network efficiently.