تلرانس خطا در شبکه حسگر بی سیم (WSN) با مبادله و تنظیم قدرت دینامیک

ABSTRACT Fault tolerance in wireless sensor network using hand-off and dynamic power adjustment approach

Wireless Sensor Networks (WSNs) are emerging as computing and communication platforms for monitoring various environments such as remote geographical regions, office buildings and industrial plants (Lee and Choi, 2008). The applications of WSNs are in various areas ranging from environment monitoring to battlefield scenarios. Sensor networks are composed of a large number of tiny sensor nodes equipped with limited computing and communication capabilities.

Each sensor node in WSN typically comprises of four units as shown in Fig. 1. They are as follows. (a) Sensor unit consists of a sensor to sense the environmental conditions such as temperature, pressure, humidity, etc. The sensed parameters are converted into digital form using ADC (Analog Digital Converter). (b) Processor unit includes a processor such as microcontroller and memory. (c) Transceiver unit includes wireless radio transmitter and receiver sections and (d) Power unit uses batteries that provide necessary power to remaining units. Each sensor node is operated by a battery, and usually, it is not feasible to replace or recharge this battery after deployment. The useful operational period or the lifetime of a sensor network is considered over as soon as the battery power of the critical nodes in the network is completely depleted (Bari et al., 2012).

Sensor nodes are used for monitoring environmental conditions such as temperature, pressure, humidity, fog, rainfall, smoke, etc.

These environmental conditions are monitored by exchanging the information among sensor nodes that are in the coverage area with the help of communication protocols. Communication protocols designed to exchange such information among the nodes of a sensor network should be designed to adapt to the dynamic conditions of either fixed topology or changing topology of a network depending upon the application for which the network is designed.

In the application scenario described above, there is a prime requirement to make the operation of a network without any type of disturbances. The disturbances in WSN are triggered by various reasons such as network failure, connectivity failure, node failure, link failure, unavailability of network due to misbehaving nodes that lead to inefficient functioning of the network. It is necessary to identify such faults in a network and fix them appropriately.

Our contributions in this paper are as follows. (a) Modeling node active status to identify node faults using the parameters such as battery power of a node and interference. (b) Designing fault tolerant mechanisms based on node battery power and interference. (c) Initiation of hand-off mechanism to a neighboring node whenever a node battery power reduces. (d) Dynamic power level adjustment of neighboring nodes if not involved in communication. (e) Performance evaluation of AFTBI for Packet Delivery Ratio (PDR), control overhead and fault recovery delay are analyzed. (f) Comparison of simulation results of AFTBI with FDWSN.

The rest of the paper is organized as follows. Section 2 discusses the active node model to identify faulty nodes along with an algorithm for assessing active node status. In Section 3, we described the fault tolerant mechanism using redundancy provisioning, Section 4 discusses the simulation environment, its procedure, parameters and results are discussed in Section 5. Section 6 concludes the paper.