Over the last few years, we have seen a rapid increase in the number of applications for wireless sensor networks (WSNs). WSNs can be deployed in battlefield applications, and a variety of vehicle health management and condition-based maintenance applications on industrial, military, and space platforms. For military users, a primary focus has been area monitoring for security and surveillance applications.
A WSN can be either source-driven or query-based depending on the data flow. In source-driven WSNs, sensors initiate data transmission for observed events to interested users, including possibly reporting sensor readings periodically. An important research issue in source-driven WSNs is to satisfy QoS requirements of event-to-sink data transport while conserving energy of WSNs. In query based WSNs, queries and data are forwarded to interested entities only. In query-based WSNs, a user would issue a query with QoS requirements in terms of reliability and timeliness. Adaptive Fault Tolerant QoS Control Algorithms for Maximizing System Lifetime of Query-Based Wireless
Data sensing and retrieval in wireless sensor systems have a widespread application in areas such as security and surveillance monitoring, and command and control in battlefields. In query-based wireless sensor systems, a user would issue a query and expect a response to be returned within the deadline. While the use of fault tolerance mechanisms through redundancy improves query reliability in the presence of unreliable wireless communication and sensor faults, it could cause the energy of the system to be quickly depleted. Therefore, there is an inherent tradeoff between query reliability vs. energy consumption in query-based wireless sensor systems. In this paper, we develop adaptive fault tolerant quality of service (QoS) control algorithms based on hop-by-hop data delivery utilizing “source” and “path” redundancy, with the goal to satisfy application QoS requirements while prolonging the lifetime of the sensor system. We develop a mathematical model for the lifetime of the sensor system as a function of system parameters including the “source” and “path” redundancy levels utilized. We discover that there exists optimal “source” and “path” redundancy under which the lifetime of the system is maximized while satisfying application QoS requirements. Numerical data are presented and validated through extensive simulation, with physical interpretations given, to demonstrate the feasibility of our algorithm design.