INFORMATION ROUTING AND RELIABILITY ISSUES IN DISTRIBUTED SENSOR NETWORKS

Communication issues and problems in information routing in distributed sensor networks (DSN's) are considered in this paper. We identify two important communication constraints, viz., the delay constraint and the reliability constraint: the impact of these on information routing are discussed. It is shown that the maximum end-to-end delay in a network depends on the diameter of the network, and efficient distributed algorithms are presented to determine the diameter of asynchronous networks. We present a new distributed algorithm to determine the diameter of an asynchronous tree network, when an arbitrary node in the network initiates the algorithm. It is shown that the start node determines the diameter of the network in 2h(max) units of time, using exactly 2(n - 1) messages where n is the number of nodes in the tree. Another efficient algorithm is presented to determine the diameter when multiple nodes initiate the algorithm. It is established that in the worst case, each start node determines the diameter in less than 2h(max) (S) + D units of time, using at most 4(n - 1) messages, where h(max) (S) is the maximum height of a subtree rooted at any start node, and D is the diameter of the tree. An algorithm to determine the diameter of arbitrary networks is presented, and its message complexity is shown to be O (n, Absolute value of E) where Absolute value of E is the number of edges in the network. The effects of link/node failures on network delay are studied, and important network structure design criterion incorporating a specified degree of reliability, and maximum end-to-end delay are discussed. Finally, the distributed, dynamic routing algorithms are reviewed, and their adaptations to the DSN environments are discussed.