Natarajan Meghanathan

On the stability of paths, Steiner trees and connected dominating sets in mobile ad hoc networks

We propose algorithms that use the complete knowledge of future topology changes to set up benchmarks for the minimum number of times a communication structure (like paths, trees, connected dominating sets, etc.) should change in the presence of a dynamically changing topology. We first present an efficient algorithm called OptPathTrans that operates on a simple greedy principle: whenever a new source-destination (s-d) path is required at time instant t, choose the longest-living s-d path from time t. The above strategy when repeated over the duration of the s-d session yields a sequence of long-lived stable paths such that number of path transitions is the global minimum. We then propose algorithms to determine the sequence of stable Steiner trees and the sequence of stable connected dominating sets to illustrate that the principle behind OptPathTrans is very general and can be used to find the stable sequence of any communication structure as long as there is a heuristic or algorithm to determine that particular communication structure in a given network graph. We study the performance of the three algorithms in the presence of complete knowledge of future topology changes as well as using models that predict the future locations of nodes. Performance results indicate that the stability of the communication structures could be considerably improved by making use of the knowledge about locations of nodes in the near future.

A Comprehensive Review and Performance Analysis of Data Gathering Algorithms for Wireless Sensor Networks

Wireless sensor networks comprise of vast numbers of sensor nodes deployed to monitor a particular event fire, intrusion, etc. or measure a parameter like temperature, pressure value representative of the physical condition of the ambient environment. There is a growing need of using energy-efficient data gathering algorithms that can effectively aggregate the monitored/measured data from the individual sensor nodes through a properly constructed communication topology and transmit a single representative data to a control center sink that is typically located far away from the network field. In order to maximize node lifetime and be fair to all nodes in the network, such a communication topology has to be dynamically constructed for every round of data gathering by taking into consideration available energy levels of sensor nodes. This paper presents a comprehensive description of two broad categories of data gathering algorithms for wireless sensor networks-the classical algorithms that are not energy-aware and modern energy-aware data gathering algorithms. These algorithms can also be classified based on the communication topology they choose to construct and use for data gathering. The authors also present an extensive simulation study that demonstrates the individual as well as the comparative performance of these data gathering algorithms.

An Algorithm to Determine the Sequence of Stable Connected Dominating Sets in Mobile Ad Hoc Networks

We show that given the complete knowledge of future topology changes, it is possible to determine the sequence of stable connected dominating sets (called the stable mobile connected dominating set) in a network session such that the number of CDS transitions is minimum. The algorithm to determine the mobile connected dominating set and the minimum number of CDS transitions is called OptCDSTrans and is based on a simple greedy approach: whenever a CDS is required, choose the CDS that will exist for the longest time. The above strategy is repeated over the duration of the network session. We prove that OptCDSTrans gives the optimal number of CDS transitions and simultaneously yields the stable mobile connected dominating set. We study the performance of OptCDSTrans in terms of number of CDS transitions and CDS size (the number of nodes constituting the CDS) for different conditions of node mobility and network density.

Impact of the Gauss-Markov Mobility Model on Network Connectivity, Lifetime and Hop Count of Routes for Mobile Ad hoc Networks

The high-level contribution of this paper is a simulation based analysis of the network connectivity, hop count and lifetime of the routes determined for mobile ad hoc networks (MANETs) using the Gauss-Markov mobility model. The Random Waypoint mobility model is used as a benchmark in the simulation studies. Two kinds of routes are determined: routes with the longest lifetime (stable paths) and routes with the minimum hop count. Extensive simulations have been conducted for different network density, node mobility values and different values of the degree of randomness parameter for the Gauss-Markov model. In low-density network scenarios, we observe that the network connectivity under the Gauss-Markov model is significantly lower than that obtained under the Random Waypoint model. In moderate and high density network scenarios, the network connectivity obtained under the two mobility models is almost equal. The minimum hop paths determined under the Gauss-Markov model have a larger number of hops than those computed under the Random Waypoint model. The lifetime of stable paths determined under the Gauss-Markov model is smaller than those determined under the Random Waypoint model. Low-density networks using the Gauss-Markov mobility model attain larger connectivity for intermediate values of the degree of randomness parameter, while the connectivity of moderate and high-density networks is not significantly dependent on the degree of randomness parameter. The minimum hop count of the paths is not much affected by different values of the degree of randomness parameter, while maximum lifetime stable paths are obtained for larger intermediate values of the degree of randomness parameter, but not for unity.

A Data Gathering Algorithm Based on Energy-Aware Connected Dominating Sets to Minimize Energy Consumption and Maximize Node Lifetime in Wireless Sensor Networks

This paper develops an energy-aware connected dominating set based data gathering ECDS-DG algorithm for wireless sensor networks. The algorithm includes only nodes that have a relatively higher energy level in ECDS. For every round, a data gathering tree ECDS-DG tree rooted at the ECDS Leader, that is, the node with the largest available energy, which transmits the data packet to the sink, is formed by considering only the nodes in the ECDS as the intermediate nodes of the tree. The non-ECDS nodes are leaf nodes of the tree, and the upstream node of an intermediate ECDS node in the ECDS-DG tree is the closest ECDS node that is also relatively closer to the ECDS Leader. Performance comparison studies involving well-known LEACH and PEGASIS algorithms indicate that ECDS-DG incurs the lowest energy consumption per round and sustains the largest number of rounds before first node failure.

A Location Prediction-Based Reactive Routing Protocol to Minimize the Number of Route Discoveries and Hop Count per Path in Mobile Ad Hoc Networks

We propose a new mobile ad hoc network routing protocol called ‘location prediction-based routing’ (LPBR) to simultaneously minimize the number of route discoveries and hop count of the paths for a source–destination session. During a regular flooding-based route discovery, LPBR collects the location and mobility information of nodes in the network and stores the collected information at the destination node of the route search process. When the minimum hop route discovered through the flooding-based route discovery fails, the destination node attempts to predict the current location of each node using the location and mobility information collected during the latest flooding-based route discovery. A minimum hop Dijkstra algorithm is run on the locally predicted global topology. If the predicted minimum hop route exists in reality, no expensive flooding-based route discovery is needed and the source continues to send data packets on the discovered route; otherwise, the source initiates another flooding-based route discovery. Simulation results indicate that LPBR incurs a significantly reduced number of flooding-based route discoveries, lower hop count per path, smaller route discovery overhead, lower end-to-end delay per packet and higher packet delivery ratio compared with that of the minimum hop-based, stability-based and position-based routing protocols.

Stability-Energy Consumption Tradeoff among Mobile Ad Hoc Network Routing Protocols

We present an ns-2 simulation based analysis on the energy consumption of the stability-oriented on- demand mobile ad hoc network (MANET) routing protocols. The stability-oriented routing protocols studied include Associativity Based Routing (ABR) [16], Flow-oriented Routing Protocol (FORP) [15] and Route-lifetime Assessment Based Routing (RABR) [1] protocol. Our simulation results show that FORP routes are more stable than RABR routes, which are more stable than ABR routes. On the other hand, based on the energy consumed per packet and the average energy used per node, ABR is better than RABR, which is better than FORP. Thus, we see a stability-energy consumption tradeoff within the class of stability- oriented routing protocols. Regarding the fairness of node usage, we observe that there is an appreciable variation in the energy consumption per node as only the chain of nodes that form stable routes are exhausted to a greater extent.

Spectral Radius as a Measure of Variation in Node Degree for Complex Network Graphs

The spectral radius of a network graph is the largest Eigen value of the adjacency matrix of the graph. We hypothesize the spectral radius to be a measure of the variation in the degrees of the nodes. In this pursuit, we define a metric called the spectral radius ratio for node degree as the ratio of the spectral radius to the average node degree. We validate our hypothesis by determining this metric on some of the commonly studied classical large real-world complex network graphs (undirected) for network analysis. Based on the results collected, we observe the spectral radius ratio for node degree to be positively correlated (correlation coefficient: 0.75) to the coefficient of variation in node degree (the ratio of the average node degree to the standard deviation in node degree), thus confirming our hypothesis.

A location prediction based routing protocol and its extensions for multicast and multi-path routing in mobile ad hoc networks

This paper discusses a new location prediction based routing (LPBR) protocol for mobile ad hoc networks (MANETs) and its extensions for multicast and multi-path routing. The objective of the LPBR protocol is to simultaneously minimize the number of flooding-based route discoveries as well as the hop count of the paths for a source-destination (s-d) session. During a regular flooding-based route discovery, LPBR collects the location and mobility information of nodes in the network and stores the collected information at the destination node of the route search process. When the minimum-hop route discovered through flooding fails, the destination node locally predicts a global topology based on the location and mobility information collected during the latest flooding-based route discovery and runs a minimum-hop path algorithm. If the predicted minimum-hop route exists in reality, no expensive flooding-based route discovery is needed and the source continues to send data packets on the discovered route. Similarly, we propose multicast extensions of LPBR (referred to as NR-MLPBR and R-MLPBR) to simultaneously reduce the number of tree discoveries and the hop count per path from the source to each multicast group receiver. Nodes running NR-MLPBR are not aware of the receivers of the multicast group. R-MLPBR assumes that each receiver node also knows the identity of the other receiver nodes of the multicast group. Finally, we also propose a node-disjoint multi-path extension of LPBR (referred to as LPBR-M) to simultaneously minimize the number of multi-path route discoveries as well as the hop count of the paths.

A REVIEW OF THE ENERGY EFFICIENT AND SECURE MULTICAST ROUTING PROTOCOLS FOR MOBILE AD HOC NETWORKS

This paper presents a thorough survey of recent work addressing energy efficient multicast routing protocols and secure multicast routing protocols in Mobile Ad hoc Networks (MANETs). There are so many issues and solutions which witness the need of energy management and security in ad hoc wireless networks. The objective of a multicast routing protocol for MANETs is to support the propagation of data from a sender to all the receivers of a multicast group while trying to use the available bandwidth efficiently in the presence of frequent topology changes. Multicasting can improve the efficiency of the wireless link when sending multiple copies of messages by exploiting the inherent broadcast property of wireless transmission. Secure multicast routing plays a significant role in MANETs. However, offering energy efficient and secure multicast routing is a difficult and challenging task. In recent years, various multicast routing protocols have been proposed for MANETs. These protocols have distinguishing features and use different mechanisms.