g Hyun Jun

LIMOC: Enhancing the Lifetime of a Sensor Network with Mobile Clusterheads

This paper proposes a scheme for enhancement of network Lifetime using MObile Clusterheads (LIMOC) in a wireless sensor network (WSN). The low energy, static sensor nodes sense physical parameters and route the data to the highly energy-rich nodes called ClusterHeads (CHs) which are mobile and can transmit data directly to the base station (BS). A collaborative strategy among the CHs increases the lifetime (hence residual energy) of the network further. Simulation has shown that residual energy of the network can be improved by 45% by making the CHs always move towards the event in an event-driven network. For general cases, increased energy savings is obtained by making the CH move towards the center of equilibrium w.r.t. to both the total residual energy and data flow of the network.

Inherent Security Benefits of Analog Network Coding for the Detection of Byzantine Attacks in Multi-Hop Wireless Networks

Modern multi-hop wireless networks employ a number of sophisticated schemes to secure the network against hostile attacks. However, constant improvements in any security mechanism is matched by ever increasing sophisticated attacks. Therefore, there is a constant need to develop innovative schemes, especially for applications where the integrity of the message is vital. Attacks from trusted byzantine nodes that belong to the network itself are particularly challenging, as these nodes have a hidden malicious component and have complete access to the network resources. Previous works have studied these attacks and countermeasures for multi-hop networks and on networks capable of performing Network Coding. In this paper, we identify an inherent security benefit of Analog Network Coding and show how it can be used to design a novel Dual Non-adjacent Watchdog scheme that can detect a set of malicious byzantine attacks.

Proportionally fair rate allocation in regular Wireless Sensor Networks

In this paper, we consider the problem of fair rate allocation that maximizes the network throughput in regular topologies of Wireless Sensor Networks (WSNs). In order to monitor the entire coverage area of the WSN while maintaining acceptable network throughput, we need to find the optimal rate allocation for the individual/competing end-to-end sessions that maximizes the total proportionally fair throughput of the network. We provide closed form expressions for the optimal end-to-end session rates for square, triangular and hexagonal topologies as well as the bounds for the link layer transmission probabilities. We study the aforementioned problem for regular WSNs with a slotted Aloha MAC layer, which provides us with a lower bound for more realistic MAC protocols. Real world experiments using Telosb nodes validate our theories and results. Simulations carried out in Qualnet verify our comparisons of the different regular topologies as the size of network grows.

Exploring Load Balancing in Heterogeneous Networks by Rate Distribution

We present a mechanism for optimum distribution of internet traffic over heterogeneous network environment. A heterogeneous network can be considered as a combination of multiple homogenous networks available simultaneously to the end users. For simplicity, each network has been modeled as a M/M/1 queue. We aim to minimize the number of jobs in each queue subject to constraints. The optimization problem has been achieved through the use of Lagrange multiplier. Depending on their service rate the formulation done in this work is shown to optimally divide the rate of incoming traffic into different networks.

Wireless Mobile Sensor Networks: Protocols and Mobility Strategies

In the last few years, tremendous efforts have been made to enhance the performance of stationary wireless sensor networks (WSNs). However, such improvements are constrained by the limitations of being a stationary network. Recent advances in robotic and the potential usage of naturally moving objects such as vehicle, animal, and even human, enable some of the sensors in the network to be mobile, and such a network is so called a Mobile WSN (MWSN). In this chapter, we study how mobility can improve the network performance such as the network lifetime, coverage, and connectivity. For example, the lifetime of a WSN can be improved by additionally deploying some mobile sensors in the hot spot around the Base Stations (BSs). The coverage is further enhanced by allowing some or all sensors to reposition themselves or move continuously. Furthermore, high connectivity along with coverage is maintained by replacing the broken links or adding extra sensors to reconnect the partitioned networks through the use of mobile relay units. To provide a complete understanding of these aspects, we perform a comprehensive examination of existing approaches in designing a MWSN.

Demo of sensor deployment in detecting event's boundary

There are many ways to determine the boundary of an event based on Satellite imaging which does not provide accurate information. In many situations, there may not be enough time to monitor the effect of emergency and the affected area. Moreover, the event region could continuously change in the geographical region and a robust deployment of sensors is desirable that could capture maximum information about the entire event as soon as possible and continue capturing information without a break. These events are not physically accessible and most of the sensor deployments are static to check if they can fully cover an event. We explore these issues in this work and look at dynamic sensor network deployment strategies.

Average delay analysis of opportunistic single copy delivery in Manhattan area using biased random walk

In Mobile Opportunistic Networks, the cost and effectiveness of any opportunistic forwarding is measured by the expected delay of a message. Hence, its critical goal is to have low delay for a message. This paper studies the average delay of a message in a Mobile Opportunistic Network on Manhattan area. We first model the mobility of a message as a biased random walk in tilted grid and analyze the delay of a message based on the hitting time of a bias random walk. We have derived an exact expression of expected delay for a walk starting from any point in tilted grid for both biased and unbiased random walks and provide a closed form approximation of average delay of a message for the case of unbiased random walk. The key result is that the average delay of a message in Mobile Opportunistic Networks is very sensitive to the biased level of a random walk at each stage of the walk (depends on the distance from destination at its current stage). Then, this key result explains why most of the smart message forwarding algorithm in Mobile Opportunistic Network works reasonably well.