[Show abstract][Hide abstract] ABSTRACT: Generally, the lifetime of a wireless sensor network (WSN) is defined as the duration until any sensor node dies due to battery exhaustion. If the traffic load is not properly balanced, the batteries of some sensor nodes may be depleted quickly, and the lifetime of the WSN will be shortened. While many energy-efficient routing schemes have been proposed for WSNs, they focus on maximizing the WSN lifetime. In this paper, we propose a scheme that satisfies a given ‘target’ lifetime. Because energy consumption depends on traffic volume, the target lifetime cannot be guaranteed through energy-efficient routing alone. We take an approach that jointly optimizes the sensing rate (i.e., controlling the sensor-traffic generation or duty cycle) and route selection. Satisfying the target lifetime while maximizing the sensing rate is a NP-hard problem. Our scheme is based on a simple Linear Programming (LP) model and clever heuristics are applied to compute a near-optimal result from the LP solution. We prove that the proposed scheme guarantees a 1/2-approximation to the optimal solution in the worst case. The simulation results indicate that the proposed scheme achieves near-optimality in various network configurations.
No preview · Article · Jun 2014 · Computer Networks
[Show abstract][Hide abstract] ABSTRACT: Network lifetime maximization is challenging particularly for large-scale wireless sensor networks. The sensor nodes near the sink node tend to suffer high energy consumption due to heavy traffic relay operations, becoming vulnerable to energy depletion. The rationale of the sink mobility approach is that as the sink node moves around, such risk of energy depletion at some nodes can be alleviated. In this paper, we first obtain the optimal mobile sink sojourning pattern by solving a linear programming model and then we mathematically analyze why the optimal solution exhibits such sojourning pattern. We use the insights from this analysis to design a simple practical heuristic algorithm for sink mobility, which utilizes only local information. Our heuristic is very different from the existing algorithms which often use the traffic volume as the main decision factor, in that we consider the variance of residual energy of neighboring sensor nodes. The simulation results show that our scheme achieves near-optimal network lifetime even with the relatively low moving speed of the mobile sink.
No preview · Article · Feb 2014 · Wireless Networks
[Show abstract][Hide abstract] ABSTRACT: Sensor networks have become increasingly important in various areas, and most current applications require connectivity between
sensor networks and the Internet. By being seamlessly integrated into IP network infrastructure, sensor network applications
would benefit from standardized and established technology, as well as from the plethora of readily available applications.
Preparing sensor networks for IP communication and integrating them into the IP network, however, present new challenges on
the architecture and its functional blocks, e.g., the adaptation of the respective link technology for IP support, development
of security mechanisms, and autoconfiguration to support ad hoc deployment. In this paper, we focus on the IPv6 address autoconfiguration
issue and propose a proxy-based autoconfiguration protocol. The proposed protocol guarantees the assignment of a unique address
to each node in the network. The protocol is simulated and implemented on off-the-shelf sensor network platforms. The experiment
results show that our mechanism outperforms similar network address configuring mechanisms in terms of latency and overhead.
No preview · Article · Jan 2011 · Wireless Networks
[Show abstract][Hide abstract] ABSTRACT: While equilibrium analysis has been commonly used for network pricing under the assumption that user utility functions are precisely known, many researchers have criticized the validity of the assumption. In this paper, we propose a solution for bridging the gap between the existing theoretical work on optimal pricing and the unavailability of precise user utility information in real networks. In the proposed method, the service provider obtains increasingly more accurate estimates of user utility functions by iteratively changing the prices of service levels and observing the users’ service-level choices under various prices. Our study’s contribution is twofold. First, we have developed a general principle for estimating user utility functions. Especially, we present the utility estimation for dynamic user population. Second, we have developed a method for setting prices that can optimize the extraction of information about user utility functions. The extensive simulation results demonstrate the effectiveness of our method.
No preview · Article · May 2009 · Computers & Industrial Engineering
[Show abstract][Hide abstract] ABSTRACT: Traditional simulation studies often assume that there exists a complete set of data ready for analysis. Such an assumption may be justified in cases where data requirement for simulation is precisely defined and all necessary data have been collected according to such requirement. In many cases, however, existing data is incomplete, and it may not be economically feasible nor time-wise plausible to begin an extensive data collection process. Aiming at the healthcare management systems that maintain the log of operation activities using timestamps, we propose a general method to process incomplete timestamp data and obtain necessary information for simulation analysis. The proposed method is successfully applied to a case study of a mid-size hospital in Korea.