Chutima Prommak

Optimal Wireless Sensor Network Design for Efficient Energy Utilization

This paper presents a study of the optimal network design for efficient energy utilization in continuous data-gathering Wireless Sensor Networks (WSNs). We examine the problem of minimizing the network cost through the minimum number of relay-station installation. We model the network design problem as a mixed integer linear programming. Our key contribution is that the proposed model not only guarantee the network lifetime but also ensure the radio communication between the energy-limited sensor nodes so that the network can guarantee packet delivery from sensor nodes to the base station. Numerical experiments were conducted to evaluate and demonstrate the effectiveness of the proposed method.

Robust Floor Determination Algorithm for Indoor Wireless Localization Systems under Reference Node Failure

One of the challenging problems for indoor wireless multifloor positioning systems is the presence of reference node (RN) failures, which cause the values of received signal strength (RSS) to be missed during the online positioning phase of the location fingerprinting technique. This leads to performance degradation in terms of floor accuracy, which in turn affects other localization procedures. This paper presents a robust floor determination algorithm called Robust Mean of Sum-RSS (RMoS), which can accurately determine the floor on which mobile objects are located and can work under either the fault-free scenario or the RN-failure scenarios. The proposed fault tolerance floor algorithm is based on the mean of the summation of the strongest RSSs obtained from the IEEE 802.15.4 Wireless Sensor Networks (WSNs) during the online phase. The performance of the proposed algorithm is compared with those of different floor determination algorithms in literature. The experimental results show that the proposed robust floor determination algorithm outperformed the other floor algorithms and can achieve the highest percentage of floor determination accuracy in all scenarios tested. Specifically, the proposed algorithm can achieve greater than 95% correct floor determination under the scenario in which 40% of RNs failed.

Logical topology design in IP over WDM networks with load balancing under traffic uncertainty

Traffic demand uncertainty could affect the reliability of the logical connectivity in IP over WDM networks. In this paper, we investigate the effects of traffic uncertainty and load balancing in IP over WDM networks and propose new techniques for logical topology design. In particular, we model the logical topology design in IP over WDM networks as the integer linear programming problems. Our key contribution is that the proposed model can address three important issues including (a) ensuring connectivity of the IP layer (logical topology) (b) balancing traffic load in WDM networks and (c) ensuring network capacity to accommodate traffic demand under traffic uncertainty scenarios. We observe that the proposed logical topology design method with load balancing enables much higher traffic distribution across the physical links allowing up to 63 % decreasing in unbalancing index and up to 8 % increasing in the resource utilization needed to support IP traffic demand with traffic uncertainty considerations.

On the Quality of Service Optimization for WiMAX Networks Using Multi-hop Relay Stations

Network quality of services and the limitation of network installation budget are important concerns in the widespread deployment of mobile WiMAX access networks. This paper presents a novel quality of service optimization model for WiMAX networks utilizing multi-hop relay stations with special considerations of network budget limitation. The proposed model aims to optimize the network quality of services in term of the user access data rate guarantee and the radio service coverage to serve potential user traffic demand in the target service area by determining optimal locations to install base stations and relay stations in the multi-hop manner. The numerical results and analysis show that the proposed model can improve the user access data rate and enhance the network service coverage compared with other existing techniques.

Floor Determination Algorithm with Node Failure Consideration for Indoor Positioning Systems

One of challenging problems for indoor wireless multi-floor positioning systems is a presence of Reference Node (RN) failures, which causes the missing of the values of Received Signal Strength (RSS) during the online positioning phase of the fingerprinting technique. This leads to performance degradation in terms of floor accuracy which affects other localization procedures. This paper presents a robust floor determination algorithm called Robust Confidence Interval Sum-RSS (RCIS), which can accurately determine the floor where mobile objects located and can work under either the fault-free scenario or the RN-failure scenarios. The proposed fault tolerance floor algorithm is based on the confidence interval of the summation of the strongest RSS obtained from the IEEE 802.15.4 Wireless Sensor Networks (WSNs) during the online phase. The performance of the proposed algorithm is compared with those of different floor determination algorithms in literature. The experimental results show that the proposed robust floor determination algorithm outperformed the other floor algorithms and can achieve the highest percentage of floor determination accuracy in all tested scenarios. Specifically, the proposed algorithm can achieve 100% correct floor determination under the scenario in which 40% of RNs failed.

Low complexity Wireless Indoor Positioning approaches based on fingerprinting techniques

Among different Wireless Indoor Positioning Systems (WIPS) that utilize radio frequency signal to estimation an object location, the system that uses Received Signal Strength (RSS) of the wireless transceiver, such as the fingerprinting approach, has gained lot of attention and been deployed widely. This paper presents a novel wireless indoor positioning approaches based on fingerprinting technique called Fusion parameter technique with temperature level (FUSTL). The proposed technique takes into account an environmental data in conjunction with RSS information in the fingerprinting database. The environmental data, such as room temperature and humidity, is used to classify different zones of the service areas. This information could help facilitate the RSS matching process of the fingerprinting technique. The performance of the proposed algorithm is compared with those of different indoor positioning techniques in literature. The experimental results shows that the proposed technique outperformed the other techniques and can provide the highest of accuracy and precision performance at the lowest computational complexity. Specifically, the positioning accuracy of our proposed technique is 15-27% higher than those of the other techniques whereas the computational complexity of our technique is 12-36% lower than those of the other techniques.

Performance Analysis and Comparison for Wireless Indoor Positioning Systems in Multi-Floor Building

In this paper, performance analysis and comparison for Wireless Indoor Positioning Systems (WIPS) in multi-floor building are presented. Different structures of WIPS are considered. In particular, WIPS structure designed by our proposed technique was compared with other structures designed by an opportunistic approach. The comparisons were conducted by using signal strength data from the real measurement and from simulation models. An efficiency of the simulation models was compared as well. The results show that the WIPS structure designed by our proposed technique yield better indoor positioning performances in term of the accuracy and precision.

Heuristic approaches to the multi-objective network design and optimization for wireless data networks

In this paper, we present a multi-objective model for the wireless data network (WDN) design problem. The proposed model aims to determine the network configurations that optimize the network quality of services in term of the radio signal coverage and the network throughput availability to serve expected user traffic demand in the service area. The problem consists of the base station placement, the frequency channel assignment and the power level assignment. Since this problem is NP-hard, we develop a heuristic optimization techniques based on Tabu search algorithm to solve the problem. Numerical experiments were conducted to demonstrate the capability of the proposed multi-objective model and the heuristic algorithm.

Bandwidth management for hybrid association control schemes and load balancing inWLANs

This paper present a hybrid association control scheme (HA) managements that can support real-time multimedia application. We propose 3 ways of hybrid association control managements, Complete Sharing (CS), Complete Partitioning (CP), and Partial Sharing (PS) schemes. The percentage of blocking was used as performance index to compare the quality of service in WLAN. Simulation results show that the proposed schemes can satisfy the quality of service requirements of the multimedia traffic applications.