Byeongjik Lee

A Channel Switching Scheme for Avoiding Interference of between IEEE 802.15.4 and Other Networks

The key features of low-rate wireless personal area networks (LR-WPAN) are low data rate, low cost, and low power consumption. The LR-WPAN is very useful in many applications such as detection, remote control, tracking and monitoring. But, there are many different networks (WLAN, Bluetooth, HR-WPAN, LR-WPAN ) in the same unlicensed 2.4 GHz ISM band. So, much interference happens. In this paper, we propose a cognitive radio based channel switching mechanism for avoiding interference of between IEEE802.15.4 and other networks.

A partition prediction algorithm for group mobility in ad-hoc networks

One of important issues associated with group mobility in ad-hoc networks is predicting the partition time. The existing algorithms predict the partition time assuming that the partitioned groups move to opposite direction with the same speed and the same coverage. So, these algorithms could not accurately predict partition time in practical situation. In this paper, we propose a partition prediction algorithm considering network partition in any direction, at any speed, and with different coverage of group. To validate the proposed algorithm, we carried out a simulation study. We observe a sound agreement between numerical results obtained by our algorithm and computer simulation. Our algorithm can predict the partition time more accurately in real situations.

Cryptanalysis of the modified authenticated key agreement scheme

Lee and Lee recently pointed out that the Hsu et al. authenticated key agreement scheme is vulnerable to the modification attack and further proposed an improvement of Hsu et al. However, this work shows that Lee and Lee scheme is vulnerable to the man-in-the-middle attack. A slight improvement to their scheme is proposed to overcome this weakness.

Routing protocols based on super cluster header in wireless sensor network

In a variety of applications, wireless sensor networks have received more attention in recent years. Sensor nodes, however, have many limitations including limited battery power and communication range. In this network, data gathering and data fusion help to reduce energy consumption and redundant data. LEACH (Low Energy Adoptive Clustering Hierarchy) is the most representative protocol using data gathering and data fusion, but it has several problems including inefficient energy consumption by many cluster headers to the distant sink and a single-hop routing path. In this paper, we propose two routing protocols called Routing Protocol based on Super-Cluster Header (RPS) and Multi-hop Routing Protocol based on Super-Cluster Header (MRPS) in order to resolve the problems of LEACH. The key idea of our protocols is that only one node sends the combined data to the sink and every node uses multi-hop routing in order to gather data in the cluster. We evaluate performance of our protocols through simulations. Simulation results show that our protocols offer a much better performance than the legacy protocols in terms of energy cost, the network lifetime, and fairness of the energy consumption.

A server selection algorithm for group mobility

One of the most important issues associated with group mobility predicts the partition time. The existing algorithms predict partition time assuming that the partitioned groups move in opposite direction with the same speed and coverage. Thus, QoS is not guaranteed, since these algorithms could not accurately predict partition time in practical situations. We propose a partition prediction algorithm and server selection algorithm considering network partition in any direction, at any speed and with different coverage of groups. The analytical and simulation results show that our algorithm can predict partition time and select a child server more accurately in real situations.

A Location Based Energy Efficient Intersection Routing Protocol in Mobile Sensor Networks

Typically, sensor networks consist of fixed sensor nodes. Sometimes, creating such a fixed sensor networks could be a daunting task. Sensor nodes assume deploying a stationary sensor network over a dangerous area such as a battlefield. Even if an advanced method to make the deployment safer is used, diverse element will cause a coverage holes. Even though perfect coverage can be achieved initially, various factors such as malicious attacks will certainly degrade network coverage as time goes on. However, mobile sensor networks can solve some of the problems. Each node of mobile sensor network is mounted on various unmanned vehicles as a result the sensor nodes have mobility. Mobility reinforces fault-tolerance and the scalability of the network. But conventional sensor routing protocols find it hard to deal with the mobile sensor networks. Therefore, this study suggests an energy efficient routing scheme by using the location information of a Global Positioning System (GPS) and the energy levels of sensor nodes.

A locating method for ubiquitous robots based on wireless sensor networks

Applications of Ubiquitous Robot (UR) based on wireless sensor networks usually require the location information of all sensor nodes deployed on the sensor field. For this, every sensor node should be aware of its own geographical location, which forces us to pay an expensive cost and make the size of sensor node larger. In this paper, we propose a cheap solution for positioning all sensor nodes without necessitating all sensor nodes in the field equipped with GPS modules. In our method, only some sensor nodes equipped with GPS modules are initially deployed, and the other nodes without GPS modules will find out their locations through communications to GPS nodes. To show effectiveness of our method, we carried out a computer simulation, and observed that all nodes could successfully recognize their locations, which can considerably save the price for implementing wireless sensor networks.

A Probabilistic Transmission Control Scheme for Low Power Consumption in Sensor Networks

In this paper, we propose a probabilistic transmission control scheme to reduce the redundant consumption of computation power, storage, energy resources, and radio technology in sensor networks. Our scheme dynamically determines the transmission probability at application layer of each node based on the neighbor information within two-hop span. Simulation results are presented, which show our scheme may offer a better performance over the deterministic transmission control approach.