Changhwa Kim

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The underwater sensor network environment differs substantially from a terrestrial sensor network in the aspect of the communication medium so Acoustic communication is alternative, which is relatively very slow and narrow bandwidth compared with Radio Frequency. In this paper, we propose an underwater sensor network architecture and then present the(More)
Most of wireless sensor network nodes are powered not by main power but by batteries. A node which runs out of batteries cannot serve as a component of a network. This is why minimizing energy consumption of a node is important. Energy is consumed with various environment such like sensing, data processing data communication and so on, and especially data(More)
Acoustic communication is one of the essential technologies for many promising underwater systems. In this paper, we focus on the research and development of an acoustic modem for a real-time water quality monitoring system using bio-mimetic fish robots. Challengeable issues from the viewpoint of acoustic communication for the application are first(More)
A new media access control protocol for a wireless sensor network is presented in this paper, configured with sensor nodes which have several directional antennas. There are lots of cases to need data retransmission because of excessive channel competition and data collisions due to the use of one omnidirectional antenna and single channel in a wireless(More)
Recently, there has been large interest on short and medium range underwater communication systems for various applications. In this work, we investigate a moving communication system equipped with bio-inspired fish robots. A protocol stack encompassing physical layer, medium access control layer and network layer is designed for a packet-based hierarchical(More)
This paper presents the experimental results of single carrier digital modulation schemes for underwater sensor networks. To obtain a real sea data of acoustic communications, an experiment was performed at the shallow water environments. ASK and FSK were used as non-coherent modulation scheme and QPSK and 16-QAM are used as coherent modulation scheme.(More)
IP-based IMT Network Platform(IP) is an ubiquitous platform supporting mobility using two step IP address mode converting – IP host address(IPha) and IP routing address(IPra) – in a backbone network. Mobile Node(MN) in IP maintains its state as either active or dormant state, which is transferred to active state through Paging process when communication is(More)
Underwater acoustic communication can be applied to many fields, such as oceanic data collection, undersea exploration, disaster prevention, underwater environmental monitoring, and tactical surveillance. Underwater environmental monitoring system is one of basic technologies in these application fields. Therefore, there is a growing need for researching(More)
The energy of a sensor network decides how long it will be alive. Therefore, energy efficiency is the critical part of network survivability. The most energy-consuming action of a sensor network is considered as communication between nodes. For energy efficient communication, many research activities for clustering mechanisms have been conducted. But,(More)
In sensor network-related researches, communication has been the most important target for reducing energy consumption. The frequencies in communication and sensing in a sensor node affect its energy efficiency. Therefore, the sensing cycle and the transmission cycle in a sensor node need to be managed to increase energy efficiency in communication. In this(More)