hyoon_research_interest

Ad-hoc networking enables hosts to form a temporary network without any infrastructure. Because of the lack of infrastructure, every mobile host is not in the transmission range of every other mobile host. For every mobile host to communicate with each other, some hosts have to relay the packets, and act as routers. We are interested in energy-efficient routing protocols and MAC protocols, because of the battery limit of mobile hosts. Also, the service discovery in Ad-hoc networks is our research issue.

Sensor networking is a kind of Ad-hoc networking. However, sensor networking is different from Ad-hoc networking. The differences between sensor networks and ad-hoc network are the number of nodes, the density of nodes and the probability of failure etc. Sensor networking is to detect the change of the environment. For example, the sensor networking can be used for various application areas (e.g. health, military, home).

One of the hot issues in sensor networking is power consumption. In sensor networking, if the battery of a sensor node ran out, the sensor node can not be recharged. Because the number of sensor nodes is hundreds or thousands, the user cannot collect the sensor nodes which ran out of battery. For that reasons, we are interested in energy-efficient MAC protocols and routing protocols. And also, we developed MAC protocol and power-efficient routing protocol which is installed real sensor node.

We also study localization in sensor networks. Location awareness is very important because many applications such as environment monitoring, vehicle tracking and mapping depend on the locations of sensor nodes. It is not cost effective to equip every sensor node with positioning systems like GPS. In addition, because energy efficiency is critical in sensor networks as above mentioned, we study energy-efficient localization under the assumption that no sensor nodes or a few sensor nodes have positioning systems.

A lot of service providers, equipment manufacturers, and research laboratories have already begun looking beyond 3G (beyond third generation wireless systems) technologies. Our group studies various issues on the OFDM/OFDMA 4G wireless systems based on IEEE 802.16e (WiBro) and IEEE 802.20 (MBTDD/MBFDD) standards such as mobility support, handover, routing, provision of the quality of services, interference reduction, performance enhancements, etc. We are also working on the vision of 4G as well as broadband communication issues like the air interface standards, cell coverage characteristics, the adaptive modulation and coding, in all IP networks that would be relevant to 4G.

Especially, to enhance the performance of the users who are in the cell boundary area and the fast moving user in trains or buses, our group studies multi-hop relay networks and moving networks. Many research issues have being addressed in 802.16j and WINNER project. In these researches, more complex algorithms such as handover, power control, mobility management, resource management, etc. are inevitable. So we study these research issues thoroughly as well as those of cellular networks.

We are currently developing the integrated 4G system simulator to evaluate our new approaches that would be applicable to the 4G wireless systems.

Our group works on the various multimedia services have explosively increased in the Internet. Due to characteristics of IP networks, acceptable service quality for multimedia traffic may not be guaranteed. The QoS architectures to provide multimedia services can be designed at two levels, the application as well as the network layer. The examples of the network-level approaches are the integrated services, RSVP, differentiated services, etc. The SIP, RTP, RTCP and virtual cache networks are the examples of application-level approaches. We study to solve problems like "How many equipments for caching we need in the networks?" or "Where these have to be deployed to support QoS?". To develop a broad understanding of the quality of service issues in wired and wireless networks we validate our proposed architectures using simulation, analytical tools as well as experimental prototypes.