Eugene Rhee

Efficient Beacon Collision Detection/Avoidance Mechanism in WLAN-Based Mesh Networks

Every node in wireless multi-hop mesh networks periodically transmits its own beacon and then monitors the existence or activity of other nodes by checking their beacons. So, the loss of beacon message in wireless multi-hop mesh networks causes the inefficient network overhead. This paper proposed a dynamic beacon collision detection and avoidance (BCDA) mechanism that can actively adapt to beacon collision status due to node movement. Each node checks the collision status by comparing the received beacon timing information from neighboring nodes with that of its own. It is shown from the performance evaluations that the proposed BCDA mechanism provides the decrease of beacon collision ratio and the throughput enhancement.

Electric Field Uniformity Characteristic of a Reverberation Chamber with a Composite QRD

This paper presents the electric field characteristics in a reverberation chamber which is an electromagnetic compatibility test facility that uses a stirrer to generate a uniform electric field inside it. In this paper, a diffuser is introduced from acoustics and newly designed to overcome problems of a stirrer. To validate the effect of a diffuser, a composite quadratic residue diffuser and a reverberation chamber are modeled. Then, the field uniformity inside the reverberation chamber is simulated by XFDTD 6.2 simulation program. Simulation results show that the electric field uniformity in the reverberation chamber satisfies the international standard requirement. This shows that the composite quadratic residue diffuser can be substituted for a stirrer.

Optimum Patch Dimension Ratio of T-Shaped Microstrip Antenna

There are various feeding methods of antenna like as coaxial probe, coupling, parasitic elements, and impedance matching. This paper adopted the microstrip line method as the feeding method of the antenna. The high frequency structure simulator is used to analyze the characteristics of the T-shaped microstrip antenna with various patch dimensions. In comparison with the basic microstrip antenna, this proposed T-shaped microstrip antenna with 40.38 % of patch dimensions has the optimum characteristics of resonant frequency, return loss, and radiation pattern at 2.0 GHz band.

Region-Based Efficient Beam Handover Scheme in IEEE 802.11 Wireless Networks

Seamless connectivity in wireless networks is critical for various applications. So, a dynamic beamforming antenna is utilized to improve wireless connectivity. However, using a dynamic beam steering scheme has a key problem when processing a handover between access points (APs). This paper proposed a dynamic beamforming handover (DBH) scheme using the relationship between beam pattern and topology information. Each AP preconfigures the neighbor list and tries to meet what candidate APs are available during handover process. Performance evaluations indicate that the handover latency can be significantly reduced by applying the proposed scheme and the network throughput can be enhanced.