Sik Choi

Design and implementation of a simulator based on a cross-layer protocol between MAC and PHY layers in a WiBro Compatible.IEEE 802.16e OFDMA system

In this article we propose cross-layer design frameworks for 802.16e OFDMA systems that are compatible with WiBro based on various kinds of cross-layer protocols for performance improvement: a cross-layer adaptation framework and a design example of primitives for cross-layer operation between its MAC and PHY layers. In addition, we provide a simulation framework for cross-layer analysis between the MAC and PHY layers in 802.16e systems. Through this cross-layer simulator, we show that average cell throughput can be improved by 25-60 percent by applying careful cross-layer adaptation schemes.

Fast handover scheme for real-time downlink services in IEEE 802.16e BWA system

IEEE 802.16 WirelessMAN aiming to broadband wireless access (BWA) is evolving to 4G mobile communication systems through the standardization of IEEE 802.16e supporting mobility on existing fixed WirelessMAN systems. Because IEEE 802.16e system is based on OFDM(A) technology, a mobile subscriber station (MSS) basically conducts hard handover operation when it moves to another base station (BS). Therefore, the MSS is not able to send or receive the data during handover process and these data should be delayed. As a result, real-time packet could be dropped by handover delay. In this paper, we propose an enhanced link-layer handover algorithm that an MSS can receive downlink data before synchronization with uplink during handover process. Our proposed scheme reduces data transmission delay and packet loss probability for real-time downlink service.