Chang-Yeong Oh

Learn More
The interference mitigation technique based on fractional frequency reuse (FFR) provides improved cell-edge performance with similar overall cell capacity as that of systems with the frequency reuse factor of one. Furthermore, frequency sub-band allocation by FFR has the benefit of allowing flexibility for the deployment of femto-cells through frequency(More)
Femtocells are expected to be one of the emerging technologies for next generation communication systems. For successful deployment of femtocells in the pre-existing macrocell networks, there are some challenges such as the cell planning for interference management, handoff, and power control. In this paper, we focus on frequency planning which can provide(More)
We consider the joint relay and pre-coder selection in the decode-and-forward (DaF) relay network, where multiple relays are employed with multiple antennas. Depending on the channel information, the destination informs the relay and precoder selection information to the source and relays with finite bits of information. The source and the selected relay(More)
In Wireless Local Area Networks (WLANs) based on IEEE 802.11 families such as a/b/g, mobile stations can automatically adjust transmission rates according to channel conditions. However throughput performance degradation is observed by low-rate stations in multi-rate circumstances resulting in so called performance anomaly. There have been many studies to(More)
Cooperative communications using relays in wireless networks have similar effects of multiple-input and multiple-output without the need of multiple antennas at each node. To implement cooperation into a system, efficient protocols are desired. In IEEE 802.11 families such as a/b/g, mobile stations can automatically adjust transmission rates according to(More)
In multi-user OFDMA systems, adaptive resource allocation has been identified as one of the key technologies to have more flexibility and higher efficiency. Several adaptive subcarrier allocation algorithms with the objective to maximize spectral efficiency or fairness have been proposed. However, quality of service (QoS) requirement of each user may not be(More)
A mobile ad hoc network (MANET) is expected to become useful and important for some applications in the next generation wireless communication systems. An efficient routing protocol for a MANET is required to consider the mobility of nodes and the characteristics of wireless channel. To multicast data to a specific group in a network, an efficient routing(More)