Hyun Gi Ahn

A New Frequency Partitioning and Allocation of Subcarriers for Fractional Frequency Reuse in Mobile Communication Systems

Some OFDMA-based wireless commuication systems, e. g., Wireless Broadband Internet (WiBro) or Worldwide interoperability for Microwave Access (WiMAX), support frequency reuse of 1 to maximize spectral efficiency. One of the efficient methods to reduce co-channel interference (CCI) caused by frequency reuse is fractional frequency reuse (FFR). In this paper, we propose and validate a novel frequency partitioning method and subcarrier assignment mechanism to improve system and individual capacity of mobile systems using FFR.

Traffic Scheduling for MPDCF MAC to Support QoS-Sensitive Data in IEEE 802.11 Wireless LANs

In IEEE 802.11 wireless LAN (WLAN), it is very hard to meet QoS requirements (throughput, delay and loss rate) of multimedia traffic by using distributed coordination function (DCF). In order to support QoS in WLAN, enhanced IEEE 802.11 medium access control (MAC) protocol is discussed in IEEE 802.11 Task Group E. IEEE 802.11e uses the rather complex hybrid coordination function (HCF). In this paper, we propose a simple multipolling DCF (MPDCF) mechanism with the advantages of high channel efficiency and QoS support. In our proposed mechanism, an AP can decide the transmission order and duration of QoS-sensitive wireless stations and poll the stations whenever it needs based on the controlled backoff procedure. We propose a scheduling algorithm using the proposed MPDCF to serve real-time traffic with constant and variable bit rates. The simulation results show that QoS requirements of the traffic can be satisfied and the channel utilization is also increased with our scheduling mechanism