| The ISM band will soon be populated by various kinds of wireless devices. Most of these devices are likely to be in the area of wireless local area networking (WLAN) using the Wi-Fi technology and wireless personal area networking (WPAN) using the Bluetooth technology. Coexistence of devices using the same frequency band gains significance because of the potential for interference. To realize the ubiquitous communications environment through shared frequency band, devices not only need to have an efficient mechanism to access the unlicensed frequency band, but also a proactive mechanism to detect and mitigate the interference caused by another type of coexisted wireless devices. With the rapid frequency hopping mechanism and broader operating frequency band, a Bluetooth device is more capable of evading interference caused by Wi-Fi devices. There have been some works that further strengthened the interference avoidance ability of the Bluetooth system. On the other hand, a Wi-Fi device is more vulnerable to the interference caused by the Bluetooth devices due to its longer data packet and lack of agility to frequency change.
In this paper, we propose a coexistence scheme using dynamic fragmentation that can be implemented at the IEEE 802.11 in the presence of Bluetooth devices. The proposed scheme tries to optimize MAC layer packet length on Wi-Fi device such that the Wi-Fi device has better chance to evade the interference caused by Bluetooth devices. The mechanism dynamically adjusts the fragmentation level based on the current packet error rate (PER). We developed an analytical model that provides the MAC the necessary information (in terms of PER) to decide the right time for further packet fragmentation. The developed model is also employed to measure the throughput of the Wi-Fi device. Simulations are also performed to validate the developed model. We show that for an MAC with our dynamic fragmentation mechanism, in a static WLAN in the presence of Bluetooth devices, when the original PER is greater than 50%, the throughput of Wi-Fi is improved by at least 29%, and when the original PER is greater than 60%, the throughput of Wi-Fi is improved by at least 57%. With node mobility, we show that when the original PER is greater than 50%, the throughput of Wi-FI is improved by at least 16%, and when the original PER is greater than 60%, the throughput of Wi-Fi is improved by at least 39%. |
| Chia-Chun Hsu received his B.S. degree in Engineering and System Science, National Tsing-Hus University, Hsinchu, Taiwan, R.O.C., in 1997, and M.S. degree in Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana in 2002. He is currently a Ph.D. student in Department of Electrical Engineering at the University of Southern California, Los Angeles, California. He is a member of Professor Kuo's research group, Media Communiction Lab. His research interests include multi-player online game server design, multimedia on WLAN, MAC layer solution of coexistence/interference among coexsiting heterogenous wireless networks, Medium Accesss Control of 802.11 Wi-Fi, 802.15 Bluetooth, 802.15.4 Zigbee, and cognitive radio. |