Browsing by Author "Tsao, Shiao-Li (Charles)"

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Fast Handoff in Secure IEEE 802.11s Mesh Networks
(2011-01-01)
Chi, Kuang-Hui
;
Shih, Yung-Chien
;
Liu, Ho-Han
;
Wang, Jui-Tang
;
Tsao, Shiao-Li (Charles)
While mesh networking is gaining momentum with widespread application, we are concerned with fast handoff in a secure mesh environment. To this end, this paper presents a means in the context of IEEE 802.11s of letting a mesh portal act as an IEEE 802.1X authenticator to reduce costly IEEE 802.1X authentication processes during handoff. Our approach is developed for alignment with IEEE 802.11s and 802.11i, keeping protocols at the station side operable with no changes. As another strength, our design applies to generic multihop wireless networks. Both analytical and simulation modeling are conducted to evaluate our scheme as well. Performance results show that our approach reduces handoff delay by up to 268% or achieves comparable performance resulting from the counterpart IEEE 802.11i scheme with high likelihood of 70%-85% successful preauthentication. Moreover, our performance analysis suggests an optimal number of access points managed by one mesh portal in a network. Qualitative and quantitative discussions indicate that our approach is applicable in pragmatic settings.
Utilizing Multiple Channels With Fewer Radios in Wireless Mesh Networks
(2011-01-01)
Ku, Chia-Yu
;
Lin, Ying-Dar
;
Tsao, Shiao-Li (Charles)
;
Lai, Yuan-Cheng
;
交大名義發表
Wireless mesh networking (WMN) is regarded as a low-cost technology for rapid wireless network deployment. However, in a single-channel WMN, the overlapped transmission ranges between relaying mesh points could introduce serious interference. Using multiple radios over multiple channels can decrease the interference and improve the capacity of a WMN, but it increases the cost of a mesh point. One possible solution to balance between interference, hence performance, and cost is utilizing fewer radios that switch among multiple channels instead of using per-channel radios. In this paper, we propose a channel-switching method, called the traffic-aware switching scheme (TRASS), for a mesh point with a limited number of radios. TRASS utilizes the existing IEEE 802.11 mechanisms, i.e., hybrid-coordination-function-controlled channel access and power saving, to avoid packet loss during channel switching. A TRASS mesh point monitors the occupied channel time to schedule radios that switch among channels. The implemented TRASS demonstrates 75% throughput improvement by (2, 1), i.e., two-channel single-radio, over (1, 1). (3, 2) and (3, 1) achieve 69.8% and 39.7%, respectively, of the throughput of (3, 3) in the simulated TRASS.