Browsing by Author "Tsai, Tzu-Jane"

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Least-Awake-Frame Scheduling with Delay Guarantee for IEEE 802.16e Broadband Wireless Access Networks
(2008)
Lin, Chia-Yen
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Chao, Hsi-Lu
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Liao, Yang-Jang
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Tsai, Tzu-Jane
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資訊工程學系
The advancement of mobile computing is mainly limited by battery lifetime of an end device, and thus power management is always a critical design issue in various wireless networks. To conserve power consumption of mobile subscribe stations (MSSs), three types of power saving classes are defined in the IEEE 802.16e standard. However, the defined power saving mechanism is per-connection basis. When having multiple connections, the power saving efficiency of an MSS degrades significantly. In this paper, a Least-Awake-Frames Scheduling (LAFS) algorithm is proposed to achieve both energy saving and Quality-of-Service (QoS) fulfillment. The proposed LAFS consists of three phases. The goals of the first two phases are determining awake-frame candidate sets of unsolicited grant service (UGS) connections and sleep/awake intervals of remaining service-classes connections; the third phase is to determine sleep and awake frames of an MSS. The simulation results show that our proposed LAFS algorithm outperforms the power saving protocol defined in the IEEE 802.16e, and other existing power saving algorithms.
On Synchronized Channel Sensing and Accessing for Cognitive Radio Users in IEEE 802.11 Wireless Networks
(2009)
Lou, TakChon
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Chao, Hsi-Lu
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Tsai, Tzu-Jane
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資訊工程學系
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Department of Computer Science
One of the most challenging issues in cognitive radio systems is channel sensing and channel accessing. In this paper, a synchronized channel-sensing and accessing for cognitive radio users in IEEE 802.11 wireless networks is proposed. The mechanism consists of two phases: fast channel sensing and proactive channel vacating. Fast channel sensing is for a pair of cognitive radio users to search an available channel time-efficiently; proactive channel vacating is for the pair of cognitive radio users to be aware of the presence of primary users and vacate the occupied channel as quick as possible. We utilize the concept of channel hopping to reduce the average channel sensing time of cognitive radio users. Besides, through the designed interruption mechanism, cognitive radio users can create opportunities for primary users to claim the spectrum and thus minimize the caused interference to primary users. From the simulation results, our proposed protocol can efficiently balance the tradeoff between throughput performance of a cognitive radio network and waiting time of primary users to claim channels.
SYSTEM AND METHOD THEREOF FOR DYNAMICALLY ADJUSTING SLEEP/AWAKE INTERVALS OF WIRELESS NETWORK DEVICE
(2009-12-03)
Lin, Chia-Yen
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Chao, Hsi-Lu
;
Tsai, Tzu-Jane
A system and a method thereof for dynamically adjusting sleep/awake intervals of a wireless network device are provided. The system has at least one base station (BS) and at least one wireless network device. The system performs the method to dynamically adjust the sleep/awake intervals by properly delaying and combining delivery of data such that the wireless network device is turned into a sleep mode after finishing data delivery within an adjusted period. Thereby, the number of awake frames of a mobile subscriber station (MSS) can be reduced without sacrificing the quality of service (QoS).