Browsing by Author "Yeh, Jui-Hung"

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Comparative Analysis of Energy-Saving Techniques in 3GPP and 3GPP2 Systems
(2009-01-01)
Yeh, Jui-Hung
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Chen, Jyh-Cheng
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Lee, Chi-Chen
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瑞昱交大聯合研發中心
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Pealtek NCTU Joint Res Ctr
Energy conservation is essential to wireless networks, particularly for third-generation (3G) and fourth-generation (4G) wireless systems, because high-speed data transmissions would rapidly exhaust the energy of a mobile station. This paper presents the details of energy-saving mechanisms for packet data services in two major standards, namely, the Third-Generation Partnership Project (3GPP) and the Third-Generation Partnership Project 2 (3GPP2). In addition to qualitative comparison, analytic models and quantitative comparison based on the energy-saving models are provided. The proposed analytic models analyze and quantify the energy consumption for bursty and streaming traffic in cdma2000 and wideband code division multiple access (WCDMA). The impacts of an inactivity timer on energy consumption and reconnection cost are demonstrated further by simulation and analysis. The analytic results could be used to suggest proper timer lengths that can balance the energy consumption and the reconnection cost. In addition to providing insights of the energy-conservation mechanisms of 3GPP and 3GPP2, which are often difficult to directly obtain from standards specifications, results shown in this paper are also practical for 3GPP and 3GPP2 operators to determine proper parameters for energy efficiency.
Efficient dynamic frame aggregation in IEEE 802.11s mesh networks
(2009-10-01)
Lin, Ying-Dar
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Yeh, Jui-Hung
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Yang, Tsung-Hsien
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Ku, Chia-Yu
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Tsao, Shiao-Li
IEEE 802.11a could improve the network efficiency of WLAN by aggregating multiple frames into a single transmission. The frame aggregation technique especially benefits multi-hop transmissions that introduce enormous 802.11 medium access control (MAC) layer control overhead. This paper proposes a novel algorithm, namely dynamic aggregation selection and scheduling (DASS) algorithm, that can dynamically adopt the appropriate aggregation mechanism for IEEE 802.11s mesh network. The characteristics, benefits and the restrictions of three aggregation mechanisms, aggregate MAC service data units, aggregate MAC protocol data unit and aggregate physical protocol data unit, are investigated. Based on the channel condition, the quantity and the distribution of the frame arrivals, DASS could determine what aggregation mechanism to adopt and whether to wait for the next frame for aggregating transmissions. Simulation results demonstrate that the algorithm significantly increases the channel efficiency of the 802.11 MAC and further improves the overall throughput of the wireless mesh network by approximately 95%. Copyright (C) 2009 John Wiley & Sons, Ltd.
Fast Intra-Network and Cross-Layer Handover (FINCH) for WiMAX and Mobile Internet
(2009-04-01)
Yeh, Jui-Hung
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Chen, Jyh-Cheng
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Agrawal, Prathima
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瑞昱交大聯合研發中心
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Pealtek NCTU Joint Res Ctr
To support fast and efficient handovers in mobile WiMAX, we propose Fast Intra-Network and Cross-layer Handover (FINCH) for intradomain (intra-CSN) mobility management. FINCH is a complementary protocol to Mobile IP (MIP), which deals with interdomain (inter-CSN) mobility management in mobile WiMAX. FINCH can reduce not only the handover latency but also the end-to-end latency for MIP. Paging extension for FINCH is also proposed to enhance the energy efficiency. The proposed FINCH is especially suitable for real-time services in frequent handover environment, which is important for future mobile WiMAX networks. In addition, FINCH is a generic protocol for other IEEE 802-series standards. This is especially beneficial for the integration of heterogeneous networks, for instance, the integration of WiMAX and WiFi networks. Both mathematical analysis and simulation are developed to analyze and compare the performance of FINCH with other protocols. The results show that FINCH can support fast and efficient link layer and intradomain handovers. The numerical results can also be used to select proper network configurations.
Indoor deployment of IEEE 802.11s mesh networks: Lessons and guidelines
(2011-11-01)
Lin, Ying-Dar
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Chang, Shun-Lee
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Yeh, Jui-Hung
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Cheng, Shau-Yu
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資訊工程學系
Emerging wireless mesh networks (WMNs) are known for their fast and low cost deployment. Conventional mesh deployment focuses on the outdoor environment, which regards the wMNs as backbone networks. This study deploys and measures indoor IEEE 802.11s mesh networks to extend WLAN capabilities with extensive experiment configurations. The testbed is constructed in a laboratory and a field crossing three floors of a building. Disagreeing with previous research, the results of this study indicate that RTS/CTS can improve throughput by up to 87.5%. Moreover, compared with the IEEE 802.11b/g, 802.11n achieves better fairness for multi-stream or multi-hop communications. Experimental results also suggest that a longer beacon interval, e.g. 500 ms, can improve channel efficiency for a denser deployment. On the other hand, sparser deployments should use a shorter beacon interval, e.g. 100 ms, to enhance link stability. (C) 2011 Elsevier B.V. All rights reserved.
Realizing and benchmarking broadcast algorithms in wireless mesh networks
(2011-07-01)
Lin, Ying-Dar
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Chang, Shun-Lee
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Tao, Shi-Hung
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Yeh, Jui-Hung
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資訊工程學系
Broadcasting by flooding causes the broadcast storm problem in multi-hop wireless networks. This problem becomes more likely in a wireless mesh network (WMN) because WMNs can bridge wired LANs. increasing broadcast traffic and collision probability. Since the network control, routing, and topology maintenance of a WMN highly rely on layer-2 broadcasting, unreliable broadcast algorithms directly destabilize a WMN. Researchers have developed many algorithms for efficient and reliable broadcast in multi-hop wireless networks. However, real-world systems rarely verify or compare these approaches, especially in a WMN. This paper examines six representative broadcast algorithms: simple flooding, dynamic probabilistic, efficient counter-based broadcast, scalable broadcast, domain pruning, and connected-dominating-set based algorithms. This study addresses both common and algorithm-specific implementation in a real-world IEEE 802.11s WMN testbed. Experiments under various topologies and packet lengths reveal the reliability, forwarding ratio, and efficiency of these six algorithms. Quantitative survey results indicate that the scalable broadcast algorithm possesses the best reliability due to its lower collision probability. The domain-pruning algorithm is the most efficient algorithm when considering both reliability and the forwarding ratio. (C) 2010 Elsevier B.V. All rights reserved.