Browsing by Author "Ku, Chia-Yu"

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DESIGN ISSUES AND EXPERIMENTAL STUDIES OF WIRELESS LAN MESH
(2010-04-01)
Lin, Ying-Dar
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Tsao, Shiao-Li
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Chang, Shun-Lee
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Cheng, Shau-Yu
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Ku, Chia-Yu
Wireless mesh networking, as a low-cost and reliable technology for rapid network deployment, has attracted considerable attention from academia and standardization in the industry. The IEEE 802.11s standard defines a wireless LAN mesh using the IEEE 802.11 medium access control and physical layers, and is one of the most active standards with increasing commercial opportunities. This study presents the design and development of a WLAN mesh system conforming to the latest IEEE 802.11s draft amendment. Without costly hardware modifications, the proposed solution is a pure software extension for commercial off-the-shelf WLAN chipsets. This study constructs an experimental testbed, and evaluates issues such as the transmission reliability of mesh broadcast-type control messages and multichannel transmissions. Experimental results demonstrate that the delivery of mesh broadcast-type control messages, such as routing construction frames, using the multiple acknowledged unicast scheme improves mesh stability from an 86 to a 98 percent success ratio in a 16-node grid. Transmitting packets using a single radio interface switching between multiple channels reduces inter-flow interference and doubles the throughput in our testbed.
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.
In-Kernel Relay for Scalable One-to-Many Streaming
(2013-01-01)
Lin, Ying-Dar
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Ku, Chia-Yu
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Lai, Yuan-Cheng
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Hung, Chia-Fon
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電子工程學系及電子研究所
QoS-aware resource management for multimedia traffic report systems over LTE-A
(2016-01-15)
Liu, Tzu-Chin
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Wang, Kuochen
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Ku, Chia-Yu
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Hsu, Yi-Huai
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資訊工程學系
The multimedia traffic report system is a new type of applications in wireless vehicular networks equipped with sensors. This system can provide various kinds of traffic information, which are directly obtained from on-car sensors and devices via LTE-A. By leveraging LTE-A technologies, the system can support wide-range transmissions and better mobility. Despite of these improvements, the resource management problem is still a challenging issue due to a large number of on-car sensors and devices. Existing resource management studies focus on channel quality or Quality of Service (QoS) requirements for non-vehicular applications. To get the most useful and complete traffic information, including location coverage, an efficient resource management mechanism for multimedia vehicular applications is indispensable. In this paper, we propose a QoS-aware resource management mechanism for multimedia traffic report systems over LTE-A (QoS-MTRS). The main idea is to schedule resources according to the importance degrees of various traffic data. Furthermore, we take channel availability into consideration to make sure that the transmission is feasible. The objective of QoS-MTRS is to improve the diversity, completeness and overall traffic data value under radio resource limitations. We have conducted a system-level simulation that includes an LTE-A network environment to evaluate our design. Simulation results show that the proposed QoS-MTRS is better than BQA (bandwidth and QoS-aware scheduler), Greedy, and FCFS in terms of appearance probability of receiving more than one kind of traffic data types per location block, duplication ratio, overall traffic data value, end-to-end delay, system throughput, location coverage, and flow rejection rate. The significance of this work is the proposed QoS-MTRS can be applied to LTE-A for supporting high-bandwidth demands Internet of Things (IoTs). (C) 2015 Elsevier B.V. All rights reserved.
Real Traffic Replay over WLAN with Environment Emulation
(2012)
Ku, Chia-Yu
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Lin, Ying-Dar
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Lai, Yuan-Cheng
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Li, Pei-Hsuan
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Lin, Kate Ching-Ju
Real traffic replay is one of the solutions used to test network devices over complicated scenarios. Packet traces captured in a real environment hold more details than any mathematical models. However, the lack of packet-replay control and environment emulation might highly affect traffic behaviors, especially in wireless networks. Real traffic replay in wireless networks requires packet-replay control to manage the interactions with the device under test (DUT), and coordinately reproduces environment effects, such as fading, noise, and interference. In this work, we propose a method, called Event-driven Automata-synchronized Replay (EAR), to address real traffic replay over WLAN. EAR transforms the captured packet trace into a sequence of events that follow the IEEE 802.11 protocol. The three-level automata are applied to achieve packet-replay control and synchronize the environment effects in traffic replay with the packets and signals captured in a real environment. We propose a quantitative metric, called the event reproduction ratio (ERR), to evaluate the effectiveness of traffic replay. Our software implementation on the Linux-based system demonstrates that EAR achieves the ERR of 95.9% and 92.45% over the DUT-dependent traffic and fading environments, respectively. Under the same condition, the straight-forward replay can only produce the ERR of 20.6% and 0%, respectively.
UE Performance Evaluation on LTE Indoor and Outdoor Testbeds
(2013-01-01)
Hung, Jui-Tsun Jason
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Ku, Chia-Yu
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Cheng, Hsiao-Chin
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Tung, Li-Ping
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Lin, Bao-Shuh Paul
As the ever increasing demands for higher data rate, lower system latency, and high speed in mobile communications, 4G/LTE systems widely deployed provide better support for these requirements. This increased the complexity of UE (user equipment) and eNBs (evolved Node B) structures, but with simplified core networks. A more flat architecture is achieved to raise data rate and low system latency that are appreciated by users using real-time or high throughput applications such as MAR (mobile augmented reality) or video game applications. The work introduces indoor and outdoor LTE (Long Term Evolution) testbeds for UE performance evaluation via IOT (interoperability) tests and field trials. Throughput for distinct UL-DL (uplink-downlink) configurations were measured to evaluate devices' performance.
Utilizing Multiple Channels With Fewer Radios in Wireless Mesh Networks
(2011-01-01)
Ku, Chia-Yu
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Lin, Ying-Dar
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Tsao, Shiao-Li (Charles)
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Lai, Yuan-Cheng
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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.
Wi-Fi offloading between LTE and WLAN with combined UE and BS information
(2018-05-01)
Lin, Ying-Dar
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Ku, Chia-Yu
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Lai, Yuan-Cheng
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Liang, Yun-Hao
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資訊工程學系
With the increasing popularity of mobile devices, cellular networks are suffering the consequences of a mobile data traffic explosion. Operators and standard development organizations have adopted Heterogeneous Network (HetNet) solutions which offload traffic from cellular networks to other Radio Access Technologies to reduce the overloaded situation. To minimize service blocking ratios, HetNets need to be designed with an efficient approach to allocate heterogeneous channel resources. This work proposes a Combined UE and BS Information scheme (CUBI), which follows the standard architecture proposed by 3rd generation partnership project. We compare the impacts of using the User Equipment (UE) information only, and Base Stations (BS) information only to achieve network selection. We then propose a 2-round solution that benefits from both UE and BS information. The UE-information scheme is based on channel qualities of all available networks, and using it selects the network which provides the highest data rate. On the other hand, the BS-information scheme (BSI) is based on traffic loads of all UEs to allocate bandwidth, and using BSI will prevent BSs from overload situations. The simulation results demonstrate that CUBI can decrease service blocking ratios by 26 and 8.9 %, compared to schemes separately using US and BS information, respectively.