Browsing by Author "Kuo, Tung-Wei"

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Beam Configuration and Client Association for Access Points with Switched Beam Antennas
(2016-09-01)
Lin, Kate Ching-Ju
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Kuo, Tung-Wei
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Yan, Pei-Jiun
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Cheng, Wan-Jie
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Jeng, Shyh-Kang
Unlike conventional omnidirectional antennas, switched beam antennas exploit antenna arrays and signal processing techniques to focus energy in a specific beam-width and orientation. Recent research has shown that access points of a WLAN can exploit such switched beam antennas to increase the overall network capacity. The achievable sum rate of a WLAN with switch beam antennas is however mainly determined by how each AP selects its beam, including the orientation and width, and how each client associates with a proper AP. The goal of this paper is to solve the Joint Beam configuration and Client association (JBC) problem such that the sum rate of all clients in the network can be maximized. We formulate the JBC problem as a mixed integer linear programming model, and propose a 2-approximation algorithm to solve it. Our proposed algorithm has two distinctive properties: 1) it can be realized as a distributed protocol that allows the APs to configure their beams without the help of a central coordinator, and 2) it can be generally applied both in specific scenarios, where exact client locations are known, and in uncertain scenarios, where only geographic client distribution is given. Finally, we adjust the sum-rate maximization algorithm to the throughput maximization algorithm, which further takes medium sharing among clients into account. The simulation results show that the proposed algorithm outperforms both WLANs using omnidirectional antennas and other heuristics using switched beam antennas.
Deploying Chains of Virtual Network Functions: On the Relation Between Link and Server Usage
(2018-08-01)
Kuo, Tung-Wei
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Liou, Bang-Heng
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Lin, Kate Ching-Ju
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Tsai, Ming-Jer
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資訊工程學系
Recently, network function virtualization has been proposed to transform from network hardware appliances to software middleboxes. Normally, a demand needs to invoke several virtual network functions (VNFs) following the order determined by the service chain along a routing path. In this paper, we study the joint problem of the VNF placement and path selection to better utilize the network. We discover that the relation between the link and server usage plays a crucial role in the problem. Inspired by stress testing, we first propose a systematic way to elastically tune the link and server usage of each demand based on the network status and properties of demands. In particular, we compute a proper routing path length, and decide, for each VNF in the service chain, whether to use additional server resources or to reuse resources provided by existing servers. We then propose a chain deployment algorithm that follows the guidance of this link and server usage. Via simulations, we show that our design effectively adapts resource allocation to network dynamics and, hence, serves more demands than other heuristics.