Browsing by Author "Lin, Chi-Han"

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acPad: Enhancing Channel Utilization for 802.11ac Using Packet Padding
(2017-01-01)
Lin, Chi-Han
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Chen, Yi-Ting
;
Lin, Kate Ching-Ju
;
Chen, Wen-Tsuen
;
資訊工程學系
Multi-User Multiple Input Multiple Output (MU-MIMO) enables a multi-antenna access point (AP) to serve multiple users simultaneously, and has been adopted as the IEEE 802.11ac standard. While several PHY-MAC designs have recently been proposed to improve the throughput performance of a MU-MIMO WLAN, they, however, usually assume that all the concurrent streams are of roughly equal length. In reality, users usually have frames with heterogeneous lengths even after aggregation, leading to different lengths of transmission time. Hence, the concurrent transmission opportunities might not always be fully utilized when some streams finish earlier than the others in a transmission opportunity (TXOP). To resolve this inefficiency, this paper presents acPad, a PHY-MAC design that adds additional frames to fill up the idle channel time and better utilize the spatial multiplexing gain. Our acPad identifies proper users as the padding so as to improve the padding gain, while preventing this padding from harming all the ongoing streams. Our evaluation via large-scale trace-driven simulations demonstrates that acPad improves the throughput by up to 2.83x, or by 1.36x on average, as compared to the conventional 802.11ac.
FDoF: Enhancing Channel Utilization for 802.11ac
(2018-02-01)
Lin, Chi-Han
;
Chen, Yi-Ting
;
Lin, Kate Ching-Ju
;
Chen, Wen-Tsuen
;
資訊工程學系
Multi-user multiple input multiple output (MU-MIMO) enables a multi-antenna access point to serve multiple users simultaneously, and has been adopted as the IEEE 802.11ac standard. While several PHY-MAC designs have recently been proposed to improve the throughput performance of a MU-MIMO WLAN, they, however, usually assume that all the concurrent streams are of roughly equal length. In reality, users usually have frames with heterogeneous lengths even after aggregation, leading to different lengths of a transmission time. Hence, the concurrent transmission opportunities might not always be fully utilized when some streams finish earlier than the others in a transmission opportunity. To resolve this inefficiency, this paper presents full degree-of-freedom (FDoF), a PHY-MAC design that exploits a novel power allocation scheme to reduce the idle channel time and further leverages frame padding to better utilize the spatial multiplexing gain. Unlike traditional MIMO power allocation, which aims at maximizing the theoretical sum-rate, FDoF's power allocation explicitly considers heterogeneous frame lengths and minimizes the channel time required to finish concurrent frames, as a result improving the effective throughput. FDoF's padding protocol then identifies proper users to reuse the remaining idle channel time, while preventing this padding from harming all the ongoing streams. Our evaluation via large-scale trace-driven simulations demonstrates that FDoF's improves the throughput by up to 2.83x, or by 1.36x on average, as compared to the conventional 802.11ac. By combining FDoF's power allocation with frame padding, the average throughput gain can be further increased to 1.75x.
Traffic-Aware Sensor Grouping for IEEE 802.11ah Networks: Regression Based Analysis and Design
(2019-03-01)
Chang, Tung-Chun
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Lin, Chi-Han
;
Lin, Kate Ching-Ju
;
Chen, Wen-Tsuen
;
資訊工程學系
Traditional IEEE 802.11 network is designed for the use of small scale local wireless networks. However, the emergence of the Internet of Things (loT) has changed the scene of wireless communications. Thus, recently, the IEEE task group ah (TGah) has been dedicated to the standardization of a new protocol, called IEEE 802.11ah, which is customized for this type of large-scale networks. IEEE 802.11ah adopts a grouping-based MAC protocol to reduce the contention overhead for each group of devices. However, most existing designs simply randomly partition devices into groups, and less attention has been paid to the problem of forming efficient groups. Therefore, in this paper, we argue that the performance of grouping is closely related to heterogeneity in traffic demands of devices, and propose a traffic-aware grouping algorithm to improve channel utilization. Since channel utilization of a group closely depends on the collision probability, we further derive a regression-based analytical model to estimate the contention success probability with consideration of sensors' heterogeneous traffic demands. The evaluation via NS-3 simulations shows that the proposed regression-based model is quite accurate even when clients have diverse traffic demands, and our traffic-aware grouping outperforms other baseline approaches, especially when the network is nearly saturated.