Browsing by Author "Liao, Chun-Chieh"

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Analysis and determination of cooperative MAC strategies from throughput perspectives
(2013-08-01)
Chu, Jui-Hung
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Feng, Kai-Ten
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Liao, Chun-Chieh
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電機資訊學士班
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Undergraduate Honors Program of Electrical Engineering and Computer Science
In recent years, cooperative communication has been developed as a new communication strategy that incorporates a relay node to assist direct point-to-point transmission. By exploiting cooperative diversity, different types of techniques have been proposed to improve transmission reliability from the physical layer perspective. However, owing to the longer transmission time resulting from the cooperative schemes, there is no guarantee to enhance network throughput in view of the medium access control (MAC) performance. In this paper, system throughput of combined direct/cooperative communication is evaluated by exploiting the proposed analytical model based on the IEEE 802.11 MAC protocol. The feasibility of adopting either cooperative or direct communication is also studied in the analytical model. In terms of network throughput, whether to adopt cooperative schemes depends on the tradeoff between cooperative transmission delay and channel quality of direct communication. Moreover, two cooperative MAC protocols are proposed to determine the circumstances to activate cooperative communication according to the channel quality. The full-channel quality indicator based cooperative (FCC) MAC protocol is introduced to choose both the transmission scheme and the relay node according to the full channel quality information. However, the overhead caused by the FCC scheme can degrade the throughput performance as the number of available relays is significantly increased. Therefore, the bitwise competition based cooperative (BCC) MAC protocol is utilized to efficiently determine a feasible relay node for data transmission. Simulations are performed to validate the effectiveness of proposed analytical models and cooperative MAC protocols. It is observed that the proposed BCC scheme can outperform both the FCC protocol and conventional direct transmission with enhanced system throughput.
Fast Failover and Switchover for Link Failures and Congestion in Software Defined Networks
(2016)
Lin, Ying-Dar
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Teng, Hung-Yi
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Hsu, Chia-Rong
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Liao, Chun-Chieh
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Lai, Yuan-Cheng
In this paper, we present a fast failover mechanism and a fast switchover mechanism to deal with link failure and congestion problems. In the fast failover mechanism, the controller pre-establishes multiple paths for each source-destination pair in the related OpenFlow-enabled (OF) switches. When a link becomes faulty, OF switches are able to failover the affected flows to another path. Based on the pre-established paths, in the fast switchover mechanism, the controller periodically monitors the status of each port of each OF switch. When the average transmission rate of a port consistently exceeds the rate threshold, the controller would decrease the transmission rate of the port by iteratively switching the flow with the minimum rate to another path. The emulation on Ryu controller and Mininet emulator shows the average recovery time of the fast failover mechanism is less than 40 ms, compared to hundreds of ms in the fast restoration mechanism. And, the fast switchover mechanism can reduce 47.5%-72.5% sustained time of link congestion depending on the parameter setting.
Performance Analysis of Cooperative Communications from MAC Layer Perspectives
(2008)
Liao, Chun-Chieh
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Hsu, Yu-Pin
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Feng, Kai-Ten
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電信工程研究所
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Institute of Communications Engineering
In recent years, cooperative communication has been proposed as a new communication paradigm that incorporates a relay node to assist the direct point-to-point transmission. By exploiting the cooperative diversity, different types of techniques have been proposed to improve the transmission reliability from the physical layer perspective, e.g. the cooperative automatic repeat request. However, owing to the longer transmission time resulting from the cooperative schemes, there is no guarantee to enhance the network throughput in view of the medium access control (MAC) performance. In this paper, the system throughput of the cooperative communication is evaluated by exploiting the proposed analytical model based on the IEEE 802.11 MAC protocol. Both the relay-based and the original direct communications are considered in the analytical studies. Simulations are conducted to further validate the effectiveness of the proposed model. In terms of the network throughput, whether to adopt the cooperative schemes depends on the tradeoff between the cooperative transmission delay and the channel condition of the direct communication.
Scalable multicasting with multiple shared trees in software defined networking
(2017-01-15)
Lin, Ying-Dar
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Lai, Yuan-Cheng
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Teng, Hung-Yi
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Liao, Chun-Chieh
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Kao, Yi-Chih
With Software Defined Networking (SDN), IP multicast becomes promising again. For IPTV applications over SDN, existing works would not scale well since they are based on per-source trees. As control-plane in SDN is logically centralized, constructing multiple shared trees is more feasible than that in traditional IP networks. Thus, in this work, we present a locality-aware multicast approach (LAMA) to construct multi-group shared trees in SDN, where each shared tree covers multiple multicast groups. In LAMA, the controller first clusters the multicast sources located in the vicinity into the same multicast cluster. For each multicast cluster, the controller selects the center switch which has the minimum distance to all multicast sources as its rendezvous point (RP) and then constructs a shortest-path multicast tree from the RP to its hosts. Finally, based on the multi-group shared trees, the controller can establish coarse-grained flow entries into on-tree switches to reduce the number of installed flow entries. Emulations on the Ryu controller and the Mininet emulator show that only 2-5 shared trees would suffice. The computation time in the controller using LAMA is around 70 ms, much less than hundreds ms required for per-source trees. Moreover, LAMA only establishes 2300 flow entries, 4% of that with per-source trees in a large topology.