Browsing by Author "Huang, Chao-Hua"

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Performance Analysis of Block Acknowledgement Mechanisms for Next Generation Wireless Networks
(2010)
Liu, Wen-Jiunn
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Huang, Chao-Hua
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Feng, Kai-Ten
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電機工程學系
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Department of Electrical and Computer Engineering
The IEEE 802.11n standard has been proposed to provide enhanced throughput performance for the wireless local area networks. Most of the existing research work considers packet aggregation techniques for enhancing the network throughput from the medium access control perspective. Consequently, the large amount of small-sized acknowledgement (ACK) packets are aggregated via the block ACK mechanisms in order to improve the system throughput. In this paper, a block ACK classification is proposed to categorize the existing block ACK mechanisms into the greedy and the conservative schemes. Based on the Markovian techniques, the respective analytical models are constructed in order to measure the throughput-related metric of the window utilization under different packet error probabilities. Simulations are conducted to validate and compare the proposed analytical models associated with the two types of block ACK schemes. It can be observed from the numerical results that the greedy scheme outperforms the conservative approach with comparably higher window utilization.
Performance analysis of greedy fast-shift block acknowledgement for high-throughput WLANs
(2014-11-01)
Liu, Wen-Jiunn
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Huang, Chao-Hua
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Feng, Kai-Ten
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Tseng, Po-Hsuan
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電機資訊學士班
The techniques of frame aggregation and block acknowledgement (ACK) are utilized in the IEEE 802.11n standard for achieving high throughput performance from the medium access control perspective. Conventional greedy scheme for block ACK adopts the transmitter-defined starting sequence number (SSN) to construct the ACK window for recognizing the correctness of data packets. However, there exists correctly received packets that lie outside of the ACK window which will unavoidably be retransmitted by adopting the conventional scheme. In this paper, a greedy fast-shift (GFS) block ACK mechanism is proposed to provide the receiver-defined SSN, which can both implicitly acknowledge the correctly received packets before the SSN and explicitly identify the correctness information for the packets after the SSN. In order to evaluate the effectiveness of the GFS scheme, the analytical models for these two mechanisms are proposed based on the window utilization. Compared to the conventional greedy scheme, it is observed from the simulation results that the proposed GFS method can provide better performance owing to its fast-shift behavior on ACK window.
POMDP-Based Cell Selection Schemes for Wireless Networks
(2014-05-01)
Tseng, Po-Hsuan
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Feng, Kai-Ten
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Huang, Chao-Hua
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電機資訊學士班
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Undergraduate Honors Program of Electrical Engineering and Computer Science
To acquire higher network capacity, the cell selection problem is formulated based on the partially observable Markov decision process (POMDP). It observes/predicts unavailable cell loading information from those non-serving base stations and takes actions for maintaining active base station set and handover target selection. Various utility functions are designed to consider different factors in the proposed POMDP-based cell selection (POCS) schemes, including system capacity, handover time, and mobility of mobile station. With the considerations of cell load as a hidden Markov model and predicted mobility in the reward function, simulation results show that the proposed POCS schemes can outperform conventional received signal strength based and load balancing methods.