Time-Constraint Service System in Ubiquitous Computing Environments Based on Quality of Service

• Main Authors: Ding-Jung Chiang, 江定榮
• Other Authors: Timothy K. Shih
• Format: Others
• Language: en_US
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/86885610960176007963

博士 === 淡江大學 === 資訊工程學系博士班 === 99 === Network connectivity affects the quality of service (QoS) in a mobile network. Real-time broadcasting is a promising data dissemination method to improve system scalability and deal with dynamic data access pattern. This study presents an analysis model and a simulation model for real-time broadcasting systems. As this study demonstrates, traditional strategies like EDF (Earliest Deadline First) and LSF (Least Slack First) in the non-mobile real-time environment do not perform efficiently in a mobile broadcasting environment. Therefore, this study proposes an efficient scheduling algorithm with guaranteed QoS, called dynamic adjustment scheduling (DAS), which is designed for timely delivery of data to mobile clients. This study also compares DAS with traditional client/server based real-time scheduling strategies and mobile non-real-time broadcast strategies. The proposed approach generally outperforms existing real-time strategies with different deadline distributions. A series of simulation experiments evaluates the performance of the proposed scheme. The results demonstrate that this algorithm outperforms other algorithms for performance metrics such as miss rate, waiting time, and stretch. Results also show that the overhead of this algorithm is low compared with other scheduling algorithms. In the future, we plan to improve the DAS strategy by reducing its scheduling time complexity. Other topics for future research include the investigation of real-time scheduling algorithms that can handle transmission errors, update access patterns, unfixed page sizes, client cache management schemes and multi-hop communication.