Sun Wei was born in 1982. She received her B. S. degree from Hebei University in 2004, and M. S. degree from Yanshan University in 2006. She is now a Ph. D. candidate in the College of Information Science and Engineering at Yanshan University. Her research interests include queueing theory, and application in computer network, and management science. E-mail: ysusw@yahoo.com.cn Tian Naishuo was born in 1941. He is a professor of mathematics in the College of Science at Yanshan University. His research interests are stochastic process, queueing systems with vacations, and performance evaluations in computer networks. Li Shiyong was born in 1982. He received his B. S. degree from Qingdao University in 2004, and his M. S. degree from Yanshan University in 2007. Now, he is a Ph. D. candidate in the School of Electronics and Information Engineering at Beijing Jiaotong University. His research interests include universal network, congestion control in network, and queueing theory. Guan Xinping was born in 1963. He is a professor of control theory and control engineering of Yanshan University. His research interests include energyefficiency protocol design in wireless sensor networks, non-cooperative game in wireless Ad Hoc networks, and congestion control in high-speed networks.