研究会 (2010 年 04 月 28 日)

日時: 04/28(水) 14:30〜18:00

場所: 九州工業大学天神サテライトキャンパス kyutech プラザ

講演1: Robustness of A CDMA Power Update Algorithm with Respect to 
         Disturbances in the Presence of Delays
       (伊藤 博, 九州工業大学; 14:40〜15:50)

講演2: Stability of large-scale interconnected systems:
         Small-gain conditions and the comparison principle
       (Dr. Bjoern Rueffer, University of Melbourne, Australia; 16:10〜17:40)


懇親会: 福岡市中央区天神近辺
        (18:00〜)

参加者者: Dr. Bjoern Rueffer, 西村(山口大), 佐藤(佐賀大), 伊藤(九工大)

問合わせ: 伊藤博 hiroshi(a)ces.kyutech.ac.jp

                                                (以上敬称略)

Abstract:

1. In this talk , we will consider power update methodology for CDMA 
   wireless communication networks and address the problem of stability 
   and robustness of a gradient-type algorithm in the presence of 
   time-delays and disturbances. The time-delays in individual 
   communication channels between mobile users and base stations are 
   allowed to take place independently. The disturbances represent 
   power noises, unmodeled secondary interference and variation 
   of channel gains which can indirectly represent the change of 
   users' positions. It will be explained the power control system 
   remains integral input-to-state stable with respect to the 
   disturbances for arbitrarily large time-delays for a fairly 
   large class of pricing functions determining the gradient. 
   For unbounded gradients, a stronger property called the 
   input-to-state stability is proved. The results are based on 
   explicit construction of Lyapunov-Krasovskii functionals for 
   the network via an iISS small-gain theorem. For the sake of 
   simplicity, this talk will look at single-cell environment. 
   However, the analysis of multicell networks can be also 
   performed in the same line, which will be mentioned briefly. 

2. We consider the stability of network interconnections of 
   arbitrarily many systems. Each system is assumed to be input-to-state 
   stable (ISS) from the states of the other systems as disturbances to 
   its own state. We will provide sufficiency criteria on the nonlinear 
   gains of the interconnections for the composite network system to 
   satisfy the respective same stability property as all its subsystems. 
   These criteria take the form of a generalized small-gain theorems 
   and comparison principles, and we shall consider three equivalent 
   characterizations of ISS, namely trajectory estimates, the 
   implication Lyapunov form and also dissipative Lyapunov estimates. 
   We will briefly mention an application of these results to formation 
   control.

   Speaker's biographcal sketch: 
   Bjoern Rueffer (ビヨン リュッフェル) received his Master of Science 
   degree from the Department of Mathematics at the University of 
   Warwick, UK, in 2004. In 2007 he completed his PhD thesis in the 
   area of mathematical systems theory at the Center for Applied and 
   Industrial Mathematics (ZeTeM) within the Department of Mathematics 
   and Computer Science at the University of Bremen, Germany. 
   In Bremen, he was also a member of the Collaborative Research Centre 
   637 "Autonomous Cooperating Logistic Processes -- A paradigm shift 
   and its limitations." From October 2007 to June 2009 he was a member 
   of the Signal Processing Microelectronics (SPM) group and the School 
   of Electrical Engineering and Computer Science at the University of 
   Newcastle, Australia. Since July 2009 he is a research fellow with 
   the Department of Electrical and Electronic Engineering at the 
   University of Melbourne, Australia. Currently he is visiting the 
   Kyushu Institute of Technology at Iizuka, Japan, 
   (with Professor Hiroshi Ito) as a JSPS postdoctoral fellow.