Anders Möller: Modeling and Stability Analysis of Rate and Power Control Systems in Wireless Communication Networks
Anders Möller, KTH
Time: Fri 2012-04-27 11.00
Location: Room 3721, Lindstedtsvägen 25, 7th floor, Department of mathematics, KTH
He will present his thesis that will be defended May 4.
Wireless data traffic in cellular networks is currently undergoing a strong global expansion and the demand for high and reliable data throughput increases. Capacity is, however, a limited resource, and in radio resource management a trade-off has to be made between the congestion level, related to cell coverage and interference levels, and the Quality of Service (QoS) or data rates of the users. The radio channel conditions vary on a fast time scale and the measurements of the received signals are subject to disturbances and uncertainties. This motivates the use of control strategies to update the transmission powers. In fact, in implementations of uplink in cellular networks, the performance of the network is ensured by using a fast inner power control algorithm to track a QoS-target and a slower outer control algorithm to limit congestion. Several theoretical challenges arise in this problem setting. Due to the nature of the network, both information and control are distributed. Furthermore, measurements of the congestion and the QoS are used in the control loops, which introduces nonlinear feedback. Another complicating factor is that filtering, computations and information exchange in the network cause time-delays and dynamics. In this talk we address these challenges by using modeling and analysis tools in systems and control. The main methods used for stability are input-output analysis, Lyapunov analysis, the multivariate Nyquist criterion and multivariate describing functions.