Optimization and Systems Theory Seminar
April 27, at 11.00, room 3721, Lindstedtsvägen 25, KTH:
Division of Optimization and Systems Theory
Department of Mathematics
He will present his thesis that will be defended May 4:
Modeling and Stability Analysis of Rate and Power Control Systems in
Wireless Communication Networks
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
Calendar of seminars
Last update: April 20, 2012.