A thesis submitted in partial fulfillment of the requirements for the degree of Masters of Engineering in Telecommunications, School of Engineering and Technology

Thesis (M.Eng.) - Asian Institute of Technology, 2008

We design an adaptive decentralized congestion control algorithm for multi-link multiple-input multiple-output (MIMO) interference systems. In a multi-link MIMO interference system, each link is trying to maximize its own mutual information by choosing appropriate transmit powers. The scenario can be mapped to a multi-player game in which a player is a link and the utility function is the mutual information of the link. To solve this game, we apply a known decentralized link adjustment algorithm based on the gradient method. Using the power allocation obtained from this algorithm, we propose a decentralized congestion control algorithm that adaptively decides whether or not to support the traffic on each link, and chooses an appropriate modulation scheme for the link. Each link decision depends on the type of traffic (class I or class II) and the quality-of-service (QoS) requirements. In particular, a link decision is based on a metric that is a function of the bit rate and the bit error rate. When some links do not satisfy the QoS requirements, the link with the minimum metric kills itself, i.e., decides not to support traffic. Using MATLAB, we simu»late our algorithm and analyze its behaviors under different system conditions. In addition, we demonstrate the advantages of our algorithm through comparisons with the cases with»out congestion control.