Genetic Algorithms for Optimization of Wireless Devices

Abstract

As a result of the evolution in communications technology, the number of wireless nodes is growing much more quickly than the number of wired nodes. Although they offer significant benefit, wireless communications systems pose challenging design problems due to the unpredictable nature of the channel. In spite of these challenges, end users are demanding the benefits of wireless connectivity with quality similar to that of wired connectivity, which requires the devices to be able to adapt to new situations in order to mitigate the detrimental effects of the wireless channel. This dissertation presents a three-layer self-awareness mechanism embedded in the management and control plane architecture of the devices used in a wireless communications network. The proposed mechanism consists of Monitoring, Situational-awareness and Adaptation functions.The dissertation focuses on the implementation of the Adaptation function, which is at the core of the self-awareness mechanism. Using an adaptive genetic algorithm (GA) as the underlying technology, the device is able to learn and apply the acquired knowledge to adapt its operational parameters when facing unknown situations. The self-adaptive capability embedded in the GA allows the evolution parameters to be adjusted according to the current point in the search. The 'knowledge' gained by each species is embodied in the makeup of the genetic information through the chromosomes.The genetic algorithm was tested in a multi-objective scenario that aims to find the weight distribution of a linear antenna array. The goal was to obtain patterns with low sidelobe levels, while maximizing the efficiency of the array. This is achieved by setting a desired effective radiation voltage (ERV). The results of the algorithm, which were compared to those obtained using simulated annealing, show that GA exhibits a more robust performance for different values of ERV. The capability of the algorithm to deal with possible sources of interference was also tested. The patterns obtained in this case showed attenuations of around 60 dB in the direction of the jammers, while maintaining the desired ERV value. While previous approaches to this problem have dealt with different issues, this is the first reported system that optimizes these parameters simultaneously.