A Simple Comparative Evaluation of Adaptive Beam forming Algorithms

Adaptive Antennas can be used to increase the capacity, the link quality and the coverage of the existing and future mobile communication networks. Using beam forming algorithms the weight of antenna arrays can be adjusted to form certain amount of adaptive beam to track corresponding users automatically and at the same time to minimize interference arising from other users by introducing nulls in their directions. This paper presents a simulation test-bed of a smart antenna system for the comparative performance evaluation of various adaptive beam forming algorithms and the smart antenna itself. The adaptive beam forming algorithms simulated and analyzed in this work include the Least Mean Square (LMS), Direct Matrix Inverse (DMI), Recursive Least Square (RLS), Constant Modulus Algorithm (CMA), and Least Square-Constant Modulus Algorithm (LS- CMA) algorithms. The results show that LMS algorithm requires about 53 iterations before it can finally converge. The DMI algorithm is computed for a number of samples; hence it does not require iterations in its calculations. It has faster convergence than LMS but characterized by numerical instability and increased computational complexity due to matrix inversions. The RLS algorithm requires less number of iterations (about 10 iterations before it converges). This simulation and performance evaluation is done using MATLAB platform as the simulator.