NLMS/F Based Adaptive Beam former for Indoor Wireless Channel

Abstract

The paper proposes an adaptive beam forming model for indoor wireless channel and the channel characteristics are described through IEEE 802.11 model. The design consists of eight elements linear antenna array with the corresponding array factors in a given desired and interfering directions. Adaptive algorithm based steering mechanism is incorporated so as to achieve better directive gain in the desired direction and to suppress the interfering signals to large extent. The proposed adaptive beam former is based on NLMS/F algorithm which is a compromise between normalized least mean square (NLMS) and normalized least mean fourth(NLMF) that utilizes the benefits of low complexity structure of LMS and faster convergence property of LMF. The normalization of correction factor is achieved with respect to norm square of input vector. The NLMS/F beam former is tested with practical fading conditions and 16-QAM modulated data corrupted by additive channel noise. A thorough comparison is being carried out among adaptive beam formers in terms of mean square error (MSE), beam pattern and antenna gain to justify the usefulness of the proposed NLMS/F based design.