SURVEY PAPER ON ADAPTIVE BEAMFORMING LMS,NLMS AND RLS ALGORITHMS FOR SMART ANTENNA SYSTEM

Abstract

Smart antenna system is used to maximize the output power of signal in desired direction and minimize the power in unwanted direction. Smart antenna system consists of multiple numbers of elements. Basic concept in smart antenna technology is beam forming, it is mainly used to improve signal to noise ratio. Beam forming signal processing technique used in sensor arrays for directional signal transmission and reception. And it possible by combining the elements in phased array in such a way that signals at particular angles experiences constructive interference and others are destructive interferences. In smart antenna system we are using various algorithms to calculate the weights of smart antenna arrays to increase the output in desired direction and reduce the power in unwanted direction We are using different types of arrays i.e. linear array, circular array, planar array . Different algorithms are used to adjust the weights of the smart antenna system Basically Weights are nothing but Amplitude and phase of the signal. Adaptive algorithms update the weights of the array elements. LMS algorithm provides less convergence speed, and that is depends on the step size. LMS algorithm is widely used in adaptive filter due to its relative low computational complexity, good stability and relatively good robustness against the implementation errors. To improve the convergence rate NLMS algorithm is used. LMS algorithm having constant step size but in NLMS algorithm step size is depends on data at each iteration. Whereas RLS algorithm having minimum bit error rate but it required more computations than the LSM algorithm.