Abstract
One of the main objectives of adaptive antenna array processing is reducing the computational complexity and convergence time in a joint state. This article proposes a speed-sensitive adaptive algorithm for estimating the weights of smart antenna systems based on least mean squares (LMS) or constant modulus (CM) algorithms. According to the next estimated location as well as the source velocity, this novel proposed weighting algorithm selects those weights that have a higher effect on the radiation pattern and will then form the antenna pattern by only changing these weights. In this research, 3 versions of the new algorithm named as: Not-zero (Leaves half number of weights as it is the other half), Zero (Sets half number of weights to be zero and estimates other half), and Updating (Leaves half of weights unchanged and estimates other half in one phase and updates all weights in the next phase) are proposed. Through simulation of these 3 versions of speed-sensitive algorithms and comparing among conventional full weight LMS and CM algorithms, new LMS-based and CM-based algorithms have been finally proposed that offer reduced complexity and acceptable performance at different signal to noise ratios (SNRs). In this investigation, three channel scenarios are simulated which are as follows: pure noisy channel, channel with one interferer and channel with two interferers. In accordance with the simulation results, an appropriate algorithm based on weighting half number of array elements and updating all existing weights between two consecutive times to avoid error propagation effect has been proposed.
Highlights
In most communication systems, designers are faced with issues such as capacity shortage and increase of interferences in a joint state
Smart antenna systems use an antenna array with the ability to process the digital signal in the receiver port as well as the transmitter port based on an adaptive manner [1,2]
The antenna array is an 8-element ULA, the average relative angular velocity is less than 5 degrees in a second and signals are modulated using minimum shift keying (MSK) constant envelope method
Summary
Designers are faced with issues such as capacity shortage and increase of interferences in a joint state. Smart antenna systems use an antenna array with the ability to process the digital signal in the receiver port as well as the transmitter port based on an adaptive manner [1,2]. In [14], a matrix inversion normalized least mean square (MI-NLMS) adaptive beamforming algorithm is described Simulation results of this method show that the bit error rate (BER) improvement to be proportional to the number of antenna elements employed in the antenna array. In [16,17], the performance of blind adaptive beamforming algorithms for smart antennas in realistic environments with a constrained constant modulus (CCM) design criterion is described and used for deriving a RLS type optimization algorithm.
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