Semi-blind adaptive beamforming based on constant modulus algorithm for smart antennas

Adaptive beamforming plays an important role in smart antenna systems. Nonblind adaptive algorithm utilizes the known training sequence to update the weights of antenna array at the cost of low transmission efficiency. Without sending training sequences, blind adaptive algorithm is a solution to implement beamforming and increase the transmission efficiency. Two classic blind algorithms are studied, namely constant modulus (CM) algorithm and Least squares-constant modulus (LS-CM) algorithm. Considering the advantages of the nonblind and blind algorithms, a semi-blind adaptive beamforming based on CM algorithm is proposed in this paper. Simulation results indicate it has comparable performance compared with nonblind adaptive algorithm, while it only needs the training sequence in the first iteration.