A variable step size technique for CMA blind equalization in filter bank based multicarrier systems

The filter bank based multicarrier modulation (FBMC) is a transmission technique better suited for new concepts such as dynamic access spectrum management (DASM) and cognitive radio. Filter bank-based transmultiplexer systems have certain advantages compared with existing OFDM/DFT-based multicarrier systems and they are promising candidates for high rate data transmission. However, efficient channel equalization techniques for such systems are still an active area of development. In this paper we first implement the FBMC system using cosine-modulated filter banks and the prototype filter for this system is designed using the Kaiser window approach. Then, we perform blind equalization using Constant Modulus Algorithm (CMA). However, due to fixed step size, CMA suffers from a trade off between convergence rate and steady-state error. The choice of step size for updating the tap weights is very critical for CMA. Hence we introduce enhanced variable step size CMA (VSS-CMA) which utilizes a nonlinear function of the remainder error to control the step size. Simulation results show that the proposed algorithm provides better performance in terms of error convergence and bit error rate than the existing method.