Stochastic conjugate gradient constant modulus blind equalizer for wireless communications

A conjugate gradient searching method, called the Block Shanno Constant Modulus Algorithm (BSCMA), has been reported to blindly equalize constant modulus signals. A stochastic conjugate gradient algorithm (SCGA) is proposed for solving nonlinear optimization problems. We apply the SCGA to the CMA problem. The resulting algorithm is called stochastic conjugate gradient CMA (SCGCMA). As the simulations show, the SCGCMA algorithm preserves the fast convergence rate of the BSCMA algorithm, and can be configured to perform similarly to the RLS CMA algorithm for less cost. Alternatively, a window-sliding parameter may be adjusted to trade off between performance and computation to match the system requirements. Such flexibility will be helpful as technology advances to higher data rates. We study the single antenna configuration because it is the most practical for cellular and PCS systems