Blind Constant Modulus Multiuser Detection With Regularization

The problem of blind constant modulus multiuser detection in code-division multiple-access (CDMA) systems is investigated in this letter. Different from traditional approaches which either assume the amplitude of the user of interest is known or arbitrarily set the value of dispersion constant, we consider a more general case where the amplitude is unknown and the dispersion constant is deemed as an unknown parameter jointly determined with the weight vector of the detector. Moreover, a regularization term of the weight vector is incorporated into the optimization to stabilize the problem. With these considerations, an iterative framework is thus introduced to tackle the formulated problem. It is shown that for a given weight vector, the dispersion constant can be analytically determined. To handle the more challenging subproblem with respect to the weight vector, we first present a semidefinite relaxation (SDR) based scheme. Then, a Newton's method based approach is developed to release the computational burden. Simulations have been carried out to demonstrate the effectiveness of the proposed methods and superiority over conventional approaches.