Low complexity constant modulus based cyclic blind adaptive multiuser detection

Periodically time varying (PTV) filters can offer significant performance gains over conventional filtering methods in DS-CDMA communications systems that are either multirate or corrupted by narrow band interference. This paper develops a new blind adaptive PTV linear multiuser detector based on the frequency shift (FRESH) architecture. The blind adaptive algorithm is based on the linearly constrained constant modulus algorithm (LCCMA), but is modified for the FRESH architecture. The resulting stochastic gradient algorithm has significantly less computational complexity than the recently proposed recursive and cyclic subspace tracking algorithms, and can offer comparable performance. The robustness of the FRESH-LCCMA algorithm is ensured through a proof of convergence which is carried out in this paper