Normalised constant modulus algorithm with selective partial updates

A reduced complexity realisation for the normalised constant modulus algorithm (NCMA) and its soft criterion satisfaction (SCS) version is proposed based on selective partial updating. The computational complexity of NCMA and SCS is reduced by updating a block of equaliser parameters at every iteration rather than the entire equaliser. This results in a smaller number of multiplications for updating the equaliser parameters. A simple block selection criterion is derived from the solution of a constrained minimisation problem that underpins the development of NCMA. In fractionally-spaced equalisation, the proposed selective partial updating is shown to be capable of maintaining comparable convergence speed to its full-update counterpart. This implies a significant reduction in implementation cost without necessarily penalising the convergence speed.