A fast RLS algorithm for multiuser detection

The multi-input single-output (MISO) system of the decentralized (single-user) MMSE receiver for CDMA signals has precluded the exploitation of a fast RLS algorithm. Conventional multichannel lattice-based algorithms applicable to the centralized (multiuser) MMSE receiver incur a significant complexity increase due to their basis, the classical multichannel Levinson algorithm. In the author's recent paper, a new multichannel Levinson algorithm has been proposed. The new algorithm is not only more computationally efficient but more flexible than the classical algorithm. This paper shows how we can exploit the new Levinson type algorithm in a least squares (LS) fashion for such a complicated application as the CMMSE receiver requiring a high level of computational efficiency and flexibility. The proposed LS algorithm is still a fast algorithm. It is further observed that the fast RLS-driven CMMSE receiver exhibits better convergence and performance than LMS-driven MMSE receivers.