Displacement MIMO Kalman equalizer architecture for CDMA downlink in fast fading channels

Abstract

In this paper, we explore the displacement structure in a Kalman equalizer for MIMO-CDMA downlink. A streamlined MIMO Kalman equalizer architecture is proposed to extract the commonality in the data path by exploiting the displacement structure of the transition matrix and the block-Toeplitz structure of the channel matrix. Numerical matrix multiplications with O(F^3) complexity are eliminated by simple data loading process. Utilizing the block Toeplitz structure of the channel matrix, an FFT-based acceleration is proposed to avoid direct matrix multiplications in the time domain. Finally, an iterative Conjugate-Gradient based algorithm is proposed to avoid the inversion of the innovation correlation matrix in Kalman gain calculation. The proposed architecture not only reduces the numerical complexity to O(F log2 F) per chip, but also facilitates the parallel and pipelined VLSI implementation for real-time processing.