Iterative MMSE space-time equalization for turbo-coded and dual-polarized broadband wireless signals

We examine the minimum mean-square error (MMSE) turbo equalization of turbo-coded and dual-polarized broadband wireless signals for frequency selective channels. Severe multipath dispersion, represented by a long channel impulse response between each polarization state and receive sensor, makes impossible the direct application of trellis-based turbo equalizers. For this reason, we propose a computationally efficient turbo receiver that employs a soft-information aided MMSE space-time equalizer at its front-end for each polarization direction. Because the dual-polarization modulator takes the outputs of a turbo encoder, the space-time MMSE equalizer is coupled with a turbo decoder at its back-end. Therefore the proposed receiver performs a doubly-iterative operation: an outer equalization iteration for each polarization signal and an inner decoding iteration within each outer loop.