A new approach to space-time-channel layering and coding for frequency-selective channels

In this paper, the design of multiple-input multiple-output (MIMO) wireless systems is investigated. A new approach to the integrated design of diversity and layering for frequency-selective quasi-static channels is proposed. To achieve diversity gain, a novel pre-coding/framing scheme is introduced to translate a MIMO frequency-selective channel into a mathematically equivalent single-input multiple-output (SIMO) channel. As a result, the conventional trellis codes designed for fast fading channels can be used here to exploit the diversity in both spatial and frequency domains. It was shown that the diversity gain of the proposed scheme equals the effective length of the conventional trellis codes. This is in contrary to the case of conventional space-time coded orthogonal frequency division multiplexing (STC-OFDM) systems where no systematic methods exist for the design of space-time trellis codes with a given diversity target. In addition, the proposed diversity scheme also allows a simple channel layering scheme in which a set of transmit weights are used to create a number of independent SIMO channels or layers so that higher data rates can be achieved with moderate complexity. Simulations have been carried out and results are given to show the merits of the proposed scheme.