Soft-decision feedback turbo equalization for multiple antenna systems with multilevel modulations

Many communication systems today encounter the problem of data transmission over a channel with inter-symbol interference (ISI). The purpose of this paper is to develop a low-complexity, iterative soft-decision feedback equalization (SDFE) receiver for severe, frequency selective ISI channels. The proposed SDFE algorithm offers a novel approach to combat error propagation. In addition, its computational complexity grows only linearly with the number of equalizer coefficients, compared to the quadratic complexity of minimum mean square error-based linear turbo equalizer with time-varying coefficients. Performance of the proposed detection scheme is verified through simulations using different signal constellations. Simulation results show that our proposed algorithm has a significant improvement over the low complexity linear turbo equalizer. Moreover, we show that the performance of the proposed equalization scheme improves significantly when higher order constellations are used for digital modulation.