On the Use of Multiple Grossly Nonlinear Amplifiers for Highly Efficient Linear Amplification of Multilevel Constellations

Multilevel modulations can ensure high spectral efficiency but at cost of energy efficiency and envelope fluctuations that can compromise the amplification efficiency at the transmitter. Due to strict power and bandwidth constrains it is also desirable to adopt energy efficient amplification combined with powerful equalizer to reduce interference impact. In this paper we propose a method for amplification of multilevel constellations compatible with grossly nonlinear amplifiers based on the constellation´s decomposition as a sum of BPSK (Bi-Phase Shift Keying) sub-constellations. Our approach relies on an analytical characterization of the mapping rule were the constellation symbols are written as a linear function of the transmitted bits. This analytical method is then employed to design iterative receivers such as IB-DFE (Iterative Block Decision Feedback Equalization), that can cope with higher sensitivity to ISI effects (InterSymbol Interference) of the resulting high order constellations. It is also defined a pragmatic method for designing IB-DFE receivers that can be employed with any constellation. It is also shown that the resulting method for designing an SC-DFE receiver (Single Carrier-Decision Feedback Equalization) does not require a significant increase in system complexity and can be used for the computation of the receiver parameters for any constellation.