Is Ultra-High Order QAM Necessary for Delta-Sigma Modulator in Mobile Front-Haul?

We propose a delta-sigma-modulator (DSM) using multi-stage-noise-shaping (MASH) structure. Record high efficiencies of 1.016 (hard-decision forward-error-correction, FEC) and 1.166 (soft-decision-FEC) are achieved in the proposed MASH-DSM without the need of ultra-high-order quadrature-amplitude-modulation (QAM).