Partial Gaussian-Approximation Soft Demapper for the Core Layer of MIMO-LDM in ATSC 3.0

Abstract

In this paper, we propose a new partial Gaussian approximation (PGA) soft demapper for the core layer (CL) signal in the multiple-input-multiple-output layered-division-multiplexing (MIMO-LDM) of ATSC 3.0 systems. Unlike a conventional GA demapper, where enhanced layer (EL) signals are intentionally modelled as additive Gaussian noise, the proposed PGA jointly decodes the CL signal by assuming the EL signals to be QPSK signals added with the Gaussian noise irrespective of their modulation order and type. The assumed QPSK constellations are used in such a way that the residual signal power in the EL signals should be minimized. We verify the performance gains from this new PGA demapper by analyzing the variation of the received injection-level with respect to MIMO channel gains. Simulation results show that this new PGA outperforms conventional GA at the cost of an acceptable increase in decoding complexity, especially when dealing with low injection-levels or high code rates.