Energy Efficiency Optimization of FBMC/OQAM-based Massive MIMO Systems Subject to Electromagnetic Exposure Constraints

The performance of offset-quadrature-amplitude-modulated filter bank multi-carrier (FBMC/OQAM) waveform based on massive multiple-input multiple-output (MIMO) systems is investigated considering not only the transceiver's classic metrics, but also the health concerns associated with exposure to electromagnetic fields (EMF). Closed-form expressions are obtained for the lower-bounds on the uplink spectral efficiency (SE) for FBMC/OQAM-based Massive MIMO systems with both the maximum ratio combiner (MRC) and zero-forcing (ZF) receivers, in the face of realistic imperfect channel state information (CSI). Subsequently, by employing our closed-form SE expressions, a framework is developed for maximizing the global energy efficiency (GEE) of the proposed FBMC/OQAM-based system subject to both power and EMF exposure constraints. A nested quadratic-transform (NQT)-based approach is proposed next for maximizing the non-convex GEE objective by first approximating it as a concave-convex function and then by applying the quadratic transform. Subsequently, a low-complexity iterative algorithm is developed that sequentially applies the Lagrangian dual transform, quadratic transform and Dinkelbach's transform to obtain a closed-form solution of the GEE optimization problem formulated. Our simulation results verify the analytical SE expressions and also demonstrate the improved GEE of the proposed FBMC-based massive MIMO systems subject to the EMF exposure limits.