Multiuser MIMO Uplink Transmission With Electromagnetic Exposure Constraints: Spectral Efficiency and Energy Efficiency Tradeoff

Along with the relentless development of wireless communications, the electromagnetic (EM) radiation emitted by wireless devices has gradually turned into a significant concern of the public. A growing number of government departments and communication regulatory agencies require that EM radiation be limited to a suitable level with the measurement of specific absorption rate (SAR). Meanwhile, both spectral efficiency (SE) and energy efficiency (EE) are key indicators of wireless transmission systems, so that they generally need to be considered at the same time. To this end, we investigate the resource efficiency (RE), which characterizes the weighted sum of SE and EE, in uplink multiuser multiple-input multiple-output (MIMO) transmission with EM constraints. We first simplify the RE calculation by applying its deterministic equivalents (DEs) and deal with the objective function by the quadratic transform algorithm. Then, a modified RE maximization water-filling algorithm is proposed for the precoder design at the users. Numerical results indicate the superior performance of the EM aware RE oriented transmission scheme.