Position-Based Adaptive Power Back-Off for User Electromagnetic Exposure Management in Millimeter Wave Systems

Mobile devices are subject to regulatory limits on user electromagnetic radiation exposure. User exposure is dynamic and varies as a function of the transmit signal and the device orientation. In this letter, we propose the use of a signal-level power density (PD) model to adaptively reduce the transmit power of a millimeter wave (mmWave) system as the position of the device changes. We also develop a method for efficiently calculating power back-off factors for beams in a discrete Fourier Transform (DFT) codebook. Simulation results demonstrate that position-based power reduction leads to a significant performance improvement.