Power Allocation for Beam Alignment in Millimeter Wave IoT Communications

The lower transmission power capability of internet of things (IoT) devices in millimeter-wave (mmWave) networks necessitates the activation of beamforming techniques by employing multiple antennas. To ensure robust directional transmissions at mmWave frequencies, it is essential to accurately align narrow beams with the dominant channel direction. However, directional communications necessitate aligning the beam with the channel direction, resulting insignificant transmit power consumption. We aim to reduce the transmit power required to achieve a desired beam-alignment performance, taking into account the power limitations of IoT devices.We propose an analytical framework for optimizing resource utilization in the hierarchical beam alignment algorithm, designed to progressively reduce the size of the beamformer candidate set. Based on the analytical studies, we develop a resource allocation algorithm that determines the optimal transmit power and constructs the optimal set of beamformer candidates at each beam alignment stage. Numerical simulations demonstrate that the proposed power allocation algorithm effectively reduces the transmit power to meet the performance targets for IoT networks.