Power-efficient beam sweeping for initial synchronization in mm-Wave wireless networks

This paper addresses the problem of initial synchronization of users in an indoor mm-Wave scenario. With the use of a massive number of antenna elements at access nodes, the resulting beams have narrow beam width. However, the transmission of individual narrow beams may cause poor coverage in some areas as the energy is concentrated over the direction of their main lobes. To cope with that, a beam sweep procedure using phased arrays is adopted. Access nodes simultaneously transmit individual beams until a certain area of interest is thoroughly scanned. Then, distant points are covered as each beam can radiate energy using an individual transmit power. The goal is to find the minimum power setting by adjusting the individual power levels so that users over the scanned area can observe a minimum received power level. Due to the combinatorial nature and high dimensionality, this paper describes a non-iterative two-stage algorithm to perform the beam sweeping with moderate complexity, which is compared with a baseline iterative selfish algorithm. Preliminary simulation results indicate that the two-stage algorithm may perform at least equally well as the baseline approach in terms of total transmit power, consuming about 7% less power in the used simulation setup, and without suffering from any convergence issue.