Title: Throughput Optimal Beam Alignment in Millimeter Wave Networks,
Abstract: Millimeter wave communications rely on narrow-beam transmissions to cope with
the strong signal attenuation at these frequencies, thus demanding precise beam
alignment between transmitter and receiver. The communication overhead incurred
to achieve beam alignment may become a severe impairment in mobile networks.
This paper addresses the problem of optimizing beam alignment acquisition, with
the goal of maximizing throughput. Specifically, the algorithm jointly
determines the portion of time devoted to beam alignment acquisition, as well
as, within this portion of time, the optimal beam search parameters, using the
framework of Markov decision processes. It is proved that a bisection search
algorithm is optimal, and that it outperforms exhaustive and iterative search
algorithms proposed in the literature. The duration of the beam alignment phase
is optimized so as to maximize the overall throughput. The numerical results
show that the throughput, optimized with respect to the duration of the beam
alignment phase, achievable under the exhaustive algorithm is 88.3% lower than
that achievable under the bisection algorithm. Similarly, the throughput
achievable by the iterative search algorithm for a division factor of 4 and 8
is, respectively, 12.8% and 36.4% lower than that achievable by the bisection
algorithm.