Low Latency Beam-Sweeping for Millimeter Wave Systems via Pessimistic Optimization

The initial setup at millimeter-wave channels is especially challenging due to the severe propagation loss imposed on the channel gains. To overcome this loss, it is common to use large arrays and concentrate the radiated energy in certain directions through beamforming. During the initial setup process, the base station (BS) has no knowledge of the position and channel state of the user equipment (UE) in its coverage region. Therefore, it is necessary to transmit beams that cover this region, with each beam having sufficient array gain to allow for reliable communication between the BS and the UEs. At the same time, next-generation wireless networks should serve a large number of UEs with minimum latency. In our work, exploring the concept of the worst-case channel, we propose an algorithm that generates the transmitting beamforming codebook. This codebook minimizes the number of beams transmitted, resulting in reduced maximum latency while at the same time guaranteeing a minimal signal-to-noise ratio (SNR) between BS and UEs. Simulation results are conducted to show the efficacy of the proposed beam codebook design, which illustrates latency reduction without sacrificing achievable SNR.