Grid-Free Beam Management for 6G Millimeter-Wave Communications

Millimeter wave (mmWave) communications have been recognized as an important technology to address the growing data demand of next-generation wireless communications. Since mmWave communications have the inherent disadvantage of severe signal attenuation, the beamforming technique using a large antenna array is widely adopted at the base station (BS). For achieving optimal beamforming performance, a beam management process for angular channel information must be carried out. However, conventional beam management techniques suffer from long latency and inaccuracies in determining the beam direction due to the quantized codebook design. To overcome this issue, we propose an active receiver-based beam management (AR-BM) in which the user equipment (UE) determines and reports the grid-free channel direction without the need for additional refinement stages, while also achieving more accuracy. In our scheme, BS transmits wide training beams generated by partially activated arrays. Then, UE determines and reports gridfree direction by updating the estimated direction comparing the measured reference signal received power (RSRP) and the function-derived RSRP. Numerical results show that the proposed scheme achieves a <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{1 4 \%}$</tex> improvement in the data rate and a <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{9 0 \%}$</tex> reduction in the latency.