Wideband mmWave/THz Beam Alignment: Exploiting Beam Split Effect via Posterior Matching

The massive-antenna millimeter wave (mmWave)/ terahertz (THz) system inevitably suffers from a severe beam split effect, which will significantly decrease array gains and communication efficiency. However, the wideband split effect can be beneficial for channel training by sensing from splitting directions. This paper proposes a novel wideband beam alignment framework in True-Time-Delayers (TTDs) enabled hybrid beamforming systems, which can fully exploit the controllable beam split effect for efficient angle-of-arrival (AoA) estimation. A splitting-sensing enabled wideband posterior matching algorithm is developed, which proactively controls the steering direction of the splitting-sensing beams at each pilot training slot to accelerate the AoA estimation process. Numerical results verify that the proposed algorithm can significantly improve the AoA estimation accuracy at the cost of the same pilot overheads.