A novel hybrid beamforming transmission scheme for common channels and signals

Massive MIMO is envisioned as one of the key technologies for the 5th generation (5G) wireless communication systems. Hybrid beamforming is a promising and feasible solution to massive MIMO due to the achievable balance between performance and implementation cost, especially for the high frequency band. Different from user data channels and signals, common channels and signals cannot benefit from the user-specific beamforming gain, therefore, will suffer from a coverage issue due to the large propagation loss in the high frequency band. In order to provide an enhanced coverage for common channels and signals, in this paper we propose a novel hybrid beamforming transmission scheme, in which multiple analog beams are transmitted simultaneously via analog beamforming at the radio frequency (RF) front-end and cyclic shift (CS)-based beamforming is utilized in the digital back-end. With a proper CS setting, the received channel impulse responses (CIRs) from different beams can always be combined orthogonally. Therefore, a more stable and robust coverage of common channels and signals can be guaranteed. Both theoretical analysis and numerical evaluation justify its effectiveness.