Broadcast Control Strategies for mmWave Massive MIMO Leveraging Orthogonal Basis Functions

Millimeter wave (mmWave) frequencies are being considered for future generation cellular systems because of the large amount of available spectrum in those bands (e.g., 10 GHz in the E-band alone). Additionally large scale antenna arrays with high gain adaptive beamforming are viewed as critical for overcoming the poor path loss conditions in the mmWave bands. User-specific beamforming can solve the coverage problem for user-specific data and control traffic, but the coverage problem for transmitting broadcast control information must also be solved. This paper explores the problem of enhancing the performance of a broadcast control channel, where control information must be transmitted to the entire sector in a non-user specific or multicast fashion. We propose a technique for transmitting broadcast control information in a mmWave system with RF beamforming that offers improved performance and several key advantages over a grid-of-beams type of approach where control information is simply repeated in time across successive narrow RF beams.