Initial Access and Beamforming in Multi-cell mmWave Networks Using Narrowband Pilots

This paper presents an initial access protocol and beamforming techniques for millimeter wave (mmWave) networks consisting of multiple access points (APs) and mobile devices. Each frame consists of an initial access sub-frame followed by data transmission sub-frames. During the intial sub-frame, APs and user devices sweep through a set of beams and determine the best transmit and receive beams via a handshake. Narrowband pilots are transmitted to avoid mutual interference and reduce training errors. An efficient method for maximum likelihood estimation of beam directions based on the Fast Fourier transform (FFT) is also proposed. The effectiveness of the proposed scheme is demonstrated by simulation.