  To support millimeter wave (mmWave) frequency bands in cellular
communications, both the base station and the mobile platform utilize large
antenna arrays to steer narrow beams towards each other to compensate the path
loss and improve communication performance. The time-frequency resource
allocated for initial access, however, is limited, which gives rise to need for
efficient approaches for beam detection. For hybrid analog-digital beamforming
(HB) architectures, which are used to reduce power consumption, we propose a
compressed sensing (CS) based approach for 5G initial access beam detection
that is for a HB architecture and that is compliant with the 3GPP standard. The
CS-based approach is compared with the exhaustive search in terms of beam
detection accuracy and by simulation is shown to outperform. Up to 256 antennas
are considered, and the importance of a careful codebook design is reaffirmed.
