This paper presents beamforming and beam tracking techniques and downlink performance results from field experiments using a Proof-of-Concept (PoC) system. The PoC implements a 5G mobile radio access system in the millimeter wave band and utilizes beamforming and beam tracking techniques. These techniques are realized with a dielectric lens antenna fed by a switched antenna feeder array. The half-power beamwidth of the antenna is 3° corresponding to massive MIMO using approximately 1000 antenna elements. The system bandwidth is 1GHz and the center frequency is 73.5GHz. Adaptive modulation and coding using four modulation and coding schemes is implemented. The field experiment is conducted in the following small cell environments: a courtyard, a shopping mall and a street canyon. The majority of the test area is Line-Of-Sight (LOS) however the shopping mall course contains 69% Non-LOS (NLOS) conditions. The results show that the maximum throughput of over 2Gbps using rate 7/8 coded 16QAM modulation is achieved in 87%, 34% and 28% of each of the respective environments. The beam tracking achieves high availability of coverage and seamless mobility not only in LOS environments but also under NLOS conditions through the reflected paths.