  Future 5G communication systems require more demanding performances than the
existing cellular communication systems, e.g., 10 to 100 Mbps user data rate
and much larger cellular spectrum efficiency. The well-used multiple access
methods like CDMA and OFDMA are hard to achieve these challenging requirements
simultaneously even with advanced signal processing techniques and base station
cooperation. Recently, massive MIMO has gain much attention since it provides
large signal dimensions that can be used to improve future 5G cellular system
performance. This tutorial paper describes a recently proposed multiple access
scheme called multipath division multiple access (MDMA) based on massive
antennas and multipath channel characteristics in millimeter wave band, which
offers uniform user data rate and achieves high cellular spectrum efficiency
for 5G systems. We describe the fundamental principle and show the uplink and
downlink block diagrams, control signaling and the call setup process. Besides,
benefits of using MDMA as a multiple access scheme are discussed. Finally,
practical concerns are addressed for future research directions.
