  As massive multiple-input multiple-output (MIMO) becomes popular, direction
of arrival (DOA) measurement has been made a real renaissance due to the
high-resolution achieved. Thus, there is no doubt about DOA estimation using
massive MIMO. The purpose of this paper is to describe its basic principles and
key techniques, to present the performance analysis, and to appreciate its
engineering applications. It is anticipated that there are still many
challenges in DOA estimation using massive receive MIMO, such as high circuit
cost, high energy consumption and high complexity of the algorithm
implementation. New researches and breakthroughs are illustrated to deal with
those problems. Then, a new architecture, hybrid analog and digital (HAD)
massive receive MIMO with low-resolution ADCs, is presented to strike a good
balance among circuit cost, complexity and performance. Then, a novel
three-dimensional (3D) angle of arrival (AOA) localization method based on
geometrical center is proposed to compute the position of a passive emitter
using single base station equipped with an ultra-massive MIMO system. And, it
can achieve the Cramer-Rao low bound (CRLB). Here, the performance loss is also
analyzed to quantify the minimum number of bits. DOA estimation will play a key
role in lots of applications, such as directional modulation, beamforming
tracking and alignment for 6G.
