The emerging massive/large-scale MIMO (LS-MIMO) systems relying on very large
antenna arrays have become a hot topic of wireless communications. Compared to
the LTE based 4G mobile communication system that allows for up to 8 antenna
elements at the base station (BS), the LS-MIMO system entails an unprecedented
number of antennas, say 100 or more, at the BS. The huge leap in the number of
BS antennas opens the door to a new research field in communication theory,
propagation and electronics, where random matrix theory begins to play a
dominant role.
In this paper, we provide a recital on the historic heritages and novel
challenges facing LS-MIMOs from a detection perspective. Firstly, we highlight
the fundamentals of MIMO detection, including the nature of co-channel
interference, the generality of the MIMO detection problem, the received signal
models of both linear memoryless MIMO channels and dispersive MIMO channels
exhibiting memory, as well as the complex-valued versus real-valued MIMO system
models. Then, an extensive review of the representative MIMO detection methods
conceived during the past 50 years (1965-2015) is presented, and relevant
insights as well as lessons are inferred for designing complexity-scalable MIMO
detection algorithms that are potentially applicable to LS-MIMO systems.
Furthermore, we divide the LS-MIMO systems into two types, and elaborate on the
distinct detection strategies suitable for each of them. The type-I LS-MIMO
corresponds to the case where the number of active users is much smaller than
the number of BS antennas, which is currently the mainstream definition of
LS-MIMO. The type-II LS-MIMO corresponds to the case where the number of active
users is comparable to the number of BS antennas. Finally, we discuss the
applicability of existing MIMO detection algorithms in LS-MIMO systems, and
review some of the recent advances in LS-MIMO detection.Comment: 51 pages, 36 figures, 10 tables, 659 references, accepted to appear
on IEEE Communications Surveys & Tutorials, June 201