In my two previous posts, I’ve discussed the factors affecting commercialization and laid claim that some much-touted 5G technologies (e.g., millimeter-wave) will not be commercialized by 2020. Massive MIMO, on the other hand, starts with two factors heavily in its favor: implementation will require less policy change, and it has a potentially large benefit to mobile network operator (MNO) business models. Thus, developers can focus their energy and attention on the technical challenges.
Roger’s claim: Massive MIMO will be commercial in 2020.
At an IWPC meeting in the spring, representatives from China Mobile clearly stated that massive MIMO is implemented and running in its network. Some of the argument about the timing of massive MIMO depends upon one’s definition of the term.
Since Dr. Thomas Marzetta’s seminal paper in 2010, the term has come to mean just about anything with more than four antennas. What I will call the “academic definition” was clearly outlined in an excellent panel discussion (featuring Marzetta) at IEEE Globecom 2015 in San Diego. This refers to something that has the following attributes:
- Is based on TDD (although Marzetta recently suggested that FDD may be possible)[I]
- Uses only uplink pilots for the determination of channel state information (CSI)
- Provides significant gain in performance even in a non-scattered and 100 percent line-of-sight (LOS) environment
- Requires the number of antenna ports to greatly exceed the eight defined in the current 3GPP MU FD MIMO standard
On the fourth point, I have seen some definitions of massive MIMO that focus mostly on getting the antenna count to at least eight; most of the other criteria included above appear to be less important. I simply do not consider eight to be “massive.”
especially energy efficiency, is mandatory for the 5G vision to become real. At the recent IWPC meeting, multiple MNOs agreed that their number-one OPEX beyond depreciation was paying for electrical power. Massive MIMO’s approach to limiting radio energy only to where it is needed is a huge step—if the industry can manage the technical challenges and increased power demands of the incremental baseband processing and more-complex antenna schemes. The innovation that I have seen from those researching and prototyping this concept is very impressive.
Implementing the academic definition of massive MIMO puts relatively small demands on the user equipment (UE) design (i.e., fewer technical challenges), requires fewer policy changes, and has a potentially large benefit to MNO business models. China Mobile’s focus in this area is driven by annual energy consumption that is significantly north of 14 TWh, and that is motivation enough to make this technology work ASAP[ii]
I have recently read statements from some MNOs suggesting that 5G “phase 2” (i.e., 2022 or later) will include massive MIMO, thereby refuting my claim. After all, MNOs are the ones who will dictate the timing for commercialization of any of these technologies. But given China Mobile’s clear statement and the lower technological, policy, and business model hurdles, I think massive MIMO will see reality.
Will users care? Probably—this is at least one facet of creating “great service in a crowd.” What do you think?
[i] See “Massive MIMO: ten myths and one critical question” in the February 2016 issue of IEEE Communications
[ii] See “Toward green and soft: a 5G perspective” in the Feb 2014 issue of IEEE Communications