With so much focus on 5G, it can be easy at times to forget that the spectral efficiency upside with the ongoing shift from passive to active antenna systems is expected to be significantly greater than the 25% to 50% spectral efficiency increase operators can expect on a like-for-like basis when upgrading from LTE to 5G NR (Rel. 15).
One of the key takeaways from the MWC 2019 event in Barcelona was the strong focus on Massive MIMO, adding confidence to the upwardly adjusted Massive MIMO projections we outlined in conjunction with recently published Radio Access Network (RAN) reports. Given that operators have multiple tools in their toolkit to manage capacity (Figure 1), why are we so optimistic about the Massive MIMO opportunity in the sub 6 GHz spectrum?
At a big-picture level, five key factors are behind the renewed sense of optimism for Massive MIMO: (1) 2018 shipments increased at a faster-than-expected pace. (2) Preliminary real-world data are encouraging. (3) Site challenges are being addressed. (4) Prices are falling. (5) Operators are revising their Massive MIMO road maps.
First and foremost, 2018 was a pivotal year for Massive MIMO, as the demand for Massive MIMO systems increased at a significantly faster pace than expected. With shipments growing more than tenfold for the full year 2018 and the pace of acceleration improving in the second half, the momentum is likely to be extended into 2019.
While theory suggests that the upside with Massive MIMO can be significant—Prof. Emil Björnson (with Linköping University) has suggested that the theoretical capacity upside is in fact unlimited—one of the main risks when assessing the Massive MIMO business case for mobile applications relates to the actual gains for practical configurations outside the lab.