Industry Voices—Pongratz: Massive MIMO moves to center court in Barcelona

Stefan Pongratz

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?  

Pongratz fig 1

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.

Preliminary data from real-world deployments are mixed but for the most part encouraging, with tangible throughput and capacity improvements evident when comparing 32T32R and 64T64R deployments with Non-Massive MIMO configured systems. The upside will naturally vary, depending on a wide range of factors. Initial field data from deployments in China, Germany, Japan, Philippines, Russia, Thailand and the United States, however, suggest that cell capacity gains on the order of 2.5x to 4x are realistic. One operator indicated that the upside, in hotspot environments, is actually closer to the 5x to 10x range. Though still at an early stage of field verification for mobile applications, challenged by instances when Massive MIMO has underperformed, there is now increased confidence that further advancements will improve the likelihood these initial performance gains can be replicated in a variety of settings.

Business case

To ensure a viable business case for midband 5G NR Massive MIMO deployments, operators need to rely on the existing macro grid, implying that the inherent range extension becomes an important consideration. Huawei shared results from multiple deployments during its MBB2018 Summit in London, providing additional details during MWC 2019. Operators are also discussing the link budget benefits with Massive MIMO. Preliminary findings indicate that the DL C-band range—relative to the equivalent 1800 MHz coverage—will be better using the 64T configuration, the same with 32T, and worse with 16T/8T.

With sites increasingly crowded, it is not surprising that operators are pushing suppliers to improve the power consumption, weight, and overall form factor of these Massive MIMO systems. China Mobile actually shared power consumption targets during the MWC event. Our understanding is that equipment weight played a significant role for some of the early 5G adopters when deciding between 32T32R and 64T64R systems. And vendors are not just highlighting the speed and capacity gains anymore when trying to differentiate their solutions. Huawei emphasized that its 200 MHz/200 W 64T64R/32T32R AAUs are the lightest (40 kg/20 kg) and smallest products with the widest BW and highest output power, with the lowest power consumption available on the market. While there is little doubt that operators will ask for more product configurations and smaller, lighter, and more power-efficient base stations, the progress over just the past year adds confidence that the suppliers are getting closer.

The anticipated price discrepancy between Massive MIMO and Non-Massive MIMO systems may potentially inhibit broader adoption, even if the financial benefits of paying a bit more for the radio using the existing macro site versus saving radio capex and deploying another cell site are rather straightforward when taking into consideration the fact that the RAN represents only about a fifth of the overall capex. The positive development, in any event, is that prices in competitive markets are falling rapidly. Discussions with both operators and suppliers suggest that the price delta between Massive MIMO and Non-Massive MIMO systems will be manageable. 

Pongratz fig 2

Operators with the appropriate spectrum assets are increasingly adjusting their Massive MIMO road maps, reflecting to some degree the reduced risks and greater confidence with regard to a technology that is expected to play a fundamental role in maximizing ROI using the midband and the existing macro grid. 

In sum, operators will need to rely on all the tools in the toolkit to manage the unabated demand for data traffic. There is room left in the sub-6 GHz tank, and service providers are eager to capitalize on the improved spectral efficiency made possible with Massive MIMO. We recently adjusted our Massive MIMO projections upward (Figure 2). As with any forecast, both upside and downside risks are involved. For now, though, the risks appear to be broadly balanced, with a slight tilt to the upside.

"Industry Voices" are opinion columns written by outside contributors—often industry experts or analysts—who are invited to the conversation by FierceWireless staff. They do not represent the opinions of the editorial board.