Massive MIMO is one of the best innovations in the radio business. It boosts spectral efficiency, which creates more capacity in the network. It also extends coverage with high antenna gain. Wonderful.
The problem with Massive MIMO is that the half-wavelength spacing between antenna elements can result in HUGE antenna systems when the wavelengths are long, such as lower frequencies below 2 GHz. For this reason, very few operators have used Massive MIMO in FDD bands over the past 10 years.
All of this will be changing, as recent trials demonstrate substantial benefits in capacity for Massive MIMO upgrades in FDD.
If you’ve read my recent articles, you know that I am sounding the alarm that uplink capacity will be an issue for mobile networks…and over the past six months, I have met with more than 10 different mobile operators, all of whom agree that uplink is likely to become the bottleneck in their mobile network.
Massive MIMO can boost capacity in two ways:
- The simple part: Spectral efficiency in a typical FDD uplink band can be doubled, or even more.
- The not-so-simple part: Because low bands have better in-building penetration than high bands, an improved FDD radio will offload traffic from the high-capacity bands at 2.5-4 GHz. Basically, the network will send its “problem users” with low SINR onto the low band, which improves the average SINR for the users in the upper bands. The result is a capacity boost in the mid-band 5G network.
Now that uplink capacity is becoming critical, these improvements to uplink capacity are becoming valuable enough to overcome the objections of larger antenna units. Yes, there are problems with a heavy unit. If you’re a tower guy, eat a protein bar to get ready for this. And the wind loading will be an issue that requires better mounting brackets and structures. But we need these products so that our smartphones can run the cool new artificial intelligence applications from the basement.
I expect to see some great new products at Mobile World Congress that show off Massive MIMO in some of the FDD bands, probably in the higher frequencies between 1.7 and 2.1 GHz.
Will this result in a nationwide roll-out? No. The uplink challenge is happening in urban centers, so you should expect to see the bigger, heavier antenna units deployed by the hundreds and thousands in urban hotspots. Not in hundreds of thousands for nationwide upgrades.
Joe Madden is principal analyst at Mobile Experts, a network of market and technology experts that analyze wireless markets.
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