SoftBank thinks Massive MIMO is the key to solving capacity problems and to creating 5G.

The Japanese operator, one of the world's first service providers to deploy Massive MIMO technology, says it has seen a tenfold boost in capacity since it began rolling it out two months ago.

The technology works by adding more antennas to the radio communications equipment to increase capacity.

Hidebumi Kitahara, a senior director of mobile network planning, says SoftBank Corp. so far has upgraded around 100 cell sites, mostly in Tokyo. He expects Massive MIMO to be deployed in "a few thousand sites" around the country next year.

Kitahara says the Massive MIMO kit, supplied by ZTE Corp. (Shenzhen: 000063; Hong Kong: 0763) and Huawei Technologies Co. Ltd. , can improve throughput and user experience at the bottom end of the network performance scale.

"We don't care about peak throughput," he told a media briefing in Tokyo today. "We want to minimize the low throughput, which is between 1 Mbit/s and 5 Mbit/s." At those speeds the network will struggle to deliver a good video experience. Prior to deployment, around 20% of all users were experiencing throughput below 2 Mbit/s. Now, it's "only a few percent," he said.

The massive MIMO solution, using 128 transmitters, ensured that users were getting at least 5 Mbit/s data throughput.

But currently it's only available for SoftBank's LTE-TDD network. Kitahara says the standard is still being finalized, but he's urging vendors to develop it for FDD equipment.

Massive MIMO is more easily deployed on TDD, where the same channel is used for both the uplink and the downlink, but FDD technology is more commonly used in global communications networks. One vendor, China's ZTE, expects to have an FDD Massive MIMO solution ready some time next year.

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SoftBank believes it has narrowly beaten China Mobile Ltd. (NYSE: CHL) to become the world's first operator to commercially deploy Massive MIMO, although Kitahara acknowledges the Chinese telco is deploying it on a much larger scale. (See China Mobile Launched World's First Commercial Wideband Massive MIMO.)

Nevertheless, the SoftBank executive sees Massive MIMO as a key technology for ensuring 5G delivers the kind of capacity improvements that users expect.

Operators are in a continual race against the escalation in data demand. In the last ten years, traffic levels have risen 2,000 times, Kitahara reckons, and they are likely to rise another 500 to 600 times between now and 2020.

That's why he expects Massive MIMO to play a central role in 5G. "I am crazy about Massive MIMO," he acknowledged, while recognizing that other technologies will also be important to 5G, including carrier aggregation -- which is already being used commercially -- and millimeter wave.

SoftBank is under additional pressure because of the Japanese government goal of ensuring 5G is available for the 2020 Summer Olympics.

However, like other operators, it is still waiting for industry consensus to emerge on radio interfaces and spectrum bands.

— Robert Clark, contributing editor, Light Reading