MIMO becoming a “must” as capacity solutions get exhausted, claims new report

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MIMO technology will play a central role in operators' network upgrade strategies in the coming years, a new report has claimed, as other options for boosting capacity become exhausted and new site building remains prohibitively expensive.

A white paper from Northstream, titled Finding MIMO, said despite the technology's inability to catch on in great volume in the market since research on it first began in the 1990s, momentum was growing amid the shift from LTE to 5G.

Northstream CEO Bengt Nordstrom said 2x2 MIMO had been hamstrung by an "unremarkable" performance due to its original algorithms, as well as poor processing power in handsets and limited space to fit a sufficient number of antennas for the technology to work.

Another issue had been the requirement to set up antennas some distance apart on base stations when low frequencies were used, something that was difficult on site towers.

Nordstrom argued as higher frequencies, such as 3.5GHz, have come into play, more antenna columns can be housed on a base station. He said: "The advent of 5G spectrum in the millimetre wave does promise significant reduction in the physical size of antenna array and make Massive MIMO a tangible solution."

However, the advent of higher frequency spectrum was not the panacea. He added: "Installing additional antennas means more energy consumption, more wind load, more site rental cost and not to mention the actual labour cost.

"The capacity requirement for fronthaul (the data connection between radio units and digital units) also scales up with the number of antennas used for MIMO, which can become rather challenging to meet even with fibre connections."

Challenges aside, Nordstrom said Multi-User MIMO will become increasingly popular in the years ahead. He said: "As operators gradually exhaust other less costly options for boosting capacity, like upgrading to 256 QAM, adding another carrier or refarming 2G spectrum to 4G, they will soon resort to advanced MIMO solutions to meet the ever growing traffic demand. Expensive as it may be, adding antennas is still cheaper than building a new site."

Operators are increasingly looking to explore the technology's capability as a capacity boosting solution, with Vodafone and Huawei recently completing a trial of Massive MIMO on 2.6GHz spectrum.

As 5G becomes the norm, beamforming will become a more popular feature of MIMO, in order to handle the propagation of frequency bands above 6GHz. Nordstrom said: "MIMO is no longer an option but a must in this paradigm shift from cell centric to beam centric architecture."