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Massive MIMO - Massive Importance?

  • 3 minute read
  • Published by Dr. Abhaya Sumanasena on 30 Apr 2018
  • Last modified 17 May 2018
To achieve operators’ cost: performance targets for 5G, Massive MIMO will be a key enabler. Once considered highly speculative technology, arrays of tens or hundreds of antennas, splitting the signal workload between them, are now in the mainstream of 5G thinking.

There are a number of reasons for this but the most obvious is that a MIMO network can play an important part in improving the capacity of a wireless network – without that network requiring more spectrum. In an ideal world a wireless network should be able to cope with many users and many devices at the same time – and manage fast data rates without impacting performance. Massive MIMO, it is argued, can make that ideal world a reality.

Thus Massive MIMO will play a key part in the 5G networks of the future. Indeed, several mobile network operators around the world have already begun rolling the technology out. 

Vodafone and BT/EE have both conducted recent Massive MIMO 5G tests in the UK and the former’s CTO, Johan Wibergh, believes this technology will be key to achieving his aim of 10 times greater cost efficiency for 5G than for 4G. This will enable operators to meet users’ rising data demands while reducing budgets and clinging on to profit margins, even amid price wars.

“The increased efficiency that you get from Massive MIMO and radio that can handle up to 100 MHz means 5G is about 10 times more cost efficient than 4G. We should be talking more about this because at first it will be about mobile broadband, and cost is a challenge with growing data volumes.”

Johan Wibergh, CTO, Vodafone

However, there may be trade-offs in terms of making Massive MIMO deployable. You don’t really want a forest of vast, expensive antennas, after all. Thus some operators believe the use of mmWave spectrum will be important to making Massive MIMO deployable, as it will help keep the antenna size and cost under control.

Others, however, think there is too much trade-off with the limited range of a cell in high frequency mmWave spectrum. John Saw, CTO of Sprint, for instance, is deploying small cells and Massive MIMO in 2.5 GHz spectrum, to support LTE and 5G simultaneously and create a “bridge to 5G”.

“As we build massive MIMO this year, we’re really starting to build a 5G network that also supports LTE Advanced. And then over the same Massive MIMO base stations, we’re going to launch 5G NR when it’s available. So it’s a more pragmatic plan”

John Saw, CTO, Sprint

A number of projects and research efforts are already looking into how to deploy massive antenna arrays, without having to venture into those technically challenging mmWave frequencies – at least for now.