Add more antennas to base stations for 5G efficiencies, say researchers

Spectrum efficiencies can be gained with ‘massive’ antenna arrays, says scientists.

mimo 5g lead image
Credit: University of Bristol

Samsung, Huawei and others maybe barking up the wrong tree, or wrong cell tower, when it comes to 5G, if researchers at two universities in Europe are correct.

The scientist there think that it might not be necessary to shift mobile networks up the frequency spectrum and into the millimeter bands to gain efficiencies, and thus serve more users with increasing speeds and bandwidth.

+ MORE ON 5G 5G: A look at radios and spectrum +

All you need do is create bigger antenna arrays, the scientists from the University of Bristol and Lund University believe. With a “massive antenna system,” existing microwave frequencies would work just fine for 5G, they surmise.

The engineers believe that their huge array of 128 antennas could provide 12-times greater spectrum efficiencies compared to existing 4G networks. They believe that their system, which they say they’ve successfully tested using microwave frequencies, and a prototyping platform called LabView from U.S.-based National Instruments in the 3.5GHz band, would be a better solution for 5G than other 5G proposals.

Spectrum efficiency, sometimes called bandwidth efficiency, is related to the information rate in a given amount of bandwidth sent over radio. The more data, the more efficient the system is thought to be.

5G players such as Samsung have been experimenting with much smaller, and harder to work with 28GHz frequencies. Huawei, as another 5G player example, has been trialing sub-6-GHz radio.

Millimeter frequencies are thought to be the best bet for 5G partly because they’re not used much, so have plenty of available bandwidth, and don’t suffer from the same levels of interference as lower-down-the-spectrum bands, such as those used in existing 2.4 GHz Wi-Fi do, for example.

The main problem though is it’s an unknown.

The smaller the frequency, the more easily it can get lost and trickier it is to work with in a mobile or outdoors environment. In other words it might be hard to get it to work reliably. That’s one reason why 5G in the new millimeter bands is a few years off. They’re still working on how to do it. The new mobile phone tech will probably not come in until around 2020, say experts.

The university researchers, on the other hand, are using more common frequencies, with known behavior, half way between the two common Wi-Fi bands of 2.4GHz and 5GHz. That existing, well-tested spectrum could be an advantage over the new millimeter bands.

If they can eek out a better information rate from 3.5 GHz, as they say they can with additional antennas, they could be on to something.

“We see massive MIMO as the most promising 5G technology,” says Ove Edfors, professor of radio systems at Lund University, in a press release on the University of Bristol’s website.

Multiple antenna tech, or MIMO (multiple-input and multiple-output) is the key to their 12-fold gain, the team says in the news release. Standard “MIMO,is already used in many Wi-Fi routers and 4G cellular phone systems.” It takes advantage of multipath.

“Normally this involves up to four antennas at a base station,” they say. However, with their super-system they’re using 128 antennas, which they call “massive MIMO.”

With it, up to 12 single antenna clients can be served, they say. Each of those 12 clients “shares a common 20MHz radio channel,” they explain. Bandwidth obtained was the equivalent of 1.59Gbps in that 20MHz channel. The team says that bandwidth efficiency is “unprecedented.”

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