NEC and Docomo push the Massive MIMO boundaries in 5G test

Japanese company NEC may never have secured a significant share of the wireless access network business, but its close relationship with operators in its homeland still make it influential on emerging wireless platforms and it is particularly prominent in cutting edge antenna designs. So while the firm’s MWC presence will mainly center on its virtualization, backhaul and smart city activities, as well as its new telco AI technology, its RAN initiatives are still closely watched.

This week, the company has announced the results of trials of 5G Massive MIMO, conducted with Japan’s leading MNO, NTT Docomo, one of the most advanced operators in pushing towards next generation architectures.

The partners said their 5G base station verification tests showed spectral efficiency at eight times higher than that of LTE using spectrum between 3 GHz and 6 GHz – in other words, not the rarefied reaches of millimeter wave, but well-understood mid-band wireless spectrum.

Nozomu Watanabe, general manager of the company’s Mobile RAN division, commented: “Among the high frequency bands, we are working especially hard to put the low-SHF band into practical use, since it is expected to enter into commercial use around 2020.”

The SHF (low super high frequency) band encompasses centimeter wave spectrum in the 3 GHz to 30 GHz range, and Low-SHF refers to spectrum in the 3 GHz to 6 GHz area.

The tests were conducted in central Tokyo and Kanagawa Prefecture, using NEC’s massive-element Active Antenna System (AAS). The focus was on mitigating the effect of obstacles, since these midrange bands have limited range and so lend themselves to small cell densification – but that means being installed close to the ground, or indoors, where there are many objects in the way of the radio waves. The NEC/Docomo trial focused on the effects of outdoor vehicles, utility poles and even people, as well as indoor obstacles like columns and walls.

The use of beamsteering, in combination with large numbers of antennas, helps compensate for the challenges of higher frequencies and small cells, which will be magnified when operators venture up to even higher bands such as 28 GHz or 60 GHz.

NEC’s solution uses fully digitized antenna beam control technology, which it says improves the precision of beamforming. While transmitting to the handset, this technology enables beams to be formed which counteract interfering signals using multipath techniques. These combine the antenna’s direct signal with indirect signals that are reflected due to obstructions, to improve signal quality.

The solution also supports concurrent communication with several handsets, even when close together.

“NEC research into core technologies for 5G, including the massive-element AAS and antenna beam control, will contribute to the successful roll-out of 5G in the near future,” said Watanabe.

“Thanks to NEC’s contribution on the massive-element AAS supporting the low-SHF band, we were able to achieve highly successful outcomes from the trials,” said Takehiro Nakamura, head of Docomo’s 5G Laboratory.

The intense operator interest in Massive MIMO and beamforming is opening new opportunities for the antenna specialists, as well as the network OEMs. While some vendors, especially Huawei, design some of their own antennas, many rely almost entirely on third parties such as Kathrein, CommScope and others.

These companies will be focusing on 5G and virtualized network developments in Barcelona. CommScope said this week that it will demonstrate its “5G foundations” at the show. These will revolve around a combination of technologies, most of them being originally created for current LTE-Advanced projects and then evolved towards 5G.

“Operators are addressing their current challenges with a focus on LTE optimization, small cell deployments and in-building wireless, plus looking ahead with 5G development and trials,” said Ben Cardwell, SVP of CommScope Mobility Solutions. “With our expertise and extensive portfolio of wireless and fiber optic solutions, CommScope is helping customers through this important transition, as it has through other technology generations.”

The stepping stones on this vendor’s road to 5G include:
Ultra-wideband base station antennas to boost capacity, and now extended to new bands (1.4 GHz and 600 MHz)
Integrated metrocells, indoor small cells and DAS for densification in LTE and 5G
A portfolio of fiber fronthaul and backhaul solutions for virtualized networks and a small cell Cloud-RAN, the latter courtesy of its acquisition of Airvana
Network optimization aids such as the XG microwave planning software, and plug-and-play DC power supply offering, PowerShift.