5G must use millimetre wave links, says Intel
After leading a successful charge to bring 60GHz to wireless LANs, an Intel executive is driving research to define a proposal for using millimetre wave wireless in next-generation cellular systems.
The technology "will play a very serious role as an augmentation of the cellular infrastructure, but it won't replace it in the same way that WiGig augments WiFi," Ali Sadri, a senior director of millimetre wave standards in Intel's mobile and wireless group, told EE Times.
Sadri led the WiGig effort that defined a specification for 60GHz as a local-area network. The spec became the basis for today's IEEE 802.11ad standard, and the WiGig group was folded into the WiFi Alliance last year.
Sadri's team is now working on a tech demo of 60GHz as a backhaul link for so-called small cell base stations that could be shown at the Mobile World Congress in February. The team is also researching 28GHz and 39GHz as access links to mobile devices, targeting a throughput of 1Gbit/s or more at distances of at least 200m. "Our target is to start working on new media access controller and physical layer chips in 2016-2017, and we are also shooting for a project the industry can launch in 2020."
Intel is among the growing ranks of companies that say 5G cellular systems will need to use millimetre wave links to meet rising numbers of subscribers using more mobile data. Late last year, the European Commission kicked off a $1.8 billion 5G research effort that includes plans for millimetre wave research. Forums in Asia are pursuing similar goals.
The higher frequencies promise more spectrum and faster data throughput, though at shorter ranges. They also pose significant technical and regulatory challenges.
As part of his efforts, Sadri went to the 2014 CES to have dinner with Federal Communications Commission officials. "We're at the educational level. A lot of study has to be done, shared simulations and test deployments, so it will be a couple years before the FCC can consider rule changes" to open up millimeter wave spectrum.
Intel is working with two consortia in Europe and has collaborated with Samsung and others on 5G millimetre projects. It is also tracking 5G efforts in places like China and Korea. "It's a huge project. It will be by far one of the most extensive and complex project in wireless to date."
A debate already is emerging about the use of 28GHz and 39GHz bands for linking mobile devices to 5G networks. "Samsung very interested in 28GHz and has spent considerable time on that, but from a regulatory point of view, 39GHz is more suitable for rule modification," Sadri said. That's because satellite services use portions of the 28GHz band. By contrast, 39GHz has significantly more than 1GHz available for use.
On the technology front, systems typically have a fixed space of about 10 cm2 for an antenna. The 39GHz band allows smaller antennas and thus could pack more of them into that space than a 28GHz link—an important factor given phased-array antennas with beam forming are a likely requirement.
In addition, Sadri estimates 39GHz offers 3-5 dB signal improvement over 60GHz. The 28GHz band offers a benefit of only about 1.5 dB over 39GHz.
Future research will explore such trade-offs in more detail. Engineers will also explore techniques to work around challenges such as roaming at the high frequencies, linking millimetre and traditional services, and handling reach issues in urban areas where skyscrapers would block high-frequency signals.
- Rick Merritt
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