If operators are to build 5G mobile networks with download speeds at 10Gb/s and above, they are going to need a lot more spectrum, but getting it won’t be easy. The amount of spectrum allocated to 5G will determine how fast networks based on the technology will eventually become. Until recently, only frequencies below 6GHz have been considered for mobile networks, mostly because they are good for covering large areas. But there’s now a growing need to unlock new spectrum bands in the 6 to 100GHz range too, attendees at the recent LTE and 5G World Summit conferences in Amsterdam heard. The use of spectrum in these bands is immensely important for 5G networks to be able to offer multiple gigabits per second, Robert DiFazio, chief engineer at wireless R&D company lnter Digital Communications, said. By raising communication speeds, they are also expected to help lower latency in mobile networks. Even though spectrum from 6 to 100GHz won’t be used in cellular access networks for at least another five years, vendors are keen to show they can handle all the technical challenges those frequencies present.
The development of WiGig, which uses the 60GHz band, has already showed that using such high frequencies works, and on the show floor in Amsterdam, Huawei Technologies and Samsung Electronics both talked up pilot studies of other technologies they have conducted. For the potential of spectrum above 6GHz to be realised, a new generation of antennas will be required, capable of directing multiple beams of data to different users at the same time. New systems will likely also need new modulation schemes to encode the data on the radio waves more efficiently.
There are ways for mobile networks to increase download speeds using existing spectrum, including using carrier aggregation or sharing spectrum with Wi-Fi networks. But at the end of the day, none of these options come close to the potential that as-yet-unused frequency bands above 6GHz offer. There is nowhere else to go but up, according to Samsung. Rolling out networks isn’t just about hardware and software, according to regulators. “We have made clear our intention to make large quantities of spectrum available in these frequencies, which is increasingly also the view of other regulators around the world,” said Andrew Hudson, director of spectrum policy at British regulator Ofcom, who spoke on the subject at the Amsterdam conference. The current focus of Ofcom’s work isn’t whether to make spectrum available, but how to identify the best spectrum in this range.
This involves finding bands with a combination of good physical characteristics and good prospects for international harmonization, while taking into account current use, according to Hudson. A final decision on what if any bands will be allocated isn’t expected until 2019. After technical and regulatory challenges have been overcome, the networks also have to be rolled out. If extreme speeds are the upside of frequencies over 6GHz, poor coverage is the downside. These high frequencies don’t have good reach and aren’t very much use if you want to penetrate walls. To get around these weaknesses, mobile operators will have to install lots of smaller base stations, but finding enough places to put even the current generation of small-cell base stations has already proved difficult. So taking full advantage of spectrum bands above 6GHz won’t be easy, but if equipment and device vendors want 5G to become something more than an incremental upgrade over the LTE networks that exist in 2020, all technical and political challenges have to be overcome.
The first commercial networks using 5G technologies are expected to go live in 2020, but will initially use spectrum below 6GHz because the infrastructure is already out there for those bands, according to DeFazio: Networks using the new frequency bands will only arrive later