By Lynn Greiner
TORONTO – We hear so much hype about 5G it’s difficult to figure out what it really can or can’t do, or will or won’t do in the future.
To hear the proponents, it will solve all of our communications problems and render everything else obsolete, but so many things stand in the way of that rosy future.
At CommTech East this week Jason Lowe, vice president of professional services at Clearcable Networks, took a dive into the technology to explain what it is, and what it can (and can’t) do – beginning with a little walk down memory lane, pointing out that since the beginning, the user experience often turns out to provide somewhat less than what the technology was capable.
4G, for example, typically provides 20-30 megabits per second in urban areas with good coverage. The 5G hype promises up to gigabit speed and touts 100x the speeds we have now with 4G – basically fibre to the home speeds over wireless – the ability to download 4K or UHD movies in seconds. It’s supposed to enable the Internet of Things and to power many, many more devices including self-driving cars and enable automation.
“One of the things that keep getting keeps getting promised is that it’ll change the world,” Lowe said. “We’ll see about that.”
5G isn’t just one thing, he noted. It encompasses two frequency ranges, imaginatively dubbed Frequency Range 1 (FR1) and Frequency Range 2 (FR2). FR1 occupies frequencies less than 6 GHz, with 5-100 MHz channel bandwidth. FR2, also known as millimeter wave, is above 24 GHz, with 50-400 MHz channels.
By comparison, 4G in North America uses frequencies less than 3.6 GHz, with 1.4-20 MHz channels, so there’s a lot of overlap with FR1. FR1 is already being licensed and deployed, but it’s living in an already crowded spectrum, Lowe pointed out. “Below 6 GHz, we have Wi-Fi at 5 GHz and 2.4 GHz, and some of the new Wi-Fi is even talked about in the 6 GHz range,” he said. “We have unlicensed point-to-point wireless deployed down there, we have licensed point-to-point wireless. And of course, we have 4G, 3G and a bunch of other stuff.” He predicted some service providers will phase out their 3G offerings to make room.
The real speeds, he said, will come with the arrival of FR2, but that comes at a cost. The higher frequencies can only travel a short distance, so carriers will need many, many more small cells to propagate the signal. And there are other challenges as well.
“We don’t want to design a system that only works in the winter, when all the leaves fall.” – Jason Lowe, Clearcable Networks
First, transmission must be line of sight. If there’s anything in the way – a tree, a house, a hill – the signal won’t get past it. It will have to zigzag from small cell to small cell to get around them. Weather causes signal loss as well, so rain, snow, or even fog will cause problems. And the signal can’t penetrate aluminum siding or energy efficient windows or other construction materials. Lowe said there may need to be fixed antennas on the outside walls of houses, with Wi-Fi picking up the slack indoors.
Radio engineers also have to worry about Mother Nature. “Above 20 GHz, we’re really not going to be able to go through leaves, we’re not going to be able to go through evergreen trees,” he explained. “We don’t want to design a system that only works in the winter, when all the leaves fall. We also have to consider that trees grow, so when we’re doing all of this engineering, we don’t want to have a system that maybe works today, but five years from now, as that tree got bigger, it now is blocking our service.”
FR2 does have some benefits. Its antennas are small, so many more can be fit into a given array footprint. It facilitates MIMO and beamforming. Smaller cell sizes means nodes are smaller – there are fewer people or devices per cell. Lowe sees an opportunity for dark fibre providers to link together all of those small cell sites.
The latency question is another myth he addressed. Some of the use cases being cited for 5G just won’t work, he said – it’s a matter of physics. For long distance applications, such as remote surgery with the physician in Toronto and the patient in the Yukon, for example, there will probably be 50 milliseconds latency as the signal travels over fibre between cells. The 5G leg will add another millisecond.
“[Latency] still has a high dependency that the two devices that are communicating with each other are close by so that they’re not going through thousands of kilometers of fiber,” he said. “When we’re talking about 5G, we’re really talking about that local access time being as short as possible.”
Despite the challenges, Lowe thinks 5G has a lot of potential. “It’s here, it’s here now for frequency range one, but frequency range two is coming and there’s going to be a lot of exciting things and a lot of exciting challenges to deal with that,” he said.
