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28 February 2019

Confusion over 5G fundamentals still evident at MWC 2019

5G is a multiheaded monster compared with its predecessors, with no clear idea which of the heads, or areas of research, is leading the charge.

Any hope that this week’s Mobile World Congress (MWC) 2019 would establish clearly why consumers need 5G, and what the direction of travel should be, will be disappointed amid a plethora of conflicting demonstrations and absence of compelling use cases. This was rather amusingly laid bare at the congress by Qualcomm, BT and fast-growing Shenzhen-based Chinese smartphone maker OnePlus, talking about their collaboration over 5G while appealing to developers for apps that would bring it to life. This absence of apps was dressed up in hyperbole about the wonderful use cases that 5G will enable, but which no one has yet dreamed of.

The real story is that 5G has been pushed with great determination by the big infrastructure vendors and Telcos for commercial and competitive reasons without selling the benefits on top of 4G/LTE to consumers or the developer community.

There was greater alignment between commercial and consumer aspirations (and equipment vendor and operator aspirations) with previous generations. Capacity was always a factor to cope with ever increasing mobile data. Otherwise 3G was about making mobile Internet access as ubiquitous as possible, while 4G was more about increasing bit rates and closing the performance gap on fixed communications.

4G transformed the Internet from being image to video centric and this really stoked demand for mobile data, but it was debatable whether this immediately called for 5G on capacity grounds. Recent research from Rethink’s RAN Research shows that operators want one thing from 5G and vendors are offering another, and this mismatch threatens to draw out implementation over a 10 to 12 year period.

In some senses 5G can be likened to a major railway infrastructure project in being driven by demand for increased capacity, speed and ability to reach more locations. 5G is said to be needed to meet expectations of mobile data growth, providing high bit rates and low latency for delivering live video at high quality, while the ability to support large numbers of end devices under the banner of massive machine connectivity is required for the IoT (Internet of Things). However operators are saying, they first and foremost want more data, which suppliers are saying “but what about IoT?”

These requirements for capacity, low latency and massive connectivity are conflicting and are being met to some extent from different parts of the spectrum. 3G focused on the 2.1 GHz range to obtain more capacity, while 4G came down to 800 MHz to tuck into spectrum stolen (acquired?) from broadcasters or liberated from analog switchover depending on your point of view.

5G is doing some more feeding off spectrum originally used for broadcast in the 700 MHz range, while seeking additional capacity in the 3.5 GHz CBRS range (in the US). But it has become clear that if mobile data continues growing at its current rate a massive amount of additional spectrum will be required, irrespective of progress made on various fronts to reduce demand, such as advances in video compression. This is where millimeter wave technology comes in, which is a misnomer because no 5G network will be transmitting at wavelengths anywhere near as low as that any time soon.

A wavelength of one millimeter corresponds to a frequency of about 300 GHz but in practice lower frequency bands will be used in 5G. The 28 GHz and 39 GHz bands are cited in the 5G New Radio (NR) standard for the air interface, which has now been cast in stone and there has been talk of 60 GHz. However, there is still uncertainty over how millimeter wave technology will evolve, even though operators have been acquiring spectrum. Verizon for example bought Straight Path Wireless in May 2017 for $3.1 billion to acquire millimeter-wave spectrum licenses.

Even though the wavelengths are nearer 10 mm, these bands still provide a big gain in capacity, but at the expense of range and susceptibility to atmospheric conditions. We have pointed out before that they would have trouble getting through a single sheet of glass used in office buildings. With wavelengths closer to the size of many common objects the signals are susceptible to attenuation by plants, people and even mobile handsets themselves.

Line of sight (or near line of sight) is required and high-density beam forming antennae to ensure robust propagation even over short distances. This hikes costs enormously, as Verizon has found in having to revert, at least temporarily, to engineer visits for installation of its on-premise equipment for in-home broadband exploiting 5G connectivity.

Millimeter wave requires much greater cell density and has raised the specter of widespread drone deployments instead of conventional phone masts, or most likely lamppost deployments, with the benefit both of flexibility by being relocatable, as well as greater line-of-sight. But this is also up in the air at the moment, resting on regulatory approval, as well as investment by operators.

One of the issues lies in overcoming the short battery life drones have, which would render them economically unfit to operate as cell towers. The answer could lie in wireless charging so that drones never need to come down to earth and on this front Huawei was claiming at MWC 2019 its X Labs project was on the way to a solution. It is certainly not there yet given that it is only just possible to charge a phone a few feet away at present, but progress is being made and there is hope that this will play a big role in a number of 5G use cases. The current technology for wireless charging is based on “near field” induction, where an electromagnetic field transfers energy between two closely located ferrimagnetic objects.

This has come to popular attention through induction hobs for cooking, where ferromagnetic pans in effect become heating elements.

But this principle would be unwieldy for some of the proposed 5G scenarios, including drone charging.

What Huawei and others are working on is the alternative approach to transfer of electromagnetic energy via “far field” induction using radiation, also known as power beaming where electromagnetic energy can be transferred over long distances by say microwaves or laser beams. This work is closely related to the beam forming for transfer of data, with the difference that it is applied to transfer or electrical energy rather than information. This has become a hot area of research because of its potential for reducing dependence on batteries and charging many systems in the field, including electric cars as well as drones and even conceivably extending to aircraft.

Wireless charging apart, we can say that Huawei had a good MWC, winning support from a number of European operators in its campaign to be approved for use in evolving 5G networks. The US may be a lost cause for Huawei but Europe and the rest of the world is up for grabs. Vodafone CEO Nick Read warned that Europe’s 5G rollout would be set back two years if Huawei was banned and that concentrating the field down to just two players, Ericsson and Nokia, was unhealthy. That is clearly correct and there is also the possibility of stealing a march in the US in 5G roll out.

Otherwise Huawei was able to focus attention back to its technology lead in 5G as well as matching Samsung in foldable handsets that open out to yield more tablet like screens. This comes in a year when, like it or not, serious 5G roll out will begin because the standards for standalone 5G not dependent on LTE as an anchor were set in June 2018. This kicked off field trials based on interoperable systems with operators in 2018, leading towards the first commercial launches early in 2019.

Yet there are still plenty of obstacles, including concerns over safety of electromagnetic radiation at the much higher frequencies in millimeter wave systems. We have been there before and no convincing evidence of risks to health from current systems have materialized, but equally it is difficult to prove absence of hazard. That burden of proof will become harder with 5G and it could be a decade or even almost a generation before fears over long-term effects of 5G can be allayed. Before that regulators will have to take a position and until that situation clarifies there is no clear road ahead for 5G, quite apart from lack of compelling use cases to convince consumers.