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Time for a 5G Reality Check

18 November 2016

If you’ve tried to get definitive answers about how, when and in what form 5G will appear, you’ve probably thrown up your hands, but don’t despair—no one else has the answers either. That’s not for a lack of opinions as there are many, but regardless of the credibility of the source, projections made today are purely speculative. There are far too many problems to be solved before a clear picture can emerge, and here are some of the most formidable.
It’s nowhere near “cooked” yet: The Third Generation Partnership Project plans to submit detailed specifications in October 2020 that will initially define 5G. Even though academia and private industry throughout the world have been working feverishly to solve the challenges posed by this sea change in wireless connectivity, the “whole package” won’t magically appear all at once. Rather, it is more likely to emerge in stages based on the maturity of its enabling technologies and the funds available to deploy them. So 3GPP doesn’t expect 5G to become the dominant technology until 2030.
Achieving sub-1-ms latency: Many applications such as virtual reality, gaming, autonomous vehicles and telesurgery require an almost instantaneous round-trip response time. That will pit latency against the immutable laws of physics that dictate theoretical distance at which 1-ms latency can be achieved, which will be only short distances. This appears to indicate that massive numbers of small base stations (pico and femto cells) will be needed virtually everywhere. Not only is achieving sub-millisecond latency arguably 5G’s most difficult challenge, but also it will be incredibly expensive to implement.
Operating at millimeter wavelengths: Cellular networks currently operate at frequencies of about 3.5 GHz. To this, 5G networks will add frequencies up to 60 GHz and ultimately even higher. There are good reasons why only a handful of applications have ever used these high frequencies: signals are impeded by almost anything in their path; loss is much greater than at lower frequencies; and penetrating buildings and even so-called green windows is impossible. Operating in this new spectral frontier will require active antenna technologies, including massive MIMO, beamforming, Active Electronically Steered Array (AESA) antennas today used only by the military, and others.
Shoehorning more functions in smartphones: Some current smartphones have radios covering cellular bands from 700 MHz to at least 2 GHz, as well as for Bluetooth, Wi-Fi, NFC and a GPS receiver. Adding more bands, more antennas and MIMO will be very difficult in the confines of a pocket-sized device, especially considering the challenges of signal loss posed by millimeter-wave frequencies.
Reaching gigabit-per-second speeds: In real-world operating conditions, maximum speeds are never achieved, and while it’s possible today to experience download speeds of 30 Mb/s or so with an LTE-Advanced network today in the U.S., it’s exceedingly rare. Speeds are typically less than half of this, even with the fastest networks with blanket LTE coverage. Achieving speeds 100 times faster (or more) will be a monumental challenge that will require small cells as well as techniques still in development.
These five factors are the tip of the 5G iceberg. For example, network architectures will need to be different; small cells must be reduced in size, cost and weight to be affordable by carriers in numbers; and backhaul must be significantly increased, to name a few. In short, 5G is coming as it’s essential to achieve next-generation applications, and huge technical and financial hurdles must be overcome. Beyond this, not much else is certain.



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