Will 5G improve our mobile experience everywhere?
“Everywhere” is a word that appears in a number of 5G visions. Yet the focus of attention of the research community appears to be mainly on massive data rates and huge capacity. This is being coupled more and more with the use of milli-metre (mm) wave spectrum bands that can support the very wide radio channels needed. By default 5G is being steered towards a dense-urban story. It would be a great pity if the benefits of a generation change of cellular technology stopped at the City limits and enjoyed only by the 40% or so of the population living in Cities.
The reason why 5G is becoming so urban-centric is that nobody appears to have any “big” technology ideas for a 5G universal service that could leap over the performance foreseen for 4G. If we still have in mind a 2020 first launch of 5G now is the time to pause and see if and how 5G could bring benefits to everyone, even to rural area.
One possible line of inquiry is to stop thinking about massive data rates and turn our attention to other customer demands. The ones that may be well worth exploring are reliability, reach and rural. “Reliability” is particularly essential if mobile broadband access is to become less of a “best endeavor” and offer instead a far more predictable quality of service. It means coverage must always exist within coverage maps (which is not always the case today) and signals remain reliably connected if we are to put more and more essential services in our lives on a wirelessly connected Internet.
But where is the big technology breakthrough to be found? A safe starting point is to assume that there isn’t one. Instead the innovation will need to come from thinking differently about every element in the end-to-end link and doing things differently for any element where this can make marginal improvements in reliability, reach and/or rural performance. The leap forward can come from the cumulative effect of a number of modest improvements. For example, instead of looking for a big technology idea to deliver 10 dB of improvement in the radio link budget we could re-purpose existing ideas to deliver say 5 lots of 2 dB’s (the numbers are purely illustrative). Both deliver the same “factor of 10” big leap forward but adding together a number of incremental improvements not only looks promising but is the only feasible approach for a technology scheduled to be delivered by 2020.
There is a second compelling reason to think about the “universality” of 5G coverage. Europe has new 700 MHz spectrum being re-assigned for broadband mobile services on an ideal time-scale. So far most people have assumed this will be used for 4G. It that is all that happened to this spectrum it would be a great pity. In capacity terms it adds very little. A brief slurping noise as it is sucked in to meet the voracious demand for capacity and 18 months later nobody will remember the spectrum was ever released. Surely something more worthwhile could be delivered to the digital economy and connected society by this valuable spectrum? The 5G research community needs to be challenged to come up with some better ideas.
An ultra-reliable 5G signal that is universal has a number of potential applications. For example one strong 5G theme is the separation of the control plane from the user plane. This is directionally correct but there will always be an element of a hybrid arrangement as 5G will have a number of control planes if it embraces 4G and other existing networks. They will all have to be managed. If a new low band RAT is developed focusing strongly on reliability, reach and rural that would make for an excellent characteristics of a “Master” or “universal” control plane – a sort of “Home Page” of control planes. Or put another way it could be the central nervous system of the 5G HetNet. There is no reason for that to be the only job it does as there is likely to be enough spare capacity to also provide ultra-reliable data access of modest capacity for wide area critical IoT applications and also bolstering the capacity of rural (universal) broadband services and advance a national coverage obligation from its 4G position of a 90% probability of getting 2 Mb/s off-peak. The above ideas are not intended as any sort of blueprint but enough to show the technical and commercial feasibility to deliver the “everywhere” in a global 5G vision.