Scientific Challenges towards 5G Mobile Communications?

IC1004The European COST Action IC1004 on “Cooperative Radio Communications for Green Smart Environments” published its visions for the future of wireless in their White Paper on “Scientific Challenges towards 5G Mobile Communications” the other week. Sounded great, but I must say the content was somewhat disappointing as the paper is mostly listing a number of straight-forward extrapolations of current trends – some of which are even dubious. In short, here are the main items in the IC1004 report:

  • Cloud-RAN and Virtual Access Networks – sounds great, but remember that cloud solutions generally assume “free”, unlimited wired access. As the backhaul seems to become THE major cost item and bottleneck as we keep densifying networks, I am no longer so sure we can afford this solution except in hot-spots with extreme user densities, where other simple solutions based on existing, best-effort wired IP-access (e.g. WiFi) fails to provide the necessary capacity.
  • Wireless Body Network Communications: Yes, there are many exiting applications, but is there a communication bottleneck ?
  • Yep, Massive MIMO is here again – sure, it may improve radio performance in certain outdoor scenarios by reducing/utilizing multipath fading, but it cannot make access systems “walk on water”, e.g. penetrate walls to provide better and “greener” indoor coverage (the latter is done with much simpler, low power, indoor systems). If its worth the “massive” effort (and the space on the walls for all the antennas) remains to be seen.
  • Access relays on moving vehicles, in particular mass transit vehicles (trains, buses, aircraft ..) is definitely a challenge when it comes to high data rates !
  • New approaches to Spectrum management needed – can’t agree more, in particular for the high density short range networks that we need to deal with the capacity challenges. The potential for more spectrum in this domain is huge.
  • “Network Aware PHY-layer coding”? Multihop networking? Excellent, interesting, mathematical exercises, but hardly a key bottleneck in future systems. There are probably half a dozen really good arguments why its not going to be a mainstream feature in foreseeable future. Among them are that all applications are build on IP and the end-to-end principle, which relies on data agnostic lower layers. Even if this could be managed, the gains shown in the literature are marginal and limited to certain scenarios to motivate the added complexity and reliability issues in network coding, relaying or multihop. In rural networks there may be applications, but in high density urban networks, its simply much easier to add another access point or use more (secondary) spectrum, if you need more capacity.

About Jens Zander

Professor Jens Zander is professor in Radio Communication Systems at the Royal Institute of Technology, Stockholm, Sweden. He has been among the few in Swedens Ny Teknik magazine's annual list of influential people in ICT that have been given the epithet “Mobile Guru”. He is one of the leading researchers in mobile communication and is the Scientific director of the industry/academia collaboration center Wireless@KTH. His research group focuses on three main areas – the efficient and scalable use of the radio frequency spectrum, economic aspects of mobile systems and application and energy efficiency in future wireless infrastructures.
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