The new October 2014 issue of IEEE Wireless Communications magazine is a special issue on mulithop cellular - one of the technologies that will likely be part of 5G cellular. While there is no consensus yet on what exactly 5G will be, one article reports:

“it is widely agreed that in contrast to 4G networks, 5G network should achieve 1000 times the system capacity, 10 times the spectral efficiency, higher data rates (i.e., 10 Gb/s for cell center users and 5 Gb/s for cell edge users), 25 times the average cell throughput, and 5 times reduction in end-to-end (E2E) latency, and support 100 times more connected devices with 10 times longer battery life for low-power devices.”

By contrast, gsmhistory.com gives 3 different visions of 5G:

• A super-efficient “universal” mobile network that is always attentive to demand and where resources are continuously optimised to deliver a performance that is “always sufficient” – so users will perceive that they are connected to a network of infinite bandwidth. It would not just be data speed performance that is optimised but low latency needed by applications such as the Internet of Things. It is a revolution in “efficiency” delivering much better performing networks for a lower cost of investment. (Such networks are sometimes called DAN or Demand Attentive Networks). It would re-purpose existing spectrum to work in more efficient ways.
• A super-fast “mobile” network comprising the next generation of small cells densely clustered together to give a contiguous coverage over at least urban areas and delivering peak data rates of up to 1 Gb/s. It gets the world to the final frontier for true “wide area mobility”. Spectrum for this would be under 4 GHz (in order to make wide area coverage economically feasible). Since nobody is likely to reserve spectrum for 5G such a network would enter the market through advanced spectrum sharing – so in this vision 5G might be the first global implementation of Dynamic Spectrum Access. The band 3.4-3.6 GHz has been talked about for such a “spectrum sharing” market entry for 5G.
• A converged wireless-fiber network that uses, for the first time for wireless Internet access, the millimeter wave bands (20 – 60 GHz) so as to allow very wide bandwidth radio channels able to support data access speeds of up to 10 Gb/s. The connection essentially comprises “short” wireless links on the end of local fiber optic cable. It takes data over wireless to the state of the art. But this very high data speed comes at a price for consumers in terms of very much reduced coverage. It would be more a “nomadic” service (like WiFi) ie to fixed locations rather than a wide area “mobile” service

The IEEE WCM article goes on to enumerate the technologies that are likely to be in a final aggregation of technologies for 5G:

• Advanced coding and modulation techniques for 5G such as non-orthogonal wave form (NOMA).
• Spatial modulation (SM)
• Millimeter wave (mmWave)
• Visible light communication (VLC)
• Massive MIMO
• Cognitive radio networks (CRNs)
• Integration of Wi-Fi and core
• Local caching
• New heterogenous architecture - separate indoor and outdoor technologies
• Direct mobile-to-mobile communications

The introductory editorial explains the significance of the last point

“It has been more than a decade since the multihop cellular network (MCN) architecture was first proposed and analyzed in 2000. As the transmission range decreases k times, the number of simultaneous transmissions and hop count increase by k squared and k times, respectively, which leads to k times cellular capacity increase. Fundamental research projects have demonstrated the benefits of MCN interms of system capacity, service coverage, and network connectivity. Many special issues have been devoted to this stream of research. The actual concept behind the MCN architecture could be regarded as a hybrid of mobile ad hoc networks (MANETs) and cellular networks. This concept of “relaying within a cell” also pushed standard bodies to consider solutions embedded with mesh or ad hoc architectures, such as IEEE 802.11s, IEEE 802.15.5 , and IEEE 802.16j . Now, in the recent standards of the Third Generation Partnership Project (3GPP), Proximity-Based Services (ProSe) related work items also cover the MCN concept. In addition to device-to-device (D2D) direct communications, user equipment (UE)–UE relay and UE–network relay are also supported features.”

Note that in the above discussion new spectrum is included, but is not a “magic bullet” to achieve 5G goals of capacity increase. Synergy among a variety of approaches is needed for such increases. Although not explicitly mentioned, a massive increase of sites for cellular infrastructure is also needed, as has been previously discussed.

Note also that there is a dynamic interaction between unlicensed technology discussed in IEEE802 and licensed technology discussed in fora such as 3GPP. For example, LTE is a close technological cousin of WiMax. These interactions between the licensed and unlicensed communities are beneficial for all involved, although this is rarely discussed in policy circles.

So why is new spectrum the only 5G issue getting attention at FCC?

Tags: NBP, 5G, innovation