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While there is already a common understanding of the services, which 5th generation (5G) mobile communications systems should support, and the key technology components needed to achieve this, there is still the need for further clarification and consensus among key players on the overall 5G radio access network (RAN) architecture and its detailed functional design. The 5G public private partnership (5G PPP) project METIS‐II has the objective to foster exactly this consensus building before and in the early days of the standardisation work for 5G. This paper lists the 5G RAN design requirements as identified in the project and summarises the latest considerations of METIS‐II on the air interface landscape in 5G, the envisioned logical RAN architecture and related aspects, as well as key functional design considerations in 5G, which have found wide endorsement within the project. Copyright © 2016 John Wiley & Sons, Ltd.

IntroductionWireless networks traffic has experienced unparalleled growth in recent years, and this trend is expected to continue: users are increasingly reliant on pervasive wireless connectivity, and the amount of data shared wirelessly is forecast to grow exponentially, with a steadily varying type of content. This will be compounded by the proliferation of the machine-to-machine communication and cloud computing paradigms, which will see the connection of tens of billions of objects to the Internet over the next 10 years, much of it wirelessly. Measures to meet the growing demand, such as traffic offloading, mean that wireless small cells will become omnipresent. While this enables user devices to transmit at lower power, it also moves the transmitters closer to the user. Moreover, dedicated wireless systems will emerge to carry new services, thereby contributing to the increase in transmitter sites, especially in urban environments. Such increase in the density of all the radio connected objects and their proximity to users reinforce the public concern about RF-EMF exposure [1] even if this rising number of RF sources does not necessarily lead to an increase in exposure.Stringent regulations exist that protect users from RF-EMF exposure [2]. To test compliance with respect to these regulations, evaluation procedures have been standardized. However, these compliance tests are based on worst-case assumptions (i.e. maximum power emitted), and are not necessarily representative of day-to-day network functioning and management.European Union has specifically addressed the need for low-EMF technologies in its Seventh Framework Programme (FP7, ICT Call 8), by designating low-EMF system designs as a target outcome. This target outcome recognises that there is a clear need for new network topologies and management which reduce the EMF levels without compromising the user's Quality of Service (QoS). In response to this need, 17 leading telecommunications operators, manufacturers, research centres and academic institutions have launched the LEXNET (Low EMF Exposure Future Networks) project [3], a research endeavour which aims to pave the way for low-EMF networks of the future.In this paper we start by discussing the user perception of exposure to RF-EMF and shed new light on this issue by presenting preliminary results of LEXNET-devised surveys. This is followed with a look at existing EMF regulations and metrics, which serves to highlight the fact that EMF exposure is not commonly one of the network management key performance indicators (KPIs). We then present one of the key concepts of LEXNET-population exposure due to both personal devices and network transmitters-and how networks could be designed with a view to minimising this exposure and in line with the pervasive trend towards human-centric computing and networks. The sections that follow look at a variety of commonly used radio access technologies (RATs), the ways in which they are managed, and how their deployment and management impact the EMF levels. And la...

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