Radio-over-fibre for ultra-small 5G cells

The need of a wireless network with a very low latency, a high bandwidth, and a high cellular density is paramount for serving futuristic applications. For this purpose, we design a very dense wireless network, consisting of radio cells of less than 10 m². To serve these small cells, a backbone network implemented over a radio-over-fibre (RoF) based architecture can be an ideal solution. In this paper we propose different RoF architectures that are varying in architectural complexity, flexibility, supported user densities (depending on the sharing ratio of the optical transceivers between cells) and the number of users per cell. We indicate their main challenges and propose some specific scenarios where they can be applied. Not only there are architectural challenges to design the RoF network to bring a high capacity to every small cell, but also a medium access control (MAC) protocol is needed to confirm the quality of service (QoS) bounds of a low latency, seamless handovers, and a high throughput. We differentiate between two approaches to design such a MAC protocol, either distributed or centralized mechanisms.