Hybrid passive optical network–free-space optic-based fronthaul architecture for ultradense small cell network

Abstract

In future Radio Access Network (RAN), many small cells will be densely deployed to meet the capacity demand of mobile users. Centralized Radio Access Network (CRAN) is a potential solution to increase the capacity demand of RAN. CRAN breaks the functionality of RAN between Remote Radio Head (RRH) and Base Band Unit (BBU) where RRH and BBU are preferably connected by an optical link called fronthaul link. However, the deployment of fiber for fronthaul connectivity, at each Small Cell (SC) location, is impossible or impractical due to cost or other constraints. As such, Passive Optical Network (PON) and Free Space Optic (FSO) technologies have emerged as potential candidates for fronthaul transmission when the complete optical fiber-based infrastructure for fronthaul network cannot be deployed alone. In this paper, we propose a hybrid PON and FSO based method for SC fronthaul connections that considers three different network constraints i.e. bandwidth, data rate, and latency. Based on this, we formulate the problem and propose a novel method to perform cell association, namely Minimum Sum Selection (MSS). The performance is evaluated in terms of the number of SCs connected and the proposed method is compared with two other baselines, namely: Minimum Rate Selection (MRS) and Random Selection Method (RSM). The results show that despite MSS requiring knowledge of all network constraints, it has a better performance at the cost of more computation resources, achieving gains of 7% and 6.5% in cell connections when compared to the other two baseline methods.

Beyond 5G Fronthaul Based on FSO Using Spread Spectrum Codes and Graphene Modulators

“…A hybrid FSO and passive optical network (PON) as mobile fronthaul for the development of ultra-dense small cells was proposed in Ref. [27]. Such a hybrid network architecture is interesting, since optical fiber deployment as a fronthaul for every small cell is not feasible due to the high-costs or physical constraints.…”

Flexible Free-Space Optical CDMA Networks

“…It is also a statistical multiplexing technique that supports multiple data rate transmissions at the physical layer. Whilst OCDMA-based PON may be the optimal technology for future access networks, its deployment is restricted by geographical challenges, limited optical fiber deployment, and site access rights limitations, among others [4], [6].…”