RRH and small cells ? The implications for spectrum sharing

This paper considers the implications of different infrastructure options on a spectrum sharing scenario in cellular networks, featuring a mixture of macro cells and low-power nodes (LPNs). Our aim is to provide a systematic approach to spectrum sharing. This requires dealing not only with various aspects of the spectrum but also understanding the infrastructure requirements. Considering the general trends towards deployments of dense and ultra-dense networks of LPNs, of particular interest are two types of nodes - remote radio heads (RRHs) and small cells. They pose different requirements on the transport network - RRHs have strict requirements on throughput, latency, and jitter while small cells allow the use of different transport network technologies. The spectrum sharing model considered here is based on the well-known Carrier Aggregation of LTE-Advanced, designed to support topologies with RRHs, and Dual Connectivity, introduced to support deployments with small cells. In addition, the model also incorporates spectral resources from two distinct shared spectrum classes that are heterogeneous in a number of aspects. They include spectrum access rights, together with the cost of accessing the spectrum, as well as the quality of spectrum in terms of its availability and protection from inter-system interference. The analysis in this paper is focused on the downlink throughput for a typical user, where a cellular operator determines the required spectrum resources from a particular spectrum class. The objective is to meet a particular Quality of Service (QoS) requirement, defined as the minimum average throughput. In that, the paper analyses interaction between the options supporting RRHs that is small cells, and the sharing model, taking into account certain implementation aspects of LTE-Advanced. It provides a comprehensive evaluation and sensitivity analysis of a number of parameters of interest to the cellular operator, such as network load, the density of LPNs, inter-system interference, power levels, and QoS targets.