The densification of small cell base stations in a 5G architecture is a promising approach to enhance the coverage area and facilitate the ever increasing capacity demand of end users. However, the bottleneck is an intelligent management of a backhaul/fronthaul network for these small cell base stations. This involves efficient association and placement of the backhaul hubs that connects these small-cells with the core network. Terrestrial hubs suffer from an inefficient non line of sight link limitations and unavailability of a proper infrastructure in an urban area. Realizing the popularity of flying platforms, we employ here an idea of using networked flying platform (NFP) such as unmanned aerial vehicles (UAVs), drones, unmanned balloons flying at different altitudes, as aerial backhaul hubs. The association problem of these NFP-hubs and small-cell base stations is formulated considering backhaul link and NFP related limitations such as maximum number of supported links and bandwidth. We then present an efficient and distributed solution of the designed problem, which performs a greedy search in order to maximize the sum rate of the overall network. A favorable performance is observed via a numerical comparison of our proposed method with optimal exhaustive search algorithm in terms of sum rate and run-time speed. Backhaul hub routes the traffic between SBSs and the core network using either wired (e.g., fiber optics) [4] or wireless (e.g., microwave or millimeter wave (mmWave)) technologies [5] . Wired optical fiber connection is always the best option but not the best choice due to its high capital expenditure (CAPEX). Wireless backhaul links can be categorized into line of sight (LoS) and non line of sight (NLoS) cases. LoS backhaul links use free space optics (FSO) or mmWave/microwave bands that leads to less coverage due to short range communication. On the other hand, NLoS radio frequency (RF) backhaul links do not have the coverage issue but they suffer from low data rate and hub placement problems because of few available ground locations in an urban area. Recently, a cost effective and a scalable idea of replacing the terrestrial backhaul network with an aerial network is presented in [6] , which employs networked flying platform (NFP) such as unmanned aerial vehicles (UAVs), drones, unmanned balloons, as aerial backhaul hubs. These NFP-hubs are meant for wireless communication as they are capable of communicating signalling and control information. Further, they hover at an altitude ranging from few hundred meters up to 20 kms including low altitude platforms (LAPs), medium altitude platforms (MAPs) and high altitude platforms (HAPs), depending upon coverage area, weather conditions and other related factors. Here, we use the idea of employing NFPs as backhaul hubs and present an efficient distributed algorithm for the association of multiple aerial NFP-hubs with the ground SBSs. Within a short span of time, the idea of using NFPs as relays and SBSs have attracted an eye of various researchers. The air to ground propagation model was presented in [7] for communication between LAP such as UAVs and terrestrial nodes. Then later on, a closed form expression was presented for this model and considering a fixed path loss (PL), an optimal altitude of a single UAV is analytically derived to maximize radio coverage [8] . In [9], the geographical coverage area is optimized for the case of two UAVs, considering 978-1-5090-5019-2/17/$31.00 ©2017 IEEE
In REF , authors study small-cells-UAVs association under backhaul capacity, bandwidth constraint, and maximum number of links limitation.
A Distributed Approach for Networked Flying Platform Association with Small Cells in 5G+ Networks
GLOBECOM 2017 - 2017 IEEE Global Communications Conference
GLOBECOM 2017 - 2017 IEEE Global Communications Conference
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