Abstract
The expected growth in carried traffic and the added complexity of different deployment approaches (distributed vs. centralized), showing different requirements, make transport network one of the main design challenges in 5G. One of those challenges is posed by the Centralized Radio Access Network (CRAN) paradigm, whereby different functionalities of the base station are split between a central unit and a remote unit, both connected by a fronthaul/midhaul network. When this centralization includes physical layer functions, stringent capacity and delay constraints are imposed on the fronthaul, thus making its design and deployment more challenging and costly. At this point, the anticipated capacity requirements for fronthaul links are enormous and, as of today, no single technology can support such requirements. Hence, the complex transport network will be heterogeneous in nature. There is consensus in following two approaches to tackle the fronthaul challenge: i) building a heterogeneous network by combining different technologies; and ii) employing different functional splits, which have the potential to reduce the capacity requirements on fronthaul links. Hence, it is important that we exploit different potential technologies and a functional split approach for 5G fronthaul networks design. As our contribution, we show how intelligently selected functional splits at physical layer can be utilized to serve the radio access networks in a capacity-limited scenario. From a different point of view, we also propose maximizing the centralization by means of a heterogeneous combination of functional splits in a budget-limited scenario. Results presented in this paper show that the combination of functional splits has the potential to enable the design of heterogeneous fronthaul networks combining wireless and wired links, and reducing drastically both the required capacity (to 40%) and the total cost of ownership (to 35%).
Highlights
5G is expected to start globally by year 2020, with a promise to provide ubiquitous connectivity with a targeted traffic capacity of 10 Mbps per m2 [1]
In this work we focus on the functional splits within the Physical layer (PHY) layer, which still allow a great level of centralization until the Medium Access Control (MAC) layer
We consider a large number of dummy scenarios, each of 1 km2 area, served by 25 MBSs3(100% loaded) and 200 Small Cells (SC) (50% loaded), where the Baseband Units (BBU)/Distributed Unit (DU)/FH aggregator is located at the centre of the
Summary
Copper line-based technologies, i.e., Asymmetric DSL (ADSL) and Very high speed DSL (VDSL), have been popular wired options for backhauling wireless networks in the past They suffer from insufficient bandwidth to be considered for future mobile backhaul/fronthaul solutions. Because of its high capacity and low cost deployment, mmWave is becoming a very attractive option for future FH networks, and is already being considered as one of the key enablers of 5G These high frequencies suffer from larger pathlosses. Split-A represents total centralization of functionalities or CRAN, i.e., 3GPP Option 8 Using this split, maximum centralization gain is achievable with the cost of huge capacity and latency requirements on the FH links. For SCs, higher splits (i.e. Split-C/D) can be utilized to remain within the available capacity
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