19,221 research outputs found

    Fronthaul-Constrained Cloud Radio Access Networks: Insights and Challenges

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    As a promising paradigm for fifth generation (5G) wireless communication systems, cloud radio access networks (C-RANs) have been shown to reduce both capital and operating expenditures, as well as to provide high spectral efficiency (SE) and energy efficiency (EE). The fronthaul in such networks, defined as the transmission link between a baseband unit (BBU) and a remote radio head (RRH), requires high capacity, but is often constrained. This article comprehensively surveys recent advances in fronthaul-constrained C-RANs, including system architectures and key techniques. In particular, key techniques for alleviating the impact of constrained fronthaul on SE/EE and quality of service for users, including compression and quantization, large-scale coordinated processing and clustering, and resource allocation optimization, are discussed. Open issues in terms of software-defined networking, network function virtualization, and partial centralization are also identified.Comment: 5 Figures, accepted by IEEE Wireless Communications. arXiv admin note: text overlap with arXiv:1407.3855 by other author

    In-Building Capacity Enhancement using Small Cells in Mobile Networks: An Overview

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    In this paper, we give an overview of the state-of-the-art research studies to present the potential of small cells to address the high capacity demands of in-building users in mobile networks. In doing so, we discuss relevant theoretical backgrounds and carry out performance evaluations of key enabling technologies along with three major directions toward improving the network capacity, including spectrum accessibility, Spectral Efficiency (SE) improvement, and network densification. For the spectrum accessibility, numerous types of Small Cell Base Station (SBS) architectures of a Mobile Network Operator (MNO) are evaluated. For the SE improvement, cognitive radio techniques are evaluated for the Dynamic Spectrum Sharing (DSS) among multiple MNOs in a country. For the network densification, the spectrum reuse is evaluated at both intra-and inter-building levels for a given Co-Channel Interference (CCI) constraint. It is shown that multi-band multi-transceiver enabled small cells operating in the high-frequency millimeter-wave licensed or unlicensed spectrum to realize DSS techniques by exploiting SBS architectures for the spectrum accessibility, a hybrid interweave-underlay spectrum access in Cognitive Radio Networks for the spectral efficiency improvement, and both vertical and horizontal spectrum reuse in small cells deployed densely within buildings for the network densification can address high capacity demand in indoor mobile networks
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