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2 - Design and performance analysis of multi-radio small cell networks
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- By Nageen Himayat, Intel Corporation, Shu-Ping Yeh, Intel Corporation, Shilpa Talwar, Intel Corporation, Mikhail Gerasimenko, Tampere University of Technology, Sergey Andreev, Tampere University of Technology, Yevgeni Koucheryavy, Tampere University of Technology
- Edited by Alagan Anpalagan, Ryerson Polytechnic University, Toronto, Mehdi Bennis, University of Oulu, Finland, Rath Vannithamby
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- Book:
- Design and Deployment of Small Cell Networks
- Published online:
- 05 December 2015
- Print publication:
- 17 December 2015, pp 31-57
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- Chapter
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Summary
Multi-tier, heterogeneous networks (HetNets) using small cells (e.g., pico and femto cells) are an important part of operators’ strategy to add low-cost network capacity through aggressive reuse of the cellular spectrum. In the near term, a number of operators have also relied on un-licensed WiFi networks as a readily available means to offload traffic demand. However, the use of WiFi is expected to remain an integral part of operators’ long-term strategy to address future capacity needs, as licensed spectrum continues to be scarce and expensive. Efficient integration of cellular HetNets with alternate radio access technologies (RATs), such as WiFi, is therefore essential for next-generation networks.
This chapter describes several WiFi-based multi-RAT HetNet deployments and architectures, and evaluates the associated performance benefits. In particular, we consider deployments featuring integrated multi-RAT small cells with co-located WiFi and LTE interfaces, where tighter coordination across the two radio links becomes feasible. Integrated multi-RAT small cells are an emerging industry trend toward leveraging common infrastructure and lowering deployment costs when the footprints of WiFi and cellular networks overlap. Several techniques for cross-RAT coordination and radio resource management are reviewed and system performance results showing significant capacity and quality service gains are presented.
Introduction
Multi-tier HetNets based on small cells (e.g. pico cells, femto cells, relay cells, WiFi APs, etc.) are considered to be a fundamental technology for cellular operators to address capacity and coverage demands of future 5G networks. Typical HetNet deployment architectures comprise an overlay of a macro cell network with additional tiers of densely deployed cells with smaller footprints, such as picos, femtos, relay nodes, WiFi access points, etc. Figure 2.1 illustrates the various deployment options in a multi-radio HetNet.
HetNets allow for greater flexibility in adapting the network infrastructure according to the capacity, coverage, and cost needs of a given deployment. As shown, the macro base station tier may be used for providing wide area coverage and seamless mobility, across large geographic areas, while smaller inexpensive low-powered small cells may be deployed, as needed, to improve coverage by moving infrastructure closer to the clients (such as for indoor deployments), as well as to add capacity in areas with higher traffic demand. Conceptually, mobile clients with direct client-to-client communication may also be considered as one of the tiers within this hierarchical deployment, wherein the clients can cooperate with other clients to locally improve access in an inexpensive manner.
Crystal structure and physical properties of GaSe single crystals annealed in sulfur atmosphere
- Olga V. Voevodina, Aleksandr N. Morozov, Sergey Yu. Sarkisov, Yuri M. Andreev, Nils C. Fernelius, Jonathan T. Goldstein
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- Journal:
- MRS Online Proceedings Library Archive / Volume 891 / 2005
- Published online by Cambridge University Press:
- 01 February 2011, 0891-EE03-25
- Print publication:
- 2005
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- Article
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In spite of the progress in GaSe growing technology (high-quality crystals grown by the latest technology are characterized by low values of optical losses with the absorption coefficient values lying below 0.1 cm−1) the work continues on improving crystal properties for nonlinear optical applications. This paper presents the results of investigations on the influence of annealing in a sulfur atmosphere and in a vacuum on the properties GaSe single crystals, grown by the Bridgman method from the melt. The objective of this work was to study the possibility of intercalating GaSe with sulfur from the gas phase, and to compare the influence of doping with sulfur from melt and vapor phase on the structure and properties of GaSe crystals. Three series of annealing experiments have been conducted at temperatures 773, 923, 1073 K and the samples obtained have been studied by Hall effect, photoconductivity, optical absorption, microhardness measurements and X ray diffractometry. The results obtained are explained by assuming the intercalating of sulfur to the interlayer space and substitution of Se with S.