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QoS Aware Radio Access Technology Selection Framework in Heterogeneous Networks using SDN
Alessandro Raschellà,Faycal Bouhafs,Deepak G.C.,Michael Mackay 한국통신학회 2017 Journal of communications and networks Vol.19 No.6
This paper addresses the problem of radio access technology(RAT) selection in heterogeneous networks (HetNets). Currentapproaches rely on signal related metrics such as signal tointerference plus noise ratio (SINR) for selection of the best networkfor the wireless user. However, such approaches do not takeinto account the quality of service (QoS) requirements of wirelessusers and therefore often do not connect them to the most suitablenetwork. We propose a QoS aware RAT selection frameworkfor HetNets based on software-defined networking (SDN). The proposedframework implements a RAT selection strategy that reflectsQoS requirements of downlink flows using a metric called fittingnessfactor (FF). The framework relies on the flexibility and centralisednature of SDN to implement monitoring and RAT capacityassessment mechanisms that help in the realisation of the selectionstrategy. The simulation campaign illustrates the important gainsachieved by our RAT selection framework in terms of data ratesassigned to the wireless users, their satisfaction, and their qualityof experience (QoE) compared against other state of the art RATselection solutions.
Kim, Sung-Kon,Kim, Dong-Gyun,Lee, Aeri,Sohn, Hae-Sung,Wie, Jeong Jae,Nguyen, Ngoc A.,Mackay, Michael E.,Lee, Jong-Chan American Chemical Society 2012 Macromolecules Vol.45 No.23
<P>A series of organic/inorganic hybrid block and random copolymers were prepared by reversible addition–fragmentation chain transfer (RAFT) polymerization using poly(ethylene glycol) methyl ether methacrylate (PEGMA) and 3-(3,5,7,9,11,13,15-heptaisobutylpentacyclo[9.5.1.1<SUP>3,9</SUP>.1<SUP>5,15</SUP>.1<SUP>7,13</SUP>]octasiloxane-1-yl)propyl methacrylate (MA-POSS) as monomers in order to study the effect of polymer morphology and POSS content on the properties of polymer electrolytes. Flexible and dimensionally stable free-standing films were made from the hybrid block and random copolymers mixed with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) when the contents of MA-POSS unit were larger than 31 and 16 mol %, respectively. The ionic conductivity of the solid-state block copolymer (PBP) electrolyte was found to be 1 order of magnitude higher than that of the random copolymer (PRP) electrolyte when they had similar MA-POSS content, although their glass transition temperature values of their ion-conducting segments were quite close. Moreover, the ionic conductivity of the PBP electrolyte was not much different from that of the wax state poly(poly(ethylene glycol) methyl ether methacrylate) (P(PEGMA)) electrolyte. For example, the ionic conductivity values for the PBP electrolyte containing 31 mol % of MA-POSS, the PRP electrolyte containing 29 mol % of MA-POSS, and P(PEGMA) electrolyte were 2.05 × 10<SUP>–5</SUP>, 3.00 × 10<SUP>–6</SUP>, and 4.23 × 10<SUP>–5</SUP> S cm<SUP>–1</SUP>, respectively, at 30 °C. The large ionic conductivity value of the block copolymer electrolyte is ascribed to the nanophase separation forming the ion-conducting channels.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/mamobx/2012/mamobx.2012.45.issue-23/ma301404q/production/images/medium/ma-2012-01404q_0011.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ma301404q'>ACS Electronic Supporting Info</A></P>