Real-Time Misbehavior Detection in IEEE 802.11e Based WLANs

The Enhanced Distributed Channel Access (EDCA) specification in the IEEE 802.11e standard supports heterogeneous backoff parameters and arbitration inter-frame space (AIFS), which makes a selfish node easy to manipulate these parameters and misbehave. In this case, the network-wide fairness cannot be achieved any longer. Many existing misbehavior detectors, primarily designed for legacy IEEE 802.11 networks, become inapplicable in such a heterogeneous network configuration. In this paper, we propose a novel real-time hybrid-share (HS) misbehavior detector for IEEE 802.11e based wireless local area networks (WLANs). The detector keeps updating its state based on every successful transmission and makes detection decisions by comparing its state with a threshold. We develop mathematical analysis of the detector performance in terms of both false positive rate and average detection rate. Numerical results show that the proposed detector can effectively detect both contention window based and AIFS based misbehavior with only a short detection window.Comment: Accepted to IEEE Globecom 201

Modelling the integration between the design and inspection process of geometrical specifications for digital manufacturing

Geometrical Product Specifications (GPS) is a technical language which covers the standardization for micro/macro- geometry specifications. In today’s environment of globalization, out-sourcing and sub-contracting is increasing. Geometrical specifications of a product need to be detailed to a degree where nothing is left open to interpretation. To fulfil this, and to meet the requirements of digital manufacturing, it is necessary to integrate the design and inspection process of a geometrical specification. At the technical level, many functional operator/operations are employed in a geometrical specification. These functional operators/operations are based on rigorous mathematics, and they are intricately related and inconvenient to be used directly. Consequently, it is of practical utility to build an integrated information system to encapsulate and manage the information involved in GPS. This thesis focuses on geometrical tolerancing, including form/orientation/ location tolerancing, and its integrated geometry information system. The main contributions are: Firstly, a global data expression for modelling the integration between the design and inspection process of a geometrical tolerance is presented based on category theory. The categorical data model represents, stores and manipulates all the elements and their relationships involved in design and inspection process of a geometrical tolerance, by categories, objects and morphisms, flexibly; the relationships between objects were refined by pull back structures; and the manipulations of the model such as query and closure of query are realized successfully by functor structures in category theory. Secondly, different categories of knowledge rules have been established to enhance the rationality and the intellectuality of the integrated geometry information system, such as the rules for the application of geometrical requirement, tolerance type, datum and datum reference framework and, for the refinement among geometrical specifications. Finally, the host system for drawing indication of geometrical tolerances in the framework of GPS was established based on AutoCAD 2007 using ObjectARX.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Hexaaqua­magnesium(II) bis­{[N-(4-meth­oxy-2-oxidobenzyl­idene)glycyl­glycinato(3−)]cuprate(II)} hexa­hydrate

In the title complex, [Mg(H2O)6][Cu(C12H11N2O5)]2·6H2O, the CuII atoms lie at the center of the square plane of triple negatively charged O,N,N′,O′-tetra­dentate Schiff base ligands, which are coordinated by one phenolate O atom, one imine N atom, one deprotonated amide N atom and one carboxyl­ate O atom. The MgII center, which sits on an inversion center, is coordinated by six aqua ligands and exhibits a slightly distorted octa­hedral conformation. The asymmetric unit consists of an [N-(4-meth­oxy-2-oxidobenzyl­idene)glycyl­glycinato]cuprate(II) anion, one half of an [Mg(H2O)6]2+ cation and three free water mol­ecules. The cations and anions form columns by O—H⋯O hydrogen bonds

Triaqua­bis{μ-N-[N-(4-meth­oxy-2-oxidobenzyl­idene)glyc­yl]glycinato(3−)}cadmium(II)dicopper(II) dihydrate

In the title compound, [CdCu2(C12H11N2O5)2(H2O)3]·2H2O, the CuII atoms are in a square plane of N2O2 atoms contributed by the tetra­dentate Schiff base trianion. The CuII atoms are coordinated by one phenolate O atom, one imine N atom, one amido N atom and one carboxyl­ate O atom. The CdII atom is connected via the carboxyl­ate groups, forming a heterotrinuclear CuII–CdII–CuII system. The CdII atom is seven-coordinate in a penta­gonal-bipyramidal geometry with four O atoms from two carboxyl­ate groups and three aqua ligands. The heterotrinuclear mol­ecules are linked to the uncoordinated water mol­ecules by O—H⋯O hydrogen bonds into a three-dimensional framework

Hexaaqua­cobalt(II) bis­{[N-(4-meth­oxy-2-oxidobenzyl­idene)glycylglycinato]nickel(II)} hexa­hydrate

In the title compound, [Co(H2O)6][Ni(C12H11N2O5)]2·6H2O, the NiII atom has a nearly square-planar coordination with two N and two O atoms of the N-(4-meth­oxy-2-oxidobenzyl­idene)glycylglycinate Schiff base ligand (L 3−). The CoII atom sits on an inversion center and is coordinated to six aqua ligands in a slightly distorted octa­hedral geometry. The [Co(H2O)6]2+ cations and [NiL]− anions form columns along the a axis by O—H⋯O hydrogen bonds. Additional hydrogen bonds between the uncoordinated and coordinated water molecules help to consolidate the crystal packing