When the Hammer Meets the Nail: Multi-Server PIR for Database-Driven CRN with Location Privacy Assurance

We show that it is possible to achieve information theoretic location privacy for secondary users (SUs) in database-driven cognitive radio networks (CRNs) with an end-to-end delay less than a second, which is significantly better than that of the existing alternatives offering only a computational privacy. This is achieved based on a keen observation that, by the requirement of Federal Communications Commission (FCC), all certified spectrum databases synchronize their records. Hence, the same copy of spectrum database is available through multiple (distinct) providers. We harness the synergy between multi-server private information retrieval (PIR) and database- driven CRN architecture to offer an optimal level of privacy with high efficiency by exploiting this observation. We demonstrated, analytically and experimentally with deployments on actual cloud systems that, our adaptations of multi-server PIR outperform that of the (currently) fastest single-server PIR by a magnitude of times with information theoretic security, collusion resiliency, and fault-tolerance features. Our analysis indicates that multi-server PIR is an ideal cryptographic tool to provide location privacy in database-driven CRNs, in which the requirement of replicated databases is a natural part of the system architecture, and therefore SUs can enjoy all advantages of multi-server PIR without any additional architectural and deployment costs.Comment: 10 pages, double colum

Expanding the Bandwidth of Rectangular Microstrip Antenna by Inserting a Slot

In this work we were able to improve the reflection coefficient S11 and bandwidth BW of a rectangular microstrip antenna fed by a coaxial cable firstly by adjusting a the feed point and secondly by inserting a rectangular slot in the radiating element The results obtained using the HFSS software, have been compared by those published. These results are very satisfying

Synthesis, quantum chemical computations and x-ray crystallographic studies of a new complex based of manganese (+II)

The ligand oxime, C7H9N5O2, was Synthesis and characterises with different characterization methods such as 1H NMR and FTIR spectroscopy. The complexation of this ligand with manganese (II) perchlorate yielded pink crystals of formula [Mn (C7H9N5O2)2]2+, 2[ClO4]-, which crystallized in the monoclinic space group P21/n with a = 12.824(3), b=13.799(2), c=15.441(4)Å, β = 100.17(2), and Z = 4. The complex consists of cations (+II) and two perchlorate anions, the cations part existing in a slightly distorted octahedral complex. Computational investigations of manganese (II) complex are done by using the DFTmethod with B3LYP functional in conjunction with the 6-31G(d,p) and lanl2dz basis sets in the gas phase imposing the C1 and C2v symmetries.Keywords: Manganese complex; Crystal structure; DFT method; B3LYP functional; 6-31G(d,p) and (LANL2DZ) basi

Synthesis, crystal structures, hydrogen bonding graph-sets and theoretical studies of nickel (+II) co-ordinations with pyridine-2,6-dicarboxamide oxime

The pyridine-2,6-dicarboxamide oxime, C7H9N5O2, was Synthesis and  characterises with 1H NMR and FTIR spectroscopy . The reaction of this ligand with nickel (II) perchlorate yielded green crystals of formula  [Ni(C<sub>7</sub>H<sub>9</sub>N<sub>5</sub>O<sub>2</sub>)<sub>2</sub>]<sup>2+</sup>,2[ClO<sub>4</sub>]-, which crystallized in the monoclinic space group C2/c with a = 14.915(2), b = 0.895(2), c = 8.205(1) Å, β = 114.69(1), and Z = 4. The complex consists of discrete cations (+II) and one perchlorate anion, the  cations existing in a slightly distorted octahedral  complex with bonding through the heterocyclic and oxime nitrogen atoms. The structure is held together through N-H…O, O-H…O and C-H...O hydrogen bonds occurring  between the coordinated oxime  molecules and the perchlorate counter-ion. Computational investigations of nickel(II) complex are done by using M062X method with 6-31+G(d)(LANL2DZ) basis set in vacuo.Keywords: Oxime complexe; Crystal structure; Hydrogen-bonding graph-set; DFT; M062X method; 6-31+G(d)(LANL2DZ) basis

Performance of distributed mechanisms for flow admission in wireless adhoc networks

Given a wireless network where some pairs of communication links interfere with each other, we study sufficient conditions for determining whether a given set of minimum bandwidth quality-of-service (QoS) requirements can be satisfied. We are especially interested in algorithms which have low communication overhead and low processing complexity. The interference in the network is modeled using a conflict graph whose vertices correspond to the communication links in the network. Two links are adjacent in this graph if and only if they interfere with each other due to being in the same vicinity and hence cannot be simultaneously active. The problem of scheduling the transmission of the various links is then essentially a fractional, weighted vertex coloring problem, for which upper bounds on the fractional chromatic number are sought using only localized information. We recall some distributed algorithms for this problem, and then assess their worst-case performance. Our results on this fundamental problem imply that for some well known classes of networks and interference models, the performance of these distributed algorithms is within a bounded factor away from that of an optimal, centralized algorithm. The performance bounds are simple expressions in terms of graph invariants. It is seen that the induced star number of a network plays an important role in the design and performance of such networks.Comment: 21 pages, submitted. Journal version of arXiv:0906.378