The Experts below are selected from a list of 72 Experts worldwide ranked by ideXlab platform

Reena Kumbhare - One of the best experts on this subject based on the ideXlab platform.

  • Channel Allocation for Cellular Networks Using Genetic Algorithm
    Communications in Computer and Information Science, 2013
    Co-Authors: Jish Elizabeth Joy, Reena Kumbhare
    Abstract:

    With the limited frequency spectrum and increasing demand for cellular communication services, the problem of channel assignment becomes increasingly important. The three main Constraints impeding the efficient usage of frequency spectrum are co-channel Constraint (CCC), the adjacent channel Constraint (ACC) and the co-Site Constraint (CSC). The objective is to obtain a conflict-free channel allocation scheme using modified immune genetic algorithm which satisfies both the electromagnetic compatibility (EMC) Constraint and traffic demand requirement. The minimum separation encoding scheme is introduced to meet the co-Site Constraint. The genetic operators, viz. crossover and mutation are proposed to ensure the traffic demand through the iterative process. To increase the efficiency and velocity of convergence, immune operators are given, such as immune clone, vaccination, immune selection etc.

  • Channel Allocation for Cellular Networks
    International Journal of Global Technology Initiatives, 2012
    Co-Authors: Jish Elizabeth Joy, Reena Kumbhare
    Abstract:

    With the limited frequency spectrum and increasing demand for cellular communication services, the problem of channel assignment becomes increasingly important. The three main Constraints impeding the efficient usage of frequency spectrum are cochannel Constraint (CCC), the adjacent channel Constraint (ACC) and the co-Site Constraint (CSC). The objective is to obtain a conflict-free channel allocation scheme using modified immune genetic algorithm which satisfies both the electromagnetic compatibility (EMC) Constraint and traffic demand requirement. The minimum separation encoding scheme is introduced to meet the co-Site Constraint. The genetic operators, viz. crossover and mutation are proposed to ensure the traffic demand through the iterative process. To increase the efficiency and velocity of convergence, immune operators are given, such as immune clone, vaccination, immune selection etc Keywords: cellular networks, channel assignment problem, genetic algorithm, electromagnetic compatibility Constraints

Lata Narayanan - One of the best experts on this subject based on the ideXlab platform.

  • Approximation algorithms for channel assignment with Constraints
    Theoretical Computer Science, 2001
    Co-Authors: Jeannette Janssen, Lata Narayanan
    Abstract:

    AbstractCellular networks are generally modeled as node-weighted graphs, where the nodes represent cells and the edges represent the possibility of radio interference. An algorithm for the channel assignment problem must assign as many channels as the weight indicates to every node, such that any two channels assigned to the same node satisfy the co-Site Constraint, and any two channels assigned to adjacent nodes satisfy the inter-Site Constraint. We describe several approximation algorithms for channel assignment with arbitrary co-Site and inter-Site Constraints for odd cycles and the so-called hexagon graphs that are often used to model cellular networks. The algorithms given for odd cycles are optimal for some values of Constraints, and have performance ratio at most 1+1/(n−1) for all other cases, where n is the length of the cycle. Our main result is an algorithm of performance ratio at most 43+1100 for hexagon graphs with arbitrary co-Site and inter-Site Constraints

  • ISAAC - Approximation Algorithms for Channel Assignment with Constraints
    Algorithms and Computation, 1999
    Co-Authors: Jeannette Janssen, Lata Narayanan
    Abstract:

    Cellular networks are generally modeled as node-weighted graphs, where the nodes represent cells and the edges represent the possibility of radio interference. An algorithm for the channel assignment problem must assign as many channels as the weight indicates to every node, such that any two channels assigned to the same node satisfy the co-Site Constraint, and any two channels assigned to adjacent nodes satisfy the inter-Site Constraint. We describe several approximation algorithms for channel assignment with arbitrary co-Site and inter-Site Constraints and reuse distance 2 for odd cycles and so-called hexagon graphs that are often used to model cellular networks. The algorithms given for odd cycles are optimal for some values of Constraints, and have performance ratio at most 1+1=(n- 1) for all other cases, where n is the length of the cycle. Our main result is an algorithm of performance ratio at most 4/3+Ɛ for hexagon graphs with arbitrary co-Site and inter-Site Constraints.

J. Safranek - One of the best experts on this subject based on the ideXlab platform.

Bert F Sels - One of the best experts on this subject based on the ideXlab platform.

  • shape selectivity vapor phase conversion of lignin derived 4 ethylphenol to phenol and ethylene over acidic aluminosilicates impact of acid properties and pore Constraint
    Applied Catalysis B-environmental, 2018
    Co-Authors: Yuhe Liao, Martin Dhalluin, E V Makshina, Danny Verboekend, Bert F Sels
    Abstract:

    Abstract Selective dealkylation of alkylphenols, the oppoSite reaction of the more commonly studied phenol alkylation, may represent an important reaction in the production of base chemicals like phenol and olefins from fossilized and raw lignocellulosic matter. This study reports the first thermodynamics and kinetics studies of the vapor-phase conversion of ethylphenol (EP) over acidic γ-Al2O3, amorphous (ASA) and crystalline aluminosilicates (like ferrierite, ZSM-22, ZSM-5, beta, and USY) in the absence of hydrogen and noble metals, as a way to produce phenol and ethylene. The reaction was studied deliberately in presence of steam to get stable time on stream catalysis. The thermodynamic analysis shows an endothermal EP conversion to phenol and ethylene, favoured at high reaction temperature, while isomerisation, disproportionation and transalkylation are thermodynamically preferred at low temperature. The kinetic study examines the role of the catalytically active Sites; it reveals the importance of Site Constraint on the activity, selectivity and stability, and shows the complex temperature dependency of the dealkylation. Both Bronsted and Lewis acid Sites are active, but multifactor dependency (such as acid strength and Site accessibility) complicates the establishment of simple quantitative relationships with the acid type. EP does not enter the micropores of ferrierite and ZSM-22, as suggested by adsorption experiments. Kinetics without significant diffusion limitations were obtained with ZSM-5, beta and USY. Thus, in absence of intracrystalline diffusion limitation (as verified by calculations using reported effective diffusivities, and substantiated by a comparably high apparent activation energy for all zeolites), the increased reaction turnover rate with increasing pore size from medium to large pore zeolites is largely explained by a change in reaction pathway (from monolecular to bimolecular) to convert EP to phenol and ethylene. A pathway proceeding through fast thermodynamically favourable bimolecular reactions occurs in the spatially non-constrained pores and crystal surface, whereas monomolecular reactions take place in the micropores of ZSM-5. Despite the lower rate, the selectivity over ZSM-5 strongly benefits from active Site confinement, being responsible to achieve quantitative formation of phenol and ethylene from ethylphenol. The excellent performance of ZSM-5 thus accords with its shape selective property that avoids undesired side reactions such as the sterically demanding bimolecular reactions like disproportionation, transalkylation and C-C cracking, and severe cokes formation.

M. H. Wang - One of the best experts on this subject based on the ideXlab platform.