Amilcar C. Cesar

Adaptive Genetic Algorithms for Dynamic Channel Assignment in Mobile Cellular Communication Systems

Two adaptive genetic algorithms (GAs), namely GA for locking channel (GALC) and GA for switching channel (GASC), are proposed for a dynamic channel assignment in mobile cellular communication systems. The algorithms aim to minimize the blocking probability of new calls and the dropping probability of handoff calls in channelized systems, simultaneously considering three types of electromagnetic compatibility (EMC) constraints: 1) the cochannel; 2) the adjacent channel; and 3) the cosite. The proposed algorithms add a number of mechanisms to the canonical GA in order to increase their efficiency and velocity of convergence. Such mechanisms are adaptive parameters, random immigrants, a greedy policy, a reservoir to assist the initial population, a truncation selection scheme, and a three-point crossover. The GASC allows call switching between channels during the call holding time, whereas the GALC does not allow it. Computer simulations evaluated the performance of the proposed models considering a benchmark cellular environment formed by 49 cells with 70 channels and nonuniform traffic load characteristics. The impact of EMC constraints on the blocking probability of new calls and on the dropping probability of handoff calls was assessed, and the proposed models reached suitable performance. Equipment failure tests showed robust performance of the two adaptive GA schemes during the fault occurrence and recovery capability after the fault ends. The results suggest that the GASC has lower overall blocking probability of new calls than the GALC; however, the GALC may do better than the GASC in a number of combinations of handoff requests and EMC restrictions.

Optical network optimization with transmission impairments based on genetic algorithm

We propose routing and wavelength assignment in WDM networks based on a genetic algorithm. Two transmission impairments are added to the usual set of routing constraints. They are polarization mode dispersion (PMD) and amplified spontaneous emission (ASE). Through simulation, we find substantial savings in terms of equipment cost, optimizing the placement of wavelength converters and PMD compensators. Also, the proposed technique limits the number of cascaded amplifiers and reduces the number of wavelength conversions, enhancing the optical signal quality.

EDFA adaptive gain control effect analysis over an amplifier cascade in a DWDM optical system

In this paper, we analyze the EDFA adaptive gain control impact on 80 modulated C-band channels (10 Gbps NRZ) in a DWDM optical system composed of four cascaded amplifiers. System performance was evaluated in terms of channels optical signal-to-noise ratio (OSNR), noise figure (NF), bit error rate (BER), and gain flatness (GF) measurements. The adaptive EDFA scheme aims to optimize NF and GF spectra by adjusting its setpoint gain based on static information about these parameters and was improved here to prioritize NF when BER of the received signal remains under the FEC limit.

Impact of PMD on hybrid WDM/OCDM networks

In this work, we investigated the impact of polarization-mode dispersion (PMD) in optical networks using the hybrid technology of wavelength-division multiplexing and optical code-division multiplexing. In these networks, virtual paths based on code/wavelength channels (VCP/VWP) are dynamically established to attend the traffic demand. We use a routing channel assignment based on genetic algorithm to establish the VCP/VWPs. The main results show that the network blocking probability caused by PMD depends on parameters of optical orthogonal codes like weight and length.

Dynamic channel assignment in mobile communications based on genetic algorithms

We investigate dynamic channel assignment (DCA) in mobile communications systems using genetic algorithms (GA). Two new strategies using GA are proposed. In the first strategy, GAL, channels previously assigned are kept locked during the call holding time. In the second strategy, GAS, calls can be switched to different channels during the connection time. We evaluate the performance of the proposed GAs in a 49 hexagonal cell arrangement operating under uniform and nonuniform traffic distributions. Numerical results show that the average call blocking probability of the GAS strategy is lower than that of fixed channel assignment with a borrowing directional channel-locked(BDCL) scheme and of DCA based on Q-learning. The performance of the GAL strategy is better than Q-learning-based DCA for all the investigated cases.

A new full-vectorial FD-BPM scheme: application to the analysis of magnetooptic and nonlinear saturable media

A new three-dimensional (3-D) full-vectorial finite-difference (FD)-based beam-propagation method (BPM) is introduced for the analysis of magnetooptic and nonlinear materials. The refractive-index growth in the nonlinear material is allowed to saturate at high optical power densities (cubic-quintic media). The new formalism is capable of handling any combination of linear, nonlinear, and magnetooptic media, and combines, for the first time, the alternating-direction implicit technique (to improve computational performance) with the leapfrog longitudinal scheme (to simplify the solution of the coupled equations for transverse field components). The result is a numerical method that is both computationally efficient and numerically robust. The proposed BPM formalism is applied to investigate a (nonreciprocal) magnetooptic rib waveguide, as well as the new striking phenomena of light condensates propagation in cubic-quintic (saturable) media, the dynamics of which resemble those of liquid droplets.

An improved wide-angle FD-BPM for nonlinear and nonreciprocal waveguides

An improved wide-angle finite-difference beam-propagation method for the simulation of multifunction optical waveguides employing simultaneously nonlinear and nonreciprocal materials is introduced in this paper. This formalism can be applied to nonlinear Kerr-type materials exhibiting any kind of nonlinearity mechanisms. The nonreciprocal behavior is based on the difference between forward and backward propagation constants for TM modes. The z derivatives of the inverse permittivity are also taken into account so that longitudinal varying structures can be more accurately simulated.

SDN-enabled EDFA gain adjustment cognitive methodology for dynamic optical networks

We propose and experimentally validate an SDN-enabled cognitive methodology for EDFA gain adjustment that relies on case-based reasoning. Results show OSNR improvements over time demonstrating the cognition process regardless the deployed amplifier type.

Cognitive Methodology for Optical Amplifier Gain Adjustment in Dynamic DWDM Networks

Our recently proposed cognitive methodology for optical amplifier gain adjustment, that relies on case-based reasoning, showed optical signal-to-noise ratio improvements over time demonstrating the cognition process regardless the deployed amplifier type. In this paper, we extend our preliminary analysis exploring the cognitive methodology benefits for different and larger network topologies. The obtained results show agreement between networks, demonstrating the methodology suitability regardless the network scenario.

Design of a multifunctional integrated optical isolator switch based on nonlinear and nonreciprocal effects

The design of a new multifunctional integrated optical device capable of operating simultaneously as an optical switch and optical iso- lator is presented. The device consists of a multilayer directional coupler employing one nonlinear and one magneto-optic layer, with all other lay- ers being linear and isotropic. Therefore, only phase matching conditions are required for the device operation irrespective of the propagation di- rections and operation regime linear/nonlinear. The structure is opti- mized via a genetic algorithm and tested with a numerical formalism based on the wide-angle finite-difference beam propagation method. The results clearly demonstrate the ability of performing two distinct functions on the same device.