Notícias

Banca de DEFESA: ADRIANA DE NAZARE FARIAS DA ROSA

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
DISCENTE: ADRIANA DE NAZARE FARIAS DA ROSA
DATA: 26/06/2015
HORA: 15:00
LOCAL: Auditorio do Instituto de Tecnologia - ITEC
TÍTULO:

MODELING AND PERFORMANCE EVALUATION OF DYNAMIC SPECTRUM ALLOCATION SCHEMES IN ELASTIC OPTICAL NETWORKS


PALAVRAS-CHAVES:

ELASTIC OPTICAL NETWORKS; SPECTRUM ALLOCATION. SPECTRUM FRAGMENTATION. BLOCKING PROBABILITY. MARKOV MODELING


PÁGINAS: 50
GRANDE ÁREA: Engenharias
ÁREA: Engenharia Elétrica
RESUMO:
The current trends in optical fiber communications are rapidly approaching the physical capacity  
limit of standard optical fiber. It is becoming increasingly important to efficiently utilize spectral resources 
wisely to accommodate the ever-increasing Internet traffic demand. However, the rigid and coarse ITU-T grid 
specifications regarding the spectrum usage restrict the granularity of bandwidth segmentation and allocation, 
which frequently causes a mismatch between the allocated and the actual requested link bandwidth. This often 
leads to over provisioning, where usually more resources are provided than necessary. Recently, the concept 
of elastic optical networks (EONs) has been proposed in order to reduce the waste of spectra resources. In 
networks with such feature enabled, modulation parameters and central frequencies are not fixed as in the 
traditional WDM networks: the resources can be allocated with fine granularity, which can adapt to the 
granularity of the requested bandwidth without over provisioning. This results in efficient usage of spectra  
resources. However, elastic optical networks must satisfy dynamic connection add and drop over spectral  
resources that inevitable results in fragmentation of the spectrum. In EONs, spectrum fragmentation is an 
important and inevitable problem, because it reduces the spectral efficiency. As consequence, the blocking 
probability (BP) is increased due to scattered gaps in the optical grid. Currently, several metrics have been 
proposed in order to quantify a level of spectrum fragmentation. Approximation methods might be used for 
estimating average blocking probability and some fragmentation measures, but are so far unable to accurately 
evaluate the influence of different requested connection bandwidths and do not allow in-depth investigation of  
blocking events and their relation to fragmentation. This thesis presents the analytical study of the effect of  
fragmentation on requests' blocking probability, which is still under-explored. In this study, new definitions for 
blocking that differentiate between the reasons for the blocking events were introduced. An analytical framework based on Markov modeling was proposed in order to calculate steady-state probabilities for the  
different blocking events and to analyze fragmentation related problems in elastic optical links under dynamic 
traffic conditions. Statistical investigations were derived in order to investigate how different allocation request 
sizes contribute to fragmentation and blocking probability. This work is complemented with the introduction of  
a new accommodated fragmentation metric that allows better differentiating between very small variations of  
spectrum occupancy. Moreover, we show to which extend blocking events, due to insufficient amount of  
available resources, become inevitable and, comparing to the amount of blocking events due to fragmented 
spectrum, we draw conclusions on the possible gains one can achieve by system defragmentation. We also  
show how efficient spectrum allocation policies really are in reducing the part of fragmentation that in particular 
leads to actual blocking events. Simulation experiments are carried out showing good match with our  
analytical results for blocking probability in a small scale scenario. Simulated blocking probabilities for the 
different blocking events are provided for a larger scale elastic optical link.

MEMBROS DA BANCA:
Presidente - 2153181 - JOAO CRISOSTOMO WEYL ALBUQUERQUE COSTA
Interno - 1353026 - CARLOS RENATO LISBOA FRANCES
Externo à Instituição - MARCELO EDUARDO VIEIRA SEGATTO
Externo à Instituição - MARIA JOSE PONTES
Externo à Instituição - MARIA THEREZA MIRANDA ROCCO GIRALDI
Externo à Instituição - SOLON VENÂNCIO DE CARVALHO
Notícia cadastrada em: 29/04/2015 09:42
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