Research On Routing And Spectrum Allocation Issues In Elastic Optical Networks

Traditional Wavelength Division Multiplexing(WDM)system uses the fixed wavelength resource allocation scheme,which cannot meet the rapid growing service demand due to the fast developing of Internet.Based on the Optical Orthogonal Frequency Division Multiplexing(O-OFDM),Elastic Optical Network(EON)can provide spectrum division with fine granularity(named frequency slot),which effectively improving the bandwidth resource utilization and bandwidth allocation flexibility.This thesis presents a in-depth research on routing spectrum allocation(RSA)and spectrum defragmentation in EON with theoretical analysis and numerical simulation.This thesis firstly gives a brief introduction of the principle,architecture and key technology of EON.The routing and spectrum algorithms are analyzed in detail.The problem of spectrum defragmentation in EON is analyzed and a fragment dispersion evaluation scheme is proposed.According to the quatity of the fragment,this thesis proposes a routing and spectrum algorithm based on the evaluation of spectrum fragment weight value.The improved algorithm treats the fragment degree as a prerequisite for choosing the route when service requirement comes.Theoretical analysis and numerical simulation show that this algorithm can make better use of the spectrum fragment and help improve the spectrum utilization.A periodic defragmentation algorithm based on the spectrum shifted is also proposed in this thesis.By combining two defragmentation schemes,the improved algorithm help redistribute the spectrum when traffic congestion happens.And the spectrum will be reconstructed only when the fragment degree reaches the threshold.Simulation shows that this algorithm has an improvement in the performance of traffic congestion rate and spectrum utilization.