Multicast Routing And Spectrum Allocation In Elastic Optical Networks

With the increasing demand for high-bandwidth services such as multimedia and cloud computing,the tremendous increase in the annual communication bandwidth has brought great challenges to the current communication network.Wavelength division multiplexing(WDM)networks has a low utilization of spectrum due to its coarse granularity distribution.Thus,researchers have proposed flexible optical networks with features such as large capacity,high speed,and spectral flexibility.In elastic optical network,the spectrum is divided into smaller grid sizes,and the spectrum resources can be dynamically allocated according to requests size,which effectively improves the utilization of spectrum resources.On the other hand,multicast is an important transmission method in the network and is widely used to support applications such as cloud computing,Internet of Things,video conferencing.It is becoming an important part of Internet traffic.Compared with traditional IP multicast,multicast in optical layer avoids some inefficient optical to electorial to optical(O/E/O)conversion and provides better support for multicast.However,since the elastic optical network is subject to many constraints in spectrum allocation,like spectrum continuity and spectrum consistency constraints,the problem of multicast routing and spectrum allocation in elastic optical networks is more complicated.In this thesis,the issue of multicast routing and spectrum allocation(MRSA)is studied in elastic optical networks.The purpose of this study is to solve the problem of multicast routing and spectrum allocation under sparse splitting optical networks.An efficient strategie is proposed in Chapter 3.Some restrictions including modulation level assignment,maximum number of multicast capable(MC)nodes,and select of MC nodes,are considered.In addition,an effective algorithm is presented for MRSA,namely Pre-computing Shortest Path Tree-Distance adaptive Routing and Spectrum Allocation(PSPT-DMRSA).Before multicast routing,the appropriate pre-selected MC nodes are put in the network,and then the minimum spanning tree is established from source to destinations so as to reduce the number of links and transmission distance occupied by the entire multicast request.Furthermore,distance adaptive modulation level assignment is used for spectrum allocation.Simulation results show that the proposed algorithm achieves better performance in spectrum utilization.The establishment and dismantling of links dynamics discretizes available spectrum resources and inevitably generates spectrum fragments.For the large-capacity data transmission with time delay tolerance,this thesis proposes a holding-time-aware large-capacity data multicast routing and spectrum allocation algorithm in Chapter 4.Two-dimensional time-frequency domain has been used in this section.Moreover,the arrival time,deadline,and data amount of requests are comprehensively considered.The duration of requests are controlled by changing the bandwidth allocated.So the difference of the duration between adjacent requests could be minimized by this method.Hence,the generation of spectrum fragmentation in networks could be reduced.Simulation results show that the proposed algorithm can effectively reduce the blocking probability and improve the utilization of spectrum resources.