Protection Techniques And Resource Optimization For Next Flexible Optical Networks

With the rapid development of technologies such as cloud computing,big data,artificial intelligence,virtual reality,and new Internet services such as video broadcasting and information streaming,the network capacity is urgently required in order to meet the high speed and greater capacity requirements for high-bandwidth and on-demand applications.With the advantage of flexible bandwidth allocation,diverse modulation methods,distance adaptation,etc.,FON has become one of the important evolution solutions of next-generation optical network technology.Network protection and resource optimization are critical issues for optical network survivability to maintain resilience against network failures.The transmission capacity has largely increased in which a single optical fiber can carry over Tbps-level network capacity,then the network failures can cause huge data loss and service disruptions,especially for the increasing EODN.Therefore,it is urgent to conduct research on protection and optimization,providing the network survivability solutions for next-generation FON.This dissertation addresses several protection techniques and resource optimization approaches for next-generation FON single-link failure and disaster failure.The past few decades have witnessed the evolution of optical networks from SLR-WDM towards MLR WDM and EONs architectures.Two classic protection schemes,namely p-Cycle protection and path protection,are are studied to are studied to achieve high protection capacity efficiency via ILP/MILP,heuristic algorithms and exact algorithms,solving 100% capacity protection,spectrum resource allocation and distance adaptive rate/modulation selection.These protection approaches are studied to achieve high protection capacity efficiency while taking into account the equipment cost,power consumption and resource usage.The main work has been carried out as follows:1.p-Cycle protection and resource optimization are studied for MLR-WDM networks with rate flexibility against single link failure scenario.Considering the advantage of using multi-rate transponders,a distance-adaptive and low CAPEX cost p-cycle protection scheme is proposed without candidate cycle enumeration.Specifically,path-length-limited p-cycles are designed to use appropriate line rate depending on the transponder cost and transmission reach.A MILP model is formulated to directly generate the optimal p-cycles with the minimum CAPEX cost.Additionally,Graph Partitioning in Average algorithm and Estimation of cycle numbers algorithm are developed to make the proposed MILP model scalable.Simulation results show that the computational time is largely reduced with a good solution when using the Graph Partitioning in Average algorithm and Estimation of cycle numbers algorithm at the same time.Compared with conventional p-cycle protection without candidate cycle enumeration in(Single-Line-Rate,SLR)-WDM,and p-cycle protection with candidate cycle enumeration in MLR-WDM,the proposed p-cycle protection without candidate cycle enumeration in MLR-WDM reduces the CAPEX up to 40%,mainly in transponder cost.The number of transponder utilization in proposed p-cycle protection decreased to less than half of the conventional ones.The results indicate that the protection cost can be greatly reduced by p-cycle protection with candidate cycle enumeration in MLR-WDM.2.Regarding the power consumption in survivable EONs,power-efficient directed p-cycle protection scheme for asymmetric traffic is proposed.Owing to the advantage of distinguishing traffic amount in two directions,directed p-cycles consume low power by allocating different Frequency Slots(FSs)and modulation formats for each direction.An MILP model is formulated to minimize total power consumption under constraints of directed cycle generation,spectrum assignment,modulation adaptation and protection capacity allocation.To increase the scalability,the MILP model is decomposed into an improved cycle enumeration and a simplified ILP model.Compared with conventional undirected p-cycle protection,as the traffic asymmetry increases from0% to 100%,the energy reduction in the proposed directed p-cycle protection grows from 0% to40%.In addition,the energy reduction in the proposed directed p-cycle protection begins with35% after introducing the any-casting service in elastic data center networks.The results indicate that directed p-cycle protection offers an efficient solution for energy-efficient protection in EONs under asymmetric traffic.3.In order to improve the spectrum usage efficiency in p-cycle protection,SS-p-cycle protection is proposed for survivable EONs with and without spectrum conversion.SS-p-cycles permit to reduce spectrum usage and Spectrum Fragmentation Ratio(SFR)by leveraging potential spectrum sharing among multiple p-cycles that have common link(s).The ILP formulations are designed in both cases of with and without spectrum conversion to minimize the spectrum usage of SS-p-cycles which can obtain the optimal solution in small instance,and a time-efficient heuristic algorithm is developed to solve large-scale instances.The simulation results show that the maximum spectrum index is almost the same in SS-p-cycles with/without spectrum conversion,in which the difference appears in the total link spectrum utilization.Compared with the no spectrum shared p-cycle protection,the proposed SS-p-cycles earn spectrum reduction up to 28% and 57% for total link spectrum utilization and maximum spectrum index,respectively.The results indicate that SS-p-cycles can largely reduce spectrum usage for EON protection.4.Large-scale disaster failures are being threatening the survivability of EODN although single link failure is the most common failure scenario.The disaster-survivable cloud service provisioning problem is investigated regarding the content placement,routing,protection of path and content,and spectrum allocation.Cloud services allow to use another DC node with replicated content to ensure disaster survivability.ILP models are formulated for DEBPP and SEBPP,both of which aim at minimizing the spectrum usage.To increase the scalability,a CG based approach decomposes the ILP models into a master problem and a price problem,and solve the two problem iteratively.The master problem selects the optimal routing path and spectrum allocation for the configuration set while the price problem calculate and update the configuration set.The simulation results show that the CG based approach effectively solves the large-scale problem.The spectrum usage in SEBPP is reduced by 15% compared with the DEBPP.As the number of DC nodes and replicas increase,the spectrum usage goes down in the begging,but it does not continue to decrease.The results indicate that a reasonable number of DC nodes and replicas is enough to earn the efficient spectrum usage in disaster-survivable EODN.