Investigation Of Dynamic Protection In Elastic Optical Networks

Nowadays, the rapid development of multimedia services brings the problem that the required bandwidth resources grow exponentially. Meanwhile, the rapid development of Internet applications makes more and more services need the future network to provide large and variable capacity and flexible services. In this context, the optical networks with large communication capacity must become an essential part of network infrastructure in the future. Unlike the traditional wavelength-division multiplexing networks that operate on discrete wavelength channels with a bandwidth of50or100GHz, the new elastic optical networks realize the exchange of sub-wavelength granularity in the physical layer and can allocate optical spectrum with a finer granularity. Therefore, the EONs have attracted intensive research and industry interests, as it can manage the bandwidth flexibly and improve the spectral efficiency and become a direction of the future intelligent optical networks. Meanwhile, in order to keep the services transmitting stably in the EONs, this paper studies the problem of the survivability of EONs. From the aspect of fast recovery, this paper designs several dynamic p-cycle protection algorithms in the O-OFDM based EONs which ensure100%recovery under any link failure.According to the research of two main protection schemes which are the path protection and the link protection, this paper chooses the link protection scheme to realize the fast recovery in the EONs. In the research about the link protection, we find that the p-cycle has both the effective recovery efficiency (p-cycle has the same level of recovery efficiency as the mesh networks) and fast recovery speed (the recovery speed of p-cycle can be compared with line-switched self-healing ring). Inspired by the p-cycle configuration algorithm in the WDM networks, we first designs a p-cycle protection algorithm which uses the dynamic configuration based on protection efficiency (PE-p-cycle). This algorithm configures a p-cycle for each link on the working path of the request and multiple requests which do not share the working link can share the same p-cycle. At the same time, we introduce the metric of protection efficiency for each p-cycle and configure the p-cycle (s) dynamically according to the protection efficiency from high to low efficiency until the request is fully protected.In order to reduce the spectrum fragmentation caused by the dynamic setting up and tearing down protection resources and to improve the protection efficiency, this paper researches the p-cycle protection problem which uses the static pre-configured protection resources. We employ the PWCE technology for the spectrum resources planning and divide the whole resources into three layers which are the backup FS-layer, the working FS-layer and the hybrid FS-layer (The hybrid FS-layer is used to solve the "limited covering" problem caused by the conflict of the p-cycle set in the protection FS-layer). The backup FS-layer is for the FS’that are reserved to configure p-cycles and the working FS-layer contains the FS’ that can be allocated to the working paths of the requests. According to the characteristic of the PWCE technology, the designed PWCE based p-cycle protection algorithm (PWCE-p-cycle-SP) brings down the computational complexity and the spectrum fragmentation degree. Simulation results show that PWCE-p-cycle-SP can achieve lower blocking probability than the PE-p-cycle algorithm which uses the dynamic p-cycle configuration method.For the network topologies with proper connectivity, we can obtain Hamiltonian cycles that traverse all nodes in the topology only once. By replacing the PWCE p-cycle set (i.e. the p-cycle set in the protection FS-layer) with Hamiltonian cycles, the hybrid FS-layer is eliminated and the "limited covering" problem in PWCE-p-cycle-SP is settled. Simulation results show that compared with the PWCE-p-cycle-SP, the Hamiltonian cycle based p-cycle protection algorithm (Ham-p-cycle-SP) reduces the blocking probability significantly.Although Ham-p-cycle-SP algorithm enhances the protection efficiency, it makes the length of the protection path become longer and causes excessive delay as well as intolerable physical impairments. Besides, the Hamiltonian cycles do not exist in all the network topologies. In order to make the general network also have the ideal protection efficiency, this paper proposes the partition technology which divides the whole topology into several small areas and makes sure that each area has a Hamiltonian cycle. In this way, we can respectively use Ham-p-cycle-SP algorithm in each area and among these areas for individual protection. Simulation results show that the p-cycle protection algorithm with the partition technology (P-Ham-p-cycle-SP) shortens the average length of protection path and achieves low blocking probability at the same time.