| With the rapid spread of video applications and the appearance of new services, the bandwidth demand of users is increasingly growing. On the one hand, to meet the fast increasing bandwidth demand, the capacity of access networks is required to be improved greatly. On the other hand, with the increase in network capacity, the boosting speed of capital expenditure (CAPEX) and operating expense (OPEX) is obviously faster than the operating income. It leads that the operators’profit margins shrink. Therefore, with the ever-increasing bandwidth demand and the shrinking profit margins, the broadband optical access network is developing toward larger capacity, wider coverage, and higher cost efficiency. The metro aggregation network and access network will be converged into optical metro-access network.This dissertation studies on the key techniques, including network architecture, protection mechanism of survivability, dynamic resource scheduling mechanism and algorithms, and power saving mechanism and algorithms, of the optical metro-access network. A series of innovative research results have been achieved. The main innovative contribution and work of this dissertation are as follows:1) Aiming at the evolution demand including large capacity, wide coverage, flat structure, dynamic two-dimensional wavelength and timeslot resource allocation, backward compatibility, strong survivability, and low power consumption of optical access network, we propose a ring-tree time and wavelength division multiplexing optical metro-access network architecture based on wavelength selection and conversion in remote nodes (RNs). The proposed network architecture enhances network capacity and coverage via optical amplification and optical-electrical-optical relay at RNs. The node merging and integration of metro and access reduce the CAPEX and OPEX. By common-channel and channel associated controlling signals two-dimensional wavelength and timeslot resource of the whole network are dynamically scheduled. The centralized controlling signals dynamically control RNs to choose adding and dropping wavelengths by tuning optical switches and control the upstream and downstream bandwidth of optical network units (ONUs). The backward compatibility is achieved by the adoption of wavelength conversion at RNs. By the ring-tree topology, cost-effective survivability protection is realized and to reduce power consumption the sleep of the whole network is executed under centralized control of the central office (CO). Simulation results show that with320Gbps total capacity,1OGbps rate of a single wavelength and forward error correction the proposed network architecture can have100km metro coverage and20km access coverage, and carry25RNs and3200ONUs.2) It is a key technology problem to locate failure correctly and perform protection switching for strong survivability in optical metro access network architecture with dynamic wavelength scheduling such as the above proposed architecture. Moreover, existing survivability evaluation methods do not take the failure probability differences caused by differences in the fiber link length into account. There is no quantitative analysis for the compromise of the cost and survivability performance. To solve the above problems, this dissertation presents a cost-effective survivability protection scheme based on fault location with control channel and dynamic wavelength scheduling. For the proposed scheme, the quantitative comprehensive analysis of survivability and cost of the whole network with caution of link length is carried on. The proposed survivability protection scheme provides protection to metro trunk fiber of the greatest failure impact by using the fiber ring. The control channel is used to locate and detect failure. To finish protection switching, the CO and RNs tune the protection switches respectively. At the same time, the proposed scheme utilizes dynamic wavelength scheduling ability to transfer traffic for aborted traffic line card in the CO. Analysis and calculations show that at most the proposed scheme can pay only1percent of the cost for survivability protection and bring in54%improvement in survivability. The proposed scheme can finish protection switching within50ms.3) In order to reduce unit bandwidth cost for the network, extend lifetime of optical switches and other components, and reduce the gain transient effect on transmission performance in network with dynamic wavelength scheduling, the dynamic wavelength and bandwidth allocation (DWBA) mechanism and the heuristic algorithm aiming at the minimum tuning times are proposed in this dissertation. The proposed DWBA mechanism and algorithm improve resource utilization by balancing loads on different wavelengths. By following the previous wavelength allocation results first, the lifetimes of optical switches and other components are extended. The Erbium doped fiber amplifier gain transient effect is relieved by limiting the changing magnitude of wavelength number and adding guard interval. Simulation results show that compared to the static wavelength allocation, the proposed DWBA mechanism and algorithm can bring in32.9%improvement for bandwidth utilization, reduce5.1active wavelengths in average, reduce the unit bandwidth cost by28.7%at least and support10-year component lifetime.4) Most of the existing mainstream sleep-based power saving schemes only take effect under light load. The performance of intra-cycle sleep of RNs and ONUs will be affected by cyclic sleep of the CO. It results in that the power saving effect of the whole network is hard to be the best. For the above problems, this dissertation proposes the hybrid intra-cycle and cyclic sleep power saving scheme for the whole network. Under heavy load in the proposed power saving scheme CO, RNs and ONUs perform short intra-cycle sleep by using idle slots among the sending and receiving traffic windows. Under light load RNs and ONUs perform long cyclic sleep to reduce unnecessary overhead time, whereas the CO still performs intra-cycle sleep to improve the power saving performance of RNs and ONUs and achieve the best power saving effect for the whole network. Simulation results show that under different loads besides the heavy load, the proposed scheme can save54.0%power consumption at least and is suitable to scenarios of different traffic distributions. Compared to existing sleep-based schemes, in the proposed scheme under different loads in average41.6%power consumption is further reduced. Compared to schemes in which the CO performs hybrid intra-cycle and cyclic sleep, the proposed scheme can further improve the whole power saving effect by3.5%at most by entering intra-cycle sleep only for the CO. |
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