| Summary: | 碩士 === 輔仁大學 === 電子工程學系 === 91 === We studied the performance problem and scheduling problem for using optical network to be an access network in different optical network topology. In this study, optical access network is divided into two types to be considered. One is the passive optical access networks, the other is active optical access network.
When studying an optical passive access network, we considered an Ethernet Passive Optical Network (EPON), which is an emerging access network architecture and combining low-cost point-to-multipoint fiber infrastructure with Ethernet. This paper presents a group polling media access control (MAC) protocol for an EPON. For heavy traffic load, conventional polling scheme obtains a high throughput; however, for light traffic load, conventional polling scheme wastes polling/reply time and obtains a longer access delay since most polls obtain negative replies and therefore waste bandwidth and enlarge delay. In this paper, we compromise the above conditions and propose a group-polling scheme for media access control in an EPON. The performance of the proposed MAC protocol is evaluated through simulations. Simulation results demonstrate that the proposed scheme significantly improve mean packet delay and reduce average queue size.
When studying an active optical network, we consider the problem of QoS (Quality of Service) guaranteed traffic scheduling in W/TDM (Wavelength/Time Division Multiplexing) networks with arbitrary tuning latencies. The emerging multimedia applications require highly heterogeneous and time-varying quality of service. To meet the diverse service requirements, two classes of traffic are considered: constant bit rate (CBR), variable bit rate (VBR). To minimize the required switching modes so as to reduce the impact of tuning latencies and system’s blocking rate, an efficient time slot assignment heuristic algorithm is proposed. To exploit the on-off and bursty nature of VBR traffic, the proposed traffic scheduling algorithm enables the statistical multiplexing (i.e., share concept) for carrying VBR service meanwhile the QoS is also guaranteed. The performance of the proposed algorithm is evaluated via simulations. Simulation results demonstrate that the proposed algorithm significantly improve the system performance.
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