Routing and Wavelength Assignment Algorithms for Multicast Communication in All-optical WDM Access Networks

• Main Authors: San-Nan Lee, 李勝楠
• Other Authors: 黃依賢
• Format: Others
• Language: zh-TW
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/01710498959949715079

博士 === 元智大學 === 資訊工程學系 === 94 === The rise of the Internet has caused enormous variations in network applications, especially for multimedia. On the WDM system, the routing and wavelength assignment problem can be solved by the contention-based scheme or the reservation-based scheme. Several important multimedia applications, such as video on demand, video conferencing, and distribution networks, share this characteristic that is suitably transmitted by the multicast scheme. In this dissertation, the contention-based schemes, stochastic model and PEM algorithm, are proposed to aggregate packets and reschedule real-time packets in the WDM ring access network. The reservation-based scheme, RTRWA-DC, is proposed in the WDM mesh access network. It uses the virtual ring to connect all multicast session member and improve the performance in terms of the call blocking probability, channel utilization and user capacity. At first, this dissertation discusses the scheduling/rescheduling algorithms for ring topology. The Self-Organized Map (SOM) neural network is used to generate a stochastic generative model to assign a proper channel to a packet and achieve packet aggregation on a cost-effective OADM. Finding a way to decrease the transmission time can increase the performance of a WDM access network. In general, the applications for packet transmission between several nodes, such as multicast communication, voice, and video, share a property: same destination. This is why a heuristic algorithm is proposed to aggregate packets. Secondly, a novel real-time packet rescheduling algorithm, called the PEM (PDS-EAC-MTD) algorithm, is proposed. This algorithm uses a token-passing protocol to achieve QoS on a WDM Ring Access Network. The PDS (Priority-Differentiated Scheduling) algorithm deals with real-time packets, allowing them to be transmitted first so that the front line of the prescheduled nonreal-time packets can be inserted into the queue. The EAC (Earliest Available Channel) algorithm selects the earliest available data channel independently of the availability of the destination. The MTD (Minimum Time Difference) algorithm selects the minimum-time-to-wait channel to transmit the nonreal-time packet and quickly establishes the path of real-time packets. The discussion of the ring algorithm leads to a virtual ring using the ring-tree-based routing and wavelength assignment (RTRWA) algorithm. Multicast session communications in WDM mesh networks require the development of efficient multipoint-to-multipoint multicast algorithms. Several heuristics have approximate solutions using lightpath or light-tree for one-to-multipoint multicast communications and few papers discuss the multipoint-to-multipoint multicast problems in WDM mesh networks. We propose a ring-tree-based routing and wavelength assignment (RTRWA) algorithm to enhance the network performance for multipoint-to-multipoint multicast communications. The RTRWA algorithm can find an optimal ring that covers all multicast group members to establish a connection. The simulation results show that the proposed algorithm outperforms the light tree-based algorithm in terms of blocking probability, user capacity, and mean maximum transmission time for various numbers of wavelengths, request rates, and session sizes, especially those featuring larger session sizes and lower request rates. How to ensure that a packet is transmitted given the limited transmission time is very crucial. A ring-tree-based routing and wavelength assignment with delay constraint (RTRWA-DC) reduces the number of searching ring paths to achieve low complexity and sufficient number of links to increase the chance of successful connections. The fuzzy logic control (FLC) in FLC LLR algorithm is based on the traffic load and hop counts to determine whether or not the lightpath can be established. The fuzzy logic theory enhances the ring-tree-based routing and wavelength assignment with delay constraint (RTRWA-DC) algorithm. Simulation results show that the RTRWA-DC is more effective for resource utilization than the tree scheme in terms of lower call blocking probability and link utilization even in strict delay constraint. It is suitable for big group size and long holding time of multipoint-to-multipoint multicast communication.