Abstract
As more andmore development in the broadband services and multimedia applications, the bandwidth requirement continues to grow. Providing high-speed and high-capacity communication networks has become a significant subject. Owing to the progress of optical technologies in recent years, the optical networks have become the most potential candidate for future high-speed and high-capacity communications networks. Especially, the Wavelength-Division Multiplexing (WDM) based systems have received significant investigations. The bandwidth allocation problem is a significant research subject in WDM-based networks since the number of wavelength channels in a fiber is limited. In this dissertation, the bandwidth allocation problems for connection-oriented communications in three different kinds of WDM-based optical networks are investigated. The first subject is the isochronous bandwidth allocation problem on an interconnected WDM Network. A novel architecture named as Star Coupler Bridge (SCB) is proposed for interconnecting WDM-based LANs or MANs with slot-based bandwidth access scheme. The novel characteristic of SCB is its capability of merging and splitting the bandwidth of different isochronous connections into and from the same time-slots. This scheme will raise the bandwidth utilization and reduce the call blocking rate. The architecture and the operation of SCB is detailed. The isochronous bandwidth allocation problem is formally defined and its NP-hardness is proved. A heuristic algorithm is proposed for the isochronous bandwidth allocation problem. The simulation results demonstrates the effectiveness of merging and splitting by the proposed SCBs. In the second subject, a novel architecture of all-optical WDM-based transport network with time-shared wavelength channels is developed and the the corresponding bandwidth allocation problem is discussed. The network is composed by interconnecting the novel architecture named as Time-Wavelength-Space Router (TWSR). The major property of TWSR is that no complicated optical buffering and optical contention resolution schemes is exploited, but only the simplified time-slot synchronization and alignment components are adopted. This design compromises the merits and demerits of the conventional wavelength routers and optical packet switches. The bandwidth of each wavelength is accessed by cyclic TDM mode. The time-slot, route and wavelength assignment of each connection request must be decided before starting the communications. According this pre-determined assignment, the TWSRs tune their switching of the input/output ports to let the optical signal of the connections passes by. This bandwidth allocation problem is named as Routing, Wavelength and Time-slot Assignment (RWTA) problem. The RWTA problem is formally defined and a heuristic algorithm is proposed. The effectiveness of the proposed network is evaluated by comparing the simulation results with the ones of the traditional wavelength-routed networks. The third subject is the node placement problem in WDM-based multihop local network. The network consists of a passive star-coupler and the attached communication nodes. Each communication node is equipped with fixed wavelength transmitters and fixed wavelength receivers. The wavelengths and the communication nodes compose the virtual topology which is independent of the physical star structure of the network. The node placement problem is defined as to place each node on a appropriate vertex of the given virtual topology under the condition of given amount of traffic between each pair of nodes. Double Fixed-step Loop Network (DFLN) is used as the virtual topology. The mathematical model of the node placement problem is formally defined. In addition, the post-optimization problem occurring when the objective values become non-optimal as the traffic has been changed is also investigated. The heuristic algorithms for these problems are proposed and the effectiveness is demonstrated by simulation results.