The Optical Network Planning And Optimization Of System Design RWA Problem

With the development of networking technologies and new services of Internet, there is an explosive growth trend of Internet traffic, which needs tremendous network bandwidth. Wavelength Division Multiplexing (WDM) is a promising, as well as flexible approach that exploits the enormous bandwidth of the optical fiber to satisfy the urgent needs. By utilizing equipments like Optical Cross Connect (OXC), WDM networks could provide end-to-end light-paths to source-destination node pairs and re-use wavelength resources. On the other hand, a single node or span failure will cause severe service disruptions in such networks, since large amount of traffic is aggregated to less equipment owing to the use of WDM technology. Hence, survivability has becoming a critical problem in network design.Since mesh-based solution could offer efficient capacity configuration, it has becoming the major architecture of long-haul networks. Based on the"engineering-oriented SDH, DWDM network planning and optimization software"(abbr. NPO), which the author has took part in, Routing and Wavelength Assignment (RWA) in survivable networks is brought forward as a key problem during the process of planning and optimizing of mesh optical network. Given a set of requests, it is defined as RWA, or RCA (Routing and Channel Assignment) problem that to route light-paths and allocate wavelengths properly so as to minimize the block probability as well as the required number of wavelengths to establish light-paths. In path restorable optical networks, RWA algorithms aim to ensure the survivability by (1) finding a pair of physical disjoint paths for every demand, and (2) assigning reasonable wavelength for every path. Combined with survivability design, this type of RWA algorithm would be called for iteratively by the topology planning and optimization module, thus it has great influence on final result.Two different types of circumstances are investigated: (Ι) every node has the ability of full-range wavelength conversion; and (ΙΙ) none node could be able to convert wavelength.As there is no wavelength continuity constraint for networks belong to (Ι), the RWA problem is simplified into capacity placement problem like in any traditional circuit-switching networks. Chapter 3 presents a heuristic algorithm, called MSC-JOCP, to address this issue. The key idea of this algorithm is choosing a pair of link/node-disjoint primary (/working) route and backup (/protection) route for every demand, given attention to load balancing, as well as maximally sharing the spare capacity, by dynamically modulating the metrics of network spans. Furthermore, this algorithm would not change the routes of existed traffic, which is viewed as the main drawback of joint optimization algorithms. MSC-JOCP has been applied successfully in NPO Version 1.0, and is proved to be applicable for SDH networks, too.RWA algorithms for network in category (ΙΙ) is more complex because of the wavelength continuity constraint, i.e. a light-path should use the same wavelength on all spans along its route. The TA-RWA algorithm proposed in Chapter 4 solves RWA in two parts: In routing sub-problem, it improves the Trap Avoidance routing algorithm (namely xdh-TA algorithm) under SRLG-disjoint constraint. The new method presented could be able to avoid traps as well as to balance the load. In wavelength assignment sub-problem, TA-RWA uses different graph coloring algorithms and then compares their performance according to the simulation statistics. This thesis also makes comparative research on different traffic pre-treatment methods by simulation.