The problem of RWA with tunnel allocation in the MG-OXC networks is considered by us first. We propose an ILP formulation that gives the optimal solution for the static traffic under the tunnel length constraint. We extend the auxiliary graph model from our previous work to the layered auxiliary graph model to facilitate our ILP formulation. This allows us to consider the RWA and fix-length tunnel allocation sub-problems simultaneously in order to exploit optimal solution. We conduct the simulation experiments to compare the performance between different heuristics and the ILP solution. We first determine a set of fix-length tunnels using WTA, which are based on the auxiliary graph model [7]. Then we adapt one of the routing sequence schemes to route the static traffic over the tunnels. The simulation results show that WTA with the Shortest Path First scheme reaches nearest to the optimal solution. For the dynamic traffic, the results show that WTA and PC-WTA outperform CB-STA significantly. In the 10-node network topology, the performance of WTA and PC-WTA is even compatible with optimal solution. We also observed that PC-WTA outperforms WTA when the number of wavelength-switching ports is small. In MG-OXC networks wavelength-switching ports are critical resources and PC-WTA utilizes the wavelength-switching ports more efficiently.
In chapter 3, we arrive at a preliminary conclusion that the tunnel length constraint is important in terms of blocking performance when we allocate tunnels in MG-OXC optical network. If the length of a tunnel is too long, it consumes more fiber/waveband link recourses, which means fewer tunnels can be established later.
On the contrary, if the length of a tunnel is too short, even more tunnels can be established later; since more wavelength switching ports would be consumed with more tunnels, it results that less ports are available on the routing in the future.
Therefore, the tunnel length is a tradeoff between fiber links and switching ports. In this paper, we use both analysis and simulation results to prove that. The numerical results tell us preliminarily that the most suitable length of a tunnel should be the smallest integer greater than the average hop distance as claimed in [2] or the smallest integer greater than the average hop distance plus 1 which depends on that the average hop distance is far from or close to the smallest integer greater than the average hop distance. However, in order to obtain a more general conclusion, we will compare more numerical results for different network topologies especially for networks with larger average hop distance in the future.
In chpapter 4, we investigate the protection schemes for the single link failure in the MG-OXC networks. Path protection based scheme TPP provide a straightforward resolution. However, the absence of taking protection requirement into consideration when allocating tunnels propels us to provide another scheme, TSP, to improve the performance of TPP. In TSP, a backup tunnel is always allocated with a working tunnel. Hence, the working path of a lightpath request can be naturally segmented according to the switching types along its route, with each segment protected in its corresponding layer. In addition to the intrinsic superiority of resource sharing in segment protection than in path protection, TSP also utilizes less wavelength-switching ports for a lightpath request. Simulations are conducted to compare the performance of TPP and TSP. The results show that TSP outperforms TPP in terms of blocking probability, due to the better sharing efficiency of TSP in link capacity and wavelength-switching ports.
Despite the advances in wireless physical-layer technologies, interference is still the main factor of the decreasing in wireless network bandwidth. However, when multiple channels are available, equipping each mesh node with multiple NICs allows
the network to use different radio channels simultaneously. Then the available bandwidth can be increased because of the decreasing of interference.
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