We consider off-line capacity assignment in wavelength-routed ring networks with path restoration under arbitrary traffic patterns. We present service and restoration wavelength-assignment (WA) algorithms under shortest-path routing and analyze their performance in terms of the wavelength requirement. We obtain bounds to the wavelength requirement, using a routing-independent traffic parameter, and we show that both the service wavelength requirement and the total wavelength requirement under these algorithms lie within a factor of 2 of the optimal that can be achieved by any routing and WA algorithm. These results are among the few analytical results regarding the wavelength requirement in rings without wavelength conversion. We also propose vertex-coloring-based WA algorithms and demonstrate their efficiency through performance bounds and simulations. Results also show that knowledge of which link failed provides little capacity savings, and hence our algorithm with failure-independent restoration WA offers an attractive solution to reduce the fault-monitoring costs and the restoration signaling complexity.
© 2002 Optical Society of AmericaPDF Article