 In Routing and Wavelength Assignment (RWA) problem,
in the absence of wavelength converters,
the task is to find such a route and a wavelength for each endtoend lightpath
so that no link has two lightpaths sharing the same wavelength.
 In dynamic RWA problems, lightpath requests arrive according to (Poisson) process
 Currently established lightpaths correspond to the state of the system
 Decision on how customer/request is handled triggers a state change in the system
 Constitutes a MDP, where the objective is to minimize the blocking probability
 Enormous state space defies the computation of value functions, and thus also the policy iteration
 First policy iteration can be carried out by estimating the relative values by onthefly simulations [13]
Related publications:
[1] 
E. Hyytiä and J. Virtamo,
Dynamic Routing and Wavelength Assignment Using First Policy Iteration,
in the Fifth IEEE Symposium on Computers and Communications, ISCC'2000,
pp. 146151, 2000, Antibes, Juan les Pins, France.

[2] 
E. Hyytiä and J. Virtamo,
Dynamic Routing and Wavelength Assignment Using First Policy Iteration, Inhomogeneous Traffic Case,
in the International Conference on Performance and QoS of Next Generation Networking, P&QNet2000, pp. 301316, 2000, Nagoya, Japan.

[3] 
E. Hyytiä and J. Virtamo,
Adaptive Importance Sampling in Routing and Wavelength Assignment,
European Transactions on Telecommunications (ETT), vol. 13, no. 4, pp. 331339, 2002, Special Issue on Rare Event Simulation.



Figure: A sample RWA problem with 8 lightpaths.
References:
 Richard Bellman, Dynamic programming, Princeton University Press, 1957.
 Sheldon M. Ross, Applied Probability Models with Optimization Applications,
HoldenDay Inc., 1970.
 Ronald A. Howard, Dynamic Probabilistic Systems, Volume II:
SemiMarkov and Decision Processes, Wiley Interscience, 1971.
