Select line speeds for single-hub SONET/WDM ring networks

Minimizing SONET ADM costs in single-hub SONET/WDM ring networks via traffic grooming has been discussed in a number of recent works. Recent work [9] gives the exact minimum costs of uniform traffic in both UPSR and BLSR/2 and proves that the BLSR/2 would never be more expensive than UPSR under any traffic pattern, if all wavelengths have same capacity. In this paper we consider how to groom both uniform and non-uniform traffic to minimize the cast of ADMs in the single-hub UPSR and BLSR/2 with mixed lint speeds. We especially explore the grooming of traffic when wavelengths have two different capacities g(1) = 1 and g(2) = 4. We show that the problem can be confined to just consider the traffic request r(i) less than or equal to 4 for all non-hub node i. By adopting the same cost model as in [3], i.e., ADMs with speed g(1) = 1 and g(2) = 4 cost 1 and 2.5 respectively, we provide optimal traffic partition and grooming for uniform traffic demands, and develop optimal or suboptimal solutions for non-uniform traffic demands, depending on the range of all demands from nonhub nodes.