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 previous works. Previous work gives the exact minimum costs of uniform traffic in both unidirectional path-switched ring (UPSR) and two-fiber bidirectional line-switched ring (BLSR/2) and proves that the BLSR/2 would never be more expensive than UPSR under any traffic pattern, if all wavelengths have the same capacity. We consider how to groom both uniform and non-uniform traffic to minimize the cost of ADMs in the single-hub UPSR and BLSR/2 with mixed line speeds. We especially explore the grooming of traffic when wavelengths have two different capacities g/sub 1/=1 and g/sub 2/=4. We show that the problem can be confined to just consider the traffic request r/sub i//spl les/4 for all non-hub nodes i. By adopting the same cost model of Gerstel, Lin and Sasaki (see Proc. IEEE Infocom 99), i.e., ADMs with speed g/sub 1/=1 and g/sub 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 non-hub nodes.