Combined WDM and SONET network design

Abstract

This paper considers grooming of low speed traffic into high speed lightpaths in a WDM based optical ring with a primary goal of reducing the cost of the entire system, which is dominated by the cost of the SONET transmission equipment connected to the optical ring. The paper attempts to enumerate the architectural options provided by SONET to arrive at a cost-effective solution, including unidirectional path-switched rings (UPSR) and bidirectional line-switched rings (BLSR), use of back-to-back connections between SONET ADMs to reduce the overall cost, and use of different ring speeds (OC-48 and OC-12). To demonstrate each of the architectures, a uniform traffic is considered and its grooming and resulting SONET architecture demonstrated. The paper deviates from earlier approaches which break the problem into two steps: traffic grooming and assignment of lightpaths to rings, in that it looks at the problem as a whole and tries to solve it in a single step. The paper also considers the characteristics of SONET UPSR and BLSR rings and how these affect the grooming. The paper derives lower and upper bounds to these problems for uniform traffic and shows how these improve on known results.