Results

**1 - 3**of**3**### Survivable Routing and Regenerator Placement in Optical Networks

, 2012

"... The large capacity of WDM optical networks facilitates the transportation of impressive volumes of traffic, which make survivability schemes that can reroute traffic upon a failure in the network highly important. Besides survivability, the signal quality in optical networks, which degrades along i ..."

Abstract
- Add to MetaCart

(Show Context)
The large capacity of WDM optical networks facilitates the transportation of impressive volumes of traffic, which make survivability schemes that can reroute traffic upon a failure in the network highly important. Besides survivability, the signal quality in optical networks, which degrades along its path due to physical impairments, needs consideration. In this paper, we consider the design problem of where to place regenerators in the network such that both the primary and backup lightpaths for a (predicted) traffic matrix obey the impairment constraints. We study the survivable routing and regenerator placement problem under dedicated and shared protection schemes, analyze the complexity of both problem variants, and subsequently propose efficient algorithms to solve or approximate them.

### Online Regenerator Placement

"... Connections between nodes in optical networks are realized by lightpaths. Due to the decay of the signal, a regenerator has to be placed on every lightpath after at most d hops, for some given positive integer d. A regenerator can serve only one lightpath. The placement of regenerators has become a ..."

Abstract
- Add to MetaCart

(Show Context)
Connections between nodes in optical networks are realized by lightpaths. Due to the decay of the signal, a regenerator has to be placed on every lightpath after at most d hops, for some given positive integer d. A regenerator can serve only one lightpath. The placement of regenerators has become an active area of research during recent years, and various optimization problems have been studied. The first such problem is the Regeneration Location Problem (Rlp), where the goal is to place the regenerators so as to minimize the total number of nodes containing them. We consider two extreme cases of online Rlp regarding the value of d and the number k of regenerators that can be used in any single node. (1) d is arbitrary and k unbounded. In this case a feasible solution always exists. We show an O(log |X | · log d)-competitive randomized algorithm for any network topology, where X is the set of paths of length d. The algorithm can be made deterministic in some cases. We show a deterministic lower bound of Ω log(|E|/d)·log d log(log(|E|/d)·log d) where E is the edge set. (2) d = 2 and k = 1. In this case there is not necessarily a solution for a given input. We distinguish between feasible inputs (for which there is a solution) and infeasible ones. In the latter case, the objective is to satisfy the maximum number of lightpaths. For a path topology we show a lower bound of √ l/2 for the competitive ratio (where l is the number of internal nodes of the longest lightpath) on infeasible inputs, and a tight bound of 3 for the competitive ratio on feasible inputs.