Optimizing meta-slots for nonblocking elastic optical switching networks

Elastic optical network is a promising technology for building flexible and wideband communication systems. This technology features the frequency slot unit (FSU) concept, which defines the bandwidth unit in the frequency domain. The utilization of a specified number of consecutive FSUs allows the bandwidth to be flexibly assigned to a data stream. For a successful elastic optical network operation, the use of nonblocking optical switching networks is indispensable. This paper focuses on two previously proposed W-S-W switching network architectures, namely, WSW1 and WSW2. With regard to WSW1, a previous study elucidated that the hardware complexity, which is evaluated by the number of FSUs, decreases by employing the meta-slot scheme. A meta-slot is a frequency range containing one or more FSUs. Although its effectiveness depends on the sizes of meta-slot classes, the previous study did not present how to optimize the meta-slot class sizes. Moreover, the employment of meta-slots was not considered for WSW2 in the previous study. This paper investigates the optimization of meta-slot class sizes and demonstrates that such optimization is modeled as the shortest path problem. For WSW1, the meta-slot scheme optimized by the shortest path model is compared with the previously reported nonblocking conditions. The result confirms the superiority of the optimized meta-slot scheme. For WSW2, the assignment of meta-slots among S-switches is also essential. The paper models the assignment of meta-slots as a bin-packing problem. Thus, the near-optimal assignment can be obtained by a known bin-packing heuristic. For WSW2, the number of S-switches is evaluated for the optimized meta-slot scheme and the previously known nonblocking conditions. The result confirms that the meta-slot scheme is advantageous for WSW2 as well as for WSW1.

Modelling and Optimization of Multi-Service Optical Switching Networks with Threshold Management Mechanisms

DWDM networks make use of optical switching networks that allow light waves of multiple lengths to be serviced and provide the possibility of converting them appropriately. Research work on optical switching networks focuses on two main areas of interest: new non-blocking structures for optical switching networks and finding traffic characteristics of switching networks of the structures that are already well known. In practical design of switching nodes in optical networks, in many cases, the Clos switching networks are successfully used. Clos switching networks are also used in Elastic Optical Networks that can effectively manage allocation of resources to individual multi-service traffic streams. The research outcomes presented in this article deal with the problems of finding traffic characteristics in blocking optical switching networks with known structures. This article aims at presenting an analysis of the influence of traffic management threshold mechanisms on the traffic characteristics of multi-service blocking Clos switching networks that are used in the nodes of elastic optical networks as well as their influence on the traffic efficiency of network nodes. The analysis was carried out on the basis of research studies performed in a specially dedicated purpose-made simulation environment. The article presents a description of the simulation environment used in the experiments. The study was focused on the influence of the threshold mechanism, which is one of the most commonly used and elastic traffic management mechanisms, and on the traffic characteristics of switching networks that service different mixtures of multi-service Erlang, Engset and Pascal traffic streams. The conducted study validates the operational effectiveness and practicality of the application of the threshold mechanism to model traffic characteristics of nodes in an elastic optical network.

Finite/Infinite Queueing Models Performance Analysis in Optical Switching Network Nodes

In optical switching networks, optical information (packets/bursts) that are forwarded from an optical switch to another through the network could entering a queue of a certain length in each node and may be waiting inside this node before it will be transmitted to the next node. Various queueing models have been widely applied as the main tool in optical switching networks for modeling and performance evaluation analysis of the switching nodes. In this paper, studying the performance analysis of an optical switching node is discussed at Finite and Infinite queueing models to have the optimum queueing model for optical core node switch design. The waiting delay time, the average expected number of optical packets and the loss probability of packets in the optical switch are estimated at variable traffic loads and different wavelength channels.