Quoc Viet Phung

Dynamic p-cycles selection in optical WDM mesh networks

P-cycles have been recognized as a useful protection scheme in WDM mesh networks. This is a type of shared link protection that not only retains the mesh-like capacity efficiency, but also achieves the ring-like protection switching speed. However, finding the optimal set of p-cycles for protecting traffic demands is not a simple task and is an NP-hard problem. A general approach is to determine a set of candidate p-cycles and then determine optimal or near-optimal solutions by using integer linear programming (ILP) models or heuristics. In a dense mesh network, however, the number of candidate cycles is huge, and increases exponentially if the node number is increased. Thus, searching for a suitable set of efficient candidate cycles is crucial and imperative to balancing the computational time and the optimality of solutions. In this paper, we propose a dynamic P-cycles selection (DPS) algorithm that improves the efficiency of enumerating candidate p-cycles. The dynamic approach for cycle selection is based on the network state. In the DPS algorithm, all cycles are found and stored, then an efficient and sufficient set of p-cycles is extracted to achieve 100% working protection, minimize the spare capacity, and reduce time complexity.

Dynamic Wavelength Routing in All-Optical Mesh Networks

Wavelength-division multiplexing (WDM) offers the capability to handle the increasing demand of network traffic in a manner that takes advantage of already deployed optical fibers. Lightpaths are optical connections carried end-to-end over a wavelength on each intermediate link. Wavelengths are the main resource in WDM networks. Due to the inherent channel constraints, a dynamic control mechanism is required to efficiently utilize the resource to maximize lightpath connections. In this paper, we investigate a class of adaptive routing called dynamic wavelength routing (DWR), in which wavelength converters (WCs) are not utilized in the network. The objective is to maximize the wavelength utilization and reduces the blocking probability in an arbitrary network. This approach contains two sub-algorithms: least congestion with least nodal-degree routing algorithm (LCLNR) and dynamic two-end wavelength routing algorithm (DTWR). We demonstrate that DWR can significantly improve the blocking performance, and the results achieved as good as placing sparse WCs in the network

QRP02-6: Efficient p-Cycles Design By Heuristic p-Cycle Selection and Refinement for Survivable WDM Mesh Networks

Using p-Cycles to protect against single span failures in Wavelength-Division Multiplexing (WDM) networks has been widely studied. p-Cycle retains not only the speed of ring-like restoration, but also achieves the capacity efficiency over mesh networks. However, in selecting an optimal set of p-cycles to achieve the minimum spare capacity and fast computational time is an NP-hard problem. To address this issue, we propose a heuristic approach to iteratively select and refine a set of p-cycles, which contains two algorithms: the Heuristic p-Cycle Selection (HPS) algorithm, and the Refine Selected Cycles (RSC) algorithm. Our simulation results show that the proposed approach is within 3.5% redundancy difference from the optimal solution with very fast computation time even for large networks.

A Shared Backup Path Protection Scheme for Optical Mesh Networks

We propose a new heuristic ILP model for share backup path protection (SBPP) scheme of mesh networks, which used the sets of disjoint-joint primary-backup path candidates of using path-pair candidates. The solution of the model is near optimal and provides all the routing details of demands as well as the sharing information between backup paths, and also simplifies the wavelength assignment problem if the wavelength continuity is a consideration. The new entities are introduced into this model that allow to control the resource utilization as well as congestion level of the network for optimization purposes and the pre-processing of data offers more control in properties of the path candidates

A Green Communication Model for 5G Systems

Small cell networks (SCNs) are envisaged as a key technology enabling the fifth-generation (5G) wireless communication system to address the challenge of rising mobile data demand. Green communications will be another major attribute of 5G systems, as power consumption from the information and communication technology sector is forecast to increase significantly by 2030. Accordingly, energy-efficient SCN design has attracted significant attention from researchers in recent years. In addition, to enable the ubiquitous deployment of dense small cells, service providers require energy-efficient backhauling solutions. In this paper, we present an energy-efficient communication model for 5G heterogeneous networks (HetNets). The proposed model considers both the access and backhaul network elements. We formulate and present an analytical model to calculate the optimum number of small cells that need to be kept active at various times of the day in order to minimize power consumption while meeting users’ quality of service demands. Based on our critical investigation of backhaul power consumption, we also isolate and present two energy-efficient backhauling solutions for 5G HetNets. Simulated results reveal that the proposed green communication model saves up to 48% more power than other existing models.

Efficient optimization of network protection design with p-cycles

The purpose of this paper is to consider network survivability designs that utilize the p-cycle, and to propose a novel ILP formulation for capacity design based on network fundamental cycles, as well as the available straddling links. Concepts of visible and hidden straddling links—which are essential components of the model presented herein—are also introduced. The proposed model caters for the case of joint optimization of a p-cycle network that can be solved without enumerating p-cycle candidates. In addition, the complexity of the proposed model is much less than any conventional model dealing with large size networks and suitable for the design of networks having multiple quality of protection (MQoP) service classes using mixed protection techniques.

A Segmentation Method for Shared Protection in WDM Mesh Networks

Shared link and shared path protections have been recognized as preferred schemes to protect traffic flows against network failures. In recent years, another method referred to as shared segment protection has been studied as an alternative solution for protection. This method is more flexible and efficient in terms of capacity utilization and restoration time. However, to our best knowledge, this method has mostly been studied in dynamic provisioning scenarios in which searching for restoration paths is dynamically performed after a failure has occurred. In this paper, based on the path segmentation idea, we propose a method to generate good candidate routes for traffic demands in static provisioning. These candidates are used as input parameters of an integer linear programming (ILP) model for shared backup protection. Numerical results show that the capacity efficiency resulting from these candidates is much better than the best known shared backup path protection (SBPP) schemes. In addition, although the restoration time of our scheme is a little bit longer than those implementing link protection, it is still faster than path protection schemes

K Pairs of Disjoint Paths Algorithm for Protection in WDM Optical Networks

Survivable routing in wavelength division multiplexing (WDM) optical networks has been proven to be NP-hard problem. There is a trade-off between the computational time and the optimality of solutions in existing approaches to the problem. Existing heuristic approaches purely based the graph algorithms are efficient in computational time but do not offer optimal solutions and may fail in some cases even when a solution exists. Meanwhile, the integer linear programming (ILP) models offer optimal solutions but are intractable even with moderate scale networks. In this paper, we introduce a new algorithm for finding K pairs of disjoint paths which are employed as K candidate pairs for each connection in the ILP models. We introduce an ILP model for dedicated path protection in which the number of decision variables is mainly dependant on traffic requests and the constant K, not on the network size

A Hybrid p-Cycle Search Algorithm for Protection in WDM Mesh Networks

p-cycle is a type of shared link protection for survivable wavelength-division multiplexing (WDM) mesh networks. p-cycle not only retains ring-like restoration speeds, but also achieves capacity efficiency in mesh networks. However, finding the optimal set of p-cycles to protect all traffic demands within a reasonable response time is difficult. This is particularity true with dense meshes or large networks, because the number of candidates is huge. Generally, p-cycles are determined by using either integer linear programming (ILP) or specifically designed heuristic algorithms. However, both methods need a set of efficient candidate cycles to tradeoff between the computational time and the optimality of solutions. For this reason, constructing an efficient set of candidate p-cycles is crucial and imperative. In this paper, we propose the span-weighted cycle searching (SCS) algorithm to generate and select an adequate number of p-cycles to minimize the spare capacity, while achieving 100% restorability, within low computational complexity

Establishing Physical Survivability of Large Networks using Properties of Two-Connected Graphs

Establishing the physical survivability of large networks is not a trivial task. Some techniques for assessing physical survivability such as the cutset method can not deal with large size networks (S. Ramamurthy and B. Mukherjee), (W.N. Grover and J. Doucette, 2001). A fast technique for finding biconnected components of a graph and testing the network for node-/link-bridges, presented in (W.D. Grover, 2004), does not provide any further information, such as identifying the fundamental cycles within the network, which would significantly benefit the next phase of network design for protection using such techniques as shared backup path protection (SBPP), p-cycle, or ring protection (W.D. Grover, 2004). This paper presents an alternative technique, based on graph theory, for evaluating the physical survivability of networks. This technique can deal with network sizes of many thousand nodes, with computational times which are comparable with the biconnected components method, whilst providing more information about the susceptibility of a network to individual link and node failures in preparation for the next phase of network protection design.