WDM Ring Networks Research Articles

Wide-Sense Nonblocking Multicast in WDM Optical Linear Array and Ring Networks with 2-Length Extension under Index Based Routing

Multicast communication is the concurrent transmission of data from one source node to many destination. It is widely deployed in high performance computing and communication networks.In this paper, a linear array and ring networks are extended by directly linking all nodes which are separated by one intermediate node with additional fibers which is referred as linear array and ring network with 2-length extension and wide sense nonblocking multicast is studied. The wavelength allotment methods are proposed to realize one-to-many communication over wavelength division multiplexing optical linear array and ring with 2-length extension under index-based routing and the minimum wavelength number needed is determined. The minimum wavelength number needed to support for the extended linear array and ring topologies is reduced approximately by half when compared with that of a linear array network and ring network.

Optical Stabilization of Waveguide Amplifiers for WDM Ring Network with Recirculating Optical Power

Optical Stabilization of Waveguide Amplifiers for WDM Ring Network with Recirculating Optical Power

Hierarchical MEC Servers Deployment and User-MEC Server Association in C-RANs over WDM Ring Networks.

With the increasing number of Internet of Things (IoT) devices, a huge amount of latency-sensitive and computation-intensive IoT applications have been injected into the network. Deploying mobile edge computing (MEC) servers in cloud radio access network (C-RAN) is a promising candidate, which brings a number of critical IoT applications to the edge network, to reduce the heavy traffic load and the end-to-end latency. The MEC server’s deployment mechanism is highly related to the user allocation. Therefore, in this paper, we study hierarchical deployment of MEC servers and user allocation problem. We first formulate the problem as a mixed integer nonlinear programming (MINLP) model to minimize the deployment cost and average latency. In terms of the MINLP model, we then propose an enumeration algorithm and approximate algorithm based on the improved entropy weight and TOPSIS methods. Numerical results show that the proposed algorithms can reduce the total cost, and the approximate algorithm has lower total cost comparing the heaviest-location first and the latency-based algorithms.

Delay Differentiated IP over Hierarchical WDM Ring Networks

Delay Differentiated IP over Hierarchical WDM Ring Networks

Short-term fairness in slotted WDM rings

Single-hop WDM ring networks are promising architectures for future broadband access and metro networks. However, ring networks exhibit significant fairness issues, which must be handled by a fairness enforcing protocol. Fairness is usually ensured over a time window of several network propagation delays. Thus, data flows might experience large access delays which might be not compatible to support time-sensitive applications. We solve this issue proposing the Multi-Fasnet protocol, which is able to enforce fairness in a relative short time scale, in the order of few propagation delays, without trading off the aggregated throughput network performance. We discuss Multi-Fasnet limitations and propose several novel strategies that achieve high and fair network throughput as well as low, bounded and fair access delays.

A Optimization Traffic Grooming Algorithm Based on Bidirectional SONET Ring Topology Network

The issue of WDM network traffic grooming has been a hot in the field of research. The implementation of traffic grooming technology can improve the utilization of wavelength channels, reducing the link delay and the blocking rate of the network, which to improve network resource utilization and optimize network performance. This article mainly studies all-optical network routing algorithm utilizing WDM technology to achieve the dynamic traffic grooming and propose a optimization grooming policy -HaffmanGroom (M) algorithms which based on SONET / WDM ring network. The most important feature of this algorithm is that the SONET / WDM ring network of multiple multicast request packet , with a minimum weight of the light path priority selection method, the flow of requests each group effectively optimize ease . The algorithm takes into account the impact of the link request factor and link hops to optimize the link selection. The simulation results show that under the conditions of factors and the number of hop a request fully consider the impact of these two factors to the link, and can achieve optimal link with the smallest weights for effective data transmission, improving resource utilization, reducing blocking rate in order to achieve the purpose of optimizing network performance.

Wavelength assignment for all-to-all broadcast in bidirectional WDM optical ring with limited drops

All-to-all broadcast is to disseminate a unique message from each node to every other node in a network. This problem is significant in the context of control plane design as it relates to status information dissemination. In this paper, a wavelength assignment method to reduce the number of wavelengths is proposed to establish all-to-all broadcast in a bidirectional WDM ring network. The network model is an all-optical network, in which a message from source node can be dropped (or split) only at a limited number of destination nodes along a light path due to power loss of dropping optical signals. An expression for the upper bound on the number of wavelengths required to support all-to-all broadcast is derived for certain cases of WDM ring while for other cases, an attractive algorithm is given to identify the lengths of connection sets that can be grouped together with suitable wavelength assignment strategies. Numerical results are computed to show that the results obtained are close to the lower bound.

Optimal Wavebanding in WDM Ring Networks

Savings in switching costs of an optical cross-connect can be achieved by grouping together a set of consecutive wavelengths and switching them as a single waveband. This technique is known as waveband switching. While previous work has focused on either uniform band sizes or nonuniform band sizes considering a single node, in this paper we focus on the number of wavebands and their sizes for ring topologies. First, we show that such solutions are inadequate when considering the entire network. We then present a novel framework for optimizing the number of wavebands in a ring network for deterministic traffic. The objective of the Band Minimization Problem is to minimize the number of nonuniform wavebands in the network while using the minimum possible number of wavelengths. We show that the problem is NP-hard and present heuristics for it. We then consider a specific type of traffic, namely all-to-all traffic, and present a construction method for achieving the minimum number of wavebands in the ring. Our results show that the number of ports can be reduced by a large amount using waveband switching compared to wavelength switching, for both all-to-all traffic and random traffic. We also numerically evaluate the performance of our waveband design algorithms under dynamic stochastic traffic.

An efficient access protocol and a node multi-buffer architecture for bandwidth utilization improvement in WDM ring MANs

In this paper we study a slotted WDM ring network architecture with a suitable access protocol that avoids both data channels collisions and destination conflicts and decreases the packets dropping probability. Our intention is to increase throughput and to decrease transmission delay. The key idea of this paper is the exploitation of a number of buffers at each access node, in conjunction with the appropriate allocation of the incoming traffic among them and the effective decision algorithm for the appropriate buffer selection for transmission. Simulation results approximate the necessary number of buffers at each access node that maximizes the fiber bandwidth utilization.

Free-Space Optoelectronic Switching Cores With MPLS for SANs Over WDM Ring Networks

With increasing demands on storage devices in the modern communication environment, the storage area network (SAN) has evolved to provide a direct connection allowing these storage devices to be accessed efficiently. To optimize the performance of a SAN, a three-stage hybrid electronic/optical switching node architecture based on the concept of a MPLS label switching mechanism, aimed at serving as a multi-protocol label switching (MPLS) ingress label edge router (LER) for a SAN-enabled application, has been designed. New shutter-based free-space multi-channel optical switching cores are employed as the core switch fabric to solve the packet contention and switching path conflict problems. The system-level node architecture design constraints are evaluated through self-similar traffic sourced from real gigabit Ethernet network traces and storage systems. The extension performance of a SAN over a proposed WDM ring network, aimed at serving as an MPLS-enabled transport network, is also presented and demonstrated.

Design and characterization of a modified WDM ring network – An analytical approach

The present paper proposes the design of a modified ring network topology with a significant improvement in average delay and blocking probability over the simple ring network. The backbone ring network is modified by connecting the alternate nodes in regions identified statistically as of high traffic density. A mathematical model for the proposed modified network has been developed to investigate the blocking probability and average delay as the data traverses from source to destination. The analysis reports an improvement in the average delay performance with the inception of call priority at the processing node and thus provides a scope to implement the given grade of service.

Multicast capacity of optical ring network with hotspot traffic: The bi-directional WDM packet ring

Packet-switching WDM ring networks with a hotspot transporting unicast, multicast, and broadcast traffic are important components of high-speed metropolitan area networks. For an arbitrary multicast fanout traffic model with uniform, hotspot destination, and hotspot source packet traffic, we analyze the maximum achievable long-run average packet throughput, which we refer to as multicast capacity, of bi-directional shortest path routed WDM rings. We identify three segments that can experience the maximum utilization, and thus, limit the multicast capacity. We characterize the segment utilization probabilities through bounds and approximations, which we verify through simulations. We discover that shortest path routing can lead to utilization probabilities above one half for moderate to large portions of hotspot source multi- and broadcast traffic, and consequently multicast capacities of less than two simultaneous packet transmissions. We outline a one-copy routing strategy that guarantees a multicast capacity of at least two simultaneous packet transmissions for arbitrary hotspot source traffic.

ROADM optimization in WDM ring networks

Reconfigurable optical add–drop multiplexers (ROADMs) and tunable transceivers play an important role in optical network reconfigurability and cost saving. ROADMs provide support to dynamic traffic demands, enable new services, and save capital expenditure (CapEx) along with the operational expenditure (OpEx). Limiting the range of wavelengths that can be accessed at a node reduces costs, and possibly reduces flexibility in reconfigurability. The limited range (band size) of wavelengths is a result of the limited add/drop range of the ROADMs and/or limited tuning range of transceivers. In either case, limited reconfigurability introduces a new constraint in the wavelength assignment of connections called as the wavelength termination constraint. Limited ROADMs (L-ROADMs) can add and drop only a subset of (contiguous) wavelengths (a waveband) and are less costly than fully reconfigurable OADMs (F-ROADMs). In order to quantify the trade-offs between the number of L-ROADMs and their band sizes and compare those with F-ROADMs, optimization solutions must be obtained. In this paper, we consider two models of L-ROADMs and present optimization problems specific to each model under all-to-all traffic for ring networks. We consider two ring topologies, uni- and bi-directional rings. We give integer linear programming formulations and present heuristic solutions to minimize the worst-case band size and the total number of wavebands for the two L-ROADM types. For the uni-directional ring in the first model, we present a lower bound of ⌈ ( W + 2 ) / 2 ⌉ for the band size of ROADMs, where W is the number of wavelengths. For the upper bound, our results show that the worst-case band size of L-ROADMs is only about 65% of the full range for large network sizes. For the bi-directional ring of N nodes, our heuristic algorithm, Algorithm-Min-Bi, produces a worst-case band size of b ( w ) = N 2 − 4 N + 19 8 . This produces a reduction of 10% to 20% in the band size for typical network sizes. When the band size b s is fixed under the second model, we observe the trade-off between the total band size of L-ROADMs and the number of L-ROADMs. For both uni- and bi-directional ring networks, our results are close to optimal. We also examine the performance of our models under dynamic traffic.

Comparison of routing methods in optical multicast WDM ring networks

Multicast routing and wavelength assignment (MC-RWA) is an important issue when designing multicast WDM ring networks. Two heuristic multicast routing methods, minimum spanning tree (MST) and shortest path routing (SPT), have been studied extensively. However, the comparison of those two heuristics in terms of the number of required wavelengths is still an open issue because of the lack of efficient optimization methods for MC-RWA. In this paper, using a recently developed optimization algorithm, we compare the two multicast routing methods and optimal MC-RWA. The results show that SPT requires about 1---12% more wavelengths than MST. Moreover, the number of required wavelengths under MST routing is shown to be very close to that of the optimal solution.

A novel look-ahead collision-free optical burst transmission scheme

This paper presents a novel collision-less optical burst transmission scheme, namely, look-ahead optical burst transmission (LAOBT) for WDM ring networks. In the LAOBT, bursts are generated and inserted into burst streams by utilizing the void intervals of incoming bursts (IBs) in advance. The void size is estimated by splitting optical power into two paths, delaying one of the signals at the fiber delay line (FDL) and calculating IBs' residual time from the splitter to the optical cross-connect (OXC). The performance evaluation results show that our proposed scheme increases link utilization without significant increment of end-to-end delay and signaling overhead.

On providing metro ethernet services over transparent WDM optical rings

The long list of benefits (especially cost and capacity) of Ethernet LANs has made the IEEE, the ITU-T, and the Metro Ethernet Forum define the requirements for taking Ethernet beyond the local area, toward the metropolitan region. In addition, the ever-increasing traffic demands of new applications and users can only be met by the huge bandwidth capacity provided by optical fibers. This work studies how to provide metro Ethernet services over transparent tunable-transmitter fixed-receiver WDM optical ring networks. A new adaptation layer of ME to WDM is proposed, and its benefits and drawbacks are studied. It is shown that such a transparent WDM ring network can be seen as a logical full-mesh topology by the upper ME layer, thus reducing to one the number of optical-electronic-optical conversions per unicast frame. Additionally, two different approaches are proposed in the case of broadcast/multicast traffic, since this may bring scalability difficulties in ring topologies.

Traffic grooming in bidirectional WDM ring networks

AbstractWe study the minimization of ADMs (Add‐Drop Multiplexers) in optical WDM bidirectional rings considering symmetric shortest path routing and all‐to‐all unitary requests. We precisely formulate the problem in terms of graph decompositions, and state a general lower bound for all the values of the grooming factor C and N, the size of the ring. We first study exhaustively the cases C = 1, C = 2, and C = 3, providing improved lower bounds, optimal constructions for several infinite families, as well as asymptotically optimal constructions and approximations. We then study the case C > 3, focusing specifically on the case C = k(k + 1)/2 for some k ≥ 1. We give optimal decompositions for several congruence classes of N using the existence of some combinatorial designs. We conclude with a comparison of the cost functions in unidirectional and bidirectional WDM rings. © 2010 Wiley Periodicals, Inc. NETWORKS, Vol. 58(1), 20–35 2011

Routing and wavelength assignment for hypercube communications embedded on optical chordal ring networks of degrees 3 and 4

Routing and wavelength assignment for realizing hypercube communications on WDM ring networks has been discussed in previous research. To reduce the wavelength requirement, we study routing and wavelength assignment for realizing hypercube communications on WDM ring networks with additional links. We design the embedding schemes and derive the numbers of wavelengths required on WDM chordal ring networks of both degrees 3 and 4. Based on our proposed embedding schemes, we provide the analysis of chord length with optimal number of wavelengths to realize hypercube communications on 3-degree and 4-degree chordal rings. Results show that the wavelength requirement for realizing hypercube communications on optical chordal ring networks is significantly lower than that on optical ring networks. In addition, our research also provides solutions for embedding hypercube graph on chordal rings in graph embedding theory.

Optimal routing and wavelength assignment to minimize the number of SONET ADMs in WDM rings

In this study, we consider the routing and wavelength assignment problem on SONET over WDM ring networks. Our problem is the minimum ADM (add-drop multiplexer) cost problem of minimizing the number of ADM equipment instead of the minimum wavelength problem. To deal with the complexity of the problem, we create a new mathematical formulation and suggest an efficient solution method based on the branch-and-price method. We exploit the structure of the ring network to develop an efficient algorithm and show the efficiency using computer simulations.

A High-Speed Protection Scheme for Multiple-Priority-Class Traffic in WDM Ring Networks

We propose a high-speed protection scheme for multiple-priority-class traffic transmission in WDM ring networks. This scheme achieves high-speed protection by quickly suspending transmission of low-priority traffic when a failure is detected. Each node suspends transmission of the low-priority traffic being sent over the backup path corresponding to the impaired primary path after receiving a failure notification and checking a table that includes the primary paths passing through the node, the backup paths corresponding to the primary paths, and low-priority traffic transmitted by the node. If a node detects a failure, it sends a single failure notification for each ring to the source node of the primary path, and the nodes on the route sequentially suspend low-priority traffic. Simulation shows that the proposed scheme reduces the failure-recovery time by up to 60% compared with the conventional scheme.