Efficient scheduling algorithms for real-time service on WDM optical networks

To utilize the wavelength resources of Internet protocol (IP) over wavelength division multiplexing (WDM) optical networks, a multi-constrained multicast traffic grooming algorithm is proposed in this paper. This algorithm can achieve multicast traffic grooming in IP over WDM optical networks under multi-constraints, including the number of optical transceivers, wavelength conversion capability and wavelength splitting capability. We simulated the traffic grooming algorithm using the topology of GEANT. Emulation results show that our algorithm has a lower blocking proportion compared with the multi-hop traffic grooming algorithm, which can achieve multicast traffic grooming more effectively.

In this paper, we compare performance of fixed-grid Wavelength Division Multiplexing (WDM) and Elastic Optical Networks (EONs) in dynamic provisioning of many-to-many (m2m) flows. Currently, with a growth of services relying on many-to-many communication paradigm such as distributed computing, inter-Data Center communication, content delivery networking or other requiring high-bandwidth in group communication, it is vital to deliver new solutions facilitating these demanding transmissions. Therefore, the authors investigate provisioning of m2m traffic in high-performance optical networks. This work focuses on dynamic Routing and Wavelength Assignment (RWA) problem in WDM networks as well as Routing and Spectrum Allocation (RSA) problem in EONs for m2m flows using replicated communication through auxiliary rendezvous servers.

In a many-to-many session, a participant distributes and receives traffic flows to/from all others in the same session. It is desirable to achieve both high resource utilization and low power consumption when such sessions are provisioned. In wavelength division multiplexing (WDM) optical networks, traffic grooming has been widely applied as the key technology for aggregating sessions to improve resource utilization. However, the current many-to-many grooming approaches, the lightpath circle and hubbed light-tree, do not make an effort to reduce the power consumption of many-to-many sessions. In this paper, we formulate the green routing and aggregation of many-to-many sessions problem and prove its NP-completeness. For problem solving in WDM optical networks, we apply a rational combined method of lightpaths. Both an integer linear programming-based approach and a novel graph-based heuristic are devised. We further provide an illustrative comparison between our heuristic and the existing benchmarks in terms of power consumption. Extensive simulation results demonstrate that, compared with the benchmarks, our heuristic improves the average power efficiency in the range of 13-19%.

Addresses the problem of efficient communication in unreliable multi-hop optical networks supported by wavelength division multiplexing (WDM). We first define a new cost model for routing in (optical) WDM networks that is more general and realistic than the existing models. Our model takes into consideration not only the cost of wavelength access and conversion but also the cost for wavelength switching when several optical channels of the same wavelength arrive at the same node. We then propose a set of efficient algorithms in both reliable and unreliable WDM networks on the new cost model respectively for each of three important communication patterns-multiple point-to-point routing, multicast and multiple multicast.

We address the issue of inapproximability of the wavelength assignment problem in wavelength division multiplexing (WDM) optical networks. We prove that in an n-node WDM optical network with m lightpaths and maximum load L, if NP ≠ ZPP, for any constant δ>0, no polynomial time algorithm can achieve approximation ratio n1/2−δ or m1−δ, where NP is the class of problems which can be solved by nondeterministic polynomial time algorithms, and ZPP is the class of problems that can be solved by polynomial randomized algorithms with zero probability of error. Furthermore, the above result still holds even when L=2. We also prove that no algorithm can guarantee the number of wavelengths to be less than $$(\sqrt{n}/2)L$$ or (m/2)L. This is the first time inapproximability results are established for the wavelength assignment problem in WDM optical networks. We also notice the following fact, namely, there is a polynomial time algorithm for wavelength assignment which achieves approximation ratio of O(m(log log m)2/(log m)3). Therefore, the above lower bound of m1−δ is nearly tight.

Message sequencing and channel assignment are two important issues that need to be addressed when scheduling variable-length messages in a wavelength division multiplexing (WDM) network. Channel assignment addresses the problem of choosing an appropriate data channel via which a message is transmitted to a node. This problem has been addressed extensively in the literature. On the other hand, message sequencing which addresses the order in which messages are sent, has rarely been addressed. In this paper, we propose a set of scheduling techniques for single-hop WDM passive star networks, which address both the sequencing aspect and the assignment aspect of the problem. In particular, we develop two priority schemes for sequencing messages in a WDM network in order to increase the overall performance of the network. We evaluate the proposed algorithms, using analytical modeling and extensive discrete event simulations, by comparing their performance with state-of-the-art scheduling algorithms that only address the assignment problem. We find that significant improvement in performance can be achieved using our scheduling algorithms where message sequencing and channel assignment are simultaneously taken into consideration. This suggests that, when scheduling messages in WDM networks, one has to consider message sequencing, as well as channel assignment. As a result, we anticipate that this research will open new directions into the problem of on-line scheduling in WDM networks.

The widespread deployment of wireless telecommunication networks and growing Internet traffic globally leads to a substantial increase in signal traffic demands in fiber optic networks. This demand surge places significant pressure on the survivability of optical networks, specifically when faced with fiber cable failures that prevent failed optical fibers from satisfying connection requests. To address this challenge, in this paper, we consider integrated planning of regenerator installation, optical connection routing, and wavelength assignment (RWA) for wavelength division multiplexing (WDM) optical networks under link failures. To the best of our knowledge, we are the first to consider such an integrated problem. We minimize the number of backup regenerators required to fulfill all connection requests under all potential link failures while accounting for the wavelength and routing constraints. We formulate the problem as an integer program, while its size exponentially increases with the network size by nature. To solve large-scale instances for practical uses in the industry, we propose efficient algorithms to generate near-optimal solutions that are practically implementable. We perform extensive numerical experiments to demonstrate the effectiveness of our approach in solving real-world instances provided by our industry partners. The results show that our approach can efficiently obtain high-quality solutions while ensuring a minimal increase in backup regenerators as the network grows. Our solutions also offer valuable insights into planning a cost-effective and reliable fiber optic network for network operators.

This chapter discusses the causes of impairments in the optical network and how one takes them into account in the design, followed by the survivability issues in optical networks. It outlines the basic concepts of survivability and different protection and restoration schemes used in optical networks. Survivability can be provided in different layers in network: logical layers and optical layer. The fault‐management schemes in each layer have their own functionalities and characteristics. The chapter also discusses the survivability in the multilayer wavelength division multiplexing (WDM) optical networks. The protection techniques in the synchronous optical network and synchronous digital hierarchy networks are briefly described, which are still used in many of the current protocols in the WDM networks. It looks at protection functions in the optical layer and discusses how protection functions in the different layers of the network can work together.

In all-optical Wavelength Division Multiplexing (WDM) technique, data contention is an inevitable challenge. For reliable data transmission, contention resolution is very much essential. There are different contention resolution techniques that are used in optical WDM network. In this paper, wavelength converter is used for contention resolution in optical WDM network. Here Semiconductor Optical Amplifier (SOA) is used to implement wavelength converter based on a special third-order nonlinear susceptibility phenomenon of silica fiber, called Four-Wave Mixing (FWM) technique. Realization of wavelength converter is done for two different sets of WDM networks. Performance of the wavelength converter was estimated in terms of number frequencies generated, number of new wavelength generated, its corresponding power, etc. Result shows that four-wave mixing is a very effective technique to generate new wavelengths at the output to overcome the problems due to contention in an optical WDM network. OptiSystem of Optiwave is used to design schematic layout for the wavelength converter using SOA.

Dynamic survivable mapping through reconfiguration in IP over WDM network

Solving multi-objective routing and wavelength assignment in WDM network using hybrid evolutionary computation approach

Closed all-optical cycles in wavelength division multiplexing (WDM) optical networks may generate lasing resulting in adverse effects to network performance. In this paper, causes and physical conditions for both all-optical idle cycles and all-optical leakage cycles are analyzed by using optical spectrum of the network. A five-node experimental optical network is built. Multiple lasing peaks are observed to co-exist and compete in a fiber. Affects of the filtering characteristic mismatch of optical nodes to all-optical lasing cycles are discussed. We point out that multiple closed leakage cycles may occur in one optical channel in the case of bandwidth mismatch. Two lasing peaks of leakage cycles are observed in one channel and they can co-exist with the signal wavelength. Finally, harms of lasing cycles are discussed and methods are proposed for eliminating them.

In this letter, we propose a computational model for calculating blocking probabilities of multifiber wavelength division multiplexing (WDM) optical networks. We first derive the blocking probability of a fiber based on a Markov chain, from which the blocking probability of a link is derived by means of conditional probabilities. The blocking probability of a lightpath can be computed by a recursive formula. Finally, the network-wide blocking probability can be expressed as the ratio of the total blocked load versus the total offered load. Simulation results for different fiber-wavelength configurations conform closely to the numerical results based on our proposed model, thus demonstrating the feasibility of our proposed model for estimating the blocking performance of multifiber WDM optical networks.

In optical wavelength-division multiplexing (WDM) networks, traffic can be very “bursty” at a fine time scale, even though it may seem to be smooth at coarser scales (e.g., Poisson or Poisson-related traffic). This paper analyzes the instantaneous characterization of Poisson traffic at a fine time scale. The analysis shows that the irregular oscillation of the instantaneous traffic load and the occurrence of blockings in a light-loaded network are highly correlated. Specifically, most blockings occur concentratively at the peaks of the instantaneous load. In some other time, network resources may not be sufficiently utilized. To make better utilization of network resources, a novel wavelength-buffering (WB) scheme is proposed for the first time in this paper. By reserving a portion of resources in a “wavelength buffer” under light loading and releasing them when the load goes up, a number of blockings brought by the oscillation of the traffic load can be avoided. Simulation results show that compared with other schemes such as adaptive routing, wavelength conversion (WC), and rerouting, the novel wavelength-buffering scheme achieves significantly better performance with respect to the network utilization and overall blocking probability.

In anycast, connection requests are routed to one of multiple destination candidates, thus helping improve the overall acceptance of service requests in the network when compared to traditional unicast. In this paper we develop a new analytical model to compute the network-wide blocking performance for anycast routing and wavelength assignment (ARWA) in wavelength division multiplexing (WDM) optical networks using the reduced-load fixed-point approximation analysis. This model is based on conventional queuing theory for loss systems combined with a joint probability analysis of the anycast service alternatives. Performance results show that our model provides good accuracy compared to simulation results.