Routing, Modulation Level And Spectrum Assignment Research Articles

Dynamic Spectrum Assignment in Passive Optical Networks Based on Optical Integrated Microring Resonators Using Machine Learning and a Routing, Modulation Level, and Spectrum Assignment Method

The rising demand for bandwidth in optical communication networks has led to the need for more efficient solutions for spectrum allocation. This article presents a solution to enhance the capacity and efficiency of passive optical networks (PON) using optical microring resonators and dynamic spectrum allocation. The solution relies on wavelength division multiplexing (WDM). It proposes using a support vector machine (SVM) and a Routing, Modulation Level, and Spectrum Assignment (RMLSA) method to manage spectrum allocation based on the bandwidth and distance of multiple requests. The network employs a pulse shaper to physically allocate the spectrum, allowing for the separation of the spectrum generated by the microring resonators into different wavelengths or wavelength ranges (super-channel). Additionally, the SVM and RMLSA algorithms regulate the pulse shaper to execute the allocation. This photonic network achieves improved spectrum utilization and reduces the network blocking probability. Our proposal shows that we successfully addressed 1090 requests with a zero blocking probability, accounting for 81% of the total requests. These request scenarios can simultaneously accommodate up to 200 requests, with a maximum bandwidth of 31 THz. This highlights the efficacy of our approach in efficiently managing requests with substantial processing capacity.

Routing, Modulation Level, and Spectrum Assignment in Elastic Optical Networks—A Serial Stage Approach with Multiple Sub-Sets of Requests Based on Integer Linear Programming

This paper addresses serialized approaches of the routing, modulation level, and spectrum assignment (RMLSA) problem in elastic optical networks, using multiple sequential sub-sets of requests, under Integer Linear Programming (ILP). The literature has reported two-stage serial optimization methods referred to as RML+SA, which retain computational efficiency when the problem grows, compared to the classical one-stage RMLSA optimization approach. However, there still remain numerous issues in terms of the spectrum used that can be improved when compared to the RMLSA solution. Consequently, this paper proposes RML+SA solutions considering multiple sequential sub-sets of requests, split traffic flow, as well as path-oriented and link-oriented routing models. Simulation results on different test scenarios determine that: (a) the multiple sequential sub-sets of request-based models improve computation time without worsening the spectrum usage when compared to just one set of requests optimization approaches, (b) divisible traffic flow approaches show promise in cases where the number of request sub-sets is low compared to the non-divisible counterpart, and (c) path-oriented routing succeeds in improving the used spectrum by increasing the number of candidate routes compared to link-oriented routing.

A Bandwidth-Balanced RMLSA Solution for Static Elastic Optical Network: A Two Stages Approach

This paper addresses one of the main tasks in transparent static elastic optical networks (EONs), known as the routing, modulation level, and spectrum assignment (RMLSA) problem. We present, for the first time, a two-stage RMLSA solution, focusing on reducing spectrum consumption (or network capacity). The first macro stage, called least demand bandwidth balance (LDBB), relies on a physical layer impairment (PLI) model to jointly compute the connections’ route and modulation level (RML). We use a new balancing criterion that effectively distributes each network link’s frequency slot unit (FSU) demands, exemplifying three different balancing functions based on the maximum number of FSUs on the links and the total number of FSUs demanded and the cost of the route. In the last macro stage, using all connections chosen paths, we perform the spectrum assignment (SA) process using two specific connections prioritization criteria. We propose two SA algorithms, called sliding-fit (SF) and parcel-fit (PF), reducing the spectrum consumption. These algorithms change the SA paradigm by searching connections for a given subset of the frequency spectrum, contrary to the search of FSUs for a given connection in standard approaches. In all cases, our solution exhibited a lower total network capacity than the commonly used strategies found in the literature, with an average network capacity reduction of 5.7 % FSUs. In addition, our proposal may be used to easily dimension network capacity and determine how many extra resources may be needed to attend to all network users.

Multi-Band Elastic Optical Networks: Inter-Channel Stimulated Raman Scattering-Aware Routing, Modulation Level and Spectrum Assignment

Recently, multi-band elastic optical networks (MB-EONs) have been introduced to increase the transmission capacity of optical networks by expanding the transmission frequency range beyond the conventional C-band (e.g., O-, E-, S-, and L-band). Thus, by utilizing the idle frequency bands of the existing standard single mode fibers (SMFs), the capacity improvement in MB-EONs is achieved with lower capital expenditure compared to other techniques, such as space division multiplexing (SDM) in multi-core fibers (MCFs). The routing, modulation level and spectrum assignment (RMLSA) problem in MB-EONs is more challenging than that of the conventional single band EONs, and the inter-channel stimulated Raman scattering (ISRS) process should be considered in signal-to-noise ratio (SNR) analysis. In this article, ISRS-aware RMLSA problem in MB-EONs is studied. We obtain the optimal solution of this problem by formulating a path-based integer linear programming (ILP) model. Since the number of slots and demands are too large in a multi-band system, the ILP problem is too complex to be solved in polynomial time. Therefore, we propose heuristic algorithms to solve the ISRS-aware RMLSA problem. Then, performance of the proposed schemes is evaluated through exhaustive simulations. The results reveal that among all the proposed heuristic algorithms, the algorithm named as enhanced in-process estimation (EIPE) has the best performance in saving more frequency slots for future demands, while achieving higher spectral efficiency and SNR estimation accuracy. Moreover, for a special case of small-scale scenario, the performance of EIPE is close to the results of ILP formulation. Finally, our results indicate that by ignoring ISRS process in the SNR estimation, outage occurs for some of lightpaths, where the outage percentage depends on the launch power.

Routing, Modulation and Spectrum Assignment Algorithm Using Multi-Path Routing and Best-Fit

Elastic Optical Networks (EONs) are a promising optical technology to deal with the ever-increasing traffic and the vast number of connected devices of the next generation of the Internet, associated to paradigms like the Internet of Things (IoT), the Tactile Internet or the Industry 4.0, to name just a few. In this kind of optical network, each optical circuit or lightpath is provisioned by means of superchannels of variable bandwidth. In this manner, only the necessary bandwidth to accommodate the demand is allocated, improving the spectrum usage. When establishing a connection, the EON control layer determines the modulation format to be used and allocates a portion of the spectrum in a sequence of fibers from the source to the destination node providing the user-demanded bandwidth. This is known as the routing, modulation level and spectrum assignment (RMSA) problem. In this work, we firstly review the most important contributions in that area, and then, we propose a novel RMSA algorithm, multi-path best-fit (MP-BF), which uses a split spectrum multi-path strategy together with a spectrum assignment technique (best-fit), and which jointly exploit the flexibility of EONs. A simulation study has been conducted comparing the performance of EONs when using MP-BF with other proposals from the literature. The results of this study show that, by using MP-BF, the network can increase its performance in terms of lightpath request blocking ratio and supported traffic load, without affecting the energy per bit or the computation time required to find a solution.

Impact of Amplification and Regeneration Schemes on the Blocking Performance and Energy Consumption of Wide-Area Elastic Optical Networks

This paper studies the physical layer’s impact on the blocking probability and energy consumption of wide-area dynamic elastic optical networks (EONs). For this purpose, we consider five network configurations, each named with a network configuration identifier (NCI) from 1 to 5, for which the Routing, Modulation Level, and Spectrum Assignment (RMLSA) problem is solved. NCI 1–4 are transparent configurations based on all-EDFA, hybrid Raman/EDFA amplifiers (with different Raman gain ratio $\Gamma _{R}$ ), all-DFRA, and alternating span configuration (EDFA and DFRA). NCI 5 is a translucent configuration based on all-EDFA and 3R regenerators. We model the physical layer for every network configuration to determine the maximum achievable reach of optical signals. Employing simulation, we calculate the blocking probability and the energy consumption of the different network configurations. In terms of blocking, our results show that NCI 2 and 3 offer the lowest blocking probability, with at least 1 and 3 orders of magnitude of difference with respect to NCI 1 and 5 at high and low traffic loads, respectively. In terms of energy consumption, the best performing alternatives are the ones with the worst blocking (NCI 1), while NCI 3 exhibits the highest energy consumption with NCI $2\,\,\Gamma _{R}=0.75$ following closely. This situation highlights a clear trade-off between blocking performance and energy cost that must be considered when designing a dynamic EON. Thus, we identify NCI 2 using $\Gamma _{R}=0.25$ as a promising alternative to reduce the blocking probability significantly in wide-area dynamic EONs without a prohibitive increase in energy consumption.

Provision of adaptive guard band in elastic optical networks

Elastic optical networks are a network infrastructure capable of withstanding the high demand for data traffic from high-speed networks. One of the problems that must be solved to ensure the smooth functioning of the network is called Routing, Modulation Level and Spectrum Assignment (RMLSA). This work aims to propose a new approach to this problem with an algorithm to select the guard band in an adaptive way. Two algorithms for the adaptive selection of the guard band, called Guard Band according to Use of the Network (GBUN) and Guard Band by OSNR Margin (GBOM), are presented. The GBUN algorithm performs the guard band selection based on the usage level of network. On the other hand the GBOM algorithm uses an Optical Signal to Noise Ratio (OSNR) margin for the selection of the guard band. The performances of the proposed algorithms are compared with algorithms that use fixed guard band values and the adaptive proposal AGBA. The results showed that the GBOM algorithm presented a better performance in terms of bandwidth blocking probability for the studied scenarios. In general, GBOM also presents a better energy efficiency when compared to the other algorithms.

The RBCMLSA problem on space division multiplexing elastic optical networks

Abstract The introduction of space division multiplexing (SDM) is a promising solution to cope with ever-increasing Internet traffic. Multi-core fibers (MCFs) are a potential solution for the capacity crunch problem. In this article, the Routing, Baud rate, forward error correction (FEC) Coding, Modulation Level, and Spectrum Assignment (RBCMLSA) problem in elastic optical networks (EONs) employing MCFs and SDM is studied. An Integer Linear Program (ILP) model is used to define the studied problem and find the optimum solution in static traffic. Since the RBCMLSA problem is an NP-hard problem, for the dynamic traffic, the crosstalk-aware path routing algorithm (CAPRA) is proposed to solve this problem. Three core-selecting schemes, named Minimum Load (ML), Minimum Conflict (MC), and Minimum Weight (MW) are proposed. Simulation results show that the proposed algorithm can get lower blocking probability when compared to the algorithm for the existing simpler Routing, FEC Coding, Modulation Level, and Spectrum Assignment (RCMLSA) and Routing, Modulation Level, and Spectrum Assignment (RMLSA) problems.

Adaptive Modulation and Flexible Resource Allocation in Space-Division-Multiplexed Elastic Optical Networks

Space division multiplexing (SDM) and elastic optical networking (EON) have been proposed to increase the transmission capacity and flexibility of optical transport networks. The problem of allocating available resources over the EON network is called routing and spectrum assignment (RSA); it is called routing, modulation level, and spectrum assignment (RMLSA) if modulation adaptivity is enabled. Considering SDM adds more flexibility to the resource allocation problem. In this paper, we formulate the routing, modulation level, space, and spectrum assignment (RMLSSA) as integer linear programming (ILP) in a path-based manner for static traffic. Next, the stepwise greedy algorithm (SGA) and four different sorting policies to initiate the algorithmare proposed as a heuristic method to find a near-optimal solution of the RMLSSA problem. Finally, the paper evaluates the effectiveness of sorting policies and the SGA algorithm with different metrics. The performance results show that the SGA initiated with connection demands sorted based on increasing the number of possible space and spectrum assignment layouts (SAL) can achieve the best near-optimal solution for a small network experiment. Moreover, the ascending SAL number (ASN) policy shows the best performance for realistic networks.

Global Optimization of All-Optical Hybrid-Casting in Inter-Datacenter Elastic Optical Networks

In inter-datacenter elastic optical networks (IDC-EONs), routing, modulation-level, and spectrum assignment (RMLSA) is one of the key measures to increase network capacity and flexibility of spectrum resource management. The coexistence of unicast, anycast, multicast, and manycast traffic in IDC-EONs forms a more complex network communication scheme called hybrid cast. However, the majority of the previous RMLSA approaches focused on the network communication scheme with single traffic type and optimized network performance on the specific network metric, which leads to less practicability and a limit to one-sided network performance improvement. To achieve better network performance, we investigate the hybrid-cast RMLSA (HC-RMLSA) problem with the objective of improving IDC-EON overall performance. Specifically, a criterion is defined to estimate the overall network performance by considering both the overall network service and operation effectiveness and the network cost. An ILP model is formulated to solve the HC-RMLSA problem under static network scenario. Then, we propose an independent optimization genetic algorithm with priority-based rationality adaption (IOGA-PRA) by coordinating a set of hybrid-cast requests simultaneously to solve the HC-RMLSA problem under both static and dynamic network scenarios. Numerical results show that the performance of IOGA-PRA is very close to the optimal solutions obtained by the ILP model on the network cost-effectiveness in static network scenario. The IOGA-PRA also achieves outstanding improvement of the overall network performance compared with benchmark algorithms in the dynamic network scenario.

Energy‐efficient modulation scheme for software‐defined optical network

An energy-efficient modulation scheme (EEMS) is proposed to address the routing, modulation level and spectrum assignment (RMLSA) problem. A lot of study on RMLSA based on the assumption: the higher modulation level, the fewer frequency cost. The frequency cost is analysed and the result shows that different bandwidth request may result in same frequency slots cost. On the basis of it, an EEMS is proposed to find the lowest modulation level without impacting the spectrum usage. The results of numerical experiments verify the effectiveness of the scheme.

An Efficient IA-RMLSA Algorithm for Transparent Elastic Optical Networks

This paper proposes a new Routing, Modulation Level and Spectrum Assignment (RMLSA) algorithm that considers the effects of physical layer in transparent elastic optical networks. The goal of the algorithm is to reduce the circuit blocking probability caused by the transmission quality degradation in the establishment of new circuits. The proposed algorithm is compared with two other Impairment-Aware RMLSA (IA-RMLSA) algorithms: Modified Dijkstra Path Computation (MD-PC) and K-Shortest Path Computation (KS-PC). The IA-RMLSA algorithms are evaluated under three different composition of bandwidth request for EON and NSFNet network topologies. Besides, we also evaluated the performance of IA-RMLSA algorithms using First-Fit and Best-Fit to spectrum assignment. Simulation results show that the proposed algorithm exhibits better performance than the MD-PC and KS-PC algorithms with regard to i) the circuit blocking probability, ii) the bandwidth blocking probability, iii) the fairness of service to different source-destination pairs, and iv) the fairness of service to different bandwidths. In general, regarding the circuit blocking probability, our algorithm achieved the best performance working with First-Fit (FF). Our algorithm using the FF has a minimum gain of 78.10% and 55.75% compared to the KS-PC-FF and MD-PC-FF algorithms, respectively, when the network attends 7 different values of bandwidth. Regarding the bandwidth blocking probability, the proposed algorithm using the FF has a minimum gain of 71.96% and 41.89% compared to the KS-PC-FF and MD-PC-FF algorithms, respectively. In general, regarding fairness, the proposed algorithm exhibits superior performance compared to the KS-PC and MD-PC algorithms.

Optical ring metro networks with flexible Grid and distance-adaptive optical coherent transceivers

The utilization of distance-adaptive coherent optical transceivers in combination with a flexible finer-grained Wavelength Division Multiplexing (WDM) grid has been proposed in optical core networks to enable higher spectral efficiency and flexibility in the allocation of traffic flows. However, the application of distance-adaptive transceivers in metro networks, which are typically based on ring topologies and characterized by shorter distances and lower traffic volumes, is still an open research area both in terms of network resource savings and coherent technology requirements. This paper discusses and analyzes an optical metro ring network architecture with distance-adaptive coherent transceivers and formalizes the routing, modulation level, and spectrum assignment (RMLSA) optimization problem over such a network in order to evaluate the possible benefits introduced by the use of coherent technologies and of a spectrum grid of finer granularity in metro scenarios. Comparisons with legacy WDM systems show significant savings in terms of spectrum occupation and transceiver utilization.