Grid Optical Networks Research Articles

Research on control and management of smart grid optical network based on optical transmission control Protocol (OTN) technology

Smart grids can improve the operational efficiency and reliability of power systems, and optical transmission control protocol (OTN) technology is widely used in the field of power communication. This article focuses on the control and management of smart grid optical networks, aiming to achieve efficient control and management of smart grid optical networks through OTN technology. This article proposes a smart grid OTN management system based on Optical Transmission Control Protocol (OTN) technology. This system achieves the management and optimization of power OTN business by researching functions such as container management and service orchestration, pod and physical node management, application and cluster status monitoring, application logs and cluster logs. In this system, the sources of data are very rich. Data can be obtained from databases, file streams and Flow network. This can ensure that the system receives comprehensive data support for better business analysis and decision-making. This article further studies the optimization methods of optical network control for power OTN services to improve network reliability and reduce risk levels. The experimental results indicate that the use of OTN technology can improve the operational efficiency and reliability of the smart grid, and achieve remote monitoring and control of the smart grid.

Application of Intelligent Cloud Computing Technology in Optical Communication Network Security of Smart Grid

In order to improve the security of smart grid optical communication network, this paper combines intelligent cloud computing technology to build a security system of optical communication network of power grid. In the aspect of improving communication security performance, multi-user access is realized by non-orthogonal power domain segmentation, and different users use different powers to add and superimpose the same spectrum resources, so as to increase spectrum utilization. At the sending end, this paper improves the safe channel capacity of users by means of pre-coding and artificial noise, and realizes the safe transmission of information. In terms of transmission stability, the cloud computing platform is used as a data processing platform, and multiple nodes are processed synchronously through optical communication state identification, which can more effectively improve the speed of optical communication state identification data. In order to test the performance of the power grid information dispatching model designed in this paper in optimizing power grid configuration and improving power grid load, simulation experiments are carried out. Through the experimental analysis, we can see that the communication method proposed in this paper can accurately identify the intrusion factors, and can effectively improve the security of smart grid optical communication network.

RDMSR: A reactive defragmentation with minimum spectrum route strategy for mixed grid optical network

SummaryIn this paper, we propose a reactive defragmentation with minimum spectrum route (RDMSR) for the problem of route, spectrum, and modulation‐format allocation (RSMA) in mixed grid optical network. In mixed grid network, spectrum redundancy and its assignment problem increase due to the spectrum continuity and contiguity constrains. In the proposed RDMSR strategy, process of defragmentation initiates after the termination of the existing connections. In addition, the route that needs minimum spectrum is given priority over the other available routes. The performance of the proposed strategy is compared with the two existing strategies: shortest path first (SPF) and mixed grid aware dynamic resources allocation (MDRA). Simulations are performed on NSFNET and ARPANET topologies. The existing and proposed strategies are evaluated on the metrics of bandwidth blocking probability (BBP), network capacity (NC), and average hops (AH) at three different combinations of the network traffic. Results show the proposed strategy outperforms than the other existing state of art strategies.

A polyhedral study of a relaxation of the routing and spectrum allocation problem (Brief Announcement)

The routing and spectrum allocation (RSA) problem arises in the context of flexible grid optical networks, and consists in routing a set of demands through a network while simultaneously assigning a bandwidth to each demand, subject to non-overlapping constraints. One of the most effective integer programming formulations for RSA is the DR-AOV formulation, presented in a previous work. In this work we explore a relaxation of this formulation with a subset of variables from the original formulation, in order to identify valid inequalities that could be useful within a cutting-plane environment for tackling RSA. We present basic properties of this relaxed formulation, we identify several families of facet-inducing inequalities, and we show that they can be separated in polynomial time.

A Novel Routing Strategy Towards Achieving Ultra-Low End-to-End Latency in 6G Networks

Compared to 5G, 6G networks will demand even more ambitious reduction in endto-end latency for packet communication. Recent attempts at breaking the barrier of end-to-end millisecond latencies have focused on re-engineering networks using a hybrid approach consisting of an optical-fiber based backbone network architecture coupled with high-speed wireless networks to connect end-devices to the backbone network. In our approach, a wide area network (WAN) is considered with a high-speed optical fiber grid network as its backbone. After messages from a source node enter the backbone network through a local wireless network, these are delivered very fast to an access point in the backbone network closest to the destination node, followed by its transfer to the local wireless network for delivery to the destination node. We propose a novel routing strategy which is based on distributing the messages in the network in such a way that the average queuing delay of the messages through the backbone network is minimized, and also the route discovery time at each router in the backbone network is drastically reduced. Also, multiple messages destined towards a particular destination router in the backbone network are packed together to form a mailbag, allowing further reductions in processing overheads at intermediate routers and pipelining of mailbag formation and route discovery operations in each router. The performance of the proposed approach green based on these ideas has been theoretically analyzed and then simulated using the ns-3 simulator. Our results show that the average end-to-end latency is less than 380 µs (with only 46-79 µs within the backbone network under varying traffic conditions) for a 1 KB packet size, when using a 500 Gbps optical fiber based backbone network laid over a 15 Km × 15 Km area, a 50 Mbps uplink channel from the source to the backbone network, and a 1 Gbps downlink channel from the backbone network to the destination. The significant reduction in end-to-end latency as compared to existing routing solutions clearly demonstrates the potential of our proposed routing strategy for meeting the ultra-low latency requirements of current 5G and future 6G networks, particularly for mobile edge computing (MEC) application scenarios.

Dynamic Routing and Spectrum Assignment Based on the Consecutive Sub-Channels in Flexible-Grid Optical Networks

Using Optical Orthogonal Frequency Multiplexing (O-OFDM), variable bandwidth channels can be created in Elastic Optical Networks (EON). This allows the use of spectrum more efficiently by allocating integral multiple of basic bandwidth slots to the lightpath requests. Consequently, such networks are also called flexible grid optical networks. It also adds a constraint of keeping all the allocated slots together when deciding the routes for the requests. This constraint called the contiguity constraint makes the routing and spectrum algorithms more challenging. In any network, the lightpath requests will arrive and depart dynamically and will invariably lead to spectrum fragmentation, and hence network will have a reduction in maximum possible utilization due to increased blocking probability. In this paper, we have presented an improvised RSA algorithm that leads to lesser fragmentation. It is evident from the results that the presented RSA algorithm uses adaptive parameters to reduce the blocking probability and fragmentation compared to other algorithms reported in the recent past.

Fragmentation-Minimized Periodic Network-Bandwidth Expansion Employing Aligned Channel Slot Allocation in Flexible Grid Optical Networks

Fragmentation-Minimized Periodic Network-Bandwidth Expansion Employing Aligned Channel Slot Allocation in Flexible Grid Optical Networks

Virtual Network Provisioning over Mixed-Fixed/Flexible-Grid Optical Infrastructures

With the emergence of cloud services based on data centers, demands for bandwidth-intensive applications have increased dramatically, and application services have transferred to a more diversified direction. Management as well as capacity of the backbone network needs further development to catch up with rapidly evolved application demands. Optical network virtualization can facilitate the sharing of physical infrastructure among multiple network applications. Virtual Network Embedding (VNE), the main implementation of network virtualization, determines how to map a virtual network request onto physical substrate. To expand the network capacity, flexible-grid elastic optical networks have been considered as a promising supporting technology for the future infrastructure of the next-generation Internet. However, due to the expense of key enabling equipment for flexible grid optical networks, the brown-field migration from a fixed grid to a flexible grid gave birth to the co-existing fixed/flexible grid. Based on the co-existing fixed/flexible grid optical networks, we investigate the problem of Virtual Optical Network (VON) provisioning, and present a flexible-grid-aware virtual network embedding algorithm to map the virtual networks onto the substrate network. In addition, the performance of the algorithm was evaluated under four different network scenarios. Simulation results show that the proposed algorithm can achieve better performance in all four scenarios.

Cross-layer static resource provisioning for dynamic traffic in flexible grid optical networks

Flexible grid networks need rigorous resource planning to avoid network over-dimensioning and resource over-provisioning. The network must provision the hardware and spectrum resources statically, even for dynamic random bandwidth demands, due to the infrastructure of flexible grid networks, hardware limitations, and reconfiguration speed of the control plane. We propose a flexible online–offline probabilistic (FOOP) algorithm for the static spectrum assignment of random bandwidth demands. The FOOP algorithm considers the probabilistic nature of random bandwidth demands and balances hardware and control plane pressures with spectrum assignment efficiency. The FOOP algorithm uses the probabilistic spectrum Gaussian noise (PSGN) model to estimate the physical-layer impairment (PLI) for random bandwidth traffic. Compared to a benchmark spectrum assignment algorithm and a widely applied PLI estimation model, the proposed FOOP algorithm using the PSGN model saves up to 49% of network resources.

Dynamic adaptive spectrum allocation in flexible grid optical network with multi‐path routing

Fragmentation is one of the major issues in elastic optical network (EON) due to its dynamic characteristics which may possibly degrade the spectrum efficiency. Several techniques have been presented in the literature to get the optimal solution of this problem while multi-path provisioning comes out to be very compelling among them. In multi-path provisioning enable networks, multi-path routing and spectrum assignment (MPRSA) creates further complications due to the hardware availability and more spectrum consumption. This paper presents a novel technique termed as adaptive service provisioning (ASP) to come up with a solution of the MPRSA problem and it minimizes the spectrum fragments in the network by precisely managing the scattered spectrum slots. This technique performs the adaptive traffic demand splitting on disjoint paths in case it is unable to be served by k-shortest routing paths based on the parameters such as hardware support, capacity available and demand. An integer linear programming (ILP) model as well as a heuristic algorithm for solving MPRSA problem in large optical networks where ILP is not compliant is developed. Numerical simulations are performed to investigate the performance of the algorithm in terms of blocking probability and spectrum utilization.

Service differentiation-based spectrum defragmentation in mixed grid optical networks

Abstract As the most promising candidate for upgrading today’s fixed-grid networks, the concept of flexible grid has been introduced into elastic optical networks (EONs), which enables on-demand spectrum assignment and adaptive modulation formats. Considering the cost of network upgrade, it is practical and economical for network operators to adopt the gradual migration from fixed grid to flexible grid optical network. Thus, a mixed grid optical network is a typical network scenario in the near future where fixed grid technology coexists with flexible grid technology. Spectrum fragmentation is regarded as a significant issue in flexible grid optical network. Compared with flexible grid, with heterogeneous spectral widths, more spectrum fragmentation is induced in mixed grid optical networks. Therefore, spectrum fragmentation in mixed grid optical network is actually much more challenging than flexible grid optical network. This paper first analyzes the resource allocation and proposes a novel spectrum defragmentation algorithm based on service differentiation in mixed grid optical networks. The performance of the proposed algorithm is evaluated in simulation with different traffic profiles. Simulation results verify that the proposed algorithm can effectively reduce the blocking probability by consolidating spectrum fragmentation in mixed grid optical networks.

Resource-partitioned spectrum assignment to realize efficient multicasting for flexible grid optical networks

Abstract With the increasing demand of some novel point-to-multi-point services, such as live video delivering and interactive distance learning, efficient multicasting is highly desirable in flexible grid optical networks (FGONs). Thus, many sophisticated multicast-enabled routing and resource allocation algorithms have been proposed to realize efficient multicasting in FGONs. These algorithms, known as multicast routing and spectrum assignment (MRSA) algorithms, optimized the light-trees and the allocated spectrum resources for multicast services in FGONs. But, most of them ignored some small-sized, isolated, and un-occupied spectrum bands, which are remained after multicast services being accommodated. Due to the continuity and the contiguity constraints in service accommodation, these remained spectrum bands can hardly be allocated to subsequent multicast services and are thus known as spectrum fragments. Their existence and accumulation may exhaust available spectral resources and affect the networking performance (e.g. service blocking performance) for the multicast traffic in FGONs. In this way, the efficiency of FGONs in supporting multicast traffic may be greatly deteriorated. Therefore, the spectrum fragments generated in accommodating multicast services has become an important issue in FGONs. In this paper, we propose a resource-partitioned interval-maximized (RPIM) MRSA algorithm to restrain the generation of spectrum fragments for the multicast traffic in FGONs. The proposed RPIM MRSA algorithm does not utilize the metric, “cut”, to reduce spectrum fragments via avoiding splitting the whole spectrum band into too many band pieces as in fragmentation-aware MRSA algorithms. Instead, the proposed RPIM MRSA algorithm partitions the spectrum resources on each sought light-tree into several elastic groups according to the types of multicast services, and maximizes the group interval between two adjacent groups on the sought light-trees. Since the spectrum resources in each group can always be utilized by the multicast services of the same type, the proposed algorithm restricts the generation of spectrum fragments in group intervals. In this way, the proposed RPIM MRSA algorithm can remarkably reduce spectrum fragments generated in accommodating multicast services. Note that, different from previous group-based algorithms, the proposed RPIM algorithm allows one elastic group for the multicast services of a certain type to contain different amount of spectrum resources on different light-trees. This helps guarantee the flexibility in constructing elastic groups on diverse light-trees. Additionally, the proposed RPIM MRSA algorithm maximizes the group intervals on the sought light-trees, which helps reserve more vacant spectrum resources between two adjacent groups on the light-trees. Since these vacant spectrum resources can be merged into their adjacent groups if needed, the proposed algorithm can reduce not only the spectrum fragments generated in group intervals but also the blocked multicast services in groups by maximizing group intervals on the light-trees. Simulation results verify that the proposed RPIM algorithm can realize efficient multicasting with significantly reduced spectrum fragments and low service blocking probability in FGONs.

Converged Optical, Wireless, and Data Center Network Infrastructures for 5G Services

This paper focuses on converged access/metro infrastructures for 5G services, proposing a common transport network integrating wireless and optical network segments with compute/storage domains. To identify the optimal mix of transport network technologies (optical/ wireless) and processing modules that are required to support 5G services in a cost- and energy-efficient manner, a two-stage optimization framework is proposed. In the first stage, a multi-objective optimization scheme, focusing on the transport network segment, tries to jointly minimize the capital expenditure of the converged 5G network. This is performed through the identification of the optimal mix of wireless and optical transport network technologies. The second stage focuses on the compute network segment and aims at identifying suitable processing modules to which operational 5G services need to be allocated. The performance of the proposed approach is examined using realistic traffic statistics for various network technology choices including mmWave and passive optical networks (PONs) for transport, fixed, and elastic grid optical networks across a city-wide topology in Bristol, UK.

Energy-efficient anycast scheduling and resource allocation in optical grids

In recent years, optical grid networks has been used as an ideal infrastructure to support high-performance computing environment, data intensive applications and interconnection of data centers. Due to rapid increase in the high-bandwidth applications, the power consumption of communications equipment for such networks has been increasing steadily over the past decade. Therefore, energy efficient routing schemes and traffic models can be developed to reduce the energy consumption. In many applications it is possible to select the destination node from a set of possible destinations, which have the required computing/storage resources. This is known as anycasting compared to unicasting where there is only one destination for each communication. In this paper we adopt the sliding scheduled traffic model, where setup and tear down times may vary within larger window frame. We propose a novel problem that exploits knowledge of demand holding times using anycasting model. We show how the flexibility of anycast routing can lead to additional energy saving. The problem was formulated as an integer linear program to optimally schedule demands (in time) and route them in order to minimize overall network energy consumption. The problem of energy consumption is addressed by switching off idle network components in low utilization periods. We analyze the performance of the proposed approach for anycast and unicast routing models. Our simulation results demonstrate that the proposed approach can lead to significant reductions in energy consumption, compared to traditional routing schemes.

Efficient Hybrid Grouping Spectrum Assignment to Suppress Spectrum Fragments in Flexible Grid Optical Networks

Flexible grid optical networks (FONs) can accommodate diverse kinds of service connections with higher networking flexibility and spectrum-utilization efficiency by employing a finer resource allocation granularity (known as frequency slot) and a more sophisticated path-routing and resource-allocation algorithm (known as routing and spectrum assignment algorithm), when compared to the traditional wavelength division multiplexing optical networks. However, the continuity and the contiguity constraints in spectrum allocation may possibly introduce spectrum fragments, which cannot be utilized by the subsequent service connections and thus reduce the amount of available resources as well as the networking flexibility in FONs. Therefore, many algorithms have been proposed to decrease the amount of spectrum fragments by re-optimizing the fragmented resources. These algorithms are known as spectrum defragmentation algorithms, which always induce traffic disruption or require extra components. In order to avoid traffic disruption and the requirement of extra components, some grouping RSA algorithms have been proposed to suppress spectrum fragments from their generation by pre-dividing the spectrum resources into several either fixed or variable groups. However, since the spectrum resources in one group can only be assigned to the service connections of one specific kind, the flexibility of these grouping algorithms is always limited by the kinds of service connections. In this paper, we introduce hybrid grouping mechanism into spectrum assignment and propose a hybrid-group-based RSA algorithm, most-used-first hybrid grouping (MUFHG) RSA algorithm, to suppress the spectrum fragments generated in FONs. By employing hybrid grouping mechanism, the proposed MUFHG algorithm sorts the spectrum resources into several flexible groups with specified allocation starting FSs. And each spectrum group can accommodate several kinds of service connections if the bandwidth requirements of these service connections have multiple relations, which guarantees that the remained or the released spectrum resources in each group can always be re-used. Therefore, spectrum fragments are only generated in the spectrum bands between two adjacent flexible groups. In this way, the proposed hybrid-group-based algorithm can significantly suppress spectrum fragments from their generation. Besides, the proposed MUFHG algorithm helps improve the blocking performance of the network by employing the most-used-first strategy to maximize the number of less frequently used spectrum resources for subsequent service connections. The simulation results indicate that the proposed MUFHG algorithm gains notable reductions in both spectrum fragments and bandwidth blocking probability with neither traffic disruption nor extra components.

Energy Saving Through Traffic Profiling in Self-Optimizing Optical Networks

An increasing fraction of the electrical energy produced in western countries is being consumed by Internet infrastructure; reducing its energy footprint is therefore of utmost importance for the scalability of the Internet. We address optical transport backbones and propose a novel method to reduce the energy consumed by dynamically adjusting the number of active optical carriers to support the short-term load of the network with a small and controllable margin. This is achieved in a nondisruptive manner that does not interact with routing strategies and does not rely on any specific control plane, but exploits automated traffic profiling and prediction of the well-known circadian traffic cycle. The proposed approach works with both fixed and flexible grid optical networks. We describe a method to automatically learn these patterns and multiple techniques to predict incoming traffic. Furthermore, we present an algorithm that tunes the parameters of the proposed system in order to achieve a target a posteriori probability of causing traffic losses. The behavior of the system is studied, using simulations, under a variety of conditions. Results show that the proposed prediction algorithms can significantly reduce the number of active optical carriers, even in nonoptimal scenarios, while guaranteeing low traffic losses.

Migration From Fixed to Flexible Grid Optical Networks With Sub-Band Virtual Concatenation

A novel strategy is presented to operate a mixed fixed/flexible grid optical network which may be used to gradually migrate from a fixed to a flexible mode of operation. Routing and spectrum allocation (RSA) in an optical network where fixed and flexible grids co-exist using a multi-path sub-band virtual concatenation (VCAT) or split spectrum (SS) technique is considered. Mixed integer linear programming models and an efficient heuristic algorithm based on spectrum window planes are proposed for the RSA optimization. The results obtained for the static traffic demand indicate that it is operationally more convenient to use the multi-path VCAT only by itself in a mixed grid optical network to guarantee performance comparable to that of the joint multi-path and single-path VCAT case. Network performance is also evaluated in terms of bandwidth blocking probability (BBP) under a dynamic traffic demand. Simulation results show that the multi-path VCAT scheme can efficiently utilize the overall spectrum resources with low blocking. The results of studies with both static and dynamic traffic demands also confirm that migration from a pure fixed grid optical network to a pure flexible grid will be desirable for better network capacity utilization.

On the comparative efficiency of non-disruptive defragmentation techniques in flexible-grid optical networks

The presence of dynamic traffic in optical networks can lead to spectrum fragmentation, which significantly reduce the network performance. This problem is exacerbated in flexible grid optical networks, since the heterogeneity of channel spectral widths increases the misalignment of the available slots along the optical connections. To overcome this problem, several techniques have been devised for providing defragmentation in these networks. Spectral defragmentation aims to create large contiguous free areas in optical spectrum through rerouting or spectral reassignment of existing connections. In this paper, we revisit the push-pull and hop tuning techniques, assessing them over an unified framework under equal conditions to properly evaluate their comparative efficiency in releasing network resources. This framework also includes the re-planning technique as a lower bound benchmark for the push-pull and hop tuning. To this effect, we propose Integer Linear Programming (ILP) models and heuristic algorithms to study the effectiveness of these techniques and present a performance analysis based on spectrum usage. The relative performance of the different defragmentation techniques was validated under varying network scenarios, including an assessment of how different planning methods and policies impact the effectiveness of each defragmentation technique. Aside from benchmarking the potential spectrum efficiency gain in each non-disruptive defragmentation technique, this analysis also revealed that the gains associated with them are greatly influenced by how the networks were originally planned.

Crosstalk-Aware Routing Spectrum Assignment and WSS Placement in Flexible Grid Optical Networks

Due to crosstalk-induced interactions among different connections, malicious high-power jamming signals can potentially spread widely in a transparent optical network. Moreover, due to imperfect port isolation in wavelength selective switches (WSSs), present within the optical switching nodes, crosstalk also affects the quality of the transmitted signal. Therefore, it is necessary to design an optical network in a way that the effect of crosstalk is minimized, while at the same time keeping the cost and the power consumption of the network low. This is achieved, in this work, by the design of appropriate WSS placement and crosstalk-aware routing and spectrum assignment algorithms in flexible grid optical networks, in the form of an integer linear program formulation and a heuristic algorithm analogous to vertex coloring. The objective of the optimization algorithms is to minimize the impact of the crosstalk effect, thus minimizing the impact to the normal operation of the network. The optimization objective is enhanced with proper functions in order to minimize the capital expenditure and the operational expenditure of the networks investigated in terms of cost and power consumption, respectively. Performance results indicate that the proposed algorithms minimize the number of WSSs required to compensate for the crosstalk effect, while only slightly increasing the spectrum utilization.

Crosstalk-aware Routing Spectrum Assignment and WSS Placement in Flexible Grid Optical Networks

Crosstalk-aware Routing Spectrum Assignment and WSS Placement in Flexible Grid Optical Networks