Optical Transport Network Architectures Research Articles

Improving efficiency of network resources in elastic optical transport network by using in-network cache functions

We developed a network architecture called information-centric elastic optical transport network (i-CEON) that enables efficient content delivery. Increasing the volume of video traffic consumes network resources, so it is necessary to establish optical transport network architectures suitable for content delivery. For this purpose, we extend existing information-centric networking to be applicable to elastic optical networks. The main focus of this paper is presenting the method in i-CEON of optimizing optical-path routing by effectively using an in-network cache function to efficiently accommodate content traffic. This reduces redundant use of network resources. We formulate the joint optimization problem of elastic optical-path routing and content-replication placement as a mixed integer linear programming problem and also develop a heuristic algorithm. We conducted intensive numerical experiments to demonstrate the effectiveness of our method and confirmed that it reduced network cost by 21% and server load by 32%.

Modeling Cost Versus Flexibility in Optical Transport Networks

Optical transport networks are progressively being designed around reconfigurability. Operators require an infrastructure capable of carrying large amounts of data, but also able to deliver that data when and where needed. While centralized control plane architectures based on software-defined networking are pushing flexibility in automation and interoperability, many of these objectives are reliant on a hardware-enabled flexible data plane. At the same time, reduced operating margins imply that capacity planning through resource overprovisioning is increasingly unsustainable. Therefore, a natural tradeoff between cost and flexibility emerges in many aspects of optical transport network architectures. More complex and reconfigurable hardware, such as flexible-rate transponders or switching fabrics, can be pitted against cheaper purpose-built modules as contending alternatives for incrementally deploying networks. The added value of adaptability to changing conditions must be evaluated against its potential upfront cost and capacity overprovisioning risk. In this context, technoeconomic analysis based on multiperiod capacity optimization plays a pivotal role in identifying the target network scenarios for fixed and flexible hardware. In this paper, use cases where the cost/flexibility tradeoff emerges in optical transport scenarios are identified, such as in the design of line cards and multilayer grooming architectures, and multiperiod optimization frameworks based on integer linear programming (ILP) models are presented. More generally, this paper also discusses scalability issues affecting the use of ILPs for multiperiod capacity optimization, and proposes some simple design and modeling guidelines to help overcome them. These include either reformulating the models themselves, or identifying specific subproblems within the global framework that can be offloaded without undermining the validity of the results.

5G C-RAN With Optical Fronthaul: An Analysis From a Deployment Perspective

The fifth generation (5G) wireless technology is designed to provide significantly faster Internet access, with lower latency, and ubiquitous mobile coverage compared to its predecessors. However, as there will be hundreds and thousands of wireless cells deployed in the 5G network, transporting the enormous volume of data instigated from high capacity 5G wireless cells to the core network in a cost-effective and greener manner with a low latency still remains one of the major hurdles. Therefore, in this paper, we exploit different optical transport network architectures and technologies that can be used to build an efficient fronthaul network for 5G, in order to carry data between wireless cells and the central office. Particularly, we equitably compare multiple fronthaul architectures in terms of major requirements of 5G fronthaul network such as bandwidth requirements, delay budgets, deployment costs, complexity of radio remote head, and the ability to support advanced wireless functions. In order to analyze the deployment cost of entire 5G transport and wireless networks, we develop a joint optimization framework to optimally deploy fiber-based fronthaul network and 5G wireless network simultaneously. Our framework is also capable of setting limits on the required network coverage and capacity. We analyze the optimal deployment costs under different deployment scenarios and different fronthaul technologies. Our analyses provide insights into modeling future-proof optical transport networks to realize 5G network deployment.

Performance analysis of multicast routing and wavelength assignment protocol with dynamic traffic grooming in WDM networks

The need for on-demand provisioning of wavelength-routed channels with service-differentiated offerings within the transport layer has become more essential because of the recent emergence of high bit rate Internet protocol IP network applications. Diverse optical transport network architectures have been proposed to achieve the above requirements. This approach is determined by fundamental advances in wavelength division multiplexing WDM technologies. Because of the availability of ultra long-reach transport and all-optical switching, the deployment of all-optical networks has been made possible. The concurrent transmission of multiple streams of data with the assistance of special properties of fiber optics is called WDM. The WDM network provides the capability of transferring huge amounts of data at high speeds by the users over large distances. There are several network applications that require the support of QoS multicast, such as multimedia conferencing systems, video-on-demand systems, real-time control systems, etc. In a WDM network, the route decision and wavelength assignment of lightpath connections are based mainly on the routing and wavelength assignment RWA. The multicast RWA's task is to maximize the number of multicast groups admitted or minimize the call-blocking probability. The dynamic traffic-grooming problem in wavelength-routed networks is generally a two-layered routing problem in which traffic connections are routed over lightpaths in the virtual topology layer and lightpaths are routed over physical links in the physical topology layer. In this paper, a multicast RWA protocol for capacity improvement in WDM networks is designed. In the wavelength assignment technique, paths from the source node to each of the destination nodes and the potential paths are divided into fragments by the junction nodes and these junction nodes have the wavelength conversion capability. By using the concept of fragmentation and grouping, the proposed scheme can be generally applied for the wavelength assignment of multicast in WDM networks. An optimized dynamic traffic grooming algorithm is also developed to address the traffic grooming problem in mesh networks in the multicast scenario for maximizing the resource utilization and minimizing the blocking probability. Copyright © 2011 John Wiley & Sons, Ltd.

Elastic and adaptive optical networks: possible adoption scenarios and future standardization aspects

There is growing recognition that we are rapidly approaching the physical capacity limit of standard optical fiber. It is important to make better use of optical network resources to accommodate the ever-increasing traffic demand. One promising way is to introduce elasticity and adaptation into the optical domain through more flexible spectrum allocation, where the required minimum spectral resources are allocated adaptively based on traffic demand and network conditions. In this article, we discuss elastic and adaptive optical networks from the perspective of future standardization. We first overview the architecture, enabling technologies, and benefits of elastic and adaptive optical networks with the new concept of an optical corridor. We then present possible adoption scenarios from current rigid optical networks to elastic and adaptive optical networks. We discuss some possible study items that are relevant to the future standardization activities. These items include optical transport network architecture, structure and mapping of the optical transport unit, automatically switched optical network/generalized multiprotocol label switching control plane issues, and some physical aspects with possible extension of the current frequency grid.

Spectrum-efficient and scalable elastic optical path network: architecture, benefits, and enabling technologies

The sustained growth of data traffic volume calls for an introduction of an efficient and scalable transport platform for links of 100 Gb/s and beyond in the future optical network. In this article, after briefly reviewing the existing major technology options, we propose a novel, spectrum- efficient, and scalable optical transport network architecture called SLICE. The SLICE architecture enables sub-wavelength, superwavelength, and multiple-rate data traffic accommodation in a highly spectrum-efficient manner, thereby providing a fractional bandwidth service. Dynamic bandwidth variation of elastic optical paths provides network operators with new business opportunities offering cost-effective and highly available connectivity services through time-dependent bandwidth sharing, energy-efficient network operation, and highly survivable restoration with bandwidth squeezing. We also discuss an optical orthogonal frequency-division multiplexing-based flexible-rate transponder and a bandwidth-variable wavelength cross-connect as the enabling technologies of SLICE concept. Finally, we present the performance evaluation and technical challenges that arise in this new network architecture.