Mirror-aided non-LOS VLC channel characterizations with a time-efficient simulation model

Photonic Network Communications - The emerging cost-efficient visible light communication (VLC)-based indoor wireless network requires an economical solution for backhaul transmission....     

Power consumption modeling in optical multilayer networks

The evaluation of and reduction in energy consumption of backbone telecommunication networks has been a popular subject of academic research for the last decade. A critical parameter in these studies is the power consumption of the individual network devices. It appears that across different studies, a wide range of power values for similar equipment is used. This is a result of the scattered and limited availability of power values for optical multilayer network equipment. We propose reference power consumption values for Internet protocol/multiprotocol label switching, Ethernet, optical transport networking and wavelength division multiplexing equipment. In addition we present a simplified analytical power consumption model that can be used for large networks where simulation is computationally expensive or unfeasible. For illustration and evaluation purpose, we apply both calculation approaches to a case study, which includes an optical bypass scenario. Our results show that the analytical model approximates the simulation result to over 90% or higher and that optical bypass potentially can save up to 50% of power over a non-bypass scenario.     

Logical topology design for IP rerouting: ASONs versus static OTNs

IP-based backbone networks are gradually moving to a network model consisting of high-speed routers that are flexibly interconnected by a mesh of light paths set up by an optical transport network that consists of wavelength division multiplexing (WDM) links and optical cross-connects. In such a model, the generalized MPLS protocol suite could provide the IP centric control plane component that will be used to deliver rapid and dynamic circuit provisioning of end-to-end optical light paths between the routers. This is called an automatic switched optical (transport) network (ASON). An ASON enables reconfiguration of the logical IP topology by setting up and tearing down light paths. This allows to up- or downgrade link capacities during a router failure to the capacities needed by the new routing of the affected traffic. Such survivability against (single) IP router failures is cost-effective, as capacity to the IP layer can be provided flexibly when necessary. We present and investigate a logical topology optimization problem that minimizes the total amount or cost of the needed resources (interfaces, wavelengths, WDM line-systems, amplifiers, etc.) in both the IP and the optical layer. A novel optimization aspect in this problem is the possibility, as a result of the ASON, to reuse the physical resources (like interface cards and WDM line-systems) over the different network states (the failure-free and all the router failure scenarios). We devised a simple optimization strategy to investigate the cost of the ASON approach and compare it with other schemes that survive single router failures.     

Data-centric optical networks and their survivability

The explosive growth of data traffic-for example, due to the popularity of the Internet-poses important emerging network requirements on today's telecommunication networks. This paper describes how core networks will evolve to optical transport networks (OTNs), which are optimized for the transport of data traffic, resulting in an IP-directly-over-OTN paradigm. Special attention is paid to the survivability of such data-centric optical networks. This becomes increasingly crucial since more and more traffic is multiplexed onto a single fiber (e.g., 160×10 Gb/s), implying that a single cable cut can affect incredible large traffic volumes. In particular, this paper is tackling multilayer survivability problems, since a data-centric optical network consists of at least an IP and optical layer. In practice, this means that the questions "in which layer or layers should survivability be provided?" and "if multiple layers are chosen for this purpose, then how should this functionality in these layers be coordinated?" have to be answered. In addition to a theoretical study, some case studies are presented in order to illustrate the relevance of the described issues and to help in strategic planning decisions. Two case studies are studying the problem from a capacity viewpoint. Another case study presents simulations from a timing/throughput performance viewpoint     

Influence of the IP Traffic Asymmetry on the Cost of the Optical Network Layer

The main traffic to be carried by a backbone network in the future (or even now) will be (is) IP traffic, which is unidirectional and asymmetric in nature. Today, most backbone networks are still designed for bidirectional, symmetrical services like SDH/SONET. In the future, the transmission links in the optical layer will probably still be symmetric (same amount of capacity installed in both directions of the optical link), and operators will probably continue to lease bidirectional capacity to their customers. However, the traffic that will be conveyed over those bidirectional transmission links will be mainly unidirectional and asymmetric. This paper studies the influence of the asymmetric nature of IP traffic on the underlying optical layer. In case the optical layer contains bidirectional symmetric capacity (as is almost always the case nowadays), it shows how cost(in)efficient this optical capacity is used for IP traffic patterns with varying asymmetry. The comparison is also made with a unidirectional optical layer, in which the capacity (line-systems) installed in the network is asymmetric (more capacity can be present in one direction of an optical link than in the other direction), or in which the capacity that is leased by operators is asymmetric (e.g., an ISP can choose to lease two wavelengths from city A to city B and five wavelengths in the other direction, from city B to city A).     

All-optical tree-based greedy router using optical logic gates and optical flip-flops

Due to ever-increasing throughput demands, the lookup in conventional IP routers based on longest prefix matching is becoming a bottleneck. Additionally, the scalability of current routing protocols is limited by the size of the routing tables. Geometric greedy routing is an alternative to IP routing which replaces longest prefix matching with a simple calculation employing only local information for packet forwarding. For the first time, in this paper we propose a novel and truly all-optical geometric greedy router based on optical logic gates and optical flip-flops. The circuit of the router is constructed through the interconnection of SOAs and directional couplers. The successful functionality of the proposed router is verified through simulation. The circuit enables high data rate throughput.     

Energy efficiency of femtocell deployment in combined wireless/optical access networks

Optical/wireless convergence has become of particular interest recently because a combined radio wireless and optical wired network has the potential to provide both mobility and high bandwidth in an efficient way. Recent developments of new radio access technologies such as the Long Term Evolution (LTE) and introduction of femtocell base stations open new perspectives in providing broadband services and applications to everyone and everywhere, but the instantaneous quality of radio channel varies in time, space and frequency and radio communication is inherently energy inefficient and susceptible to reflections and interference. On the other hand, optical fiber-based networks do not provide mobility, but they are robust, energy efficient, and able to provide both an almost unlimited bandwidth and high availability.In this paper, we analyze the energy efficiency of combined wireless/optical access networks, in which LTE technology provides ubiquitous broadband Internet access, while optical fiber-based technologies serve as wireless backhaul and offer high-bandwidth wired Internet access to business and residential customers. In this contest, we pay a particular attention to femtocell deployment for increasing both access data rates and area coverage. The paper presents a novel model for evaluating the energy efficiency of combined optical/wireless networks that takes into account the main architectural and implementational aspects of both RF wireless and optical parts of the access network. Several hypothetical network deployment scenarios are defined and used to study effects of femtocell deployment and power saving techniques on network’s energy efficiency in urban, suburban and rural areas and for different traffic conditions.     

Benchmarking and viability assessment of optical packet switching for metro networks

Optical packet switching (OPS) has been proposed as a strong candidate for future metro networks. This paper assesses the viability of an OPS-based ring architecture as proposed within the research project DAVID (Data And Voice Integration on DWDM), funded by the European Commission through the Information Society Technologies (IST) framework. Its feasibility is discussed from a physical-layer point of view, and its limitations in size are explored. Through dimensioning studies, we show that the proposed OPS architecture is competitive with respect to alternative metropolitan area network (MAN) approaches, including synchronous digital hierarchy, resilient packet rings (RPR), and star-based Ethernet. Finally, the proposed OPS architectures are discussed from a logical performance point of view, and a high-quality scheduling algorithm to control the packet-switching operations in the rings is explained.     

Hybrid optical network architectures: bringing packets and circuits together

In recent years hybrid optical network architectures, which employ two or more network technologies simultaneously, were proposed. They aim at improving the overall network design by combining the advantages of different technologies while avoiding their disadvantages. In order to structure this developing research field, we classify such hybrid architectures based on the degree of interaction and integration of the network technologies. Also, we discuss the three classes and their main representatives regarding key characteristics, performance benefits, and realization complexity. Finally, we highlight two hybrid architectures and show their key benefits compared to the respective non-hybrid architectures through a dimensioning case study.