Metro Area Networks Research Articles

Telecommunications network design with multiple technologies

In this paper we consider a telecommunications network design problem allowing for multiple technologies. The problem arises in wide-area network and metro-area network design for which a combination of technologies may be necessary due to high traffic volumes, long-distance transmission, and design restrictions. The network design problem builds the best network to channel traffic between a set of origins and destinations, which requires selecting links, equipping them with fiber, deciding on the type of technology, and locating switches. The goal is to minimize the total cost of the network, which accounts for the flow cost, the fiber and technology costs, and the switch-location cost. We model the problem using a multicommodity network design formulation with side constraints. We apply Benders decomposition to the problem and develop a two-phase solution method that uses a number of improvements over the basic Benders algorithm. We present promising results on randomly generated test problems.

Performance evaluation of the phase encoded optical CDMA system

Recently, there has been increasing interest in field of Optical CDMA due to its potential for offering unmatched features at ultra high data rates in field of local and metro area networks. In this paper, a very simple method of Optical CDMA encoding known as the Temporal Phase Encoding is discussed and the performance of the system with this encoding technique is evaluated on the basis of number of users, length of the spreading code for 4-phase and 8-phases. Simulation results for the system are presented for upto seven users. Bit error rate curves are plotted with data rate of 1 Gbps. This has been found that performance improves if normalized threshold higher than 0.5 is used.

CORNet: An OBS metro ring network with QoS support and fairness control

The rapid evolution of networks has been driven by new advances in enabling technologies and the explosive growth of Internet traffic. Optical Burst Switching (OBS) is not only cost-effective, but also provides high throughput, high bandwidth utilization, and low transmission latency. These benefits make OBS a viable solution for next-generation Metro Area Networks (MANs) in which the traffic models will be changed more dramatically than in today's networks. This paper employs Wavelength Division Multiplexing (WDM) technology to construct a loss-free OBS metro ring architecture designated as the Collision-free Optic-burst Ring Network (CORNet). The proposed architecture ensures a collision-free transmission of data bursts, while retaining the advantage of the statistical multiplexing provided by conventional OBS networks. A novel distributed Medium Access Control (MAC) protocol to integrate the support of differentiated service and fairness access in CORNet is presented. The proposed Quality of Service (QoS) provisioning mechanism adopts a bandwidth-reservation approach which combines real-time transmission establishment and termination routines. Furthermore, a credit-based fairness control scheme is designed to guarantee the transmission fairness of best-effort traffic. Simulation results are presented to demonstrate that the proposed CORNet system provides good performance for real-time traffic while simultaneously providing significant performance improvements for best-effort traffic.

Towards a Wi-Fi ecosystem: Technology integration and emerging service models

This paper outlines emerging business models of heterogeneous wireless networks that are mainly Wi-Fi centric. Wi-Fi networks can be integrated with the Internet and cellular infrastructures to offer innovative services (data and voice) to individuals and businesses. In the metro area network or a “hot city” type of coverage, an integration of WiMAX and Wi-Fi technologies will provide the most cost-effective solution of backhaul and access, for both voice and data services. In the cellular arena, as mobile operators look for new ways to connect, Wi-Fi can easily be integrated with the existing mobile data networks (2.5 G/3 G). An integrated offering that combines the mobility of cellular and the speed of Wi-Fi is an ideal mix for mobile broadband subscribers. This article also analyzes how Wi-Fi technology is being complementary to other wireless technologies, leading to an expansion of an organized Wi-Fi ecosystem. From an integration standpoint, this article shows the importance of Wi-Fi for cellular operators and also shows how Wi-Fi is crucial for WiMAX technology to evolve, till the mobile version of WiMAX becomes a reality. Finally, the paper describes why regulators and policy makers should seek suitable strategies to promote or encourage Wi-Fi as an alternative broadband access technology.

First Experimental on OXADM Restoration Scheme Using Point-to-Point Configuration

This paper introduces a new optical device model named as Optical Cross Add and Drop Multiplexer (OXADM) which is potentially useful in CWDM metro area network. The device uses the combined concepts of optical add/ drop multiplexing and optical cross connect between two main transmission lines in order to implement the wavelength routing operation [10]. Thermal-optical switches are integrated in the device to make it re-configurable. With its excellent features, the device is particularly designed to improve the network efficiency, flexibility and survivability [7, 8]. The device can be used in point-to-point, ring or mesh network topology to provide functionalities such as routing, supervision, transport, multiplexing and restoration of client digital signals processed predominantly in the optical domain [7]. The wavelengths on each optical trunk can be switched into each other while implementing add and drop functions simultaneously. The paper highlights on first experimental work on 2x2 OXADM prototype to measure OSNR values for single operation of OXADM. The results show the condition is in safe with (OSNR>20dB) for every function of OXADM. With 6 dB insertion loss, the maximum achievable transmission length by the OXADM is 71 km without amplification and the maximum achievable node is 6 units.

OBT: Optical Burst Transport in Metro Area Networks

For the past few years, the evolution of electro-optical technology has driven change in optical networks in the access and backbone areas. Optical bypassing and traffic aggregation mitigate the scalability problem in backbone networks, and burst mode transmission can provide a cost-efficient solution for access networks. Using those technologies, a new solution can be found for metro area networks, which interconnect access and backbone networks. In this article, we introduce a new solution for metro area networks, called optical burst transport (OBT). OBT is designed to use the promising technologies of backbone and access networks so that it provides all benefits, such as dynamic bandwidth provisioning, scalability, and robustness for unbalanced traffic. The performance evaluation of OBT also is verified by means of a testbed implementation.

Optical Cross Add and Drop Multiplexer (OXADM) in CWDM Ring Network

This paper introduces a new optical device model named as Optical Cross Add and Drop Multiplexer (OXADM) which is potentially useful in CWDM metro area network. The device uses the combined concepts of optical add/drop multiplexing and optical cross connect between two main transmission lines in order to implement the wavelength routing operation [10]. MEMs optical switches are integrated in the device to make it re-configurable. With its excellent features, the device is particularly designed to improve the network efficiency, flexibility and survivability [7, 8]. The device can be used in point-to-point, ring or mesh network topology to provide functionalities such as routing, supervision, transport, multiplexing and restoration of client digital signals processed predominantly in the optical domain [7]. The wavelengths on each optical trunk can be switched into each other while implementing add and drop functions simultaneously. The multiplexer has undergone performance test at 2.5 Gbit/s (OC-48) with BER less than 10 -9 . The maximum achievable transmission length by the OXADM is 71 km without amplification with insertion loss of 6 dB.

Difficulties involving dynamic polarization-based impairment measurements using Jones matrices

The concurrent realization of multiple polarization-based link impairments such as polarization-mode dispersion, polarization-dependent loss, and differential-attenuation slope creates a nontrivial measurement and analysis problem. The difficulties concerning the robustness of raw data, of minimizing drift artifacts experienced during multiple wavelength measurements, and the analysis methods that lead to physical significant interpretations are addressed. Measurements of an in-service wavelength-division-multiplexed metro-area network are presented that explicitly illustrate the limitations when using industry-standard commercial test equipment.

A Reconfigurable Ethernet/SONET Circuit-Based Metro Network Architecture

We propose a service concept in which high-speed Ethernet interfaces from end hosts are dynamically cross-connected to equivalent-rate Ethernet-over-SONET (EoS) optical circuits for transport across metro-area networks and/or wide-area networks. We call our service concept reconfigurable Ethernet/SONET circuits to end users (RESCUE). We describe how RESCUE can be used for two applications: dial-up service to Internet service provider routers and file transfers. We propose to deploy RESCUE service as an add-on to current Internet access for many reasons. Primary among these is that it allows a metro optical circuit-switched network to be operated at a high utilization, which is important to achieve a cost-effective bandwidth-efficient network. Given that end hosts with access to RESCUE service will have a choice of two paths, the primary Internet path and a secondary RESCUE option, end-host applications will need to make a routing decision. We carry out a quantitative analysis to provide a basis for this routing decision for both dial-up service and file transfers. For example, with the file-transfer application, if call-blocking probability on the optical circuit-switched network is 30% and the packet-loss rate on the transmission control protocol/Internet protocol path is 1%, a circuit setup should be attempted for files 180 KB or larger in low-propagation delay environments.

Global Open Ethernet (GOE) System and its Performance Evaluation

This paper presents an overview of global open Ethernet (GOE) architecture as a cost-effective Ethernet-based virtual private network (VPN) solution, and discusses a hardware and software implementation of a prototype system. Three main approaches have been proposed for a VPN solution on metro-area network: resilient packet ring, Ethernet over multiprotocol label switching (EoMPLS), virtual bridged local area network-tag stacking (Q-in-Q). None of these schemes can satisfy the following requirements at the same time: network topology flexibility, affordable network functionalities, low equipment cost, and low operational cost. The proposed GOE system is designed to solve VPN management problems of these approaches with MPLS VPN functionality at a low cost of Ethernet-based solution. The key components of GOE are: 1) a novel GOE tag for high-speed switching and 2) a novel routing and protection module via per-destination multiple rapid spanning tree protocol (PD-MRSTP). Via the analytical performance evaluation of EoMPLS, Q-in-Q, and GOE, we show that the memory cost and the network utilization of GOE is two-three times smaller and 22% higher than the other approaches, respectively. We also have developed a GOE prototype system and obtained the following remarkable hardware and software performance results. The GOE core switch delivered 100% of theoretical maximum throughput (10 G) with zero packet loss even with the field programmable gate array platform, and its 10-G port density is 1.5 times denser than the best currently available products. The GOE switch using PD-MRSTP also delivered a significantly fast protection switching time (1.975 ms), which was significantly faster than legacy Ethernet switches. These performance evaluation results prove that the proposed GOE system can be used as a cost-effective high-performance Ethernet-based VPN solution.

Operation, administration, and maintenance of Ethernet services in wide area networks

Recent developments in Ethernet technology, such as 10G Ethernet interfaces, Ethernet passive optical networks, and resilient packet rings are pushing Ethernet from the local area network environment to metropolitan and wide area network environments. For Ethernet service providers, managing Ethernet services efficiently is key to a sustainable business model. This article discusses issues in providing OAM features and capabilities to Ethernet services over metro and wide area networks. We analyze current Ethernet features that can be leveraged in an Ethernet OAM framework, and introduce requirements and new functionalities to support Ethernet services in wide area networks.

Performance improvement of transmission of 10 Gb/s DML in metro area network

AbstractA novel method to improve the performance of 10‐Gb/s directly modulated laser (DML) transmission along single‐mode fiber (SMF) in a metro‐area network (MAN) is proposed. It is demonstrated that by adapting the filter with a special central frequency shift and suitable bandwidth, the dispersion power penalty can be effectively reduced. A distance limit of 10 Gb/s DML along SMF is extended to 51 km in simulation and elementary experiment. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 40: 130–132, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11306

Metropolitan area optical networks

Presented the requirements, architectures, and performance of optical MANs. We outlined our considerations about the evolution of metro area networks from SONET rings to transparent WDM rings. We also described the major transport impairments that the network designer should account for in transparent WDM MANs. A properly engineered network utilizing application-optimized components and fiber will enable the buildup of cost-effective metro/regional WDM optical networks that satisfy all the requirements and demands.

A stateful multicast access control mechanism for future metro‐area‐networks

Multicasting is a necessity for a broadband metro‐area‐network. Discusses the security problems with current multicast protocols. To make the multicast delivery infrastructure more secure and reliable, a stateful multicast access control mechanism, based on MAPE, is proposed. This mechanism expands the current forwarding procedure of a layer 2 switch so that stateful multicast access control can be carried out at the very edge of the metro area network. The architecture of MAPE is discussed in detail, as well as the states maintained and messages exchanged. Further explains that the scheme is flexible and scalable.

Capacity expansion of fiber optic networks with WDM systems: problem formulation and comparative analysis

In this paper we provide an arc-path formulation for the problem of locating and sizing wavelength division multiplexing (WDM) and optical cross-connect (OXC) equipment in a fiber optic network. The problem is heuristically solved by limiting the number of paths for each demand and applying CPLEX to the resulting formulation. The results obtained are then compared to those given by a metaheuristic method previously developed for this problem. A set of real and randomly generated instances with different characteristics associated with actual telecommunication networks are used to assess the performance of both solution approaches. Scope and purpose The problem that we address in this paper deals with the effective utilization of new technology designed to increase the capacity of a fiber optic telecommunication network. The problem arises when the demand for bandwidth in a fiber optic network exceeds the current capacity. The new technology, wavelength division multiplexing (WDM), can expand the capacity of a fiber optic network without requiring additional fiber. The decision problem is to find the most cost-effective combination of WDM equipment and fiber that increases the capacity of the network to a point where all the expected demand can be handled. The purpose of our paper is to introduce a new mathematical formulation for this combinatorial optimization problem that we use in two different ways: (1) finding heuristic solutions to the problem and (2) assessing the quality of the solutions found with a metaheuristic procedure. We test our approach with real data from metro area and long haul networks. The computational tests show that the proposed metaheuristic is capable of finding near-optimal solutions to this difficult problem.

Extraction of laser rate equations parameters for representative simulations of metropolitan-area transmission systems and networks

In this paper we present procedures for the extraction of laser rate equation parameters. The parameters are extracted using fitting of static and dynamic measurements with simple theoretical expressions. In particular, chirp related parameters are extracted directly through measured chirp and power waveforms. The extracted parameters are used in a large-signal rate equation laser model to calculate the power and chirp waveforms. The simulations are compared with experiments and the agreement is excellent. The procedures have been applied to directly modulated lasers having different chirp characteristics and designed for either 2.5 or 10 Gb/s operation. Using the rate equation laser model with the extracted parameters, we performed a simulation study to identify the value of employing a negative dispersion fiber in metro-area networks. It is shown that dispersion shifted fibers with negative dispersion across the entire usable fiber bandwidth (1280–1620 nm) advances the performance of directly modulated lasers used in wavelength division multiplexed metropolitan-area transmission systems and networks. At 2.5 Gb/s transmission over 300 km of negative dispersion fibers is possible for directly modulated lasers across the erbium doped fiber amplifier bandwidth, while at 10 Gb/s an impressive distance of 100 km can be achieved.

Tunable long-wavelength vertical-cavity lasers: the engine of next generation optical networks?

The incredible growth of the Internet and data transmission are pushing the bandwidth requirements for fiber networks and expansion of metro and local area networks at an unprecedented pace. One of the key requirements for a great expansion of optical networks is low cost, high-performance tunable lasers that are easily packaged and coupled to fiber. The paper reviews the terrain of both materials and device technologies that are currently driving this optical revolution and speculates on the future directions and if a single, all encompassing technology, the Holy Grail, might be realized by any of the contenders.

Cable-Based Metro Area Networks

This paper examines the system design considerations of metropolitan area networks utilizing cable television networks for the delivery of a variety of services to residential customers. Specifically, this paper focuses on the technology, marketplace, and regulatory aspects of this new and expanding market.