Andreas Gladisch

Power efficiency of optical versus electronic access networks

Based on a model of a typical operator network we have compared the power consumption of different broadband access technologies and architectures especially DSL, FTTN + VDSL and FTTH. Even though power management improves the performance there is still clear advantage of FTTH with respect to energy efficiency.

Application of amplitude histograms for quality of service measurements of optical channels and fault identification

A novel method for the characterisation of channel quality is investigated theoretically and experimentally. It is based on the evaluation of amplitude histograms generated by asynchronous sampling. The method enables estimation of the bit error ratio and identification of the source of perturbation.

Cost analysis of the service migration problem between communication platforms

Increased competition in the telecommunications industry pushes network operators to rationalize their total costs. Models and simulations appear as major tools aiming at better understanding the expenditures and to allow a more realistic network planning. However, their focus was, in the past, mostly limited to infrastructure investments. Because emerging services pose special requirements towards the networks, operators have not only to extend the capacity of their transport networks, but also need to optimize the architecture for differentiated services with advanced packet switching technologies, referred to as Next Generation Networks (NGN). During network evolution with disruptive technology changes, a general problem faced by network operators is the service migration of active services from an existing platform into a newly setup platform. This work investigates strategies for service migration at minimized overall operational costs. A novel service migration cost model based on queueing theory and hill climbing optimization is provided in order to tackle the employee allocation optimization problem. Based on this framework, a thorough techno-economic analysis of costs and benefits is presented.

Field demonstration of a transparent optical 10 Gbit/s-WDM-network based on normalized transmission sections

Error-free 10 Gbit/s transmission and flexible reconfiguration of transparent wavelength channels over a fully transparent optical network was demonstrated in a field experiment. The test network was realized by cascades of numerically optimized basic transmission sections consisting of a combination of standard single-mode fibers and dispersion compensating modules. A maximum optical path-length of 1720 km was successfully realized without opto-electrical signal conversion.

Quantitative evaluation of architectures for multilayer transport networks

This paper evaluates different architectures for multilayer IP transport networks. The evaluation is based on an exemplary network dimensioning of a reference IP backbone network topology, connecting 63 points of presence (PoPs) in Germany. The network dimensioning results are used for a techno-economic analysis of the different network architectures, taking into account hypothetical but realistic cost models.

Service cost model and cost comparative studies

Purpose – The purpose of this paper is to propose a service cost model which can be used to evaluate the impact of different management functionalities or network platforms to the service cost.Design/methodology/approach – Following the validation of the importance that OpEx has on the overall TCO, a classification of the costs is proposed, based on their relation to the network. Two main types of costs have been identified: network based costs and service based costs. Both cost types have been modeled as a set of interconnected processes based on the network and service life cycle respectively. Network and service cost models have been integrated into a single framework. These models have been implemented as Markov chains, which include the dynamic behavior of services. Two different methods for the implementation (analytical versus non‐analytical) have been compared from the implementation and computation time point of view. The proposed service model has been used in two case studies: cost comparison o...

Assessment of network architecture with respect to different service scenarios

The suitability and efficiency of network architectures strongly depend on the service requirements and the mixture of services at different network levels. A case study has been performed in which five different service scenarios have been defined considering the characteristics of network operators. Starting with a service scenario which assumes only Layer 3 IP services, the amount of Layer 2 (Ethernet) and Layer 2 services (leased line) have been increased subsequently in the remaining four scenarios. Moreover, Layer 1 services have been differentiated with respect to broadband leased lines and narrowband services. The service scenarios have been applied to assess network architectures based on IP/MPLS, Ethernet and flexible and static optical systems, respectively. The impact of control plane implementations, i.e GMPLS and ASON, have been analyzed. Ethernet is making its way into metro and core networks. The development of Ethernet services and technology and their integration into MPLS/GMPLS based networks is still hampered by open issues. Evolutions in this area will be a key differentiator for network architecture evolutions.

Global seamless network demonstrator: carrier grade automatic switched transport network implementation in realistic telecom field environment

The Global Seamless Network (GSN) Demonstrator is presented, a joint effort of system vendors and Deutsche Telekom Group R&D to demonstrate network functions and management integration and enable, for the first time, experiences with a carrier grade Automatically Switched Transport Network (ASTN) implementation and the envisaged main ASTN clients, IP and Ethernet. For end-to-end monitoring capability, integrating the view on the ASTN and Ethernet-MAN configuration, an UMS (Upper Monitoring System) is being developed. Furthermore broadband application were implemented to visualise the network functions. The ASTN backbone consists of four cross connects and an ULH-WDM system with 3x 10Gbit/s channels (OCh) between Berlin and Darmstadt, whereby each OCh is treated as a virtual fibre.

Field demonstration of a transparent optical WDM network with 10- Gbit/s maximum channel data rate applying an optimized optical link design

A concept to design robust and flexible, fully transparent, optical long-haul networks without additional Raman-Amplification is demonstrated theoretically and experimentally. Excellent performance and flexibility at data rates up to 10 Gbit/s and transparency lengths of more than 1700 km are predicted by computer-simulations and successfully demonstrated in a field-test. Error-free transmission of arbitrary data-rates up to 10 Gbit/s over variable link distances up to 1720 km could be demonstrated without intermediate 3R-regeneration and without additional Raman-Amplification and Forward Error Correction. This field-experiment demonstrates the technical feasibility of extensive and flexible, fully transparent optical WDM-Networks.

Optics and the Challenge of Carrier Network Transformation

The transformation of network architecture towards a multi-service packet network is explained and the dependencies between new optical technologies and network architectures are discussed.