Manfred Huber

An optical infrastructure for future telecommunications networks

For the transport of the increasing traffic volume caused by existing and new narrowband services and evolving broadband services, the enhancement of the existing public telecommunication transport network is necessary. For this purpose an optical network layer with cross-connect and add/drop functionalities will be added to the existing transport network. A comparative analysis of space, time, and optical frequency division multiplexing has shown that for the time being optical frequency multiplexing is best suited for the realization of that new network layer. This multiplexing scheme offers the greatest advantages such as very high bandwidth utilization in the fiber and simple and efficient cross-connecting of high bitrate streams. In the near future, technology will be mature enough for the realization of a demonstrator network based on optical frequency division multiplexing. The functionalities of the optical network are evaluated and the results clearly show that optical frequency conversion and regeneration should be provided by the optical network. The article also deals with the realization aspects (cross-connecting, supervision, and operation and maintenance) of an optical node. >

Towards carrier-grade next generation networks

This paper describes the objectives, concepts and solution approach of the KING research project, which is carried out jointly by a number of leading research organisations in Germany. Our overall objective is to develop efficient solutions for carrier-grade IP networks. The distinguishing characteristic of our approach is that we pursue an integrated solution to achieve the carrier-grade requirements for quality of service (QoS) and resilience as well as low-cost efficient operation.

ATM-based signaling network topics on reliability and performance

The authors consider some reliability and performance aspects of ATM-based signaling networks. They present ideas on how ATM technology, suitable system concepts, as well as simplified and enhanced protocols could maintain or even improve the reliability level of the existing Common Channel Signaling System No. 7. They also discuss possible scenarios for the interworking of ATM-based signaling networks with existing signaling networks. They also examine the aspect of performance enhancement in terms of reduced delays and increased throughput due to the ATM signaling connections with higher bit rates and protocol simplifications. >

VHDL-based communication and synchronization synthesis

This paper describes an approach for VHDL-based communication and synchronization synthesis. This design step transforms a system level VHDL description into an RT-level description. The idea is, not to synthesize system level implementations of communication, and synchronization mechanisms but to perform the synthesis step as a mapping step of an abstract communication or synchronization mechanism to one of a set of RT-level implementations. The major sub-problem, which needed to be solved for the synthesis algorithm was the topology dependent mapping of implementations.

Multichannel circuit switching-performance evaluation of switching networks

An approximate analytical method is presented for the estimation of the loss probability for single and multichannel calls in TST (time-space-time) switching networks. Two extended methods are described. The assumptions for the basic method are that: all occupation patterns of the two internal highways between a certain start and destination highway for a given number of occupied channels have the same probability, and that the state probabilities of the start and destination highway are given by a multidimensional Erlang distribution. Based on this method, the second approximation considers calls that are switched from start to destination highway. In a third method, the dependency of the states of all input and output highways is taken into account. The basic approximation has shown the best agreement with the simulation results. The other methods take into account additional properties of TST switching networks for single and multichannel connections. In order to keep the state space in a reasonable size, additional assumptions had to be used which impair the results significantly compared to the basic approximation method. >

Performance Analysis of a Combined WDM/TDM Network Based on Fixed Wavelength Assignment

Photonic telecommunication networks gain increasing importance in various fields extending from access to wide area networks. Due to limitations of fast all-optical switching technology, many promising concepts are based on circuit switching. In this paper, we propose a new and simple star topology using fixed wavelength assignment and a combination of wavelength and time division multiplexing. Owing to the fixed assignment, no tunable components or wavelength converters are needed in the central star element. For this system architecture, we present a performance evaluation based on a probabilistic method to calculate call blocking probabilities, which is validated by simulation and compared to a rough approximation based on a simple loss system. The results allow to evaluate the trade-off between capacity increase either by additional wavelengths or additional time slots in the system.

Bandwidth Management of Virtual Paths - Performance Versus Control Aspects -

In the B-ISDN the asynchronous transfer mode is used, which is subdivided into the virtual path (VP) level and the virtual channel (VC) level. For an efficient network operation, economic resource management at both levels is required. In our paper we will focus on VP management. We will evaluate the performance of different bandwidth allocation strategies for VPs (e.g. loss probability for VC connections) and their influence on the processing load for the VP bandwidth manager, which is part of the VP management. These investigations show that an improvement in performance, relating to decreased loss probability and/or increased offered traffic, is possible by using virtual path bandwidth management based on a partial-sharing strategy with two limits. It is shown that these limits of an optimal strategy can easily be determined in a totally symmetric system (i.e. all VPs and VCs on a link are of the same kind and the same bandwidth demand, all VPs have the same offered traffic). The evaluations for an asymmetric system show that it is very difficult to determine the optimal strategy because there are too many variable, correlating parameters. This paper elaborates some rules to obtain a strategy for improved performance despite these difficulties.