Ericsson (Denmark)

We present a unifying framework for a new class of receivers that employ linearly-constrained interference cancellation (IC). The associated multiuser detectors operate in various modes and options ranging in performance from that of IC detectors to that of linear receivers, yet provide more attractive performance/complexity tradeoffs. They exploit both space and time diversities as well as the array-processing capabilities of multiple antennas and carry out simultaneous channel and timing estimation, signal combining and interference rejection. Additionally, they can operate on both links and in multiple mixed-rate traffic scenarios. The improved performance can be translated to increased utilization of wideband code division multiple access networks, particularly at high data rates.

We report a comprehensive crosstalk investigation of a packaged InGaAsP/InP 4/spl times/4 semiconductor optical amplifier gate switch matrix, experimentally as well as theoretically. For a fully loaded switch with the same wavelength on all four inputs, all possible switching combinations are analyzed, thus yielding realistic crosstalk figures. Coherent and incoherent crosstalk phenomena are identified, and a switch crosstalk less than -40 dB has been measured.

Packaged 4/spl times/4 semiconductor optical amplifier gate switch arrays have been studied experimentally and analytically. Experimentally, a dynamic range of the input power to the switch of more than 20 dB was obtained at 622 Mb/s with less than 2 dB power penalty. Wavelength division multiplexing transmission with four channels at 622 Mb/s each through the same path was successfully demonstrated. The switch was also evaluated in an installed fiber network, where a 2.5 Gb/s signal was transmitted through three cascaded switch routes and 160 km fiber. A numerical time-domain model incorporating an electrical filter in the receiver confirmed the experimental results. It furthermore indicated that residual reflections between the different waveguide sections within the switch and at the chip facets may degrade the performance of the switch.

General, statistical properties of accumulation of interferometric crosstalk due to a number of interfering signals are analyzed. The probability density function of the total crosstalk is derived as function of the sum of the incoherent crosstalk contributions associated with the interfering signals, Because the total crosstalk level can be expected to vary only slowly as compared to the time duration of one bit, the probability p that the total crosstalk exceeds a maximum tolerable value is introduced as a parameter in the crosstalk and bit error rate analysis of optical networks. General computations show that the crosstalk requirement on optical network elements may be significantly relaxed if it can be accepted that it is possible, although most unlikely, that the total crosstalk may exceed this maximum tolerable value. The statistical crosstalk model is then illustrated by investigation of optical network examples with respect to their crosstalk and transmission properties, and, finally, compared with previous crosstalk models.

<p>We consider a naive, quadratic string matcher testing whether a <br />pattern occurs in a text; we equip it with a cache mediating its access to the<br />text; and we abstract the traversal policy of the pattern, the cache, and<br />the text. We then specialize this abstracted program with respect to a<br />pattern, using the off-the-shelf partial evaluator Similix.<br />Instantiating the abstracted program with a left-to-right traversal policy<br /> yields the linear-time behavior of Knuth, Morris and Pratt's string<br />matcher. Instantiating it with a right-to-left policy yields the linear-time<br />behavior of Boyer and Moore's string matcher.</p>

One of the most popular ways to improve the software development capability in organizations is to embark upon a Software Process Improvement (SPI) program often based on a normative model. Main concerns in such a SPI program includes creating commitment towards SPI, involving all parts of the organization in the SPI program, and creating opportunities for learning. We suggest the use of project assessments to support SPI programs in addressing these and other important concerns. In this paper we present two techniques to perform project assessments. The paper contains actual results from applying the two techniques in two longitudinal SPI projects in Danske Data and L.M. Ericsson Denmark. The techniques have proven to be effective tools to support the SPI process in terms of the three concerns; commitment participation, and learning.

In this paper we focus on adaptive modulation strategies for multicast service in orthogonal frequency division multiple access systems. A reward function has been defined as the optimization target, which includes both the average user throughput and bit error rate. We also developed an adaptive modulation strategy, namely local best reward strategy, to maximize this reward function. The performance of different modulation strategies are compared in different SNR distribution scenarios, and the optimum strategy in each scenario is suggested.

Management of Virtual Private Networks (VPNs) is becoming an increasingly important issue in the context of integrated broadband communication (IBC). In the near future corporate customers may want to subscribe to broadband VPN services offered by globally operating service providers to replace most of their leased line services that are used today to build their corporate networks. The concepts historically known as characterizing VPNs, such as the concept of closed user groups, will still be valid, but the importance of VPN service features and, in particular, the set of VPN management services offered to VPN customers will become dominant. In this paper we present a detailed technical approach to the management of broadband VPNs based on current technology and common standards. In particular, we discuss architectural solutions, management interfaces and management services provided at these interfaces, as well as managed objects.

Abstract Never before have there been so many organizations working with process improvement as today. These organizations have higher demands on the improvement concepts that they adopt from research and consulting than the ‘pioneer’ organizations had. Concepts must have a track‐record of proven success in other organizations and they should be directly transferable and adoptable. This requires packaged knowledge, ready to use and including a suitable level of support. This paper describes such packaged knowledge on how to run improvement programs and the experiences from applying it in real industrial software development organizations. This paper describes a model and method for how an organization can introduce and implement a successful improvement program. The model, named the Accelerator model, points out key activities necessary for leading an improvement program and gives recommendations on how to implement those activities based on experience and best practice. This paper also describes a method for how to apply the model to accelerate an improvement program, and finally presents real experiences from the full‐scale implementation at two of Ericsson's software design centres, one in Norway and one in Denmark. Copyright © 2001 John Wiley & Sons Ltd

The article describes the application of the integrated services concept where IP is using ATM as the transport layer for providing QoS control. Integrated services technologies based on IPv6 have been developed and implemented in a pan-European field trial where students are evaluating distance learning applications with QoS control. An overview of the architecture is given, followed by a description of the features of the basic technologies. The background for selecting the technologies is described. The focus is on the access network domain, and the objective is to reduce the resources required and be able to offer a range of premium services. The work of extending user applications for distance learning with QoS is described. The technical performance and user perception of QoS control were tested and evaluated in the trials. The main conclusions and recommendations are discussed. The integrated services concept is recommended for use in the access network. It was found that QoS control of end-user applications is of benefit for distance learning. However, the design of the user interface should hide all network-relevant parameters from the end user. There is a need for standard software to support integrated services.

The evolution of an open market for telecommunication services provides a wide range of opportunities for the provision of value added services by providers other than public network operators. One service already available today is that of a virtual private network that provide dispersed corporate sites with wide area data and telephony capabilities using public network services. The introduction of B-ISDN allows for the provision of VPN services in a much more integrated fashion is the current practice. However in the short to medium term any effective VPN service must be able to deal with the technological and organisational heterogeneities that are present when providing a high level of service functionality over an arbitrary number of administrative domains. This paper presents the design of a management service for a VPN that addresses some of these multi-domain and network heterogeneity issues. It outlines how a design based on the ITU-T's TMN recommendations was developed and how working prototypes were developed over a series of demonstration testbeds based on real broadband networks.

IP layer neighbor discovery mechanisms rely highly on broadcast/multicast capabilities of the underlying link layer. The Bluetooth personal area network (PAN) profile has no native link layer broadcast/multicast capabilities and can only emulate this by repeatedly unicast link layer frames. This paper introduces a neighbor discovery mechanism that utilizes the resources in the Bluetooth PAN profile more efficient. The performance of the new mechanism is investigated using a IPv6 network simulator and compared with emulated broadcasting. It is shown that the signaling overhead can be significantly reduced at the cost of a slight increase of processing complexity at the Bluetooth master device.

This paper describes an IP multicast implementation based on multicast extensions to open shortest path first (MOSPF) protocol. The MOSPF forwarding model presented in this study is used to forward multicast datagrams. The forwarding model has focused on interaction between MOSPF and OSPF in terms of group-membership link state advertisement (type-6 LSA) as well as developing a multicast routing table (MRT) and multicast forwarding cache (MFC). The MRT has been organised as a Patricia-based tree while the MFC has been maintained as hash-table data structures. The MFC entries are built from the local group database and the shortest path first (SPF) tree calculation. Since MOSPF protocol can only be deployed in networks running OSPF protocol, routing functionalities, such as flooding process, forming adjacencies, election of the designated router (DR) and the backup designated router (BDR), will be provided by the OSPF protocol. Implementation of MOSPF is required since MOSPF is the only multicasting routing protocol that can be configured for hierarchical multicast routing and also support for IP multicast's expanding ring search. In addition to that, MOSPF, like the other dense mode multicast routing protocols-distance vector multicast routing protocol (DVMRP) and protocol independent multicast (PIM) dense mode-is effective in commercial Internets.

To investigate the importance of nutritive environment in the healing of reconstructed ligaments, the morphology of sutured free patellar ligaments in synovial fluid of the contralateral knee joint, without re-establishment of microcirculation, was studied in rabbits. After two weeks (n = 6) and one (n = 6) and three (n = 5) months, the sutured ligament was removed from the joint and fibroblasts were seen growing into the suture gap. The ligaments were enveloped in a capsule of fibroblasts, which was more developed in those ligaments that were studied three months after operation. The collagen of the piece of ligament was disorganised at all time points, and tensile strength (n = 6) was low compared with non-sutured patellar ligament. Some ligaments disappeared or were partly attached to the synovial membrane and revascularised. The findings indicate that diffusion of nutrients may be important for the survival and healing of reconstructed ligaments, as the ligaments can heal in synovial fluid without re-establishment of the microcirculation.

It is today commonly acknowledged that the optical switch will be a key component in future optical communications networks [1,2,3]. Apart from requirements such as high flexibility and transparency to bit rate and format, optical switches must be able to support wavelength division multiplexed (WDM) networks and already existing components as especially erbium doped fibre amplifiers (EDFA’s). Several designs have been suggested and implemented including both lithium-niobate [4] and semiconductor based [5] devices. Among the latter, loss-compensating components [6,7] are believed to be advantegeous, since the switch architectures will probably get rather extended. The main disadvantage compared to switches without amplification is that a limited dynamic range is obtained due to the semiconductor gain medium. The switch evaluated here (see fig 1) is a monolithic strictly non-blocking device based on semiconductor optical amplifier (SOA) gates in InGaAsP/InP, operated in the 1550 nm window [8]. Publications of optical switches have so far mainly dealt with unpackaged components. Performance has often been measured with a cw source as to achieve gain optimisation. In this paper, extensive bit error rate (BER) measurements on fully packaged InP switches are presented concerning dynamic range and dependence upon polarisation of the incoming signal. The system has been optimised for low BER rather than maximum gain. Furthermore, cascading of several switches and a WDM experiment demonstrate the usefulness of this component in future optical WDM networks, and theoretical simulations investigate dependence of reflections and bit rate.

Management of Virtual Private Networks (VPNs) is becoming an increasingly important issue in the context of integrated broadband communication (IBC). In the near future corporate customers may want to subscribe to broadband VPN services offered by globally operating service providers to replace most of their leased line services that are used today to build their corporate networks. The concepts historically known as characterizing VPNs, such as the concept of closed user groups, will still be valid, but the importance of VPN service features and, in particular, the set of VPN management services offered to VPN customers will become dominant. In this paper we present a detailed technical approach to the management of broadband VPNs based on current technology and common standards. In particular, we discuss architectural solutions, management interfaces and management services provided at these interfaces, as well as managed objects.

Get PDF Email Share Share with Facebook Tweet This Post on reddit Share with LinkedIn Add to CiteULike Add to Mendeley Add to BibSonomy Get Citation Copy Citation Text L. Gillner, E. Berglind, C. P. Larsen, and E. Almströmtt, "Dynamic effects in integrated 4×4 InGaAsP/InP semiconductor optical gate amplifier switch matrices," in Optical Amplifiers and Their Applications, Vol. 18 of 1995 OSA Technical Digest Series (Optica Publishing Group, 1995), paper FA2. Export Citation BibTex Endnote (RIS) HTML Plain Text Citation alert Save article

AbstractThis chapter presents results on mass customization of wireless communications services and tariffs. It advocates for a user-centric view of wireless service configuration and pricing as opposed to present-day service catalogue options. The focus is on design methodology and tools for such individual services and tariffs, using altogether information compression, negotiation algorithms, and risk portfolio analysis. We first analyze the user and supplier needs and aspirations. We then introduce the systematic design-oriented approach which can be applied. The implications of this approach for users and suppliers are discussed based on an end-user survey and on model-based calculations. It is shown that users can achieve desired service bundle cost reduction, while suppliers can improve significantly their risk-profit equilibrium points, reduce churn as well as marketing costs, and simplify provisioning.

We present for the first time to our knowledge a comprehensive investigation of linear optical cross talk in an integrated switch-a packaged 4 X 4 semiconductor optical amplifier (SOA) gate switch matrix in InGaAsP-InP and show that the cross talk is a combination of interferometric and noninterferometric effects occuring on the chip.

Integration of management systems across technological and administrative domain boundaries is a necessary prerequisite for automating or optimising service management. Despite many years of standardisation effort the number of management technologies and interface specifications seems to continue to increase. An architectural approach to integrated network management, therefore, cannot be based on any single architecture or technology, but must instead be based on recognition of diversity and interoperability. The TMN-architecture is basically such an integration architecture, although OSI is sometimes assumed to be the only realisation option. This paper presents experiences with the approach taken to realise integrated network management in the European ACTS project Prospect (project number AC052). Several layers of integration have been realised, including multi-vendor and inter-domain management, and several management technologies have been integrated, namely CORBA, OSI and SNMP.