Electronic and photonic switching in the atm era

Broadband networks require high-capacity switches in order to properly manage large amounts of traffic fluxes. Electronic and photonic technologies are being used to achieve this objective both allowing different multiplexing and switching techniques. Focusing on the asynchronous transfer mode (ATM), the inherent different characteristics of electronics and photonics makes different architectures feasible. In this paper, different switching structures are described, several ATM switching architectures which have been recently implemented are presented and the implementation characteristics discussed. Three diverse points of view are given from the electronic research, the photonic research and the commercial switches. Although all the architectures where successfully tested, they should also follow different market requirements in order to be commercialised. The characteristics are presented and the architectures projected over them to evaluate their commercial capabilities.Peer ReviewedPostprint (published version

Analysis of Migration Scenarios from Synchronous to Packet Transmission in an Operator Network

Tietoliikenneverkkojen kehitys on johtanut tilanteeseen, jossa kiinteän verkon teleliikennepalvelujen käyttöä on korvattu langattomilla ja IP-pohjaisilla ratkaisuilla. Verkko-operaattorit ovat tunnistaneet tämän kasvavan trendin ja ovat alkaneet muuttamaan verkkojaan IP-pohjaiseen seuraavan polven verkkoon. Verkkomigraatio on monimutkainen prosessi ja se vaatii paljon analyysityötä tuekseen. Migraatio täytyy optimoida niin, että saavutetaan maksimaalinen liikevaihto siirtymävaiheen aikana ja samalla ylläpidetään myös asiakastyytyväisyyttä. Tämä työ tutkii miten analyysejä hyödynnetään migraation hallinnassa ja ennustamisessa. Työssä esitellään kaksi eri esimerkkiä analyyseistä: Analyysiratkaisu, jolla kyetään ennustamaan liittymämäärien muutosta, sekä analyysi, jota hyödynnetään optimaalisen migraatiojärjestyksen määrittelyssä. Näistä analyyseistä saatava kokonaishyöty selviää vasta, kun projekti on edennyt hieman pidemmälle, mutta alustavat tulokset ovat rohkaisevia. Analyysejä implementoitaessa tunnistettiin tarve paremmalla analyysityökalulle tällä hetkellä käytössä olevan Microsoft Excelin tilalle.The evolution of telecommunication networks has led to a situation where the usage of traditional fixed telecom services has been replaced with wireless and IP-based solutions. Network operators have identified this trend and have started to migrate their networks towards IP based Next Generation Network. Network migration is a complicated process and requires a lot of different analyses. Migration needs to be optimized so that the maximum revenue is obtained during a transition process while at the same time customer satisfaction is maintained. This thesis describes how analyses help to manage and predict migration process effectively. Two separate analysis solutions are presented: A tool to predict the development of customer amounts and a tool that helps to obtain the most optimal migration order. The overall benefits of these tools will become evident in the future when the migration has progressed further but the first obtained results are encouraging. During the implementation of the analyses it was identified that a more evolved analysis platform is needed to replace Microsoft Excel currently in use

Modelling and analysis of asymmetrical latency in packet-based networks for current differential protection application

Current differential protection typically requires symmetrical communications channels—with equal latency in each direction—for correct operation. Conventionally, this has been delivered using protocols such as IEEE C37.94 over a Time-Division Multiplexing (TDM) wide-area network (WAN). Modern packet-based WANs offer improvements in efficiency, flexibility, and cost-effectiveness for utility applications. However, jitter is unavoidable in packet-based networks and, in extreme cases, jitter inevitably results in substantial asymmetrical latency in communications paths. This paper clearly defines how a new source of asymmetry arises due to the use of "de-jitter" buffers, which can jeopardize critical protection services. This is demonstrated using an analytical modelling approach, which precisely quantifies the degree of risk, and through real-time demonstration with actual devices, involving current differential protection over an IP/MPLS WAN. Using a novel method of real-time manipulation of Ethernet traffic to emulate large WANs, the modelling approach has been validated. It is shown how the sensitivity of relays to asymmetry depends on the protection settings and the magnitude of the measured load current. To address the risk of protection maloperation, a new approach for compensating for asymmetrical latency has been comprehensively validated. These developments will be of immediate interest to utilities operating, or migrating to, a packet-based infrastructure

Validating secure and reliable IP/MPLS communications for current differential protection

Current differential protection has stringent real-time communications requirements and it is critical that protection traffic is transmitted securely, i.e., by using appropriate data authentication and encryption methods. This paper demonstrates that real-time encryption of protection traffic in IP/MPLS-based communications networks is possible with negligible impact on performance and system operation. It is also shown how the impact of jitter and asymmetrical delay in real communications networks can be eliminated. These results will provide confidence to power utilities that modern IP/MPLS infrastructure can securely and reliably cater for even the most demanding applications

Application of MPLS-TP for transporting power system protection data

Power utilities are increasingly dependent on the use of communications networks. These networks are evolving to be packet-based, rather than using conventional Time-Division Multiplexing (TDM) technologies. Transporting current differential protection traffic over a packet network is especially challenging, due to the safety-critical nature of protection, the strict requirements for low delay and low asymmetrical delay, and the extensive use of legacy TDM-based protocols. This paper highlights the key technical characteristics of Multi-Protocol Label Switching-Transport Profile (MPLS-TP), and demonstrates its application for transporting current differential protection traffic. A real-time hardware-in-the-loop testing approach has been used to thoroughly validate the technologies in various configurations. It is demonstrated that MPLS-TP technologies can meet the requirements of current differential protection and other, less critical applications. In particular, it is shown that delay and asymmetrical delay can be controlled through the inherent use of bi-directional paths---even when “hitless” link redundancy is configured. The importance of appropriate traffic engineering, clocking schemes, circuit emulation methods is also demonstrated

Teleprotection signalling over an IP/MPLS network

Protection of electricity networks have developed to incorporate communications, referred to as protection signalling. Due to the evolution of the electricity supply system, there are many developments pending within the scope of protection signalling and protection engineering in general. This project investigates the use of current and emerging communications technologies (i.e. packetised networks) being applied and incorporated into current protection signalling schemes and technologies. The purpose of the project is to provide a more cost-effective solution to protection schemes running obsolescent hardware. While the medium-term goal of the industry is to move entirely to IEC 61850 communications, legacy teleprotection relays using non-IP communications will still exist for many years to come. For companies to be ready for an IEC 61850 rollout a fully deployed IP/MPLS network will be necessary and it can be seen that various companies worldwide are readying themselves in this way. However, in the short-term for these companies, this means maintaining their existing TDM network (which runs current teleprotection schemes) and IP/MPLS network. This is a costly business outcome that can be minimised with the migration of services from and decommissioning of TDM networks. Network channel testing was the primary testing focus of the project. The testing proved that teleprotection traffic with correct QoS markings assured the system met latency and stability requirements. Furthermore, MPLS resiliency features (secondary LSPs & Fast-reroute) were tested and proved automatic path failover was possible under fault conditions at sub-30ms speeds

Análisis de viabilidad de la integración de los circuitos IRR, ADL y HOT en el Sistema de Defensa Aérea a través del terminal satélite TLB-50 IP.

El proyecto abarca una propuesta de mejora de los equipos en dotación que se encuentran actualmente en la Unidad de Transmisiones del Mando de Artillería Antiaérea (UTMAAA), así como las diferentes Baterías de Artillería Antiaérea a las que esta Unidad presta apoyo. La propuesta se centra principalmente en aumentar la operatividad de la Artillería Antiaérea en cuanto a capacidades de despliegue, dotando a la UTMAAA de terminales satélite TLB-IP y equipos que posibiliten su compatibilidad con los equipos multiplexores que se emplean en la Artillería Antiaérea. Las mejoras que se proponen permitirán desplegar tanto las Baterías como el Centro Director de Fuegos (FDC) en cualquier asentamiento sin depender de ningún punto de integración terrestre y sin comprometer su capacidad operativa gracias al uso de enlace satélite con el terminal TLB-IP. De esta manera, durante las misiones en el extranjero se podrá contar con enlace directo con la red estratégica española y acceder a la información aérea que pueda otorgar. Además, las Baterías no dependerán de tendido de cable o radioenlace con Línea de Visión Directa con el FDC para su emplazamiento, lo que les permitirá situarse en lugares tácticamente mejores, más ocultos y más seguros, sin comprometer el enlace ni su estabilidad. Para el desarrollo de este proyecto se ha tenido en cuenta la experiencia aportada por el personal de la 2ª Compañía de la UTMAAA en cuanto al uso de equipos y conocimientos técnicos, así como experiencia en maniobras y operaciones reales. Se ha contado, además, con diversa documentación técnica proporcionada por la propia Compañía y por las empresas de telecomunicaciones INDRA, RAD y SISTELEC.<br /