An Introduction to the Ericsson Transport Network Architecture ...

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An Introduction to the Ericsson Transport Network Architecture Stefan Danielsson The telecommunications industry has formulated a number of new standards for a new transmission hierarchy, the Synchronous Digital Hierarchy, for the purpose of reducing operating costs and improving the service offered to users. Today's fixed transmission network will evolve into a managed and software-controlled Transport Network. The Transport Network will form the infrastructure of the future telecom network and so make for successful introduction of new services, such as broadband data. The author describes the Ericsson Transport Network Architecture (ETNA), a complete system solution for a manageable synchronous Transport Network. digital communication systems telecommunication networks telecommunication network management Today's digital transmission systems are based on the Plesiochronous Digital Hierarchy (PDH) standard, which was introduced step-by-step to cater for demands for higher transmission capacity in the voice traffic network. This has resulted in a network that allows interconnection between different vendors' transmission equipment at certain standardised electrical interfaces, but also a network in which configuration changes are effected through hard-wiring and for which standards for interconnection at the optical level have been lacking. The complex network is difficult to manage and costly and time-consuming to adapt to changing requirements for transmission capacity. It consists of a large number of multiplexers at different levels and volumes of cabling between them. The line systems are underutilised; often, less than 50 % of the capacity is used. Until now, this approach has been acceptable, because the dominating voice-only traffic is predictable to some degree. But today, public network operators around the world are faced with increasing financial pressure, growing competition due to deregulated markets, and unprecedented demands from users who now view communications as a strategic business tool. Business users, notably those requiring both data and voice communications, are seeking new levels of guaranteed quality and services. The time it takes to arrange leased-line services - several weeks, sometimes months - will no longer be tolerated. The network must provide bandwidth on demand. Synchronous Digital Hierarchy Recognising these problems and demands, the telecommunications industry has formulated a number of new standards for a new transmission hierarchy, the Syn- Fig. 1 Ericsson's centre for transmission research and development at Kungens Kurva, Stockholm, Sweden ERICSSON REVIEW No. 3, 1992
59 STEFAN DANIELSSON Ericsson Telecom AB chronous Digital Hierarchy, aimed at easing the difficulties for operators and improving the services offered to users. Included in SDH are standards for new transmission bit-rates, optical interfaces, information models and communication protocols for network management and proposals for network structures. Future Transport Networks SDH offers many advantages and forms the foundation for the future transport network. SDH also underlies the Ericsson Transport Network Architecture (ETNA). ETNA is a single, open system concept that enables a public network operator to optimise his use of existing resources and make a smooth migration towards future broadband digital services. Included in ETNA are all the transmission links, switching, routing and management facilities needed to deliver wideband and broadband services - data, voice, image and video. Network management is of the utmost importance. It is only through powerful network management that the cost and service benefits from SDH can be fully utilised. ETNA consists of a family of Network Elements and one common Network Management system, FMAS (Facility Management System). The Network Elements have basic functionality in common; they terminate electric and optical signals, perform switching at various signal levels and are controlled from FMAS. Due to somewhat different applications and optimisation criteria, two product lines are defined: Digital Cross Connect Systems (DXC) and SDH Transmission Systems (SMUX). Digital Cross-Connect Systems DXCs are transmission channel switches for semi-permanent connections. With totally transparent switching characteristics, the DXC can terminate any PDH or SDH signal for selection and rerouting at any lower-order level. DXCs provide extensive switching capabilities for network restoration and network configuration in central hubs with heavy concentrations of circuits. SDH Transmission Systems SDH transmission systems include a range of terminal multiplexers, intermediate regenerators and add/drop multiplexers based on SDH standards for transmission at 155 Mbit/s, 620 Mbit/s and 2.5 Gbit/s. The systems are built from a common set of modules to reduce the stockholding of spares and to simplify capacity upgrades. SMUXs are used in pointto-point, bus or ring configurations and provide a distributed type of network configuration with line or ring protection for network restoration. Fig. 2 ETNA supports a layered-architecture approach to Transport Network configurations AXD 4/1 (DXC) AXD 1/0 (DXC) Add/Drop Multiplexer (SMUX) AXD 2500 (SMUX) AXD 620 (SMUX) ACXD 155 (SMUX)
Page 1: ERICSSON REVIEW 3 1992 An Introduct
Page 6 and 7: 60 Fig. 3 AXD 155 system integratio
Page 8 and 9: Control and Operation of SDH Networ
Page 10 and 11: 64 These functions and a number of
Page 12 and 13: 66 to the OS upon detection of a se
Page 14 and 15: 68 BOX 3 The SDH NE MANAGEMENT ORGA
Page 16 and 17: Fig. 4 Control System Architecture
Page 18 and 19: 72 Fig. 6 Software Architecture CSA
Page 20 and 21: 74 Functional requirements Certain
Page 22 and 23: 76 Fig 10 SMUX Control System Hardw
Page 24 and 25: AXD 4/1, a Digital Cross-Connect Sy
Page 26 and 27: 80 Fig. 2 AXD 4/1, System Architect
Page 28 and 29: 82 Fig. 3 Time Space Switch structu
Page 30 and 31: 84 Fig. 4 AXD 4/1 Devices Devices o
Page 32 and 33: 86 The control signals, which come
Page 34: 88 Fig. 8 Protection Switch Unit st

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