HQ TELECOM ASSET MANAGEMENT

ORR have requested information on the scope and specification of the new telecom system.

This is to include a description of the functional architecture, estimated costs and

implementation timing. ORR also requires details of the fall-back contingency plans in the event

that the GSM-R systems are not implemented by 2006.

Feasibility studies for the fixed network are continuing. When these are completed specific

definition of the system elements will be made. However the architecture and functional

requirements are understood and are discussed below.

The GSM-R solution is now in Design Development phase. This must be completed before total

system size and migration strategy is understood.

This paper describes the system at high level, and will be subject to enhancement as the detail

of system elements and quantities are defined.

Railtrack's Fixed Telecom network was installed piecemeal as part of BR's electrification

and signalling projects between 1960 and 1993. Because the requirements were based

around individual project needs, technology types vary across and within zones. Fault

reporting is localised and system failure is generally uncovered only as a consequence of a

customer complaint.

Railtrack will replace this ageing network in modern form to provide a single fault tolerant

network with centralised performance and maintenance management.

The network will be required to provide essential circuits for signalling, electrification, radio

and customer information systems, as well as for more general business needs.

Functional Architecture

The network functional architecture will comprise of a high level backbone based upon

optical fibre transmission, underlaid by a mix of technology solutions related to the

bandwidth requirements (and topology) of different grades of railway lines.

The high level design proposes a number of high availability links meshed to form 9 core

rings. These are designed to provide a high degree of reliability to the order of 30 minutes

outage per link per 30 years. Further links create 35 further rings which are designed to

provide connectivity to the rest of the railway. Core links will be of the order of 10x STM-4

and the remainder 2x STM-1.

The remaining lines are expected to have relatively low bandwidth requirements, with a

number of possible technology options. These include microwave (between GSM-R radio

towers), and HDSL where continued use of copper cable is deemed feasible.

There will be a local distribution network of trackside fibres and possibly copper cables.

PDH systems will deliver the majority of the trackside transmission providing connectivity to

the lineside assets.

A concept feasibility diagram has been prepared (see over), which identifies the core and