BT 21CN Telephone Network Upgrade
Published 21st January 2008
Between 2007 and 2011, BT will be managing the upgrade of its public switched telephone network (PSTN), ISDN and Broadband lines to its next generation network. 21 CN is an entirely new digital network that provides many services on one platform, replacing for example the existing separate PSTN and Broadband platforms.
The new network is designed to support BT’s future rollout of internet and TV services and other new digital services.
It will involve the migration of every end user, which represents approximately 30 million PSTN lines and around 8M Broadband lines.
BT is carrying out a Pathfinder exercise in South Wales to check all aspects of how the 21CN will operate. To date only one small exchange (Wick near Cardiff) is operational and intense testing is being carried out. It is envisaged that a small number of other exchanges in the Cardiff area will be upgraded before the end of 2007.
The rollout of other areas will start when BT have carried out an in depth review of the Pathfinder project, this is currently anticipated to begin June 2008 onwards
Telecare Services Association
The Telecare Services Association (TSA) on behalf of its members, is facilitating close working between BT & the Supply Sector to prepare Telecare Service providers for the migration to 21CN.
The TSA, BT and the supply sector-working group agreed that a list of responsibility would be generated, and that each supplier would then be responsible for testing the equipment it has responsibility for.
21CN Testing Programme
BT have provided test facilities to telephony equipment manufacturers so that the equipment can be tested on a simulated representation of a 21CN network in order to demonstrate their level of compatibility.
The testing focuses’ on the main changes of 21CN:
- Balanced ringing – this can affect older equipment in such a way that the equipment may no longer recognise the incoming ringing signal.
- Line lengths – the maximum length of telephone lines from the exchange will increase from 6km to 10km, and may result in lower speech volumes and potentially unreliable communications.
- Reduced line current – the telephone line current available for equipment in the home has been reduced from 40mA to 25mA – performance of receiver and hands free may be reduced.
- End to end delays – the new network will have a higher nominal end to end delay and this is likely to increase over time as new digital services are added and the network load increases; this will cause some protocols to operate unreliably and may result in alarm calls not getting through to the alarm receiving centre.
BT categorise the outcome of this testing as follows:-
- Pass – equipment functionality not affected by 21CN
- Pass 1 – user perception affected (e.g. ringing tone different)
- Pass 2 – user operation affected (e.g. user has to switch from pulse to tone dialling)
- Partial fail – some functionality lost. The reliability of the equipment is reduced and may mean that the end user of the equipment could be at increased risk.
- Fail – equipment not advised to be used on 21CN
21CN and Telecare Equipment
The potential effect of 21CN on telecare equipment can be measured in several ways, firstly whether the equipment will continue to operate without risk on the new network, and secondly what impact will there be on the day of changeover to both equipment in the service users home and in the monitoring centre.
Manufacturers recommendations
Given the life critical nature of telecare equipment and services, any increased risk to the service user must be identified as quickly as possible.
Telecare equipment signals alarms through to the monitoring centre using one of a number of proprietary communication protocols, these protocols have evolved over time to meet the changing needs of the telephone network and the telecare service providers, however some of the older equipment uses protocols that were not designed to cope with the changes introduced by the 21CN network, and this may result in erratic or unreliable operation, and with the potential for failure as the network loading increases with the provision of new digital services.
Pass (and Pass 1 or 2)
Equipment categorised as a Pass is ready to integrate, and when integrated onto the 21CN network it will not effect user perception or operation.
Where equipment is categorised as Pass 1 (or 2) some user perception or operation may be affected and service providers should consult the manufacturers for advice.
Partial Failure
Equipment that is categorised as Partial Failure, may have significant functionality lost for example scheme equipment may not be able to detect incoming calls, leaving the monitoring unable to contact service users through this route.
One of the principal causes of ‘partial failure’ in older telecare equipment is through the effects on communication protocol of increased end to end delays, this at best would cause significantly reduced reliability when alarms are being signalled through to the monitoring centre, at worst, it could result in total communications failure. – these effects are difficult to quantify as equipment may operate on the 21CN when nominally loaded, but over time, or as the network load increases, the equipment can be left in a state where it is unable to raise an alarm call.
We have categorised equipment in the partial failure category, where the more prevalent communication protocol suffers these effects (although it may be possible to pass if a different protocol is selected, this would be subject to a site visit to assess the equipment and the monitoring centre receiving the alarm call).
Failure
Equipment in this category will not operate on the 21CN network.
The British standard BS7369 (originally published 1991) has been comprehensively tested and does not provide reliable communications at nominal network loads and is therefore not recommended for use on 21CN.
21CN Compliance statement
Chubb Community Care (formerly Initial Attendo) has completed the testing of its current range of products, and has also completed testing of a wider range of legacy equipment where practical (i.e. that is no longer for sale or obsolete). The testing was undertaken on the 21CN network emulator provided by British Telecom at their testing labs in Martlesham. All of the current range of Chubb Community Care products are fully compatable with, and ready to migrate to the new network.
As agreed by the TSA / BT supply sector working group, the testing performed by Chubb Community Care encompassed the following branded equipment Initial Community Care, Telefusion, Raitel, Shorrock Community Care, Wolsey, Attendo Systems Ltd & Cass.
The results of this testing have been published as a table that shows the brand, approximate age, test status and comments.
The testing status column shows the categories that have been defined by British Telecom (see previous information on Pass / Partial Fail / Fail).
The information pack and test results are available through our helpdesk on 01254 688548, please note for audit purposes we will need to record the customers name and contact details before it is released.
Next Steps
We are strongly recommending to all of our customers that you review your asset register against the results of this testing and use this as the basis for your risk register as soon as possible.
At a minimum it is recommended that you record :
- Equipment brand,
- Equipment type,
- Monitoring centre,
- Communications protocol used,
- Approximate age of equipment,
- Maintaining organisation,
- Telephone number of equipment.
Please consult your regional sales manager if you need any assistance in gathering this information and to discuss the potential impact.
Our service team can assist you in compiling a 21CN equipment audit, please contact our helpdesk on 01254 688548 for further details.
BS7369 and the revised Common Protocol
Published 20th June 2007
The following statement has been released by TSA and it’s Supply Sector technical committee to clarify the situation regarding the introduction of the 21CN telephone system.
Members of the Supply Sector have been preparing for the introduction of the 21CN system by testing their existing equipment. Tests have revealed that equipment that relies on the existing BS7369 protocol may not deliver a robust performance during heavy load/traffic conditions on the new network. Members of the Supply Sector technical working group have been addressing this issue and have now designed a protocol specifically to work with 21CN. The new protocol also features enhancements designed to meet the expected growth in Telecare provision in the coming decades. The project is targeted for completion by Autumn 2007 with a view to submitting it to BSI for review and approval.
Further information.
The new enhanced protocol is the only one that has been specifically designed for the new 21CN.
The new protocol is open to the industry and the enhancements are designed to allow greater flexibility as the Telecare market expands.
The format of the new protocol has been agreed, software implementation is complete and interoperability testing has been performed at BT laboratories on the 21CN simulator
The following links give further information –
Some Questions and Answers can be found on the TSA website http://www.asap-uk.org
General information about 21CN can be found at: http://www.btplc.com/21cn
Information about 21CN and migration can be found at: http://www.switchedonuk.org
BT Supplier Information Notes (SINs) can be found at: http://www.sinet.bt.com
The UK Transmission Plan can be found at: http://www.nicc.org.uk
Customer Premise Equipment (CPE) enquiries can be made by email at:
Back