Supplementary memorandum submitted by
British Telecommunications PLC
TETRA AIRWAVE SERVICE
I am very pleased to respond to Trade and Industry
committee members' interest in issues raised in connection with
the TETRA-based Airwave service, as a result of your Inquiry into
mobile mast infrastructure.
The Airwave Service is an integrated digital
radio communications network for the exclusive use of "Public
Safety Organisations". It enables the emergency services
to communicate with each other far more effectively than their
current very dated technology permits or by using the standard
communications facilities offered by existing mobile phone systems.
Airwave uses the Terrestrial Trunk Radio System
(TETRA). Airwave base stations emit a continuous tone, which is
not amplitude modulated. TETRA terminals however use a burst of
energy from the terminal at a rate of 17.6HZ per second. They
comply fully with the guidelines on exposure to electro-magnetic
fields produced by the National Radiological Protection Board
(NRPB) as well as those of the International Commission on Non-Ionising
Radiation Protection (ICNIRP).
The Stewart Report included references to the
possible effects of radio frequency emissions at or near a modulation
of 16Hz on the release of calcium from brain tissue. However,
no health risks were suggested in the report and none have been
In recognition of this, and the many benefits
that Airwave will undoubtedly bring the police service, the Home
Secretary has concluded that the roll-out should continue as planned,
but that in parallel, the Defence Evaluation and Research Agency
and the NRPB should undertake a review of existing scientific
data. BT fully supports the Home Office approach on its approach
to this issue. Interestingly and quite coincidentally, the Western
Daily Press newspaper of 16 March carried a report that Professor
Colin Blakemore of Oxford University, who wrote the cautionary
note about TETRA in the Stewart Report, is now saying that "on
reflection (there is) absolutely no cause for alarm at all".
The attached document contains further details
on the characteristics of this service in the form of questions
and answers. I apologise that some of the material repeats the
points made in BT's earlier submission to the committee on this
issue, but we felt it important that the TETRA material was grounded
in the same context as the rest of the Inquiry.
20 March 2001
BT AIRWAVE SERVICE
This document describes the Airwave Service
and in addition provides answers to some of the most commonly
asked questions about the service. It explains why the system
is needed and sets out BT's position on such issues as health,
mast location and environment impact.
1. ABOUT THE
1.1 What is the Airwave Service?
The Airwave Service is an integrated digital
radio communications network exclusively for Public Safety Organisations.
1.2 What is BT's Interest in the Service?
BT's role is that of a service provider. We
will build the network and then manage the service on behalf of
the Police Information Technology Organisation (PITO) and the
1.3 Why is it being introduced?
At present each of the 51 police forces in England,
Wales and Scotland run their own analogue radio systems, many
of which now need to be replaced urgently. Many also have difficulty
inter-operating with neighbouring forces, a situation that can
hamper operations during major incidents. Users that have a national
remit such as British Transport Police, the National Crime Squad
and the Scottish Crime Squad, all need access to a modern nationwide
service to operate effectively.
The situation is the same for the Fire and Rescue
and Ambulance Trusts as well as other Public Safety Organisations,
each of whom are responsible for their own radio systems. At major
incidents it can be very difficult for the emergency services
to inter-operate with each other and the wider pool of public
safety organisations. Lack of adequate communications at major
incidents such as the Clapham Junction train crash, Lockerbie,
Hillsborough, Kings Cross and Hungerford has been highlighted
as a major factor hampering effective rescue co-ordination.
The situation is further complicated by the
fact that by 2005 the Government will have withdrawn the existing
frequencies used by the emergency services for their radio systems.
Therefore the emergency services will have to migrate to alternative
systems before the frequencies are withdrawn.
During the 1980s, a Home Office study into the
future of police radio communications concluded that there was
a need for a project to plan the procurement of a modern, cohesive
nationwide radio service for the Police which should also be available
to other Public Safety Organisations. This became the Public Safety
Radio Communications Project (PSRCP).
1.4 When will it be introduced?
Implementation of a pilot service with Lancashire
Police is already under way. Other Police forces in England, Wales
and Scotland will migrate to the service over the next four years.
It is expected all forces in England and Wales will be fully operational
by the end of 2004 with Scottish forces being fully operational
2. BENEFITS OF
2.1 What are the benefits of Airwave Service?
The Airwave Service offers its customers the
Digital voice quality, leading to
improved voice clarity and reduced chance of misunderstanding.
Direct access to local and national
databases, leading to better and timely provision of information
to officers/personnel in the field.
Terminals will act as an integrated
communications platform offering radio, mobile telephone and data
Secure communications, which cannot
be easily scanned or monitored, will contribute to combating crime
and safeguarding sensitive information from unauthorised access.
More effective use of control room
resources to deal with complex incidents.
Automatic vehicle and person location
will give accurate information to the location of vehicles and
officers/personnel, leading to quicker response to incidents,
more efficient use of resources, and improving officer safety.
Access to comprehensive management
information will enable better control of resources.
Interoperability between the Public
Safety Organisations will lead to a more effective co-ordination
of major incidents.
From the public's perspective, the Airwave Service
will facilitate much needed improvements in public safety by allowing
the emergency services to work more efficiently and effectively
and in a co-ordinated manner.
2.2 Is it future proof?
The Airwave Service is designed to last for
a minimum of 15 years plus. During this time we expect there to
be many advances in technology. As and when appropriate these
will be incorporated into the services. The system was independently
evaluated by an expert in the field from Imperial College London.
His report clearly indicates that Airwave Service offers the best
option for the short and medium term and is adaptable to change
in the longer term.
2.3 Will other emergency services use this
The Fire/Ambulance and a whole range of other
Public Safety Organisations are all potential users of this service.
The Airwave Service will not be available for use by commercial
3. HEALTH AND
3.1 What is BT's overall position on the health
Our position is summarised as:
There is some speculation about health
and safety issues surrounding base stations and the TETRA technology
upon which the Airwave Service is based. BT is very conscious
of its responsibility to the public, employees, customers and
other stakeholders in this, as in all of our other mobile communications
BT bases its installation and development
specifications on recommendations from The National Radiological
Protection Board (NRPB), the independent, expert body in the UK
that advises on this subject and publishes guidelines for operators
to follow. The NRPB and other reputable agencies have advised
that there is currently no convincing scientific evidence of a
risk to health through exposure to radio frequency (RF) waves
below the national guidelines. The views of the NRPB are supported
by other international expert groups, such as the World Health
Organisation (WHO) and the International Commission on Non-Ionising
Radiation Protection (ICNIRP).
BT welcomes the findings of the Independent
Expert Group on Mobile Phones (IEGMP), which was commissioned
by the Department of Health, under the chairmanship of Professor
Sir William Stewart. Whilst recognising that the remit of the
Stewart report was primarily concerning itself with the cellular
industry, we support the spirit and sentiment of the report as
applied to our broader wireless portfolio and will continue to
implement the Airwave Service to the highest health and safety
Despite current scientific opinion
that there is no convincing evidence of a risk, we will undertake
a series of measures in keeping with the recommendations of the
Stewart report. In particular we will work to ICNIRP (public)
guidelines and will support the need for continuing, relevant
and high quality research to ensure this issue is subject to the
most up-to-date and rigorous scientific scrutiny.
3.2 What is being done to look into alleged
associated health risks?
We recognise the need for continuing, relevant
and high quality research, to ensure this issue is subject to
the most up-to-date and rigorous scientific scrutiny. We support
and contribute to continuing research and are pleased to be involved
in this important and developing area.
3.3 What is BT's contribution to this?
BT has committed to contributing our share toward
funding the Government's £7.68 million radio frequency research
programme as recommended by the Stewart Report. The programme
will be conducted independently of industry and will be managed
by an expert scientific advisory committee chaired by Sir William
Stewart. The World Health Organisation (WHO) co-ordinates and
interprets research, shares the results and, most importantly,
recommends what further research needs to be done at a global
level. Moreover, the European Union has announced a major research
and risk evaluation programme related to the safety of mobile
communications. BT continues to track these and other relevant
developments as part of our ongoing commitment to addressing any
concerns. BT and the UK government have people monitoring the
issues around "Wireless Health" and attending international
conferences to keep abreast of the very latest research results.
3.4 What are base stations and are they safe?
A base station is a low power radio transmitter
with an antenna to transmit radio waves to mobile phones or handsets.
According to The World Health Organisation (WHO) one of the international
expert bodies that monitor research in this area and advise on
safety, "RF field levels around base stations are not considered
a health risk".
3.5 What if I live near a base station, am
I in danger?
Base stations operate at power levels many times
below the National Radiological Protection Broad (NRPB) guidelines.
The Independent Expert Group established by the Minister of Health
concludes "the balance of evidence indicates that there is
no general risk to the health of people living near to base stations
on the basis that exposures are expected to be small fractions
of the guideline".
3.6 The Stewart Report stating that as a precautionary
measure, amplitude modulation around 16Hz should be avoided, if
possible, in future development of signal coding. Does this not
pose question mark over the safety of base stations and terminals?
Airwave base stations emit a continuous tone,
which is not amplitude modulated.
TETRA terminals use Time Division Multiple Access
(TDMA) to enable up to four users to access a single TETRA radio
channel simultaneously. It is this TDMA which produces a "burst"
of energy from the terminal at the rate of 17.65 times per second.
Whilst there is no convincing scientific evidence of a health
risk to humans resulting from mobile phone use, it is a precautionary
measure to minimise the power level within these bursts. TETRA
terminals use a process known as "Power Control" which
dynamically controls the power transmitted by a terminal to keep
it to the minimum necessary to maintain communication with the
BT has agreed to follow the "precautionary"
approach as recommended by the Stewart Report. Emissions from
the system are within the levels specified by NRPB and ICNIRP.
These levels are based on independent research by a large number
of expert bodies, subject to extensive peer review and are set
many times below the levels where adverse health effects can be
4. PLANNING IMPLICATIONS
4.1 How many masts or base stations will be
needed to provide the Airwave Service?
To provide the geographical coverage and capacity
that Public Safety Organisations demand, it is currently estimated
that around 3,000 masts will be needed.
4.2 What criteria does BT use to decide where
to site base stations?
The positioning of any new installations is
always considered very carefully. Mindful of the need to minimise
inconvenience and visual impact, we work in close consultation
with local authorities, the Police as the primary users and many
other relevant organisations to select sites that provide the
coverage needed. Unlike mobile networks, the Airwave Service needs
to provide a very high level of national geographical coverage,
regardless of population density. In keeping with the spirit of
a precautionary approach and mindful of public concern, we will
commit to locate, as far as possible, new base stations on sites
that minimise their social impact on the local community. We also
support the development of new technology to help improve base
4.3 Do you consult local planning authorities?
We recognise that local planning authorities
are a key participant in the network development process and that
improved communication with them is a vital element in addressing
the issue. To this end, we, together with other operators, will
increase the provision of information to planners on network design
strategies and give them access to the Radio Sites Databank.
4.4 Do you share with other operators?
We aim to use existing sites and masts and only
build new ones where this option is not available to us. We redevelop
sites and share with others wherever possible.
4.5 How does BT engage in community consultation?
BT takes its responsibility for any effects
on the community very seriously. We have a dedicated team of people
who work in close partnership with the police and local planning
authorities to deliver a bespoke programme of community consultation
activities. We undertake surveys to ensure areas of outstanding
natural beauty and special scientific interest are respected.
4.6 What steps are BT willing to take to minimise
the visual impact of masts and aerials?
In sensitive areas we aim to erect the minimum
installation which will provide optimum coverage. Where possible,
we will try to meet any requests to disguise masts by altering
the colour and/or providing screening such as foliage.
4.7 What is BT's response to groups that are
taking action to prevent masts being built?
We work with the relevant bodies and organisations
to ensure we are aware of all opinions and concerns. These help
inform the process for deciding the most appropriate site, which
will also take account of other factors, such as planning and
5.1 What technology is the Airwave Service
TETRA (Terrestrial Trunked Radio) is an open
standard for digital private mobile radio approved by the European
Telecommunications Standards Institute (ETSI) and used by Public
Safety Organisations throughout Europe and beyond for a number
5.2 In basic technical terms how does the
Airwave Service enable forces to speak directly to each other?
Since the Airwave Service uses a single national
infrastructure, there is no technical restriction on where an
individual user can be located (provided they are within radio
coverage) or on the Public Safety Organisation to which they may
belong. The functionality within the service enables users to
make calls, send and receive data messages including status messages
and access the telephone network. The Airwave network comprises
of a series of base stations connected to switches. Users access
the network over the air interface (radio link to a base station)
using either a vehicle mounted or handportable terminal.
5.3 In basic terms what is amplitude modulation?
In order to transmit information some form of
modulation is necessary. Amplitude Modulation (AM) is the variation
of the power level radiated from a radio transmitter. TETRA uses
a modulation type that modulates the phase of the carrier signal.
There is an important distinction between AM and Time Division
Multiple Access (TDMA). It is the TDMA that causes the "burst"
of energy from the handset at the rate of 17.65 times per second.
TETRA does not use Amplitude Modulation.
5.4 Do transmissions from Tetra handsets have
an element of amplitude modulation in the signal coding?
TETRA terminals use a type of modulation that
modulates the phase of the transmitted power level rather than
amplitude. However, in order to allow up to four TETRA handsets
to use the same radio channel simultaneously, their transmissions
are confined to "bursts" of approximately 14 milliseconds
every 56 millisecondsa technique known as Time Division
Multiple Access (TDMA).
5.5 Does transmission from a TETRA base station
have an element of amplitude modulation?
Motorola TETRA base stations, as used for the
Airwave Service have a constant RF transmission and do not transmit
5.6 Does TETRA radiate energy at 17.6Hz?
TETRA systems radiate energy in accordance with
the conditions of their licence. For example, in the UK, public
safety operators radiate energy from 380 MHz to 400 MHz. However,
in order to allow up to four TETRA terminals to use the same radio
channel simultaneously, their transmissions are confined to "bursts"
at a rate of 17.65 times per second.
5.7 In basic terms what is signal coding?
Signal (or Channel) Coding is a process whereby
additional data is added to the user signal (digitized voice or
data) being transmitted over the radio channels in order to make
it less sensitive to errors introduced by the radio environment.
This process enhances the transmission quality of the user signal
in the presence of disturbances such as electrical noise, interference
from other radio sources and so on. Coding of the signals in a
particular arrangement conveys a certain character or message
(eg Morse Code). Present systems are designed to efficiently utilise
the available medium whilst also combating the effects of transmission
errors. An effective coding system will remove all unnecessary
symbols but add others to allow the checking to detect errors.
The Airwave Service uses an efficient Adaptive Code Excited Linear
Predictive (ACELP) voice coding.
5.8 Is the TETRA Technology more powerful
The TETRA and GSM standards define several classes
of power for mobile stations. These are maximum powers that are
considerably reduced by the power control mechanisms in both systems.
Whilst the TETRA standard actually allows for a higher power level
than a GSM mobile station, a typical TETRA mobile station would
be expected to transmit no more than half the power that a GSM
mobile station transmits.
4 The Radio Sites Databank outlines the location of
many UK radio communications structures, and can be used to locate
existing structures appropriate for base station sites. Back