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RAKE
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Radio Activated Key Guidelines |
AA (Automobile Association)
EVSA (Electronic Vehicle Security Association) LPRA (Low Power Radio Association)
MIRA (Motor Industry Research Association)
Motor Insurance Repair Research Centre
PSDB (Police Scientific Development Branch)
RAC Motoring Services
RA (Radiocommunications Agency)
RSGB (Radio Society of Great Britain)
SMMT (Society of Motor Manufacturers and Traders)
Sold Secure Ltd
The Radio Activated Key Entry (RAKE) Committee has been established in response to the increasing number of UK motorists who are experiencing a problem with vehicles fitted with 433MHz radio controlled security systems. RAKE has been formed to try and resolve the problem. RAKE members include motoring organisations, radio users, representatives of vehicle, radio and security equipment manufacturers and representatives from UK central government departments.
The number of cars using radio key fobs to unlock doors and de-activate security systems was estimated to be more than 2 million at the end of 1996. The problem is expected to get steadily worse. The AA and RAC estimate that more than 8,800 breakdowns attended in 1996 were a result of remote key fobs being blocked by radio interference.
In 1993 a European frequency of 433.92 MHz for radio car keys was allocated by the European Radio Committee (ERC); this became European Law in 1995. The same frequency was already legally allocated to other users: the primary UK user being the Ministry of Defence, with secondary users including amateur radio operators and traffic information systems. Some private and public access mobile radio networks operate close to the 433MHz band. These stronger sources of radio transmissions can sometimes block the signal from a radio activated key.
RAKE is suggesting the following actions to resolve the problem.
These Guidelines have been produced by RAKE to fulfill the short and medium term objectives. The document is aimed at those organisations specifying or designing vehicle equipment employing radio activated keys; these include vehicle manufacturers, aftermarket suppliers and manufacturers of low power radio devices. It is also intended to aid legislators and competent authorities involved with radio key systems.
Following a description of the problem, the general operational and technical requirements of the radio related equipment are presented.
The RAKE Committee (more simply referred to as 'RAKE' in the remainder of this document) has been established in response to the increasing number of UK motorists who are experiencing problems with vehicles fitted with 433 MHz radio controlled security systems. The radio key access problem has been extensively highlighted in the UK media. RAKE comprises organisations whose members or customers are adversely affected by these problems. These include the Radio Society of Great Britain, the Motor Industry Research Association representing the Society of Motor Manufacturers and Traders, the Royal Automobile Club, the Automobile Association, the Low Power Radio Association, the Radiocommunications Agency, Sold Secure Ltd, the Motor Insurance Repair Research Centre (Thatcham), the Electronic Vehicle Security Association and the Police Scientific Development Branch. Addresses and telephone numbers of participating organisations can be found on the back cover of this document.
Failure of the 433MHz key fob transmission to gain access to the vehicle and to disable the vehicle alarm and immobiliser is resulting in motoring organisations in the UK experiencing tens of thousands of calls per year for assistance. A RAKE survey of manufacturers has revealed that more than 2 million vehicles have been sold up to the end of 1996 with a 433MHz system fitted. This is expected to increase at a rate of 1.1 million vehicles per year. These figures exclude aftermarket fitted systems. Based on the motoring organisations records to date, 3% to 5% of these vehicles will experience a problem with their 433MHz radio key security system.
Such a problem is inevitable when using an unprotected frequency for radio control of vehicle systems and when employing receiver designs which may suffer blocking in the presence of strong signals on frequencies well away from the receiver's centre frequency. Whilst, ultimately, the ideal solution must be an exclusive, primary frequency allocation for vehicle radio keys, significant improvement can be obtained through careful system design and specification. User Guidelines, at the end of this document, contain RAKE advice on measures available to a vehicle user to minimise the chances of a frequency blocking problem.
In the UK the primary users of the 433MHz frequency are government services with secondary users including amateur radio operators, traffic information systems and car key fobs. Some private and public access mobile radio networks operate close to the 433MHz band.
RAKE has collated information from around mainland Europe and has discovered that the problem is not just a UK concern. In addition to primary users, in mainland Europe the frequency is used for many other purposes including remote control of dockyard cranes, vehicle winches, cordless hi-fi systems and children's' walkie-talkies.
RAKE has three clear objectives.
These Guidelines are intended to be supportive of the European Vehicle Security Directive [Ref 1] and may assist in its interpretation.
The implications of escalating numbers of unintentionally immobilised vehicles resulting from background radio frequency (RF) interference include:
RAKE is concerned about the:
Although RAKE has confined its investigations to RF key systems, the use of an infrared alternative is not without problems. Range reduction through bright sunlight or dirty vehicle glass and blocking by infrared floodlights, now commonly associated with urban CCTV security systems, are all possible problems with the most likely alternative to the RF key. These issues are however, beyond the current scope of RAKE.
These Guidelines are intended to benefit those specifying or designing vehicle equipment employing radio activated keys; these include vehicle manufacturers, aftermarket and original equipment (OE) suppliers and manufacturers of low power radio devices. The Guidelines are also intended to aid legislators and competent authorities involved with radio key systems.
In the context of these Guidelines, the following definitions have been employed:
| Radio Key | A low power radio frequency transmitter, compliant with the MPT 1340 specification, used to operate vehicle alarms, immobilisers, central locking and other secondary vehicle functions (e.g. sunroof and window closure). It is usually enclosed within a keyfob. Operation at 418MHz is legal in the UK and at 433MHz in the UK and Europe. The radio key operates in conjunction with a receiver located within the vehicle. |
| Frequency blocking | Prevention of radio key operation through the presence (or jamming) of a stronger signal at the vehicle receiver. This interfering signal may be on the same precise centre frequency as that of the radio key (e.g. 433.92MHz) or it may contain sufficient energy in a frequency range in which the radio key receiver is still sensitive. Note: A poorly designed receiver may have a wide frequency band over which it is sensitive, making it prone to blocking. |
| Original Equipment (OE) | Equipment fitted by the vehicle manufacturer in the production plant or at an import centre prior to delivery to the customer. |
| Aftermarket | Either manufacturer approved equipment fitted by a franchised dealer or other equipment independently fitted after the vehicle has left the franchised dealer. |
The following sections provide advice to vehicle manufacturers on the specification offered to their radio key system suppliers and give advice to equipment suppliers on their target product performance.
Vehicle systems employing radio activated keys can be divided between those which are convenience features and those which are safety critical or have a major impact on vehicle operation. Vehicle access, sunroof and electric window operation are examples of convenience features whilst vehicle immobilisation systems can generally be considered safety critical.
Safety Features
Radio keys should never be used as the sole means of activation for
safety critical applications and the use of radio keys should always be carefully weighed
against the convenience of operation.
In all applications where radio activation is used , any failure of or interference to the communications link should result in the system remaining safe.
General Features
For use under conditions of suspected interference, the customer should be given
guidance on how to identify sensitive areas on the outside of the vehicle, close to the
vehicle receiver antenna, at which to operate the key fob. From this
position the keyfob should operate more effectively. This information should be available
in the vehicle handbook, marked as a 'hot spot' on the dash or headlining as appropriate
and should be available to roadside rescue and recovery organisations.
An alternative means of vehicle entry and mobilisation, which does not compromise the vehicle security, should be provided. In addition, alternative methods of operation of all radio key functions, such as the sunroof or boot opening, should be available. Any alternative systems should not compromise the safety or security of the vehicle.
Written advice should be provided to customers to the effect that ' ... since this system operates by use of radio it is possible that it will be subject to interference which may result in the system failing to operate in its normal manner ... '.
Concise, durable instructions should be available as a reminder of the alternative access systems. These should not include any information that may compromise the vehicle security. Location options may include markings on the dashboard, sunvisor or keyfob rather than loose cards. They should be clear and easy to follow.
The keyfob should be marked with its operating frequency. Radio activated key systems should be 'user friendly'. Consistent with the overriding security considerations, operation of the key, for example to re-synchronise a rolling code, should be as intuitive as possible and anticipate likely actions of a non-technical customer.
As good practice, requirements of the Vehicle Security Directive [1] should be implemented in advance of the legally enforceable dates: 1 January 1997 for new products; 1 October 1998 for all products.
Technical Features
Products should comply with current, relevant legal requirements. Currently, those in
force, or pending, are listed at references [1] to [4].
These features apply to systems using a uni-directional radio link.
Radio Key
Note: other restrictions on duty cycle and transmission time may be imposed by the radio regulatory authorities.
Receiver
Early receiver designs have resulted in excessive broadband emissions. Hence compliance with the requirements of references [1] to [4] is paramount.
Combined System
The bandwidth of a receiver may be significantly greater than the bandwidth of other services which may fall within its passband. A well designed receiver will be sensitive over a narrow bandwidth around its nominal operating frequency, making it more selective and hence less prone to blocking.
With the radio key held in a position declared by the manufacturer, the system should operate successfully in the presence of interfering signals of the following field strengths:
Frequency offset (Df) from centre frequency of key transmission (fo) |
Compliance 1997 |
Compliance from 1 Jan 2000 |
Df >= 5% fo |
3V m-1 |
3V m-1 |
5% fo > Df > 500kHz |
100mV m-1 |
1V m-1 |
Df <= 500kHz |
1mV m-1 |
1mV m-1 |
Interfering signals on image frequencies, and other declared frequencies, should not be omitted from this test. Unless otherwise stated the test procedures are those set out in the EMC standard for Short Range Devices [3].
The long term RAKE objective is to establish, in conjunction with the UK Radiocommunications Agency and its European counterparts, an appropriate frequency, and ideally, one allocated solely for radio key entry systems.
Over the next few years, the number of vehicle radio key users will approach the number of mobile phone users (30 million in Europe and 90 million world-wide). Comparison with the internationally allocated bandwidth available to mobile phone users, and even broadcast use, should help the argument for a common radio key frequency across Europe.
As a first step, in the UK, the next 2 years will see the removal of some users of the 433MHz band to other parts of the spectrum.
Improved technology, particularly a reduction in transmitter and receiver bandwidths, and possible introduction of harmonised band planning, will help the situation at 433MHz.
Manufacturers should be aware of pending new European harmonised frequency bands for Short Range Devices. It is RAKE's objective to secure appropriate allocations within these, or other bands, to ensure the reliable use of automotive radio systems.
These Guidelines will be updated as required in the light of revised legislation and technology developments.
Radio Type Approval Standards. Spectrum Management Approval;
Recent media articles have highlighted the potential problems of radio interference affecting the operation of electronic key fobs for car alarms and immobilisers. While this problem currently affects a limited number of vehicles, the Radio Activated Key Entry (RAKE) committee believes the problems will increase as the number of new vehicles fitted with these systems multiplies.
Car security systems which potentially suffer problems are those operating on 433.92MHz in both the UK and Continental Europe. The frequency was assigned to electronic vehicle key entry systems by the Frequency Management Working Group of the European Radio Committee (ERC) of the CEPT* and it was widely accepted by European Motor Manufacturers. The Radiocommunications Agency agreed to the harmonised assignment reluctantly, knowing that there were other high power users near or on the frequency selected. This allocation became European Law in 1995.
The systems affected are generally security and entry systems, operated using a remote key fob at a short distance away from the car; typically not more than 3 metres. The system can be fitted as original equipment, or as an aftermarket unit. They can be affected by interference from stronger signals on or around the same frequency 'blocking' the signal from the key fob and preventing the security system from being armed or disarmed.
At present, RAKE - which includes the RAC, the AA, the SMMT, the Radio Society of Great Britain, the Electronic Vehicle Security Association, the Low Power Radio Association and other interested parties - is in the process of identifying all the possible sources of interference which can 'block' vehicle security systems. However, the primary legal user allocated to this frequency is the Ministry of Defence and other government communications networks, with secondary legal users including: amateur radio operators; mobile radios; some private radio networks; and more recently some motorway traffic information systems.
The solutions to the problem can be relatively simple. RAKE offers the following advice:
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Automobile Association Fanum House Basing View Basingstoke Hampshire, RG21 2EA |
Tel: 0990 500600 Fax: 01256 491429 |
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Electronic Vehicle Security Association Forbes House Halkin Street London, SW1 7DS |
Tel: 020 7235 7000 Fax: 020 7235 7112 |
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Low Power Radio Association Secretariat Brearley Hall Luddenden Foot Halifax, HX2 6HS |
Tel: 01422 886463 Fax: 01422 886950 |
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Motor Insurance Repair Research Centre Colthrop Lane Thatcham Berkshire, RG13 4NP |
Tel: 01635 868855 Fax: 01635 871346 |
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Motor Industry Research Association Watling Street Nuneaton Warwickshire, CV10 0TU |
Tel: 01203 355495 Fax: 01203 350322 |
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Police Scientific Development Branch Woodcock Hill Sandridge St Albans Hertfordshire, AL4 9HQ |
Tel: 01727 865051 Fax: 01727 850642 |
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RAC Motoring Services RAC House Brockhurst Crescent Walsall, WS5 4QZ |
Tel: 01922 721313 Fax: 01922 642352 |
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Radio Society of Great Britain Lambda House Cranborne Road Potters Bar Hertfordshire, EN6 3JE |
Tel: 01707 659015 Fax: 01707 645105 |
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Radiocommunications Agency Wyndham House 189 Marsh Wall London, E14 9SX |
Tel: 020 7211 0502 Fax: 020 7211 0507 |
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Society of Motor Manufacturers and Traders Forbes House Halkin Street London, SW1 7DS |
Tel: 020 7235 7000 Fax: 020 7235 7112 |
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Sold Secure Ltd Langhurst House Langhurstwood Road Horsham West Sussex, RH12 4WX |
Tel: 01403 262404 Fax: 01403 269348 E-mail: soldsecure@online.rednet.co.uk |
| © Copyright RAKE 1997 Copyright of this document is vested in the RAKE Committee. The document may be freely reproduced in its entirety but selective reproduction is not permitted. First published July 1997 Further copies of these Guidelines may be obtained from any of the contributing organisations |
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