AU2400599A

AU2400599A - A system and method of communication

Info

Publication number: AU2400599A
Application number: AU24005/99A
Authority: AU
Inventors: Gianfranco Pavatich; Stephan Schmitz
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1998-05-11
Filing date: 1999-04-28
Publication date: 1999-11-18
Anticipated expiration: 2019-04-28
Also published as: WO1999059284A3; AU763156B2; ES2182548T3; EP1082712B1; WO1999059284A2; JP2002515687A; EP1082712A2; DE59902278D1

Description

Regulation 3.2

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

(ORIGINAL)

.4 0* 0 Name of Applicant: ROBERT BOSCH GmbH of Postfach 30 02 20, D-70442 Stuttgart, Germany

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a a a Actual Inventor(s): Address for Service: Invention Title: DAVIES COLLISON CAVE, Patent Attorneys, of 1 Little Collins Street, Melbourne, Victoria 3000, Australia "A SYSTEM AND METHOD OF COMMUNICATION" Details of Associated Provisional Application Nos: PP3464/98 and PP6470/98 The following statement is a full description of this invention, including the best method of performing it known to us: -1- P:\OPER\DBW\PP3464.98 28/4/99 -2- A SYSTEM AND METHOD OF COMMUNICATION Field of the Invention The invention relates to a method of communication and a system adapted to minimise radio interference and relay station attack. The invention is particularly, but not exclusively, for use with a radio frequency based vehicle security system.

Background of the Invention •A relay station essentially comprises a receiving and transmitting antennae and an amplifier which increases gain in a received signal to extend the effective range of a communication link between two transmission devices. The relay station also introduces an increased noise factor, as a result of the combined noise factors of each of the antennae and the amplifier. A relay station attack results when the relay station amplifies a signal transmission between two devices, such as transceivers of an RF vehicle security system.

In addition to relay station attack, general signal and/or noise levels on available transmission frequency channels can compromise communications reliability.

Object of the Invention The present invention seeks to prevent the occurrence of relay station attack and provide a reliable method of communication which is secure from interference affects generated by external sources and is suitable in, for example, a system for security and access control, which utilises RF communication between transceivers.

r P:\OPER\DBW\PP3464.98 -28/4/99 -3- Summary of the Invention In accordance with the invention there is provided a method of communication including: providing first and second devices, where both devices are adapted to transmit and receive; characterised in that either of the devices perform as an initiation device and the respective other device serves as a responding device; scanning multiple frequency channels; 0registering signal and/or noise levels on the channels; and o*oo communicating between the devices on a selected channel of the multiple frequency 00:0 channels, based on signal and/or noise evaluation on at least one of the channels.

S0 o In another aspect, there is provided a system for security or access control, including:

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o• 0 a portable first transceiver; and a control unit coupled to a second transceiver, associated with a secured enclosure; characterised by the first and second transceivers being adapted to generate an initiation signal, in the event of actuation of either the first or second transceiver, respectively, to facilitate security information transmission and access to the enclosure and the first and second transceivers including a channel scanner for cycling through monitored transmission frequency channels and a channel selector to determine a channel with low signal/noise levels for transmission of the initiation signal.

Brief Description of the Drawings The invention is described, by way of non-limiting example only, with reference to the accompanying drawings, in which: Figure 1 is a diagrammatic representation of a communications system; Figure 2 is a flow chart illustrating channel scanning; Figures 3 and 4 are flow charts illustrating a first mode of operation of the system; Figure 5 illustrates a second mode of operation of the system; Figures 6 and 7 are flow charts illustrating selection of power transmission; and r P:\OPER\DBW\PP3464.98 28/4/99 -4- Figure 8 is a diagrammatic view of a vehicle security system.

Detailed Description of a Preferred Embodiment A communications system is shown schematically in Figure 1, as including a first transmission device A and a second transmission device B with a communications link 1 established therebetween utilising respective antennae 3, 4. A second optional communications link 2 may also be established utilising antennae 5, 6. In use of the invention, one of the devices serves as an initiating device to commence communication therebetween, and the 10 other of the devices serves as a responding device.

At least one of the devices A, B includes a channel scanning facility to scan and monitor signal and/or noise levels on multiple frequency channels, in accordance with Procedure 1, as illustrated in Figure 2. Procedure 1 is indicated by reference numeral 10, and involves selection of a first frequency channel at 11. An assessment is made at step 12 as to whether the signal and/or noise level on the channel is below a predetermined threshold. If the channel is sufficiently quiet, the channel is registered at step 13 and, in any event, a determination is made at 14 as to whether all of the available channels have been scanned. If additional :channels still need to be scanned, the next available channel is selected at 15, followed by a repeat of step 12. Prior to selecting the next channel to be scanned, a check is made at 16 as to whether communication has been initiated by the other device on communications link 1 in which case a Procedure 3, indicated by reference numeral 30 is commenced, as described with reference to Figure 4. If, at step 24, it is determined that all of the channels have been scanned, the procedure 10 is recommenced, unless the device itself is actuated for transmission at step 17, in which case a Procedure 2, indicated by reference numeral 20 is adopted.

The channel scanning procedure thereby provides a method for selecting a low signal and/or noise level frequency for transmission between the devices to achieve the most favourable frequency for communication. Device A and/or device B preferably continuously scan all available channels (up to 16 possible channels are envisaged) on communications link 1. Such r P:\OPER\DBW\PP3464.98 28 /4/99 that a "noise" or "signal" map for each channel may be established and continuously updated.

Once an appropriate low signal and/or noise channel has been selected, communication proceeds in one of the following modes.

Mode 1 A first communication mode utilises procedures 2 and 3 in a manner described with reference to Figures 3 and 4. Procedure 2, indicated by reference numeral 20 is adopted by the initiating device, as illustrated in Figure 3. Upon actuation of the initiating device, the quietest channel is locked into at step 21 and an initiation signal/preamble and data is transmitted at step 22 on the link 1. Following transmission, the initiating device awaits for a reply from the responding device at 23. If a reply is received it is processed at 24 followed by return of the initiating device to the Procedure 1. Alternatively, if no reply is received, a wait time is established at 25. If no reply has been received by expiration of the wait time, the initiating -device again reverts to procedure 1. In the meantime, if the responding device has received the initiation signal/preamble, Procedure 3 is commenced whereby the responding device locks onto the channel selected by the initiating device at 31 and awaits for the preamble to S°finish. A determination is made at 32 as to when the preamble finishes and, upon termination, the responding device proceeds to receive data at 33. An assessment is made at 34 to check if all data has been received and upon completion of the data, the responding device transmits a reply at 35, followed by return to Procedure 1.

In normal operation, both devices are in channel scanning mode and either may perform the role of the initiating device, dependant upon which device is activated first. Upon activation, the initiating device preferably transmits the preamble for at least the total channel scanning period.

Mode 2 A second mode of operation is described with reference to Figure 5. The initiating device r P:\OPER\DBW\PP346498 28/4/99 -6operates in an identical manner to that described with reference to Figure 3. However, the responding device does not undertake any active scanning of frequency channels until a wake up signal is received. Specifically, the responding device executes a Procedure 4, indicated by reference numeral 40 which includes a wake up program 41 which allows the responding device to receive a preamble from the initiating device on the second communications link.

At step 42 a check is made as to whether the preamble has been received. If the preamble is not received the responding device returns to a sleep mode 43. Alternatively, the scanning Procedure 1 is commenced for receiving data on the communications link 1.

Accordingly, in this mode, communications links 1 and 2 are both used. In normal operation, one of the devices only is in channel scanning mode and the other device is "asleep". To initiate data communication the initiating device transmits a preamble to the responding device on communication link 2 to wake up the responding device which then initiates the channel S. S~ scanning mode. As such, after a predetermined time on communication link 2, communication proceeds on communications link 1.

S...i Mode 3

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S"In a third mode of operation, the initiating device again functions in a manner identical to that described with reference to Figure 5, except that transmission of data occurs on one or more selected channels determined by the initiating device. In normal operation, the initiating device is again in channel scanning mode and the other device is asleep. To initiate data communication, the initiating device transmits a preamble followed by a data message on communications link 2. The data message contains channel information relating to a channel of communication link 1. The preamble and initial data message are transmitted on communications link 2. As such, the preamble wakes up the responding device which then receives and decodes the message on communications link 2. If the responding device detects the correct preamble it will subsequently change to the second selected channel, as determined by the initiating device. Further communication is conducted by the initiating device roving over additional selected channels. The additional channels may be randomly selected with the information relating to the additional selected channels having encrypted to improve security P:\OPER\DBW\PP3464.98 28/4/99 -7of communication.

Channel Segregation During Message Response More particularly, in communication mode 3, the initiating device transmits an initial preamble and data message to the receiving device on communication link 2. The data section of this message contains encrypted information pertaining to more than one channel on communication link 1 e.g. channels 2, 4 and 5. The channels selected are from the channels registered as "not noisy".

.o This causes the receiving device to segregate it's response to the initiating device into the corresponding channels e.g. 2, 4 and The initiating device expects the response to be structured in the above manner and hence is able to configure it's receiver accordingly.

This method further enhances system security by forcing the "relay station" to maintain it's wideband frequency amplification characteristics. This decreases the probability of the "relay station" to lock in to the correct channel and thus become undetected.

Relay Station Attack In any of the above operating modes, the channel scanning facility may also be used to record frequency channels with signal and/or noise levels higher than a predetermined threshold. Any channels with such levels may then be excluded from the scanning procedure. A channel with a particular level of signal may indicate the presence of a "relay station". An alternative manner of identifying relay stations is to make a comparison of noise signatures over the frequency channels. In any event, if a relay station is detected, the scanning procedure may be aborted.

The invention thereby provides for enhanced security against relay station attack and general P:\OPER\DBW\PP3464.98 28/4/99 -8- RF interference. Further, the provision of a second communications link allows the invention to be configured so as to provide for different power requirements for selected transmissions.

In particular, there are scenarios where an intentional variation in transmitted RF output power is desirable to achieve a greater range, when initiating communication between remote devices or to achieve a shorter range when the devices are proximate. This has security advantages and can save on power consumption as well.

Adaptive power transmission may be utilised in a situation where, for example, both a transmission devices may be activated either locally or via RF communications.

Adaptive Power Figures 6 and 7 illustrate an example where one of the devices is a master device which is operated in accordance with a procedure 50 where an interrogation is made at 51 as to -Wes.. whether the master device has been activated locally, such as by means of a detector or switch. If the master device is activated in that manner, then transmission from the master device occurs at low power at step 52. The other device of the system is in the form of a slave device which would also transmit at low power upon activation through receipt of a low power transmission from the master device. In particular, the slave device may operate in accordance with procedure 60 where a determination is made at 61 as to whether the slave device has been locally activated. If the slave device is locally activated by, for example, a manual switch, the device transmits at high power at step 63. Alternatively, if the device is activated by virtue of the low power transmission from the master device, then the slave device will also transmit on low power at step 32.

Such a system has particular application in a vehicle security system where, if the slave device is in proximity (less than 2.5 metres) to the master device, high power transmission is not required. This has the advantage of a reduced range and reduced vehicle battery power consumption. When communication is initiated by the master device, both devices transmit on communications link 1 at low power. Communication can, however, be initiated on either 0

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P:\OPER\DBW\PP3464.98 28/4/99 -9communications link 1 or 2 in accordance with one of the abovedescribed modes. When, however, the slave device is not in proximity to the master device high power transmission is required such that the system can operate at an increased range for remote control.

Security and/or Access Control A more specific example of the system is shown with application to a vehicle security system in Figure 8.

The system 100 includes a slave device in the form of a portable first transceiver 102 arranged for communication with a master device including a second transceiver 103, located in a vehicle 104, via antenna 105. The second transceiver 103 is operably coupled to a control unit 106 which is in turn coupled to a detection device 107 located in a door 108 of the vehicle.

The detection device is activated by a hand of a person seeking entry into the vehicle, such as by lifting the door handle, and may be in the form of a micro-switch or capacitive :i proximity sensor or piezoelectric device.

The control unit 106 is arranged to select transmission power of signals from the transceiver .o 103 between a high power mode and a lower power mode. The low power mode is for transmitting over short distances, when the portable transceiver is assumed to be adjacent or proximate the vehicle. The low power mode is triggered when a person intending to enter the vehicle activates the detection device 107 with their hand. The high power mode is used for transmitting over longer distances and is triggered by the person pressing a transmission switch 100 on the portable transceiver 102. For either power mode, the antenna 105 may alone suffice, however, it is also envisaged that a plurality of antennae may be utilised and, in one possible embodiment, low frequency antennae positioned at, for example, locations 111, 112 whilst the antenna 105 would be in the form of a UHF antenna. In that embodiment, the antenna 111 would be used for communicating with the portable transceiver adjacent the vehicle, to facilitate access to the vehicle, while antenna 112 would be used to ensure the person, once in the vehicle, was authorised to operate the vehicle such that the engine could then be enabled/disabled accordingly.

P:\OPER\DBW\PP3464.98 28/4/99 The UHF antenna may be in the form of a dipole or loop antenna and may be tuned to, for example, 315 MHZ, 433.92 MHZ and 868 MHZ whereas the low frequency antennae may be in the form of multi-turn wire loop ferrite antennae for transmission of frequencies in the range 30 to 300 KHz and, more preferably, in the range of 90 to 140 KHz.

Communication between the transceivers may be in accordance with any one of the above described communication modes.

The invention has been described by way of non-limiting example only, and many modifications and variations may be made thereto without departing from the spirit and scope of the invention described.

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Claims

2. A method as claimed in claim 1, characterised in that scanning of the frequency channels is effected by the initiating device and communication between the devices is commenced by transmission of a initiation signal from the initiating device, on the at least one ••selected channel, followed by data transmission.
3. A method as claimed in claim 2, characterised in that the responding device also effects scanning of the frequency channels and, upon receipt of the signal, locks into the at least one selected channel for receipt of the data from the initiating device.
4. A method as claimed in claim 2, characterised in that the responding device commences scanning of the frequency channels upon receipt of the initiation signal, for receipt of data from the initiating device. A method as claimed in any one of claims 2 to 4, characterised in that communication between the devices includes transmission on a plurality of selected channels.
6. A method as claimed in claim 5, characterised in that transmission between the devices occurs on a second selected channel determined by the initiating device, with second channel identification information being transmitted with the data, the responding device changing P:\OPERDBW\PP3464.98 28/4/99 -12- frequency channels to receive further data on the second selected channel following receipt of the information.
7. A method as claimed in claim 6, characterised in that the second channel identification information is crypto-coded for transmission to enhance security.
8. A method as claimed in claim 1, characterised in that alternative communications links are established for effecting communication between the devices.
9. A method as claimed in claim 7, characterised in that the communications link utilised S:oo for transmitting an initiating signal is determined based on which device is actuated as the initiation device.
10. A method as claimed in claim 7, characterised in that communication is initiated on a first one of the links on the at least one selected channel and is continued on a second one of the links, on the second selected channel, determined by the initiating device.
11. A method as claimed in claim 7, characterised in that the links are adapted for So. transmitting at either low power or high power and the transmission power is determined by which device initiates communications.
12. A method as claimed in any one of the preceding claims, characterised in that the at least one selected channel is determined to be a low noise channel.
13. A method as claimed in any one of the preceding claims, characterised in that any channel with a signal and/or noise level above a threshold is removed as a scanned frequency channel.
14. A method as claimed in any one of the preceding claims, characterised in that a comparison of noise signatures is made over the frequency channels to identify relay stations or the like. P:\OPER\DBW\PP3464.98 28/4/99 13 A method as claimed in any one of the preceding claims, characterised in that the method is for security or access control and the first device is a portable first transceiver and the second device is a second transceiver, coupled to a control unit for controlling security or access to an enclosure, the method further including: generating the initiation signal, on the at least one selected channel, either from the first transceiver if the first transceiver is activated or the second transceiver if the second transceiver is activated, combined with transmission of security information between the transceivers to facilitate access to the enclosure. 9004 *444 .6 10 16. A method as claimed in claim 16, characterised in that the first transceiver includes a manually operable transmission switch and the control unit is linked to a detection device which is activated by proximity of, or contact by, a person seeking entry into the enclosure, wherein the first transceiver is activated via the switch and the second transceiver is activated 6*o if the detection device is actuated.
17. A system for security or access control, including: a portable first transceiver; and a control unit coupled to a second transceiver, associated with a secured enclosure; :characterised by the first and second transceivers being adapted to generate an initiation signal, in the event of actuation of either the first or second transceiver, respectively, to facilitate security information transmission and access to the enclosure and the first and second transceivers including a channel scanner for cycling through monitored transmission frequency channels and a channel selector to determine at least one channel with low signal/noise levels for transmission of the initiation signal.
18. A system as claimed in claim 17, characterised by a detection device which is activated by proximity of, or contact by, a person seeking entry into the enclosure, the device being linked to the control unit, and the first transceiver including a manually operable transmission switch, the first transceiver being activated via the switch and the second transceiver being activated upon actuation of the detection device. P:\OPER\DBW\PP3464.98 28/4/99 -14-
19. A system as claimed in claim 18, characterised in that the control unit is adapted to select transmission power of the second transceiver between a low power mode, if the detection device is activated, and a high power mode, if the switch is actuated.
20. A system as claimed in any one of claims 17 to 20, characterised in that the transceivers are adapted for transmission on a plurality of frequency channels.
21. A system as claimed in any one of claims 17 to 21, characterised in that the enclosure is defined by a vehicle. DATED this 28th day of April, 1999 ROBERT BOSCH GmbH By its Patent Attorneys DAVIES COLLISON CAVE DAE hs2t ayo pi,19