WO2011078679A1

WO2011078679A1 - Radio wave transmitter

Info

Publication number: WO2011078679A1
Application number: PCT/NL2010/050890
Authority: WO
Inventors: Eric Ewout Geelhuysen; Antonius Alphonsus Gerardus Van Buul; Hendrik Jan Van Der Neut; Bart Christiaan Lugtmeijer
Original assignee: Flister B.V.
Priority date: 2009-12-24
Filing date: 2010-12-24
Publication date: 2011-06-30
Also published as: NL2004016C2

Abstract

A radio wave transmitter for transmitting alarm signals to radio wave receivers in an area, comprises a transmitter module, arranged for transmitting a radio signal at at least one carrier frequency. The radio wave transmitter further comprises a control module for controlling the transmitter module. The control module comprises a memory for storage of radio broadcasting data related to the area, the control module being arranged to determine the at least one carrier frequency from the radio broadcasting data as stored in the memory and to control the transmitter module so as to transmit the radio signal at the at least one carrier frequency.

Description

Title: Radio wave transmitter

The invention relates to a radio wave transmitter for transmitting alarm signals to radio wave receivers, an emergency vehicle comprising such radio wave transmitter a wireless communication device anda method for transmitting alarm signals to radio wave receivers in an area.

Emergency vehicles such as ambulances, police and others have made use of acoustic and visual alarming since many years, including for example sirens, blue and/or red lights etc. In the past years, vehicles have become better isolated which results in a driver of the vehicle less easily recognizing a siren, furthermore audio devices such as radio, CD or computer music files, and corresponding audio installations have become better and able to produce louder sounds. At the same time, traffic has become more dense. Furthermore, mobile telephony and associated hands free transmission in vehicles ("car kits") also tend to deviate the attention of the driver from any outside signalling such as from an emergency vehicle. These factors together may have resulted in the past years in more and more difficulties for a staff of an emergency vehicle to reach a desired destination in due time.

Attempts have been made to signal drivers of vehicles by means of radio transmission, so as to make them aware of an approaching emergency vehicle. Thereby, use has been made of a radio transmitter which transmits a radio wave in a public radio broadcasting frequency band, so as to warn a driver that has switched on his radio receiver. These solutions have however until now been unsatisfactory given the many possible frequencies to which a radio receiver could be tuned. Taking the FM band as an example, a frequency band is assigned reaching from 87.5 - 108 MHz. In this frequency band, a spacing of for example 100 kHz, may be applied. In dense regions, a frequency spacing may even be reduced to 50 kHz between stations. Thereby, referring to the example of the FM band, different stations may transmit at roughly 200 - 400 different frequencies within this band. An emergency vehicle approaching a traffic situation would want to provide alarm signals to drivers of different vehicles, each of which may have his of her radio tuned to a different frequency. In order to warn a driver sufficiently early to provide any benefit at all, a warning would have to be transmitted at each respective frequency within seconds or an even shorter time frame. As a result, in order to be able to warn drivers at each possible frequency, hundreds of possible frequencies would have to be covered by warning device virtually simultaneously. Furthermore, at each of the frequencies, a signal would have to be transmitted for a sufficient long time to allow the driver to be aware of the situation, which practical implementations have appeared to fail for the reasons cited above. Furthermore, it is to be noted that emergency vehicles such as ambulances are normally equipped with a large range of electronic devices such as medical measurement equipment, medical patient surveyance equipment, communication equipment, etc, which would risk to be disturbed by a radio wave transmitter that would transmit radio signals at each of the above referenced hundreds of frequencies within the referred frequency band. This may especially be the case, as a transmission power of the radio wave transmitter would have to be sufficiently high at each of the frequencies to "push away" a regular transmission of a radio station at such frequency.

The invention intends to provide a workable warning for drivers that an emergency vehicle is within vicinity.

In order to reach this goal, the radio wave transmitter in accordance with an embodiment of the invention comprised the features of claim 1 . In accordance with claim 1 , a transmitter module is provided for transmitting a radio signal at at least one carrier frequency. Furthermore, a control module is provided for controlling the transmitter module. The control module comprises a memory in which data can be or is stored providing information about a radio broadcasting spectrum at a certain position, respectively in a certain (coverage) area. The control module can now specifically control the transmitter module so as to transmit one or more radio signals at the specific carrier frequencies at which radio stations are available at that specific position resp. in that specific area. As a result, the radio wave transmitter does not need to transmit in a whole frequency band, such as a whole FM band, but in stead thereof may be operated so as to transmit a radio signal at the specific carrier frequencies at which radio stations are active at that specific position.

In an embodiment, the control module further comprises a position data input for entry of a position data from a position measurement system, the position measurement system to measure a position of the radio wave transmitter and/or the vehicle to which it is attached, the control module being arranged to take account of the position data when determining the at least one carrier frequency. By making use of position data, such as derived from a GPS position measurement system or other position measurement system, a larger region may be covered which allows the radio wave transmitter, or the emergency vehicle comprising it, to move throughout the region, the position data from the position measurement system thereby providing information on the actual position, and the control module to take account of the position when determining the at least one carrier frequency, so as to take account of differences in the frequency spectrum at different positions in the region. In a preferred embodiment, the radio broadcasting data comprises at least one of antenna position, antenna height, and transmission power of radio broadcasting

transmitters, and wherein the control module is arranged to determine a radio broadcasting spectrum at the position identified by the position data, from the radio broadcasting data, and to control the transmitter module in accordance with the determined radio broadcasting spectrum. From data such as antenna position, antenna height and transmission power of one or more radio broadcasting transmitters, a radio spectrum at a certain position may be determined. The transmitter module may then transmit the signal in accordance with the determined spectrum so as to specifically transmit the alarm signals at the frequencies of radio stations that provide, according to the calculation, a usable signal strength at the determined position. As a result, using only a limited amount of data, namely characteristics of radio transmitters that transmit into an area of interest.

A transmission power level of the radio signal as transmitted by the radio wave transmitter may be kept at a substantially constant power level (i.e. for example independent of a power level of the radio stations in that area). In another embodiment, the transmission power level may be set in dependency of a velocity of the emergency vehicle, for example linearly or quadratically dependent on the velocity, or in two or more discrete steps. As an example, a first power level is employed in a first velocity range (for example 0 - 70 kilometers per hour which speeds may be driven by the emergency vehicle in urban area's) while a second power level is employed in a second velocity range (for example above 70 kilometers per hour which speeds may be driven by the emergency vehicle outside urban area's, so as to warn a driver more early thereby taking account of higher driving velocities..

A data message may be generated and transmitted with the radio signal for one or each of the carrier frequencies. The data message may for example comprise an RDS (radio data system) message thereby transmitting e.g. a text message to be displayed on a display of the radio wave receiver, a code for stopping a play-back (such as a CD play-back or a play-back of a computer music file), or an RDS message to put the radio wave receiver in an emergency mode in which normal music or audio reproduction is interrupted. The RDS message may comprise a program information (PI) code, the message generator preferably being arranged to set for each of the carrier frequencies the program information code to a data value which is the same as a program information code broadcasted at that carrier frequency (i.e. of the regular program broadcasted in that area and to which a radio receiver may be tuned). As a result, a radio receiver that receives the signal transmitted by the radio wave transmitter, may be frequency locked and thereby prevented from skipping to another carrier frequency at which the same program (having the same program information (PI) code, is transmitted, in an attempt to keep tracing the program material, as this could impede a transmission of a warning to a user, such as a driver of a vehicle. The data may also comprise a TMC (traffic management control) message thereby allowing to provide a message to e.g. a navigation system which may apply the TMC message to provide a warning on a display of the navigation system and/or to provide the user with router direction so as to direct it away from the intended route of the emergency vehicle. In case of multiple carrier frequencies simultaneously, the same or different data messages may be transmitted via each carrier frequency. In order to make a receiving navigation device to take account of a TMC message, the navigation device commonly requires a same TMC message to be received three times. To timely warn the user, the message generator may be arranged to transmit the TMC message at least 3 times per second at each carrier frequency, so that successive TMC messages are received shortly after each other and taken into account by the navigation device quickly. Furthermore, the TMC message may comprise a position and/or a heading speed of an emergency vehicle that carries the radio wave transmitter, to enable the position and/or direction of the emergency vehicle to be displayed on a display of the driver's navigation system. As a result, the driver may be informed about the position and/or direction of the emergency vehicle, even if the driver may not yet be able to see the emergency vehicle itself.

In order to make radio receivers to act on any transmitted data signal early (i.e.

already at a relatively large distance when the emergency vehicle is approaching) the radio wave transmitter may be arranged to transmit the data message at a modulation level or signal strength that exceeds a modulation level or signal strength of a data message broadcasted at that carrier frequency.

In case a plurality of radio stations are available at a certain position, each transmitting at a different carrier frequency, the radio wave transmitter may transmit a signal at each of those frequencies simultaneously, however, depending on the hardware of the radio wave transmitter, it may also be possible that a sequential transmission of the carrier frequencies or of subsets of the carrier frequencies are provided, which may for example be advantageous in a situation where more transmissions at different carrier frequencies are required than the amount of carrier frequencies that can be transmitted at a same time by the radio wave transmitter.

On each of the carrier frequencies, a warning tone signal can be transmitted (e.g. modulated onto the carrier) so as to alarm a driver of the vehicle in question.

In an embodiment, the radio wave transmitter may comprise a tachometer input for receiving tachometer data providing information about a speed of the vehicle to which the radio wave transmitter is attached, the control module of the radio wave transmitter thereby being arranged to control an output power of the transmitter module in accordance with the received tachometer data so as to adapt the output power to the speed of the vehicle: if the vehicle is driving at a higher speed, drivers in a larger range are to be alarmed, hence requiring a higher transmission power. The radio signal transmitted by the radio wave transmitter will, within an area, e.g. an area surrounding the emergency vehicle to which the radio wave transmitter is mounted, transmit the radio signal at a carrier frequency which may correspond to a frequency of a public radio station and at a power level with which the public radio station transmission will be overridden within that area, thereby effectively "pushing away" the public radio station in the area. A listener to the radio station, including drivers of vehicles, will, in stead of receiving the public radio station, be warned by the alarm signal transmitted by the radio wave transmitter.

In a further embodiment, the data message comprises an activation message (e.g. an RDS message or other signal) arranged to activate a wireless communication device so as to transmit a warning signal. In case of an emergency, it may be highly relevant to know if there are any persons in a certain area, for example in case of avalanches, fires, earthquakes, etc, where a localization and rescue of survivors may be needed. At present, many wireless communication devices are provided with a radio receiver (e.g. a radio broadcast receiver), e.g to enable a user to listen to radio program material and/or to receive data messages, such as TMC messages that are transmitted with radio signals in the radio broadcasting frequency band. The activation message may alternatively or additionally be transmitted in any other suitable form, such as a pilot tone. The wireless communication devices may be arranged to be activated by the activation message so as to transmit the warning signal. The warning signals thus transmitted by the wireless telecommunication devices (such as mobile telephones, personal digital assistants, smart-phones, etc) may enable to more quickly localize any potential survivors in the area of interest. The warning signal may comprise a radio broadcasting band signal (such as an FM or AM signal), an avalanche transponder warning signal, a wireless telecommunication network signal (such as GSM signal, CDMA, W-CDMA or UMTS signal), a mobile data communication network signal (such as a Bluetooth signal, a wireless local area network signal, etc.). In case the wireless telecommunication device comprises a position measurement device, such as a GPS receiver, the warning signal may comprise a position so as to allow to determine where possible survivors can be found with a high likelihood. The radio wave transmitter may further be arranged to receive the warning signal and provide (data enabling) a display of presence and/or position of the wireless communication device to a rescuer.

In accordance with the above disclosure, the invention further comprises a wireless communication device having a radio frequency receiver arranged for receiving a radio broadcast signal, and a warning signal generator arranged for transmitting a warning signal to inform a rescue worker about at least one of a presence, identity and position of the wireless communication device, the wireless communication device being arranged to transmit the warning signal upon receipt of an activation message by the radio frequency receiver.

The wireless communication device may be arranged to maintain the radio frequency receiver in an active or standby mode even when the wireless communication device is in a switched off mode, and to activate the warning signal generator upon receipt of the activation message, so that, even when the mobile communication device is switched off, it may be activated to transmit the warning signal.

The wireless communication device may further comprise a position measurement device for measuring a position of the wireless communication device, a memory for storing a most recently measured position, the wireless communication device being arranged for, if a position can be measured by the position measurement device, storing the measured position in the memory, and if no usable position measurement can be performed, keeping a previously measured position in the memory, the warning signal generator being arranged for receiving the measured position as stored in the memory and transmitting the warning signal comprising the measured position as stored in the memory. As a result, in case a disruption of the receipt of signals enabling the wireless communication device to perform a position measurement (e.g. GPS signals or mobile telephone network signals), a usable position, namely the latest determined position, may be transmitted nevertheless.

In order to provide a low cost and highly reliable module, the radio frequency receiver and warning signal generator may be comprised in a frequency modulation or amplitude modulation transceiver, such as a radio transceiver integrated circuit, e.g an FM transceiver..

The invention further comprises an emergency vehicle comprising the radio wave transmitter according to the invention.

Still further, the invention comprises a method for transmitting alarm signals to radio wave receivers in accordance with claim 13. With the method, similar advantages and effects may be achieved as with the radio wave transmitter. Furthermore, similar preferred embodiments as described above with reference to the radio wave transmitter according to the invention, are also applicable to the method according to the invention, thereby achieving same or similar effects.

Further preferred embodiments, advantages and features of the invention will become clear from the appended drawings, in which non-limiting embodiments of the invention are depicted, wherein:

Fig.1 depicts a highly schematic block diagram of a radio wave transmitter according to the invention;

Fig. 2 depicts a highly schematic block diagram of control module of the radio wave transmitter according to fig. 1 ; Fig. 3 depicts a table based on which an embodiment of a memory contents in a accordance with embodiments of the invention will be explained

Fig. 4 depicts radio broadcasting transmitters in a region based on which an aspect of the invention will be explained, and

Fig. 5 schematically depicts a. wireless communication device in accordance with an embodiment of the invention.

Fig. 1 depicts a block diagram of a radio wave transmitter comprising a position measurement module PM as a GPS receiver, a control module such as a microprocessor based control, a transmitter module TM comprising a radio wave transmitter, and an antenna AN for transmitting the radio signal as generated by the transmitter module into an area. The position measurement system PM provides at an output thereof position data in the form of any suitable signal, such as a digital data signal, which is transmitted by any suitable means, such as a data bus, a direct data connection, wireless transmission, serial or parallel electric data connection to the control module CM. The control module CM comprises any suitable control device, such as a microprocessor, microcontroller, programmable integrated circuit, programmable logic circuit (PLC), etc and a memory, referred to in fig. 2 as control device CD and memory MM. The control module is connected to the transmitter via any suitable connection including analogue, digital, etc the transmitter in response to a control signal from the control module generating a radio signal at the carrier frequencies in question to be transmitted via the antenna AN. Depicted in fig. 2, the control module CM comprises a memory MM, the memory for storage of radio broadcasting data e.g. related to a region. Making use of the data in the memory, the control module is able to determine at which frequencies radio stations will be active in the region in question. Thereby, in stead of transmitting radio signals at any frequency or at arbitrary frequencies or at alternating frequencies in the radio band, the radio wave transmitter may according to an aspect of the invention, transmit the alarm signals in an area specifically at the frequencies at which, in that area, radio stations are transmitting, hence the frequencies at which radio wave receivers will be turned in that area. As a result, time loss due to transmission at many, alternating frequencies, resulting in possible delays until the frequency at which a particular radio wave receiver in the area is tuned, has been reached, avoiding possible access disturbance to sensitive equipment in the emergency vehicle (medical measurement and monitoring equipment), and furthermore allowing to simplify the design and construction of the radio wave transmitter, as hardware that would enable the transmission at possibly even hundreds of radio carrier frequencies at a same time, which would be required in solutions according to the state of the art, may significantly be reduced as the transmitter would, according to an aspect of the invention, only require to transmit a signal with carrier frequencies corresponding to the frequencies of radio stations that can be received in the particular area. In particular, in case an emergency vehicle equipped with the radio wave transmitter would only be employed in a certain, restricted geographical zone, such as a part of a city, throughout which geographical zone the same radio stations are receivable and at the same frequencies, a measurement of the position of the vehicle may be omitted, thereby making it possible to omit an entry of the position data. In that case, a one time

programming of those frequencies, or related data into the memory MM of the control module CM may be sufficient. In case of application of the radio wave transmitter in a more wide geographic zone, over which differences in the radio spectrum may be observed, measurement of the position, and taking into account the position when determining the carrier frequencies for transmission, may be advantageous. Thereby, the local situation in the particular area where the vehicle is present, may be taken into account. In practical situations, the transmitter will transmit the radio signal with a transmission power that is sufficient to overrule the radio station at those frequencies in an area of several tenths to several hundreds of meters around, preferably in front of the emergency vehicle. Thereto, a transmission power of in general 100 milliWatt per carrier will be sufficient, however strongly depending on the local field strength of the radio station in question. The position of the may be measured periodically or constantly so that, when the vehicle moves, the required carrier frequencies and the corresponding transmission powers may be determined periodically, so as to adapt them to the radio spectrum in situ. The carrier frequencies and corresponding transmission powers may thus change dynamically as the position changes. In order to determine the carrier frequencies at a certain position, several techniques may be used. A first example will be described with reference to fig. 3.

Fig. 3 depicts a table in which channels in the radio frequency spectrum are set out against a plurality of different regions, each region being referred to by a letter A, B, C, D etc. The channels at which a radio transmission of a radio station may take place are referred to by respective numbers 1 , 2, 3, etc. As can be seen in fig. 3 in this example in the geographical zone referred to by A, transmission of radio stations takes place at channels 1 , 4 and 8, while in the geographical zone B, transmission takes place at channels 2 and 4, etc. Having such data available in the memory MM, the measurement of the position will allow the control module to define in which zone the vehicle is at present, thereby allowing to look up the corresponding radio stations in a table in accordance with fig. 3. The control module may now control the transmission module to transmit at carrier frequencies corresponding to the channels retrieved from the table.

Alternatively to, or supplementary to the technique described with reference to fig. 3, a technique will now be described with reference to fig. 4. Fig. 4 schematically depicts a map of a region in which radio broadcasting transmitters RB1 , RB2, RB3 and RB4 are located. Each of the radio broadcasting transmitters transmits radio stations each at a carrier frequency and each having a particular transmission power. Typically, different carrier frequencies are applied by different radio broadcasting transmitters RB1 , RB2, RB3, RB4, however, it may also be the case that the same or partly the same carrier frequencies are applied. In the memory MM of the control module CM, the positions, antenna height and transmission power of the radio broadcasting transmitters are stored, possibly in

combination with other data such as names of the radio stations, RDS data such as pi- codes, etc, which enable the control module to calculate a to be expected spectrum at each position within reach of one or more of the radio broadcasting transmitters RB1 - RB4.

Radio broadcasting transmitter RB1 transmits some radio stations which are receivable in a range indicated by A, while also some stations are transmitted at a higher transmission power and being able to be received in the range A1 . The radio stations transmitted by radio broadcasting transmitter RB2 are receivable in range B and the radio stations transmitted by radio broadcasting transmitter RB3 and RB4 are receivable in the ranges C and D

respectively. As an example, at the position P in fig. 4, radio stations are received from radio broadcasting transmitter RB3 and RB4, while also some stations are received from radio broadcasting transmitter RB1 . This is because the position P is in the ranges C, D and A1 . The control module may now determine the corresponding frequencies that are available at the position P, and the corresponding signal power at each of those frequencies, from data such as the transmission power, antenna height and distance towards the respective radio broadcasting transmitters, and control the transmitter module to transmit at those

frequencies. In an embodiment a transmission power at each of those frequencies is adapted to a signal strength of the radio broadcasting at the particular position P as obtained from the calculation.

In each of the above embodiments, a message, such as an RDS message or TMC message may be generated by e.g. a message generator MG of the control module CM, and transmitted at the carrier frequencies for reception by the radio wave receivers. Furthermore, a warning tone such as a siren may be generated and transmitted to alert drivers of vehicles. Still further, speech recorded via a microphone may be transmitted to the drivers by modulating it onto one or more of the carrier frequencies. A transmission power of the radio wave transmitter may be set in accordance with a speed of the emergency vehicle, speed information being obtained from e.g. a tachometer of the vehicle. Alternatively, a speed information may be derived from a rate of change of position data obtained from the position measurement system. The RDS message may comprise a program information code, the message generator preferably being arranged to set for each of the carrier frequencies the program information code to a data value which is the same as a program information code broadcasted at that carrier frequency, As a result, a radio receiver that receives the signal transmitted by the radio wave transmitter, may be frequency locked and thereby prevented from skipping to another carrier frequency at which the same program (having the same program information (PI) code, is transmitted, in an attempt to keep tracing the program material, as this could impede a transmission of a warning to a user, such a s driver of a vehicle. In order to make a receiving navigation device to take account of a TMC message, the navigation device commonly requires a same TMC message to be received three times. To timely warn the user, the message generator may be arranged to transmit the TMC message at least 3 times per second (e.g. between 3 and 6 times per second) at each carrier frequency, so that successive TMC messages are received shortly after each other and taken into account by the navigation device quickly. Furthermore, the TMC message may comprise a position and/or a heading speed of an emergency vehicle that carries the radio wave transmitter, so that the position and direction of the emergency vehicle can be displayed on a display of the driver's navigation system. As a result, the driver may be informed about the position of the emergency vehicle, even if the driver may even not yet be able to see the emergency vehicle itself,

In order to make radio receivers to act on any transmitted data signal early (i.e. already at a relatively large distance when the emergency vehicle is approaching) the radio wave transmitter may be arranged to transmit the data message at a modulation level or signal strength that exceeds a modulation level or signal strength of a data message broadcasted at that carrier frequency.

As will be illustrated below with reference to fig. 5, in a further embodiment, the data message comprises an activation message (e.g. an RDS message or other signal) arranged to activate a wireless communication device so as to transmit a warning signal. In case of an emergency, it may be highly relevant to know if there are any persons in a certain area, for example in case of avalanches, fires, earthquakes, etc, where a localization and rescue of survivors may be needed. At present, many wireless communication devices are provided with a radio receiver, e.g to enable a user to listen to radio program material and. or to receive data messages, such as TMC messages that are transmitted with radio signals in the radio broadcasting frequency band. The wireless communication devices may be arranged to be activated by the activation message so as to transmit the warning signal. The warning signals thus transmitted by the wireless telecommunication devices (such as mobile telephones, personal digital assistants, smart-phones, etc) may enable to more quickly localize any potential survivors in the area of interest. The warning signal may comprise a radio broadcasting band signal (such as an FM or AM signal), an avalanche transponder warning signal, a wireless telecommunication network signal (such as GSM signal, CDMA, W-CDMA or UMTS signal), a mobile data communication network signal (such as a

Bluetooth signal, a wireless local area network signal, etc.). In case the wireless telecommunication device comprises a position determination device, such as a GPS receiver, the warning signal may comprise a position so as to allow to determine where possible survivors can be found with a high likelihood.

Fig. 5 schematically depicts two wireless communication devices WCD each having a radio frequency receiver RFR arranged for receiving (e.g. via antenna ANT) a radio broadcast signal RBS from an emergency vehicle EV, and a warning signal generator WSG arranged for transmitting (e.g. via antenna ANT) a warning signal to inform a rescue worker about at least one of a presence, identity and position of the wireless communication device WCD, the wireless communication device being arranged to transmit the warning signal WS (e.g. omni-directionally) upon receipt of an activation message by the radio frequency receiver RFR. The Emergency vehicle may be provided with the above described radio wave transmitter arranged to transmit the radio broadcasting signal RBS and activation signal AS (or any other suitable transmitter arranged to transmit such activation signal). The wireless communication device WCD may be arranged to maintain the radio frequency receiver in an active mode even when the wireless communication device is in a switched off mode, and to activate the warning signal generator upon receipt of the activation message, so that, even when the mobile communication device is switched off, it may be activated to transmit the warning signal if needed.

In case of a calamity or catastrophe, communication networks such as mobile telephony networks may break down, and receipt of signals enabling the wireless communication device to perform a position measurement (e.g. GPS signals or mobile telephone network signals) may be disrupted. As a result, the wireless communication device may not be able any more to determine its position, nor to transmit a signal via the regular communication means, such as the mobile telephone network. In such situations, use of radio broadcasting (e.g. amplitude modulation, frequency modulation, e.g. using for example the HF or VHF frequency band, for example in a VHF frequency range between 76 and 108MHz, such as in the range of 76 - 90 MHz or the range of 87 - 108 MHz) may be preferred due to for example simplicity, radio coverage, rugged construction and easy of use of the required equipment. Furthermore, receivers able to receive such radio broadcast signals are widespread. The wireless communication device may hence transmit the warning signal using AM or FM, for example within one of the above mentioned frequency bands, so that even when communication networks such as the mobile telephone network are disrupted, transmission of the warning signal from the wireless communication device, can take place. The wireless communication device may store in a memory (not depicted) a last measured position, and transmit that position when transmitting the warning signal, so that position information of the wireless communication device may be provided even in a disruptive situation. In order to enable a widespread use of wireless communication devices being equipped with a radio frequency receiver and warning signal generator as described, these items may be comprised in a low cost FM or AM transceiver, for example a radio transceiver integrated circuit that provides reception of radio signals for e.g. information and amusement purposes while also enabling to provide the functionality as described here at a minimum of extra cost. The position information and/or other information may be comprised in the warning signal in the form of an RDS signal or using any other known modulation technique. The warning signal may comprise a code, such as an RDS code that represents a warning message. For identification purposes, the warning signal may further comprise information that identifies the wireless communication device or its user, for example an international mobile subscriber identity (I MSI) code that contains a unique mobile telecommunication network subscriber identification, or a personal profile (comprising e.g. personal data, medical data, a personal identification number or other data). The personal profile may be stored in a memory in the wireless communication device, e.g. using encrypted storage so as to prevent unauthorized access to the personal data. The warning signal may further or instead thereof comprise any other suitable warning signal, such as a pilot tone.

Claims

1. A radio wave transmitter for transmitting alarm signals to radio wave receivers in an area, comprising:

- a transmitter module, arranged for transmitting a radio signal at at least one carrier frequency,

- a control module for controlling the transmitter module,

wherein the control module comprises a memory for storage of radio broadcasting data related to the area, the control module being arranged to determine the at least one carrier frequency from the radio broadcasting data as stored in the memory and to control the transmitter module so as to transmit the radio signal at the at least one carrier frequency.

2. The radio wave transmitter according to claim 1 , wherein the control module further comprises:

a position data input for entry of a position data from a position measurement system, the position measurement system to measure a position of the radio wave

transmitter, the control module being arranged to take account of the position data when determining the at least one carrier frequency.

3. The radio wave transmitter according to claim 2, wherein the radio

broadcasting data comprises at least one of antenna position, antenna height, and transmission power of radio broadcasting transmitters, and wherein the control module is arranged to determine a radio broadcasting spectrum at the position identified by the position data, from the radio broadcasting data, and to control the transmitter module in accordance with the determined radio broadcasting spectrum.

4. The radio wave transmitter according to any of the preceding claims, wherein the control module further comprises a message generator for generating a data message,

the message generator being connected to the transmitter module for receiving the data message, the transmitter module being arranged for transmitting the data message with the radio signal for each of the carrier frequencies. 5. The radio wave transmitter according to any of the preceding claims, wherein the control module is arranged to repeatedly change a carrier frequency when the transmission of the data message has been completed, and to repeat the transmission for the changed carrier frequency.

6. The radio wave transmitter according to any of the preceding claims, wherein the transmitter is arranged to transmit a warning tone signal on each carrier frequency.

7. The radio wave transmitter according to any of the preceding claims, wherein the data message comprises an RDS message, the RDS message preferably comprising a program information code, the message generator preferably being arranged to set for each of the carrier frequencies the program information code to a data value which is the same as a program information code broadcasted at that carrier frequency. 8. The radio wave transmitter according to any of the preceding claims, wherein the data message comprises a TMC message, wherein preferably the message generator is arranged to transmit the TMC message at least 3 times per second at each carrier frequency, and/or the TMC message comprises a position and heading speed of an emergency vehicle that carries the radio wave transmitter.

9. The radio wave transmitter according to any of the preceding claims, being arranged to transmit the data message at a modulation level or signal strength that exceeds a modulation level or signal strength of a data message broadcasted at that carrier frequency

10. The radio wave transmitter according to any of the preceding claims, wherein the data message comprises an activation message arranged to activate a wireless communication device so as to transmit a warning signal. 11. The radio wave transmitter according to any of the preceding claims, comprising a tachometer input for receiving tachometer data, the control module being arranged to control the output power of the transmitter module in accordance with the received tachometer data. 2. An emergency vehicle comprising the radio wave transmitter according to any of the preceding claims.

13. A method for transmitting alarm signals to radio wave receivers in an area, comprising:

- determining at least one carrier frequency from radio broadcasting data stored in a memory, and

- transmitting in the area a radio signal at the at least one carrier frequency.

14. The method according to claim 13, further comprising:

- measuring by a position measurement system a position at which the alarm signal is to be transmitted,

- taking account of the measured position when determining the at least one carrier frequency,

the radio broadcasting data stored in the memory comprising position related information. 15. The method according to claim 14, further comprising:

- determining a radio broadcasting spectrum at the measured position, the radio broadcasting data thereto comprising at least one of antenna position, antenna height, and transmission power of radio broadcasting transmitters, and

- the transmitting of the radio signal taking place at carrier frequencies occurring in the determined radio broadcasting spectrum.

16. The method according to any of claims 13 - 15, wherein the radio signal transmitted at the at least one carrier frequency comprises a data message, the data message comprising an activation message arranged to activate a wireless communication device, the method further comprising activating the wireless telecommunication device so as to transmit a warning signal.

17. The method according to any of claims 13 - 16, wherein the radio signal transmitted at the the at least one carrier frequency comprises a data message, the data message comprising an RDS message, the RDS message comprising a program information code, the method further comprising setting for each of the carrier frequencies the program information code to a data value which is the same as a program information code broadcasted at that carrier frequency. 18. The method according to any of claims 13 - 17, wherein the radio signal transmitted at the the at least one carrier frequency comprises a data message, the data message comprising an RDS message, the RDS message comprising a T C code, the method further comprising transmitting the T C message at least 3 times per second at each carrier frequency, the TMC message preferably comprising a position and heading speed of a vehicle that carries the radio wave transmitter. 19. The method according to any of claims 13 - 18, wherein the radio signal transmitted at the carrier frequency comprises a data message, the method comprising transmitting the data message at a modulation level or signal strength that exceeds a modulation level or signal strength of data broadcasted at that carrier frequency.

20. A wireless communication device having a radio frequency receiver arranged for receiving a radio broadcast signal, and a warning signal generator arranged for transmitting a warning signal to inform a rescue worker about at least one of a presence, identity and position of the wireless communication device, the wireless communication device being arranged to transmit the warning signal upon receipt by the radio frequency receiver of an activation message.

21. The wireless communication device in accordance with claim 20, being arranged to maintain the radio frequency receiver in an active or standby mode even when the wireless communication device is in a switched off mode, and to activate the warning signal generator upon receipt of the activation message.

22. The wireless communication device according to claim 20 or 21 , further comprising a position measurement device for measuring a position of the wireless communication device, a memory for storing a most recently measured position, the wireless communication device being arranged for, if a position can be measured by the position measurement device, storing the measured position in the memory, and if no usable position measurement can be performed, keeping a previously measured position in the memory, wherein the wireless communication device is arranged for providing the measured position as stored in the memory to the warning signal generator and transmitting by the warning signal generator the warning signal comprising the measured position as stored in the memory.

23. The wireless communication device according to any of claims 20 - 22, wherein the radio frequency receiver and warning signal generator are comprised in a frequency modulation or amplitude modulation transceiver, such as a radio transceiver integrated circuit.