GB2344023A

GB2344023A - A communications system

Info

Publication number: GB2344023A
Application number: GB9921290A
Authority: GB
Inventors: Raymond Ross Lann
Original assignee: TAYLOR LANN TECHNOLOGY Ltd
Current assignee: TAYLOR LANN TECHNOLOGY Ltd
Priority date: 1998-09-10
Filing date: 1999-09-10
Publication date: 2000-05-24
Anticipated expiration: 2019-09-10
Also published as: GB9921290D0; GB2344023B; GB9819737D0

Abstract

A communication system which includes at least one receiver 14a -g located within range of a first transmitter 34, the receives 14 being coupled or in communication with a second transmitter 24. A receiver 14 is used to receive a transmission from the first transmitter 34, the transmission being directed to the second transmitter 24 for re-transmission to, for example, a remote receiver. The first transmitter could be a thermal image camera 36 carried by a firefighter 38. Images are transmitted to the receivers 14a-g, which are connected by cables 22a-g to a roof mounted transmitter 24 which radiates to a mobile control unit. The system may be used within the structure of a shopping complex with individual units 12a-f.

Description

"Communication System" The present invention relates to a communication system.

Conventional microwave communication systems are generally limited by the range over which signals may be transmitted. Signals are constrained to certain frequency ranges, such as the licence exempt frequency of around 1.4 giga-Hertz (GHz). As the number of communication systems which are permitted to use this frequency is quite large, the output power of the transmitters is limited to prevent neighbouring signals from interfering with one another.

For example, a transmitter operating at 1.4 GHz at a power output of 500 milliwatts (mW) has a range of about 1 kilometre (km) in free space (ie without intervening obstructions). Thus, any other similar systems operating on a similar frequency may interfere with one another.

However, when operating such a transmitter within structures, such as a railway station, shopping centre, factory or the like, the range of the transmitter is reduced as the signal is reflected and refracted by the structure.

An increase in power input to transmitters located within a structure would result in an increased range.

However, neighbouring signals may interfere, and a large increase in input power can often result in a small increase in power output, as most systems are relatively inefficient.

According to the present invention there is provided a communication system comprising a first transmitter, at least one receiver located within range of the first transmitter, the receiver being in communication with a second transmitter located remote from the receiver, characterised in that a signal emitted from the first transmitter can be received by the receiver, the signal being communicated to the second transmitter for retransmission.

The receiver is typically located in a structure but may simply be in a defined area. The receivers may be located on ceilings within the structure. Where false ceilings are used, the receivers may be located within a space between the ceiling and the false ceiling.

Alternatively, the receivers may be located at positions around the first transmitter. For example, where the first transmitter is being used in a built-up area, the receiver (s) may be located on surrounding buildings, or may be located on mobile units.

The second transmitter is typically located outwith the structure. The second transmitter typically retransmits the signal for reception by a remote receiver. The remote receiver may be part of a mobile unit such as a vehicle or the like.

Optionally, there is at least two, and preferably more receivers. The receivers are preferably spaced apart so that at least one receiver is positioned at a point which is within the range of the first transmitter.

Thus, wherever the first transmitter is located within the structure, there is at least one receiver which is capable of receiving the signal therefrom. The receivers are typically positioned at similar intervals to smoke detectors in the structure e. g. at 3-30m spacing.

Optionally, at least three receivers are used. This allows calculations to be made to estimate the approximate location of the first transmitter.

Typically, the range from the first transmitter to the receiver (s) is calculated using a time delay between transmission and reception of the signal.

Alternatively, the phase delay between transmission and reception may be used to calculate the distance between the first transmitter and the receiver.

The first transmitter is typically electrically coupled to, or comprises, a video capture device. The video capture device typically comprises a thermal imaging camera (TIC). Alternatively, the video capture device may be a video camera.

The first transmitter may be coupled to any source of data (including digital data), video and/or audio signals to be transmitted outwith the structure.

The receiver (s) are preferably coupled to a signal selector, the selector being located at or near the second transmitter. The signal selector typically selects one of a plurality of input signals and outputs said one input signal. The output of the selector is typically controlled remotely. This allows a user at the remote receiver to select a signal from a particular receiver within the structure, for retransmission by the second transmitter, and subsequent reception at the remote receiver.

Alternatively, the selector may combine all the signals from each receiver to provide a superimposed output signal. Alternatively, the selector may scan the input signals to automatically detect the strongest input signal and output this signal.

The receivers and transmitter are typically broad-band transmitters and receivers, for example microwave transmitters and receivers. Alternatively, infra-red transmitters and receivers may be used.

Embodiments of the present invention shall now be described, by way of example only, with reference to the accompanying drawings in which: Fig. 1 is a schematic cross-section of a typical shopping centre showing an embodiment of a communication system according to the present invention; and Fig. 2 is a schematic view of a signal selector for use with the communication system of Fig. 1.

Referring to the drawings, Figs 1 and 2 show an embodiment of a communication system according to the present invention.

Fig. 1 shows a typical example of a shopping centre, generally designated 10, in cross section. The centre comprises a plurality of units 12a-12f, which may be individual shops, offices or the like. It will be appreciated that although Fig. 1 shows a shopping centre 10, the communication system of the present invention may be used in any structure which has a plurality of individual units or rooms, such as an office block, industrial factory complex, or the like.

Receivers 14a-14g are located at various positions within the centre 10, and are advantageously distributed throughout the centre 10 in a similar pattern to smoke detectors (not shown). In this example, each unit 12a-12f is provided with a remote receiver 14a-14f. The remote receivers 14a-14f are positioned on the ceilings of the units 12a-12f.

Alternatively, where there is a false ceiling 16, a remote receiver 14g may be positioned within a space 18 created between the false ceiling 16 and an actual ceiling 20 (or upper floor level).

The receivers 14a-14g are preferably hard-wire linked by cables 22a-22g (shown schematically as dotted lines) to a base transmitter 24. It should be noted that hard-wiring the receivers 14a-14g to the base transmitter 24 is not essential. The receivers 14a-14g may be coupled to the base transmitter 24 using any conventional means. The base transmitter 24 is advantageously located at a highest point 26 of the shopping centre 10, but may be located at any position outwith the centre 10.

Fig. 2 schematically shows the receivers 14a-14g connected to an optional signal selector 28, the signal selector 28 typically forming part of the base transmitter 24. The output 30 of the signal selector 28 gathered from the receivers 14 is re-transmitted via an antenna 32 to a remote receiver (not shown). The remote receiver may be located, for example, at a mobile base unit which monitors the signal from the base transmitter 24. The mobile unit may be, for example, a communications vehicle or the like.

Transmission to the remote receiver can be via hardwire connections, or by microwave or radiowave broadcast.

The signal selector 28 has cables 22a-22g electrically connected thereto and facilitates selection of one of the signals from the receivers 14a-14g to be output to the antenna 32 for retransmission. The signal selector 28 may be operated manually by remote control (eg from the mobile unit) so that a user of the system can select the signal from a particular receiver 14a-14g to be retransmitted by the antenna 32. Alternatively, the signal selector 28 may be programmed to automatically detect the strongest signal from the receivers 14a-14g by scanning the signal on each of the cables 22a-22g, and subsequently outputting this to the antenna 32.

A further alternative would be to program the signal selector 28 to superimpose each of the signals from the receivers 14a-14g on one another. This superimposed output would then be fed through to the antenna 32 for retransmission. The superimposed signal can then be detected at the remote receiver and processed to give individual outputs from each of the receivers 14a-14g using any conventional method or technique.

In use, a first transmitter 34 generates a signal which is subsequently received by the receivers 14a-14g. The signal from the first transmitter 34 may be a broadband signal (ie data, video and/or audio) which is generated by, for example, a video capture device 36.

In this example, the video capture device is a handheld thermal imaging camera (TIC) 36 operated by a user 38. The user 38 may be a fireman who is searching for people in the shopping centre 10 which is filled with smoke from a fire. The video signal from the TIC 36 is transmitted by the first transmitter 34 and is subsequently received by at least one of the receivers 14a-14g.

By providing a plurality of receivers 14a-14g, the signal from the transmitter 34 at the TIC 36 is received by at least one of the receivers 14a-14g. The signal is then communicated to the base transmitter 24 through the cables 22a-22g, and subsequently retransmitted to the remote receiver.

Thus, wherever the user 38 is within the centre 10, a receiver 14a-14g is within range of the transmitter 34, ensuring that a signal generated by the TIC 36 is relayed to the mobile unit outwith the centre 10.

Furthermore, it is possible to calculate the position of the user 38 within the centre 10 using shortbaseline radio position-fixing techniques if the location and identity of the nearest three receivers is known eg by triangulating the distances from receivers 14b, 14c and 14d (Fig. 1). This is accomplished by coding part of the signal from the transmitter 34 during a period when it is not sending its primary information. For example, a pulse code on the signal may be used to provide a measure of the video flyback period (ie the period between successive frames of video image from the TIC 36), which can be used to calculate the distance to each receiver 14b, 14c, 14d, which are in known positions. These distances can be triangulated allowing determination of the position of the user 38. The techniques are well known in the fields of radio position-fixing and electronic distance measurement.

It is also possible to use the phase delay of the video signals, as opposed to the time delay, to calculate the position of the user 38.

It should be noted that any broad-band signal may be used to transmit the video signals from the transmitter 34 to the receivers 14a-14g, for example infra-red.

In addition, it is possible to use the communication system with other sources of broad-band (ie video and/or audio) signals. For example, the remote transmitter may be coupled to a video camera in a shopping centre, industrial unit or the like, and the present invention is not limited to the example shown.

A television camera crew may use the communication system to send signals from within structures to a mobile communications unit outwith the structure.

It should be noted that use of the communication system described herein is not limited to use within structures. For example, the communication system may be used in built-up areas where the transmission of a signal is inhibited by surrounding buildings or the like.

Modifications and improvements may be made to the foregoing without departing from the scope of the present invention.

Claims

CLAIMS 1. A communication system comprising a first transmitter, at least one receiver located within range of the first transmitter, the receiver being in communication with a second transmitter located remote from the receiver, characterised in that a signal emitted from the first transmitter can be received by the receiver, the signal being communicated to the second transmitter for retransmission.

2. A communication system according to claim 1, wherein the receiver is located within a structure.

3. A communication system according to claim 1 or claim 2, wherein the receiver is located on a ceiling within a structure.

4. A communication system according to claim 2 or claim 3, wherein the second transmitter is located outwith the structure.

5. A communication system according to any preceding claim, wherein the second transmitter retransmits the signal for reception by a remote receiver.

6. A communication system according to claim 5, wherein the remote receiver forms part of a mobile unit.

7. A communication system according to any preceding claim, wherein the receivers are spaced apart so that at least one receiver is positioned at a point which is within the range of the first transmitter.

8. A communication system according to any preceding claim, wherein at least three receivers are used.

9. A communication system according to any preceding claim, wherein a range from the first transmitter to the receiver (s) is calculated using a time delay between transmission and reception of the signal.

10. A communication system according to any preceding claim, wherein the phase delay of the signal between transmission and reception is used to calculate a distance between the first transmitter and the receiver (s).

11. A communication system according to any preceding claim, wherein the first transmitter is coupled to, or comprises, a video capture device.

12. A communication system according to claim 11, wherein the video capture device comprises a thermal imaging camera (TIC).

13. A communication system according to claim 11, wherein the video capture device comprises a video camera.

14. A communication system according to any preceding claim, wherein the receiver (s) is coupled to a signal selector.

15. A communication system according to claim 14, wherein the selector is located at or near the second transmitter.

16. A communication system according to claim 14 or claim 15, wherein the signal selector selects one of a plurality of input signals and outputs said one input signal.

17. A communication system according to any one of claims 14 to 16, wherein an output of the selector is controlled remotely.

18. A communication system according to any one of claims 14 to 16, wherein the selector combines all the signals from each receiver to provide a superimposed output signal.

19. A communication system according to any one of claims 14 to 16, wherein the selector scans the input signals to detect the strongest input signal and outputs this signal.

20. A communication system according to any preceding claim, wherein the receivers and the transmitters are broad-band transmitters and receivers.

22. A communication system according to any one of claims 1 to 20, wherein the transmitters and receivers comprise infra-red transmitters and receivers.

23. A communication system as described herein with reference to Fig. 1 of the drawings.