GB2552783A

GB2552783A - Communications method and system

Info

Publication number: GB2552783A
Application number: GB1613250.8A
Authority: GB
Inventors: Martinez Richardo
Original assignee: BULL PRODUCTS Ltd
Current assignee: BULL PRODUCTS Ltd
Priority date: 2016-08-01
Filing date: 2016-08-01
Publication date: 2018-02-14
Anticipated expiration: 2036-08-01
Also published as: GB2552783B; GB201613250D0

Abstract

A communications method and system for controlling power consumption of wireless units. The wireless units can be sensors for use in a fire alarm system such as smoke or heat detectors. The power consumption of the wireless devices is controlled by managing the transmission power of the devices using a closed loop transmitter power control scheme. Figure 1 shows units 12 and a control unit 10. Units 10 and 12 have a transceiver 16 and an antenna 18. The transceivers include a power control module 16a. The control unit 10 can conduct a signal strength test by sending a signal to units 12 which respond with an acknowledgement signal. The acknowledgement signal gives an indication of the received signal strength by units 12. If the received signal strength is assessed to be higher than necessary the transmission power of unit 10 is reduced and similarly increased when the received signal strength is too low. Assessment of received signal strength continues until the minimum value for transmission power that meets received signal strength requirements is found.

Description

(54) Title of the Invention: Communications method and system

Abstract Title: Optimizing transmission power of wireless devices in a fire alarm system (57) A communications method and system for controlling power consumption of wireless units. The wireless units can be sensors for use in a fire alarm system such as smoke or heat detectors. The power consumption of the wireless devices is controlled by managing the transmission power of the devices using a closed loop transmitter power control scheme. Figure 1 shows units 12 and a control unit 10. Units 10 and 12 have a transceiver 16 and an antenna 18. The transceivers include a power control module 16a. The control unit 10 can conduct a signal strength test by sending a signal to units 12 which respond with an acknowledgement signal. The acknowledgement signal gives an indication of the received signal strength by units 12. If the received signal strength is assessed to be higher than necessary the transmission power of unit 10 is reduced and similarly increased when the received signal strength is too low. Assessment of received signal strength continues until the minimum value for transmission power that meets received signal strength requirements is found.

12a 12b 12c

Figure 1

At least one drawing originally filed was informal and the print reproduced here is taken from a later filed formal copy.

1/1

10 17

Figure 1

COMMUNICATIONS METHOD AND SYSTEM

This invention relates to a communications method and system, and in particular to a communications method and system whereby a plurality of individual units are able to communicate with one another. In particular, the invention relates to a communication system in which at least one of the individual units is battery powered or has a restricted power supply. Whilst the invention may be employed in a range of applications, one application in which it is envisaged that the invention may be employed is in an alarm system, for example to a fire alarm system, and in particular to a system of the type in which a plurality of battery powered units are arranged to communicate with one another by way of wireless communications links.

Where a plurality of battery powered units are required to communicate with one another, it is desirable to be able to avoid unnecessary consumption of electrical power in order to extend the useful working life of the batteries used in the units. Where units have, for example, photovoltaic panels associated therewith to provide electrical power for use in the operation of the units, again there is a desire to avoid unnecessary power consumption.

In a fire alarm system of the type made up of a network of individual units that are arranged to communicate with one another by way of wireless radio communications links, a significant part of the power demand of the units relates to the consumption associated with the operation of the communications transceivers of the units, and especially in the transmission of signals the primary purpose of which is to ensure that the individual units of the system and the communications links therebetween are functioning correctly.

A typical fire alarm system of the type outlined hereinbefore comprises a control unit and number of sensor units, warning units and activations points. The sensor units, warning units and activation points are typically grouped into a series of zones. By way of example, a building in which the system is installed may be divided up into floors, and the units located on a single floor of the building may be grouped together to form a zone. It will be appreciated, however, that this represents merely one approach to the grouping of the units, and a number of other arrangements are possible.

It is important, in use, to ensure that all of the units are able to communicate with other units of the system so that, in the event that a fire is detected, all relevant parts of the system can be operated in such a manner as to ensure that an appropriate warning is triggered throughout the building, or through all desired parts of the building. Furthermore, the operability of each unit needs to be tested periodically. One way of achieving this is for each unit of the system to be polled periodically to ensure that it is still capable of receiving signals, and to ensure that signals transmitted therefrom are at a sufficiently high strength that they can be received by other parts of the system. This may be achieved by arranging from the control unit to periodically poll each unit. However, the power consumption associated with such transmissions is high, and it is an object of the invention to provide a communications system whereby power consumption is reduced.

Rather than having the control unit directly poll each and every unit of the device, such polling may be undertaken at a zone or group level. However, this 'chatter' still represents a significant consumer of electrical power, especially as, in order to ensure that the system is operating correctly, this polling operation is undertaken very frequently.

Not only do the high power transmissions represent a significant power drain, but they may also lead to interference with the operation of other nearby, unrelated systems.

It is an object of the invention to provide a communications method and system in which at least some of the disadvantages associated with known arrangements are overcome or are of reduced impact.

According to the present invention there is provided a communications method for use in communication between first unit including a transceiver, the transmission power of which can be controlled, and a second unit including a transceiver, the method comprising the steps of transmitting a strength test signal from the first unit for reception by the second unit, transmitting an acknowledgement signal from the second unit to the first unit upon reception of the strength test signal by the second unit, the acknowledgement signal containing information indicative of the signal strength of the received strength test signal, and modifying the transmission power of the transceiver of the first unit based, at least in part, upon the information contained within the acknowledgement signal.

The signal strength information may include a numeric representation of the received signal strength, or may simply indicate that the received signal strength is too high, too low or within an acceptable range.

It will be appreciated that the invention allows the transmission strength from the first unit to be reduced to a minimum acceptable level, thereby making power consumption savings, whilst still ensuring that the transmission power is sufficiently high to ensure reliable reception of a transmitted signal. Not only does the use of the invention reduce power consumption, but it may further be advantageous in that the risk of transmitted signals being received by other unrelated systems is reduced.

Additional units may be provided, and the method may be employed with each unit to ensure that a signal transmitted by each unit can be received, reliably, by at least one other of the units.

In the event that one or more of the units is required to transmit a critical signal, for example in the case of a fire alarm system, in the event that one or more of the units needs to transmit a signal indicative that a fire has been detected and that warning devices associated with the system need to be activated, then the transmission power for such transmission is preferably set at a high level in order to ensure reliable reception of the signal by other units of the system.

The invention further relates to a communications system configured to perform the method set out hereinbefore. Such a system comprises a first unit including a transceiver, the transmission power of which can be controlled, and a second unit including a transceiver, the first unit including a control unit operable to cause the first unit to transmit a strength test signal from the first unit for reception by the second unit, receive an acknowledgement signal from the second unit transmitted upon reception of the strength test signal by the second unit, the acknowledgement signal containing information indicative of the signal strength of the received strength test signal, and to modify the transmission power of the transceiver of the first unit based, at least in part, upon the information contained within the acknowledgement signal. The modification may be undertaken by a transmission power control module.

The invention will further be described, by way of example, with reference to the accompanying drawing, Figure 1, which is a diagrammatic representation of a communications system in accordance with an embodiment of the invention.

Figure 1 illustrates, diagrammatically and in simplified form, a communications system in accordance with an embodiment of the invention. The communications system is employed, in this embodiment, in a fire alarm system comprising a control unit 10 and a plurality of individual units 12. The units 12 take a range of forms. By way of example, some of the units 12 take the form of sensor units 12a, for example smoke or heat detectors. Others of the units 12 take the form of warning units 12b, for example in the form of alarms or sounders operable to provide a warning to occupants of a building in which the system is installed in the event that a fire is detected. Yet others of the units 12 may take the form of activation points 12c that can be activated by occupants of the building in the event that they notice that a fire has broken out. The units 10, 12 are in wireless communication with one another.

In use, in the event that one orother of the sensor units 12a or one orother of the activation points 12c is activated, then a signal is transmitted from that one of the units 12 to provide an indication that a fire has broken out. The signal may further include data indicative of which of the units 12 has caused the transmission of the signal. Upon receipt of the signal by one or more of the warning devices 12b, the warning devices 12b are activated to generate an alarm or warning to occupants of the building to indicate that the building should be evacuated. Upon receipt of the signal by the control unit 10, information may be displayed or otherwise output from the control unit 10 to provide an indication of which of the units 12 resulted in the generation of the alarm, hence providing an indication of the likely location of the fire. The control unit 10 may be configured, in some applications, to automatically place a call to the fire services or to an alarm monitoring service to result in the fire services attending the building. In addition, the control unit 10 may transmit an additional, high power signal to ensure that all of the warning devices 12b are activated and that they remain activated until such time as the system is reset.

The units 12 are grouped into a series of groups or zones 14a, 14b, 14c. By way of example, the zones 14a, 14b, 14c may be indicative of the locations of the units 12 of that zone within the building. However, this need not always be the case.

The control unit 10 and the various units 12 are each arranged to communicate with one another via radio based two way communications links. To this end, each unit 10, 12 includes a radio transceiver 16 and associated antenna 18. The transceivers 16 each include a power controller module 16a operable to control the signal strength at which signals are transmitted by the transceiver 16. Each unit 12 is conveniently provided with an internal power supply, for example in the form of a replaceable and/or rechargeable battery 20 or the like. It will be appreciated that by holding the signal transmission strength at a relatively low power, under the control of the power controller module 16a, battery life can be extended through reducing the power consumption of the unit 12.

Each module 12 further comprises a controller 22 operable to control the operation of the various parts thereof.

The system has several modes of operation, some of which may be undertaken substantially simultaneously, as set out below.

In use, and when armed, each unit 12 of the system operates so that, depending upon the nature of the unit 12, the controller 22 thereof controls the operation so as to ensure that any sensors associated with the unit operate to detect the occurrence of a fire, or to detect if activation has taken place, or to detect whether an alarm signal has been generated from another of the units 12, in which case it will control operation of an alarm or sounder in response thereto.

In the event that a fire is detected, then the unit 12 that has detected the out-break of the fire will transmit an alarm signal. In order to ensure that the alarm signal has the best chance of being received, the alarm signal being a critical signal, the power control module 16a of the unit 12 operates to ensure that the alarm signal is transmitted by the transceiver

16 thereof at a high signal strength, preferably at the highest signal strength possible. The reception of the alarm signal by others of the units 12 and by the control unit 10 results in the warning units 12b of the system being activated to generate an alarm or warning for occupants of the building to warn them of the out-break of the fire and the need to evacuate the building or take other appropriate action.

Since alarm signals of this type are only transmitted in the event of the detection of a fire, it will be appreciated that these high power critical signals are only transmitted very infrequently, and so their impact upon battery life is not a concern.

Depending upon the nature of the system, the control unit 10 may, upon receipt of the alarm signal, generate signals to summon the emergency services. It may also produce an output providing an indication of the location of the fire.

Since this function is the primary function of the fire alarm system, it will be appreciated that this functionality is operative in the background at all points in time when the system is armed, even if other operating modes of the system are active.

In addition to the above mode of operation, periodically, the control unit 10 may conduct a test during which it sends signals to be received by each unit 12, and the units 12 may respond by transmitting an appropriate acknowledgement signal, which may include, for example, status information setting our system status information relating to the status of that one of the units 12. Since these communications are direct between the control unit 10 and the units 12, it will be appreciated that each power control module 16a will control the operation of the associated transceiver 16 to ensure that the communications signals are transmitted at high power during this mode of operation. It is envisaged that these types of communication will only occur relatively infrequently and so, whilst they do represent a drain on battery power, they do not significantly reduce battery life.

In order to ensure that all of the units 12 within a particular zone 14 are functioning correctly, test signals are transmitted at a very regular basis between the units 12 within each module 14. As these signals are transmitted very frequently, the signal strength at which these signals are transmitted makes a significant impact upon the power consumption of each unit 12, and hence upon the battery life of each unit 12. These signals are used to ensure that all parts of the system are functioning correctly, and are able to communicate with one another. If, during these communications, it is established that one or more of the units 12 are failing to respond to communications, then this may serve to flag that maintenance of at least part of the system is required. By way of example, it may be an indication that one or more of the units 12 has a flat battery which requires replacement, or that a more serious fault has developed that requires investigation.

In accordance with the invention, therefore, periodically each unit 12 is arranged to undertake a procedure to ensure that the signals transmitted between the units 12 of a zone 14 are transmitted at as low a power level as possible whilst still at a power level high enough to ensure reliable receipt. The test procedure involves each unit 12 within the zone transmitting a strength test signal under the control of the controller 22 thereof, the strength test signal being transmitted at a low power controlled by the power control module 16a.

Provided the strength test signal is transmitted at a high enough power level that it is received by at least one other of the units 12, then the receiving unit 12 transmits, under the control of the controller 22 thereof, an acknowledgement signal. The acknowledgement signal contains information indicative of the strength of the received strength test signal. The first unit 12 which transmitted the strength test signal, upon receipt of the acknowledgement signal, analyses the acknowledgement signal to ascertain whether the strength of the strength test signal is at an acceptable level. If the strength test signal was found to be at a higher power level than necessary, then the power controller 16a may make adjustments to reduce the transmission power at which signals are transmitted to units 12 within the zone 14. On the other hand, if it is found that the strength test signal was transmitted at too low a power, then the power control module 16a can operate to increase the power of subsequent transmissions to units 12 within the zone 14. If no acknowledgement signal is received, then this is an indication that the test transmission signal was transmitted at too low a power, and the test procedure is repeated at a higher transmission power.

The procedure set out above may be repeated until it is determined that all of the transmissions between the units 12 within a zone 14 are at the minimum acceptable level.

It will be appreciated that by periodically repeating the test procedure, it can be ensured that the frequent transmissions between the units 12 within each zone 14 are undertaken at as low a transmission power as possible whilst still maintaining reliable communication between the units. Accordingly, unnecessary power consumption is avoided and battery life is extended.

As well as enhancing battery life, the frequent 'chatter' between the units 12 in this mode of operation is unlikely to be received by other systems in the vicinity of the system, and so are unlikely to interfere with the operation thereof.

It will be appreciated that as critical signals are still transmitted at high power as mentioned hereinbefore, the power consumption savings achieved in accordance with the invention as outlined hereinbefore do not come at the expense of safety or system reliability.

Whilst the invention is described hereinbefore in connection with a fire alarm system, it will be appreciated that this represents just one application in which the communications system of the invention may be employed. It may be employed with other types of alarm system. Furthermore, many devices are known that frequently communicate with one another wirelessly, and the invention may be applied to many of such arrangements. By virtue of the nature of the invention, it is most applicable to systems in which the individual units thereof do not frequently move significantly relative to one another as, for systems in which individual units are frequently moved, the signal strength test would need to be repeated with greater regularity.

Accordingly, it will be understood that a number of modifications and alterations may be made to the arrangement described hereinbefore without departing from the scope of the invention as defined by the appended claims.

Claims

CLAIMS:

1. A communications method for use in communication between first unit including a transceiver, the transmission power of which can be controlled, and a second unit including a transceiver, the method comprising the steps of transmitting a strength test signal from the first unit for reception by the second unit, transmitting an acknowledgement signal from the second unit to the first unit upon reception of the strength test signal by the second unit, the acknowledgement signal containing information indicative of the signal strength of the received strength test signal, and modifying the transmission powerof the transceiver of the first unit based, at least in part, upon the information contained within the acknowledgement signal.
2. A method according to Claim 1, wherein the signal strength information includes a numeric representation of the received signal strength.
3. A method according to Claim 1, wherein the signal strength information contains an indication that the received signal strength is too high, too low or within an acceptable range.
4. A method according to any of the preceding claims, further comprising at least one additional unit, the method being employed with each unit to ensure that a signal transmitted by each unit can be received, reliably, by at least one other of the units.
5. A method according to any of the preceding claims, wherein, in the event that one or more of the units is required to transmit a critical signal, the transmission power for such transmission is set at a high level in order to ensure reliable reception of the signal by other units of the system.
6. A method according to any of the preceding claims, wherein in the event that one or more of the units is required to transmit a test signal, the transmission power for such transmission is set at a low level in order to minimise power consumption, but at a high enough level to be received by at least one of the other units of the system.
7. A method according to any of the preceding claims, and applied to a fire alarm system, controlling the operation thereof.
8. A communications system comprises a first unit including a transceiver, the

10 transmission power of which can be controlled, and a second unit including a transceiver, the first unit including a control unit operable to cause the first unit to transmit a strength test signal from the first unit for reception by the second unit, receive an acknowledgement signal from the second unit transmitted upon reception of the strength test signal by the second unit, the acknowledgement signal containing information indicative of the signal

15 strength of the received strength test signal, and to modify the transmission power of the transceiver of the first unit based, at least in part, upon the information contained within the acknowledgement signal.
9. A system according to Claim 8, wherein the modification is undertaken by a

20 transmission power control module.
10.

A system according to Claim 8 or Claim 9 and forming part of a fire alarm system.

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Office

Application No: GB1613250.8