EP3017435A2

EP3017435A2 - Low power protocols and processes for an alarm monitoring system

Info

Publication number: EP3017435A2
Application number: EP14786262.7A
Authority: EP
Inventors: Stephen Williamson
Original assignee: Quatro Electronics Ltd
Current assignee: Quatro Electronics Ltd
Priority date: 2013-05-03
Filing date: 2014-05-05
Publication date: 2016-05-11
Also published as: WO2014188282A3; WO2014188282A2

Abstract

The present invention provides a monitoring system having an alarm base and one or more remote sensors and data collecting devices. The alarm base and remote sensors communicate over a wireless connection and use a frequency hopping technique to implement a highly efficient communication protocol. By predefining and fixing both hop channels and ordering, the system is able to operate with reduced power demand. The communication protocol has very low power requirements in the alarm base and even lower power requirements in each of the remote sensors. The communication protocol is robust providing 100% data communications even at the edge of range,

Description

LOW POWER PROTOCOLS AND PROCESSES FOR

AN ALARM MONITORING SYSTEM

Related Applications

[0001] This application claims priority to U.S. provisional application number 61/819,008, filed May 3, 2013, and entitled "Low Power Smart Alarm," which is incorporated herein in its entirety.

Field of the Invention

[0002] The present invention relates to security monitoring systems having an alarm base and one or more remote sensors. In particular, the invention relates to wireless protocols for establishing low power and efficient communications between the alarm base and the one or more remote sensors.

Background

[0003] Communication monitoring systems are in wide use today to protect both property and people. In some cases, the computer monitoring system may be permanently installed in a location, and thereby it may be cost effective to provide electrical power to each of the alarm bases and the associated remote sensors. However, there is a substantial need for monitoring systems that can be temporarily installed and used for a limited period of time. In such a case, it is often impractical or too expensive to provide a permanent power source such as AC current, so the devices need to operate on batteries. It is desirable to keep battery size low to control costs and allow for smaller housings, but in contrast it is advantageous to have the battery last as long as possible to limit the frequency at which the batteries need to be changed. In this way, it is important that the communication protocol be able to keep a low power profile.

Summary of the Invention

[0004] Briefly, the present invention provides a monitoring system having an alarm base and one or more remote sensors and data collecting devices. The alarm base and remote sensors communicate over a wireless connection and use a frequency hopping technique to implement a highly efficient communication protocol. By predefining and fixing both hop channels and ordering, the system is able to operate with reduced power demand. The communication protocol has veiy low power requirements in the alarm base and even lower power requirements in each of the remote sensors, The communication protocol is robust providing 100% data communications even at the edge of range.

[0005] In one example of the invention, the monitoring system has a set of predefined hop channels arranged in a predefined pseudo random order, National or regional communication standards may set a required number of channels and an ordering construct. The alarm base is set to transmit small synchronization packets at the beginning of each hop period. Once paired so that the base and the remote devices are synchronized, the remote sensor only opens a listen period once every full cycle through the hop frequencies, which is about once every 20 seconds. However, if a sensor detects an alarm condition, it opens a listen window just prior to the next hop transition, detects the synchronization data, and then responds with a data packet that indicates alarm data is available. Then, in the following hop periods, the base instracts the sensor as to which data packet it is expecting so that the sensor can transmit the data to the alarm base. In this way, the use of acknowledgement packets or error correction can be avoided.

[0006] Advantageously, the monitoring system implements a communication protocol that enables an alarm base and its sensors can run on physically small batteries for a time in excess of 3 years without battery changing or charging. Further, computational demands are reduced by the heavy use of predefined channels and ordering, as well as the reduction in error correcting processes

Brief Description of the Drawings

[0007] FIG. 1 is a representation of an alarm monitoring system in accordance with the present invention.

[0008] FIG. 2 is a flowchart of alarm monitoring processes in accordance with the present invention.

[0009] FIG. 3 is a flowchart of a remote sensor monitoring process in accordance with the present invention. [0010] FIG, 4 is a flowchart of a remote sensor monitoring process in accordance with the present invention.

[0011] FIG. 5 is a timing diagram for communication protocols between an alarm base and a remote sensor in accordance with the present invention

[0012] FIG. 6 is a timing diagram for communication protocols between an alarm base and a remote sensor in accordance with the present invention.

[0013] FIG. 7 is a timing diagram for communication protocols between an alarm base and a remote sensor in accordance with the present invention.

Detailed Description of the Preferred Embodiment

[0014] Referring now to figure 1, a monitoring system 10 in accordance with the present invention is illustrated. Monitoring system 10 generally comprises an alarm base 12 which wirelessly communicates to one or more sensor devices such as sensor and camera device 15. It will be appreciated that the monitoring system 10 may have a single sensor/camera system 15, or can have multiple sensors and cameras such as remote devices 17 and 19. It will also be appreciated that other types of sensors may be used in monitoring system 10.

[0015] In one example, alarm base 12 may be positioned inside a building, such as a vacant warehouse, and various sensors and cameras may be positioned throughout the facility at strategically selected locations, In operation, the sensors are positioned to detect alarm activities within the property. For example, a sensor may be configured to detect the presence of likely human activity, which may indicate an intrusion into the building, Upon detecting such an intrusion, an alarm condition may be declared, and the camera contained within the sensor housing may be activated and allow for images or video to be collected. In other examples, the sensors may be used to detect flooding, glass breakage, smoke, or fire. It will be appreciated that other types of sensors may be used.

[0016] Alarm base 12 communicates to sensors 15, 17, and 19 using a wireless protocol. In one example, the monitoring system 10 is constructed for low power operation. In this way, the system may be advantageously installed temporarily into a facility, and then uninstalled when the need for security monitoring has been completed. In this way, it is desirable that the communication protocol establish and promote a highly efficient data and alarm communication for increasing communication range, while simultaneously reducing power consumption.

[0017] Although monitoring system 10 is described as a battery-powered monitoring system for usage in a temporary installation, it will be appreciated that broader applications may be used. In one example, the monitoring system 10 may be used to monitor outdoor activities for public events. In another example, monitoring system 10 may have a more permanent installation, with the alarm base being permanently powered, while the sensors are battery-powered. It will be appreciated that many configurations for monitoring system 10 are within the scope of the disclosed invention.

[0018] As will be described more completely below, the low power protocol provides meaningfully lower power consumption as compared to prior monitoring systems, thereby allowing for smaller and less expensive batteries, or longer operational life for installations. This is highly advantageous as the ability to enable the monitoring system 10 to function without battery replacement or maintenance is a significant cost saving for building managers. The low power protocol also enables extended transmission distance while managing data transmission errors and enhancing security for the overall transmission systems.

[0019] Generally, the low power protocol employs a wideband frequency hopping technology. Many respects of wideband frequency hopping technology are well understood, so therefore the general application of frequency hopping will not be described in detail. In particular, the wideband frequency hopping technology may be implemented according to standards effected in applicable jurisdictions. For example, the FCC provides for wideband frequency hopping in a band at 914 MHz. In another example, the European Union allows for wideband frequency hopping in the 868 MHz bands. It will be appreciated that other countries and jurisdictions may use different frequency bands. Although these bands are illustrated herein, it will be appreciated that other communication technologies and standards may be employed at different frequencies and standards consistent with this disclosure. [0020] It is typical that a frequency hopping technology defines the number of channels available for use within the hopping protocol. Further, it is often required that the sequence of hopping channels be defined in a pseudo random manner. To simplify processes and conserve power, the low power protocol used in the monitoring system 10 pre-defines the allowed channels and channel order. Also, the number of channels for hopping may be defined or limited by the relevant jurisdictional control. For example, the United States allows for a minimum of 50 hopping channels, while the European Union allows for a minimum of 47 channels for hopping, in an implementation, the minimum may be used, but to reduce the risk of transmission collision, additional hop channels may be used. It will be appreciated that other jurisdictions may have different hopping bands, ordering requirements, and channel designations. It will also be appreciated that other frequency bands and technologies may permit or require a different ordering or number of hopping frequencies.

[0021] Referring now to figure 2, a low-power communication protocol 25 is illustrated for use on a base alarm system. In particular, the protocol may be useful for a base alarm, such as base alarm 12 discussed with reference to figure 1. As generally described above, the protocol pre-defines a number of hop frequencies 27 for use within a particular frequency band. These predefined hop frequencies are also arranged in a fixed pseudorandom order 29. In one example, the European Union defines that there must be a minimum of 47 hop frequencies defined in a pseudo random order in the 868 MHz band, in one example the protocol uses 48 hop frequencies, although other set sizes can be used. In a second example, the United States requires that a minimum of 50 channels are arranged in a pseudorandom order in the 914 MHz band, in one example the protocol uses 54 hop frequencies, although other set sizes can be used. The standard does not dictate that the order be fixed, but doing so simplifies the processing and computational requirements. It will be appreciated that other hopping technologies or jurisdictions may have other requirements.

[0022] The alarm base has a counter, such as counter 32. The counter generally sets out the length of time or period that each hop frequency will be used. In this way, a hop frequency will be used for 375 ms, and then the system will advance to the next available hop frequency 34. Accordingly, every 375 ms a different hopping frequency will be selected according to the fixed pseudo random order. With a 375 ms channel period, and about 50 hop channels, the communication process does a full cycle through the hop list approximately every 20 seconds. It will be appreciated that other channel periods and number of hop channels may be substituted,

[0023] In operation, the counter 32 will provide a signal that activates the transceiver 36 at the start of every hop transmission period, which here is illustrated with a transmission period of 375 ms. Once the transceiver has settled, it detects if there is any communication activity or noise on the selected channel and determines if the channel is clear for transmission is illustrated in block 39. If the currently selected channel is not clear, such as there is activity or interference on the channel, the process will turn off the transceiver as illustrated in block 43. The system will then go back and wait for the next 375 ms transmission to begin.

[0024] In some examples, the system may provide for additional wait time such that one or more transmission periods are allowed to pass before retrying to send, However, if the channel is clear, then the alarm base sends out a synchronization packet 41. The synchronization packet may include various instructional and status information for the one or more remote receivers. One skilled in the art will appreciate the types of data, instructions, or status information that may be communicated in a synchronization packet. The transceiver will remain active for a short period of time after sending out the synchronization packet, in this way, the alarm base may receive data packets or other interrupt indications from a remote sensor. If no communication is detected from any sensor within the short listen period, the transceiver will shut down as shown in block 43. In this way, substantial power is conserved, as the transceiver uses considerable power as compared to the low-power counters and small processes that need to stay active.

[0025] Advantageously, the low power protocol 25 enables a very power efficient coordination and synchronization between a base unit and remote devices. Further, as the system detects interference or other issues on channels prior to using them, communication efficiency and robustness is provided.

[0026] Referring now to figure 3, a low-power protocol operating on a remote sensor or camera device is illustrated. The protocol 50 operates, for example, on a camera and sensor device 15 is illustrated in figure 1. Generally, the remote sensor has a complementary counter 52 which is kept in synclironism with that from an alarm base. It will be appreciated that pairing or synchronization routines are well known to initially establish a timing relationship between the master alarm base and the one or more remote slave devices. In this way, the remote sensor and the alarm base are cycling through the available pseudo random hop frequencies in the same order 54 and at substantially the same time. In typical operation the remote sensor only checks for information or synchronization after a complete cycle of all available hopping frequencies. For example, the full cycle 56 in the United States would represent, for example, 54 hop frequencies, each lasting 375 ms. In this way, a full cycle of the pre-defined hop order is approximately 20 seconds. Accordingly, approximately every 20 seconds the remote camera opens a listen window as illustrated in block 58.

[0027] The transceiver detects the synchronization packet sent from the alarm base as illustrated in block 61. If the synchronization packet is not detected, the remote sensor goes through a re-synchronization process as illustrated in block 67. However, if the synchronization packet is detected, then the remote sensor turns off its transceiver as shown in block 63 and determines if there is a drift in the synchronization. If so, the process adjusts the remote sensor's clock counter to align more correctly with the alarm base time. It is well known that clocks may drift with time, and that lower cost components have more drift. Accordingly, the alarm protocol provides that after every full cycle, a counter 65 adjusts according to the specific lead or lag for the detected synchronization packet. In this way, even with lower cost components, it is relatively rare to lose synchronization between the base and its sensors.

[0028] As generally described above, the remote sensor allows for extreme low power operation and only activates for resynchronization and instructions approximately once every 20 seconds. However, upon detecting any alarm event as shown in block 72 the sensor can immediately react for urgent attention. Accordingly, the alarm event will open the next listen window available at the next hopping frequency as shown in block 74. The remote sensor then detects the synchronization package as shown in block 76, and upon detecting the synchronization packet sends a small data packet to the alarm base as shown in block 78. For efficient and robust communication, the sensor waits for an acknowledgment from the alarm base, and if it does not receive one it will turn off the transceiver as shown in block 85, and then wait for the next hop cycle to open the listen window 74, detect the synchronization packet 76 and finally resend the data package 78. However, if the acknowledgment is received as shown in block 81, the transceiver is deactivated as shown in block 83, and the acknowledgement packet evaluated for its content.

[0029] Referring now to figure 4, a flowchart of the process by which the remote sensor sends image or image sequence data to the alarm base is illustrated. As with the rest of the processes for the low power protocol, process 100 also operates on the same 375 ms counter 102. If the remote sensor has image data to send as illustrated in block 104, upon the start of a new transmission hopping frequency, the transceiver will turn on as illustrated in block 106. The sensor opens a listen window as shown in 108 and then waits to detect a synchronization packet as shown in block 111. The sensor then sends a data packet 113 declaring a video file transfer request and defining the file parameters to the alarm base. The sensor continues to monitor and listen for data, and waits to receive an alarm request 115. The alarm request 115 generally may indicate three instructions, although it will be appreciated that other information may be communicated. First, the alarm request 1 15 may instruct the sensor not to send data 121 as the alarm base is busy. Second, the alarm request 1 15 may alternatively instruct the sensor to send a specified packet of data 122. Importantly, the alarm request data 115 may instruct the sensor to re- send the specified packet if the previous request was unsuccessful Thus this alarm data packet 115 operates to provide acknowledgment to efficiently increase the robustness of the wireless communication. Third, the alarm request data may indicate that the last data packet has been received for the image as illustrated in block 123.

[0030] Referring now to figure 5, a timing diagram for a monitoring system in accordance with the present invention is illustrated. Timing diagram 200 is not drawn to scale, and is for illustrative purposes only. For example, it will be appreciated that the length of the data packets is artificially emphasized for illustrative purposes only. Figure 5 shows a base 202 and a sensor 204. In particular, three pseudo-random frequencies are illustrated in hop sequence. It will be appreciated that the hop sequence is pre-defined and repetitive. As generally described above, each hop frequency is used for 375 ms 205. It will be appreciated that longer or shorter durations may be used for each hop frequency, and in some cases the length may be variable. In operation, the base 202 sends a synchronization package 207 which could be received by the one or more sensors 204. The timing of each syncliiOnization packet 207 aligns with the start of each transmission period 205. It will be appreciated that various instructional and status information may also be communicated within the synchronization packet.

[0031] The sensor 204 opens up a listen window 210 just prior to the expected receive time for the synchronization packet 207. It will be appreciated that the listen window can be opened sooner or later depending on the required level of service and the quality of component counter parts. In this way, opening the window earlier will use more power, but will have a reduced risk of losing synchronization. As the base and sensor are operating on the same order of predefined hop sequences, and the timing has been synchronized during a pairing process, these open windows can be relatively short. However, due to expected drift in the underlying timers and oscillators, the listen window 210 can be adjusted shorter or longer for accommodating drift and reliability issues. As soon as a sensor receives the synchronization packet 207, the sensor transceiver is shut down. Accordingly, as illustrated in figure 5, in normal operation the sensor only opens its listen window once every full hop cycle, which is approximately once every 20 seconds. Accordingly, the low-power process is highly efficient and robust.

[0032] Referring now to figure 6, the communication protocol 225 is illustrated for the condition when a trigger is detected in a remote device within a particular frequency period. In operation, the protocol 225 normally operates as described with reference to figure 5. However, at some point a trigger 226 may be activated within a sensor. Trigger 226 can be generated in the sensor due to, for example, a motion detector detecting a human like motion, fire, smoke, glass breakage, or other type of alarm event. If the sensor detects an alarm event 226, it will activate and notify the alarm base in the next available frequency period. Although the sensor typically only wakes up about every 20 seconds, it will immediately activate in the very next available frequency period, as it is desirable to quickly react to alarm conditions. [0033] In the next available frequency the sensor will open a listen window 227 and wait to receive a synchronization packet 228 from the alarm base. Upon receiving the synchronization packet 228, the sensor sends data packet 232 back to the base. The data packet 232 may contain several types of information, including an indication of the type of alarm event detected. The base then sends an acknowledgment packet 235 which is received by the sensor in listen window 237. At this point, the sensor has notified the alarm base of an intrusion or other alarm event, and has determined that the alarm base has acknowledged the event. The sensor will continue sending the data packet in each successive hop periods until an acknowledgement is received from the base alarm.

[0034] Responsive to the alarm event 226, the sensor may also be performing various actions under the local control of the remote sensor. For example, the remote sensor may be capturing an image or image sequences. In another example, the remote system could be recording audio, or broadcasting alerts. In this way, the remote sensor can independently be reacting to the specific type of alarm generated, and in near real time provide notification and information to the alarm base. In some cases, a simple communication that an alarm event has occurred may be sufficient. However, in many cases the sensor will have collected additional data that needs to be communicated to the base.

[0035] In this respect, figure 7 shows a highly efficient process 250 for communicating the additional available alarm data to the base. As illustrated in figure 7, the base sends a synchronization packet to the sensor according to the usual 375 ms hop period. After receiving the synchronization data the sensor responds with a data packet 255. The data packet 255 may include various types of data, such as the amount of data to be sent and the parameters of that data. In response, the base sends a specific data request 261 to the sensor. The data request 261 may request that no data be sent if the base is busy, or may instruct the sensor to send a specified packet of data. It will be appreciated that this is a typical master-slave relationship, so the details will not be set forth in detail. More particularly, if the alarm request packet 261 is responded to by the sensor or is responded with incorrectly formatted data then the alarm will re-request the specified packet with a data request 262. This re-try strategy has a maximum number of attempts before a failure is determined. However, if the alarm request data 261 was successfully responded to, the alarm will request the next packet 252 from the sensor. It will be appreciated that various specific communication processes may be used to transfer the data packet 252 to the base. For example, the data packet 252 may be divided into several small data packets, with each data packet having its own acknowledgment requirement. It will be appreciated that the specific length of the individual packets may be determined on an application specific basis,

[0036] It will be appreciated that in some cases the data to be transferred from the sensor to the base may be quite large, particularly in the case of image sequences. Accordingly, the image sequence or other data may take many channel periods before the data transfer is complete. When the final data packets have been received by the base, the base will respond with a completed transmission package 263, which will indicate to the sensor that the final data package has been successfully received. At this point the sensor can go back to its normal 20 second synchronization routine as described with reference to figure 5.

[0037] At some point, either after the trigger event or after receiving some or all of the data from the remote device, the alarm base may initiate a communication session with a central office, typically using a cellular communication device. It will be appreciated that other wide area communication devices and processes can be used.

[0038] As described above, the communication protocol uses a single set of predefined hop channels to implement the monitoring system. However, in more complex monitoring environments, it may be useful or necessary to have multiple alarm bases in close proximity, with each alarm base having its own set of associated remote sensors. In such a case, the communication protocol may provide for multiple sets of hop channels, each having predefined channels arranged in a fixed pseudo random order. In this way, during configuration of the alarm bases, each base and its remote devices can be configured to operate on a distinct hop set, thereby reducing the risk of interference or transmission collisions. Further, the monitoring system may be set to autonomously attempt a new channel set if an unacceptable level of interference or collision is found while using the current set of hop channels. [0039] While particular preferred and alternative embodiments of the present intention have been disclosed, it will be appreciated that many various modifications and extensions of the above described teclinology may be implemented using the teaching of this invention. All such modifications and extensions are intended to be included within the true spirit and scope of the appended claims.

Claims

Claims What is claimed, is:

1. A battery powered sensor for use in a computer monitoring system, comprising: a transceiver,

a processor implementing a communication protocol further comprising:

providing a set of predefined and fixed hop channels;

arranging the set of hop channels into a predefined and fixed pseudorandom sequence

predefining a fixed period for each hop channel;

activating, just prior to the start of a hop period, the transceiver to open a listen window;

detecting a synchronization packet that was sent from an alarm base;

turning off the transceiver if no interrupt condition exists, and waiting for a full cycle of hop periods to elapse to activate the transceiver to open a next listen window.

2. The battery powered sensor according to claim 1 wherein the communication protocol further includes adjusting a counter in the sensor to compensate for synchronization drift.

3. The battery powered sensor according to claim 1 wherein the communication protocol further includes:

receiving the interrupt in the form of a trigger that indicates an alarm condition has been detected by the sensor;

activating, just prior to the start of the next hop period, the transceiver to open a listen window;

detecting a synchronization packet that was sent from an alarm base; and sending a data packet to the base alarm the indicates that an alarm condition has been detected.

4. The battery powered sensor according to claim 3 wherein the communication protocol further includes:

waiting for an acknowledgment packet responsive to sending the data packet; receiving the acknowledgment packet; and

turning off the transceiver.

5. The battery powered sensor according to claim 3 wherein the communication protocol further includes:

waiting for an acknowledgment packet responsive to sending the data packet; not receiving the acknowledgment packet in an expected period of time;

turning off the transceiver;

activating, just prior to the start of a future hop period, the transceiver to open a listen window;

detecting a synchronization packet that was sent from an alarm base; and sending the data packet to the base alarm the indicates that an alarm condition has been detected.

6. The battery powered sensor according to claim 1 wherein the communication protocol further includes:

receiving the interrupt in the form of a status indicator that an alarm data set is available for transmission;

turning off the transceiver;

detecting a synchronization packet that was sent from an alarm base; and sending a data packet to the base alarm the indicates that alarm data is available to be transmitted;

receiving from the base alarm an instruction packet; and

performing the instruction.

7. The battery powered sensor according to claim 6 wherein the instruction is to send the next available alarm data packet.

8. The battery powered sensor according to claim 6 wherein the instruction is to resend the prior alarm data packet.

9. The battery powered sensor according to claim 6 wherein the instruction is to not send any data.

10. The battery powered sensor according to claim 6 wherein the instruction indicates that the last alarm data packet has been received; and

turning off the transceiver.

11. The battery powered sensor according to claim 1 wherein the transceiver operates according to a Unites States standard that requires 50 or more hop channels.

12. The battery powered sensor according to claim 1 wherein the transceiver operates according to a European Union standard that requires 47 or more hop channels.

13. The battery powered sensor according to claim 1 wherein the hop period is about 375 ms.

14. The battery powered sensor according to claim 1, further comprising a camera unit.

15. The battery powered sensor according to claim 14, wherein the sensor is a passive infrared sensor that is arranged to trigger the camera unit to take an image.

16. The battery powered sensor according to claim 14, wherein the sensor is a passive infrared sensor that is arranged to trigger the camera unit to take a sequence of images.

17. The battery powered base alarm unit for use in a computer monitoring system, comprising :

a transceiver,

a processor implementing a communication protocol further comprising:

providing a set of predefined and fixed hop channels;

predefining a fixed period for each hop channel;

activating, at the start of a next hop period, the transceiver; determining if the current hop channel is clear;

if the current hop channel is clear, sending out a synchronization packet: and;

if the current hop channel is not clear, turning off the transceiver and waiting a predetermined number of hop periods before proceeding to the activating step.

18. The battery powered base unit of claim 17, wherein the communication protocol further includes opening a listen period after transmitting the synchronization packet.

19 The battery powered base unit of claim 17, wherein the communication protocol further includes transmitting to the remote sensor an instruction to indicating what portion of the alarm data set to send in the next available frequency period.

20 The battery powered base unit of claim 19, wherein the instruction is to send the next portion of the alarm data set, to resend the prior portion of the alarm data set, or to send no data.