WO2013004849A1

WO2013004849A1 - System for reporting the position of a transponder

Info

Publication number: WO2013004849A1
Application number: PCT/EP2012/063422
Authority: WO
Inventors: Anne NÄrhi; Tony Westman
Original assignee: Comtrack Ab
Priority date: 2011-07-07
Filing date: 2012-07-09
Publication date: 2013-01-10
Also published as: SE1130067A1

Abstract

System for reporting the position of a transponder comprising an activating unit (A3) comprising software for transmitting an activating command over a radio frequency and a transponder (A2) able to receive an activating command and to transmit a message containing its identity and position in response to an activating command characterised in that said transponder comprises a GNSS receiver for determining its position, radio frequency transceiver means for transmitting its position and transponder software for controlling said GNSS receiver and said transceiver.

Description

SYSTEM FOR REPORTING THE POSITION OF A TRANSPONDER

TECHNICAL FIELD

The present invention relates to transponders suitable for tracking the position of objects and the distribution of information.

BACKGROUND

In emergency situations such as avalanches and earthquakes it is very important to be able to quickly determine the number of victims of the incident and to determine their positions in order to optimise the use of the resources available to rescue them.

A prior art rescue system to help localise victims of an avalanche from the company RECCO AB is described in EP2362960. It uses passive transponders which return a signal when interrogated by a search radar. A problem with this system is the limited range which typically is a maximum of 200 metres, a lack of precision in the position indicated by the search unit and the risk that the transponder is in a position, e.g. under the victim, where it does not respond, or only responds weakly, to the search radar.

Another rescue system is described in WO2006015721. A first subunit is carried by a locatable person and this subunit receives a position signal in the form of a GPS signal and at least intermittently transmits a location signal containing information derived from the GPS position signal. A searcher has a second subunit which receives the location signal and the second subunit informs the searcher of the position of the first subunit. This system and other GPS-based systems suffer from the problem that terrain such as mountains or crevasses or the position of the wearer over the GPS receiver's antenna can mean that the GPS signal is not received by a transponder and that it can't give an accurate position.

SUMMARY

A system in accordance with the present invention solves the problem of how to locate the position of people or objects which are lost, e.g. people buried in snow or debris such as in the remains of buildings.

The present invention relates to a system which includes an activating unit which sends command instructions and receives information, and at least one transponder which receives command instructions and transmits information through a WLAN and/or an UHF- transceiver. Each transponder has an unique identity and is controllable with the use of a WLAN (Wireless Local Area Network) and/or an UHF-transceiver. The transponder comprises a Global Navigation Satellite System (GNSS) receiver which is used to determine the position of the transponder. The system further comprises an activating unit which can send command instructions to one or more transponders in the system and which can receive information transmitted by those one or more transponders. The activating unit could be a dedicated activating unit comprising software, memory, a screen, user input means such as a touch screen and/or, keypad and/or mouse and/or tracker ball and/or the like, radio frequency communication means, GNSS receiver means and a power supply. Alternatively, and as illustrated below, the activating unit comprises a cell phone with a screen able to display maps and/or images. Such a cell phone can be an iPhone, ZTE, iPAD or the like with a GNSS receiver and local access to maps installed internally in the cell phone. Access to the maps can also be achieved by using the USB connection of the cell phone connected to external device media such as a hard disk including maps files. The access to that media can also be achieved over the air by using the WLAN or UHF-transceiver.

The activating device can command a transponder to transmit a message through the WLAN and/or the UHF-transceiver to the activating unit wherein the message from the transponder contains at least the GNSS position determined by the GNSS receiver in the transponder. The transmitted position of the activated transponder can be displayed in an image on the screen of the activating unit along with the position of the activating unit. Alternatively, or in combination with the image, the position of the transponder can be displayed as text, for example as a bearing and distance from the activating unit.

The following satellite positioning systems are included in GNSS;

The American GPS (Global Positioning System), the Russian GLONASS (Globalnaya Navigatsionnaya Sputnikovaya Sistema), the European GALILEO, the Chinese COMPASS, the Indian IRNSS (Indian Regional Navigation Satellite System) and the Japanese QZSS (Quasi-Zenith Satellite System).

The transponder may contain a beeper which generates a sound and/or a vibrator unit which vibrates that can be activated through the WLAN or the UHF-transceiver by the user of the activating device, for example rescue personal, to confirm to the wearer of the transponder that the rescue team have determined the position of the user of the transponder.

The transponder may also contain a feature that allows program code or/and data to be up- and down-loaded by use of the WLAN and/or the UHF-transceiver in order to allow software modifications to be made to the unit and information collected by the transponder to be used by other parts of the system.

The transponder may also communicate with other transponders using the built-in WLAN and/or UHF-transceiver. The transponder may be able to receive commands and transmit commands. It may also be able to transmit a signal suitable for radio-frequency direction finding to enable a searcher to home in on its position.

The transponder may include a light source, for example, several high- intensive LED:s BIO that can be activated by a sending a "LED activating" command code to the transponder.

Preferably, it should be possible to address this command to a specific transponder, a group of transponders or all transponders within range of the activating unit in order to help find the transponder. DESCRIPTION OF THE DRAWINGS

The invention, together with further objects and advantages thereof, may best be understood by referring to the following detailed description taken together with the accompanying drawings, in which:

Figure 1 shows an embodiment of a system for activating a transponder and determining its position.

Figure 2 shows a block diagram showing schematically the elements of a transponder for use in the system of the present invention.

Figure 3 shows schematically the use of a system in accordance with the present invention to determine the position of transponders. DETAILED DESCRIPTION

Figure 1 shows an overview of the components of a system for activating a transponder and determining its position. It comprises at least one transponder A2 together with a cell phone- based communication system Al and an activating unit A3. The system may interact with a cell phone-based communication system Al shown in dashed lines. The cell phone-based communication system Al may be used to connect the activating unit A3 with the internet to enable it to download maps and other data if necessary. Figure 2 shows a block diagram of the transponder A2 in accordance with an embodiment of the present invention. The transponder A2 comprises a microcontroller Bl connected to a satellite receiver B3 with the corresponding antenna B7, a wireless local network B4 with corresponding antenna system B8, optionally a movement sensor B5, optionally a light- emitting device for example one or more high- intensive LEDs BIO or light bulbs, optionally a vibrator unit Bl 1, optionally a sound generating unit, such as a buzzer unit B12, and a power supply, for example a battery unit B9. These are contained in a housing (not shown) which can be attached to, or carried by, a person or object.

Figure 3 shows an illustration of the rescue team's usage of the tracking system A3 and A3: l to locate the people C2 each of whom is equipped with a transponder unit.

The microcontroller Bl has a built-in application program which is stored in the

microcontroller's memory. The microcontroller Bl and its software control the functions of the transponder. The microcontroller Bl preferably is adapted for usage in battery-based application where a low power consumption is mandatory. In the low power mode described below, the power consumption is only a few μΑ (micro-Ampere). Preferably the

microcontroller Bl has an internal flash-memory of approximately 60K Bytes and an internal Random Access Memory (RAM) of 4K Bytes. The GNSS satellite receiver B3 is preferably based on an advanced GPS processor which is small and has a very high sensitivity. An example of such a processor is the Origin ORG4472 which is 7 mm x 7 mm x 1.4 mm and has a navigation sensitivity of -163 dBm. A satellite receiving antenna B7 is connected to the satellite receiver B3 or may be integrated into the receiver. An example of a GPS receiver with integrated antenna is the Origin ORG1410 which is 10 mm x 10 mm x 5mm in size.

The UHF transceiver B4 is preferably based on PLL technology and preferably features an built-in automatic antenna tuner. Preferably it has a high transmission speed, up to 115.2 kbps and preferably it covers most of, all of, or at least, the frequency range 420.000 MHz - 440.000 MHz.

The transponder A2 is arranged to receive control commands and transmit data through the WLAN and/or a UHF-transceiver B4. Preferably, control commands can also be received in the transponder from the moving sensor unit B5.

The transponder's position is determined by the output of the GNSS receiver B3. When starting the transponder in response to an internally or externally commanded RESET or restarting after recharging or exchanging an empty battery, an initializing sequence is executed. The GNSS receiver will execute a "cold start" e.g. satellite data must be obtained from scratch. Once this has been achieved and a valid transponder position is received from the GNSS satellite receiver, the GNSS satellite receiver will switch to the hibernation mode - this is a power saving mode.

The microcontroller's Bl normal mode is stand-by and this occurs whenever a STOP instruction has been executed. The power consumption at this moment is very small, only a few μΑ (micro Ampere) as only the microcontroller Bl built-in RTI (Real Time Interrupt) timer is active. The TRI can generate a system interrupt. The system interrupt wakes up the microcontroller. The microcontroller decrements Timer 1 and continues to execute program code after the STOP instruction. During stand-by two timers are monitored - Timer 1 which relates to the GNSS system and Timer 2 which relates to the transceiver system.

If Timer 1 has elapsed, then the GNSS satellite receiver B3 is woken up from hibernation mode by issuing a "hot start" command. The GNSS satellite receiver will then update the satellite position. Satellite data is preferably outputted as ASCII characters following the NMEA-0183 protocol at the speed of 4800 Baud on one of the microcontroller's interrupt- controlled Serial Communication Interface (SCI) channels. When the update is done, the GNSS satellite receiver B3 will revert to hibernation mode and the power consumption will again drop to only a few μΑ.

In the hibernation mode, the GNSS satellite receiver will store the current ephemeris data internally in RAM. The hibernation mode is preferably limited to 2 hours or less so that the stored satellite orbit information is still valid for updating satellite positions when a hot start is made. This waking/hibernation sequence, controlled by Timer 1 is repeated continuously.

Timer 2 controls the activation of the UHF-transceiver B4. If Timer 2 has elapsed, then the UHF-transceiver B4 is activated in receive mode. The interrupt-driven driver of the UHF- transceiver will read any frequency shift keying (FSK) data during a pre-defined time.

Received data will be sent to the Parser. The Parser evaluates the contents of the data.

Valid data from the Parser will be sent to the requested program routine for execution together with parameters (if any). Invalid data is deleted and the Timer 2 is initialized to the default time whereupon the UHF-transceiver B4 is then completely shut down to avoid power consumption. When Timer 2 elapses again, the main program will activate the UHF- transceiver again and wait for FSK data. This is an endless loop. Control information comprises at least the following components; synchronization bytes, length of the data package, command code, identity of the sender, identity of the receiver, parameters and checksum.

The contents and length of the parameter area is depending on the command code sent.

In the BNF (Backus Naur Form) syntax command information is presented as follows:

<sync><datalength><command><transmitter address><receiver

address><parameters><checksum> To avoid that several transponders transmit their messages at the same time and thereby cause interference, a random delay generator in each transponder calculates a random length for a delay. A delay timer is then executed to implement the delay before the actual message is transmitted. Preferably every transmission starts with a newly calculated random delay. Each transponder is provided with a power supply. Preferably the battery system comprises one power cell or a plurality of serial- or parallel-connected power cells. A power cell can be, for example, a Lithium-Ion battery cell, a dry cell, a solar cell or a fuel cell. A first embodiment of a transponder, which may be of the physical size and shape of a wrist watch, may be used to locate the position of people, animals or objects. These may, for example, be buried in snow or debris following a natural disaster such as earthquake, hurricane or avalanche or a man-made disaster such as a terrorist or military action. In this embodiment of the invention a transponder A2 can be activated from an application in an activating unit A3 such as a dedicated unit designed and constructed only for this purpose or an iPhone or cell phone, that uses an appropriate operating system, for example Android, Windows Mobile, Palm or Symbian. The activating unit A3 has a radio communication system which, depending on the type of activating unit, may be a built-in WLAN system such as Bluetooth or an external electronic unit (a "dongle") with a battery system A3: l, and/or a UHF transceiver which works, for example, on the 400 MHz band, connectable to the activating unit's external communication port e.g. a USB port, or a dongle comprising a UHF-transceiver and a Bluetooth function accessible over the air.

As mentioned above a transponder comprises a GNSS satellite receiver B3 preferably with high sensitivity, a preferably low noise active GNSS antenna B7, a miniaturized UHF- transceiver B4 working on the same frequency band as the activating unit, preferably with a low power consumption, a microcontroller preferably with a low power consumption, a power supply such as a battery system B9, optionally a light unit , for example containing several high-intensivity LED:s B10, optionally a vibrator unit Bl 1 and optionally a beeper unit B12.

The transponder's normal state is sleep. In this state only the GNSS satellite receiver B3 is active, and a hibernation mode timer, Timer 1, is used to cause it to alternate between an active satellite-receiving mode and a hibernation mode. The power consumption in the hibernation mode of the GNSS satellite receiver is typically only a few μΑ (micro Amps). In order to maintain the satellite date valid, the hibernation mode is preferably equal to or less than 2 hours. Once the time determined by the hibernation mode timer Timer 1 has elapsed the GNSS satellite receiver is only active for a length of time which is sufficient to update ephemeris data and then it enters the hibernation mode again.

The transponder A2 listens for an addressed command which may be transmitted via the WLAN and/or on one or more different pre-defined radio frequencies via the UHF-transceiver B4. The addressed command may be addressed to an individual transponder, a group of transponders or all transponders. In order to avoid high power consumption, the WLAN and/or the UHF-transceiver of each transponder is only active for a portion, which is preferably only a very short time which preferably is between 1/100 and 1/1000 of the of a repeating receiving time window of, for example, length 15 seconds which is controlled by Timer 2. In other words, in this example, every 15 seconds the WLAN and/or the UHF- transceiver is/are activated for a very short time which preferably is between 1/100 and 1/1000 of the receiving time window e.g. 15 micro-seconds (μβ) or 50 or 200 μβ, etc. Preferably the length of one or both of the receiving time window Timer 2 and the activation time of the WLAN and/or UHF-transceiver are adjustable.

To ensure that all transponders in the coverage area of the activating (transmitting) unit A3, will be able to receive the transmission, the length of the time window of the transmission from activating unit A3 will be at least as long as the WLAN and/or the UHF-transceiver repeating receiving time window determined by the length of Timer 2, e.g. in the example above a time of at least 15 seconds.

A global activating command (CQ = Seek you) is repeatedly transmitted by the activating unit for the duration of the transmission time window. This ensures that all transponders within the coverage area of the radio transmission will receive the transmission. All transponders that receive the CQ message respond by transmitting a response message at least once and preferably a predetermined number of times.

To avoid that several transponders respond and transmit their response messages at the same time thereby causing interference on the receiving frequency, preferably a random generator in each transponder calculates the length of a transmission delay. The delay timer, Timer 3, is executed before the actual response message is transmitted. Every response message transmission starts with a new calculated delay. Thus, for each transmitting sequence, a new delay time is randomly generated for Timer 3. When the pre-determined number of retransmissions has elapsed, the program will revert to receive mode.

After having received the responses from the transponders the activating unit A3 will populate an ID list in the memory which will contain at least the identify of each responding transponder and its position. The activating unit and the activating unit application will preferably display on the screen the position of the activating unit A3 and the position and identification of all the transponders A2 currently answering the CQ. If the activating unit is a cell phone then, depending on the type of cell phone used for localization and the circumstances in the rescue area, it is possible that the cell phone system may be out of order or non-existent. In this case, locally stored maps in the cell phone can be used instead of accessing maps in real time. The transponder A2 preferably also contains a beeper B12 and a vibrator unit Bl 1 that can be activated through the WLAN and/or UHF-transceiver to be used as an verification for the bearer of the transponder that the rescue team have determined the transponder user's position and that help is on the way. The transponder A2 preferably includes several high- intensity LED B10 that can be activated by a sending a "LED activating" command code to the transponder. Preferably it is possible to address this command to a specific transponder, a group of transponders or all transponders in the transmitting area. With the application program GARMIN Mobile XT installed in a NOKIA 5800 cell phone using the Symbian operating system, the transponder position can be displayed directly on the map on the screen of the cell phone. The transponder position may also be shown in WGS84 format together with a text message containing personal data. The format of the data may be, for example, Garmin PeerPoint Messaging System.

The relay transmission function could be used to send messages to a transponder outside the radio signal coverage area of the activating unit A3. This is done by forwarding the message through one or several other transponders using the WLAN or the UHF-transceiver of the transponder. As shown in figure 3, by appending the signal path (the direct or indirect address of the transponder outside the radio signal coverage area of the activating unit A3) as a parameter in the message transmitted from the activating unit, the message will be forwarded to the final destination (transponder). As shown in figure 3, the signal path can in this particular case look like; C2:4,C3: 1,C4: 1,C5: 1 The signal path to the transponder(s) outside A3 's radio signal coverage area can be determined by first issuing the HEARD command.

The HEARD command works as follows:

When the activating unit A3 transmits the CQ command, all the transponders which receive the command will respond by transmitting a response message which contains the GPS- determined position of the transponder and its identity. The transponder identities and their positions are stored in the flash memory of the activating unit A3 (or its dongle A3 : 1). It is possible that there are one or more transponders which receive the CQ command and respond but which are not detected by the activating unit A3 due to low signal strength. It is also possible that one or more transponders are positioned in a radio shadow so that the receiver signal strength indicator (RSSI) value of their signals indicate that they are at a greater distance from the activating unit A3 than they actually are. It is also possible that one or more transponders are out of the coverage area of the activating unit. The RSSI value of a transponder can be used to identify which transponders are furthest away, or appear to be furthest away, from the activating unit A3. The RSSI value is available as an output from a UHF-transceiver, for example from the Hoperf Electronic RFM20BS, and comprises an 8-bit digital valve which reflects the signal strength of the transmission from the activating unit as received by the receiving (and responding) transponder. The RSSI value corresponds to a signal strength between -120dBM (RSSI value =0) and 20dBm (RSSI value = 255). In order to identify these transponders which are far away or in the radio shadow or outside the coverage area of the activating unit A3, the activating unit can issue the command HEARD. This is equivalent to a command CQA = Seek You All. The HEARD command can be addressed to all transponders or a specific group of transponders or an individual transponder. Each of the addressed transponders which receive the HEARD command from the activating unit will respond by retransmitting a HEARD command. All transponders in the range of the transponder or transponders retransmitting the HEARD will reply to the CQ command in the same way as if they had received the CQ command from the activating unit. In other words the transponder software is adapted to cause the transponder transceiver means to transmit a HEARD activating command which HEARD command orders receiving transponders to transmit a message containing at least the receiving transponder's identify and position. The responses received by each transponder to its retransmitted HEARD command will be reported back to the activating unit in the parameter field of the transponders' responses to the HEARD command. The activating unit will populate the ID list using these transponder responses and any new transponders on the list will include a data entry which mentions the indirect address to the transponder, i.e. which transponders a command has to be relayed through in order to reach that transponder. Thus when a transponder retransmits a HEARD command in response to a previous HEARD command from the activating unit that it has received then all of the information or some of the information (for example just the transponder identity and position) in messages received by said transponder in response to its HEARD command are retransmitted by it to the originator of the previous HEARD command.

If a transponder receives a HEARD command only from another transponder then this will indicate that it is out of range of the activating unit. In order to detect further transponders which are out of range of the activating unit such a transponder will retransmit the HEARD command and respond to the transponder(s) which it received the HEARD command from by retransmitting the information (for example just the transponder identity and position) in messages received by said transponder in response to its HEARD command. Preferably the activating can transmit a RECEIPT signal which can be addressed to an individual transponder to indicate that its identity and position has been received by the activating unit. A transponder can activate a visual or audible indicator to inform the person wearing it that its position has been received by an activating unit. A second embodiment of a transponder in accordance with the present invention may be provided with means to help pinpoint the position more accurately. This can be in the form of means for providing a continuous or repeating localisation radio transmission on one or more radio frequencies which can be received by the activating unit. The activating unit can be provided with a directional antenna and signal strength measuring means which enable it to determine from which direction the strongest signal is being received. It can be provided with means to display this direction on a screen and/or by means of an audible signal indicate when the activating is pointed towards the transponder transmitting the localisation radio

transmission. The activating unit can be provided with means for issuing a CONTINUOUS WAVE (CW) command which can be directed to a specific transponder, a group of transponders or all transponders. The CW command causes the appropriate transponder to transmit a localisation signal on the UHF and/or WLAN and/or GPS frequency. This signal can be continuous or, in order to save power, repeating at short time intervals. The activating unit is provided with an appropriate GPS antenna such as an HB9CV 2.4 GHz antenna which can, for example, be integrated with appropriate connectors into its casing. If the activating is based on a cell-phone or the like then the antenna can be integrated in a casing, for example a snap-on casing, which can be attached to, and electrically interconnected with, the cell phone.

The activating unit can be provided with software for measuring the signal strength and a display which shows the direction of the highest signal strength. The display can be complemented by or replace with an audible signal indicator which issue a tone which increase in volume as the signal strength increases, thus enabling the rescuer to hear in which direction the signal strength is highest. This can be determined by the user rotating the activating unit in an arc which will show increasing and then decreasing signal strength as the arc approaching and then passes beyond the direction in which the transponder lies. The strength of the signal can be used to give an estimated distance to the transponder being localised.

Such a system can be used to find a transponder unit which has been able to determine its own position. This could be due, for example, to terrain which prevents sufficient GPS signals being received by the transponder, an unfavourable orientation of the unit or malfunction of the transponder. Such a position-unknown transponder will reply to a CQ or HEARD command with a response which contains its identity but lacks a GPS-derived position.

Software in the application unit can be used to bring such units to the attention of the rescuer using the application unit. The rescuer can then active the CW command for the position- unknown transponder and localise the transponder by following the direction and distance display and/or audible signal. Thus, when said activating unit receives a message from a transponder in which the position of the transponder is unknown then it is adapted to transmit a CONTINUOUS WAVE command which causes said transponder to transmit a localisation signal. In order to enable the localisation signal to be detected it can be transmitted on more than one frequency, for example on two or more of the WLAN, UHF and GPS frequencies.

A transponder in accordance with the present invention may be equipped with a pulse sensor. This detects the pulse of the wearer of the unit and information regarding the pulse of the wearer can be transmitted in the personal data in a message from a transponder. This gives rescue personal information on the condition of the wearer.

A transponder in accordance with the present invention may be equipped with an alarm call activating means such as an alarm button or switch or the like. This can be used by a wearer of the transponder to send an alarm message from the transponder in order to call for help. This could be used, for example if the wearer is injured or trapped. Preferably the activating means would need to be activated for a predetermined length of time, for example 5 seconds, before it transmits an alarm message in order to reduce the risk of false alarms. An activating unit could be provided with software so that when an alarm message is received the activating unit in the range of the transponder the activating unit produces light and or sound signals to alert people in the vicinity of it that an alarm message has been received. An activating unit which is used indoors, for example if the unit is normally positioned near the reception of a building in a winter sport resort, could be provided with an external antenna in order to increase its range.

The present invention is not limited to the embodiments described and modifications can be made to these embodiments without departing from the scope of the invention as set forth in the appended claims.

Claims

1. System for reporting the position of a transponder comprising an activating unit (A3) comprising software for transmitting an activating command over a radio frequency and a transponder (A2) able to receive an activating command and to transmit a message containing its identity and position in response to an activating command wherein the transponder comprises a GNSS receiver for determining it position, radio frequency transceiver means for transmitting its position and transponder software for controlling said GNSS receiver and said transceiver, characterised in that said transponder software is adapted to cause the transponder transceiver means to transmit a HEARD command which HEARD command orders receiving transponders to transmit a message containing the receiving transponder's identify and information regarding its position wherein said transponder software causes said transponder to transmit said HEARD command and receipt of a HEARD command from an activating unit.

2. System, according to claim 1, characterised in that said transponder software causes said transponder to transmit said HEARD command if it receives said HEARD command from another transponder without previously having received a HEARD command from an activating unit.

3. System according to any of the previous claims, characterised in that said transponder software comprises a timer which determines a receiving time window and said software is adapted to activate the transponder transceiver means for an activation time which is shorter than said receiving time window.

4. System according to claim 3, characterised in that the activating command is repeatedly transmitted for the duration of a transmission time window which is longer than the receiving time window.

5. System according to any of claims 1-4, characterised in that when said activating unit receives a message from a transponder in which the position of the transponder is unknown then it is adapted to transmit a CONTINUOUS WAVE command which causes said transponder to transmit a localisation signal.

6. System according to claim 5, characterised in that said localisation signal is transmitted two or more of the WLAN, UHF and GPS transmission frequencies.

7. System according to claim 4, characterised in that said localisation signal is repeating.