WO2007031843A1

WO2007031843A1 - A portable tracking device

Info

Publication number: WO2007031843A1
Application number: PCT/IB2006/002513
Authority: WO
Inventors: Gerhard Stephanus Mynhardt
Original assignee: Sygade Solutions (Proprietary) Limited
Priority date: 2005-09-14
Filing date: 2006-09-13
Publication date: 2007-03-22

Abstract

A portable tracking device includes a connector for connecting the device to the body of a person to be tracked. A location module is used to determine the location of the portable tracking device. A short-range wireless communication module communicates with a base monitor and a long range wireless communication module communicates with a host system, A control module controls the operation of the portable tracking device.

Description

A PORTABLE TRACKING DEVICE

BACKGROUND OF THE INVENTION

This invention relates to a portable tracking device, particularly for use in secure offender tracking units.

In many countries, suitable offenders are allowed house arrest rather than being placed in a prison and tracking units are attached to the offenders to monitor their movements.

There are a number of known offender tracking systems. However, requirements now exist to track offenders who are allowed to leave their homes, for example to go to work or to shop. Prior art systems include specific offender tracking systems to either only track offenders in the home or to track them outside of the home. These also suffer from a number of drawbacks related to limited battery life and in determining that it is in fact the offender who is actually being tracked. In addition, the common use of Global Positioning (GPS) for tracking offenders inside their homes is extremely unreliable, rendering it effectively useless for determining that an offender is actually in the house or building where the GPS based location system last placed the offender.

This invention addresses these problems. SUMMARY OF THE INVENTION

According to the present invention there is provided a portable tracking device comprising:

a connector for connecting the device to the body of a person to be tracked;

a location module used to determine the location of the portable tracking device;

a short-range wireless communication module for communicating with a base monitor;

a long range wireless communication module for communicating with a host system; and

a control module for controlling the operation of the portable tracking device.

The connector may take the form of an ankle strap.

Preferably, the connector includes an electronic lock and a body capacitance sensor to detect when the portable tracking unit has been removed from the person to which it is connected.

The short-range wireless communication module is used to determine whether or not the person being tracked is in proximity to the base monitor.

The location module is used for tracking the person when they are not in proximity to the base monitor.

The device preferably includes a fingerprint sensor for reading a fingerprint of the person to be tracked, wherein the control module is adapted so that when the fingerprint is sensed, the fingerprint is transmitted to the central station using the long-range wireless communication module.

Alternatively, software operating in the portable tracking device may determine that the fingerprint being presented is that of the person being tracked.

The portable tracking device may also include a battery.

Preferably, the portable tracking device includes a removable first battery and an integrated second battery wherein both the batteries are rechargeable.

Preferably, the integrated second battery can be recharged via the removable first battery.

The short-range wireless communication module may be a short-range wireless modem operating in the license free 915 or 868 megahertz bands.

The long-range wireless communication module is preferably a GSM or CDMA cellular network compliant modem.

Preferably, the iocation module is a GPS module.

BRiEf DESCRIPTION OF THE DRAWINGS

Figure 1 is a schematic representation of an example embodiment of an offender tracking system;

Figure 2 illustrates a portable tracking device of the system of Figure 1 ; Figure 3 illustrates the portable tracking device of Figure 2 with the removable battery clipped into the device;

Figure 4 illustrate the portable tracking device with the fingerprint door open;

Figure 5 is a schematic representation of the fingerprint sensor;

Figure © is a schematic representation of a user's fingerprint being sensed;

Figure 7 is a schematic representation of a house base module;

Figure s is a schematic circuit diagram of the portable tracking device;

Figure 9 is a schematic circuit diagram of the base monitor;

Figure 10 is a schematic circuit diagram of a capacitive sensor; and

Figure 11 is a schematic circuit diagram of a tamper proof electronic lock.

PESCRIPHON OF EMBODIMENTS

Figure 1 shows the various elements of a secure offender tracking system according to an example embodiment.

A portable tracking device 30 is securely fixed to a limb of an offender by a connector. In most cases this will be fixed to an ankle of the offender.

A fixed house base monitor 32 is installed in a house 34 in a position where it can optionally also receive GPS signals. This monitor 32 also contains a charger for two battery packs, as well as a wireless or dial-up modem to an offender tracking host system 36. This will be described in more detail below.

The offender tracking host system 36 is where the actual tracking takes place. This host system does not form part of this patent application as the house base monitor 32 and the portable tracking device 30 can be used with a variety of offender tracking host systems.

Signals received from GPS satellites 38 are used to provide location information to the house base monitor 32 and the portable tracking device 30. Therefore, both of these units are location aware and report their locations to the offender tracking host system 36. Therefore, if the GPS option is installed in the house base monitor, it means that this equipment cannot be moved without this being detected.

The portable tracking device 30 includes a location module used to determine the location of the portable tracking device. The location module is typically a GPS module.

The portable tracking device 30 also includes a short-range wireless communication module for communicating with the base monitor 32 and a long range wireless communication module for communicating with the host system 36. A control module controls the operation of the portable tracking device. All of these will be described in more detail below.

An important element is the short-range wireless electronic tether, which takes place via short range wireless communications between the house base monitor 32 and the portable tracking device 30, This communication can only take place while the offender is in or around the house.

Thus, an essential aspect of the operation of the system is that when the portable tracking device 30 is within range of the house base monitor 32, it communicates with the house base monitor 32 thereby confirming that the offender is located in or near the house. However, when the portable tracking device 30 goes beyond the range of the house base monitor 32, its position is now detected by the location system, specifically the GPS system.

All communications between the house base monitor 32, the portable tracking device 30 and the offender tracking host system 36 are encrypted, allowing authentication of devices and messages. This is important to avoid the possibility of spoofing, where external radio transmission equipment is programmed to emulate the offender tracking devices, therefore pretending that they are indeed in specific allowed locations. The fact that the messages are encrypted with secure cryptographic communications means that spoofing is not generally possible, even to most of those well versed in the art of cryptography.

Figure 2 illustrates the portable tracking device 30 with a removable battery 40 disconnected.

What can also be more clearly seen in the figure is the tamper proof connector 42 in the form of an ankle strap.

Figure 3 illustrates the portable tracking device 30 of Figure 2 with the removable battery clipped into the device.

Figure 4 illustrate the portable tracking device 30 with a fingerprint door 44 open to reveal a fingerprint sensor 46 for reading a fingerprint of the person to be tracked.

In Figυr© 5, a schematic representation of the fingerprint sensor is shown. The sensor has a rubber encapsulation 48 to protect the sensor from moisture.

Figure 6 shows a user's fingerprint being sensed. Ih addition to the sensor 46, the system has a function button 50 and some LED's 52 which the user uses to operate the sensor and which will tell the user when a fingerprint has been correctly sensed.

Figure 7 is a schematic representation of the house base module 32 which includes an LCD display 54.

The unit has two antennas, the first being a GSM antenna 56 for communicating with a Global System for Mobile communication (GSM) network and the second being a GPS antenna 58 for communicating with the GPS network.

The unit includes two plates 62 for receiving the batteries of the portable unit 30 to be recharged.

Finally, the unit includes an AC power plug 60, as it is mains powered.

The portable tracking device 30 is implemented as illustrated in Figure 8. A highly integrated 16-bit microprocessor type Hitachi H8S2238 10 is used. This processor has an integrated flash memory for software, as well as integrated RAM for temporary data, stacks etc. It also contains a number of internal UART ports for serial communications to external devices as well as a high speed SPI serial device interface. An advantage of the portable tracking device 30 is that it operates on very low current and that it can be put into a sleep mode, from which it will exit upon pre-programmed timeouts, or when certain activity occurs. This forms part of the strategy to conserve battery power,

A solid-state capacitive fingerprint sensor 11 underlies the fingerprint sensor 46 referred to above. The fingerprint sensor 11 may be a Fujitsu™ type MBF100 which is used to sense fingerprint images. This is interfaced to the processor 10 via a high speed SPI serial bus 14. The offender will be requested to verify themselves which will mean placing their finger on the sensor 11 until the relevant "OK" indicator 20 comes on. This will mean that the embedded software has picked up a fingerprint image with sufficient quality for a possible match. This is accomplished by counting up the number of extracted minutiae points. The template is sent to the offender tracking host system 36 for verification at the offender tracking host system. Alternatively, the fingerprint match can be performed locally by the processor. If no match occurs, an alarm condition will result with immediate transmission of the alarm condition to the offender tracking host system, The offender's fingerprint image and the minutiae template will have been extracted previously as part of the arresting process and will be made available for matching purposes thereafter.

Various wireless long distance modems can be used, depending on the country of deployment. For countries where GSM capability is available, a GSM modem 15, such as those provided by Siemens™, is used, with data being communicated in a GPRS mode. A Code Division Multiple Access (CDMA) modem may also be used. An integrated triple band GSM patch antenna is used which is tuned specifically to allow operation when the antenna is close to the human body and to allow for it to be integrated into the enclosure,

This link is used to provide communications between the portable tracking device 30 and the offender tracking host system 36. The communications on this link is fully encrypted using the industry standard DES encryption. Each processor is programmed with a unique internal silicon serial number, which also allows the specific unit to be recognized and authenticated at the host.

A commercially available standard GPS module 13 is used, such as those supplied by Trimble™. An active GPS ceramic patch antenna is used for higher sensitivity, such as those provided by Sarantel™. This antenna is fully integrated and is able to operate satisfactory when in close proximity to a human body.

An integrated short-range wireless modem 12 is provided for the electronic tether function according to which the portable tracking device 30 communicates to the house base monitor 32 when within range of the house base monitor 32, such as when the offender is in or around the house. A commercially available wireless modem, type DR3000-2 from RFM™, is used, it operates in the 915Mhz band. An internal ceramic patch antenna is used.

A unique feature of the portable tracking device 30 is its double battery operation. The portable tracking device 30 contains both a removable battery 16 as well as an integrated secondary battery 18. Both batteries are Lithium Ion batteries that can be recharged. A double cell is used for the removable battery pack so that its combined nominal battery voltage is 7.2V. A single cell is used for the internal secondary battery 18, with a battery voltage of nominally 3.6V, The removable battery pack is used to charge the secondary battery 18. This is accomplished by trickle charging the secondary battery 18 when the battery pack is inserted and has enough capacity to power the portable tracking device 30, as well as to charge the secondary battery 18. The charging circuitry is contained in a single integrated circuit 17 from Texas Instruments™. Two schottky diodes are used to allow the secondary battery to supply the required voltage when the battery pack is removed or has no capacity. The GSM module, which contains its own regulator, is powered directly from the secondary battery voltage.

A low drop out regulator 19 from Linear Technology™ is used to provide 3.3V DC power to the processor and other peripherals.

The portable tracking device 30 is housed in a secure and rugged plastic housing. The ankle strap 42 can only be removed by authorized personnel.

The housing also contains two LED indicators 20 as well as two push buttons switches 21. These correspond to LED's 52 and buttons 50 in Figure 6.

House base monitor 32 is implemented as illustrated in Figure 9. A highly integrated 16-bit microprocessor type Hitachi™ H8S2238 1 is used, which is the same processor as used in the portable tracking device 30.

The house base monitor 32 requires a link to the host system and normally dial-up is used for this. However, reliability of dial-up, ability to tamper with the line or communications, need to install a special line (in most cases) etc. makes this a problem. In this embodiment a wireless link to the host system 36 is deployed. This is the same wireless modem as used as in the portable tracking device 30. Various wireless long distance modems can be used, depending on the country of deployment. For countries where GSM capability is available, a GSM modem 4, such as those provided by Siemens™, is used. An external triple band GSM ornπi directional antenna is used. This link is used to provide communications between the house base monitor 32 and the portable tracking device 30. Similar to the portable tracking device 30, the communications on this link is fully encrypted using the industry standard DES encryption. Each house base monitor processor is programmed with a unique internal silicon serial number that also allows the specific unit to be recognized and authenticated at the host.

Since a potential danger exists in that a house base monitor 32 may be moved without this being detected, a commercially available standard GPS module 3 is used to provide location awareness to the house base monitor 32. The same GPS module as used in the portable tracking device. An external active GPS antenna is used to ensure that GPS reception is available. This may mean that the portable tracking device 30 is mounted near at next to a window in the house or apartment.

An integrated short-range wireless modem is provided for the electronic tether function to the portable tracking device 30. The same short wireless modem as used in the portable tracking device 30 is used. However, in this case an external omni directional antenna is used. All .communications between the portable tracking device 30 and the house base monitor 32 is encrypted using DES, This allows authentication as well as non-spoofing.

The house base monitor 32 also has an alphanumeric display 5 (corresponding to display 54 in Figure 7). An LCD module from Epson able to display 256 pixels by 64 pixels is used. This allows for messages to be downloaded and displayed to the offender. Two switches 6 are provided as well as four LED indicators. The indicators will also be used to indicate battery condition.

The house base monitor 32 can simultaneously charge two battery packs via chargers 11 and 12 illustrated above as metal plates 62. Fast charge controllers from Texas Instruments™ are used. An integrated mains to DC switching power supply 13 provides power for the chargers as well as for the house base monitor 32 to operate. An interna! Lion battery will power the house base monitor 32 during any mains failure conditions. This battery 41 is also charged by a fast charger controller. A low drop out regulator is used to provide 3,3 volts to the circuitry. Two schottky diodes enable a voltage from either the battery or the 6VDC mains power, supply. The GSM module, Which contains it's own regulator, is powered directly from the battery voltage.

The house base monitor 32 is housed in a plastic housing which can also accommodate two battery packs for charging,

The software implementation allows for certain tracking parameters to be downloaded:

- Regularity of location tracking for both the portable tracking device 30 and the house base monitor 32

- Regularity of reporting from the portable tracking device 30 and the house base monitor 32

- Regularity and schedule of fingerprint verification Siπce communication is rapid when using GSM GPRS, it is deemed to be advantageous if the analysis of the portable tracking device 30 and house base monitor 32 data is performed on the host's system.

Referring to Figure 10, a capacitive sensor is one form of tamper proofing as it continually senses the presence of a person to which the device is attached. If the presence of a person is not detected, an alarm signal is issued to the host system.

A single IC is used to detect body capacitance when the portable tracking device has been fitted to a limb. This uses an off the shelf capacitance sensing IC from Quantum™. This IC provides an output indicating the presence or not of body capacitance. The output from this IC is connected via an interrupt to the processor. Forcible removal of the portable tracking device will therefore be sensed even if the external battery pack has been removed and will result in an alarm condition which will also be reported Wirelessly to the offender tracking host system.

In Figure 11 , a tamper proof electronic lock is illustrated which can only be centrally engaged and disengaged. This is accomplished through a miniature mechanically bi-stabie latch that is operated by the processor 10. This latch has two coils for engaging and disengaging respectively. Once engaged, it will mechanically stay in the particular position, regardless of mechanical shock, vibrations or movement, until de-activated by the processor. The processor will therefore activate the latch when the ankle strap connector has been fitted to the offender. Upon a complete fitment, the official responsible for fitting the portable tracking device will typically press both buttons 21 simultaneously for at least 3 seconds, after which the processor will engage the latch. The processor cannot unlatch it thereafter without being commanded to unlatch by the offender tracking host system.

Upon release, or when the portable offender tracking device ankle strap connector must be removed, the offender tracking host system will be informed typically by an officer or suitably authorized official phoning an operator at the offender tracking host system who will issue the unlatch command to the particular offender portable tracking device, after satisfying and security requirements such as proper official authentication procedures, and determining that the portable tracking device may be removed,

Thus, a single integrated system can determine the location of the offender regardless of whether the offender is in their house, where GPS location can not be reliably used, or not. This integrated hybrid approach also provides the ability to automatically sense when the offender is in or near their house, and vice versa, if the offender is outside the house without having to strap on any additional tracking devices, which may easily be forgotten, and which leads to unreliability in the overall system.

For out-of-house offender tracking a GPS positioning methodology is used while the in-house tracking uses an electronic tether to the fixed house monitor base unit is used, since GPS is particularly unreliable indoors. However, this house monitor base unit also contains a fixed GPS unit which means that it cannot be moved without this being detected.

Fingerprint verification of the offender/wearer is provided as a means to establish the presence of the particular offender as and when required. This allows verification of the offender to take place remotely from the Offender Tracking Host System.

Wireless long range communications is build into the Offender Secure Offender Tracking Unit and into the house monitor base unit. This increases reliability of communications and allows both house based and out-of-house based tracking to occur seamlessly.

The full cryptology house monitor based encrypted messages pass between all the Offender Tracking Host System elements. Since each component is also uniquely identifiable, it provides the following high security advantage Secure Offender Tracking Unites. AII units are authenticated, meaning that a unit cannot be replaced or simulated.

No message replacement, modification or spoofing is possible, Therefore, only authentic Offender Tracking Host System components can be used and any attempt to replace or simulate these will be detected.

The Secure Offender Tracking Unit contains dual batteries to increase operating life and improve reliability. One of these is a removable battery pack, charged by the house monitor base unit. This battery in turn charges the secondary fixed battery in the Secure Offender Tracking Unit.

Intelligent charging will ensure rapid charging, and also accurate determination of the amount of battery energy available.

Claims

1. A portable tracking device including:

a connector for connecting the device to the body of a person to be tracked;

a control module for controlling the operation of the portable tracking device.

2. A portable tracking device according to claim 1 wherein the connector takes the form of an ankle strap.

3. A portable tracking device according to claim 1 or claim 2 wherein the connector includes an electronic lock and a body capacitance sensor to detect when the portable tracking unit has been removed from the person to which it is connected.

4. A portable tracking device according to any preceding claim wherein the short-range wireless communication module is used to determine whether or not the person being tracked is in proximity to the base monitor.

5. A portable tracking device according to claim 4 wherein the location module is used for tracking the person when they are not in proximity to the base monitor.

6. A portable tracking device according to any preceding claim wherein the device includes a fingerprint sensor for reading a fingerprint of the person to be tracked.

7. A portable tracking device according to claim 6 wherein the control module is adapted so that when a fingerprint is sensed, the fingerprint is transmitted to a central station using the long-range wireless communication module.

S. A portable tracking device according to claim 6 wherein the control module is adapted so that when a fingerprint is sensed, software operating on the portable tracking device determines that the fingerprint being presented is that of the person being tracked.

9. A portable tracking device according to any preceding claim wherein the device includes a battery.

10. A portable tracking device according to claim 9 wherein the device includes a removable first battery and an integrated second battery,

11. A portable tracking device according to claim 10 wherein both the batteries are rechargeable.

12. A portable tracking device according to claim 10 or claim 11 wherein the integrated second battery is recharged via the removable first battery.

13. A portable tracking device according to any preceding claim wherein the short-range wireless communication module is a short-range wireless modem.

14. A portable tracking device according to any preceding claim wherein the long-range wireless communication module is a GSM or CDMA cellular network compliant modem.

15. A portable tracking device according to any preceding claim wherein the location module is a GPS module.