NZ570126A - Location feature for cellular telephones - Google Patents

Abstract

A system for locating cellular telephones is disclosed. The system comprises a single portable device and operates from a single location. The system also operates independently of and without utilising a cellular telephone network. The system triggers a cellular phone or device to transmit, irrespective of whether the identity of the cellular phone or device is known and then detects a standard cellular telephone radio frequency (RF) transmission from that cellular phone or device in order to positively identify and locate that cellular phone or device by providing range and bearing data.

Description

W-e'e priority as proviced by sabsect on {2} or subsection (3) ot section ' 1 of the Pafe-ts Act 1953 is waited \r -espect of o-e o" nore pi visional specific at ons, p ease quote the nunbertsi be cw Patent Number (s) Date(s) 570126, 570127 -JUL-2008 575833 27-MAR-2009 Title Of i'venian: System for Locating Cellular Telephones (^or ft'ei i 1 Kenneth John BAGNALL, 9 Carlisle Place, Marchwiel, TIMARU 7910, NZ. (British). hereby cec aie the nvention, for which I (or we) pra§r that a oaten: nay r>e granted to ne io<' ust, a'd the nerod by v ch it is to be pedomed, to be part cularly describec in and by the following slatene^t 1 ■■ coniimaion of the specification should tm upm paper of the same size as this form, on one side only, with the lues weH spaced and with a margin of 2,5 cm on the left hand part: of the paper. The completion of the description sfmuid be Miomed by the claim or clams numbered' consectsfiveiy, (See mteb&fmr,} The specification must be signed at the end) NOTE,- The claims must relate to a single invention, must be dear and sucdnct and must tm fairly based on the matter disclosed in the spedfication. They should form in brief a dear statement of that which censituies the invention. Applicants sitculd be careful thai their claims Include neither more nor less (ten they desire to protBci by their patent Any unnecessary multiplicity of claims or prolixity of languaoe should be avoided. Claifns sfwxjId not b& made for <S>J for assistance completing this form please call 0508 4 IPONZ {0508 447 669} wwwJponz.govt.nz Patents Form No. 5 Description This invention relates to the location of cellular telephones where network coverage is poor or nonexistent.

Problem Addressed Every year thousands of people become lost or stranded, often with tragic consequences.

People who are prepared to be lost or require rescue will often carry radio communications such as HF or VHF/UHF Transceivers, Satellite Telephones or an Emergency Position Indicating Radio Beacon (EPIRB), Avalanche Beacon etc. However, many people find themselves in need of assistance that do not carry this level of equipment, often because they were not expecting to be in danger. For example motorists on a rural highway, trampers on a short day tramp, fishermen on a river mouth. Yet people in these everyday situations can and do, end up in jeopardy. They may lose control on a bend in a ravine, stray from a path in dense bush or be trapped by an incoming tide.

Natural disasters such as floods, cyclones or earthquakes or conflict may render large numbers of people in need of assistance at any one time. Location of people trapped in rubble can be very difficult for emergency and rescue services.

Yet often many of these people are carrying a sophisticated piece of modern communications technology which could be used to uniquely identify them and their exact position whilst also providing communications with rescue authorities. This equipment is the Cellular Phone, so ubiquitous an item that it is now carried almost everywhere by almost everybody irrespective of whether users expect to be within a service area throughout their journey. This is particularly true where these phones now also provide an ever increasing range of secondary functions such as cameras, mp3 players, email clients, web browsing and personal data assistants and even in built Global Positioning by Satellite (GPS) capability.

All Cellular Phones and Cellular Telephony based devices are Radio Frequency (RF) Transceivers and therefore are capable of producing an RF signal which can be detected and triangulated using standard radiolocation techniques independently of any cellular network service.

Furthermore, each cellular phone / device can transmit its own unique identifying data, e.g. International Mobile Subscriber Identity (IMSI) & International Mobile Equipment Identity (IMEI), allowing it to be positively identified and matched with known information (if any) about it or against other data such as the identities of known equipment, such as cell phone belonging to searchers.

Although, in many countries, cell phone services now cover increasingly remote terrain; coverage is often patchy with large cell areas and many radio blind spots. New Zealand's coasts and mountains are a classic example of this.

In the case of a natural disaster or conflict, it is highly probable that public cellular telephone networks will fail over large areas.

Hitherto, cellular phones can provide an effective means of location only when operating within an area with good cellular network service coverage with reasonably small cells and preferably within range of multiple base stations. A small fraction of cell phones have in-built GPS locators but these are only of use if the phone is both within cellular network service coverage and has an adequate view of the sky. 2 Patents Form No. 5 Characteristics of a Location System for SAR Use To be an effective Search and Rescue (SAR) tool, any device or system needs to meet the following criteria: 1. Must be capable of operating beyond cellular telephone network coverage in order to provide a usable tool in remote and unpopulated areas or in difficult terrain 2. Should be capable of operating independently of any telephone cellular network as even where there is some cellular network coverage, SAR operators themselves may not have access to any networks themselves due geographical, other operational, technical or even legal reasons 3. Must be portable / transportable in order to be operated in remote areas, small vehicles, air or sea vessels (Ideally the device/system can be configured into a single device) 4. Can overcome technical issues of triggering an RF signal from a cellular phone in order to detect then locate that signal, even where there is no cellular telephone network coverage.

Previous Techniques Because of the intermittent transmission patterns exhibited by cell phones, standard radio location techniques are largely ineffective for detecting / locating them, particularly in remote areas where there is little or no cellular network service coverage.

By design, idle cell phones do not transmit continuously. Once a cell phone has been switched on and registered on the network it may only update its presence in short bursts periodically if at all.

Where a Cellular Phone is located outside of a Cellular Network, once it has established a that there is no network coverage it will 'listen' for a valid network signal but not transmit, rendering standard Direction Finding (DF) techniques all but useless.

Technology already available includes small 'cell phone detectors' which give simple audiovisual feedback that a cell phone is operating nearby. In a Search and Rescue (SAR) scenario, these would only function if the cell phone was within network coverage and the searcher was in very close proximity to a cell phone whilst it attempted to connect (attach) to the network or was communicating with the network in some way. These detection devices themselves are very crude with no directional or distance indication and a maximum range of a few metres.

More sophisticated DF equipment has long been available utilising a variety of directional and phase based techniques but is still reliant on receiving transmissions from the target transmitter. The lack of activity by cell phones / devices at idle is a severe limitation here.

Furthermore, analogue based Direction Finding (DF) equipment would be unable to decode the digital signal traffic to positively identify the telephone / device as the search target.

It is possible to temporarily extend cellular network coverage. Cellular 'repeaters' are available and can be utilised by emergency services to improve local network coverage; these simply rebroadcast cellular network signals back over a limited area - typically a large building or small city block. Extending the range of such systems to provide network coverage for Search and Rescue (SAR) is hampered by several factors: Limitations to RF isolation achievable between the high gain, directional antenna connecting to the network and the low gain 'broadcast' antenna used to provide the local coverage. Although suitable 3 Patents Form No. 5 for small search areas, close to existing network coverage, repeaters would not function where the existing network signal was very weak or some distance away. Even with a repeater, for a Global System for Mobile Communications (GSM) system, the total distance between the Target cellular phone or device and the cellular network node could not exceed 22miles (35Km) due to the limitations of packet collision and the Timing Advance (TA) system.

In a large scale natural disaster or conflict, any lack of cellular network coverage due to network or other equipment failure would render repeaters ineffective without a functioning substitute or surrogate network for them to operate with.

Many techniques have been described to specifically locate cellular telephones using a variety of techniques including, but not limited to: locating the phone within a particular network cell, or network cell sector, the measurement of phase differences or triangulation between adjoining network cell transmitter / antenna arrays. Digital techniques such as measurement of Timing Advance data can also be utilised in order to estimate distance from a network cell transmitter. (Accuracy of this technique is limited to approx 550m for GSM systems). Even with line of sight propagation over open ground or coastal waters, technical limitations may prevent a cellular network from establishing a connection with a telephone. These may include transmitter power, receiver sensitivity, cross talk with other channels antenna and cabling losses and a cap on the range available utilising Timing Advance in GSM systems. (22 miles or 35km).

A system has been described in U.S. Patent US 05777580 A (Janky et al, 7 July 1998) in which Location Determination Systems (LDS) equipment can be fitted to a vehicle which can be interrogated remotely to transmit its location as determined from any suitable system such as the Global Positioning System (GPS). Additionally, an event in the vehicle such as an unauthorised entry can cause the vehicle mounted equipment to initiate the location transmission.

In this patent, Janky et al describe several options by which the vehicle equipment can transmit its location in response to a trigger, including via cellular telephone. However, the system they describe does not seek to locate the vehicle directly, but to cause the vehicle to communicate its position as determined by another system, e.g. GPS. Additionally, the system they describe does not actively overcome cellular telephone communications problems. Where cellular telephone equipment is used to communicate with the vehicles on board equipment, this is entirely contingent on there being a cellular telephone network available.

Where there is no cellular telephone network available, the system proposed by Janky et al may use other forms of communication such as packet radio Wide Area Network (WAN), Local Area Network (LAN) or satellite communications. However, this does not address the issue of how an existing, standard cellular telephone could be used to communicate its position where no cellular telephone network was available.

The equipment described in Janky et al is complex, designed to be vehicle mounted and requires a network infrastructure for its operation. It could not be operated with existing cell phones, manufactured without embodying the additional features of the system described by them.

A system has been described in U.S. Patent US 05929777 A (Reynolds, 27 July 1999) in which a suitably manufactured or modified portable device can be caused to generate a coded Infra Red (IR) optical beacon, either at the initiation of the device user or in response to a triggering signal from searchers equipment. However, this system relies on a potential search victim carrying such a device 4 Patents Form No. 5 and would not operate with existing cellular phones. Furthermore, the range of an IR beacon may be extremely limited by rough terrain or bush through which a cellular phone's RF signal could penetrate further.

A system has been described in E.U. Patent DE 10005049108 Al (NEC Europe Ltd, 12 April 2007) in which a cellular phone which connects to either a Global System for Mobile Communications (GSM) network or a Wide Area Network (WAN). In this system, the accessibility of the cellular phone from a further network e.g. the Internet is determined by using the Internet Protocol "Ping" echo request packet process.

This system relies on the cellular phone being registered and in communications with either or both the GSM or WAN network. It uses the specific internet protocol message; Ping, to determine through which of these networks the cellular phone can be reached to interact with the further network [internet].

In no way does this system seek to address the issue of locating the cellular phone's physical location. This system offers no solution to locating or communicating with a cellular phone which is outwith an established communications network.

Further, IP, Internet Control Message Protocol (ICMP) messaging and Ping are not native to much existing cellular phone build and design, so therefore would not function with basic existing phones, manufactured before the system described in DE10005049108 Al is widely implemented by cell phone manufacturers.

This system relies on using an internet protocol event (Ping) which is a network level Internet procedure utilising an ICMP packet which requires the receiving device (the cellular phone) to have a known Internet Protocol (IP) address assigned. Where the cellular phone was enabled to operate on IP enabled networks, this system would require the IP address of the cellular phone to be known in order to communicate with it. This would be a disadvantage in search and rescue applications where details of the cell phone or even its user may be unclear or unknown.

A system has been described in U.S. Patent US 5327144 A (Stilp et al, 5 July 1994) describing a Cellular Telephone Location System.

Briefly, this system is designed to work in concert with a Cellular Network in order to provide location data for cellular phones, for example for billing purposes.

The system described by Stilp et al utilises "existing cellular telephone protocols" and the receivers used in the system are able to detect and receive control channel signals from a phone which is in communication with an existing cellular telephone network. A limitation of this system for use in a Search and Rescue context, however, is that as noted above, Cellular Phones / Devices will normally only transmit when within Cellular Telephone Network coverage but the system designed by Stilp et al does not itself include a transmitter element to replace or supplant cellular network transmissions.

The locator system described by Stilp et al "...comprises three or more cell site systems ... Each cell site system is located at a cell site of a cellular telephone system." The receiver sites are then linked to a "central site". Stilp et al describe in detail their methods of location which "...comprises at least three and preferably more, cell site systems". This is because the methods used within the system to calculate the location are dependent on producing bearing, distance and other data by comparing signals from three sites. In order to calculate the location of the cellular phone / device, the design Patents Form No. 5 described by Stilp et al utilises a "complex correlator" to measure and compare the "time of arrival" of cellular phone / device signals at three or more fixed / cell site receivers which they state "... is critical to calculating the delays between pairs of cell sites, and therefore to calculate position." Their system as described utilises Time Difference of Arrival (TDOA) and also Frequency Difference of Arrival (FDOA) between multiple cell sites. The system described, operates from existing cell sites or other fixed sites, whose locations are known, in order to calculate the location of the Cellular Phone. This design utilises standard cellular telephone network signals which occur within the Cellular Network coverage area and in response to the cellular networks "overhead messages". Their design utilises receivers which "... listen to the mobile control channel commands/responses normally occurring in the cellular system and estimate the physical location of each cellular telephone operating within the system." Thus, the system described by Stilp et al is not a single or portable device/system capable of being operated independently of a Cellular Telephone Network or outwith i.e. outside of Cellular Network coverage and does not itself include a transmitter capability to instigate cellular telephones to transmit.

Stilp et al state in their Patent that "embodiments of the invention may also advantageously include means for transmitting a signal to selected cellular telephone to cause the selected telephone to transmit a signal over a control channel" this "...involves detecting a lack of signal transmissions by a given telephone and in response thereto automatically paging the telephone to cause it to initiate a signal transmission." Their Patent indicates that their system may be "embodied within system that employs much of the existing infrastructure of a cellular system" in order to determine the location of ... cellular telephones. There is no description within their patent; of precisely how this Paging would be undertaken. Certainly there is absolutely no description whatsoever within their patent, text or drawings to indicate that this paging could be carried out by their system independently of existing Cellular Network infrastructure, by what equipment or means and how they could overcome the difficulties of attempting to independently instigate communication with a cellular phone / device which is outside of Cellular Network coverage. As noted above, if a cellular phone / device receives no network coverage it will 'listen' for a valid network signal but not transmit. Further, in order to establish a communications link, any Cellular Network present must recognise and accept the cellular phone / device onto the network, which may not happen for rival networks subscribers.

Paging Channels are found in all cellular network designs from early AMPS through to modern 3G CDMA. However, the Paging events their system is designed to detect are network controlled and must either be accessed through a cellular network or replicated by some other means.

Any system, such as the one described by Stilp et al must overcome these limitations in order to establish communication allowing the location techniques they describe to be utilised. Their patent does not describe any means for independently Paging a Cellular phone / device either within or outwith cellular network coverage nor means by which their system could instigate communication with a cellular phone/device whose identification details e.g. IMSI & IMEI were unknown.

The means to support the statement that their invention may also cause a phone to transmit or automatically page a phone are not demonstrated within the design as published.

In the absence of a cellular network, the system described by Stilp et al, would be unable, of itself, to trigger a cellular phone / device to transmit and therefore unable to detect or locate it. 6 Patents Form No. 5 Finally, a system is described in NZ Patent 306501, (US Patent US 6201803B1) submitted by Munday, Goetz and Gannon, 1996. This system describes location of a cellular phone utilising GPS equipped Base Stations and the use of Timing Advance (TA) network signals.

However, this system is dependent on usage of a "plurality" of 4 or 5 base stations.

In one embodiment, they describe the ability to determine the range of a phone from a base station and to locate this within a 60° or 120° azimuth sector of a network cell. However, this is not sufficient to provide a precise location, particularly in a large cell (for example a 120° sector of a rural Base Station with an operating Cell radius of 35Km would cover over 1200 square Km. In this scenario, using GSM TA with an accuracy of 550m could give an arc shaped search area of up to 107 sq Km. For a similarly sized cell node serviced by a unipolar antenna array, the search area could be over 300 sq km.

The system designed by Munday, Goetz and Gannon is entirely a network based system, entirely contingent on a satisfactory connection between the cellular network and the mobile telephone / device. The system described will only be capable of determining location data for a telephone which is operating within the network coverage area and subscribed to the cellular network in question.

Thus, in terms of search and rescue utility, the system they describe could not be utilised outside of cellular telephone network coverage and would have limited utility where coverage was limited to fewer than four base stations. They do not describe a portable system utilising a single locator device. Further, the system described would only work with telephones subscribed to the network on which the system was implemented. 7 Patents Form No. 5 Summary of Previous Techniques Although many techniques are useful in a commercial or Location Based Service (LBS) setting, they have two major drawbacks for Search and Rescue use. Firstly, they are all Network techniques, reliant on the target telephone or other cellular device, being within cellular or other network coverage e.g. WAN. Secondly, they will only assist searchers where the subscriber's phone details are known.

The development of sophisticated techniques such as the application of Kalman filtering may also require a network structure in their implementation.

It could also be noted that the current techniques may also be hampered operationally, by delayed communication between searchers and the cellular network operators in order to get location data back to search teams. 8 Patents Form No. 5 Objective of this System The purpose of this system is to produce a locator system which, operating independently of cellular telephone network(s), can cause a cellular phone / device to transmit and then detect that transmission in order to positively identify and locate the cellular phone / device and then to communicate with it.

The primary objective is therefore to produce a system which operates independently of a cellular telephone network but triggers a cellular phone / device to transmit a standard cellular telephone radio frequency (RF) signal, without first needing to know the phone / device identity, e.g. IMSI & IMEI and to then detect that transmission in order to locate the cellular phone / device by a number of means.

The secondary objective is that the design allows the system operator to then decode the phone / device identity, e.g. IMSI & IMEI, thus positively identifying that it is a possible target or known target and to eliminate other signal returns e.g. from searchers own equipment.

A third objective is to establish a communications link directly with the cell phone / device, independent of a cellular telephone network by acting as a self contained surrogate cellular network node, replicating or emulating network functions required to support establishment of such a communications link. In addition to communicating with the user of the cell phone / device, such a link may also enable the operator to remotely listen to sounds around the target cell phone / device, remotely visualise images from an in-built or attached camera and cause the target cell phone / device to emit visual and audible signals i.e. to Ring. These actions may be possible even if the user of the cell phone / device is incapacitated. Furthermore, the design may allow the operator to interrogate the cell phone / device for on board data such as a GPS location fix if the has an in-built or attached GPS device.

The main feature of the locator system is that it can function beyond and independently of cellular network(s). However, it can also be employed within an area that has cellular network coverage.

The locator's receiver can be extremely sensitive and will not be subject to the same design limitations as cellular network base stations which have multiple transmitters and losses associated with crosstalk and losses from antenna combiners etc.

This could be particularly relevant in areas of fringe or patchy coverage or where cell sizes are too large or the terrain too rugged for network based location methods to be useful.

This locator design also places a single, portable search and location tool directly in the hands of searchers who may be working in remote or inhospitable circumstances and may themselves have communications difficulties with their own control centres and with the staff of the cellular networks.

Variations of the design utilise Repeaters, 'Leaky Feeder' cables and small 'cell phone detectors' are described below. 9 Patents Form No. 5 Variation 1: Combined Active Base Transceiver Station (BTS) Emulator with Repeaters All cellular phones and cellular telephony based devices are Radio Frequency (RF) Transceivers and therefore are capable of producing an RF signal which can be detected and triangulated using standard radiolocation techniques independent of a cellular network service.

Utilising this locator system, two additional measures can be utilised to improve detection and location within a search area - for example a large building or city block damaged by earthquake or other natural disaster or conflict.

Firstly, a cellular repeater linked to the Locator can now be deployed with a directional antenna and signal strength indicator. This repeater/detector/locator can be compact as it does not need to include any surrogate network functions - these being handled by the core locator design.

Secondly, small 'cell phone detectors' which give simple audiovisual feedback that a cell phone is operating nearby can now be used to detect cellular phone signal responses to the locator or locator / repeater combination (or to any cellular network signal that may be present).

For small area search scenarios, the short detection range of these simple 'cell phone detectors' may be useful, to localise a more precise location, for example under a collapsed building.

Variation 2: Active Base Transceiver Station (BTS) Emulator with 'Leaky Feeder' Utilising the core locator design, it may be possible to substitute directional and non directional antennas within that design with a run of high loss coaxial or other cable - 'leaky feeder' which has been designed to allow a fraction of the signal transmitted along the cable to 'leak' therefore broadcasting along the entire cable run.

This variation would allow searchers to feed the leaky feeder cable into restricted spaces e.g. pipes or conduits or possibly to have the cable fed into rubble or dragged by rescuers, robotic, canine or other assistants.

In addition to localising a detected signal to the cables position itself, the small 'cell phone detectors' which give simple audiovisual feedback that a is operating nearby as described for Variation 1 above, can be utilised to localise a more precise location for a cellular phone which is transmitting a 'responding' signal to that produced by the locator (or to any cellular network signal that may be present).

Patents Form No. 5 Brief Description of Drawings & Tables The first drawing provides an overview of the basic system as used to detect, triangulate and locate a cellular telephone operating beyond cellular network coverage.

The second drawing shows in basic unit form the components of a basic system meeting the primary, secondary and third objective sets. The second drawing also shows the basic system required to trigger, detect and locate a Cellular Phone or Device (the Target Terminal).

The third drawing shows how this could be expanded to include a digital receiver / decoder which could extract identifying data from the signal transmitted by the Cellular Phone or Device in response to a triggering signal.

The fourth drawing shows how this could be developed into an integrated portable communications device for detecting, locating and communicating with the Target Cellular Phone or Device in isolation from a Cellular Telephone Network.

The fifth drawing shows an optional unit which could be utilised with all of the designs to detect the presence of any Cellular Networks in the area and adjust the output of the Locators transmitter to avoid or reduce the possibility of interference to the operation of either.

The sixth drawing illustrates the use of a repeater with the Locator. Also illustrated is the use of a short range 'proximity' detector with this configuration.

The seventh drawing illustrates the use of a 'Leaky Feeder' 'Antenna' with the Locator. Also illustrated is the use of a short range 'proximity' detector with this configuration. 11 Patents Form No. 5 Drawing 1. System Overview The Locator System hardware, including both omni directional and directional antennae is shown (1) at two locations.

The Target Terminal (cellular telephone) being sought in a search is shown (2). The system produces a digital signal which emulates the transmission at idle of a cellular telephone network or networks (3) configured so as to replicate those signals which will cause the cellular phone (2) to attempt a connection, irrespective of whether its identity (e.g. IMSI & IMEI) is known, i.e. this network carrier transmission will alert the Target Terminal to the presence of a 'Network' with which it will attempt to register, thus transmitting a responding signal (4).

The system is used to obtain a bearing (and where possible) range to the cellular phone. Once the signal has been detected, a series of bearings can be taken to improve the accuracy of the location data by allowing triangulation from different locations of the Target Terminals position by the operator. (5).

Drawing 2. The Basic Locator.

The Target Terminal is a cellular telephone or device equipped with a cellular radio device designed to connect to a cellular telephone network carried by the person being searched for (A Combination of Mobile Station (MS) (1) / Mobile Equipment (ME) (2) uniquely identified through a Subscriber Identity Module (SIM) (3) or similar). This can be any generation of device, the locator being configured so as to operate with the type(s) of device utilised locally.

The Target Terminal will have identifying data stored within it which it would normally share with an available cellular telephone network on attempting to register with the network. This data is held on both the Terminal itself-the Mobile Equipment (ME) and may also be held on any interchangeable subscriber module, e.g. the Subscriber Identity Module (SIM) or the similar CDMA or 3G modules etc.

The core of the Locator is the Base Transceiver Station (BTS) Transmission Emulator (8). This transmitter unit produces a digital signal which emulates the transmission at idle of a cellular telephone network or networks and normally transmits these via an omni-directional antenna (5). The transmitter may simultaneously produce signals at different frequencies and utilising different modalities to match those produced by the cellular telephone network or networks which operate locally. This may be achieved by using a modular design with several programmable modules (9) being interfaced to the BTS Transmitter Emulator core. In a GSM network, for example, this unit will produce a surrogate signal with dummy data but which will include a valid 51 frame Control Channel with Broadcast Control Channel (BCCH) and Frequency Correction Channel (FCCH) data etc. Where the Target Terminals identity data is known, the locator could be programmed to transmit valid Paging Requests on the Paging Channel (PCH).

This network carrier transmission will thus alert the Target Terminal to the presence of a 'Network' with which it will attempt to register.

Note: as there is no actual interaction between the Target Terminal and the locator in the basic design, it is anticipated that the locator transmission will require to be pulsed on and off to force the Target Terminal to attempt to register each time it is presented with a 'new' network carrier.

Once the Target Terminal is transmitting, the locator's operator can utilise the directional antenna, loop antenna or phased array or other arrangement (4) with a receiver unit within the Signal 12 Patents Form No. 5 Detector and Direction Indicator equipment (6) to attempt to ascertain a heading for the incoming signal. The receiver can be extremely sensitive and will not be subject to the same design limitations as cellular network base stations which have multiple transmitters and losses associated with crosstalk and losses from antenna combiners. An optional Antenna Switch / Splitter (7) allows the operator to both transmit and receive via the omni-directional antenna (5) or directional antenna (4) if necessary to overcome signal / interference conditions. Once the signal has been detected, a series of bearings can be taken to allow triangulation from different locations of the Target Terminals position by the operator.

All functions can be overseen by the operator via a User Control Interface (10) which may ultimately be operated through a user interface such as a lap top computer (11).

Drawing 3. The Intermediate Locator.

As for the Basic Locator in drawing 22., the Target Terminal is a cellular telephone or device equipped with a cellular radio device designed to connect to a cellular telephone network carried by the person being searched for (A Combination of Mobile Station (MS) (1) / Mobile Equipment (ME) (2) uniquely identified through a Subscriber Identity Module (SIM) (3) or similar). This can be any generation of device, the locator being configured so as to operate with the type(s) of device utilised locally.

The Target Terminal will have identifying data stored within it which it would normally share with the cellular telephone network on attempting to register with the network. This data is held on both the Terminal itself - the Mobile Equipment (ME) and may also be held on any interchangeable subscriber module - e.g. the Subscriber Identity Module (SIM) or the similar CDMA or 3G modules etc.

The core of the Locator is the Base Transceiver Station (BTS) Transmission Emulator (8). As with the Basic Locator design, this transmitter unit produces a digital signal which emulates the transmission at idle of a cellular telephone network or networks and normally transmits these via an omnidirectional antenna (5). The transmitter may simultaneously produce signals at different frequencies and utilising different modalities to match those produced by the cellular telephone network or networks which operate locally. This may be achieved by using a modular design with several programmable modules (9) being interfaced to the BTS Transmitter Emulator core. In a GSM network, for example, this unit will produce a surrogate signal with dummy data but which will include a valid 51 frame Control Channel with Broadcast Control Channel (BCCH) and Frequency Correction Channel (FCCH) data etc. Where the Target Terminals identity data is known, the locator could be programmed to transmit valid Paging Requests on the Paging Channel (PCH).

This network carrier transmission will thus alert the Target Terminal to the presence of a 'Network' with which it will attempt to register.

An optional Antenna Switch / Splitter (7) allows the operator to both transmit and receive via the omni-directional antenna (5) or directional antenna (4) if necessary to overcome signal / interference conditions. Once the signal has been detected, a series of bearings can be taken to allow triangulation from different locations, of the Target Terminals position by the operator.

Once the Target Terminal is transmitting, the locator's operator can utilise the directional antenna, loop antenna or phased array or other arrangement (4) with a receiver unit within the Signal Detector and Direction Indicator equipment (6) to attempt to ascertain a heading for the incoming signal. The receiver can be extremely sensitive and will not be subject to the same design limitations 13 Patents Form No. 5 as cellular network base stations which have multiple transmitters and losses associated with crosstalk and losses from antenna combiners.

Additionally, the signal received from the Target Terminal is fed through to the Receiver / Decoder unit (10) which is configured to operate with the appropriate frequencies and modes of local cellular telephone networks. This may be achieved by using a modular design with several programmable modules (11) being interfaced to the Receiver / Decoder. For example, a GSM module would be designed to extract the Network Attach signal, the Access Burst or Access Control Burst (AB) transmitted on the Random Access Channel (RACH) by the Target Terminal.

The Receiver / Decoder extracts identifying data such as the IMSI & IMEI, from the received signal and feeds this through to the operator via the User Control Interface.

Here the data will be available to be matched with known information (if any) about the Target Terminal or against other data such as the identities of other known equipment e.g. cell phones belonging to searchers to eliminate these.

Note: as there is no two way communication between the Target Terminal and the locator in the basic or intermediate designs, it is anticipated that the locator transmission will require to be pulsed on and off to force the Target Terminal to attempt to register each time it is presented with a 'new' network carrier.

All functions can be overseen by the operator via a User Control Interface (12) which may ultimately be operated through a user interface such as a lap top computer (13).

Drawing 4. The Advanced Locator / Communicator.

As for the Basic and Intermediate Locator designs in drawing 2 & 3., the Target Terminal is a cellular telephone or device equipped with a cellular radio device designed to connect to a cellular telephone network carried by the person being searched for (A Combination of Mobile Station (MS) (1) / Mobile Equipment (ME) (2) uniquely identified through a Subscriber Identity Module (SIM) (3) or the similar CDMA or 3G modules etc.).. This can be any generation of device, the Locator being configured so as to operate with the type(s) of device utilised locally.

In addition to the signal detection and location capabilities described in the Basic and Intermediate locator designs, comprising a directional antenna(4), an omni-directional antenna (5) and optional Antenna Switch / Splitter (7) the locator design shown in Drawing 4 encompasses a fully functioning Base Transceiver Station (BTS) (8) (which may simultaneously produce signals at different frequencies and utilising different modalities to match those produced by the cellular telephone network or networks which operate locally using a modular design with several programmable modules (9) being interfaced to the BTS Transmitter Emulator core). The BTS unit is controlled by surrogate Base Station Control (BSC) (10) and surrogate Mobile Switching Centre (MSC) (11) components designed to provide all the control functions required to set up a valid two way link with the Target Terminal. Connected to the MSC unit will be a programmable unit (13) providing surrogate database functions i.e. Home Location Register (HLR), Visitor Location Register (VLR) and Authentication function (AuC).

In this design, the locator is in effect a 'Network in a Box'. It will be programmed to present the Target Terminal with a valid physical cellular network signal (Layer 1). It is also able to locate, page and register a phone onto a dedicated 'network' implementing, for example in GSM mode by 14 Patents Form No. 5 providing valid Layers 2 and 3 - the data and GSM Layers concerned with identifying and authenticating a phone onto the network and connecting a call. This will exploit the design feature of cellular phone network standards which allow cell phones to 'roam' to any network ready to place emergency calls.

The unit will have programmable on board database functions through which the Mobile Switching Centre (MSC) and database functions will be enabled to accept the Target Terminal onto the 'network'. However, this database will also allow the operator to positively identify the target Terminal while screening out other signals utilising identifying data such as the IMSI &IMEI.

The unit will be constructed and programmed to enable the operator to carry out all of the location functions embodied in the Basic and Intermediate designs but will also have a communicator module (12) and interface (16) through which the operator can open a voice link to the user of the Target Terminal.

In addition to communicating with the user of the cell phone / device, such a link may also enable the operator to remotely listen to sounds around the target cell phone / device which could further localise the location - e.g. the sound of running water from a nearby river or the sound of searchers whistles may be overheard. If the Target Device has an in-built or attached camera, it may be possible to remotely visualise images from this which might assist searchers. Simply ringing the phone may alert nearby searchers to its precise location. The useful factor here is that no input is needed from the phone user and so the system can be utilised even if the phone user being searched for is incapacitated.

Received data, e.g. IMSI & IMEI, will be available to be matched with known information (if any) about the Target Terminal or against other data such as the identities of known equipment. Such as cell phone belonging to searchers for example to eliminate these.

As with the Basic and Intermediate Locator designs, once the Target Terminal is transmitting, the operator of the Locator can utilise the directional antenna, loop antenna, phased array or other arrangement with a receiver unit within the Signal Detector and Direction Indicator equipment (6) to attempt to ascertain a heading for the incoming signal. The Signal Detector and Direction Indicator equipment can be programmed and controlled from the User Control Interface.

Once the signal has been detected, a series of bearings can be taken to allow triangulation from different locations, of the Target Terminals position by the operator.

In addition to a bearing, the Advanced Locator will be able to analyse the Timing Advance (TA) signal data from any GSM links to give an approximate estimate of the distance between the Target Terminal and the locator. This will be limited to an initial accuracy of @ 550m along each bearing line and an absolute range of approximately 35km.

The design may allow the operator to interrogate the cell phone / device for on board data such as a GPS location fix if the has an in-built or attached GPS device. This feature alone could save hours of searching.

All functions can be overseen by the operator via a User Control Interface (14) which may ultimately be operated through a user interface such as a lap top computer (15).

Patents Form No. 5 Drawing 5. The Optional Cellular Network Awareness Module As described above (p8) the main strength of the locator is that it can function beyond and independently a cellular network. However, it may also be desirable that the locator is employed within an area that has cellular network coverage, particularly where coverage is poor, cell sizes are large and the terrain is poor, in order to speed or augment search capability.

The fifth drawing shows an optional unit which could be utilised with all of the designs to detect the presence of any cellular networks in the area and adjust the output of the locator's (1) transmitter to avoid or reduce the possibility of interference to the operation of either.

This unit would have a receiver capable of establishing the transmission frequency(ies), coding and relative signal strengths of any cellular network(s) in the area (3). It could have its own omnidirectional input antenna (4).

This data would then be fed into the User Control interface (2) (combined with a user interface such as a lap top computer (5), which would then control the locator transmitter to ensure the transmitter was broadcasting on the optimum frequency or code for the bands/modes it was operating, in order to maximise the search capability and minimise interference to the Cellular Networks themselves.

Drawing 6. Variation 1: Combined Active Base Transceiver Station (BTS) Emulator with Repeaters The Target Terminal is a cellular telephone or device equipped with a cellular radio device designed to connect to a cellular telephone network carried by the person being searched for (A Combination of Mobile Station (MS) (1) / Mobile Equipment (ME) (2) uniquely identified through a Subscriber Identity Module (SIM) (3) or similar). This can be any generation of device, the locator being configured so as to operate with the type(s) of device utilised locally.

The core of the system is the locator described in drawings 2-5 above - shown as (9) and control system e.g. laptop computer (10). The locator broadcasts and receives via an antenna (8) which need not be directional. This application combines the locator with repeater equipment (5) which is comprised of an RF repeater linked to the Locator via an antenna (7) and which is coupled to a search antenna (4) which may be directional. The repeater equipment (5) includes a signal strength and bearing indicator (6).

The repeater retransmits any signal received from the Target Terminal via an antenna (7). This antenna also receives the Locator signal from the locator.

The locator itself (9) transmits and receives via its own antenna (9) and is controlled via a user interface e.g. laptop computer (10).

Detection and localisation of the Target Terminal may also be assisted through small hand held, short range 'proximity' detectors (11) which will provide an alerting audio, visual or other indication when receiving the transmission stimulated by the locator and or repeater or any other cellular network signal which may be present.

This configuration, utilising repeater technology enables searchers to minimise the amount of equipment to be carried, for example, in difficult terrain as the repeater unit will be lighter, less complex and probably more robust than the main locator system. 16 Patents Form No. 5 Drawing 7. Variation 2: Active Base Transceiver Station (BTS) Emulator with 'Leaky Feeder' The Target Terminal is a cellular telephone or device equipped with a cellular radio device designed to connect to a cellular telephone network carried by the person being searched for (A Combination of Mobile Station (MS) (1) / Mobile Equipment (ME) (2) uniquely identified through a Subscriber Identity Module (SIM) (3) or similar). This can be any generation of device, the Locator being configured so as to operate with the type(s) of device utilised locally.

The core of the system is the locator described in drawings 1-4 above - shown as (5) and control system e.g. Laptop Computer (6). The locator broadcasts and receives via a run of high loss coaxial or other cable - 'leaky feeder' (4) which has been designed to allow a fraction of the signal transmitted along the cable to 'leak' therefore broadcasting along the entire cable run. This also allows signals from devices situated near the cable to be received by the locator through the cable.

Detection will be limited to a specific area close to the 'leaky feeder' cable run. Detection and localisation of the Target Terminal may also be assisted through small hand held, short range 'proximity' detectors (7) which will provide an alerting audio, visual or other indication when receiving the transmission stimulated by the locator and or repeater or any other cellular network 17 Patents Form No. 5 Summary The Locator design options described above all have the ability to provide additional tools to Search and Rescue (SAR) operations when searching for those who have become lost in circumstances where they have not been equipped with dedicated communications or Personal Beacon equipment.

The social engineering required to persuade people to carry radios and beacons whenever they go beyond cell phone coverage would be an enormous challenge and possibly inappropriate. With Cell Phones, the social engineering is already achieved. Tourists can be found today on any of the tracks of New Zealand, well beyond the net, happily snapping away taking photos with their phones.

Searches take time, cost money and can endanger those who undertake them. These designs will help reduce these costs and dangers as well as helping to save lives. 18 Patents Form No. 5

Claims (10)

Claims What I claim is

1. A system, comprising a single portable device, operating from a single location which, operating independently of and without utilising a Cellular Telephone Network, can trigger a Cellular Phone / Device to transmit, irrespective of whether the identity of the Cellular Phone / Device is known and then detect a standard cellular telephone radio frequency (RF) transmission from that Cellular Phone / Device in order to positively identify and locate that Cellular Phone / Device by providing range and bearing data.

2. A system as claimed in claim 1 which can be relocated in order to obtain multiple location data for the Cellular Phone / Device over a period of time, facilitating triangulation or tracking of the Cellular Phone / Device.

3. A system as claimed in any one of the claims 1 to 2 which having established a communications link with the Cellular Phone / Device, can activate any audio-visual or vibrating alert on that Cellular Phone / Device.

4. A system as claimed in any one of the claims 1 to 3 which having established a communications link with the Cellular Phone / Device, can enable voice communication with that Cellular Phone / Device contacted.

5. A system as claimed in any one of the claims 1 to 4 which having established a communications link with the Cellular Phone / Device, can activate and access images from any camera on that Cellular Phone / Device.

6. A system as claimed in any one of the claims 1 to 5 which having established a communications link with a Cellular Phone / Device, can access any Global Positioning System (GPS) data stored or produced on that Cellular Phone / Device.

7. A system as claimed in any preceding claim, in which the range of the system can be extended through integration of cellular repeater(s) into the system, operating independently of and without utilising a Cellular Telephone Network.

8. A system as claimed in any preceding claim, in which the reach of the system can be extended underground or through rubble by utilisation of a leaky feeder antenna with the system, operating independently of and without utilising a Cellular Telephone Network.

9. A system as claimed in any preceding claim which can receive, decode and display any Short Message Service (SMS) message transmitted by the Cellular Phone / Device.

10. A system substantially as described and illustrated on the accompanying drawings. 19