EP4684592A1

EP4684592A1 - Method and system for detecting a user equipment

Info

Publication number: EP4684592A1
Application number: EP24712472.0A
Authority: EP
Inventors: Igor COMPASSI
Original assignee: Telecom Italia SpA
Current assignee: TIM SpA
Priority date: 2023-03-20
Filing date: 2024-03-18
Publication date: 2026-01-28
Also published as: WO2024194242A1; IT202300005199A1

Abstract

It is disclosed a method for detecting a user equipment enabled to access a mobile network and located in a geographical area where the network has substantially no coverage. The method comprises establishing an emergency communication link between a base station of the network and the user equipment by: providing a system comprising a first antenna, a repeater unit and a second antenna; aligning the first antenna towards the base station to receive a downlink RF signal therefrom; amplifying the received signal by the repeater unit connected to the first antenna; and transmitting the amplified signal by the second antenna connected to the repeater unit towards the geographical area. The method further comprises, in case the second antenna is receiving an uplink RF signal, setting up a call to the user equipment through the network and determining that the uplink RF signal is coming from the user equipment.

Description

METHOD AND SYSTEM FOR DETECTING A USER EQUIPMENT

Technical field

The present invention relates to the field of telecommunications networks. In particular, the present invention relates to a method for detecting a user equipment enabled to access a mobile telecommunications network, the user equipment being located in a geographical area where the mobile telecommunications network has substantially no coverage. The present invention also relates to a system configured to detect said user equipment.

Background art

As known, in a mobile telecommunications network (simply, mobile network) the radio coverage is provided by deployment of a number of base transceiver stations or, simply, base stations (BTS) transmitting radio signals in respective cells. BTSs usually cover large geographic areas reaching distances of, for instance, tens of kilometres. A “user equipment” or UE is any device that may be directly used by an end user to communicate, the user equipment being a device enabled to access the mobile telecommunications network.

In geographical areas where the radio coverage is substantially absent, due to, for example, a natural disaster that interrupts the communication links of the mobile network, it is known to provide the radio coverage by transporting in the area, usually by means of appropriate vehicles, the apparatuses needed to create a new cell of radio coverage that may establish new communication links within the disaster area. Indeed, these communication links are essential to set up rescue operations for the victims of the natural disaster.

EP2661142 A1 discloses a method of detection of a user terminal for cellular wireless telecommunications as being in a femtocell, the method comprising: sending a paging message from a portable femtocell base station, the paging message including an indicator that any user terminal receiving the paging message is to respond; the user terminal responding by sending a response message including an identifier of the user terminal; and the response message being detected by the portable femtocell base station.

Summary of the invention

The inventor noticed that in certain situations, it may happen that a rescue operation is to be set up for locating and assisting a single person who accidentally finds herself/himself in a geographical area where substantially no radio coverage is provided. In this case, indeed, this person, although provided with a user equipment, is typically unable to make even an emergency call. In particular, a person may be lost in a valley, a canyon, a cave, a ravine, a sinkhole, etc., where the radio coverage is substantially absent.

In this case, setting up a new cell of radio coverage to search for a single person would not provide an effective and timely intervention. As a matter of fact, it is required that an apparatus such as the femtocell base station of EP2661142 A1 is provided with, e.g., a microwave or satellite connection to a core network and with suitable modules to implement dedicated procedures to reach the user equipment of a disaster’s victim. It is hence a complex and expensive apparatus, whose setting up requires the intervention of specialized technicians to assemble the hardware and software modules, switch on the apparatus and make it work properly. The apparatus, once set up, cannot be switched off and moved away quickly to cover another disaster area, as it usually requires e.g., one or two days to be disassembled. Moreover, such an apparatus may be transported only where a wheeled vehicle is able to arrive.

In view of the above, the Applicant has tackled the problem of providing a method for detecting a user equipment and a system for detecting said user equipment which allow providing a more effective and timely intervention than a vehicle-transportable base station. In particular, the Applicant has tackled the problem of providing a method for detecting a user equipment which does not require neither the intervention of specialized technicians nor long times for its setting up. Moreover, the Applicant has tackled the problem of providing a system for detecting said user equipment, which is less complex and expensive than a vehicle-transportable base station and which is adapted to be portable even by a single person in order to reach areas that are inaccessible by a wheeled vehicle.

According to a first aspect, the present invention provides a method for detecting a user equipment enabled to access a mobile network, the user equipment being located in a geographical area where the mobile network has substantially no coverage, the method comprising establishing an emergency communication link between a base station of the mobile network and the user equipment by: a) providing a system comprising a first antenna, a repeater unit and a second antenna; b) aligning the first antenna towards the base station to receive a downlink RF signal from the base station; c) amplifying the received downlink RF signal by the repeater unit connected to the first antenna; and d) transmitting the amplified downlink RF signal by the second antenna connected to the repeater unit towards the geographical area, wherein the method further comprises, in case the second antenna is receiving an uplink RF signal, setting up a call to the user equipment through the mobile network and determining that the uplink RF signal is coming from the user equipment.

Preferably, the call is set up according to the GSM communications standard.

According to a second aspect, the present invention provides a system for detecting a user equipment enabled to access a mobile network, the user equipment being located in a geographical area where the mobile network has substantially no coverage, the system being configured to establish an emergency communication link between a base station of the mobile network and the user equipment, the system comprising: a first antenna configured to receive a downlink RF signal from the base station of the mobile network; a repeater unit connected to the first antenna, the repeater unit being configured to amplify the received downlink RF signal; and a second antenna configured to transmit the amplified downlink RF signal towards the geographical area and to receive an uplink RF signal from the user equipment, wherein the system further comprises a further user equipment to set up a call to the user equipment through the mobile network and wherein the repeater unit comprises a signal analyzing unit to determine that the uplink RF signal is coming from the user equipment.

Preferably, the system is configured to be housed in a human- bearable container, i.e. in a container that a single person is capable to bear.

Preferably, the system is configured to operate in a frequency range comprised between 824 MHz and 960 MHz

According to an embodiment, the second antenna is a sector antenna. Preferably, the second antenna is a cross-polarized panel antenna.

According to an embodiment, the first antenna is a Yagi antenna.

According to another embodiment, the first antenna is a sector antenna.

Preferably, the signal analyzing unit comprises a spectrum analyzer. Preferably, the repeater unit comprises a RF repeater with adjustable gain.

Preferably, the system further comprises a battery.

Brief description of the drawings

The present invention will become clearer from the following detailed description, given by way of example and not of limitation, to be read with reference to the accompanying drawings, wherein:

- Figure 1 schematically shows a system for detecting a user equipment according to embodiments of the present invention;

- Figure 2 is a block scheme of a repeater unit of the system of Figure 1 ; and

- Figure 3 is a flowchart illustrating steps of a method for detecting a user equipment according to embodiments the present invention.

Detailed description of preferred embodiments of the invention

Figure 1 schematically shows a scenario of application of the method for detecting a user equipment according to the present invention and a block scheme of a system 1 for detecting said user equipment according to embodiments of the present invention. The system for detecting the user equipment according to the present invention will be indicated as, for simplicity, “detection system”.

In the considered scenario, a base station (or, simply, BTS) 2 of a mobile network managed by a mobile network operator is connecting a number of user equipment (UEs) located under its radio coverage to the mobile network. In the same scenario, the site of the considered BTS 2 may comprise multiple apparatuses providing access to mobile networks managed by different mobile network operators. Each of these mobile networks may be a 2G/3G/4G/4.5G/5G network and any combination or evolution thereof. Typically, a mobile network supports different mobile communications standards, such as 2G (namely, GSM) and 3G (namely, UMTS), 2G and 4G (namely, LTE) and son on.

A user equipment according to the present invention may be a mobile phone, a smartphone, a tablet, a notebook or any similar equipment provided with one or more subscriber identity modules such as a SIM card or an eSIM (embedded SIM) provisioned to the user by one or more respective mobile network operators, wherein each subscriber identity module is configured to enable the user equipment to connect to a respective mobile network, namely to identify and authenticate the UE within the respective mobile network.

In the following description, it will be disclosed a method for detecting a user equipment which is provisioned with at least one subscriber identity module configured to enable the user equipment to connect to one of the mobile networks provisioned at base station 2. It will be assumed that the base station 2 is transmitting a radio (RF) signal of the mobile network of a given mobile network operator and the user equipment is provisioned with the subscriber identity module configured to enable the user equipment to connect to said mobile network of a given mobile network operator. The expression “RF signal” used herein after will hence refer to an RF signal of said mobile network. As known, if the considered mobile network is a GSM network, the base station is assigned given carrier frequencies for the uplink (UL) and downlink (DL) communication channels with the user equipment.

It is assumed that a person (or animal, vehicle or other object or item) equipped with a user equipment 3 is lost in a geographic area at a certain distance from the base station 2, the area having substantially no radio coverage. This area will be indicated as “search area”. The search area may comprise a valley, a canyon, a cave, a ravine, a sinkhole, etc. Moreover, it is assumed that an alarm is raised to trigger a rescue operation and that a rescuer in charge of going in search of the missing person or item is provided with data identifying the missing person or item, these data comprising a telephone number associated with the subscriber identity module of the user equipment of the missing person or item. Reference to “person” in the present description and claims is to be intended as extended to a possible animal, vehicle or other object or item that is to be searched.

In this situation, the rescuer may be equipped with a detection system according to the present invention and approach the considered area where the lost person is presumed to be.

According to advantageous embodiments of the present invention, the detection system is configured to be portable by a single rescuer. According to these embodiments, the detection system is preferably configured to be housed in a human-bearable container, namely a container that a single person is capable to bear, such as a backpack or similar equipment. In this way, the detection system of the present invention may be advantageously carried by one person and reach areas that are inaccessible by a wheeled vehicle.

According to embodiments of the present invention, the detection system 1 comprises:

- a first antenna 11 ;

- a second antenna 12;

- a repeater unit 13; and

- a battery 14.

The repeater unit 13 is preferably connected to the first antenna 11 and to the second antenna 12. The battery 14 is connected to the repeater unit 13 and provides electrical power to it.

In the downlink direction, the first antenna 11 is configured to receive the radio (RF) signal coming from the base station 2, while the second antenna 12 is configured to transmit the RF signal (possibly, after the signal is being processed at the repeater unit 13) into the search area. In an uplink direction, the second antenna 12 is configured to receive a RF signal coming from the UE 3 located within the search area and the first antenna 11 is configured to transmit the RF signal to the base station 2. The repeater unit 13 is preferably configured to receive from the first antenna 11 the RF signal coming from the base station 2, amplify it and provide it to the second antenna 12 to transmit it, as it will be described in greater detail herein after.

The first antenna 11 is preferably a directional antenna with high gain. The first antenna 11 may have a beam width, in the horizontal plane, comprised between 10° and 50° and a gain comprised between 12 dBi and 15 dBi. For instance, the first antenna 11 may be a Yagi antenna. According to a preferred embodiment, the first antenna 11 is configured to operate within the GSM 850 and/or GSM 900 frequency bands, namely within the frequency band 824 MHz - 960 MHz. For sake of example, a Yagi antenna configured to operate in the considered frequency band may be the TY-900 Yagi antenna manufactured by Kathrein Broadcast USA, USA, having dimensions equal to about 584 x 173 mm and weight equal to about 1 .4 kg.

The second antenna 12 is also preferably a directional antenna with high gain. According to some embodiments of the present invention, the second antenna 12 has a larger beam width, in the horizontal plane, than the first antenna 11. The second antenna 12 may have a beam width comprised between 40° and 70° in the horizontal plane and a gain comprised between 12 dBi and 15 dBi. According to preferred embodiments, also the second antenna 12 is configured to operate within the GSM 850 and/or GSM 900 frequency bands.

The second antenna 12 is preferably a sector antenna, for instance a panel antenna. An example of an antenna that may be used is the cross-polarized panel antenna XPol Panel 806-960 65° 15.5dBi, type number 739 622 manufactured by Kathrein-Werke KG, Germany. This panel antenna is dual polarized (+45°/-45°) and has a half power beam width of about 65° in the horizontal plane and about 15° in the vertical plane. Moreover, this panel antenna operates within the frequency range 806 MHz - 960 MHz. This exemplary antenna has dimensions equal to about 1296 mm x 262 mm x 116 mm and weight equal to about 11 kg. Another example of an antenna that may be used is the Scala HP9-915 panel antenna manufactured by Kathrein Broadcast USA, USA, dimensions equal to about 737 mm x 267 mm x 178 mm and weight equal to about 5.2 kg.

Figure 2 is a block scheme of a repeater unit 13 according to embodiments of the present invention.

The repeater unit 13 preferably comprises a RF repeater 21. As already anticipated above, preferably, the RF repeater 21 is configured to, in the downlink direction, pick up the RF signal received by the first antenna 11 from the base station 2, amplify it and make it available at the second antenna 12 for transmission towards the search area. In the uplink direction, the RF repeater 21 is configured to pick up the RF signal received by the second antenna 12 from the UE 3 and make it available at the first antenna 11 for transmission to the base station 2. Preferably, the RF repeater is configured to operate within the GSM 850 and/or GSM 900 frequency bands. Moreover, according to advantageous embodiments, the RF repeater is a programmable repeater having an adjustable gain. The gain of the RF repeater may be comprised between 40 dB and 70 dB.

In particular, the RF repeater 21 comprises a first antenna connector for connecting the first antenna 11 and a second antenna connector for connecting the second antenna 12. Moreover, the RF repeater 21 comprises a modem, comprising a port to which the first antenna 11 is connected via the first antenna connector, and at least one amplifier to amplify the RF signal before transmission by the second antenna 12. Moreover, the RF repeater 21 comprises a display. Further, the RF repeater 21 may be connected to a PC or laptop, via, e.g., an Ethernet connector, through which a user may configure and possibly modify the RF repeater settings (frequency band, gain in the uplink and downlink directions, output power in the uplink and downlink directions, alarms, modem control, LAN connectivity, and so on) by using a dedicated software. The user may also acquire information such as the identifier of the cell to which the RF repeater 21 is connected and the RSSI (Received Signal Strength Indicator) of the received RF signal at the antenna port of the modem. The display of the RF repeater 21 may provide the user with information on, for instance, the RSSI, the gain in the uplink and downlink directions and the output power in the uplink and downlink directions. The components of a RF repeater are known and will not be detailed further in the present description.

The RF repeater 21 may be a single band repeater (e.g., a GSM repeater), a dual band repeater (e.g., a GSM/UMTS repeater or GSM/LTE repeater), or a multi band repeater (e.g., a GSM/UMTS/LTE repeater). An example of an RF repeater that may be used in the detection system of the present invention is the MR918 repeater manufactured by CommScope Inc. This exemplary RF repeater is configured to operate in the GSM 900, LTE 900 and UMTS 900 frequency bands. Its dimensions are approximately 240 mm x 240 mm x 35 mm.

As it will be clearer from the following description, a detection system configured to operate in the GSM 900 frequency band may have some advantages. Indeed, as known, the distance that may be reached by the RF signal transmitted by the system operating in this frequency band is of a few kilometres, up to 35 kilometres. This allows providing a radio coverage within a large search area. Moreover, according to embodiments of the present invention, the repeater unit 13 may comprise a signal analysing unit 22 connected to the RF repeater 21 and configured to analyse any RF signal received by the second antenna 12 and determine whether an RF signal received by the second antenna 12 is coming from the UE 3. In particular, the signal analysing unit 22 is preferably configured to provide the frequency spectrum of the received RF signal. The signal analysing unit 22 may comprise a spectrum analyser or a field meter. Preferably, the signal analysing unit 22 is provided with a display 22a.

The battery 14 is preferably a portable battery, for instance a 12V, 7 Ah battery. An exemplary battery of this type may have dimensions equal to about 150 mm x 100 mm x 60 mm and weight equal to about 2.4 Kg.

Figure 3 is a flowchart of the method for detecting a user equipment according to embodiments of the present invention.

It is assumed that a rescuer, equipped with the detection system 1 described above, approaches the search area to search the person who is missing. It is assumed, for sake of example, that the missing person is located in a valley with no coverage. In this scenario, the system is advantageously equipped with a second antenna 12 having a larger beam width than the first antenna 11. The first antenna 11 may be a Yagi antenna and the second antenna 12 may be a sector antenna such as the panel antenna mentioned above.

When the rescuer is in the vicinity of the search area (preferably, in a raised position over the search area), she/he preferably switches on the detection system 1 by switching on the RF repeater 21 of the repeater unit 13 (step 301 ). When the RF repeater 21 is switched on, the rescuer preferably starts a procedure to align the first antenna 11 towards the base station 2 (step 302). In particular, the rescuer may align the first antenna 11 towards the base station 2 by adjusting the position of the first antenna 11 until the highest RSSI value is reached. The rescuer may check the RSSI value at the display of the RF repeater 21 (step 303).

When the first antenna 11 is aligned, it receives a downlink RF signal from the BTS 2. The rescuer preferably sets the position of the second antenna 12 towards the search area (step 304). In this way, the second antenna 12, which has a larger beam width than the first antenna 11 , sends the downlink RF signal towards the search area, which covers at least a portion of the search area where the missing person might be. In the meantime, at step 305, the rescuer preferably waits and checks whether an RF signal in the uplink direction is received by the second antenna 12. This check may be performed by checking the output power of the RF repeater 21 in the uplink direction, which can be provided at the display of the RF repeater 21 . In alternative or in addition, this check may be performed by controlling a display 22a of the signal analysing unit 22 and checking whether a signal is present, at the output of the signal analysing unit 22, within the frequency band assigned to the base station 2 for the uplink communication in the considered mobile network. Indeed, as already mentioned above, if operating in a GSM network, the BTS 2 is assigned given carrier frequencies for uplink and downlink communication channels in the considered mobile network. Hence, in this case, if the user equipment 3 of the missing person is actually in the search area and it is reached by the downlink RF signal transmitted by the second antenna 12, the uplink communication channel between the UE 3 of the missing person and the BTS 2 is associated with a single carrier frequency among the carrier frequencies assigned to the BTS 2. The RF signal which is received at that frequency may be clearly identifiable on the display 22a of the signal analysing unit 22 when such display shows the frequency spectrum of the received RF signal, as it provides a peak in the frequency spectrum.

The RF repeater 21 settings may be adjusted by the rescuer to be tuned on the frequencies of the uplink communication, in order to filter out noises and disturbances. In this phase, it may be assumed that any user equipment, i.e., a cell phone, of the rescuer is switched off not to interfere with any uplink RF signal coming from the UE 3 of the missing person.

If the second antenna 12, in the considered position, is receiving an uplink RF signal (step 306), then an emergency communication link is established, which, in principle, may be a link connecting the base station 2 with the UE 3 of the missing person. If the second antenna 12, in the considered position, is not receiving any uplink RF signal, the rescuer may modify the position of the second antenna 12 until an uplink RF signal is received. The position of the second antenna 12 may be modified by, for instance, rotating the second antenna 12 about a vertical axis thereof, to move the antenna beam on the horizontal plane and cover another portion of the search area.

When the second antenna 12 receives an uplink RF signal, the rescuer preferably sets up a call to the UE 3 (step 307) by using the telephone number of the UE 3, or another unique identifier of the UE 3. Then, the rescuer preferably checks whether the uplink RF signal that the second antenna 12 is receiving is actually an uplink RF signal coming from the UE 3 of the missing person and hence whether the emergency communication link is actually connecting the base station 2 with the UE 3 of the missing person (step 308). According to the present invention, detection of the UE 3 is achieved once it is established that the emergency communication link is actually connecting the base station 2 with the UE 3 of the missing person.

To perform the call, the rescuer may switch on and use a cell phone that she/he has available, or any other user equipment equivalently enabled to access the mobile network and set up a call.

If the detection system 1 is operating in a GSM mobile network, the check of step 308 may be performed by checking the signal that is output by the signal analysing unit 22, in particular by, e.g., a spectrum analyser comprised in the signal analysing unit 22. Indeed, as known, before receiving the call, the UE 3 is substantially inactive. When the UE 3 receives the call (namely, when the UE 3 receives the request from the mobile network to set up the call), it starts sending bursts to the BTS 2 (in particular, an access burst) for accessing the mobile network, which require a higher output power. Therefore, if the UE 3 receives the call, the peak shown on the display 23a of the spectrum analyser as associated with the uplink RF signal becomes higher and it is determined that the uplink RF signal received by the second antenna 12 is coming from the UE 3.

Once the user equipment has been detected, the rescuer may implement additional steps to provide information to determine the location of the UE 3 in the considered search area. In particular, in case the second antenna 12 is a cross-polarized panel antenna as described above, the following steps may be implemented. It is to be noticed that the following steps may be implemented by using any equivalent antenna or a system comprising two antennas, wherein one antenna has a large beam width (namely, larger than 40°) in the horizontal plane and the other antenna is a more directional antenna having a narrower beam width (for instance, about 15°) in the horizontal plane. For example, this system may comprise a sector antenna and a Yagi antenna.

In case the uplink RF signal that the second antenna 12 is receiving is actually an uplink RF signal coming from the UE 3 of the missing person, the rescuer may rotate the panel antenna 12 by 90°. In this way, the beam width of the panel antenna 12 in the horizontal plane becomes narrower. For instance, the exemplary panel antenna mentioned above, has a half power beam width of about 65° in the horizontal plane and about 15° in the vertical plane. When the panel antenna 12 is used to transmit the RF downlink signal in the search area, the beam with is about 65°. If the panel antenna is rotated by an angle of 90°, the beam width in the horizontal plane reduces to about 15°. Then, the rescuer may further move the panel antenna 12 by rotating it about its vertical axis at discrete angular steps of, e.g., 20°. The angular steps define a set of corresponding directions of the beam of the panel antenna 12. While moving the panel antenna 12, the rescuer may determine the direction which is associated with the highest value of the output power associated with the received uplink RF signal, which, as mentioned above, may be provided by the RF repeater 21. In this way, the rescuer may determine the direction of the uplink RF signal with a good accuracy.

If the rescuer moves and reaches another position over the search area, she/he may repeat the method of the flowchart of Figure 3 and the additional steps described above and find another direction of the uplink RF signal. With at least two such different directions, it is possible to perform a known triangulation procedure and approximately locate the UE 3 of the missing person. Indeed, when the UE 3 accesses the mobile network, in a GSM network it is possible to determine the distance of the UE 3 from the BTS 2 by exploiting the timing advance (TA) value, which, as known, changes each time the distance between the BTS and the UE changes by about 550 m and hence gives a range of distance at which the user equipment may be located, such range being about 550 m wide. Hence, the network provider may acquire an information indicating the distance of the UE 3 of the missing person in correspondence of the at least two different directions determined as described above, which may be used to actually locate the UE 3.

In the exemplary situation considered above, the first antenna 11 and the second antenna 12 are directional antennas with substantially different beam widths in the horizontal plane. However, it is to be noticed that the system of the present invention may be equipped with antennas having different features from those described above, depending on the scenario where the emergency communication link is to be established. Another scenario where the system of the present invention may be advantageously used is a scenario in which a person is lost in an area where a spotted coverage by the mobile network is present or in a cave (or sinkhole, a tunnel, a ravine, a gorge, a crevasse, or the like). In this case, the detection system must be configured to repeat the downlink RF signal of the base station into a more confined area, possibly having walls that are blocking the propagation of the RF signals. Hence, according to further embodiments of the present invention, to repeat the downlink RF signal in such a confined area, the emergency communication system of the present invention is preferably equipped with a first directional antenna 11 , for instance a panel antenna such as the panel antenna already described above, and with a second directional antenna 12 having a narrower beam width than the first antenna 11 on the horizontal plane. For instance, the second antenna 12 may be a Yagi antenna with a beam width of about 15°. The second antenna 12 may be used by the rescuer to direct the downlink RF signal towards the confined area with high accuracy and also reach hidden places. Alternatively, in a scenario such as a crevasse or a ravine, the second antenna 12 may be an omnidirectional antenna connected to a cable in turn connected to the repeater unit 13, to drop the second antenna 12 into the crevasse or ravine.

Finally, a skilled person will appreciate that in scenarios that are particularly impervious, for instance when a natural obstacle has to be overcome, the method of the present invention may provide for using two or more detection systems as those described above in a bridged configuration. In this case, the two or more detection systems are chained together. For example, a first detection system may be brought in a raised position over a valley to send and RF signal towards the valley and towards a second detection system positioned in the valley in the vicinity of a cave, so that the second detection system may in turn send the RF signal into the cave.

The system of the present invention has a number of advantages.

As a matter of fact, the system and method of the present invention provide a more effective and timely intervention than a vehicle-transportable base station. Firstly, the system may be used in a wide variety of different and complex scenarios where a missing person is to be detected. Then, the system may be put in operation in a simple manner without requiring neither the intervention of specialized technicians nor long times for the setting up and the switching off. The setting up, for instance, may be performed in a few minutes. As apparent, the system is less complex and expensive than a vehicle-transportable base station and is adapted to be portable even by a single person in order to reach areas that are inaccessible by a wheeled vehicle. It guarantees a quick intervention as it is advantageously operable while being carried towards the search area. On the other side, once the intervention is terminated, the system may be switched off quickly and carried to another area. Finally, the system allows to detect by simply calling the user equipment of the missing person.

The system may further provide first information for eventually locating the missing person. Hence, detection of the user equipment is advantageously performed as soon as the user equipment rings when called by the rescuer, without involving the mobile operator (indeed, the specific mobile operator may be unknown), namely without exploiting information that are available to the network provider (as a matter of fact, the access burst mentioned above is transmitted by the user equipment before the BTS determines its position), and this advantageously further speeds up the intervention times.

Claims

1 . A method for detecting a user equipment (3) enabled to access a mobile network, the user equipment (3) being located in a geographical area where said mobile network has substantially no coverage, the method comprising establishing an emergency communication link between a base station (2) of said mobile network and said user equipment (3) by: a) providing a system (1 ) comprising a first antenna (11 ), a repeater unit (13) and a second antenna (12); b) aligning said first antenna (11 ) towards said base station (2) to receive a downlink RF signal from said base station (2); c) amplifying said received downlink RF signal by said repeater unit (13) connected to said first antenna (11 ); and d) transmitting said amplified downlink RF signal by said second antenna (12) connected to said repeater unit (13) towards said geographical area, wherein the method further comprises, in case said second antenna (12) is receiving an uplink RF signal, setting up a call to said user equipment (3) through said mobile network and determining that said uplink RF signal is coming from said user equipment (3).

2. The method according to claim 1 or 2, wherein said call is set up according to the GSM communications standard.

3. A system (1 ) for detecting a user equipment (3) enabled to access a mobile network, the user equipment (3) being located in a geographical area where said mobile network has substantially no coverage, the system (1 ) being configured to establish an emergency communication link between a base station (2) of said mobile network and said user equipment (3), the system (1 ) comprising: a first antenna (11 ) configured to receive a downlink RF signal from said base station (2) of the mobile network; a repeater unit (13) connected to said first antenna (11 ), the repeater unit (13) being configured to amplify said received downlink RF signal; and a second antenna (12) configured to transmit said amplified downlink RF signal towards said geographical area and to receive an uplink RF signal from said user equipment (3), wherein the system (1 ) further comprises a further user equipment to set up a call to said user equipment (3) through said mobile network and wherein said repeater unit (13) comprises a signal analyzing unit (22) to determine that said uplink RF signal is coming from said user equipment (3).

4. The system (1 ) according to claim 3, said system (1 ) being configured to be housed in a human-bearable container.

5. The system (1 ) according to claim 3 or 4, wherein the system (1 ) is configured to operate in a frequency range comprised between 824 MHz and 960 MHz

6. The system (1 ) according to any of claims 3 to 5, wherein said second antenna (12) is a sector antenna.

7. The system (1 ) according to claim 6, wherein said second antenna (12) is a cross-polarized panel antenna.

8. The system (1 ) according to any of claims 3 to 7, wherein said first antenna (11 ) is a Yagi antenna.

9. The system (1 ) according to any of claims 3 to 7, wherein said first antenna (11 ) is a sector antenna.

10. The system (1 ) according to any of claims 3 to 9, wherein said signal analyzing unit (22) comprises a spectrum analyzer.

11. The system (1 ) according to any of claims 3 to 10, wherein said repeater unit (13) comprises a RF repeater with adjustable gain.

12. The system (1 ) according to any of claims 3 to 11 , wherein it further comprises a battery.