Abstract:
The present disclosure relates to a sensor network, Machine Type Communication (MTC), Machine-to-Machine (M2M) communication, and technology for Internet of Things (IoT). The present disclosure may be applied to intelligent services based on the above technologies, such as smart home, smart building, smart city, smart car, connected car, health care, digital education, smart retail, security and safety services. Disclosed are an apparatus and method for generating distress signals in a mobile device. The apparatus comprises a coil antenna for NFC communication, a first communication circuit configured to perform the NFC communication using the coil antenna in a normal mode, a second communication circuit transmitting a distress signal having a rescue-dedicated frequency through the coil antenna in a distress mode, a switch connecting the coil antenna to the first communication circuit or the second communication circuit, and a processor determining the normal mode or the distress mode to control the switch.

Description:
RELATED APPLICATION(S) 
       [0001]    This application claims the benefit under 35 U.S.C. §119(a) of a Korean patent application filed in the Korean Intellectual Property Office on Dec. 29, 2014 and assigned Serial No. 10-2014-0191955, the entire disclosure of which is incorporated herein by reference. 
       BACKGROUND 
       [0002]    The present disclosure relates to wireless communication, and more particularly to apparatuses and methods for generating distress signals from mobile devices. 
         [0003]    The Internet, which is a human centered connectivity network where humans generate and consume information, is now evolving to the Internet of Things (IoT) where distributed entities, such as things, exchange and process information without human intervention. The Internet of Everything (IoE), which is a combination of the IoT technology and the Big Data processing technology through connection with a cloud server, has emerged. As technology elements, such as sensing technology, wired/wireless communication and network infrastructure, service interface technology, and Security technology have been demanded for IoT implementation, a sensor network, a Machine-to-Machine (M2M) communication, Machine Type Communication (MTC), and so forth have been recently researched. 
         [0004]    Such an IoT environment may provide intelligent Internet technology services that create a new value to human life by collecting and analyzing data generated among connected things. IoT may be applied to a variety of fields including smart home, smart building, smart city, smart car or connected cars, smart grid, health care, smart appliances and advanced medical services through convergence and combination between existing Information Technology (IT) and various industrial applications. 
         [0005]    A mobile terminal, such as a cellular phone or smartphone, may connect itself to a cellular system, i.e., a mobile communication network, to establish a call through a base station of the mobile communication network. A smartwatch or other additional devices interworkable with the cellular phone or smartphone may perform communication alone or in association with the mobile terminal. 
         [0006]    Such a mobile device may have call failures or call drops in a non-service area not covered by radio signals from the base station. This may happen, for example, in rural areas, a shadow area to signals, at a mountain or at sea. Also, absent battery power sufficient to access the network, the mobile device cannot establish a call nor can it send out distress signals. The user also may not be able to dispatch distress signals through his mobile device in emergency situation, such as, for example, natural disaster, distress, or unconsciousness. Thus, there is a need for technology to generate distress signals through a mobile device in such emergencies. 
         [0007]    The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present disclosure. 
       SUMMARY 
       [0008]    The present disclosure provides an apparatus and method for increasing the probability of detecting a person in distress. 
         [0009]    The present disclosure provides an apparatus and method for generating distress signals through a mobile device. 
         [0010]    The present disclosure provides an apparatus and method for generating distress signals using a communication antenna of a mobile device. 
         [0011]    The present disclosure provides an apparatus and method for generating distress signals using a cellular antenna of a mobile device. 
         [0012]    The present disclosure provides an apparatus and method for generating distress signals through a mobile device when the mobile device runs out of battery. 
         [0013]    According to an embodiment of the present disclosure, the apparatus comprises a coil antenna configured for short-range communication, a first communication circuit configured to perform the short-range communication using the coil antenna in a normal mode; a second communication circuit configured to transmit a distress signal having a rescue-dedicated frequency through the coil antenna during a distress mode, a switch configured to connect the coil antenna to any one of the first communication circuit and the second communication circuit, and a processor configured to determine the normal mode and the distress mode to control the switch. 
         [0014]    According to an embodiment of the present disclosure, a method for generating a distress signal from a mobile device comprises determining, by a processor, a distress mode, connecting the coil antenna to a second communication circuit when the distress mode is detected, wherein the second communication circuit is configured to generate a distress signal having a rescue-dedicated frequency, and connecting a coil antenna for short-range communication to a first communication circuit configured to perform the short-range communication when the distress mode is not detected. 
         [0015]    According to an embodiment of the present disclosure, an apparatus for generating a distress signal in a mobile device comprises a radio frequency (RF) module configured to perform cellular communication using a cellular antenna in a normal mode, a reflecting circuit configured to transmit a distress signal by reflecting a detection signal received through the cellular antenna in a distress mode; a switch configured to connect the cellular antenna to any one of the RF module and the reflecting circuit, and a processor configured to determine the normal mode or the distress mode to control the switch. 
         [0016]    According to an embodiment of the present disclosure, a method for generating a distress signal from a mobile device comprises determining, by a processor, a distress mode, connecting a cellular antenna for cellular communication of the mobile device to a reflecting circuit configured to transmit a distress signal by reflecting a detection signal received through the cellular antenna when the distress mode is detected, and connecting the cellular antenna to an RF circuit configured to perform the cellular communication when the distress mode is not detected. 
         [0017]    Other aspects, advantages, and salient features of the disclosure will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses exemplary embodiments of the disclosure. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    Various embodiments of the present disclosure and the foregoing and other aspects, features, and advantages will be apparent from the following detailed description taken in conjunction with the accompanying drawings, wherein: 
           [0019]      FIG. 1  illustrates a typical rescue process; 
           [0020]      FIG. 2  is a flowchart illustrating a distress mode operation according to an embodiment of the present disclosure; 
           [0021]      FIG. 3  illustrates a structure of a mobile device according to an embodiment of the present disclosure; 
           [0022]      FIG. 4  illustrates sending out a distress signal at a rescue-dedicated frequency according to an embodiment of the present disclosure; 
           [0023]      FIG. 5  illustrates a structure of an apparatus for sending out a distress signal at a rescue-dedicated frequency in a mobile device according to an embodiment of the present disclosure; 
           [0024]      FIG. 6  illustrates a variation in strength of a distress signal according to an embodiment of the present disclosure; 
           [0025]      FIG. 7  illustrates a structure of a mobile device having a coil antenna embedded in a cover case according to an embodiment of the present disclosure; 
           [0026]      FIG. 8  illustrates a structure of a distress signal transmitter embedded in a cover case of a mobile device according to an embodiment of the present disclosure; 
           [0027]      FIG. 9  is a timing view illustrating an operation of automatically transmitting a distress signal according to an embodiment of the present disclosure; 
           [0028]      FIG. 10  illustrates a structure of a rescue system according to an embodiment of the present disclosure; 
           [0029]      FIG. 11  illustrates a structure of a distress signal transmitter including a reflecting circuit in a mobile device according to an embodiment of the present disclosure; 
           [0030]      FIG. 12  illustrates an example of a manual reflecting circuit according to an embodiment of the present disclosure; 
           [0031]      FIG. 13  illustrates an example of a manual reflecting circuit according to an embodiment of the present disclosure; 
           [0032]      FIG. 14  illustrates an example of the result of a transmission/reception test of a distress signal using backscattering according to an embodiment of the present disclosure; 
           [0033]      FIG. 15  illustrates a structure of a reflecting device embedded in a cover case of a mobile device according to an embodiment of the present disclosure; and 
           [0034]      FIG. 16  is a flowchart illustrating a distress mode operation by a mobile device according to an embodiment of the present disclosure. 
       
    
    
       [0035]    It should be noted that the same or similar reference denotations may be used to refer to the same or similar elements, features, or structures throughout the drawings. 
       DETAILED DESCRIPTION 
       [0036]    Hereinafter, embodiments of the present disclosure are described in detail with reference to the accompanying drawings. 
         [0037]    In describing the embodiments, description of technologies that are known in the art and are not directly related to the present disclosure is omitted. This is to further clarify the gist of the present disclosure without clutter. 
         [0038]    For the same reasons, some elements may be exaggerated or schematically shown. The size of each element does not necessarily reflect the real size of the element, or proportional sizes to other elements. The same reference numeral is used to refer to the same element throughout the drawings. 
         [0039]    Advantages and features of the present disclosure, and methods for achieving the same may be understood through the embodiments described below taken in conjunction with the accompanying drawings. However, the present disclosure is not limited to the embodiments disclosed herein, and various changes may be made thereto. The embodiments disclosed are provided to inform one of ordinary skill in the art of the category of the present disclosure. The same reference numeral denotes the same element throughout the specification. 
         [0040]    It should be appreciated that the blocks in each flowchart and combinations of the flowcharts may be performed by computer program instructions. Since the computer program instructions may be equipped in a processor of a general-use computer, a special-use computer or other programmable data processing devices, the instructions executed through a processor of a computer or other programmable data processing devices generate means for performing the functions described in connection with a block(s) of each flowchart. Since the computer program instructions may be stored in a computer-available or computer-readable memory that may be oriented to a computer or other programmable data processing devices to implement a function in a specified manner, the instructions stored in the computer-available or computer-readable memory may produce a product including an instruction means for performing the functions described in connection with a block(s) in each flowchart. Since the computer program instructions may be equipped in a computer or other programmable data processing devices, instructions that generate a process executed by a computer as a series of operational steps are performed over the computer or other programmable data processing devices and operate the computer or other programmable data processing devices may provide steps for executing the functions described in connection with a block(s) in each flowchart. 
         [0041]    Further, each block may represent a module, segment, or part of a code including one or more executable instructions for executing a specified logical function(s). It should also be noted that in some replacement execution examples, the functions mentioned in the blocks may occur in different orders. For example, two blocks that are consecutively shown may be performed substantially simultaneously or in a reverse order depending on corresponding functions. 
         [0042]    As used herein, the term “unit” means a software element or a hardware element such as a field-programmable gate array (FPGA) or an application specific integrated circuit (ASIC). A “unit” may be configured in a storage medium that may be addressed or may be configured to reproduce one or more processors. Accordingly, as an example, a “unit” includes elements, such as software elements, object-oriented software elements, class elements, and task elements, processes, functions, attributes, procedures, subroutines, segments of program codes, drivers, firmware, microcodes, circuits, data, databases, data architectures, tables, arrays, and variables. A function provided in an element or a “unit” may be combined with additional elements or may be split into sub-elements or subunits. Furthermore, an element or a “unit” may be implemented to reproduce one or more central processing units (CPUs) in a device or a security multimedia card. 
         [0043]    Although the description of embodiments herein primarily focuses on mobile terminals operating on typical cellular mobile communication systems, the subject matter of the present disclosure may also be applicable to other communication systems and services having similar technical backgrounds without departing from the scope of the present disclosure. 
         [0044]      FIG. 1  illustrates a typical rescue process. Referring to  FIG. 1 , the user is in distress ( 105 ), and the user himself or the mobile device carried by the user detects the distress ( 110 ). As an example, the mobile device may be any one of a cellular communication device, such as a smartphone, and a short-range communication device or an additional device that may interwork with the cellular communication device and may access a mobile communication network directly or via the cellular communication device. A scheme for the mobile device to detect the user&#39;s distress is described below. The mobile device alerts (advertises) a specified or unspecified recipient(s) to the distress automatically or in response to the user&#39;s manipulation ( 115 ). A rescue team who receives the distress alert does its rescue operation ( 120 ), and the rescue operation is done ( 125 ). 
         [0045]    However, sometimes the mobile device may not be able to normally access the network. For example, the mobile device cannot dispatch distress signals through the mobile communication network when the mobile device is positioned in a non-service area or shadow area of the cellular mobile communication network, or if its battery is too low. Accordingly, different distress mode operations may need to be carried out depending on different circumstances. 
         [0046]      FIG. 2  is a flowchart illustrating a distress mode operation according to an embodiment of the present disclosure. Referring to  FIG. 2 , distress may be detected by at least one of external recognition  205 , user recognition  220 , and automatic recognition  245 . 
         [0047]    The user recognition  220  means that the user himself recognizes the distress. Upon sensing the distress, the user manipulates his mobile device, and the mobile device attempts to connect to the mobile communication network in response to the user&#39;s manipulation ( 225 ). When access to the mobile communication network is possible, the mobile device determines whether the battery level exceeds a minimum value (e.g., 0.1%) needed for communication ( 230 ). When the remaining battery power is high enough to establish a connection to the mobile communication network, i.e., when the battery level exceeds 0.1%, the mobile device determines whether the connection to the mobile communication network succeeds ( 235 ). When the connection to the mobile communication network is successful, the mobile device may establish a call to a phone number that has been previously determined or requested by the user or establish a call to a rescue team (e.g., a 911 team) ( 265 ) and may send a request for rescue through the call. 
         [0048]    When it is determined in operation  225  that the connection to the mobile communication network by the user&#39;s manipulation is impossible, the mobile device enters into a passive (manual detection) distress mode ( 250 ). In the passive distress mode, the mobile device may passively generate a distress signal in response to an external signal. As an example, the passive distress mode may use a harmonic radar scheme or harmonic backscattering using an unbiased diode. 
         [0049]    When it is determined in operation  230  that the battery level is not more than 0.1%, the mobile device determines whether there is any power remaining in the battery, i.e., whether the battery level exceeds 0% ( 240 ). When the battery level is 0%, the mobile device operates in the passive distress mode ( 250 ). By contrast, when the battery level exceeds 0%, the mobile device operates in a hybrid detection distress mode ( 255 ). In the hybrid detection distress mode, the mobile device sends out a distress signal using a harmonic backscattering scheme using a biased diode or using a low-power communication scheme such as Bluetooth low energy (BLE). The distress signal may be detected by an ambient detector using the same communication scheme. 
         [0050]    When the connection to the mobile communication network fails in operation  235 , the mobile device enters into a distress communication mode ( 260 ). In the distress communication mode, the mobile device sends out distress signals using a predetermined communication scheme, such as BLE, Wi-Fi, long-term evolution direct (LTE-D), or a 457 kH beacon. The distress signal may be detected by an ambient detector using the same communication scheme. 
         [0051]    The external recognition  205  may be achieved by a third party or external signal other than the user or the mobile device. When distress is detected by the external recognition  205 , the user or the third party attempts to connect to the mobile communication network through the mobile device ( 210 ). Upon successful connection to the mobile communication network, the mobile device may establish a call to a phone number that has been previously determined or requested by the user or may establish a call to the rescue team (e.g., a 911 team) to request rescue. 
         [0052]    Automatic recognition  245  means that the mobile device detects distress on its own. As an example, the mobile device traces its movement through its equipped motion sensor, and when there is no motion (still state) for a predetermined time after sensing sudden movement, the mobile device determines it as distress. As another example, when a still state lasts a predetermined time within a portion of a day (abnormal time period) set by the user or the mobile device itself, for example, from 6:00 AM to 12:00 PM, the mobile device may determine that there is distress. As still another example, when there is no response to incoming calls continues, for example, when the number of missed calls for a predetermined period exceeds a threshold, the mobile device may determine that there is distress. When detecting the user&#39;s movement after sensing the distress and entering the distress mode, or when the distress mode is requested to be canceled by the user, the mobile device may exit the distress mode. 
         [0053]    When distress is detected by automatic recognition  245 , the mobile device attempts to connect to the mobile communication network and determines whether the connection succeeds ( 235 ). Upon successful connection to the mobile communication network, the mobile device may establish a call to a phone number that has been previously determined or requested by the user or may establish a call to the rescue team (e.g., a 911 team) ( 265 ) and may send a request for rescue through the call. When the connection to the mobile communication network fails in operation  235 , the mobile device enters into the distress communication mode ( 260 ) to send out a distress signal using a predetermined communication scheme. 
         [0054]    Although the description of embodiments herein primarily focuses on smartphones connecting to the mobile communication network, the subject matter of the present disclosure may also be applicable to other communication apparatuses and devices having similar technical backgrounds without departing from the scope of the present disclosure. 
         [0055]    For example, the electronic device according to embodiments of the present disclosure may include at least one of, for example, a smartphone, a tablet personal computer (PC), a mobile phone, a video phone, an e-book reader, a laptop computer, a netbook computer, a personal digital assistant (PDA), a portable multimedia player (PMP), a MPEG-1 audio layer-3 (MP3) player, a mobile medical device, a camera, or a wearable device. Examples of a wearable device may be, for example, smart glasses, a head-mounted device (HMD), electronic clothes, electronic shoes, an electronic bracelet, an electronic necklace, an electronic appcessory, an electronic tattoo, a smart mirror, and a smart watch. 
         [0056]      FIG. 3  illustrates a structure of a mobile device according to an embodiment of the present disclosure. 
         [0057]    Referring to  FIG. 3 , a controller  305  controls the overall operation of the mobile device  300  and may include a central processing unit (CPU), a read only memory (ROM) storing a control program to control the mobile device  300 , and a random access memory (RAM) to record signals or data input from the outside of the mobile device  300  or used as a storage area for tasks performed on the mobile device  300 . The CPU may comprise, for example, a single core, a dual core, a triple core, or a quad core. The CPU, the ROM, and the RAM may be interconnected with one another via an internal bus. The controller  305  may operate in distress mode by detecting distress on its own, analyzing results sensed by a motion sensor  315 , or receiving a user input through an input unit  335 . The controller  305  may also include an application processor (AP) or a sensor hub configured to detect distress. The sensor hub may compile data from at least one sensor and analyze the data to detect a given circumstance, especially distress. 
         [0058]    A display unit  310  may include at least one of a display screen and a touchscreen and may output a user interface to activate or exit the distress mode under control of the controller  305 . 
         [0059]    A codec  320  outputs a voice, music, or sound through a speaker under control of the controller  305  or transfers a signal sensed by a microphone to the controller  305 . 
         [0060]    A sub-communication module  325  for short-range communication may be connected to a sub-antenna  325   a  for wired or wireless communication (hereinafter, auxiliary communication) other than the cellular mobile communication network. The sub-communication module  325  may be configured to support, for example, at least one of Bluetooth, BLE, near-field communication (NFC), Wi-Fi, or Wi-Fi-direct. The sub-antenna  325   a  may include an antenna module to support the various communication schemes. Furthermore, the sub-antenna  325   a  may include a receiving coil for wireless charging such as wireless power consortium (WPC), alliance for wireless power (A4WP), or wireless power transfer (WPT), and a magnetic signal transmission coil such as magnetic secure transmission (MST). 
         [0061]    A memory  330  stores data, parameters, and program codes necessary for the operation of the controller  305 . 
         [0062]    The input unit  335  is configured to be able to receive a user input such as, for example, a request for distress mode, and may include at least one of a keypad, a touchpad, and a touchscreen. 
         [0063]    A modem  340 , configured to support at least one communication protocol for mobile communication networks, converts a signal to be transmitted into a format according to the communication protocol of the mobile communication network under the control of the controller  305  and transfers the signal to a radio frequency (RF) module  345  or demodulates a signal received by the RF module  345  and transfers the demodulated signal to the controller  305 . The RF module  345  is connected with a cellular antenna  345   a  to communicate RF signals in a frequency band of the mobile communication network. 
         [0064]    A distress signal generator  350  may be connected with at least one of the cellular antenna  345   a  and the sub-antenna  325   a  to generate a distress signal. The distress signal generator  350  may be connected with at least one of the cellular antenna  345   a  and the sub-antenna  325   a  when the mobile device  300  is operating in distress mode due to actions of the controller  305  or the user. 
         [0065]      FIG. 4  illustrates sending out a distress signal at a rescue-dedicated frequency according to an embodiment of the present disclosure. 
         [0066]    Referring to  FIG. 4 , a mobile device  405  including a distress signal generator generates a low-frequency signal having a rescue-dedicated frequency such as, for example, a frequency of 457 kHz using an antenna embedded in the mobile device  405 . 457 kHz is an international standard frequency used for rescue. The distress signal at this frequency may propagate through barriers such as water, concrete, earth, or snow, where the propagation may depend on an amount of the specific barrier. A detector  410  may detect a distress signal to locate the person carrying the mobile device  405 . 
         [0067]    The following major issues are presented to equip a typical mobile device with a distress signal generator. 
         [0068]    (1) Minimize the space for antennas 
         [0069]    (2) Minimize the number of circuit parts added 
         [0070]    (3) Minimize power consumption 
         [0071]    In the following embodiments, a shared-antenna distress signal generator is configured by coupling a switch and a power amplifier having a rescue-dedicated frequency to a sub-antenna  325   a  of the mobile device. 
         [0072]      FIG. 5  illustrates a structure of an apparatus for sending out a distress signal at a rescue-dedicated frequency in a mobile device according to an embodiment of the present disclosure. Although a coil antenna  510  (or loop antenna) for NFC already embedded in the mobile device is shown as an example of the sub-antenna  325   a , an antenna for sub-communication other than the NFC antenna may also be used to transmit signals at the rescue-dedicated frequency. 
         [0073]    Referring to  FIG. 5 , the coil antenna  510  may be a legacy NFC antenna used for NFC, and the coil antenna  510  is connected to a matching circuit  525  of an NFC chip  520  via a switch  540  or connected to a matching circuit  555  and a power amplifier (PA)  550  to generate distress signals. 
         [0074]    When the mobile device operates in a normal mode, the switch  540  connects the coil antenna  510  to the NFC chip  520  via the matching circuit  525 . The matching circuit  525  may include a capacitor suitable for NFC frequency of 13.56 MHz. The coil antenna  510  connected with the NFC chip  520  may perform normal NFC transmission/reception. 
         [0075]    A processor  530  may be embedded in the controller  305  of the mobile device or may be provided independently from the controller  305 . When automatically detecting distress or receiving a request to operate in a distress mode from the user, the processor  530  controls the switch  540  to connect the coil antenna  510  to the power amplifier  550  via the matching circuit  555 . The power amplifier  550  may receive a signal having the rescue-dedicated frequency, for example, 457 kHz, from the processor  530  and amplifies the signal. The amplified signal may be received by the coil antenna  510  via the matching circuit  555  and the switch  540 , and may be transmitted by the coil antenna  510 . 
         [0076]    In an embodiment, the power amplifier  550  may be configured as a variable power amplifier (or tunable PA) that is able to vary the signal strength of the 457 kHz distress signal.  FIG. 6  illustrates a variation in strength of a distress signal according to an embodiment of the present disclosure. That is, the pulses of the 457 kHz distress signal are transmitted at predetermined periods, and the pulses may be sent out with higher power or lower power. 
         [0077]    In an embodiment, the matching circuit  555  may be configured as a variable matching circuit (or a tunable matching circuit) varying the matching value depending on the state and circumstance of the mobile device. The coil antenna  510  may include an NFC antenna and an expanded coil antenna occupying the area of the cover case covering the mobile device, and in such case, the matching value of the variable matching circuit may vary depending on whether the cover case is opened or closed. A matching value for the opened state of the cover case and a matching value for the closed state of the cover case may have been previously stored in the matching circuit  555  or the processor  530 , and the matching value of the variable matching circuit may be determined under the control of the processor  530 . 
         [0078]      FIG. 7  illustrates a structure of a mobile device having a coil antenna embedded in a cover case according to an embodiment of the present disclosure. 
         [0079]    Referring to  FIG. 7 , a mobile device may include an NFC antenna  705  configured with a relatively smaller area of coil antenna. The NFC antenna  705  is connected to a matching circuit  725  of the NFC chip or a matching circuit  755  for generating distress signals via a switch  740 . The mobile device may be coupled with a cover case  700  that may cover the housing of the mobile device or may be integrally formed with the battery cover, and the cover case  700  includes a cover coil antenna  710  having an area including the area of the NFC antenna  705 . The cover coil antenna  710  may be disposed along the edges of the cover case  700  of the mobile device to surround the NFC antenna  705 . The cover coil antenna  710 , while not in direct contact with the NFC antenna  705 , may be electronically (or magnetically) coupled with the NFC antenna  705  to reinforce the near field of the NFC antenna  705 . 
         [0080]    The matching circuit  725  for the NFC chip may include a capacitor C 1  having a fixed capacitance of C 1 . The matching circuit  755  for generating distress signals may include a variable capacitor C 2  having a capacitance C 21  or C 22  depending on whether the cover case  700  is opened or closed. The capacitance of the variable capacitor C 2  may be controlled by the processor  530 . 
         [0081]      FIG. 8  illustrates a structure of a distress signal transmitter embedded in a cover case of a mobile device according to an embodiment of the present disclosure. 
         [0082]    Referring to  FIG. 8 , the cover case  820  for a mobile device includes a distress signal transmitter  805  that may send out distress signals having a rescue-dedicated frequency and a cover coil antenna  800  along the edges of a surface of the cover case  820 . The distress signal transmitter  805  may receive power from a battery  810  of the mobile device through the back surface of the cover case  820 . 
         [0083]    The cover case  820  shown in  FIG. 8  may be a dedicated case for sports or exploration, and the distress signal transmitter  805  is configured to turned on or off by the user or by a processor of the mobile device. 
         [0084]    As set forth above, the distress signal transmitter periodically sends out distress signal pulses in the distress mode. Automated transmission of distress signals may be initiated when the user&#39;s movement is not detected for a predetermined time after setting up the mobile device for distress detection, as long as the user is not using the mobile device for activities such as, for example, having the display on, making voice call, data communication, running an application, etc. Distress may not be determined until lack of movement is noted for a predetermined time such as, for example, four minutes, after meeting a given transmission condition. Alternatively, the user may manually start the automated transmission of distress signals through the mobile device. Further transmission may depend on, for example, settings for distress transmission. 
         [0085]    In an embodiment, the automated transmission of distress signals sends out distress signal pulses at given periods. Alternatively, the automated transmission of distress signals may be carried out at periods set depending on the remaining battery power of the mobile device. As an example, when the battery level of the mobile device exceeds a predetermined threshold, the transmission of distress signals may be every second. As another example, when the battery level of the mobile device is less than the threshold, the transmission of distress signals may be every two seconds and the transmission interval may increase as the battery level decreases. 
         [0086]    As an embodiment, the mobile device may automatically send out distress signals for a predetermined time. Alternatively, the mobile device may pause the automated transmission of distress signals in response to a request from the user. In another embodiment, the mobile device may perform automated transmission of distress signals until the battery power runs out while gradually increasing the interval for transmission of distress signals based on the remaining battery power. 
         [0087]      FIG. 9  is a timing view illustrating an operation of automatically transmitting a distress signal according to an embodiment of the present disclosure. 
         [0088]    Referring to  FIG. 9 , in an active mode  905  in which the mobile device is in use for calling, data communication, or running an application, the distress mode does not run, and the mobile device abstains from sending out distress signals. In such normal circumstance, the processor  530  controls the switch  540  to connect the coil antenna  510  to the NFC chip  520 . 
         [0089]    When a standby mode  900  is maintained for a predetermined time  915  from the time  910  when the standby mode  900  begins, the mobile device transmits distress signals ( 920 ). The mobile device sends out distress signals for a predetermined transmission time  915   a  that may be, for example, three seconds, and after waiting for a T time  915   b , resumes the transmission of distress signals for the transmission time  915   a . The transmission time  915   a  may gradually increase according to a predetermined pattern or according to the remaining battery power of the mobile device. 
         [0090]    In the following embodiments, distress signals are transmitted via a cellular antenna of the mobile device. When the battery power of the mobile device has run out or is too low to operate the distress signal transmitter at the distress signal-dedicated frequency, the mobile device may send out distress signals by passively reflecting signals through the cellular antenna. A detector positioned near the mobile device may then be able to locate the person in distress by receiving a reflected signal. 
         [0091]      FIG. 10  illustrates a structure of a rescue system according to an embodiment of the present disclosure. 
         [0092]    Referring to  FIG. 10 , the rescue system includes a detector  1000  transmitting detection signals having a predetermined frequency f 0  and a reflector  1050  transmitting distress signals of  2   f   0  in response to reception of the detection signals. In an embodiment, the frequencies f 0  and  2   f   0  may be determined to avoid the frequency band of the cellular mobile communication network. In the example illustrated, f 0 =915 MHz. 
         [0093]    A transmission path of the detector  1000  includes a signal generator  1005  generating detection signals of f 0 , a band pass filter (BPF)  1010  filtering out signals other than signals within a predetermined bandwidth centered on f 0 , and a transmission antenna  1015  transmitting the filtered signals. The reception path of the detector  1000  includes a reception antenna  1030  receiving distress signals of  2   f   0 , a high pass filter (HPF)  1025  selectively receiving only signals with frequencies higher than  2   f   0 , and a signal analyzer (SA)  1020  analyzing the reception strength of the filtered signals. 
         [0094]    The reflector  1050  may be embedded in the mobile device accessible to the cellular mobile communication network and shares the cellular antenna  1055  used for cellular mobile communication by the mobile device. The reflector  1050  includes a cellular antenna  1055  capable of receiving detection signals of frequency f 0  and transmitting distress signals of frequency  2   f   0 , a dual-band matching circuit  1060  configured to operate with matching values corresponding to frequencies f 0  and  2   f   0 , and a reflecting circuit  1065  receiving the detection signals via the dual-band matching circuit  1060 . The reflector  1050  may convert the detection signals into distress signals of frequency  2   f   0  and re-transmit the distress signals. The reflector  1050  may operate by the principle of passive backscattering and may send out distress signals even when the battery power of the mobile device has run out. 
         [0095]      FIG. 11  illustrates a structure of a distress signal transmitter including a reflecting circuit in a mobile device according to an embodiment of the present disclosure. 
         [0096]    Referring to  FIG. 11 , the cellular antenna  1105  is used for typical cellular mobile communication in the mobile device and is connected to an RF module  1115  by a switch  1110  or connected to a reflecting circuit  1125  for generating distress signals. In an embodiment, the reflecting circuit  1125  may be connected to the switch  1110  via a matching circuit  1120 . 
         [0097]    The reflecting circuit  1125  may include a Schottky diode that may be biased by a voltage V bias . When a detection signal of frequency f 0  received through the cellular antenna  1105  is input by the switch  1110 , the reflecting circuit  1125  converts the detection signal into a distress signal of  2   f   0  and transmits the distress signal. 
         [0098]    When the mobile device operates in the normal mode, the switch  1110  connects the cellular antenna  1105  to the RF module  1115 . The RF module  1115  outputs RF signals for normal cellular communication of the mobile device or processes RF signals inputted. 
         [0099]    A processor  1130  may be embedded in the controller  305  of the mobile device or may be provided independently from the controller  305 . When automatically detecting distress or receiving a request to operate in a distress mode from the user, or when determining that there is little to no battery power remaining, the processor  1130  controls the switch  1110  to connect the cellular antenna  1105  to the reflecting circuit  1125  directly or via the matching circuit  1120 . When there is a detection signal coming in through the cellular antenna  1105 , the reflecting circuit  1125  generates a distress signal, and the distress signal is transmitted by the cellular antenna  1105  through the switch  1110 . In an embodiment, the processor  1130  may connect the cellular antenna  1105  to the reflecting circuit  1125  through the switch  1110  depending on the user&#39;s selection when operating in the normal mode. As an example, in standby mode when the cellular mobile communication is not in use, the processor  1130  connects the cellular antenna  1105  to the reflecting circuit  1125  instead of the RF module  1115  for a period that is previously determined or selected by the user. During the remaining period of the standby mode or in an active mode where the cellular mobile communication is used, the cellular antenna  1105  may be connected to the RF module  1115 . 
         [0100]      FIG. 12  illustrates an example in which a manual reflecting circuit is equipped according to an embodiment of the present disclosure. 
         [0101]    Referring to  FIG. 12 , the cover case  1200  may be configured to cover the housing of the mobile device or to be integrally formed with the battery cover of the mobile device, and the Schottky diode  1210  constituting the reflecting circuit  1065  or  1125 , which may be passive, is positioned on a hinge  1205  of the cover case  1200 . Accordingly, the reflecting circuit may perform well regardless of whether the cover case is open or closed, detection signals getting cut off by the position or state that the mobile device is placed may be minimized, and the Schottky diode  1210  may be spaced apart from the display and antenna of the mobile device. 
         [0102]      FIG. 13  illustrates an example in which a manual reflecting circuit is equipped according to an embodiment of the present disclosure. 
         [0103]    Referring to  FIG. 13 , the cover case  1300  may be configured to cover the housing of the mobile device or to be integrally formed with the battery cover of the mobile device, and the Schottky diode  1310  constituting the reflecting circuit  1065  or  1125  is positioned on a hinge  1305  of the cover case  1300 . A band stop filter  1315  and a capacitor  1320  may be connected in parallel with the Schottky diode  1310  to filter out signals other than signals within the  2   f   0  bandwidth. The  2   f   0  signals may be re-radiated by the Schottky diode  1310 , the power from the filtered out signals may be stored in the capacitor  1320 , and a bias may be applied to the Schottky diode  1310  by the power stored in the capacitor  1320 . 
         [0104]    The passive reflecting circuit is known to have a maximum detection distance of 200 m line of sight (LoS) distance. The detection distance may be less when the reflection efficiency is lowered in the mobile device. When a bias is applied to the Schottky diode  1310 , the detection distance may be increased by two times. As illustrated in  FIG. 13 , bias application power may be collected by the RF energy harvesting structure constituted of the band stop filter  1315  and the capacitor  1320 . In an exemplary experimental environment, when a direct current (DC) bias of 0V is applied to the Schottky diode of the reflector, the detector was able to receive signals only up to 5 m, and the signal strength was about −110 dBm. By contrast, when a DC bias of 0.5V is applied to the Schottky diode of the reflector, the detector was able to receive −97 dBm signals up to 30 m away. 
         [0105]      FIG. 14  illustrates an example of the result of a transmission/reception test of a distress signal using backscattering according to an embodiment of the present disclosure. 
         [0106]    Referring to  FIG. 14 , the mobile device  1405  having a reflector embedded to transmit distress signals is positioned on the fifth floor underground and is sending out 457 kHz distress signals at a power level of 30 dBm. The detector  1400  having a spectrum analyzer embedded therein to detect distress signals was able to detect distress signals at power levels −78 dBm, −93 dBm, and −104 dBm on the fourth, third, and second floors underground, respectively. The reception level on the first floor was −120 dBm which is less than noise level. However, a −105 dBm distress signal, which exceeds the noise level, could be detected by gripping the antenna of the detector  1400  with a hand. 
         [0107]      FIG. 15  illustrates a structure of a reflecting device embedded in a cover case of a mobile device according to an embodiment of the present disclosure. 
         [0108]    Referring to  FIG. 15 , the detector  1500  transmits detection signals of frequency f 0  through the transmission antenna  1505  and monitors whether distress signals of frequency  2   f   0  are detected through the reception antenna  1510 . 
         [0109]    The cover case  1520  of the mobile device has an input antenna  1525  in its front surface to receive signals of frequency f 0  and an output antenna  1530  in its back surface to transmit signals of frequency  2   f   0 . A reflecting circuit  1535  including a DC-biased diode is positioned between the input antenna  1525  and the output antenna  1530 . Accordingly, the use of the biased diode may lead to a reduction by about 12 dB in the conversion loss between detection signals and distress signals and an increase by about two times in the maximum detection distance as compared with that by the passive scheme. 
         [0110]      FIG. 16  is a flowchart illustrating a distress mode operation by a mobile device according to an embodiment of the present disclosure. 
         [0111]    Referring to  FIG. 16 , the mobile device connects an NFC antenna to an NFC chip in operation  1605 . Or, the mobile device connects a cellular antenna to an RF module. The mobile device determines whether distress has occurred in operation  1610 . As an example, when there is no movement (still state) for a predetermined time or more after detection of a sudden movement, the mobile device may determine that distress has taken place. As another example, when the still state is during an abnormal time period, the mobile device determines that distress has occurred. As still another example, when there is no response to incoming calls, the mobile device may determine that there is distress. 
         [0112]    When no distress is detected, the mobile device determines whether a user has requested distress mode in operation  1615 . 
         [0113]    After detecting distress on its own in operation  1610  or requested by the user to activate the distress mode in operation  1615 , the mobile device proceeds to operation  1620  to connect the NFC antenna to the distress signal transmitter instead of the NFC chip. The distress signal transmitter may comprise a variable power amplifier and a variable matching circuit. Or, the mobile device may connect the cellular antenna to the reflecting circuit comprising the Schottky diode, instead of to the RF module. Thereafter, the mobile device may transmit 457 kHz distress signals through the NFC antenna on its own or transmit distress signals of frequency  2   f   0  in response to detection signals of frequency f 0  received through the cellular antenna. 
         [0114]    The apparatuses and methods according to embodiments of the present disclosure may be implemented in hardware, software, or a combination of hardware and software. The software, which includes any executable code whether compiled or interpretable, may be stored in a machine or computer readable form in volatile or non-volatile storage devices such as, for example, various types of read-only memory (ROM), random access memory (RAM), memory chips, memory devices, or integrated circuit devices, as well as compact disks (CDs), DVDs, magnetic disks, magnetic tapes, or other optical or magnetic storage devices, including those that may be introduced in the future. 
         [0115]    The methods according to embodiments of the present disclosure may be implemented by a computer or a portable terminal including a controller and a memory, and the memory may be an exemplary machine or computer readable storage medium that may properly retain program(s) containing instructions for implementing the embodiments of the present disclosure. The software may be distributed over a network via wired or wireless methods, for example, by data transmission over the Internet, and accordingly, the software may be stored and executed in a distributed manner. Functional programs, codes, and code segments to attain various embodiments of the present disclosure may be readily interpreted by those of ordinary skill in the art to which the present disclosure pertains. 
         [0116]    The embodiments herein are provided merely for better understanding of the present disclosure, and the present disclosure should not be limited by these embodiments. The embodiments set forth herein are merely examples, and it will be apparent to one of ordinary skill in the art that various changes may be made thereto without departing from the scope of the present disclosure.