WO2016099300A1 - Methods and systems for augmented direct-mode detection of emergency signals and selective conveyance of emergency notifications - Google Patents

Abstract

Disclosed herein are methods and systems for augmented direct- mode detection of emergency signals and selective conveyance of emergency notifications. One embodiment takes the form of a process carried out by a mobile radio operating in a trunked mode with respect to a wireless network that includes a network base station, the process includes (i) monitoring a dedicated direct-mode emergency frequency (102), (ii) confirming each emergency-relay criterion in a set of one or more emergency-relay criteria, the set of emergency-relay criteria comprising detecting a signal having a predefined type of digital modulation on the direct-mode emergency frequency (104); and (iii) responsive to confirming each emergency- relay criterion in the set of one or more emergency-relay criteria, preparing an emergency-relay message (106) and transmitting the prepared emergency-relay message to the network base station (108). The base station can be a Tetra or PLMN (LTE, GSM etc.) base station.

Description

METHODS AND SYSTEMS FOR AUGMENTED DIRECT-MODE DETECTION OF EMERGENCY SIGNALS AND SELECTIVE CONVEYANCE OF EMERGENCY NOTIFICATIONS

BACKGROUND OF THE INVENTION

[0001] It is important for public-safety responders to be able to communicate with each other on a regular basis. As a result, one of the most commonly used tools in the public-safety context is a mobile radio. Some mobile radios communicate via cellular radio networks (operating in what is often termed a "trunked mode"), some communicate via ad-hoc device-to-device connections (as part of, e.g., an ad-hoc network of such connections) (operating in what is often termed a "direct mode").

[0002] Some mobile radios are equipped, programmed, and configured to be able to communicate in both trunked mode and direct mode, perhaps in addition to being able to communicate according to one or more other modes. Mobile radios may be incorporated into or with one or more other devices such as cell phones, smartphones, tablets, notebook computers, laptop computers, and the like. Moreover, some mobile radios are portable mobile radios that are referred to at times using terms such as handheld, handheld transceiver, walkie-talkie, two-way radio, and the like. As one example, some devices include the functionality of both a smartphone and a mobile radio. And certainly many other examples could be listed, as known to those having skill in the relevant art.

[0003] Public-safety portable radios have the ability to transmit emergency signals in the event that the public-safety responder is in distress. It is desirable for a public-safety responder to be able to communicate the emergency signal with as many allies as possible as efficiently as possible for at least the reason that the immediacy and efficacy with which public-safety responders can communicate with one another are quite often determinative with respect to how positive the ultimate outcome of a given incident can be. Accordingly, for these reasons and others, there is a need for methods and systems for augmented direct-mode detection of emergency signals and selective conveyance of emergency notifications. BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0004] The accompanying figures, where like reference numerals refer to identical or functionally similar elements throughout the separate views, together with the detailed description below, are incorporated in and form part of the specification, and serve to further illustrate embodiments of concepts that include the claimed invention, and explain various principles and advantages of those embodiments.

[0005] FIG. 1 depicts an example process, in accordance with an embodiment.

[0006] FIG. 2 depicts an example mobile radio, in accordance with an embodiment.

[0007] FIG. 3 depicts a first example scenario involving a plurality of mobile radios, in accordance with an embodiment.

[0008] FIG. 4 depicts a second example scenario involving a plurality of mobile radios, in accordance with an embodiment.

[0009] FIG. 5 depicts an example communication system, in accordance with an embodiment.

[0010] FIG. 6 depicts a further example of the communication system of FIG. 5, in accordance with an embodiment.

[0011] Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.

[0012] The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein. DETAILED DESCRIPTION OF THE INVENTION

[0013] Disclosed herein are methods and systems for augmented direct-mode detection of emergency signals and selective conveyance of emergency notifications. One embodiment takes the form of a process carried out by a mobile radio operating in a trunked mode with respect to a wireless network that includes a network base station, the process includes (i) monitoring a dedicated direct-mode emergency frequency, (ii) confirming each emergency-relay criterion in a set of one or more emergency-relay criteria, the set of emergency-relay criteria including detecting a signal having a predefined type of digital modulation on the direct-mode emergency frequency; and (iii) responsive to confirming each emergency-relay criterion in the set of one or more emergency-relay criteria, preparing an emergency-relay message and transmitting the prepared emergency-relay message to the network base station.

[0014] Another embodiment takes the form of a mobile radio operating in a trunked mode with respect to a wireless network that includes a network base station. The mobile radio includes a wireless-communication interface, a processor, and data storage containing instructions executable by the processor for causing the mobile radio to carry out at least the functions described in the preceding paragraph.

[0015] Moreover, any of the variations and permutations described in the ensuing paragraphs and anywhere else in this disclosure can be implemented with respect to any embodiments, including with respect to any method embodiments and with respect to any system (e.g., mobile radio) embodiments. Furthermore, this flexibility and cross-applicability of embodiments is present in spite of the use of slightly different language (e.g., process, method, steps, functions, set of functions, and the like) to describe and or characterize such embodiments.

[0016] In at least one embodiment, the mobile radio is configured to monitor the direct-mode emergency frequency at times when the mobile radio is idle on a multicast control channel (MCCH).

[0017] In at least one embodiment, monitoring the direct-mode emergency frequency includes periodically monitoring the direct-mode emergency frequency. In at least one such embodiment, periodically monitoring the direct-mode emergency frequency includes periodically tuning away from a given channel on which the mobile radio is idling in order to check the direct-mode emergency frequency. In at least one such embodiment, the given channel is an MCCH.

[0018] In at least one embodiment the set of emergency-relay criteria further includes determining that the detected signal is an emergency signal.

[0019] In at least one embodiment, the set of emergency-relay criteria further includes determining that the detected signal is an encrypted emergency signal. In at least one such embodiment, the set of emergency-relay criteria further includes attempting and failing to decode the encrypted emergency signal.

[0020] In at least one embodiment, the set of emergency-relay criteria further includes satisfaction of one or more preconfigured rules.

[0021] In at least one embodiment, the set of emergency-relay criteria further includes determining that the detected signal was transmitted by a mobile radio in a predetermined set of mobile radios.

[0022] In at least one embodiment, preparing the emergency-relay message includes determining a location of the mobile radio and including the determined location in the emergency-relay message.

[0023] In at least one embodiment, preparing the emergency-relay message includes measuring a received signal strength indicator (RSSI) of the detected signal and including the measured RSSI in the emergency-relay message.

[0024] In at least one embodiment, preparing the emergency-relay message includes obtaining additional information and including the additional information in the emergency-relay message. In at least one such embodiment, the additional information is selected from the group consisting of GPS coordinates, available hotspots, Wi-Fi networks, an identification of one or more nearby subscribers, and identification of one or more nearby radios, a current speed of the mobile radio, and a current speed of a mobile radio that transmitted the detected signal.

[0025] In at least one embodiment, the process further includes transmitting the prepared emergency-relay message to a second mobile radio.

[0026] In at least one embodiment, transmitting the prepared emergency-relay message to the network base station includes transmitting the prepared emergency- relay message to a second mobile radio for forwarding to the network base station. [0027] In at least one embodiment, the predefined type of digital modulation is a Tetra modulation.

[0028] In at least one embodiment, the mobile radio transmits the prepared emergency-relay message to the network base station according to a specific network protocol. In at least one such embodiment, the specific network protocol is selected from the group consisting of P25, Tetra, LTE, Bluetooth, and NFC.

[0029] Before proceeding with this detailed description, it is noted that the entities, connections, arrangements, and the like that are depicted in— and described in connection with— the various figures are presented by way of example and not by way of limitation. As such, any and all statements or other indications as to what a particular figure "depicts," what a particular element or entity in a particular figure "is" or "has," and any and all similar statements— that may in isolation and out of context be read as absolute and therefore limiting— can only properly be read as being constructively preceded by a clause such as "In at least one embodiment,...." And it is for reasons akin to brevity and clarity of presentation that this implied leading clause is not repeated ad nauseum in this detailed description.

[0030] FIG. 1 depicts an example process, in accordance with an embodiment. In particular, FIG. 1 depicts a process 100 that in at least one embodiment is carried out by a mobile radio operating in a trunked mode with respect to a wireless network. The description of the process 100 as being carried out by a mobile radio is provided by way of example, as other suitably equipped and programmed devices could carry out the process 100.

[0031] At step 102, the mobile radio monitors a dedicated direct-mode emergency frequency. In at least one embodiment, the dedicated emergency frequency is a radio frequency, or channel, that is reserved for the use of reporting emergency situations. Example dedicated emergency frequencies include frequencies selected by police forces, or fire departments, or other government agencies, frequencies reserved for international aeronautical or nautical emergencies, and/or any other frequency used as a dedicated emergency frequency.

[0032] In some embodiments, the mobile radio is configured to monitor the dedicated direct-mode emergency frequency at times when the mobile radio is idle on an MCCH (as an example). It may be the case that mobile radios that are active on the MCCH (or on a channel other than the MCCH, as the MCCH is an example) are unable to detect a direct-mode emergency signal. An example MCCH is a control channel that carries information needed for multicast reception, as known by those with skill in the relevant art.

[0033] In some embodiments, monitoring the dedicated direct-mode emergency frequency includes periodically monitoring the dedicated direct-mode emergency frequency. Periodic monitoring of the dedicated direct-mode emergency frequency permits the mobile radio to perform other functions. As an example of periodically monitoring the dedicated direct-mode emergency frequency, the mobile radio may periodically tune away from a given channel on which the mobile radio is idling in order to check the dedicated direct-mode emergency frequency. In some embodiments, the given channel is an MCCH.

[0034] At step 104, the mobile radio confirms each emergency-relay criterion in a set of one or more emergency-relay criteria. The set of emergency-relay criteria includes detecting a signal— having a predefined type of digital modulation— on the direct-mode emergency frequency. In at least one embodiment, that criterion (i.e., the detection of the predefined type of digital modulation on a dedicated direct-mode emergency frequency) is the only emergency-relay criterion in the set of emergency- relay criteria. That is, in at least one embodiment, satisfaction of that criterion is both necessary and sufficient to trigger the mobile radio to carry out the below-described steps 106 and 108 of the example process 100.

[0035] As described throughout this disclosure, in at least one embodiment, the set of emergency-relay criteria further includes one or more additional emergency- relay criteria.

[0036] In some embodiments, the set of emergency-relay criteria includes the mobile radio determining that the detected signal is an emergency signal. The emergency signal may be sent from a mobile radio or another similar device.

[0037] In some embodiments, the set of emergency-relay criteria includes the mobile radio determining that the detected signal is an encrypted emergency signal. The contents of the encrypted emergency signal cannot be determined without properly decrypting the message, as known by those with skill in the relevant art. In some such embodiments, the set of emergency-relay criteria further includes attempting and failing to decode (i.e., decrypt) the encrypted emergency signal. Although the contents of the encrypted emergency signal are not known in such a scenario, the presence of the encrypted emergency signal being transmitted on the dedicated direct-mode emergency frequency can still indicate an emergency situation. A mobile radio may fail to decode the encrypted emergency signal for a variety of reasons. Some example reasons for failing to decode the encrypted emergency signal include: incorrect encryption/decryption information, mobile radios belonging to different public-safety organizations, poor radio-frequency (RF) conditions (e.g., long transmission distances, indoor locations, interference, high speeds, etc.), only a partial emergency signal being received due to periodic scanning, and/or any other reason for failing to decode an encrypted signal as known by those with skill in the relevant art.

[0038] In some embodiments, the set of emergency-relay criteria includes satisfaction of one or more preconfigured rules. In such embodiments, the preconfigured rules act as a filter, preventing the mobile radio from considering the full set of emergency-relay criteria to be satisfied for each detected signal having the predefined type of digital modulation. Example preconfigured rules include verifying that the received signal was from a close location, perhaps as determined by RSSI and/or GPS, the received signal is from an appropriate group of subscribers, the contents of the message include a keep-alive/heartbeat message, or any other preconfigured rule as deemed suitable by those with skill in the relevant art.

[0039] In some embodiments, the set of emergency-relay criteria includes determining that the detected signal was transmitted by a mobile radio in a predetermined set of mobile radios. This predetermined set could correspond to any particular list or set of mobile radios, one or more talkgroups, and/or any other list or set of mobile radios.

[0040] In some embodiments, the predefined type of digital modulation is a Tetra modulation, though certainly the present methods and systems could be implemented with respect to any suitable type of digital modulation deemed suitable by those having skill in the relevant art for a given context or in a given implementation.

[0041] At step 106, the mobile radio, responsive to confirming each emergency- relay criterion in the set of one or more emergency-relay criteria, prepares an emergency-relay message. In some embodiments, preparing the emergency-relay message includes determining a location of the mobile radio (using, e.g., GPS) and including the determined location in the emergency-relay message.

[0042] In some embodiments, preparing the emergency-relay message includes measuring an RSSI of the detected signal and including the measured RSSI in the emergency-relay message. Among other data, the measured RSSI indicates the relative proximity of the mobile radio sending the emergency signal to the mobile radio receiving the emergency signal.

[0043] In some embodiments, preparing the emergency-relay message includes obtaining additional information and including the additional information in the emergency-relay message. In some such embodiments, the additional information is selected from the group consisting of GPS coordinates, available hotspots, Wi-Fi networks, an identification of one or more nearby subscribers, an identification of one or more nearby mobile radios, a current speed of the mobile radio, and a current speed of a mobile radio that transmitted the detected signal. And certainly one or more other types of additional information could be obtained and included in the emergency- relay message. The additional information that the mobile radio obtains and includes in the emergency-relay message may assist recipients of the emergency-relay message in better identifying the precise location and the extent of the emergency, among many other possible aspects. Moreover, in at least one embodiment, multiple mobile radios carry out the present methods and systems, facilitating triangulation of location of a distressed user, among other advantages of having richer information about a given emergency. As one non-limiting example, such additional information may indicate the number and various identities of the emergency-response personnel associated with a given emergency (or with a given emergency distress signal).

[0044] At step 108, the mobile radio transmits the prepared emergency-relay message to the network base station. In some embodiments, the mobile radio transmits the prepared emergency-relay message to the network base station according to a specific network protocol. In at least one embodiment, the specific network protocol is selected from the group consisting of P25, Tetra, LTE, Bluetooth, and NFC, though any suitable network protocol may be selected in a given context or for a given implementation by those with skill in the relevant art. [0045] FIG. 2 depicts an example mobile radio, in accordance with an embodiment. In particular, FIG. 2 depicts an example mobile radio 200 as including a communication interface 202, a transmitter 204, a receiver 206, a channel list 208, an emergency frequency 210, a channel 212, a channel 214, a processor 216, a data storage 218, program instructions 220, operational data 222, and a user interface 224, all of which are communicatively coupled with one another via a system bus 226 (or other suitable communication connection, network, or the like). The example mobile radio 200 can be used to carry out and embody the present methods and systems. By way of example explanation, the below discussion of FIG. 2 includes examples of the example mobile radio 200 performing various aspects of the example process 100 of FIG. 1.

[0046] In the depicted example, the communication interface 202 includes the transmitter 204 and the receiver 206. The transmitter 204 can be configured to transmit on one of a set of channels. The receiver 206 can be configured (e.g., tuned) to receive on one of a set of channels. The communication interface 202 may be configured to be operable for communicating according to one or more wireless- communication protocols, some examples of which include RF, LTE, APCO P25, ETSI DMR, TETRA, Wi-Fi, Bluetooth, and the like. The communication interface 202 may also include one or more wired-communication interfaces (for communicating according to, e.g., Ethernet, USB, and/or one or more other protocols). As such, the communication interface 202 may include any necessary hardware (e.g., chipsets, antennas, Ethernet cards, etc.), any necessary firmware, and any necessary software for conducting one or more forms of communication with one or more other entities as described herein.

[0047] In the depicted example, the preconfigured channel list 208 contains the emergency frequency 210, the channel 212, and the channel 214. In at least one embodiment, the emergency frequency 210 is a dedicated direct-mode emergency channel. In performing step 102 of Fig. 1, the mobile radio 200 tunes the receiver 206 to monitor the emergency frequency 210. In at least one embodiment, multiple dedicated direct-mode emergency frequencies are allocated in a given geographical area; in such embodiments, multiple dedicated direct-mode emergency frequencies may be stored in the preconfigured channel list 208, and the mobile radio 200 may monitor those multiple frequencies in the manner generally described herein with respect to the example emergency frequency 210.

[0048] In some embodiments, the channel 212 is an MCCH. In some embodiments, the channel 214 is a voice channel, a data channel, a list of channels, or may be omitted from the mobile radio 200. And certainly the channel list 208 may take other forms, have different contents, be stored in the data storage 218, and/or take on one or more other forms as deemed suitable by those having skill in the relevant art for a given implementation. In at least one embodiment, in performing step 102 of FIG. 1, the mobile radio 200 periodically monitors the emergency frequency 210 when idle on the MCCH (i.e., channel 212 in some embodiments).

[0049] The processor 216 may include one or more processors of any type deemed suitable by those of skill in the relevant art, some examples including a general-purpose microprocessor and a dedicated digital signal processor (DSP).

[0050] The data storage 218 may take the form of any non-transitory computer- readable medium or combination of such media, some examples including flash memory, read-only memory (ROM), and random-access memory (RAM) to name but a few, as any one or more types of non-transitory data-storage technology deemed suitable by those of skill in the relevant art could be used. As depicted in FIG. 2, the data storage 218 contains program instructions 220 executable by the processor 216 for carrying out various functions described herein, and further is depicted as containing operational data 222, which may include any one or more data values stored by and/or accessed by the example mobile radio 200 in carrying out one or more of the functions described herein, such as the example process 100 of FIG. 1.

[0051] The user interface 224 may include one or more input devices (a.k.a. components and the like) and/or one or more output devices (a.k.a. components and the like). With respect to input devices, the user interface 224 may include one or more touchscreens, buttons, switches, microphones, and the like. With respect to output devices, the user interface 224 may include one or more displays, speakers, light emitting diodes (LEDs), and the like. Moreover, one or more components (e.g., an interactive touchscreen and display) of the user interface 224 could provide both user-input and user-output functionality. And other user- interface components (e.g., a PTT button) could be present, as known to those of skill in the art. In some embodiments, the mobile radio 200 does not include a user interface.

[0052] FIG. 3 depicts a first example scenario involving a plurality of mobile radios, in accordance with an embodiment. In particular, the FIG. 3 depicts the example scenario 300. The example scenario 300 includes the mobile radio 200 (the example mobile radio 200 of FIG. 2), a mobile radio 302, a base station 304, a mobile radio 306, an emergency signal 308, and an emergency-relay message 310. The mobile radios 302 and 306 may be similar to the mobile radio 200 and may be (though need not be) configured to carry out and embody the methods and systems of this disclosure.

[0053] In the example scenario 300, the mobile radio 302 transmits a radio signal 308. The radio signal 308 is of a predefined type of digital modulation and is transmitted via the direct-mode emergency frequency. In some embodiments, the predefined type of digital modulation is a Tetra modulation. In some embodiments, the radio signal 308 is an emergency signal. The emergency signal may include predetermined message headers that identify the radio signal as an emergency signal.

[0054] In the example scenario 300, the mobile radio 200 performs the example process 100 of FIG. 1. At step 102, the mobile radio 200 monitors the emergency frequency. At step 104, the mobile radio 200 detects the radio signal 308, which is of a predefined type of digital modulation, on the direct-mode emergency frequency. At step 106, the mobile radio 200 prepares an emergency-relay signal responsive to detecting the radio signal 308. At step 108, the mobile radio 200 transmits the emergency-relay message 310 to the base station 304. In the example scenario 300, neither the base station 304 nor the mobile radio 306 detected the radio signal 308.

[0055] FIG. 4 depicts a second example scenario involving a plurality of mobile radios, in accordance with an embodiment. In particular, FIG. 4 depicts the example scenario 400. The example scenario 400 includes the mobile radio 200 (the example mobile radio 200 of FIG. 2)), a mobile radio 402, a base station 404, a mobile radio 406, an emergency signal 408, an emergency-relay message 410, and a forwarded emergency-relay message 412. [0056] In the example scenario 400, the mobile radio 402 transmits the radio signal 408. The radio signal 408 is of a predefined type of digital modulation and is transmitted via the direct-mode emergency frequency.

[0057] In the example scenario 400, the mobile radio 200 performs the example process 100 of FIG. 1. At step 102, the mobile radio 200 monitors the emergency frequency. At step 104, the mobile radio 200 detects the radio signal 408, which is of a predefined type of digital modulation, on the direct-mode emergency frequency. At step 106, the mobile radio 200 prepares an emergency-relay signal responsive to detecting the radio signal 408. At step 108, the mobile radio 200 transmits the emergency-relay message 410 to the mobile radio 406. The mobile radio 406 transmits the forwarded emergency-relay message 412 to the base station 404. In the example scenario 400, neither the base station 404 nor the mobile radio 406 detected the radio signal 408.

[0058] The next part of this disclosure includes descriptions of FIG. 5 and FIG. 6, which provide an example context in which the present methods and systems can be carried out and embodied. In FIG. 3, above, it can be seen that the mobile radio 200 is operating at times in direct mode (e.g., when detecting the radio signal 308) and at times in trunked mode (e.g., when transmitting the emergency-relay message 310 to the base station 304). Moreover, in FIG. 4 above, it can be seen that the mobile radio operates in direct mode (e.g., when detecting the radio signal 408 and when transmitting the emergency-relay message 410 to the mobile radio 406), and it can also be seen that the mobile radio 406 operates at times in direct mode (e.g., when receiving the emergency-relay message 410 from the mobile radio 200) and times in trunked mode (e.g., when transmitting the forwarded emergency-relay message 412 to the base station 404). Thus, it is clear that the present methods and systems can be carried out by mobile radios that can operate in direct mode, and also by mobile radios that can operate in both direct mode and trunked mode. FIGs. 5 and 6, together with the below descriptions thereof, provide some general description of mobile devices operating in trunked mode (i.e., communicating via one or more radio access networks (RANs).

[0059] FIG. 5 depicts an example communication system, in accordance with an embodiment. In particular, FIG. 5 depicts an example communication system 500 that includes one or more commercial RANs 502, a public-safety RAN 504, a data network 506, a circuit network 508, wireless-communication devices (WCDs) (e.g., mobile radios) 510, and communication links 512-526. An example commercial RAN 502 is discussed below in connection with FIG. 6, though in general, each RAN 502 and the RAN 504 may include typical RAN elements such as base stations, base station controllers (BSCs), routers, switches, and the like, arranged, connected, and programmed to provide wireless service to user equipment (e.g., the WCDs 510) in a manner known to those of skill in the relevant art.

[0060] The public-safety RAN 504 may include one or more packet-switched networks and/or one or more circuit-switched networks, and in general functions to provide one or more public-safety agencies with any necessary computing and communication needs. Thus, the public-safety RAN 504 may include a dispatch center communicatively connected with the data network 506 and also with the circuit network 508, for retrieving and transmitting any necessary public-safety-related data and communications. The public-safety RAN 504 may also include any necessary computing, data-storage, and data-presentation resources utilized by public-safety personnel in carrying out their public-safety functions. Moreover, the public-safety RAN 504 may include one or more network access servers (NASs), gateways, and the like for bridging communications to one or more other entities and/or networks, such as the commercial RANs 502, the data network 506, and the circuit network 508, as representative examples.

[0061] The data network 506 may be, include, or be a part of the global network of networks typically referred to as the Internet. The data network 506 may be a packet-switched network, and entities (i.e., servers, routers, computers, and the like) that communicate over the data network 506 may be identified by a network address such as an Internet Protocol (IP) address. Moreover, the data network 506 may include one or more NASs, gateways, and the like for bridging communications to one or more other entities and/or networks, such as the commercial RANs 502, the public-safety RAN 504, and the circuit network 508, as representative examples.

[0062] The circuit network 508 may be, include, or be a part of the circuit- switched telephone network commonly referred to as the public switched telephone network (PSTN), and in general functions to provide circuit-switched communications to various communication entities as is known in the art. Moreover, the circuit network 508 may include one or more NASs, gateways, and the like for bridging communications to one or more other entities and/or networks, such as the commercial RANs 502, the public-safety RAN 504, and the data network 506, as representative examples.

[0063] The depicted example communication system 500 includes communication links 512-526, any one or more of which could include one or more wireless-communication links and/or one or more wired-communication links. In FIG. 6, the communication links 512 and 514 are depicted with respective lightning- bolt graphics; while this graphic typically denotes wireless communication, and does in this example as well, this is not to the exclusion of one or more of the other communication links 514-526 being or at least including wireless-communication links as well.

[0064] As can be seen in FIG. 5, the communication link 512 (as mentioned above) connects the commercial RANs 502 and the WCDs 510, the communication link 514 (as mentioned above) connects the public-safety RAN 504 and the WCDs 510, the communication link 516 connects the commercial RANs 502 and the public- safety RAN 504, the communication link 518 connects the commercial RANs 502 and the data network 506, the communication link 520 connects the commercial RANs 502 and the circuit network 508, the communication link 522 connects the public-safety RAN 504 and the data network 506, the communication link 524 connects the data network 506 and the circuit network 508, and the communication link 526 connects the public-safety RAN 504 and the circuit network 508. This arrangement is provided purely by way of example, as other arrangements could be implemented by those of skill in the relevant art in various different contexts.

[0065] The WCDs 510 may be any suitable computing and communication devices configured to engage in wireless communication with one or both of (i) the commercial RANs 502 over the air interface 512 as is known to those in the relevant art and (ii) the public-safety RAN 504 over the air interface 514 as is known to those in the relevant art. Some example WCDs 510 and communication links 512 are discussed below in connection with the various figures. [0066] FIG. 6 depicts a further example of the communication system of FIG. 5, in accordance with an embodiment. FIG. 6 depicts the communication system 500 of FIG. 5, though in more detail regarding some example WCDs 510, the mobile radio 200, and an example commercial RAN 502, although a similar figure could be depicted with the sole change being the use of an example public-safety RAN 504 instead of the example commercial RAN 502. In particular, FIG. 6 depicts the RAN 502 as including an eNodeB 602, which communicates directly or indirectly with an evolved packet core (EPC) 604 over a communication link 606. As is the case with each of the links mentioned above, and as is the case with any of the links mentioned anywhere else in this disclosure, the communication link 606 may be or include one or more wireless-communication links and/or one or more wired-communication links, as deemed suitable by those of skill in the relevant art in a given context.

[0067] In at least one embodiment, the eNodeB 602 includes the hardware and software (and/or firmware) necessary for the eNodeB 602 to function as an eNodeB, a NodeB, a base station, a base transceiver station (BTS), a Wi-Fi access point, and/or the like, as known to those having skill in the relevant art. In some instances, the eNodeB 602 in the example RAN 502 may also include functionality typically associated in the art with entities that are often referred to by terms such as BSCs, radio network controllers (RNCs), and the like. Also, while one eNodeB 602 is depicted by way of example in FIG. 6, any suitable number of eNodeBs could be deployed as deemed suitable by those of skill in the relevant art.

[0068] In general, the eNodeB 602 is an entity that, on one side (i.e., the wireless- network side (interface)), engages in wireless communication over the air interface 512 with one or more WCDs 510 (and the mobile radio 200, which is another example of a WCD) according to a protocol such as LTE or the like and, on the other side (i.e., the "backhaul" side), engages in communications with the EPC 604 via the communication link 606, to facilitate communications between various WCDs 510 (and the mobile radio 200) and networks such as the networks 504, 506, and 508.

[0069] In at least one embodiment, the mobile radio 200 transmits an emergency- relay message (e.g., the emergency-relay message 310) via the communication link 512 to a commercial RAN 502 (or via the communication link 514 to the public- safety RAN 504). In at least one embodiment, the mobile radio 200 transmits an emergency-relay message (e.g., the emergency-relay message 408) to any of the WCDs 510 for forwarding (via the communication link (i.e., air interface) 512) to a commercial RAN 502 (or via the communication link (i.e., air interface) 514 to the public-safety RAN 504).

[0070] The EPC 604 may include one or more network entities such as one or more mobility management entities (MMEs), one or more serving gateways (SGWs), one or more packet data network (PDN) gateways (PGWs), one or more evolved packet data gateways (ePDGs), one or more home subscriber servers (HSSs), one or more access network discovery and selection functions (ANDSFs), and/or one or more other entities deemed suitable for a given implementation by those of skill in the relevant art. Moreover, these entities may be configured and interconnected in a manner known to those of skill in the relevant art to provide wireless service to the WCDs 510 (and the mobile radio 200) via the eNodeB 602, and to bridge such wireless service with various transport networks. In general, a commercial RAN and a public-safely RAN may each provide wireless service according to a protocol such as LTE, Wi-Fi, and/or the like. These examples are provided for illustration and not by way of limitation; moreover, those of skill in the relevant art are aware of variations among different protocols and among different implementations of a given protocol, and of similarities across different protocols.

[0071] In the foregoing specification, specific embodiments have been described. However, one of ordinary skill in the art appreciates that various modifications and changes can be made without departing from the scope of the invention as set forth in the claims below. Accordingly, the specification and figures are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of present teachings.

[0072] The benefits, advantages, solutions to problems, and any element(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential features or elements of any or all the claims. The invention is defined solely by the appended claims including any amendments made during the pendency of this application and all equivalents of those claims as issued. [0073] Moreover in this document, relational terms such as first and second, top and bottom, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. The terms "comprises," "comprising," "has," "having," "includes," "including," "contains," "containing," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises, has, includes, contains a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element preceded by "comprises... a," "has... a," "includes... a," "contains... a" does not, without more constraints, preclude the existence of additional identical elements in the process, method, article, or apparatus that comprises, has, includes, contains the element. The terms "a" and "an" are defined as one or more unless explicitly stated otherwise herein. The terms "substantially," "essentially," "approximately," "about," or any other version thereof, are defined as being close to as understood by one of ordinary skill in the art, and in one non-limiting embodiment the term is defined to be within 10%, in another embodiment within 5%, in another embodiment within 1% and in another embodiment within 0.5%. The term "coupled" as used herein is defined as connected, although not necessarily directly and not necessarily mechanically. A device or structure that is "configured" in a certain way is configured in at least that way, but may also be configured in ways that are not listed.

[0074] It will be appreciated that some embodiments may be comprised of one or more generic or specialized processors (or "processing devices") such as microprocessors, digital signal processors, customized processors and field programmable gate arrays (FPGAs) and unique stored program instructions (including both software and firmware) that control the one or more processors to implement, in conjunction with certain non-processor circuits, some, most, or all of the functions of the method and/or apparatus described herein. Alternatively, some or all functions could be implemented by a state machine that has no stored program instructions, or in one or more application specific integrated circuits (ASICs), in which each function or some combinations of certain of the functions are implemented as custom logic. Of course, a combination of the two approaches could be used. [0075] Moreover, an embodiment can be implemented as a computer-readable storage medium having computer readable code stored thereon for programming a computer (e.g., comprising a processor) to perform a method as described and claimed herein. Examples of such computer-readable storage mediums include, but are not limited to, a hard disk, a CD-ROM, an optical storage device, a magnetic storage device, a ROM (Read Only Memory), a PROM (Programmable Read Only Memory), an EPROM (Erasable Programmable Read Only Memory), an EEPROM (Electrically Erasable Programmable Read Only Memory) and a Flash memory. Further, it is expected that one of ordinary skill, notwithstanding possibly significant effort and many design choices motivated by, for example, available time, current technology, and economic considerations, when guided by the concepts and principles disclosed herein will be readily capable of generating such software instructions and programs and ICs with minimal experimentation.

[0076] The Abstract of the Disclosure is provided to allow the reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. In addition in the foregoing Detailed Description, it can be seen that various features are grouped together in various embodiments for the purpose of streamlining the disclosure. This method of disclosure is not to be interpreted as reflecting an intention that the claimed embodiments require more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive subject matter lies in less than all features of a single disclosed embodiment. Thus the following claims are hereby incorporated into the Detailed Description, with each claim standing on its own as a separately claimed subject matter.

Claims

1. A method carried out by a mobile radio operating in a trunked mode with respect to a wireless network that includes a network base station, the method comprising:

monitoring a dedicated direct-mode emergency frequency;

confirming each emergency-relay criterion in a set of one or more emergency- relay criteria, the set of emergency-relay criteria comprising detecting a signal having a predefined type of digital modulation on the direct-mode emergency frequency; and responsive to confirming each emergency-relay criterion in the set of one or more emergency-relay criteria, preparing an emergency-relay message and transmitting the prepared emergency-relay message to the network base station.

2. The method of claim 1, wherein the mobile radio is configured to monitor the direct-mode emergency frequency at times when the mobile radio is idle on a multicast control channel (MCCH).

3. The method of claim 1, wherein monitoring the direct-mode emergency frequency comprises periodically monitoring the direct-mode emergency frequency.

4. The method of claim 3, wherein periodically monitoring the direct- mode emergency frequency comprises periodically tuning away from a given channel on which the mobile radio is idling in order to check the direct-mode emergency frequency.

5. The method of claim 4, wherein the given channel is a multicast control channel (MCCH).

6. The method of claim 1, wherein the set of emergency-relay criteria further comprises determining that the detected signal is an emergency signal.

7. The method of claim 1, wherein the set of emergency-relay criteria further comprises determining that the detected signal is an encrypted emergency signal.

8. The method of claim 7, wherein the set of emergency- relay criteria further comprises attempting and failing to decode the encrypted emergency signal.

9. The method of claim 1, wherein the set of emergency-relay criteria further comprises satisfaction of one or more preconfigured rules.

10. The method of claim 1 , wherein the set of emergency-relay criteria further comprises determining that the detected signal was transmitted by a mobile radio in a predetermined set of mobile radios.

11. The method of claim 1, wherein preparing the emergency-relay message comprises determining a location of the mobile radio and including the determined location in the emergency-relay message.

12. The method of claim 1, wherein preparing the emergency-relay message comprises measuring a received signal strength indicator (RSSI) of the detected signal and including the measured RSSI in the emergency-relay message.

13. The method of claim 1, wherein preparing the emergency-relay message comprises obtaining additional information and including the additional information in the emergency-relay message.

14. The method of claim 13, wherein the additional information is selected from the group consisting of GPS coordinates, available hotspots, Wi-Fi networks, an identification of one or more nearby subscribers, an identification of one or more nearby mobile radios, a current speed of the mobile radio, and a current speed of a mobile radio that transmitted the detected signal.

15. The method of claim 1, wherein transmitting the prepared emergency- relay message to the network base station comprises transmitting the prepared emergency-relay message to a second mobile radio for forwarding to the network base station.

16. The method of claim 1, further comprising transmitting the prepared emergency-relay message to a second mobile radio.

17. The method of claim 1, wherein the predefined type of digital modulation is a Tetra modulation.

18. The method of claim 1, wherein the mobile radio transmits the prepared emergency-relay message to the network base station according to a specific network protocol.

19. The method of claim 18, wherein the specific network protocol is selected from the group consisting of P25, Tetra, LTE, Bluetooth, and NFC.

20. A mobile radio operating in a trunked mode with respect to a wireless network that includes a network base station, the mobile radio comprising:

a wireless-communication interface;

a processor; and

data storage containing program instructions executable by the processor for causing the mobile radio to carry out a set of functions, the set of functions comprising:

monitoring a dedicated direct-mode emergency frequency; confirming each emergency-relay criterion in a set of one or more emergency-relay criteria, the set of emergency-relay criteria comprising detecting a signal having a predefined type of digital modulation on the direct- mode emergency frequency; and

responsive to confirming each emergency-relay criterion in the set of one or more emergency-relay criteria, preparing an emergency-relay message and transmitting the prepared emergency-relay message to the network base station.