Abstract:
Each of a number of gateway network radios operates with a transmission protocol of an associated one of plural incompatible communication networks. Each network radio has an audio terminal for producing first audio signals detected from transmissions of user radios in its associated network, and a microphone terminal for receiving second audio signals for transmission to the user radios. A voice bridging gateway server has multiple ports each corresponding to one of the networks for coupling to the network radio associated with the one network. Each port receives the first audio signals from the audio terminal of the associated network radio, and produces the second audio signals for applying to the microphone terminal of the network radio. The server implements a private branch exchange application whereby user radios in a given communication network can be voice bridged with user radios in a selected one or more of the other networks.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority under 35 U.S.C. Sec. 119(e) of U.S. Provisional Patent Application No. 61/326,926 filed Apr. 22, 2010, and titled Method and Apparatus to Provide a Situational Awareness Integrated Network Technologies (SAINT) System; and No. 61/326,932 also filed Apr. 22, 2010, and titled Method and Apparatus for a Voice Bridge Gateway (VBG). The two mentioned patent applications are incorporated herein by reference in their entireties. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to communications systems, and particularly to a method and system for bridging voice communications. 
     2. Discussion of the Known Art 
     Many wireless voice radios and devices are unable to link with one another because of different network frequency allocations and transmission protocols, end usage, proprietary technology, and/or limitations of currently available connectivity solutions. The use of incompatible voice communication radios by first responders including fire, police and rescue personnel at an incident can cause serious problems if all responders and their lines of command are not frequently updated because of their inability to communicate with one another in real time. 
     A system known as First InterComm offered by BAE Systems enables responders whose radios operate on different frequencies and use different transmission protocols, to communicate with one another by using their existing radios and a separate module mounted in each responder&#39;s vehicle. When installed, the module operates to create a temporary digital mesh network that includes the vehicle in which it is mounted, and all other vehicles equipped with the module in the vicinity of the incident. Each module monitors both the mesh network and the radio channel normally used by the responder in whose vehicle the module is installed. 
     When a responder originates a voice message using his or her radio, the module detects the corresponding voice signal, converts it to a digital format, and relays the message digitally across the mesh network. The modules in the other responders&#39; vehicles re-convert the digital message into an analog voice signal, and transmit the voice signal on the same RF channels and with the same modulation protocols used by each of the other responders&#39; radios. The other responders can therefore hear the original voice message over their own radios with little if any time delay. See, U.S. Pat. No. 7,508,840 (Mar. 24, 2009), U.S. Pat. Application Pub. 2009/0174547 (Jul. 9, 2009), and U.S. Pat. Application Pub. 2009/0207852 (Aug. 20, 2009). 
     Notwithstanding the known art, a need continues for a system and technique for bridging voice communications among users of disparate voice communication radios that are located or may travel far away from one another, particularly during the course of military and tactical missions in potentially hostile environments. 
     SUMMARY OF THE INVENTION 
     According to the invention, a method and system for voice bridging user radios in multiple radio communication networks each of which operates according to a different radio transmission protocol that is incompatible with the protocols of the other networks, includes providing a number of gateway network radios each configured to operate according to a transmission protocol of an associated one of two or more radio communication networks whose transmission protocols are not compatible. An audio terminal of each gateway network radio produces first voice or audio signals when detected by the network radio from radio transmissions of user radios in the communication network associated with the network radio, and a microphone terminal of each network radio receives second voice or audio signals for transmission by the network radio to the user radios in the communication network associated with the network radio. 
     A voice bridging gateway (VBG) server is provided with a number of server ports each of which corresponds to one of the radio communication networks and is configured for coupling to a gateway network radio associated with the corresponding communication network. Each server port is operative for (a) receiving first signals corresponding to the first voice or audio signals produced from the audio terminal of the associated network radio, and (b) producing second signals corresponding to the second voice or audio signals for applying to the microphone terminal of the associated network radio. 
     The VBG server is configured to implement a private branch exchange (PBX) application for voice bridging user radios in a given one of the communication networks, with the user radios in a selected one or more of the other communication networks in response to a corresponding configuration command identifying the communication networks to be bridged, by (a) switching the first voice or audio signals received at the server ports coupled to the gateway network radios associated with the other selected communication networks, if any, to the server port corresponding to the given communication network for applying as the second signals to the microphone terminal of the corresponding network radio, thus allowing user radios in the given communication network to receive and detect the first voice or audio signals originating from the user radios in the other selected networks, and (b) switching the first voice or audio signals received at the server port coupled to the gateway network radio associated with the given communication network, to the server ports corresponding to the other selected communication networks, if any, for applying as the second signals to the microphone terminals of the network radios associated with the other selected communication networks, thus allowing user radios in the other selected communication networks to receive and detect the first voice or audio signals originating from the user radios in the given communication network. 
     For a better understanding of the invention, reference is made to the following description taken in conjunction with the accompanying drawing and the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       In the drawing: 
         FIG. 1  is a graphic representation of a tactical communications system wherein situational awareness (SA) information from multiple sources is distributed to soldiers equipped with conventional wireless devices; 
         FIG. 2  is a block diagram illustrating an embodiment of the inventive voice bride gateway (VBG); 
         FIG. 3  is a block diagram of an architecture for the VBG; 
         FIG. 4  is a schematic diagram of a first embodiment of a USB radio adapter (URA) and an associated cable according to the invention; 
         FIG. 5  is a schematic diagram of a second embodiment of a URA and an associated cable according to the invention; 
         FIG. 6  shows a panel of a VBG server including a number of USB ports and a telephone communication cable connector; 
         FIG. 7  is a table defining different bridging configurations that the VBG can implement for four radio networks according to the invention; 
         FIG. 8  shows the four radio networks in an independent or unbridged configuration; and 
         FIG. 9  shows two of the networks in  FIG. 8  bridged with one another according to the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A tactical gateway product suite developed by BAE Systems and called Situational Awareness Integrated Network Technologies or SAINT, extends the common operating picture (COP) to the tactical edge by distributing geospatially relevant information among various participants on a given mission. SAINT leverages commercial technology and networks to provide a warfighter with on-demand location based services. Its capabilities include wireless communications using commercial off the shelf (COTS) fixed/mobile base stations, IEEE 802.11 wireless access and GFE tactical radios; geo-referenced blue force tracking, targeting, and imaging (still and video); and gateway functionality among commercial networks including MOTOTRBO, Garmin radios, SOF, and Army networks such as Land Warrior, Raptor X (SOF GIS), PRC-117G, SINCGARS, and FBCB2. The geo-referenced information may be imported from outside sources such as Land Warrior, shared by a community of local users, and exported to outside consumers of interest such as FBCB2 or CPOF. 
     The SAINT suite includes an application package that operates on COTS handheld hardware including smart phones, cell phones, rugged PDAs, and UMPCs that can be easily carried by soldiers on the ground and which use commercial cellular and/or IEEE 802.11 access protocols. SAINT also allows voice interoperability between mobile phones and tactical PTT radios (e.g., ATT Tilt to PRC-117G), as well as message or data interoperability across heterogeneous networks (e.g., JVMF to CoT). 
       FIG. 1  illustrates the use of SAINT to provide secure location based services at low cost to tactical users, including individual dismounted soldiers carrying COTS cellular telephone or other standard handheld wireless communication devices. SAINT offers self protection by informing each warfighter of where are my buddies and where are the hostiles, providing a secure geo-referenced tactical map with points of interest (POIs) and other imagery, allowing push to talk communications over cellular networks with tactical radios such as SINCGARS, and providing interoperablity with various databases and Command and Control (C2) applications (e.g., Land Warrior and FBCB2). 
     The geo-referenced map may feature thumb friendly pop-up menus that allow the user to (a) add, modify, or attach comments or media files to POIs, (b) find, follow, and connect quickly to buddies, (c) access geo-referenced information such as pictures, and (d) obtain bearing and distance information to POIs. Buddy lists can provide status information and a quick interface for finding and collaborating with other users. SAINT also allows for group or individual text chat with visual indications to confirm delivery. 
     As mentioned, in addition to creating a tactical message gateway for interoperability with legacy situational awareness (SA) and command and control systems, the SAINT suite provides for voice bridging among non-compatible voice communication systems. The voice bridging feature, referred to herein as a Voice Bridge Gateway or VBG, is the subject of the present patent application and is described in further detail below. 
       FIG. 2  is a block diagram depicting the operation of the VBG  10  to enable voice interoperability between disparate voice technologies, for example, SINCGARS to PRC-117G, and Thuraya Satellite Phone to VoIP, according to the invention. The VBG  10  combines various COTS products and available software in such a manner as to provide the warfighter with a variety of communication options. The VBG creates a network in which voice or audio signals transmitted over radio frequency (RF) channels from legacy and commercial radios, and VoIP soft phones, may be distributed selectively among all the connected radios and phones. To carry out such functions, the VBG  10  incorporates, e.g., an open Phone Branch Exchange (PBX) application such as Asterisk and conventional communications protocols such as SIP (Session Initiation Protocol). 
     In the disclosed embodiment, the VBG  10  is implemented on a server  14  having, inter alia, a number of USB ports configured to receive voice or audio signals originating from one or more network radios having standard audio connectors (e.g., type U-229), after the signals are converted into a digital format by USB Radio Adapters (URAs) connected to each port as described below. The USB ports are also, configured to direct voice or audio signals originating from a given network radio through the connected URAs to the audio connectors of other network radios with which the given network radio is to be bridged. For example, pin B of the mentioned U-229 connector is used as an analog audio output or speaker terminal for the associated radio, pin D is the radio&#39;s analog audio input or mic terminal and, when grounded, pin C activates push-to-talk (PPT) operation for the radio. See, http://www.prc68.com/I/U229PO.shtml. 
     Accordingly, in  FIG. 2 , if a SINCGARS radio  16  in a SINCGARS radio communication network  18  using defined wireless RF channels  20  and transmission protocols, is to be voice bridged with a PRC-117G radio  22  in a PRC radio communication network  24  that uses different RF channels  26  and protocols, the VBG  10  can bridge audio signals originating from any radio in either communication network for reception by the radios in the other network. Another desirable feature of the VBG  10  is its ability to bridge audio from one or more different network radios with a mobile, fixed, or other remote phone by use of a plain old telephone system (POTS) communication cable  28  that connects the server  14  with a public switched telephone network (PSTN)  30 . 
       FIG. 3  shows a preferred architecture for the VBG  10 . Persons skilled in the art will understand that other architectures may also be devised and used to practice the present invention. 
     In  FIG. 3 , one or more network radios  30  each has a defined audio (e.g., headset or speaker) terminal, and a defined microphone (mic) terminal, for example, pins B and D of the mentioned U-229 connector. Each network radio  30  may be located in the vicinity of the VBG  10 , and be in the form of a military or commercial PTT type two-way radio that operates to (a) monitor one or more voice channels of its associated network, and (b) transmit audio or voice signals over the channels wherein the voice signals originate from radios of other networks and/or mobile or fixed telephones linked with the VBG  10 , and are selected by the VBG for transmission over the network radio&#39;s channels. 
     The PLMN-to-VoIP I/F in  FIG. 3  may be H.323, SIP or PSTN. For example, in legacy cellular networks, a circuit-switched portion of the PLMN is routed through a mobile switching center (MSC) and onto a PSTN. If a PLMN is connected to (e.g., UMTS) or integrated with (e.g., LTE) an IP Multimedia Subsystem (IMS) core, then the PLMN-to-VoIP I/F will be SIP. 
     As used herein, the terms voice and audio are used interchangeably to refer to intelligible voice messages transmitted by users of radios or other communication devices (e.g., wired or wireless telephones) linked with the VBG  10 , as well as audible or sub-audible tones that are transmitted alone or together with voice messages for purposes of network access, audio frequency shift keying and/or other conventional communication techniques. 
     Nomenclature used to label the blocks in  FIG. 3  is as follows:
         DSP—Digital Signal Processor   RoIP—Radio over Internet Protocol   VoIP—Voice over Internet Protocol   SIP—Session Initiation Protocol—an IETF voice call control protocol   H.323—ITU Standard for VoIP signaling, control, and transport   IAX2—Inter-Asterisk Exchange Protocol v.2   IP-PBX—Internet Protocol Private Branch Exchange   PSTN—Public Switched Telephone Network   I/F—interface       

     Analog audio supplied from the audio terminal of each network radio  30 , is supplied through an associated cable  30   a  to a USB radio adapter (URA)  32 . The URA  32  operates to sample and digitally encode analog audio signals detected by the associated network radio  30  on its network channels. Such encoding preferably obtains a 64 bit PCM full rate digital audio stream in a standard Radio over Internet Protocol (RoIP) format. The RoIP digital audio from the URA  32  is applied through a RoIP interface  34  within the VBG server  14  and is processed by the PBX application (e.g., Asterisk) on the server. Voice or audio to be transmitted by the network radio  30  over its associated network channels, is output from the RoIP interface  34  in the server  14  and converted into analog form by the URA  32 . Analog audio from the URA  32  is applied through the cable  30   a  to the microphone terminal of the network radio  30 . 
       FIG. 4  is a schematic diagram showing the radio cable  30   a  in  FIG. 3  terminated at one end with a type U-229 audio plug connector  42  for electrically connecting to a mating connector on a network radio  30 . The cable  30   a  is terminated at the other end with a USB sound card  44  with certain discrete components to define the URA  32  in  FIG. 3 . The sound card  44  is preferably built around a USB audio input/output (I/O) controller such as, e.g., a type CM108 or CM119 integrated circuit chip  48  available from C-Media Electronics Inc., in Taiwan. Note that the cable  30   a  connects the speaker pin B of the plug connector  42  to an AI (audio in) pin no.  27  of the chip  48  through a 100 K-ohm resistor, and connects the mic pin D of the connector  42  through a 10 uf capacitor to an AO (audio out) pin no.  30  of the chip  48 . Pin no.  13  of the chip  48  is configured to drive a switching transistor Q 1  so as to ground the PPT pin C of the plug connector  42  through the cable  30   a.    
       FIG. 5  is a schematic diagram of another embodiment of the radio cable  30   a  in  FIG. 3 . As in  FIG. 4 , the cable  30   a  is terminated at one end with a type U-229 audio plug connector  42  for electrically connecting to a mating connector on a monitor radio  30 . The other end of the cable terminates with a type 9080 USB radio interface (URI)  50  available from DMK Engineering Inc. of Rancho Palos Verdes, Calif. 90275. The DMK 9080 URI is also built around the mentioned CM108 USB audio I/O controller chip, and is provided with a standard DB-25 pin connector  52  for cable connection. Conductors in the cable  30   a  connect to the following pins of the DB-25 connector on the DMK 9080 URI: 
     
       
         
               
               
               
             
               
               
               
             
           
               
                   
               
               
                 URI DB-25 Pin 
                 Function 
                 Connect to U-229 Pin 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 1 
                 PTT 
                 C 
               
               
                 13 
                 GND 
                 A 
               
               
                 21 
                 Mic (AC coupled) 
                 B (Speaker) 
               
               
                 22 
                 Speaker (AC coupled) 
                 D (MIC) 
               
               
                   
               
             
          
         
       
     
     Connecting the VBG Radio Cables 
     One or more USB radio cables  30   a  terminated as in either  FIG. 4  or  FIG. 5  may be used with the VBG  10 . For the system to operate properly, it may be necessary to attach the USB connector end of the cable to a corresponding USB port on the server  14  before the server is turned on. As mentioned, the server  14  may have, e.g., four USB ports on a back panel wherein each port is configured to interface with the URA  32  on a different USB radio cable  30   a . See  FIG. 6 . The USB ports can be numbered and associated with different extension numbers, as in the following example. The ports may also be configured manually if desired. 
     USB Port No.
         19=Port 1=Device 4-1=6001=Extension 9101   20=Port 2=Device 4-2=6002=Extension 9102   21=Port 3=Device 3-1=6003=Extension 9103   22=Port 4=Device 3-2=6004=Extension 9104       

     In the above configuration, for example, a SIP user can dial 101 and the VBG  10  will operate to connect the user with the network radio  30  to which port 1 is connected through the corresponding cable  30   a . The user may then communicate with other radios on the same network as the network radio  30  linked to Port 1, and with radios on other networks that are bridged with Port 1 using, e.g., a [*] key on the keypad of his/her device to key push-to-talk (PTT) operation of the radio  30  and transmit, and a [#] key to un-key the PTT operation and receive. 
     USB Radio Adapter Status Lights 
     The URAs  32  may be configured to include status lights to indicate if a given adapter is communicating with the VBG server  14  properly. For example, a steady red light may indicate that the adapter is not configured, while a blinking red light indicates the device is operating properly and is talking to the system. 
     Radio Group Settings 
     As seen in the table of  FIG. 7 , the VBG  10  can implement any one of, e.g., 16 different bridging configurations for four different voice communication networks  60 ,  62 ,  64 ,  66  shown in  FIG. 8 . A desired bridging configuration may be defined on the VBG server  14  by using a configuration command such as, e.g., saint rpf.sh together with the desired configuration. 
     In the configuration of  FIG. 8 , each network is independent, i.e., the radios in each network are not bridged with radios in any of the other three networks. An example of a configuration command syntax to achieve the independent configuration of  FIG. 8 , is:
         [root@localhost˜]#saint_rpt.sh radio1 — 2 — 3 — 4       

       FIG. 9  shows a configuration in which the radios in network  60  and the radios in network  62  are bridged, while the radios in networks  64  and  66  are not bridged out of their respective networks. A corresponding configuration command is then, for example;
         [root@localhost˜]#saint_rpt.sh radio12 — 3 — 4       

     It will be understood that with the appropriate command, configurations in which the radios of all four networks  60 ,  62 ,  64 ,  66  are bridged with one another, or where the radios in a given network are bridged with the radios in one or more other selected networks, can be implemented. 
     POTS Line Connection to PTT Radios 
     The VBG  10  preferably has a standard telephone connector  70  (e.g., type RJ-14) mounted on a panel of the server  14  as in  FIG. 6 . To enable an outside user who can access an available public switched telephone network (PSTN) with a wired or wireless phone and wants to communicate with the VBG over the POTS line  28  in  FIG. 2 , the telephone connector  70  on the server  14  must be connected through a phone line or cable to an active PSTN jack in the vicinity of the server. 
     Calling the VBG from a Phone 
     Once connected to a PSTN network, the VBG server  14  may be programmed to be called from any phone (a cell phone or an internal telephone handset) that has access to the PSTN. When called, the server may answer after, e.g., two rings, and a pre-recorded announcement can state: “Welcome, enter the extension of the person you are trying to call.” A number of extensions may be available for use, as follows: 
     
       
         
               
               
             
           
               
                   
               
               
                 Extension 
                 Description 
               
               
                   
               
             
             
               
                 9101 
                 Radio Network 60; Cable Port 19 
               
               
                 9102 
                 Radio Network 62; Cable Port 20 
               
               
                 9103 
                 Radio Network 64; Cable Port 21 
               
               
                 9104 
                 Radio Network 66; Cable Port 22 
               
               
                 8050 
                 Conference Room 
               
               
                   
               
             
          
         
       
     
     Radio Signal Training the VBG  10   
     Each time a new network radio  30  is linked with the VBG  10 , certain steps should be followed to set appropriate threshold levels for voice signals and for noise that will be input to the VBG. The settings may be accomplished in a known manner using a commercially available calibrated radio communications test set, or a separate radio frequency signal generator and a modulation analyzer. 
     To begin a signal training session for a given network radio  30  and its associated RF channel(s), and if the mentioned Asterisk software is incorporated, a command such as the following is entered in the VBG;
         [rootlocalhost−]#asterisk—vvvr       

     The particular network radio to be trained among, e.g., four radios identified as usb, usb 1 , usb 2 , and usb 3 , may be selected by entering, e.g;
         &gt;radio active usb 2 
 
to select the network radio associated with usb 2 . A menu list of options is then displayed, including setting voice signal and noise level thresholds for the URA  32  associated with usb 2 .
       

     To make an input noise level adjustment for the URA associated with usb 2 , the corresponding network radio  30  must be turned on with no voice signal being received on its assigned frequency. Because the URA is connected to receive the radio&#39;s unfiltered and unsquelched voice output, the URA is subject to a maximum amplitude white noise signal from the radio. A command such as the following is then entered;
         &gt;radio tune rxnoise
 
The VBG server  14  is preferably configured to adjust the input threshold of the URA in view of the radio&#39;s output noise signal, and to display a Success message if the configuration is accepted.
       

     To make a voice level adjustment for the URA  32 , a command such as
         &gt;radio tune rxvoice
 
is entered and a strong, on-channel, full-quieting RF signal modulated by a one KHz tone at 60% modulation is received by the network radio  30  associated with usb 2 . For example, a user of another radio on the same network may say “ahhhhh” for five seconds. The VBG  10  adjusts the threshold level of the URA for voice modulation, and outputs a Success message when the configuration is accepted. After each configuration change, the edited configuration may be saved using a command such as, e.g.;
   &gt;radio tune save       

     If the mentioned Asterisk PBX software is incorporated in the VBG  10 , it may be required to restart the Asterisk service in order to apply the edited configurations, by entering:
         &gt;amportal kill
 
If the VBG monitor screen closes, a new screen may be opened upon entering:
   &gt;amportal start       

     Full Radio Tune Menu List and Description 
     The following commands may be used to invoke the described functions: 
     radio active—Selects by name a specific USB radio adapter (URA) for display or tuning (e.g., usb, usb 1 , usb 2 , or usb 3 ). 
     radio tune—Displays information about a current active network radio  30 . 
     radio tune rxnoise—Automatically adjusts the selected URA input sensitivity to match the maximum noise signal output from the connected network radio  30 . This is the audio from the radio when no RF signal is present on the radio&#39;s receive frequency. If the USB adapter  32  is connected directly to an unmuted and unfiltered demodulated audio output terminal of the radio  30  and no RF signal is present on the radio channel, then this is the open channel reference signal. If the connection to the radio is not via an unsquelched and unfiltered audio output terminal, the maximum noise signal can be obtained by user controls to unmute the radio and open the squelch. 
     radio tune rxvoice—To set a selected URA radio voice level adjustment, transmit an on-channel, strong, full-quieting RF signal modulated by a 1 KHz tone at 60 percent of maximum modulation. 
     radio tune rxsquelch—This sets the selected URA radio noise squelch sensitivity. It provides a measurement of the current signal strength as a reference value. For example, if a configuration is needed, entering this command can display the current no-signal strength and the current squelch setting. Enter the command “radio tune rxsquelch xxx” where “xxx” is the current signal strength reading plus 150. The squelch setting can be tested and a final adjustment made later. 
     radio tune txtone—This sets the modulation amplitude of a sub-audible tone or data that is transmitted simultaneously with a voice signal. 
     radio tune txvoice—This sets the modulation amplitude of the voice signal by generating a reference signal of 1 KHz at a 60 percent modulation level. 
     radio tune save—This saves adjustments made to a configuration file for a specific channel. The adjustments are automatically loaded when the VBG server  14  is restarted. 
     As disclosed herein, it will be understood that the present invention provides a reliable, low cost interface among recent VoIP protocols for over IP communications, as well as standard H.323, SIP, PSTN, and any analog voice system. 
     While the foregoing represents preferred embodiments of the invention, those skilled in the art will understand that various changes and modifications may be made without departing from the spirit and scope of the invention. For example, two or more VBG servers  14  may be situated at determined locations in a defined geographic region, wherein each VBG server is linked with one or more network radios  30 , and the servers are connected through a VoIP trunk.  72  in  FIG. 3 . It will be understood that such a configuration can enable all of the radio networks linked to the connected VGB servers to be bridged in a desired configuration by the combined operations of the servers. 
     It will also be understood that, as disclosed, the VGB  10  will support voice level detection (i.e., VOX) so that PTT operation via the [*] and the [#] keys on a telephone touch pad is not necessary required. PTT operation by way of the [*] and [#] keys is preferred, however, since it has been found to provide significantly better performance. Accordingly, the present invention includes all such changes and modifications as are within the scope of the following claims.