Multimode land mobile radio

0001This invention relates generally to land mobile radios, and more particularly, to a land mobile radio providing communication of land mobile radio content using a land mobile radio network or a cellular data network.

0002Land mobile radios (LMRs) may be used to provide communication between different mobile units. Land mobile radio band communication, for example, public safety radio communication (e.g., police, fire department, etc.) is generally available within the VHF, UHF, 700 MHz and 800 MHz frequency bands. Part of each of these frequency bands is allocated by the Federal Communications Commission (FCC) for public safety communication services and are also referred to as Public Safety Frequency Bands. These communications also may be provided using private land mobile radio services (PLMRS).

0003Cellular networks also provide communication between different mobile users, for example, cellular telephones. These cellular networks, as well as LMR networks, continue to be enhanced and allow for improved operation and communication. For example, cellular networks now provide Push-to-talk (PTT) services that allow direct connect capabilities. Thus, a cellular phone user may request a direct connect communication link with another cellular phone user in a two way radio or "walkie talkie" type communication. As another example, cellular networks provide high-speed data services, such as, for example, General Packet Radio Service (GPRS), Enhanced Data Rates for GSM Evolution (EDGE), Evolution Data Optimized (EV-DO) and Universal Mobile Telephone Service (UMTS).

0004Known systems providing enhanced services or features, such as enhanced calling or voice features, which may be used, for example, for mission critical wireless applications, such as public safety applications, use commercial cellular services, such as PTT services, to augment and or replace traditional LMR systems. These known systems are provided using specialized gateway equipment that enable certain interoperability capabilities between an LMR system and a cellular network with, for example, PTT capabilities. The interoperability is provided by translating and/or transforming the data or voice communications to be communicated between the networks, for example, from an LMR network to a cellular network.

0005In the LMR area, new technologies are also being provided, including the use of digital communication instead of analog communication. Additionally, LMR systems are now using packet switching instead of circuit switching, for example, using Internet Protocol (IP) and Voice Over IP (VoIP) to enable construction of highly scalable and cost effective LMR networks.

0006However, these improvements also result in need to support migration to new technologies. Further, interoperability between systems deployed either by different LMR owners/operators or between different cellular carriers, particularly when different technologies are used in different systems, is increasingly important. It is known to utilize multimode terminal devices to facilitate both migration and interoperability. In LMR, these devices are often referred to as multimode radios, and in the cellular area these devices are often referred to as multimode phones.

0007Multimode terminal devices enable inter-system roaming, and specifically, roaming from one network and/or technology to another, without user intervention. These terminal devices change mode as a user roams between different systems provided using different technologies. Further, components for operation in multiple protocols and frequency bands may be integrated into a single terminal device. For example, in the cellular area, multimode phones can roam between TDMA and CDMA networks. In the LMR are, radios can roam between an analog trunked system and a digital trunked system.

0008Multimode operation is provided by the interconnection of corresponding network infrastructures. Thus, to provide transparency to a user, gateway equipment may be used to connect the various systems or networks. Known devices for communicating between different types of networks or systems use different communication components (e.g., hardware and software) each configured specifically to communicate with a particular network or system. For each system or network, the functions and operations for that system or network are implemented using the capabilities and protocols specific to that system or network. However, these systems are limited in the set of overall functions that are available because the functions and user interface available to a user depend on the system into which the terminal device has roamed.

0009Further, the functions of one system may differ significantly from the functions available on another system. Additionally, because of these protocol incompatibilities certain end-to-end services cannot be provided, for example, end-to-end encryption. For voice communications, the use of a gateway to interconnect systems can introduce degradation in voice quality as a result of the voice data being converted from one format to another.

0010Thus, these systems not only may operate at non-satisfactory quality levels, but may require additional controls and equipment to implement the interconnectivity, thereby adding complexity and cost to the overall systems.

0011The solution is provided by, a land mobile radio (LMR) is provided that includes an LMR communication portion configured to provide communication with an LMR network and a cellular data network communication portion configured to provide communication with a cellular data network.

0012The solution is also provided by a multimode terminal device is provided that includes a land mobile radio and a cellular radio modem.

0013The solution is also provided by a method of communicating land mobile radio (LMR) content using an LMR device is provided. The method includes configuring a land mobile radio to communicate LMR content using one of an LMR network and a cellular data network. The LMR content is encapsulated using a packet switching protocol when communicating using the cellular data network.

0014The invention will now be described by way of example with reference to the accompanying drawings in which:

0015<figref idref="f0001">Figure 1</figref> is a block diagram of a Land Mobile Radio (LMR) communication system constructed in accordance with an exemplary embodiment of the present invention.

0016<figref idref="f0002">Figure 2</figref> is a block diagram of an LMR unit constructed in accordance with an exemplary embodiment of the present invention.

0017<figref idref="f0003">Figure 3</figref> is a block diagram illustrating an internal configuration of an LMR unit constructed in accordance with an exemplary embodiment of the present invention.

0018<figref idref="f0004">Figure 4</figref> is a perspective view of an LMR unit illustrating an external configuration constructed in accordance with an exemplary embodiment of the present invention.

0019<figref idref="f0005">Figure 5</figref> is a perspective view of an LMR unit illustrating an external configuration constructed in accordance with another exemplary embodiment of the present invention.

0020<figref idref="f0006">Figure 6</figref> is a perspective view of an LMR unit illustrating an external configuration constructed in accordance with another exemplary embodiment of the present invention.

0021<figref idref="f0006">Figure 7</figref> is an elevation view of an LMR unit illustrating an external configuration constructed in accordance with another exemplary embodiment of the present invention.

0022<figref idref="f0007">Figure 8</figref> is a block diagram illustrating protocol stacks in accordance with an exemplary embodiment of the present invention.

0023<figref idref="f0008">Figure 9</figref> is a flowchart of a method for controlling communication of LMR content in an LMR communication system in accordance with an exemplary embodiment of the present invention.

0024<figref idref="f0008">Figure 10</figref> is a block diagram of a packet switched protocol interface constructed in accordance with an exemplary embodiment of the present invention.

0025<figref idref="f0009">Figure 11</figref> is a block diagram showing formatted LMR content in accordance with an exemplary embodiment of the present invention.

0026<figref idref="f0009">Figure 12</figref> is flowchart of a method for selecting the operating mode of an LMR unit in accordance with an exemplary embodiment of the present invention.

0027<figref idref="f0010">Figure 13</figref> is a flowchart of a method for processing LMR content in accordance with an exemplary embodiment of the present invention.

0028<figref idref="f0011">Figure 14</figref> is a block diagram of an LMR communication system constructed in accordance with an exemplary embodiment of the present invention showing communication coverage areas.

0029<figref idref="f0011">Figure 15</figref> is block diagram of an LMR communication system constructed in accordance with an exemplary embodiment of the present invention showing data flow.

0030Various embodiments of the present invention include a multimode terminal device having a land mobile radio (LMR) unit providing LMR content, for example, LMR services using both an LMR network and a cellular data network. The LMR content retains an LMR application layer, but instead of using the LMR frequency bands with LMR transport protocols, the LMR content is communicated using cellular frequency bands over cellular packet switched data networks.

0031The multimode device is configured to provide inter-system roaming between, for example, LMR systems and cellular systems. Operation using the cellular system is provided generally by including a cellular radio modem into an LMR device, and supporting LMR features through encapsulation and transport of LMR voice, data and control information, utilizing end-to-end packet switched protocols between the LMR device and a packet switched infrastructure.

0032In the various embodiments, the data services of a cellular system are used when communicating using the cellular system. The cellular radio modem provides data services between an application layer within the LMR device and a gateway that bridges the LMR system or network and the cellular system or network. The end-to-end protocols between the multimode LMR device and the gateway utilize encapsulation techniques to transport LMR voice and data services over the cellular data network. The processes and techniques for performing the encapsulation and packet switched transport also may be referred to as LMR-over-cellular protocols.

0033It should be noted that when reference is made herein to LMR content, this refers generally to any type or kind of LMR voice and/or data content, and may define particular LMR services, operations, controls, etc. For example, the LMR content may include, but is not limited to, voice data, emergency signal data, control data relating to selecting a particular talk group, LMR data for transfer between a radio unit and a server, reprogramming data (e.g., software upgrade data), etc.

0034A wireless communication system will first be described followed by a description of an LMR unit in accordance with various embodiments of the invention.

0035As shown in <figref idref="f0001">Figure 1</figref>, a wireless communication system, and more particularly, an LMR communication system 20 constructed according to various embodiments of the invention provides communication between a plurality of multimode devices, and more particularly, a plurality of LMR units 22 or LMR terminals. Communication between the LMR units 22 is provided via either an LMR network 24 or a cellular data network 26. Each of the LMR units 22 is configured to provide communication, for example, with other LMR units 22 using one of the LMR network 24 and the cellular data network 26. In particular, each of the LMR units 22 is configured to switch between one of the LMR network 24 and the cellular data network 26, for example, based on the available network, available bandwidth, the coverage area, the communication signal strength, etc. Optionally, or in another embodiment, switching between one of the LMR network 24 and the cellular data network 26 is based on the type of communication or content. Thus, in addition to providing communication over the LMR network 24, wireless data services of the cellular data network 26 may be used to support the communication and/or transport of LMR application layer protocols.

0036Various embodiments of the present invention enable end-to-end LMR services to be overlaid on top of the cellular data network 26, thereby allowing, for example, implementation of mission critical LMR systems within the service area of these cellular data networks 26. In order to provide this functionality and communication of LMR content using the cellular data network 26, each of the LMR units 22, for example, LMR radios, is provided with a cellular radio modem to allow operating end-to-end LMR application layer protocols and services between the LMR units 22 and the packet switched LMR infrastructure.

0037More particularly, and as shown in <figref idref="f0002">Figure 2</figref>, a multimode terminal device, illustrated as the LMR unit 22, includes a plurality of modules or components configured to provide communication via the LMR network 24 or the cellular data network 26. Specifically, the LMR unit 22 includes an LMR application module 30 connected to an LMR transport module 32 for configuring voice and/or data for communication via the LMR network 24 (having one or more LMR base stations 46) using an LMR transmitter/receiver 34, which may be separate units or provided as a single transceiver (e.g., an LMR radio). The LMR application module 30, LMR transport module 32 and LMR transmitter/receiver 34 generally define an LMR communication portion 40 of the LMR unit 22. The LMR unit 22 further includes an LMR encapsulation module 36 for encapsulating the voice and/or data for communication via the cellular data network 26 using a cellular radio modem 38. The LMR application module 30, LMR encapsulation module 36 and cellular radio modem 38 generally define a cellular data network communication portion 42 of the LMR unit 22.

0038Specifically, and as shown in <figref idref="f0003">Figure 3</figref>, the LMR unit 22 includes the LMR communication portion 40 and the cellular data network communication portion 42 each connected to a selector 43. The LMR communication portion 40, cellular data network communication portion 42 and selector 43 are each also connected to a processor 45. Further, a memory 47 (e.g., RAM and/or ROM) and a display 246 are each connected to the processor 45. An input/output 51 is connected to the processor 45 and the selector 43. A user interface 250 is connected to the processor 45.

0039In operation, and as described in more detail herein, the processor 45 is configured to control selection of either the LMR communication portion 40 or cellular data network communication portion 42 using the selector 43. The processor 43 may access the memory 47 to obtain, for example, user preferences or predefined operating parameters. The processor 47 also may receive inputs (e.g., commands) from a user via the user interface 250, for example, to activate or select a certain function or operation. The input/output 51 may include different transmission and/or receiving components for transmitting and receiving to and from the LMR network 24 or the cellular data network 26 (shown in <figref idref="f0002">Figure 2</figref>). The display 246 displays information from the processor 45, for example, communication information, such as channel or network selection information.

0040Additional or different components may be provided to the LMR unit 22. For example, a global positioning system (GPS) unit may be provided as part of the LMR unit 22 to determine the location of the LMR unit 22.

0041The LMR unit 22 may be configured having different external configurations, for example, based on the specific application for the LMR unit 22. Various embodiments of different external configurations for LMR units are illustrated in <figref idref="f0004 f0005 f0006">Figures 4 through 7</figref>. It should be noted that the internal configuration for each of the LMR units is the same or similar to the configuration shown in <figref idref="f0002">Figures 2</figref> and <figref idref="f0003">3</figref>. Modifications may be made, for example, to the size of the memory 47 or display 246, or the configuration of the user interface 250. More particularly, and for illustrative purposes, as shown in <figref idref="f0004">Figure 4</figref>, an LMR unit 220 may be provided as a portable or mobile unit having a housing 222 configured for handheld operation. The LMR unit 220 includes a power/volume knob 224 on a top portion 228 of the LMR unit 220 to turn power on and off and to control volume. A system or channel knob 226 on the top portion 228 of the LMR unit 220 is provided to, for example, change channels or talk groups within a particular network (e.g., LMR network 24 or cellular data network 26) and may have a predetermined number of rotary positions. An emergency button 230 and a selector knob 232 are also provided on the top portion 228. The emergency button 230 is used to transmit an emergency signal to other LMR units, which provides an alert to the other units. The selector knob 232 is used to select a bank or set of channels or talk groups. An antenna 234 extends from the top portion 228 to facilitate bi-directional communication with the LMR unit 220.

0042A side portion 236 of the LMR unit 220 also includes control members for controlling operation of the LMR unit 220. In this embodiment, an option button 238, a clear/monitor button 240 and a push-to-talk (PTT) button 242 are all provided on the side portion 236. The option button 238 is used to select different options, for example, within a particular operating mode (e.g., high/low power settings, keypad lock, display contrast, keypad lighting, etc.) and the clear/monitor button is used, for example, to clear a setting or end a call. The PTT button 244 is used to activate and deactivate PTT operations.

0043A front portion 244 of the LMR unit 220 generally includes the display 246, a speaker 248, a microphone 259 and a user interface 250. The user interface 250 includes a plurality of user depressible buttons that may be used, for example, for entering numeric inputs and selecting various functions of the LMR unit 220. This portion of the user interface may be configured, for example, as a numeric keypad. Additional control buttons also may be provided, for example, a menu button 252 and an increase and a decrease button 254 and 256, respectively. The increase button 252 and decrease button 254 may be used to provide the same functions as other user inputs, for example, correspond to the same operations as the system or channel knob 226. The menu button 252 is used to access a stored menu and/or activate an item within a list displayed on the display 246.

0044With respect to the plurality of user depressible buttons corresponding to numeric inputs, each may also provide control or activation of a particular function of the LMR unit 220. For example, numeric button (1) 258 also may be used to select a specific system or network, for example, the LMR network 24 or cellular data network 26 (shown in <figref idref="f0001">Figures 1</figref> and <figref idref="f0002">2</figref>), which switches between the LMR communication portion 40 and the cellular data network communication portion 42 (shown in <figref idref="f0002">Figure 2</figref>), respectively. Numeric button (2) 260 also may be used to select a specific group of users, for example, a predetermined group of users on a particular system. Numeric button (3) 262 also may be used to select a scan mode of operation for scanning channels within a particular system or network. Numeric button (4) 264 also may be used to activate encryption, for example, turn on and off a private encryption mode. Numeric button (6) 266 also may be used to add a group or channel for accessing with the LMR unit 220. Numeric button (7) 268 also may be used to access or provide to another LMR unit status of the LMR unit 220. Numeric button (8) 270 also may be used to access a list of predetermined messages that can be transmitted by the LMR unit 220. Numeric button (9) 272 also may be used to delete selected groups or channels of a currently selected system within a scan list. Button (*) 274 also may be used to initiate a interconnect call with other units. Button (#) 276 also may be used to initiate an individual call.

0045The display 246 may be configured having a plurality of lines, for example, for displaying a system designation on one line, a group designation on another line and icons or other information (e.g., mode of operation) on additional lines. Other information may be provided on the display 246, for example, a battery power level indicator.

0046The LMR unit 220 also may be referred to as a system unit. An LMR unit 280 configured as a scan unit is shown in <figref idref="f0005">Figure 5</figref>. Like numerals represent like components as shown in <figref idref="f0004">Figure 4</figref>. The user interface 250 of the LMR unit 280 includes only an A/D button 282 to add and delete selected talk groups or channels from a scan list of a currently selected system, an SCN button 284 to turn on and off a scan operation and an OPT button 286 to activate one or more options.

0047Various other embodiments provide configurations of LMR units for use in different applications or in different settings. For example, an LMR unit 300 as shown in <figref idref="f0006">Figure 6</figref> may be configured for desktop or dashboard operation (e.g., mounting thereon) and an LMR unit 310 as shown in <figref idref="f0006">Figure 7</figref> may be integrated within a dashboard 312 of, for example, an automobile. Like numerals in <figref idref="f0006">Figures 6 and 7</figref> correspond to like numerals in <figref idref="f0004">Figures 4</figref> and <figref idref="f0005">5</figref>.

0048The LMR units may include additional components, for example, filters (not shown), such as a receive filter and a transmit filter for filtering signals that are received and transmitted, respectively, by the LMR units. The LMR units also may include, for example, a dedicated switch (not shown) or other controller for switching between the LMR communication portion 40 and the cellular data network communication portion 42 (shown in <figref idref="f0002">Figure 2</figref>).

0049It should be noted when reference is made below to LMR unit 22, any of the various embodiments may be used, including LMR units 220, 280, 300 and 310.

0050In operation, the LMR system 20 may provide communication via the LMR network 24 using different known protocols, for example, LMR airlink protocols. For example, these LMR airlink protocols include the Project 25 (TIA 102) and ETSI TERRA standards, among others. These LMR airlink protocols specify the format and procedures for information exchange between the LMR unit, for example, LMR unit 22 and the LMR network 24, and in particular, the LMR base station 46. It should be noted that when the base station(s) 46 are part of a larger system, the base station(s) 46 are interconnected to switching equipment (not shown) that routes voice and data between different parts of the system, such as to other LMR base stations or dispatch consoles.

0051As is known, the LMR base station 46 processes, for example, manipulates, the voice, data and control information received over the airlink into an alternate format suitable for communication within the LMR network 24, for example, for transport to switching equipment. For example, received discrete voice, data and control transmissions may be encapsulated in TCP/IP or UDP/IP packets as is known, with the resultant IP packets communicated between the LMR base station(s) 46 and the switching equipment over an IP network.

0052The LMR unit 22 also may provide communication via the cellular data network 26 using different known protocols, for example, General Packet Radio Service (GPRS), Enhanced Data Rates for GSM Evolution (EDGE), Evolution Data Optimized (EV-DO), Universal Mobile Telephone Service (UMTS), and 802.16 standards, among others. These cellular protocols specify the format and procedures for information exchange between the LMR unit 22 and in particular, the cellular radio modem 38, and the cellular data network 26.

0053For example, a cellular tower (not shown) having base station (not shown) may be provided for receiving and processing signals from the LMR unit 22, for example, manipulating the received voice, data and control information into an alternate format suitable for communication within the cellular data network 26, for example, for transport to a router and server (not shown) based on an IP address for the data packets received. For example, received encapsulated signals are decapsulated and appropriately routed within the cellular data network 26.

0054Thus, communication of data from either the LMR network 24 or the cellular data network 26 to a packet switched LMR infrastructure 41 is provided. It should be noted that the LMR content and LMR network may be configured based on different airlink protocols. In order to provide communication via either the LMR network 24 or the cellular data network 26 using the LMR unit 22 the communication protocol stacks for communication with each of these networks is partitioned as shown in <figref idref="f0007">Figure 8</figref>. In particular, and with respect to communication with the LMR unit 22 using the LMR network 24, the LMR protocol stack 60 is partitioned into multiple layers, which in an exemplary embodiment, is a two-layer protocol stack having an LMR application layer 62 and an LMR transport layer 64. The application layer 62 and the LMR transport layer 64 may be provided, for example, by the LMR application module 30 and LMR transport module 32 (both shown in <figref idref="f0002">Figure 2</figref>), respectively. The LMR application layer 62 is configured to provide interpretation and processing of the voice, data and control information and the LMR transport layer 64 is configured to provide delivery of the voice, data and control information over the transmission medium. As described herein, an LMR airlink protocol defines the both the LMR application layer 62 and the LMR transport layer 64.

0055In this two-layer protocol stack model, the LMR base station 46 (shown in <figref idref="f0002">Figure 2</figref>) and switching equipment in the LMR network 24 (shown in <figref idref="f0002">Figure 2</figref>) receive content from the LMR communication portion 40 (shown in <figref idref="f0002">Figure 2</figref>) and communicate content of the LMR application layer 62 therebetween with a different transport layer. In particular, and as shown in <figref idref="f0003">Figure 3</figref>, the content of the application layer 62 is encapsulated at the LMR base station 46 (shown in <figref idref="f0002">Figure 2</figref>) using LMR content encapsulation 66 as is known. In an exemplary embodiment, discrete transmission units are encapsulated within transport datagrams, and in particular, packet switched transport datagrams 68, that are communicated using a transport protocol. Upon receipt of an encapsulated datagram, the application layer content then may be recovered, and in particular, decapsulated.

0056Further, this two-layer protocol stack model enables delivering LMR application layer services over non-LMR wireless networks using, for example, the cellular data network communication portion 42 (shown in <figref idref="f0002">Figure 2</figref>). Specifically, the cellular data network communication portion 42 is configured to provide the LMR application layer 62, but instead of using the LMR transport Layer 64, the transport services of a wireless cellular data network 26 (shown in <figref idref="f0002">Figure 2</figref>) are used. In particular, an LMR encapsulation layer 70 is used with the packet switched transport datagrams 68 such that the wireless cellular data network 26 communicates with switching equipment using suitable transport protocols, thereby delivering the identical LMR application layer services as the LMR communication portion 40. Specifically, the packet switched LMR infrastructure 41 (shown in <figref idref="f0002">Figure 2</figref>) communicates the LMR application services using LMR application layer switching 72 in combination with packet switched transport datagrams 68.

0057It should be noted that the various embodiments are not limited to a two-layer protocol stack and additional layers may be provided to the multi-layer protocol stack as desired or needed. For example, different session layers, such as a bulk encryption layer may be provided. Further, and for example, an RTP layer may be provided.

0058Various embodiments of the present invention provide for controlling communication of LMR content in an LMR communication system using an LMR network and a non-LMR wireless network, in particular, a wireless cellular data network. In particular, a method 100 of controlling communication of LMR content is shown in <figref idref="f0008">Figure 9</figref> and includes determining at 102 the network to use to communicate the LMR content. In an exemplary embodiment, a determination is made as to whether the LMR content is to be communicated using an LMR network or a cellular data network. The determination may be based on a manual selection, for example, based on a user input selection of which network to use. The selection may be made, for example, using a button or switch on the LMR unit 22 (shown in <figref idref="f0002">Figure 2</figref>). Alternatively or optionally, the determination of which network to use may be automatic. For example, the selection of a network for communicating LMR content may be based on the amount of data traffic on a particular network or available bandwidth, a transmission priority level, the type of communication or content (e.g., voice or emergency broadcast signal, emergency communication or PTT request), the signal strength for the LMR unit, the geographic location of the LMR unit, a user preference, etc. The operation and selection of the network to use when communicating with the LMR unit is described in more detail below in connection with <figref idref="f0009">Figure 12</figref>.

0059After a determination of the network to use to communicate the LMR content is made at 102, a method of communication is selected at 104 based on the determined network to use. For example, the speed or baud rate of the communication may be selected (manually or automatically) from a range of communication data rates. Additionally, the setup procedures for establishing and connecting to the determined network may be selected. For example, if the LMR network is to be used, an LMR network communication setup routine may be executed wherein a communication link is established between the LMR unit and the LMR network via an LMR transmitter/receiver within the LMR unit. If the cellular data network is to be used, a cellular data network communication setup routine may be executed wherein a communication link is established between the LMR unit and the cellular data network via a cellular radio modem of the LMR unit. The setup routine may include any suitable process as is known for establishing a wireless communication link.

0060Thereafter, at 106 the LMR content is configured for communication based on the determined network and selected method of communication. For example, if the LMR content is to be communicated using the LMR network, a selection of a particular LMR standard in which to configure or format the LMR content is selected. In particular, an LMR standard in which to configure the voice and/or data payload defining the LMR content is selected. This may include, for example, selecting one of a Project 25 (TIA 102) or an ETSI TETRA standard for the method of communication. Further, and for example, a proprietary format may be selected, for example, an OpenSky M/A-COM proprietary format, a NetworkFirst or EDACS system proprietary format.

0061Further and for example, if the LMR content is to be communicated using the cellular data network, a selection of a particular wireless cellular data network standard in which to configure or format the LMR content is selected. In particular, a wireless cellular standard in which to configure the voice and/or data payload defining the LMR content is selected. This may include, for example, selecting one of a General Packet Radio Service (GPRS), Enhanced Data Rates for GSM Evolution (EDGE), Evolution Data Optimized (EV-DO), Universal Mobile Telephone Service (UMTS) or 802.11 system standard.

0062Additionally, and as described in more detail above in connection with <figref idref="f0007">Figure 8</figref>, depending on the network to be used to communicate the LMR content, a particular protocol stack may be used. Further, if the LMR content is to be communicated using the LMR network, an LMR protocol header is added to the LMR data payload. If the LMR content is to be communicated using the cellular data network, then a packet switch protocol header is added. As described in more detail below, if the LMR content is to be communicated using the cellular data network, then the LMR content is encapsulated, for example, Internet Protocol (IP) encapsulated with an IP wrapper prior to communicating to or from the cellular data network. The method for encapsulating the data is described in more detail below in connection with <figref idref="f0010">Figure 13</figref>.

0063Referring again to <figref idref="f0008">Figure 9</figref>, after the LMR content is configured at 106, the configured LMR content is communicated at 108. For example, if the LMR content is configured for communication using the LMR network, an LMR transmitter and receiver may be used to communicate the LMR content. If the LMR content is configured for communication using the cellular data network, a cellular radio modem may be used to communicate the LMR content. It should be noted that the cellular radio modem may be configured to operate in a single mode of operation or may be configured to operate in a multiple modes. In another embodiment, more than one cellular radio modem may be provide, each of which may be configured to operate in a single mode of operation or may be configured to operate in multiple modes of operation.

0064After the LMR content is communicated and received, for example, by a base station of the network, the LMR content is processed at 110 to determine an action. For example, this may include a determination to communicate voice data or to issue an emergency signal or PTT request to a talk group. For example, if the LMR content is communicated using the cellular data network, the IP destination address of an encapsulated datagram may first be determined and then communicated to that location for processing using a router in the network.

0065Referring now to <figref idref="f0008">Figure 10</figref> and an another embodiment of the present invention, a packet switched protocol interface 120 may be provided in connection with the cellular data network 26 (shown in <figref idref="f0002">Figure 2</figref>). The packet switched protocol interface 120 may be provided, for example, as a separate unit (e.g., stand alone module), a card for connection to a server within the cellular data network or software for downloading to a server within the cellular data network. The packet switched protocol interface 120 includes a processor 122 for processing received packet switched encapsulated LMR content for communication to, for example, the packet switched LMR infrastructure 41 (shown in <figref idref="f0002">Figure 2</figref>). In particular, and as described in more detail herein, the processor may receive LMR content formatted as shown in <figref idref="f0009">Figure 11</figref>. The LMR content generally includes an LMR data portion and a packet switching protocol encapsulation portion. Specifically, the LMR content 130 may include a packet switch protocol header 132, an LMR protocol header 134 and LMR data 136, for example, an LMR data payload.

0066This LMR content 130 is essentially encapsulated, for example, encapsulated in an IP wrapper. The processor 122 decapsulates the LMR content 130, for example, by removing the packet switch protocol header 132 and may store the decapsulated LMR content 130 in a memory 124. The LMR content 130 then may be further processed by the processor 122 to determine an action to be performed or an address within the packet switched LMR infrastructure to which the LMR content 130 is to be communicated. Essentially, once the LMR content 130 is decapsulated, the LMR content 130 is configured for communication within a packet switched LMR infrastructure or an LMR network. The control of communication of the LMR content 130 is controlled by a controller 126 that may include a router 128 for routing the LMR content 130 to a destination within, for example, the LMR network. It should be noted that the LMR content may be reencapsulated for transmission within the LMR network or within the cellular data network.

0067The operation and selection of the network to use by the LMR unit, and more particularly, the selection of either an LMR network or a non-LMR network, for example, a cellular data network, to communicate the LMR content will now be described. In general, an LMR unit may automatically select the network to use based on, for example, a user setting, a predetermined setting, a user defined setting, an operating condition of the LMR unit, etc. The system selection also may be made by a user using a selector or input on the LMR unit. A method 350 for selecting the operating mode of the LMR unit, and more particularly, for determining when to use a particular network for communication is shown in <figref idref="f0009">Figure 12</figref>. Specifically, a determination is made at 352 as to the current network or communication system being used. Next, a determination of the operating conditions of the LMR unit is made at 354. This may include, for example, the current signal strength, the current geographic location, etc. Thereafter, at 356, a determination is made as to any user input or preference for a particular network. For example, a user may input a particular network preference based on geographic area, such as a preference for using an LMR network in an area where the user knows that the cellular data network coverage is weak or alternatively for using a cellular data network where the user knows there is no LMR network coverage. The user preference also may be, for example, to first always use a cellular data network if available. The input also may be based on a manual user selection of the LMR network or the cellular data network using a button or selector on the LMR unit.

0068Thereafter at 358 a determination is made as to the LMR settings of the LMR unit. This may include, for example, determining preprogrammed settings or preferences for the LMR unit, such as, for example, based on threshold levels of data traffic on a particular network or available bandwidth on that network, a transmission priority level, the type of communication or content (e.g., voice or emergency broadcast signal, emergency communication or PTT request), the current network being used for communication, etc. A determination is then made at 360 as to whether the LMR settings override the user input or preference, or vice versa. For example, the LMR unit may be configured such that an emergency broadcast message must be transmitted over the LMR network and this overrides any user inputs or preferences. If the LMR settings do not override the user inputs or preferences, then at 362 a network to use for communication is selected based on the user inputs or preferences and the corresponding communication portion of the LMR unit is accessed, for example, the LMR communication portion 40 of the LMR unit 22 or the cellular data network communication portion 42 of the LMR unit 22 (all shown in <figref idref="f0002">Figure 2</figref>). This also may include using the determined operating conditions of the LMR unit to make the selection.

0069If at 360 a determination is made that the LMR settings override the user inputs or preferences then at 364 the network to use for communication is selected based on the LMR settings. This also may include using the determined operating conditions of the LMR unit to make the selection. It should be noted that selection of the network to use at either 362 or 364 may result in a new network selected or no change in the network (i.e., continue using the current network for communication). Further, after the selection of the network at either 362 or 364, if the network is changed then an indication may be provided at 366, for example, and audible indication (e.g., sound) or visual indication (e.g., LED on LMR unit illuminated or network selection displayed on display).

0070The method 350 may be performed, for example, periodically or upon certain events such as a user input, change in operating condition of the LMR unit, which may include exceeding a predetermined threshold, etc.

0071Referring now to <figref idref="f0010">Figure 13</figref> and a method 150 for processing the LMR content, at 152 a determination is made as to whether the LMR content is to be communicated using an LMR network. If a determination is made at 152 that the LMR content is to be communicated using an LMR network then at 154 the LMR content is communicated to the LMR network. This may include communicating the LMR content to a base station of the LMR network based on an LMR protocol header provided in combination with the LMR content. Thereafter, the LMR content is encapsulated at 156, for example, encapsulated in a wrapper defined by the airlink protocol as described herein and routed accordingly at 158. For example, the encapsulated LMR content, which may be configured as a datagram, may be routed within the packet switched LMR infrastructure.

0072At the destination of the LMR content, the LMR content is processed at 160, for example, decapsulated and then an action determined at 162 based on the processed data. For example, a determination may be made at 162 that an emergency signal is to be transmitted or that the LMR content is to be further routed to another base station. The corresponding action is then performed at 164, for example, within the packet switched LMR infrastructure.

0073If a determination is made at 152 that the LMR content is not going to be communicated using the LMR network, then the LMR content is encapsulated for communication at 166. For example, in an exemplary embodiment, the LMR encapsulation module 36 (shown in <figref idref="f0002">Figure 2</figref>) implements the LMR encapsulation layer 70 (shown in <figref idref="f0007">Figure 8</figref>) to encapsulate the LMR content in a wrapper, for example, an IP wrapper. The encapsulated LMR content is then communicated using a cellular data network at 168. This may include routing the encapsulated LMR content in the cellular data network at 170. The LMR content is then communicated to the packet switched infrastructure at 172, for example, based on the IP address from the IP wrapper.

0074The LMR content is then processed at a destination, which may include decapsulating the LMR content and determining an action at 162. For example, a determination may be made that an emergency signal is to be transmitted or that the LMR content is to be further routed to another base station. The corresponding action is then performed at 164, for example, within the packet switched LMR infrastructure.

0075Thus, various embodiments of the present invention provide for communicating LMR content using an LMR network or a non-LMR network, for example, a cellular data network. If the LMR content is to be communicated using the cellular data network, the LMR content is encapsulated into a packet switching protocol before transmission. For example, and as shown in <figref idref="f0011">Figure 14</figref>, an LMR communication system 200 generally includes a plurality of cellular data network base stations 202 and a plurality of LMR network base stations 204. Each of the plurality of cellular data network base stations 202 and plurality of LMR network base stations 204 have a corresponding cellular data network communication coverage area 206 and an LMR network communication coverage area 208, respectively. The cellular data network communication coverage area 206 and LMR network communication coverage area 208 may be overlapping at some locations. The various embodiments of the invention as described herein allow an LMR unit 210, for example, an LMR radio in a mobile unit or vehicle, to communicate via either a cellular data network or an LMR network depending on, for example, the location of the LMR unit 210 and the corresponding available coverage area. More particularly, communication towers (not shown) corresponding to each of the plurality of cellular data network base stations 202 and each of the plurality of LMR network base stations 204 allow wireless communication as described herein.

0076Further, as shown in <figref idref="f0011">Figure 15</figref>, a controller 212 within the packet switched infrastructure 41 may be configured to control communications from the plurality of cellular data network base stations 202 and plurality of LMR network base stations 204 as described herein. The controller may process a plurality of data packets received from either the LMR network 24 and/or cellular data network 26 to determine an appropriate action or routing procedure for the particular data packets as described herein.

0077The various embodiments or components, for example, the LMR communication system 20 or controllers therein, or the LMR units or controllers therein, may be implemented as part of one or more computer systems, which may be separate from or integrated with the LMR communication system 20 or LMR unit, respectively. The computer system may include a computer, an input device, a display unit and an interface, for example, for accessing the Internet. The computer may include a microprocessor. The microprocessor may be connected to a communication bus. The computer may also include a memory. The memory may include Random Access Memory (RAM) and Read Only Memory (ROM). The computer system further may include a storage device, which may be a hard disk drive or a removable storage drive such as a floppy disk drive, optical disk drive, and the like. The storage device may also be other similar means for loading computer programs or other instructions into the computer system.

0078As used herein, the term "computer" may include any processor-based or microprocessor-based system including systems using microcontrollers, reduced instruction set circuits (RISC), application specific integrated circuits (ASICs), logic circuits, and any other circuit or processor capable of executing the functions described herein. The above examples are exemplary only, and are thus not intended to limit in any way the definition and/or meaning of the term "computer".

0079The computer system executes a set of instructions that are stored in one or more storage elements, in order to process input data. The storage elements may also store data or other information as desired or needed. The storage element may be in the form of an information source or a physical memory element within the processing machine.

0080The set of instructions may include various commands that instruct the computer as a processing machine to perform specific operations such as the methods and processes of the various embodiments of the invention. The set of instructions may be in the form of a software program. The software may be in various forms such as system software or application software. Further, the software may be in the form of a collection of separate programs, a program module within a larger program or a portion of a program module. The software also may include modular programming in the form of object-oriented programming. The processing of input data by the processing machine may be in response to user commands, or in response to results of previous processing, or in response to a request made by another processing machine.

0081As used herein, the terms "software" and "firmware" are interchangeable, and include any computer program stored in memory for execution by a computer, including RAM memory, ROM memory, EPROM memory, EEPROM memory, and non-volatile RAM (NVRAM) memory. The above memory types are exemplary only, and are thus not limiting as to the types of memory usable for storage of a computer program.

0082It also should be noted that the various embodiments of the present invention also may provide different and/or additional functionality. For example, end-to-end encryption may be performed, thereby eliminating the use of intervening encryption equipment and the security risk encountered by having such intervening equipment with access to encryption keys. Further, various embodiments of the present invention may provide end-to-end digital voice coding, thereby eliminating the use of intervening transcoding equipment and hence the fidelity loss encountered when one digital voice format is converted to another format.

0083Additionally, the various embodiments of the present invention may provide mission critical functions such as, for example, PTT, scanning, priority calls with preemption, emergency alerting and notification, content scanning and tracking, navigation, dispatch and GPS location. The mission critical functions may be implemented in different mission critical applications, including, but not limited to, public safety, utility industry and public transit industry.

0084Thus, the various embodiments provide multimode operation that allows implementing the same features, functions and user interface, independent of the system (e.g., LMR network or cellular network) on which the LMR unit is operating. The various embodiments also allow end-to-end encryption between LMR devices across different systems. Additionally, coding and recoding of the voice content is eliminated, thereby preserving voice quality.