Multiple protocol land mobile radio system

The present invention relates generally to terrestrial mobile radio (LMR), and more particularly to systems for providing terrestrial mobile radio services using a plurality of LMR communication protocols.

The land mobile radio can be used for communication between different mobile units, for example, between land mobile radios in different vehicles. Communications in the terrestrial mobile radio band, such as public safety radio communications (eg, police, fire departments, etc.), are generally available within the VHF, UHF, 700MHz, and 800MHz frequency bands. Part of each of these frequency bands has been allocated for public security communications services by the Federal Communications Commission (FCC) and is also known as the public security frequency band. These communications can also be made using a private land mobile radio service (PLMRS).

Traditionally, LMR networks have been used for critical applications such as public security communications. In addition to providing a very high level of system availability with LMR networks, LMR networks are designed to support PTT services such as dispatch operating modes. These LMR systems use a specialized LMR Airlink protocol for wireless communication between the LMR radio and the LMR infrastructure.

<p> Known LMR systems use a single protocol for different layers in the communication protocol stack. For example, the same protocol must be used for both the transport layer and the application layer of the protocol stack. Furthermore, when attempting to interconnect multiple systems, each using a different protocol, transcoding and Transcription of the LMR content to be communicated is required. Therefore, these system designs may not be optimal and may increase the cost of these systems.</p>

<p> The solution is provided by a method of communicating land mobile radio (LMR) content. The method involves communicating LMR content using multiple LMR transport protocols within a single LMR network. The method further includes configuring the LMR content based on the LMR application layer protocol that targets part of a single LMR network through which the LMR content is communicated.</p><p> The solution is also provided by a radio communication system that includes a land mobile radio (LMR) infrastructure configured to communicate with multiple LMR units within multiple areas of communication in the LMR system. At least some of the communication areas have different transport protocols. The wireless communication system further encapsulates the LMR content again to process the LMR content received using the first LMR transport protocol and to communicate using the second LMR transport protocol. Includes an interface configured to be a protocol.</p><p> The solution is also provided by a land mobile radio (LMR) unit that includes at least one voice encoder / decoder and multiple modems connected to at least one voice encoder / decoder. Each modem is configured to communicate using a different LMR transport protocol.</p><p> Next, the present invention will be illustrated with reference to the accompanying drawings.</p>

<figref num="1">FIG. 5 shows a land mobile radio (LMR) communication system configured according to an exemplary embodiment of the present invention.</figref><figref num="2">It is a figure which shows the communication area in a part of the LMR communication system of FIG.</figref><figref num="3">FIG. 6 is a block diagram of a land mobile radio (LMR) unit configured according to an exemplary embodiment of the invention communicating with an LMR network.</figref><figref num="4">FIG. 6 is a block diagram of a land mobile radio (LMR) unit configured according to another exemplary embodiment of the invention.</figref><figref num="5">FIG. 6 is a block diagram showing a protocol stack according to an exemplary embodiment of the present invention.</figref><figref num="6">It is a flowchart of the communication control method of the LMR content in the LMR communication system by the exemplary embodiment of this invention.</figref><figref num="7">FIG. 6 is a block diagram of a transport protocol interface configured according to an exemplary embodiment of the present invention.</figref><figref num="8">FIG. 6 is a block diagram showing formatted LMR content according to an exemplary embodiment of the present invention.</figref><figref num="9">It is a block diagram of the LMR communication system configured according to the exemplary embodiment of the present invention, and shows the communication area.</figref><figref num="10">It is a block diagram of the LMR communication system configured according to the exemplary embodiment of the present invention, and shows the flow of data.</figref>

Various embodiments of the present invention include systems for providing land mobile radio (LMR) content, such as LMR services over LMR networks that use multiple communication protocols. More specifically, multiple LMR transport layer protocols are used to communicate with LMRs that may hold a single LMR application layer protocol.

It should be noted that when referring to LMR content herein, it generally refers to any type or type of LMR audio and / or data content, and can define specific LMR services, operations, controls, etc. .. For example, LMR content includes voice data, emergency signal data, control data related to the selection of a particular talk group, LMR data for transfer between the wireless unit and the server, and reprogramming data (eg, software upgrades). Data) etc. are included, but not limited to these.

Specifically, as shown in FIG. 1, according to a wireless communication system, more specifically, an LMR communication system 20 configured according to various embodiments of the present invention, such as being located within various vehicles 22 and moving. Communication between multiple LMR units (not shown) that can be configured for operation or between multiple LMR terminals (not shown) is provided. For example, communication between LMR units located within different vehicles 22 takes place over an LMR network having a communication area. Here, a plurality of communication base stations and a corresponding communication tower 24 (for example, a part of a communication repeater tower) define a communication area. Within the LMR communication area, each base station 24 defines a radio frequency (RF) communicable range, but the RF communicable ranges may overlap.

In various embodiments, the communication protocol defined by the base station and its corresponding communication tower 24 may vary from base station to base station. More specifically, the transmission protocol, specifically the transport layer protocol, is different for some base stations and their corresponding communication towers 24. For example, one base station and its corresponding communication tower 24 may have a Terrestrial Trunked Radio (TETRA) transport protocol (eg, for example) for the RF communication area of that base station and its corresponding communication tower 24. ETSI TETRA standard) can be used. Other base stations can also use the P25 transport protocol (eg, Project 25 (TIA102) standard) for the base station and its corresponding RF communication area of the communication tower 24. Note that some base stations and their corresponding communication towers 24 may use the same transport protocol. Also, for example, M / A-COM Other types of LMR communication protocols such as OpenSky and EDACS protocols and LMR standards may be used.

During operation, the plurality of LMR units are respectively configured to communicate LMR contents using different communication protocols via the LMR communication system 20. In particular, as described in more detail herein, each LMR unit selects one of a plurality of transport layer protocols for LMR content communication (transport layer protocols differ from application layer protocols). May be). The LMR content is then configured to communicate using the communication protocol of choice. More specifically, the LMR content is encapsulated based on the communication protocol selected. Note that different application layer protocols may be used.

The LMR communication system 20 can include one or more communication areas 30, a portion of one communication area is shown in FIG. The communication area 30 is composed of a plurality of RF communication areas 32, and the services of the RF communication area 32 are provided by one or more base stations and their corresponding communication towers 24 (shown in FIG. 1). Each communication area 32 can be configured to communicate LMR content using different transport layer protocols. Here we show the case where three different transport layer protocols are used: the LMR-1 transport, the LMR-2 transport, and the LMR-3 transport. The transport layer protocol used in the adjacent RF communication area 32 may be the same or different.

Various embodiments make it possible to provide LMR services between terminations via multiple protocols, such as multiple radio and / or airlink protocols. In general, the LMR unit 40 (also called the LMR terminal) shown in FIG. 3 is the LMR application layer protocol between terminations between the LMR unit 40 and the LMR network 42, which can include multiple LMR base stations 44. The service is configured to be executable. Note that each of the LMR base stations 44 may be configured to communicate using a different protocol.

More specifically, the LMR unit 40 includes a plurality of modules or components configured for communication over the LMR network 42. Specifically, the LMR unit 40 includes an LMR application module 46 connected to an LMR transport module 48. The LMR transport module 48 configures voice and / or data for communication over the LMR network 42 (having one or more LMR base stations 44) using the LMR transmitter / receiver 50. Be prepared to do. The LMR transmitter / receiver 50 may be a separate unit or a single transmitter / receiver. The LMR unit 40 further includes an LMR encapsulation module 52 connected between the LMR transport module 48 and the LMR transmitter / receiver 50. The LMR encapsulation module 50 encapsulates voice and / or data for communication using one of a plurality of communication protocols. The LMR transport module 48, the LMR encapsulation module 52, and the LMR transmitter / receiver 50 together constitute the multiple protocol communication unit 54.

The LMR unit 40 can include additional components, such as known antennas (not shown) used to transmit and receive signals. Further, for example, the LMR unit 40 includes a filter (not shown) such as a reception filter for filtering the signal received by the LMR unit 40 and a transmission filter for filtering the signal transmitted by the LMR unit 40. Can be done. The LMR unit 40 can also include components for processing LMR content and for interacting with users. For example, the processor 56 connected to the memory 58 may be configured to receive different LMR content. Also, as detailed below, processor 56 encapsulates the LMR content, or LMR, based on input 60 from the user or other information (eg, configuration or protocol description information in the LMR content signal). You may decide how to decapsulate the content. For example, processor 56 can be configured to send control commands to selector 62 of LMR transport module 48 to select a protocol for LMR content communication. In addition, a display 64 may be provided, and for example, for the LMR unit 40, the display 64 may be configured to display the current channel, frequency, communication mode, communication type, communication protocol, and the like.

In operation, the LMR communication system 20 with the LMR unit 40 provides communication over the LMR network 42 using different known protocols, eg, using the LMR airlink protocol within a single LMR network 42. be able to. For example, these LMR airlink protocols include the Project 25 (TIA102) standard and ETSI, among others. Includes TETRA standard. These LMR airlink protocols define formats and procedures for exchanging information between the LMR unit 40 and the LMR network 42 (particularly the LMR base station 44). If the base station 44 is part of a larger system, the base station 44 is interconnected to a switching device (not shown) that routes voice and data in different parts of the system. Examples of the switching device include other LMR base stations and dispatch consoles. As is known, the LMR base station 44 transfers voice, data, and control information received over the airlink to an alternative format suitable for communication within the LMR network 42 (eg, to a switching device). Process into a suitable format), eg, manipulate the data.

For example, based on the current RF communication area 32 (shown in Figure 2) and the corresponding communication protocol, the LMR content is first generated by the LMR application module 46 located at the application layer. The communication protocol may be determined automatically using, for example, the header information in the LMR signal, or may be determined manually, for example, by selection by the user. The LMR content is then encapsulated by the LMR encapsulation module 52 located at the transport layer, as selected by the LMR transport module 48. Note that when LMR content is communicated via the LMR network 42, transport layer encapsulation can be modified, for example, based on the protocol used by the current LMR base station 44, but application layer encapsulation. Remains unchanged. Therefore, in various embodiments, the LMR unit 40 is configured to have at least one voice encoder / decoder 70 connected to the multiple protocol communication unit 72, as shown in FIG. In this embodiment, the multiple protocol communication unit 72 includes an interface 74. Interface 74 communicates with a voice encoder / decoder 70 and a plurality of modems 76, each configured to communicate using different LMR communication protocols. The number of modems 76 or other communication units is variable and may be increased or decreased, for example. It may also include a single communication unit configured to communicate using a plurality of different communication protocols. Further, when the communication of the LMR contents is performed using a plurality of different application layers, the voice encoder / decoder 70 may be changed, or the voice encoder / decoder 70 may be added. Further, the LMR unit 40 may include a speaker 78 configured to output decapsulated LMR content.

In operation, the LMR unit 40 receives the LMR content in the multiple protocol communication unit 72, or inputs from the user in the voice encoder / decoder 70 (for example, voice message by a microphone (not shown) or input by pressing a button. ) Is received. In the case of the LMR content received by the multiple protocol communication unit 72, the LMR content is decapsulated and processed, and the processing can include decryption and decryption of the LMR content. The LMR content can then be output, for example, via the speaker 78. For inputs received by the voice encoder / decoder 70, the inputs are, for example, encrypted (eg, encapsulated based on the encapsulation layer), using one of a plurality of modems 76. It is transmitted from the multiple protocol communication unit 72. This transmission is based on the communication protocol for that portion of the LMR network 42 (shown in FIG. 3) and as determined by the transport layer.

In this way, the communication of the LMR contents is performed via the LMR network 42. The communication involves sending and receiving using a number of different transport protocols and configuring the LMR content accordingly, eg, configuring the LMR content using a number of different airlink protocols. Can include. In order to communicate over the LMR network 42 using the LMR unit 40, the communication protocol stack for communicating using a plurality of different protocols is divided as shown in FIG. In particular, regarding communication with the LMR unit 40 using the LMR network 42, the LMR protocol stack 80 is divided into a plurality of layers. In this embodiment, it is a two-layer protocol stack that includes an LMR application layer 82 and an LMR transport layer 84. For example, the LMR application module 46 shown in FIG. 3 can provide the LMR application layer 82 and the LMR transport module 48 shown in FIG. 3 can provide the LMR transport layer 84. The LMR application layer 82 is configured to interpret and process voice, data, and control information throughout the LMR network 42. The LMR transport layer 84 is configured to transmit voice, data, and control information via a transmission medium. The transmission medium may be responsible for transmitting only a part of the LMR network 42 defined by the RF communication area 32 (shown in FIG. 2). As described herein, the LMR airlink protocol defines at least one of the LMR application layer 82 and the LMR transport layer 84 for a particular part of the LMR network 42, eg, RF communication area 32. ..

In this two-tier protocol stack model, the LMR base station 44 (shown in Figure 3) and the switching device in the LMR network 42 (shown in Figure 3) are content from the LMR unit 40 (shown in Figure 3 and Figure 4). To receive. The contents of the LMR application layer 82 are then exchanged between the LMR base station 44 and the switching device using one or more different transport layers. In particular, as shown in FIG. 5, the content of application layer 82 is encapsulated at LMR base station 44 (shown in FIG. 3) using LMR content encapsulation 86, as is known. In an exemplary embodiment, individual transmission units are encapsulated within the transport datagram, especially within the packet-switched transport datagram 88, and the communication of the encapsulated datagram is multiple. It is done using one of the transport protocols. Upon receipt of the encapsulated datagram, the content of the application layer can be restored, specifically decapsulated.

In addition, this two-tier protocol stack model allows multiple layers of the network to use different transport layers defined by different communication protocols or different transport layers defined by different protocols than the application layer. It will be possible to provide services for the LMR application layer over a portion. Specifically, as shown on the left side of FIG. 5, the application layer 82 and the transport layer 84 are configured based on the same communication protocol, that is, LMR-1. The LMR-1 can be, for example, a Tetra-based communication protocol. However, as shown on the right side of FIG. 5, the application layer 82 is LMR-1 as on the left side, while the transport layer 84a is LMR-2 unlike the left side. The LMR-2 can be, for example, a P25-based communication protocol. Therefore, the content encapsulation of the application layer is the same, but the encapsulation of the transport layer is different.

In particular, the LMR content encapsulation 86 is used with the packet-switched transport datagram 88 so that the LMR network 42 (shown in Figure 3) can communicate with the switching device using the appropriate transport protocol. This allows the same LMR application layer service to be provided across the LMR network 42 while using LMR base station 44 (shown in Figure 3) configured to communicate using different LMR communication protocols. it can. Specifically, the LMR infrastructure uses packet-switched transport datagram 88 with LMR application layer switching 92 to exchange LMR application services with different transport layers 84,84a.

It should be noted that the various embodiments are not limited to the two-layer protocol stack and additional layers may be added to the multi-layer protocol stack if desired or as needed. For example, different session layers such as a bulk encryption layer can be provided. Further, for example, an RTP layer can be provided. In addition, the example in Figure 5 is shown to communicate using the same protocol for both (i) the application layer and the transport layer, and (ii) different protocols for the transport layer. Note that changes are intended in various embodiments. For example, the same transport layer can be used with multiple different application layers.

Various embodiments of the present invention control the communication of LMR content in an LMR communication system using an LMR network with multiple LMR base stations or other repeaters or routers capable of using different communication protocols. In particular, a method 100 for controlling the communication of LMR content is shown in FIG. The method, at 102, comprises determining the protocol used to communicate the LMR content, more specifically the transport layer protocol used. In an exemplary embodiment, a decision is made regarding the transport protocol for the current communication area. The decision can be made based on a manual selection, for example, based on the input selection from the user regarding which protocol to use, or based on the input position of the LMR unit. The selection can be made, for example, using a button or switch on the LMR unit 40 (shown in FIG. 3). Alternatively or optionally, it may automatically determine which protocol to use. For example, the selection of the protocol for LMR content communication may be based on the LMR unit's automatic position detection (eg, using GPS), or within the LMR content, eg, in the header portion of the LMR content. , Or it may be based on the information received in the setup message or the configuration message.

In 102, the transport protocol for LMR content communication is determined, and in 104, the communication method is selected based on the protocol decided to be used. For example, communication speed or baud rate) can be selected (manually or automatically) from a range of communication data rates. In addition, you can choose the setup procedure for establishing a determined part of the network and connecting to it. For example, if the first communication protocol is used, the network communication setup routine of the LMR-1 transport layer can be executed, in which the routine is via the LMR transmitter / receiver in the LMR unit. A communication link is established between the LMR unit and that part of the LMR network. If a second communication protocol is used, the LMR-2 transport layer network communication setup routine can be run, in which the LMR unit and the LMR network (unlike the first part). A communication link is established with the different parts. The setup routine can include any suitable process known to establish a wireless communication link.

Then, at 106, the LMR content is configured to communicate based on the application layer protocol and the communication method chosen. For example, when communicating LMR content using the LMR-1 transport layer, a selection of specific LMR standards is made to configure or format the LMR content. Specifically, the LMR-1 standard that configures the audio and / or data payload that defines the LMR content is selected. This can include, for example, selecting either Project 25 (TIA102) or the ETSI TETRA standard for the communication method, and encapsulating the data accordingly. Data encapsulation can be done using, for example, IP wrapper encapsulation and specific application layer protocols, such as the LMR-1 application layer protocol. For example, OpenSky You can select the format that M / A-COM has the right to, the format that the Network First or EDACS system has the right to, and so on. For example, if parts of the LMR network require communication in the LMR-2 standard, different communication protocols or formats can be used.

In addition, a particular protocol stack may be used, depending on the protocol for communication of the LMR content, as detailed above in connection with FIG. In addition, an LMR protocol header that identifies the transport layer and protocol used to encapsulate the data can be added to the payload of the LMR data. As further described below, the LMR content is encapsulated, for example, by IP encapsulation using an IP wrapper prior to communication. The encapsulation can include multi-layered encapsulation.

Referencing FIG. 6 again, 106, the LMR content is configured, and then 108, the configured LMR content is communicated. For example, when LMR content is configured for communication using the LMR-1 communication protocol, the modem corresponding to that protocol communicates LMR content from the LMR unit and with the LMR unit. Used to do. For example, if LMR content is configured for communication using another protocol, such as the LMR-2 protocol, different modems corresponding to that protocol can communicate LMR content from the LMR unit and with the LMR unit. Used to communicate content. It should be noted that the LMR unit may be configured to operate in two or more modes of operation, i.e., in association with two or more different communication protocols.

After the LMR content is communicated and received, for example, by a network base station, at 110, the LMR content is processed to determine the action. For example, this can include a decision to send audio data, or a decision to issue an emergency signal, or a decision to issue a PTT request to a talk group. Further, for example, when communicating LMR content using different transport layers, the IP destination address of the encapsulated datagram is first determined and then its location for processing using a router in the network. Can be sent to. The LMR content can then be re-encapsulated.

In various embodiments, the transport protocol interface 120 can be provided with the base station 44 (shown in FIG. 3), as shown in FIG. The transport protocol interface 120 is, for example, as a separate unit (eg, a stand-alone module), as a card for connecting to a server in LMR network 42 (shown in Figure 3), or as a server in LMR network 42. It can be provided as software for downloading to. The transport protocol interface 120 includes a processor 122 for processing received encapsulated LMR content for communication within the infrastructure of the LMR network 42. In particular, as described in more detail in connection with FIGS. 5 and 6, the processor can receive LMR content formatted as shown in FIG. LMR content generally includes an LMR data portion and an encapsulated portion of a packet-switched protocol. Specifically, the LMR content 130 can include a transport layer protocol header 132, an application layer protocol header 134, and LMR data 136, such as the LMR data payload.

This LMR content 130 is basically encapsulated. For example, the LMR content 130 is encapsulated in one or more IP wrappers so that different communication protocols can be used to communicate with the LMR content 130. The processor 122 can decapsulate the LMR content 130 by removing, for example, the transport layer protocol header 132, and can store the decapsulated LMR content 130 in the memory 124. The LMR content 130 is then further processed by processor 122 to determine the action to be taken or to determine the address in the packet-switched LMR infrastructure that is the destination of the LMR content 130. It may include re-encapsulation with different transport layers identified by different transport layer protocol headers 132. Basically, after the LMR content 130 is decapsulated, the LMR content 130 is configured to communicate within the LMR infrastructure or within other parts of the LMR network 42. The communication of the LMR content 130 is controlled by the control device 126. The control device 126 may include, for example, a router 128 for routing the LMR content 130 to a destination within the LMR network 42.

Thus, various embodiments of the present invention provide communication of LMR content using one or more protocols within an LMR network. The content is encapsulated for communication based on multiple different transport layers, and accordingly one of the multiple modems in the LMR unit can be used for communication. For example, as shown in FIG. 9, the LMR communication system 200 is generally used for communication using a plurality of LMR network base stations 202 configured for communication using the first LMR communication protocol and communication using the second LMR communication protocol. Includes a plurality of LMR network base stations 204 configured in. The plurality of network base stations 202 have a corresponding communication area 206, and the plurality of network base stations 204 each have a corresponding communication area 208. Communication areas 206 and 208 may overlap at several locations. According to various embodiments of the invention described herein, the LMR unit 210, eg, the LMR radio in a mobile unit or vehicle, varies depending on, for example, the location of the LMR unit 210 and the corresponding available communication area. It is possible to communicate using the LMR communication protocol (for example, a different transport layer protocol). More specifically, the communication towers (not shown) corresponding to each of the plurality of LMR network base stations 202 and 204 enable the wireless communication described herein.

Further, as shown in FIG. 10, the controller 212 in the LMR network infrastructure 211, for example, the LMR communication system 200 (shown in FIG. 9), is moved from the plurality of LMR network base stations 202, 204 described herein. It may be configured to control the communication of. The controller can process multiple data packets received from different parts of the LMR network, eg, different RF communication areas 214 and 216 with different communication requirements or different transport protocol requirements. The controller can then determine the appropriate action or routing procedure for a particular data packet, as described herein. Thus, for example, various embodiments may use Tetra-based communication protocols for short distances in urban areas for higher capacity communications. Also, for lower capacity communications, long-range VHF-based communication protocols can be used in rural areas. In addition, the transport layer can be selected based on the type of service or the type of service.

Various embodiments or components, such as an LMR communication system, network, or control device thereof, can be implemented as part of one or more computer systems, which is separate from the LMR communication system. It is possible to make it or to integrate it. A computer system can include a computer, an input device, a display device, and, for example, an interface for accessing the Internet. The computer can include a microprocessor. The microprocessor can be connected to the communication bus. The computer can also include memory. Memory can include random access memory (RAM) and read-only memory (ROM). The computer system can further include a storage device, which can be a hard disk drive or a removable storage drive such as a floppy disk drive or an optical disk drive. The storage device may also be another similar means for capturing and retaining computer programs or other instructions within a computer system.

As used herein, the term "computer" may include any processor-based or microprocessor-based system. The term "computer" refers to microcontrollers, reduced instruction set circuits (RISCs), application-specific ICs (ASICs), logic circuits, and any other circuits capable of performing the functions described herein. Systems that use processors can be included. The above examples are merely exemplary and are therefore not intended to limit the definition and / or meaning of the term "computer" in any way.

A computer system executes a series of instructions stored in one or more storage elements to process input data. The storage element can also store data or other information as desired or as needed. The storage element can be in the form of an information source, or a physical storage element within a processing device.

The set of instructions can include various commands that instruct a computer as a processing device to perform specific operations such as methods and processes of various embodiments of the present invention. The series of instructions can be in the form of a software program. The software can be in various formats, such as system software or application software. In addition, the software can be in the form of separate collections of programs, program modules within a larger program, or parts of a program module. The software can also include modular programming in the form of object-oriented programming. The processing of the input data by the processing device can be performed in response to a user command, in response to the result of previous processing, or in response to a request made by another processing device.

As used herein, the terms "software" and "firmware" are interchangeable, and these terms include any computer program that is stored in memory and executed by a computer. Memory includes RAM memory, ROM memory, EPROM memory, EEPROM memory, and non-volatile RAM (NVRAM) memory. However, the above memory types are merely exemplary and therefore do not limit the types of memory that can be used to store computer programs.

It should also be noted that the various embodiments of the invention can also provide different functionality and / or additional functionality. For example, end-to-end encryption can be performed, eliminating the need for intervening cryptographic devices and eliminating the security risks posed by such intervening cryptographic devices with access to encryption keys. can do. In addition, various embodiments of the invention can provide digital voice coding between terminations. This eliminates the need for intervening converters and transfer devices, thus eliminating the lack of fidelity that occurs when one format is converted to another.

40 ... Land Mobile Radio (LMR) Unit, 42 ... LMR Network, 46 ... LMR Application Layer Module, 48 ... LMR Transport Layer Module, 70 ... Encoder / Decoder, 76 ... Modul, 80 ... Multilayer Protocol Stack, 82 ... LMR Application Layer, 84 ... LMR Transport Layer, 120 ... Interface, 130 ... LMR Content, 200 ... LMR System, 208. .. Communication Area, 210 ... LMR Unit, 211 ... LMR Infrastructure