Multiple protocol land mobile radio system

A multiple protocol land mobile radio (LMR) and a method for communicating LMR content are provided. The method includes communicating the LMR content using a plurality of LMR transport protocols within a single LMR network. The method further includes encapsulating the LMR content based on an LMR application layer protocol for a portion of the single LMR network through which the LMR content is to be communicated.

BACKGROUND OF THE INVENTION

This invention relates generally to land mobile radios, and more particularly, to a system for providing land mobile radio (LMR) services using multiple LMR communication protocols.

Land mobile radios may be used to provide communication between different mobile units, for example, land mobile radios in different vehicles. 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).

Traditionally, LMR networks have been used to provide mission critical applications such as public safety communications. In addition to providing a very high level of system availability, LMR networks are designed to support PTT services, such as a dispatch mode of operation. These LMR systems use specialized LMR airlink protocols to communicate wirelessly between LMR radios and the LMR infrastructure.

Known LMR systems use a single protocol for the various layers in the communication protocol stack. For example, the same protocol must be used for both a transport layer and an application layer of the protocol stack. Further, when trying to interconnect multiple systems, with each system using a different protocol, transcoding and trascryption of the communicated LMR content is needed. Thus, design of these systems may result in sub-optimal performance and the cost of these systems may be increased.

BRIEF DESCRIPTION OF THE INVENTION

In one exemplary embodiment, a method for communicating land mobile radio (LMR) content is provided. The method includes communicating the LMR content using a plurality of LMR transport protocols within a single LMR network. The method further includes encapsulating the LMR content based on an LMR application layer protocol for a portion of the single LMR network through which the LMR content is to be communicated.

In another exemplary embodiment, a wireless communication system is provided that includes a land mobile radio (LMR) infrastructure configured to communicate with a plurality of LMR units within a plurality of coverage areas of an LMR system. At least some of the plurality of coverage areas have different transport protocols. The wireless communication system further includes an interface configured to process received LMR content that is communicated using a first LMR transport protocol and reencapsulate the LMR content for communication using a second LMR transport protocol.

In yet another exemplary embodiment, a land mobile radio (LMR) unit is provided that includes at least one voice encode/decoder and a plurality of modems connected to the at least one voice encoder/decoder. The plurality of modems are each configured to communicate using a different LMR transport protocol.

DETAILED DESCRIPTION OF THE INVENTION

Various embodiments of the invention include a system for providing land mobile radio (LMR) content, for example, LMR services via an LMR network using multiple communication protocols. More particularly, multiple LMR transport layer protocols are used to communicate LMR that can retain a single LMR application layer protocol.

It 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.

Specifically, as shown inFIG. 1, a wireless communication system, and more particularly, an LMR communication system20constructed according to various embodiments of the invention provides communication between a plurality of LMR units or LMR terminals (not shown), which may be configured for mobile operation, such as located in various vehicles22. Communication between the LMR units, for example, located in different vehicles22is provided via an LMR network having a communication coverage area defined by a plurality of communication base stations and associated communication towers24, for example, as part of communication repeater towers. Within the LMR coverage area, Radio Frequency (RF) coverage is provided by each of the base stations24. The RF coverage may overlap.

In various embodiments, the communication protocol provided by different base stations and associated communication towers24may be different. More particularly, the transmission protocol, and specifically, a transport layer protocol is different for some of the base stations and associated communication towers24. For example, one base station and associated communication tower24may use a Terrestrial Trunked Radio (TETRA) transport protocol (e.g., ETSI TETRA standard) for the RF coverage area of that base station and associated communication tower24and another base station may use a P25 transport protocol (e.g., Project 25 (TIA 102) standard) for the RF coverage area of that base station and associated communication tower24. It should be noted that some of the base stations and associated communication towers24may use the same transport protocol. Additionally, it should be noted that other types of LMR communication protocols and standards may be used, including, for example, M/A-COM OpenSky and EDACS protocols.

In operation, each of the LMR units is configured to communicate LMR content via the LMR communication system20using different communication protocols. In particular, and as described in more detail herein, the LMR units select between one of a plurality of transport layer protocols for use in communicating the LMR content (that may be different than an application layer protocol). The LMR content is then configured for communication using the selected communication protocol, and more particularly, encapsulated based on the selected communication protocol. Additionally, different application layer protocols may be used.

The LMR communication system20may include one or more communication areas30, a portion of one communication area is shown inFIG. 2. The communication area30is formed from a plurality of RF coverage areas32that are serviced by one or more base stations and associated communication towers24(shown inFIG. 1). Each coverage area32may be configured to communicate LMR content using a different transport layer protocol, shown as LMR-1 Transport, LMR-2 Transport and LMR-3 Transport, indicating that three different transport layer protocols are being used. It should be noted that adjacent RF coverage areas32may use the same or different transport layer protocols.

Various embodiments enable end-to-end LMR services to be provided over a plurality of protocols, for example, a plurality of radio and/or airlink protocols. In general, an LMR unit40(also referred to as an LMR terminal) as shown inFIG. 3is configured to allow operating end-to-end LMR application layer protocols and services between the LMR units40and an LMR network42that may include a plurality of LMR base stations44, each of which may be configured to communicate using a different protocol.

More particularly, the LMR unit40includes a plurality of modules or components configured to provide communication via the LMR network42. Specifically, the LMR unit40includes an LMR application module46connected to an LMR transport module48together provided for configuring voice and/or data for communication via the LMR network42(having one or more LMR base stations44) using an LMR transmitter/receiver50, which may be separate units or provided as a single transceiver. The LMR unit22further includes an LMR encapsulation module50connected between the LMR transport module48and the LMR transmitter receiver50for encapsulating the voice and/or data for communication using one of a plurality of communication protocols. The LMR transport module48, the LMR encapsulation module52and the LMR transmitter/receiver50generally define a multiple protocol communication portion54.

The LMR unit40may include additional components, for example, an antenna (not shown) for use in transmitting and receiving signals as is known. Additionally, and for example, the LMR unit40may include filters (not shown), such as a receive filter and a transmit filter for filtering signals that are received and transmitted, respectively, by the LMR unit40. The LMR unit40also may include components for processing LMR content and for interfacing with a user. For example, a processor56connected to a memory58may be configured to receive the different LMR content and based on a user input60or other information (e.g., configuration or protocol description information in the LMR content signal) determine the manner is which to encapsulate or decapsulate the LMR content as described in more detail below. For example, the processor56may be configured to communicate control commands to a selector62of the LMR transport module48to select a protocol for use in communicating the LMR content. A display64also may be provided and configured to display, for example, the current channel, frequency, mode of communication, type of communication, communication protocol, etc, for the LMR unit40.

In operation, the LMR communication system20with the LMR unit40may provide communication via the LMR network42using different known protocols, for example, LMR airlink protocols within a single LMR network42. For example, these LMR airlink protocols include the Project 25 (TIA 102) and ETSI TETRA standards, among others. These LMR airlink protocols specify the format and procedures for information exchange between the LMR unit40and the LMR network42, and in particular, the LMR base stations44. It should be noted that when the base station(s)44are part of a larger system, the base station(s)44are 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. As is known, the LMR base station44processes, for example, manipulates, the voice, data and control information received over the airlink into an alternate format suitable for communication within the LMR network42, for example, for transport to switching equipment.

For example, based on the current RF coverage area32(shown inFIG. 2) and associated communication protocol, which may be automatically determined (e.g., using header information in the LMR signal) or manually selected (e.g., selected by a user), LMR content is first generated by the LMR application module46based on an application layer and then encapsulated by the LMR encapsulation module52based on a transport layer as selected by the LMR transport module48. It should be noted that when LMR content is communicated through the LMR network42, the encapsulation of the transport layer may change based on, for example, the protocol used by the current LMR base station44, but the encapsulation of the application layer remains unchanged. Accordingly, in various embodiments, the LMR unit40is configured having at least one voice encoder/decoder70connected to a multiple protocol communication portion72as shown inFIG. 4. In this embodiment, the multiple protocol communication portion72includes an interface74for communicating with the voice encoder/decoder70and a plurality of modems76each configured to communicate using a different LMR communication protocol. The number of modems76or other communication units may be modified, for example, increased or decreased. Additionally, a single communication unit configured to communicate using a plurality of different communication protocols may be provided. Also, the voice encoder/decoder70may be modified or additional voice encoders/decoders70added if LMR content is to be communicated using different application layers. In addition, the LMR unit40may include a speaker78configured to output the decapsulated LMR content.

In operation, the LMR unit40either receives LMR content at the multiple protocol communication portion72or a user input (e.g., voice message via a microphone (not shown) or button depression input) at the voice encoder/decoder70. For LMR content received at the multiple protocol communication portion72, the LMR content is decapsulated and processed, which may include decoding and decrypting the LMR content, and then output, for example, via the speaker78. For inputs received at the voice encoder/decoder70, the input, for example, is encoded (e.g., encapsulated based on an encapsulation layer) and then transmitted from the multiple protocol communication portion72using one of the plurality of modems76based on the communication protocol for that portion of the LMR network42(shown inFIG. 3) and as determined by a transport layer.

Thus, communication of LMR content is communicated over the LMR network42and which may include transmitting and receiving using a plurality of different transport protocols and configuring the LMR content accordingly, for example, configuring the LMR content using different airlink protocols. In order to provide communication via the LMR network42using the LMR unit40, the communication protocol stacks for communication using different protocols is partitioned as shown inFIG. 5. In particular, and with respect to communication with the LMR unit40using the LMR network42, an LMR protocol stack80is partitioned into multiple layers, which in an exemplary embodiment, is a two-layer protocol stack having an LMR application layer82and an LMR transport layer84. The LMR application layer82and the LMR transport layer84may be provided, for example, by the LMR application module46and LMR transport module48(both shown inFIG. 3), respectively. The LMR application layer82is configured to provide interpretation and processing of the voice, data and control information across the entire LMR network42and the LMR transport layer84is configured to provide delivery of the voice, data and control information over the transmission medium, which may be only over a portion of the LMR network42defined by a RF coverage area32(shown inFIG. 2). As described herein, an LMR airlink protocol defines at least one of the LMR application layer82and the LMR transport layer84for a particular portion of the LMR network42, for example, an RF coverage area32.

In this two-layer protocol stack model, the LMR base station44(shown inFIG. 3) and switching equipment in the LMR network42(shown inFIG. 3) receive content from the LMR unit40(shown inFIGS. 3 and 4) and communicate content of the LMR application layer82therebetween with a one or more different transport layers. In particular, and as shown inFIG. 5, the content of the application layer82is encapsulated at the LMR base station42(shown inFIG. 3) using LMR content encapsulation86as is known. In an exemplary embodiment, discrete transmission units are encapsulated within transport datagrams, and in particular, packet switched transport datagrams88, that are communicated using one of a plurality of transport protocols. Upon receipt of an encapsulated datagram, the application layer content then may be recovered, and in particular, decapsulated.

Further, this two-layer protocol stack model enables delivering LMR application layer services over portions of the network using different transport layers defined by different communication protocols or a protocol different from the application layer. Specifically, as shown on the left side ofFIG. 5, the application layer82and transport layer84are configured based on the same communication protocol, namely, LMR-1, which may be, for example, a Tetra based communication protocol. However, as shown on the right hand side ofFIG. 5, the application layer82is the same, namely LMR-1, but the transport layer84ais different, namely, LMR-2, which may be, for example, a P25 based communication protocol. Accordingly, the application layer content encapsulation is the same, but the transport layer encapsulation is different.

In particular, the LMR content encapsulation86is used with the packet switched transport datagrams88such that the LMR network42(shown inFIG. 3) can communicate with switching equipment using suitable transport protocols, thereby delivering the identical LMR application layer services over the LMR network42using LMR base stations44(shown inFIG. 3) configured to communicate using different LMR communication protocols. Specifically, the LMR infrastructure communicates the LMR application services using an LMR application layer switching92in combination with packet switched transport datagrams68with different transport layers84and84a.

It 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. Further, it should be noted that although the example inFIG. 5is shown as providing communication using (i) the same protocol for both the application layer and transport layer and (ii) a different protocol for the transport layer, modifications are contemplated in the various embodiments. For example, the same transport layer may be used with different application layers.

Various embodiments of the invention provide for controlling communication of LMR content in an LMR communication system using an LMR network having a plurality of LMR base stations or other repeaters or routers that may use different communication protocols. In particular, a method100of controlling communication of LMR content is shown inFIG. 6and includes determining at102the protocol to use to communicate the LMR content, and more particularly, the transport layer protocol to use. In an exemplary embodiment, a determination is made as to the transport protocol for the current coverage area. The determination may be based on a manual selection, for example, based on a user input selection of which protocol to use or the inputted location of the LMR unit. The selection may be made, for example, using a button or switch on the LMR unit40(shown inFIG. 3). Alternatively or optionally, the determination of which protocol to use may be automatic. For example, the selection of a protocol for communicating LMR content may be based on the automatic location detection of the LMR unit (e.g., using GPS) or based on information received in the LMR content, for example, in a header portion of the LMR content, or in a setup or configuration message.

After a determination of the transport protocol to use to communicate the LMR content is made at102, a method of communication is selected at104based on the determined protocol 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 portion of the network may be selected. For example, if a first communication protocol is to be used, an LMR-1 transport layer network communication setup routine may be executed wherein a communication link is established between the LMR unit and that portion of the LMR network via an LMR transmitter/receiver within the LMR unit. If a second communication protocol is to be used, an LMR-2 transport layer network communication setup routine may be executed wherein a communication link is established between the LMR unit and that different portion (different from the first portion) of the LMR network. The setup routine may include any suitable processes as are known for establishing a wireless communication link.

Thereafter, at106the LMR content is configured for communication based on application layer protocol and the selected method of communication. For example, if the LMR content is to be communicated using the LMR-1 transport layer, a selection of a particular LMR standard in which to configure or format the LMR content is selected. In particular, an LMR-1 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 and encapsulating the data accordingly, for example, using IP wrapper encapsulation with a particular application layer protocol, for example, an LMR-1 application layer protocol. Further, and for example, a proprietary format may be selected, for example, an OpenSky MIA-COM proprietary format, a NetworkFirst or EDACS system proprietary format. A different communication protocol or format may be used, for example, if the portion of the LMR network requires communication in an LMR-2 standard.

Additionally, and as described in more detail above in connection withFIG. 5, depending on the protocol to be used to communicate the LMR content, a particular protocol stack may be used. Further, an LMR protocol header identifying the transport layer and protocol used to encapsulate the data may be added to the LMR data payload. As described in more detail below, the LMR content is encapsulated, for example, IP encapsulated with an IP wrapper prior to communication. It should be noted that this may include multiple layers of encapsulation.

Referring again toFIG. 6, after the LMR content is configured at106, the configured LMR content is communicated at108. For example, if the LMR content is configured for communication using an LMR-1 communication protocol, the modem corresponding to that protocol is used to communicate the LMR content from and with the LMR units. If the LMR content is configured for communication using, for example, another protocol such as an LMR-2 protocol, a different modem corresponding to that protocol is used to communicate the LMR content from and with the LMR units. It should be noted that the LMR unit may be configured to operate in two or more modes of operation, namely, in connection with two or more different communication protocols.

After the LMR content is communicated and received, for example, by a base station of the network, the LMR content is processed at110to 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. Further and for example, if the LMR content is communicated using different transport layers, 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. The LMR content then may be reencapsulated.

In the various embodiments, as shown inFIG. 7, a transport protocol interface120may be provided in connection with the base stations44(shown inFIG. 3). The transport protocol interface120may be provided, for example, as a separate unit (e.g., stand alone module), a card for connection to a server within the LMR network42(shown inFIG. 3) or software for downloading to a server within the LMR network42. The transport protocol interface120includes a processor122for processing received encapsulated LMR content for communication within the infrastructure of the LMR network42. In particular, and as described in more detail in connection withFIGS. 5 and 6, the processor may receive LMR content formatted as shown inFIG. 8. The LMR content generally includes an LMR data portion and a packet switching protocol encapsulation portion. Specifically, the LMR content130may include a transport layer protocol header132, an application layer protocol header134and LMR data136, for example, an LMR data payload.

This LMR content130is essentially encapsulated, for example, encapsulated in one or more IP wrappers such that different communication protocols may be used to communication the LMR content130. The processor122decapsulates the LMR content130, for example, by removing the transport layer protocol header132and may store the decapsulated LMR content130in a memory124. The LMR content130then may be further processed by the processor122to determine an action to be performed or an address within the packet switched LMR infrastructure to which the LMR content130is to be communicated, which may include reencapsulation using a different transport layer identified by a different transport layer protocol header132. Essentially, once the LMR content130is decapsulated, the LMR content130is configured for communication within the LMR infrastructure or within another portion of the LMR network42. The control of communication of the LMR content130is controlled by a controller126that may include a router128for routing the LMR content130to a destination within, for example, the LMR network42.

Thus, various embodiments of the invention provide for communicating LMR content using one or more protocols within an LMR network. The content may be encapsulated for communication based on a plurality of different transport layers and communicated accordingly using one of a plurality of modems of an LMR unit. For example, and as shown inFIG. 9, an LMR communication system200generally includes a plurality of LMR network base stations202configured to communicate using a first LMR communication protocol and a plurality of LMR network base stations204configured to communicate using a second LMR communication protocol. Each of the plurality of network base stations202and204have a corresponding coverage area206and208, respectively. The communication coverage areas206and208may be overlapping at some locations. The various embodiments of the invention as described herein allow an LMR unit210, for example, an LMR radio in a mobile unit or vehicle, to communicate via different LMR communication protocols (e.g., different transport layer protocols) depending on, for example, the location of the LMR unit210and the corresponding available coverage area. More particularly, communication towers (not shown) corresponding to each of the plurality of LMR network base stations202and204allow wireless communication as described herein.

Further, as shown inFIG. 10, a controller212within an infrastructure211of an LMR network, for example, the LMR communication system200(shown inFIG. 9) may be configured to control communications from the plurality of LMR network base stations202and204as described herein. The controller may process a plurality of data packets received from different portions of the LMR network, for example, different RF coverage areas214and216, having different communication or transport protocol requirements, to determine an appropriate action or routing procedure for the particular data packets as described herein. Accordingly, and for example, the various embodiments may provide for using a Tetra based communication protocol in urban areas for shorter range, higher capacity communications and a VHF based communication protocol in rural areas for longer range, lower capacity communications. Further, the transport layer may be selected based on the type or kind service.

The various embodiments or components, for example, the LMR communication systems, networks 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. 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.

The 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.

It also should be noted that the various embodiments of the 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 invention may provide end-to-end digital voice coding, thereby eliminating the use of intervening transcoding and transcription equipment and hence the fidelity loss encountered when one format is converted to another format.