BACKGROUND

Mission critical, push to talk (MCPTT) refers to a PTT product functionality that meets the requirements of Public Safety mission-critical voice communication, which include high availability/reliability, low latency, support for group calls and 1:1 calls, talker identification, device-to device (D2D) direct communication, emergency calling, clear audio quality, and the like. In conjunction with other organizations, the Third Generation Partnership Project (3GPP) is developing standards for implementing MCPTT over networks that operate according to the Long Term Evolution (LTE) standards and Fifth Generation (5G) defined by the 3GPP. The MCPTT standards for LTE/5G operation address call types, floor control, priority, preemption, performance, group management, off-network use, security, interworking with non-LTE PTT systems, and the like. Communication within railway systems is an important application and 3GPP is currently developing a mobile communication system for railways that is based on MCPTT. A user equipment in a railway mobile communication system establishes a session using an application implemented on the user equipment, which communicates with an MCPTT server that connects to an LTE core network. The MCPTT system is required to interconnect and interoperate with other networks, e.g., to support communication in numerous regions traversed by a railway system. Implementing MCPTT without interoperability would severely impact voice communications where coverage is poor or in regions that choose other vendors that implement different networks. Thus, limited interoperability would reduce the value of the MCPTT system to railway organizations.

SUMMARY

The following presents a simplified summary of the disclosed subject matter in order to provide a basic understanding of some aspects of the disclosed subject matter. This summary is not an exhaustive overview of the disclosed subject matter. It is not intended to identify key or critical elements of the disclosed subject matter or to delineate the scope of the disclosed subject matter. Its sole purpose is to present some concepts in a simplified form as a prelude to the more detailed description that is discussed later.

In some embodiments, an apparatus is provided that includes a transceiver configured to receive a call request for a mission critical, push to talk (MCPTT) call and a processor configured to access, in response to receiving the call request, a mapping of an MCPTT identifier of a user equipment with an interworking identifier that is formed according to an address format implemented in Global System for Mobile communications (GSM) for Railways (GSM-R). The transceiver forwards the call request based on the mapping.

In some embodiments, the MCPTT identifier is a uniform resource identifier (URI) and the interworking identifier is represented in an e164 format.

In some embodiments, the mapping is stored in a user profile that includes a binding between the MCPTT identifier, the interworking identifier, and an identifier of the apparatus.

Some embodiments of the apparatus include a memory configured to store the user profile in a routing table, wherein the processor is configured to access the mapping from the memory.

Some embodiments of the processor are configured to access the mapping from a database that is implemented external to the apparatus.

Some embodiments of the transceiver are configured to receive the call request including the MCPTT identifier in response to the user equipment initiating the MCPTT call. Some embodiments of the processor are configured to add the interworking identifier to the call request prior to forwarding the call request to an interworking function associated with a GSM-R system.

In some embodiments, the interworking identifier is displayed to a GSM-R client or used to initiate another call to the user equipment by the GSM-R client.

Some embodiments of the transceiver are configured to receive the call request including an identifier in the address format implemented in GSM-R in response to a GSM-R client initiating a call.

Some embodiments of the processor are configured to resolve the identifier into the MCPTT identifier of the user equipment, and wherein the transceiver is configured to forward the call request to the user equipment based on the MCPTT identifier.

In some embodiments, a method is provided that includes receiving, at a server, a call request for a mission critical, push to talk (MCPT) call and accessing, from the server and in response to receiving the call request, a mapping of an MCPTT identifier of a user equipment with an interworking identifier that is formed according to an address format implemented in Global System for Mobile communications (GSM) for Railways (GSM-R). The method also includes forwarding the call request from the server based on the mapping.

In some embodiments of the method, the MCPTT identifier is a uniform resource identifier (URI) and the interworking identifier is represented in an e164 format.

Some embodiments of the method include storing the mapping in a user profile that includes a binding between the MCPTT identifier, the interworking identifier, and an identifier of the server.

In some embodiments of the method, storing the mapping in the user profile includes storing the user profile in a routing table implemented in the server and accessing the mapping includes accessing the mapping from the user profile.

In some embodiments of the method, accessing the mapping includes accessing the mapping from a database that is implemented external to the server.

Some embodiments of the method include receiving, at the server, the call request including the MCPTT identifier in response to the user equipment initiating the MCPTT call, adding, at the server, the interworking identifier to the call request, and forwarding, from the server, the call request to an interworking function associated with a GSM-R system.

Some embodiments of the method include displaying the interworking identifier to a GSM-R client.

Some embodiments of the method include receiving, at the server, an other call request from a GSM-R client to initiate another call to the user equipment, wherein the other call request includes the interworking identifier.

Some embodiments of the method include receiving, at the server, the call request including an identifier in the address format implemented in GSM-R in response to a GSM-R client initiating a call.

Some embodiments of the method include resolving, at the server, the identifier into the MCPTT identifier of the user equipment and forwarding, from the server, the call request to the user equipment based on the MCPTT identifier.

In some embodiments, an apparatus is provided that includes means for receiving, at a server, a call request for a mission critical, push to talk (MCPTT) call and means for accessing, from the server and in response to receiving the call request, a mapping of an MCPTT identifier of a user equipment with an interworking identifier that is formed according to an address format implemented in Global System for Mobile communications (GSM) for Railways (GSM-R). The apparatus also includes means for forwarding the call request from the server based on the mapping.

In some embodiments of the apparatus, the MCPTT identifier is a uniform resource identifier (URI) and the interworking identifier is represented in an e164 format.

Some embodiments of the apparatus include means for storing the mapping in a user profile that includes a binding between the MCPTT identifier, the interworking identifier, and an identifier of the server.

Some embodiments of the apparatus include means for storing the user profile in a routing table implemented in the server and accessing the mapping includes accessing the mapping from the user profile.

Some embodiments of the apparatus include means for accessing the mapping from a database that is implemented external to the server.

Some embodiments of the apparatus include means for receiving the call request including the MCPTT identifier in response to the user equipment initiating the MCPTT call, means for adding the interworking identifier to the call request, and means for forwarding the call request to an interworking function associated with a GSM-R system.

Some embodiments of the apparatus include means for displaying the interworking identifier to a GSM-R client.

Some embodiments of the apparatus include means for receiving, at the server, an other call request from a GSM-R client to initiate another call to the user equipment. The other call request includes the interworking identifier.

Some embodiments of the apparatus include means for receiving, at the server, the call request including an identifier in the address format implemented in GSM-R in response to a GSM-R client initiating a call.

Some embodiments of the apparatus include means for resolving, at the server, the identifier into the MCPTT identifier of the user equipment and forwarding, from the server, the call request to the user equipment based on the MCPTT identifier.

In some embodiments, an apparatus is provided that includes at least one processor and at least one memory including computer program code. The at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus at least to perform receiving a call request for a mission critical, push to talk (MCPTT) call. The at least one memory and the computer program code are also configured to, with the at least one processor, cause the apparatus at least to perform accessing, in response to receiving the call request, a mapping of an MCPTT identifier of a user equipment with an interworking identifier that is formed according to an address format implemented in Global System for Mobile communications (GSM) for Railways (GSM-R) and forwarding the call request based on the mapping.

In some embodiments of the apparatus, the MCPTT identifier is a uniform resource identifier (URI) and the interworking identifier is represented in an e164 format.

Some embodiments of the apparatus include means for storing the mapping in a user profile that includes a binding between the MCPTT identifier, the interworking identifier, and an identifier of the server.

In some embodiments, the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus at least to perform storing the user profile in a routing table implemented in the server and accessing the mapping includes accessing the mapping from the user profile.

In some embodiments, the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus at least to perform accessing the mapping from a database that is implemented external to the server.

In some embodiments, the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus at least to perform receiving the call request including the MCPTT identifier in response to the user equipment initiating the MCPTT call, adding the interworking identifier to the call request, and forwarding the call request to an interworking function associated with a GSM-R system.

In some embodiments, the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus at least to perform displaying the interworking identifier to a GSM-R client.

In some embodiments, the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus at least to perform receiving, at the server, an other call request from a GSM-R client to initiate another call to the user equipment. The other call request includes the interworking identifier.

In some embodiments, the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus at least to perform receiving, at the server, the call request including an identifier in the address format implemented in GSM-R in response to a GSM-R client initiating a call.

In some embodiments, the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus at least to perform resolving, at the server, the identifier into the MCPTT identifier of the user equipment and forwarding, from the server, the call request to the user equipment based on the MCPTT identifier.

