The following relates generally to wireless communication, and more specifically to the wireless transmission and receipt of telematics data and metadata. In some systems, telematics data (e.g., sensor readings and other data) may be transmitted from an intelligent terminal to a central service for processing. For example, a terminal associated with a vehicle experiencing a collision may transmit location and airbag deployment data over a wireless communication system to a public safety answering point (PSAP) in connection with a request for emergency services. In some systems, the data may be transmitted to a third-party service center, which may then convey some or all of the data to a PSAP.
Terminals associated with vehicles offering automatic crash response and emergency calling functionality generally use the voice channel of a cellular network to establish a voice call between a vehicle occupant and a PSAP operator. Telematics data may then be transmitted from the terminal to a central service (e.g., a PSAP server or a third-party service center) by modulating the voice channel using in-band signaling, Baudot tones, or other modem techniques. Metadata associated with the telematics data, such as an acknowledgement that the telematics data was satisfactorily (e.g., successfully) received or a request for a retransmission of the telematics data, may also be communicated from the central service to the terminal by modulating the voice channel in the reverse direction. The transmission of telematics data and metadata over a voice channel in this way can be problematic in that voice communication may be blocked or experience interference during the transmission of telematics data and metadata. Moreover, the transmission of modulated digital data through voice channels may provide limited data throughput or be unreliable due to voice processing functions in the network (e.g., improperly tuned echo-cancellers and use of compression on network trunks). These limitations may be further exacerbated in systems such as Long Term Evolution (LTE) and High Speed Packet Access (HSPA) when a voice channel is provided through packet rather than circuit means. Thus, more efficient and reliable methods of transmitting telematics data and metadata between a terminal and a central service are needed.