Cellular In-Band Modem Solution for eCall Emergency Data Transmission

eCall is a project of the European Commission for the improvement of transportation safety by providing rapid assistance to motorists involved in a collision anywhere in the European Union. In the event of a collision, the intended solution employs an in-band modem that transmits vehicle location, airbag deployment, and other relevant information timely and reliably from the in-vehicle system (IVS) over the cellular network voice channel to the public safety answering point (PSAP). This paper describes the requirements, system design and performance of the eCall in-band modem solution that was selected by 3GPP. Due to the employment of this solution in life-critical situations, transmission reliability and speed are of utmost importance. The effective transmission channel is characterized by the highly nonlinear speech codec, as well as radio channel impairments, constituting a challenge for the in-band transmission of digital data. Several innovative transmission concepts were developed for our eCall in-band modem solution to address this challenge.