eCall refers to an interoperable in-vehicle emergency call service which is envisioned to be introduced and operated across Europe in 2014. According to reports from the European Commission, it is foreseen that eCall will be offered on all new vehicles in the EU by 2014. The European Commission has brought together standardization bodies, the automotive industry, mobile telecommunication industry, public emergency authorities and others in the eSafety Forum initiative which has identified high-level requirements, recommendations and guidelines for this eCall service [9] and [10]. The eSafety Forum has assigned ETSI MSG to standardize those parts of the eCall service that affect the mobile communication system. The development of the eCall standard has been further delegated to the 3rd Generation Partnership Project (3GPP).

The present document specifies the eCall In-band Modem, which is used for reliable transmission of the eCall Minimum Set of Data (MSD) from an In-Vehicle System (IVS) to the Public Safety Answering Point (PSAP) via the voice channel of cellular and PSTN networks. The European Union eCall requirements, recommendations and guidelines were developed by eSafety Forum [10] and [11], with important additional work produced by ETSI MSG, GSME, 3GPP, and CEN. Previous work in TR 22.967 "Transfer of Emergency Call Data", examined the issues associated with the transmission of emergency call data from a vehicle to a PSAP. This analysis identified that the preferred option be based on an in-band modem solution. eCall provides reliable full-duplex data communications between IVS and PSAP in addition to emergency voice call (E112) via the cellular network, and can be initiated either automatically or manually [1]. The eCall In-band Modem uses the same voice channel as used for the emergency voice call. eCall allows reliable transmission of MSD alternating with a speech conversation through the existing voice communication paths in cellular mobile phone systems. The expected benefit is that emergency services will be made aware of accidents much more rapidly, will get precise information on location, vehicle type etc. and therefore will be able to reach accident victims faster, with the potential to save many lives annually. The eCall in-band modem solution described here exceeds the eCall requirements (see Annex A) by means of a combination of innovations in data modulation scheme, synchronization, forward error correction coding, hybrid ARQ (HARQ) and incremental redundancy transmission. The present document provides a general overview and algorithm description of the eCall in-band modems, including IVS modem and PSAP modem, to form the complete full-duplex transmission. The eCall in-band modems (IVS and PSAP) are fully specified by this TS together with the C-code reference as provided in TS 26.268. 3GPP TS 26.269 deals with the conformance testing for eCall modem implementations, and TR 26.969 contains a characterization report of the in-band modem.