1. TSG-AC
TITLE: eCall inband modem overview
SOURCE:
Intel: Mike Lim Tony Lee
ABSTRACT: This contribution provide an overview of the modifications needed to modify the 3gpp inband modem to use with 3gpp2 vocoder.
RECOMMENDATION: FYI
China Telecom and Intel grants a free, irrevocable license to 3GPP2 and its Organizational Partners to incorporate text or other copyrightable material contained in the contribution and any modifications thereof in the creation of 3GPP2 publications; to copyright and sell in Organizational Partner's name any Organizational Partner's standards publication even though it may include all or portions of this contribution; and at the Organizational Partner's sole discretion to permit others to reproduce in whole or in part such contribution or the resulting Organizational Partner's standards publication. China Telecom and Intel are also willing to grant licenses under such contributor copyrights to third parties on reasonable, non-discriminatory terms and conditions for purpose of practicing an Organizational Partner’s standard which incorporates this contribution.
This document has been prepared by China Telecom and Intel to assist the development of specifications by 3GPP2. It is proposed to the Committee as a basis for discussion and is not to be construed as a binding proposal on China Telecom and Intel. China Telecom and Intel specifically reserves the right to amend or modify the material contained herein and to any intellectual property of Intel other than provided in the copyright statement above. 1

2. Background 3GPP released in-band modem for eCall (TS 26.267).
3GPP in-band modem can not deliver in-band data in 3GPP2 network because of RCELP characteristics of EVRC family vocoders.
EVRC family vocoders introduces several samples of jitter, which cause sync detection failure.
3GPP in-band modem does not allow jitters in sync detection algorithm.
Proposed 3GPP2 in-band modem allows jitters in sync detection and MSD detection, and it can compensate EVRC family vocoders jitter.

3. eCall modem block diagram

4. Proposed eCall modem for EVRC
Based on 3gpp eCall inband modem
Added Auto mode for full half-duplex mode
Removed full-duplex mode to avoid LEC side-effect

5. Proposed 3gpp2 eCall modem , uplink
Used independent IVS sync frame for EVRC-A and EVRC-B.
Removed sync tone used for mode detection. Use only fast mode.
Removed UL_Delay1. Zero delay between Ivs Tx and Encoder.
Mixed 800Hz tone to sync frame to indicate current vocoder type is EVRC- A vocoder.
Used independent modulation & demodulation waveform table for EVRC- A and EVRC-B
Updated sync detection algorithm to allow jitter for sync detection.
Added sync majority voter to allow jitter for sync detection to enhance sync detection in noisy channel.

6. Proposed eCall modem update, downlink
Used independent PSAP sync frame.
Removed sync tone used for mode detection. Use only fast mode.
Removed DL_Delay2. Zero delay between Decoder and Ivs Rx.
Added 800 Hz tone detection mixed in sync frame to detect vocoder type.
Used independent modulation & demodulation table for EVRC-A and EVRC-B.
Removed DC offset from Sync frame.
Removed Sync Tracking.
Added transmission delay adjustment in IVS transmitter.
Added sync frame delay adjustment in PSAP transmitter.

7. THANK YOU!