1. 3GPP2 eCall In-band Modem - ConsiderationsAC
3GPP2 TSG-AC WG1 Teleconference
January 12, 2016
3GPP2 eCall In-band Modem - Considerations

2. Overview History of eCall in 3GPP In-band modem for 3GPP2 PSAPs
Requirements from MNOs
Limitations of study
Selecting, verifying, specifying, implementing, field-testing, and updating in–band modem
Lessons Learned
In-band modem for 3GPP2
PSAPs
Timelines
Conclusions

3. eCall in 3GPP
History
2006: GSM Europe completed extensive study of solution framework for eCall signalling
“Options for eCall MSD signaling”, GSM Europe Position Paper, April 21, 2006
Studied SMS, User to User Signalling, Unstructured Supplementary Service Data, GSM Circuit-Switched Data, DTMF, In-band Modem/Signalling application
Chose In-band Modem:
Leveraged use of already being deployed E112 routing to PSAPs for circuit-switched emergency voice calls
Packet-Switched/IMS based solution was not considered at the time as support was not yet prevalent
“… the initial eCall service must operate in the CS domain, however, a hybrid CS and PS, or PS only, based solution can be expected in the future e.g. when IMS support and VoIP emergency calls become prevalent. SIP signalling and other IP /TCP or UDP solutions for eCall might then be possible. “
The reasons/criteria for choosing an in-band solution in 2006 are no longer valid today
2006: 3GPP set technical requirements/criteria for in-band modem solution
2007: 3GPP began competition for in-band modem selection, including establishing testplan, contracting independent 3rd party testing labs

4. eCall in 3GPP
History (2)
2008: 3GPP completed competition and selection of in-band modem
3GPP Rel-8 specs updated to support eCall identification and routing to a PSAP and avoidance of network signaling for terminals configured for “eCall-only mode”
2009: 3GPP completed verification, characterization, and specification of modem
2011: 3GPP completed significant update to modem specifications based on results of field testing and trials
Performance of in-band modem affected by non-standardized voice processing in the network (e.g., network echo-cancelling, noise-suppression, transcoding, proprietary compression algorithms on link between MGWs from the same vendor) through different paths (VoIP backhaul, different vendor MGWs).
These effects could not be predicted or simulated when selecting the in-band modem
Needed extensive (~ 2 years) field tests and trials to update modem and ensure robust performance

5. eCall in 3GPP History (3): European Field-Test Campaign
48 Networks in 15 countries
22 stationary locations
12 mobility routes
>16000 calls
>25000 MSD transmissions
Networks by country
Countries with 3GPP2/cdma2000 networks cover more than 3x land area of Europe

6. eCall in 3GPP
History (4)
2015: Russia mandated deployment of in-band modem with ERA GLONASS system for all vehicles (9 years after GSME completed study)
Russian eCall service is still not yet commercially deployed as of January 2016 (~10 years later)
2018: European Union mandated deployment of in-band modem in vehicles
Still On-going: development of comprehensive certification program for eCall system: vehicles, mobile network, PSAPs

7. eCall in 3GPP Lessons Learned about In-band Modem Solution
Not future proof
It has proven not suitable for LTE or any packet-switched access in the presence of voice de-jitter buffering
While applicable to GSM and WCDMA, EU operators are expected to migrate to 4G and 5G over the next decade, rendering the solution obsolete
Interferes with voice communication
During MSD transfer which can occupy 5-10 seconds, the user and PSAP cannot communicate
EENA (European Emergency Number Association) regard this as a severe limitation
Takes a long time to define, standardize and field-test
An in-band voice modem solution requires meticulous design, simulation, and extensive field-testing due to the presence of non-standardized network voice processing implementations which do not cause perceptual degradation in voice quality, but can greatly impact the performance of the in-band modem
Costly for PSAPs
PSAPs in some EU countries (e.g. UK, France) are expected to delay in-band modem support due to cost
Will reduce the effectiveness of eCall (e.g. if routed to a PSAP without support or handling a very large area)

8. In-band Modem for 3GPP2
3GPP in-band modem solution uses pulse-position-modulation (PPM) to achieve relatively high raw data rate
AMR and AMR-WB are waveform coders that maintain pulse positions in the CELP voice model
After applying Turbo-channel coding, Hybrid ARQ, and higher-layer START/ACK/NACK protocols, PPM enables transmission of 140 bytes of data within ~ 6 seconds voice channel blocking
Competing technologies in 3GPP that used FSK-based modulation had at least 3x slower MSD transmission
3GPP2 EVRC codec is not a waveform coder -> “perceptual coder”
To achieve better compression, uses Relaxed-CELP (RCELP) which performs some time-warping of the signal with minimal perceptual distortion
Have tested 3GPP in-band modem with EVRC
Can not support the 3GPP in-band modem reliably without changes to the EVRC codec in the terminal and network
3GPP2 will need to design a new, incompatible, in-band modem for EVRC
If 3GPP2 in-band modem is used for data transmission throughout the call (not just at initiation) then each transmission will disrupt the voice conversations by >6 seconds

9. Public-Safety Answering Points (PSAPs)
Considerations
In-band modem solutions
Requires upgrade to PSAP to support modem bank
Will require network upgrade to identify an eCall and route to an eCall capable PSAP (as in Europe)
3GPP and 3GPP2 (and possibly other air interfaces/vocoders) require different in-band modem versions
Multiple modem versions at PSAP
Have to distinguish from which network/vocoder the incoming call is coming from, e.g., differentiating trunks
Experience in the EU, where even one in-band modem solution has proven too costly for many PSAPs, means that PSAP uptake of a multiple (e.g. dual) modem solution could be very low

10. eCall Standardization and Deployment Timelines
Realistic Estimate for 3GPP2 In-Band Modem
2016 complete study of which eCall technologies (in-band, PS, USSD, SMS, etc…) to develop
2018 complete technical requirements, competition, test plan, selection, verification, and characterization of in-band modem solution
2020 complete field-testing of in-band modem solution, update specifications as needed
2021 terminals ready for deployment
20XX Develop packet-based solution for All-IP networks
Develop solutions for migration from in-band to PS-based eCall
Manage deployment/migration of PSAPs, mobile networks, and terminals from in-band to PS-based eCall

11. Conclusions
Specifying use of in-band modem technology needs to be carefully studied
Solution has limitations and requires extensive selection, verification, field-testing to develop robust solution
Other solutions are possible that can be deployed in the same time frame and with less limitations
PSAPs
Migration to SIP/IP is extensible, evolutionary, provides more features, will be necessary eventually and its complexity should be compared to managing multiple in-band modem upgrades and their management
Proposal
3GPP2 evaluate all potential solutions, especially packet-based, and not just in-band modem solution