ETSI TS 103 625 V1.1.1 (2019-12)

Emergency Communications (EMTEL); Transporting Handset Location to PSAPs for Emergency Calls - Advanced Mobile Location

DTS/EMTEL-00044

General Information

• Status: Published
• Publication Date: 15-Dec-2019
• Technical Committee: EMTEL - Emergency Communications
• Current Stage: 12 - Completion
• Due Date: 18-Dec-2019
• Completion Date: 16-Dec-2019

Standards Content (Sample)

ETSI TS 103 625 V1.1.1 (2019-12)






TECHNICAL SPECIFICATION
Emergency Communications (EMTEL);
Transporting Handset Location to PSAPs for
Emergency Calls - Advanced Mobile Location

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2 ETSI TS 103 625 V1.1.1 (2019-12)



Reference
DTS/EMTEL-00044
Keywords
emergency, handset, location, mobile, transport
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3 ETSI TS 103 625 V1.1.1 (2019-12)
Contents
Intellectual Property Rights . 5
Foreword . 5
Modal verbs terminology . 5
Introduction . 5
1 Scope . 6
2 References . 6
2.1 Normative references . 6
2.2 Informative references . 6
3 Definition of terms, symbols and abbreviations . 7
3.1 Terms . 7
3.2 Symbols . 7
3.3 Abbreviations . 7
4 Overview . 8
5 Handset Functionality. 8
5.1 Positioning methods and time needed to precisely locate . 8
5.2 Triggered by emergency call without impacting voice . 8
5.3 Availability of MSISDN . 9
5.4 Data connectivity . 9
5.5 Battery life . 9
6 Location data and data transport . 9
6.1 Location data provision by the handset . 9
6.1.1 Data provided . 9
6.2 SMS transport . 10
6.2.1 SMS transport overview . 10
6.2.2 SMS Formats . 12
6.2.3 Security of SMS transport . 13
6.2.4 Limitations . 13
6.2.4.1 Roaming . 13
6.2.4.2 Limited Service State/National Roaming . 14
6.3 HTTPS . 14
6.3.1 Overview of using HTTPS . 14
6.3.2 General Format . 14
6.3.3 Security considerations . 14
6.3.4 Header . 14
6.3.5 Body. 15
6.3.6 Detailed Format . 15
6.3.6.1 Header . 15
6.3.6.2 Body . 15
6.3.7 Receipt of HTTPS Message by PSAP . 15
6.3.7.1 Overview of message receipt . 15
6.3.7.2 Example Message Sequence . 16
6.3.7.3 Example Message Content . 16
6.3.7.4 Response Values . 16
6.3.8 Limitations . 17
6.3.8.1 Availability of MSISDN . 17
6.3.8.2 Data connectivity . 17
6.4 SIP (network, terminal and PSAP support) . 17
6.5 Next Generation 112 . 17
7 Mobile Network capabilities . 18
7.1 Simultaneous SMS/HTTPS and emergency voice . 18
8 Operational Guidance . 18
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4 ETSI TS 103 625 V1.1.1 (2019-12)
8.1 PSAP reception of location (location endpoint) . 18
Annex A (normative): SMS Format . 19
Annex B (normative): HTTPS message format . 24
B.1 HTTPS fields . 24
Annex C (informative): Management of location best practice by PSAPs . 26
History . 27


ETSI

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5 ETSI TS 103 625 V1.1.1 (2019-12)
Intellectual Property Rights
Essential patents
IPRs essential or potentially essential to normative deliverables may have been declared to ETSI. The information
pertaining to these essential IPRs, if any, is publicly available for ETSI members and non-members, and can be found
in ETSI SR 000 314: "Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to ETSI in
respect of ETSI standards", which is available from the ETSI Secretariat. Latest updates are available on the ETSI Web
server (https://ipr.etsi.org/).
Pursuant to the ETSI IPR Policy, no investigation, including IPR searches, has been carried out by ETSI. No guarantee
can be given as to the existence of other IPRs not referenced in ETSI SR 000 314 (or the updates on the ETSI Web
server) which are, or may be, or may become, essential to the present document.
Trademarks
The present document may include trademarks and/or tradenames which are asserted and/or registered by their owners.
ETSI claims no ownership of these except for any which are indicated as being the property of ETSI, and conveys no
right to use or reproduce any trademark and/or tradename. Mention of those trademarks in the present document does
not constitute an endorsement by ETSI of products, services or organizations associated with those trademarks.
Foreword
This Technical Specification (TS) has been produced by ETSI Special Committee Emergency Communications
(EMTEL).
Modal verbs terminology
In the present document "shall", "shall not", "should", "should not", "may", "need not", "will", "will not", "can" and
"cannot" are to be interpreted as described in clause 3.2 of the ETSI Drafting Rules (Verbal forms for the expression of
provisions).
"must" and "must not" are NOT allowed in ETSI deliverables except when used in direct citation.
Introduction
One of the biggest challenges facing the Emergency Services is determining the location of mobile callers. Cell based
location has been available to the Emergency Services since 2003. While cell data can help with verbal establishment of
a caller's location, a more precise location will allow an even quicker emergency response.
Advanced Mobile Location (AML) allows use of native smart phone technology to pass (Assisted) GNSS or Wi-Fi
based location data to Emergency Service PSAPs. These technologies can provide a location precision as good as 5 m
outdoors (and averaging to within circular areas of ~25 m radius for indoor locations), a significant improvement on
existing cell coverage provided by mobile networks, which average (across the UK as an example) circular areas of
about 1,75 km radius.
The present document builds on the Advanced Mobile Location initiative described in ETSI TR 103 393 [i.1] now
being used in an increasing number of countries to improve the precision and accuracy of a caller's location information
for emergency calls from mobile handsets.

ETSI

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1 Scope
The present document describes the transport methods used for AML messages with handset derived location
information and associated data, the content of the AML messages, and allows for the data sent within the message to
include further attributes than supported in current deployments.
It also considers the future evolution of transport methods as PSAPs, networks and terminals become increasingly IP
based.
2 References
2.1 Normative references
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
referenced document (including any amendments) applies.
Referenced documents which are not found to be publicly available in the expected location might be found at
https://docbox.etsi.org/Reference/.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long term validity.
The following referenced documents are necessary for the application of the present document.
[1] ETSI TS 123 040: "Digital cellular telecommunications system (Phase 2+) (GSM); Universal
Mobile Telecommunications System (UMTS); Technical realization of the Short Message Service
(SMS) (3GPP TS 23.040)".
[2] ETSI ES 203 283: "Protocol specifications for Emergency Service Caller Location determination
and transport".
[3] IETF RFC 6442: "Location Conveyance for the Session Initiation Protocol".
[4] IETF RFC 5491: "GEOPRIV Presence Information Data Format Location Object (PIDF-LO)
Usage Clarification, Considerations, and Recommendations".
[5] ETSI TS 103 479: "Emergency Communications (EMTEL); Core elements for network
independent access to emergency services".
[6] ETSI TS 123 038: "Digital cellular telecommunications system (Phase 2+) (GSM); Universal
Mobile Telecommunications System (UMTS); LTE; Alphabets and language-specific information
(3GPP TS 23.038)".
2.2 Informative references
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
referenced document (including any amendments) applies.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long term validity.
The following referenced documents are not necessary for the application of the present document but they assist the
user with regard to a particular subject area.
[i.1] ETSI TR 103 393 (V1.1.1): "Emergency Communications (EMTEL); Advanced Mobile Location
for emergency calls".
ETSI

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7 ETSI TS 103 625 V1.1.1 (2019-12)
3 Definition of terms, symbols and abbreviations
3.1 Terms
Void.
3.2 Symbols
Void.
3.3 Abbreviations
For the purposes of the present document, the following abbreviations apply:
3GPP 3G (mobile) Partnership Project
AGNSS Assisted Global Navigation Satellite System
AML Advanced Mobile Location
ASCII American Standard Code for Information Interchange
DCS Data Coding Scheme
GNSS Global Navigation Satellite System
GSM Global System for Mobile
HTTP HyperText Transfer Protocol
HTTPS HyperText Transfer Protocol Secure
ICCID Integrated Circuit Card IDentifier
IEI Information Element Identifier
IMEI International Mobile Equipment Identity
IMSI International Mobile Subscriber Identity
IP Internet Protocol
ISDN Integrated Services Digital Network
LOC Level Of Confidence
LS Location Server
MCC Mobile Country Code
MNC Mobile Network Code
MNO Mobile Network Operator
MSISDN Mobile Station International Subscriber Directory Number
NG Next Generation
NTP Network Time Protocol
OS Operative System
PDU Packet Data Unit
PSAP Public Safety Answering Point
RFC Request For Comments
SIM Subscriber Identity Module
SIP Session Initiation Protocol
SMPP Short Message Peer to Peer
SMS Short Message Service
SMSC Short Message Service Centre
UCS Universal Character Set
UTC Universal Time Coordinated
WGS World Geodetic System
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8 ETSI TS 103 625 V1.1.1 (2019-12)
4 Overview
AML functionality is triggered by an emergency call (which is progressed normally by the handset and the network),
and is designed to supplement the basic network location provided wherever possible, i.e. with some acknowledgement
of limitations in GNSS or Wi-Fi availability for the handset and the time required to acquire location using GNSS.
Location information established by the handset, using its built-in GNSS and Wi-Fi connectivity, together with user
plane assistance data from a handset-selected service where available, is transported (e.g. through use of SMS) to the
Emergency Service PSAPs. Handsets can use more than one location technology to establish a location, for example the
handset may combine location information from Cell and Wi-Fi sources to obtain the best possible, "hybridised", result.
It is important that AML doesn't interfere with the voice call so both the handset and mobile network shall be
configured to be able to simultaneously support a standard 3GPP mobile emergency voice call, location determination
using GNSS/Wi-Fi capabilities and SMS and/or HTTPS transmission of the location information over the 3GPP mobile
network.
5 Handset Functionality
5.1 Positioning methods and time needed to precisely locate
GNSS, or Assisted GNSS, normally offers the best location information but is slower than other methods. At the other
end of the spectrum cell based location is quick but typically returns a larger location area. The general rule is that
PSAPs need the best data as long as it doesn't take too long to determine, so a 'send us what you have now' timeout [T1]
is used.
T1 is the maximum time between the emergency call being initiated and the location message being sent. T1 should be
configurable with a T1 value selected in consultation with the provider of the AML functionality on the handset to give
best balance between quicker availability to PSAPs and the even higher precision that may become available with a
longer T1.
As soon as the emergency call is initiated the handset shall immediately attempt to determine the best possible current
location within the period set by the T1 timeout.
This should allow all location capabilities that the handset provides to be used, respecting the end user's preferences by
enabling any capability not normally available only to assist for AML functions on an emergency call, and subject to a
battery check.
If it is not been possible to get a location from any method then a message shall be sent indicating that all positioning
methods have failed.
5.2 Triggered by emergency call without impacting voice
The AML software shall be integrated into all existing emergency call mechanisms available on the handset including
manual dial of 112 (or any other national emergency number specified for the mobile network and country being used),
and use of the Emergency Call button (as appropriate).
In an emergency callers are often stressed or panicking so it is important that the AML functionality and transmission of
the AML message shall be automatically triggered without any manual intervention by the user. The handset software
shall be invisible to the users so as not to cause confusion when they are trying to get help, and so as not to attract
attention from those who intend to abuse the facility. No record of the AML message shall be available to the user
either during or after the emergency call.
If an emergency SMS service, typically for deaf or hard of hearing users is provided in a country, then AML should also
be triggered by an emergency SMS message being sent.
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9 ETSI TS 103 625 V1.1.1 (2019-12)
5.3 Availability of MSISDN
PSAPs need to be able to match the voice call with the AML data, and to do so they use the MSISDN (Mobile
Subscriber ISDN). The MSISDN is included within an SMS message so this is straightforward if SMS is used for AML
transport. In some instances, the MSISDN can be accessed by the handset's AML functionality and, if AML is using
HTTPS to transport the location data, it shall therefore be included when possible in the HTTPS data string (see
clause B.1).
5.4 Data connectivity
The mobile handset requires data connectivity to allow communication with servers operated by the providers of the
phone's operating system that:
a) provide assistance information to allow quick establishment of a GNSS position (AGNSS); and
b) provide access to primarily crowd sourced databases for location information related to Wi-Fi access points.
In addition such a data connection may support one of the transport mechanisms for AML using an HTTPS message
(see clause 6.3).
This data connectivity can be through the mobile network or Wi-Fi access points.
Without such a data connection AML messages are still possible using a GNSS location (without assistance) and SMS
transport (see clause 6.1).
5.5 Battery life
Before invoking the AML functionality, the handset should check there is sufficient battery life so that the caller can
still make a short 5 minute voice call. The priority in the emergency situation is to allow voice connection to the PSAP.
6 Location data and data transport
6.1 Location data provision by the handset
6.1.1 Data provided
AML is required to communicate a location in the form of a circle.
The location and size of the circle determined by the handset shall be communicated using the attributes of a WGS 84
latitude and longitude measured in decimal degrees for the centre of the circle, and a radius measurement for the
location circle in metres. A precision of 5 decimal degrees should be provided which will equate to 1,1 m precision on
the ground.
The following attributes are those that are normative for implementation using transport methods described in
clauses 6.2 and 6.3:
• The Time of Positioning (TOP): The accuracy of this date and time is important as it will be used to filter out
any messages that appear to be too old or have a time in the future. In the first instance the handset should
attempt to use the time established by an NTP server, this should be possible if a network connection is
available. If NTP is not available then GNSS can be used to give time. Only if these two methods fail then, as
a last resort, the handset time and date can be used.
• The Level of Confidence is a percentage probability that the mobile handset is within the area being
communicated, for example a 95 % value tells the Emergency Services that there is a 5 % probability that the
caller is not within the location area specified by the latitude, longitude and radius values. It is recognized that
methods for determining mobile handset location have limitations. For example, the impact of buildings,
topography and weather conditions introduce a margin of error into location calculations, and different
methods will have different error factors that need to be communicated to the Emergency Services.
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10 ETSI TS 103 625 V1.1.1 (2019-12)
• The predominant positioning method used to determine the location area is indicated as one of the following:
- GNSS or AGNSS;
- Wi-Fi signals;
- Cell;
- Hybridised results shall be used and should be classified according to predominant location method.
It shall also be indicated if it has not been possible to determine the location - see annexes A and B.
• The SIM card identifier of the handset that has made the emergency call (IMSI) and the identifier of the
handset that made the emergency call (IMEI).
• Mobile Country Code of the network, used to confirm/determine the country in which the emergency call was
made.
• Mobile Network Code, to confirm/determine the mobile network used to make the emergency call.
NOTE 1: The MCC and MNC of the network will normally be the same as the MCC and MNC within the IMSI.
Differences between them indicate if the handset is roaming.
A header attribute shall be used to differentiate AML messages from other emergency SMS messages and to also
indicate a version number for the interface. For SMS transport, a Message Length attribute shall also be used - see
annex A.
In future, when it becomes technically feasible and reliable, and if the transport method has sufficient space available,
the following optional information should be passed and the inclusion of additional data indicated by use of a different
interface version number:
• Altitude (in metres above the WGS 84 ellipsoid).
NOTE 2: The WGS 84 ellipsoid is a reasonable approximation for the shape of the earth. Altitude above the
WGS 84 ellipsoid can differ from the actual altitude above mean sea level.
• Altitude Variance: Indicates the vertical variance, plus or minus, from given altitude.
• Floor number.
• Emergency number used to make the call, including whether voice or SMS activation (to assist PSAPs
matching with calls).
• Source to indicate which version of the handset's AML functionality is being used. This is helpful in
diagnosing any issues.
The presence of most of these optional information elements is already included for HTTPS - see annex B.
6.2 SMS transport
6.2.1 SMS transport overview
When a PSAP selects SMS transport (see clause 8), the standard mobile network SMS service shall be used to send the
AML message from the phone to the SMSC (SMS Centre) within each mobile network (using normal 3GPP network
standards).
The Short Message Peer-to-Peer (SMPP) open industry standard protocol for transfer of short message data outside
mobile networks should then be used to transport the data from the SMSC to the SMS Aggregator (organization that
aggregates SMS messages from various mobile networks).
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11 ETSI TS 103 625 V1.1.1 (2019-12)
The Aggregator should then forward the message to the PSAP using an Aggregator-defined format, typically an HTTPS
post message that includes all the AML data, including the MSISDN which forms part of the SMS message. The PSAP
then makes the AML location available to be used to supplement the location available from the mobile network. Either
the Aggregator or the PSAP operating the AML Reception server may decode the binary data within the SMS payload -
see clause 6.2.2.
Figure 1 shows how the AML location may reach a PSAP organization. The exact details for how AML information is
made available to the PSAP that has received the associated voice call will vary from country to country, depending on
how PSAPs are organized in that country. This is considered further in clause 8.
Short Message Peer-to-Peer (SMPP)
SMS message
open industry protocol
SMS
...