ETSI TS 100 392-18-4 V1.2.1 (2015-07)

Terrestrial Trunked Radio (TETRA); Voice plus Data (V+D) and Direct Mode Operation (DMO); Part 18: Air interface optimized applications; Sub-part 4: Net Assist Protocol 2 (NAP2)

RTS/TCCE-03230

General Information

• Status: Published
• Publication Date: 02-Jul-2015
• Technical Committee: TCCE 3 - TCCE Air Interface and Network Protocols
• Current Stage: 12 - Completion
• Due Date: 03-Jul-2015
• Completion Date: 03-Jul-2015

Standards Content (Sample)

TECHNICAL SPECIFICATION
Terrestrial Trunked Radio (TETRA);
Voice plus Data (V+D) and Direct Mode Operation (DMO);
Part 18: Air interface optimized applications;
Sub-part 4: Net Assist Protocol 2 (NAP2)

2 ETSI TS 100 392-18-4 V1.2.1 (2015-07)

Reference
RTS/TCCE-03230
Keywords
air interface, location, TETRA, V+D
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ETSI
3 ETSI TS 100 392-18-4 V1.2.1 (2015-07)
Contents
Intellectual Property Rights . 6
Foreword . 6
Modal verbs terminology . 7
1 Scope . 8
2 References . 8
2.1 Normative references . 8
2.2 Informative references . 9
3 Definitions and abbreviations . 10
3.1 Definitions . 10
3.2 Abbreviations . 10
4 Net Assist Protocol . 12
4.1 General . 12
4.2 Location information protocol system architecture . 12
4.3 Net assist protocol service description . 13
4.3.1 General on services . 13
4.3.2 Services available at the NAP-SAP . 13
4.3.3 Service primitives at the NAP-SAP . 13
4.3.4 Service primitive parameters at the NAP-SAP . 14
4.3.5 State description . 14
5 Net assist protocol description . 14
5.1 Description of information elements . 14
5.1.1 General on network assistance information elements . 14
5.2 Information flows . 14
5.2.1 General on information flows . 14
5.2.2 Transport layer requirements . 15
5.2.3 Pseudo-segmentation . 15
5.2.4 NAP2 duplicate detection . 16
5.2.5 NAP2 Acknowledgement . 17
5.2.5.1 General . 17
5.2.5.2 Procedure related to acknowledgement . 17
5.2.6 NAP2 retransmission . 17
5.2.6.1 General . 17
5.2.6.2 Procedure related to Retransmission . 17
5.2.7 MS receiving network assistance . 18
5.2.8 MS receiving network assistance and sending response . 19
5.2.9 MS requesting network assistance . 19
5.2.10 MS requesting network assistance and receiving a reject . 19
5.2.11 Allocation of entities . 20
5.3 Procedures . 20
5.3.1 General on procedures . 20
5.3.2 Service availability . 20
5.3.3 Rejection of request for assistance . 20
5.3.4 Routing net assistance to specific terminal groups . 20
5.4 GNSS assistance types . 21
5.4.0 General . 21
5.4.1 GNSS Ephemeris assistance . 22
5.4.2 GNSS Almanac assistance . 22
5.4.3 GNSS Ionosphere and UTC correction assistance . 22
5.4.4 GNSS Time assistance . 22
5.4.5 Location assistance . 22
6 Net assist protocol coding requirements. 23
6.1 General . 23
6.2 Net assist protocol PDU definitions . 24
6.2.1 Net assist protocol description tables . 24
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4 ETSI TS 100 392-18-4 V1.2.1 (2015-07)
6.2.1.0 General . 24
6.2.1.1 LPP-PDU-Definitions . 24
6.2.1.2 NAP-Message . 25
6.2.1.3 LPP-MessageBody . 26
6.2.1.4 NAP-TransactionID . 26
6.2.2 Common IEs . 26
6.2.2.0 General principle . 26
6.2.2.1 Abort . 27
6.2.2.2 Error . 27
6.2.2.3 CommonIEsRequestAssistanceData . 27
6.2.2.4 CommonIEsProvideAssistanceData . 27
6.2.2.5 CommonIEsAbort . 28
6.2.2.6 CommonIEsError . 28
6.2.2.7 RequestAssistanceData . 29
6.2.2.8 ProvideAssistanceData . 29
6.2.2.9 A-GNSS-ProvideAssistanceData . 30
6.2.2.10 GNSS-CommonAssistData . 30
6.2.2.11 GNSS-GenericAssistData . 30
6.2.3 GNSS Assistance Data Elements . 30
6.2.3.1 GNSS-ReferenceTime . 30
6.2.3.2 GNSS-SystemTime . 32
6.2.3.3 GPS-TOW-Assist . 33
6.2.3.4 NetworkTime . 33
6.2.3.5 GNSS-ReferenceLocation . 34
6.2.3.6 EllipsoidPointWithAltitudeAndUncertaintyEllipsoid . 34
6.2.3.7 GNSS-IonosphericModel . 34
6.2.3.8 KlobucharModelParameter . 35
6.2.3.9 NeQuickModelParameter . 36
6.2.3.10 GNSS-EarthOrientationParameters . 36
6.2.3.11 GNSS-TimeModelList . 37
6.2.3.12 GNSS-DifferentialCorrections . 38
6.2.3.13 GNSS-NavigationModel . 40
6.2.3.14 StandardClockModelList . 42
6.2.3.15 NAV-ClockModel . 43
6.2.3.16 CNAV-ClockModel . 44
6.2.3.17 GLONASS-ClockModel . 45
6.2.3.18 SBAS-ClockModel . 45
6.2.3.19 NavModelKeplerianSet . 46
6.2.3.20 NavModelNAV-KeplerianSet . 47
6.2.3.21 NavModelCNAV-KeplerianSet . 48
6.2.3.22 NavModel-GLONASS-ECEF . 50
6.2.3.23 NavModel-SBAS-ECEF . 51
6.2.3.24 GNSS-RealTimeIntegrity . 51
6.2.3.25 GNSS-DataBitAssistance . 52
6.2.3.26 GNSS-AcquisitionAssistance. 53
6.2.3.27 GNSS-Almanac . 56
6.2.3.28 AlmanacKeplerianSet . 57
6.2.3.29 AlmanacNAV-KeplerianSet [8] . 58
6.2.3.30 AlmanacReducedKeplerianSet . 60
6.2.3.31 AlmanacMidiAlmanacSet . 60
6.2.3.32 AlmanacGLONASS-AlmanacSet . 61
6.2.3.33 AlmanacECEF-SBAS-AlmanacSet. 62
6.2.3.34 GNSS-UTC-Model . 63
6.2.3.35 UTC-ModelSet1 . 64
6.2.3.36 UTC-ModelSet2 . 64
6.2.3.37 UTC-ModelSet3 . 65
6.2.3.38 UTC-ModelSet4 . 66
6.2.3.39 GNSS-AuxiliaryInformation . 67
6.2.4 GNSS Assistance Data Request . 68
6.2.4.1 A-GNSS-RequestAssistanceData . 68
6.2.4.2 GNSS-CommonAssistDataReq . 68
6.2.4.3 GNSS-GenericAssistDataReq . 68
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5 ETSI TS 100 392-18-4 V1.2.1 (2015-07)
6.2.5 GNSS Assistance Data Request Elements . 69
6.2.5.1 GNSS-ReferenceTimeReq . 69
6.2.5.2 GNSS-ReferenceLocationReq . 70
6.2.5.3 GNSS-IonosphericModelReq. 70
6.2.5.4 GNSS-EarthOrientationParametersReq . 70
6.2.5.5 GNSS-TimeModelListReq . 71
6.2.5.6 GNSS-DifferentialCorrectionsReq . 71
6.2.5.7 GNSS-NavigationModelReq . 72
6.2.5.8 GNSS-RealTimeIntegrityReq . 73
6.2.5.9 GNSS-DataBitAssistanceReq . 73
6.2.5.10 GNSS-AcquisitionAssistanceReq . 74
6.2.5.11 GNSS-AlmanacReq . 74
6.2.5.12 GNSS-UTC-ModelReq . 75
6.2.5.13 GNSS-AuxiliaryInformationReq . 76
6.2.6 GNSS Error Elements . 76
6.2.6.1 A-GNSS-Error . 76
6.2.6.2 GNSS-LocationServerErrorCauses . 76
6.2.6.3 GNSS-TargetDeviceErrorCauses . 76
6.2.7 Common GNSS Information Elements. 77
6.2.7.1 GNSS-ID . 77
6.2.7.2 GNSS-ID-Bitmap . 77
6.2.7.3 GNSS-SignalID . 77
6.2.7.4 GNSS-SignalIDs . 78
6.2.7.5 SBAS-ID . 79
6.2.7.6 SBAS-IDs . 79
6.2.7.7 SV-ID . 79
6.2.7.8 EPDU-Sequence . 80
6.2.8 TETRA Network related IEs . 80
6.2.8.0 Guiding principle . 80
6.2.8.1 Tetra Local Area and Mobile Network Identifier . 81
6.2.8.2 Net assist group address . 81
6.2.8.3 CellGlobalIdTETRA . 81
6.2.8.4 Result code . 82
6.2.8.5 Net assist type . 82
6.2.8.6 Retry interval. 83
Annex A (informative): Change Requests . 84
History . 85

ETSI
6 ETSI TS 100 392-18-4 V1.2.1 (2015-07)
Intellectual Property Rights
IPRs essential or potentially essential to the present document 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 (http://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.
Foreword
This Technical Specification (TS) has been produced by ETSI Technical Committee TETRA and Critical
Communications Evolution (TCCE).
The present document is part 18, sub-part 4 of a multi-part deliverable covering the Voice plus Data (V+D), as
identified below:
ETSI EN 300 392-1: "General network design";
ETSI EN 300 392-2: "Air Interface (AI)";
ETSI EN 300 392-3: "Interworking at the Inter-System Interface (ISI)";
ETSI ETS 300 392-4: "Gateways basic operation";
ETSI TS 100 392-5: "Peripheral Equipment Interface (PEI)";
ETSI TS 100 392-7: "Security";
ETSI EN 300 392-9: "General requirements for supplementary services";
ETSI EN 300 392-10: "Supplementary services stage 1";
ETSI TS 100 392-11: "Supplementary services stage 2";
ETSI EN 300 392-12: "Supplementary services stage 3";
ETSI ETS 300 392-13: "SDL model of the Air Interface (AI)";
ETSI ETS 300 392-14: "Protocol Implementation Conformance Statement (PICS) proforma specification";
ETSI TS 100 392-15: "TETRA frequency bands, duplex spacings and channel numbering";
ETSI TS 100 392-16: "Network Performance Metrics";
ETSI TR 100 392-17: "TETRA V+D and DMO specifications";
ETSI TS 100 392-18: "Air interface optimized applications":
Sub-part 1: "Location Information Protocol (LIP)";
Sub-part 2: "Net Assist Protocol (NAP)";
Sub-part 3: "Direct mode Over The Air Management protocol (DOTAM)";
Sub-part 4: "Net Assist Protocol 2 (NAP2)";
Sub-part 5: "SDS Based Supplementary Service Management (SBSSM)".
ETSI
7 ETSI TS 100 392-18-4 V1.2.1 (2015-07)
NOTE 1: Part 3, sub-parts 6 and 7 (Speech format implementation), part 4, sub-part 3 (Data networks gateway),
part 10, sub-part 15 (Transfer of control), part 13 (SDL) and part 14 (PICS) of this multi-part deliverable
are in status "historical" and are not maintained.
NOTE 2: Some parts are also published as Technical Specifications such as ETSI TS 100 392-2 and those may be
the latest version of the document.
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.

ETSI
8 ETSI TS 100 392-18-4 V1.2.1 (2015-07)
1 Scope
The present document defines Net Assist Protocol 2 that is optimized for TETRA air interface. It defines services:
• allowing information to be passed to a location determining entity also called MS (Mobile Station);
• allowing a location determining entity to request assistance information to an assistance server.
The information passed to the location determining entity by the assistance server, when relevant, reflects the content
and format of the equivalent information (navigation data) which passes from satellites to the location determining
entity.
The protocol is capable of supporting more than one position determining technology. Presently it covers multiple
GNSS, and is extensible to all network positioning methods.
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
reference document (including any amendments) applies.
Referenced documents which are not found to be publicly available in the expected location might be found at
http://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] IS-GPS-200H (September 2013): "Navstar GPS Space Segment/Navigation User Interfaces".
NOTE: Available at: http://www.gps.gov/technical/icwg/#is-gps-200.
[2] ETSI EN 300 392-1: "Terrestrial Trunked Radio (TETRA); Voice plus Data (V+D);
Part 1: General network design".
[3] ETSI EN 300 392-2: "Terrestrial Trunked Radio (TETRA); Voice plus Data (V+D); Part 2: Air
Interface (AI)".
[4] ETSI TS 100 392-18-1: "Terrestrial Trunked Radio (TETRA); Voice plus Data (V+D) and Direct
Mode Operation (DMO); Part 18: Air interface optimized applications; Sub-part 1: Location
Information Protocol (LIP)".
[5] IS-GPS-705B (September 21, 2011): "Navstar GPS Space Segment/User Segment L5 Interfaces".
[6] IS-GPS-800 (September 4, 2008): "Navstar GPS Space Segment/User Segment L1C Interfaces".
[7] IS-QZSS (Ver.1.1, July 31, 2009): "Quasi Zenith Satellite System Navigation Service, Interface
Specifications for QZSS".
[8] European GNSS: "Galileo OS SIS ICD (Open Service Signal-in-Space Interface Control
Document)", Issue 1.1 September 2010, Galileo Joint Undertaking.
NOTE Available at: http://ec.europa.eu/enterprise/policies/satnav/galileo/open-service/index_en.htm.
[9] Russian Institute of Space Device Engineering: "Global Navigation Satellite System GLONASS,
Interface Control Document", Version 5.1, 2008.
ETSI
9 ETSI TS 100 392-18-4 V1.2.1 (2015-07)
[10] US Department of Transportation, Federal Aviation Administration: "Specification for the Wide
Area Augmentation System (WAAS)", DTFA01-96-C-00025, 2001.
NOTE Available at:
http://www.faa.gov/about/office_org/headquarters_offices/ato/service_units/techops/navservices/gnss/libr
ary/documents/media/waas/2892bC2a.pdf.
[11] RTCM 10402.3 (August 20, 2001): "RTCM Recommended Standards for Differential GNSS
Service (v.2.3)".
[12] Recommendation ITU-T X.680: "Information technology - Abstract Syntax Notation One,
(ASN.1): Specification of basic notation".
[13] Recommendation ITU-T X.681: "Information technology - Abstract Syntax Notation One,
(ASN.1): Information object specification".
[14] Recommendation ITU-T X.690: "Information technology - ASN.1 encoding rules: Specification of
Basic Encoding Rules (BER), Canonical Encoding Rules (CER) and Distinguished Encoding
Rules (DER)".
[15] Recommendation ITU-T X.691: "Information technology - ASN.1 encoding rules: Specification of
Packed Encoding Rules (PER)".
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
reference 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 TS 136 355 (V10.4.0): "LTE; Evolved Universal Terrestrial Radio Access (E-UTRA); LTE
Positioning Protocol (LPP) (3GPP TS 36.355 version 10.4.0 Release 10)".
[i.2] LPP Extensions Specification, Open Mobile Alliance OMA-TS-LPPe-V1-0-20110929-C.
[i.3] ETSI TS 144 031 (V10.0.0): "Digital cellular telecommunications system (Phase 2+); Location
Services (LCS); Mobile Station (MS) - Serving Mobile Location Centre (SMLC) Radio Resource
LCS Protocol (RRLP) (3GPP TS 44.031 version 10.0.0 Release 10)".
[i.4] ETSI TS 100 392-18-2: "Terrestrial Trunked Radio (TETRA); Voice plus Data (V+D) and Direct
Mode Operation (DMO); Part 18: Air interface optimized applications; Sub-part 2: Net Assist
Protocol (NAP)".
[i.5] ETSI TS 143 059 (V10.0.0): "Digital cellular telecommunications system (Phase 2+); Functional
stage 2 description of Location Services (LCS) in GERAN (3GPP TS 43.059 version 10.0.0
Release 10)".
[i.6] ETSI TS 123 032 (V10.0.0): "Digital cellular telecommunications system (Phase 2+); Universal
Mobile Telecommunications System (UMTS); Universal Geographical Area Description (GAD)
(3GPP TS 23.032 version 10.0.0 Release 10)".
[i.7] ETSI TS 100 392-2: "Terrestrial Trunked Radio (TETRA); Voice plus Data (V+D); Part 2: Air
Interface (AI)".
[i.8] ETSI TR 102 300-5: " Terrestrial Trunked Radio (TETRA); Voice plus Data (V+D); Designers'
guide; Part 5: Guidance on numbering and addressing".
ETSI
10 ETSI TS 100 392-18-4 V1.2.1 (2015-07)
3 Definitions and abbreviations
3.1 Definitions
For the purposes of the present document, the terms and definitions given in ETSI EN 300 392-2 [3] and the following
apply:
assistance server: entity that maintains location assistance information and sends location assistance information to its
clients
navigation data: data that is passed from satellites to the location determining entity and supports location
determination, for example by defining satellite positioning
NOTE: For GPS assistance this data is defined by ICD-GPS-200H [1], IS-GPS-705 [5], IS-GPS-800 [6], for
QZSS, it is defined in IS-QZSS, [7], for Galileo in OS SIS ICD [8], and for GLONASS in GLONASS
ICD [9].
TETRA domain: all entities that are addressed using TETRA defined addresses and understand the binary format of
Net Assist Protocol
3.2 Abbreviations
For the purposes of the present document, the following abbreviations apply:
ACK ACKnowledgement
AGNSS Assisted Global Navigation Satellite System
A-GNSS Assisted- Global Navigation Satellite System
AI Air Interface
ASN.1 Abstract Syntax Notation 1
BIPM Bureau International des Poids et Mesures
BS Base Station
BTS Base Tranceiver Station
C Conditional
CA Conventional Access
CGI Cell Global Identification
CMCE Circuit Mode Control Entity
CNAV Civil Navigation
CRL Communications Research Laboratory
DGNSS GNSS Differential Corrections
DMO Direct Mode Operation
DN Day Number
ECEF Earth Centred Earth Fixed (coordinate system)
ECI Earth Centered Inertial (coordinate system)
EGNOS European Geostationary Navigation Overlay Service
EOP Earth Orientation Parameters
EPDU Extended Protocol Data Unit
FDMA Frequency Division Multiple Access
FE Functional Entity
FEC Forward Error Correction
GAGAN GPS Aided Geo Augmented Navigation
GEO Geostationary
GLONASS GLObal'naya NAvigatsionnaya Sputnikovaya Sistema
NOTE: English: Global Navigation Satellite System.
GNSS Global Navigation Satellite System
GPS Global Positioning System
GSSI Group Short Subscriber Identity
HOW Handover Word
ICD Interface Control Document
IE Information Element
IGS International GNSS Service
ETSI
11 ETSI TS 100 392-18-4 V1.2.1 (2015-07)
IOD Issue of Data
IODC Issue of Data Clock
IRNSS Indian Regional Navigation Satellite System
ISI Inter System Interface
ITU-T International Telecommunications Union - Telecommunication
LA Location Area
LIP Location Information Protocol
LOC LOCation group (at OMA)
LPP LTE Positioning Protocol
LSB Least Significant Bit
M Mandatory
MN Multiframe Number
MNI Mobile Network Identity
MO-LR Mobile Originated Location Request
MS Mobile Station
MSAS MTSAT Satellite Augmentation System
MTSAT Multifunctional Transport Satellites
MSB Most Significant Bit
NAP Net Assist Protocol
NAV Navigation
OMA Open Mobile Alliance
PDU Protocol Data Unit
PEI Peripheral Equipment Interface
PICS Protocol Implementation Conformance Statement
PLMN Public Land Mobile Network
PRC Pseudo-Range Correction
PRN Pseudo Random Noise
QZSS Quasi-Zenith Satellite System
QZST Quasi-Zenith Satellite Time
RRC Range-Rate Correction
SAP Service Access Point
SBAS Space Based Augmentation System
SDL Specification and Description Language
SDS Short Data Service
SDS-TL Short Data Service - Transport Layer
SFN Single Frequency Network
SNDCP SubNetwork Dependent Convergence Protocol
SNDCP SAP SubNetwork Dependent Convergence Protocol Service Access Point
SSI Short Subscriber Identity
SV Space Vehicle
SV-ID Satellite Vehicle Identifier
TBD To Be Defined
TCP Transmission Control Protocol
TLM Telemetry
TOD Time Of Day
TOW Time Of Week
UDP User Datagram Protocol
UDRE User Differential Range Error
URA User Range Accuracy
USNO U.S. Naval Observatory
UTC Universal Coordinated Time
WAAS Wide Area Augmentation System
WGS-84 World Geodetic System 1984
ETSI
12 ETSI TS 100 392-18-4 V1.2.1 (2015-07)
4 Net Assist Protocol
4.1 General
The Net Assist Protocol (NAP) is a TETRA air interface optimized application layer protocol that can utilize various
transport mechanisms.
The net assist protocol may use SDS-TL service at SDS-TL SAP, refer to ETSI EN 300 392-2 [3], clauses 29.1.1 to
29.5.12 in the case of TETRA MS, though it does not use SDS-TL transport mechanisms to ensure delivery. The same
protocol can use packet data at SNDCP SAP as defined in ETSI EN 300 392-2 [3], clause 28 in the case of TETRA MS.
The net assist protocol defines an extendable protocol that can provide net assist information, initially in a GNSS
technology based location determination scenario. Resource optimization is achieved by ensuring data is transported in
its most compact form as binary data and not in an expanded human readable form. Because of the volume of data and
because of the number of satellites it should be noted that some messages have a length which exceeds 500 bits and
multiple messages (one for each satellite) may need to be sent.
The net assist protocol can be used in various system configurations including:
• MS to assistance server communication (request for assistance information).
• Assistance server to MS communication (transmission of assistance information).
• MS to MS communication (request for and transmission of assistance information).
NOTE: Although NAP2 supports direct MS to individual MS communication; the use of it is discouraged as the
optimized air interface usage may be compromised. One possibility to maintain air interface optimization
is the use of a group address as the destination address.
4.2 Location information protocol system architecture
Physical entities identified for the purpose of the present document are:
• Mobile Station (MS) and location accessory requiring net assist information. It is referred as the "Target
Device" of location.
• Assistance server inside the TETRA domain with available net assist information (which may have been
sourced outside the TETRA domain and passed to it using a suitable protocol which is outside the scope of the
present document). It is also called a "Location Server".
How the assistance server acquires its net assist information and how it decides when to make that information available
are outside the scope of the present document.
Similarly, how the MS determines when and what assistance information is required is outside the scope of the present
document.
The assistance information exchange contains scenarios:
• MS determines the type of assistance that it would like and makes a request to the assistance server for
information.
• Assistance server to MS, where the assistance server has net assist information, and the assistance server
distributes the information to MS.
• MS to MS net assist information exchange without any action in any other entities.
For the purposes of the present document, the TETRA domain consists of entities that are addressable using TETRA
addressing and understand the net assist protocol NAP in the binary format of the protocol.
ETSI
13 ETSI TS 100 392-18-4 V1.2.1 (2015-07)
For the purposes of the present document protocol Functional Entities (FE) are used in some clauses instead of physical
entities:
FE1: MS requiring net assist information.
FE2: Assistance server.
Figure 4.2.1 defines a typical scenario for the net assist protocol usage.
In figure 4.2.1 the MS FE1 requests assistance information from the assistance server FE2.
In figure 4.2.1 the assistance server FE2 acts as the distribution point for assistance information to one or more MSs
FE1 requiring and able to accept assistance information.
Assistance info destination Assistance server
FE1 FE2
TETRA domain
Figure 4.2.1: Simple system with assistance server in TETRA domain
4.3 Net assist protocol service description
4.3.1 General on services
The majority of the location information protocol (ETSI TS 100 392-18-1 [4]) is independent of position determination
technology. Assistance data, delivered via the TETRA network, can improve the performance of some GNSS receivers,
particularly when they are in areas of poor GNSS satellite signal reception, such that they cannot reliably receive
navigation data from the satellites themselves. Additional information is made available in the form of time and location
(with uncertainty) assistance data. This release support all known Global Navigation Satellite System (GNSS) covering
GPS as well as other constellations such as GLONASS, GALILEO, BEIDOU as well as satellite based augmented
systems (EGNOS, WAAS, MSAS) and regional navigation systems (IRNSS, Q
...