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TECHNICAL SPECIFICATION
Terrestrial Trunked Radio (TETRA);
Voice plus Data (V+D);
Part 19: Interworking between TETRA and Broadband systems;
Sub-part 2: Format for the transport of TETRA speech over
mission critical broadband systems
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2 ETSI TS 100 392-19-2 V1.1.1 (2019-03)
Reference
DTS/TCCE-04194
Keywords
broadband, interworking, mission critical
applications, mission critical communications,
radio, security, speech, TETRA, V+D
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3 ETSI TS 100 392-19-2 V1.1.1 (2019-03)
Contents
Intellectual Property Rights . 5
Foreword . 5
Modal verbs terminology . 6
Introduction . 6
1 Scope . 7
2 References . 7
2.1 Normative references . 7
2.2 Informative references . 7
3 Definition of terms, symbols and abbreviations . 8
3.1 Terms . 8
3.2 Symbols . 9
3.3 Abbreviations . 9
4 Overview . 9
5 Broadband Traffic PDU format and procedures . 10
5.1 General on broadband traffic PDU contents . 10
5.2 TETRA payload . 10
5.2.1 TETRA payload encoding . 10
5.2.2 Broadband traffic PDU . 11
5.2.3 Basic Payload . 12
5.3 Broadband traffic PDU information elements . 13
5.3.1 Additional information . 13
5.3.2 Basic payload . 13
5.3.3 E2EE . 13
5.3.4 Information element control . 14
5.3.5 Payload type. 14
5.3.6 Phase . 14
5.3.7 Phase-0 basic block . 15
5.3.8 Phase-1 basic block . 15
5.3.9 Phase-2 basic block . 15
5.3.10 Signalling packet . 16
5.3.11 Signalling packet type . 16
5.3.12 Signalling packet status . 16
5.3.13 Speech frame pair number . 16
5.3.14 Speech frame status . 17
5.3.15 Supplementary signalling packet type . 17
5.3.16 Traffic type . 17
Annex A (normative): User information transport in RTP session . 18
A.1 General . 18
A.2 RTP usage . 18
A.3 Session Description Protocol . 19
A.3.1 General . 19
A.3.2 Protocol Version ("v=") . 19
A.3.3 Origin ("o=") . 19
A.3.4 Session Name ("s=") . 19
A.3.5 Connection Data ("c=") . 19
A.3.6 Timing ("t=") . 19
A.3.7 Media Type ("m=") and associated Attributes ("a=") . 19
A.3.8 Example of SDP Content . 20
A.4 IANA considerations . 21
A.4.1 General . 21
ETSI
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4 ETSI TS 100 392-19-2 V1.1.1 (2019-03)
A.4.2 Details . 21
Annex B (informative): Change requests . 22
History . 23
ETSI
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5 ETSI TS 100 392-19-2 V1.1.1 (2019-03)
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 Technical Committee TETRA and Critical
Communications Evolution (TCCE).
The present document is part 19, sub-part 2 of a multi-part deliverable covering the Terrestrial Trunked Radio
(TETRA); Voice plus Data (V+D), as identified below:
Part 1: "General network design";
Part 2: "Air Interface (AI)";
Part 3: "Interworking at the Inter-System Interface (ISI)":
Part 4: "Gateways basic operation";
Part 5: "Peripheral Equipment Interface (PEI)";
Part 7: "Security";
Part 9: "General requirements for supplementary services";
Part 10: "Supplementary services stage 1";
Part 11: "Supplementary services stage 2";
Part 12: "Supplementary services stage 3";
Part 13: "SDL model of the Air Interface (AI)";
Part 14: "Protocol Implementation Conformance Statement (PICS) proforma specification";
Part 15: "TETRA frequency bands, duplex spacings and channel numbering";
Part 16: "Network Performance Metrics";
Part 17: "TETRA V+D and DMO specifications";
Part 18: "Air interface optimized applications";
ETSI
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6 ETSI TS 100 392-19-2 V1.1.1 (2019-03)
Part 19: "Interworking between TETRA and Broadband systems";
Sub-part 1: "Critical Communications Architecture for Interworking between TETRA and Broadband
applications";
Sub-part 2: "Format for the transport of TETRA speech over mission critical broadband systems".
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.
Introduction
The present document defines a TETRA speech transportation format that may be applied over IP networks using RTP
and UDP encapsulation.
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7 ETSI TS 100 392-19-2 V1.1.1 (2019-03)
1 Scope
The present document defines a media format for the transport of TETRA air interface circuit mode speech over IP
networks at the 20 ms packet delivery rate typically used by broadband networks.
The present document does not apply to the transportation of TETRA speech over the TETRA ISI. The transportation of
TETRA speech over the TETRA ISI is defined by ETSI TS 100 392-3-8 [1].
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 100 392-3-8: "Terrestrial Trunked Radio (TETRA); Voice plus Data (V+D);
Part 3: Interworking at the Inter-System Interface (ISI); Sub-part 8: Generic Speech Format
Implementation".
[2] ETSI EN 300 392-2: "Terrestrial Trunked Radio (TETRA); Voice plus Data (V+D); Part 2: Air
Interface (AI)".
[3] ETSI EN 300 395-2: "Terrestrial Trunked Radio (TETRA); Speech codec for full-rate traffic
channel; Part 2: TETRA codec".
[4] ETSI EN 302 109: "Terrestrial Trunked Radio (TETRA); Security; Synchronization mechanism
for end-to-end encryption".
[5] IETF RFC 3550: "RTP: A Transport Protocol for Real Time Applications".
[6] IETF RFC 4566: "SDP: Session Description Protocol".
[7] IETF RFC 3264: "An Offer/Answer Model with Session Description Protocol (SDP)".
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 TS 122 280: "LTE; Mission Critical Services Common Requirements (3GPP TS 22.280)".
[i.2] ETSI TS 123 379: "LTE; Functional architecture and information flows to support Mission
Critical Push To Talk (MCPTT); Stage 2 (3GPP TS 23.379)".
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8 ETSI TS 100 392-19-2 V1.1.1 (2019-03)
[i.3] IETF RFC 3095: "RObust Header Compression (ROHC): Framework and four profiles: RTP,
UDP, ESP, and uncompressed".
[i.4] IETF RFC 3261: "SIP: Session Initiation Protocol".
3 Definition of terms, symbols and abbreviations
3.1 Terms
For the purposes of the present document, the following terms apply:
C-plane signalling: TETRA control plane signalling messages [2]
NOTE: C-plane signalling can contain DTMF signalling
encryption synchronization information: sequence of symbols that is transmitted to the receiving terminal to
synchronize an encryption key stream generator in the receiving terminal with an encryption key stream generator in the
transmitting terminal
end-to-end encryption: encryption that is applied by an originating terminal or client and is decrypted only by chosen
terminating terminals or clients
first half slot signalling packet: signalling packet that is associated with a first half slot speech frame
first half slot speech frame: TETRA ACELP speech frame that can be sent in the first half of a TETRA TDMA time
slot [3]
NOTE: The TETRA ACELP codec generates first half slot speech frames and second half slot speech frames, and
the decoder needs to be able to distinguish between these.
interworking function: function that enables interworking between land mobile radio systems and 3GPP defined
mission critical systems
land mobile radio: Private Mobile Radio (PMR)
mission critical: quality or characteristic of a communication activity, application, service or device that requires low
setup and transfer latency, high availability and reliability, ability to handle large numbers of users and devices, strong
security and priority and pre-emption handling [i.1]
mission critical system: 3GPP system providing mission critical communication services [i.1]
payload block: information element that can contain a speech frame and/or a partial or full signalling packet
second half slot signalling packet: signalling packet that is associated with a second half slot speech frame
second half slot speech frame: TETRA ACELP speech frame that can be sent in the second half of a TETRA TDMA
time slot [3]
NOTE: The TETRA ACELP codec generates first half slot speech frames and second half slot speech frames, and
the decoder needs to be able to distinguish between these.
signalling packet: block of data comprising U-plane signalling or C-plane signalling
speech frame pair: pair of speech frames comprising a first half slot speech frame and a second half slot
speech frame [3]
speech frame pair number: cyclical sequence number of a speech frame pair and any associated signalling packets
NOTE: The speech frame pair number is incremented at 60 ms intervals even if there are no speech frames or
signalling packets to be transmitted for that speech frame pair number.
TDMA frame: repeating time unit comprising a set of timeslots and representing a time subdivision of a frequency
channel [2]
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9 ETSI TS 100 392-19-2 V1.1.1 (2019-03)
TDMA frame number: cyclical sequence number of a TDMA frame [2]
timeslot: defined time interval within a TDMA frame [2]
U-plane signalling: TETRA encryption synchronization information and/or user-to-user signalling messages [2]
user-to-user signalling: signalling messages private to user applications
3.2 Symbols
Void.
3.3 Abbreviations
For the purposes of the present document, the following abbreviations apply:
3GPP Third Generation Partnership Project
ACELP Algebraic Code-Excited Linear Predictive
BB BroadBand
CSRC Contributing SouRCe
DTMF Dual Tone Multiple Frequency
E2EE End-to-End Encryption
TM
IANA Internet Assigned Numbers Authority
IE Information Element
IETF Internet Engineering Task Force
IP Internet Protocol
ISI Inter System Interface
IWF InterWorking Function
MCPTT Mission Critical Push To Talk
MS Mobile Station
PDU Protocol Data Unit
PSTN Public Switched Telephone Network
RFC Request For Comment
RoHC Robust Header Compression
RTP Real-time Transport Protocol
SDP Session Description Protocol
SIP Session Initiation Protocol
SSRC Synchronization SouRCe
SwMI Switching and Management Infrastructure
TDMA Time Division Multiple Access
TETRA Terrestrial Trunked Radio
UDP User Datagram Protocol
V+D Voice plus Data
4 Overview
Independently of SwMI or broadband network implementation, TETRA speech, U-plane signalling and C-plane
signalling can be carried in packets over broadband networks.
The media format defined in the present document allows RTP packets [5] containing TETRA ACELP speech
frames [3] and signalling to be transported through an IP network at 20 ms intervals.
A typical application is end-to-end encrypted voice calls between TETRA users and mission critical users [i.2]:
end-to-end encrypted TETRA speech is carried between the TETRA interworking function (IWF) and mission critical
users via the transport protocol defined in the present document.
The transmission defined in the present document is "packet mode" and packets may be subject to jitter. The maximum
jitter is a system specific characteristic. The value of the allowable maximum jitter value is outside the scope of the
present document.
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10 ETSI TS 100 392-19-2 V1.1.1 (2019-03)
5 Broadband Traffic PDU format and procedures
5.1 General on broadband traffic PDU contents
TETRA is a radio system where normally at least one end of the communication uses the TETRA air interface. Where
there is a requirement for TETRA equipment to interwork with equipment on a broadband network, TETRA speech and
traffic mode signalling can be transported over the broadband network in "broadband traffic" PDUs. The structure of the
TETRA air interface sets some requirements on the broadband traffic PDU contents and format. The main structure of
TETRA speech encoding and traffic mode signalling is retained. TETRA-compatible MSs, the TETRA SwMI and the
TETRA traffic PDU support:
• 30 ms speech frame and/or traffic mode signalling generation period [3]; and
• ACELP speech coding and reservation for other codecs.
The TETRA speech and traffic mode signalling can originate from a TETRA MS, an MCPTT client [i.2] containing a
TETRA speech codec or a TETRA or MCPTT despatcher or a PSTN gateway.
TETRA voice media comprises a sequence of speech frame pairs, each pair comprising a first half slot speech frame
and a second half slot speech frame, although individual speech frames may be dropped or "stolen" (i.e. replaced by an
associated signalling packet). The receiver needs to be able to distinguish between first half slot and second half slot
speech frames, and the broadband traffic PDU provides this distinction. A stolen or otherwise unavailable speech frame
is indicated in the broadband traffic PDU to facilitate re-use of the relevant TDMA timeslot for other signalling
purposes within a terminating TETRA system. A second half slot speech frame cannot be stolen unless the first half slot
speech frame has also been stolen.
TETRA traffic mode signalling needs to be associated with a specific speech frame, and the broadband traffic PDU
provides this association. The traffic mode signalling can carry TETRA U-plane signalling [2]. U-plane signalling can
be used to carry end-to-end encryption synchronization information as specified in ETSI EN 302 109 [4].
The traffic mode signalling is carried in a "signalling packet". A signalling packet can contain a TETRA
MAC-U-SIGNAL PDU. The use of this PDU shall be as specified in ETSI EN 300 392-2 [2].
The broadband traffic PDU is transported as RTP payload [5], there being one broadband traffic PDU per RTP packet.
RTP usage is defined in Annex A. Padding bits ensure that the broadband traffic PDUs end on octet boundaries. This
causes the containing RTP packets to end on octet boundaries, as required when sent via UDP.
5.2 TETRA payload
5.2.1 TETRA payload encoding
The protocol has been designed to support the transport of TETRA voice media in the form of speech codec frames
(single/dual) and TETRA U-plane and C-plane services. The present document describes in detail the broadband traffic
PDU formats for TETRA speech codec frames and TETRA U-plane and C-plane services. The generic payload
structure is presented in figure 5.1.
Payload Header Payload Block
Figure 5.1: TETRA payload structure
The payload header (contents control information element) indicates the presence and contents of the payload block
(e.g. speech frame and/or signalling packet or no traffic).
The TETRA speech and signalling are transmitted over the broadband network in RTP packets. The RTP packets are
transmitted at 20 ms intervals in a three-phase cycle (phase-0, phase-1 and phase-2) that allows the 20 ms broadband
delivery rate to be reconciled with the TETRA 60 ms speech frame pair generation rate.
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11 ETSI TS 100 392-19-2 V1.1.1 (2019-03)
The payload format allows some or all signalling packets to be transmitted without stealing speech frames, facilitating
fast end-to-end encryption synchronization without speech quality loss for TETRA speech that originates and
terminates within the broadband network. The speech frames include a "stealing recommendation" indication that is
used by the TETRA IWF to determine which speech frames to steal when delivering the speech and signalling to a
TETRA SwMI. An originator in the broadband network should set the "stealing recommendation" indication at intervals
suitable for a receiver using a TETRA SwMI as illustrated in ETSI EN 302 109, clause 4.4.3 [4].
When stealing is used, either the first half slot speech frame is stolen or both the first half slot and the second half slot
speech frames are stolen. A second half slot shall not be stolen unless the preceding first half slot has been stolen.
RTP packets contain a timestamp [5]. Because the sample period for speech in the TETRA codec is 0,125 ms and there
are 30 ms of coded speech in each speech frame, the timestamp is incremented by 240 units between RTP packets that
can contain consecutive speech frames.
More specifically:
• the present document specifies which RTP packets can contain speech frames;
• the timestamp is incremented by 240 units between RTP packets that can contain consecutive speech frames
(even if the speech frame or RTP packet is absent);
• an RTP packet that cannot contain a speech frame carries a timestamp equal to that in the immediately
preceding RTP packet.
5.2.2 Broadband traffic PDU
The broadband traffic PDU carries TETRA voice media in the form of speech frames. The PDU may also carry
signalling packets associated with the speech frames. The PDU is comprised of the following information elements, see
table 5.1:
• Speech frame pair number: this information element indicates the sequence of speech frame pairs and the
relationship of signalling packets to speech frame pairs in the payload block.
• Information element control: this information element indicates the presence or absence of the "additional
information" information element.
• Additional information: this information element allows for future expansion of the broadband traffic PDU.
• Traffic type: this information element identifies the type of circuit mode speech.
• Payload type: this information element indicates type of payload that follows.
• Basic payload, reserved, reserved, reserved: one of these information elements is selected by the "payload
type" information element. The basic payload carri
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