SIST EN 300 395-3 V1.2.1:2006

• Abstract:

  The present document describes all the functions associated with the TETRA speech codec, except the specification of the codec by itself which is entirely defined in EN 300 395-2 [1]. Clause 4 of the present document provides a description of the functions associated with the speech encoder, while clause 5 is its counterpart for the speech decoder. Clause 6 describes the contents and the format of the signalling data block included in a stolen frame when used for transferring information relevant to the codec in a U-plane signalling message. In addition, annex A provides indications and preferred solutions for the implementation of optional features.

• Status: Published
• Publication Date: 31-Mar-2006
• ICS: 33.070.10 - Terrestrial Trunked Radio (TETRA)
• Technical Committee: SS EIT - Technical Board for the electrotechnical, information technology and telecommunications fields
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 01-Apr-2006
• Due Date: 01-Apr-2006
• Completion Date: 01-Apr-2006
• Ref Project: ETSI EN 300 395-3 V1.2.1 (2005-01) - Terrestrial Trunked Radio (TETRA); Speech codec for full-rate traffic channel; Part 3: Specific operating features

Overview

SIST EN 300 395-3 V1.2.1:2006 provides a comprehensive overview of specific operating features associated with the Terrestrial Trunked Radio (TETRA) speech codec used on full-rate traffic channels. While the detailed specification of the codec itself is defined in EN 300 395-2, this part of the standard outlines the critical operational functions related to the speech encoder and decoder, the format of the signalling data block used in U-plane signalling messages, and recommendations for implementing optional features. The standard ensures consistent operation, reliable voice communication quality, and interoperability within TETRA-based digital trunked radio systems.

Key Topics

• Speech Encoder and Decoder Functions
  The standard describes both encoding and decoding processes, including homing, comfort noise, frame stealing, speech importance, and test modes for conformance testing.
• Signalling Data Block Format
  It defines the structure and contents of signalling messages in "stolen" frames (those temporarily taken over for signalling rather than speech).
• Optional Feature Implementation
  Recommendations and guidelines are offered for features like Voice Activity Detection (VAD), Discontinuous Transmission (DTX), error concealment, and comfort noise generation.
• Encryption Interface
  Defines requirements and operational details for integrating with the TETRA encryption unit, supporting both encrypted and non-encrypted speech frames.
• Handling of Missing or Bad Frames
  Provides methods for generating and substituting missing frames to enhance robustness against transmission errors or link failures.

Applications

This standard is applicable in a variety of professional and mission-critical communication environments where TETRA is deployed, such as:

• Public Safety and Emergency Services
  Ensures reliable voice communication through robust speech codecs capable of handling frame losses and degraded transmission conditions.
• Transportation and Utilities
  Supports efficient, clear communication over digital radio networks, essential for operational coordination and safety.
• Industrial and Commercial Sectors
  Facilitates standardized integration of TETRA devices, allowing multi-vendor compatibility and consistent audio performance.

By specifying features like frame stealing (for urgent signalling), comfort noise handling (for call quality during silence or interruptions), and encryption interfaces (for secure communication), the standard underpins stable, high-quality digital voice communication across TETRA networks.

Related Standards

For full implementation and conformance, SIST EN 300 395-3 V1.2.1:2006 should be used alongside the following key standards:

• EN 300 395-2: TETRA speech codec specification (core codec functions and algorithms)
• EN 300 392-7: TETRA Voice plus Data (V+D) - Security, including encryption interfaces and signalling formats
• EN 300 395-1: General description of speech functions in TETRA systems
• 3GPP 26-Series: Optional AMR (Adaptive Multi-Rate) codec implementation referenced in the context of TETRA

Practical Value

Adhering to the requirements and recommendations in SIST EN 300 395-3 V1.2.1:2006 ensures that TETRA radio equipment:

• Achieves interoperability across different manufacturers and network providers
• Maintains high audio quality, even under challenging radio conditions
• Supports seamless integration of optional speech features such as DTX, VAD, and error concealment
• Delivers secure and resilient voice communication essential for critical operations

By following this standard, organizations deploying and maintaining TETRA infrastructure can provide reliable, high-quality voice communications that meet both operational needs and regulatory demands.

SLOVENSKI STANDARD
01-april-2006
Prizemni snopovni radio (TETRA) – Govorni kodek za kanal s polno hitrostjo – 3.
del: Posebne obratovalne lastnosti
Terrestrial Trunked Radio (TETRA); Speech codec for full-rate traffic channel; Part 3:
Specific operating features
Ta slovenski standard je istoveten z: EN 300 395-3 Version 1.2.1
ICS:
33.070.10 Prizemni snopovni radio Terrestrial Trunked Radio
(TETRA) (TETRA)
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

European Standard (Telecommunications series)

Terrestrial Trunked Radio (TETRA);
Speech codec for full-rate traffic channel;
Part 3: Specific operating features

2 ETSI EN 300 395-3 V1.2.1 (2005-01)

Reference
REN/TETRA-05118-3
Keywords
codec, TETRA
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ETSI
3 ETSI EN 300 395-3 V1.2.1 (2005-01)
Contents
Intellectual Property Rights.4
Foreword.4
1 Scope.5
2 References.5
3 Definitions and abbreviations.5
3.1 Definitions.5
3.2 Abbreviations.5
4 TETRA Speech encoder.6
4.1 Encoder homing function.7
4.1.1 Definition of encoder homing frame.7
4.1.2 Encoder homing.7
4.2 Speech importance function.7
4.3 Comfort noise function.7
4.4 Frame stealing function.8
4.5 Test mode functions .8
4.6 Encryption interface.8
5 TETRA Speech decoder.8
5.1 Encryption interface.9
5.2 Decoder homing function.10
5.2.1 Definition of decoder homing frame.10
5.2.2 Decoder homing.10
5.3 Missing frame generation.10
5.4 Missing frame substitution .10
5.5 Test mode functions .10
6 Signalling data block format .11
7 AMR speech encoder and decoder.12
Annex A (informative): Implementation of optional features .13
A.1 Speech importance calculation.13
A.2 Voice Activity Detection (VAD) .13
A.3 Discontinuous Transmission (DTX).13
A.4 CNF computation.13
A.5 Missing Frame Generation (MFG).13
A.5.1 Error concealment.13
A.5.2 Comfort noise generation.14
A.6 Setting BFI.14
A.7 U-plane frame stealing .14
A.8 Receiver muting.14
A.9 Response to U-plane signalling.14
Annex B (informative): Bibliography.15
History .16

ETSI
4 ETSI EN 300 395-3 V1.2.1 (2005-01)
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://webapp.etsi.org/IPR/home.asp).
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 European Standard (Telecommunications series) has been produced by ETSI Project Terrestrial Trunked Radio
(TETRA).
The present document is part 3 of a multi-part deliverable covering speech codec for full-rate traffic channel, as
identified below:
Part 1: "General description of speech functions";
Part 2: "TETRA codec";
Part 3: "Specific operating features";
Part 4: "Codec conformance testing".

National transposition dates
Date of adoption of this EN: 21 January 2005
Date of latest announcement of this EN (doa): 30 April 2005
Date of latest publication of new National Standard
or endorsement of this EN (dop/e): 31 October 2005
Date of withdrawal of any conflicting National Standard (dow): 31 October 2005

ETSI
5 ETSI EN 300 395-3 V1.2.1 (2005-01)
1 Scope
The present document describes all the functions associated with the TETRA speech codec, except the specification of
the codec by itself which is entirely defined in EN 300 395-2 [1].
Clause 4 of the present document provides a description of the functions associated with the speech encoder, while
clause 5 is its counterpart for the speech decoder.
Clause 6 describes the contents and the format of the signalling data block included in a stolen frame when used for
transferring information relevant to the codec in a U-plane signalling message.
In addition, annex A provides indications and preferred solutions for the implementation of optional features.
2 References
The following documents contain provisions which, through reference in this text, constitute provisions of the present
document.
• References are either specific (identified by date of publication and/or edition number or version number) or
non-specific.
• For a specific reference, subsequent revisions do not apply.
• For a non-specific reference, the latest version applies.
Referenced documents which are not found to be publicly available in the expected location might be found at
http://docbox.etsi.org/Reference.
[1] ETSI EN 300 395-2: "Terrestrial Trunked Radio (TETRA); Speech codec for full-rate traffic
channel; Part 2: TETRA codec".
[2] ETSI EN 300 392-7: "Terrestrial Trunked Radio (TETRA); Voice plus Data (V+D);
Part 7: Security".
3 Definitions and abbreviations
3.1 Definitions
For the purposes of the present document, the terms and definitions given in EN 300 392-2, clause 3 apply.
3.2 Abbreviations
For the purposes of the present document, the abbreviations given in EN 300 392-2, clause 3 and the following apply:
AMR Adaptive Multi-Rate
BFI Bad Frame Indicator
CNF Comfort Noise Frame
DTX Discontinuous Transmission
LTP Long Term Predictor
MAC Medium Access Control
MFG Missing Frame Generation
PCM Pulse Coded Modulation
RMS Root Mean Square
VAD Voice Activity Detector
ETSI
6 ETSI EN 300 395-3 V1.2.1 (2005-01)
4 TETRA Speech encoder
A diagram of the speech encoder and associated functions is given in figure 1. A more general overview is given in
EN 300 395-1. The speech encoder is defined in EN 300 395-2 [1] and the other functions form the speech encoder
control unit. The speech encoder control unit shall have access to all the internal data and functions of the speech
encoder (including the input speech).
SPEECH ENCODER
2 Reset
TEST MODE ENCODER HOMING
FUNCTIONS FUNCTION
FRAME STEALING COMFORT NOISE SPEECH IMPORTANCE
FUNCTION FUNCTION FUNCTION
ENCRYPTION
INTERFACE
Speech Encoder Control
1) 16-bit uniform PCM, 8 000 samples/s.
2) Encoded speech frame 30 ms, 137 bits/frame.
3) Encoded speech frame in "TMD_UNITDATA_request" message.
4) Stolen indication in "TMD_REPORT_indication" message.
5) Test mode control.
Figure 1: Overview of speech encoder specific operating features
The speech encoder as defined in EN 300 395-2 [1] shall receive speech in the form of 16-bit uniform PCM at a rate of
8 000 samples per second.
The coded data corresponding to each 30 ms speech frame shall be output from the speech encoder control unit via the
encryption interface to the encryption unit (or directly to the MAC if encryption is not used). The interfaces with the
encryption unit, namely interface points 3 and 4 in figure 1, shall be as defined in EN 300 392-7 [2], clause 7. Message
"TMD_UNITDATA_ request" is the means of conveying half-slots from the U-plane to the MAC, while
"TMD_REPORT_indication" enables the MAC to pass control information to the U-plane.
Comfort noise parameters may be generated and their presence in the coded speech data shall be indicated by a U-plane
signalling message conveyed using the frame stealing mechanism.
A speech importance indication shall be provided.
The presence of a homing sequence in the input speech shall be recognized and the encoder reset to a defined state.
All functions necessary to support conformance testing shall be implemented.
ETSI
7 ETSI EN 300 395-3 V1.2.1 (2005-01)
An appropriate U_device destination address shall be set for each half slot of coded speech data to allow correct routing
at the receiver.
4.1 Encoder homing function
4.1.1 Definition of encoder homing frame
The encoder homing frame shall consist of 240 identical samples (corresponding to a 30 ms speech frame), each 16 bits
long with the value 0x0008.
NOTE: 0x0008 is a number represented in hexadecimal notation.
4.1.2 Encoder homing
Whenever the speech encoder receives at its input an encoder homing frame exactly aligned with its internal speech
frame segmentation, the following events shall take place:
Step 1: the speech encoder performs its normal operation and produces a spe
...