ETSI TR 102 398 V1.3.1 (2013-01)

Electromagnetic compatibility and Radio spectrum Matters (ERM); Digital Mobile Radio (DMR) General System Design

RTR/ERM-TGDMR-307

General Information

• Status: Published
• Publication Date: 30-Jan-2013
• Technical Committee: ERM TGDMR - Digital Mobile Radio
• Current Stage: 12 - Completion
• Due Date: 06-Feb-2013
• Completion Date: 31-Jan-2013

Standards Content (Sample)

Technical Report
Electromagnetic compatibility
and Radio spectrum Matters (ERM);
Digital Mobile Radio (DMR)
General System Design
2 ETSI TR 102 398 V1.3.1 (2013-01)

Reference
RTR/ERM-TGDMR-307
Keywords
digital, PMR, radio
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3 ETSI TR 102 398 V1.3.1 (2013-01)
Contents
Intellectual Property Rights . 6
Foreword . 6
Introduction . 6
1 Scope . 7
2 References . 7
2.1 Normative references . 7
2.2 Informative references . 7
3 Definitions, symbols and abbreviations . 8
3.1 Definitions . 8
3.2 Symbols . 10
3.3 Abbreviations . 11
4 Overview of DMR . 12
5 Over-the-air protocol summary . 14
5.1 Over-the-air protocol description . 15
5.1.1 Signalling advantages . 16
5.1.2 6,25 kHz equivalence . 17
5.1.3 The vocoder . 17
5.1.4 Radiated power and range . 17
5.2 Frequency considerations . 18
5.3 DMR Burst and frame structure . 20
5.4 Frame synchronization . 22
5.5 Basic channel types . 24
5.5.1 Traffic channel with CACH . 24
5.5.2 Traffic channel with guard time . 24
5.5.3 Bi-directional channel . 25
5.5.4 Direct Mode with continuous transmission . 25
5.5.5 TDMA direct mode timing . 26
5.6 Channel access . 26
6 DMR services . 27
6.1 DMR services overview . 28
6.2 Description of voice services. 28
6.2.1 Individual call service . 28
6.2.2 Group call service . 29
6.2.3 Unaddressed voice call service . 29
6.2.4 Open Voice Channel Mode service . 29
6.2.5 All Call Voice service . 30
6.2.6 Broadcast Call Voice service . 30
6.3 Description of data services. 30
6.3.1 IP over PDP . 30
6.3.2 Short Data Services over PDP . 30
6.3.2.1 Short Data over PDP - Status/Precoded . 31
6.3.2.2 Short Data over PDP - Raw Data . 31
6.3.2.3 Short Data over PDP - Defined Data . 31
7 DMR data services . 31
7.1 The Packet Data Protocol (PDP) . 31
7.2 Internet Protocol over PDP . 32
7.2.1 IPv6 transport over PDP . 33
7.3 Short Data Services over PDP . 33
8 Trunking (DMR tier III) . 34
8.1 Introduction . 35
8.2 Feature set . 36
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4 ETSI TR 102 398 V1.3.1 (2013-01)
8.3 Single Site/Wide Area . 37
8.4 MS location and registration . 38
8.5 Power Save . 38
8.6 Security features . 39
8.7 MS management from the system . 39
8.8 Physical link organization . 39
8.8.1 Radio frequency allocation . 39
8.8.2 Colour Code . 39
8.9 Unified Data Transport mechanism (UDT) . 40
8.10 Tier III frame structure . 40
8.10.1 TSCC structure . 40
8.10.2 Payload channel structure . 41
8.10.3 Random access . 41
8.11 Tier III user services . 42
8.11.1 MS initiating calls . 42
8.11.2 MS receiving calls . 42
8.11.2.1 MS receiving individual calls . 42
8.11.2.2 MS receiving calls to talkgroups . 43
8.11.3 Some Examples of Tier III calls . 43
8.11.3.1 An individual MS/MS voice call example . 43
8.11.3.2 An MS calls a talkgroup example . 44
8.11.3.3 A Call to the PSTN (PABX) example . 44
8.11.3.4 A short data call example . 45
8.12 The use of the CACH . 45
8.12.1 System identity code subset . 46
8.12.2 Reg bit . 46
8.12.3 Common Slot Counter . 46
9 Numbering and dialling plan . 46
9.1 Abbreviated dialling . 48
9.2 The concept of the wildcard character . 48
9.3 Gateway calls . 49
9.4 Call modifiers . 49
10 Network design and management . 49
10.1 General issues for DMR tier III networks . 49
10.2 Network design process . 50
10.2.1 Performance analysis . 50
10.2.1.1 Grade of service . 50
10.2.1.2 Channel hold time . 50
10.2.1.3 Performance results . 50
10.2.2 Traffic estimate . 51
10.2.3 Network radio environment . 51
10.3 Network management . 52
10.4 Features . 52
10.5 General recommendations (for all DMR tiers) . 53
10.6 Using network management as a tool (all DMR tiers) . 53
10.7 Network management functions (all DMR tiers) . 54
Annex A: Power save for DMR tier III systems . 55
A.1 Wake up based power save . 55
A.1.1 Introduction . 55
A.1.2 Expected improvement from power save . 57
A.1.2.1 Analysis of voice and packet data . 58
A.1.2.2 Analysis of short data . 58
A.2 Synchronized power save operation . 59
A.2.1 Use of the timers . 60
A.2.2 Power save for a single Talkgroup . 61
A.2.3 Power save for multiple Talkgroups . 61
Annex B: DMR tier III channel access . 62
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5 ETSI TR 102 398 V1.3.1 (2013-01)
B.1 Withdrawing slots . 62
B.2 Maintaining optimum throughput . 63
B.2.1 Mask and service function . 63
B.2.2 Random backoff . 63
B.3 Characteristics of DMR tier III random access . 64
Annex C: DMR protocol architecture . 67
C.1 Introduction . 67
C.1.1 Air Interface physical layer (layer 1) . 67
C.1.2 Air Interface Data Link Layer (layer 2) . 68
C.1.3 Air Interface Call Control Layer (layer 3) . 68
Annex D: Power Control . 69
D.1 Introduction . 69
D.2 Closed Loop Power Control . 69
History . 70

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6 ETSI TR 102 398 V1.3.1 (2013-01)
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://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 Report (TR) has been produced by ETSI Technical Committee Electromagnetic compatibility and Radio
spectrum Matters (ERM).
Introduction
The present document has been produced to provide an introduction to DMR for potential system purchasers, network
operators and service users.
It is in relation to multi-part TS 102 361 [i.1] to [i.4] covering the technical requirements for Digital Mobile Radio
(DMR), as identified below:
Part 1: "DMR Air Interface (AI) protocol";
Part 2: "DMR voice and generic services and facilities";
Part 3: "DMR Data protocol";
Part 4: "DMR trunking protocol".
It provides an overview, a description on the DMR services and facilities, technical background and radio aspects,
protocol and service performance, and guidance on numbering and addressing.
It should be understood that, as in all standard setting activities, there is an inherent conflict between the wish to have as
broad a standard as possible and at the same time wanting to have as much of that broad standard available and
implemented right from the beginning. Potential system purchasers, network operators and service users should make
sure they influence the suppliers to have their required functionality available when they need it.
Equipment manufacturers will use the broad flexibility provided within the standard to develop and implement systems
in various ways, and still be conforming according to the standard. This broad availability of systems, each optimized
around certain features and functionalities, needs to be carefully analysed by a network operator and system user to find
the supplier with a system suited best for their needs.
Clause 5 provides an overview of the DMR over-the-air protocol.
Information about DMR services is given in clause 6. In addition, clause 7 contains a summary of the DMR data
services.
Information on DMR trunking is in clause 8 as well as annex A (power save) and annex B (channel access and
throughput).
A short introduction to numbering and addressing is in clause 9.
Information on network design and management is in clause 10.
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7 ETSI TR 102 398 V1.3.1 (2013-01)
1 Scope
The present document is written as a "Read-me-first" manual or "Getting started with DMR". It is not intended to be a
complete guide to the DMR technical specifications. If any conflict is found between the present document and the
clauses in the DMR specifications then the technical specifications in TS 102 361 (all parts) [i.1] to [i.4] take
precedence.
The aims of the present document are many, for example:
1) to provide the reader with sufficient knowledge to engage in qualified discussions with the equipment and
service suppliers;
2) to expose the reader to the specific language and technical terminology used in the DMR specifications;
3) to enable the reader to understand the flexibility in system design, system network topography, system
availability and various modes of operation;
4) information on radio aspects and network design and management is given.
2 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.
2.1 Normative references
The following referenced documents are necessary for the application of the present document.
Not applicable.
2.2 Informative references
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 102 361-1: "Electromagnetic compatibility and Radio spectrum Matters (ERM); Digital
Mobile Radio (DMR) Systems; Part 1: DMR Air Interface (AI) protocol".
[i.2] ETSI TS 102 361-2: "Electromagnetic compatibility and Radio spectrum Matters (ERM); Digital
Mobile Radio (DMR) Systems; Part 2: DMR voice and generic services and facilities".
[i.3] ETSI TS 102 361-3: "Electromagnetic compatibility and Radio spectrum Matters (ERM); Digital
Mobile Radio (DMR) Systems; Part 3: DMR Data protocol".
[i.4] ETSI TS 102 361-4: "Electromagnetic compatibility and Radio spectrum Matters (ERM); Digital
Mobile Radio (DMR) Systems; Part 4: DMR trunking protocol".
[i.5] ETSI EN 300 113-2: "Electromagnetic compatibility and Radio spectrum Matters (ERM); Land
mobile service; Radio equipment intended for the transmission of data (and/or speech) using
constant or non-constant envelope modulation and having an antenna connector;
Part 2: Harmonized EN covering the essential requirements of article 3.2 of the R&TTE
Directive".
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8 ETSI TR 102 398 V1.3.1 (2013-01)
[i.6] ETSI EN 300 390-2: "Electromagnetic compatibility and Radio spectrum Matters (ERM); Land
mobile service; Radio equipment intended for the transmission of data (and speech) and using an
integral antenna; Part 2: Harmonized EN covering essential requirements under article 3.2 of the
R&TTE Directive".
[i.7] CEPT Recommendation T/R 25-08: "Planning criteria and coordination of frequencies in the Land
Mobile Service in the range 29.7-921 MHz".
[i.8] CEPT ERC Report 25: "The European table of frequency allocations and utilizations covering the
frequency range 9 kHz to 275 GHz".
[i.9] MPT1318: "Engineering Memorandum, Trunked Systems in the Land Mobile Service". February
1986, United Kingdom Department of Trade and Industry.
[i.10] CEPT ECC/DEC/(05)12: "ECC Decision of 28 October 2005 on harmonized frequencies,
technical characteristics, exemption from individual licensing and free carriage and use of digital
PMR 446 applications operating in the frequency band 446,1-446,2 MHz".
[i.11] Draft CEPT ECC Decision (06)06 (WGFM, Cavtat, April 2006): "ECC Decision on the
availability of frequency bands for the introduction of Narrow Band Digital Land Mobile
PMR/PAMR in the 80 MHz, 160 MHz and 400 MHz bands".
[i.12] IEC 61162-1: "Maritime navigation and radiocommunications equipment and systems - Digital
Interfaces - Part 1: Single talker and multiple listeners".
[i.13] IETF RFC 2529: "Transmission of IPv6 over IPv4 Domains without Explicit Tunnels".
[i.14] IETF RFC 3056: "Connection of IPv6 Domains via IPv4 Clouds".
[i.15] IETF RFC 3142: "An IPv6-to-IPv4 Transport Relay Translator".
[i.16] IETF RFC 4213: "Basic Transition Mechanisms for IPv6 Hosts and Routers".
[i.17] "Unicode: technical standards".
NOTE: www.unicode.org.
[i.18] ISO 8859 (parts 1 to 16): "Information technology - 8-bit single-byte coded graphic character
sets".
[i.19] IETF RFC 791: "Internet Protocol".
3 Definitions, symbols and abbreviations
3.1 Definitions
For the purposes of the present document, the following terms and definitions apply:
2:1-mode: 2 traffic channel mode
NOTE: 2:1-mode supports two independent calls which may be either "MS to fixed end" duplex calls, simplex
calls using a two frequency BS or simplex calls between MS units on a single frequency.
Base Station (BS): fixed end equipment that is used to obtain DMR services
bearer service: telecommunication service providing the capability for information transfer between access points
burst: elementary amount of bits within the physical channel
NOTE 1: Three different bursts exist with different number of bits. The Traffic burst contains 264 bits, the CACH
burst contains 24 bits and the RC burst contains 96 bits.
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9 ETSI TR 102 398 V1.3.1 (2013-01)
NOTE 2: The burst may include a guard time at the beginning and end of the burst used for power ramp-up and
ramp-down.
NOTE 3: For detailed burst definition see TS 102 361-1 [i.1], clause 4.2.1.
call: complete sequence of related transactions between MSs
NOTE: Transactions may be one or more bursts containing specific call related information.
channel hold time: total period for which a payload channel payload channel is assigned for a call
NOTE: Channel hold time is applicable to DMR tier III systems.
Control plane (C-plane): part of the DMR protocol stack dedicated to control and data services
conventional: non-trunked communication
NOTE: This is a communication technique where any radio unit (MS) may communicate with one or more other
radio units (MSs) without using a trunking protocol, and may be either in direct mode or using any
additional equipment (e.g. BS).
Digital Mobile Radio (DMR): physical grouping that contains all of the mobile and/or fixed end equipment that is
used to obtain DMR services
direct mode: mode of operation where MSs may communicate outside the control of a network
NOTE 1: This is communication technique where any radio unit (MS) may communicate with one or more other
radio units (MSs) without the need for any additional equipment (e.g. BS).
NOTE 2: Supports one transmission per 12,5 kHz frequency; 12,5 kHz equivalent (12.5e) spectral efficiency.
duplex: mode of operation by which information can be transferred in both directions and where the two directions are
independent
NOTE: Duplex is also known as full duplex.
forward: logical channel from source to target in direct mode
frame: two continues time slots labelled 1 and 2
NOTE: A frame has a length of 60 ms.
grade of service: probability that a call will be queued at the point where the system is experiencing its most busy
period (this is sometimes termed "the busy hour")
NOTE: Grade of service is applicable to DMR tier III systems.
inbound: MS to BS transmission
logical channel: distinct data path between logical endpoints
NOTE: The logical channels are labelled 1 and 2. The logical channel may consist of sub-channels, e.g. SYNC,
embedded signalling, etc.
Mobile Station (MS): physical grouping that contains all of the mobile equipment that is used to obtain DMR mobile
services
outbound: BS to MS transmission
payload: bits in the information field
physical channel: RF carrier who will be modulated with information bits of the bursts
NOTE: The RF carrier may be a single frequency or a duplex pair of frequencies. The physical channel of a DMR
subsystem is required to support the logical channels.
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10 ETSI TR 102 398 V1.3.1 (2013-01)
polite protocol: "Listen Before Transmit" (LBT) protocol
NOTE: This is a medium access protocol that implements a LBT function in order to ensure that the channel is
free before transmitting.
Protocol Data Unit (PDU): unit of information consisting of protocol control information (signalling) and possibly
user data exchanged between peer protocol layer entities
Radio Frequency (RF) channel: radio frequency carrier (RF carrier)
NOTE: This is a specified portion of the RF spectrum. In DMR, the RF carrier separation is 12,5 kHz. The
physical channel may be a single frequency or a duplex spaced pair of frequencies.
Reverse Channel (RC): signalling burst from target to source
signalling: exchange of information specifically concerned with the establishment and control of connections, and with
management, in a telecommunication network
simplex: mode of working by which information can be transferred in both directions but not at the same time
superframe: 6 continuous traffic bursts on a logical channel labelled "A" to "F"
NOTE: A superframe has a length of 360 ms and is used for voice traffic only.
TDMA direct mode: Direct mode operation that supports two transmissions per 12.5 kHz frequency
NOTE: Supports 6,25 kHz equivalent (6.25e) spectral efficiency.
time slot (or slot): elementary timing of the physical channel
NOTE: A timeslot has a length of 30 ms and will be numbered "1" or "2".
transmission: transfer period of bursts containing information or signalling
NOTE: The transmission may be continuous, i.e. multiple bursts transmission without ramp-up, ramp-down, or
discontinuous, i.e. single burst transmission with ramp-up and ramp-down period.
trunking: network controlled communication
NOTE: This is a communication technique where any radio unit (MS) may communicate with one or more other
radio units (MSs) using a trunking protocol and all MSs will be under control of a network.
unicode: 16 bit character encoding
User plane (U-plane): part of the DMR protocol stack dedicated to user voice services
vocoder socket: 216 bits vocoder payload
3.2 Symbols
For the purposes of the present document, the following symbols apply:
dBm absolute power level relative to 1 mW, expressed in dB
dBp Power relative to the average power transmitted over a burst in decibel
e Natural logarithm
Eb Energy per bit
ms millisecond
No Noise per Hz
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11 ETSI TR 102 398 V1.3.1 (2013-01)
3.3 Abbreviations
For the purposes of the present document, the following abbreviations apply:
4FSK Four-level Frequency Shift Keying
AI Air Interface
AT Access Type
BCV Broadcast Call Voice
BS Base Station
NOTE: A reference designating a fixed end device.
CACH Common Announcement CHannel
CC Colour Code
CCL Call Control Layer
CLI Call Line Information
C-plane Control plane
CRC Cyclic Redundancy Checksum for data error detection
CSBK Control Signalling BlocK
DLL Data Link Layer
DMR Digital Mobile Radio
ERC European Radiocommunication Committee
FDD Frequency Division Duplex
FEC Forward Error Correction
FID Feature set ID
FLCO Full Link Control Opcode
ID IDentifier
LBT Listen Before Transmit
LC Link Control
LCD Liquid Crystal Display
MBC Multiple Block Control packets
MFID Manufacturer's FID
MS Mobile Station
NOTE: MS - it is a reference designating a mobile or portable radio.
OACSU Off Air Call Set-Up
OVCM Open Voice Channel Mode
PA Power Amplifier
PABX Private Automatic Branch eXchange
PAMR Public Access Mobile Radio
PATCS Press And Talk Call Setup
PDP Packet Data Protocol
PDU Protocol Data Unit
PL Physical Layer
PMR Private Mobile Radio
PSTN Public Switched Telephone Network
PTT Press To Talk
RC Reverse Channel
RF Radio Frequency
SAP Service Access Point
NOTE: SAP - it is where a network provides a service.
SDS Short Data Service
SFID Standards FID
SLCO Short Link Control Opcode
SYNC SYNChronization
TCP Transmission Control Protocol
TDD Time Division Duplex
TDMA Time Division Multiple Access
TS Trunked Station
TSCC Trunk System Control Channel
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12 ETSI TR 102 398 V1.3.1 (2013-01)
U-plane User plane
UDP User Datagram Protocol
UDT Unified Data Transport
VOX Voice Operated transmit/receive switch
4 Overview of DMR
There are three tiers of DMR equipment:
• tier I equipment is for the lowest-cost "digital PMR446" application;
• tier II is for professional market offering peer-to-peer mode and repeater mode; and
• tier III is for trunked operation.
DMR tier II and tier III products encompass both simulcast and non-simulcast systems.
The present document describes a Digital Mobile Radio (DMR) system for tier II and tier III products which employs a
Time Division Multiple Access (TDMA) technology with a 2-slot TDMA solution and RF carrier bandwidth of
12,5 kHz. Additionally, a DMR system for tier I products is described which employs a continuous transmission
variation (FDMA) of the above mentioned technology.
More recently, the professional environment has undergone a change whereby old operational models are no longer
applicable in many cases. This has meant that the operational requirements placed on communication equipment have
evolved, and the traditional analogue service is no longer able to meet the users' needs completely. It is therefore
appropriate that more sophisticated services are made available which will meet this need. This raises the need for a
technology enhancement that allows the PMR model (which remains very attractive in many regards) to support the
basic and enhanced features and facilities existing and future users will require.
Industry research has indicated that in the event that certain key facilities can be provided, it may be expected that a
significant improvement in the current market performance of this service can be expected. There are only a relatively
small number of such features and facilities that are needed. However, these will dramatically change the value that the
users can derive from the equipment and services.
The main user required features are:
Basic Features:
1) Improved audio quality.
2) Improved battery performance.
3) Better range performance (this is taken to mean a good quality of service out to the range boundary rather than
much greater absolute range).
Enhanced Features are:
1) Hands-free operation.
2) Duplex (on the same channel), which also provides an appropriate means to communicate over the PSTN.
3) Security of communication.
4) The possibility of integrating the radio scheme into the specific operational methods of the undertaking.
DMR is recognized as having specific advantages when used in applications relating to public services and similar
environments. These are rarely quantified in economic terms due to the complexity of making such an analysis.
However, due to the importance of these uses, it is important to recognize how the introduction will improve the
operational efficiency of the service achieved. Here are a small number of examples by way of illustration.
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13 ETSI TR 102 398 V1.3.1 (2013-01)
1) Security Services
The introduction of digital signalling greatly facilitates the inclusion of location and status services such as
GPS. This could easily be integrated with automatic units providing details of status at particular locations
under this security umbrella. The end impact to the security organization is greatly improved awareness of the
location of all the security personnel and much faster response to incidents or other unusual situations. This in
turn leads to improved levels of security and also improves the safety of the individuals involved.
2) Site Safety
The introduction of significantly improved emergency facilities through reverse channel signalling means that
an immediate notification can be sent to site personnel that an incident is in progress. This can be accompanied
by data giving further details. It is equally possible to interrupt the current communication to pass the
information by voice if so desired.
This can have extremely important safety implications in very high noise or low-visibility environments
because having a hands-free possibility may encourage the use of headsets and similar accessories.
3) Local Government and Social Services
Location information, coupled with status information can more easily be accumulated and sent back to other
officers. This allows them a better ability to respond to incidents or perhaps aid co-workers who are in
dangerous situations.
The superior signalling allows a very large degree of automation at the application level to be employed. This
therefore offers the potential of having much improved operation with only small headcount implications.
4) Utilities
Maintenance workers in the field can be supported with much improved information through the signalling
capability while maintaining the important closed user group structure. This information cannot currently be
reliably provided through the analogue systems.
5) Specific Public Safety Applications
Whilst many public safety organizations are moving to sophisticated schemes, there remain some
organizations whose needs are not so complex.
Typically, these users already have an analogue scheme and are seeking to upgrade to a scheme that meets
their current and future needs. It may be that DMR with this level of signalling may provide a suitable
platform for their use.
In technical terms these requirements can be all met by using a low-latency, DMR protocol employing a suitable quality
vocoder. The coding gain is used to recover good quality audio at the coverage boundary rather than to extend the range
to distances not achievable by analogue schemes at the same transmit power.
As this is intended to be an enhancement that existing analogue users will most likely wish to take advantage of in the
near term, it is assumed that the preferred approach will be to locate these new schemes on their existing frequency
assignments wherever possible and in any event to be within the allocated land mobile service bands. Therefore, in
preparation for this, every effort has been undertaken to ensure that the digital protocol complies with the harmonized
spectrum regulation, the adjacent channel performance, and be carefully adjusted to not disturb with the existing
spectrum planning by excessive ranges being achieved in the field. Thus, the proposed protocol is to be designed to fit
into the existing regulatory environment and spectrum planning assumptions with an absolute minimum of disruption.
The DMR protocol is required to support a very wide variety of applications. Many users will continue to require
customized solutions. However, it is recognized that in some instances, users will require units from a variety of
suppliers, perhaps fulfilling different needs within the same overall operational environment. To assist this, the
technical specifications on DMR in TS 102 361 (all parts) [i.1] to [i.4] for applications and interoperability have been
created that defines an agreed list of specific features and facilities that are to be implemented and give sufficient detail
to allow them to be implemented in a
...