DMR (Digital Mobile Radio) Notlarım

Kişisel Notlar

DMR standardı, ETSI, European Telecommunications Standards Institute tarafından yazılmış.

İngilizce kullanımda portable radio el telsizi demek. Yani

Portable Radio - El telsizi

Mobile Radio - Araç Telsizi

Tiers

Açıklaması şöyle

Understanding the DMR Tiers is not strictly necessary but knowing which Tier your radio is, is very important.

TIER 1 - Radio to Radio

  Simplex only. No Time slots. This means it cannot be used on amateur repeaters as it would use up both time slots.

The original Boefeng DM5R was Tier 1 only. DM5R+ had Tier 2.

TIER 2 - Repeater-based

   Supports 2 Time Slots (TDMA). What us Amateurs Use

TIER 3

Advanced Trunked system. Complicated Commercial system allows for automatic repeater switching plus many other things.

Similar to the Airwave system used by the emergency services.

Tier 2 - Conventional DMR

Site yoktur. Şeklen şöyle

Talkgroup <-->  Repeater

Tier 2 - Wide-Area DMR

Site vardır. Şeklen şöyle. Burada telsizler sitelerle ilişkilenir. Sitelerin kimlik numarası vardır ve birbirlerine yönlendirmeyi ağ yönetim Ip uygulaması bilir ve yapar. Yani routing statiktir.

Talkgroup <-->  Site <--> Repeaters

Channel Plan

Açıklaması şöyle

A channel plan is the mapping between logical channel numbers (LCNs) and actual RF frequencies used by a DMR system.

Açıklaması şöyle

The DMR standard defines the concept of logical channels and how channel information can be communicated, but the actual channel plan (the specific frequencies and LCN assignments) is determined by the system operator or vendor deployment.

Açıklaması şöyle

A grant such as:

> Talkgroup 1001 → LCN 2 → Slot 1

means:

> Tune to 451.0125 MHz and use Slot 1.

 OTAP — Over-The-Air Programming

Açıklaması şöyle

OTAP allows a radio's configuration (codeplug) to be updated remotely through the radio network instead of connecting a programming cable.

OTAP protokolü üreticiye mahsustur ve muhtemelen all radios gönderim yeteneği vardır.

OTAR — Over-The-Air Rekeying

Açıklaması şöyle

OTAR is completely different. OTAR updates cryptographic keys, not radio configuration.

CSBK - Control Signalling Block

Bir CSBK mesajı şu hedeflere adreslenebilir

A specific radio (Individual ID)

A talkgroup (Group ID)

All radios (Broadcast)

A subset of radios depending on the CSBK type

DMR 24-bit adresler kullanır. Bazı özel adresler şöyle

0xFFFFFF (16777215) All Radios / Broadcast / All Call

0xFFFFFE (16777214) Reserved special address

0x000000 Often used as Null Address depending on context

CSBK Mesaj Grupları

The CSBK contains a 6-bit CSBKO (CSBK Opcode) field. The opcode determines the message family and how the 64-bit data field is interpreted.

Common ETSI CSBK families include:

Group                                         Purpose

Channel Grants                         Assign traffic channels for voice or data

Announcement Messages         Broadcast system information

Voting / Adjacent Site Messages Roaming and site selection

Random Access / ALOHA         Registration and access control

Acknowledgement Messages         Confirm requests

Negative Acknowledgement           Messages Reject requests

Maintenance / Control                 System management

Manufacturer Specific                 Vendor extensions using MFID

OpCode dışında FID alanı da önemli. Açıklaması şöyle

Also note that ETSI defines a second level of grouping through the FID (Feature ID) field. The same CSBKO value can have different meanings depending on the FID. ETSI reserves FIDs for standard features and manufacturer-specific features.

Talk Group

Açıklaması şöyle

A DMR GROUP  (Often called a “talkgroup” ) is a method of grouping or assembling multiple users (Radio ID’s) to a single contact. A Group or “talk group” is simply a group of users that need to talk to each other and hear all the communications in that group. 

- An example would be all the maintenance personnel at a hospital would need to all share communications with each other. So, you would create the  “maintenance” group.

Broadcast: Bazı gruplar abone üye olsun olmasın global kabul edilir ve tüm telsizlere yayın yapar

Roaming : Telsiz site değiştirdikçe roaming bayrağına göre bu gurubu dinlemeye devam eder. 

Tier 1 – RF Control & Channel Architecture (DMR Systems)

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1. Trunking Architecture Types

1.1 Site-Controlled Channel Allocation

• Each site manages its own channel allocation
• Decisions are made locally at site level
• Traffic channel assignment is handled by the site
• No mandatory centralized routing entity

1.2 Centralized Architecture (Star Topology)

Central system is managed by ISS (Integrated Soft Switch) in a star topology.

Topology

• Star topology
• All sites connect to central ISS
• Routing decisions are centralized

Call / Channel Allocation Flow

1. Radio locks to site control channel
2. Site forwards registration to ISS
3. ISS performs authorization and routing decision
4. ISS instructs site to assign traffic channel
5. Site executes RF channel assignment

Summary: Site executes, ISS decides.

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2. Channel Types

2.1 RF carrier bandwidth

Dijital kanal 12,5 kHz bant genişliğindedir. Analog kanal DMR standardı değildir ama kullanılır ve genellikle 25 kHz bant genişliğindedir

2.2 Analog Channel

• Not part of DMR traffic
• Supported for legacy systems

2.3 DMR Conventional Channel

Simplex (P2P)

• Radio-to-radio communication
• No repeater
• Direct communication model

Repeater Mode

• Uses repeater infrastructure
• Extends coverage
• Frequency pair operation

2.4 DMR Trunked Channel (Tier III)

• Dynamic channel allocation
• Separation of control and traffic planes

Channel Types:

• Control Channel: signaling and system control
• Traffic Channel: voice/data communication

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3. Squelch (Muting Mechanism)

Squelch is a receiver function that mutes speaker output when no valid signal is present. Without it, constant background noise ("hiss") would be heard.

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4. Squelch Types

4.1 Color Code (Digital Squelch)

• Used in digital DMR channels
• Equivalent to CTCSS/DCS in analog systems
• Range: 1–15
• Filters unrelated digital systems on same frequency

4.2 Tone Squelch (CTCSS – Analog)

• Uses sub-audible tones (e.g. 88.5 Hz)
• Must match for audio to open
• Allows frequency sharing without interference

4.3 Digital Squelch (DCS – Analog)

• Digital code-based squelch
• Alternative to CTCSS
• Uses digital patterns instead of tones

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5. ANI - Automatic Number Identification

Sadece analog kanallarda olur. Analog tone ile arama yapan telsiz kimliği karşı tarafta gösterilir.

5. SelectiveCall

Sadece analog kanallarda olur. Analog tone ile aranan telsizin ses çıkarması sağlanır.

6. Kripto

Aslında DMR standardında kripto tanımlı değil. Çoğu üretici kanala bağlı bir kripto tanımlıyor. Telsiz kanal değiştirince, o kanal için tanımlı kripto algoritmasını kullanıyor

7. Repeater

Repeater'lar katmanlı çalışır ve birbirlerine trafik gönderebilirler

8. System Mental Model

More to come