Digital Mobile Radio (DMR) Communication

A Technical Seminar for Radio Communication Professionals

Presenters

Saumik Ghosh

VU3IAZ

Amateur Radio Operator with expertise in Digital Technologies, VHF/UHF Operation.

Jaiyanta Baidya

VU2TFR

Amateur Radio Operator, RF Enthusiast specializing in Radio hardware including MMDVM systems and hotspot configurations.

Soumya Chakrabarti

VU3FWK

Amateur Radio Operator with expertise in Radio programming and Brandmeister integration,VHF/UHF/HF/FT8 Operation.

Arnab Roy Chaudhury

VU2TFQ

Amateur Radio Operator, Electronics Enthusiast with specilization in Emergency communications systems.

1. Basic Introduction to Digital Communication

Digital vs Analog Paradigm Shift

Digital communication converts voice and data into discrete binary signals (1s and 0s) rather than continuous waveforms.

Key Technical Advantages

Superior Audio Quality: Digital encoding with FEC eliminates static and interference
Enhanced Spectrum Efficiency: TDMA enables multiple conversations per channel
Network Integration: IP connectivity and internet protocol support
Advanced Features: Text messaging, GPS, caller ID, encryption

Digital vs Analog Comparison

📊 Spectrum Efficiency: 2:1 with TDMA
🔊 Audio: Consistent vs variable quality
📡 Coverage: Cliff effect vs gradual
🔋 Battery: Longer operational time
⚡ Features: Voice + data capabilities

2. Introduction to DMR Radio

What is DMR?

Digital Mobile Radio (DMR) is an open digital radio standard developed by the European Telecommunications Standards Institute (ETSI), ratified as ETSI TS 102 361. Operates within 12.5 kHz channel spacing.

DMR Tier Architecture

Tier I - License-Free DMR

Power output: ≤0.5W
Direct mode (radio-to-radio)
Specific frequency bands
Consumer applications

Tier II - Conventional DMR

Licensed operation
Repeater-based systems
Amateur radio standard
Power up to regulatory limits

Tier III - Trunked DMR

Advanced trunked systems with automatic channel assignment
Professional and commercial applications
Network-controlled operations

3. How DMR Works

TDMA (Time Division Multiple Access)

DMR uses TDMA to enable two simultaneous conversations on a single 12.5 kHz channel.

Frame Structure: 30ms frames divided into two 15ms time slots

Time Slot Architecture

Slot 1: First conversation channel (30ms duration)
Slot 2: Second conversation channel (30ms duration)
Guard Time: Synchronization pause between slots
Total Frame: 60ms structure (effectively doubles capacity)

4FSK Modulation & AMBE+2™ Vocoder

Modulation Parameters

4-level Frequency Shift Keying
Symbol rate: 4,800 symbols/sec
Data rate: 9,600 bits/sec
Deviation: ±648 Hz

AMBE+2™ Vocoder

Advanced Multi-Band Excitation codec
3,600 bits/sec digital stream
Optimized for low bit rate
Proprietary licensed implementation

4. DMR Protocol Stack

Based on ISO OSI model, defined by ETSI TS 102 361 standards

Physical Layer

Modulation: 4FSK at 4,800 symbols/second
Transmission Control: TX/RX mode switching
TDMA: Two-slot operation in 12.5 kHz channel
Synchronization: Frequency, symbol, and burst sync

Data Link Layer

Channel Coding: FEC and CRC implementation
MAC: TDMA time slot management
Interleaving: Protection against burst errors

Call Control Layer (CCL)

Call Control: Group, private, emergency calls
Supplementary Services: Text messaging, radio check

5. Components of DMR Communication

DMR Repeater System

                Core Repeater Functions
                Receives and retransmits with higher power
TDMA time slot coordination
Network gateway operations
User authentication and emergency handling

            

DMR Network Infrastructure

Master Server

Central coordination point
User registration management
Call routing between talk groups

Bridge Systems

Connect different DMR networks
Protocol translation
Network redundancy

DMR Radio Equipment

Handheld (HT): Portable, battery powered
Mobile: Vehicle installation, higher power
Base Station: Fixed location, AC power
Hotspot Devices: Low-power personal repeaters

6. RadioID – Your Digital Callsign

What is a RadioID?

A unique seven-digit numerical identifier assigned to each DMR user worldwide, serving as your digital "call sign" for network routing.

RadioID Structure

Format: X-XXX-XXX (seven digits)

First digit: Country/region identifier
Remaining digits: Unique user identifier

Examples:

3123456 - North American region
2621234 - European region
4401234 - Asia-Pacific region
404xxxx - India (VU operators)

RadioID Functions

Network Authentication: Validates user access
Call Routing: Directs private calls to specific users
System Integration: Links call sign with digital ID

7. How to Create RadioID - Step by Step

1Obtain Official License

Get your official amateur radio license in PDF format from licensing authority

2Register on RadioID.net

Visit https://radioid.net/
Click "Log In/Sign Up" → "USER REGISTRATION"
Fill registration form (callsign, email, personal info)
Upload official license document (PDF)
Submit registration

3Wait for Verification

Processing time: 1-3 days
Email notification with your DMR ID
SAVE THIS EMAIL - contains your unique 7-digit DMR ID

RadioID Registration Process

Registration Form: RadioID.net user registration page showing callsign input, personal details, and license upload section

Approval Email: Confirmation email with assigned DMR ID number and account activation details

8. Brandmeister Network

What is Brandmeister?

World's largest DMR network providing internet-based connectivity between DMR repeaters and hotspots globally.

Key Features

Global Coverage: 2,000+ connected repeaters worldwide
Talk Group Management: Dynamic assignment and scheduling
Self-Care Portal: User account and configuration management
Advanced Services: Parrot echo test, network monitoring, API access

Regional Master Structure

Master ID	Region	Coverage
BM 3101	North America	USA, Canada, Mexico
BM 2621	Central Europe	Western Europe
BM 4401	Asia-Pacific	Asia, India, Pacific
BM 5051	Africa	African continent

9. Brandmeister Account Setup

Registration Process

Website: https://brandmeister.network/

Click "Register"
Enter call sign and email
Enter your DMR ID (RadioID)
Create password
Answer: "What is the wavelength of UHF in cm?" = 70
Click "Register"
Verify email and login

API Key Management

Location: Profile Settings → API Keys

To Create API Key:

Navigate to Profile Settings → API Keys
Click "Generate New Key"
Name your key (e.g., "Pi-Star Dashboard")
Copy key immediately (shown only once)

Brandmeister Configuration Interface

Self-Care Portal: Main dashboard showing user profile, connected hotspots, active talk groups, and real-time network status

API Keys Page: Profile settings displaying API key management interface with QR codes for third-party integration

10. Brandmeister Talk Groups

Talk Group Numbering System

Regional (TG 1-999)

Country and regional groups
Example: TG 404 - India
Example: TG 40433 - DMR Kolkata

Worldwide (TG 1000-9999)

TG 91: Worldwide English
TG 92: Worldwide German
TG 93: North America

Special Purpose (TG 90000+)

TG 9990: Parrot (Echo Test)
TG 91011: Tech Talk

Operation Modes

Static Subscriptions

Always connected, automatic routing

Dynamic Connections

On-demand activation

Talk Group Configuration

TG Browser: Brandmeister talk group directory showing worldwide, regional, and local groups with subscriber counts

My Talk Groups: Personal subscription manager showing active and available talk groups for your hotspot

11. MMDVM Overview and Purpose

Multi-Mode Digital Voice Modem

Open-source platform for building digital voice repeaters and hotspots. Developed by Jonathan Naylor (G4KLX).

Supported Digital Modes

DMR: ETSI Tier II, TDMA, Brandmeister compatible
D-Star: JARL/ICOM standard, AMBE vocoder
System Fusion (YSF): Yaesu standard, C4FM
P25: APCO Project 25, public safety
Cross-mode: YSF2DMR, DMR2YSF, NXDN

Applications

Personal Hotspots

Low-power, single-user, home/office coverage

Community Repeaters

Multi-user, local area coverage

MMDVM Hardware Examples

MMDVM HAT: Raspberry Pi HAT board with RF module, STM32 microcontroller, and antenna connector

Assembled System: Raspberry Pi with MMDVM HAT, OLED display, case, and antenna in operational configuration

MMDVM Dual HAT: Advanced dual-band HAT supporting simultaneous VHF/UHF operations with enhanced RF capabilities

12. Pi-Star Configuration

Pi-Star: Pre-configured software for Raspberry Pi. Developed by Andy Taylor (MW0MWZ).

Website: https://www.pistar.uk/

Installation Steps

1Download and Image

Download Pi-Star image, use Raspberry Pi Imager, write to SD card

2Initial Boot

Access via http://pi-star.local/ → Admin → Expert

Configuration

General

Call Sign
DMR ID
Frequency

DMR Settings

Master: BrandMeister
Server: Regional
Color Code: 1

Pi-Star Configuration Interface

Main Dashboard: Real-time status with last heard stations

Config Page: General settings and DMR ID entry

DMR Config: Master server and color code settings

Log Viewer: Real-time system and network logs

13. WPSD Configuration

W0CHP-PiStar-Dash (WPSD)

Enhanced dashboard based on Pi-Star with additional features and improved performance.

Website: https://w0chp.radio/wpsd/

Enhanced Features

Dashboard Improvements

Real-time spectrum display
Advanced diagnostics
Enhanced mobile interface

Additional Services

NextionDriver support
Improved YSF/P25 gateways
Performance monitoring

Configuration Backup

Admin → Backup/Restore → Create backup → Download file

WPSD Enhanced Interface

Enhanced Dashboard: WPSD interface with real-time frequency spectrum analyzer and improved status displays

Performance Monitor: CPU, memory, temperature monitoring with detailed network statistics

15. MMDVM Hotspot Devices

Popular Options

Pi-Star Hotspot

Raspberry Pi with MMDVM HAT
Multi-mode capability
Web configuration
Most flexible option

Jumbo SPOT

Ready-to-use solution
Dual mode operation
USB powered
Compact portable design

OpenSpot

Simple configuration
WiFi/Ethernet capable
Affordable entry-level

Hotspot Device Examples

Raspberry Pi Setup: Complete MMDVM hotspot with Pi, HAT board, OLED display, antenna, and protective case

Ready-to-Use Devices: Jumbo SPOT and OpenSpot commercial hotspots with integrated antennas and USB power

16. Baofeng DM-32 Configuration

Overview

Entry-level DMR handheld transceiver with dual-band VHF/UHF operation.

Key Specifications

Frequency: VHF 136-174MHz, UHF 400-480MHz
Power: 5W (High), 1W (Low)
Channels: 3000 programmable
Programming: PC software required

Configuration Steps

1Install Software & Drivers

Download CPS software, install USB drivers

2Program DMR Settings

Radio ID: Your DMR ID
Color Code: 1
Time Slot: 2 (typical)

Baofeng DM-32 Programming

CPS Interface: Baofeng Customer Programming Software showing channel list, contacts, and digital configuration options

LCD Display: DM-32 color screen showing DMR mode, talk group number, signal strength, and channel name

26. Digital APRS System Overview

What is Digital APRS?

Digital Automatic Packet Reporting System (APRS) integrated with DMR networks, enabling position reporting, messaging, and telemetry over digital radio infrastructure.

Key Features

GPS coordinate transmission
Real-time position tracking
Text message exchange
Weather data transmission
Emergency position alerts

Network Integration

Brandmeister DMR network
APRS-IS gateway connection
Cross-platform compatibility
Emergency communication support

Primary Applications

Emergency Communications: Disaster response coordination
Event Support: Public event tracking and management

Fleet Management: Vehicle and personnel tracking
Weather Reporting: Automated station data collection

27. Digital APRS Configuration

Hardware Requirements

DMR Radio: APRS-capable (AT-D878UV)
GPS Module: Internal/external receiver
Programming Cable: USB configuration
Antenna: Dual-band VHF/UHF

Configuration Steps

1Enable APRS in CPS software
2Configure GPS and beacon settings
3Set DMR ID and call sign
4Test network connectivity

Key APRS Parameters

Call Sign: Amateur radio identifier • SSID: Station type (-9 mobile)
Beacon Interval: 30s to 30min • Symbol: Map icon selection

Important: Ensure proper licensing and regulatory compliance for APRS operations.

Summary

Key Takeaways

                DMR Fundamentals
                ETSI TS 102 361 standard
TDMA: 2:1 spectrum efficiency
4FSK modulation at 9,600 bps
AMBE+2™ vocoder

            

Network Infrastructure

RadioID: 7-digit identifier
Brandmeister network
Talk Groups system

Implementation

MMDVM platform
Pi-Star/WPSD software
Hotspot devices

Resources

RadioID: https://radioid.net/
Brandmeister: https://brandmeister.network/
Pi-Star: https://www.pistar.uk/
WPSD: https://w0chp.radio/wpsd/

Questions & Discussion

Thank You

For attending this technical seminar on Digital Mobile Radio Communication

73. See you on AIR !