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SOUTH WALES DIGITAL GROUP

DMR (Digital Mobile Radio)

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What is DMR?

DMR stands for Digital Mobile Radio and uses the Motorola TRBO protocol for communications. Like other digital modes such as D-Star, C4FM and APCO P25, the TRBO protocol converts your voice into a digital form and sends it out via RF (with other bits of information included) and allows you to communicate to other DMR radios and also DMR repeaters, which are networked together around the world via the internet.

What makes DMR stand out from some of the other digital modes is that it utilizes TDMA (Time-Division Multiple Access) to divide a single frequency into 2 distinct “channels” or time slots. By doing this, you can have two conversations going on at the SAME TIME, using one frequency.

Imagine using one frequency while radio A is talking to radio B on time slot 1, and radio C is talking to radio D on time slot 2 … SIMULTANEOUSLY. Pretty neat, huh?

Here is a nice graphic to help visualize and understand what is going on…

Although the graphic above relates to how a DMR repeater works, this same principal applies to using a simplex frequency as well.

To make matters a little more fun and complicated, each radio must have a unique Radio ID for digital identification between radios and you can also use Talkgroups to separate traffic and target specific groups of DMR users.

What Is The BrandMeister Network?

 The BrandMeister Network was born from several worldwide hams and software engineers who joined together to create a digital repeater network consisting of master servers and peer repeaters all over the world. The network has over 1300 repeaters and more than 3000 hotspots across the globe and it’s growing every day!

BrandMeister is tailored to the Motorola TRBO technology and allows for DMR repeaters to connect worldwide via the internet and link systems together by utilizing organized Talkgroups.

The BrandMeister Network offers several neat features for amateur radio enthusiasts to take advantage of:

    • Private Call
    • Talkgroups
    • APRS
    • SMS Text Messaging
    • D-Star Gateway
    • EchoLink Gateway
    • Autopatch Call Gateway
    • Roaming via Hytera Equipment
    • and more…

Here’s a simple graphic depicting how this all happens:

 

 

As you can see, there is a lot going on all at once. But that is the beauty in a DMR network. Many people can communicate at the same time, without stepping on each other. Traffic actually gets routed specifically between, radios, repeaters and locations.

Keep in mind that the above graphic only shows one BrandMeister Master server, when in the real world there are over 46 Master Servers connected together across the globe doing all of this in real-time.

BrandMaster/BrandMeister is an operating software for Master servers participating in a worldwide infrastructure network of amateur radio digital voice systems.

    • If you are an amateur radio operator working in digital voice modes like D-Star, DMR, C4FM, APCO P25 or others (not all are supported yet!!). You do not need to know much about BrandMeister, and it’s very easy to operate on its infrastructure.
    • If you are an amateur radio operator that runs a repeater in your local area, you may be interested in learning some more about BrandMeister and how you can take part in it.

A brief overview of BrandMeister core features:

    • Switching system for IP-enabled conventional Tier-2 DMR radio
    • Supports the most known network-access and end-user equipment making it easily expandable
    • Performs switching on the Layer 3 (Call Control) of the DMR stack
    • Has an embedded data stack (Layer 4)
    • Has embedded data and voice applications
    • Flexible routing based on data stored in a global database, local memory cache, and Lua scripts
    • Event notification using messaging queues (calls, connections, alarms, messages, locations and telemetry)
    • Implements mesh-topology for inter-node communications

BrandMeister allows you to connect to MOTOROLA DMR-MARC and Hytera DMRplus networks, this means you can operate with other DMR amateur radio operators on both infrastructures at the same time.

BrandMeister allows me…

    • To roam automatically from repeater to repeater
    • To make private QSOs on any time-slot
    • To make world-wide QSOs with any type of amateur DMR network
    • To send my location to APRS
    • To send and receive SMS messages
    • To send and receive SMS messages to or from APRS
    • To control some electrical apparatus using my DMR radio as a remote control device

Embedded Applications

Interactive voice response for status messages (with support for 5 languages),

Signaling expansion (UU-Req/UU-Resp)

Automatic registration/roaming (Hytera RRS)

Auto-Patch call gateway

SMS gateway (vendor independent, supporting ETSI/Hytera/Motorola)

    • Common-use applications:
    • IP Gateway
    • Examples of some Amateur Radio usage applications:D-STAR D-Extra to talking group gateway
    • D-STAR G2 call routing to private call gateway
    • APRS position and telemetry reporting
    • APRS text message gateway
    • AMPR access service
    • Gateway for EchoLink or any other IP-based PTT applications

Architectural principles

The general architecture of BrandMeister consists of three different layers:

    • the first layer provides drivers for frontend/radio interfaces like Hytera Repeaters, Motorola repeaters, UP4DAR, homebrew repeaters
    • the second layer is built by the logical kernel with an implemented routing mechanism
    • the third layer consists of interfaces supporting communication service protocols to the WAN (IPSC, CC-Link, APRS, XRF)

All BrandMeister Master servers communicate with each other through the BrandMeister FastForward (FF) high-speed protocol.

    • BrandMeister is only a front-end application that works in real-time
    • All business logic to distribute routing lists and user profiles implemented outside of BrandMeister like a set of back-end applications and scripts
    • BrandMeister supports multiple sources of routing information: scripts, databases, in-memory cache, configuration files at the same time
    • Web applications and diagnostic tools are also separated out from the main program
    • BrandMeister uses event-driven mechanisms (MQ) to notify backends about events, in-memory data storage and relational database to get location, routing and user profiles

We are in the process of implementing mesh-based distributed network storage which will allow all network servers will be equivalent nodes. This is a prerequisite to maintain high availability of the network and will help keep the infrastructure more resistant to temporary or permanent loss of single nodes.