How the Digital Mobile Radio (DMR) Standard Enhances the Performance and Capacity of Two-Way Radio Communications
The Digital Mobile Radio (DMR) is a digital radio standard used in professional mobile radio applications. DMR offers numerous advantages over analog radio systems, such as improved voice clarity, better range, longer battery life, and increased calling capacity.
Digital Mobile Radio (DMR) is the open radio industry standard developed by the European Telecommunications Standards Institute (ETSI) and promoted worldwide by the DMR Association. Hytera was instrumental in the development of the DMR standard, and was the first company to deploy a fully compliant DMR Tier III radio system.
The Importance of DMR Standard Compliance
DMR standards compliance ensures that all radios and base stations operate on a common standard and enables the creation of a robust and reliable communication system that is more effective than a system based on proprietary technologies.
Manufacturer Interoperability – DMR standards compliance ensures that radios and repeaters from different manufacturers can interoperate seamlessly. A user can purchase a radio from one manufacturer and a repeaters from another manufacturer and still have them communicate with each other. This interoperability increases flexibility in equipment choices and reduces costs for users.
Improved Performance – Compliance with DMR standards ensures that all equipment meets certain technical specifications, which improves the performance of the entire radio communication system. This results in better voice quality, improved coverage, and reduced interference.
Future-Proofing – Compliance with DMR standards ensures that equipment is compatible with future upgrades and improvements to the technology. This future proofing allows users to invest in equipment with confidence that it will remain compatible and functional for years to come.
For a deep dive into DMR technology, download the DMR Association white paper
DMR digital capabilities improve radio communications and provide several advantages over legacy analog radio systems:
- Instant push-to-talk individual and group calling with radio identification
- Doubles the capacity of existing licensed radio channels
- Provides efficient use of infrastructure equipment
- Enables power efficiency for longer battery life
- Superior audio performance over longer distances
- Supports data transmission for digital applications
TDMA and 12.5 MHz Channel Spacing
Time Division Multiple Access (TDMA) and 12.5 MHz channel spacing are two key technologies that are utilized in DMR two-way radios. These technologies provide a range of benefits that improve the performance and reliability of DMR radios. This is a key benefit over analog radios that have one frequency shared by all users.
TDMA allows multiple users to share the same radio frequency by dividing it into time slots. Each radio is assigned a specific time slot in which it can transmit and receive data, and the radio switches between these time slots rapidly, giving the impression of simultaneous communication. This technology is highly efficient as it allows multiple users to use the same radio frequency without causing interference or congestion.
Under the DMR standard, TDMA retains the 12.5 kHz channel width and divides it into two alternating timeslots A and B (illustrated in the Diagram above) where each timeslot acts as a separate communication path. Radios 1 and 3 are talking on timeslot 1, and Radios 2 and 4 are talking on timeslot 2.
TDMA technology and 12.5kHz channel spacing provides several benefits:
Double the Call Capacity – TDMA technology doubles the number of users that can access a radio frequency. In contrast to analog systems, which can only allow one user at a time to communicate on a channel, TDMA technology can support two users per channel. This capability results in a more efficient use of radio spectrum, which is a finite resource.
Superior Voice Quality – Unlike analog systems that are susceptible to interference and background noise, TDMA provides clear and crisp audio quality, even in noisy environments.
Longer Battery Life – TDMA transmits information in short bursts, which conserves the radio’s battery power, resulting in longer battery life. For example, in a typical duty cycle of 5 percent transmit, 5 percent receive, and 90 percent idle, the transmit time accounts for a high proportion of the drain on the radio’s battery. By cutting the effective transmit time in half, two-slot TDMA can enable up to 40 percent improvement in talk time in comparison with analog radios. This feature is particularly useful in environments where a radio user may be away from a power source for an extended period, such as in remote areas or during extended shifts.
Longer Range and Coverage – TDMA 12.5 MHz channel spacing allows for better frequency reuse, which increases the coverage area of the radio system. This capability is particularly useful in large-scale operations, such as transportation, and education.
TDMA technology and 12.5 MHz channel spacing are two important technologies utilized in DMR two-way radios. These technologies provide a range of benefits that improve the performance, reliability, and efficiency of DMR radios, and has resulted in the widespread adoption of DMR radios.
DMR Audio Quality
Digital two-way radios provide excellent audio quality, which is essential for clear and effective communication. Unlike analog radios, digital radios support advanced noise-canceling features that provide clear and crisp sound that makes it easier to communicate even in noisy environments.
DMR digital technology reduces noise and preserves voice quality over a greater range than analog radios, especially at the farthest edges of the transmission range. One of the reasons that DMR has an excellent range performance is the Forward Error Correction (FEC) and Cyclic Redundancy Check (CRC) coders specified in the DMR standard. These coders enable receiving radios to detect and correct transmission errors by analyzing bits inserted into messages that allow the receiving radio to tell if there is an error.
Using coders and other techniques, digital processing can screen out noise and reconstruct signals from degraded transmissions. The result is an increase in the radio system’s effective range where users can hear everything being said more clearly over longer distances.
Transmission of Digital Data
The end-to-end digital nature of DMR enables applications such as text messaging, GPS, and telemetry to be easily added onto radio devices and systems. As the DMR standard also supports the transmission of IP data over the air, this enables the easy development of standard applications. In a world which increasingly relies on data as well as voice communication, this ability to add a wide range of data applications to your system results in the greatest possible return on your investment. In fact, one of the key drivers for users switching to digital is to add business enhancing data services and applications to radio systems. The doubling of channel capacity that DMR implementations achieve is also key to adding data applications.
Flexible Calling and Interconnect Options
The DMR standard defines a variety of call types that give users the communication flexibility to define specific types of radio calls that fit the circumstances of each specific application.
- Individual (or Private) one-to-one calls
- Group Calls from an individual to a group, or from one group to another
- All Call (Broadcast call) to everyone regardless of what Group they are in
- Conference calls that enable anyone in two groups talking together on a group call, and typically requires a dispatching application
- Emergency Calls (Including Lone Worker and Man-down Calls)
- Calls requiring GPS information
DMR also supports telephone and gateway calls. PSTN and PABX telephone systems can be connected to DMR radios using DMR repeaters. Gateway calls support connectivity with Push-to-Talk over Cellular (PoC) and analog radio systems. Radio over IP (RoIP) Gateways are inexpensive devices that connect LTE PoC radios, analog radios, and even non-DMR-compliant third-party radios to DMR radio systems.
Caller Identification
An important part of radio communications is knowing who is making a call. Whether it is an individual, a group or a dispatcher, DMR radios can display the Caller ID using the Talking Party Identification service in the DMR standard to display the identity of the radio terminal or dispatcher transmitting in an individual or group call in all other radio terminals receiving the call.
Organizing Communications with Channels, Groups, and Zones
DMR radio systems utilize radio frequencies, channels, groups, and zones to organize clear and effective communication between individuals or groups within a specific range. Understanding the differences between these terms is critical to use two-way radios effectively.
Learn more about DMR Channels, Groups, and Zones
Support for Advanced Features
DMR radios support a variety of advanced features that provide professional users with the functions that enable location tracking, radio configuration options, secure encryption, and text messaging.
DMR radios with GPS can report current location information to other radios, the dispatcher, or third-party applications in real time, enhancing the efficiency of visualized dispatch applications. GPS data can be transmitted during voice calls for immediate location targeting, and GPS data can be compressed to increase channel capacity and reduce hardware cost.
Learn more about the benefits of two-way radios with GPS
DMR radios with display screens and keypads provide clear display of calling information and device status, and enable configuration of device settings. For example, the multiple user profiles feature can be configured to set different tones, volumes, and vibration settings to match the environment, such as in a noisy outdoor environment or in a conference room meeting.
DMR radios also feature encryption for secure and private communications. Advanced 256 bit encryption is supported through the radio hardware and software with the secure and reliable ARC4 and AES encryption algorithms. Radio authentication is a feature that prevents unauthorized users from listening to calls or accessing the system.
Worker Safety Features
DMR two-way radios support several features designed for worker safety. If employees work alone, in remote areas, or in a potentially dangerous environment, these safety features can be critical in preventing injury or death.
DMR radios feature emergency buttons for generating emergency alarms or calls. The emergency button on a radio is usually a raised orange button at the top of the radio so it is easily visible and found by touch. Once the emergency button is pressed, an alarm is sent over the radio system along with the user ID of the sender, and that alarm can be a voice or text message, or a tone alarm.
Learn how two-way radios improve worker safety
Other DMR radio safety features include:
The Man Down option automatically triggers an emergency alarm if a radio is laying down flat or at a certain angle for a pre-defined period of time. This may happen if the user has fallen or is unconscious or injured.
The Lone Worker option has a timer in the radio which measures inactivity. When the pre-programmed time period is reached, a warning is issued, and if there is no response from the user, the alarm is triggered. This is designed to function as a check-in system to ensure safety for workers alone in remote areas. Radios that feature integrated GPS can send a signal that can help locate the person who has issued the alarm or who is in a man-down situation.
Priority Interrupt allows a dispatcher to clear a channel in an emergency by interrupting existing calls on a channel with important emergency information. The emergency call button can also be programmed for Priority Interrupt to clear the channel and ensure the emergency call gets across.
Remote Monitor allows dispatcher to remotely initiate the PTT button on a radio and listen in an emergency. This is useful if someone sends an emergency alarm, but the dispatcher cannot get a reply. Using Remote Monitor, the dispatcher can listen to the radio’s microphone and possibly determine details about the situation.
Stun and Revive prevents access to secure radio communications, malicious use, and unauthorized use of lost or stolen radios by centrally deactivating (stun) and reactivating (revive) radios by dispatch if required.
Scalable Growth with Repeaters and Trunking Systems
One of the key advantages of DMR radio systems is the ability to scale up repeater systems as the number of users and call capacity increases. There are several DMR radio systems available, including DMR Tier II Conventional Repeater Systems, IP Connect, XPT Pseudo Trunking, and DMR Tier III Trunking.
Reliability and Continuity
Another advantage of DMR radio systems is the uptime and reliability. When lives are on the line and effective communication can make all the difference, having a robust and dependable system is crucial. Unlike broadband cellular systems, DMR radio systems have proven to be the “last man standing” during a natural disaster, ensuring seamless communication in critical situations.
One of the key aspects that set DMR radio systems apart from cellular broadband systems is their built-in redundancy. DMR networks often employ a combination of repeaters, base stations, and redundant infrastructure to establish a comprehensive communication ecosystem. This redundancy ensures that even in the face of equipment failure or network congestion, communication channels remain operational. In contrast, cellular broadband networks, while widely available, are heavily reliant on centralized infrastructure. A single point of failure, such as a damaged cell tower or overloaded network, can cripple the entire communication system. DMR radio systems, on the other hand, offer distributed architecture, allowing for localized coverage and self-sufficiency.
During emergencies or critical events, it is essential to prioritize communication for security professionals, facility managers, and authorized personnel. DMR radio systems offer features that provide priority access and preemptive capabilities, ensuring that critical messages reach their intended recipients without delay. DMR systems can prioritize specific talk groups or individuals, guaranteeing that urgent communications take precedence over non-essential traffic.
Power outages are not uncommon during critical events or even during daily operations. DMR radio systems address this challenge by employing efficient power management techniques that extend the battery life of devices. Additionally, they often have independent power sources, such as batteries, uninterruptable power supplies, or generators, to ensure continuous operation in the event of a power failure. Cellular broadband systems, on the other hand, rely heavily on centralized power infrastructure and may experience disruptions in communication during power outages.
While cellular broadband systems have revolutionized the way we communicate, DMR radio systems continue to be the go-to choice for operations where reliability is paramount. The inherent redundancy, resiliency, priority access, and independent power sources of DMR systems make them ideal for organizations where reliable communications is critical.
Summary
The Digital Mobile Radio (DMR) standard, developed by the European Telecommunications Standards Institute (ETSI) and promoted by the DMR Association, significantly enhances professional mobile radio communications. Compared to analog systems, DMR offers improved voice clarity, extended range, longer battery life, and increased calling capacity. Compliance with the DMR standard ensures interoperability between equipment from different manufacturers, leading to greater flexibility and cost savings for users. It also enhances performance through adherence to stringent technical specifications, resulting in better voice quality, improved coverage, and reduced interference. Future-proofing is another advantage, as DMR equipment remains compatible with future technological upgrades, ensuring long-term reliability and functionality.
DMR’s digital capabilities extend beyond voice communication to support instant push-to-talk, efficient use of infrastructure, and superior audio performance over longer distances. The use of Time Division Multiple Access (TDMA) technology allows multiple users to share the same frequency, effectively doubling channel capacity. DMR radios also support data transmission, enabling applications such as text messaging, GPS, and telemetry. Advanced features like GPS tracking, encryption, emergency call functions, and worker safety options, such as Man Down and Lone Worker, make DMR a versatile and robust choice for various industries. The scalability, reliability, and continuity of DMR systems, especially in critical situations, underscore their importance in ensuring seamless and effective communication.
