Although analog technology offers some great benefits such as low total cost of ownership, customizable coverage, features and simple / reliable implementation, it has reached its peak. Some limitations include are battery life, voice quality (near the edge,) low productivity in communication and integrated data applications. In addition, analog radio users are facing spectrum shortages resulting in overcrowding and interference.
Over the years, LMR systems have used wideband 25 kHz channel spacing. The current spectrum efficiency cannot meet the new mandate. In December 2004, the Federal Communications Commission mandated that all private LMR users operating below 512 MHz move to 12.5 kHz narrowband voice channels and high efficient data channel operations by January 1, 2013. If you are operating a wideband (25 kHz) system in the VHF or UHF land mobile band, you may continue to do so until the deadline January 1, 2013. All radio users should start to plan and prepare for the narrowband migration now. Furthermore, on January 1, 2011, licensees will be permitted to apply for new systems or to expand their existing systems only if they will be utilizing 12.5 kHz bandwidth (or less) equipment or equipment that satisfies the new 6.25 Khz standard. Users will need to take this deadline into consideration if you are planning to implement a new system or to make modifications to your existing system.
Digital Mobile Radio (DMR) is a digital radio standard specified for professional mobile radio (PMR) users developed by the European Telecommunications Standards Institute (ESTI), and first ratified in 2005. The DMR protocol covers unlicensed (Tier I), licensed conventional (Tier II) and licensed trunked (Tier III) modes of operation, although commercial applications today are focused on the Tier II and III licensed categories.
The standard is designed to operate within the existing 12.5 kHz channel spacing used in licensed land mobile frequency bands globally and to meet future regulatory requirements for 6.25 kHz channel spacing. The primary goal is to manufacture affordable digital systems that are easy to operate. DMR provides voice, data, and other auxiliary services. Today, products designed to DMR specifications are sold in all regions of the world.
DMR technology helps alleviate analog issues by providing increased capacity and spectral efficiency resulting in clear, unbroken, reliable communications. End user benefits include improved productivity, low cost savings and increased customer satisfaction.
About The DMR Association
The DMR Association was first set up in 2005 as the DMR-MOU Association by a group of leading public mobile radio manufacturers to support ETSI during the DMR standardization process. The DMR Association is open to any organization or individual interested in using or building DMR products or in supporting the DMR standard in other ways. The Association maintains links with regulators, trade bodies and standards organizations around the world.
The companies below are members of the DMR Association. But, only Hytera and Motorola own the DMR terminal products so far.
Distinguished Aspects of DMR Standard
Although DMR, TETRA, P25, and MPT-1327 are all based on open standards, they are also based on different protocols and targeted at different markets (e.g., TETRA and P25 are largely used by public safety organizations) and are not technically compatible. Another standard created by ETSI, dPMR, is considered a competitor to DMR in the business market, but as of today, products built to the standard are targeted at the low power, unlicensed part of the specification, best suited for personal use, recreation, small retail and other settings that do not require wide area coverage or advanced features.
The coverage area of a TETRA base station is approximately between half and one third compared to that of an analog or DMR radio system, therefore TETRA needs a lot of more sites. A medium size TETRA system may costs 3 to 5 times more than a DMR one. The features of these systems are near the same (digital encryption, positioning, messaging) than the DMR, however developing rapidly for the commercial applications.
TETRA is a trunking system targeted to point-to-point communication in a multi cell and high traffic environments. Like a telephone network, hundreds of users in a little area require a lot of radio cells to deliver the communications. DMR is a dedicated channel or trunking system targeted to provide robust coverage rather than capacity.
The Market Tiers of DMR
The PMR market can be divided into three tiers: commercial, public safety and mission critical. Different products and standards address different tiers. DMR crosses all three tiers such as Public safety, Private security, Government, Education Campuses, Hospitality, Manufacturing and construction, Utilities, Transport, and Oil/Gas.
The Advantages of DMR Technology
Superior audio performance
DMR Digital technology provides better noise rejection and preserves voice quality over a greater range than analog, especially at the farthest edges of the transmission range based on the combined efforts of narrowband codec and digital error-correction technology. The digital processing is able to screen out noise and re-construct signals from degraded transmissions. Users can hear everything being said much more clearly, thus increasing the effective range of the radio and keeping users responsive to dynamic situations in the field.
Doubling capacity in your existing 12.5 kHz licensed channels
One of the main benefits of DMR is that it enables a single 12.5 kHz channel to support two simultaneous and independent calls.
How this is achieved?
Under the DMR standard, Time Division Multiple Access (TDMA) retains the 12.5 kHz channel spacing and divides it into two alternating time slots. Each time slot acts as a separate communication channel with an equivalent bandwidth of 6.25 kHz, but the channel as a whole, maintains the same profile as an analog 12.5 kHz signal.
This means that DMR will fit into your existing licensed PMR bands so there is no need for re-banding or re-licensing simultaneously doubling the capacity of your 12.5 kHz channel.
While the voice channel is utilizing the first time slot, the second time slot, in a TDMA system, is used for transmitting application data such as text messaging or location data in parallel with call activity. This is useful in dispatch systems that provide both verbal and visual dispatch instructions. In an increasingly data rich world, this enhanced data capability will become important. The future roadmap for two slot TDMA applications will include the ability to temporarily combine both slots to effectively double the data rate, or to use both slots together to enable full-duplex private calls. FDMA solutions can not deliver these capabilities on a single channel.
Efficient usage of DMR infrastructure equipment
The main advantage of the DMR TDMA approach is that you get two channels with one repeater, one antenna, and a simple duplexer. Compared to FDMA solutions, two slot TDMA allows you to achieve 6.25 kHz equivalent efficiency while minimizing investments in repeaters and combining equipment. The required equipment of the two approaches for a simple system is shown below.
FDMA requires a dedicated repeater for each channel, plus expensive combining equipment to enable multiple frequencies to share a single base station antenna. It can be very expensive to make combining equipment work with 6.25 kHz signals. The end result is a typical loss in signal quality and range when configured as such.
Two slot TDMA achieves stable two channel equivalency using single channel equipment. No extra repeaters or combining equipment are required (and there is lower drain on air conditioning and less back up power supplies needed). End result, lower cost and simpler site planning for DMR users.
Longer battery life and greater power efficiency
One of the biggest challenges with mobile devices has always been battery life. In the past, there have been limited options for increasing the talk time on a single battery charge.
Since each call uses only one of the two time slots, it requires only half of the transmitter’s capacity. 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. With overall battery consumption per call dramatically reduced, longer usage time in the field between recharges is achieved. Modern digital devices also include sleep and power management technologies that increase battery life even further.
These power efficient features give DMR users a leaner and greener radio network as well as the benefit of long battery life on the radios themselves.
Ease of use in data applications
The end-to-end digital nature of DMR enables applications such as text messaging, GPS, and telemetry to be easily added into radio devices and systems.
As the DMR standard, it also supports the transmission of IP data over the air, which 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.
Compatible with current FM analog system and support to migrate to DMR system
DMR can operate in either analog or digital mode. DMR allows migration to take place one radio at a time, one channel at a time or the entire system at a time
Since DMR is a fully public open standard backed by a wide variety of vendors, buyers can be assured of continuity of supply. Today DMR is the most widely adopted digital two-way radio system, is active in over 100 countries, and is the market leading digital PMR technology.
DMR is the best established digital technology in the market today and is the clear choice for organizations looking to deploy new digital two-way radio systems, or to upgrade their existing analog radio to digital.
Tags: digital mode, Distinguished Aspects, DMR, Education Campuses, ESTI, ETSI, European Telecommunications Standards Institute, FDMA, Federal Communications Commission, FM, GPS, GSM, interference, LMR, Market Tiers, MOU, MPT, Oil Gas, PMR, radio, results, TDMA, TETRA, Time Division Multiple Access, VHF