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Digital Mobile Radio

Digital Mobile Radio (DMR) is an open digital radio standard for Professional Mobile Radio (PMR) users specified in the European Telecommunications Standards Institute (ETSI) Standards. Its primary goal is to specify a digital system with low complexity, low cost and interoperability across brands, acting as a direct replacement for analogue PMR. DMR provides voice, data and other supplementary services. DMR is a two-slot, Time Division Multiple Access (TDMA) system offering voice, data and a range of other features and applications.

Available for both licensed and unlicensed spectrum use, PMR applications extend from low-cost walkie-talkies aimed at the consumer market through to public safety and mission-critical systems. The PMR/DMR markets can be roughly divided into three broad categories. DMR has the capability to serve them all:

  • Consumer and short-range industrial
  • Professional / Business-Critical applications
  • Public Safety / Mission-Critical applications.

DMR is a scalable system that can be used in unlicensed mode (in a 446.1 to 446.2 MHz band), and in licensed mode, subject to national frequency planning. It is developed in three 'tiers':

  • Tier 1 is the low-cost, license-exempt 'digital PMR446'
  • Tier 2 is for the professional market offering peer-to-peer mode and repeater mode (licensed)
  • Tier 3 is for trunked operation (licensed).

Tetra Technology

TETRA offers the automatic operation and frequency efficiency of trunking, combined with the terminal autonomy of a conventional PMR. TETRA provides multi-mode capability by combining the trunking and direct (conventional) modes into a single terminal equipment, yet allowing a standardized way of interworking between the two modes. TETRA is designed to offer bandwidth-on-demand; a facility to have a variable amount of bandwidth allocated for the call duration, depending on the application.

Benefits of Tetra

TETRA is also designed for emergency situations, when almost instantaneous communication is required, both between individuals and within an unlimited size group. Priority calls can be made, backed by call pre-emption if required, and on occasions an all-informed communication.

TETRA offers fast call set-up time, group communication support, direct mode operation between radios, packet data and circuit data transfer services, f requency economy and security features. TETRA uses time division multiple access (TDMA) technology with four user channels on one radio carrier and 25kHz spacing between carriers. This makes it inherently efficient in the way that it uses the frequency spectrum. For emergency systems in Europe the frequency bands 380-383MHz and 390-393MHz have been allocated by a single harmonized digital land mobile system. Additionally, whole or appropriate parts of the bands 383-395MHz and 393-395MHz can be utilized should the bandwidth be required.
For civil systems in Europe, the frequency bands 385-389.9MHz and 395-397.9MHz, 410-420MHz and 420-430MHz, 450-460MHz and 460-470MHz, 870-876MHz and 915-921MHz have been allocated for TETRA. A TETRA trunking facility provides a pooling of all radio channels, which are then allocated on demand to individual users, in both voice and data modes. By the provision of national networks, countrywide roaming can be supported, the user being in constant seamless communications with his colleagues. TETRA supports point-to-point and point-to-multipoint communications both through the TETRA infrastructure and by use of direct mode without infrastructure.

Public Safety LTE

Long-term evolution (LTE) is a ferociously growing wireless technology that is continuously evolving to provide unprecedented data rates, higher capacity, and new levels of user experience. It is an easily deplorable network technology, offering high speeds and low latencies over long distances with data rates upto Gbps in latest releases.

Today there are two separate technology families for providing wide-area wireless communications: commercial cellular networks and dedicated public safety systems. Public safety networks provide communications for services like police, fire and ambulance. In this realm, the requirement has been to develop systems that are highly robust and can address the specific communication needs of emergency services. This has fostered public safety standards – such as TETRA and P25 – that provide for a set of features that were not previously supported in commercial cellular systems. These standards support mission critical voice communication, but are limited to narrow band data. Though initially LTE was developed for commercial purposes, its robust features and high data rates paved way for this standard to be incorporated as public safety standard also.
High speed mobile broadband can help emergency services significantly, for example with live mobile video, situation aware dispatching, remote diagnostics and deploy IoT equipped robots to rescue operations, control them manually even from remote locations. Hence Public Safety LTE is the need of the hour. The TETRA and Critical Communications Association (TCCA) has an objective of driving the development of Mobile Broadband solutions for the users of Mission Critical and Business Critical mobile communications. Having reviewed existing technologies the TCCA believes that LTE holds the greatest prospect for delivering such solutions.
SIGTECH along with its partner company CETRONICS are now working on LTE UE solution for PMR application confirming to 3GPP Release 10 with plans for upgrade to Release-13. With our profound experience and competence in the design and development of professional Mobile Radio application, Sigtech is now concentrating on the research and development of eNodB, UE solutions.

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