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Digital Microwave Radio (DMR) communication

  Digital Microwave Radio line- It is a type of radio receiver-transmitter chain formed by Digital Microwave Radio stations.

Digital Microwave Radio communication advantages:

- the possibility of organizing a multi-channel communication and any signals, narrowband and broadband;    

- the possibility of two-way communication between subscribers;

- the ability to create 2-wire and 4-wire output channels;

- lack of atmospheric and industrial clutter;- narrowly focused radiation antenna devices;

- reduction of time communication in comparison with a wired connection.

 Digital Microwave Radio communication disadvantages:
-the need to ensure direct geometric visibility between antennas of neighboring stations;
-the necessity of using height elevated antennas;
-the use of intermediate stations to communicate over long distances, that is the reason of decrease in the reliability and quality of communication;
- the complexity of the equipment;
- the difficulty in the construction of radio relay lines in difficult terrain
  Intended use the Digital Microwave Radio communication systems fall into three categories, each of which on the territory of Russia their frequency bands:
local communication lines from 0.39 GHz to 40.5 GHz
intra line from 1.85 GHz-15.35 GHz
trunk lines from 11.7 GHz to 3.4 GHz
  Digital microwave radio equipment is usually built on the modular principle.
  In technical literature module of standard interfaces (PDH (E1, E3), SDH (STM-1), Fast Ethernet or Gigabit Ethernet etc.) commonly referred to as the indoor unit (IDU). Data streams from several standard interfaces are combined into a single frame in IDU. Next to the received frame added service channels required for management and monitoring. All that data form radio frame. Radio frame from IDU on intermediate frequency translated to outdoor unit (ODU). ODU performs encoding of radio frame, modulation and converts the total data stream with intermediate frequency at the operating microwave radio frequency.
  Structurally ODU is a sealed unit with a single interface that connected to IDU. Location of ODU in the vicinity of the antenna is usually due to the desire to reduce attenuation of high-frequency signal in various transitional waveguides or coaxial cables.
  For the especially difficult circumstances where difficult maintenance of communications facilities, apply bottom location of ODU. Operating frequency is transmitted to the antenna through the waveguide. This option allows servicing of radio equipment without egress on antenna-mast constructions.
  The most important areas in order to increase the reliability of Digital Microwave Radio line is used various methods of equipment redundancy. Usually, redundant equipment configuration designate as a sum of N+M, where N indicates the total number of barrels, M-number of reserved barrels (all the equipment in each direction connecting on one radio channel, called barrel of Digital Microwave Radio  line). After the amount added by HSB, SD, or abbreviation FD, indicating the method of reservation of DMR.
  Reservation is accomplished by actually duplication of all or part of the functional blocks of the Digital Microwave Radio system.
  Thanks to its multi-functionality, Digital Microwave Radio communication lines are able to provide access to broadband Internet and digital telephony, combine the interlocutors in videoconferencing and support electronic document circulation.
  The length of the terrestrial radio-relay communication lines can be up to 10000 km.
  In the Russian Federation for the newly introduced trunk Digital Microwave Radio lines defined transmission speed 155 Mbit/s (STM-1 flow synchronous digital hierarchy, SDH) or 140 Mbps (E4 flow of plesiochronous digital hierarchy PDH that is passed in the STM-1 signal).


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