Duplex (communications engineering)

from Wikipedia, the free encyclopedia

In communication technology, a duplex is the directional independence of a communication channel .

designation English abbreviation description Application examples
Simplex, or
directional operation
simplex SX Data can only be transmitted in one direction,
this technology does not allow an answer
Radio , pager
Half duplex, or
alternating operation
half duplex HX, sometimes
Data can
flow alternately, but not simultaneously, in both directions
Intercom , CB radio , USB up to 2.0
Full duplex, or
counter operation
full duplex DX, sometimes
Data can be
transmitted in both directions at the same time.
Intercom , POTS , GSM , USB 3.0 or higher
Dual simplex dual simplex DSX similar to full duplex, but separate transmission and reception paths PCI Express , Serial ATA

The German terms described in DIN 44302 are not in use:

  • unilateral data transmission ( one-way communication )
  • mutual data transmission ( half duplex transmission, two-way alternate communication )
  • Two-way data transmission ( both-way communication, two-way simultaneous communication )
  • Alternating operation ( half duplex transmission )
  • Counter operation ( duplex transmission )

When radio (. Eg bad radio , marine radio ) is the term intercom for duplex or simplex communication for half-duplex mode using.

If information is transferred in both directions on the same medium, the information must be merged and separated using duplex processes .

Basic principle of the duplex process

Some practical examples:

  • In analog telephony, the hybrid circuit is responsible for merging and separating the voice signals in both directions.
  • Time division duplex ( Engl. Time Division Duplex, TDD ) is z. B. used in DECT telephones. The transmission and reception channels use the same frequency, but are separated in time. The information is transmitted in short sequences with the help of a fixed timer. By digitizing the voice signal, the voice signals can be transmitted in blocks. Nevertheless, there is a continuous speech connection in both directions on the analogue level. Another example of TDD is the ping-pong method used in telephone systems , which is also referred to as U p0 .
  • Frequency division duplex ( Engl. Frequency Division Duplex, FDD ) means the information for each direction using a different carrier frequency to transmit (see. Strip position ). This can be achieved technically with a duplex switch . It enables a device to send and receive at the same time.
    Frequency duplex is used for historical, analog methods for radio telephony, e.g. B. in the A network , B network and C network typical in Germany.
    In satellite communication , a distinction is made between uplink and downlink frequencies , which can even be in different frequency bands .
    When amateur radio it is called "split traffic" when sending and receiving different than usual (but the same on different frequencies amateur radio band ) is performed (BE208) . For example, an amateur radio station that is rarely heard and called simultaneously by many others ( "pile up" (BE202) ) can indicate that it wants to listen to you in a frequency range above its own transmission frequency (BE204) . Also relay stations send to avoid feedback, not on their reception frequency, but usually at a higher. The difference is referred to as "offset" and can be standardized according to the frequency range; 600 
    kHz is usual in the 2-meter band . , P. 8 Fine-tuning the reception frequency without changing the transmission frequency is no longer necessarily frequency duplex in the sense that both can be used at the same time, but it also occurs in amateur radio. The device for this is called Receiver Incremental Tuning (RIT), Clarifier or Telegraphy Overlay . , P. 284
  • Code Duplex ( Engl. Code division duplex, CDD ) Here the information for each direction by different spreading coded and can thus be transmitted at the same time on the same frequency.

A combination of time and frequency duplex is usually used in mobile communications today. The mobile participant sends z. B. on the "uplink frequency" 890 MHz in time slot 1 and receives on the "downlink frequency" 935 MHz with a time delay on time slot 5.

Norms and standards

  • DIN 44302, February 1987 edition, information processing - data transmission, data transmission - terms

See also


  • Martin Werner: communications engineering. An introduction to all courses, 7th edition, Vieweg + Teubner Verlag, Wiesbaden 2010, ISBN 978-3-8348-0905-6 .
  • Harald Schumny: Signal transmission. Textbook of communications engineering with remote data processing, 2nd edition, Friedrich Vieweg & Sohn Verlag, Wiesbaden 1987, ISBN 978-3-528-14072-4 .
  • Martin Bossert: Introduction to communications technology. Oldenbourg, Munich 2012, ISBN 978-3-486-70880-6 .
  • Reinhold Franck: Computer networks and data communication. Springer Verlag, Berlin / Heidelberg 1986, ISBN 978-3-642-70267-9 .
  • Karl Steinbuch, Werner Rupprecht: communications engineering. An introductory presentation, 2nd edition, Springer Verlag, Berlin / Heidelberg 1973, ISBN 978-3-642-96135-9 .

Web links

Individual evidence

  1. ^ Mike Rupprecht: Frequencies of the active amateur radio satellites. October 2, 2014, accessed February 22, 2020 .
  2. a b c Examination questions in the examination sections "Operational Knowledge" and "Knowledge of Regulations" for examinations for the acquisition of amateur radio certificates of classes A and E, 1st edition. Federal Network Agency for Electricity, Gas, Telecommunications, Post and Railways , October 2006, pp. 21–22 , accessed on February 22, 2020 (each with correct answer A, see p. 5).
  3. a b Frank Sichla, Max Perner: The big amateur radio dictionary. 1st edition. Verlag für Technik und Handwerk, Baden-Baden 2001, ISBN 3-88180-372-6