Self-Organized Time Division Multiple Access

Self-Organized Time Division Multiple Access (STDMA) is a channel access method which was designed by Håkan Lans,[1] based on time-division multiplexing.

The term "Self-Organized" describes the manner in which time slots are assigned to users. Time division multiple access (TDMA) divides a channel into frames, which furthermore are subdivided into a vast number of time slots. Users transmit in rapid succession, one after the other, each using his own time slot. One of the drawbacks of TDMA is that it requires a central station for slot assignment and time synchronisation. STDMA proposes a method for assigning slots without the involvement of a central station. Time synchronisation is usually taken care of using Coordinated Universal Time (UTC).

STDMA is in use by the Automatic Identification System (AIS), a standard marine short range coastal tracking system, and is the base of the International Civil Aviation Organization VHF Data Link Mode 4 .

While the method was patented,[1] a US patent ex-parte reexamination certificate was issued in 2010 canceling all claims.[2]


  1. 1 2 US patent 5506587, Lans, Håkan, "Position indicating system", issued 1996-04-09, assigned to GP&C Systems International AB
  2. USPTO ex-parte reexamination certificate (7428th), issued on March 30, 2010

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