[[File:Joint Tactical Information Distribution System Users, 1990.jpg|thumb|320px|Joint Tactical Information Distribution System Users, 1990]]
The '''Joint Tactical Information Distribution System (JTIDS)''' is an [[L band#IEEE L band|L band]] Distributed [[Time Division Multiple Access]] (DTDMA) network radio system used by the [[United States Department of Defense]] and their allies to support [[data communication]]s needs, principally in the air and missile defense community. It produces a [[spread spectrum]] signal using [[Frequencyfrequency-shift keying]] (FSK) and [[Phasephase-shift keying]] (PSK) to spread the radiated power over a wider spectrum (range of frequencies) than normal radio transmissions. This reduces susceptibility to noise, jamming, and interception. In JTIDS Time Division Multiple Access (TDMA) (similar to [[cell phone]] technology), each time interval (e.g., 1 second) is divided into time slots (e.g. 128 per second). Together, all 1536 time slots in a 12-second interval are called a "frame". Each time slot is "bursted" (transmitted) at several different carrier frequencies sequentially. Within each slot, the phase angle of the transmission burst is varied to provide PSK. Each type of data to be transmitted is assigned a slot or block of slots (channel) to manage information exchanges among user participation groups. In traditional TDMA, the slot frequencies remain fixed from second to second (frame to frame). In JTIDS TDMA, the slot frequencies and/or slot assignments for each channel do not remain fixed from frame to frame but are varied in a [[pseudo-random]] manner. The slot assignments, frequencies, and information are all [[encrypted]] to provide computer-to-computer connectivity in support of every type of military platform to include [[U.S. Air Force|Air Force]] [[Fighterfighter aircraft|fighters]] and [[United States Navy|Navy]] [[submarine]]s.
The full development of JTIDS commenced in 1981 when a contract was placed with Singer-Kearfott (later GEC-Marconi Electronic Systems, now [[BAE Systems Electronics and Integrated Solutions|BAE Systems E&IS]]). Fielding proceeded slowly throughout the late 1980s and early 1990s with rapid expansion (following the [[9-11|9/September 11 attacks]] in 2001) in preparation for [[Operation Enduring Freedom]] (Afghanistan) and [[Operation Iraqi Freedom]]. Development is now carried out by [[Data Link Solutions LLC|Data Link Solutions]], a joint [[BAE Systems|BAE]]/[[Rockwell Collins]] company, [[ViaSat]], and the MIDS International consortium.
