B.1.1 Waveform

JTIDS operates in the L-band. It divides the spectrum into 51 channels between 969 MHz and 1209 MHz, with a channel spacing of 3 MHz. Certain portions of the spectrum are also used for identification, friend or foe (IFF), tactical air and navigation (TACAN), distance measuring equipment (DME), and Mode S, which excludes two subbands and imposes some restrictions on exactly how JTIDS can be used in noncombat situations. In particular, time-slot duty cycles for JTIDS must be restricted to no more than 20 percent under normal conditions. Exercise conditions do not have duty-cycle restrictions, and full combat conditions have no restrictions.

JTIDS uses a TDMA waveform. Every 24-hour day is divided, in the JTIDS waveform, in 112.5 epochs. Each epoch lasts 12.8 min and is subdivided into 64 frames of 12 s apiece. Each flame is further subdivided into 1536 time slots.

tional Academy Press, Washington, D.C. Information on JTIDS has been derived from two sources: (1) Welch, LCDR David, USN, “U.S. Navy Tactical Data Links,” briefing to the Tactical Network Panel of the Committee on Network-Centric Naval Forces on February 17, 1999, Command and Control Systems Directorate, Office of the Chief of Naval Operations (N62G), Washington, D.C., and (2) U.S. Army Program Executive Office Air and Missile Defense and Life Cycle Engineering Center, Missile Research Development and Engineering Center, U.S. Army Aviation and Missile Command, “Introduction to JTIDS,” Redstone Arsenal, Ala.