A terminal access control system for FLEETSAT

Lincoln Laboratory's Terminal Access Control System (TACS) provides demand assigned time division multiple access TDMA to GAPSAT or FLEETSAT 25 kHz channels. TACS is centrally controlled by a multiple access controller (MAC), nominally located at a shore station. Users of TACS who can be on shorebased or mobile platforms, enter requests for service via a Terminal Access Controller (TAC). The TAC provides error control and data buffering functions in addition to demand assignment control. The MAC automatically responds to the user request with an assignment or busy indication. TACS initially will utilize WSC-3 radios and modems, modified for 19,200 symbol per second operation and for rapid turn around time. TDMA frame formats are designed to maximize system efficiency and utility. For example, a mobile platform equipped with one half duplex WSC-3 has use of two 2.4 kbps circuits simultaneously. A platform with a full duplex radio has use of four such circuits.