Patent ID: 7379504

Claim:
A variable data rate Trellis Code Modulation (TCM) encoder comprising: a variable rate input that receives at least one input bit each symbol period; a Finite State Machine (FSM) receiving two FSM inputs, wherein a first FSM input of the two FSM inputs receives a first input bit of the at least one input bit, wherein a second FSM input of the two FSM inputs receives a second input bit of the at least one input bit when present and receives a zero when the second input bit of the at least one input bit is not present, wherein each symbol period the FSM produces an FSM output bit based upon the two FSM inputs, wherein: the FSM includes three storage elements and two modulo-two adders that are inter-coupled with one another; and the FSM is characterized by a parity check matrix of [D 2 , D, D 3 +D 2 +1] or the time-reversed equivalent thereof; a variable rate symbol mapper operably coupled to the variable rate input and to the FSM, wherein the variable rate symbol mapper, for each symbol period, receives the at least one input bit, the FSM output bit, and a mode selection input that selects a constellation of a plurality of supported constellations including a Quadrature Phase Shift Keying (QPSK) constellation and at least one higher order constellation; wherein at least the FSM output bit is employed to indicate a plurality of valid constellation points of a selected constellation, wherein the plurality of valid constellation points is a subset of all constellation points of the selected constellation; and wherein the variable data rate TCM encoder produces TCM codes with optimal Euclidean distance properties for the QPSK constellation and near optimal Euclidian distance properties for the at least one higher order constellation.