Variable code rate and signal constellation turbo trellis coded modulation (TTCM) codec. The decoding can be performed on signals whose various symbols have been mapped to multiple modulations (constellations and mappings) according to a rate control sequence. The rate control sequence may include a number of rate controls arranged in a period that is repeated during encoding to generate the signal that is subsequently decoded. Either one or both of an encoder that generates the signal and a decoder that decodes the signal may adaptively select a new rate control sequence based on operating conditions of the communication system, such as a change in signal to noise ratio (SNR).