An error bound for reduced-state Viterbi decoding of TCM codes

An upper bound is given on the error event rate of reduced-state Viterbi decoding of trellis-coded modulation (TCM) codes. Such reduced-state decoding could form the heart of an adaptive-complexity approach that saves substantially on required decoding power consumption, an important consideration in handheld portable communications. The bound is based on a difference-state formulation utilizing the uniform error properties of the codes. It fully includes the effect of finite decoding depth L, and is efficiently computed with a single forward pass through the encoder trellis.