The authors present a low power and area efficient turbo soft-input soft-output (SISO) decoder based on two-step soft-output Viterbi algorithm (SOVA) targeting wireless mobile communication systems. Our turbo SISO decoder is based on trace back algorithm (TBA) and saves area and power by replacing the FIFO memory with an additional transition metric unit (TMU). The paper presents the implementation of SOVA decoder for constraint lengths K=3, 4, and 5, describing the design methodology and evaluation environment. Simulation results are provided showing up to 20% power saving and 46% area saving compared to a conventional SOVA decoder implementation.