Design of a low-power Viterbi decoder for wireless communications

In this paper we investigate power dissipation for the Viterbi algorithm. We modified the Viterbi algorithm in a power-aware way and employed several low-power techniques to reduce its power dissipation. The first modification is re-arranging of arithmetic operations to reduce the number and complexity of computational components. Another simplification is made in the survivor memory unit by storing only one bit to identify the previous state in the survivor path, and by assigning each register to the decision vector of each clock cycle. This approach eliminates unnecessary shift operations and enables us to apply a clock-gating technique to disable all of the registers but one. The final modification stems from the property of converging all of the trace-back paths at a same state regardless of their initial state. Thus, there is no need to store a global winner path. The schemes employed in our low-power design are precomputation, clock-gating, toggle filtering, and using double edge-triggered flip-flops. The power estimation obtained through gate level simulations indicates that the proposed design reduces the power dissipation of an original Viterbi decoder design by 88%.