Tunable word length architecture for low power wireless OFDM demodulator

This paper proposes a low power architecture that dynamically controls a word length in a wireless OFDM demodulator. Finding the optimum word length for digital systems is a difficult problem because the trade-off between hardware cost and system performance is not conclusive. Actual digital systems prepare a more than enough word length in circuit design level to avoid the worst condition caused by lack of dynamic range. It indicates that they still have room to reduce power during better conditions. We propose tunable word length architecture (TWA) that dynamically changes its own word length according to communication environments. The proposed OFDM demodulator measures error vector magnitude (EVM) from de-modulated signals and tunes a word length to satisfy required quality of communication by monitoring the EVM performance. Our result reports that the demodulator reduced dissipated energy by the maximum 32% and 24% in AWGN and multipath fading channels, respectively, compared to use of a fixed word length