A low power OFDM receiver monitoring subcarrier SNRs in time-varying fading channels

In wireless communication, received signal amplitude varies with time under multipath fading environments. A receiver must cope with the worst case that signals are heavily attenuated for reliable communication, which requests a large wordlength in digital circuits. However, a receiver has good chances to use a small wordlength in most cases that signals are not attenuated much. We study a variable wordlength method that an OFDM receiver switches between small and large wordlengths by monitoring subcarrier SNRs. The proposed method reduces power consumption and preserves higher communication quality over the conventional method. In the evaluation, the proposed method has reduced power consumption by up to 30% with keeping almost the same packet error rates in the fixed wordlength.