Frequency Offset Tolerant Demodulation for Low Data Rate and Narrowband Wireless Sensor Node

The issue of frequency offset in low data rate, narrowband and low power communication nodes is considered in this paper. To avoid power hungry precise frequency generation, offset tolerant demodulation and detection schemes are investigated. A Short-Time DFT (ST-DFT) based detection for BFSK is introduced which improves the BER performance of an existing design by almost 1dB. Its BER performance and complexity are also compared to frequency offset tolerant DDBPSK demodulation. Additionally, the effect of wider filter required to capture signal in presence of frequency offset is considered. The trade-off between performance and complexity for different offset values and filter bandwidths is discussed. Both methods work independent of frequency offset; however, it is shown that wider filters do not affect ST-DFT BER performance in contrast with DDBPSK. This robustness is obtained at the expense of increased computational load.