Optimal Threshold of Welch's Periodogram for Sensing OFDM Signals at Low SNR Levels

Spectrum sensing is one of the key technologies to realize dynamic spectrum access in cognitive radio systems, especially being able to reliably detect primary user signal in low signal-to-noise ratio (SNR) levels. In this paper, a new optimal threshold setting algorithm based on the conventional Welch's energy detection algorithm is proposed to achieve an efficient trade-off between the detection probability and false alarm probability for OFDM signals at the low SNR levels. The proposed optimal threshold algorithm in the Welch's method demonstrates a better spectrum sensing performance at the low SNR levels. The relationship between the spectrum utilization and optimal threshold is derived. The effect of spectrum utilization on the performance of spectrum sensing is also analyzed.