Adaptive threshold for energy detector based on Discrete Wavelet Packet Transform

One promising approach to achieving high precision and low complexity in a cognitive radio system is the energy detector based on the Discrete Wavelet Packet Transform (DWPT). However, the thresholds used in previous spectrum detection algorithms are fixed values determined by false alarm probability and sample points. When the Signal to Noise Ratio (SNR) is lower than 5dB, an energy detector with fixed threshold may falsely determine some unoccupied sub-channels as occupied. In this paper, a threshold adapter adopting adaptive threshold is proposed to increase the detection sensitivity, meanwhile, reduce the computational complexity. Simulation results are presented to demonstrate the effectiveness of this algorithm.