SNR Improvement for Energy Detection of Narrow Band Signal in OFDM System

For orthogonal frequency division multiplexing (OFDM) based cognitive systems, the narrow band signal of the primary users (PU) is difficult to detect when it straddles the boundaries of two adjacent subcarriers. In this paper, we propose a novel energy detection (ED) method with time domain noise smoothing to improve the performance of the conventional ED of the OFDM system under the quasi-static multipath channel for detecting the narrow band primary signals. The effect of noise smoothing of the proposed ED method is analyzed. The close-form solution of probability of detection for OFDM system under quasi-static multipath channel is derived and verified by simulations. Simulations show that the proposed ED method can achieve the expected high signal-to-noise ratio (SNR) gain.