A low complexity time domain spectrum sensing technique for OFDM

Abstract

Due to the widespread deployment of OFDM and recent advent of cognitive radio communications, robust and simple spectrum sensing techniques for OFDM signals receive significant research interest. In this paper, a time domain pilot correlation (TDPC) technique, which overcomes the complexity of FFT-based pilot sensing methods, is proposed. The TDPC technique provides an efficient and simple spectrum sensing scheme for OFDM signals using frequency domain in-band pilots. The proposed technique is based on the cyclic correlation between the complex conjugate product of adjacent OFDM signal segments and two orthogonal local references deriving from the time domain pilot sequence. Interference mitigation techniques, including periodic segmentation of the received OFDM signal, complex conjugate multiplication-based phase rotation locking, and magnitude-based correlation ratio, are adopted in this algorithm to improve the sensing performance. It is validated by simulations that the TDPC scheme achieves satisfactory sensing reliability at low SNR and is robust to both timing and frequency offsets.