Collaborative autocorrelation-based spectrum Sensing of OFDM signals in cognitive radios

A simple and efficient spectrum sensing scheme for orthogonal frequency division multiplexing (OFDM) signals of primary user in cognitive radio systems is proposed in this paper. A detector exploiting the well-known autocorrelation property of cyclic prefix (CP) based OFDM signals is developed. The proposed scheme is then extended to the case of many secondary users collaborating in order to detect the primary user in the face of shadowing and fading. The amount of information each user sends to other users or fusion center is constrained by censoring scheme where only informative decision statistics are sent. Censoring allows reducing the power consumption in battery operated mobile terminals. The statistical properties of the decision statistics are established. Limits on the censoring region are found under constraints on false-alarm and transmission rates. The distribution of the test statistics for cooperative detection with censoring is approximated using characteristic functions. The performance of the scheme is studied by simulations.

[1]  H. Bohman.  Numerical inversions of characteristic functions , 1975 .

[2]  Georgios B. Giannakis,et al.  Statistical tests for presence of cyclostationarity , 1994, IEEE Trans. Signal Process..

[3]  Y. Bar-Shalom,et al.  Censoring sensors: a low-communication-rate scheme for distributed detection , 1996, IEEE Transactions on Aerospace and Electronic Systems.

[4]  Per Ola Börjesson,et al.  ML estimation of time and frequency offset in OFDM systems , 1997, IEEE Trans. Signal Process..

[5]  Pramod K. Varshney,et al.  Distributed detection with multiple sensors I. Fundamentals , 1997, Proc. IEEE.

[6]  Petre Stoica,et al.  Introduction to spectral analysis , 1997 .

[7]  V. Veeravalli,et al.  Robust and locally-optimum decentralized detection with censoring sensors , 2002, Proceedings of the Fifth International Conference on Information Fusion. FUSION 2002. (IEEE Cat.No.02EX5997).

[8]  F. Lad,et al.  Approximating the Distribution for Sums of Products of Normal Variables , 2003 .

[9]  H. Poor,et al.  Censoring for Collaborative Spectrum Sensing in Cognitive Radios , 2007, 2007 Conference Record of the Forty-First Asilomar Conference on Signals, Systems and Computers.

[10]  H. Vincent Poor,et al.  Spectrum Sensing in Cognitive Radios Based on Multiple Cyclic Frequencies , 2007, 2007 2nd International Conference on Cognitive Radio Oriented Wireless Networks and Communications.