Using OFDM pilot tone information to detect active 4G LTE transmissions

The paper studies the use of pilot tone information for detecting active transmissions from Long Term Evolution (LTE) wireless systems. LTE employs Orthogonal Frequency Division Multiplexing (OFDM) at the physical layer and, according to the LTE standard specifications, the transmitted signals contain periodic pilot information placed on specific subcarriers to be used for synchronization and channel estimation. The pilot tone information can also be used for detecting the presence of active LTE signals by using a cross-correlation approach. The method presented in the paper uses the Time-Domain Symbol Cross-correlation (TDSC) technique and takes advantage of the fact that the mean of the cumulative correlation of distinct symbols with the same pilot tone positions is constant while its variance changes, allowing it to be used for detecting LTE transmissions in environments with low signal-to-noise ratios (SNRs). Application of the TDSC method for LTE systems is presented analytically and is illustrated with numerical results obtained from simulations that include additive white Gaussian noise (AWGN) as well as Rice and Rayleigh channel models outlined in the LTE standard.