A Cepstrum-Based Spectrum Sensing Approach for Detecting Spread Spectrum Signals

In this manuscript, we introduce a semi-blind spectrum sensing technique based on cepstral analysis for interweave cognitive systems. The misdetection problem of spread spectrum signals leads to erroneous sensing results, which affect the quality-of-service of a legitimate user. The simplicity and accuracy of cepstral analysis approaches make them reliable for signals detection. Therefore, we formulate the averaged autocepstrum detection technique that utilizes the strength of the autocepstral features of spread spectrum signals. The proposed technique is compared with the energy detection and eigenvalue-based detection techniques and shows reliability and efficacy in terms of detection accuracy.

Detection and Direction-of-Arrival Estimation of Weak Spread Spectrum Signals Received with Antenna Array

This paper presents a method for the joint detection and direction of arrival (DOA) estimation of low probability of detection (LPD) signals. The proposed approach is based on using the antenna array to receive spread-spectrum signals hidden below the noise floor. Array processing exploits the spatial correlation between phase-delayed copies of the signal and allows us to evaluate the parameter used to make the decision about the presence of LPD transmission. The DOA estimation is based on the covariance between signals received by sensors for the fixed geometry of the antenna array. Moreover, the paper provides a method for mitigating narrowband interferences prior to signal detection. The presented methods were verified through simulations which proved that the confident detection of a one-second transmission in an additive white Gaussian noise channel is possible even when the noise is 24 dB higher than the power of the received signal. The performance of DOA estimation is analyzed in a wide range of signal-to-noise and interference-to-noise ratios. It is found that the DOA may be estimated with an RMS error not exceeding 10 degrees, even if interference occupies 15% of the analyzed frequency band.

Theoretical study of methods of finding signals and synchronization of the earth stations of satellite communications

When using spread-spectrum signals, the problem of searching by frequency and delay must be solved before the signal is processed. For demodulation of simple signals with AM, CHM and FM, it is fundamentally necessary to provide only a frequency search, and clock synchronization can be carried out after the first decision circuit, i.e. in the signal conversion equipment, usually placed in the interface equipment or channel-forming equipment. The paper presents a theoretical analysis of the methods of the search of signals and synchronization in earth stations - search and tracking of singaporemetro signals with an expanded range and features auto scan and auto-tracking frequency when receiving simple signals.