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Jun 17, 2010

New sensing schemes (ICC 2010)

ICC 2010.Yesterday Spain could not have started worse the World Cup Soccer championship in South Africa. At least I had a chance to look at the ICC proceedings (from South Africa too), with better results. In a previous post I had made a list of the papers related to spectral sensing. I will leave out for now the papers related to cooperative sensing and comment only on the non-cooperative sensing schemes:

The paper Wavelet-Thresholded Multitaper Spectrum Sensing for Cognitive Radios in Unknown Noise by Jitendra Tugnait deals with spectrum sensing techniques belonging to the class of wavelet-thresholded multitaper spectrum estimators using sine tapers and relates it to the classical Welch windowed spectral estimator. The resulting detector does not need knowledge of the background noise level.

In Spectrum Sensing of OFDM Waveforms Using Embedded Pilot Subcarriers, Arash Zahedi-Ghasabeh et al. propose a new detection method for OFDM signals exploiting the available embedded pilot tones that translates into spectral correlation between the frequencies associated to the different pilots. Just looking at the signal model I realized that a certain synchronization is assumed at the cognitive receiver.

I could not find in the proceedings the papers related to "Stochastic Resonance" based spectrum sensing I had seen in the ICC program. Where did they go?

The paper Spectrum Sensing based on the Detection of Fourth-Order Cyclic Features by Julien Renard et al. proposes a fourth-order detector that performs similarly to the more complex second order detectors at SNR around 0 dB. The proposed detector is derived using the theory of higher-order cyclostationarity (HOCS). The performance is shown in the simulations section by means of a 4-QAM signal.

In Trace Based Semi-blind and Blind Spectrum Sensing Schemes for Cognitive Radio by Xi Yang et al. propose an ad-hoc detector based on the fact that the statistical covariance matrices of received signal samples and noise samples are different with high probability. The resulting detector is something like the trace of the prewhitened empirical covariance matrix.

The abstract of Cognitive Radio Wideband Spectrum Sensing Using Multitap Windowing and Power Detection with Threshold Adaptation Tsung-Han Yu et al. reads:
A common technique for cognitive radio wideband spectrum sensing is energy/power detection of primary users (PU) in frequency domain. Specifically, power spectrum estimation methods are combined with power detection statistics to test the PU presence. However, when detecting in a particular band of interest these techniques suffer from energy leakage and adjacent channel interference. In this paper, we derive a common matrix framework for the analytical performance of power detectors when FFT, windowed FFT, or multitap windowed FFT are used. Our matrix model is verified by simulations of modulated PU signals. We further propose a low-complexity compensation method to adapt the thresholds in the presence of large power difference between channels. By using both the multitap windowing and the constant false-alarm-rate method in the presence of strong signals, we demonstrate a 2-times increase in the detection rate performance as compared to existing methods. The proposed algorithm achieves similar P_FA and P_D as FFT at lower sample complexity, leading to reduced sensing times.

The paper Cyclostationarity Approach for the Recognition of Cyclically Prefixed Single Carrier Signals in Cognitive Radio by Qiyun Zhang et al. does not address the detection of primary users, but the recognition of which modulation they are employed. To this end it uses a cyclostationarity approach that does not require the recovery of carrier, waveform, and symbol timing information.

In Spectrum Sensing for DTMB System Based on PN Cross-Correlation Aolin Xu et al. disscuss spectrum sensing methods based on PN cross-correlation (PNCC) are proposed for the digital terrestrial television broadcasting standard in China (DTMB). This standard features a PN sequence both as guard interval between data blocks which gives cyclic property to DTMB signals.

Finally, the abstract of Spectrum Sensing Technique for Cognitive Radio Systems with Selection Diversity by Chang Kyung Sung et al. reads:
In this paper, we consider complementary sensing nodes to increase the spectrum sensing efficiency of cognitive radio (CR) systems. As the CR system has no prior knowledge about the operation of the licensed network, it is difficult to employ efficient diversity techniques such as the selection diversity. In this paper, by jointly designed with a medium access layer protocol, we propose a sensor node selection technique on the channel where the primary user is active. Collaborated with the mode of operation defined for CR nodes, the proposed scheme selects the dedicated sensing node for the channel with the best sensing performance. Numerical results show that the performance of the proposed scheme is almost the same as the cooperative spectrum sensing while our proposed scheme requires only one sensing node for the spectrum sensing.

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