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Impropriety-Based Multiantenna Spectrum Sensing With I/Q Imbalanced Radios

Research output: Contribution to journalArticleScientificpeer-review


Original languageEnglish
Pages (from-to)8693-8706
Number of pages14
JournalIEEE Transactions on Vehicular Technology
Issue number9
Publication statusPublished - Sep 2019
Publication typeA1 Journal article-refereed


Direct conversion radios are widely recognized as the most appealing approach for reducing the hardware cost as well as power consumption in upcoming communication systems. However, such radios are known to entail gain and phase uncertainties along the analog inphase/quadrature (I/Q) paths. In this paper, we address the effects of the transmitter (TX) and receiver (RX) I/Q errors or mismatches on the improperness of the transmitted and received signals, respectively. We analytically show how the properness of a transmitted signal and the receiver thermal noise can be destroyed, respectively, under the transmitter and receiver I/Q errors, given that the corresponding ideal signals are proper under perfect I/Q balance. Then, we address the spectrum sensing problem in cognitive radio systems through modeling it as a composite binary hypothesis testing task, and apply the likelihood ratio test approach to solve it. To this end, we propose three impropriety-based multiantenna spectrum sensing algorithms under the transmitter and receiver I/Q uncertainties. The principle of invariance is exploited to examine the potential constant false alarm rate (CFAR) behavior of the proposed detectors. We analytically prove that all the proposed sensing methods possess CFAR behavior against the noise variance uncertainty, while only two of them have CFAR property against the receiver I/Q mismatch values. The achievable sensing performance of the proposed methods is then analyzed through extensive numerical experiments, and the devised alternative detectors are mutually compared. Finally, analytical solutions are derived to quantify the improvement/degradation in the effective received signal SNR under I/Q imbalanced radios.


  • antenna arrays, cognitive radio, numerical analysis, radio receivers, radio spectrum management, radio transmitters, signal detection, thermal noise, direct conversion radios, power consumption, spectrum sensing problem, cognitive radio systems, composite binary hypothesis testing task, likelihood ratio test approach, impropriety-based multiantenna spectrum sensing algorithms, noise variance uncertainty, effective received signal SNR, constant false alarm rate behavior, CFAR property behavior, received signal transmission, I-Q imbalanced radios, analog inphase-quadrature imbalanced radios, transmitter I-Q errors, receiver I-Q errors, Receivers, Uncertainty, Radio transmitters, Detectors, Task analysis, Signal to noise ratio, Spectrum sensing, improper/ proper random signals, I/Q imbalance, likelihood ratio test, CFAR property, invariance, multiantenna receivers

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