Blind Compensation of Frequency-Dependent IQ Imbalance for Various Modulation Schemes in Cognitive Radios

Abstract

Cognitive radios adaptively sense and use available spectrum but suffer performance loss due to IQ imbalance, which causes interference from gain and phase mismatches in transceivers. Blind IQ-imbalance compensation avoids pilots and suits cognitive radios that must continually adjust to changing channels. While OFDM and SC-FDE have known blind-compensation methods, CE-OFDM has not been studied, and immunity to frequency-dependent imbalance remains unreported. This paper presents the first unified comparison of OFDM, CE-OFDM, and SC-FDE under frequency-dependent IQ imbalance, enabled by adapting an SC-FDE blind-compensation technique.