Estimation of the Channel and I/Q Imbalances with Zero Correlation Zone Sequences and Superimposed Training

In this paper, the use of superimposed training (ST) and zero-correlation-zone (ZCZ) sequences is considered to estimate the joint effects of the channel response and radiofrequency (RF) impairments in the analogue-front-end (AFE) of the transmit and receiving terminals in a communications system. The RF impairments assumed are in-phase and quadrature-phase (I/Q) imbalances as well as local oscillator (LO) leakages. The analysis shows that zero mean ZCZ sequences with good periodic auto-correlation and good periodic complementary autocorrelation properties are adequate to decouple the variables of interest at the receiver. The performance of the technique is evaluated analytically and through numerical examples.