Full-Duplex Wireless Transceiver in Presence of I/Q Mismatches: Experimentation and Estimation Algorithm

In a previous work of the authors, it was shown that I/Q imbalance in the transmitter and receiver chains significantly deteriorates the achievable amount of self-interference suppression. Having there only analytically and simulatively analyzed the effect of I/Q imbalance, this paper gives experimental results and additionally extends the algorithm to also correct for the I/Q imbalance at the receiver. To avoid its degrading effect in the parameter estimation phase, the receiving chain is equipped with a tunable local oscillator (LO), allowing to receive the pilot signal at an intermediate frequency and then to digitally down-convert it. In this way, the transmitter I/Q imbalance parameters are correctly estimated. During normal operation, the LO is then set to the same frequency as the transmit chain. Experimental results show that incorporating RX I/Q imbalance increases the amount of self-interference cancellation from 45.3 dB to 53.9 dB.