In-Phase Phase and Quadrature Timing Mismatch Estimation and Compensation in Millimeter Millimeter-Wave Communication Systems
Abstract: The emerging millimeter millimeter-wave (mm-wave) wave) MIMO systems are subject to strong radio frequency (RF) distortions and their compensation is crucial to realize such systems. In the existing literature, several estimation and compensation schemes have been proposed for RF distortions, such as carrier frequency offset, phase noise, and in-phase phase and quadrature amplitude and phase imbalance (IQI). However, in-phase phase and quadrature timing mismatch (IQTM) is largely ignored. This paper investigates the effect of the IQTM on mm-wave wave system performance and reveals that IQTM causes a specific image rejection ratio characteristic, which is substantially different from the regular frequency frequency-dependent dependent IQI and it substantially prolongs the effective channel length. If not compensated, compens the IQTM can degrade system performance significantly. As a solution to this IQTM problem, this paper proposes novel pilot designs for transmit and receive IQTM estimation, and develops corresponding estimators, transmission protocol, and compensation n schemes. MIMO averaging is also proposed, which substantially enhances the IQTM estimation performance. Simulation results show that our proposed pilot designs and estimators offer an efficient solution to the IQTM problem.