Beamforming OFDM Performance under Joint Phase Noise and I/Q Imbalance

Abstract

Phase noise (PHN) and in-phase/quadrature (I/Q) imbalance are two major RF impairments in direct-conversion wireless transceivers. Beamforming and orthogonal frequency division multiplexing (OFDM) schemes have been adopted in broadband wireless standards due to their significant performance gains. In this paper, we analyze the impact of joint I/Q imbalance and PHN on beamforming OFDM direct-conversion transceivers. We derive an exact normalized mean squared error (NMSE) expression and examine several special and asymptotic cases to gain insights. One such insight is that asymptotically, for both large SNR and the beamforming array size, the PHN and I/Q imbalance effects become decoupled.