In this paper, we investigate the optimization of non-uniform linear antennaarrays (NULAs) for millimeter wave (mmWave) line-of-sight (LoS) multiple-inputmultiple-output (MIMO) channels. Our focus is on the maximization of the systemeffective multiplexing gain (EMG), by optimizing the individual antennapositions in the transmit/receive NULAs. Here the EMG is defined as the numberof signal streams that are practically supported by the channel at a finiteSNR. We first derive analytical expressions for the asymptotic channeleigenvalues with arbitrarily deployed NULAs when, asymptotically, theend-to-end distance is sufficiently large compared to the aperture sizes of thetransmit/receive NULAs. Based on the derived expressions, we prove that, theasymptotically optimal NULA deployment that maximizes the achievable EMG shouldfollow the groupwise Fekete-point distribution. Specifically, the antennasshould be physically grouped into K separate uniform linear antenna arrays(ULAs) with the minimum feasible antenna spacing within each ULA, where K isthe target EMG to be achieved; in addition, the centers of these K ULAs followthe Fekete-point distribution. We numerically verify the asymptotic optimalityof such an NULA deployment and extend it to a groupwise projected arch type(PAT) NULA deployment, which provides a more practical option for mmWave LoSMIMO systems with realistic non-asymptotic configurations. Numerical examplesare provided to demonstrate a significant capacity gain of the optimized NULAsover traditional ULAs.
展开▼
