Per-Antenna Power Distribution of a Zero-Forcing Beamformed ULA in Pure LOS MU-MIMO

Navid Amani, Andres Alayon Glazunov, Marianna V. Ivashina, Rob Maaskant
2018 IEEE Communications Letters  
An analytical model is presented to determine the perantenna power distribution of a beamformed M -element uniform linear array (ULA) as a base station antenna (BSA). The analysis assumes a single sector cell serving two user equipments (UEs) in a downlink multiuser multiple-input multiple-output (MU-MIMO) system employing zeroforcing (ZF) transmission. Determinative design parameters of the BSA configuration are identified. Afterwards, their effects on the power spread across the array are
more » ... stigated when the positions of the users are random and they are uniformly distributed over the cell. It is shown that the power distribution across the ULA antenna aperture is a periodic function whose characteristics mainly depend on the angular separation of two UEs and the number of BSA antenna elements. A significant variation between ULA input powers is seen to occur if the number of elements in the ULA is smaller than one period of this power distribution function. In order to mitigate the dynamic range of the power variation across the array, an upper bound for the inter-element spacing, depending on the field-of-view (FoV) of the BSA, is defined. It is shown that, in a 20-element ULA, increasing the inter-element spacing from 0.5λ to 1.4λ reduces the power variation from 19 dB to 10 dB for differentiating two close-by UEs with 1 • angular separation. Index Terms-5G, base station antenna, beamforming, massive MIMO, uniform linear array, zero-forcing. N. Amani, M. V. Ivashina and R. Maaskant are with the
doi:10.1109/lcomm.2018.2871828 fatcat:hzlsywlnajcifjxp4krie4xe4u