Radio base station and method for limiting the upward tilt of beamformed signals

摘要

Embodiments herein relate to a method in a radio base station (12) for transmitting a data signal to a user equipment (10) in a radio communications network. The radio base station (12) is connected to an active antenna array of a number of active transmitting antennas and the radio base station (12) serves the user equipment (10) in the radio communications network. Each active transmitting antenna comprises sub elements. The radio base station (12) transforms a precoded data signal using a transformation, which transformation directs signals vertically. Furthermore, the radio base station (12) transmits the transformed data signal over at least one sub element to the user equipment (10). The transmitted data signal is enabled to be directed vertically, and the transformed data signal is limited to be transmitted in a direction within a range of elevation angles.

主权项

1. A method in a radio base station for transmitting a data signal to a user equipment in a radio communications network, wherein the radio base station is connected to an active antenna array of a number of active transmitting antennas and the radio base station serves the user equipment in the radio communications network, and wherein each active transmitting antenna comprises sub elements, and the method comprises:
precoding a data signal to obtain a precoded data signal, said precoding performed with a precoder from a precoder codebook for azimuth beamforming; transforming the precoded data signal to obtain a transformed data signal using a transformation that imparts elevation beamforming, said elevation beamforming restricting elevation beamforming angles such that the transformed data signal is directed no higher than a top elevation angle defined below a horizontal center axis extending from the sub elements; and transmitting the transformed data signal from the sub elements mapped by the transformation.