  Multi-antenna techniques capable of exploiting the elevation dimension are
anticipated to be an important air-interface enhancement targeted to handle the
expected growth in mobile traffic. In order to enable the development and
evaluation of such multi-antenna techniques, the 3rd generation partnership
project (3GPP) has recently developed a 3-dimensional (3D) channel model. The
existing 2-dimensional (2D) channel models do not capture the elevation channel
characteristics lending them insufficient for such studies. This article
describes the main components of the newly developed 3D channel model and the
motivations behind introducing them. One key aspect is the ability to model
channels for users located on different floors of a building (at different
heights). This is achieved by capturing a user height dependency in modelling
some channel characteristics including pathloss, line-of-sight (LOS)
probability, etc. In general this 3D channel model follows the framework of
WINNERII/WINNER+ while also extending the applicability and the accuracy of the
model by introducing some height and distance dependent elevation related
parameters.
