This work studies a supervised learning method using 3D LiDAR data for autonomous driving applications. A system of semantic segmentation, including range image segmentation, sample generation, track-level annotation and supervised learning, is developed. The formation and content of a data sample is studied intensively to address the specialty of 3D LiDAR data, which can be represented at a Cartesian or a 2D polar coordinate system, and composed of a segment as the foreground and/or the neighborhood points as the background. A CNN-based classifier is trained to map a given sample to an object label. Qualitative and quantitative experiments show that the background information and multiple feature map fusion significantly improve the performance of the classifier.