The fifth generation (5G) is expected to include new requirements, applications, and scenarios, and it will need massive and 3D multiple-input multiple output (MIMO), and increased spectrum via the use of millimeter-wave (mmWave) bands. The emerging techniques also pose new challenges to channel models. The articles in this special section examine the differences between propagation characteristics at microwave bands and at mmWave bands, summarize the current status of the 5G wireless channel modeling, and demonstrate the performance impact of channel models on system design and deployment. These considerations will enable simulation, evaluation, performance optimization, and network deployment of future 5G systems.