AI-Enabled Sub-6-GHz and mm-Wave Hybrid Communications: Considerations for Use With Future HSR Wireless Systems

Due to abundant spectrum resources, communications in the millimeter-wave (mm-wave) bands have been widely considered as the key enabler for next-generation wireless systems, including future high-speed railway (HSR) wireless systems, to dramatically increase data rates. To overcome the hostile propagation properties of mm-wave bands, antenna arrays, which enable directional transmissions with extended transmission distance, become essential techniques. Nevertheless, the high cost of antenna arrays and the limited battery lifetime of user equipment are slowing down the practical deployment of mm-wave communications. Without these limitations, an HSR scenario is better suited for mm-wave communications. However, the point-like coverage of mmwave directional beams cannot provide robust access for high-mobility scenarios.