Millimeter wave (mmWave) communications is a promising technology to increase data rates to users. In mmWave communications, large antenna arrays are needed to form directional beams to overcome the high pathloss. Power consumption becomes a significant challenge. By reducing the number of RF chains and adapting the analog-to-digital converter (ADC) resolution in each RF chain, power consumption can be dramatically lowered.
mmwave channel estimation
Due to hardware constraints, millimeter wave (mmWave) channel is not directly accessible and hence estimating mmWave channel for beamforming is difficult. Further, sub-6 GHz and mmWave systems are envisioned to work together, so assuming the knowledge of sub-6 GHz channel is reasonable. Hence, it is worthwhile to investigate how the channel at sub-6 GHz and mmWave relate. This is particularly important for high mobility scenarios like vehicular communication, where frequent beam-training results in significant overhead.