A key challenge in mmWave mobile systems is channel dynamics. MmWave channels are highly susceptible to blocking and thus can vary rapidly due to motion of obstacles or changes in the orientation of the handset. These dynamics have wide-ranging impact through all layers of the protocol stack. Prior work in studying blocking has been based on capturing and analyzing real-time traces of mmWave channel in blocking situations. However, these measurements were made in a single direction with a fixed horn antenna.
In this project, we develop a spatial, dynamic channel sounder using a 60 GHz mmWave phased arrays. The phased array has 12 steerable elements with 45 degree steerable beamwidth and 23 dBi gain. These phased arrays allow for very rapid switching between different pointing angles, with a settling time of approximately 1 micro-second when switching between them. A flexible baseband system implemented in LabVIEW field-programmable gate array (FPGA) is capable of performing wideband measurements with approximately 1 GHz of RF bandwidth, with absolute timing information available between the transmitter and receiver.
For the dynamic channel measurements, the channel is rapidly scanned over multiple TX-RX direction pairs. Specifically, we perform a complete 12 x 12 directional scan approximately once per 2.5 ms. The scans are then repeated during a simple human blocking events to observe how the channel varies spatially and temporally. Channel measurements are reported in a variety of indoor scenarios both on and off boresight. The effect of local scatterers is also studied.
C. Slezak, A. Dhananjay, S. Rangan