mmWave Dynamic Channel Measurements using Phased Arrays

Dynamic channel measurements and 5G prototyping at 60 GHz are currently being conducted by Ph.D. candidate Chris Slezak under the supervision of postdoc Aditya Dhananjay. Crucial to the project are two SiBeam phased arrays and a flexible National Instruments baseband system, which were purchased with support from a National Science Foundation EAGER grant.

The National Instruments system consists of multiple powerful FlexRIO FPGA modules that generate baseband signals, as well as control signals for the arrays. These control signals set the phases on each of 12 antenna elements that are available in transmit or receive mode. Different combinations of phases across these antenna elements will result in different pointing angles for the array, effectively allowing the array to “look” in different directions without any moving parts. The arrays are capable of switching between pointing angles in just a few microseconds, allowing for channel behavior across multiple paths to be studied almost simultaneously. These results will be essential in determining how mmWave 5G systems should react when a link is suddenly lost due to rapid variations in the channel.

Initial measurements will consist of a simple blockage study with a person walking between the transmitter and receiver. All possible angular combinations will be frequently and periodically measured to find alternate paths between the transmitter and receiver. This experiment will help answer important questions such as how long to wait before scanning for new paths, how many pointing angles should be searched, and how the transmitter and receiver can cooperate during the search. Candidate algorithms to solve these problems can be proposed and tested via simulation, but real measured data is required before standards can be developed and devices built. Measurement campaigns employing mechanically steerable antennas have confirmed that mmWave will work. This system and its results are a crucial step in answering how they will work.