Millimeter waves hitch a ride

July 15, 2015 // By Jessica Lipsky
Researchers at the University of Texas at Austin are studying millimeter wave (mmW) wireless signals could be used in cars. They believe mmW bands will provide the high data rates and accuracy needed in communication between connected cars, while also improving the resolution of radar operations.

Frequencies between 10 GHz and 30 GHz have been used in cellular research by NYU Wireless, whose director is a former UT Austin professor. While NYU Wireless studied mmW propagation in New York City, the UTA Wireless Networking and Communications team lead by Professor Robert Heath Jr. is trying to predict mmW performance.

Heath said UTA faculty and students have taken the insights from NYU Wireless and developed mathematical performance models for mmW and massive MIMO (multiple-input multiple-output), a technique for using a large number of antennas seen as key to future cellular base stations.

Millimeter waves work well when densely deployed in areas that don’t have much blockage, Heath told EE Times. Massive MIMO on a low frequency could overlay a whole city, then small areas could be lit up with mmW for additional cellular coverage.

Heath expanded upon this idea for use in connected or automated vehicles.

Partially automated car UT vision for the future of transportation. Source: University of Texas, Austin

UTA leveraged the mmW consumer WLAN standard 802.11ad to develop a vehicular communication-radar waveform for long range automotive radar (LRR) and vehicle-to-vehicle communication (V2V) at 60 GHz. Automotive radar operates at 77 GHz, making the bands close together enough to do radar on mmW.

Communication is lagging tremendously behind everything [in connected cars]. We have radars on cars, cameras, interest in IR, and yet communications is through the DSRC [dedicated short-range communications] standard or cellular. The problem is all sensors generate a huge amount of raw data. I think car companies are going to want to get access to sensor data on other vehicles….I think there’s going to be interest in streaming high data low latency data from cars.

Heath’s team of 15 researchers have modeled how mmW could serve as the framework for V2V and vehicle-to-infrastructure (V2I) communications for congestion or collision reduction. The model shows both the effects of beam width and pointing error (the ease with which a narrow beam is pointed at an incorrect location) to show how signals vary over time. The team found that directional antennas with an approximately 3 degree width support stable channels when well pointed.

Millimeter waves could be beamed from atop a light pole (above), though building communications into infrastructure poses its own challenges. Source: University of Texas, Austin
Millimeter waves could be beamed from atop a light pole (above), though building communications into infrastructure poses its own challenges. Source: University of Texas, Austin

“There are a lot of claims made that millimeter waves are not suitable for use in vehicles because they move too fast and the wavelength is too small,” Heath said, adding that higher frequencies propagate faster, making communications difficult. “If you point a very narrow beam these effects go away. The narrower it is, the longer the channel takes to change.”

Heath will present the model at IEEE’s vehicular conference this fall. He hopes the mathematical models will help inform engineers how many antennas to use at a given time.