NSF funds exploration of millimeter wave impact on 5G cellular systems

Posted: February 20, 2017

Emre Koksal, assistant professor of electrical and computer engineering, and doctoral student Amr Abdelaziz discuss the mobile millimeter wave communication research in the Wireless Communications Laboratory.
By opening up new realms of research into the high frequency electromagnetic spectrum, The Ohio State University is solving problems standing in the way of next generation cellular systems.

Global mobile data traffic is expected to grow sevenfold from 2016 to 2021, reaching 49 exabytes per month—the equivalent of 12,238 million DVDs—according to new Cisco projections.

In order to support this deluge of mobile traffic, Ohio State researchers hope to incorporate portions of the millimeter wave (mmWave) band into 5G cellular systems, thus significantly increasing the spectrum available to cellular providers. Before mmWave communication can be implemented, however, significant challenges must be addressed, such as intermittent connectivity, high delay and high energy requirements.

A team led by Electrical and Computer Engineering Associate Professor C. Emre Koksal, received a three-year, $302,000 grant from the National Science Foundation to tackle these challenges and make mobile mmWave communication a reality. Project co-investigators are Kubilay Sertel, assistant professor of electrical and computer engineering, and Ness Shroff, Ohio Eminent Scholar of electrical and computer engineering, and computer science and engineering.

The Buckeye engineers propose a hybrid architecture and algorithms that combine both radio frequency (RF) and mmWave technologies for 5G cellular systems. The approach could significantly alleviate the current spectrum crunch experienced by cellular providers, which are currently confined to the frequency spectrum between 700MHz and 2.6GHz, with only 780MHz of bandwidth allocated for all current cellular technologies.

With its increased capacity to deliver more data more quickly, mmWave shows significant promise in handling exploding rates of mobile traffic.

“Due to the high bandwidth availability, the rates that we can transmit over those bands are quite high,” he said. “Data rates of a few gigabytes per second could be achievable for mobile mmWave communication if we do it right.”

The problem, Koksal added, is that unlike the radio frequencies currently used for mobile communication, mmWave has high transmission losses due to atmospheric absorption and low penetration. While using large antenna arrays can potentially make up for this loss, they also consume a lot of energy. But the team’s combined approach shows promise in overcoming these issues.

“Whenever the mmWave channel is available, you have this huge bandwidth and this very high-rate channel, which the RF interface helps you exploit in a timely fashion,” Koksal explained. “Whenever the mmWave channel is more fragile, which we can detect by the help of RF, we switch the data to the RF interface and we suppress the high variability of the mmWave channel. Also we achieve a much lower energy communication overall.”

Preliminary results of the research are already challenging existing assumptions.

“Unlike common belief, there are high correlations between mmWave and radio frequency channels, specifically in line-of-sight situations,” Koksal said. “Exploiting this, we can get an order of magnitude gain in performance over existing mobile mmWave communication proposals.”

The project will also develop a novel framework using small-scale models that enables accurate mobile measurements jointly at the RF and mmWave interfaces without building real-world systems.

Despite the challenges, Koksal expects mobile mmWave technology to be integrated into smart devices in the not-so-distant future.

“We will probably see the first examples of mobile mmWave in smart mobile devices, like the next-generation of smartphones, in three to five years,” he said.

by Candi Clevenger, College of Engineering Communications, clevenger.87@osu.edu