As mobile wireless communications progress, the Federal Communications Commission (FCC) is exploring technologies that could lead to the emergence of a new generation of millimeter wave (mmWave) wireless spectrum by the year 2020. Before mmWave carrier frequencies can be applied to cellular networks, spectrum allocations and regulatory frameworks must be determined.
As a leader in wireless, with some of the most publicized field studies on mmWave mobile services, WNCG Prof. Robert Heath and his graduate student assistants prepared a public comment in response to the FCC Notice of Inquiry on frequencies above 24 GHz for mobile applications.
“Our comment sheds light on challenges facing mmWave communications and provides optimism that such challenges can be solved,” Prof. Heath states.
The WNCG research team believes further research and development of mmWave cellular is essential to demonstrate the viability of this technology for 5G systems.
“We believe that mmWave spectrum is vital to the continued expansion and innovation within the wireless industry,” Prof. Heath mentions.
Prof. Heath’s official comment, which draws on his extensive mmWave research, focuses on current design and research challenges that must be overcome before 5G can become standardized reality. Important issues facing the adoption of mmWave communication include blockages, system coverage, sensitivity to interference and antenna arrays.
Blockages and Sensitivity to Interference
Blockages affect the ability of signals to transmit on a mmWave system. Buildings and human bodies both block signals differently. Since bodies move, base stations and signal transmissions must be able to adapt if someone steps in the way of a mid-signal transmission. In other words, signals must be able to steer around a blockage to create a direct connection with the receiver.
According to Prof. Heath’s research group, signal transmission techniques need to be designed to work around these blockages.
“At WNCG, we have made progress on understanding the impact of blockages on system performance. We believe the impact of blockage can be overcome through careful system design,” Prof. Heath states.
Coverage and Capacity in mmWave Systems
One of Prof. Heath’s current research directions focuses on finding ways mmWave can provide adequate coverage and rates to users across the system.
“It is critical to use large antenna arrays at both the transmitter and the receiver,” Prof. Heath states. “This array gain ensures sufficient link margins and provides spatial multiplexing gains for higher spectral efficiency.”
WNCG researchers are developing hybrid beamforming transmission strategies to adaptively configure arrays at the transmitter and receiver. They are also developing ways for propagation channel estimation, which can aid the beamforming process.
According to Prof. Heath, density will also be critical in mmWave systems. Cell coverage must be dense for mmWave to work properly and efficiently in urban areas.
The benefits of mmWave outweigh these current design challenges and WNCG has already made great strides in pushing mmWave design forward. WNCG developed analyses of mmWave cellular systems that depend on both the antenna geometry and the density of blockages. The research team discovered that systems can either be interference or noise limited depending on the antenna and deployment parameters.
New Spectrum Models
Given the highly directional nature of each beam that transmits signals and communications, mmWave allows spectrum to be shared with other users and base stations of different networks.
“This would reduce competition for each band of frequency and allow multiple operators to share the entire spectral band in a fair way,” Prof. Heath states.
Prof. Heath and his colleague, WNCG Prof. Jeff Andrews are actively developing models and analysis of new models for spectrum sharing.
Going Forward
The battle over spectrum leads to heated discussions throughout academia, industry and government institutions. With several faculty and students working on key research challenges at mmWave and other carrier frequencies, WNCG is well-equipped to meet challenges facing 5G cellular systems. This year’s Texas Wireless Summit, The View to 5G, which will take place on October 16, 2015 at UT Austin, will focus on research challenges and solutions facing the future of 5G.