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When Bodhisatwa (Bodhi) Sadhu was starting out his undergraduate degree in Electrical and Electronics Engineering at BITS Pilani in India in 2003, students would have to wait in line 30 minutes or more to make calls home on one of the two landline phones on campus. By the time he graduated in 2007, everyone had a mobile phone; the technology behind the cell phone fascinated Bodhi, setting his career on a path toward the development of wireless technology and radio frequency integrated circuits.
Today, Bodhi is presenting a paper at the International Solid-State Circuits Conference, announcing the world’s first reported Si-based 5G mmWave phased array antenna module operating at 28GHz. The reported work, which is the result of a two-year collaboration between IBM Research and Ericsson, could help effectively build 5G access infrastructure.
Bodhi tells us what to expect in the next several years as technological advances move 5G wireless experiments from prototype to a commercial reality.
Group photo of members of the IBM Research & Ericsson teams outside the IBM T. J. Watson Research Center, NY. This group jointly developed a millimeterWave phased array module designed for 5G base station communications
Q: What is 5G and why does it matter?
A: Today, we’re on the cusp of a new generation of wireless communications called 5G. It is necessary to support soaring mobile data consumption rates driven by ever-expanding consumption of video content, as well as by the Internet of Things and its associated projected billions of connected devices. 5G is expected to support data rates that exceed 10Gbps in specific scenarios such as indoor and dense outdoor environments.
In order to support increased traffic capacity and to enable the transmission bandwidths needed to support very high data rates, 5G is expected to extend the range of frequencies used for mobile communication. This includes new spectrum below 6GHz, as well as spectrum in higher frequency bands. The millimeter wave (mmWave) frequency spectrum, which lies between the microwave spectrum and infrared spectrum, offers an entirely new source of bandwidth for cellular networks that are being made available for 5G networks. This spectrum offers dramatically wider bandwidths for data transmission than have been allocated in previous generations.
However, for 5G to leverage this new mmWave spectrum, new equipment and radio access will be required, including new base station designs that support transmission and reception at these frequencies, and ultimately new smartphones with mmWave wireless capability.
Q: What are phased arrays and why do we need them at mmWave frequencies?
A: A phased array is an array of antennas which can be used to create a narrow beam of radio
Close up of the silicon-based millimeterWave phased array antenna module mounted on a test board.
signals that can be directed toward a specific point in space exclusively through electronic control. To put it in context, most of today’s 2G/3G/4G cellular communications use base-station antennas with broad fixed beams like that of a street lamp, to communicate between the user and the base-station. As a result, there are some inefficiencies from the energy that is wasted in unwanted directions. The future 5G radio system will use advanced beamforming and beam tracking to overcome these inefficiencies. Phased array antennas will be used to create narrow ‘searchlight’ beams that will stay focused on each user even as they move.
Phased arrays can be designed at any frequency. However, the size of the antenna array depends on the frequency. While a phased array at 2G/3G/4G frequencies will be at least a few feet in size, the smaller wavelength at 28GHz allowed us to create a far more compact solution. Ultimately, we were able to engineer our 28GHz base-station phased array to be only 2.8 inches a side (about half the size of a typical smartphone).
Q: How will the average consumer benefit from the technology you’ve helped develop?
A: In a world dominated by photos and videos, there is a constant hunger for data rate. Applications such as virtual reality, 360-degree video, and high-end online gaming are all hindered by the relatively low mobile data rates of today. 5G technology, aided by phased arrays will not only deliver the data rates required for these applications, but will do so at imperceptible latencies, making these experiences truly immersive and available on-demand.
I am most excited about virtual reality because I love to be transported to different countries I have never visited before, but for the most robust VR experiences today, headsets need a thick cable to be connected to a computer. In the future, the VR experience will be truly tetherless and tactile – mmWave data links will reduce latency, making users ‘feel’ the environment they’re in much more realistically.
Moreover, due to the use of broad beams in today’s communications, each user creates electromagnetic interference for their neighbors, resulting in drastic connectivity degradation in crowded places. By virtue of using highly directed beams for 5G phased array communications, such interference will be minimized, and high data rates will be maintained even in extremely crowded environments. Imagine being at a football game where every fan in the stadium could also live stream the game to see it from different angles!
Q: What other ways could this innovation be applied?
Members of the IBM Research team inside the 5G millimeterWave antenna chamber at the IBM T. J. Watson Research Center, NY., who designed and developed the millimeterWave phased array antenna module. From left to right: Bodhisatwa Sadhu, Alberto Valdes-Garcia & Xiaoxiong Gu
A: The mmWave phased array technology we have developed can be used in the base station as well as in transportable devices for the home and the car. For example, for last-mile connectivity to the home, instead of hooking up cable or fiber to homes, the last link will become wireless. This approach has tremendous potential to bring communications and connectivity to rural areas and developing countries. I also see a big potential opportunity in automotive, particularly in providing connectivity to cars for in-car entertainment, especially in the era of self-driving vehicles. While drivers are going from point A to point B in a self-driving taxi or car, they’ll begin to treat the vehicle as an internet hub and a place to do work or watch programming. With 5G’s high data rate connections, there will be unlimited data.
Another potential use of this phased array is for mmWave radar as opposed to communications. Building off existing work in our labs, such a device could find use in automobiles to “see through” fog, rain, snow and smog, for 3D rendering of a scene, and for accurately measuring the distances of objects.
However, if the evolution of wireless is anything to go by, I believe that the most important application enabled by mmWave phased arrays is the one none of us have thought of today. Only time will tell what ingenious application we will come up with to make the world even more amazingly connected and exciting in the days to come.