The FCC held a Spectrum Frontiers and 5G Workshop last Thursday that Julius Knapp, Chief of the Office of Engineering & Technology, called a “landmark day” in wireless history. He likened the event to a similar conference thirty years ago when the industry was transitioning from analog to digital technologies, now referred to as the 1G to 2G transition.
“We didn’t even have a name for it then,” Knapp said.
These days, we have a name for the thing – 5G – but we may have even less of an understanding about what this thing is and what it is supposed to do. Through panel discussions and five vendor demonstrations, the FCC’s workshop offered some answers to these questions and, at a minimum, helped debunk the common misconception that 5G is narrowly focused on enhancing wireless data rates. Although many of the details of 5G remain murky, it is clear that 5G is being designed to support a very broad variety of applications and use cases, including novel uses not yet imagined.
FCC Chairman Tom Wheeler started the FCC’s 5G event by saying that “5G is a national priority.” He said that 5G is an “issue of national leadership to ensure that consumers and enterprises benefit from the next generation of wireless connectivity.” Wheeler added that he views 5G as an opportunity for the US economy to grow, but only if the US leads the worldwide roll out of 5G. The way he envisions the US to lead is by not waiting for standards to emerge, but rather to develop in parallel sound spectrum policy and flexible regulations that allow open innovation. As Wheeler said, “It all starts with spectrum – the ‘Mother’s Milk’ of connectivity in the 21st century.”
Novel Uses of Millimeter Wave Spectrum
The spectrum to which the Chairman referred is called millimeter wave spectrum. This spectrum comprises much higher frequencies than is typically used for mobile wireless communications. Currently most bands used for mobile wireless communications are between roughly 0.5 GHz and 2.5 GHz, but millimeter wave bands are in the range of 24 GHz, 28 GHz, 37 GHz, 60 GHz and higher. Until recently, these high-frequency millimeter wave bands were not viewed as suitable for mobile communications because poor propagation characteristics limit them to short range and typically require line-of-sight between the transmitter and receiver. Therefore, these bands were not viewed as being able to communicate reliably with moving objects. This perceived limitation was unfortunate because the amount of bandwidth available at higher frequencies is enormous. Much more contiguous spectrum is available at these high frequencies than in traditional mobile bands, and very high bandwidth supports very high data rates. For example, most of the 5G demos at the FCC workshop generated multi-gigabit per second data rates using a single millimeter wave channel whose bandwidth represented more spectrum than the sum of all bands available for mobile broadband today.
But as the keynote speaker, Dr. Ted Rappaport, explained, the propagation problems of millimeter wave frequencies can be solved with better antenna technology. Because the frequencies are so high, the wavelengths are small (thus “millimeter” wave) and antenna size is proportional to wavelength. So antennas at these frequencies are, like the wavelengths themselves, very small, which allows engineers to “stack” multiple antenna elements into a single package that sums to about the same size as the current, lower frequency antennas. This use of multiple elements increases the antenna’s gain which helps negate some of losses due to poor propagation characteristics of the spectrum. But high gain also means high directionality, so the antenna must be pointing toward the target for the gain to be realized. Highly directional antennas were historically viewed as incompatible with mobility because the antenna must be pointed in just the right direction to maintain a reliable connection. But “beamforming” technology can solve this problem. Beamforming utilizes complex signal processing that allows the base station antenna to “track” the mobile devices within a cell’s coverage area. This and other advances in antenna and signal processing technology have unleashed the massive bandwidth available at millimeter wave frequencies that will help fuel the next generation of mobile connectivity.
The 5G Triangle
But an excessive focus on the truly revolutionary technologies that have allowed engineers to harness the power of millimeter waves implies that 5G is solely limited to very high data rates enabled by high frequency spectrum. This focus also implies that 5G and the use of millimeter waves for mobile broadband are synonymous. But there is much more to 5G than just high data rates.
Two standards bodies – the ITU and 3GPP – recommend thinking about 5G as a triangle in which each of the three corners represents a primary and distinct set of properties. Many of the use cases that we can imagine today are dominated by the primary properties of one of the three corners, while others will draw from the properties of more than one corner.
- High Data Rate: The first corner of the 5G triangle is the one that receives the most attention – enhanced mobile broadband that will enable very high data rate communications.
- Low Latency, High Reliability: The second corner of the triangle is low-latency, ultra-reliable communications. Applications for public safety, eHealth, self-driving cars, and the “tactile” internet will require low-latency and high reliability more than they will need high data rates. But other applications will require a combination of high data rate and low-latency, such as augmented reality and certain cloud applications.
- Internet of Things: The third corner of the 5G triangle involves massive machine-to-machine communications, also known commonly as the Internet of Things (“IoT”), where ubiquitous connectivity to an extremely large number of devices is more important than either data rate or latency. For example, a smart-city application to improve the efficiency of garbage collection may require a very large number of connected devices (e.g., a sensor on every dumpster), but will depend far less on high data rates or low-latency to receive the relatively small amount of data that each sensor will occasionally transmit. But other IoT applications may also require high bandwidth connectivity, and therefore will require the properties of both the first and third corners of the triangle. Finally, certain mission critical IoT applications may require the properties of both the second and third corners of the triangle.
These three corners of the 5G triangle both complement and compete with each other. For example, the optimal solution for each use case may have very different technical requirements for the physical waveform as well as for the ideal frequency band in which to deploy the service. Most commenters therefore agree that “5G” won’t be a single technology or deployed in a single band, but rather, as David Parish of Google said during one the panel discussions, an “amalgamation of technologies” to solve the many problems of 5G. On the same panel, Matt Grob, the Chief Technology Officer of Qualcomm said that “all spectrum bands will play a role in 5G,” from the current wireless bands to the millimeter wave bands. And Sanyogita Shamsunder of Verizon described the three aspects of 5G as presenting a “rainbow of opportunities” for operators in terms of the broad range of applications the 5G suite will enable. As several panelists alluded throughout the workshop, the 5G applications we can envision now are only the beginning.
Refining the 5G Triangle
The FCC’s Spectrum Frontiers workshop helped shatter the misconception that 5G is only about high data rates. It is not. On the contrary, 5G incorporates a broad range of services and service delivery platforms –terrestrial, satellite, and hybrid technologies –that promise to grow the economy and enhance our lives. The FCC workshop, which is available for viewing here, offers an excellent foundation for the upcoming technical forum Hogan Lovells will host in May 2016. We’ll try to sharpen the edges of the 5G Triangle so we can better understand how each of the three primary use cases is helping shape this pivotal new technology. We’ll also explore some of the technical challenges of 5G, including cybersecurity, infrastructure, and backhaul. As wireless rapidly transitions to new, more subtle mechanisms for satisfying wildly divergent user demands, understanding what 5G is and how it will work is something every business and consumer should know.