The 18th IEEE Wireless and Microwave Technology Conference (WAMICON) was held April 24-25, 2017 in Cocoa Beach, Florida. WAMICON is a regionally held conference with international attendance and impact. WAMICON is always a warm inviting networking event combined with an outstanding program of papers presenting innovations and research updates from industry, academia and government laboratories.  This year’s peer reviewed papers were enhanced with high-level invited papers and future-oriented plenary talks. This year’s conference was chaired by Craig Sapashe of Keysight Technologies, with a theme of “Emerging Technologies for 5G Systems,” and a highlight was an engaging panel session entitled “The Push and Pull of Technology Solutions for 5G” that featured a panel of five industry experts selected from companies on the leading edge of 5G developments.

The WAMICON 2017 Panel Session on 5G

“The Push and Pull of Technology Solutions for 5G” was the topic of a 5-member panel session. While 5G promises unprecedented high speed mobile and fixed wireless data rates, it will require utilization of frequencies into the mm-wave spectrum, requiring solutions to new engineering challenges. 5G is a strong, but not yet completely defined, market pull for creative and cost effective technology solutions. The pull is coming from the wireless operators, who want to deliver higher performance (bandwidth) to customers, with the goal of providing mobile capability that matches—or at least approaches—fixed services like high rate DSL, cable modem, and fiber-to-the-premises (FTTP).  

This pull is driving advances in technology: semiconductor devices, circuit design, test and simulation, heterogeneous integration and packaging. In addition, significant new work is underway in system-level design, including modulation schemes and waveform shape, coding, and signal processing techniques to deal with the unique propagation effects at mm-wave.

Of course, various commercial interests have incentives to push their own specific technology solutions to “push” for adoption by this new market. This panel allowed speakers from different industry segments to present their vision for 5G Technology evolution and discuss their perspectives on the push and pull of the solutions required to realize the promise of 5G for practical applications.

Session moderators were Dr. Larry Dunleavy of Modelithics Inc. and Michael P. Hallman of the Microwave Journal. Panelists included: Vincent Pelliccia, VP of Business Development, Anokiwave; Paul Colestock, Ph.D., Founding Director, Head of Exploratory Design Group, GlobalFoundries; Moray Rumney, Lead Technologist, Keysight Technologies; Takao Inoue, Ph.D., Wireless Solutions Architect, AWR Group, National Instruments; and Bror Peterson, Principal Systems Engineer, Infrastructure and Defense Products, Qorvo.

The 5G Panel of experts at WAMICON 2017. From left to right: Colestock, Pellicia, Peterson, Inoue and Rumney.

The panel noted that many of the specific techniques required to implement 5G are still in development, and that both system operation and physics-based technical issues remain to be solved. However, significant work has been done that identifies pathways to an eventual 5G standard. Inoue pointed out that the first “soft rollout” of 5G technology is expected by the end of 2017. This initial rollout will not be an official 5G standard, but rather operator-specific system protocols and hardware that will become part of the standards development process.

Several areas of technology where major challenges remain were noted repeatedly during the discussion:

The mm-wave spectrum — to support the bandwidth required for all visions of 5G performance, radios must use higher frequencies, whether 28 GHz, 60 GHz or perhaps multiple segments of the spectrum. Such mm-wave systems have a number of performance characteristics that offer significant challenges, a few of which are:

• High path loss:  Path loss at 60 GHz is 35 dB greater than at 1 GHz, according to Friis equation. Peterson put different numbers on the issue, “For 85 percent coverage we need more than 160 dB path loss link budget.” Even though cell sizes must be 500 meters or less, a base station may need 65 dBm EIRP (effective isotropic radiated power), achieved with a combination of transmitter power and antenna gain.

Qorvo’s Bror Peterson noted the high EIRP required at mm-wave to overcome the increased path loss.

• Complex propagation behaviors:  The very short wavelength at mm-wave means that all propagation-related impairments are multiplied, including multipath, reflections, diffraction and doppler. For mobile operation, this means that even at walking speed, fading can be deep and rapid. While there are techniques to address these issues, they become more complex at mm-wave frequencies. Or, as Pellicia put it, “There is nothing about 5G that’s simple.”
• Small geometry semiconductors:  Device physics must also be managed at smaller wavelengths, where both smaller physical size and higher energy density must be considered. A type of “Moore’s Law” for RF devices is required: continued progress in the ability to achieve smaller geometries with the necessary performance and reliability. The methods for producing low-cost mm-wave ICs vary with the process technology being used, which are primarily RF CMOS, SiGe, and silicon-on-insulator (SOI). Additional devices for switching and power amplification may use GaN and GaAs.
• High cost of manufacturing:  Will a billion handsets and millions of short-range base stations result in the kind of economy-of-scale necessary for prices expected by consumers? mm-wave technology’s complex radios, combined with the computing power needed for baseband processing, represent much higher costs than any prior technology. The panel cannot provide answers yet, but the semiconductor experts suggested that history shows that lower costs will follow demand, while admitting that it may take longer for 5G to get there.

Antenna beamforming — The propagation and path loss at mm-wave will require adaptable antenna arrays to maintain transmitted EIRP, and reduce the effects of propagation (such as reflections and doppler delay spread) when receiving. Design issues include multiple RF paths in the radios, types and location of antenna arrays, switching and steering circuits and their control algorithms, and of course, the overall complexity of such a system.

The addition of the circuits that drive elements of an adaptable antenna array may be the deciding factor in the designers’ choice of semiconductor process. Questions remain about whether RF CMOS can support the functionality and performance needed, or will a step up to a silicon-on-insulator (SOI) fabrication technology be needed. Or will SiGe be the process of choice?

Where do you put the antennas? Rumney showed a test plot of signal strength response of a 4G iPhone. When placed on the left side of the head, the signal strength spread was 15 dB greater than on the right side. This clearly illustrated the challenge of antenna placement, regardless of frequency. And again, the problem is multiplied at mm-wave.

System modeling and measurement — Both Inoue and Rumney commented on system and test matters, with Rumney pointing out one of the major realities of mobile system testing at mm-wave: “that will be an over the air test, since we can’t measure with cables anymore.” The short wavelength at mm-wave makes it impossible to perform conventional measurements of equipment using interconnecting cables, due to losses, cable matching and the discontinuities of interconnections. The full system must be in operation, and performance measured from end-to-end. This places higher demand on system models, which must include propagation (in 3D), as well as hardware—both of which are more complex at the frequencies involved.

“…we can’t measure with cables anymore,” says Moray Rumney of Keysight Technologies, referring to mobile mm-wave systems.

Mobile or handheld operation — At mm-wave, the effects of propagation while a user is in motion are multiplied over what occurs in present 4G systems. As noted above, these effects can be mitigated with steerable, narrow beamwidth antennas configured as adaptable arrays. But in mobile or handheld devices, there is limited room to place multiple antennas, and the devices are subject to highly variable environments and placement with respect to the body (hands, head).

Inoue (seated at left in the above photo) included an illustration of a proposed 5G metropolitan architecture that included fixed base stations to distribute signals over the service area, plus mobile user support using what he described as micro base stations, or ‘Transmission/Reception Points’, as the connection between the network backbone and mm-wave handsets. While this configuration adds another level to the organization of the system, it may be an acceptable method to meet mm-wave 5G’s need for much smaller cell sizes.

Colestock noted that the first offerings of 5G technology would likely be sub-10 GHz systems. mm-waves may be part of early fixed point systems, but, as he made clear, some of the above issues are far from being solved, such as, “mm-wave mobile? Really?”

“mm-wave Mobile? Really?” says Paul Colestock.

Overall, the panel’s contribution to the ongoing discussion of 5G was pointing out where progress has been made (such as semiconductor technology and propagation analysis), where further work is needed (e.g., adaptable antenna arrays and cost), and a few areas where major technical issues remain to be solved, such as modulation schemes and many aspects of mobile and handheld operation.  There was a lively audience Q&A session that followed opening remarks from each of the panelists that added much welcome color to the present picture and future imagery of 5G challenges and solutions that are very large part of the focus for many engineers in our wireless and microwave industry.

Summary

The IEEE Wireless and Microwave Technology Conference (WAMICON) has a history of a strong technical program, augmented with plenary speakers, invited talks, and panel sessions such as this insightful look at 5G. The organizers invest much time and effort to find experts who can clearly present information, and their educated opinions, on timely topics.

WAMICON 2018

In 2018, the 19th WAMICON will return to the Gulf side of the state, to be held April 9-10, 2018 at the Sheraton Sand Key, Sand Key, Florida. The Call for Papers can be found at www.wamicon.org. Deadline for proposed papers is February 9, 2018.