Last week, I had the opportunity to attend Keysight’s 5G Tech Connect conference near San Francisco. It was a private one-day event that included many 5G thought leaders. The speakers and panel participants ranged from researchers to service providers, who provided insight into the issues presented by 5G.
The issues were oriented towards the development and testing challenges, but also included some interesting applications. There was a room nearby with Keysight test equipment, but it was far from a sales event. In fact, Roger Nichols (Keysight 5G Program Manager and the event host) promised to boot out anyone filling out a lead form. Many of the new test products shown are still under wraps, you’ll have to wait until 2018 to hear about them. But, the discussions were riveting, and the small crowd of about 200 allowed full audience participation.
Given that, here are my top five takeaways about 5G.
Over the air testing becomes essential
For years, the cellular industry has relied on conducted measurements to validate RF parameters in devices and base stations. 5G mmWave will end that. There won’t be any connectors because phased array antennas span a device. Instead of conducted power, Equivalent Isotropically Radiated Power (EIRP) becomes the key specification. EIRP is essentially the transmitter power multiplied by the antenna gain compared to an isotropic antenna. Measuring EIRP typically requires a far-field anechoic chamber (Figure 1).
Figure 1 For R&D testing in a typical far-field anechoic chamber, the device-under-test (DUT) is mounted on a positioner that rotates in two planes. But how feasible is this in the manufacturing environment? Note that shorter wavelengths lengthen the size of the chamber due to the formula above. Image courtesy of Keysight Technologies.
OTA will impact the entire testing chain, not only how test is performed, but where as well. R&D may be able to afford far-field anechoic chambers for development, but people in the manufacturing supply chain will have to think this through. Test every device in an anechoic chamber? Go to near-field testing to reduce chamber size? Drive six-sigma quality through the supply chain, and merely test of the final device functions? All these options were discussed during the conference. Lucas Hansen, Senior Director for Chipset and Component Testing at Keysight, opined that the first manufacturing runs would require some anechoic testing. Later, devices would deploy self-testing or DUT-assisted testing techniques to eliminate this requirement.
Is this feasible? Perhaps. Dr. Gabriel Rebeiz showed the results of phased-array antennas “built like digital boards” at UC San Diego (Figure 2). Solder in the components and go. They delivered impressive performance and repeatability, even without calibration. He emphasized how modern foundries and manufacturing methods have “made phased-array easy” and noted that one particularly impressive array was created by just two students. Students, he reminded us, have other priorities on campus, often social, yet still pulled this off.
Figure 2 This 64-element phased-array antennas developed at UC San Diego showed results showed high performance and repeatability, even without calibration. Image courtesy of Keysight Technologies.
R&D plays a proportionally bigger role
Beamforming adds a great deal of complexity to 5G. It’s not just the physical characterization of the devices, or the measurement of the beam patterns—it’s the entire set of protocols to even know where to aim the beam. Moray Rumney, Keysight’s representative on the 3GPP radio committee, walked us through the ladder diagram of how a device is bonded to a base station while both units are aligning their beams. Will it work? Maybe. Fixed Wireless Access (FWA) will be easier as both devices are essentially motionless. Mobile communications is, however, much harder. These tests are all in the R&D area. Once the beamforming algorithms are developed, there is no manufacturing test.
Low latency testing is another R&D-centric test. 5G includes a specific use case called Ultra-Reliable Low Latency Communication (URLLC), which promises to enable safety-critical applications such as remote surgery or autonomous vehicles. The one-millisecond latency goal is needed for enabling any application that requires tactile feedback.
Shown at the conference, and announced this week is the Keysight UXM 5G wireless test platform (Figure 3), which performs beamforming algorithms and latency tests. It is essentially a network emulator for device software testing. While the UXM isn’t new, up until now it tested devices to the Verizon pre-5G Technical Forum (5GTF) specifications. This week, Keysight announced that the New radio (NR) specifications have been incorporated into the tester, matching the long-term 5G radio specifications.
Figure 3 Keysight unveiled the UXM 5G wireless test platform. The UXM now supports the NR waveforms and tests for Advanced channel bandwidth, beamforming, latency, 8CC aggregation, and a comprehensive set of L1/L2 actions. Photo by Martin Rowe.
The silicon wild card
Can silicon be effective at mmWave frequencies? Will silicon’s lower efficiency eliminate it for power amp applications?
The pre-event dinner featured a keynote by Maryam Rofougaran, Co-CEO and COO at Movandi Corporation. Rofougaran led us through her history of designing silicon RF devices that had previously been thought of as impossible. After her first start-up Innovent Systems was acquired by Broadcom, she was promoted to senior VP of Radio Engineering, and led a worldwide team of more than 300 engineers at Broadcom developing wireless radios for combination chips. She and her brother recently cofounded Movandi to create high performance mmWave devices using low cost bulk CMOS processes. Movandi recently announced the BeamX, a complete 28 GHz front end module, from the phased-array antenna to the baseband interface. Movandi seeks to deliver 4.5 db better link budgets while consuming 30 percent less transmit power (Figure 4).
Figure 4 The original Movandi BeamX prototype is a 64-element phased array antenna based on bulk CMOS processes. Image courtesy of Movandi Corporation.
The jury is still out on silicon versus III-V processes, but it is clear silicon is making gains.
Wait for mobility
Beamforming is hard. Beamforming with a quickly moving object at mmWave frequencies is even harder. I’m sure it will be solved (see my next takeaway), but fixed beamforming will be solved first, and will be an industry-wide learning experience. A year and a half ago I predicted that fixed wireless access would be the first 5G killer application. It’s the combination of lower degree of difficulty and known business opportunity that keeps me sticking with this prediction. Verizon has already announced its intent to do exactly that in 2018.
Figure 5 Delivering fixed broadband using wireless technology will be Verizon’s first commercial deployment of 5G technology. Image courtesy of Verizon.
There are a number of unknowns that will need to become “knowns” for mmWave mobile to work. Beamforming at speed, over-the-air performance and testing, and finally what business model and applications can justify billion dollar investments in mobile remain challenges. If 5G mobile is deployed this decade, expect it to be in the sub-6GHz spectrum using massive MIMO.
5G represents the most disruptive generational change in cellular networks since the movement to digital. Everything is hard- higher frequencies, ill-behaved propagation, beamforming, and over-the-air testing. We don’t even know what we don’t know yet.
That said, the pace of 5G innovation is simply breathtaking. Whether the business case demands this or not, an ecosystem ranging from academia to component suppliers to carriers has emerged with giant investments behind them all. Perhaps it’s the fear of being left out. Like a western town in the late 1800s, the players feel compelled to belly up to the bar and place their pistols on the counter. The conference ended with a talk by Dr. Mischa Dohler, from King’s College London and head of the Centre for Telecommunications Research. It was an inspiring talk where Dohler led us through new applications being conceived and prototyped through his research. While Industry 4.0 empowers robots, he has dubbed Human 4.0 for empowering humans. Remote stroke detection in ambulances, exoskeletons training new surgeons from a master, and remote practice of the performing arts were just some of the examples he presented.
Figure 6 With 5G communications, a surgeon could wear a sensing glove while performing remote surgery. Image courtesy of Ericsson.
Empowering humans, indeed.
Author: Larry Desjardin served in several R&D and executive management positions with Hewlett-Packard and Agilent Technologies.