Industry Voices—Madden: Manufacturing for 5G—the testing challenge

Joe Madden Industry Voices

As the industry ramps up for 5G deployments, there’s a great deal of focus on technology features such as network slicing and massive MIMO. These features have been proven to work in various field tests, and the standards groups are starting to accelerate the release of 5G NR specifications. We’ve recently released a forecast that calls for more than a million 5G RRH units to be deployed over the next five years.

So, now we turn our attention to practical matters. Here’s an example: How will a million 5G radios be tested in production?

This is not a kindergarten question. In the past, every Remote Radio Head (RRH) and every client device was tested with a simple coaxial connector at the RF output to the antenna. Below 3 GHz, it’s convenient to place a connector at the output of the PCB, for a coaxial cable or antenna to plug in. Final acceptance of a production unit is verified by testing at the connector, not through radiated testing.  

Above 20 GHz, it’s not so simple. We can’t insert a coax connector between the antenna element and the radio module, because at high frequencies the electrical loss would wreck the performance of the massive MIMO array. This problem applies to infrastructure and to any millimeter-wave client device (CPE, tablet, hotspot, or handset).

Mechanical questions also come into play. At 28 GHz, the spacing between antenna elements doesn’t leave much space for coaxial connectors. Imagine the poor technicians trying to screw in 128 SMA connectors for the antenna array, or fumbling to click 128 blind-mate connectors into place.

At lower frequencies, such as the 3.5 to 5 GHz bands considered for mobile 5G in Asia, connectors are possible, but testing of individual transceiver elements will not certify that beamsteering is working as required. Some level of over-the-air testing will be required to make sure that massive MIMO will work.

For production, the OEMs will need to test radios at a radiated level. That means testing in a chamber, isolated from the outside world, with precisely calibrated antennas measuring signals over the air. This is not a cheap and simple process, and today the infrastructure does not exist to test 500,000 radios per year.

Of course, there are clever engineers at test equipment suppliers and OEM companies that have good ideas to speed up over-the-air tests, to minimize the investment involved, and to produce large numbers of radios. I’m simply pointing out that the wider industry needs to pay attention to this issue, because testing will require intense capital investment and may slow the industry down as we try to accelerate the deployment of 5G.

Joe Madden is Principal Analyst at Mobile Experts LLC, a network of market and technology experts that analyze wireless markets. The team provides detailed research on Small Cell, Base Station, Carrier Wi-Fi, and IoT markets. Mr. Madden currently focuses on trends in 5G, IoT, and Enterprise markets for wireless infrastructure. Over 26 years in mobile communications, he accurately predicted the rise of Digital Predistortion, Remote Radio Heads, Small Cells, and the rise of a Mobile IT market. He validates his ideas with mobile and cable operators, as well as semiconductor suppliers to find the match between business models and technology. Mr. Madden holds a Physics degree from UCLA. Despite learning about economics at Stanford, he still obeys the laws of physics.