Only a few years ago, six billion hertz was plenty to manage Facebook, WeChat, and YouTube. But mobile wireless owns a fraction of that six billion so we are driving to frequencies far beyond what many of us consider our radio comfort zone.
I have seen multiple radio engineering labs coming to grips with these new frequencies. As 5G mmWave goes from obscure to elite to mainstream, the number of engineers doing component, subsystem, and radio design in these rarified wavelengths will skyrocket.
Many will have little experience with wavelengths no wider than their thumbs, and with bandwidths that sound like carrier frequencies. How will you set up your lab to ensure success? I offer the following questions and suggestions to those braving this territory.
1. Which frequency bands are you targeting?
While 3GPP’s new radio (NR) development is aimed at carriers up to 100 GHz, I do not see a 5G wireless future in which this entire range will be used for access. So you not only have to anticipate which bands the policy groups will stipulate, you must speculate on which will be used for your target application spaces.
I also have doubts about 5G mobile multi-user access above 45 GHz. 802.11ad/ay will occupy the current 60 GHz band (and possibly the FCC’s extension of this band to 71 GHz). Point-to-point for backhaul, distributed antenna systems, and fronthaul will be implemented above 45 GHz. There is also early work in high-speed train communications up to 100 GHz (for on-board Wi-Fi “backhaul”).
Do you need to cover this entire range? Only part of it? Consider carefully because the tools and accessories become more expensive as you get closer to triple-digit gigahertz.
2. What bandwidth do you need to support?
While there is talk about information bandwidths of 2 GHz, consider the following for frequencies below 45 GHz:
- Licensed bands will be divided between at least two licensees.
- The widest in the FCC’s recent announcement is 425 MHz (28 GHz band)
- The new air interface access designs are aimed at aggregating carriers modulated to no more than 200 MHz.
Notwithstanding your potential need to manage aggregated carriers and perhaps do work above 45 GHz, consider how wide—and thus how complex and expensive—you will want your lab to go.
3. How will you connect to your device-under-test?
I have yet to see a serious design of a commercial mmWave transceiver system that includes a connector between the antenna and the amplifier. Thus, the labs I have seen all include anechoic chambers equipped with directional antennas with varying styles of positioners, and (often) open on one side. Smaller wavelengths and antenna apertures, highly directional propagation, and the lower likelihood of interfering signals allow for a different approach. But the requirement to make calibrated measurements in free space without violating regulations means a mix of enclosure, positioner, antenna, measurement equipment, and the necessary software.
4. What software tools will your team need?
Your software arsenal ought to include six items: EDA; system design and simulation; EM simulation, measurement and analysis; device and test-equipment control; data manipulation and management; and mathematics tools. While the associated learning curve for your engineers is substantial, the productivity gains of working in the virtual world, particularly in the uncharted seas of small waves, quickly repay this investment. Then, the software-enabled power to generate test stimuli for radio components and systems, and analyze measurement and sample results, will give your designers new insights in time for your target release date.
5. How do you future-proof your investments?
The world of commercial wireless is not for the faint of heart, and the foray into millimeter wave technology is an expensive step deeper into fraught territory. Short wavelengths mean exotic materials; tighter mechanical tolerances; and bandwidth, sampling rates, and digital speeds requiring significant CAPEX for a productive lab. CAPEX also implies these purchases must hold their value throughout and even after your depreciation period.
Successful organizations will future-proof these investments. Things to look for include capabilities to serve needs that arise during your depreciation period; modular software and hardware with an upgrade path; and proven vendors with technology-upgrade programs and expert support staff.
Lastly, stay close to what is going on in the market. Your view of the considerations listed above will clarify as new policy emerges, 3GPP standardizes, and innovators make new and more capable technology available for your own building blocks.