One of the biggest challenges for 5G fixed wireless access is bringing millimeter wave signals from the outdoors to the inside. The short wavelengths at those high frequencies mean that mmWave is very susceptible to being blocked or reflected by standard building materials, making it difficult to complete and sustain a link between a nearby mmWave tower and in-home customer premise equipment. Low emissivity or low-e glass, which has a thin coating to reflect energy from the inside and outside in order to reduce heat loss of the home, has a reputation as a notorious signal killer.
Semiconductor company MaxLinear and antenna developer AirGain have developed a way around — or more precisely, though — low-e glass for use in 5G mmWave systems. They have done a number of demos of their technology in the past year, with the most recent one achieving transfer rates of 2 Gbps through low-e glass. Their strategy is to use a set of small internal and external antennas to create a very wideband point-to-point link that can penetrate building materials without requiring drilling for installation. The external antenna feeds the signal through the glass through a wireless link to the other antenna, which then transmits it to customer premise equipment that can serve consumer devices.
Jim Kappes, marketing director at MaxLinear, said that the company’s solution is aimed squarely at the 5G fixed wireless access market to tackle the challenge of in-building penetration and come up with a strategy for an easier installation process for FWA. Although the recent demonstration focused on low-e glass penetration, he said that the solution can also be used to penetrate other building materials . The MaxLinear/AirGain solution transmits at very low power levels: “So low, it appears like background noise to other devices, and because of that, we pass the FCC emission limits on radiated emissions,” Kappes said. He said the solution is tunable between 400 MHz to 1.7 GHz to take advantage of various unlicensed bands around the world, and has sub-millisecond latency so as not to become a bottleneck. It also incorporates wireless power for the external unit, he said, which has been a sticking point for external antennas because of the need to armor external power connections.
“We knew that for it to be a really effective solution, we needed to pair it with wireless power,” Kappes said, adding that the company turned to external partners to incorporate wireless power into the solution. Between the wireless power of the outside antenna and the use of the wireless link to bridge to the outside, plus the unit’s small size — just a few square inches — Kappes said the goal is to make something that customers can easily install.
“This technology will enable self-installation, or partial self-installation,” he said. “That in itself has a lot of value.”
Kappes said that the companes first came up with the concept about five years ago.
“At that time, nobody was really talking about gigabit speeds into homes,” he said. “So there wasn’t a lot of interest. It seemed too far away and too high-end for the mainstream operators.” The conversations around 5G FWA have changed that, along with the progress in the cable industry on the roll-out of DOCSIS 3.1. MaxLinear is already sampling the chips and software and enabling demonstrations, Kappes said, while seeking to integrate new features such as an even smaller antenna and simple indicators for alignment between the outside and the inside antennas even when the installation is non-line-of-sight. The point-to-point link between them is surprisingly robust, Kappes said, and the signal still successfully adapts when they are a few inches out of exact alignment.
In the meantime, he said, the two companies have customers that intend to take the solution to the field for testing in 5G FWA systems and 60 GHz WiGig fixed wireless broadband access.
