Ookla wrote a recent article that highlights an increasing problem of poor indoor cellular coverage. The article notes that this is a growing problem since the public increasingly relies on cell phone apps.

Indoor cell coverage is growing poorer for several reasons. First, 5G carriers are migrating to higher mid-band frequencies, which don’t penetrate buildings as well as the lower frequencies used in the past. Years ago, cellular networks widely used 700 MHz and 900 MHz frequencies, which had the wonderful property of penetrating almost anything. I remember being amazed a decade ago when I didn’t lose a cell call in an interior elevator of a building. In recent years, I’ve noticed that my cell phone doesn’t work at the back of my neighborhood grocery store – but it did a decade ago. The problem is only going to get worse as cellular carriers migrate more 5G traffic to higher mid-band spectrum bands (3 GHz and higher).

There are also some changes in buildings that make it harder for wireless signals to penetrate. Ookla cites the increasing use of low-E glass, an energy-efficient glass with a microscopic coating that reflects heat and light – and also cellular signals. Ookla says that modern insulation materials, in general, are less friendly to cell signals.

Ookla also lays some of the blame on regulations that completely focus on outdoor cell coverage and has never acknowledged that 80% of cellular traffic originates from indoors (Ookla cites Ericsson for that statistic). The FCC adopted a minimum standard for outdoor cellular speeds of 25/3 Mbps in October 2020 as part of the 5G Fund for Rural America order. Interestingly, at that time, that was a higher speed than the definition of landline broadband that was still stuck at 25/3 Mbps. A few countries like Germany and Ireland require decent indoor cellular speeds for structures like hospitals, busy business districts, and tourist attractions.

There are some solutions to the problem. One would be for regulators to require better cellular speeds to match how people use it. That may sound like an easy fix, but it’s not.

The best way to improve cellular speeds is to use small cell sites that are closer to homes and businesses. A signal from a cell site in a neighborhood will penetrate nearby buildings a lot better than a signal from a tall tower a mile or more away. One of the limiting factors of cellular call strength that doesn’t get mentioned very often is that the power from cell site is restricted and limited. This is done to stop neighboring tall towers from interfering with each other. Stronger signals would penetrate buildings better but would wreak havoc with existing cellular networks.

Some businesses have tackled the problem on their own. Many hotels, hospitals, and business high-rises have invested in a rooftop cellular repeater (which is really a small cell site) that beams a signal down through the building. That strengthens the signal inside a building but nowhere else.

Ookla recommends an interesting solution, which is to embrace a neutral host model of telecommunications. This would have third party companies build, own, and operate cellular infrastructure, which would be leased to multiple service providers on a wholesale basis. Think of this as the open-access version of infrastructure. A neutral host company would build cell sites where they are most needed by the public and lease capacity to all cellular carriers. Unfortunately, that model has not ever been embraced in the U.S. In fact, Crown Castle, which was the predominant company chasing the neutral hosted model, announced in March that it is selling its small cell business and related fiber networks to Zayo and EQT.