5G offers faster download speeds than previous cellular standards, but the technology may not offer anywhere near the coverage of 3G and 4G networks, depending on the frequencies the base stations use.
One of the frequency ranges 5G uses is millimeter wave (mmWave), at 30 GHz to 300 GHz. The main drawback with mmWave-based mobile 5G is that wireless high-band technology does not work well indoors. This is because mmWave signals struggle to penetrate building walls and certain types of glass, thus hobbling indoor 5G performance.
In fact, since AT&T and Verizon first deployed mmWave 5G in 2019, users have found it difficult to access high-band 5G signals. While users can get fast mobile 5G download speeds of more than 1 Gbps if they're outdoors and close to a 5G cell tower, this isn't always possible for those in an office or working from home.
Small cells boost indoor coverage
Cellular small cells are one answer to this coverage problem. First introduced as part of the 3rd Generation Partnership Project 4G LTE specification in 2009, these radio access points (APs) can increase the density of a cellular network.
A small cell is a low-powered cellular base station that operates using a variety of frequencies. Depending on their size, small cells can offer a transmission range from 40 feet up to a few kilometers. These mini base stations link back to the main cellular network via an Ethernet, fiber or wireless connection.
Small cells can be deployed indoors or outdoors. The indoor variety is generally small -- around the size of a pizza box. These mega- or gigabit speed gadgets can be installed on the ceilings and walls of homes and offices to boost the radio frequency (RF) signal strength of cellular networks.
5G networks are becoming increasingly dependent on indoor small cells. This trend is likely to continue as more 5G small cells are deployed in offices, homes and apartments.
Carrier developments in the indoor 5G network space
With the deployment of low-band and midband 5G cellular networks by U.S. mobile network operators (MNOs), indoor access to 5G wireless technology is becoming more commonplace.
The three major MNOs in the U.S. -- AT&T, T-Mobile and Verizon -- now offer a mixture of low-, mid- and high-band 5G networks, although none of the 5G frequencies from these carriers completely blanket the U.S. yet.
As macro networks continue to roll out, general 5G access -- indoor and outdoor -- is better than it was just a few years ago. In addition, major carriers are deploying small cells to broaden and intensify coverage as the cellular 5G network expands.
In January 2021, Verizon, the largest U.S. MNO, announced it is leasing 15,000 small cells from shared communications infrastructure provider Crown Castle to support its nationwide 5G deployment through 2025. Once operational, the lease on each 5G radio will last 10 years. This deal supplements the thousands of 5G small cell sites Verizon has built itself.
The operator is rolling out new C-band midband 5G spectrum to extend its 5G Ultra Wideband service to cover 175 million potential customers in the U.S. by the end of 2022. Verizon said it will deploy small cells that are compatible with C-band spectrum after the initial expansion.
The second largest U.S. mobile operator T-Mobile has also signed a deal with Crown Castle to deploy 35,000 small cells through 2027. The lease on the units runs for 12 years. At a conference in January 2022, Crown Castle CFO Daniel Schlanger said the T-Mobile agreement was "the largest small cell order in our history."
Verizon and T-Mobile are battling it out over which carrier will offer the fastest and most dense 5G coverage in the U.S. Small cells will be a big part of that push in 2022 and beyond.
The third-ranked MNO, AT&T, has said it is trying to cut down the time it takes to acquire sites and permits to deploy small cells. In February 2022, AT&T said it is field testing and deploying commercially available Ericsson Street Radio 4402 small cells in multiple U.S. cities.
It can take an MNO anywhere from 12 to 18 months to add new micro 5G sites. Any infrastructure that can be deployed in less time is an advantage for a carrier. AT&T, however, hasn't said how many indoor or outdoor small cells it plans to deploy.
How do small cells aid 5G indoor coverage?
Despite ambitious plans from major MNOs, the majority of 5G small cells will be deployed by private enterprises. IDTechEX predicted that 45 million 5G small cells will be distributed globally by 2031.
Some of these small cells will be installed by companies looking to create their own private 5G network for business. By combining a private 5G core with a small cell network, enterprises can implement a secure, reliable, low-latency and high-speed private network on premises.
Despite all the hype about private 5G, the technology that enables these exclusive corporate networks is just starting to become available. Private 5G deployments won't become more mainstream until 2025 or 2026.
In the meantime, enterprises will continue to install indoor small cells, albeit with the micro radios connected to an MNO's public network.
Increasing 5G network densification will greatly improve indoor coverage. As noted, indoor environments are not particularly friendly to high-band mmWave 5G radios. Walls can block high-band signals entirely, but even midband 5G RF can be weakened by office partitions and furniture.
Enterprises that require their employees to have access to high-speed -- 1 Gbps-plus -- data downloads over cellular networks will need multiple mmWave small cells to ensure reliable, uninterrupted data coverage indoors.
The majority of 5G small cells deployed will likely use midband or low-band frequencies. These bandwidths don't totally rely on compatible indoor micro radios to provide coverage, but businesses that depend on solid 5G signals indoors should look to install midband 5G small cells to be certain.
Distributed antenna systems
Many enterprises use a distributed antenna system (DAS) to carry a cellular signal from a central source throughout a building. Small cell networks can supplement these systems for improved indoor mobile coverage.
DAS vendors, such as CommScope and Corning, work with major carriers to install indoor antenna systems in hotels, hospitals, large office buildings and stadiums. Deploying a DAS, however, is more expensive than installing one or several small cells in a building, with costs dependent on supported frequencies and equipment, according to Waveform, a cell signal boosting provider.
Many smaller businesses can use Wi-Fi to provide indoor mobile coverage for employees, particularly because most cellphones available these days support Wi-Fi calling. Modern Wi-Fi 6 -- 802.11ax -- APs increase throughput and decrease the congestion of public network bandwidth. Compared with previous Wi-Fi standards, Wi-Fi 6 interoperates better with 5G, enabling a more heterogeneous network when using both technologies.
Key players in the indoor 5G space
Prominent vendors in the 5G small cell market include the following, in alphabetical order:
- Cisco Systems
- NEC Corp.
The blocklisting of Chinese vendors Huawei and ZTE Corp. in 2019 has splintered the global radio access network market, including small cells. In the U.S. and parts of Europe, Chinese vendors are banned from selling telecom infrastructure. In the rest of the world, Huawei is the top telecom vendor.