Small Cells and Distributed Antenna Systems (DAS) networks are being deployed in cities and towns across the United States to augment towers. Indeed, many people are asking: i) What are Small Cells and Distributed Antenna Systems?, and ii) What do they do?

Below we answer these important questions. Specifically, small cells and distributed antenna systems (DAS) impact your ability to stay connected to the network and use the services on your smartphone, that matter most to you.

Small Cells & Distributed Antenna Systems – Classification

Small Cells are also known as outdoor distributed antenna systems (DAS). However, for clarity, this article will distinguish Small Cells as providing coverage and capacity outdoors.

Distributed Antenna Systems (DAS) are also known as indoor distributed antenna systems (DAS). However, for clarity, this article will refer to all indoor forms of coverage and capacity as simply, Distributed Antenna Systems (DAS).

Overall, small cells and distributed antenna systems (DAS) represent a focused way of enhancing network coverage and capacity. Indeed, both systems consist of individual antennas, placed at low elevations relative to the wireless user. Furthermore, small cells and distributed antenna systems (DAS) allow for densification of wireless networks. This enables the widespread adoption of 5G wireless networks.

Network Capacity and Coverage – Case Study – Phoenix, Arizona

Below we walkthrough an example of Phoenix, Arizona to help answer the common question of: Why do we need Small Cells & Distributed Antenna Systems? Specifically, this case study uses the example of small cells, in an outdoor environment. However, the same takeaways from small cells, apply to distributed antenna systems (DAS), in an indoor environment.

Outside of its downtown area, Phoenix in Arizona, and its surrounding suburbs, including Chandler and Scottsdale, are largely residential communities. Indeed, these suburbs of Phoenix have numerous cellular towers that provide wireless voice and data coverage to their respective communities.

For this example, we focus on one cellular tower, in one suburb of Phoenix. On this tower are several antennas of the wireless carriers, like Verizon, AT&T, and T-Mobile, that serve Phoenix. These antennas broadcast and pick-up signals from residents’ devices and transmit the data they receive to adjacent equipment, nearby the tower. Subsequently, a wired connection transmits the information on to the internet or phone system.

When this tower was originally built, over 20 years ago, it served the residents of Phoenix well. Indeed, people were using cell phones to talk, and text with barely any issues. Besides experiencing a few “dead zones” and limited coverage areas, this tower in Phoenix provided good, reliable service that kept its residents connected.

However, Today, the Devices of Phoenix Residents Are Not Always Connecting to the Network

Phoenix’s population has grown throughout the years and its residents have begun to notice that even when their device shows that it has a signal, they are not always able to connect to the network. Years ago, cell phone users in Phoenix had no problems connecting to the wireless carriers’ networks. However, as more people use more data, some users are not able to connect to the network.

What Happened to the Network of Phoenix?

Firstly, people today have more powerful smartphones and are using significantly more data. Specifically, users are streaming music on Spotify, videoconferencing with friends or co-workers over Zoom, and watching and posting large videos on YouTube.

Secondly, many Phoenix residents also have multiple devices that now connect to the cellular network. These devices are not only smartphones, but also tablets, smartwatches, and connected cars.

So why is this causing problems now? Coverage and capacity are the answer.

Coverage and Capacity

Notably, coverage and capacity are two important concepts for providing wireless users with optimal service. While these two concepts are related, the causes and solutions for each can differ.


Coverage is the area that a particular type of digital infrastructure covers, meaning how far the signal reaches. Using the example of the tower in Phoenix, this is able to send its signal across hundreds of homes in a 1-mile to 2-mile radius. Indeed, there are a few areas with hills and tall buildings, which can cause the signal to drop. However, Phoenix’s coverage, overall, does not change.


Capacity becomes evident if you have ever had full signal bars on your device but cannot place a call or load a web page. Indeed, this means you have coverage, but not capacity. This is because you are not having an issue connecting to the network, but for some reason your data is not getting through.

Why does this happen? A concept called “wireless density” is the answer.

Small Cells Network Capacity Needed 2021
Source: Crown Castle

Wireless Density

Wireless signals that connect the tower, to the device of a resident in Phoenix, are only capable of carrying so much data at once. This is the concept of wireless density. Indeed, the more data and devices people use on the network, the slower everyone’s connections become. To solve this problem, the networks that serve Phoenix need more wireless density.

Small Cells – Solution to Adding More Wireless Density in Phoenix

Given the wireless density challenges that Phoenix faces, this is an ideal situation for a small cell network deployment. Specifically, a small cell network consists of a series of small, low-powered antennas, often called nodes, that provide coverage and capacity in a similar way to a tower, with a few important differences.

Small cells are always connected by fiber optic cable, and attached to city infrastructure like streetlights, utility poles, light poles, and slim line poles. Indeed, there is a good chance that you have walked by these small cells before and never even noticed.

Small Cells What Do They Look Like 2021
Source: Crown Castle

In turn, small cells are more discreet to local residents, while also bringing them closer to smartphones and other devices, which improves both coverage and capacity. Similar to a tower though, small cell nodes communicate wirelessly over radio waves, and then send the signals to the internet or phone system. An additional benefit of small cells is that because they are connected with fiber (as opposed to copper), they are able to handle massive amounts of data, at fast speeds.

Capacity Improvements – Wireless Density

With the frequency bands that carriers currently use to transmit their signals, if too many people are connected at once, data rates can slow down. By adding small cell nodes, Phoenix can increase its wireless density significantly and is able to handle many more simultaneous connections.

Each small cell node is capable of sending and receiving the same amount of data as the tower. However, since each small cell covers a smaller geographic area, it is much less likely that any one small cell node will become capacity constrained. Therefore, with small cells, network capacity in Phoenix improves.

Coverage Improvements – Wireless Density

Small cells also provide the benefit of improving coverage for wireless networks. Historically, the network in Phoenix originated from one location, being the cellular tower. Indeed, the tower covered a broad geography, but in certain areas of Phoenix, such as behind a building, the signal would get lost.

However, after deploying a small cell network, the network signal, in Phoenix, originates from many separate locations. Specifically, these are the small cell nodes, most of which are much closer to end user devices than towers. In turn, this proximity to user devices provides much more consistent coverage throughout Phoenix.

Small Cells – Shared or Neutral Host Infrastructure

Small cells are a form of shared infrastructure, meaning that multiple wireless carriers like Verizon, AT&T, and T-Mobile can be accommodated on the same pole. Indeed, this maximizes the benefits for residents, regardless of which carrier they get their wireless service from. With a small cell network, Phoenix residents can now use their devices and fully embrace the newest technologies like 5G.

Small Cells – Digital Infrastructure Overview

Small cells are small, low-powered antennas, also known as nodes. Indeed, small cells are connected via fiber optic cable that is typically deployed in dense configurations and closer to wireless customers than tower sites. Specifically, examples of small cells include microcells, picocells, and femtocells.

READ MORE: Small Cells – Microcell, Picocell and Femtocell Comparison

Overall, small cells are up to 15-feet in height, and located closer to where mobile customers need to connect to the network. Importantly, small cells bring wireless signals into areas that need better coverage or more capacity.

Small cells can provide coverage for more than 100 users in about a 1,000-foot radius. Whereas, a cellular tower site can support more than 1,000 users in a 1-mile to 2-mile radius. Therefore, tower sites provide “blanket coverage”. Subsequently, small cell deployments can augment that tower blanket coverage, in high population density areas, where specific capacity needs exist.

Physical Asset – Small Cells

Small cells consist of antennas and radios deployed along a city block or travel corridor. Specifically, small cells are mounted on streetlights, utility poles, light poles, and slim line poles. In terms of radio frequencies, small cells, have antennas operating on mid-band and high-band (or millimeter wave) spectrum.

Small cells typically have a design that enables them to blend-in with city infrastructure. Indeed, this makes them easier for local authorities to accept in urban areas from a zoning perspective. Finally, small cells require radios to be co-located near each antenna, which differs from DAS.

Customers – Small Cells

Small cells are particularly apt to support wireless carrier deployments of spectrum at high-band (millimeter wave) frequencies. Indeed, at these frequencies, traditional tower sites are not able to maximize capacity. Specifically, this is because these higher frequency signals travel shorter distances, meaning the antenna or node needs to be closer to the end user. Therefore, small cells are more optimal than towers to support high-band (millimeter wave) spectrum deployments.

Wireless Carriers

Wireless carriers, including Verizon, AT&T, and T-Mobile, use small cells as an effective means for both coverage and capacity. Coverage applications for small cells are in very specific outdoor areas that need service. Additionally, small cell coverage can supplement outdoor areas, that have difficult zoning restrictions for towers. For example, certain cities make obtaining zoning approval for a tower too difficult.

Because small cell antennas are individual antennas on low-elevation structures, rather than as highly visible arrays (i.e., cellular towers), zoning authorities that are resistant to towers are often more accepting of small cells. This is because small cells are easier to blend-in to the aesthetic of a city. Additionally, in very dense cities like New York, space constraints prevent the installation of larger equipment like towers, in the middle of the city. Therefore, small cells which are physically smaller, can have deployments occur at street-level.

Capacity-offload, is another application for small cells, which reduces the amount of data that cellular towers carry and moves it to small cells. In turn, small cells improve overall capacity in the areas of wireless networks where data demand is the greatest.

Cable Companies

Comcast, through Xfinity Mobile and Charter Communications, through Spectrum Mobile, are two cable companies that are customers of small cells. Indeed, these cable companies use small cells to augment their wireless services.

Contract Terms – Small Cells

Overall, small cells have contracts, similar to DAS, that are often 10 to 15+ years in initial term. Additionally, these small cell contracts have multiple 5-year renewals and built-in rental escalators of 1% to 1.5% per year.

Providers – Small Cells

Small cells require a significant upfront capital investment to build the fiber, radio equipment, and supply the site with power. Therefore, the U.S. wireless carriers often rely on independent third-party providers for a significant portion of their small cell deployments. Examples of the leading providers of small cells in the United States include:

Small Cells Providers
  • Crown Castle: 50k small cell nodes on-air, which rises to 70k small cells including those under contract, but not yet built out yet
  • ExteNet Systems: 32.3k nodes (mainly DAS sites, but includes small cells) and 430 networks
  • Verizon: in 2020, Verizon deployed 10k small cells in order to use more of its high-band (millimeter wave) spectrum, for what it brands as 5G Ultra Wideband
  • Zayo Group: 2.5k+ nodes
  • Uniti Group: 2.4k nodes installed or in backlog
  • Freshwave Group: ~5k nodes in the United Kingdom and ~150 networks

Distributed Antenna Systems (DAS) – Digital Infrastructure Overview

Distributed Antenna Systems (DAS) address coverage and capacity requirements, from an indoor perspective. Indeed, these systems reduce the network load on cellular towers, which improves overall network performance. Distributed antenna systems range from small single-carrier, single-band, low-capacity systems for use in enterprise buildings to large multi-carrier, multi-band systems for use in high-capacity public venues.

Physical Asset – Distributed Antenna Systems (DAS)

Distributed antenna systems are a wireless network structured as a number of antennas that are connected to and distribute signals from a common base station, via fiber. Specifically, distributed antenna systems are deployed within a discrete location, building, venue, or structure.

The base station acts like a headend (i.e., holds the electronics) for a footprint of antennas. Specifically, the base station radio is a single unit that connects via fiber to the DAS antennas. Indeed, this base station can be located at a remote site because of the minimal signal loss over fiber. Recall that small cells are different from DAS and require radios to be co-located near each antenna.

Distributed antenna systems (DAS) are deployed in high-demand venues. Specifically, these venues include stadiums, hotels, hospitals, shopping malls, casinos, racetracks, convention centers, airports, subway stations, and tunnels. Indeed, distributed antenna systems can be thought of as having two unique purposes, for in-building deployments:

  • Low Coverage: an example being a subway station
  • High Density: an example being a sports stadium
American Tower – Distributed Antenna Systems (DAS) – Case Study

American Tower installed DAS systems at five of International Speedway’s racetracks for motor sports. Notably, International Speedway hosts the Daytona 500 NASCAR Cup Series. Depending on the event and size of the particular venue for the race, there could be anywhere from 20k to 100k people attending an event at a single track.

Overall, the majority of people attending these racetracks will want cellular connectivity. Indeed, American Tower’s DAS solutions support users receiving optimal coverage at the racetrack.

Office Building – Distributed Antenna Systems (DAS) – Case Study

Below is an example of a typical office building, which helps to further explain the key components of distributed antenna systems (DAS) and how these networks are deployed. The distributed antenna systems in the office building have four key components:

Distributed Antenna Systems DAS Office
(1) Equipment Room

The Equipment Room is a telecommunications rack delivering power and signal to the Telecom Closet, while backhauling traffic to the mobile network.

(2) Telecom Closet

The Telecom Closet is a free-standing or wall-mounted rack for managing and interconnecting the cabling between Cellular / Wi-Fi devices and the Equipment Room.

(3) Cellular

The Cellular device is a single antenna supporting multiple wireless carriers and frequency bands for cellular voice, 4G/LTE, and 5G communications.

(4) Wi-Fi

The Wi-Fi device is a single cable deployment carrying low-voltage power and high-speed data, reaching up to 100 meters from the Telecom Closet.

Customers – Distributed Antenna Systems (DAS)

Similar to small cells, the wireless carriers, including Verizon, AT&T, and T-Mobile are the key customers of distributed antenna systems. As there are generally few options for providing competitive in-building coverage, indoor DAS tenancy levels range between 2 to 4 carriers in the United States. Therefore, each of Verizon, AT&T, and T-Mobile can often all co-locate on the same equipment in the same building.

Customer Groupings by Venue – Distributed Antenna Systems (DAS)

Distributed antenna systems are typically classified into four different types of networks. Indeed, this depends on the type of building that the distributed antenna system is intended to provide coverage and capacity for.

Distributed Antenna Systems DAS Types
(1) Standalone DAS

Standalone DAS are self-contained mini-base stations. For example, these apply to buildings including the home and branch office. Indeed, the purpose of these systems is to provide support for 1 user, and up to 100 users. Furthermore, these systems can host 1 to 4 different frequency bands or wireless carriers.


C-RAN DAS is where the majority of baseband processing is in a central location, in a baseband controller that provides capacity. Simultaneously, numerous radio points throughout the building “distribute” and provide coverage. For example, these apply to hospitals and high-rise office buildings. Indeed, the purpose of these systems is to provide support for up to 10,000 users. Furthermore, these systems can host 1 to 5 different frequency bands or wireless carriers.

(3) Enterprise DAS

Enterprise DAS solves the need for robust, scalable, multi-carrier mobile communications, with coverage and capacity for enterprises and large venues. Specifically, Enterprise DAS utilizes fiber-optic and Ethernet structured cabling architecture, common to many enterprises and commercial buildings. In turn, this makes Enterprise DAS easier for IT professionals to deploy.

For example, these apply to buildings including shopping malls and convention centers. Indeed, the purpose of these systems is to provide support for tens of thousands of users. Furthermore, these systems can host up to 6 different frequency bands or wireless carriers.

(4) DAS

DAS is where signal distribution occurs through a tower baseband unit, base transceiver station with radio frequency, or Common Public Radio Interface (CPRI).

For example, these apply to buildings including major airports and large stadiums. Indeed, the purpose of these systems is to provide support for hundreds of thousands of users. Furthermore, these systems can host more than 6 different frequency bands or wireless carriers.

Contract Terms – Distributed Antenna Systems (DAS)

Overall, distributed antenna systems (DAS) networks have contracts, similar to small cells, that are often 10 to 15+ years in initial term.

Providers – Distributed Antenna Systems (DAS)

Distributed antenna systems also require a significant upfront capital investment to build the network. Therefore, independent third-party providers perform a significant portion of distributed antenna system deployments. Examples of the leading providers of distributed antenna systems in the United States include:

Small Cells and DAS Providers
  • Boingo Wireless: operates 40.8k DAS nodes and 73 DAS networks. Indeed, this makes Boingo the largest operator of indoor DAS networks in the world
  • ExteNet Systems: 32.3k nodes (mainly DAS sites, but includes small cells) and 430 networks
  • American Tower: owns 1,774 DAS nodes and ~500 DAS networks. Specifically, 407 of these DAS nodes are in the United States, 1,079 are in India, and 231 are in Latin America, with the remainder being in Africa and Europe
Adam Simmons covers Towers for Dgtl Infra, including American Tower (NYSE: AMT), Crown Castle (NYSE: CCI), SBA Communications (NASDAQ: SBAC), Cellnex Telecom (BME: CLNX), Vantage Towers (ETR: VTWR), IHS Holding (NYSE: IHS), and many more. Within Towers, Adam focuses on the sub-sectors of ground-based cell towers, rooftop sites, broadcast / radio towers, and 5G. Adam has over 7 years of experience in research and writing for Towers.


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