Internet service providers (ISPs)—typically private businesses, electric and telephone cooperatives, or municipal utilities—own and operate broadband networks, which employ a range of technologies to connect customers to the internet. Those technologies are generally described in terms of the “speeds,” rates at which they transmit data, and “latencies,” the amount of time required for data to travel to its destination and back along the network, of the connections they provide. Understanding how the various technologies work and their relative strengths and limitations is important for policymakers engaged in debates around broadband funding and deployment.
Wireline connections are most common
Most broadband customers in the United States are connected to the internet by a wireline connection, which involves a physical line—typically using fiber optic cables, hybrid coaxial cable, or copper telephone wire—running to a structure. There are three primary types of wireline service:
- Cable internet service is provided by cable television companies over a hybrid network that uses fiber lines to connect to neighborhood nodes and then coaxial cable to transmit data to individual residences and businesses. Cable television providers have added high-speed internet access to their offerings through Data Over Cable Service Interface Specification (DOCSIS), an international telecommunications standard that allows the addition of high-bandwidth data transfer to existing cable television systems. Cable service offers asymmetrical speeds—downloads are faster than uploads. Cable, which is primarily available in urban and suburban areas, is the most common type of internet service in the U.S. and continues to grow. The top cable companies added more than 4.8 million subscribers in 2020—the most since 2006.
- Digital Subscriber Line (DSL) internet service uses a two-wire copper telephone line that allows consumers to simultaneously use the internet and a landline telephone without disrupting either connection. DSL service varies in terms of speed and distance the signal will travel; the most efficient forms can deliver speeds up to 24 megabits per second (Mbps) on a single telephone wire, which is below the Federal Communications Commission’s (FCC) definition of broadband. However, some companies bond two sets of telephone wires together and offer speeds up to 48 Mbps. The most important characteristic of DSL is that its data speed decreases as the distance increases: The farther a signal must travel, the slower it will be, and as a result, DSL speeds differ throughout a community and even within a neighborhood. DSL is the oldest internet service technology currently in use in the U.S. and has been losing customers because of its slower speeds. As a result, ISPs have begun phasing out the service.
- Fiber to the Home (FTTH), otherwise known as Fiber to the Premises (FTTP), can provide the fastest speeds with low latencies. The service relies on fiber optic cables—flexible, hair-thin glass strands—that can transmit large amounts of data at high transfer rates. In the newest networks, fiber can deliver speeds of 10 gigabits per second (Gbps), or 10,000 Mbps, with a latency of 1.5 milliseconds. Fiber also offers symmetrical download and upload speeds. And it is more future-proof than other technologies; it can be continually scaled to faster speeds over time with limited maintenance. For all of these reasons, policymakers should prioritize investment in fiber when allocating state and federal broadband funds.
However, FTTH coverage remains well below that of cable. According to the Fiber Broadband Association, fiber accounts for 20% of internet service market share in the U.S., compared with just above 50% for cable. To help expand the availability of fiber networks nationwide, ISPs have committed to investing $60 billion over the next five years to build out FTTH. And the guidelines for the American Rescue Plan Act’s Coronavirus State and Local Fiscal Recovery Funds and Capital Projects Fund prioritize funding for fiber infrastructure projects.
Fixed wireless and satellites offer options for rural areas
In rural areas and places with low housing density or long distances between homes, wirelines for last-mile connections—the segment of the network that connects an ISP to a customer—are cost prohibitive. However, ISPs are increasingly using fixed wireless or satellite service to deliver internet access to homes and businesses in these more remote communities.
Fixed wireless connections are transmitted through towers, similar to cell phone towers, to an antenna mounted on a customer’s premise. Like DSL, fixed wireless connections get slower as distance from the transmitting tower increases, so the service is fast and reliable for consumers close to a tower but slower and less reliable for those farther away, particularly if the line of sight between the tower and the antenna is disrupted. Although fixed wireless covers less than half of U.S. households to date, it does provide a reliable last-mile option for rural areas, especially when the towers are connected to fiber cables.
Similarly, internet provided via satellites may present another alternative for consumers in rural or remote areas. Traditional geostationary satellite technologies use individual satellites orbiting at over 22,000 miles above the Earth to deliver service at speeds of up to 40 Mbps. However, geostationary satellite service is marked by high latencies, up to 900 milliseconds, which create challenges for customers seeking to use real-time applications, such as online gaming and video streaming. A new technology, low-earth-orbit satellite broadband, uses constellations of satellites in orbit 200-800 miles above the Earth to offer greater reliability, faster speeds, and lower latencies compared with geostationary service, but it does not yet have the capacity to support the large subscriber bases reached by the dominant wireline providers.
Mobile devices supplement access for most Americans, but are the only access for many
More than 83% of people in the U.S. access the internet on their smartphones, tablets, or other mobile devices. And these devices are the only means of internet connection for 15% of Americans. In general, because mobile access and wireline connections offer different speeds and functionality, consumers tend to view the two types of service as complementary and subscribe to both if they have the means.
ISPs deliver mobile connections via three technologies:
- 3G: Third generation, usually with network speeds of less than 1 Mbps. Although some rural cellular towers still use 3G, this technology has been phased out in most parts of the country, which has cut off internet access for older cellphones, as well as some medical, security, and personal devices.
- 4G: Fourth generation, usually with network speeds greater than 1 Mbps. Most 4G networks in the U.S. use LTE (Long Term Evolution) standard, which provides speeds up to 100 Mbps. Most contemporary mobile devices are connected to the internet through a 4G connection.
- 5G: Fifth generation, usually with network speeds of 1 Gbps or more. All four of these connections are currently in use, but the country is in a moment of transition. Although 3G is still used in some rural areas, most people are connected to 4G, and service providers are actively deploying 5G.
Wireless infrastructure depends on spectrum—electromagnetic radio frequencies—to transmit data to end users’ devices. Spectrum may be “licensed,” specific frequencies granted by the FCC to individual ISPs for their exclusive use, or “unlicensed,” that is, available for use by anyone. Different technologies require different spectrum. For instance, 5G uses high frequencies that enable data to travel faster but not as far as lower frequencies, and so it requires a greater density of receivers and transmitters to move data across long distances than do 4G and earlier generations of wireless service.