Broadband Network Deployment Engineering


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BROADBAND NETWORK DEPLOYMENT ENGINEERING
AN OVERVIEW

Overview
The Bipartisan Infrastructure Law is historic in its size – the largest ever investment in broadband, rail and transit, clean energy, and water, including $65B to help close the digital divide through broadband deployment, improved affordability, and digital equity.
Addressing persistent barriers to universal broadband deployment in unserved and underserved areas requires a strong understanding of the different components of a broadband Internet network. This brief provides an overview of broadband deployment engineering, covering network architecture, infrastructure elements, business models, and technologies, as well as the relationships between each.

Network Architecture
Broadband networks transmit and receive data between end users (e.g., households, businesses, anchor institutions) and interconnection points of the core Internet, allowing users to connect to the Internet’s global resources. This requires data to flow seamlessly over three types of networks: core Internet backbone, middle mile, and last mile. It is critical to understand the functions and interactions of each, as they form the foundation of a comprehensive network that enables Internet service provision. To close the digital divide, the IIJA includes programs to fund the deployment of both middle mile and last mile networks.

CORE INTERNET BACKBONE
The core Internet backbone is comprised of interconnected networks that transmit data between and across countries and continents. To ensure reliable service, backbone networks build in redundancy through path diversity. They also contain critical databases and standards that ensure effective and secure Internet operation.
Global telecommunications and technology companies typically own and operate backbone networks, which principally use terrestrial and submarine fiber-optic cable for connectivity.

DEFINITION OF KEY TERMS
Contention: Competition for bandwidth. A contention ratio is the potential maximum demand on a network compared to actual bandwidth available; a lower ratio signifies better service, while a higher ratio signals oversubscription and reduced quality of service.

MIDDLE MILE
Middle mile networks connect an area node with the core Internet. The area node is a local connection point for the last mile network elements. Where feasible, middle mile networks should employ path diversity to increase redundancy. In addition, these networks need sufficient capacity to carry the traffic from the local network without contention.
In the U.S., large Internet service providers and specialized long-haul companies typically own and operate middle mile networks, which deploy fiber-optic cable or, in some cases, wireless technologies.

Path diversity: The principle that a network has multiple potential physical paths between interconnection points and the backbone to increase redundancy.
Redundancy: A characteristic of a network that has multiple paths or devices that help sustain network availability in the event of a single path or device failure.

Website: ntia.gov Email: [email protected]

March 2022

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LAST MILE
Last mile networks, also called access or local networks, connect end users via an area node to a middle mile network, which enables connection into the core Internet backbone. Unlike backbone and middle mile networks, which aggregate traffic from multiple customers (e.g., Internet service providers, other network owners), last mile networks provide connectivity between end users and an area node.
A range of organizations own, operate, and provide Internet services over last mile networks, including large and small Internet service providers, cable companies, municipalities, and rural electric or telephone cooperatives. Last mile networks use many technologies to transmit data (see Network Technology section).

Figure 1. A last mile network with multiple technologies deployed connected to a middle mile network at an area node
Network Infrastructure Elements
Broadband networks consist of both passive and active elements. When integrated, they enable the provision of Internet service. It is critical to understand the purpose of each, as decisions on materials and network design will shape deployment economics and logistics, as well as network performance and path diversity.
PASSIVE INFRASTRUCTURE
Passive infrastructure is the physical layer of material needed to enable connectivity. For fixed broadband, examples include fiber-optic and copper cables, ducts, conduit, utility poles, adaptors, and splitters. For wireless broadband, examples include towers, antennas, buildings, fiber conduit, and power equipment.
ACTIVE INFRASTRUCTURE
Active infrastructure refers to the electronic elements that enable passive infrastructure to transmit data by accurately routing it, changing the medium (e.g., optical to electrical), amplifying it, or adding value in other ways. Examples include fiber-optic terminals, routers, servers, and switches.

Website: ntia.gov Email: [email protected]

March 2022

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Network Business Models
In the U.S., a range of network business models are available. For network owners, operators, and Internet service providers, the model they use will impact deployment costs, market dynamics, and competition.

Network business models exist on a spectrum. On one end, vertical integration is where one entity owns the passive infrastructure, owns and operates the active infrastructure, and provides Internet services over the network to end users. On the other, open access is where an infrastructure owner provides wholesale access to the network for lease on a non-discriminatory basis but does not themselves provide residential services to end users. In between are a range of infrastructure sharing models in which a network owner and/or service provider makes portions of their passive and/or active infrastructure capacity available for use to other entities (e.g., wholesale peering and transit).

Vertical Integration

Infrastructure Sharing

Open Access

Owners

1

1 or more

1 or more

Owners providing services

1

Variable

None

Providers operating

1

1 or more

Many

Competitive use of facilities

None

Limited

Encouraged

Major Internet backbone providers typically utilize an infrastructure sharing model in which they exchange traffic freely between entities, called settlement-free peering, or charge a transit fee to other entities for access. Middle mile network models are more varied, and there are successful models across the spectrum in the U.S. Finally, owners of last mile networks typically opt for vertical integration, though a handful of open access last mile networks exist in the U.S.

Spotlight on Different Business Models
Dakota Carrier Network (DCN) is a middle mile network that utilizes an infrastructure sharing model. Founded in 1996 by 15 local telephone cooperatives and companies, the DCN connects each owner’s last mile network to the core Internet backbone and sells wholesale access to other entities.1 Due in part to DCN’s efforts, the percentage of North Dakotans with access to 1,000/100 Mbps broadband Internet is 18 percent higher than the U.S. average.2
Northwest Open Access Network (NoaNet) is an open access middle mile network owned by nine public utility districts (PUD) in Washington State. Over 100 retail Internet service providers lease a connection to NoaNet’s network to provide Internet services to 170 communities and 200 anchor institutions.3

Network Technology
Over the past three decades, Internet service providers have pursued a variety of technologies to provide end users with affordable, reliable, high-speed broadband. It is important to know how these technologies function and the contexts in which they operate, as they greatly influence the quality of Internet service provided. Speed, latency, reliability, and prevalence can vary based on several variables:

◊ Distance to area nodes
◊ The complexity of the design (e.g., the amount of equipment and splice points)

◊ The number of end users on the network
◊ Impediments to transmission (e.g., lineof-sight obstructions, adverse weather)

1. Institute for Local Self-Reliance, “How Local Providers Built the Nation’s Best Internet Access in Rural North Dakota” (2020). 2. Federal Communications Commission, "Compare Broadband Availability in Different Areas" (2019). 3. NoaNet.net, “Our Story” (2020).

Website: ntia.gov Email: [email protected]

March 2022

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Terrestrial broadband
Fiber Transmits data as pulses of light through fiber-optic cable made from glass or plastic
Hybrid Fiber Coaxial (HFC) Transmits data through fiber that feeds into coaxial lines to the end user
Digital Subscriber Line (DSL) Transmits data over existing copper phone lines
Wireless broadband
Fixed Wireless Access (FWA) Transmits data over radio waves between two fixed points
TV White Space (TVWS) Transmits data over unused radio wave frequencies between TV channels
Low Earth Orbit (LEO) Satellite Transmits data over radio waves using constellations of satellites <1k miles above earth
Geosynchronous Equatorial Orbit (GEO) Satellite Transmits data over radio waves using several geostationary satellites 22k miles above earth

Considerations in unserved and underserved areas
Speed: Fastest download and upload speeds on average Latency: Very low Reliability: High except for risk of damage to aerial and buried lines Prevalence: Increasing as Internet service providers replace copper; has become default for new builds or upgrades in urban areas and many rural areas
Speed: Varies based on number of end users on coax segment; upload speed often slower than download speed under DOCSIS Latency: Relatively low Reliability: High except for risk of damage to aerial and buried lines Prevalence: Common in most areas, though less widespread in rural areas
Speed: Slower on average; depends on length and quality of copper Latency: Relatively low Reliability: High except for risk of damage to aerial and buried lines Prevalence: Less common as fiber has supplanted it but it is often left in place
Considerations in unserved and underserved areas
Speed: Varies based on spectrum availability and potential congestion Latency: Very/relatively low; depends on design, spectrum, and enviro. conditions Reliability: May be lower in adverse weather (e.g., rain fade) over longer distances or with line-of-sight obstructions (e.g., high-density foliage) Prevalence: Available in many rural areas, especially with difficult terrain
Speed: Relatively slow, though it is new and in the early stages of deployment Latency: Theoretically can be relatively low under ideal conditions Reliability: Can penetrate dense foliage, avoiding some line-of-sight issues Prevalence: Several pilot projects underway
Speed: Relatively fast speeds (>100 Mbps) theoretically possible Latency: Relatively low but can vary as satellites move relative to end users Reliability: As a newer technology evolving rapidly, difficult to ascertain Prevalence: As a newer technology, unclear at this time
Speed: Varies based on number of concurrent end users and satellite line-of-sight Latency: Relatively high due to longer distance radio waves must travel Reliability: May be lower in adverse weather (e.g., rain fade) or with line-of-sight obstructions (e.g., high-density foliage) Prevalence: Most common in remote areas

Want to learn more?
To stay up to date on the latest available information, including Notices of Funding Opportunity when released, visit our website.

ntia.gov broadbandusa.ntia.gov
[email protected]
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Broadband Network Deployment Engineering