Broadband technologies

Broadband access

The term broadband includes a broad range of technologies, all of which provide higher data rate access to the Internet. These technologies use wires or fiber optic cables in contrast to wireless broadband described later.

Multilink dial-up

Multilink dial-up provides increased bandwidth by bonding two or more dial-up connections together and treating them as a single data channel. It requires two or more modems, phone lines, and dial-up accounts, as well as an ISP that supports multilinking - and of course any line and data charges are also doubled. This inverse multiplexing option was briefly popular with some high-end users before ISDN, DSL and other technologies became available. Diamond and other vendors created special modems to support multilinking.

Integrated Services Digital Network (ISDN)

Integrated Services Digital Network (ISDN), a switched telephone service capable of transporting voice and digital data, is one of the oldest Internet access methods. ISDN has been used for voice, video conferencing, and broadband data applications. ISDN was very popular in Europe, but less common in North America. Its use peaked in the late 1990s before the availability of DSL and cable modem technologies.

Basic rate ISDN, known as ISDN-BRI, has two 64 kbit/s "bearer" or "B" channels. These channels can be used separately for voice or data calls or bonded together to provide a 128 kbit/s service. Multiple ISDN-BRI lines can be bonded together to provide data rates above 128 kbit/s. Primary rate ISDN, known as ISDN-PRI, has 23 bearer channels (64 kbit/s each) for a combined data rate of 1.5 Mbit/s (US standard). An ISDN E1 (European standard) line has 30 bearer channels and a combined data rate of 1.9 Mbit/s.

Leased lines

Leased lines are dedicated lines used primarily by ISPs, business, and other large enterprises to connect LANs and campus networks to the Internet using the existing infrastructure of the public telephone network or other providers. Delivered using wire, optical fiber, and radio, leased lines are used to provide Internet access directly as well as the building blocks from which several other forms of Internet access are created.

T-carrier technology dates to 1957 and provides data rates that range from 56 and 64 kbit/s (DS0) to 1.5 Mbit/s (DS1 or T1), to 45 Mbit/s (DS3 or T3). A T1 line carries 24 voice or data channels (24 DS0s), so customers may use some channels for data and others for voice traffic or use all 24 channels for clear channel data. A DS3 (T3) line carries 28 DS1 (T1) channels. Fractional T1 lines are also available in multiples of a DS0 to provide data rates between 56 and 1,500 kbit/s. T-carrier lines require special termination equipment that may be separate from or integrated into a router or switch and which may be purchased or leased from an ISP. In Japan the equivalent standard is J1/J3. In Europe, a slightly different standard, E-carrier, provides 32 user channels (64 kbit/s) on an E1 (2.0 Mbit/s) and 512 user channels or 16 E1s on an E3 (34.4 Mbit/s).

Synchronous Optical Networking (SONET, in the U.S. and Canada) and Synchronous Digital Hierarchy (SDH, in the rest of the world) are the standard multiplexing protocols used to carry high data rate digital bit streams over optical fiber using lasers or highly coherent light from light-emitting diodes (LEDs). At lower transmission rates data can also be transferred via an electrical interface. The basic unit of framing is an OC-3c (optical) or STS-3c (electrical) which carries 155.520 Mbit/s. Thus an OC-3c will carry three OC-1 (51.84 Mbit/s) payloads each of which has enough capacity to include a full DS3. Higher data rates are delivered in OC-3c multiples of four providing OC-12c (622.080 Mbit/s), OC-48c (2.488 Gbit/s), OC-192c (9.953 Gbit/s), and OC-768c (39.813 Gbit/s). The "c" at the end of the OC labels stands for "concatenated" and indicates a single data stream rather than several multiplexed data streams.

The 1, 10, 40, and 100 Gigabit Ethernet (GbE, 10GbE, 40GbE, and 100GbE) IEEE standards (802.3) allow digital data to be delivered over copper wiring at distances to 100 m and over optical fiber at distances to 40 km.

Cable Internet access

Cable Internet or cable modem access provides Internet access via Hybrid Fiber Coaxial wiring originally developed to carry television signals. Either fiber-optic or coaxial copper cable may connect a node to a customer's location at a connection known as a cable drop. In a cable modem termination system, all nodes for cable subscribers in a neighborhood connect to a cable company's central office, known as the "head end." The cable company then connects to the Internet using a variety of means – usually fiber optic cable or digital satellite and microwave transmissions. Like DSL, broadband cable provides a continuous connection with an ISP.

Downstream, the direction toward the user, bit rates can be as much as 400 Mbit/s for business connections, and 100 Mbit/s for residential service in some countries. Upstream traffic, originating at the user, ranges from 384 kbit/s to more than 20 Mbit/s. Broadband cable access tends to service fewer business customers because existing television cable networks tend to service residential buildings and commercial buildings do not always include wiring for coaxial cable networks. In addition, because broadband cable subscribers share the same local line, communications may be intercepted by neighboring subscribers. Cable networks regularly provide encryption schemes for data traveling to and from customers, but these schemes may be thwarted.

Digital subscriber line (DSL, ADSL, SDSL, and VDSL)

DSL technologies
ADSL ANSI T1.413 Issue 2
ITU G.992.1 (G.DMT)
ITU G.992.2 (G.Lite)
ADSL2 ITU G.992.3
ITU G.992.4
ITU G.992.3 Annex J
ITU G.992.3 Annex L
ADSL2+ ITU G.992.5
ITU G.992.5 Annex M
HDSL ITU G.991.1
VDSL ITU G.993.1
VDSL2 ITU G.993.2

Digital Subscriber Line (DSL) service provides a connection to the Internet through the telephone network. Unlike dial-up, DSL can operate using a single phone line without preventing normal use of the telephone line for voice phone calls. DSL uses the high frequencies, while the low (audible) frequencies of the line are left free for regular telephone communication. These frequency bands are subsequently separated by filters installed at the customer's premises.

DSL originally stood for "digital subscriber loop". In telecommunications marketing, the term digital subscriber line is widely understood to mean Asymmetric Digital Subscriber Line (ADSL), the most commonly installed variety of DSL. The data throughput of consumer DSL services typically ranges from 256 kbit/s to 20 Mbit/s in the direction to the customer (downstream), depending on DSL technology, line conditions, and service-level implementation. In ADSL, the data throughput in the upstream direction, (i.e. in the direction to the service provider) is lower than that in the downstream direction (i.e. to the customer), hence the designation of asymmetric. With a symmetric digital subscriber line (SDSL), the downstream and upstream data rates are equal.

Very-high-bit-rate digital subscriber line (VDSL or VHDSL, ITU G.993.1) is a digital subscriber line (DSL) standard approved in 2001 that provides data rates up to 52 Mbit/s downstream and 16 Mbit/s upstream over copper wires and up to 85 Mbit/s down- and upstream on coaxial cable. VDSL is capable of supporting applications such as high-definition television, as well as telephone services (voice over IP) and general Internet access, over a single physical connection.

VDSL2 (ITU-T G.993.2) is a second-generation version and an enhancement of VDSL. Approved in February 2006, it is able to provide data rates exceeding 100 Mbit/s simultaneously in both the upstream and downstream directions. However, the maximum data rate is achieved at a range of about 300 meters and performance degrades as distance and loop attenuation increases.

DSL Rings

DSL Rings (DSLR) or Bonded DSL Rings is a ring topology that uses DSL technology over existing copper telephone wires to provide data rates of up to 400 Mbit/s.

Fiber to the home

Fiber-to-the-home (FTTH) is one member of the Fiber-to-the-x (FTTx) family that includes Fiber-to-the-building or basement (FTTB), Fiber-to-the-premises (FTTP), Fiber-to-the-desk (FTTD), Fiber-to-the-curb (FTTC), and Fiber-to-the-node (FTTN). These methods all bring data closer to the end user on optical fibers. The differences between the methods have mostly to do with just how close to the end user the delivery on fiber comes. All of these delivery methods are similar to hybrid fiber-coaxial (HFC) systems used to provide cable Internet access.

The use of optical fiber offers much higher data rates over relatively longer distances. Most high-capacity Internet and cable television backbones already use fiber optic technology, with data switched to other technologies (DSL, cable, POTS) for final delivery to customers.

Australia has already begun rolling out its National Broadband Network across the country using fiber-optic cables to 93 percent of Australian homes, schools, and businesses. Similar efforts are underway in Italy, Canada, India, and many other countries.

Power-line Internet

Power-line Internet, also known as Broadband over power lines (BPL), carries Internet data on a conductor that is also used for electric power transmission. Because of the extensive power line infrastructure already in place, this technology can provide people in rural and low population areas access the Internet with little cost in terms of new transmission equipment, cables, or wires. Data rates are asymmetric and generally range from 256 kbit/s to 2.7 Mbit/s.

Because these systems use parts of the radio spectrum allocated to other over-the-air communication services, interference between the services is a limiting factor in the introduction of power-line Internet systems. The IEEE P1901 standard specifies that all powerline protocols must detect existing usage and avoid interfering with it.

Power-line Internet has developed faster in Europe than in the U.S. due to a historical difference in power system design philosophies. Data signals cannot pass through the step-down transformers used and so a repeater must be installed on each transformer. In the U.S. a transformer serves a small clusters of from one to a few houses. In Europe, it is more common for a somewhat larger transformer to service larger clusters of from 10 to 100 houses. Thus a typical U.S. city requires an order of magnitude more repeaters than in a comparable European city.

ATM and Frame Relay

Asynchronous Transfer Mode (ATM) and Frame Relay are wide area networking standards that can be used to provide Internet access directly or as building blocks of other access technologies. For example many DSL implementations use an ATM layer over the low-level bitstream layer to enable a number of different technologies over the same link. Customer LANs are typically connected to an ATM switch or a Frame Relay node using leased lines at a wide range of data rates.

While still widely used, with the advent of Ethernet over optical fiber, MPLS, VPNs and broadband services such as cable modem and DSL, ATM and Frame Relay no longer play the prominent role they once did.

Wireless broadband access

Wireless broadband is used to provide both fixed and mobile Internet access.


Wi-Fi is the popular name for a "wireless local area network" that uses one of the IEEE 802.11 standards. It is a trademark of the Wi-Fi Alliance. Individual homes and businesses often use Wi-Fi to connect laptops and smart phones to the Internet. Wi-Fi Hotspots may be found in coffee shops and various other public establishments. Wi-Fi is used to create campus-wide and city-wide wireless networks.

Wi-Fi networks are built using one or more wireless routers called Access Points. "Ad hoc" computer to computer Wi-Fi" networks are also possible. The Wi-Fi network is connected to the larger Internet using DSL, cable modem, and other Internet access technologies. Data rates range from 6 to 600 Mbit/s. Wi-Fi service range is fairly short, typically 20 to 250 meters or from 65 to 820 feet. Both data rate and range are quite variable depending on the Wi-Fi protocol, location, frequency, building construction, and interference from other devices. Using directional antennas and with careful engineering Wi-Fi can be extended to operate over distances of up to several kilometers.

Wireless ISP

Wireless ISPs typically employ low-cost 802.11 Wi-Fi radio systems to link up remote locations over great distances, but may use other higher-power radio communications systems as well.

Traditional 802.11b is an unlicensed omnidirectional service designed to span between 100 and 150 meters (300 to 500 ft). By focusing the radio signal using a directional antenna 802.11b can operate reliably over a distance of many kilometres (miles), although the technology's line-of-sight requirements hamper connectivity in areas with hilly or heavily foliated terrain. In addition, compared to hard-wired connectivity, there are security risks (unless robust security protocols are enabled); data rates are significantly slower (2 to 50 times slower); and the network can be less stable, due to interference from other wireless devices and networks, weather and line-of-sight problems.

Rural Wireless-ISP installations are typically not commercial in nature and are instead a patchwork of systems built up by hobbyists mounting antennas on radio masts and towers, agricultural storage silos, very tall trees, or whatever other tall objects are available. There are currently a number of companies that provide this service.

Motorola Canopy and other proprietary technologies offer wireless access to rural and other markets that are hard to reach using Wi-Fi or WiMAX.


Worldwide Interoperability for Microwave Access

WiMAX (Worldwide Interoperability for Microwave Access) is a set of interoperable implementations of the IEEE 802.16 family of wireless-network standards certified by the WiMAX Forum. WiMAX enables "the delivery of last mile wireless broadband access as an alternative to cable and DSL". The original IEEE 802.16 standard, now called "Fixed WiMAX", was published in 2001 and provided 30 to 40 megabit-per-second data rates. Mobility support was added in 2005. A 2011 update provides data rates up to 1 Gbit/s for fixed stations. WiMax offers a metropolitan area network with a signal radius of about 50 km (30 miles), far surpassing the 30-metre (100-foot) wireless range of a conventional Wi-Fi local area network (LAN). WiMAX signals also penetrate building walls much more effectively than Wi-Fi.

Satellite broadband

Satellites can provide fixed, portable, and mobile Internet access. It is among the most expensive forms of broadband Internet access, but may be the only choice available in remote areas. Data rates range from 2 kbit/s to 1 Gbit/s downstream and from 2 kbit/s to 10 Mbit/s upstream. Satellite communication typically requires a clear line of sight, will not work well through trees and other vegetation, is adversely affected by moisture, rain, and snow (known as rain fade), and may require a fairly large, carefully aimed, directional antenna.

Satellites in geostationary Earth orbit (GEO) operate in a fixed position 35,786 km (22,236 miles) above the earth's equator. Even at the speed of light (about 300,000 km/s or 186,000 miles per second), it takes a quarter of a second for a radio signal to travel from the earth to the satellite and back. When other switching and routing delays are added and the delays are doubled to allow for a full round-trip transmission, the total delay can be 0.75 to 1.25 seconds. This latency is large when compared to other forms of Internet access with typical latencies that range from 0.015 to 0.2 seconds. Long latencies can make some applications, such as video conferencing, voice over IP, multiplayer games, and remote control of equipment, that require a real-time response impracticable via satellite. TCP tuning and TCP acceleration techniques can mitigate some of these problems. GEO satellites do not cover the earth's polar regions. HughesNet and ViaSat are GEO systems.

Satellites in Low Earth orbit (LEO, below 2000 km or 1243 miles) and Medium earth orbit (MEO, between 2000 and 35,786 km or 1,243 and 22,236 miles) are less common, operate at lower altitudes, and are not fixed in their position above the earth. Lower altitudes allow lower latencies and make real-time interactive Internet applications feasible. LEO systems include Globalstar and Iridium. The O3b Satellite Constellation is a proposed MEO system with a latency of 125 ms. COMMStellation™ is a LEO system, scheduled for launch in 2015, that is expected to have a latency of just 7 ms.

Mobile broadband

Mobile broadband is the marketing term for wireless Internet access delivered through mobile phone towers to computers, mobile phones (called "cell phones" in North America and South Africa), and other digital devices using portable modems. Some mobile services allow more than one device to be connected to the Internet using a single cellular connection using a process called tethering. The modem may be built into laptop computers, tablets, mobile phones, and other devices, added to some devices using PC cards, USB modems, and USB sticks or dongles, or separate wireless modems can be used.

Roughly every ten years new mobile phone technology and infrastructure involving a change in the fundamental nature of the service, non-backwards-compatible transmission technology, higher peak data rates, new frequency bands, wider channel frequency bandwidth in Hertz becomes available. These transitions are referred to as generations:

Second generation (2G) from 1991:

  • first mobile data services
  • GSM CSD (2G): 9.6 kbit/s
  • GSM GPRS (2.5G): 56 to 115 kbit/s
  • GSM EDGE (2.75G): up to 237 kbit/s

Third generation (3G) from 2001:

Fourth generation (4G) from 2006:

  • HSPA+: 21 to 672 Mbit/s down; 5.8 to 168 Mbit/s up
  • Mobile WiMAX (802.16): 37 to 365 Mbit/s down; 17 to 376 Mbit/s up
  • LTE: 100 to 300 Mbit/s down; 50 to 75 Mbit/s up
  • LTE-Advanced: 100 Mbit/s moving at higher speeds to 1 Gbit/s not moving or moving at low speeds
  • MBWA: (802.20): 80 Mbit/s

The download (to the user) and upload (to the Internet) data rates given above are peak or maximum rates and end users will typically experience lower data rates.

WiMAX (described in more detail above) was originally developed to deliver fixed wireless service with wireless mobility added in 2005. CDMA2000 EV-DO and MBWA (Mobile Broadband Wireless Access) are no longer being actively developed.

In 2011, 90% of the world's population lived in areas with 2G coverage, while 45% lived in areas with 2G and 3G coverage.

Local Multipoint Distribution Service

Local Multipoint Distribution Service (LMDS) is a broadband wireless access technology that uses microwave signals operating between 26 GHz and 29 GHz. Originally designed for digital television transmission (DTV), it is conceived as a fixed wireless, point-to-multipoint technology for utilization in the last mile. Data rates range from 64 kbit/s to 155 Mbit/s. Distance is typically limited to about 1.5 miles (2.4 km), but links of up to 5 miles (8 km) from the base station are possible in some circumstances.

LMDS has been surpassed in both technological and commercial potential by the LTE and WiMAX standards.