Broadband modem

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Broadband Internet access, often shortened to "broadband Internet" or just "broadband" is a high data-transmission rate internet connection. DSL and cable modem, both popular consumer broadband technologies, are typically capable of transmitting 512 kilobits per second (kbit/s) or more, approximately nine times the speed of a modem using a standard digital telephone line.

Broadband Internet access became a rapidly developing market in many areas in the early 2000s; one study found that broadband Internet usage in the United States grew from 6% in June 2000 to over 30% in 2003. Modern consumer broadband implementations, up to 20 Mbit/s, are several hundred times faster than those available at the time of the birth of the internet (such as ISDN and 56 kbit/s) while costing less than ISDN and sometimes no more than 56 kbit/s; though performance and costs vary widely between countries.

Contents
1 Overview
2 Technology
2.1 Satellite Internet
2.1.1 Reducing satellite latency
2.2 Remote DSL
2.3 DSL repeater
2.4 Power-Line Internet
2.5 Wireless ISP
2.6 T-1/DS-1

Overview
Broadband transmission rates Connection Transmission Speed
DS-1 (Tier 1) 1.544 Mbit/s
E-1 2.048 Mbit/s
DS-3 (Tier 3) 44.736 Mbit/s
OC-3 155.52 Mbit/s
OC-12 622.08 Mbit/s
OC-48 2.488 Gbit/s
OC-192 9.953 Gbit/s
OC-768 39.813 Gbit/s
OC-1536 79.6 Gbit/s
OC-3072 159.2 Gbit/s
Broadband is often called high-speed Internet, because it usually has a high rate of data. In general, any connection to the customer of 256 kbit/s (0.256 Mbit/s) or more is considered broadband Internet. The International Telecommunication Union Standardization Sector (ITU-T) recommendation I.113 has defined broadband as a transmission capacity that is faster than primary rate ISDN, at 1.5 to 2 Mbit/s. The FCC definition of broadband is 200 kbit/s (0.2 Mbit/s) in one direction, and advanced broadband is at least 200 kbit/s in both directions. The OECD has defined broadband as 256 kbit/s in at least one direction and this bit rate is the most common baseline that is marketed as "broadband" around the world. There is no specific bitrate defined by the industry, however, and "broadband" can mean lower-bitrate transmission methods. Some Internet Service Providers (ISPs) use this to advantage, in marketing lower-bitrate connections as broadband.

In practice, the advertised bandwidth is not always reliably available to the customer; ISPs often allow a greater number of subscribers than their backbone connection can handle, under the assumption that most users will not be using their full connection capacity very frequently. This aggregation strategy works more often than not, so users can typically burst to their full bandwidth most of the time; however, peer-to-peer file sharing systems, often requiring extended durations of high bandwidth, stress these assumptions, and can cause major problems for ISPs who have excessively overbooked their capacity. For more on this topic, see network traffic engineering. As takeup for these introductory products increases, telcos are starting to offer higher bit rate services. For existing connections, this most of the time simply involves reconfiguring the existing equipment at each end of the connection.

As the bandwidth delivered to end-users increases, the market expects that video on demand services streamed over the Internet will become more popular, though at the present time such services generally require specialised networks. The data rates on most broadband services still do not suffice to provide good quality video, as MPEG-2 quality video requires about 6 Mbit/s for good results. Adequate video for some purposes becomes possible at lower data rates, with rates of 768 kbit/s and 384 kbit/s used for some video conferencing applications. The MPEG-4 format delivers high-quality video at 2 Mbit/s, at the high end of cable modem and ADSL performance. The Ogg Tarkin format is intended to deliver similar performance.

Increased bandwidth has already made an impact on newsgroups: postings to groups such as alt.binaries.* have grown from JPEG images to entire CD and DVD images. According to NTL, the level of traffic on their network increased from a daily inbound news feed of 150 gigabytes of data per day and 1 terabyte of data out each day in 2001 to 500 gigabytes of data inbound and over 4 terabytes out each day in 2002.

Technology
The standard technology in most areas is DSL, followed by cable modem. Newer technologies for twisted pair phone lines such as VDSL and pushing fiber optic connections closer to the subscriber in both telephone and cable plants are opening up the possibility of higher performance for streaming data, such as audio and video streams. There are now many streaming audio services, and several streaming video services. In a few of the many areas not served by cable or ADSL, community organizations have begun to install Wi-Fi networks.

ISDN is an older telephone data service that can operate at speeds of up to 128 kbit/s. It is therefore not really considered a true form of broadband, but it does have the advantage that it can share an existing phone line, and it has no distance limitations like DSL. When a phone call occurs, some of the bandwidth is allocated to the call, reducing the connection speed. When the call ends, the connection increases speed again. ISDN is a relatively low-cost option for rural users with otherwise terrible dialup access speeds, but it is starting to be phased out and is no longer available in some areas.

One of the great challenges of broadband is to provide service to potential customers in areas of low population density, such as to farmers and ranchers. In cities where the population density is high, it is easy for a service provider to recover equipment costs, but each rural customer may require thousands of dollars of equipment to get connected. A similar problem existed a century ago when electrical power was invented. Cities were the first to receive electric lighting, as early as 1880, while in the United States some remote rural areas were still not electrified until the 1940's, and even then only with the help of federally-funded programs like the Tennessee Valley Authority (TVA).

Several rural broadband solutions exist, though each has its own pitfalls and limitations. Some choices are better than others, but depend on how proactive the local phone company is about upgrading their rural technology.

Satellite Internet
This employs a satellite in geostationary orbit to relay data from the satellite company to each customer. Satellite Internet is usually among the most expensive ways of gaining broadband Internet access, but in rural areas it is often the only viable option. However costs have been coming down in recent times to the point that it is becoming more competitive with other high speed options.

Satellite Internet also has a high latency problem caused by the signal having to travel 22,000 miles (35,000 km) out into space to the satellite and back to Earth again. The signal delay can be as much as 500 milliseconds to 900 milliseconds, which makes this service unsuitable for applications such as multiplayer Internet gaming or live interactive access to a distant computer, but tolerable for just basic email access and web browsing.

There is no simple way to get around this problem. The delay is primarily due to the speed of light being only 186,000 miles per second (300,000 km/second). Even if all other signalling delays could be eliminated it still takes the electromagnetic wave 233 milliseconds to travel from ground to the satellite and back to the ground, a total of 44,000 miles (70,000 km) to travel from you to the satellite company.

Since the satellite is being used for two-way communications, the total distance increases to 88,000 miles (140,000 km), which takes a radio wave 466 ms to travel. Factoring in normal delays from other network sources gives a typical connection latency of 500-700 ms. This is far worse latency than even most dialup modem users experience, at typically only 150-200 ms total latency.

Reducing satellite latency
The only real alternative is to use satellites in much lower orbit very close to the Earth, to shorten the travel distance. Such orbital paths are no longer geostationary, and so would require a large number of satellites in orbit so that at least one is visible in the sky at all times. Communication dishes could no longer be fixed, and would either need some way to track the satellites as they move across the sky, or to work in an omnidirectional manner without causing interference for anything else. The lower orbits would also subject the satellites to a slight drag effect from the upper atmosphere, requiring a need for some way to boost the orbits back up as the satellites gradually slow down.

A theoretical alternative to satellites that is being explored is the use of ultralight solar-powered gliders that could fly in a continuous a circling path perhaps 70,000 feet (2 km) high. These would act as flying satellites, providing high-speed service to customers below the circling glider. Since the roundtrip signal distance would only be 30 miles, the latency caused by the speed of light is an almost insignificant 0.1 ms. (Note that the glider work is still in the earliest experimental stages.)

Remote DSL
This allows a service provider to set up DSL hardware out in the country in a weatherproof enclosure. However, setup costs can be quite high since the service provider may need to install fiberoptic cable to the remote location, using horizontal boring equipment at a cost of $1 million per mile ($600/m). Also, the remote site has the same distance limits as the metropolitan service, and can only serve an island of customers along the trunk line within a radius of about 7000 feet (2 km).

Remote DSL access is becoming a sore point for many rural customers, as the technology has been available for some time now and phone companies keep promoting its availability, but at the same time the phone companies keep dragging their feet and are not doing anything to install the remote services. This is particularly a problem with the very large multistate conglomerates that serve mostly rural areas.

DSL repeater
This is a very new technology which allow DSL to travel longer distances to remote customers. One version of the repeater is installed every 10,000 feet (3 km) or so along the trunk line, and strengthens and cleans up the DSL signal so it can travel another 10,000 feet (3 km).

Power-Line Internet
This is a new service still in its infancy that may eventually permit broadband Internet data to travel down standard high-voltage power lines. However, the system has a number of complex issues, the primary one being that power lines are inherently a very noisy environment. Every time a device turns on or off, it introduces a pop or click into the line. Energy-saving devices often introduce noisy harmonics into the line. The system must be designed to deal with these natural signaling disruptions and work around them.

The second major issue is signal strength and operating frequency. The system is expected to use frequencies in the 10 to 30 MHz range, which has been used for decades by ham radio operators. Power lines are unshielded and will act as transmitters for the signals they carry, and have the potential to completely wipe out the usefulness of the 10 to 30 MHz range for shortwave communications purposes.

Wireless ISP
This typically employs the current low-cost 802.11 Wi-Fi radio systems to link up remote locations over great distances, but can use other higher-power radio communications systems as well.

Traditional 802.11b was licensed for omnidirectional service spanning only 300 to 500 feet. By focusing the signal down to a narrow beam with a yagi antenna it can instead operate reliably over a distance of many miles.

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.

T-1/DS-1
T-1/DS-1 is a type of service which is possible for a rural customer desiring broadband speeds, but the cost can be in the hundreds or thousands of dollars per month depending on the distance from the provider.

These are highly-regulated services traditionally intended for businesses, that are managed through Public Service Commissions in each state, must be fully defined in PSC tariff documents, and have management rules dating back to the early 1980s which still refer to teletypes as potential connection devices. As such, T-1 services have very strict and rigid service requirements which drive up the provider's maintenance costs and may require them to have a technician on standby 24 hours a day to repair the line if it malfunctions. (In comparison, ISDN and DSL are not regulated by the PSCs at all.)

On August 13, 2004 the ISP Wanadoo (formerly Freeserve in the UK) were told by the Advertising Standards Authority to change the way that they advertised their 512 kbit/s broadband service in Britain, removing the words "full speed" which rival companies claimed was misleading people into thinking it was the fastest available service. In a similar way, on April 9, 2003 the Advertising Standards Authority ruled against ISP NTL, saying that NTL's 128 kbit/s cable modem service must not be marketed as "broadband". Ofcom reported in June 2005 that there were more broadband than dial-up connections for the first time in history

Broadband modem