Broadband Internet access: Encyclopedia II - Broadband Internet access - Technology

Broadband Internet access - 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.

Broadband Internet access - 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.

Broadband Internet access - 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. In the United States, this is particularly a problem with the very large multistate conglomerates that serve mostly rural areas.

Broadband Internet access - 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).

Broadband Internet access - 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.

Broadband over power lines (BPL) has developed faster in Europe than in the US due to a historical difference in power system design philosophies. Nearly all large power grids transmit power at high voltages in order to reduce transmission losses, then near the customer use step-down transformers to reduce the voltage. Since BPL signals cannot readily pass through transformers, repeaters must be attached to the transformers. In the US, it is common for a small transformer hung from a utility pole to service a single house. In Europe, it is more common for a somewhat larger transformer to service 10 or 100 houses. For delivering power to customers, this difference in design makes little difference, but it means delivering BPL over the power grid of a typical US city will require an order of magnitude more repeaters than would be required in a comparable European city.

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, as well as international shortwave broadcasters and a variety of communications systems (military, aeronautical, etc.). 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.

Broadband Internet access - 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.

Broadband Internet access - 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.)

People attempting to establish rural service via a Wireless ISP, ISDN, or T-1 will run into an additional cost issue, where the physical connection (or local loop) is considered separate from the actual Internet service provided from a Point of Presence (POP). This is as if you had to pay the water utility to rent the water main in the ground, in addition to paying to get water delivered through the main from the tower. For a T-1, for example, in the US the loop alone may cost $1200 per month, and the 1.5 megabit per second business-class Internet service (with fixed a IP address and a subnet) may cost an additional $1000 per month. Attempting to reduce monthly costs by establishing your own non-profit Wi-Fi network and sharing the T-1 connection costs has an additional pitfall: your service provider may want to charge you an additional "ISP reseller's fee" of $800 per month.

Adapted from the Wikipedia article "Technology", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki