DSL Options


• Family of transmission technologies that move data over copper pairs

• Different types of xDSL (Asymmetric/Symmetric)

• All types of DSL are Layer 1 technologies

• ATU-C = ADSL Transmission Unit - Central

DSL is a group of technologies that use the unused bandwidth on a regular copper telephone line to deliver fast digital data transmission. DSL connections are as easy to obtain as dial access. Like leased lines, DSL connections can be always on if the DSL modem of the customer connects to a CO DSL termination. Occasionally, the DSL modem may need to place a telephone call if the provider has oversubscribed the service.

There are two disadvantages to DSL:

1. DSL has a maximum distance requirement from the PSTN CO of 18,000 feet.

2. Not all PSTN central offices have been built-out to support DSL. As a result, you may live in a neighborhood that is not serviced by a DSL-capable CO while a neighborhood down the street may have access to DSL service.

© 2004 Cisco Systems, Inc. All rights

Satellite Options

Satellite Options

• First came the original (bigger) C-band backyard satellite dish in the 1980s

• Followed by direct broadcast satellite (DBS) in the 1990s

• DBS uses smaller-size dishes to receive the satellite signals

• The satellite orbits the earth 22,300 miles above the equator

The main issue that satellite access resolves is getting high-bandwidth remote access to places without a high-bandwidth infrastructure. The only way to receive broadband communications in many rural or low-population areas is via a two-way satellite.

Satellite services deliver downstream data in bursts up to 400 kbps, with upstream speeds as much as 125 kbps. A computer connected to the satellite network does not require time-consuming dialup protocols to log in. However, because of the asymmetric nature of satellite communication, certain applications such as VoIP do not perform very well over satellite. Also, heavy activity on the network can affect satellite speeds.

The typical satellite system requires a small, 1.2-meter or less satellite dish, two standard coaxial cables to connect the satellite dish to a satellite modem, and a satellite modem that connects to a PC through an Ethernet or Universal Serial Bus (USB) port. The latest satellite systems allow subscribers to send and receive information using a satellite dish and still receive television programming.

Satellite networks include geostationary orbit (GSO) satellites and nongeostationary orbit (NGSO) satellites. The latter includes low-earth orbit (LEO) satellites. Latency is higher for GSO satellites than for LEO satellites because the GSO is much higher. Most broadband satellite options use a satellite in orbit approximately 22,300 miles above the equator.

© 2004 Cisco Systems, Inc. All rights

Wireless Options

Wireless Options

© 2004 Cisco Systems, Inc. All rights

© 2004 Cisco Systems, Inc. All rights

Wireless technology provides line-of-sight bridging at 2-Mbps throughput at distances of up to 25 miles (40.2 km) in U.S. Federal Communications Commission (FCC)-regulated countries or 6.5 miles (10.5 km) in Europe. This technology can provide up to 11-Mbps connectivity from one site to another or from the main site to many remote sites. You need only a bridge and an antenna for each site, which can connect to either a wired or wireless network within those sites. Wireless technology also enables multiple buildings to share a single high-speed connection to the Internet without cabling or dedicated lines. However, you must have line of sight.

Fixed-wireless systems have a long history. Point-to-point microwave connections have long been used for voice and data communications. As technology has continued to advance, higher frequencies have been employed. Thus, smaller antennas can be used, resulting in lower costs and easier-to-deploy systems for private use. The reduction in cost has resulted in a whole generation of carriers that are planning to use wireless access as their last mile of communication.

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