Broadband Access: Wireline and Wireless - Alternatives for Internet Services

9Advanced DSL Techniques and Home Networking

9.1 Repeaters and Bonding

A repeater is a transmission device placed near the mid-point of a telephone line that receives an attenuated and distorted signal and then transmits a pristine digital copy at full power over the remaining portion of the line. A repeater placed at the mid-point of the line cuts the effective length of the line in half, thereby enabling a given bit rate to be sent approximately twice the distance. Two or more repeaters may be inserted into the line at approximately equidistant positions, thereby increasing the attainable line reach by a factor of three or more. For a fixed distance between the network and customer, repeaters can also be used to provide a higher data rate.

A repeater is essentially a pair of back-to-back receivers and transmitters. For each direction of transmission, the signal is received, the modulated symbols are detected, and then a new, full-power signal is transmitted to the remaining section of the line. A regenerator is similar to a repeater, but it does not detect the modulated symbol. A regenerator performs analog amplification and, possibly, filtering. It is a simpler device, but it provides less performance because the noise is amplified as well as the signal.

Repeaters are similar to bonding, because both techniques may be used to increase the total line length for a given service bit rate or to increase the service bit rate for a given line length. The price paid for bonding ...