Chapter 9. High-Speed Digital Access: DSL, Cable Modem, and SONET. 9.1 DSL Technology. ADSL Other DSL Technologies. Note :. ADSL is an asymmetric communication technology designed for residential users; it is not suitable for businesses. Note :.
High-SpeedDigital Access:DSL,Cable Modem,
9.1 DSL Technology
Other DSL Technologies
ADSL is an asymmetric communication technology designed for residential users; it is not suitable for businesses.
The existing local loops can handle bandwidths up to 1.1 MHz.
ADSL is an adaptive technology. The system uses a data rate based on the condition of the local loop line.
Figure 9.3ADSL modem
9.2 Cable Modem
Traditional Cable Networks
CM and CMTS
Figure 9.5Traditional cable TV network
Communication in the traditional cable TV network is unidirectional.
Figure 9.6HFC network
Communication in an HFC cable TV network can be bidirectional.
Figure 9.7Coaxial cable bands
Downstream data are modulated using the 64-QAM modulation technique.
The theoretical downstream data rate is 30 Mbps.
Upstream data are modulated using the QPSK modulation technique.
The theoretical upstream data rate is 12 Mbps.
Figure 9.8Cable modem
Synchronous Transport Signals
SONET is a synchronous TDM system controlled by a master clock.
Figure 9.10A SONET
Figure 9.11Frame format
Table 9.1 SONET rates
Figure 9.12Data rate
Figure 9.13VT types
Figure 9.14STS multiplexing