10.3.1.1 Transmission medium

Within CATV networks digital video signals are typically transmitted via 8-MHz channels. The theoretical maximum symbol rate ( r _s,max) depends on the roll-off factor (alpha) of the raised cosine filter. Hence, r _s,max = 8 MHz/(1 + alpha). For alpha = 0.15 this implies r _s,max = 6.96 MBaud.

In cable networks the transmitted signals attenuate after traveling a certain distance through the network. In order to obtain an adequate S/N at the receiving end, the cable network is equipped with repeaters. A repeater filters the noise and amplifies the digital signals to the required power level for further transmission through the network.

10.3.1.2 Signal reflection

The reflection of signals is another typical aspect of cable communication. This occurs, for example, when cables are not ideally connected. As a result, the cable impedance is no longer characteristic. At the point of connection a part of the signal is reflected and travels back in the direction of its origin. The reflected signal may be reflected once again...