EECS20N: Signals and Systems

Digital networks

Today's digital networks involve almost all of the sorts of signals and systems that we have discussed. Physically-based signals are involved in transport and perception-based signals such as audio and video are involved in multimedia services. Moreover, today's networks are mostly packet based, which means that they divide the digital information into chunks called packets that are transported separately. The packets carry address information that enables them to be separately routed. Arrivals of packets are event sequences. A sequence of packets can provide a logically continuous bit stream, for example to support digital telephony over the internet, even if underlying packets are separately routed and take different paths through the network. Call processing, which refers to the establishment and termination of telephone connections, and well as the establishment and termination of broadcast and multicast services on a network are event sequences. Voiceband data modems, which are still a major gateway to the internet, are a microcosm of the network, in that they also involve event sequences (call processing), physically-based signals (voice-like), and several types of signals and systems in between.