Summing up the CSIs

A CSI is like a highway system that lays out  all the  many  roads that enable people to drive  to their destinations. Within our highway system, we could characterize some roads as being large or wide, some roads as small or narrow, and  some roads as being  between these two extremes. Roads may be further broken  down  by type  of surface, that is, asphalt, concrete, gravel, or dirt.

The wireless CSI

Wireless telecommunications have  been around for more  than eight decades. First we had  the  radio in the  1920s. During World War II, we had the  inception of walkie-talkies. These  led to the development of cell division multiple access (CDMA), one of the  most popular carrier services supporting cell phone net- working  today. In the  1960s, the  first wireless transports connected mobile telephones using  radio telemetry, which connected the  caller (using radio fre- quency channels) to the circuit-switched PSTN.
 

The hybrid fiber-coaxial CSI

When fiber-optic cable began to be deployed widely, the  cable companies started using  fiber to build  out  their infrastructure. But by that time,  much of the  coaxial cable infrastructure supporting localized connections had already been established. This is why a large share of today’s cable customers have  coaxial cable coming into their premises from the  nearby telephone pole.