The twisted pair copper wire network is quite dense because of the telecommunication construction over the past hundreds of years. Besides, coaxial cable network of the cable TV system, fiber network, power supply network, and wireless communication have been considered as the replacement as well. Fiber is without doubt the best candidate but not widespread enough. Power supply network and wireless cannot combine both a longer transmission distance and a higher transfer rate. Therefore, cable modems that operate on the coaxial cable network of the cable TV system become the only competitor of ADSL modems.
Some countries have the same density for their cable network as telecommunication network.
At the time that the copper wire operated at the bandwidth of 200KHz, the coaxial cable already has a surprising bandwidth of 500MHz for video transmission. Everywhere in the Internet is full of business change. Of course, the cable TV companies will not miss any chance to get involved in the Internet business. Similar to ADSL's skip of the frequency range of the telephone service to ensure the backward compatibility, cable modem also uses the non-occupied channels for data service. Depending on the quality of the channel, each 6MHz-wide NTSC channel can provide a data channel at the rate ranging from 30Mbps to 40Mbps.