Information rate of a coaxial cable with various modulation systems

In contrast to inherently broadband media, such as radio, TE 01 waveguide, or guided coherent light, the attenuation of a coaxial cable increases rapidly with frequency. Thus, while for broadband media broadband transmission schemes (FM or PCM, for example) decrease the power required for a given channel capacity, they would seem to be ill-suited to coaxial cable. Idealized comparisons are made among digital systems which transmit pulses of various numbers of amplitudes or levels. These show multilevel digital pulse transmission or analog transmission to have greater channel capacity (in the sense of information theory) than digital pulse transmission. Practical difficulties or cost of instrumentation may, in particular instances, dictate the use of single-sideband frequency-division multiplex for efficient voice transmission or binary pulse transmission for efficient digital transmission. Multilevel pulse transmission is a possible alternative if problems of instrumentation can be overcome.