Efficient use of the radio spectrum and bandwidth expansion

Using the definition that the most efficient use of the radio-frequency spectrum is that which produces maximum communication with a point or into and through an area, it is shown that considerable bandwidth expansion is required to achieve optimum communication capacity. The effectiveness of digital modulation in trading bandwidth for interference protection is demonstrated in the environment of a dense urban network. The considerable benefits obtained from the use of highly directive antennas with small off-angle response are demonstrated. Effects produced by reflection and scattering from objects on or near the radio path are studied parametrically. It is concluded that very large amounts of communication can be realized in a restricted area and bandwidth if bandwidth expanding digital modulation techniques are employed in combination with high-quality antennas mounted so as to minimize effects of the environment.