Radio Wave Spectrum
The radio waves are distributed in 3Hz ~ 3000GHz. This spectrum is divided into 12 bands, as shown in the above table. The frequencies in each specific band present unique propagation features: The lower the frequency is, the lower the propagation loss will be, the farther the coverage distance will be, and the stronger the diffraction capability will be.
However, lower-band frequency resources are stringent and the system capacity is limited, so they are primarily applied to the systems of broadcast, television and paging. The higher-band frequency resources are abundant and the system capacity is large;
however, the higher the frequency is, the higher the propagation loss will be, the shorter the coverage distance will be, and the weaker the diffraction capability will be.
In addition, the higher the frequency is, the higher the technical difficulty will be, and the higher the system cost will be. The band
for purpose of the mobile communication system should allow for both coverage effect and capacity. Compared with other bands, the UHF band achieves a good tradeoff between the coverage effect and the capacity, and is hence widely applied to the mobile communication field. Nevertheless, with the increase of mobile communication demand, more capacity is required. The
mobile communication system is bound to develop toward the high-frequency band.