Cellular system offers very high capacity in a limited spectrum allocation without any major technologies changes.
It replaces a single high power transmitter(large cell) with many low power transmitters(small cells).
It only provides coverage to small portion of area.
Each BS is allocated a portion of the total numbers of channels available to the entire system and nearby BSs are assigned different groups of channels so that all available channels are assigned to a relatively small number of neighboring BSs
Neighboring BSs are assigned different groups of channels so that the interference between BSs is minimized.
Concept of Frequency Reuse
Each and every base station is allocated a group of radio channels to be used within a small geographic area called "Cell".
The base station antennas are designed to achieve the desired coverage within the particular cell.
By limiting the coverage area to within the boundaries of a cell, the same group of channels may be used to cover different cells.
The design process of selecting and allocating channel groups for all the cellular base stations within a system is called frequency reuse.
Basically, hexagonal cell shape is used for conceptual and symbolic model of the radio coverage since fewer number of hexagonal shapes can cover a geographic region.
