A cellular land mobile radio network is a collection of base stations (BSs) that serve defined geographical areas called cells. By integrating the coverage over a plurality of cells, continuous radio coverage is provided over a large geographic area. Cellular systems partition the available radio resources among the cells, and the radio resources are reused in geographically separated cells. Frequency reuse causes co-channel interference, which is the primary impediment to high-capacity cellular systems. Radio resources are generally reused at the closest possible geographical distance that the cellular link budget will allow. The chapter begins with the concept of cellular frequency reuse. It is explained how cell splitting can be used to accommodate traffic growth in a cellular deployment. Frequency planning is considered for OFDM/OFDMA air interfaces used in 4G and 5G cellular systems. The cellular link budget is introduced that is critical for cellular deployment, including margins in the link budget for co-channel interference, shadowing, and handoff gain. The chapter concludes with the coverage and spectral efficiency of cellular systems.