Radio Resource Sharing and Capacity of Some Multiple Access Methods in Hierarchical Cell Structures

To decrease total system cost and improve efficiency, in future mobile communication systems, we can implement a structure of multiple cells covering an area. This is often referred to as a Hierarchical Cell Structure, HCS. We compare five methods of sharing the scarce radio resources in a two layer HCS: I) DS-CDMA in macro cells and TDMA in micro cells, II) TDMA in macro cells and DS-CDMA in micro cells, III) DS-CDMA in both macro and micro cells on the same frequency band, IV) TDMA in both layers with frequency splitting and V) TDMA in both layers with reuse of macro frequencies in micro cells. Through simulation we study the system capacities i.e. the number of users supported per cell. Highest capacities are achieved by method IV and V. Method V could also be used in a CDMA type of system if it is possible to have more than one carrier.