A spectrally overlaid flexible bandwidth utilization scheme for cellular CDMA systems

Future wireless communication systems need to utilize bandwidth very efficiently in order to manage the evergrowing traffic conditions. The capacity of a link can be improved by spectrally overlaying narrowband subsystems over a single wideband subsystem. A micro/macro cellular CDMA overlay system is considered. The important issues such as the interference and the desired user signal power in the reverse link, the system parameters affecting the reverse link capacity, the spectral overlay ratio and distance between microcells and macrocells base stations are analyzed. The relative power used, the interference obtained due to the neighbouring cells and maximum total throughput in a particular cell have been analyzed. A real time simulation of a CDMA system in a cellular environment consisting of several narrowbands overlaid on a wideband system is carried out which clearly shows the capacity tradeoffs between the narrowband and wideband CDMA systems.