Multi-layered underlay overlay frequency planning scheme for cellular networks

Conventional frequency planning techniques allow only a single frequency reuse factor for the whole system. This reuse factor is determined by the performance of the user at the cell boundary. Consequently this scheme does not take advantage of the higher reception quality of users close to the base station. Underlay overlay (UO) systems that have been proposed for TDMA cellular networks take advantage of the high reception quality of users close to the base station and improve the frequency efficiency of the system. In this paper a multilayered UO system is considered where the layer boundaries are defined by the mean C/I threshold. The analysis presented considers the dimensioning of multilayered UO systems and the frequency efficiency of the UO system is compared with the conventional single layered frequency reuse systems. The analysis shows that the UO system can provide 25-40% and 20-25% improvement in frequency efficiency in GSM and IS-54 TDMA (DAMPS) networks respectively.