Traffic control schemes in hierarchically structured CDMA cellular systems

Abstract

Hierarchical cell structure(HCS) describes a system where at least two types of cells (e.g, macrocell and microcell) operate one upon another. Due to increasing demand in the capacity of future cellular systems, HCS is expected to be increasingly popular trend in cellular system design. In this thesis, first, we analyzed capacity of hierarchically structured CDMA cellular systems with a hot spot microcell overlayed in a macrocell. The analyses were performed for systems providing only voice service as well as voice and data service. Further, we proposed a traffic control mechanism for HCS, which dynamically adapts to varying traffic environment by redistributing traffic between macrocell and microcell. The proposed scheme dynamically adjusts coverage area of microcell to maintain a required signal to interference ratio in both microcell and macrocell. Performances were measured in terms of call blocking probability and call failure probability. Performance improvements were significant especially when microcell is heavily loaded while macrocell is lightly loaded.