Frequency planning techniques for cellular mobile radio systems

Abstract

The thesis considers a number of aspects of intermodulation interference phenomena as they arise in conventional mobile radio systems and may be anticipated to occur in cellular radio systems. Early Chapters take as a starting point the assumption that spectrum pollution by intermodulation originates in inter-transmitter interactions at communal base station sites and extends previouswork on the generation of intermodulation compatible frequency assignments by developing a recurrence relationship for derivation of fifth older compatible frequency lists. Extension of this work to the case of cellular radio systems considers the problem of frequency assignment in cell clusters to achieve intermodulation compatibility. General formulae are developed for identifying the frequency bands accepted by intermodulation-products of any specified order and relationships are demonstrated between the achievement of third order compatibility, cell cluster size and minimum transmitter frequency spacing (a factei which has important implications in multicoupler design). The thesis concludes by turning attention to the interference characteristics of receivers and it is shown that receiver generated intermodulation may represent a major factor in limiting the overall effectiveness of cellular systems in terms of user capacity per sq km per MHz of allocated bandwidth. Estimates are made of interference probabilities due to intermodulation in centre illuminated cells and consideration given to the relative merits of centre and corner illumination strategies.