A statistical approach to the analysis of DS/CDMA cellular radio systems

Abstract

This thesis presents mathematical models to estimate the system performance of DS/CDMA cellular radio systems. These models are developed to study the effects of the propagation environment, multiple interferers and performance enhancing techniques on the system performance. This work is not restricted to the analysis of any one particular system, but could be used to analyse the performance of a range of DS/CDMA cellular systems. Mathematical tools of this kind are becoming increasingly useful to system planners as they are forced to design spectrally efficient cellular radio systems. A statistical approach is used in the development of the mathematical models presented in this thesis. This statistical approach has previously been used to analyse the performance of DS/CDMA cellular systems. However, in these analyses only the immediately adjacent interferers with equal means were considered. The mathematical models developed in this thesis not only treat multiple interferers with unequal mean powers but also consider the independent variability of each interferer. Prior to this research systems of this nature were generally studied using time consuming simulation techniques. The statistical approach used in this thesis significantly reduces the computational time required for the estimation of system performance. The system performance measures (average BER, service reliability) are estimated as a function of either the number of active users per cell or the average signal-to-interference ratio. These results are later used to estimate blocking probability of the system as a function of offered traffic. The performance measures are estimated using statistical descriptions of the received signals (both desired and interfering). The derivation of expressions for system performance measures for situations where signals suffer both fast fading (Rayleigh fading or Nakagami_m fading) and log-normal shadowing simultaneously have been the major aim of this research. Practical DS/CDMA cellular systems employ performance enhancing techniques such as diversity reception and error correction. The analysis of these techniques is also considered in this thesis.