A framework for analyzing the user membership in cellular CDMA networks

A theoretical framework is developed to analyze the user membership in cellular networks. The main interest is on code-division multiple-access (CDMA) networks, although the validity of the proposed approach is not restricted to these networks. The membership of a user terminal to a certain base station (BS) is established if the local mean attenuation to this BS is the lowest one among all surrounding BSs. The estimate of local mean attenuation on the radio links from a mobile terminal to each of the surrounding BSs is carried out through proper filtering of the sequences of received signal strength measurements taken on broadcast signals at regular time intervals. In CDMA networks, pilot channels can be considered, while broadcast control channels can be generically considered in narrow-band systems. A decision is made each time on whether the terminal is to be assigned to its "current" BS or if it would be better served by a different BS. Two performance measures are considered: the probability that the best BS is not selected and the average number of membership switchings per time unit. A channel model with log-normal shadowing and fast fading superimposed is considered. Analytical expressions for the above-mentioned performance measures are derived in a general system scenario. From numerical results, it is seen that a proper choice of filter parameters is required to achieve the lowest values for both performance measures. Moreover, these values are not negligible when the mobile terminal is close to a boundary cell region. The obtained results are considered to be of interest in handover and power control algorithms.