Improving the Erlang capacity of a CDMA cellular network under bursty user mobility

Considerable efforts in the recent technical literature have been devoted to the capacity evaluation of the radio interface of mobile cellular networks adopting CDMA. However, few works cater for the variability of the user spatial density due to mobility, which could impact significantly on offered traffic characteristics and hence on the CDMA radio interface capacity, especially in a microcellular environment. The major aim of this work is to define traffic control mechanisms to counteract the detrimental effects of large fluctuations of 'bursty' user mobility on the capacity of the CDMA radio interface. To this end, we introduce a user mobility model apt to describe large fluctuations of the number of users in a radio cell area. We use a reference model of a CDMA network, accounting for shadowing, call attempt process, voice activity and antenna directivity and assuming perfect power control. We show that, in cases when user mobility can remarkably affect the CDMA capacity, admittance threshold based traffic control schemes improve significantly the CDMA radio interface capacity. Both off line optimal setting of threshold and an adaptive threshold mechanism are defined.