On the maximum uplink capacity per km2 of CDMA systems

In the recent literature, many works have concentrated on system performance of CDMA networks. In particular, numerous analytical derivations of CDMA cell capacity have been carried out. However, to the authors´ knowledge, the issue of capacity per km² has never been addressed directly nor extensively in the past. In the present work, a thorough analysis of coverage and capacity issues for the reverse link is conducted, leading to a theoretical evaluation of the capacity per km² of CDMA systems. Our approach applies to a multicell environment and takes into account voice activity and imperfect power control. The blocking probability in conjunction with minimum received power constraints at the base station are derived. In addition to this, we consider the capacity limits of a CDMA system. The maximum achievable capacity per km² is viewed as a meaningful figure of merit for a cellular system and a method is proposed here to estimate the minimum achievable distance between adjacent base stations in the case of CDMA. The probability for entering in soft handover state is used as a limit for densification in a CDMA system. From this criterion, conditions on the minimum possible cell radius are derived. It is shown that the capacity of CDMA systems in maximum densification conditions can be evaluated in a rigorous way. Hence this approach allows to evaluate and compare different CDMA technologies. The IS-95 system is treated as an example to illustrate the application of the method