Capacity improvement in UMTS by dedicated radio resource management

The IMT-2000 standard UMTS (universal mobile telecommunications system) is based on wideband CDMA (code division multiple access). The service quality in terms of coverage, data rates, bit error rates, etc., and the system capacity depend on the radio resource management (RRM), i.e., the service-specific dynamic allocation of transmit powers, spreading factors, and codes to the individual users. In addition, macrodiversity allows "soft handoff" and load distribution between adjacent cells. Two new dedicated downlink RRM functions are presented to increase the average signal-to-interference power ratio (SIR) and the user capacity, taking into consideration the assignment of scrambling codes (SC) and the power allocation in case of macrodiversity. The presented scrambling code allocation method is shown to enhance the cell capacity in a UMTS-FDD system. The improvement is derived analytically and confirmed by statistical system simulations. For macrodiversity, a combination of power partitioning and pilot power control can increase the capacity of a single cell. The size of macrodiversity areas can be adjusted to a certain extent by these mechanisms. Thus, the power resources of less loaded cells can be exploited more efficiently.