Capacity analysis of spectrally overlaid narrowband and wideband CDMA systems for future mobile communications services

As a means of CDMA network evolution toward future wireless services, a spe ctral overlay of narrowband CDMA (N-CDMA) and wideband CDMA (W-CDMA) system s is proposed in [8]. In order to justify the overlaying strategy, the reve rse link capacity is examined in the same work. Although the capacity of co nventional CDMA cellular systems is usually limited by the reverse link, th e limit could occur at the forward link depending on the transmission techn ologies adopted by specific CDMA proposals. Especially, the number of users that can be simultaneously accommodated in the system would be limited by the forward link in future mobile service environments where unequal traffi c is offered between two links. In this paper, we first examine the forward link capacity of the spectrally overlaid narrowband and wideband CDMA (N/W CDMA) system. And we compare it with the reverse link capacity to obtain t he overall performance. The effects of various parameters on the capacity o f N/W CDMA system are numerically evaluated for different mobile environmen ts.