CDMA capacity with added carriers in a cellular network

The question of how many users a code division multiple access (CDMA) system can accommodate as multiple radio-frequency (RF) carriers are added to the system is of increasing interest as the number of users increases. We study this problem by considering the forward-link capacity when the system is interference limited. We show that the probability of blocking for fixed traffic per carrier decreases as the number of carriers is increased. Trading this decrease in blocking probability for an increase in the per-carrier traffic with the addition of carriers would constitute conventional trunking efficiency. Our analysis demonstrates that, under a set of simplified field conditions, the power requirements of users increase rapidly as the per-carrier traffic increases above the single-carrier capacity, thereby limiting an increase in the per-carrier traffic as the number of CDMA carriers is increased. This limitation in the capacity increase with the addition of carriers is due to a single-carrier capacity in CDMA that is already quite high and close to fundamental limits.