Research on Capacity of Multicarrier CDMA

Theorelical and mathematical analyses of multicarrier CDMA capacity planning are proposed and the expressions of capacity for multicarrier CDMA are derived both in uplink and downlink. Through extremum of a multivariate function (by Lagrange multipliers), the maximum capacity of multicarrier CDMA is achieved from the viewpoint of voice and data, respectively. Simultaneously, the important conclusions are got for multicarrier CDMA: when BS maximum transmit power is average distributed for all subcarriers, the maximum of capacity is achieved. Simulation results show that capacity of all kinds of service will decrease rapidly as average path loss increase. The essence is opened out between capacity and coverage: capacity and coverage restrict each other, decreasing in capacity means extend in coverage, and vice versa. When transmit power is in higher level, increasing power is not an effective way to improve capacity. From comparison between GSM, WCDMA and multicarrier CDMA, the conclusion are achieved that the spectrum efficiency of multicarrier CDMA is 1.7 times that of WCDMA, and 2.7 times that of GSM in downlink; and 2.1 time that of WCDMA, and 2.4 times that of GSM in uplink.