Capacity analysis of macro/microcellular CDMA with power ratio control and tilted antenna

The reverse link capacity is obtained analytically for macro/microcellular code-division multiple-access (CDMA) systems operating in the same frequency band. The focuses are on the ratio of required receive power of the macrocell base station (BS) to that of the microcell BS and the tilt angle of the microcell antenna to increase the system capacity. The microcell-to-macrocell interference is derived in closed form by geometric approximation, and the macrocell-to-microcell interference is calculated on the divided regions of macrocell. The optimal tilt angle is obtained by defining the minimum interference tradeoff factor that maximizes the system capacity. It is shown that the system capacity increases remarkably with power ratio control in macro/microcellular environments. Also, the properly chosen antenna tilt angle adds more capacity, and enables the microcell users to save on the transmit power