A hierarchical TDD microcell/FDD macrocell CDMA system using antenna arrays and power ratio adjustments

In this paper, we present a new hierarchical cell system with an underlaid TDD/CDMA microcell and overlaying FDD/CDMA macrocells. With an objective to exploit the underutilized FDD uplink capacity due to traffic asymmetry, the TDD/CDMA microcell is operated within the uplink frequency band of the overlaying FDD/CDMA macrocells. By jointly applying the proposed antenna arrays at the cell site and a new power ratio adjustment technique, we evaluate the outage probabilities of the macrocell and the microcell. From the simulation results, we demonstrate that the full capacity of the TDD/CDMA microcell can be obtained without degrading the performance of FDD/CDMA macrocells.