Interference analysis of TDD-CDMA systems with directional antennas

This paper explores the advantages of using directional antennas in TDD-CDMA systems with asymmetric traffic. In a TDD-CDMA system, asymmetric traffic from neighboring cells may cause cross-slot interference, which can seriously degrade system capacity. We analyze the cross-slot interference of a TDD-CDMA system with a trisector cellular architecture, where three directional antennas are employed at each base station. We find that the directivity of directional antennas can provide an additional degree of freedom for allocating resources. This advantage enables the TDD-CDMA system to support asymmetric uplink and downlink traffic with different rates of asymmetry among neighboring cells in the entire system.