Interference diversity through random time slot opposing (RTO) in a cellular TDD system

In this paper a new dynamic channel assignment (DCA) technique for a time division duplex (TDD) air-interface is proposed. This DCA exploits the fact that a cellular TDD system experiences additional interference scenarios compared with a frequency division duplex (FDD) air-interface. The principle of interference diversity is utilised to reduce the total interference from neighbouring cells. This is achieved by a new DCA algorithm which is named: random TS opposing (RTO) algorithm. It is demonstrated that even for up to 90 % of all users, the new RTO algorithm yields a significant interference reduction (minimum 3 dB) compared with systems that are operated using disjoint uplink and downlink channels through the entire network (e.g. the FDD mode). The gains are in the range of 3 dB - 10 dB with the largest gains obtained in the uplink direction. The RTO algorithm enables great flexibility since cell independent asymmetry can be supported without loss of system performance.