Performance Evaluation of A Cross-Link Interference Canceller for Dynamic TDD in Distributed Antenna Systems

A DAS (distributed antenna system) which covers a service area using multiple DAs (distributed antennas) has been considered for mobile communications that utilize high frequency bands. In dynamic TDD (Time Division Duplexing) which allows each DA to independently switch transmission timing of up/downlink signals, a DA might receive downlink signals from the other DAs, in addition to the desired uplink signal from user equipment. It causes cross-link interference, which in turn leads to a serious transmission quality degradation of the uplink signal.To address this problem, a new cross-link interference canceller has previously been proposed. It successively cancels interfering downlink signals in descending order of their received interference power at a DA, using highly accurate replicas generated based on each downlink signal stored at the DAS base station. While previous study has shown the BER (bit error rate) performance improvements for QPSK modulation scheme, this paper extends the evaluation to 16QAM and 64QAM through computer simulations. The simulation results clarify the required number of downlink signals that must be canceled to achieve a target BER for each modulation scheme and confirm that the proposed canceller significantly improves BER performances under dynamic TDD operation.