Suppression of non-reciprocal interference in adaptive MIMO-OFDM cellular systems

In a time-division-duplex system the channel state information can be obtained at the transmitter side due to channel reciprocity and it can be used to increase the spectral efficiency of a multiple-input multiple-output (MIMO) system. However, the interference structure between transmission directions does not necessarily correlate. The transmission parameters assigned based on the reverse link measurements may lead to excessively high frame error rates, if the interference structure between transmission directions differs significantly. In this paper, the performance of an adaptive MIMO-OFDM cellular system is studied in the presence of non-reciprocal multi-cell interference when the downlink interference structure is known at the receiver and/or also known at (reported to) the transmitter. The impact of realistic interference non-reciprocity scenarios for continuous real-time services is studied. Linear minimum mean squared error (MMSE) filter is applied at the receiver to suppress the impact of structured inter-cell interference, together with a simple and bandwidth efficient closed-loop compensation algorithm. Both link and system level simulation results show that the performance gain from interference suppression in the receiver is high, especially at low signal-to-interference-plus-noise ratio (SINR) region (close to the cell edge). The proposed MMSE receiver combined with simple scalar power offset feedback to the transmitter results in nearly the same performance as the case where the interference structure per sub-carrier is perfectly known at the transmitter.