Elimination of Interference Non-Reciprocity in TDD MIMO-OFDM Systems

In wireless communications systems with time-division duplex (TDD) deployment, channel reciprocity and symmetric interference between transmitter and receiver sides are two widely-adopted assumptions for the design of optimal adaptation transmission mode. However, in practice, there is an undesirable but non-negligible effect, namely the asymmetric interference, that makes the assumptions no longer valid. In such a case, the downlink modulation/coding parameters assigned based on the uplink measurements may lead to excessively high frame error rate (FER). In this paper, a simple closed-loop feedback method of compensating interference asymmetry in TDD multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems is proposed, which makes the transmit side estimated interference tracks the instantaneous receive side interference dynamically. The proposed method maintains constant FER by adopting adaptive modulation coding (AMC) and power loading. The final simulations have verified the effectiveness of the new method.