Location-aware ICI Reduction in MIMO-OFDM Downlinks for High-speed Railway Communication Systems

摘要

High mobility may destroy the orthogonality of subcarriers in OFDM systems,resulting in inter- carrier interference (ICI), which may greatly reduce theservice quantity of high-speed railway (HSR) wireless communications. Thispaper focuses on ICI mitigation in the HSR downlinks with distributed transmitantennas.For such a system, its key feature is that the ICIs are caused bymultiple carrier frequency offsets corresponding to multiple transmit antennas.Meanwhile, the channel of HSR is fast time varying, which is another bigchallenge in the system design. In order to get a good performance, lowcomplexity real-time ICI reduction is necessary. To this end, we first analyzedthe property of the ICI matrix in AWGN and Rician scenarios, respectively.Then, we propose corresponding low complexity ICI reduction methods based onlocation information. For evaluating the effectiveness of the proposed method,the expectation and variance of remaining interference after ICI reduction isanalyzed with respect to Rician K-factor. In addition, the service quantity andthe bandwidth and computation cost are also discussed. Numerical results arepresented to verify our theoretical analysis and the effectiveness of proposedICI reduction methods. One important observation is that our proposed ICImitigation method can achieve almost the same service quantity with thatobtained on the case without ICI at 300km/h,that is, ICI has been completelyeliminated. Numerical results also show that the scenarios with RicianK-factors over 30dB can be considered as AWGN scenarios, which may providevaluable insights on future system designs.