| There has been considerable recent interest in MIMO system, due to its potential for significant gain in channel capacity. By using channel reciprocity in time division duplex (TDD) MIMO systems, channel state information (CSI) was directly provided to BS, which reduced the additional system overhead. But in fact,channel reciprocity was destroyed because of unsymmetrical interference between uplink and downlink. To solve this problem,the impact of interference on the channel reciprocity of TDD-MIMO systems was analyzed. The main contributions are as follows:1 Simulation model of single-link MIMO-OFDM systems are built, and the key technologies in the system such as precoding and water flooding are analyzed in detail. 3GPP spatial channel model is studied and several environments used in simulation are introduced.2 Simulation model of multi-cell multi-user systems are built based on SCM-E channel model. Difference of interference between uplink and downlink in the previous models was compared.3 System capacity is derived and verified in different simulation scenarios. Simulation results show that interference destroys the channel reciprocity and degrades the system capacity of TDD-MIMO systems.4 A new interference suppression algorithm is given, which is used to suppress inter-cell interference and intra-cell interference. Its performance is simulated in different environments. Simulation results show that, interference can be suppressed effectively by the proposed algorithm without any feedback for the transmitter. |
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