上下行信道不对称性对TDD-MIMO系统的影响

Effect of the Asymmetry between Downlink and Uplink on TDD-MIMO Systems

时分双工和多输入多输出技术均是超三代移动通信中的关键技术。在传统的关于时分双工的文献中,发送端信道状态信息均通过上下行信道的对称性获得。然而实际中由于受温度、湿度等影响,射频电路增益会缓慢变化,于是关于上下行信道对称的假设不再成立,这必定会对性能产生影响。本文详细分析了该影响并提出通过采用射频电路参数反馈法来解决这一问题。仿真结果表明,相对于传统的上行信道重用法,采用射频参数反馈法提高了系统信道容量。

Time-Division Duplex （TDD） and Multiple-Input Multiple-Output （MIMO） are the key techniques in the beyond third generation （B3G） mobile communication systems. In the conventional literatures on TDD, the channel state information at transmitter is obtained by assuming the reciprocity between uplink and downlink. However, affected by the unbalance of the Radio-Frequency （RF） circuitries in practice, the reciprocity between uplink and downlink can not be maintained, which will cause a decrease of the performance. In this paper, the asymmetry effect is analyzed in detail and the RF feedback strategy is proposed to eliminate it. Simulation results show that the RF feedback strategy performs much better than the conventional uplink reuse and the capacity of the MIMO systems is greatly improved.