论文标题
正确地对（分布式）大型MIMO建模TX和RX链 - 一致性的新基本见解
Correctly Modeling TX and RX Chain in (Distributed) Massive MIMO -- New Fundamental Insights on Coherency
论文作者
论文摘要
这封信表明，在文献中通常用于下行链路（分布式）大量MIMO的TX和RX模型不准确，也导致了不准确的结论。特别是，局部振荡器（LO）效果应在发射机链中建模为$+φ$，在接收器链中，即不同的符号。文献中的一个普遍误解是为这两个链使用相同的符号。通过正确对TX和RX链进行建模，人们意识到LO相包含在相互校准中，并且每当LO相位分开时，都必须进行新的相互校准（适用于时间漂移）。因此，自由运行的LOS和通常的理想互惠校准的假设（以实现盲目DL通道估计）都不是那么有用，因为它们需要过多的校准开销。取而代之的是，基本站的LOS应锁定，并应采用相对互惠校准与下行链路解调参考符号。
This letter shows that the TX and RX models commonly used in literature for downlink (distributed) massive MIMO are inaccurate, leading also to inaccurate conclusions. In particular, the Local Oscillator (LO) effect should be modeled as $+φ$ in the transmitter chain and $-φ$ in the receiver chain, i.e., different signs. A common misconception in literature is to use the same sign for both chains. By correctly modeling TX and RX chain, one realizes that the LO phases are included in the reciprocity calibration and whenever the LO phases drift apart, a new reciprocity calibration becomes necessary (the same applies to time drifts). Thus, free-running LOs and the commonly made assumption of perfect reciprocity calibration (to enable blind DL channel estimation) are both not that useful, as they would require too much calibration overhead. Instead, the LOs at the base stations should be locked and relative reciprocity calibration in combination with downlink demodulation reference symbols should be employed.
