5G NR/LTE学习笔记: 多天线传输

我们听过时空复用，频分复用，多天线实际上是空分复用。
我们常常听到TM = transmission mode这个传输模式，就是表示不同的天线传输模式，或者再通俗地讲，就是每个天线的端口 port的数据是如何映射到时频资源块的。同时不同的传输方式下，用不同的参考信号，和CSI的类型。

The symbols of each antenna port are subsequently applied to the OFDM > modulator – that is, mapped to the basic OFDM time–frequency grid > corresponding to that antenna port.

目前传输方式有：

• Transmission mode 1: Single-antenna transmission.
• Transmission mode 2: Transmit diversity.
• Transmission mode 3: Open-loop codebook-based precoding in the case of more than one layer, transmit diversity in the case of rank-one transmission.
• Transmission mode 4: Closed-loop codebook-based precoding.
• Transmission mode 5: Multi-user-MIMO version of transmission mode 4.
• Transmission mode 6: Special case of closed-loop codebook-based precoding limited to singlelayer transmission.
• Transmission mode 7: Release-8 non-codebook-based precoding supporting only single-layer transmission.
• Transmission mode 8: Release-9 non-codebook-based precoding supporting up to two layers.
• Transmission mode 9: Release-10 non-codebook-based precoding supporting up to eight layers.
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