Why 5G NR has not opted for CRS and instead used CSI-RS?

5G NR
1

Hi Experts.

Why 5G NR has not opted for CRS and instead used CSI-RS?

Disadvantages of CRS:

  1. Wastage of power due to always on signal
  2. It is transmitted (omnidirectional)across the cell area irrespective of the Ue position.
  3. More RE is used for sending CRS.
  4. It cannot be used for Beamforming because of its omnidirectional nature.

Advantages of CSI- RS:

  1. It is ue specific and configured via rrc reconfiguration.
  2. It saves energy compared to CRS
  3. Transmitted in less RE (1 or 2 RE)
  4. It is used for Beamforming because it is ue specific.

Exception: Though TM-8 defines Beamforming using CRS. But there is no deployment because of limitations of CRS omnidirectional signal characteristics.

CRS: Cell reference signal
CSI-RS: Channel state information reference signal
RE: Resource elements.

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