CSI-RSs consume fewer air interface resources to perform channel measurement/feedback.It can be used for power measurements to estimate path loss and channel quality but due to limited bandwidth and low duty cycle, SS Block is not very suitable for more detailed channel sounding aimed at tracking channel properties that vary rapidly in time/frequency. SS Block is transmitted over a limited bandwidth but with a much larger periodicity compared to LTE CRS. Why SS Block is not used for channel sounding in 5G NR?
Also, CSI-RS is transmitted on different antenna ports (15-22) than CRS and CSI-RS uses code-domain orthogonality along with time/frequency orthogonality unlike CRS which used only time/frequency orthogonality.Īs 5G NR minimizes always on strategy (Except for SS Block), there are no CRS-like signals in NR, but the same concept of CSI-RS is reused and extended in NR to provide support for beam management and mobility in the connected mode.
Extending CRS to 8 layers would have added more signaling overhead than desired, resulting in introduction of CSI-RS. In contrast to Cell Specific Reference signal (CRS) from LTE Release 8, LTE release 10 introduced this concept of CSI-RS with the addition of up to 8-layer spatial multiplexing where the Reference Signals are not transmitted continuously, which led to requirement of 8-layer channel estimation while only 4-layer spatial multiplexing was used in LTE Release 8. What is the difference between CSI-RS and CRS?ĬSI-RS is configured per device rather than per cell, as it was in LTE. These are well defined reporting parameters and comprises of: Channel state information (CSI) is the way of indicating certain reports by the UE to the network.
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