What is the periodicity of CSI-RS signals repetitions?

Hello Experts,
In your experience, what is the periodicity of CSI-RS signals repetitions?
I have seen in some logs that are repeated every 20 msec and that there are 64 CSI-RS beams in mmwave.

I dont see a specific periodicity in one sample log for CSI-RSRP.
Maybe it’s aperiodic.

I mean how often it is transmitted CSI-RS, not how often it is measured or how often it is reported.

Ok. Will we get it in UE logs? I mean, UE logs will have what it measures and reports back, right?
May be a network config can give the periodicity?

I don’t think it is in UE logs how often CSI-RS are transmitted.
Only how often UE has to measure CSI_RS and how often UE has to report it.

Correct, we have to get that from the N/w Vendors, I guess.

In vendor’s documentation it is usually written that are transmitted every 20 msec, this is how I know it is 20 msec for that vendor in mmwave, otherwise I would not know.

May be in RRCreconfig or setup it can be there. (Wild guess).

CSI-RS Periodicity (T_CSI-RS)

This is read only parameter automatically set by the CSI-RS Subframe Configuration (I_CSI-RS).

This is coupled to CSI-RS Subframe Configuration (I_CSI-RS).

Subframes containing CSI reference signals shall satisfy:

I_CSI-RS = 0 to 4 , T_CSI-RS = 5
I_CSI-RS = 5 to 14, T_CSI-RS = 10
I_CSI-RS = 15 to 34, T_CSI-RS = 20
I_CSI-RS = 35 to 74, T_CSI-RS = 40
I_CSI-RS = 75 to 154, T_CSI-RS = 80

Refer to TS 36.211 / 36.213 / 38.211.

I think for Ericsson it is 40.

40 msec at a speed of 100 km/h is like 27 m/sec meaning in 40 msec the UE changes around 1m.
I think it is ok also 40 msec.

But that unit is slot not subframe. So it is 40 slots not 40 msec. Means it is much faster than 40 msec.

Why does it says unit=slot, in TS? It is not unit = subframe or msec.

In Huawei, a set of CSI-RS is APERIODICALLY sent by the serving and cooperating cells togheter for channel status information measurement.

In Huawei depends on the band.
In mmwave is periodically each 20 msec.

In TS 38.211, the slot is the part of the frame, as per the definition.

Th number of slots per subframe depends on numerology.

Please note user scheduling in 5G is per slot like in LTE per TTI.
Slot 0.5 ms for 30 Khz.
As of now one UE can be scheduled per slot.

If csi-rs are sent aperiodically how ue knows when to measure them?

Periodicity of SSB and CSI-RS always defined in terms if Slot, instead of Subframe.
Because SS Blocl or CSI resource may have different numerology.

1 PRB = 14 OFDM Symbol ×12 Subcarrier / Slot for 5G.

Here you have an example:


However, periodicity of CSI-RS can be periodic, Semi periodic and aperiodic also.

In the case of aperiodic CSI-RS, no periodicity is configured. Rather, a device is explicitly informed (“triggered”) about each CSI-RS transmission instant by means of signaling in the DCI.

Yes indeed, it is in DCI format 1_1 “ZP CSI-RS Trigger”.