Whats the best way to check if DSS is indeed working?
Look for “lte-CRS-ToMatchAround” and “frequencyShift7p5khz : true”.
In UE logs.
In which message?
Trying SA DSS.
My suggestion was for NSA
In rrc connection reconfiguration you can find the 2 IE that I mentioned.
Isn’t it true for even SA?
Because anyway UE has to ratematch CRS.
I think UEs will not have to rate match if they are in SA mode.
LTE CRS are transparent to them so they need to rate matching around it.
Why CRS will be transparent to NR device?
NR device will expect NR PDSCH at LTE CRS.
It has to be rate matched.
I could be wrong (don’t understand this in great detail) but here is my understanding:
NSA UEs need to read both LTE frames (LTE anchor) and NR frames (LTE frames used by NR). Hence it needs to rate match.
SA UEs in DSS will behave as if 5G is using its spectrum and will not need to do rate matching. NW will schedule control and data in other frames than LTE CRS subframes.
Sorry but its not like that.
NSA UE monitor LTE anchor and secondary NR carrier which is shared with other LTE carrier.
In the NR subframe of DSS, LTE CRS are also transmitted except MBSFN subframe.
Hence when UE decode NR subframe of DSS carrier, it has to rate match around LTE CRS.
Situation is not different for SA device…just there is no anchor.But rate matching is required.
Your explanation also make sense.
As I said I could be wrong.
I will try to read more about it.
Why SA device require rate matching if it doesnt use LTE?
Otherwise network should have Dual connectivity (MRDC) in SA where 5G and 4G is used by the Ue where rate matching may br required?
SA device is not using LTE. But it is using LTE carrier, a part of which is being used by NR.
In DSS, NR subframe carries LTE CRS.
Except in MBSFN subframe.
So rate matching would be required.
I someone want to add on this, please add. No one knows 100%.
Have a look at this document (probably most detailed document on DSS):
P.13: In Idle mode, prior to receiving SIB1, the DSS UE in SA is unaware of the LTE
reference signals. 3GPP specifications do not allow the activation of rate matching around CRS in idle mode and connected mode until a certain point in the call setup when the signaling messages are sent to the UE indicating DSS operation.
My take from this --> for SA UEs, network will either schduel in MBSFN frames or do RB puncturing if scheduling in LTE subframes carrying CRS.
Yes. MBSFN subframe can be used, and configuration made such that most of possible signalling should carried in MBSFN subframe.
But while decoding NR PDSCH, in non MBSFN subframe, rate matching required.
RE level, or symbol level, rate matching is again option available.
Rate matching (in my understanding) mean that UE is aware of specific REs carrying CRS and it will avoid those in order to process NR and LTE.
For NSA, this is necessary, since UE needs LTE CRS (for RSRP/RSRQ etc).
For SA, NW will allocate only those REs which will not collide with LTE CRS (puncturing or non-allocation).
For me this is not rate-matching as UE isn’t aware of why RE wasn’t allocated.
LTE CRS symbols/REs are punctured by NR, so SA UE will not decode or read those REs.
Rate matching is necessary when we do RE/symbol puncturing, I think.
Because it has to adjust existing data in less available resource.
So we can’t differentiate puncturing and rate matching.
Not disagreeing with you.
We are probably saying same thing in different ways
As long as we are discussing SA DSS, I have one more question to add. When SA DSS is deployed on LTE resource grid, does network need to deploy 5G core network too along with LTE EPC core?