Question: Because LTE TTI (1ms), in DSS (LTE/NR), the NR need to set only with SCS=15KHz.
Is it correct?
I don’t think so.
In DSS, resources between LTE and NR are divided either at frame level, subframe level or at frequency level.
In all above configuration NR will have dedicated BW or portion of BW available to use.
So it may possible to use different SCS.
Please correct me if I am wrong.
I think it’s fixed at TTI level.
In DSS 5G necessarily borrows subframes.
Till Rel 15 I also see that PDSCH needs to be at 15 Khz for DSS.
Not sure if this changes in Rel 16.
We can configure 15 kHz and 30 kHz.
I think that only 1ms can be used.
Not really, SSB can be transmitted on 30 kHz in DSS.
SSB and PDSCH as well.
Very good paper of Mediatek which explain DSS in high level of details.
It is worth mentioning in SCS of 30 kHz is used, rate matching is needed.
Yes , for DSS both SCS 15 KHZ an 30 KHZ can be used simultaneously but both required different MBSFN subframe. we know MBSFN subframe restricts CS RS to 1st two symbol in a subframe . so , suppose Subframe 1 and Subframe 2 is for MBSFN subframe ,then we can use SF#1 for SCS 30 and SF#2 for SC15 . for SCS 30 KHZ ,SSB transmission needed and 1 SSB need 4 consecutive symbol .
As said in MBSFN , only 1st two symbol will be used for Control signaling and 3rd symbol will be used for PDSCH-DMRS . so that we need to adjust SSB between remaining 11 symbol in that subframe .
if 1st ssb using Symbol 4,5,6,7th and 2nd SSB using 8,9,10,11th symbol then 11th Symbol will be overlapping with PDSCH -DMRS . so to avoid this collision with SSB with 11TH Symbol of PDSCH-DMRS , Symbol 12 used for PDSCH-DMRS and thsi is the only change required when SCS 30 KHZ used in DSS
On TTI level resources are utilized either for LTE or NR, according to dynamic pattern
MBSFN subframes are used to clear legacy LTE from NR TTIs
Phase 1 of DSS supports the operating bands Frequency Range 1 for FDD (15 kHz)
Why in 5G generally vendors use SCS 30 kHz?
Just noticed almost SCS 30 kHz is useable. But why not 60 Khz?
60 KhZ can be used, but almost preferable SCS 30 kHz.
Any reasonable explanation for why perferred SCS 30 kHz?
Due to mobility and depnds on band.
URLCC will have shorter kHz for less latency.
But SCS 60 kHz can have also high mobility. Why preferred 30 kHz?
LTE underlying system.
60 kHz used for extended cp.
So for ISI purposes?
Smaller the scs more the symbol length and better coverage, so scs 30 preferred over 60.
I doubt scs has anything do with radius?
Higher scs is used for low latency, to reduce frequency offsets caused by high frequency and doppler shifts.
Please can you explain , how does the 11th symbol of 2nd SSB collides with PDSCH DMRS as it is mentioned PDSCH DMRS is contained within the 3rd symbol out of 14.
Perhaps I have missed something.