Hello Experts.
We know in SS block we have PSS SSS PBCH(DMRS in that).
According to 3gpp specs we measure SSRSRP which is defined as the RSRP from SSS .
Any specific reason for measuring SSS?
The center 20 RB carry the SSS. It also carries the reference signals.
So, the UE does not have to scan the entire NR bandwidths.
Remember, NR supports bandwidths of upto 400MHz, and scanning this entire range will drain the UE’s bandwidth.
Why not PSS and Why SSS for measuring this?
I think SS-RSRP means SS Block RSRP, not secondary sync. signal RSRP
hi , i am not expert but as i understood. there are different types of measurements, ss-rsrp is mainly used in idle mode to avoid searching for detailed positions of reference signals (thats why there is no cell specific reference signal in 5g ) , in connected mode csi-rsrp(its ue specific) is mainly used . why ss not ps is used because after ue reads ss ue can detemine the phyical cell id so ue can choose between cells . thats my understanding i am not expert you can read this for more info : https://www.etsi.org/deliver/etsi_ts/138200_138299/138215/15.02.00_60/ts_138215v150200p.pdf
1 Like
First off, SS-RSRP doesn’t only refer to RSRP measured over secondary synchronisation signals. It may refer to RSRP measured over DMRS within PBCH or RSRP measured over CSI-RS. However, The question why SS-RSRP doesn’t refer to RSRP measured over primary synchronisation signals remains there. It may be due to ease of implementation or some other design decision at the time of specification finalisation.
Maybe due to the PSS is transmitted sometimes with an unknow “offset” power, and the UE is not provided with this “offset”, so the UE must deduce the value of the transmit power offset.
The idea was extracted from: “5G New Radio IN BULLETS”, from Chns Johnson, Section: DOWNLINK POWER CONTROL (Page 457)
“The Primary Synchronisation Signal (PSS) may be transmitted using an EPRE which is equal to the SSS EPRE, or it may be transmitted with an EPRE which is 3 dB greater than the SSS EPRE. There is scope to increase the transmit power of the PSS becausethere are unused Resource Elements both above and below the PSS (within the set of20 Resource Blocks used by an SS/PBCH Block).
Increasing the EPRE by 3 dB means that the total power within each symbol of an SS/PBCH Block remains approximately constant. The UE is not provided with information regarding the transmit power of the PSS so the UE must deduce the value of the transmit power offset. Having knowledge of the offset is useful for UE which are capable of Interference Cancellation ( IC). Knowledge of the offset simplifies the generation of the signal to be subtracted from the wanted signal. In addition, having knowledge of the offset is useful for the VE receiver Automatic Gain Control (AGC) which can be tuned according to the power or each symbol belonging to the SS/PBCH Block”
3 Likes
Its indeed Secondary Sync signal ref power. The spec definition goes by: SS reference signal received power (SS -RSRP) is defined as the linear average over the power
contributions (in [W]) of the resource elements that carry secondary synchronization signals
(SS).
1 Like
Hi Carlos
Reason for measuring ss-rsrp using only SSS as SSB carries other info PSS PBCH:
Some answers from internet:
- NR supports bandwidths upto 400MHz and scanning this entire range will drain UE power.
The center 20 RB carry SSS which also carries reference signals. So UE does not have to scan entire bandwidth.
-The Primary Synchronisation Signal (PSS) may be transmitted using an EPRE which is equal to the SSS EPRE, or it may be transmitted with an EPRE which is 3 dB greater than the SSS EPRE. There is scope to increase the transmit power of the PSS because there are unused Resource Elements both above and below the PSS (within the set of20 Resource Blocks used by an SS/PBCH Block).
Increasing the EPRE by 3 dB means that the total power within each symbol of an SS/PBCH Block remains approximately constant. The UE is not provided with information regarding the transmit power of the PSS so the UE must deduce the value of the transmit power offset. Having knowledge of the offset is useful for UE which are capable of Interference Cancellation ( IC). Knowledge of the offset simplifies the generation of the signal to be subtracted from the wanted signal. In addition, having knowledge of the offset is useful for the UE receiver Automatic Gain Control (AGC) which can be tuned according to the power or each symbol belonging to the SS/PBCH Block.
1 Like