Cellular communication uplink SR - scheduling request- problem in lte 4G

my UE transmits SR to EnodeB but I have SR fail it means the EnodeB not collecting / recognizing / detecting SR requests from the uplint transmission , what attempts should I do /implement in order to solve that problem? it means that the UE isn’t receiving the Up link grant from EnodeB despite that UE transmits SR to ENODEB - fail in getting uplink scheduling grants … the UE is not getting at all the grants back from the EnodeB.

thanks alot for any help on which approaches should I take in order to figure out why this problem is happen … really weird and I dont know what steps should I take to fix the problem.

Any help guys?

To improve SR success
Increase p0-nominal for pucch
If deltashift =1 you can increase it to 2 or 3

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Could you please elaborate what do you mean by that?
I didn’t understand you well when you said increasing p0-nominal for pucch … what does that mean? I understand what’s po-nominal but how that helps to improve SR success or actually to help me to understand why SR’s failure occurs…

moreover if I increased po-nominal for pucch …then I increase deltashift to 2 and then I ask myself again if deltashift=2 then I increase it to 3? …I really still confused and didn’t understand you well.

Appreciated for any good explanation about your suggestion.

“EnodeB not collecting / recognizing / detecting SR requests from the uplint transmission” is very uncommon scenario and only reason I could think of is UE TX power is too low. Increasing UE power through increasing P0-pucch if UE is not on celledge

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O.B I increased the deltashift and still facing the same problem and this is really weird, CQI is all fine and all others parameters are fine .
if you didn’t understand me … what I’m trying to fix is that EnodeB isn’t detecting the SR signal from the UEs ? at the EnodeB there’s no detecting at all of SR signals that uE definitely transmits. In the EnodeB if it detects the SR signal then pingo all fine … but the problem that EnodeB isn’t detecting the uplink SR signals.

That’s really weird , I appreciate your help on that.

May you suggest something that I could try or something that could I execute in order to fix the problem? really I dont know what to do in order to fix that bug that I face.

Deltashift suggestion assumed enodeb is receiving a lot of fake SR (due to interference on pucch) that enb cannot handle simultaneously. Seems it is not the case here.

What is your current value of P0-pucch? What is RSRP value at UE side?

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You know it’s not concrete values - not certain values.

RSRP is for me range between -80 to -95 , so my question what range of p0-PUCCH -Min and Max values- should I try or increase for p0-pucch? could you please give me ranges of P0-pucch that I need to try regarding to what I’ve RSRP range -80to -95?
PS. I already said that parameter CQI is good and fine …

P0-nominal-PUCCH is configured by the network and is fixed value Sent in sib2

Hi @Ryan, before I could help you, could you pls give me some more details as below?

  1. How do you identify the problem of uplink scheduling request? By drive test, OSS?

  2. Did you also notice the buffer status report from UE?

  3. How big the issue is any particular eNB or larger area if Network?

  4. Have you enabled smart/enhanced pre scheduling or preallocation feature in your Network? Or on affected eNB?

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I understand , I will check and come back to you sooner with updated values of RSRP , P0-PUCCH.

Moreover if you notice the other reply mentioned that I need to look to buffer status uE report … is that relevant? because I’m confused on how buffer status related to my problem / my case …

Hi and thanks for your reply.

  1. I didn’t understand you what do you mean by drive test , OSS? I see in my simulation/logs that uE isn’t getting grants from EnodeB.
  2. didn’t check it.
  3. how big the issue is any particular eNB or larger area if Network?
  4. no I didn’t use any pre-scheduling or preallocation feature in my network before.

Hi @Ryan,
Thanks for your response,

So, if you have got UE logs, then you have UE TX power visibility, did you check PUCCH UE Tx power, does it exhaust to max UE power 23dBm?, What’s BLER, Path loss, UL MCS?

If you see grants initially… once only and subsequent grants are missing…which may because of UE uplink buffer is zero (in buffer status report)

Still am not sure, you are working on live network? However, you may rule out few aspects UL RF, DL RF, eNB under severe congestion ( no grants available) , very high BLER causes no scheduling?

To rule out these aspects, enable very aggressive pre scheduling or pre allocation with very little interval period between two pre scheding/ allocation period …this will make eNB to assign frequent grants without UE SR request…then you may know …where and what is wrong…?

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I understand you very well I will try to do what you suggest sooner and update you with parameters that you asked me here to assign/answer ; but to let you know that I ofcourse don’t see at all any returned grants from EnodB to uE(even initially grants I dont see).
I work with live network( means that various uEs connecting to EnodeB…it’s live network )

In this case that I dont see even initials grants from EnodeB in response to SR requests of uE …do you suggest something to check/attempt to verify the problem/the case?

also what do you mean by this ‘’ enable very aggressive pre scheduling or pre allocation with very little interval period between two pre scheding/ allocation period …this will make eNB to assign frequent grants without UE SR request ‘’ … I didn’t understand you well …could you elaborate more about that procedure ? didn’t understand what do you mean by ’ enable very aggressive pre sheduling’ ? in other words to make many uEs transmit SR to same EnodeB?

Hi , for your question I’m attaching you here values of RSRP , P0-PUCCH that my network have when the problem is occurred -
Here’s the samples for more than uE

for UE id 123 -

P0-pucch -113 dbm , deltEnabled= 0 , P0-pusch=-113dmb , TargetSNIR=0x8d ,
RSRP=-99dbm , ReferenceSignalPower= -104 dbm.
After milliseconds in time the same UE has;
P0-pucch -120 dbm , deltEnabled= 0 , P0-pusch=-113dmb , TargetSNIR=0xa4 ,
RSRP=-94 , ReferenceSignalPowerl= -104 dbm.

for UE id 44 -

P0-pucch -120 dbm , deltEnabled= 0 , P0-pusch=-113dmb , TargetSNIR=0xa4 ,
RSRP=-76, ReferenceSignalPower= -104 dbm.
after milliseconds in time the same UE has;
P0-pucch -113 dbm , deltEnabled= 0 , P0-pusch=-113dmb , TargetSNIR=0x91 ,
RSRP=-74 , ReferenceSignalPower= -104 dbm.

Now all parameters I’ve give … So any suggestion needed to fix the problem?

Hi , for your question I’m attaching you here values of RSRP , P0-PUCCH that my network have when the problem is occurred -
Here’s the samples for more than uE

for UE id 123 -

P0-pucch -113 dbm , deltEnabled= 0 , P0-pusch=-113dmb , TargetSNIR=0x8d ,
RSRP=-99dbm , ReferenceSignalPower= -104 dbm.
After milliseconds in time the same UE has;
P0-pucch -120 dbm , deltEnabled= 0 , P0-pusch=-113dmb , TargetSNIR=0xa4 ,
RSRP=-94 , ReferenceSignalPowerl= -104 dbm.

for UE id 44 -

P0-pucch -120 dbm , deltEnabled= 0 , P0-pusch=-113dmb , TargetSNIR=0xa4 ,
RSRP=-76, ReferenceSignalPower= -104 dbm.
after milliseconds in time the same UE has;
P0-pucch -113 dbm , deltEnabled= 0 , P0-pusch=-113dmb , TargetSNIR=0x91 ,
RSRP=-74 , ReferenceSignalPower= -104 dbm.

Now all parameters I’ve give … So any suggestion needed to fix the problem?

Hi @Ryan, as you said no grants for uplink for any UE in a live commercial network? Do you see uplink data volume on problematic sites? Which is not possible without Grant’s.
Something is missing here…

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Sorry Deepak yes there was initially grants.
there was an initially grants at the commercial network but because I’ve in the log a sampling data -sampling data from what happened at ENODEB when the problem occurs .
the log is sampled from specific time to specific time …so maybe there was an initial grants but I don’t see them - don’t see them in my log because maybe they happened before my sampling time.
As you see I gave you the uplink data parameters that I see when two uEs sent SR message to EnodeB and they didn’t get grants in reponse to their SR message - in other words EnodeB didn’t detect their SR messages …otherwise if EnodeB detects their SR messages it will send grants to them.

The parameters as I shown to you isn’t saying maybe something?

It is weird that p0 is oscillating between -113 & -120 dbm. Perhaps power control.
In general, -120 dbm is quite low specially if delta-pucch-format1 is negative

I would suggest to make sure p0-pucch stays at -113dbm

I understand , what do you mean by “delta-pucch format1”? You mean deltashift?