SNR fluctuating and RSCP Dropping

[ssameeru]

Hi All,

I have an issue for NSN 3G WBTS's.

You can sit in the exact same location and put Your Cell phone down and watch the RSSI fluctuate up and down to the point of dropping and going roaming.

Also SNR fluctuates & RSCP dropping is observed .

Kindly share your observations for the same.

Regards,

Md Sameer

[babak1349]

Hello,
There are 2 different things you should consider, RSSI is affected by load. It means more load in your cell (and neighboring cells) higher DL RSSI (and also UL RSSI) would be expected.
RSCP should be stable regarding CPICH power is fixed normally. So if your RSCP is fluctuating a lot , it means something is wrong.
Please bear in mind you should consider some other things regarding to drop call, the CPICH EcNo and also your power control setting ( RL power might be limited )
The signal normally is affected by environmental conditions,. if even a person or a car is passing it might affect your RSCP/RSSI

if the RSCP is fluctuating a lot in a cell you should suspect, some hardware fault in nodeB or maybe your drive test HW
So you need to stationary tests in different cells or do the drive test with different UEs to make sure the fault is not due to drive test HW
It could be also faulty HW in nodeB (TRU) or Antenna system which causes RSCP degrade or fluctuate abnormally ( a few dB could be due to environmental conditions) So you need to check the HW

Cheers

[ssameeru]

32645

Hi, Thanks for your reply.

could you provide further suggestions,
As seen from the attached snapshot when the speed test is performed on UE and the same is being scanned on TEMS unit, the Ec/No goes from -3.00 to -10.00 and then returns back again to -3.00 after speed test.

[babak1349]

Hi,
What do you mean by saying"speed test"? do you mean you used HSPA?
When you are using HSPA in DL, the Cell most probably using maximum available power to provide the best throughput for UEs in this case your EcNo decreases and example consider you have a cell and CPICH is 33 dBm and Maximum Cell Transmission power could be 43 dBm (20 Watts) and 46 dBm( 40 watts)
EcNo is RSCP/RSSI in UE (RSSI is not only received signal from serving cell but also received signal from other cells )
So as rough estimation you can consider EcNo< (CPICH power/ Maximum Transmission power)

if your cell maximum Transmission power is 20 Watts: EcNo < -10 dB (HSDPA is used)
if your cell maximum Transmission power is 40 Watts: EcNo < -13 dB (HSDPA is used)

If you have a cell which is not loaded and considering 20% of Maximum Transmission power is used for Common channels
in this case
Ec/No < -1.6 dB

So as you can see the Ec No all depends on cell load and use of HSDPA

Cheers

So if you don,t have HSDPA Maximum transmission power will be limited to R99 users

32645

Hi, Thanks for your reply.

could you provide further suggestions,
As seen from the attached snapshot when the speed test is performed on UE and the same is being scanned on TEMS unit, the Ec/No goes from -3.00 to -10.00 and then returns back again to -3.00 after speed test.

[ssameeru]

Hi,

Thanks for your feedback.

I will let you know regarding speed test. Whether the user was using HSDPA/HSUPA.

Means that the Ec/No will definitely vary for that cell as per user availaibility.

Just i wanted to know the CPICH Ec/No range.
What can be the values suggested for this parameter that will signify better coverage or better quality or in other words we can tell us that the site is absolutely radiating fine.

Many Thanks//

[babak1349]

Hi,
When you are doing speed test, there might be other users who are using HSDPA (in this case CPICH EcNo is affected) and you don't know about them
EcNo is an indicator which shows the quality of potential connection But please note that for a Traffic connection the quality is controlled by BLER or BER and the radio link connection for user is subject of powe control It means power control can increase Radio link power in order to maintain required BLER/BER
in 3G 2 set of parameters are used to provide information for user to trigger events
in idle
qQualmin and qRxlevmin for example qqualmin can go even lower as -24 dB or qRxlevmin to -115 dBm
For dedicated there are event 2d and 6b thresholds to trigger compressed mode and further even csn be reported to do IFHO, IRAT please check your vendor documentation

Cheers

Hi,

Thanks for your feedback.

I will let you know regarding speed test. Whether the user was using HSDPA/HSUPA.

Means that the Ec/No will definitely vary for that cell as per user availaibility.

Just i wanted to know the CPICH Ec/No range.
What can be the values suggested for this parameter that will signify better coverage or better quality or in other words we can tell us that the site is absolutely radiating fine.

Many Thanks//