Big variations in EcNo readings observed (EcNo Jitter)

[eric4good]

Dear Experts out there,

Using different drive test tools and phones we have observed a big varaition in EcNO readings obtained from (scanner, idle and CS dedicated).
There is no real explanation as its happening all over the network. It is as if there is an "EcNO jitter" if I may put it this way, values jump from -6 to -13 and back to -7 within very short distance and no real traffic profile change? Any idea what could be causing such varaiation to occur? Parameters? Antennas? Transmission? Vendors are Huawei and ZTE.

Thanks in advance.

eric4good

[fenixchoo]

Hi Eric,

Can you describe more on the testing field?
Is this on the road? Indoor? Outdoor stadium? Sky crappers?

How many active set?

[eric4good]

Its a street outdoor drive with in car mobile, no external antennas, max active set is 3


Hi Eric,

Can you describe more on the testing field?
Is this on the road? Indoor? Outdoor stadium? Sky crappers?

How many active set?

[Philippe]

Is there HSDPA traffic? This will make Ec/Io decrease rapidly during HSDPA call.

[fenixchoo]

As you mention there is no real traffic in that cell, you might set the CPICH power to 33dBm,
drive to test LOS 200m at the main beam for that antenna with proper Mtilt & Etilt to make sure it is not the BTS antenna problem.
In additional please check the alpha, beta & gamma all 3 sector both (TxRx & Rx) ports connected to their respective antenna ports.


Its a street outdoor drive with in car mobile, no external antennas, max active set is 3

[tharinduwije]

If the cell is not loaded may be due to external interference spikes coming on downlink.You sure its not pilot pollution? Better to down all cell at night time & check with a Spectrum Analyzer to be sure.Further Check CQI Counters to monitor CQI variation

[wolverine]

Hi, in my opinion this behaviour is natural to an extent. I see it in all networks. You even see it in a screened room. It is down to the nature of RF, multipath, constructive, destructive interference etc. You might also occasisonally get another cell radiating in your area so the RSSI will increase momenteraly etc.

It is also worth bearing in mind that a scanner and a UE do not measure at the same intervals and do not apply the same averaging. Also the measurement requirements between idle and connected mode differ. In connected mode the UE is measuring more often so you will see more variations in measurement.

[webkasperl]

If Ec/No is jumping rapidly from -6 dB to -13 dB and a few seconds later back to -6 dB this is normal behavior if any customer is doing some data download with HSDPA in that cell. To test this, just disable HSDPA and drive again. With R99 PS connections the cell breathind should be much lower.
Regards