Ghost or Phantom PRACH in LTE domain

4G LTE
1

Hi All,
Anyone has any idea on “Ghost or Phantom PRACH” in LTE domain?
At time of 2G I heard but any feature in 4G to overcome it?

1 Like
2

Can you explain this bit more detail?
I have heard about it but may need to check some old email and notes.

Anyway, here what i think it is:

PRACH False Alarm
If a UE does not send a preamble but the eNodeB detects a preamble from the UE during a random access procedure, this falsely detected preamble is called a PRACH false alarm. If a received preamble is considered as a PRACH false alarm, the eNodeB does not respond with a Random Access Response message or count the preamble into the preamble-related counters.

3

Yes, that is called Ghost or Phantom PRACH.
Any feature to overcome this?

4

I had a similar problem some time ago, but I solved it with a RSI replanning.

5

It depends on vendor.
Huawei has a parameter to disable this.

6

For Nokia any idea?

7

What is the parameter?

8

CellRachAlgo.PrachFalseAlarmDetRadThd

9

Sorry, i haven’t worked a lot with Nokia.

10

It is not activated on our network.
How can you spot the need for it (KPIs, user experience)?
What are the gains?

11

I don’t think there is end user benefit.
I think you will probably see MSG1 count count go do down.
Can not remember counter name, but PreambleA counter will reduce.

Also if you see big difference, this should point towards some planning issue (i.e. why false preamble in first place).

12

Any improvement in the main KPIs?

13

Can not remember (long time ago).
But even if there is some improvement, it will be superficial.
Better to check Huawei documentation.