2 eNodeBs using same Root Sequence Index

Hi Experts,
I have one question:
Let’s suppose 2 eNodeBs using same Root Sequence Index.
Then it this case if your will use same preamble and rarnti.
Then will rach happen sucessfully or rach will fail?

prachConfIndex specifies in which subframes the RA can occur.

PRACH Configuration Index cannot be the same for different cells at the eNB.

So same rootseqindex may create same preamble by UEs but UE wont be sending preamble at same time due to different prachconfiindex, so rarnti will always be different.

But its better to keep different rootseqindex for nbr cells.

Thanks @jsdeoraj.
What could be all possible reasons that X2 link not get setup?

I think might be ANR table not configured properly, resources NA at node, pci collison could be reason.
Is it correct?
I want to know, please suggest.

Generally in networks PrachConfigIndex is kept same and RSI planning is done.
RSI is avoided by means of SON function.

Yes because rsi are way more than in number than prachconfindex so collisions chances decreases drastically with different rsi.

X2 setup process failed duo to no IP connectivity between two sites
X2 link unavailable –—> X2 setup process failed

Hi Experts,
I know when 2 eNodeB have same root sequence index with in cell radius then in that case rach will fail.
I want to know how we calculate cell radius and where we get this info in logs?

You can check TA sample to check your cell coverage.
Cell radius is driven by link budget.

You can get cellradius from zerocorrelationzoneconfig in logs.
There are tables about this in 5G NR in Bullets book.

Hi @RFSpecialist, please tell why we linked it with cell radius actually value in table indicates value of range from which UE can get rach access.
Cell radius is from link budget according to which site planning done but generally no one do ideal planning.

Please correct if it’s wrong.

@Pankaj just asked how can he checks from logs.
This is one way to check from logs.

Table 169 (in 5G NR in bullets book).
Zero Correlation Zone Configuration AND Cell Range columns.

Those are just the distances that rach could be decoded.
In reality cell may overshoot a lot.
Even rach coming from 10-15 in L800 for example.
10-15 km.

What about 4G?
Do we have same table in 4G as well?

Book LTE in bullets 2nd edition.
You need also to take into account delay spread.
So use last column of the table for safety.

This is 1.25 khz RACH. How about other scs?

There are other tables for each case.

Going with context your primary question. X2 link setup should not get impacted by rsi/pci planning.

Generally what I have seen mostly is IP related issue. Make sure IP addresses for each plane is correct if not already checked.