Why we need SIB4, SIB5, SIB6, 7, 8...?

Hi Experts,

In SIB3 we already have information about all neighbour cell information of intra, inter, inter-RAT for reselection.

Then why we need SIB4, SIB5, SIB6, 7, 8…?

Sib4 not mandatory to transmit UE can do intra Freq reselection without it.

Sib5 having threshold x high and threshold x low as well absolute priority for target cell used by UE in reselection criteria similarly with sib 6, 7 used for inter RAT reselection mandatory to broadcast.

  • UE will reselect to high prio inter Freq cell if Srx (target) > thershxhigh
  • UE will reselect to lower prio inter / inter rat Freq cell if Srxlev( serving) < snonintraserach and < threshservinglow ( part of sib3) and Srxlev(target) > threshold x low
  • UE will reselect to same prio intra Freq cell if Srxlev( serving) < Sintraserach and Rn > Rs
  • UE will reselect to same prio inter Freq cell if RN> Rs

Are you sure here that SIB4 not mandatory for Intra Freq handover?

As per your last comment, Rn>Rs, how is UE calculating Rn (its using q-OffsetCell, which is provided by SIB4).

Yes for SIB4 I’m sure not mandatory to broadcast.
Let me tell calculation Part for Rn as I seen value taken from SIB4 tends to not used if SIB4 not broadcast.

If it is not mandatory, then why 3GPP introduced SIB4?
Based on the Ranking of the cell in Intra_Frequency neighbour cell reselection will happen.

My question is simple: SIB3 it’s the common neighbor information for all inter, intra and inter-RAT.
But why we still have SIB4 to SIB6?

Sib4 having other options as well like blacklisting of PCI if wish to use although it’s not mandatory.
But as mentioned sib 5 to sib 7 mandatory.

SIB4 (Intra freq only) contains Qoffset value, so whenever UE calculate ranks for neighbours it reads SIB4 from all available eNB’s and figures out Rn = RSRP - Offset, Rs = RSRP + hys. And based upon Rn> Rs it performs cell reselection.

For equal priority inter Freq, I think Serving RSRP should also been < SnonIntraSearch.