What is Cell Status and Cell Reservation ?

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Whether you like it or not Telecom operators have full control on your calls, text, data usage and the type of content you visit and view via connected devices.

Perhaps, this is known by anyone and everyone who uses a smart phone everyday.

The interesting thing to know is (maybe not interesting to you, if you know it already), operators can even control what particular tower or base station a user can access or cannot access any given time.

 

tower_access

Dick wins as usual among John and Larry !

 

Yes, we are talking about cell status and cell reservation.

 

Cell Status and Cell Reservation Information allows operators to impose access restrictions on certain cells over the others.

 

What is cell Status ?

Cell status refers to the fact whether the cell is barred or not ?

 

You ask,  “Ok Azar, I get it. But what the heck is this cell barring itself ? ”

Good question 🙂

 

 

Cell Barring information is broadcasteded in SIB 1. It is applicable to all PLMNs.

 

If a cell is barred or not is decided by the barring information which is received

in SIB 1.

 

In simple words, on account of cell barring certain category users (belonging to a specific access class users) will be able to access a cell earlier than other category users.

 

access_categories

There are total fifteen Access categories for cell Barring

 

You can go home peacefully understanding that Cell barring does not block a user permanently from accessing a cell but only for a certain time duration. It is not a permanent blockage of users from accessing the cell.

More information about access classes can help you understand Cell barring and how it is computed.

 

 

What is Cell Reservation ?

 

Cell Reservation is more severe restricted access than cell barring. In case of cell reservation there are two options

  • Cell Reserved
  • Cell Not Reserved

 

The parameter which arrives in SIB 1 and dictates if a cell is reserved or not is called Cell Reserved for Operator User

It can  have two of the above mentioned values, either the cell is reserved or cell is not reserved. This value is specified per PLMN.

 

sib_1_cell_reserved

cell Reserved Information arrives in SIB 1

 

What if a cell is reserved and barred or Not barred and reserved and/or Vice Versa ?

 

Are you wondering about the mix and match of cell barring and cell reservation ??

If so, these are all great questions and scenarios. In order to answer them let’s take a look at the table below.

 

cell_status_vs_reservation

User-UE behavior as a function of cell barring and cell reserved for Operator Use . Credits to LTE in Bullets

 

Regarding the table above one important thing to keep in mind is. The above table does not specify the behavior of Access classes 11 or 15 when UE is not camped on its Home PLMN (HPLMN) or Equivalent to HPLMN  , because these access classes are only valid within the HPLMN or  Equivalent to HPLMN . ( In case if you are not familiar with Access classes read here )

 

Conclusion: 

 

The point you can take home is simple. Cell Barring and Cell Reserved for Operator use DO impact cell  selection and reselection but they DO NOT impact incoming handovers. For example a UE which is already in RRC connected mode can complete a handover onto a barred cell.

 

Interested in getting more information like this. Give me your autograph below.

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