Relation between BSIC and CELLID


#1

Hi!
I’m doing a survey of the existing cellular antenna towers in my city. Using a 2G chip (SIM800L) and with an AT command (AT + CENG) I get a list of the closest towers.

Analyzing the data of a single cellular company I see the following:

-I read the LAC, BSIC and the CELLID, among other data.
-The LAC is unique in the whole area. So it’s not a problem
-I need to identify a tower with a unique code, so I assume that the BSIC should be a unique number for each tower. And that there could be several CELLID in each tower.
-I see in the obtained data that there are CELLID’s that are repeated in different BSIC.

I do not understand the relationship between BSCI and CELLID.
Any help with this?


#2

Hi Mariano,

The Base Station Identity Code is a component of Synchronization Channel (SCH) that provides information needed to search base stations, identify them and synchronize with them.

BSIC = NCC + BCC (Network Colour Code + Base Colour Code)
It contains 8 bits and is Primarily used to differentiate between operators utilizing the same frequencies.

There are 4 basic parts of a cell identifier: MCC-MNC-LAC-CID
MCC-MNC is set by International Telecommunication Union. All telecom firms have access to this information as it is publicly available.
LAC-CID can be decided by the telecom firm. This is an internal decision and telecom firms don’t share this with each other

LAC:
This is decided by a telecom firm based on its own logic. Some telecom firms decide on LAC by region, others by a cluster. If a large amount of CID’s belonging to a particular telecom firm are in a particular area, all these will likely have the same LAC. This helps telecom firms organize information.
CID:
This is a unique id assigned to a physical cell unit.

If your survey isn’t related to frequency/ Synchronization channels, just looking at MCC-MNC-LAC-CID would be good enough.