We will say that a person named Ahmad wants to call a person named Muhammad and Ahmad uses a landline phone, for example, or a network other than Muhammad’s network. What will happen in detail is that when Ahmad calls Muhammad’s number, Ahmad’s network addresses Muhammad’s network through the GMSC of Muhammad’s network and from  In order to connect the call to Muhammad’s phone, he wants to locate the phone, what they call LR, an abbreviation for the term “Location Aria” so that the caller (Ahmed) is connected to the person who will receive the call (Mohammed).

From this we understand that there is a code for you that determines your place in the network. This code is called MSRN

Through it, your location or the nearest network tower to you is determined, and this number is stored in the VLR, and of course there are more than one VLR, and this means that the GMSC now needs to locate the VLR near you (because the network has a VLR group in it, not just one) and this information is found in  The HLR sends to the HLR and asks it to identify the VLR near you so that it obtains from it the MSRN number of your phone so that it can locate you and here the HLR also does not know the MSRN, but it is sad that it contains the imsi number for your number and sends it to the VLR because the HLR knows the  The VLR that belongs to every MS (mobile station or phone), so the VLR sends the MSRN to the HLR, and after the HLR receives it, it sends it to the GMSC, so the GMSC can know the LR of the MS and determine its location because it now knows the closest VLR

He addresses the MSC and then the MSC addresses the BSC through a new number called the TMSI. Here we know that the end of the MSRN path has ended as soon as it reaches the MSC and its VLR, and the BSC addresses the BTSs (all the towers of the mobile phone network in this  Region)

All BTSs send a PCH to all MSs (mobile phones belonging to each tower), and then the intended phone answers through RACH to the nearest tower, and that tower informs BSC that the requested phone has been found, and the BSC addresses the remaining towers to stop looking for the phone

The rest of the network towers stop searching for the phone, and here begins another stage. The BSC authenticates the mobile phone before giving it to Channel to make the call

All this happens in less than one second

Now we know how the network can locate a mobile phone