In telecommunication, a public land mobile network (PLMN) is a combination of wireless communication services offered by a specific operator in a specific country.
[3] From PLMN assignments, it is apparent that such dualities of two-digit and three-digit MNCs with the same number value are avoided (see the list of mobile country codes and mobile network codes).
The IMSI, which identifies a SIM or USIM for one subscriber, typically starts with the PLMN code.
Mobile phones use this to detect roaming, so that a mobile phone subscribed on a network with a PLMN code that mismatches the start of the USIM's IMSI will typically display an "R" on the icon that indicates connection strength.
A PLMN typically offers the following services to a mobile subscriber: The availability, quality and bandwidth of these services strongly depends on the particular technology used to implement a PLMN.