In LTE (Long-Term Evolution), PLMN stands for Public Land Mobile Network. It is a fundamental concept in mobile telecommunications that represents a network infrastructure that provides wireless communication services to mobile device users. The PLMN serves as the overarching structure that encompasses multiple base stations, mobile switching centers, and other network elements to facilitate mobile connectivity over a specified geographic area. Let’s delve into the details of the Public Land Mobile Network in the context of LTE.
PLMN Overview:
Definition:
A Public Land Mobile Network (PLMN) is a wireless communication network that allows mobile devices to connect and communicate with each other as well as with external networks, such as the public switched telephone network (PSTN) or the internet. PLMN is a term widely used in the context of cellular networks, including LTE.
Network Infrastructure:
The PLMN infrastructure typically consists of the following key components:
- Base Stations (eNodeBs in LTE): These are radio transceiver stations that provide the radio interface for communication between mobile devices and the network.
- Mobile Switching Center (MSC): The MSC manages the call switching and connection to external networks.
- Home Location Register (HLR): The HLR stores subscriber information and handles call routing.
- Visitor Location Register (VLR): The VLR stores temporary information about subscribers currently in the coverage area.
- Evolved NodeB (eNodeB): In the context of LTE, eNodeB is the equivalent of a traditional base station, responsible for radio communication with UEs (User Equipment).
PLMN Functions:
Mobile Connectivity:
The primary function of a PLMN is to provide mobile connectivity, allowing users to make voice calls, send text messages, and access data services using their mobile devices.
Roaming:
PLMNs support roaming, enabling mobile subscribers to use services while outside their home network’s coverage area. Roaming agreements between different PLMNs facilitate seamless connectivity for users.
Handovers:
PLMNs manage handovers, ensuring that a mobile device can transition smoothly between different cells or eNodeBs without interrupting the ongoing communication.
Subscriber Authentication:
PLMNs authenticate subscribers to ensure secure and authorized access to the network. Authentication helps prevent unauthorized usage and enhances network security.
Call Routing:
The network elements within a PLMN, especially the MSC, play a crucial role in call routing, directing calls to the appropriate destination within the PLMN or to external networks.
PLMN Identification:
PLMN Code:
Each PLMN is identified by a unique PLMN code. The PLMN code consists of a Mobile Country Code (MCC) and a Mobile Network Code (MNC). The MCC identifies the country, and the MNC identifies the specific mobile network within that country.
Location Area Identity (LAI):
The Location Area Identity is another identifier associated with PLMNs. It represents a group of cells in a specific geographic area. The LAI helps in location management and tracking the movement of mobile devices within the network.
PLMN in LTE:
Evolution to LTE:
With the introduction of LTE technology, the PLMN concept has evolved. In LTE, the traditional MSC is replaced by the evolved packet core (EPC), which includes elements like the Serving Gateway (SGW), PDN Gateway (PGW), and Mobility Management Entity (MME).
Core Network Evolution:
The LTE EPC architecture enables high-speed data services, low-latency communication, and improved overall network performance compared to earlier generations.
Backward Compatibility:
LTE networks maintain backward compatibility with previous generations of mobile networks, allowing seamless communication between LTE-enabled devices and devices using older technologies.
PLMN and Network Operators:
Operator-Specific PLMNs:
Each mobile network operator is associated with a specific PLMN or set of PLMNs. The PLMN code uniquely identifies the operator’s network, allowing for interoperability with other networks and supporting roaming.
Roaming Agreements:
Operators enter into roaming agreements to allow their subscribers to use services when outside their home network’s coverage. These agreements often involve interconnection between different PLMNs.
Conclusion:
In conclusion, the Public Land Mobile Network (PLMN) in LTE represents the infrastructure that enables mobile communication services. It includes base stations, switching centers, and other network elements that facilitate voice and data communication for mobile subscribers. The PLMN concept has evolved with LTE technology, providing enhanced capabilities for high-speed data services and improved network performance. PLMNs play a crucial role in mobile telecommunications, supporting features like roaming, handovers, and subscriber authentication, contributing to the seamless connectivity experienced by mobile users.