Radio Network Controllers (RNCs) are crucial components in the UMTS (Universal Mobile Telecommunications System) architecture, which is commonly known as 3G. The RNC is responsible for controlling multiple NodeBs, which are essentially the base stations in UMTS that handle the radio communication with the user equipment (UE), such as mobile phones.
Here are the main aspects and functionalities associated with RNCs:
- Control and Coordination: RNCs play a pivotal role in the control and coordination of the radio resources. They manage and supervise the resources for the NodeBs under their control.
- Handovers: One of the key responsibilities of the RNC is to manage handovers. When a mobile device moves from the coverage area of one NodeB to another, the RNC ensures a smooth transition, especially in the case of soft handovers where a device is simultaneously connected to multiple NodeBs.
- Connection Mobility: The RNC handles the mobility of a connection within its controlled area. This means it keeps track of the mobile device’s location and ensures that the connection is maintained as the device moves.
- Admission Control: It also manages admission control, which is the process of determining whether new devices can be allowed to establish a connection based on the current resource utilization.
- Data Encryption: RNCs are responsible for the encryption and decryption of data on the Iu interface, which is the interface between the RNC and the core network.
- Protocol Conversion: RNC manages the conversion between different protocol layers. For instance, it handles the transition between the radio-side protocols and the network-side protocols.
- Load Balancing: RNCs can distribute the traffic load among multiple NodeBs to optimize performance and ensure that no single NodeB is overwhelmed.
- Connection to Core Network: The RNC connects to the core network through the Iu interface. This interface links the RNC to the Circuit Switched (CS) domain for voice and the Packet Switched (PS) domain for data.
- Segmentation and Reassembly: The RNC handles the segmentation and reassembly of data packets, ensuring that data is appropriately formatted for transmission over the radio interface.
- Compression and Decompression: To optimize bandwidth utilization, the RNC can also perform data compression and decompression.
In LTE (4G) systems, the architecture evolved, and the functionalities of the RNC were integrated into the eNodeB, resulting in a more streamlined and flat architecture. This eliminated the need for a separate RNC layer, simplifying the network and reducing latency.