Add N2 handover documentation

doc/RRC/rrc-usage.md

@@ -99,6 +99,26 @@ the [MAC configuration](../MAC/mac-usage.md) as well for SIB configuration.
 
 ### Neighbor-gNB configuration
 
-    TBD
+#### What is a gNB neighbor?
+
+Network continuity is a key aspect of 5G. In the 5G architecture, gNB neighbors play a central role in maintaining service continuity through mechanisms such as handover and load balancing.  By definition, a gNB neighbor is another gNB that can be measured and linked by the UE. If the current serving gNB is no longer optimal, the UE may connect to a neighbor gNB.
+
+To support this behavior, the network configuration specifies additional frequencies and cells that the UE should measure. The UE reports these measurements to the network, which then decides whether or not to initiate a handover.
+
+Neighbor types include:
+- **Intra-gNB neighbors** - cells belonging to the same gNB
+- **Inter-gNB neighbors** - cells belonging to different gNBs
+- **Inter-RAT neighbors** - cells belonging to another RAT (e.g., LTE)
+
+#### Required configuration parameters
+
+To define a neighbor cell in the configuration file, the following parameters are typically needed:
+- **gNB ID** - unique identifier of the gNB
+- **Cell ID** - identifier of the cell within the gNB
+- **Physical Cell ID** - identifier of the cell’s synchronization signal (PCI)
+- **Absolute Frequency** - frequency used by the SSB (absoluteFrequencySSB)
+- **Subcarrier Spacing** - numerology (e.g., 15 kHz, 30 kHz)
+- **PLMN configuration** - MCC, MNC, and MNC length
+- **Tracking Area Code (TAC)** - identifier of the tracking area
 
 Refer to the [handover tutorial](../handover-tutorial.md) for more information.