In Single Registration mobile network, the UE registers only with one network, either the 4G network, or the 5G network.

This means that the UE establishes a connection and exchanges data through either the 5G or the 4G network, but not both simultaneously as what happens in "Dual Registration".

As a result, Handovers between the 5G and 4G networks require the UE to re-register with the new network.

This approach is simpler to implement and may be more suitable for early 5G deployments.