Signal Measurement: The mobile device continuously measures the signal strength and quality of neighboring cells, including both 4G and 5G cells.
Thresholds: There are predefined thresholds for signal strength and quality that determine when a handover should be initiated. When the signal in the current cell falls below these thresholds, the handover process begins.
2. Handover Request:
Initiation: The mobile device initiates a handover request to the 5G base station (eNodeB in 4G, gNB in 5G) when it detects that the quality or strength of the current 5G connection is degrading.
Decision Making: The base station evaluates the request and decides whether a handover is necessary. This decision is based on various factors such as signal strength, quality, load balancing, and network policies.
3. Resource Allocation:
Reservation in 4G Network: If the decision is made to hand over to a 4G cell, the 4G resources are reserved in advance to accommodate the incoming connection.
Configuration: The handover process involves configuring the parameters for the 4G connection, such as frequency, modulation, and coding schemes.
4. Path Switching:
Bearer Path Establishment: Once the resources are allocated, a bearer path is established in the 4G network for the ongoing communication session.
Data Forwarding: The data flow is switched from the 5G to the 4G network. This is done smoothly to avoid any disruption in the ongoing communication.
5. Handover Confirmation:
Verification: The 4G base station confirms that the handover was successful and the mobile device is now actively connected to the 4G network.
Notification: The 4G base station notifies the core network about the successful handover.
6. Session Continuation:
Resumption of Communication: The ongoing call or data session continues seamlessly on the 4G network. The mobile device and the network are now synchronized for communication through the 4G infrastructure.
7. Optional: 5G Release:
Release Resources in 5G: After successful handover to 4G, resources in the 5G network, including radio and core network resources, can be released.
Notes:
Interworking Between 4G and 5G: This process assumes that there is interworking between the 4G and 5G networks, allowing for smooth handovers between different generations of mobile networks.
Policy Considerations: The decision-making process involves network policies and priorities, including load balancing, network congestion, and user experience considerations.
