Inter-frequency handover (IFHO) in LTE involves a series of steps to seamlessly transition a user’s device from one frequency band to another. It begins with signal measurement and evaluation, triggering the handover when a neighboring cell’s signal quality is better. The serving cell informs the network, which prepares for the handover.
A Handover Command is sent to the user’s device, instructing it to switch to the target cell. Once successfully connected, data traffic is forwarded through the new cell, and the handover is confirmed. This ensures uninterrupted connectivity as users move between different frequency bands, optimizing network performance.
What is inter-frequency handover call flow in LTE?
Inter-frequency handover (IFHO) is an essential operation in Long-Term Evolution (LTE) networks that enables seamless mobility for users as they move between different frequency bands. In LTE, there are multiple frequency bands allocated for cellular communication. When a user’s device moves from one frequency band to another, the network must perform an inter-frequency handover to ensure uninterrupted service.
| Component | Description |
|---|---|
| Inter-Frequency Handover Overview | An inter-frequency handover occurs when a mobile device moves from a cell operating on one frequency band to a different frequency band, typically during mobility or coverage transitions in LTE. |
| Main Function | Ensures seamless connectivity while the mobile device switches between cells operating on different frequency bands without interrupting ongoing calls or data sessions. |
| Key Entities Involved | – eNodeB (source and target) – Mobility Management Entity (MME) – Serving Gateway (SGW) – Packet Data Network Gateway (PGW) – User Equipment (UE) |
| Handover Procedure | The process involves the following steps:
|
| Advantages | Ensures uninterrupted service, improves coverage, and enables efficient resource management by leveraging different frequency bands for optimal user experience. |
Here’s a detailed explanation of the inter-frequency handover call flow in LTE:
Measurement and Evaluation:
- The process begins with the user’s device continuously measuring the quality of neighboring cells’ signals, including cells operating on different frequency bands.
- The device periodically reports these measurements to the serving cell.
Triggering the Handover:
- When the quality of a neighboring cell’s signal exceeds a predefined threshold and is considered better than the serving cell’s signal, the network decides to initiate an inter-frequency handover.
- The decision can also be based on other factors like network congestion or load balancing.
Handover Request:
- The serving cell sends a Handover Request message to the Mobility Management Entity (MME) and the Serving Gateway (SGW) to inform them about the upcoming handover.
- The MME initiates the necessary procedures for handover preparation.
Preparation Phase:
- The MME selects the target cell (the cell on the new frequency band) and informs the serving cell.
- The serving cell configures the necessary parameters for the handover, such as the radio resources on the target cell.
- The user’s device is instructed to prepare for handover.
Handover Command:
- The serving cell sends a Handover Command message to the user’s device, instructing it to switch to the target cell.
- The message includes details such as the new frequency band, cell identity, and timing information for the handover.
Handover Execution:
- The user’s device follows the instructions in the Handover Command and tunes to the target cell’s frequency.
- It performs measurements to ensure the signal quality on the target cell is acceptable.
Handover Completion:
- Once the user’s device successfully establishes a connection with the target cell and meets the quality criteria, it sends a Handover Complete message to the serving cell.
- The serving cell notifies the MME and SGW that the handover is complete.
Data Forwarding:
- Data packets are now routed through the target cell, ensuring that the user’s ongoing communication remains uninterrupted.
- The SGW updates its routing information accordingly.
Handover Confirmation:
The MME acknowledges the handover completion and informs the core network that the user has successfully transitioned to the new frequency band.
Release Resources:
The resources on the old serving cell are released, and the network returns to its normal operation.
Inter-frequency handovers in LTE are crucial for providing a seamless user experience, especially in scenarios where different frequency bands are utilized to optimize coverage and capacity. This process ensures that users can stay connected and maintain their ongoing data sessions while moving between cells operating on different frequencies.