Sign in Subscribe

handover 4g

Last updated on 

4G (LTE - Long Term Evolution) networks, the handover process is a bit more sophisticated compared to older technologies due to the nature of the 4G architecture and the capabilities it provides.

Here's a technical breakdown of the 4G handover process:

  1. Measurement and Thresholds:
    • User equipment (UE), such as smartphones or modems, continuously measures the signal strength and quality of the serving cell.
    • The UE also measures neighboring cells, typically referred to as 'Candidate Cells,' to determine potential targets for handover.
    • Thresholds are set based on these measurements. When certain conditions are met (e.g., the signal strength of a neighboring cell becomes stronger than the serving cell), a handover decision is initiated.
  2. Handover Decision:
    • Based on the measurements, the UE decides whether a handover is necessary.
    • This decision is also influenced by various parameters like radio link failures, signal quality deterioration, or load balancing decisions made by the network.
  3. Resource Allocation and Setup:
    • Once the decision to handover is made, the network determines the appropriate resources in the target cell.
    • A connection is set up in the target cell before the actual handover to ensure there's no interruption during the transition.
  4. Handover Execution:
    • The UE and the network synchronize to switch the ongoing communication session from the source cell to the target cell.
    • The UE starts communicating with the target cell, ensuring that there's a seamless transition. This might involve briefly connecting to both cells simultaneously.
    • Packet buffering or queuing mechanisms can be employed to ensure no data packets are lost during the handover.
  5. Handover Completion:
    • Once the UE is successfully communicating with the target cell and the signal quality and other parameters are satisfactory, the handover is completed.
    • The connection with the source cell is terminated, freeing up resources in that cell.
  6. Types of Handover in LTE:
    • Inter-eNodeB Handover: This is a handover between two base stations (eNodeBs) in the same LTE network.
    • Inter-RAT (Radio Access Technology) Handover: This involves moving a user from an LTE network to another network like 3G (UMTS) or 2G (GSM) when LTE coverage is not available.
    • Intra-eNodeB Handover: This is a handover that occurs within the same eNodeB, typically between different sectors of the same base station.
  7. Challenges and Enhancements:
    • Seamless handovers require precise coordination between the UE and the network, especially as users move at high speeds or encounter varying radio conditions.
    • Advanced features like Carrier Aggregation (using multiple LTE carriers) and Dual Connectivity (using LTE and another RAT concurrently) provide more robust handover capabilities and improved user experience.

The 4G handover process is a complex mechanism that ensures users experience consistent and high-quality connectivity as they move within the coverage area. Through continuous measurements, decision-making algorithms, and resource allocation, 4G networks can seamlessly transfer ongoing sessions between cells or base stations without causing interruptions or drops.