How does handover work in LTE?

How Does Handover Work in LTE?

Let Me Explain You the Basics

Today, we’re going to discuss how handover works in LTE. Handover is a critical function in mobile networks that ensures a continuous and reliable connection when a user moves from one cell tower’s coverage area to another. Let me walk you through the process and how it’s done in LTE networks.

What Is Handover?

Handover (or handoff) refers to the process of transferring an ongoing call or data session from one cell tower to another as the user moves across different coverage areas.

In LTE, handover ensures that users maintain a stable connection even when they are on the move, like when driving or walking around. It involves seamless switching between cells to avoid dropped calls or interrupted data sessions.

Types of Handover in LTE

There are two main types of handover in LTE:

• Hard Handover: A hard handover is a break-before-make process, where the connection to the current cell is lost before the connection to the new cell is established. This type of handover is used in scenarios where the network cannot maintain the connection during the transition.
• Soft Handover: A soft handover is a make-before-break process, meaning the connection to the new cell is established before the old connection is released. This type of handover ensures no disruption in the service, and it is more common in earlier generations of cellular networks, like CDMA and WCDMA.

How Does Handover Work in LTE?

In LTE, the handover process is handled more efficiently using a hard handover approach. Let me break down the process step-by-step:

1. Initiation of Handover: As the mobile device moves closer to the edge of the current cell’s coverage area, the eNB (evolved Node B, or base station) monitoring the user’s connection detects that the signal strength is weakening. The eNB initiates a handover to a neighboring cell that offers a stronger signal.
2. Preparation: The source eNB (the current cell) sends a request to the target eNB (the next cell) to prepare for the handover. This includes sending information about the user’s current session and any necessary security or encryption keys.
3. Handover Command: Once the target eNB is ready to accept the handover, it sends a handover command to the mobile device, instructing it to switch to the new cell. This command includes the necessary details about the new cell’s settings, frequency, and timing.
4. Connection Setup: The mobile device establishes a connection with the new eNB. During this time, data sessions and ongoing calls are briefly suspended, but the process is designed to be fast enough that it’s barely noticeable to the user.
5. Completion: After the device successfully connects to the new cell, the source eNB releases its resources, and the handover process is complete. The user can now continue the call or data session on the new cell without interruption.

Let Me Show You with an Example

Imagine you’re walking down the street, and you’re on a phone call. As you approach the edge of the cell’s coverage area, the LTE network detects that the signal strength is weak and initiates a handover to the next cell tower. The call seamlessly continues without any disruption as your connection switches from one cell tower to another.

Why Is Handover Important in LTE?

Handover is crucial for several reasons:

• Maintaining Connectivity: It allows users to stay connected while moving, without experiencing dropped calls or interrupted data sessions.
• Optimizing Network Resources: Handover ensures that users are connected to the cell with the best signal, improving overall network performance.
• Reducing Latency: Smooth handovers minimize the time it takes for the device to switch between cells, reducing lag and delays in communication.

Challenges with Handover in LTE

While LTE handovers are designed to be fast and seamless, there are some challenges:

• Latency: There can be small delays during the handover process, particularly when moving at high speeds, like in a car or train.
• Signal Quality: If the target cell has a weak signal or interference, the handover process may fail, leading to service interruptions.
• Handover Failures: In some cases, if the network cannot complete the handover successfully, the call or data session may be dropped.

When Do You Monitor Handover?

Monitoring handovers is essential when:

• You need to ensure that users in high-speed environments (like trains or cars) maintain seamless connections.
• You’re troubleshooting network issues, such as dropped calls or slow data speeds, related to handover failures.
• You’re optimizing network performance to ensure smooth handovers between cells in a crowded or congested area.

In Summary

Handover in LTE ensures that users maintain connectivity when moving from one cell’s coverage area to another. I’ve explained how the process works, why it’s essential, and the challenges it faces. Smooth handovers are key to providing continuous service, especially in mobile networks where users are constantly on the move.