Why does LTE have hard handover?
In LTE networks, handover refers to the process of transferring an active connection from one cell to another without interrupting the service. Handovers are necessary when a user moves out of the coverage area of the current cell and into the coverage area of another cell. LTE, being a high-speed mobile network, ensures that the handover process happens quickly and efficiently to maintain the user’s service quality. But what sets LTE apart from older technologies is its use of **hard handover** in certain situations. Let me walk you through why this happens.
In earlier generations of mobile networks, such as 2G and 3G, handovers were often based on a continuous connection between the two cells. However, in LTE, hard handover (also referred to as **break-before-make** handover) involves a more distinct separation between the two cells during the handover process. Here’s how it works:
- Separation of Radio Resources: During hard handover, the user’s connection to the current cell is fully released before the connection to the new cell is established. This means there is a brief gap in communication.
- Control of Timing and Resources: Since LTE often uses a one-way communication method with centralized control, the release of resources in the old cell ensures that the new cell can quickly allocate resources without conflicting with the old connection.
- Efficiency in High-Speed Environments: Hard handovers are ideal in LTE for maintaining efficient resource utilization when high speeds and mobility are involved. The release of one connection before establishing the other allows the network to optimize resources quickly.
You may wonder why LTE doesn’t always rely on a softer, more seamless handover approach. The answer lies in the design of the LTE architecture, which is optimized for speed, capacity, and high-efficiency data transmission. While softer handovers allow for smoother transitions, LTE’s use of hard handovers makes it more robust, especially in situations where the mobile user is moving at high speeds or transitioning between different network types, such as from LTE to a 3G or 2G network.
Moreover, the use of hard handovers in LTE is closely tied to the **evolved packet core (EPC)**, which supports packet-switched data transmission. Unlike circuit-switched networks, where the connection remains open between cells during handover, LTE must release the current connection and establish a new one to keep data transmission optimized. This is where the concept of **break-before-make** handover becomes essential.
It’s also important to note that LTE handovers can be classified into two main categories: **intra-RAT handover** (within the same radio access technology, such as LTE to LTE) and **inter-RAT handover** (between different radio technologies, such as from LTE to 3G). The **hard handover** process is more common in inter-RAT scenarios, where different radio technologies require a complete disconnection and reconnection process.
To summarize, LTE networks use hard handover as a method to efficiently manage resources while maintaining high-speed connectivity for users. It ensures that there is no overlap or resource conflict between cells, providing an optimized, high-quality experience for mobile users, especially in dynamic and high-traffic areas.