What is handover?

Handover, also known as handoff, is a fundamental concept in mobile and wireless communications networks. It refers to the process of seamlessly transferring an active communication session or connection from one network access point or cell to another as a user or device moves between coverage areas. This ensures that the user can maintain uninterrupted connectivity as they roam within the network.

How handover works

Handover is critical for maintaining continuous service in mobile networks, as users are constantly moving between different cells or access points. The process typically involves the following steps:

Monitoring and measurement: The mobile device or network infrastructure continuously monitors the signal strength and quality of the current connection, as well as nearby cells or access points.
Handover decision: Based on predefined criteria, such as signal strength, network load, or user preferences, the network determines when a handover is necessary to maintain the best possible connection.
Handover execution: The network coordinates the transfer of the active session or connection to the target cell or access point, ensuring that the user experience is seamless and interruptions are minimized.

Types of handover

There are several different types of handover, depending on the specific network technology and deployment scenario:

Intra-system handover: This occurs within the same network technology, such as transferring a call from one 4G LTE cell to another.
Inter-system handover: This involves transferring a connection between different network technologies, such as from 4G LTE to 3G UMTS.
Horizontal handover: This refers to handover between cells or access points of the same network technology and generation, such as between two 4G LTE cells.
Vertical handover: This involves handover between different network technologies or generations, such as from 4G LTE to 3G UMTS.

Importance of handover

Handover is a critical feature in mobile and wireless networks, as it enables seamless mobility and uninterrupted service for users. Without effective handover mechanisms, users would experience dropped connections, service disruptions, and a poor overall user experience as they move between coverage areas. Proper handover ensures that:

Users can maintain continuous connectivity and uninterrupted service as they move around.
Network resources are efficiently utilized, with active sessions being transferred to the most appropriate cell or access point.
Network capacity and performance are optimized, as handover helps to balance the load across different cells or access points.

Handover challenges and considerations

Implementing effective handover mechanisms in mobile and wireless networks can be challenging, requiring careful consideration of several factors:

Timing and synchronization: The handover process must be timed correctly to minimize service disruptions and ensure a seamless transition between cells or access points.
Network coordination: Handover requires coordination between the mobile device, the current cell or access point, and the target cell or access point, which can be complex to manage.
Quality of service: Handover must be designed to maintain the required quality of service (QoS) for the active session, such as ensuring minimum latency, jitter, and data throughput.
Security and authentication: During handover, the mobile device must be re-authenticated and authorized on the target cell or access point, while ensuring the security of the communication session.

Real-world examples

Handover is a critical feature in various mobile and wireless communication networks, including:

Cellular networks: As users move between cells in 2G, 3G, 4G, and 5G cellular networks, handover ensures that their voice calls, data sessions, and other services are seamlessly maintained.
Wi-Fi networks: In enterprise or public Wi-Fi deployments, handover enables mobile devices to move between different access points while maintaining uninterrupted connectivity.
Satellite communications: In satellite-based networks, handover is necessary to transfer active sessions between different satellite coverage areas as the user or device moves.
Emergency services: Handover is crucial in emergency response and public safety communications, where first responders need to maintain reliable connectivity while on the move.