Conditional Handover (CHO) in 5G NR

Conditional Handover (CHO) in 5G New Radio (NR) is a feature designed to enhance the efficiency and reliability of handover procedures, especially in scenarios where traditional handover mechanisms may not provide the optimal user experience. The fundamental idea behind Conditional Handover is to enable the network to make handover decisions based on specific conditions or criteria, rather than solely relying on traditional signal strength or predefined handover parameters.

Here's a technical breakdown of Conditional Handover (CHO) in 5G NR:

  1. Purpose and Need:
    • 5G NR introduces new use cases and scenarios that demand advanced handover mechanisms. These might include scenarios with diverse mobility patterns, varying quality-of-service (QoS) requirements, and dynamic network conditions.
    • Traditional handover mechanisms, like the signal strength-based approach, may not always be sufficient to ensure seamless connectivity and meet specific service-level agreements (SLAs).
  2. Conditions/Criteria for Handover:
    • Instead of just relying on signal strength, the Conditional Handover mechanism considers multiple parameters or conditions to trigger a handover. These conditions can be based on:
      • Quality of Service (QoS) requirements
      • Mobility patterns
      • Network load and congestion
      • Application-specific requirements (e.g., low latency for real-time applications)
      • User preferences or profiles
  3. Dynamic Decision-making:
    • The network continuously monitors various parameters related to the user's connection and the surrounding network environment.
    • Based on the predefined conditions and thresholds, the network evaluates whether initiating a handover would enhance the user experience, maintain QoS levels, or optimize resource utilization.
    • If the conditions are met, the network triggers the handover process, ensuring that the user's session remains uninterrupted and meets the required performance criteria.
  4. Integration with 5G NR Architecture:
    • Conditional Handover is integrated into the 5G NR architecture, leveraging the capabilities of the Next-Generation NodeB (gNodeB) or base station.
    • The gNodeB monitors various Radio Resource Control (RRC) parameters, user plane data, and signaling information to evaluate the conditions for handover.
    • The Mobility Management Entity (MME) and other core network elements also play a role in facilitating the handover process, ensuring seamless connectivity and session continuity.
  5. Benefits:
    • Enhanced User Experience: By making handover decisions based on specific conditions and criteria, CHO ensures that users experience optimal connectivity, reduced latency, and improved service quality.
    • Efficient Resource Utilization: By dynamically adjusting handover decisions, the network can optimize resource allocation, reduce congestion, and improve overall network efficiency.
    • Support for Diverse Use Cases: CHO enables 5G NR networks to support a wide range of use cases, including enhanced Mobile Broadband (eMBB), Ultra-Reliable Low-Latency Communications (URLLC), and massive Machine Type Communications (mMTC).