In 5G, inter-frequency handover is a fundamental mobility management procedure that allows a User Equipment (UE) to seamlessly transition between cells operating on different frequency bands. This process is crucial for maintaining a continuous and reliable connection as the UE moves through the coverage area of the 5G network. Inter-frequency handover is particularly significant in scenarios where multiple frequency bands are utilized to provide extensive coverage and enhance network capacity.
Key aspects of inter-frequency handover in 5G include:
- Frequency Bands in 5G:
- 5G networks deploy various frequency bands, including Frequency Range 1 (FR1) and Frequency Range 2 (FR2). FR1 encompasses sub-6 GHz frequencies, while FR2 includes millimeter-wave (mmWave) frequencies. Inter-frequency handover becomes necessary when a UE transitions between cells operating on different frequency bands.
- Seamless Mobility:
- Inter-frequency handover is designed to ensure seamless mobility for UEs as they move within the network. This process allows the UE to maintain an active connection while transitioning between cells, even when these cells operate on distinct frequency bands.
- Radio Measurements:
- Prior to initiating an inter-frequency handover, the UE continuously performs radio measurements to assess the quality of neighboring cells operating on different frequency bands. These measurements include signal strength, signal quality, and other relevant parameters.
- Neighbor Cell Information:
- The network provides the UE with information about neighboring cells operating on different frequency bands. This information enables the UE to make informed decisions about initiating an inter-frequency handover based on the quality of the available cells.
- Measurement Reports:
- The UE periodically generates measurement reports based on the observed radio conditions. These reports are sent to the network, allowing it to make decisions regarding handover triggers and target cells.
- Handover Decision:
- The decision to initiate an inter-frequency handover is made by the network based on the received measurement reports. When the UE’s connection quality with the current serving cell degrades or when a neighboring cell on a different frequency band is deemed more suitable, the network triggers the handover process.
- Target Cell Configuration:
- Before executing the handover, the network configures the target cell (the cell on a different frequency band) to prepare it for the incoming UE. This involves synchronization, configuration of radio parameters, and other necessary adjustments.
- Handover Execution:
- The actual handover execution involves the UE switching its connection from the current serving cell to the target cell on a different frequency band. This process must be performed seamlessly and without service interruption to ensure a positive user experience.
- Measurement Gap:
- To facilitate the handover process, a measurement gap may be introduced during which the UE pauses data transmission temporarily to perform accurate measurements on neighboring cells.
- 3GPP Standardization:
- The procedures and protocols for inter-frequency handover are standardized by the 3rd Generation Partnership Project (3GPP). Standardization ensures that handover processes are consistent across different 5G networks and compliant with global specifications.
In summary, inter-frequency handover in 5G is a critical mobility management procedure that enables UEs to transition seamlessly between cells operating on different frequency bands. This process ensures continuous connectivity, optimizing the user experience and allowing for efficient use of diverse frequency resources within the 5G network.