Inter-RAT Handover ( IRAT Handover)

The 2G/3G inter-RAT handover involves the handover from GSM to UMTS and the handover from UMTS to GSM. The handover is controlled mainly by the network. For MSs in dedicated mode, inter-RAT handovers can be performed, including the emergency handover, better cell handover, inter-RAT load handover, and inter-RAT service handover.

Inter-RAT Handover from UMTS to GSM

MSs in dedicated mode can be handed over from a UMTS cell to a GSM cell. The handover decision and handover procedure are controlled by the RNC. The BSS considers the incoming handover from UMTS to GSM as a common inter-BSC handover.

 The parameter Inter-RAT In BSC Handover Enable determines whether inter-RAT handover from UMTS to GSM is enabled. If Inter-RAT In BSC Handover Enable is set to No, the BSS rejects all the requests for the handover from UMTS to GSM.

Inter-RAT Handover from GSM to UMTS

The parameter Inter-RAT In BSC Handover Enable determines whether the inter-RAT handover from GSM to UMTS is enabled. If Inter-RAT In BSC Handover Enable is set to NO(No), the BSS rejects all the requests for the handover from GSM to UMTS and does not select a UMTS cell as the target cell.

In dedicated mode, an MS obtains the list of neighboring UMTS cells and other information from the Measurement Information. Then, the MS reports the measurement result to the BSS through the measurement report. After receiving the measurement result, the BSS determines whether to initiate the inter-RAT handover from GSM to UMTS based on the measurement result and the handover algorithm.