Question: What happens if the Target BSS fails to allocate resources for any of the requested PFCs during an E-UTRAN to GERAN A/Gb mode Inter RAT handover?
Option 1: The UE context is established in the target SGSN/BSS and resources are allocated.
Option 2: The Source eNodeB/MME releases all resources allocated for the handover.
Option 3: The Target BSS sends a PS Handover Request Nack (Cause) message to the Target SGSN, which then clears any reserved resources for the UE.
Option 4: The Handover Preparation Failure (Cause) message is sent directly from the Target SGSN to the Source eNodeB.
Explanation: When the Target BSS fails to allocate resources for any of the requested PFCs, it sends a PS Handover Request Nack (Cause) message to the Target SGSN. This causes the Target SGSN to clear any reserved resources for the UE, effectively rejecting the handover and keeping the UE in the Source eNodeB/MME.