Question: Under what circumstances can a Source RNC initiate the Relocation Cancel procedure after starting the execution of SRNS relocation via the Uu interface?
Option 1: If the target RNC rejects the relocation request due to resource unavailability.
Option 2: If the UE experiences a radio link failure during the relocation process.
Option 3: If the source RNC detects a better serving cell within its own coverage.
Option 4: After the UE returns to the source RNC, indicated by an RRC message showing the source RNC as its serving RNC.
Explanation: This is correct because, according to the specifications, after initiating the execution of SRNS relocation, the Relocation Cancel procedure can be started if the UE returns to the source RNC and indicates this change through an RRC message, signifying the UE now considers the source RNC as its serving RNC. This scenario directly matches one of the defined conditions for initiating the Relocation Cancel procedure.