Question: What is the primary purpose of the `rf-RetuningTimeDL-r14` field in E-UTRA UE radio access capabilities?
Option 1: To indicate the time required for a UE to switch from idle to connected mode.
Option 2: To specify the maximum tolerable delay for DL data transmission on a primary cell.
Option 3: To define the periodicity of SRS transmissions on a PUSCH-less Secondary Cell (SCell).
Option 4: To inform the network about the interruption time on DL reception during RF retuning for band pair switching to transmit SRS on a PUSCH-less SCell.
Explanation: The correct answer, Option 4, accurately reflects the purpose of the `rf-RetuningTimeDL-r14` field as described. It highlights the field's role in indicating the time during which DL reception is interrupted due to RF retuning, specifically for switching between band pairs to support SRS transmission on a PUSCH-less SCell. This is crucial for network planning and ensuring seamless communication. The other options are incorrect because they either describe unrelated procedures (Options 1 and 2) or misinterpret the field's application (Option 3).