Question: In E-UTRA, when using ROHC (Robust Header Compression) for u-plane data, at what stage in the process is header decompression performed for PDCP (Packet Data Convergence Protocol) PDUs?
Option 1: Before deciphering, as part of initial PDU processing
Option 2: Simultaneously with deciphering, as an integrated step
Option 3: After integrity protection verification, but before deciphering
Option 4: After performing deciphering, as a subsequent step
Explanation: According to the specified behavior for ROHC in E-UTRA, header decompression using ROHC is performed after the PDCP PDUs have been deciphered. This sequence ensures that encrypted data is first decrypted (deciphered) to its original form before any compression headers are decompressed, maintaining the security and integrity of the data transmission process.