Question: For UTRA FDD UEs capable of receiving HS-DSCH and HS-SCCH in CELL_FACH state, what metric determines the receiver single link performance of the High Speed Physical Downlink Shared Channel (HS-DSCH), as per Release 7 and later releases?
Option 1: Throughput of the downlink shared channel
Option 2: Round Trip Time (RTT) for RLC acknowledgments
Option 3: RLC SDU error rate (RLC SDU ER)
Option 4: Signal-to-Noise Ratio (SNR) of the physical downlink
Explanation: The correct answer is Option 3 because, according to the specifications for UTRA FDD UEs in Release 7 and later releases, the receiver single link performance of the HS-DSCH is specifically determined by the RLC SDU error rate (RLC SDU ER). This metric directly reflects the reliability and efficiency of data transfer over the HS-DSCH, making it a crucial indicator of its performance. RLC SDU ER measures how often errors occur at the Radio Link Control (RLC) layer’s Service Data Unit (SDU), providing insight into the link’s overall quality and robustness in delivering data packets.