milar reasons as for HSDPA, uplink scheduling and HARQ functionalities are located in the Node B which stays close to the radio interface. Thus the Node B can track the rapid changes of the air interface and make fast decisions concerning the scheduling and retransmissions. Moreover, there is a new protocol entity for the RNC as well. When the UE is in soft handover with multiple Node Bs, different transport blocks may be successfully received by different Node Bs. Then there is a possibility that the packets from different Node Bs arrive such that the order of packets is not retained. In order to ensure in-sequence delivery of data blocks to the RLC layer, a reordering functionality is required in the RNC in the new MAC entity, the MAC-es. If such reordering is handled at the Node B, then an unnecessary delay would be introduced because the Node B would have to wait for missing packets until they could be determined to have been correctly received by another Node B in the same active set. In a similar manner to HSDPA, the RLC layer in HSUPA is involved with the retransmission of packets if the physical layer fails to correctly deliver them after the maximum number of retransmissions is exceeded. Appendix MAC-d MAC-d MAC-es MAC-es MAC-e EDCH FP EDCH FP MAC-e Physical Physical Layer Layer Node B Figure A.7: HSUPA protocol architecture Impact of HSDPA and HSUPA on the UTRAN lub Interface With the introduction of HSDPA and HSUPA in the UMTS network, the traffic on the downlink and uplink are expected to increase drastically due to a greatly improved peak data rate over the air interface. HSDPA provides data rates up to 14.4 Mbps over short (2 ms) period in the downlink and HSUPA offers uplink speeds up to 5.76 Mbps. While Rel99 UEs support data rates of at most 384 kbps, and the data rate on different interfaces, including the Iu-PS interface to the packet core network, is equal to the one used for radio interface. With HSPA, the situation has changed. Though a high peak data rate available in the air interface, it 