n control algorithms are modeled on the lub interface. They are used to avoid the link congestion and reduce the losses on the lub, therefore can provide guaranteed QoS to the end users while efficiently utilizing the lub transport resources. The detailed modeling of congestion control and flow control can be found in [WL*06]. II. Modeling of HSUPA The introduction of HSUPA functions and protocol stacks have been given in section 2.3.3 and Appendix A.9. The HSUPA protocols are implemented on top of the existing HSDPA functions in the HSPA simulation model. The modeling of the HSUPA together with the HSDPA is shown in Figure A.9. Application Internet or External Application MAC-d MAC-es MAC-d MAC-e MAC-d MAC-e MAC-hs MAC-d MAC-es Node B AAL2/ATM AAL2/ATM Figure A.9: HSPA simulator overview [LZK`08] A.11 Multiplexing Schemes for the IP-Based UTRAN As can be seen, the main enhancements of the model are the new implemented HSUPA protocol entities (MAC-e and MAC-es), the new transport channel E-DCH for each HSUPA UE, and the corresponding E-DCH FP layer over the lub interface. As well the RLC acknowledged mode is implemented for the uplink including the complete RLC functions for transmitting the HSUPA traffic. The MAC-e protocol includes HARQ and HSUPA scheduler (also called E-DCH scheduler) functionality. In the HSUPA simulation model, the implemented HARQ is based on the stop and wait protocol. There are four HARQ processes which work in parallel for a single user flow. Whenever the HARQ process is free it allows the one MAC-e PDU to be transmitted with the defined block error rate (BLER) for each retransmission. For the modeling of the HSUPA scheduler, a TTI (Transmission Time Interval) based scheduler is implemented in a way that the interference level is the main criterion for sharing the resources between the HSUPA E-DCH flows. Several HSUPA scheduler implementations and flavors are feasible, but in the current simulation model a simplified scheduler is implemented. The implemented scheduler always gives priori