es within the transport network in the 3 VPs scenario are less due to a better controlled transport network. The cell discard on the ATM layer can further have influence on the TCP transport layer of the users. When the discarded cells are not able to be recovered by the RLC retransmissions, they will cause TCP retransmissions. It is seen in Figure A.26 that resultant TCP retransmissions on HSDPA and HSUPA traffic is higher in the 2 VPs scenario than the 3 VPs scenario due to a higher cell losses. The TCP retransmissions will reduce the corresponding TCP congestion window and as a consequence decrease the user throughput. HSDPA TCP Retransmissions HSUPA TCP Retransmissions Scenario cenario Figure A.26: HSDPA and HSUPA TCP retransmissions Figure A.27 presents the HSDPA per user application throughput (left figure) and the average application throughput of all HSDPA users (right figure). It can be obviously seen that the achieved average HSDPA user application throughput is slightly lower in the 2 VPs scenario. This is due to more TCP retransmissions, as explained above. Moreover, since there are more cell losses in the transport network as shown in Figure A.25, the lub congestion control function of HSDPA will be triggered more often to reduce the data rate of the users on the downlink direction. Similar is for the HSUPA traffic. Figure A.28 compares the resultant ATM link throughput on the downlink (left diagram) and uplink (right diagram) individually. It shows that the link throughput obtained in the 3 VPs scenario is a little higher than the 2 VPs one, but the gap is not significant. HSDPA Per User Application HS DPA Average Application Throughput Throughput 2 VPs 3 VPs Scenario Figure A.27: HSDPA application throughput A.17 Dimensioning for Mixed Traffic Cases (ATM-Based lub) Downlink (HS DPA+R99) ATM Link Uplink UPA+R99) ATM Link Throughput Throughput Scenario Scenario Figure A.28: Downlink and uplink ATM link throughput As a summary, through comparing the network and user performances of using 2 and VPs as 