A.13 shows a detailed insight of how each RAB competes for the bandwidth resources in a dynamic manner. In this example, there are 3 user connections sharing a 200 kbps link: 2 users with RAB 64 kbps and 1 user with RAB 128 kbps. Each user transfers the Appendix same amount of data. In this figure, the green curve shows TCP throughput of RAB 128 kbps, blue and red curves show TCP throughputs of the other two RAB 64 kbps users. It can seen from Figure A.13 that at the beginning of the transmission, the higher RAB rate gets more transmission resources than the lower RAB rate, and as a result obtains a relatively higher throughput. After some time, the throughput of RAB 128 reduces while the throughput of RAB 64 increases until they both become equal in the stable phase. For RAB 64 kbps, the obtained average throughput on the ATM layer during the stable phase is around 62.5 kbps, and RAB 128 kbps gets around 63 kbps. But considering the overall throughput of the whole connection, RAB 128 kbps obtains a little higher throughput in average. user 1 RAB 64kbps user 2 RAB 64kbps user 3 RAB 128kbps time (s) Figure A.13: TCP connection throughput of each RAB type - multiple RABs scenario A.15 Dimensioning for HSPA Traffic The HSPA traffic is characterized by high peak data rates and high burstiness. To support such HSDPA traffic on the downlink and HSUPA traffic on the uplink, not only the UMTS air interface but also the backhaul of the UMTS access network, will require considerably high capacity for the provisioning of high-speed transmission of packet data. This poses big challenges in the dimensioning of the backhaul network due to the limited and expensive transport resources. In the framework of this thesis, HSPA is still using the ATM as the underlying transport in UTRAN. This chapter presents the dimensioning results for HSPA, which are obtained from simulations using the developed HSPA simulation model (introduced in section 5.6). Different than Rel99 traffic, the HSPA traffic has low transport delay requirement at