r to encapsulate multiple packets into one UDP/IP packet. The AAL2 over IP scheme is also above Layer 3, but utilizing the existing fragmentation and multiplexing schemes from the AAL2 protocol. Its main benefit is easier interworking with ATM legacy transport networks. In this thesis, LIPE and CIP proposals are considered for the IP-based UTRAN. They are introduced in detail in Appendix A.11. Compression Scheme UDP/IP UDP/IP UDP/IP UDP/IP L2 +PPPmux PPPmux Figure 2.2: IP-based UNTRAN Protocol Stack (CIP, LIPE, AAL2, PPPmux) In 3GPP TR 25.933 [3GP04a], Multi-Protocol Label Switching (MPLS) protocol is also proposed as a promising solution for IP transport in the UTRAN. It is an interstitial, Layer 2.5 protocol which complements and enhances the IP protocol, in that it offers a complementary method of forwarding IP packets, while reusing the existing IP routing protocols. The main idea of this approach is to establish and manage Label Switched Paths (LSPs) for interconnecting Nodes B and RNC. When the transport technology in the UTRAN is evolved from ATM to IP, this comes along with new QoS schemes, network configurations and network topologies (number of hops, star/chain connections, etc.). One of the most challenges of using the IP transport technology is how to properly differentiate the services and to provide guaranteed QoS for a wide range of services each with different QoS requirements, since IP by itself is designed for 2.3 Evolution of UMTS the "best effort" Internet where there is no guarantee for the QoS. Therefore, special attentions are paid in this thesis on setting up an appropriate QoS architecture for the IP-based transport in the UTRAN and then dimensioning such IP transport network by taking careful considerations of the applied QoS framework. In section 3.4.2, a short overview of different developed IP QoS schemes is given, and in particular a Differentiated Services (DiffServ) based QoS framework is presented, which is used in this thesis, for the IP transport in the UTRAN. 2.3.4.2 Pseudo-Wir