 possible multiplexing gain as a result of aggregating the traffic from multiple last mile links over a single backbone link. In the framework of this thesis, the network related QoS requirements such as packet delay and packet loss are considered for determining the overbooking for the backbone link, since they are also important QoS for the circuit-switched type of traffic in the UTRAN. As introduced in Chapter 1, the lub interface needs to satisfy the strict delay requirements to ensure optimal radio resource utilization. Moreover, the packets which experience excessively long delays over the lub have to be discarded as explained in section 3.3.3.4. Though packet losses usually do not trigger retransmissions for the real time applications, they usually result in service degradation for the end users due to the lost data. Therefore for dimensioning process, it is important to perform appropriate overbooking on the backbone link in order to guarantee a certain packet loss ratio or packet delay over the lub. The following subsections present the analytical approach for dimensioning the last mile link and the backbone link for the circuit-switched traffic in a star-structured multi-lub RAN. 8.2.1 Network Dimensioning Approach In this thesis, it is proposed to apply the multi-dimensional Erlang-B (MD-Erlang) model to dimension the last mile link to meet the desired CAC connection reject ratio QoS; and apply packet-level queuing models to dimension the backbone link in order to fulfill the transport network QoS requirements, i.e. packet delay and packet loss ratio. In Chapter 6.4.3, the MMPP/D/1 model has been presented and demonstrated for dimensioning a single lub link for the circuit-switched traffic to satisfy a desired packet delay or packet loss QoS. In the multi-lub scenario, it is suggested by the author to apply the MMPP/D/1 model as well to dimension the backbone link to meet the objective of a desired packet delay or packet loss ratio in the network. It is assumed that there are neglectable packet losses 