on the last mile links. As it is supposed that the given CAC guaranteed bit rate per connection on the last mile link is optimum, SO that each connection gets a sufficient bandwidth to transport and thus protect from packet losses on the last mile links. 8.2 Dimensioning for Circuit-Switched Traffic The corresponding analytical approach for dimensioning such star-structured RAN (Figure 8.1(a)) is illustrated in Figure 8.1(b), with the application of the MD-Erlang model for dimensioning the individual last mile links and the MMPP/D/1 queuing model to dimension the backbone link. Assuming there are n Node Bs in the radio access network and each Node B transmits the same circuit-switched traffic, the following parameters are defined: Let Cac_i be the last mile link capacity for Node B i; Let C bb be the capacity of the backbone link; Let n be the number of Node Bs in the radio access network; Let rm be the CAC guaranteed bit rate requested by each connection at last mile; - Let r peak be the peak data rate of each connection Let pb denote the desired connection reject ratio as the QoS target for dimensioning the last mile link; Let a be the amount of offered user traffic on the last mile link i in Erlang; Let y be the carried traffic on each last mile link i as a result of CAC in Erlang; Let qos bb denote the desired packet loss ratio as the required network QoS for dimensioning the backbone link. As mentioned above, the packet losses are caused by the extremely long transport delays over the link which exceed a maximum allowed delay threshold. Here the packet loss ratio is equal to the ratio of the amount of packets whose delays exceeding a predefined maximum value to the total amount of packets. As shown in Figure 8.1, the capacity of each last mile link Cac_iis calculated by using the MD-Erlang model. Given a certain last mile link capacity, based on the offered traffic a and the requested CAC guaranteed bit rate rm , the connection reject ratio can be directly calculated from the MD-Erlang Model. Then for bandwi