also important to measure the channel utilization a. The utilization a depicts the average utilization of a channels, i.e. how often this channel is being used for transmitting traffic. (6.8) This function is shown in Figure 6.3 over different number of channels for given call blocking probabilities B. It can be observed that the utilization increases with larger number of channels, and also with a higher blocking probability value. 6.2 Dimensioning for Circuit-Switched Traffic 0.001 0.0001 Number of channels n Figure 6.3: The average utilization per channel a equation (6.8) as a function of the number of channels for given values of the blocking In this thesis, equation (6.9) is proposed to estimate the link utilization b based on equation (6.8). Assuming that the reserved bandwidth for each connection is rm and each call generates an actual mean traffic 0 (usually O <rm). If the reserved bandwidth for each call is optimally configured without overestimation or underestimation of the bandwidth usage of each call (i.e. O = rm), then the link can be maximum utilized without violating the QoS. In this case, the link utilization can be calculated with equation (6.8). But if 0 is less than the reserved bandwidth, the link utilization is calculated as a product of the utilization of channels with equation (6.8) and the average traffic carried on each channel (i.e. the amount of actual mean traffic generated by each call 0 in a percentage of the reserved channel bandwidth r'm), as given in equation (6.9). b =a.0 (6.9) 6.2.2 Multi-Dimensional Erlang-B Formula The Erlang-B formula deals only with a single traffic stream in the system where the arrival process is a Poisson process with arrival rate 2 and the service times are exponentially distributed with intensity u. But for the multiple traffic type systems, especially in today's wireless or mobile networks like UMTS, there are different classes of services with various 6 Dimensioning for Single ATM-Based lub traffic demands and QoS requirements. Each traffic class cor