ection 6.2.1 and 6.2.2 the Erlang-B formula (for a single traffic stream) and the multi- 6 Dimensioning for Single ATM-Based lub dimensional Erlang-B formula (for multiple traffic streams) shall be applied. The required input parameters for dimensioning are the offered traffic per traffic stream, the desired blocking probability as the QoS requirement, and the reserved bandwidth for each call per traffic stream. Table 6.2 gives the detailed parameters that describe a traffic stream. Traffic Parameters bearer rate in bps (i.e. peak data rate) busy hour call attempts (calls / hour) per user number of users in the system in the busy hour arrival rate of new calls (calls/second) mean duration per call in seconds, i.e. T=1/u activity activity factor of a call: defined as the ratio of the total duration of ON periods and the total lifetime of the call reserved bandwidth for a call in bps, which is used for admission control the maximum number of simultaneous connections allowed by the system traffic demand in bps Table 6.2: Dimensioning with Erlang-B formula (Traffic Parameters) It is assumed that the arrival traffic is a Poisson process with arrival rate 2. The arrival rate of the traffic stream a is derived from equation (6.15). It defines the arrival rate of new calls, i.e. the mean number of new calls every second. a = BHCA K (6.15) Given the average call duration T, the offered traffic A in Erlang can be obtained with equation (6.1). With the offered traffic A, the created traffic demand of this stream TM is calculated as the product of the peak data rate, the activity factor of a call and the offered traffic Erlang, as shown in (6.16): (6.16) In case the network has only one single traffic stream, let C denote the allocated bandwidth on the lub interface, then the maximum number of simultaneous connections allowed by the network N is calculated below. It is an integer number. N = C/2, (6.17) 6.2 Dimensioning for Circuit-Switched Traffic Thus, with the offered traffic A and maximum allowed number of simultaneous c