its/s 5000 erl 1500 Mbits/s 40% MSG-internal CE voice (E1) 5000/0.8/31 = 202 E1 202 = 13 13 boards CE voice (STM) 5000/0.8/31/63 = 4 STM-1 4 boards ATM data-access side 1500/135 = 12 STM-1 3 boards ATM data-nework side 900 Mbits/s (/135 = 7 STM-1) ATM voice 4000 X 0.064 X 1.13/0.8 = 362 Mbits/s (/150 = 3 STM-1) 3 boards E1's ==> 2 sub-rack Total (if E1): 19 boards STM-1's 1 sub-rack Total (if STM-1): 10 boards Figure A4.11 Calculation of CE/ATM interfaces in an MSG - numerical example This figure shows a numerical example of calculating the number of interface boards in MSGs. Voice traffic, access side: The total voice traffic is 50 000 X 0.1 = 5000 Erlang. Dividing the voice traffic by the utilization factor (0.8) and the number of speech channels (31) in a PCM-link (E1) gives the number of E1s needed. If we are using STM-1 interfaces instead of E1 interfaces, we also divide by 63, which is the number of E1 that can be transferred in STM-1. Data traffic, access side: For the data traffic, we calculate the number of STM-1s by dividing the traffic with the payload (135 Mbits/s). Understanding Changing Telecommunications - Building a Successful Telecom Business Voice + Data, network side: For the voice (mapped into ATM cells) on the network side, we use the expression: traffic (in Erlang) X 0.064 X 1.13/0.8 in order to calculate the number of Mbit/s. As voice and data can be mixed in the ATM network, we simply add the needed capacity (Mbits/s) for voice and data and divide with 135 to get the number of STM-1s. Result: The result shows that we will need two sub-racks when using E1 interfaces, and one sub-rack when STM-1 interfaces are used. PROCESSOR DIMENSIONING: BASIC PRINCIPLES Goal and Methodology To find out the number of telephony servers needed, we have to calculate the load on the processor (CP) and the ML/MGW in the telephony server. We also have to check the processor capacity in the MSG, which can be a limiting factor in some cases. For reasons of simplicity permanent virtual circuits (PVCs) are assumed f