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Example calculation

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How much bandwidth in Mbps should I provide through an IP based network to carry if 522.1 Erlangs of traffic is offered to the system in its busiest hour.  I am using the G.729A codec.  I am using cRTP header compression to reduce the packet header to 2 octets and one packet is being transmitted in each direction every 30 milliseconds.  I accept that 1% of calls will be blocked.


To find out the answer to this question, follow these steps:


Select G.729A using the Coding algorithm drop down box.
Select 30ms using the Packet duration drop down box.
Select cRTP header compression (2 bytes) using the RTP header compression drop down box.
Choose Mbps as the bandwidth unit by clicking on the Mbps radio button on the right side of the window.
Click on the Erlangs radio button on the right side of the window to indicate that you will be entering the busy hour traffic figure in Erlangs.
Click the Unknown radio button in the B/W (Mbps) area to indicate that you wish to calculate the bandwidth.
Enter 522.100 in the edit box in the B.H.T. area.
Enter 0.010 in the edit box in the Blocking area.
Press the Calculate button.



After a short time, 4.686 will be displayed in the grey edit box.  This is the result of the calculation, and shows that 4.686 Mbps should be provided through an IP based network using the selected VoIP characteristics if 522.1 Erlangs of busy hour traffic is offered to the system.  This result does not take any layer two overhead into account.