The calculations performed by CC-Excel are based on the Erlang traffic models developed in the first half of the last century. Two models are used:
The Erlang C traffic model is used for estimating call handling performance where calls are queued and makes the following assumptions:
• Calls are offered randomly to a queue (Poisson arrivals).
• Users wait if they find the system busy.
• Service times are exponential.
• Users are served in the order of arrival.
• Users are directed to the first available server (agent).
• Queue sizes are unlimited.
The Erlang B traffic model is used for estimating the number of lines required into a call centre facility and makes the following assumptions:
• Calls are presented randomly to a trunk group (Poisson arrivals).
• Call times are fixed or are exponentially distributed.
• Blocked calls are cleared.