# Cellular Traffic Calculator.

Cellular Traffic Calculator

The number of voice circuits, grade of service and quantity of traffic in a telephone network is related according to a formula first published by A. K. Erlang in 1917.

That formula is rather tedious to manually apply quickly, and telephone traffic engineers often use "Traffic Tables' with pre-calculated values that simplify the procedure for several common applications.

The short computer program shown on this page, written in common BASIC, automates Erlang's formula. It will precisely calculate either of the following items:

Grade of Service (GS) or Blocking-- Inputs required are the number of voice circuits (VC) available to all users, and the number of users (CU).

Number of Voice Circuits Required (VC)--Inputs required are the number of users (CU) and the desired grade of service (GS).

The program as written is especially intended for study of cellular mobile telephone requirements, although it may be easily changed to suit different applications.

It assumes that a user will make one call per busy hour, and that each call will last 100 seconds, including call set-up time.

These values result in a traffic quantity of 1/36 or 0.028 Erlangs per customer, which is a common assumption for cellular traffic. This assumption may be altered by changing Lines 130 and 190. For example, changing Lines 130 and 190 to read ER=CU/1 changes the traffic quantity per customer to 1 Erlang and causes the program to substitute Erlangs for number of users (CU), thus duplicating exactly a standard traffic table.

Any computer that will run BASIC may be used, including personal computers. Calculations involving large numbers of trunks or users will take a long time (depending on the speed of the computer used).

For example, entries of 1,000 customers and two-percent grade of service will require approximately 80 seconds before the answer of 37 voice circuits is displayed using a Commodore 64 personal computer.

The actual implementation of the Erlang formula is the subroutine in Lines 2000 through 2130.
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