Unit of Traffic - Erlang

Few question can be asked
-> what is the unit of traffic intensity
-> What is Erlang
-> Definition of erlang
-> How erlang is measured
-> What is use of erlang B table
-> Difference between Erlang B and Erlang C table

Here we comes with answers:

Erlang is the unit of telephone traffic intensity. This mane put in honor of danish mathematician.

Definition of Erlang: It is a total traffic volume of one hour (3600 Second).
In other words - one erlang is one channel occupied continuously for one hour.

Erlang calculation can be done via following methods:
1. Erlang B Table
2. Erlang B extended Table
3. Erlang C Table

One important factor GOS (Grade of Service) is consider to read Erlang table. Every operator decides its grade of service.
TRAI (Telecom Regulatory) fixed GOS 2% i.e. 2 calls can be blocked out of 100 calls.

Erlang Table is used to check how many lines required in busiest hour.

Erlang B table is most common used traffic model in telecom sector. This model consider all block calls clear immediately.
Erlang B extended table consider block calls cleared immediately and tried again.
Erlang C table consider all blocked calls queued until traffic channel is assigned.

How to read Erlang B Table:
Erlang B table consist GOS in X axis and No. of lines in Y axis. If our system capacity is 26.4 erlang and GOS is 2%, then we see the value of y axis where 26.4 or higher found below 2%. In below picture we can see we will be require 35 lines to satisfy condition.