Grade of Service - What Is Grade of Service and How Is IT Measured?

What Is Grade of Service and How Is It Measured?

When a user attempts to make a telephone call, the routing equipment handling the call has to determine whether to accept the call, reroute the call to alternative equipment, or reject the call entirely. Rejected calls occur as a result of heavy traffic loads (congestion) on the system and can result in the call either being delayed or lost. If a call is delayed, the user simply has to wait for the traffic to decrease, however if a call is lost then it is removed from the system.

The Grade of Service is one aspect of the quality a customer can expect to experience when making a telephone call. In a Loss System, the Grade of Service is described as that proportion of calls that are lost due to congestion in the busy hour. For a Lost Call system, the Grade of Service can be measured using Equation 1.

For a delayed call system, the Grade of Service is measured using three separate terms:

• The mean delay – Describes the average time a user spends waiting for a connection if their call is delayed.
• The mean delay – Describes the average time a user spends waiting for a connection whether or not their call is delayed.
• The probability that a user may be delayed longer than time t while waiting for a connection. Time t is chosen by the telecommunications service provider so that they can measure whether their services conform to a set Grade of Service.