GoS (Grade of Service) is the probability of a call in a circuit group being blocked or delayed for more than a specified interval, expressed as a vulgar fraction or decimal fraction. This is always with reference to the busy hour when the traffic intensity is the greatest.
P.01 Grade of Service
A standard of service quality reflecting the probability that no more than one call out of 100 during the average busy hour will be blocked.
Relevant NENA Documents