(1) Blockage:

• There are two types of blockage

a) Set up blockage: To a mobile several calls can inter-collide simultaneously. If this no exceeds 10 then mobile is said to be blocked and this blockage is called as setup channel blockage.

b) Voice channel (Call) blockage: Simultaneously when many calls come in , calls are rejected because there are no voice channels available and this blockage is called as voice channel blockage.

(2) Call drops: Defined as the calls that are dropped because of factors after the voice channel is allocated to a mobile because of weak signals. It depends on hand off traffic model and signal coverage.

(3) Voice quality: It is the ratio of signal to distortion (SINAD), usually expressed in dB and quoted alongside the receiver RF sensitivity, to give a quantitative evaluation of the receiver sensitivity.

(4) Word error rate: WER is a common metric of the performance of a speech recognition or machine translation system and given as

WER= (S+D+I)/N ,Where, S= ni of substitutes