VoIP quality measurement: Enhanced E-model using bias factor

To enhance the standard E-model, this paper proposes the new factor called Bias factor. Based-on the Thai environment, this factor can be computed by subtracting the subjective test results using conversation tests with native Thai users from the objective test results using an E-model tool. Both E-mode tests and conversation tests were conducted with the same VoIP system and test conditions. Then, the enhanced E-model using the Thai bias factor was evaluated with the test set from other groups of native Thai users. After evaluation, it has been found that the enhanced E-model can gain higher confidence. It delivers improved accuracy and reliability at approximately more than 20% when compared to the standard E-model.