Analysis of speech data rate in voice over IP conversation

For quality of voice over IP (VoIP) service, the properties of VoIP traffic need to he considered. This paper presents the traffic characteristics of conversational speech data rate measured in VoIP network of Thailand. The results show that the mean and peakedness of the distribution of data rate conversational speech are 27 and 2.4 packet/s, respectively. The data rates in forward and reverse directions of a VoIP call are not equal. The average speech data rates for "less speaking" and "more speaking" users are 23 and 32 packet/s, respectively. The ratio of "lower speech data rate" to "higher speech data rate " in a call is distributed from 0.1 to 1 with mean 0.72. We compare the measured speech data rate with the data rate models given in other research works. The results confirm that VoIP speech data rate depends on the language.