Evaluating the Quality of Service in VOIP and comparing various encoding techniques

Abstract

Technology in which the communication done using IP (Internet protocol) as an alternative for the traditional analog systems is “Voice over internet protocol”(VOIP). One of the emerging or the attractive communication systems in the present era is VoIP.. Several technologies within VoIP are emerging and there are more to come in the near future. Services offered by this technology need Internet connection and/or telephone connections. It offers services that allow making calls such as long distance calls, local calls, wireless calls and International calls. VoIP acts as a medium that changes the analog signal (Telephone signal) to digital signal. The converted signal travels through the Internet medium to the destination. In this dissertation, main encoding techniques are considered based on the level of the security they provide and their usage in the present market. Encoding techniques considered are G.711, G.723 & G.729. The usage of these techniques can be done in various networks however; one should know the Quality of service (QoS) that these techniques provide. With the QoS, one will know where these techniques fit, what level of security they provide, where they can be used and how efficient each technique is. In this dissertation, an implementation is done in OPNET to compare the characteristics of each encoding technique. Implementation is done by designing two scenarios with a network that connects different networks over a wide area and the second scenario with a small area network. VoIP service is configured in both the scenarios. Each scenario is then implemented with the encoding techniques considered. Finally the characteristics of the encoding techniques are evaluated and analysed using the graphical results obtained. There are several QoS parameters in place but Throughput, Load, MOS (mean opinion score), Jitter and PDV (Packet delay variation) parameters are measured in this implementation as the characteristics can be evaluated for encoding technique comparisons graphically. These comparisons would allow us to carefully design the encoding techniques for security enhancements in future.