Voip

“Research and Development of VoIP Techniques” ABSTRACT The purpose of this report is firstly to provide an insight into the communications medium Voice over IP (VoIP) and secondly investigate the problematic areas evolved with the Quality of Service (QoS) delivered by a VoIP system. The report focuses on specific areas such as delay and packet loss and offers hypothesises to why they are created and how they can be minimised. The testing is conducted in three stages; the first is a set of subjective tests that have been created for the purpose of this project, to see how a test candidate’s ability to hear a set of words varies with network load. The second test generates a mean opinion score for different parameters that define the call quality delivered by the VoIP system, again with an investigation into they change will network load. The last test measures network statistics such as the delay and packet loss, generated while the VoIP system is used for communication. The results generated from the testing showed that the caller’s ability to hear individual words did not vary with increased network load there was however a certain level of ambiguity regarding these results. The testing also showed that the major factor that affected the QoS delivered by the VoIP system was delay and gave an insight into the amount of delay (seconds) was present in the VoIP system. The comparison of how the delay varied with network load showed that there was a directly proportional relationship. A quantitative result was generated for the amount of audio lost during a 17 minute (1022 seconds) VoIP transmission, which was calculated to be 4.4 seconds. In conclusion hypotheses are drawn regarding the future application of VoIP and factors that might affect its commercial success.

CHAPTER 1: Introduction Voice over IP (VoIP) is a technology that has emerged over the last twenty five years. The technology has evolved from the idealistic concept of free phone calls, too a