Voice applications has gained a lot of importance these days and most of the service providers are offering a wide range of voice applications in terms of voice chats across the wireless networks. There are many voice applications used across the wired and wireless networks and the most common among them are Skype, Gtalk and Yahoo messenger and most of these voice applications run purely on the lever of quality of service requirements provided by the service providers.

In general there are many issues with these voice applications in terms of quality of service and common among them are jitter, MOS value and traffic aspects and all these should be considered to ensure the maximum quality of service requirements. In this project this point is considered as the main aim and the quality of service requirements for voice applications wireless LAN is evaluated.

A simple wireless LAN based MANET is used for the simulation and the simulation is done using the OPNET modeler and based on the results it is clear the quality of service requirements is analyzed. Three scenarios are considered across the simulation, where the first scenario deals with the low quality speech, IP telephony is used for the second scenario and a GSM quality speech is used across the third scenario and few Voice and WLAN metrics are used for the results evaluation and the simulation is run for 5 minutes. Based on the results achieved the three scenarios are compared and the key findings are as listed below 

It is observed that the jitter imposed by the IP telephony is more when compared to the other scenarios and even the value is not constant throughout the simulation and there is lot of variations which indicates that there is lot of packet loss with the IP telephony. The overall performance of the GSM quality voice is better when compared to the other scenarios as the speech is suppressed and in this context the overall performance of the application has increased due this low jitter value and thus the quality of service is enhanced is many aspects.

The performance of low quality speech voice application is better than the IP telephony as the quality consumed by a simple speech application is very less and thus the noise across the speech is suppressed at a constant rate and thus the overall quality of service is enhanced. This value is more than the GSM quality as the propagation aspects followed across the GSM are inbuilt with the default quality metrics and thus the overall jitter is very less and constant throughout the simulation.

From this analysis it is clear that the overall quality of service can be improved with the low jitter value and in this context the speech noise depressed and thus GSM has shown a constant jitter and this indicates that the packet delay variation is constant and also the packet delivery is at the idle conditions and thus the overall quality of service is improved.

It is observed that a value of 3.6 is recorded for GSM quality and with this range it is clear that a good quality speech is incurred against the quality of service for voice application where the MOS value for low quality speech is only 2.5 which indicates that a fair quality is incurred with the voice and the MOS value recorded by IP telephony is around 3 and even in this case a fair quality speech is delivered and it can also observed that the MOS value for IP telephony and low quality speech are not constant and they were initially high and later at the end of the simulation their quality has dropped to a bad range.

This indicates that the quality of service requirements for IP telephony and low quality speech are depressed when the communication is proceeding and but with the case of GSM quality speech a constant MOS value is recorded and even this value indicates that a good quality of service requirements are imposed by GSM on the overall network performance. From this analysis it can be concluded that when the MOS value is more the overall quality of service is improved across the voice applications.