Quality assessment and usage behavior of a mobile voice-over-IP service

Voice-over-IP (VoIP) services offer users a cheap alternative to the traditional mobile operators to make voice calls. Due to the increased capabilities and connectivity of mobile devices, these VoIP services are becoming increasingly popular on the mobile platform. Understanding the user's usage behavior and quality assessment of the VoIP service plays a key role in optimizing the Quality of Experience (QoE) and making the service to succeed or to fail. By analyzing the usage and quality assessments of a commercial VoIP service, this paper identifies device characteristics, context parameters, and user aspects that influence the usage behavior and experience during VoIP calls. Whereas multimedia services are traditionally evaluated by monitoring usage and quality for a limited number of test subjects and during a limited evaluation period, this study analyzes the service usage and quality assessments of more than thousand users over a period of 120 days. This allows to analyze evolutions in the usage behavior and perceived quality over time, which has not been done up to now for a widely-used, mobile, multimedia service. The results show a significant evolution over time of the number of calls, the call duration, and the quality assessment. The time of the call, the used network, and handovers during the call showed to have a significant influence on the users' quality assessments

A large-scale, long-term, user-centric evaluation of a commercial voice-over-IP application

To make cheap voice calls, Voice-over-IP (VoIP) services are often used as an alternative to the traditional telephone service providers. Also on the mobile platform, these VoIP services are becoming increasingly popular due to the increased capabilities and connectivity of mobile devices. Understanding the user's usage behavior and quality assessment of the VoIP service is crucial to optimize the Quality of Experience (QoE) and making the service to succeed. Whereas multimedia services are often evaluated in a controlled laboratorium setting, with a selected group of test subjects, and during a short evaluation period, this study analyzes the service usage and quality assessments in a real environment, with more than thousand users, and over a period of 120 days. The influence of various parameters (such as audio codec, handovers, platform, and manufacturer of the device) on the subjective quality of the service is validated by analyzing the quality assessments of users, provided after each voice call. The time of the day showed to have a significant influence on the number of calls, the duration, and the subjective quality assessment. Time-dependent patterns in the users' usage behavior are identified, thereby providing useful information to predict the system load. A regression analysis of the quality assessments over time shows that the perceived quality gradually decreases as users have utilized the service more, and get more familiar with it. In contrast, the mean duration of the calls increases as users get more familiar with it. This research is important in view of associating technical and contextual parameters with the QoE during service usage

Analysis of the quality of experience of a commercial voice-over-IP service

Voice-over-IP (VoIP) services, enabling users to make cheap phone calls using the Internet, are becoming increasingly popular, not only on desktop computers but also on mobile devices such as smartphones that are connected through mobile networks. Users' perception of the level of quality plays a key role in making a VoIP service to succeed or to fail. This paper demonstrates the influence of technical parameters (such as the audio codec, type of data network, and handovers during the call), device characteristics (such as the platform, manufacturer, model, and operating system), and application aspects (such as the software version and configuration) on the subjective quality of a commercial VoIP service. The relative influence of all these parameters is determined and a decision tree combines these results in order to assess the subjective quality. Combining a large number of objective parameters in a decision tree to determine the user's subjective evaluation of the quality of a VoIP call is a novel and complex procedure. The subjective quality, in turn, has an influence on the duration of the call, and as a result an influence on the usage behavior of the service. The users' assessment of the service quality is not evaluated by merely taking a snapshot of the perceived quality at one moment in time but rather by analyzing the perceived quality over a longer period of time during service usage, which has not been done up to now. Analyzing the VoIP service using a regression analysis over a period of 120 days showed that the perceived quality decreases slightly when the user utilizes the service more often and gets more familiar with it