Study on the QoE for VoIP Networks Weiwei Zhang 1 , Yongyu Chang 1 , Yitong Liu 1 , Atif Hameed 1 , and Yuan Tian 2 1. School of Information and Communication Engineering, Beijing University of Posts and Telecommunications 2. National Astronomical Observatories, Chinese Academy of Sciences Email: zweiwei506@gmail.com, tianyuan@lamost.org Abstract—In recent years, people are recognizing that the quality in VoIP application should be evaluated according to the QoE (Quality of Experience). The main goal of this paper is to analyze the different factors on the impact of voice quality for VoIP networks. Our contributions are thus threefold: First, we establish a new VoIP simulation platform. The network simulation software is WANem, the voice communication protocol is implemented by Open Phone. This simulation system is more ‘real’ than other researcher’s system. Secondly, we analyze the factors that affect the voice quality of VoIP networks. Thirdly, we use the VoIP networks simulation platform to test the network performance impact on the quality of voice service. Through the experiment result, we can conclude that in order to get the better voice quality, we use the iLBC codec when the VoIP network is exist packet loss. And use the AMR 12.2 kb/s when the VoIP network is exist time delay. Index Terms—VoIP Networks; Quality of Experience (QoE); Perceptual Evaluation of Speech Quality (PESQ); Network Packet Loss I. INTRODUCTION With the development of computer and networks technology, the multimedia communication service based on IP networks becomes more and more popular. There are colorful multimedia information service, such as voice, video, images and graphics. Among of them, the voice communication service is indispensable [1]. We focus on the research of Voice over IP (VoIP).networks. VoIP namely IP telephony, the voice is converted into data, and use IP network for transmission. It has been regarded as a new era of telephone development [2]. VoIP is based on the existing computer network and avoid the repeated construction of the network. It combines the telecommunications and internet technology, transforms the traditional way of telecommunications. It is the important part of next generation network (NGN). The goal of VoIP is to provide reliable, high-quality voice services similar to the PSTN. However, the IP network provides ‘best effort’ service; there are existing unreliable data transmission services [3]. Due to the network load and the dynamically change topology, the network may be congested and lead to packet loss, delay, packet reordered [4]. The audio information is delay- sensitive, and excessive packet loss will bring decline in voice quality. Therefore, the quality service of VoIP has become a complex and challenging issue [5] [6]. For QoS (Quality of service) [7] monitoring or control purposes to ensure that the technical and commercial requirements are met, we need measure the voice quality. The service providers focus their efforts on Quality of Service (QoS) in VoIP, while end users expect improvement in QoE (Quality of Experiment) [8]. The QoE is dedicating to user perception of application directly, instead of considering network effects [9]. The QoE is more close to the human perception, so the QoE has instead of QoS, and has widely used by service providers [10]. We use PESQ (Perceptual Evaluation of Speech Quality) algorithm to represent the QoE values. The PESQ is the most commonly used intrusive measurement method for voice QoE evaluation in VoIP applications. The PESQ method is proposed by International Telecommunication Union, it is approved as the ITU-T P.862 Recommendations [11]. In this paper, we construct a VoIP network simulate platform. And through experiment to analyze the network factors affect on the performance of VoIP networks. II. SYSTEM MODEL FOR VOIP A. VoIP Network The VoIP network connection is shown in Figure 1. The VoIP network transmission way include three ways including phone to phone, phone to PC (IP terminal or H.323/SIP terminal), PC to PC connection [12]. The SCN (Switched Communication Network) may be wired or wireless network, such as PSTN (Public Switched Telephone Network), ISDN (Integrated Services Digital Network) or GSM (Global System for Mobile Communications) etc. Figure 1. VoIP network connection JOURNAL OF NETWORKS, VOL. 9, NO. 2, FEBRUARY 2014 515 © 2014 ACADEMY PUBLISHER doi:10.4304/jnw.9.2.515-522