International Journal of Engineering Trends and Technology (IJETT) - Volume4Issue4- April 2013 Improved Quality of voice in mobile environment using integrated WiMAX and WiFi Karthika A L1, SumithraM G2, Shanmugam A3 1 1,2,3 M.E. Student, 2,3Professor Dept. of Electronics and Communication Engineering, Bannari Amman Institute of Tech, Sathyamangalam, India Abstract—In recent days, compare to fixed users, the mobile users are increasing day by day.It becomes necessary to provide better quality of data delivery to the end mobile user. Formerly, the quality of data delivery at the destination is good for pedestrian users when compared to the users in vehicular environment. It is due to the lack of coverage of area. The coverage area can be increased with the help of heterogeneous network which improves the quality of service for vehicular environment. In this paper, the integrated WiMAX-WiFi networkis implemented and analyzed by comparing the performance of vehicular environment and pedestrian environment by transmitting the voice packets based on Mean Opinion Score value, jitter, end to end delay and throughput. IndexTerms—WiMAX, WiFi, Heterogeneous network, VoIP, MOS I. INTRODUCTION Currently, internet is not only used for the transmission of text and images but also used for voice and video transmission. The efficient transmission of voice is done by VoIP which uses traditional Internet Protocol to transmit the voice packets. Since it uses the existing Internet Protocol [17], the cost for voice/video transmission is low (transmission between mobile phone and PC) or completely free (transmission between two PCs). Example Skype, Oovoo. The transmission of voice over VoIP is done better by WiMAX [16]. But highly developed areas are using only WiFi. Since WiFi is a wireless technology and have many benefits, the number of fixed and mobile users in the particular coverage area also increases. The users in pedestrian environment get frequent connection to the network than the users in vehicular environment especially train [23]. The solution to this problem is integrating WiMAX and WiFi[15],since it is very difficult to replace the WiFi with WiMAX and also many of the handset supports WiFi and not WiMAX. This integrated network gives better quality of voice by increasing the coverage area. Generally, the increase in number of users and increase in coverage area reduces the performance of voice transmission also the clarity of voice at the destination. This drawback can be easily overcome by the real time switches, routers, and firewall. A. Heterogeneous network It represents the combination of two or more network into a single network. The integration between the networks is easy when they are infrastructure networks. BS AP ss Fig. 2. Heterogeneous network Fig. 1. VoIP The above diagram shows the VoIP calls function. The voice quality is easily determined with the help of Mean Opinion Score (MOS) value [19] which has the range of 1 to 5. The range 1 indicates the very poor voice quality and 5 denotes the better quality of voice at the destination. The MOS value is of different types: Network MOS, Listening MOS, Conversational MOS and Sending MOS. In this paper, Network MOS is taken into account since it considers network parameters like jitter, delay and voice codec used. ISSN: 2231-5381 The figure 2 indicates the heterogeneous network where the WiFi Access Point (AP) gets signal from the WiMAX Base Station (BS). The user who can access both the network can get signal from the network which gives high signal strength. For example, if a man is between wifi AP and WiMAX BS, and he can get both the signal, then he will choose one network which gives better signal strength. http://www.ijettjournal.org Page 723 International Journal of Engineering Trends and Technology (IJETT) - Volume4Issue4- April 2013 B. Pedestrian environment vs. Vehicular environment voice application is mainly depends on the type of encoder scheme and the MOS value which is described in paper [15]. The authors in paper [16] said that the distance plays an important role in the transmission of voice. The shorter distant communication has more latency than larger distance which is due to interference is in paper [17]. The authors in paper [20][22] gave an idea about the scenario model for the heterogeneous network. III. SIMULATION RESULTS Fig. 3. Pedestrian and Vehicular Environments Figure 3 depicts the pedestrian and vehicular environment. The pedestrianenvironment has the mobility speed as normal walking speed of human and thevehicular environment has the speed of mobility as the speed of modern train in China,Tokyo and so on. The nodes in this set up is mobile i.e. move frequently from oneplace to another. These mobile nodes are connected to the server via wireless andwired link with the help of server and switch. The wireless communication is donebetween the node and the station and the wired communication is made between IP andserver. C. Simulation Tool For networks and communication, there are many tools like NS 2, Qualnet and so on. But when compare to these tools, OPNET supports easy real time routers, switches. It also provides broader coverage area which is very helpful in trying out the interworking network architecture [18]. So in this paper, the comparison between users in pedestrian environment and improved vehicular environment is done with the help of OPNET simulation tool. II. RELATED WORKS In paper [1] and [2], the authors said that the WiMAX gives better quality of service with the help of UGS service flow since it offers low jitter, low delay and high throughput. The WiMAX is better for VoIP due to its cost, data rate and coverage area [3]. The WiMAX gives guaranteed better quality for real time applications and also for interactive audio and video which has been reported in paper [4]. In WiMAX, the 64-QAM modulation gives better performance than adaptive and QPSK is in paper [5]. The WiFi is very sensitive to delay factor and packet loss and also has some challenges in security issues due to increasing number of users which is reported in paper [6]. In paper [7], the authors stated that the security issues can be solved by using IPsec and firewall. It provides data integrity, authenticity and encryption. In paper [8]-[11], the authors said that the integrated WiMAX and WiFi covers larger area and also reduces the cost. So the voice transmission over this heterogeneous network is very efficient. The best voice codec for the best voice at the end user is G.711 since it gives good MOS value which is in paper [12] and [13]. The authors in paper [14] described about the types of MOS values and also offered the formula to calculate the MOS values. The ISSN: 2231-5381 Fig. 4. OPNET Scenario model for both the environments Figure 4 illustrates the outlook of mobile environment. The three subnets contain the mobile nodes and its specifications. TABLE I PARAMETERS USED IN THIS SETUP Parameters No. of subnets No.of nodes in WiMAX& WiFi Mobility of nodes Application Coder Traffic Type Simulation Time Simulation Area Speed Pedestrian Environment 3 Vehicular Environment 3 4 (each subnet) 4 (each subnet) Mobile G.711 VoIP 1 hour 100x100km 2.8 mph Mobile G.711 VoIP 1 hour 100x100km 302 mph The above table shows the parameters that are used in this simulation setup. http://www.ijettjournal.org Fig. 5. Voice Application: Jitter Page 724 International Journal of Engineering Trends and Technology (IJETT) - Volume4Issue4- April 2013 As it is one of the important parameter for voice application, the vehicular environment must have less jitter. The above figure describes that the jitter is more for vehicular environment at the starting time, since it takes some time for the network to adapt to the router configuration. But after the environment gets adapted to the configuration, the jitter got reduced in it and its value is approximately equal to the value of pedestrian environment. i.e. approx. 15 mins, the delay for vehicular environment than pedestrian but both are more or less same. Fig. 8. WiMAX: Delay Fig. 6. Voice Application: Network Mean Opinion Score value Figure8 illustrates the delay for pedestrian environment and vehicular environment. The delay is more for pedestrian environment since the user moves from one place to another place in a frequent manner. So it becomes very difficult to deliver the voice to the destination. Figure 6 says that the quality of voice in vehicular environment achieves the voice quality in pedestrian environment which is because of the integrated network which gives more coverage area, less jitter (both are nearly 0.01sec) at the receiver side and effective encoder scheme as G.711. Here the NMOS value is above 4 which represent the good voice quality. Fig. 9. WiMAX: Throughput As the delay and jitter is less for vehicular environment and also the effective router and switch configuration is used, the throughput gets increased. Figure 9 illustrates that the throughput of vehicular environment and pedestrian environment. Fig. 7. Voice Application: End to End Delay In figure 7, for first 8 mins, the end to end delay for vehicular environment is 7% more than the pedestrian environment which is due to the heavy traffic at the initial stage. Later on this problem is solved with the help of getting adaptive to the effective Cisco router. So after some more time ISSN: 2231-5381 IV. CONCLUSION In this paper, we proposed a heterogeneous network to improve the quality of voice over vehicular environment. The basic idea is to increase the coverage area by integrating WiMAX and WiFi network and reducing the jitter and delay by using effective router and switch so as to maximize the voice quality in vehicular environment. In order to prevent the http://www.ijettjournal.org Page 725 International Journal of Engineering Trends and Technology (IJETT) - Volume4Issue4- April 2013 network from attacks, the firewall and IPsec is implemented in this paper. Finally, the experimental results show the better performance at the end mobile user. REFERENCES [1] Cavalcanti. D, “Issues of Integrating Cellular Networks, WLANS and MANETs: a Futuristic Heterogeneous Wireless Networks,” IEEE Wireless Commun. Mag., vol.12, no. 3, pp. 30-41, 2005. 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