Improving Quality of VoIP over WiMax

Transcription

1 Improving Quality of VoIP over WiMax Muaz Omer Mahmoud Mudawi 1 and Dr. Amin Babiker A/Nabi Mustafa 2 1,2 Deptt. of Communication Engineering, Faculty of Engineering, Alneelain University, Khartoum, Sudan 1 muazomer2000@gmail.com and 2 amin31766@gmail.com Publishing Date: August 29, 2016 Abstract VoIP is coated from voice over internet protocol also is known as IP telephony and it becoming a common term now a days in government and education organizations. The mean advantages of this technology provide a good service with low coast it has been found to replace the traditional TDM and old networks technology. It lies on digitized the voice put it into packets and send it via IP protocols. The old networks replaced by the WiMAX network which is the most compatible network for VoIP. in this paper we simulate this net work holding VoIP service class to determined the QoS considering many performance metric parameters like jitter, throughput, load,mos and delay. The aim of this paper to explain the impact of using different voice CODECs G.711, G.723 and G.729 to determine how it affect the in WiMAX network also different topology have been applied " dividing area into cells" to enhance the performance of VoIP over WiMAX. Keywords: VoIP, WiMax, QoS. Introduction In this era the perfect evaluation of communication networks and wireless systems has been increasing rabidly not only this it also has been considered an essential requirement for modern life [1]. VOIP easily means using internet lines to transfer the voice calls instead of traditional PSTN technologies and that provide the low cost in addition of high quality of service and the tools were needed to initiate the network are very simple like PBX to determined the path for VoIP call, RTP real time protocol to grantees that the process will be done life and to mix the IP protocol with the voice packets. and ITU H323 must be found for user accessibility the bell ADC also is requirement to convert the signal from analog to digital in the TX terminal and vice versa its worth mentioned in this point to say that the recently usage of OFDMA in a TCP model exactly in a physical layer offers the capability of using the IP applications IP telephony service [2] [3]. And WIMAX network provide a speed reaches to 70 (mbps) and low rate of delay, congestion, load and jitter. the cell topology it an effective factor in the WIMAX design because the ability frequency reuse in addition of any cell have it own base station depends on this the band width well be utilized perfectly so we require at least 1Mbps from this bandwidth between the subscriber and base station [5]. CODECs Audio CODECs (compression/decompression) protocols or (coder/decoder) have a various models widely used for implement VOIP phones include G.711, G.729, G.723, G.726 and G.728. a brief note about each one will be given [4] [5]. Codec Bit Rate Technology G kbps TDM T1 voice traditional technology G kbps (MP-MLQ) Multi-Pulse - Maximum Likelihood Quantizer algorithm G , 16, 40, and 32 kbps (PBX) private branch exchange interconnections G kbps Compression algorithm G kbps Compression algorithm 177

2 Simulation Setup To evaluate the performance of VoIP over the WiMAX network, the OPNET Modeler version 14.5 with WiMAX Module capability was used to design scenario to determined jitter with the assumption that the only traffic generated in this network model is VoIP. There are only peer-to-peer voice calls throughout the simulation, which means there is no voice conferencing and the workstations are considered as fixed during the simulation runs. Fig. 1 illustrates the WiMAX network model considered in the simulations. The WiMAX network consists of seven Cells and an IP backbone. The cell radius is set to1 Kilometers. Each cell consists of four workstations and one Base Station (BS) in each cell. We use an application configuration and profile Configuration to insert the VoIP application in work stations shown in figure (5).we use point to- point (PPP DS3) as a connection between the backbone (internet) and every base station in cell and also as connection between the voice server and backbone there is a server backbone containing only one Voice Server. Our experiment was performed to show Voice quality is important for VoIP system because of the users high demands for good quality voice services. In these scenarios, We considered the use of various voices CODECs in the same WiMAX network in order to investigate the performance of voice CODECs for VoIP. G.711 (64kpbs), G.729 (16kbps) And G.723 (5.8kbps) were considered for this experiment shown in figures blew. Figure 1: WiMAX Network Model Figure 2: VoIP Application Profile 178

3 Figure 3: Configurations for ITTs G.729 Encoder Schemes Figure 4: Configurations for ITU-Ts G.711 Encoder Schemes 179

4 Figure 5: Configurations for ITU-Ts G.723 Encoder Schemes Simulation Results and Analysis The figures above from (1 5) viewed the configurations of WiMAX network, which has been collected via OPNET modeler Any one of the figures contains a result in a comparative form for a three scenarios using various voice CODECs scheme like G.711, G.723 and G.729. The result summarize the impact of using various CODECs to test various performance metric parameters in VoIP over WiMAX network like MOS, delay, throughput, load and jitter. Figure 6: The Average in Voice MOS 180

5 MOS is a common parameter in VoIP applications it used widely to describe the quality of voice perception. Fig. (6) represent the MOS value for three codec G.711 have a good MOS value (2.5) and G.729 get acceptable value (2.0) and finally G.723 have MOS value (1.7) which shows is provide poor QoS if we use this CODEC. Figure 7: The Average WiMAX Delay (sec) Fig. (7) represent the average delay in WiMAX network from the curve above we find that codec G.723 is the best one compared to the three because it have the lowest delay value and G.729 is better than G.711 because G.729 have good transfer rate (8 kbps) and also has small packet size (20 bytes) compared to G.711 which have a large packet size (160 byte). The delay increase by increasing the packet size and transfer rate. Figure 8: The Average in Voice Jitter (sec) 181

6 Fig. (8) explains the average in voice Jitter over various CODECs the above result shows that CODEC G.729 have a better result than other CODECs. Low value of Jitter indicate for a good performance for the network because that makes the voice clearly and understood. Using CODECs G.723 and G.711 make the voice packets arrives at different times. Figure 9: The Average in WiMAX load (packet/sec) The fig. (9) above represent the WiMAX load as it shown in the result the codec G.723 provide the best delay value for the network reaches to ( bit/sec) compared to codec G.729 which have a delay value about ( bit/sec) and the codec G.711 was a wariest case which get the highest delay value about ( packet/sec). Figure 10: The Average in WiMAX throughput (bit/sec) 182

7 Fig. (10) Determined the average in VoIP over WiMAX throughput which has been examining under various CODECs according to the result we find that CODEC G.711 is the best one because it has the highest value of throughput and codec G.723 lies on the second order and after that G.729. Conclusion In this paper we discuss the performance analysis of VoIP over WiMAX by using three different voices CODECs G.711, G.723 and G.729 depending on our simulation results we discover that the voice QoS became better if the best codec has been chosen. also different topology have been used and this definitely improving the QoS because the area have been divided into seven cells each one have its own base station and continue a certain number of workstation in instead of one base station cover all the area and this has positive effect on decreasing bad effect for other parameters. References [1] White paper, WiMAX Deployment Considerations for Fixed Wireless Access in the 2.5 GHZ and 3.5 GHZ Licensed Bands, [2] Alejandro Serrano, Jesús García Ramos, VoIP over WiMAX,, [3] N. Ansari and E. Haghani, "VoIP traffic scheduling in WiMAX networks, [4] M. Sharifi H. Behrooz, A.Yarali, J. Wheatley, J. Ponder, Wireless Cellular and PCS Network Cell Count Estimator, [5] I. Adhicandra, "Measuring data and voip traffic in wimax networks", About Authors Muaz Omer Mahmoud Mudawi: has a B.Sc. in Computer Engineering from Future University (Computer Man College) in Working in Ministry of education (Khartoum State) in Examination Network from 2007 till now. Working in Saudi Arabia in teaching field (maintenance, programming, designed) from 2002 to Amin Babiker A/Nabi Mustafa: obtained his B.Sc. & M.Sc. from University of Khartoum in 1990 & 2001 respectively. He obtained his Ph.D from Alneelain University in He was the head of Computer Engineering Dept. from 2001 to Then he become the vice-dean. He has been the dean, faculty of Engineering Alneelain University since 2009 upto March 2015 and then the Secretary of Academic Affairs from April 2015 upto December His research areas include QoS in Communication Systems, traffic Engineering, Service Costing Disciplines and Networking Assonciate Prof. Dr. Amin is a Consultant Engineer. He is a member of the Sudan Engineering Council. He is also a member of the Executive Committee of the Federation of Sudanese Engineers. Dr. Amin supervised or supervising more than 80 Ph.D or M.Sc students. He published over 150 papers in International Scientific Journals. 183