CHAPTER 6. VOICE COMMUNICATION OVER HYBRID MANETs

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1 CHAPTER 6 VOICE COMMUNICATION OVER HYBRID MANETs Multimedia real-time session services such as voice and videoconferencing with Quality of Service support is challenging task on Mobile Ad hoc Network (MANETs). For providing multimedia services and Voice over Internet Protocol in MANET, support of Session Initiation Protocol (SIP) is essential. In this chapter, we have analyzed various QoS parameters on different routing protocols for voice transmission using OPNET simulator. The performance metrics comprises of QoS parameters such as packet delivery ratio, end to end delay, packet delay variation, routing overhead, throughput and jitter. 6.1 INTRODUCTION Wireless networks are nowadays one of the most spread communication technologies. The demand of multimedia services over wireless networks, such as Video On Demand (VOD) or Voice over IP (VoIP), has experienced a huge increase over last years. These multimedia services have certain Quality of Service (QoS) requirements which have to be accomplished. These features lead to a promising situation where the delivery of multimedia contents to mobile users through the establishment of MANETs can open new markets and services. Thus, the provision of QoS to the final user over these constrained networks must be a reality to success in the deployment of MANETs. Nonetheless, the inherent features of these networks make this issue certainly complicated. Since nodes are mobile, the network topology may change rapidly and unpredictably throughout time. Node mobility, short-life batteries of the nodes, time-varying link capacity and a dynamic topology make the problem of providing QoS over MANETs rather complex and challenging. The QoS parameters differ from application to application e.g., in case of multimedia application bandwidth, jitter and delay are the key QoS parameters [RAJ2010]. Two major trends in technology can be observed over the last decade: pervasive communication and the Internet. Pervasive communication is slowly but surely becoming an integral part of our daily life. The Internet has also become a central aspect for almost everybody, both in business, at home or during education. It is thus essential for us to bridge 96

2 those two technologies, where future wireless communication systems are expected to provide a broad range of multimedia services. MANETs are reaching a stage where they can support these services in order to provide an infrastructure useful for the common user. Thus, the interconnection of MANETs to fixed infrastructure based IP networks is very important in order to provide the ubiquitous user access to internet anywhere at any time [MCC2005] [JRO2002]. In such scenarios, also known as Internet connected MANET, or Hybrid MANET, the user within an ad hoc network will get access to the public internet by using the packet forwarding capabilities of intermediate ad hoc network nodes towards the Access Router (AR) or gateway to the Internet, providing the user with access to different services through a diversity of interconnected networks (fixed, wireless and ad hoc networks). Figure 6.1, illustrates two different MANETs which are connected through internet to form a hybrid MANET and they can make voice calls to each other using VoIP application. Figure 6.1 Hybrid MANET The main objective of the current research work is to analyze the performance of QoS parameters on ad hoc routing protocols for voice communication support over hybrid MANETs. In [ADL2008], authors investigated VoIP, factors like delay, packet loss over three reactive routing protocols in IEEE s-based wireless mesh networks. Best-effort routing is not adapted to voice communication due to real-time and quality of service constraints. A QoS extension model of OLSR is proposed in [PAT2009]. This model is then evaluated using the OPNET simulator. Besides confirmation of the fact that end-toend delay and jitter constraints of voice applications are fulfilled, the simulation results show an improvement of the packets delivery ratio in comparison with native OLSR. 97

3 In [CAR2007], authors developed a new routing protocol named MMDSR (Multipath Multimedia Dynamic Source Routing). It is a multipath routing extension of the well-known DSR (Dynamic Source Routing) protocol for MANETs. MMDSR is capable of maintaining more than one active path simultaneously between the source and destination nodes involved in a video-streaming session. It has been designed according to a cross-layer architecture which gathers information of the different levels of the stack protocols and takes the most proper configuration decisions to maximise the final performance. Special control packets have been designed to be sent periodically to monitor the status of the network. The objective is to be able to identify which are the most reliable and stable paths, which are going to be used for the multimedia transmission. The framework MMDSR periodically monitors the network and analyze QoS parameters gathered from the paths that constitute the multipath forwarding schemes of each one of the connections. The state of a path is summarized in a list of QoS parameters. A model is proposed requiring neither modifications on SIP messages nor dependencies on the underlying routing protocols to achieve better interoperability [CHN2010]. 6.2 PERFORMANCE ANALYSIS The performance of routing protocols during transmission of voice is simulated using OPNET simulator. Figure 6.2(a-d) shows the parameter setting of various routing protocols and configuration of Routing Protocol, Proxy Server, SIP Client, Voice Encoding and Voice Table Configuration on each node is depicted in Figure 6.3(a-e) Performance Metrics The performance metrics includes the following QoS parameters: Packet Delivery Ratio: The fraction of packets sent by the application that are received by the receivers. End-to-End Delay: It indicates how long it took for a packet to travel from the source to the application layer of the destination. Jitter: It is the variation in the time between packets arriving, caused by network congestion, timing drift or route changes. 98

4 Throughput: It is defined as the total amount of data a receiver receives from the sender divided by the time it takes for the receiver to get the last packet. Routing Load: It is the ratio of total number of the routing packets to the total number of received data packets at destination. Packet Delay Variation: Difference in end-to-end delay between selected packets in a flow is called Packet Delay Variation. 6.3 SIMULATION RESULTS AND DISCUSSION The parameters used for simulation and different scenario on which they are analyzed are shown in Table 6.1 and Table 6.2 respectively. The Hybrid MANET consist of 16 different hybrid devices in the form of PDA and laptop to participate in voice communication along with a SIP proxy server configured to provide proxy services to the SIP clients (mobile nodes) as shown in Figure 6.4. TABLE 6. 1 Simulation Parameters TABLE 6.2 List of Scenarios Parameters Value Simulation 600 sec Number of nodes 16 Ad hoc Network 02 Proxy Server 01 Router/Access Point 01 Node(8) Internet Connection 2 Routing Protocols AODV,DSR.TORA,OLSR Scenario Name Scenario1_AODV Scenario2_DSR Scenario3_OLSR Scenario4_TORA Routing Protocol Used AODV DSR OLSR TORA ( c) (a) (b) (d) Figure 6.2 (a-d) Parameters Setting for Routing Protocols 99

5 (a) (d) (b) (c) (e) Figure 6.3 (a-e) Configured Routing Protocols, Proxy Server, SIP Client, Voice Encoding and Voice Table Configuration on each Node Figure 6.4 Hybrid MANET for the Voice Communication (Network Topology Used) 100

6 For simulation, we have configured the mobile devices to support different protocols and then the VoIP traffic is generated. The mobile devices have been categorized in two different groups: Calling node and Called node as indicated in Figure 6.5 and Table 6.3. Voice Application: It is installed on each node to support voice communication. Voice Calling Node: It makes a call to called node. Voice Called Node: It receives a call made by calling node TABLE 6. 3 Voice Communication Setup N12 N13 M7 N11 Calling node Called node M-3 N12 N10 M3 N13 M7 M-7 N-13 N-10 N-11 Figure 6.5 Calling and Called Nodes in MANET The Figure 6.6 and Figure 6.7 illustrates that the SIP active calls are increased over the time and SIP Clients (mobile nodes) are making requests to start the voice communication to the SIP proxy Server.Table 6.4 shows the Call Setup, Active Calls, Voice Traffic Sent and Voice Traffic Received over different Routing Protocols. UAS Active Calls Figure 6.6 SIP Active Calls 101

7 UAS Call Setup Requests Figure 6.7 SIP Enabled Client Requests for Voice Communication to the SIP Proxy Server TABLE 6.4 Comparisons of Call Setup, Active Calls, Voice Traffic Sent and Voice Traffic Received Protocols SIP UAS Call Setup Requests SIP UAS Active Calls Voice Traffic Sent (Packets) Voice Traffic Received (Packets) AODV DSR OLSR TORA Voice Packet Sent Figure 6.8 Voice Traffic Sent 102

8 Voice Traffic Received Figure 6.9 Voice Traffic Received Figure 6.8 and Figure 6.9 illustrates that the number of packets sent and received in OLSR and AODV are maximum and are at lower side in TORA and DSR. Voice Packet End-to-End Delay Figure 6.10 Voice Packet End-to-End Delay 103

9 Voice Jitter Figure 6.11 Voice Jitter The end-to-end delay in OLSR and AODV is at lower side and is maximum in TORA and DSR as shown in Figure Figure 6.11 illustrates the comparative results in which maximum jitter is produced in DSR and TORA and is at lower side in case of OLSR and AODV. Packet Delay Figure 6.12 Voice Packet Delay Variation 104

10 The Packet Delay Variation in TORA is maximum as compared to other protocols and as depicted in Figure Tables 6.5 summarize the performance of different routing protocols under various QoS parameters. TABLE 6.5 Performance Analysis of Different Routing Protocols Protocols Throughput Packet Delivery Ratio Routing Load End-to- End Delay Jitter Packet Delay Variation AODV DSR OLSR TORA CONCLUSION In this chapter, we have concluded that it is possible to launch voice transmission with acceptable quality and throughput over Hybrid MANETs. The overall performance of OLSR is best with QoS parameters among DSR, AODV and TORA because of limited flooding during route discovery phase as results shown in Table 6.5. The performance of TORA protocol is less than OLSR and AODV protocol but it is better than performance of DSR protocol. DSR protocol has minimum throughput and maximum end-to-end delay with highest jitter and all these factors make this protocol unsuitable for voice transmission. 105