A DYNAMIC SOURCE ROUTING PROTOCOL FOR WIRELESS MESH NETWORK USING SIGNAL-TO-NOISE RATIO SAMIH EISA SULIMAN ABDALLA

Transcription

1 A DYNAMIC SOURCE ROUTING PROTOCOL FOR WIRELESS MESH NETWORK USING SIGNAL-TO-NOISE RATIO SAMIH EISA SULIMAN ABDALLA DISSERTATION SUBMITTED IN FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF COMPUTER SCIENCE FACULTY OF COMPUTER SCIENCE AND INFORMATION TECHNOLOGY UNIVERSITY OF MALAYA KUALA LUMPUR MAY 29

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3 To my beloved mother Haram III

4 Abstract For routing in multi-hop Wireless networks, the minimum hop-count metric focuses on finding the shortest path between nodes taking into account the mobility of the nodes as an important factor for identifying the best routes. However, in Wireless mesh networks (WMNs) due to the static nature of the nodes, minimum hop-count is not always the best criteria for routing; the shortest path might be slow or lossy leading to poor network throughput. In this research work, we use the Signal-to-Noise Ratio (SNR) metric as link-quality metric for finding high-throughput routes in WMNs. We modify the Dynamic Source Routing (DSR) protocol to choose routes according to the SNR metric. We apply the SNR as routing metric in the DSR module offered by OPNET simulator. The simulation results show that, the modified SNR- DSR protocol has higher throughput than the original DSR protocol throughout all simulation scenarios. IV

5 Acknowledgments First and foremost I would like to thank ALLAH (SWT), most gracious and most merciful. I would like to thank my supervisor Mr. Abdulla Gani for giving me the opportunity to be one of his students. I would like to thank him for his continue support, encouragement and valuable discussions during my research work. Thanks also extended to my friends and colleagues for their emotional support. Special thanks go to my roommates (Gassan and Mansoor) for their support and the family life that we spent together. It was a pleasure life. Finally, I would like to express my special gratitude to my family for their patient and their unconditional support. V

6 Contents Abstract...IV Acknowledgments V List of Figures...IX List of Tables...XI List of Abbreviations XII 1 Introduction Background Motivation Problem Statement Statement of Objectives Scope Proposed solution Thesis Organization Wireless Mesh Networks (WMNs) Introduction Wireless Mesh Networks (WMNs) Wireless Mesh Network Architecture Infrastructure/Backbone WMNs Client WMNs: (client meshing) Hybrid WMNs Wireless Mesh Networks Characteristics Mesh standards for IEEE s standard Wireless Mesh Networks (WMNs): Current Challenges Physical Layer MAC layer Wireless Mesh Networks (WMNs) Routing process The Existing Routing Protocols for Mesh Networks Proactive (Table Driven) routing protocols Optimized Link State Routing (OLSR) Reactive (On-Demand) routing protocols Ad hoc On-demand Distance Vector (AODV) Hybrid routing protocols Temporally-Ordered Routing Algorithm (TORA)..24 VI

7 Routing Metrics for Wireless Mesh Networks Hop-Count Per-Hop Round Trip Time (RTT) Expected Transmission Count (ETX) Per-Hop Packet Pair Delay (PktPair) Routing Protocol Performance Metrics Packet Delivery Ratio Throughput End-to-End Packet Delay Routing Protocol Overhead Related Work Dynamic Source Routing (DSR) protocol DSR Quick view DSR Basic Operations Route Discovery Route Maintenance DSR performance Strengths Weaknesses Problem in DSR route Discovery process Methodology OPNET Simulator : an Overview Why use OPNET OPNET modeling hierarchy Global Network Domain Node Model Domain Process Model Domain DSR model in OPNET Node Model Process Modes Implementing SNR-DSR model in OPNET Signal-to-Noise-Ratio (SNR) OPNET Pipeline Stages Passing SNR to DSR routing layer SNR-DSR route Discovery Process Route Selection Mechanism Simulation Simulation Environment setup Communication and Network parameters DSR and TORA simulation scenarios DSR and SNR-DSR simulation scenarios Routing Protocols Configurations DSR Configuration 66 VII

8 TORA Configuration MANET Traffic Generation parameters Data Analysis Tool T-Test T-Test Example Data Analysis & Results Discussion Data Analysis Network Throughput: T-Test analysis results Evaluation Comparison of DSR and TORA Throughput Static scenario results Discussion Mobility-support scenario results Discussion End-to-End Delay Static scenario results Mobility-support scenario results Discussion Routing Load Static scenario results Mobility-support scenario results Discussion Comparison of SNR-DSR against DSR and TORA Throughput Discussion End-to-End Delay Discussion Routing Load Discussion Conclusion & Future work Summary Contributions Findings Future work..1 Appendix A 12 Appendix B 12 References 18 VIII

9 List of Figures 2.1 Community Mesh Network WMNs with Infrastructure/Backbone Client WMNs Hybrid WMNs WMN in military communication Ad hoc Routing protocol hierarchical OLSR Multipoint Relay (MPR) AODV Route Request Message Format (RREQ) AODV Route Reply Message Format (RREP) AODV Route Error Message Format (REER) Route Creation process in TORA Route Maintenance in TORA DSR Route Discovery process DSR Route Maintenance process DSR Route Discovery process with Multiple paths OPNET Global Network Domain with sub-net component Mobile MANET node Model OPET TCP process Model OPNET DSR Node Model OPNET DSR process Model OPNET MANET physical layer pipeline stages Creation of snr_value ICI at the MAC Layer Passing SNR value to DSR routing layer DSR Route Discovery process with SNR parameter OPNET 1mX1m topology of 25 MANET mobile nodes with mobility OPNET 5mX5m topology of 25 MANET mobile nodes OPNET Ad hoc Routing Protocol Configuration OPNET DSR protocol Configuration OPNET TORA protocol Configuration DSR Wireless LAN Throughput of 1 MANET mobile nodes DSR Wireless LAN Throughput of 25 MANET mobile nodes DSR Wireless LAN Throughput of 1 Vs 25 MANET mobile nodes TORA Wireless LAN Throughput of 1 MANET mobile nodes TORA Wireless LAN Throughput of 25 MANET mobile nodes TORA Wireless LAN Throughput of 1 Vs 25 MANET mobile nodes DSR Vs TORA Wireless LAN Throughput of 1 MANET mobile nodes in static 77 topology 6.8 DSR Vs TORA Wireless LAN Throughput of 25 MANET mobile nodes in static 77 topology DSR Wireless LAN Throughput of 1 MANET mobile nodes DSR Wireless LAN Throughput of 25 MANET mobile nodes DSR Wireless LAN Throughput of 1 Vs 25 MANET mobile nodes TORA Wireless LAN Throughput of 1 MANET mobile nodes TORA Wireless LAN Throughput of 25 MANET mobile nodes TORA Wireless LAN Throughput of 1 Vs 25 MANET mobile nodes 8 IX

10 6.15 DSR Vs TORA Wireless LAN Throughput of 1 MANET mobile nodes with mobility 81 support 6.16 DSR Vs TORA Wireless LAN Throughput of 25 MANET mobile nodes with mobility 81 support 6.17 DSR vs TORA Wireless LAN Delay of 1 MANET mobile nodes DSR vs TORA MANET Delay of 1 MANET mobile nodes DSR vs TORA Wireless LAN Delay of 25 MANET mobile nodes DSR vs TORA MANET Delay of 25 MANET mobile nodes DSR vs TORA Wireless LAN Delay of 1 MANET mobile nodes DSR vs TORA MANET Delay of 1 MANET mobile nodes DSR vs TORA Wireless LAN Delay of 25 MANET mobile nodes DSR vs TORA MANET Delay of 25 MANET mobile nodes DSR vs TORA Wireless LAN load of 1 MANET mobile nodes DSR vs TORA Wireless LAN load of 25 MANET mobile nodes DSR vs TORA Wireless LAN load of 1 MANET mobile nodes DSR vs TORA Wireless LAN load of 25 MANET mobile nodes SNR-DSR Throughput 1 MANET mobile nodes SNR-DSR Throughput 25 MANET mobile nodes DSR Vs SNR-DSR Throughput of 1 MANET mobile nodes DSR Vs SNR-DSR Throughput of 25 MANET mobile nodes DSR & TORA Vs SNR-DSR Throughput of 1 MANET mobile nodes DSR & TORA Vs SNR-DSR Throughput of 25 MANET mobile nodes DSR vs SNR-DSR Wireless LAN Delay of 1 MANET mobile node DSR vs SNR-DSR MANET Delay of 1 MANET mobile nodes DSR vs SNR-DSR Wireless LAN Delay of 25 MANET mobile nodes DSR vs SNR-DSR MANET Delay of 25 MANET mobile nodes SNR-DSR vs DSR and TORA for Wireless LAN Delay of 1 MANET mobile 94 nodes. 6.4 SNR-DSR vs DSR and TORA for MANET Delay of 1 MANET mobile 94 nodes SNR-DSR vs DSR and TORA for Wireless LAN Delay of 25 MANET mobile 94 nodes SNR-DSR vs DSR and TORA for MANET Delay of 1 MANET mobile 94 nodes DSR vs SNR-DSR for Wireless LAN load of 1 nodes MANET mobile nodes DSR vs SNR-DSR for MANET load of 25 nodes MANET mobile nodes SNR-DSR vs DSR and TORA for Wireless LAN load of 1 MANET mobile nodes SNR-DSR vs DSR and TORA for Wireless LAN load of 25 MANET mobile nodes 96 X

11 List of Tables 2.1 Physical layer properties of standards Routing metrics for mesh networks summary The modified SNR-DSR Route Request Option The modified SNR-DSR Route Reply Option The modified SNR-DSR Route Cache table SNR-DSR RREQ process pseudo code DSR/TORA Communication & Network simulation parameters SNR-DSR/DSR &TORA Communication & Network simulation parameters MANET traffic Generation details End-to-End Throughput generated: sample Data for 6 min simulation time Throughput Analysis: Paired T-Test Analysis: sample statistics Throughput Analysis: Paired T-Test Analysis: Throughput analysis results DSR, TORA and SNR-DSR Average Throughput (bits/sec).. 92 XI

12 List of Abbreviations Term AODV ARP CLR D DSDV DSR EFDC ETX FSM ICI LAN MAC MANET MPR OLSR PCF PDR PktPair QoS QRY RERR RMS RREP RREQ RTS RTT S SNR TBRPF TC TCP TLL TORA UPD WiFi WiMAX WMNs Definition Ad hoc On-demand Distance Vector Address Resolution Protocol Clear Destination node Distance Sequenced Distance Vector Dynamic Source Routing Effective Communication Distance Expected Transmission Count Finite State Machine Interface Control Information Local Area Network Media Access Control Mobile Ad hoc Network Multipoint Relaying Optimized Link state Routing Point Coordination Function Packet Delivery Rate Per-hop Packet Pair Quality of Service Query Route Error Root Mean Square Route Reply Route Request Request To Send Round Trip Time Source node Signal-to-Noise-Ratio Dissemination Based on Reverse-Path Forwarding Topology Control Transmission Control Protocol Time To Live Temporally-Ordered Routing Algorithm Update Wireless Fidelity Worldwide Interoperability for Microwave Access Wireless Mesh Networks XII

13 Chapter 1: Introduction CHAPTER 1 Introduction 1.1 Background Over the last five years, Wireless Mesh Networks (WMNs) are gaining more attention and considered as a convincing solution for providing better Internet access services for end users (JUN 22; RAGHAVAN 23). The attention comes according to the unique features of WMNs including reliability, scalability and self-configuring wireless network technology. These features offer a suitable wireless network technology for next-generation networks. WMNs consist of a collection of wireless nodes. Each node operates not only as a host, but also as a router forwarding packets for other nodes. The main goal of WMNs is to allow neighbors in residential and business areas to connect their home networks together forming a Community Mesh Network. Providing such kind of connectivity allows neighbors to share single Internet access and accordingly reduce the cost of individually install it in each home network (Daves, Padhye & Zill 28). 1

14 Chapter 1: Introduction From network architecture point of view, the architecture of WMNs is quite similar to mobile ad hoc networks. Both network technologies offer simple methods for communication in multi-hop wireless network environments. The major difference between the two types of networks is the mobility consideration (Akyildiz & Wang 25). In ad hoc network, handling the frequent topology changes is considered the main design goal of the existing routing protocols. However, in WMNs, nodes are static and accordingly, the dynamic topology changes are rarely occurred. As a result, the design goal of the routing protocols has been shifted from maintaining connectivity due to mobility to finding high-throughput paths between source and destination nodes (Couto et al. 23). 1.2 Motivation Wireless mesh network (WMN) is an emerging technology that offers a cost-effective and scalable method to connect wireless devices. Although WMN is considered a convincing candidate for better wireless services, research to enhance its functionality is still in its infancy. Achieving high user data rates over multi-hop wireless paths is considered the ultimate goal for WMN. Towards this goal many enhancement can be done by using advance Mac/routing layer solutions. In this research work, due to the static nature of WMN, we study the use of Signal-to-Noise Ratio (SNR) as link-quality metric to provide an alternative routing metric rather than the classical hop-count. We believe that by modifying the existing routing protocols to use the SNR as routing criteria, routing protocols will perform well and achieve better route decision in WMN. Choosing the SNR 2

15 Chapter 1: Introduction as link-quality metric is due to the low overhead caused in calculating the SNR value of the wireless link comparing to other link-quality metrics. 1.3 Problem Statement Most of the existing ad hoc routing protocols (e.g. Ad-hoc On-demand Distance Vector (AODV), Destination Sequenced Distance Vector (DSDV), Temporal Ordered Routing Algorithm (TORA), Dynamic Source Routing (DSR)) simply use minimum hop-count as metric for identifying the best packet routes (JUN 22). However, in Wireless Mesh Networks (WMNs) due to the static nature of the nodes, paths with minimum hop-count can have poor performance because they may tend to include wireless links between distant nodes. These wireless links can be slow or lossy, leading to poor network throughput. Therefore, a routing protocol can select better routes by explicitly taking into account the quality of the wireless links rather than the number of hops between source and destination nodes (Sabyasachi Roy et al. 27). Various link-quality metrics have been proposed for measuring the quality of the wireless links. Some of these metrics are based on measuring the round trip delay between neighboring nodes (e.g. Per-Hop Round Trip Time (RTT) and the Per-Hop Packet Pair Delay (PktPair)) whereas, some of these metrics are based on measuring the average loss rate of packets between pair of neighboring nodes (e.g. Expected Transmission Count (ETX)) (Sabyasachi Roy et al. 27). Although these metrics evaluate the quality of the wireless link properly, but they send periodic network probes between neighboring nodes to help in measuring the quality of the 3

16 Chapter 1: Introduction link. These additional probes add undesirable overheads which in turn reduce the overall network throughput and accordingly lead to network performance degradation. Consequently, the need for link-quality metric which reduce the overheads of measuring the quality of the link and improve the routing capability of the existing routing protocols is required to provide high-throughput and to achieve better packet route decision in WMNs Statement of Objectives Our research aims at improving the performance of Dynamic Source Routing protocol. This aim is translated into set of objectives which can be summarized as follows: To investigate the existing routing protocols for Wireless Mesh Networks (WMNs). To propose and model an improved routing protocol through the use of Signal-to- Noise Ratio (SNR) as routing metric into DSR routing protocol. To simulate the SNR-DSR model by OPNET simulator and evaluate the overall network throughput as a performance metric. 1.5 Scope In our research work, we select the Dynamic Source Routing (DSR) protocol as an example of routing protocol used in WMNs. We select DSR protocol to evaluate the overall network throughput after applying the Signal-to-Noise Ratio (SNR) as routing metric into DSR protocol. Our research work focuses on modifying the route discovery process of DSR protocol to select a route based on the SNR feedback from the physical layer. Each node monitors the 4

17 Chapter 1: Introduction quality of the link s statistics by measuring the SNR of all packets received from immediate neighbors. We use OPNET simulator for simulation purposes. The DSR routing module provided by OPNET simulator has been changed to use SNR metric instead of hop-count for packet route selection. To calculate the SNR value of the wireless link, OPNET simulator offers special module embedded in each node model for measuring the SNR of the wireless link whenever a node receives a packet in its interface. 1.6 Proposed Solution In this research work, we propose the use of Signal-to-Noise Ratio (SNR) as routing metric to measure the quality of the wireless link in Wireless Mesh Networks (WMNs). We propose a simulation study to evaluate the routing capability of Dynamic Source Routing (DSR) protocol after applying SNR as routing metric. The evaluation includes the comparison of the overall network throughput of DSR protocol before and after applying SNR as routing metric. We intend to modify the route discovery process of DSR protocol to use the SNR feedback from the physical layer as routing metric rather than the classical hop-count. The modified DSR protocol will evaluate routes based on the accumulative SNR value along each route path from a source node to its intended destination. The highest SNR route will be selected as the best path for routing. 5

18 Chapter 1: Introduction For measuring the SNR value of the wireless link, we use the physical layer model offered by OPNET simulator which provides 15 pipeline stages to calculate step by step the total effect of the physical transmission medium (OPENT Technologies Inc 28). 1.7 Thesis Organization The remainder of this thesis is organized as follows: Chapter 2 presents an overview about Wireless Mesh Networks (WMNs), their characteristics, architectures, some challenges, and reviews the existing protocol for routing in WMNs. The chapter also presents the related work. Chapter 3 discusses the Dynamic Source Routing (DSR) protocol in details. The chapter presents the routing operations of DSR protocol and discusses the major strengths and weaknesses of DSR protocol. Chapter 4 presents the research methodology and discusses how Signal-to-Noise Ratio (SNR) can be applied to DSR protocol to provide better routing capabilities. The Chapter presents the modification of DSR protocol to accept the SNR as routing criteria instead of the classical hop-count metric. Chapter 5 discusses the simulation environment setup and presents the configuration parameters of the routing protocols used in our simulation study. Chapter 6 presents the results obtained from T-Test Data analysis tool for the purpose of data verification and also analyzes and discusses the simulation results. Chapter 7 presents the conclusion and summarizes the major contributions and findings of this master thesis followed by some future work. 6

19 Chapter 2: Literature Review CHAPTER 2 Wireless Mesh Networks (WMNs) In this chapter we present an overview of Wireless Mesh Networks (WMNs) and explain their main features, architectures, characteristics, and some of the current challenges facing WMNs. In this chapter also we discuss the major families of the routing protocols used in multi-hop wireless networks. We present one protocol from each family to show the routing behavior of the family. Additionally, we present some of the routing metrics used in WMNs followed by the performance metrics definitions. Finally, we conclude the chapter with the related works. 2.1 Introduction With the ever increasing number of wireless devices, the popularity of wireless networks has been rapidly increased to provide better wireless services and to achieve good user satisfaction (Robinson 26). Traditionally, wireless networks are either point-to-point network, where each wireless device (wireless node) needs its own dedicated connection, or point-to-multipoint network, where all wireless nodes are within range of a multi-point node which considered as a master node to ensure connectivity among nodes. 7

20 Chapter 2: Literature Review Recently, another topology called Wireless Mesh Network has emerged to provide reliable and scalable wireless network (Daves, Padhye & Zill 28). Wireless Mesh Network (WMN) consists of mesh of wireless devices (nodes), where each node is connected only to the nodes that are closest to it. Every node in the mesh network operates not only as a host but also as a router to forward messages to nearby nodes. Therefore, nodes that are not within communication range still can communicate to each other (Akyildiz & Wang 25; Hussain 27). 2.2 Wireless Mesh Networks (WMNs) WMN is a wireless technology for various applications e.g. broadband home networking, community and neighborhood networks, and enterprise networking (Akyildiz & Wang 25). The most important attention of WMN application is made towards a cost-effective Internet access in a community mesh network. In such network environment all mesh network users can share only one Internet gateway without the need for individually install it. Thus packets dynamically find a route and hopping from one node to another to get access to the Internet (Daves, Padhye & Zill 28). WMNs can be deployed easily, because all the required components are already available in the form of Ad hoc network routing protocols and IEEE82.11 MAC protocols. Although all these existing components are available, research efforts are still needed to make WMNs more reliable. For instance, the available IEEE82.11 MAC layer and routing protocols applied to WMNs do not have enough scalability; the overall throughput drops significantly as the number of nodes or hops increases. 8

21 Chapter 2: Literature Review Consequently, all current protocols from the application layer to physical layer need to be revised or enhanced to meet the WMNs needs (Akyildiz & Wang 25; Hussain 27). Figure 2.1: community mesh network (R. Daves 28) Wireless Mesh Network Architecture As show in figure 2.1, WMN consists of two types of nodes: mesh router and mesh client (End-Device). A mesh router contains additional routing functions to support mesh routing. It is usually equipped with multiple interfaces built on either the same or different wireless access technologies. The main difference between a conventional wireless router and a mesh router is that a mesh router can achieve much lower transmission power through multi-hop communication and optionally the MAC protocols in mesh router is enhanced with better scalability feature in multi-hop mesh environments (Robinson 26). Mesh routers are usually static or have minimal mobility and form a backbone infrastructure, which provides connectivity to mesh clients. Mesh routers act as a gateway for clients and also provide access to the wired networks. 9

22 Chapter 2: Literature Review In contrast, Mesh clients are normal clients which send and receive their own packets. In addition to that, they also have an important functionality to act as a router to forward packets of other nodes which are not in the direct transmission range of their destinations. Mesh client has only one interface and its hardware and software features are much simpler comparing to mesh router. However, it doesn t have the ability to become a gateway (Akyildiz & Wang 25). The network architecture of WMNs can be classified into three main groups based on the functionality of the nodes. These groups are: WMNs with infrastructure, client WMNs, and hybrid WMNs Infrastructure/Backbone WMNs Infrastructure/Backbone WMN architecture is considered the most common type used for community and neighborhood networks. In this type of architecture, mesh routers form an infrastructure for all clients that connect to them. As shown in figure 2.2, where dashed and solid links indicate wireless and wired links respectively. The mesh routers form a mesh self-configuring, self-healing links among themselves with gateway functionality to connect to the Internet. This approach also referred to as infrastructure meshing which provides backbone for conventional clients and also enables the integration of WMNs with the existing wireless networks (Akyildiz & Wang 25). 1

23 Chapter 2: Literature Review Infrastructure/Backbone WMNs can be built using various types of radio technologies, in addition to the mostly used IEEE technologies. The conventional clients with Ethernet interface can be connected to mesh routers via Ethernet link, whereas clients with the same radio technologies as mesh routers can directly communicate. If the clients have different kind of radio technologies, they must communicate with base stations that have Ethernet connections to mesh routers. Figure 2.2: WMNs with Infrastructure/Backbone (Akyildiz & Wang 25) Client WMNs (client meshing) In this type of architecture, the network consists of mesh clients which have the ability to perform routing and configuration functionalities as well as providing end-user applications to customers. As shown in figure 2.3, client nodes communicate directly with each other with the absence of mesh routers. 11

24 Chapter 2: Literature Review Client WMNs architecture usually formed using one type of radios technology on devices. In Client WMNs, a packet destined to a node in the network hops through multiple nodes to reach its destination. Figure 2.3: Client WMNs (Akyildiz & Wang 25) Hybrid WMNs Hybrid WMNs architecture is the combination of infrastructure and Client meshing WMNs. It gets the benefits of both types. Mesh Clients can access the network through mesh routers or directly meshing with other mesh clients while the infrastructure meshing provides connectivity to other networks such as Internet, WiFi, WiMAX, Cellular, and sensor networks. Figure 2.4 shows the Hybrid WMNs architecture (Hussain 27). 12

25 Chapter 2: Literature Review Figure 2.4: Hybrid WMNs (Akyildiz & Wang 25) Wireless Mesh Networks Characteristics Wireless mesh network (WMN) is a multi-hop wireless network that can provide wireless connectivity across wide areas (Akyildiz & Wang 25). Although WMN inherits many characteristics from MANET network (Mobile Ad hoc Network), WMN has many unique features that make it a good solution for next-generation networks. These unique features can be summarized as follows: 1 WMNs support ad hoc networking, and have the capability of self-forming, and self-configuration. 2 WMNs are multi-hop wireless networks, but with a wireless infrastructure/backbone provided by mesh routers. 3 Mesh routers have minimal mobility and perform dedicated routing and configuration, which significantly decreases the load of mesh client and other end nodes. 13

26 Chapter 2: Literature Review 4 Mobility of end nodes is supported easily through the wireless infrastructure. 5 Mesh routers integrate heterogeneous networks, including both wired and wireless. Thus, multiple types of networks access exist in WMNs. 6 Power-consumption constraints are different for mesh routers and mesh clients. 7 WMNs are not stand-alone and need to be compatible and interoperated with other wireless networks. 8 WMNs have civilian applications as main target Mesh standards for IEEE The IEEE82.11 specification is a set of standards that defines the communication process between wireless nodes in Wireless LAN (WLAN). The specification is defined by the IEEE LAN/MAN standards committee to carry out wireless communications in 2.4, 3.6, and 5 GHz frequency bands (Syddansk Universitet 22). The specification includes family of standards that use the same basic protocol for communication. The most popular are those defined by the 82.11b, 82.11g and 82.11n protocols. However, 82.11b is considered the most widely accepted one. Table 2.xx below describes the Physical layer properties of 82.11family (Bahr 26). Table 2.1: Physical layer properties of standards 82.11b 82.11a 82.11g 82.11n Physical layer DSSS OFDM OFDM OFDM/ Maximum rate 11 Mbps 54 Mbps 54 Mbps 54 Mbps Frequency band 2.4 GHz 5 GHz 2.4 GHz 2.4 GHz 14

27 Chapter 2: Literature Review s standard IEEE82.11s is a proposed standard defined to specify the functionality of wireless mesh networks. The main aim of 82.11s standard is to apply multi-hop mesh techniques to specify the functionality of a wireless distribution system for interconnection access points together. This feature can be used to build a wireless infrastructure for small-tolarge-scale WLANs. The implementation of 82.11s standard will be on the existing PHY layer of 82.11a/b/g operating in the unlicensed spectrum of 2.4 and 5 GHz frequency bands. The main functional feature of the standards will include a new MAC layer that supports multiradio/multichannel operation, a MAC routing layer protocols, a MAC layer broadcast/multicast mechanism and support for extensive auto-configuration (Bahr 26; Huovila et al. 26) Wireless Mesh Networks (WMNs) Current Challenges As mentioned earlier, deploying WMNs in residential areas is considered a good solution to provide broadband internet access for a community. Providing such kind of connectivity requires relatively higher bandwidth and various Quality of Service (QoS) provisions. However, the current wireless standard protocols may not completely satisfy all these requirements. Accordingly, considerable work at all communication layers of these standards is still required before a realistic wide deployment of WMNs. In the next sections we examine the key challenges at Physical, MAC and Routing layers and discuss some issues related to these layers (Akyildiz & Wang 25). 15

28 Chapter 2: Literature Review Physical Layer With the fast growing developments in digital communication technology, the data rates supported at the physical layer are rapidly increasing. However, these data rates are only achieved theoretically under perfect environment conditions with no interference at all. In real environment, these ideal conditions rarely exist. As the distance increases, the Signal to Noise Ratio (SNR) decreases. Thus, avoiding interference by using accurate modulation techniques is considered one of the key challenges that face researchers in wireless network field. Power control is another interesting aspect that should be thoroughly investigated. Since the nodes in WMNs can be placed anywhere, topology control becomes important. Typically, assigning optimal power for controlling the topology can reduce the interference and as a result it can help in improving the overall network performance. Having control to parameters such as transmission power, modulation, and signal strength will help in optimizing the overall network performance (Akyildiz, Wang & Wang 25) MAC layer In multi-hop wireless networks, a packet has to be forwarded by many intermediate nodes. Whenever an intermediate node receives a packet for forwarding, it has to perform an IP layer lookup, Address Resolution Protocol (ARP) lookup and then contend for the channel at the MAC layer at each hop. This long process increases end-to-end delay and also increases the probability of packet loss. Consequently, research efforts still needed to suggest some changes in the MAC layer protocols to speed up the process of forwarding packets. 16

29 Chapter 2: Literature Review Prior researches in MAC layer protocols have been primarily oriented towards energy conservation. However, in WMNs, for mesh router, power is no longer a constraint and accordingly, the focus of the MAC layer protocols should be towards achieving higher throughput rather than energy conservation. Currently in the market, mesh routers are offered by many commercial vendors. These routers use multiple radios with multi-channel capability. As all vendors use their own proprietary MAC and Routing protocols for their products, the interoperability still cannot be guaranteed. Thus a research effort is required to manage multiple radios and offer good interoperability. Another important issue is the QoS provisioning. The envisioned scenario of WMN is expected to support application like broadband internet access, and real time applications such as video streaming and voice conferencing. QoS provisioning for such applications is an essential requirement and a key challenge issue. In summary, Wireless Mesh Networks (WMNs) define a new paradigm for a true wireless internet access providing a maximum degree of flexibility and reduce the cost needed. The scalability and self-configuring features of WMNs make it a suitable technology for many applications. However, many issues must be discussed further in order to overcome all the challenges facing this technology. In this section we discuss some of its current challenges. Particularly, we highlight some issues at the Physical and MAC layers (Akyildiz & Wang 25). 17

30 Chapter 2: Literature Review Wireless Mesh Networks (WMNs) Routing process Due to the unpredictable environment of the Wireless Networks, designing a good routing protocol is considered an active research question among researchers in Wireless Networks field. The unpredictability of the Wireless environment includes the rapid changes in the network topology caused by nodes mobility, low bandwidth, power constraints and high error rates which are considered the main challenges facing researchers in Wireless Networks environment. The existing Routing protocols for traditional Wired Networks are unable to deal with the above mentioned limitations of Wireless Networks due to the increasing number of control messages required to maintain connectivity information for routing in Wireless Networks. This increased number of control messages can consume an observable amount of the available bandwidth which leads to less and poor network performance. Thus, the need for new routing protocols to provide peer-to-peer routing capability that reacts efficiently to topological changes while maintaining effective communication in a mobile environment is required in order to overcome the limitations of the wireless environments (Hussain 27) The Existing Routing Protocols for Mesh Networks Routing protocols designed for Mobile Ad hoc Networks (MANETs) can be considered as platform for Wireless Mesh Networks, due to the common similarities between the two types of wireless networks. Ad Hoc Network is a collection of Wireless mobile nodes which dynamically forms peer-to-peer networks with no centralized control and no wired infrastructure. 18

31 Chapter 2: Literature Review Ad hoc networks can be used in many applications to allow simple and reliable communications between mobile nodes. For instance, it can be used in business organizations to share information during meetings or it can be used in military applications to allow soldiers relaying information for situation awareness on the battlefield (Giannoulis et al. 25). Figure 2.5 shows the use of WMN in military communication. Figure 2.5: WMN in military communications (MeshDynamics 28) Due to the limitation range of the Wireless Networks, multiple hops may be needed for one node to exchange data with another node across the network. In such network environment, each mobile node operates not only as a host but also as a router, forwarding packets for other nodes. Thus, routing packets between any pair of nodes becomes an important and challenging issue in mobile Ad hoc networks (Couto et al. 23; Giannoulis et al. 25). As shown in figure 2.6, routing protocols for Ad hoc network can be classified into three main families. Under each family, there are more than one protocol have been proposed. The following sections describe briefly these families and overview one protocol from each family as an example to show the behavior of the family. 19

32 Chapter 2: Literature Review Figure 2.6: Ad hoc Routing Protocols hierarchical classification Proactive (Table Driven) routing protocols Each node in this routing protocol family maintains a routing table which contains routing information for all nodes in the network. Nodes continually exchange their routing information to offer consistent up-to-date routing information from each node to every other node in the network. As a result, the number of control messages propagated in the network is increased in order to update the nodes routing tables. Optimized Link State Routing (OLSR) protocol is described in the following section as an example of proactive routing protocol (Giannoulis et al. 25; Othman 27). 2

33 Chapter 2: Literature Review Optimized Link State Routing (OLSR) OLSR is a pro-active, decentralized, link-state routing protocol. It is a hop-by-hop routing protocol, meaning that each node uses its local information to route packets. Network topology information is continuously distributed over the network and stored locally at each node. The continuous flooding of these control messages generates a lot of redundancy which increases the possibility of network collision and might waste a lot of bandwidth. OLSR uses an optimized forwarding mechanism called multipoint relaying (MPR) to optimize and reduce the distribution of topology control (TC) messages over the network. Each node selects a set of one hop neighboring nodes to act as its multipoint relays nodes (MPR). Figure 2.7 shows OLSR Multipoint Relay (MPR) node for a group of nodes. MPRs are selected such that when node N (MPR node) transmits a broadcast message, it is received by all nodes two hops away from node N. MPRs are used in route calculation to establish a route from a given node to any destination. They are responsible for forwarding control messages to the entire network and for announcing the link-state information periodically. A neighbor of node N that is not its MPR receives and processes broadcast messages but does not retransmit the messages it received from node N (Sommer 27). Figure 2.7: OLSR Multipoint Relay (MPR) (Sommer 27) 21

34 Chapter 2: Literature Review Reactive (On-Demand) routing protocols In this family, a source node (sender) initiates route discovery when it needs to send a packet to a destination. Once the route is discovered, the node stores it in its route cache in order to use it for sending packets. Comparing to proactive protocols, reactive protocols generate less overhead in maintaining routing info. The following section discusses on- Demand Distance Vector (AODV) protocol as an example of this family (Othman 27) Ad hoc On-demand Distance Vector (AODV) Ad-hoc On Demand Distance Vector (AODV) is a re-active routing protocol for Ad hoc networks. It provides a dynamic, self-starting, multi-hop routing between mobile nodes. Packet routes are calculated on demand when a node wants to send a data packet. The algorithm provides a way for mobile nodes to respond to link break and changes in network topology. The algorithm offers a loop-free route between source and destination nodes and it can scale well for thousands of mobile nodes while handling low and high mobility rates with a variety of traffic (Othman 27; Perkins & Royer 1999). Route Discovery process in AODV protocol The Route Discovery process is started when a node S (sender node) wants to send a data packet to a Destination node D for which no route is available in the routing table of S. Node S floods a route request packet (RREQ) into the network. A route request packet contains: source identifier, source sequence number, destination identifier, destination sequence number, broadcast identifier and a time to live (TTL) as shown in figure

35 Chapter 2: Literature Review In AODV, an intermediate node replies with a route reply packet (RREP) if it knows a valid route to the destination node. Otherwise, the route request is forwarded to its neighbors. Figure 2.9 shows the message format of the Route Reply message in AODV protocol. When forwarding a route request packet, a node sets up a reverse path to node S (sender node) which uses the neighbor of S from which the request packet has first been received Type J R G D U Reserved Hop Count RREQ ID Destination IP Address Destination Sequence Number Originator IP Address Originator Sequence Number Figure 2.8: AODV Route Request Message Format (RREQ) (Perkins, Belding-Royer & Das 23) Type R A Reserved Prefix Sz Hop Count Destination IP address Destination Sequence Number Originator IP address Lifetime Figure 2.9: AODV Route Reply Message Format (RREP) (Perkins, Belding-Royer & Das 23) Route Maintenance process in AODV protocol Nodes periodically send HELLO messages to detect link failures. If a link failure is detected, a node sends a route error packet (RERR) towards the source node to notify that the link is lost. Figure 2.1 shows the message format of the Route Error packet in AODV 23

36 Chapter 2: Literature Review protocol. The RERR message indicates that the destination node no longer reachable due to the broken link. Each node maintains a routing list that contains the address of all neighboring nodes that might be used as next hop toward a destination. The route entries of the routing list that are not actively used will expire after a pre-defined interval time and accordingly remove from the routing list Type N Reserved DestCount Unreachable Destination IP Address (1) Unreachable Destination Sequence Number (1) Additional Unreachable Destination IP Addresses (if needed) Additional Unreachable Destination Sequence Numbers (if needed) Figure 2.1: AODV route Error Message Format (RERR) (Perkins, Belding-Royer & Das 23) Hybrid routing protocols This family is a combination of Reactive and Proactive routing protocols. TORA is described in the following section as an example of this family Temporally-Ordered Routing Algorithm (TORA) Temporally Order Routing Algorithm (TORA) is a fully distributed routing protocol for multi-hop wireless networks. The protocol has the ability to simultaneously support both source-initiated, on-demand routing for some destinations, and destination-initiated, proactive routing for other destinations. A key design concept of TORA is an attempt to decouple the generation of control messages from the dynamic of the network topology. In other words, it localizes the control messages to a very small set of nodes near the occurrence of a topological change. The underlying algorithm in TORA is neither distance- 24

37 Chapter 2: Literature Review vector nor link-state; it is a member of a class referred to as link reversal algorithms (Sommer 27). TORA is designed to minimize the communication overhead associated with adapting to network topological change. As mentioned, the scope of TORA s control messaging is typically localized to a very small set of nodes near a topological change. TORA routers only maintain information about adjacent routers (i.e., one-hop knowledge). It does not maintain a state on a per-destination basis. TORA Functional Description The protocol consists of three basic functions: Route Creation, Route Maintenance, and Route Erasure (Feeney 1999). Route Creation process in TORA protocol Creating routes can be initiated on-demand by a source or proactively by a destination. In either case, routers select heights with respect to the given destination and assign directions to the links between neighboring routers. Route creation is accomplished using Query (QRY) and Update (UPD) packets. The process is initialized by broadcasting a QRY packet with the destination ID in it. The height of the destination is set to and the height of all other nodes is set to null. A node with nonnull height responds to a QRY packet with a UPD packet. A node receiving an UPD packet sets its height to one more that the node that generated the packet. Therefore, a node with higher height is considered upstream and a node with lower height is considered 25

38 Chapter 2: Literature Review downstream. Each node discards a QRY packet if it has already seen the packet. Figure 2.11 below shows the route creation process in TORA (Sommer 27). Figure 2.11: Route Creation process in TORA protocol (Sommer 27) Route Maintenance process in TORA protocol When an upstream neighbor observes a link failure, it generates a new reference level. The neighboring nodes propagate the reference level and each node reverses its link to reflect the change in adapting to the new reference level. Each link reversal message is time stamped. This mechanism provides a network partition detection capability to TORA. Figure 2.12 illustrates the Route maintenance process in TORA. Figure 2.12: Route Maintenance in TORA protocol (Sommer 27) 26

39 Chapter 2: Literature Review Route Erasure process in TORA protocol In route erasure, TORA floods a broadcast Clear (CLR) packet throughout the network to erase invalid routes. TORA assumes that all nodes have synchronized clocks and cannot function properly if the timing is unreliable Routing Metrics for Wireless Mesh Networks Unlike the traditional Ad hoc networks (MANETs), routers in mesh networks are static and thus dynamic topology changes are much less of a concern in mesh network. Consequently, the design of routing metrics for mesh networks must consider the quality of the physical wireless channel and be sensitive to gradual changes in the link s quality. In the following sections, we overview some of the routing metrics proposed for mesh networks, including Hop-Count, and some of the link-state metrics used for routing (Draves, Padhye & Zill 24) Hop-Count Hop-Count is the most widely routing metric used in the existing Ad hoc routing protocols. It provides a simple and an efficient algorithm which finds a loop-free path with minimum hop-count to route packet from source to destination nodes. The major advantage of this metric is that once the network topology is known, the algorithm easily computes the minimum hop-count path. However in routing packets, hop-count does not take packet loss and bandwidth into account. Consequently, using hop-count metric might not maximize the flow throughput and accordingly, it may not result in a good network performance. 27

40 Chapter 2: Literature Review Per-Hop Round Trip Time (RTT) This metric is based on measuring the round trip time delay between neighboring nodes by sending a unicast probes (hello messages) every 5 milliseconds. The probe packet sent by a node carrying a timestamp to each of the node s neighbors. Each neighbor immediately responds to the probe with another probe called probe acknowledgment. By this mechanism, the sender node can calculate the RTT of its neighbors and know how in average, how long a packet will take to reach each of the neighbors. Accordingly, routing path is determined with the least average RTT (Couto et al. 23). The major disadvantage of this metric is the overhead caused by the 5 milliseconds advertisement messages and their responses. This overhead might reduce the possibility of using this metric in high dense networks Expected Transmission Count (ETX) This metric is based on measuring the retransmission tries a node makes to send unicast packets, by measuring the loss rate of broadcast packets between pairs of neighboring nodes. To calculate ETX, a broadcast probe packet is sent every second between pairs of neighboring nodes (like hello packet). Each node maintains a count of probes that it receives from its neighboring nodes in previous ten seconds. This count is sent in the probe packet. Each node will calculate the loss rate of probe on link between its neighbors based on the count. For example, consider two nodes X and Y. Assuming that Node X has received 6 probe packets from Y in previous ten seconds and Node Y receives 8 packets in previous ten 28

41 Chapter 2: Literature Review seconds from X. The loss rate of packet from X to Y is.4 and Y to X is.2. Thus, the probability of successful delivery of data packet on a link X to Y on a single attempt will be: (1 -.4) X (1.2) =.48 (Couto et al. 23; Hussain 27). Therefore, the expected number of retransmission before a packet is successfully delivered on this link will be 1/.48 = This value is considered as a metric value of the link between X to Y. As a result, the routing protocol will find a path with least sum of expected number of retransmissions. ETX is calculated every time when a node receives a probe packet. The main disadvantage of this metric is that, although the broadcast probe packets are small, and are sent at lowest possible rate, they may experience the same loss rate as data packet sent at higher rates. Another disadvantage of sending a probe every second would be utilizing extra bandwidth of the link, which will affect packet delivery ratio Per-Hop Packet Pair Delay (PktPair) This metric is also based on measuring the time delay between neighbors by sending backto-back packets. A sender node sends two probe packets (hello messages) to each of its neighbors one-by-one every two seconds. The first packet is small and the second one is large. Each neighbor calculates the delay between the two packets. The calculated delays are sent back to the sender. The sender maintains these delays in an exponentially weighted moving average for every neighbor. The main objective of this metric is to minimize the sum of these delays (Hussain 27). 29

42 Chapter 2: Literature Review Like RTT, the major disadvantage of this metric is its high overhead caused by sending two probes packets to each of the neighbors every two second which minimizes the likelihood of using this metric in high dense networks (Draves, Padhye & Zill 24; Sabyasachi Roy et al. 27). The following table (table 2.2) gives a summary about the above mentioned routing metrics for mesh networks. Table 2.2: Routing metrics for mesh networks summary Metric Description Advantages Disadvantages Nodes periodically Easy to implement Expensive in terms of Per-hop Round Trip Time (RTT) pings each of its neighbors. Path with least sum of Accounts for load and bandwidth Accounts for link loss delay. Self-interference due to queuing. RTT is selected. rate Node periodically Self-interference due More Expensive than sends two back-to- to queuing is not a RTT. back probes to each problem. neighbor (small and Implicitly takes load, large). bandwidth and loss Neighbor measures rate into account. delay between the Per-hop Packet Pair arrival of the two (PktPair) probes; reports back to sender. Sender averages delay samples using lowpass filter. Path with least sum of delays is selected. 3

43 Chapter 2: Literature Review Metric Description Advantages Disadvantages Estimate number of Low overhead Loss rate of broadcast times a packet has to be Explicitly takes loss probes packets is not Expected Transmissions (ETX) retransmitted on each hop. rate into account the same as loss rate of data packets. It does not take data rate or link load into account Routing Protocol Performance Metrics For Evaluation purposes, in this section we define some of the metrics used for performance analysis of the routing protocols. The performance of a routing protocol can be analyzed using two different types of metrics: the first type is used to evaluate the efficiency of a routing protocol in terms of memory usage, CPU cycles, and bandwidth or energy consumption. The second type of metrics is used to evaluate the service offered by a routing protocol to the higher layer protocols. In this section we focus on the second type of the performance metrics (Sommer 27) Packet Delivery Ratio The packet delivery ratio (PDR) is defined as the number of data packets delivered relative to the number of packets generated. Formally, PDR = packets generated (2.1) packets delivered 31

44 Chapter 2: Literature Review Throughput The throughput of a connection between two nodes is measured as the number of bytesdelivered per unit of time. Formally, Throughput = Total bytes received (2.2) Total time End-to-End Packet Delay The end-to-end packet delay is calculated as the time interval when the packet is generated and ready for the transmission until it is delivered to the receiving application at the destination node Routing Protocol Overhead The routing protocol generates a certain amount of routing packets in order to calculate paths and update the network topology information. Depending on the routing protocol used and the number of changes in the network topology due to mobility, routing packets can be accountable for a large part of the network traffic. The overhead introduced by the routing protocol can be calculated as the ratio between the number of routing packets sent and the total number of packets sent. Formally, Routing Protocol Overhead = Number of routing packets sent (2.3) Number of packets sent 32

45 Chapter 2: Literature Review 2.3 Related Work Though hop-count is considered the most common metric used in identifying the best routes, several link-quality metrics have been proposed to work as routing metrics in wireless mesh networks (WMNs). As mentioned in (Draves, Padhye & Zill 24), the performance of three link-quality metrics is compared against the use of hop-count metric in a DSR (Dynamic Source Routing) based wireless mesh network environment. The first metric is the Expected Transmission Count (ETX) which based on measuring the average loss rate of broadcast packets between pair of neighboring nodes. The second metric is the Per-hop Round Trip Time (RTT) which based on measuring the average of round trip delay between neighboring nodes. The third metric is Per-hop Packet Pair delay (PktPair) which based on the average delay between a pair of back-to-back probes to a neighboring nodes. Although the best performance was obtained by using the ETX metric under moderate mobility, hop-count performs better than these link-quality metrics. Moreover, these metrics add additional network overheads due to the exchange of the periodic probes that are used for measuring the link s quality. Additionally, to support the use of link-quality aware routing protocols, the authors of (Couto et al. 23), mention that routing through the shortest path is not always sufficient in multi-hop wireless networks. They present experimental evidence from two wireless testbeds to show that paths with minimum hop-count might have poor network performance. Moreover, in (Dube et al. 1997) based on the signal strength and the location stability of ad hoc networks, the authors propose a complete architecture for a distributed adaptive routing protocol called Signal Stability-Based Adaptive routing protocol (SSA). Their results show that the use of signal strength consistency decreases the route maintenance and offers a way 33

46 Chapter 2: Literature Review to select longer-live route based on signal strength and location stability. Although they have done an excellent work, but further simulation using a packet-level simulator is needed to determine the costs and benefits of this approach With respect to improving the existing routing protocols for wireless mesh networks, DSR and DSDV are modified to use the Expected Transmission count metric (ETX) as a criteria to select the high-throughput path in multi-hop wireless networks. Although the results show some improvement in terms of packet delivery ratio, but as mentioned before, ETX adds additional overhead which leads to performance degradation and additional network delay (Sabyasachi Roy et al. 27). In (Alilou. & Dehghan.t. 25; G.Amoussou et al. 26) the basic mechanisms of DSR protocol have been modified to add the link quality as a routing metric. For example in (G.Amoussou et al. 26), authors present an approach for designing routing protocol based on the prediction of the Effective Communication Distance (EFCD) between nodes. The EFCD is a new metric derived from the prediction of the link duration which is consider as a stability measure for routing. To achieve their goal, the authors have modified the route cache structure of DSR protocol to select a route according to the hop-count and the EFCD as well. Their work is different from ours because they consider the mobility model as the main factor to predict the link duration and compute the EFCD. But in WMNs the mobility is very rare and the nodes are approximately static. DSR routing protocol once again has been modified in (Hussain 27) to consider the link quality for packet-routing in WMNs. The key idea of this work is to calculate the link s 34

47 Chapter 2: Literature Review delay by sending a single synchronization message between a pair of nodes through a special non-delayed radio channel used for time synchronization. Before sending a packet, a sender stamps the packet with its current time. When a node receives a message, it adjusts its clock to the sender time and calculates the physical link s delay simply by subtracting the sender time from its current time. All links are stored in a link cache together with their link s delay values in order to use them for routing process. The work has been simulated using NS-2 simulator with link cache enable and zero mobility scenarios. The Ad hoc On-demand Distance Vector (AODV) routing protocol also has been modified in (Tsai, Wisitpongphan & Tonguz 26). The authors modify the Route Discovery process of AODV protocol to avoid routing through low quality links. They modify the protocol to select a route based on the hop-count and the signal quality statistics measured from the physical layer. They integrate also the handoff concept into the routing protocol to avoid link breakage during the routing maintenance. The modified version of AODV protocol that they have developed shows lower overhead than the original AODV while still providing equal performance in terms of throughput and delay. In our research work, we try to improve the routing capability of Dynamic Source Routing (DSR) protocol by modifying its route discovery process to use the Signal-to-Noise-Ratio (SNR) as a routing metric rather than the classical hop-count metric. Our work will be simulated using OPNET modeler with different WMNs network topologies in order to evaluate the efficiency of DSR protocol in packet routing after applying SNR metric. 35

48 Chapter 3: Dynamic Source Routing (DSR) Protocol CHAPTER 3 Dynamic Source Routing (DSR) This chapter discusses in details the Dynamic Source Routing (DSR) protocol. The chapter presents the basic routing operations of DSR protocol including Route Discovery and Route maintenance. The chapter also presents the performance of DSR protocol and some of its strengths and weakness are summarized at the end of the chapter. 3.1 DSR Quick View As described in (D. Johnson, y. Hu & Maltz 24), DSR is a simple and an efficient reactive routing protocol that is designed especially for use in multi-hop wireless Ad hoc networks. It is designed for very high mobility rate with up to 2 mobile nodes. It incurs very low overhead but reacts very quickly to changes in the network. DSR allows an ad hoc network to be self-organizing and self-configuring without relying on an existing network infrastructure or administration. Mobile nodes cooperate to forward packets to each other to allow communications over multiple hopes between nodes that are not within communication range of each other. The protocol is composed of two mechanisms that operate on demand. 36

49 Chapter 3: Dynamic Source Routing (DSR) Protocol The Dynamic Source Routing (DSR) protocol was designed especially for MANET applications. Its main feature is that every data packet follows the source route stored in its header. This route gives the address of each node through which the packet should be forwarded in order to reach its final destination. Each node on the path has a routing role and must transmit the packet to the next hop identified in the source route. Each node maintains a Route Cache in which it stores every source route it has learned. When a node needs to send a data packet, it checks first its route cache for a source route to the destination. If no route is found, it attempts to find one using the route discovery mechanism. A monitoring mechanism, called route maintenance, is used in each operation along a route. This mechanism checks the validity of each route used (Feeney 1999; David B. Johnson & Maltz 1996; Othman 27) 3.2 DSR Basic Operations In this section, the basic operations of DSR protocol are discussed to give a clear overview about the behavior of DSR in packet-routing process in multi-hope wireless networks Route Discovery Route Discovery is a mechanism that allows a node S (sender node) that wishes to send a packet to a destination node D to obtain a source route to D. This mechanism invoked only when node S attempts to send a packet to D and it does not know the route to node D. DSR is a source routing protocol meaning that the packet header contains the complete ordered list of nodes through which the packet will pass to reach its destination. This feature allows a source node to select and control the route for its packets, supports the use 37

50 Chapter 3: Dynamic Source Routing (DSR) Protocol of multiple routes to destination, and guarantees that routes are loop-free. Besides that, this feature also allows other nodes forwarding or overhearing the packet to cache the routing information for future use. In DSR, every node maintains up-to-date route cache to store the previously learned source routes to all possible destinations. All information is added to the route cache when a node discovers or maintains some routes. Likewise, information is removed from the route cache when an error message is received to indicate that a route has been broken (Sommer 27). As shown in figure 3.1, assume that node A is a sender node wants to send a packet to a destination node E. In this scenario, node A should start the process by searching its route cache of routes previously learned to find a valid route to node E. If none is found, it initiates a Route Discovery process to find a new route to the destination node E. In route discovery, node A is called the initiator node whereas node E is called the target node. To initiate the route discovery process, node A broadcast a Route Request (RREQ) packet that is received by all nodes within the transmission range of node A. Each RREQ contains information about the initiator and the target and a unique request ID. The request ID is used to avoid receiving duplicated route request packets. Moreover, each RREQ contains a record listing the address of each intermediate node to which the request is forwarded. Initially, the route record contains only node s A (initiator node) address. When an intermediate node (e.g. node B) receives the RREQ, it checks if it is the target node or not. If it is not, it checks whether it has a cached route to the destination node (node E). If it does not have, it adds its address to the route record in the request packet header and re- 38

51 Chapter 3: Dynamic Source Routing (DSR) Protocol broadcast the RREQ again. A RREQ packet is discarded if a node s address is already present in the route record (Othman 27). In response to the RREQ, a route reply packet (RREP) is generated either by the target node (node E) or by an intermediate node that has a cached route to the target node. When an intermediate node (e.g. node C) responds to the request, first it searches its route cache for a route to the target node, if found, it appends the cached route to the route record, generates a reply to node A, and does not forward the RREQ anymore. When node E (target node) returns a RREP, it also examines if its own route cache contains a route for A. If one is found, it uses it as the source route to deliver the RREP. Otherwise it has to perform its own new route discovery for node A or alternatively, node E could simply reverse the sequence of hops in the route record and uses it to deliver the RREP. A A,B A,B,C A,B,C,D Id=2 Id=2 Id=2 Id=2 A B C D E Figure 3.1: DSR Route Discovery process (D. Johnson, y. Hu & Maltz 24) 39

52 Chapter 3: Dynamic Source Routing (DSR) Protocol Route Maintenance Route maintenance is a mechanism used only when a source node S is sending packets to a destination node D. While node S is using a source route to node D, route maintenance allows node S to be able to detect if the network topology has been changed such that it can no longer use its route to destination node D. Figure 3.2 illustrates the Route Maintenance process of DSR protocol. DSR uses Per-Hop acknowledgement and Route Error packet (RRER) to achieve route maintenance. When a node sends a packet to a destination node using a source route, each node along the route path is responsible for confirming that the packet has been successfully received by the next hop. This confirmation may be obtained in the form of link-level acknowledgements or through passive acknowledgements where a node is able to overhear the next hop forwarding the packet along the route. When a node detects a link failure, it sends a RRER to the sender. When a RRER is received, the node removes this link from its route cache and returns a RRER to all nodes that have sent a packet via that failed link (Hussain 27; Othman 27). Figure 3.2: DSR Route Maintenance process (D. Johnson, y. Hu & Maltz 24) 4

53 Chapter 3: Dynamic Source Routing (DSR) Protocol 3.3 DSR Performance For performance evaluation purposes, the behavior of Dynamic Source Routing (DSR) protocol has been simulated in many research works (D. Johnson, y. Hu & Maltz 24; David B. Johnson & Maltz 1996). The simulations were run in ad hoc network environments with different numbers of mobile nodes. It was seen that DSR protocol performed well in scenarios with small amount of mobile nodes and high movement rates. The strength and the weaknesses of DSR protocol can be summarized as follows: Strengths of DSR protocol No periodic updates needed, a route path only is created on-demand. This reduces the overheads for route maintenance. Fast route discovery if route cache is applied. Several redundant paths due to several intermediate nodes replying with cached information Weakness of DSR protocol Packet s header-size grows with the length of the route. The intermediate nodes add their addresses to the packet s header while forwarding the packet. Flooding of route request packets (RREQ) might add additional overheads to the whole network, especially if the path to the target node is unknown and no TTL can be used. To avoid collision, DSR uses random times to control sending of route request/reply packets. These random times add extra delay to the route discovery process. 41

54 Chapter 3: Dynamic Source Routing (DSR) Protocol Cached route entries can become invalid and may pollute other caches timeouts needed, but need to be adaptive, based on link stability. 3.4 Problem in DSR route Discovery process During the route discovery process of DSR protocol, the best route is selected based on the minimal hop-count criteria. The hop-count criteria might have an excellent impact in a high topology-change wireless environment. But, in Wireless Mesh Networks, due to the static nature of the nodes, routes with minimal hop-count may have poor performance because they tend to include wireless links between distant nodes. These long wireless links can be slow or can have low signal strength, leading to poor network throughput. Figure 3.3 below shows the route discovery process of DSR with hop-count as criteria for routing. As shown in figure 3.3, node A (sender node) receives a reply form node E (destination node) through shortest path. Figure 3.3: DSR route Discovery process with Multiple paths (Longbi Lin 23) 42

55 Chapter 4:Methodology CHAPTER 4 Methodology Most of the existing routing protocols for WMNs use the classical hop-count criteria when making a route selection. Although hop-count criteria achieves an excellent impact in packet routing process, but it only takes into account the mobility of the node as an important factor for packet-route selection. However, due to the static nature of WMNs, paths with minimum hop-count are not always the best choice. These paths may have lowquality links in terms of signal-strength measurement. In this chapter we discuss the modification of Dynamic Source Routing (DSR) protocol to select a route based on the signal strength. We modify the DSR protocol to select a route path based on the Signal-to- Noise-Ratio (SNR) feedback from the physical layer rather than the classical hop-count. We start the chapter with a quick overview about OPNET simulator (The tool used for simulation purposes) followed by the modeling of SNR-DSR protocol in OPNET simulator. 43

56 Chapter 4:Methodology 4.1 OPNET Simulator: an Overview OPNET is a high level and powerful event-base network simulation tool which models communication devices and protocols and offers a large variety of built-in analysis tools. It is mainly used for the simulation of networks design to evaluate the influences of changes in the network and the configuration of the network. It enables the possibility to simulate entire heterogeneous network with various types of network protocols. In OPNET, the simulation operates at packet-level for fixed and wireless network design. It contains a huge library of accurate modules of commercially available network hardware and protocols. It consists of high level user interface which is constructed from C or C++ source code blocks with a huge library of OPNET specific functions (OPENT Technologies Inc 28; Suresh 25) Why Use OPNET A good modeling tool should closely reflect the true behavior of a network or computer system. It should support a wide range of network protocols and applications. It must be easy to use and master, especially for beginners. On the other hand, a good modeling tool should provide comprehensive technical support and maintenance assistance. In summary, a good modeling tool should have following properties: Versatile: able to simulate various network protocols/applications under a wide range of operating conditions Robust: provide users with powerful modeling, simulation, and data analysis facilities. User-friendly: easy to use and master Traceable: easy to identify modeling problems and simulation faults 44

57 Chapter 4:Methodology OPNET is hailed by network professionals because it has all these properties. OPNET is a software package that has been designed with an extensive set of features. It can be tailored to suit almost every need of network protocol designers, network service providers, as well as network equipment manufacturers. OPNET supports most network protocols in existence, both wire-line and wireless. It can be used to model and analyze a complex system by performing discrete event simulations (Park & Dadej 23) OPNET modeling hierarchy The simulation modeling in OPNET is divided into three main domains: Global Network Domain The global network domain is considered a high-level description domain. It specifies the overall scope of the system to be simulated. It describes all the objects involved in the simulation as well as their physical locations, interconnections and configurations. Figure 4.1 illustrates the Global Network domain with two sub-net components in world scale. Figure 4.1: OPNET Global Network Domain with sub-net component (Suresh 25) 45

58 Chapter 4:Methodology Node model Domain The node model is the second modeling level. It describes the internal structure of each node in the network. The network nodes can be workstations, routers, packet switches or can be special type of nodes e.g. Ethernet or Token Ring network nodes. Figure 4.2 shows the internal node structure of a mobile MANET node. Figure 4.2: MANET mobile node model. (Suresh 25) Process model Domain The Process model domain is modeled as Finite State Machine (FSM) which consists of states with transitions and condition between states. Figure 4.3 shows the TCP process model. Figure 4.3: OPNET TCP process model (Suresh 25) 46

59 Chapter 4:Methodology 4.2 DSR Model in OPNET Node Model The following figure shows the DSR node model as described in OPNET software. The node model consists of a group of processes. Each process is a layer of OSI communication protocol model. Figure 4.4 below shows the node model of DSR. Figure 4.4: OPNET DSR Node Model (Park & Dadej 23) The following section describes in details the DSR node model process layers as implemented in OPNET simulator: The physical layer: As shown in figure 4.4, in OPNET, the physical layer of DSR node model composes of transmitter and receiver. Each of these blocks is not really OPNET process, but it defines every C source code that is used in the pipeline 47

60 Chapter 4:Methodology wireless communication mechanism (OPENT Technologies Inc 28). All of these source codes have been developed based on the standard wireless_lan model in OPNET The link layer: the link layer in DSR node model is the OPNET model with some modifications. The modifications have been done in order to link this MAC layer with the DSR routing layer. The modifications have been done to facilitate some processes like sending of acknowledgement and error messages, addition of the promiscuous mode, and fixing of small bugs relative to the nodes mobility. The network layer: this layer contains the DSR routing process model. It is divided into two processes. The first one is the DSR routing module, and the second one an interface with the upper layer that chooses for instance a random destination address for each data packet that must be transmitted on the network. The upper layers are mainly composed of two processes (i.e. source and receiver nodes). The source is an OPNET process that generates data packet traffic. The receiver is a sink that just destroys the packet after the reception and processing completion. 48

61 Chapter 4:Methodology Process Model The following figure illustrates the DSR process model as described in OPNET software specification. The model is described as finite state machine (FSM). The explanation of each process-state will discuss as follows Figure 4.5: OPNET DSR Process Model (OPENT Technologies Inc 28) Pre-Init State This state pre-initializes the DSR process model by managing the DSR address of the current node, and by checking that this address is valid within the network. Init State This state initializes every variable, statistic, table, and user parameter that is used by the DSR process model. Idle State This is the default state where the process waits for an event. 49

62 Chapter 4:Methodology Upper Layer Arrival State This state handles every packet generated by the upper layer that the DSR protocol must carry to a given destination MAC Layer Arrival State This state handles every packet received from the link layer. It processes the packet differently depending on its type: request, reply, data, or error. Send Reply This state is called when the current node must send a scheduled reply from relay. Thus this state just sends this scheduled Reply packet No Reply This state is called when the timeout associated with a Request packet transmitted by the node expires. That means there is no Reply packet has been received and accordingly the previous step of the route discovery failed, and a new Request packet must be generated by the node. This state does all these operations Ack State This state handles every acknowledgement coming from the link layer. An acknowledgement confirms that the current link used is valid, thus allowing the node to send other Data packets through this link. At the same time, it resets the error mechanism (no ack reception) that checks either if an explicit DSR layer 5

63 Chapter 4:Methodology acknowledgement was received (will be implemented) or if the MAC layer is working (currently implemented) Error State This state occurs when an error is detected by the DSR s error mechanism or is received from the protocol s MAC layer. After receiving the error packet, the link is declared broken and the route cache is updated to indicate that. 51

64 Chapter 4:Methodology 4.3 Implementing SNR-DSR Model in OPNET In this section we discuss the implementation of SNR-DSR model in OPNET simulator. We start with a quick overview about the SNR metric followed by the essential modifications of DSR protocol to apply SNR as routing selection metric Signal-to-Noise-Ratio (SNR) Definition SNR is defined as the ratio of a signal power to the noise power corrupting the signal. It compares the level of a desired signal to the level of background noise. The higher the ratio, the less obtrusive the background noise is. Formulation The SNR value is formulated as follow: (4.1) Where P is average power and A is root mean square (RMS) amplitude (for example, typically, RMS voltage). Both signal and noise power (or amplitude) must be measured at the same or equivalent points in a system, and within the same system bandwidth. 52

65 Chapter 4:Methodology OPNET Pipeline Stages In OPNET, the MANET node physical layer is modeled with multiple pipeline stages as shown in figure 4.6. The pipeline stages are used to calculate step by step the total effect of the physical transmission medium including all the interferences caused by other users. Each pipeline stage is a model made with OPNET flavored C or C++ code block. The transceiver pipeline stages, shown in figure 4.6, are a series of software blocks that perform all the wireless physical layer operations. Stages 1 5 are the transmitter pipeline stages and stages 6-13 are the receiver pipeline stages (OPENT Technologies Inc 28). Each stage is simply a piece of software that can be substituted or modified as desired. As show in figure 4.6, stage 1 represents the Signal-to-Noise-Ratio (SNR) module process in OPNET simulator. It shows how the MANET node physical layer measures the SNR value when receiving a packet in its interface. (Appendix A shows the OPNET SNR module). 53

66 Chapter 4:Methodology Figure 4.6: OPNET MANET physical layer pipeline stages (OPENT Technologies Inc 28) In our research work, we use the SNR module process for measuring the SNR value of the neighbor s link. Then the calculated SNR value will be sent to the DSR routing layer in order to use it for packet route selection. 54

67 Chapter 4:Methodology Passing SNR to DSR routing Layer Since the packet route selection is decided at the routing layer, we need a mechanism to pass the SNR feedback from the physical layer to the routing layer. OPNET simulator does provide a channel to pass a value from lower layers to upper layers. This section describes the changes that should be made to the MAC layer process in order to pass the SNR value up to the routing layer. To let the SNR value arrives at the routing layer, we use the OPNET Interface Control Information (ICI) packets. The ICI packet is a user-define data items that can be associated with an event. This capability allows information to be transferred from the context where an event is generated to the context where it later occurs. The ICI offers an Inter-Process Communication mechanism between processes that constitutes the node model in OPNET simulator. It provides a reliable way for exchanging information between these processes (Park & Dadej 23). To pass the SNR value, we create an ICI named snr_value at the MAC layer of MANET node model. This ICI used to cache the SNR feedback from the physical layer in order to use it later at the routing layer. Figure 4.7 show the creation of snr_value as ICI at the MAC layer. 55

68 Chapter 4:Methodology Figure 4.7: Creation of snr_value as ICI at the MAC layer (OPENT Technologies Inc 28) During the route discovery process of DSR protocol, DSR routing layer gets the SNR value from snr_value ICI and uses it as packet route selection criteria. Figure 4.8 shows passing SNR value to DSR routing layer. Passing SNR value to DSR routing layer using ICI mechanism Figure 4.8: Passing SNR value to DSR routing layer (OPENT Technologies Inc 28) 56

69 Chapter 4:Methodology SNR-DSR route Discovery Process In this section, we modify the route discovery process of DSR protocol to select a route based on the SNR feedback from the physical layer. First we modify the protocol s internal data structure to add additional field for storing the accumulative SNR value during the route discovery process. The changes have been made particularly to the Route Request option (RREQ), Route Reply option (RREP) and the Route cache data structures. The following tables (Table 4.1, Table 4.2, and Table 4.3) show these modifications. Route Request option Table 4.1: The Modified SNR-DSR Route Request Option Identification route-list_ptr Target-address route-snr Field Identification route-list_ptr Target-address route-snr Description A unique value generated by the initiator (original sender). List of hops along the route path The address of the target node. Accumulative SNR value Route Reply option Table 4.2: The Modified SNR-DSR Route Reply Option Last_hop_external Route-list_ptr route-snr Field Last_hop_external Route-list_ptr route-snr Description Boolean to indicate that the last hop is actually an arbitrary path in a network external to the DSR network. List of hops along the route path Accumulative SNR value. 57

70 Chapter 4:Methodology Route Cache: Table 4.3: The Modified SNR-DSR Route Cache Path_hops_ptr first_hop_external Last_hop_external num_hops Installed_time Last_access_time route_snr Field Path_hops_ptr First_hop_external Last_hop_external Num_hops Installed_time Last_access _time route-snr Description List of hops along the route path. Boolean to indicate that the first hop is actually an arbitrary path in a network external to the DSR network. Boolean to indicate that the last hop is actually an arbitrary path in a network external to the DSR network. number of hops Cache entry s install time last access time Accumulative SNR value 58

71 Chapter 4:Methodology Route Selection Mechanism During the route Discovery process, the source node broadcasts the Route Request (RREQ) packet which includes an additional filed, route_snr, to store the accumulative SNR value along the route path. Upon receiving the RREQ, a non-destination node updates the route_snr filed with its current SNR feedback from the physical layer. When the destination node receives the RREQ packets, it compares the accumulative SNR value associated with each RREQ packet. Then the destination node sends its Route Reply (RREP) packet through route path that has the higher SNR value. The following figure illustrates the whole route discovery process of DSR protocol after applying SNR parameter as routing metric. A RREQ [ A, B ] G 2 Path 1: [ A, B, E, G ] Accumulated SNR=3 db Wait Path 2: [ A, D, G ] Accumulated SNR=15 db Wait Path 3: [ A, C, F, G ] Accumulated SNR=5 db Wait Accept RREQ A [ A ] G B E A [ A, B, E ] RREQ G 3 Source RREQ A A [ A ] RREQ A RREP G G [ A ] [ F, C, A ] G A 1 5 G D RREP [ F, C, A ] A RREQ [ A, D ] A 5 G 15 RREP G A G [ F, C, A ] [ A, C, F ] Destination A 5 G 5 C A [ A, C ] G 3 F RREQ RREQ Source Route SNR Field RREQ: Route Request RREP: Route Reply SNR: Signal-to-Noise-Ratio A [ A, B ] G Source Destination Figure 4.9: DSR route Discovery Process with SNR parameter 59

72 Chapter 4:Methodology The following pseudo code (Table 4.4) shows the Route Request (RREQ) process of DSR protocol after applying the SNR as routing metric. Table 4.4: The modified SNR-DSR RREQ process pseudo code Receive DSR packet Calculate Link s SNR value. Case (RREQ Packet) If (Destination IP matches) - wait until receiving all RREQ packets - for all RREQ received o Get Route source with Max SNR value. - Send RREP through Route with Max SNR value. ELSE - Update the SNR Field in RREQ - Rebroadcast RREQ packet End if During the routing process of the modified SNR-DSR protocol, there are some steps needed to show how the SNR value of the wireless link can be used as routing criteria. Table 4.4 shows the steps of the Route Request process when a node receives a packet in its interface. 6

73 Chapter 5:Simulation CHAPTER 5 Simulation This chapter describes the simulation setup used in our simulation study. The chapter explains the design-parameters of the simulation environment and presents the basic configuration parameters used in our experiments. The simulation study aims to compare the performance of the standard Dynamic Source Routing (DSR) protocol against the TORA and the modified SNR-DSR protocols. For data verification, we conclude the chapter with a brief overview about T-Test data analysis tool, a statistical data analysis tool that used to verify the data generated by the simulator. 5.1 Simulation Environment setup As mentioned in chapter 4, OPNET modeler is used as simulation tool in our simulation study. We divided the simulation study into two parts. The first part deals with the comparison study of the standard DSR protocol against TORA protocol. In this part, we simulate two network scenarios of 1 and 25 MANET mobile nodes. The nodes are placed randomly in a 1mX1m area. Each scenario runs for 3 minute simulation time with mobility and non-mobility support scenarios. The details of the simulation s parameters that used in this part are presented in table

74 Chapter 5:Simulation The second part of the simulation study deals with the comparison study of the modified SNR-DSR protocol against the original DSR and TORA protocols. In this part we simulate two static network scenarios of 1 and 25 MANET mobile nodes. The nodes are placed randomly in 5mX5m area. Each scenario runs for 6 minute simulation time. Table 5.2 shows the details of the simulation s parameters that used in this part. The purpose of changing some of the simulation s parameters used in this part is because we need to study the behavior of the modified SNR-DSR protocol with different parameters and use them as design parameters in our simulation study. The simulation in this part aims to evaluate the use of SNR metric as routing criteria in SNR-DSR routing protocol. The simulation compares the modified SNR-DSR protocol against both DSR and TORA protocols. In our simulation experiments we deploy the network topologies using MANET mobile nodes spreading randomly in MANET areas with 6 minutes as maximum simulation time. The deployed areas used to simulate small WMN environments that can provide connectivity for a group of people in one business place. The aim of the simulations is to focus on the use of SNR as an alternative metric for routing in multi-hop wireless networks. The reason of using MANET components is because of the similarities between WMN and MANET networks. WMN is a multi-hop wireless network that inherits many features from MANET network and can be considered as one type of MANET network with addtional unique features. Refer to chapter 2 for further explanation. 62

75 Chapter 5:Simulation For results gathering, we exports all the simulation data from OPENT simulator into spreadsheet documents and use Microsoft Excel software for data manipulation and drawing graphs. The following sections categorize and present the simulation parameters used in our experiments: Communication and Network parameters DSR and TORA simulation scenarios Table 5.1 illustrates the communication and the network parameters used in the comparison scenarios of DSR and TORA protocols. The table shows the simulation s parameters as configured in OPNET simulator. Figure 5.1 presents the topology used for the comparison in this part. Table 5.1: DSR/TORA Communication & Network simulation parameters Parameter Value Network parameters No Of Topologies 2 No Of nodes 1, 25 Area 1mX1m Simulation Time 3 minute Nodes type MANET mobile node Communication Parameters Physical medium DSSS Data Rate 11 Mbps Transmission power.5w Packet Reception-power Threshold 7.33 E-14 RTS Threshold None MAC protocol MAC layer PCF parameters Disabled Mobility model manet_up_right 63

76 Chapter 5:Simulation Figure 5.1: OPNET 1mX1m topology of 25 MANET mobile nodes with mobility SNR-DSR against DSR and TORA simulation scenarios Table 5.2 shows the communication and the network parameters used for the comparison study of the modified SNR-DSR protocol against the original DSR and TORA protocols. The topology used for the comparison in this part is presented in figure 5.2. Table 5.2: SNR-DSR/DSR&TORA Communication & Network simulation parameters Parameter Value Network parameters No Of Topologies 2 No Of nodes 1, 25 Area 5mX5m Simulation Time 6 minute Nodes type MANET mobile node Communication Parameters Physical medium DSSS Data Rate 11 Mbps Transmission power.5w Packet Reception-power Threshold 7.33 E-14 RTS Threshold None MAC protocol MAC layer PCF parameters Disabled Mobility None (static scenarios) 64

77 Chapter 5:Simulation Figure 5.2: OPNET 5mX5m topology of 25 MANET mobile nodes Routing Protocols Configurations In this section we present the default configuration of DSR and TORA protocols in OPNET simulator. We start by showing how these routing protocols can be configured in OPNET simulator. Then we present the configuration parameters of each protocol separately. Figure 5.3 illustrates the basic configuration of ad hoc routing protocol in OPNET simulator. Figure 5.3: OPNET Ad hoc Routing Protocol Configuration 65

78 Chapter 5:Simulation DSR configuration Figure 5.4 shows the default configuration parameters of DSR protocol in OPNET simulator. Figure 5.4: OPNET DSR protocol Configuration TORA Configuration Figure 5.5 illustrates the default configuration parameters of TORA protocol in OPNET simulator. Figure 5.5: OPNET TORA protocol Configuration 66

79 Chapter 5:Simulation MANET Traffic Generation Parameters For network traffic generation purposes, we generate three MANET traffics. Table 5.3 below describes the details parameters of the generated MANET traffic. Start Time (sec) Table 5.3: MANET traffic Generation details Packet inter- Arrival Time (sec) Packet size (bits) Destination IP Address Stop Time (sec) 1. Constant (.5) Constant (124) Random End of simulation 1. Constant (1) Constant (124) Random End of simulation 1. Constant (1.5) Constant (124) Random End of simulation 5.2 Data Analysis Tool In order to verify the data generated by the simulator, in our simulation study we use T-Test data analysis tool, a statistical data analysis tool. This section gives a brief overview about T-Test data analysis tool and presents some of its important features T-Test T-Test is a Statistical Data Analysis tool used for hypothesis testing. It is simply used to test whether the means of independent population groups are statistically different or not. There are several kinds of T-Test data analysis tool, but Two-Sample T-Test is considered the most common tool used for statistical data analysis, specially when we need to assess whether the means of two independent population groups are statistically different from each other (Creech 28). 67

80 Chapter 5:Simulation The following section gives a simple example to show how T-Test analysis tool can be used to test two samples of data T-Test Example Assume we have a research hypothesis that rich people have a different quality of life than poor people. We give a questionnaire that measures quality of life to a random sample of rich people and a random sample of poor people. The null hypothesis, which is assumed to be true until proven wrong, is that there is really no difference between these two populations From the gathered sample data we observe that the two groups have different average scores. But the question is, does this different represent a real difference between the two populations, or just a chance difference in our samples? T-Test tool allows us to answer this question by using the t-test statistic to determine a p- value that indicates how likely we could have gotten these results by chance. By convention, if there is a less than 5% chance of getting the observed differences by chance, we reject the null hypothesis and say we found a statistically significant difference between the two groups (Creech 28). In our simulation study, we use T-Test analysis tool to evaluate and test the network throughput generated by OPNET simulator. We use T-Test to indicate how likely we could have significant different between the generated network throughput results before and after applying SNR as routing metric into DSR protocol. Section 6.1 of Chapter 6 presents the statistical T-Test results. 68

81 Chapter 6: Data Analysis & Results Discussion CHAPTER 6 Data Analysis & Results Discussion In the previous chapter we described the simulation setup and we presented the basic configurations used in our simulation study. In this chapter for the purpose of data verification, we present the statistical T-Test results to validate the data generated by the simulator. In this chapter also we present the results of our simulation experiments. We evaluate the performance of the modified SNR-DSR protocol relative to two existing ad hoc routing protocols DSR and TORA protocols. The main goals of the simulation study are as follows: To evaluate the performance of DSR and TORA protocols in Wireless Mesh network (WMN) environments. To study the behavior of the modified SNR-DSR protocol, analyze its performance in Wireless Mesh Network (WMN) environments. 69

82 Chapter 6: Data Analysis & Results Discussion 6.1 Data Analysis In order to verify and analyze the data generated by the simulator, this section presents the T-Test statistical results. As mentioned, T-test analysis tool is used to determine whether the difference between means of two groups of sample data is significant or not. In our simulation study, we use the paired T-test analysis to test the End-to-End throughput of DSR protocol before and after applying the SNR metric as routing criteria. The results taken from the T- test analysis indicate that there is a significant difference between the two samples of data and this difference is truly and real. Accordingly, we can be 95% confident on the accuracy of the simulation data and we can rely on it in our simulation analysis study Network Throughput: T-Test analysis Results The following tables show the T-Test analysis results of the End-to-End throughput of DSR protocol before and after applying the SNR metric. The sample data taken from a simulation scenario of a network of 25 MANTE mobile nodes distributed in 5mX5m area. Table 6.1 show the generated sample data whereas table 6.2.and 6.3 show the generated T-test results 7

83 Chapter 6: Data Analysis & Results Discussion Table 6.1: End-to-End Throughput generated: sample Data for 6 minute simulation time. Time (sec) DSR SNR-DSR Time (sec) DSR SNR-DSR Time (sec) DSR SNR-DSR Table 6.2: Paired T-Test Analysis: sample statistics 71

84 Chapter 6: Data Analysis & Results Discussion Table 6.3: Paired T-Test: Throughput analysis results Evaluation In summary, as shown in the Paired T-test results above, we can see that there is a significant difference between the network throughput sample data of DSR protocol before and after applying the SNR metric. The null hypothesis at the beginning assumes that there is no difference between these two groups of sample data. But from the results we can observe that the two groups of sample data have significant difference. less than.5. As a result, we reject the null hypothesis and accept the accuracy of the sample data. 72

85 Chapter 6: Data Analysis & Results Discussion 6.2 Comparison of DSR and TORA To compare and evaluate the performance of DSR and TORA protocols, we simulate two network topologies of 1 and 25 MANET mobile nodes. Nodes are randomly placed in 1mX1m rectangular campus area in order to simulate simple wireless mesh network environments. Chapter 5 presents the simulation setup in details. In our simulation experiments, we evaluate the performance according to the following performance metrics: Throughput The network throughput performance metric is defined as the number of bytes successfully delivered per unit time. End-to-End Delay The End-to-End Delay is defined as the average delay experienced by the data packets. It includes all possible delays caused due to route discovery, queuing, retransmission, propagation, processing and transfer times. Routing overhead (load) Routing overhead or Routing load is defined as the number of routing packets transmitted per data packet delivered at the destination. Routing packets include Route Request, Route Reply, Route setup and probe packets. 73

86 Chapter 6: Data Analysis & Results Discussion In our simulation experiments, we run each network topology two times. The first run without mobility support whereas the second run with mobility support. The manet_up_right OPNET mobility model has been used to simulate the node mobility. The purpose of applying mobility model is to evaluate the mobility influences on the performance of DSR and TORA protocols in WMNs Throughput The following figures in this section show the network Throughput results obtained from the simulation scenarios. The obtained results are categorized into two parts according to the mobility considerations Static Scenario results Figures 6.1 to 6.8 show the Throughput results obtained from two static network scenarios of 1 and 25 MANET mobile nodes. Figures 6.1 to 6.3 show DSR Throughput whereas figures 6.4 to 6.6 show TORA Throughput. All simulations run for 3 minute simulation time. The graph in figure 6.7 and 6.8 illustrate the comparison of the total network throughput between DSR and TORA protocols. 74

87 Chapter 6: Data Analysis & Results Discussion Wireless LAN Throughput Wireless LAN Throughput Throug h p ut( bits/sec) Time(sec) DSR Throug hput ( bits/sec) Time(sec) DSR Figure 6.1: DSR Wireless LAN Throughput of 1 MANET mobile nodes Figure 6.2: DSR Wireless LAN Throughput of 25 MANET mobile nodes Figure 6.1 and figure 6.2 show the DSR Wireless LAN Throughput results of static network scenarios of 1 and 25 MANET mobile nodes respectively. DSR Wireless LAN Throughput Throughput(bits/sec) Time(sec) Figure 6.3: DSR Wireless LAN Throughput of 1 Vs 25 MANET mobile nodes 25_nodes 1_nodes Figure 6.3 shows the comparison results of the DSR Wireless LAN Throughput of network of 1 MANET mobile nodes against network of 25 MANET mobile nodes. As we can see in the graph, the total network throughput increases as the number of nodes increases. 75

88 Chapter 6: Data Analysis & Results Discussion Wireless LAN Throughput Wireless LAN Throughput Throug h p ut( bits/sec) Time(sec) TORA Throughput(bits/sec) Time(sec) TORA Figure 6.4: TORA Wireless LAN Throughput of 1 MANET mobile nodes Figure 6.5: TORA Wireless LAN Throughput of 25 MANET mobile nodes Figure 6.4 and figure 6.5 show TORA Wireless LAN Throughput results of static network scenarios of 1 and 25 MANET mobile nodes respectively. TORA Wireless LAN Throughput Throughput(bits/sec) Time(sec) Figure 6.6: TORA Wireless LAN Throughput of 1 Vs 25 MANET mobile nodes 1_nodes 25_nodes Figure 6.6 shows the comparison results of TORA Wireless LAN Throughput of network of 1 MANET mobile nodes against network of 25 MANET mobile nodes. As we can see in the graph, the total network throughput increases as the number of nodes increases. 76

89 Chapter 6: Data Analysis & Results Discussion Wireless LAN Throughput Throughput(bits/sec) Time (sec) Figure 6.7: DSR Vs TORA Wireless LAN Throughput of 1 MANET mobile nodes in static topology DSR TORA Figure 6.7 shows the Wireless LAN Throughput comparison between DSR and TORA protocols. The graph shows that DSR has better throughput than TORA in 1 MANET mobile nodes static network scenario. Wireless LAN Throughput Throughput (bits/sec) DSR TORA Time(sec) Figure 6.8: DSR Vs TORA Wireless LAN Throughput of 25 MANET mobile nodes in static topology Figure 6.8 shows the Throughput comparison between DSR and TORA protocols. The results obtained from static network scenario of 25 MANET mobile nodes. As shown in the graph, DSR protocol has higher Throughput reaches at maximum 14 bits/sec. 77

90 Chapter 6: Data Analysis & Results Discussion Discussion As shown in the graphs in figure 6.7 and 6.8, DSR protocol outperform TORA protocol and has better network throughput in both network scenarios. The obtained throughput results show that DSR protocol performs well as the number of nodes increases in static environments Mobility-support scenario results: In this section, OPNET manet_up_right mobility model has been applied for mobilitysupport deployment. Figures 6.9 to 6.16 show the Throughput results obtained from network scenarios of 1 and 25 MANET mobile nodes after applying the mobility model. Figures show DSR Throughput whereas figures show TORA Throughput. All simulations run for 3 minute simulation time in 1mX1m rectangular area. Refer to chapter 5 for simulation configuration details. The graph in figure 6.15 and 6.16 illustrate the throughput results of DSR as compared to TORA protocol. 78

91 Chapter 6: Data Analysis & Results Discussion Wireless LAN Throughput Wireless LAN Throughput Throughput(bits/sec) Time(sec) DSR Throughput(bits/sec) Time(sec) DSR Figure 6.9: DSR Wireless LAN Throughput of 1 MANET mobile nodes Figure 6.1: DSR Wireless LAN Throughput of 25 MANET mobile nodes Figure 6.9 and figure 6.1 show the Wireless LAN Throughput of DSR protocol in Mobility-support scenarios of 1 and 25 MANET mobile nodes respectively. DSR Wireless LAN Throughput Throughput(bits/sec) _nodes 25_nodes Time(sec) Figure 6.11: DSR Wireless LAN Throughput of 1 Vs 25 MANET mobile nodes Figure 6.11 shows the Wireless LAN Throughput of DSR protocol of two different scenarios. As the number of nodes increases, the total Throughput increases accordingly. 79

92 Chapter 6: Data Analysis & Results Discussion Wireless LAN Throughput Wireless LAN Throughput Throug h p ut( bits/sec) Time(sec) TORA Throughput(bits/sec) Time(sec) TORA Figure 6.12: TORA Wireless LAN Throughput of 1 MANET mobile nodes Figure 6.13: TORA Wireless LAN Throughput of 25 MANET mobile nodes Figure 6.12 and figure 6.13 show the Wireless LAN Throughput of TORA protocol in Mobility-support scenarios of 1 and 25 MANET mobile nodes respectively. TORA Wirele ss LAN Throughput Throughput(bits/sec) Time(sec) Figure 6.14: TORA Wireless LAN Throughput of 1 Vs 25 MANET mobile nodes 1_nodes 25_nodes Figure 6.14 shows the Wireless LAN Throughput of TORA protocol of two different scenarios. As the number of nodes increases, the total Throughput increases accordingly. 8

93 Chapter 6: Data Analysis & Results Discussion Wireless LAN Throughput Throughput (bits/sec) Time(sec) Figure 6.15: DSR Vs TORA Wireless LAN Throughput of 1 MANET mobile nodes with mobility support DSR TORA As shown in figure 6.15 DSR has higher Wireless LAN Throughput than TORA protocol in 1 MANET mobile nodes static scenarios. Wireless LAN Throughput Throughput Time(sec) Figure 6.16: DSR Vs TORA Wireless LAN Throughput of 25 MANET mobile nodes with mobility support DSR TORA Figure 6.16 shows that DSR protocol outperform TORA protocol and has better Wireless LAN Throughput than TORA in static scenario of 25 MANET mobile nodes. 81

94 Chapter 6: Data Analysis & Results Discussion Discussion The results in figure 6.15 and 6.16 show that DSR protocol has better throughput than TORA protocol even if in mobility-support scenarios. As the number of nodes increases and the mobility model applied, DSR protocol has higher throughput up to 14 bits/sec whereas TORA protocol has maximum throughput up to 12 bits/sec only as shown in figure In summary, from the obtained results, we can see that DSR protocol has better network Throughput and it outperforms TORA protocol in all simulation scenarios including static and mobility-support scenarios. The results indicate that DSR protocol is more suitable than TORA protocol to perform packet routing in wireless mesh network environments with the static nature of the nodes. 82

95 Chapter 6: Data Analysis & Results Discussion End-to-End Delay Static scenario results: Figures 6.17 to 6.2 below show the End-to-End delay experienced by DSR and TORA protocols in static scenarios of 1 and 25 MANET mobile nodes. Wireless LAN Delay MANET Delay Delay(sec) Time(sec) DSR TORA Delay(sec) Time(sec) DSR TORA Figure 6.17: DSR vs TORA for Wireless LAN Delay of 1 MANET mobile nodes Figure 6.18: DSR vs TORA for MANET Delay of 1 MANET mobile nodes Wireless LAN Delay MANET Delay Delay(sec) Time(sec) DSR TORA Delay(sec) Time(sec) DSR TORA Figure 6.19: DSR vs TORA for Wireless LAN Delay of 25 MANET mobile nodes Figure 6.2: DSR vs TORA for MANET Delay of 25 MANET mobile nodes 83

96 Chapter 6: Data Analysis & Results Discussion Mobility-support scenario results: Figures 6.21 to 6.24 below show the End-to-End delay experienced by DSR and TORA protocols in mobility-support scenarios of 1 and 25 MANET mobile nodes. Wireless LAN Delay MANET Delay.3.25 Delay(sec) DSR TORA Delay(sec) DSR TORA Time(sec) Time(sec) Figure 6.21: DSR vs TORA for Wireless LAN Delay of 1 MANET mobile nodes Figure 6.22: DSR vs TORA for MANET Delay of 1 MANET mobile nodes Wireless LAN Delay MANET Delay Delay(sec) Time(sec) DSR TORA Delay(sec) Time(sec) DSR TORA Figure 6.23 DSR vs TORA for Wireless LAN Delay of 25 MANET mobile nodes Figure 6.24 DSR vs TORA for MANET Delay of 25 MANET mobile nodes 84

97 Chapter 6: Data Analysis & Results Discussion Discussion Figures 6.17 to 6.24 show the End-to-End delay characteristics of DSR and TORA protocols including Wireless LAN Delay and MANET Delay. The graphs show the results of two network topologies of 1 and 25 MANET mobile nodes. Figures 6.17 to 6.2 show the obtained End-to-End delay of static network scenarios whereas figures 6.21 to 6.24 show the obtained delay of mobility-support scenarios. We can see in the graphs, in both scenarios (static and mobility-support) TORA protocol has less delay than DSR protocol. The delay ranged from.16 second as maximum delay as shown in figure 6.2 to.4 second as minimum delay as shown in figure It is quite clear from the obtained results; DSR protocol suffers from small amount of delay. This delay is expected since DSR protocol uses a broadcast mechanism for route establishment (discovery) and probing technique for route maintenance. These two mechanisms add additional latencies that affect the overall delay experienced by DSR protocol. In general, we can summarize that DSR protocol has higher delay than TORA protocol in all scenarios. This higher delay decreases as the number of nodes increases particularly in static environments.. 85

98 Chapter 6: Data Analysis & Results Discussion Routing load Static scenario results: Figure 6.25 and Figure 6.26 show the routing load comparison between DSR and TORA protocols in static scenarios of 1 and 25 MANET mobile nodes respectively. Wireless LAN Load Wireless LAN Load Normalized Load Time (sec) DSR TORA Normalized Load Time(sec) DSR TORA Figure 6.25: DSR vs TORA for Wireless LAN load of 1 MANET mobile nodes Figure 6.26: DSR vs TORA for Wireless LAN load of 25 MANET mobile nodes Mobility-support scenario results: Figure 6.27 and Figure 6.28 show the routing load comparison between DSR and TORA protocols in mobility-support scenarios of 1 and 25 MANET mobile nodes respectively. Wireless LAN Load Wireless LAN Load N orm a lize d Loa d Time(sec) DSR TORA Norm alized Load Time(sec) DSR TORA Figure 6.27: DSR vs TORA for Wireless LAN load of 1 MANET mobile nodes Figure 6.28: DSR vs TORA for Wireless LAN load of 25 MANET mobile nodes 86

99 Chapter 6: Data Analysis & Results Discussion Discussion Figures 6.25 to 6.28 show the routing load comparison for DSR and TORA protocols. The first two figures (figures 6.25 and 6.26) show the routing load in static scenarios whereas the last two figures (figures 6.27 and 6.28) show the routing load in mobility-support scenarios. As shown in the graphs, DSR protocol has higher routing load than TORA protocol in all simulation scenarios. Moreover, the routing load experienced by the two routing protocols (DSR and TORA) in static scenario is approximately similar to the routing load experienced in mobility-support scenario. This similarity means that the routing packets transmitted and delivered at the destinations are approximately same in both scenarios. 87

100 Chapter 6: Data Analysis & Results Discussion 6.3 Comparison of SNR-DSR against DSR and TORA In this section we compare the performance of the modified SNR-DSR protocol against the original DSR and TORA protocols. As mentioned, we simulate two static network topologies of 1 and 25 MANET mobile nodes. Nodes are randomly placed in 5mX5m flat campus area running for 6 minute simulation time. Chapter 5 presents the simulation setup in details. In our comparison experiments, we compare the protocols only in static scenarios because we intend to compare their performance in Wireless Mesh Networks (WMNs) where nodes are mostly static. Similar to the comparison study of DSR and TORA protocols, we compare the performance of the modified SNR-DSR protocol according to network Throughput, End-to-End Delay and Routing load as performance metrics. 88

101 Chapter 6: Data Analysis & Results Discussion Throughput In the following figures we present the throughput results of the modified SNR-DSR protocol followed by the throughput results of the modified SNR-DSR as compared to DSR and TORA protocols. Wireless LAN Throughput Throughput Time (sec) SNR-DSR Figure 6.29: SNR-DSR Throughput of 1 MANET mobile nodes The graph in figure 6.29 shows the Wireless LAN Throughput of the modified SNR-DSR protocol for network of 1 MANET mobile nodes. The graph shows the Throughput results of 6 minute simulation time. Wireless LAN Throughput 2 Throughput Time (sec) SNR-DSR Figure 6.3: SNR-DSR Throughput of 25 MANET mobile nodes Figure 6.3 above shows the Wireless LAN throughput results of the modified SNR-DSR protocol for network of 25 MANET mobile nodes. 89

102 Chapter 6: Data Analysis & Results Discussion Wireless LAN Throughput Throughput(bits/sec) Time(sec) SNR-DSR DSR Figure 6.31: DSR Vs SNR-DSR for Throughput of 1 MANET mobile nodes As shown in figure 6.31 above the modified SNR-DSR protocol perform well in 1 MANET mobile nodes network scenarios. The graph shows that SNR-DSR has higher Wireless LAN Throughput that the original hop-count DSR protocol. Wireless LAN Throughput Throughput(bits/sec) Time(sec) SNR-DSR DSR Figure 6.32: DSR Vs SNR-DSR for Throughput of 25 MANET mobile nodes In Figure 6.32 above, the modified SNR-DSR protocol has higher Wireless LAN Throughput than the original hop-count DSR protocol. The graph shows the Throughput of 25 MANET mobile nodes network scenario. 9

103 Chapter 6: Data Analysis & Results Discussion Figure 6.33: DSR & TORA Vs SNR-DSR for Throughput of 1 MANET mobile nodes In figure 6.33 above, the Wireless LAN Throughput of the modified SNR-DSR protocol compared relative to the original DSR and TORA protocols. As shown in the graph, the modified protocol has better Throughput than the other two protocols. The obtained results show the Throughput of 1 MANET mobile nodes in static network scenario. Figure 6.34: DSR & TORA Vs SNR-DSR for Throughput of 25 MANET mobile nodes Figure 6.34 shows the comparison of the Wireless LAN throughout of the modified SNR- DSR protocol against the original DSR and TORA protocols. The results show that SNR- DSR has better throughput results. 91

104 Chapter 6: Data Analysis & Results Discussion Table 6.4 below shows the average Throughput results of DSR, TORA, and the modified SNR-DSR protocols. As shown in the table, the modified SNR-DSR protocol has higher average throughput than DSR and TORA protocols in both network scenarios (1 and 25 nodes). Table 6.4: Average Throughput (bits/sec) 1 nodes 25 nodes DSR TORA SNR-DSR Discussion Figures 6.29 to 6.34 show the obtained network throughput results of 1 and 25 network topologies. It is quite clear from the obtained results, the modified SNR-DSR protocol has better network throughput than the original DSR protocol in all scenarios. The original DSR protocol uses the hop-count metric as routing criteria whereas the modified SNR-DSR uses the SNR feedback from the physical layer as routing metric. The graphs in figures 6.31 and 6.32 show the throughput comparison between the original DSR and the modified SNR-DSR protocol. In both network scenarios SNR-DSR outperforms DSR protocol and has better throughput reaches in maximum 3 bit/sec as shows in figure In figure 6.33 and figure 6.34, the total throughput of SNR-DSR compared against the original DSR and TORA protocols. The results show that also SNR-DSR has better throughput comparing to both DSR and TORA protocols. In summary, from the obtained results, we can see that the modified SNR-DSR protocol has better performance than DSR and TORA protocols. As the number of nodes increases the modified SNR-DSR protocol has better network throughput. These results make the protocol more suitable to be deployed in wireless mesh network environments. 92

105 Chapter 6: Data Analysis & Results Discussion End-to-End Delay Figure 6.35 to figure 6.38 show the comparison of the Wireless LAN Delay and the MANET Delay of the modified SNR-DSR protocol against the original hop-count DSR protocol. Wireless LAN Delay MANET Delay Delay Time (sec) SNR-DSR DSR Delay Time (sec) SNR-DSR DSR Figure 6.35: DSR vs SNR-DSR for Wireless LAN Delay of 1 MANET mobile nodes Figure 6.36: DSR vs SNR-DSR for MANET Delay of1 MANET mobile nodes Wireless LAN Delay MANET Delay.3.14 Delay Time(sec) SNR-DSR DSR Delay Time(sec) SNR-DSR DSR Figure 6.37: DSR vs SNR-DSR for Wireless LAN Delay of 25 MANET mobile nodes Figure 6.38: DSR vs SNR-DSR for MANET Delay of 25 MANET mobile nodes 93

106 Chapter 6: Data Analysis & Results Discussion Figures 6.39 to 6.42 show the Wireless LAN delay and the MANET delay that experienced by the modified SNR-DSR protocol as compared to DSR and TORA protocols. As shown in the graphs the modified SNR-DSR protocol suffers from small amount of delay. Figure 6.39: SNR-DSR vs DSR and TORA for Wireless LAN Delay of 1 MANET mobile nodes Figure 6.4: SNR-DSR vs DSR and TORA for MANET Delay of 1 MANET mobile nodes Figure 6.41: SNR-DSR vs DSR and TORA for Wireless LAN Delay of 25 MANET mobile nodes Figure 6.42: SNR-DSR vs DSR and TORA for MANET Delay of 25 MANET mobile nodes 94