Comparative Study of Routing Protocols in Wireless Sensor Networks by Abid Afsar Khan Malang Palsapi


Published on

Comparative Study of Routing Protocols in Wireless Sensor Networks by Abid Afsar Khan Malang Palsapi

Published in: Technology
  • Be the first to comment

  • Be the first to like this

No Downloads
Total views
On SlideShare
From Embeds
Number of Embeds
Embeds 0
No embeds

No notes for slide

Comparative Study of Routing Protocols in Wireless Sensor Networks by Abid Afsar Khan Malang Palsapi

  1. 1. Comparative Performance Study of Routing Protocols in Wireless Sensor Network By Abid Afsar Khan Malang Palsapi (‫فی‬ ‫س‬ ‫ل‬ ‫ف‬ ‫نگ‬ ‫ل‬ ‫م‬ ‫خان‬ ‫سر‬ ‫اف‬ ‫د‬ ‫)عاب‬ This thesis is submitted to the Faculty of the Computing Griffith College in partial fulfillment of the requirements for the degree of Master of Science in Computing Under the supervision of Dr. Faheem Bukhatwa October 2012 Dublin, Leinster Copyright 2012,Abid Afsar
  2. 2. i Table of Contents Sr. No. TITLE Page No. 1. Introduction 1 1.1 Background 1 1.2 Problem Definition 2 1.3 Motivation for Current Work 3 1.4 Research Question 4 1.5 Research Methodology 5 1.6 Aims and Objectives 7 1.7 Assumption 8 1.8 Thesis Contribution 8 1.9 Related work 9 1.10 Organization of the Thesis 9 Summary 10 2. Routing Protocols in IP-Datagram Networks 11 2.1 Introduction 11 2.2 Routing 11 2.3 Proprieties of Routing Protocols 12 2.4 Classification of Routing Protocol 12 2.5 Goals of Routing Protocol 15 2.6 Conventional Routing Protocols 16 2.6.1 Adaptive Routing Protocols 16 2.6.2 Open Shortest Path First (OSPF) 17
  3. 3. ii Sr. No. TITLE Page No. 2.7 Enhanced Interior Gateway Routing Protocol (EIGRP) 22 2.7.1 Link-state-based Routing 22 2.8 Border Gateway Protocol or Path Vector- based Routing 24 2.9 Advance Routing Approaches 26 2.9.1 Self-Adjusting Routing Protocols 26 Summary 30 3. Routing Protocols in Wireless Ad-Hoc and Sensor Network 31 3.1 Introduction 31 3.2 Classification of Wireless Network 31 3.3 Conventional Ad-Hoc Routing Protocol 33 3.3.1 Optimal Source Routing (OSR) 34 3.3.2 Wireless Routing Protocol (WRP) 39 3.3.3 Global State Routing (GSR) Protocol 40 3.4 Wireless Sensor Network (WSNs) 41 3.4.1 Network Characteristics, Design Objectives 41 3.4.2 Network Design Objectives 43 3.4.3 WSNs Network Design Challenges 45 3.5 Routing 47 3.5.1 Routing in Wireless Sensor Network 47 3.5.2 Classification of Wireless Senor Network Routing Protocols 49 Summary 68 4 Design of Simulation Experiments 69 4.1 Introduction 69
  4. 4. iii Sr. No. TITLE Page No. 4.2 Scalable Ad-Hoc Network Simulator (ShoX) 70 4.3 Architecture of ShoX 71 4.4 ShoX Key Features 74 4.5 ShoX Configuration 75 4.6 Metrics 76 4.6.1 Simulation Parameters 77 4.7 Experimentation Design and Setup parameters 78 4.7.1 Experiment No.1 –Design of Small Network Topology 78 4.7.2 Experiment No.2 – Design of Medium Network Topology 80 4.7.3 Experiment No.3- Design of Large Network Topology 82 4.7.4 Experiment No. 4- Design of Simulation Time variation 84 4.7.5 Experiment No. 5- Design of Nodes Deployment Area variation 85 4.7.6 Experiment No. 6- Design of Interference Handler Model Variation 86 Summary 87 5 Implementation and Results Analysis 88 5.1 Introduction 88 5.2 Implementation 88 5.3 Experiment 1: Small Nodes Scenario 88 5.3.1 Case 1, 2, 3 & 4: Measurement of packet drop ratio in small number of stationary and mobile nodes using OSR and Rumor routing protocols 89 5.4 Experiment 2- Medium Nodes Scenario 92
  5. 5. iv Sr. No. TITLE Page No. 5.4.1 Case 1, 2, 3 & 4: Measurement of packet drop at hop in 25 stationary nodes using OSR and rumor routing algorithm 93 5.5 Experiment 3- Large Nodes Scenario 96 5.5.1 Case 1, 2, 3 and 4: Measurement of packet drop at hop in 49 stationary nodes using OSR and rumor routing algorithm 97 5.6 Experiment No. 4- Simulation Time Variation 100 5.6.1 Case 1, 2, 3 and 4: Measurement of drop packet ratio/rate at stationary topology using OSR and rumor routing algorithm 101 5.7 Experiment No. 5- Network Deployment Area Variation 105 5.7.1 Case 1, 2, 3 and 4: Measurement of drop packet ratio/rate at stationary topology using OSR and rumor routing algorithm 105 5.8 Experiment No. 7- Interference Handler Model Variation 109 5.8.1 Case 1, 2, 3 and 4: Measurement of packet drop ratio at stationary topology using OSR and rumor routing algorithm 109 5.9 Simulation Results and Performance Analysis 113 Summary 116 6 Conclusion And Future Work 117 6.1 Introduction 117 6.2 Conclusion 117 6.2.1 Reflection of our work on research question 118 6.3 Future Work 120 Bibliography 121
  6. 6. v Sr. No. List of Tables Page No. 3.1 Seven WSN’s routing protocols categories 50 4.1 Simulation Parameters Table 77 4.2 Parameters Table-Exp 1- Case 1: Rumor Routing Stationary Nodes 79 4.3 Parameters Table Experiment 1- Case 2: Rumor Routing Mobile Nodes 79 4.4 Parameters Table -Experiment 1- Case 2: Rumor Routing Mobile Nodes 79 4.5 Parameters Table -Exp1- Case 2: Rumor Routing Mobile Nodes 80 4.6 Parameters Table -Exp 2- Case 1: Stationary nodes using rumor routing 81 4.7 Parameters Table -Exp 2- Case 2: Mobile nodes using rumor routing 81 4.8 Parameters Table -Exp 2- Case 3: Mobile nodes using rumor routing 81 4.9 Parameters Table -Exp 2- Case 4: Mobile nodes using rumor routing 82 4.10 Parameters Table -Exp 3- Case 1: Stationary nodes using rumor routing 83 4.11 Parameters Table -Exp 3- Case 2: Mobile Nodes using rumor routing 83 4.12 Parameters Table -Exp 3- Case 3: Stationary Nodes using OSR routing 83 4.13 Parameters Table -Exp 3- Case 4: Mobile Nodes using OSR routing 83 4.14 Parameters Table -Experiment 4- case 1-Simulation Time 84 4.15 Parameters Table -Experiment 4- case 2-Simulation Time 84 4.16 Parameters Table -Experiment 4- case 3-Simulation Time 84 4.17 Parameters Table -Experiment 4- case 4-Simulation Time 84 4.18 Parameters Table -Experiment 5- case 1-Deployement Area 85
  7. 7. vi Sr. No. List of Tables Page No. 4.19 Parameters Table -Experiment 5- case 2-Deployment Area 85 4.20 Parameters Table -Experiment 5- case 3-Deployment Area 85 4.21 Parameters Table -Experiment 5- case 4-Deployment Area 85 4.22 Parameters Table Experiment 6- Case 1- Interference handler model 86 4.23 Parameters Table -Experiment 6- Case 2- Interference handler model 86 4.24 Parameters Table -Experiment 6- Case 3- Interference handler model 86 4.25 Parameters Table -Experiment 6- Case 4- Interference handler model 86 5.1 Parameters of IEEE802.11g WLAN standards 91 5.2 Parameters of IEEE802.11g WLAN standards 95 5.3 Parameters of IEEE802.11g WLAN standards 98 5.4 Parameters of IEEE802.11g WLAN standards 103 5.5 Parameters of IEEE802.11g WLAN standards 107 5.6 Parameters of IEEE802.11g WLAN standards 111
  8. 8. vii Sr. No. List Of Figures Page No. 1.1 Typical WSNs Components overview 1 1.2 (a) Represent small topology, ( b) Represent medium topology, (c) represent large topology 4 1.3 (a) Represents dense network in a smaller area, while figure (b) Represents sparse network of the same size but in large area 5 1.4 Bar chart representation of simulation pause time 6 1.5 Represent interference and communication range 6 2.1 Classsfication of routing proctols startegies in IP-Datagram networks 13 2.2 Shortest path finding mechanism 18 3.1 Block diagram of wireless network classification 33 3.2 Ad-hoc routing protocols classification chart 34 3.3 OSR single node movements 36 3.4 Classification of spinal routing algorithm 39 3.5 Hierarchical diagram of WSNs routing protocols classification 49 3.6 Rumor routing chart representation 52 3.7 Query is originated and query source is looking for the path to reach to the event 53 3.8 Agents aggregating to multiple events 54 3.9 Represents the greedy approach from node x to node y, because these are located in close neighborhood. 60 3.10 In Greedy Forwarding Routing the data packet is forwarded to a neighbor that which is located in a close proximity 60
  9. 9. viii Sr. No. List Of Figures Page No. 3.11 When greedy routing gets stuck in topology 61 3.12 When there is a hole in the network 61 3.13 Generic view of different faces of planner graph 62 3.14 Generic view of source and destination at planner graph 62 3.15 Represents base station, cluster head, and cluster 67 3.16 Different level of hierarchies 68 4.1 ShoX starting view 70 4.2 ShoX Configuration Panel 71 4.3 ShoX Architectural View 72 4.4 Network topology of 10 nodes 78 4.5 Network topology of 25 nodes 80 4.6 Network topology of 49 nodes 82 5.1 Relative performance comparison in small stationary topology of 10 mobile nodes 92 5.2 Relative performance comparison in small mobile topology of 10 nodes 92 5.3 Relative performance comparison in small stationary topology of 25 nodes 96 5.4 Relative performance comparison in small mobile topology of 25 nodes 96 5.5 Relative performance comparison in large stationary topology of 49 nodes 100 5.6 Relative performance comparison in large mobile topology of 49 nodes 100 5.7 Relative performance comparison at different simulation time 104
  10. 10. ix Sr. No. List Of Figures Page No. 5.8 Relative performance comparison at different simulation time 104 5.9 Relative performance comparison at deployment area of 300 x 400 m2 108 5.10 Relative performance comparison at deployment area of 300 x 400 m2 108 5.11 Relative performance comparison at minimum SNR interference model 112 5.12 Relative performance comparison at minimum SNR interference model 112 Sr. No. List of Equations Page No. 3.1 Relation between Radio Range and Grid Size r 2 + (2r)2 ≤ R2 Where r ≤ R∕√5 [8] 56 Disclaimer I hereby certify that this material, which I now submit for assessment on the programme of study leading to the Degree of Masters of Science in Computing at Griffith College Dublin, is entirely my own work and has not been submitted for assessment for an academic purpose at this or any other academic institution other than in partial fulfillment of the requirements of that stated above. Signed: _____________________ Date: ___________________
  11. 11. x Abstract Modern wireless sensor network can be expanded into large geographical areas via cheap sensor devices which can sustain themselves with very a low power usage. The networking capability enables these sensor nodes to incorporate, collaborate and coordinate with each other and this is a fundamental shift in the field of networks which differentiates sensor network nodes form other networks such as IP-datagram, Ad-Hoc and so on. Currently, routing in the wireless sensor network faces multiple challenges, such as new scalability, coverage, packet loss, interference, real-time audio and video real time streaming, harsh weather environments, energy constraints and so forth. Network routing can be called an amalgamation of routing protocol and routing algorithm. The job of the routing protocols is to provide a cohesive view of network nodes topology while routing algorithm provides the intelligence in terms of optimal path calculation. We set out to conduct a detailed study of routing protocols in a IP-datagram, wireless ad-hoc and sensor network, and also accomplished routing protocols comparison against the chosen network performance factor dropped packet ratio. Routing protocols play an important role in modern wireless communication networks. Routing protocols’ performance can be measured by a number of factors such as packet dropped rate and so forth. Rumour and Optimal Spinal Routing algorithms are compared using ShoX simulation and the results and analysis are based upon the simulation experiments.
  12. 12. xi Dedication I dedicate my thesis to my beloved family, especially To my late father: Haji. Muhammad Imran Khan ( Mamaan Khan), To my mother, To my late grandfather and grandmother, To my uncles: Haji. Muhammad Afsar Khan Haji. Muhammad Irshad Khan Haji. Tahir Muhammad Khan
  13. 13. xii Acknowledgments In the name of Allah, most Gracious, most Compassionate. First of all, I would like to offer my special thanks to Allah for the guidance and assistance in this thesis. I wish to offer my special thanks to my supervisor Dr. Faheem Bukhatwa for his advice and support during the writing of this thesis. I would like to pay special thanks to my family for their prayers and encouragement during my studies. Finally, I would like to give special thanks to my all weather friends Kalpesh Nahire (Nasik India), M. Tahir Azam (Chakwal Pakistan), Sumit Walia (Delhi India), Asif Ali (Derby UK), Dr. M. Asim ( JMU Liverpool UK), Shah Fahad (Swat Pakistan), and M. Imran Akhtar (Haripur Pakistan). Abid Afsar Khan Malang Palsapi Griffith College Dublin October 2012
  14. 14. Comparative Performance Study of Routing Protocols in Wireless Sensor Network 1 Chapter 1 Introduction 1.1. Background Wireless communication is rapidly growing in our day to day life because it is easy to deploy and is more flexible. In particular, the wireless sensor network (WSN‟s) is one of the latest innovations in the field of wireless communication. It consists of tiny mote which hold a small battery, CPU and sensor. Today, sensor motes are widely used by the military in the battle field as a means to closely monitor enemy activities. Sensor networks are also used in healthcare, wide-life, temperature monitoring and many other applications. A diagrammatic components overview of WSNs is shown below, Figure 1.1. Typical WSNs components overview The above diagram represents a number of WSNs components, such as sensor node architecture, base station, deployment area, and sensor nodes event region which are represented in blue and green colours. Routing is an important issue in a wireless sensor network and a number of routing protocols were proposed however, an efficient routing algorithm remains an issue The recent development of a wireless sensor network has led us to an innovative use of small sensory nodes which operate with a very low power in extreme environmental conditions. The group of small sensory nodes are randomly deployed in a sensor field. Theses nodes have the ability to organise themselves automatically and to detect
  15. 15. Comparative Performance Study of Routing Protocols in Wireless Sensor Network 2 neighbouring nodes to from an ad-hoc network. The nodes of the WSNs can plan what sort of sensing data to receive, send, or query some particular event. The query concept in sensor networks leads us to new ways of routing, for instance clustering sensor nodes, redundancy, and so forth. Today, there are number of sensor motes commercially with low prices ranging from 50$ to 100$ per single mote. It is further expected that the price will go down in the next five years. One of the leading manufacturers is the Crossbow Inc., which makes Intel motes. There are number of development projects is in progress, such as Smart Dust Project which are going to optimise a large number of motes into a single chip, operating system called TinyOS which is currently freely available and being developed for a senor network. A programming language called EmStar is used for the development of sensor nodes, a communication interface called NesC is developed for sensor nodes and finally a database called TinyDB was developed to transfer data between heterogeneous sensor networks. 1.2. Problem Definition The rationale of this thesis is to investigate efficient routing protocols which can successfully deliver data packets in sensor network. Wireless network protocols which are currently in place have suffered from a number of issues such as drop packets, address table overhead, topology convergence, throughput, data packets delay, routing overhead and so on. In WSNs there are number of issues which pose new challenges for the wireless sensor network. As we are aware that WSNs mote consist of a small battery with limited power and because of this limitation it gives birth to a new set of problems such as routing, and scalability in WSNs. The motes perform their operations by the sensor on board but it‟s quite challenging to route data when the intermediary motes lose battery power at transit or have low power, and it further leads to problems such as topology adjustment, mote data recovery and back-up and so forth. Therefore we believe that to route sensing data properly we need to have intelligent WSNs routing protocols which give better strategies in terms of energy and scalability WSNs routing is still a challenging area for the researcher. One problem is the energy in WSNs, so there is an open option to make routing decisions on the basis of energy awareness. The core issue involved with wireless senor network routing is related to rigorous resource constraints allocation in terms of computation, storage and energy consumption which make it not only interesting but challenging.
  16. 16. Comparative Performance Study of Routing Protocols in Wireless Sensor Network 3 In the event of a problem the associated routing algorithm does not have an intelligence to adjust them dynamically and it is also termed as non-adaptive routing protocols. In carrying out our research we found that a large amount of work has been done in the area of routing in WSNs, but these are largely individual contributions on specific routing protocols. We feel that there is a need for a detailed level of study in the area of WSNs routing protocols. There are a number of routing protocols proposed for WSNs routing but unfortunately the consideration and need for an efficient, intelligent routing mechanism was not taken on board. 1.3. Motivation for Current Work • Routing is an important research area in wireless communication networks and particularly needs more research interest due to emerging technologies such as a wireless sensor network, network on chip and so on • The wireless sensor network brought new opportunities and challenges, because of its non-infrastructure-based network, and can be deployed in a large territory having harsh environmental conditions, where sensory devices can be left unattended. We can also study environment-related events in real time with more precision and accuracy • The WSNs-based network is further evolving towards a multimedia-based network which involves heavy traffic, such as live video monitoring of a remote event and so on. Therefore, the WSN is facing significant new challenges such as drop packet, routing overhead, packet delay, and so forth • number of routing algorithms were proposed but there is an urgent need for a comparative study on these protocols which will be used as a guide tool for researcher and developer in the routing domain. 1.4. Research Questions The research is focused on the comparison between some routing protocols. After some search and studies the choice of protocols was narrowed down to two: Rumour and OSR protocols. The research question can be outlined by one main question and further clarified by four sub-questions. The main question for this research is the following: Q. Which of the two routing protocols: rumour protocol or OSR protocol, performs better under different circumstances?
  17. 17. Comparative Performance Study of Routing Protocols in Wireless Sensor Network 4 The main research question is further defined as, Q1. Which protocol performs better in small, medium, and large network topology? Figure 1.2. (a) Represent small topology, (b) represent medium topology, (c) represent large topology Q2. Which protocol performs better with a different sized deployment area? The node deployment area variants are explained with the help of the following two scenarios, where the geographical areas are different but the number of nodes remains the same. (a) (b) (c)
  18. 18. Comparative Performance Study of Routing Protocols in Wireless Sensor Network 5 Figure 1.3. (a) represents a dense network in a smaller area, while figure (b) represents a sparse network of the same size but in a larger area Q3. Which protocol performs better at different simulation times? The different variant of simulation times, such as 20, 60, and 100 seconds and so on Figure 1.4. Bar chart representation of simulation time (a) (b)
  19. 19. Comparative Performance Study of Routing Protocols in Wireless Sensor Network 6 Q4. Which protocol suffers more from interference? The interference between nodes A, C and B is illustrated as, Figure 1.5. Represents interference and communication range Moreover, the drop packet ratio will be used as a network performance evaluation metric for the aforesaid scenarios. 1.5. Research Methodology Initially, we start our research by investigating the wire network routing protocol in detail which is detailed in Chapter 2. But later on we stick to wireless network routing protocols because it is an area which is rapidly expanding due to their low cost, high mobility, scalability, easy deployment and so forth. Furthermore, our work consists of two parts. First, we design some proposed network scenarios and stimulate these by using the Scalable Ad-Hoc Network Simulator (ShoX) for the OSR routing algorithm and observe the performance and behaviour of OSR alone. Second, we apply the same network model to rumour routing algorithm using the ShoX simulator and judge the performance and behaviour of rumour alone. Furthermore, with respect to the evaluation comparison of OSR and rumour this is based on a metric such as the dropped packet ratio. ShoX simulator is used for the evolution and comparison of proposed protocols. 1.6. Aims and Objectives The main aim of this thesis is to research the problem of routing in wireless communication networks particularly wireless sensor networks, and the constraints involved with routing such as packet drop, for example.
  20. 20. Comparative Performance Study of Routing Protocols in Wireless Sensor Network 7 Our second aim is to perform a detailed study of routing protocols which are either deployed or proposed for WSNs. Third, a comparative study and analysis of routing protocols can be done by means of network simulator. Network performance can be measured against metric like the dropped packet ratio using ShoX simulator. Furthermore, we also aim to provide a precise guideline tool to the developer and researcher with regard to a selection of efficient routing protocols in the future. 1.7. Assumption Our assumption is based on routing protocols and their use in wireless sensor network application, which is listed as, • We further assume that our sensor network is homogenous by nature, where all nodes are of equal size • WSNs nodes assume that they know their local information, and are aware of their close neighbours for the purpose of packet forwarding. • Wireless sensor routing protocols assume that they know the destination address in advance • WSNs nodes can be mobile and stationary depending on the sensor application scenario. • WSN motes for sensor application can be placed an unattended environment and we also assume that these nodes have the features of being self-organising and fault-tolerant. • WSN nodes are deployed in an outdoor plain environment and environmental and atmospheric conditions are assumed at a normal level. • WSN nodes transceivers use single channel and wireless antenna, are Omni-directional and propagate isotropic signals in all direction • We also assume that mobile nodes choose their speed randomly • We further assume that the collision model we use is CSMA, 802.11g
  21. 21. Comparative Performance Study of Routing Protocols in Wireless Sensor Network 8 1.8. Thesis Contribution The core contributions of this thesis are as follows: First, the thesis provides a detailed study of routing protocols which includes wireless routing protocols and their architecture, design challenges, and other constraints. Second, a comparative study of routing algorithms wireless sensor network can be presented for the selected list of protocols in the WSN routing domain. Third, an extensive number of simulation experiments and analysis can be performed using ShoX simulation. Fourth, the thesis would be a guideline tool for the selection of an efficient routing protocol and would alleviate the work of the developer and researcher in the routing domain in the near future. 1.9. Related Work The routing has a significant function in computer networks both in terms of resource management, traffic management and routing. There are a number of routing strategies which are used such as the shortest path algorithm, optimal routing and so forth. The network‟s performance level depends on the number of routing factors such as throughput, packet overhead, delay, congestion, and so on. [AX5] Routing has been an interesting subject for last twenty years or more and significant material is available on the subject. Routing has experienced different types of loops such as forwarding loop, information loop and trace-rout loop and many of the routing algorithms have a pre-avoiding loops mechanism. [AX6] The wireless senor network consists of tiny sensory nodes and these have the capability to maintain the network topology dynamically. The sensory nodes can be mobile but this depends on their application. Routing in a wireless sensor network is challenging because it does not involve a proper infrastructure. Energy, hardware and software resources are limited which makes routing difficult. The network performance can be measured by a number of factors such as throughput, network delay and so on. A number of routing protocols was proposed for the wireless sensor network such as AODV, OLSR, DYMO and many more. [AX7]
  22. 22. Comparative Performance Study of Routing Protocols in Wireless Sensor Network 9 1.11. Organization of the Thesis Our work is broadly planned as follows the thesis consists of six chapters. Chapter 1 presents the background of the thesis and problem definition. Chapter 2 presents the IP- datagram routing protocols in detail. Chapter 3 presents routing protocols in a wireless sensor network. Chapter 4 discusses design and simulation. Chapter 5 presents the simulation results and analysis and finally Chapter 6 presents the conclusion of the whole thesis, future work and bibliography. Summary In this chapter we introduced our project and the main statements of our research question and an overview to wireless sensor network. In the next chapter we will discuss IP-datagram protocols in details.
  23. 23. Comparative Performance Study of Routing Protocols in Wireless Sensor Network 10 Chapter 2 Routing Protocols in IP-Datagram Networks 2.1. Introduction This chapter presents a detailed study of routing protocols in the context of a best effort IP network. 2.2. Routing Routing is the product of routing protocols and routing algorithms. The routing protocol gives the overview of the topology of the entire network while the routing algorithm adds the power of intelligence to how one computes the path between multiple network nodes. [swapnil] Firstly, we will perform a detailed study of routing protocols. In the literature there is an abundance of material available on routing and it is an extensive area of study in itself. In data communication routing is the core feature of guiding and directing in large networks. Furthermore, routing provides an optimal path according to the metrics mentioned. Routing is broadly divided into two main classes: adaptive routing and non-adaptive routing. In static routing a route is not maintained automatically and needs to be updated manually. In a situation where the algorithm fails to update, the only way to recover it is to restart (?) the algorithm manually in order that it can accommodate itself within the specified network link requirements. In addition, there are more routing classes such as delta routing, multi-path routing and hierarchal routing and so on. 2.3. Properties of Routing Protocols There are a number of properties which routing protocols possess and they have a wide impact on today‟s inter-connection networks. The author discusses this under the following headings:  Connectivity: It is the responsibility to assign a route for a packet coming from a source node to a destination node.
  24. 24. Comparative Performance Study of Routing Protocols in Wireless Sensor Network 11  Adaptivity: The property guarantees that there should be an alternative path for each and every packet in case of link or network device failure.  Fault Tolerance: The property sates that the fault tolerance can be attained by applying a storing-and–forwarding technique to some nodes in two or more phases, while it can also be accomplished through adaptivity but it is not always applicable and true.  Deadlock or live-lock freedom: The property states that there should be no blockade and superfluous traffic in the network. 2.4. Classification of Routing Protocols A „routing algorithm‟ can be defined as a methodology through which a node makes a decision about its neighbouring route for the purpose of sending a packet to an expected destination. A Routing Table stores the local link information and is updated from time to time. Ignasi Paredes Oliva defines the routing as “Driving packets from source node to destination node in a network”. Routing algorithms play a pivotal role in today‟s computer networks. And also with the exponential increase in computer networks and distributed systems and other web applications it is obvious that the network traffic management and routing are the core issues. [BX5] The central job of the routing algorithm is to generate a path for the network packets. There are a number of routing algorithms mentioned in the literature, but our study will focus on the routing algorithms which are of particular use for computer inter-connection networks. We also focus on those routing algorithms which are important for future studies in relation to modern computer inter-connection networks. Jose, Sudhakar, Lionel state that routing algorithms can be classified in many ways; broadly classify the routing algorithms according to the number of destination packets which need to be delivered. A packet can be sent uni-cast or multi-cast.
  25. 25. Comparative Performance Study of Routing Protocols in Wireless Sensor Network 12 Figure 2.1. Classsfication of routing proctols startegies in IP-Datagram networks In data communication networks a routing algorithm can be classified as uni-cast, broadcast, multi-cast and any-cast. Alternatively, Sharam classifies routing algorithms as flooding, static and dynamic routing. 1. Uni-cast Routing In a uni-cast routing algorithm a packet is destined only for one specific destination from a source. 2. Broadcast Routing In broadcasting a message is broadcast to all available links in the network, the reason being that the medium of communication is shared between all the network nodes. The N point-to-point algorithm is a broadcast algorithm and it sends packets to every destination. The limitation is that it wastage of bandwidth and have the pre-knowledge of all destinations.
  26. 26. Comparative Performance Study of Routing Protocols in Wireless Sensor Network 13 The next broadcast algorithm is „flooding‟. The packet is sent to every host in the network. There is a strong likelihood that some hosts will receive dual packets and because of this mechanism the duplication arises in the network but the algorithm can detect the duplication of packets. 3. Multi-cast Routing The main goal in the multi-cast routing is to send packets to a designated number of network hosts but not all. 4. Any-cast Routing The main goal in the any-cast routing is to send packets to a particular single designated computer in the network. According to Mischa Schwarz the routing algorithm is divided into four classes, Firstly, the routing path selection function and routing table creation can be performed in a centralised and decentralised or distributed approach. Secondly, the routing mechanism can follow an adaptive approach. n this approach the routing path information is updated when changes occur in the network topology. The routing mechanism adapts itself according to the topological, traffic changes taking place in the network. It dynamically responds to all sorts of traffic conditions happening in the network. Thirdly, a class of routing algorithm uses cost as a metric to link nodes for the purpose of routing path selection. In regard to cost calculation there are a number of parameters usually used such as network link bandwidth, link length, speed, expected delay, latency, level of security and so on. The cost can be a combination of multiple parameters such as link bandwidth and delay. Fourthly, it is one of the best known and popular types of routing algorithms studied in the literature which works on the basis of performance and it is called „least-cost path algorithm‟ or „shortest-path algorithm‟. In the shortest path algorithmic approach the least cost path can be defined as the linear sum of the hops between source and destination. Furthermore, it also involves adaptive routing which includes full adaptive and partial adaptive algorithms because in these algorithms the link cost can be dynamically changed due to delay, error condition or speed and so on. The shortest path algorithmic mechanism is widely used in the routing of datagram communication networks.
  27. 27. Comparative Performance Study of Routing Protocols in Wireless Sensor Network 14 In performance base routing algorithms the next category involves the use of a number of techniques to mitigate the time delay, network utilization and also use an estimated metric between source and destination. It further evaluates the performance between source and destination by using multiple paths. 2.5. Goals of Routing Protocols [Tanenbaum], suggested that the following properties in relation to routing algorithms need to be taken into consideration in order to reach a solution to the routing problem:,  Correctness: The property states that an algorithm should be able to accommodate itself within topological variation and network problematic conditions. The algorithm should also be able to find the optimal path in any circumstances for the network.  Simplicity: The property states that an algorithm needs to be simple, efficient and easy to implement.  Robustness: It is crucial that the network should have the capability to work in a situation like node failure, path congestion, like failure and so forth.  Stability: The property states that after specified runs of the time-frame window an algorithm needs to be in a stable position.  Fairness: The property states that for the delivery of a packet, the packet delivery time schedule must be followed.  Optimality: The property states that an optimal path should be found from a source to destination. The optimal path depends on the network parameter. It is not compulsory that an optimal must always be the shortest path, for instance a longest path can be considered an optimal path because of less buffer delay for example.  Scalability: The property states that an algorithm needs to be capable of improving and giving its best performance as the network resources expand and traffic grows. In the commuter network literature the routing algorithm can also be classified into non- adaptive routing and distributive adaptive routing. We further categorise the routing algorithm into two main groups, which are stated as, There are a number of routing algorithms which exist in the network routing domain but our research focuses on the set of conventional routing algorithms and an advance self-adjusting Q- learning routing algorithm and routing algorithm.
  28. 28. Comparative Performance Study of Routing Protocols in Wireless Sensor Network 15 2.6. Conventional Routing Protocols 2.6.1. Adaptive Routing Protocols In today‟s global computer networks two routing algorithms are used, the shortest path and distance vector. These algorithms provide the foundation for many routing protocols which are deployed on the internet today. The routing information protocol (RIP) and interior gateway routing protocol (IGRP) are built upon the distance vector algorithm‟s updated version. OSPF are built on the basis of the shortest path algorithm while EIGRP is the basis of the on dual routing algorithm. BGP is also based on path vector algorithm which is an improved version of distance vector algorithm. 2.6.2. Open Shortest Path First (OSPF) The Open shortest path first (OSPF) is a link state routing protocol. The protocol was developed on the basis of Dijikstra shortest path first algorithm. The link state routing strategy is also used in the IS-IS routing protocol. In the link-state base routing each network node develops its own map of network topology. OSPF is an intra-domain routing protocol and operates inside a single autonomous system and is the most dominant interior gateway protocol and is largely used in large organizational networks. OSPF is compatible with the variable link subnet mask VLSM and CIDR IP-subnet addressing mechanism. The core concept in OSPF is that every network node has knowledge of the whole network topology.  OSPF Areas OSPF divides the network routing domain into several areas and the initial area is called Area 0. A backbone is required when a packet is forwarded into another routing area.  OSPF Network Classes The OSPF routing protocol divides the network into a number of classes such as non- broadcast multi-access, multi-access, point to point and so on.  OSPF Timers OSPF uses a number of timers, for instance if links are down for less than 30 seconds and then recovered again so in this case it is not noticed. When a link goes down for half or less
  29. 29. Comparative Performance Study of Routing Protocols in Wireless Sensor Network 16 than half an hour, then in this case OSPF floods LSA for both events including both the up and down status of a link. The advantages and disadvantages are described as follows: 1. Advantages • Performs fast convergence. • Provides loop free routing paths. • It is scalable and does not restrict network to hop counts limits. • Updates occur every 30 seconds and there are no other updates. • OSPF sends hello packets for the purpose of checking the status of the link and does not send a full routing table. 2. Drawbacks • OSPF is very expensive in terms of memory and computational power. Shortest Path Routing Algorithm There are a number of algorithms in the network literature for finding the shortest path algorithm, but our study will only focus on the Dijiksta algorithm in this shortest path algorithm domain. Let s is source and u is the destination, and the shortest path from s to u can be described as, Figure 2.2: shortest path finding mechanism 1. Dijikstara Algorithm The Dijaskrta algorithm in the literature is also termed as the shortest path or Greedy Algorithm. It is the most accepted algorithm because of its enormous use in today‟s internet and because of its simplicity and ease of use. In terms of its route computation it uses cost metric. The cost metric differs as it can be computed by a number of distinct metrics such as delay, bandwidth, data rate and financial cost and so forth. The route optimization is the
  30. 30. Comparative Performance Study of Routing Protocols in Wireless Sensor Network 17 core functionality of the Dijikstar algorithm. It optimises the routing to an optimal path by performing computation at each node of network. [Firat] Furthermore, a known limitation of the Dijikstara algorithm is that it selects an optimal path irrespective of the future network needs such as congestion on a path or link failure and it is obvious that current global networks are dynamic and distributive in nature. For example, if there is a queue of packets at of the middle network node buffer, and as a result the packets are delayed for a particular destination, in this situation it would be better to go for an alternative path but there is no guarantee that an alternative path would be the shortest and as a result it can achieve the shortest time delivery but not the shortest path. [F. Tekiner et al].  Graphical Representation of Dijikstra Algorithm The Dijikstra algorithm can be graphically represented as; in the networks each node computes its routes to other connected nodes. The scenario is represented with a diagram where each node is considered as an edge and link as a vertex, a vertex connecting two edges. In relation to the cost of the vertices it is taken as non-negative. Let us consider that V is the set of all edges in the digraph, the array of the cost metrics of the vertices is c[s, w], and the array to least cost path for any node is D[w] which is to be computed. In the first step, the value for the shortest path to any edges in the digraph can be assumed as infinity i.e. D[w] =∞. Furthermore, let us consider that there are no edges in the digraph and every edge s starts its computation for the shortest path cost D[w] to connect to other neighbour w ∈ (V-s), with a minimal c[s, w] value. Next, it computes the routes for the other edges v ϵ (V-s-w), and is a neighbour of w, consequently the resultant equation becomes: D[v]= min(D[v], D[w]+c[w, v]) Where c[w, v] is the vertices cost metric connected to w, the relaxing nodes process is continued until all the digraph edges are visited. On completion of the process all the edges have the shortest path to each other node in the network. Furthermore, to make sure not to recalculate the path for visited nodes, for this purpose these edges are marked to mitigate the chance of recalculation of the path. In case there is an e number and n number of vertices in the digraph the computational complexity for the Dijikstra shortest path algorithm is:
  31. 31. Comparative Performance Study of Routing Protocols in Wireless Sensor Network 18 O(e log N), and N is the number of Nodes. [Firat][F. Tekiner et al].  Dijikstra Algorithm Pseudo-code Merin stated the Pseudo-code for Dijikstra algorithm is: which are quoted as “ Procedure Dijsktra (V: set of vertices 1... n {Vertex 1 is the source} Adj[1…n] of adjacency lists; EdgeCost(u, w): edge – cost functions;) Var: sDist[1…n] of path costs from source (vertex 1); {sDist[j] will be equal to the length of the shortest path to j} Begin: Initialize {Create a virtual set Frontier to store i where sDist[i] is already fully solved} Create empty Priority Queue New Frontier; sDist[1]←0; {The distance to the source is zero} forall vertices w in V – {1} do {no edges have been explored yet} sDist[w]←∞ end for; Fill New Frontier with vertices w in V organized by priorities sDist[w]; End Initialize; repeat v←DeleteMin{New Frontier}; {v is the new closest; sDist[v] is already correct} for all of the neighbors w in Adj[v] do if sDist[w]>sDist[v] +EdgeCost(v,w) then sDist[w]←sDist[v] +EdgeCost(v,w) update w in New Frontier {with new priority sDist[w]} endif (end of?) endfor (one word or two?) until New Frontier is empty”. [Merin].
  32. 32. Comparative Performance Study of Routing Protocols in Wireless Sensor Network 19 Related Algorithm 1. A* Algorithm A star is an algorithm from a graph tree class and it computes the path from a source node to a destination node and for the computation of a path it uses a heuristics estimate h(x). It computes the best path to a given node on the basis of these estimates. It visits every node to find the best path to fulfil the heurists estimate criteria. 2. Prime Algorithm A prime algorithm is also termed a DJP algorithm. I, it computes the minimum shortest path in a connected weighted graph. It works on the concept of searching for subset edges that to make a tree in order to minimize total weighted edges in the tree. [Merin] 2.7. Enhanced Interior Gateway Routing Protocol (EIGRP) EIGRP is an interior gateway routing protocol and was developed by Cisco. The EIGRP protocol is built on the basis of a Diffusion Update Algorithm (DUAL). EIGRP does optimization in terms of topological changes, computational power and memory consumption.  EIGRP Tables Neighbours Table: In this table it stores the routing information associated with their close neighbours interface.  Advantages i. Provides a fast convergence mechanism ii. Guaranteed loop-free routing path  Diffusion Update Algorithm (DUAL) J.J.Garcia Luna Aceves developed the DUAL algorithm at the Stanford Research Institute. The DUAL algorithm has the capability to respond dynamically to topological changes and automatically adjust the routing table entries on each individual router. The DUAL algorithm performs diffusion computation and guarantee loop free routing.
  33. 33. Comparative Performance Study of Routing Protocols in Wireless Sensor Network 20 2.7.1. Link-state-based Routing The link state routing algorithm is the replacement of the distance vector routing algorithm in the early 1970‟s by ARPANET. Distance vector routing has suffered from two major problems which are delays and count-to-infinity problems. Today, a number of variants of the link state routing algorithm are widely deployed in internetworks. Tenanbuam describes central points and the philosophy of the link state algorithm as, First, LS algorithms discover the location of the neighbour node and like to learn their address. Second, calculate the cost or delay to each of its neighbours. Third, to build a packet and inform the other neighbours what it has learned. Fourth, distribute the packet to all other neighbour routers. Fifth, calculate the shortest path to each neighbour. ink state routing algorithm works on a mechanism, a router or node advertising its local links to its neighbour unlike the distance vector algorithm‟s incremental distance computation. Furthermore, the link state algorithm uses a topological database. It is also termed as a routing table. The topological database is the core source for network mapping; it further forms a graph of the interconnected networks. In the graph each node and its interconnected link is represented in the network. In the network each node retains and tallies its routing table entries with the neighbour router, and attached links.[Firat] It uses Dijikstra Shortest path algorithm for the least cost path computation, and looks after the routing table or topological database. In regards to LSA exchanges it uses a static algorithm called flooding; it sends the incoming packets to each outgoing link except its own link. The known disadvantage of the conventional flooding algorithm is the duplication of packets; an alternative technique for more practical flooding is also used and is called „selective flooding‟. [Tenanbuam].  Link-state Routing Protocols Pseudo-code Firtat et al (No reference?) describes the pseudo-code for the link state algorithm which is quoted as, Set Dij to infinity for all j not equal to i
  34. 34. Comparative Performance Study of Routing Protocols in Wireless Sensor Network 21 Loop N Find the node K not in N for which Dik is smallest Add K to N For each j not in N If Dik + Dkj < Dij then Set Dij to Dik+ Dkj Set next_hop(i,j) to next_hop(i,k) concattensted with link from k to j 2.8. Border Gateway Protocol (BGP) or Path Vector- based Routing The Path vector routing algorithm was the replacement for the previous DARPANET distance vector algorithm. The core reasons for the development of the path vector algorithm were to use the vector to eradicate the problem of the loop unlike the distance vector algorithm. It belongs to a class of inter-domain routing algorithms, in relation to routing p; the border gateway protocol (BGP) is built on the base over path vector routing algorithm. In BGP the best-path algorithm always received a multiple number of paths to the same destination, then further the best-path algorithm making decision on which path must be installed in the routing table.  Path vector algorithm mechanics Firstly, of all BGP choose the valid path as is the best path and then further compare it with the path that comes first in the list and continue until the valid path is finished. Next it follows the rules stated for the election of best path, which are the following: Rule 1: Pick the path with the highest weight Rule 2: Choose the path with the highest local preference LOCAL_PREF Rule 3: Preference will be given to the path that was locally originated via a network Rule 4: Preference would be given to the path which has the shortest autonomous path AS_PATH Rule 5: Preference would be given to the shortest path which has the lowest origin type Rule 6: Preference would be given to the path which has the lowest multi-exit discriminator (MED)
  35. 35. Comparative Performance Study of Routing Protocols in Wireless Sensor Network 22 Rule 7: Preference would be given to eBGP over iBGP paths Rule 8: Preference would be given to the path which has the lowest BGP metric to the subsequent BGP hop. Rule 9: In case of multi-path make certain that if is there is any need for installation in the IP routing table for multiple paths. Rule 10: In a case where if both are external paths then preference would be given to the path which came first in the order. Rule 11: Preference will be given to the path which comes from the BGP router and has the lowest router ID. Rule 12: In the case where the router ID is similar for multi-path, then preference will be given to the path which has a minimum cluster list length. Rule 13: Preference would be given to the path which has a lowest neighbour address. BGP beast Path selection routing algorithm flow chart representation:  Limitation of Path Vector Routing Problem Analysis and measurement showed that a packet forwarding loop exists in the inter-domain routing. But the exact reason behind the looping problem has not yet been discovered because of the size and convolution of the internet. Paxion performed a number of end-to- end trace-route experiments in 1994 and 1995 and found that a transient loops exists in the internet. 2.9. Advance Routing Approaches 2.9.1. Self-Adjusting Routing Protocols The core disadvantage of a conventional routing algorithm is that of human intervention or algorithm designer supervision in the case of some unusual event or occurrence in the operation of an algorithm such as failure or link congestion and so forth and consequently, these algorithms are not able to adjust dynamically. Moreover, the conventional routing algorithm has a lack of intelligence and it needs human help and supervision for adjustment in problematic conditions and network topological changes. The problems of routing have been studied in the research domain for a long time. The routing problem comes within the scope of the NP-complete problem. The problem is very
  36. 36. Comparative Performance Study of Routing Protocols in Wireless Sensor Network 23 similar to sale-man route optimization problem. The need for an intelligence routing algorithm to adapt and adjust changes dynamically is introduced. With this approach not only does it boost the performance presentation of an algorithm it also improves the adaptability for associated changes in the network. With an advance learning routing approach the algorithm can automatically adopt and maintain its performance for an event which is not described by the algorithm designer. This routing learning base algorithm is more appropriate for a communication network where topological variances are unforeseen and unpredictable. Nevertheless, the introduction of this sort of algorithm involves a couple of constraints such as, more time is needed for learning and also in terms of memory storage. Reinforcement Learning Routing Protocols Reinforcement learning (RL) is a form of learning in which we interact with an environment by carrying out some action and as a result learn from that action. In this regard it is the opposite of the traditional teaching method. Furthermore, RL is a form of learning where an agent undertakes trial and error and trail interaction in a dynamic environment. Although, RL is an old field but it has attracted much attention in the last decade from machine learning and the artificial intelligence domain. The central concept of RL is the methodology of an agent reward and punishment approach. There is no pre-information stored for an agent, but it learns an input from interaction with the environment and after processing the input data it returns the output to the environment. As a result the state of the environment is updated. There is a possibility that an agent may take further action, but this is totally dependent upon the input. The aforesaid methodology is very useful in a situation where there is no supervised learning for an agent. The RL mechanism would not be called an algorithm or protocol but in reality this is a very powerful initiative for the solution of some particular class of problems. The RL methodology can be further divided into two main streams of mechanisms i.e. a genetic algorithm and genetic programming, and statistical techniques and dynamic programming. [David Kelley]. In addition, a reinforcement learning base routing algorithm does not require the pre- knowledge of the network topology and network traffic pattern and is even capable of working out the best routing policy without the need for any centralised routing control system. [Michael Littman et al].
  37. 37. Comparative Performance Study of Routing Protocols in Wireless Sensor Network 24 However, the approach of reinforcement learning can be very highly-priced in terms of space and storage but there are different variants of reinforcement learning algorithms available. The one that we are selecting is the Q-learning algorithm and, in terms of space, it requires a little bit more space for the representation of a full routing policy. [Michael Littman et al]. Q- Routing Protocols The Q-learning is a mechanism of solving a problem on the basis of the reinforcement learning philosophy; it is used for the solution of the problem which involves a poly- hierarchy of decisions. Q-learning can also be called an incremental edition of dynamic programming for the aforesaid problem. In relation to an adaptive routing problem, the Q-learning mechanism working in a model base make-up and the routing organizer does not have pre-knowledge of the topology in this type of environment. Meanwhile the routing organiser has the priority to minimise the average packet delivery timeframe and particularly in the case of a dynamic environment where changes always occur it is extremely difficult to work out an optimal routing policy. In Q-routing each individual in the network is a configured Q-routing algorithm mechanism.  Q-Routing Protocols Mechanics The core steps of algorithm are quoted from David Kelly‟s research paper, and are as follows: Step 1: Initialization with 0‟s or random values Q(s,a) for all s S and for all a A(s) Step 2: Reiterate for each occurrence Step 3: Initialise Step 4: Reiterate for each step occurrence Step 5: Choose a from s using a policy derived from Q Step 6: Take action a, observe resultant state s‟ and the reward r Step 7: Q(s,a) Q(s,a) + [r + maxa‟Q(s‟,a‟)- Q(s,a)] Step 8: s s‟; Until s is terminal.
  38. 38. Comparative Performance Study of Routing Protocols in Wireless Sensor Network 25 Ant Colony Optimization (ACO) Routing Approach Three are numerous insects living on the surface of the earth and one of them is the ant family. Ant species‟ categories are numbered at 9000. These ants have unique intelligence and smart characteristics which enable them to live in large groups in vast numbers, and they can literally be found everywhere across the globe. An Ant Colony Optimization Algorithm (ACO) is an algorithmic technique through which we can work out the reduced path in the graphs. In the recent past, the ant‟s model of organization and its associated interaction with the environment were researched and computer scientist and engineers. The focus of attention was the ant‟s unique features, such as their distributed control mechanism, fault tolerance approach, environment base interactive communication, individual level automaticity, and self-organization, strategies for collectivism and cooperation and the emergence complex behaviours, and a set of unique skills at each individual ant level. The aforesaid features of the ant societies make them an inspiration for a new multi-agent system and a way forward for the developments of new algorithms. [Gianni Di Caro] Ant-Net Adaptive Routing Protocol The protocol is useful for situation where there are simultaneous changes occurring in the network topology such as in the internet. The Ant-Net is an adaptive routing algorithm and is based on the ant colony optimization techniques. The Ant-Net algorithm uses the concept of stigmergy. While stigmergy is a communication mechanism where communication is taking place between the individuals and the local environment it is also being modified during the communication timeframe. To find the shortest path real ants make their routing policy and decisions on the basis of local information which in this case is the pheromone path dropped by the ants which has already passed through the same path.  Ant Net Protocol Mechanics The Ant-Net uses two same groups of mobile artificial agents, which are forward and backward. Step 1: A forward agent is issued at regular intervals from source node S and a destination node D is picked at arbitrary way, and the destination node fully meets the quality requirements of the traffic pattern.
  39. 39. Comparative Performance Study of Routing Protocols in Wireless Sensor Network 26 Step 2: The forward and select function-making decisions on the basis of information available in the routing table, and the selection of a node is based on the associated probability, decency, and in the case where if all neighbours are visited then a random uniform approach is followed for the selection of the next hop neighbour and is irrespective of the local queue. Step 3: In a situation where a link is not accessible, then forward waits in a local queue and is served on the basis of FIFO. [BX16] Summary: In this chapter we discussed both conventional and advance routing protocols in terms of IP- datagram routing protocols. In next chapter we will discuss routing protocols in terms of wireless Ad-hoc and sensor network in details.
  40. 40. Comparative Performance Study of Routing Protocols in Wireless Sensor Network 27 Chapter 3 Routing Protocols in Wireless Ad-Hoc and Sensor Network 3.1. Introduction The chapter presents wireless ad-hoc and sensor routing protocols in detail. Study involves both conventional and advance routing algorithm. Our study will focus on routing mechanisms and different strategies. 3.2. Classification of Wireless Network Data communication networks are rapidly evolving. In the past decade the wireless network has begun to reach its peak point because of its consistent usage in several applications, and products. Peter et al further classify the evolving network into four categories which are, peer-to-peer, mobile Ad-hoc and wireless sensor network.  Wireless Ad Hoc Network The ad-hoc networks fulfil both definitions, because they can be prepared from resources which are currently available and are structured according to the need of each specific user. Ad-hoc networks are also called „mesh networks‟ for the reason that the structure of the network is organised in a manner designed to discover a pathway for a data to be routed from source to expected destination.  Mobile Ad-Hoc Networks (MANET) MANET can be considered a type of Ad Hoc wireless network. This MANET type of network does self-configuration of mobile routers and the related hosts with their connected links. As a result, it makes an arbitrary topology, and the routers are fully independent at times and accommodate themselves in an arbitrary environment where the wireless network topology is rapidly and unpredictably changing.  Wireless Sensor Network (WSN) WSN is a collection of small sensor nodes which are dispersed in a large geographical area for the purpose of monitoring and recording real world physical events and the nodes send collected data consistently to their central base station. Nowadays, this is widely used for
  41. 41. Comparative Performance Study of Routing Protocols in Wireless Sensor Network 28 measuring environmental conditions such as temperature, humidity, pressure, air speed and many more.  Mobile Wireless Sensor Network It is a version of the wireless sensor network and the nodes in this sort of network are mobile.  Ad-Hoc Wireless Sensor Network It is a version of wireless sensor network in which the nodes can organise themselves automatically when any change occurs in the topology.  Peer-to-Peer Network A type of computer network having no consideration of clients and server and the same equal nodes can function both as server and client. [CX2]. The above listed networks types and their interconnection with other networks is diagrammatically represented below: Figure 3.1. Block diagram of wireless network classification
  42. 42. Comparative Performance Study of Routing Protocols in Wireless Sensor Network 29 3.3. Conventional Routing Algorithm in Ad-Hoc Network Wireless Routing protocols can be classified in a number of ways, such as, node centric, geocentric, data-centric, and QoS routing protocols. They can also be classified as reactive or proactive. [CX10] Wireless ad-hoc network protocols consist of two main classes which are „wireless sensor‟ and „Mobile Ad-Hoc Network‟ (MANET). In wireless networking the routing can be node- centric. The argument is that the destination is investigated by calculating the number of nodes. It is also important to note that communication in a wireless sensor network is not always node-centric. The wireless sensor network is found to be more geo-centric or data- centric. [CX10] Furthermore, we are investigating distinct routing protocols which are related to wireless networks as a whole. Below is a chart representation of traditional ad-hoc and WSNs routing protocols. Figure 3.2. Ad-hoc routing protocols classification chart
  43. 43. Comparative Performance Study of Routing Protocols in Wireless Sensor Network 30 3.3.1. Optimal Spine Routing (OSR) Algorithm Introduction The spine based routing algorithm was developed to minimise the overheads involved with the shortest path routing algorithm and non-optimal routes computation in an on-demand routing algorithm. OSR is a spine-based routing algorithm and it stores global routing information in spinal nodes and computes the shortest path between any two nodes. When a link comes alive an add wave is generated while when a link comes off, as a result a delete wave is propagated. The add wave effect is propagated but involves a slight delay while a delete wave is propagated without delay. When a delete wave is in process and at the same time an add wave is generated automatically so they cancel each other out and their effect is not propagated. Consequently, the joint effect of add and delete waves ensures only stable information is passed to spinal nodes. The OSR can be classified as the minimum weight path routing algorithm. [CX24] OSR Detail To find an optimal path OSR use a spine (virtual backbone) and the routes are kept up-to- date using query requests to sources. However, due to high overhead OSR is not a practical solution to the problem of routing. The topology is represented using undirected graphs G= (V,E), in conjunction with m edges and n nodes where V represents hosts in an ad-hoc network and E represents the wireless radio transmission range between the hosts. When changes occur in the topology, the changes are associated with either V or E. Topological changes occur usually when a node is inserted, deleted, or when an edge is inserted or deleted. A node can move from one part of G to another part of G. OSR collects global topological information on the spine graph G and the information is passed to all spine nodes which further trigger the computation of the shortest path which is based on the local knowledge of the spine graph G. Typically, the path is computed by means of spine nodes which do not go across the spine. In OSR the spine is constructed using an approximation algorithm called a minimum connection domination set (MCDS), while MCDS findings path comes under NP-Complete problem. The MCDS algorithm we are using for spine construction is distributive in nature. There is a possibility that MCDS
  44. 44. Comparative Performance Study of Routing Protocols in Wireless Sensor Network 31 nodes can be unknowingly the interior nodes of a maximum leaf spanning tree. Spine can be considered as the interior nodes of the tree.[CX24] For instance, OSR single node movements using MCDS are calculates as, Figure 3.3. OSR single node movements The figure shows that the MCDS algorithm computes that nodes 3 and 6 are in the minimal domination set (MDS) and a further MST connects to node 5 to sub-graph C. Further, we assume that nodes know their id and their neighbours id, connect edges and the degree involves.[CX24] Generic key phases involves in any spine base routing algorithm Phase 1-Spine Construction The whole network consists of a single spine which is computed on the basis of global topological latest information or maybe partial information. Phase 2 -Aggregation of states into spine nodes The aggregation consists of two steps, first non-spine nodes aggregated to their relevant denominators and secondly, spine nodes aggregated with other spine nodes in the spine.
  45. 45. Comparative Performance Study of Routing Protocols in Wireless Sensor Network 32 Phase 3 -Route Discovery Route discovery can be performed in three ways, first fully localised information, second, use a probe based technique and third a combination of both stated techniques. Phase 4 -State Maintenance Sate maintenance is consist of two steps, first, maintenance can be done by means of even based updates , second, maintenance can be done by means of periodic updates. [CX24] OSR Routing Algorithm Mechanics First calculate the spine C, where C⊆ V. Second, collect information from non-spine nodes and pass it to spine nodes. Third, broadcast the resulting topology to all spine nodes. Fourth, compute the shortest path by using global topology information received in step three. Fifth, all the sources receive latest routes updates. Sixth, an event-related update is broadcast for the purpose of performing maintenance in a situation like node insertion or deletion. Seventh, periodic updates are broadcast to make sure that the topology has the latest information available.[CX24] Core Issues with Spine-Based Routing • Spine maintenance (at global level) The spine maintenance issue determines how the spine is constructed and how the spine can be maintained during spine nodes movements or during mobility • State level maintenance (at node level) State level maintenance determines what information is collected form the whole domain and what information is broadcast to spine nodes. • Route Discovery Route discovery determines that the discovery of routes involves only local information or that/if it is probe-based. [CX 24]
  46. 46. Comparative Performance Study of Routing Protocols in Wireless Sensor Network 33 Uses of spine 1. To track changes in the topology and compute the routes 2. To offer short-term back up to fault-tolerant routes 3. To offer multi-cast backbone for multi-cast routes Spine- Based Routing Algorithm are Classification Figure 3.4. Classification of spinal routing algorithm 3.3.2. Wireless Routing Protocol (WRP) WRP is uni-cast routing protocol for the Mobile Ad-Hoc NETwork (MANET). The WRP protocol belongs to a group of routing table-based protocols. It holds and maintains whole network link information in the routing table. It is a proactive protocol and belongs to a class of path finding algorithm. In relation to nodes existence, the nodes learn about their neighbour by means of acknowledgment receipt and some other messages. In a situation where no messages have been padded so in this scenario the nodes are required to send at least „Hello‟ messages in an episodic manner for the purpose of ensuring network connectivity.
  47. 47. Comparative Performance Study of Routing Protocols in Wireless Sensor Network 34 3.3.3. Global State Routing (GSR) Protocol Global state routing (GSR) is a based on a proactive, steady and topological precise routing mechanism. It works on the mechanics of link state algorithms in which each neighbour passes their routing table update, whenever changes happen in the network topology. Furthermore, each adjacent network nodes episodically send the complete routing table to their closest neighbour. The link state topological table consists of most recent local node connectivity updates and also its contemporary link state up-to-date information about the full complete network topology. In terms of destination table entry, an entry is checked according to sequence number. When a received sequence number is greater than the current the entry is updated in the destination topological table. And for the shortest path algorithm to determine a shortest path for each entry in the routing table and further, it depends upon the topological table information and to perform this task a shortest path algorithm called Dijikstra, is selected. To narrow our research further we would particularly focus on the wireless sensor network in more detail; 3.4. Wireless Sensor Network A wireless senor network is the latest and fastest growing technology and is expected to revolutionise a wide range of applications in terms of its quality and availability in the near future. The technology has arrived because of the huge advancements over the past decades, particularly in the field of embedded microprocessors, MEMS sensor and wireless communication [CX9]. Is a wireless computer network which can be formed in a large span of space , having distributed autonomous devices which consist of sensors so as to monitor the physical environmental condition, meaning pressure, temperature, motion and so forth at a remote location. Furthermore, according to ad-hoc network classification, WSNs can be called infrastructure-less networks. [ K. E. Kannammal et al] A wireless sensor network is a group of network nodes which collaborate with each other in a sophisticated fashion. In WSNs each node has its own sort of „poly sort of memory‟, such as data and flash memories, program; and it also accommodates devices, for instance a microcontroller, CPU or DSP chips. It also consists of an RF transceiver and this typically
  48. 48. Comparative Performance Study of Routing Protocols in Wireless Sensor Network 35 involves a single –Omni-direction. Moreover, nodes in WSNs have their own power source such as batteries and solar cells and they also host a number of sensors and accumulators. Today, a modern wireless sensor network can be expanded to large geographical areas via cheap sensor devices which can sustain themselves with very a low power usage. The networking capability enables these sensor nodes to incorporate, collaborate and coordinate with each other and this is a fundamental shift in the field of networks which differentiates sensor network nodes form other networks. It is expected that in the twenty-first century our lives will be more impacted by the advances in wireless sensor network technology because of the elegant work which has been done particularly in the field of sensing, microelectronics, digital signal processing, analog, and wireless sensor wireless technology by researchers in recent years. The adoption of a different design paradigm followed by wireless senor network makes it different from the conventional network paradigm such as the internet. The wireless sensor network is application specific; hence it is designed and deployed for a particular rationale. [F. Akyildiz] The network architecture of a wireless sensor network is broadly divided into two types of single-hop and multi-hop architecture. 3.4.1. Network Characteristics, Design Objectives It is obvious that due to the non-infrastructure nature of WSNs and their application specification has a huge impact on the network characteristics, design and performance. Network Characteristics WSNs have a different set of characteristics in comparison with conventional wireless communication networks such as MANET, cellular, and so on, and these are listed as, • Dense sensor node deployment In WSNs the nodes are densely deployed and in terms of levels of magnitude, are far higher than those of MANET and others.
  49. 49. Comparative Performance Study of Routing Protocols in Wireless Sensor Network 36 • Battery-powered sensor nodes The WSNs‟ nodes or motes are deployed in a non-friendly environment where there is no possibility for recharging or replacement of battery • Severe energy, computation, and storage constraints In WSNs there is a limited amount of energy, computation and storage available because of the size and capability of sensor motes • Self-configurable The sensor motes deployed in the field are mostly on a random basis and these sensor motes have the capability to configure themselves dynamically whenever connected to a sensor network. • Unreliable Sensor Nodes The WSNs motes are highly vulnerable to error and fault, because of their deployment in a harsh or non-friendly environment • Data Redundancy The sensor motes are deployed in a specific area for a particular sensing task, so at the same time multiple sensor motes are sensing data from the same area or region and as a result there are appointed tolerable levels of redundancy • Application Specific WSNs motes are widely deployed for a particular application and the network design specification is altered with an expected application. • Many-to-one traffic pattern In a typical sensor network application many source nodes transmitting data to a sink node and the resultant data traffic represents a many-to-one traffic pattern.• Frequent Topology Change The sensor network topology is rapidly changing because of number issues such as channel fading, node failure and damage, addition, and energy depletion.
  50. 50. Comparative Performance Study of Routing Protocols in Wireless Sensor Network 37 3.4.2. Network Design Objectives WSNs are conventionally application specific and the design objectives of the network change from an appellation to application and therefore the subsequent objectives need to be chosen for WSNs design, •Small node size WSNs networks nodes are usually deployed in a non-friendly environment and the size minimization can give us advantages, such as node cost reduction, and easy deployment, and less power consumption. • Low node cast It is crucial to keep the cost of the overall network as low as possible and the nodes in WSNs are not reusable because they are deployed in a hostile environment where access to a sensor field is not possible • Low Energy Consumption In WSNs it is important to reduce per node energy consumption for the purpose of extending the life of nodes and the overall sensor network; due to the nature of network deployment it is not easy to recharge or replace the battery • Reliability It is important that the network protocol should be able to present data integrity and error correction methodology, and reliable data transmission on an error-susceptible, and time- altering wireless channels• Self-configurability It is crucial that WSNs can automatically configure themselves in the event of node failure or damage, and receive topological updates that preserve a proper connectivity • Adaptability WSNs are highly susceptible to node failure or in the case of joining and moving would result in topology changes and so the routing protocol should be capable of successfully dealing with the aforementioned situation • Channel utilization It is crucial that the routing protocols should be capable of utilizing the bandwidth in a most cost-effective way because the resources in WSNs are limited so as to achieve better utilization of a channel.
  51. 51. Comparative Performance Study of Routing Protocols in Wireless Sensor Network 38 • Fault Tolerance WSNs are typically installed in a hostile environment in an unattended way and are highly susceptible to error and failure, so it is crucial that sensor nodes should be capable of having auto-configuration, auto-recovery, auto-repairing, auto-testing and auto-calibrating • Security In WSNs it is crucial to have security procedures to secure data from any authorised attacks and ensure the integrity of the data in a node or network • QoS Support In WSNs the quality of the service depends on the application used and each specific application has its own set of QOS requirements such as packet loss and delivery latency so it is crucial that the communication protocol should keep these requirements under consideration for each particular application. 3.4.3. WSNs Network Design Challenges The design of the WSNs‟ routing protocols is a painstaking job due to the nature of the network because of the counted resources and as a result WSNs are faced with a number of constraints, such as energy consumption, CPU, bandwidth, and memory storage. The challenges are as follows, • Limited energy capacity The WSNs‟ mote consists of small battery which has limited energy capacity. In an environment which is unfriendly or hostile battery power sustenance is a serious challenge and gaining access to sensor motes is almost impossible. When a sensor node reaches a specific threshold value it considers the sensor motes faulty. Ultimately these motes have an impact on the overall efficiency of the sensor network. Consequently, it is vital that routing protocol must have intelligence to improve the overall life span and performance of the sensor network. • Sensor location Sensor location management is also a known issue in the designing of routing protocols. Modern routing protocols usually use the global positioning system (GPS) for location learning or alternatively using some other location learning mechanism
  52. 52. Comparative Performance Study of Routing Protocols in Wireless Sensor Network 39 • Limited hardware resources WSNs have limited hardware resources such as computational processing power, memory and energy capacity and due to these resource constraints software development and the designing of routing protocol for WSNs becomes a difficult task • Massive and random node deployment WSNs nodes are typically deployed in a random fashion in large numbers in an unfriendly environment and rely on application; furthermore it also has an impact on the routing protocols‟ performance and overall functionality. The sensor nodes are usually dropped over an enemy territory on a large scale and if the sensor nodes are not operating in a consistent manner then clustering of sensor s nodes is a viable option for the purpose of saving energy and improving the performance of overall WSNs. • Network characteristics and unreliable environment The WSN is consistently prone to topology changes because it is highly susceptible to node failure, node damage, energy depletion, link failure, node addition, deletion and so on. In addition it is also vulnerable to noise, time-inconsistency and errors. Consequently, in order to find an optimal path it is crucial that a network-routing protocol is capable of maintaining the topological changes and increasing the size of the network, and energy consumption level, sensor nodes mobility and their related issues such as connectivity and coverage and application specific requirements. • Data Aggregation In WSNs the redundancy of the data packets is a major concern. Therefore, it is crucial that the same packets generated from a number of nodes can be aggregated for the sake of downplaying the extra overhead of transmission traffic. Today a number of routing protocols use data aggregation techniques to optimise the level of transmission and also to improve the energy efficiency. • Diverse sensing application requirements WSNs are used for an unlimited number of applications and each individual application has its own specification and constraints. Currently, there is no such routing protocol which can fully qualify or work for every application but the task of a routing protocol is to compute an optimal path and forward data as well as ensure the accuracy to the sink node.
  53. 53. Comparative Performance Study of Routing Protocols in Wireless Sensor Network 40 • Scalability In WSNs scalability is crucial because the network size may rapidly grow so the network routing protocol needs to be able to work consistently where there is no proper infrastructure, limited sensor nodes energy resources, nodes failure or damage, unreliable wireless link, energy depletion and so on. Furthermore, there may be a situation where communication is asymmetric and symmetric is not possible so it is important to keep these factors in mind when designing the routing protocol. 3.5. Routing A wireless sensor network (WSNs) is built up from a number of small sensor network nodes and they are connected to each other via a wireless link which does not require a fixed network infrastructure. In regard to the nodes structure of WSNs nodes structure it has a short transmission range, small processing power and storage capacity and also has inadequate energy resources. WSNs routing protocols have a crucial responsibility to ensure there is a reliable, multi-hop communication between the nodes. WSN‟s require sophisticated routing algorithms because energy is the core issue in these networks and low power wireless devices are necessary to ensure that there is a low consumption of energy.[CX10] 3.5.1. Routing in Wireless Sensor Network Initially topology-based routing techniques were used in the wireless network. In the past a number of proposals were based on a proactive routing mechanism that used to collect information about all the available network paths, although those paths links were certainly not used. Furthermore, in dynamics network topologies proactive routing does not accommodate itself properly. An alternative technique was developed called „reactive routing‟ which only keeps those paths which are presently in use. Recently, location aware routing is introduced in which protocols know the physical location. Furthermore, a number of geographic- or position-based routings are also proposed. Information about physical location is required in advance; it can be taken from GPS or on the basis of a distance estimation of incoming signals. Geographic routing and topology-based routing also address the centric routing algorithm. There is another class of routing algorithm called data-centric and it is an important routing paradigm for the wireless senor network. The data-centric algorithm uses queries for the routing operation and the queries are written out by the sink node in order to acquire the requested data.
  54. 54. Comparative Performance Study of Routing Protocols in Wireless Sensor Network 41 Moreover, the routing algorithm in a wireless sensor network can also be classified according to the usage of messages. A single path routing mechanism is used when there is merely one instance of a message existing in the network at any given time. There are some more routing algorithm techniques for WSNs such as partial flooding and multiplexing. In addition to single path, a multi-path, partial, flooding-based routing strategy there is a mechanism which is called the „guaranteed delivery routing algorithmic technique‟. The routing algorithm can also be classified according to the nodes requirements for the management of ongoing tasks in the state information and in the literature it is known as memorization.[CX10] Furthermore, WSN‟s routing algorithm is broadly divided into three main classes which are flat routing, hierarchal routing and location-based routing.[ Emmanuel Sifakis] The algorithm used for the wireless senor network is mostly borrowed from the Ad-Hoc network. In the early days of the wireless sensor network a number of routing protocols were taken from the wireless ad-hoc networks and mobile wireless networks. It is evident that these protocols were built for a general wireless network and it involves no concern for precise communication patterns of WSNs. Hence, the developments of WSNs-oriented new routing techniques, and the customization of existing routing protocols represent a significant area for future research.
  55. 55. Comparative Performance Study of Routing Protocols in Wireless Sensor Network 42 3.5.2. Classification of Wireless Senor Network Routing Protocols Diagrammatical classification of a routing algorithm is shown here: Figure 3.5. Hierarchical diagram of WSNs routing protocols classification Wireless sensor network routing protocols are completely different from conventional wireless routing protocols because the network is more vulnerable to issues like abrupt change network topology, sensor node failure or damage, unreliable wireless network link, energy depletion and so on. Furthermore, the routing protocols of WSNs are obliged to follow cost-effective and strict energy requirements in order to fulfil the needs of overall routing.
  56. 56. Comparative Performance Study of Routing Protocols in Wireless Sensor Network 43 WSNs routing protocols are broadly divided into seven categories which are stated in a tabular form as follows, Routing Category List of Routing Protocols Flat/ Data centric Routing Protocols Rumour, information direct, EAD, COUGAR, ACQUIRE, Directed Diffusion, Gradient based routing, Home agent based Dissemination, SPIN Hierarchical Protocols TEEN, HEED, LEACH, PEGASIS, APTEEN Mobility Protocols Data MULES, TTDD, SEAD, Dynamic Tree based Data Dissemination, Joint Mobility and Routing Multipath Protocols Braided Multipath, N to 1 Multipath Discovery, Sensor Disjoint Mutipath Heterogeneity Protocols CHR, IDSQ, CADR Quality of Service (QoS)Protocols Energy aware routing, SPEED, SAR Geographic Routing Protocols GAF, GPSR, GEAR, energy aware routing Table 3.1. Seven Categories of wireless sensor routing protocols The objective behind the development of the routing algorithm is not only to reduce overheads, increase throughput and minimise end-to-end delay but the other important goal is the consumption of energy usage in a wireless sensor network.[M.Hadjila and M. Feham ] Routing is one of the significant tasks in a wireless sensor network, and for this reason a large amount of research material is available on this topic. The routing algorithm constructed for IP networks and MANET is not working properly in the wireless sensor network domain in comparison with the IP network that sends packets in a wire connection and there is a slight chance the packet could be damaged but in the wireless sensor network it is not the same. ire-less sensor network is one of the most significant technological advances in this century. In the past decade it received an enormous focus from academia and the industry across the globe. [Sshio et al]. The Wireless Sensor Network (WSN) is a form of distributed wireless network. It is an amalgamation of a number of the latest technologies, such as micro-mechanical technologies, distributed signal processing and an embedded system, integrated microprocessor and wireless communication, ad-hoc networks‟ routing protocols and so forth. [Shio et al.]
  57. 57. Comparative Performance Study of Routing Protocols in Wireless Sensor Network 44 The wireless sensor network technology consists of self–organised nodes which are widely deployed in environmental conditions, wireless communication, military purpose, data processing and so forth at a very low price. Nevertheless, WSN‟s technology requires a capable mechanism for data processing and forwarding. The core philosophy of WSN is that each node in the network has limited power which is sufficient for the whole proposed project, for instance a node is sensing for military surveillance or environmental monitoring and so forth. In WSN routing protocols find the route between nodes and ensure the consistent communication between the nodes in the network. The nodes are deployed in an ad-hoc structure irrespective of vigilant planning and engineering. [Shio et al]. In WNS networks the routing contradicts the approaches taken in conventional wireless communication networks. The reason behind this is that it does not have a proper communication infrastructure, the node link is unreliable and on top of all these issues, there is a tight energy consumption constraint and the routing protocol needs to work under these adverse conditions. Currently, a number of wireless routing protocols are being developed in the wireless communication domain. The routing protocols for the wireless sensor network can be divided into seven categories which we will now discuss. Rumour Routing Basics Rumour routing algorithm transmits queries when an event occurs in the network and data can be retrieved from that particular node, while the routing mechanism is independent of geographic information or addressing scheme such as IP addressing and so on. Rumour routing is a trade-off between flooding overhead and delivery consistency and can also be adjusted to other parameters. Rumour routing can be used in a situation where geographic routing is not applicable or the coordinates don‟t match.[CX25] An event is a sort of an abstract form of information from a specific group of sensor nodes and furthermore an event is considered to be a localised phenomenon in a precise region. A query can be explained as being a request for information for the purpose of accumulating data. When a query arrives at its destination the gathered data is passed to the query originator and when the query originator is satisfied with the collected data then the shortest
  58. 58. Comparative Performance Study of Routing Protocols in Wireless Sensor Network 45 path can be discovered between source and destination. [CX 25]. Rumour routing can be useful if it fulfils a certain threshold which is shown in the graph below: Figure 3.6. Rumour routing chart representation Nevertheless, finding the shortest path is not a priority for some applications. The specific application may be interested in taking a small amount of data or may be interested in doing some more attentive sensing at some targeted nodes. So for the stated situation, flooding each query would not be an efficient option in comparison with delivering it on a non- optimal path. On the other hand, flooding can be more useful in a situation where a particular application involves a smaller number of events and loads of queries. Additionally, the cost of flooding cannot be reduced when the queries per event generate a high amount of data.[CX25]. The query origination and query source path finding mechanism is shown in the image as,
  59. 59. Comparative Performance Study of Routing Protocols in Wireless Sensor Network 46 Figure 3.7. Query is originated and query source is looking for the path to reach to the event Rumour path finding mechanism Rumour routing use agents to find the path to an event area. On finding the path agents store the path at nodes as a state. An event node creates agents by the allocation of a path of length 0 to themselves. The agents are created probabilistically the reason is that many nodes watching the same event and trying to creating path to event node which as a result create huge overhead. The agents travelling to limited number of hops. On returning agents amalgamate their own routing table with the event table of visited nodes. To find a path to multiple events the agents‟ priority is to find an aggregate path to both events. [CX25] Figure 3.8. Agents aggregating to multiple events
  60. 60. Comparative Performance Study of Routing Protocols in Wireless Sensor Network 47 Related Routing Algorithm Data-Centric and Flat Architecture Protocols - Flooding and Gossiping In WSNs the flooding and gossiping are the known two approaches used for routing and it flooding performs routing operation which does not require any particular routing algorithm or topological adjustment. In the flooding routing mechanism broadcasting is the core technique used. Each and every sensor node on receiving a data packet immediately broadcasts to their neighbouring sensor nodes and the process does not stop until the packet reaches its final destination or the data packet maximum threshold value reaches its designated limit. Gossiping works on a slightly different basis from its flooding counterpart. It is a modified version of the flooding mechanism. On receiving a data packet a sensor node randomly selects one of its neighbours and the data packet is forwarded to that neighbour only and next the node which received data packet selects and forwards the packet to another node and the process continues. In relation to implementation the flooding mechanism is quite easy to implement. But at the same time it has a number of drawbacks, such as implosion which is usually caused due to the duplication of packets, overlap which is caused when two neighbours in the same region send packets to the same sensor node and it is resource blind because there is no appropriate consideration in regards to energy usage and so it guzzles a huge amount of energy. On the other hand the gossiping mechanism mitigates the implosion problem in a random fashion to select a neighbour‟s sensor nodes and then it forwards the packets to its neighbour. Moreover, due to the aforementioned approach it causes a delay in the propagation of data in the wireless senor network nodes. Geographic Adaptive Fidelity (GAF) Routing Protocol The GAF is a location-based and an energy aware routing protocol, initially developed for an ad-hoc network but it is also widely used for wireless sensor networks. In the literature it is also coined as a position-based routing protocol. The goal of the GAF is to provide an optimised performance to a wireless sensor network by means of assessment of the similar nodes according to their forward packets.
  61. 61. Comparative Performance Study of Routing Protocols in Wireless Sensor Network 48  GAF Operations Mechanism In GAF the network is divided into virtual grids, and to locate each node on the grids a GPS -based information is required and nodes which are equivalent in terms of their position in the grid and are assumed to have the same cost for packet routing. Furthermore, in order to save energy in the case of nodes which have the same cost for packet routing some of them are put to sleep in a specified grid. Therefore, the GAF obviously boosts the network life span in regards to energy usage. Meanwhile, the GAF algorithm can also be assumed to be a hierarchical routing algorithm. In terms of nodes communication in the grid, in each particular grid a single node can be represented as a leader which is involved in communication with the base station on behalf of the other nodes.  Optimal Path Calculation The GAF calculates the optimal path on the basis of residual or cost energy cost level. And the optimal is used for the data transmission. In location-based routing the routing information is predicted from the strength of the signal. The GAF algorithm assumes that all nodes existing in the same grid are equal in terms of data routing cost. Moreover, GAF divides the grid into a sub-, small, equal size grid according to the condition of the power and radio transmitters used by the sensor. Furthermore, the election process decides which node can remain active and which nodes have to be turned off. The nodes which are in sleeping mode can be awakened at any time when required to perform duties like monitoring of communication jobs such as data delivery to base station and so on. Data aggregation is not permissible particularly when the data passing operation is in progress between two different grids. [BX17]. Relation between Radio Range and Grid Size Suppose R is radio ranges which cover up the entire size of a grid. And in a virtual grid let r is the square unit size; the longest possible distance between the two adjacent grids is the longest diagonal linking two grids. Our resultant equation becomes r 2 + (2r)2 ≤ R2 --------------------------Equation 3.1 Where r ≤ R∕√5 [8]
  62. 62. Comparative Performance Study of Routing Protocols in Wireless Sensor Network 49  GAF Operational States The GAF consists of three operational states for a node inside the grid,  Discovery State In this state GAF discovers neighbours within a grid  Active State In this state, GAF nodes participates in the routing process  Sleep State In this state GAF, some of the nodes which project the same cost in the grid are put into the sleeping state. As a result the radio transceiver module of the node is turned off and an amount of energy is conserved. In GAF a node stays active for a time Ta and in time Ta active node in the grid broadcasting to other correspondent nodes. The time for sleeping Ts depends on active node time Ta. And in the discovery state each node sending packets at regular intervals Td. [CX5] The GAF transition states and routing table are visually illustrated stated as,  GAF Pseudo-code Step 1: Divide Grid into sub-virtual grid Step 2 Switch to discovery mode (node?) Step 3: Discovery of all neighbours If (neighbour node are equivalent) then Select single active node (leader) and put remaining nodes in sleep mode Endif Step 2: Perform routing operation on active nodes (leader) Path finding (join active nodes) If (active node fail) then Change sleeping node to active state in the grid Endif Step 3: loop back to Step 1 for next grid
  63. 63. Comparative Performance Study of Routing Protocols in Wireless Sensor Network 50 Step 4: connect to base station Step 5: exit  Advantages 1. GAF conserves energy during sleeping mechanism  Disadvantages 1. Only then the active node participates in communication and ultimately this can influence the accuracy of the data. 2. GAF depends on information from GPS which can limit their functionality where GPS is not available 3. If a grid consists of a single node then energy conservation cannot be balanced, and if there is a packet with low energy virtual grids then the network may suffer from network partitioning problem.[CX6] 4. It does not provide a data aggregation feature which typically exists in hierarchal routing algorithms. Greedy Perimeter Stateless Routing Protocol (GPSR)  Introduction GPSR is a beacon-based routing geographic algorithm. In GPRS the neighbour routing table is updated via periodic beacon messages. The GPRS routing mechanism is based on the position of a node and the destination of the packet in order to take routing packet forwarding decisions.  Protocol Details GPSR protocol functions in two modes which are greedy and perimeter. In greedy mode, GPRS makes greedy forwarding decisions in the network topology on the basis of its immediate neighbours‟ available information, while in perimeter mode it is required of GPRS particularly in a situation where a packet is passed on to a region where the greedy forwarding mechanism is not achievable then the algorithm recovers the region by routing all around the perimeter of the region. The phenomenon is called „face routing‟. The neighbourhood table is constructed by means of periodic beacon broadcast messages, which comprises an ID and sending node position.