1.1 Introduction
Ad hoc networks consist of wireless hosts that communicate with each other in the absence of a fixed infrastructure. A mobile ad hoc network is a temporary infrastructure fewer networks in which node communicate with each other without any centralized controlling mechanism [1]. Thus these dynamic behaviours of such network have potential applications in disaster relief, conference, with front line environments, plus it have expected significant attention in recent years. This chapter gives a brief study of MANET and its types along with essential characteristics to control such dynamic behaviour. It also take into account various consideration of mobility parameter which is the main essence of this work.
1.1.1 Preface
A mobile ad hoc network (MANET) is a group of devices or nodes that transmit across a wireless communication medium mainly based on radio frequency without any fixed infrastructure or centralized control. Cooperation of nodes is important to forward packets on behalf of every different once other destinations are out of their direct wireless transmission vary. There will be no centralized control or network infrastructure for a MANET to be set up, thus making its deployment quick and inexpensive. The nodes facility to move generously ensures a flexible and handy vibrant network topology which is another important feature of a MANET [2]. Some of the MANET applications includes emergency disaster relief, military operations over a battlefield (vulnerable infrastructure), and wilderness expeditions (transient networks), and community networking through health monitoring using medical sensor network (MSN).
There are numerous issues in MANETS which addresses the points some of them are IP address, radio interference, routing protocols, power Constraints, security, mobility management, bandwidth constraints, QOS, etc. As of now some hot issues in MANETS can be related to the routing protocols, routing mobility and position updates have raised lot of interest of researchers. Let us understand by it an actual scenario of ad hoc network i.e. A message sent by a node reaches all its neighboring nodes that are placed at distances up to the transmission radius. Because of the limited transmission radius, the routes between nodes are normally created through several hops in such multi-hop wireless networks. The use of the nodes’ position for routing poses evident problems in terms of reliability. The accuracy of the destination’s position is an important problem to consider. Here a few cases the destination is a fixed node (e.g., a monitoring centre known to all nodes, or the geographic area monitored), and some networks are static. The problem of designing location update schemes to provide accurate destination information and enable efficient routing in mobile ad hoc networks appears to be more difficult than routing itself.
1.1.2 Multi-hop Wireless Network
Wireless network refers to any type of computer network that is wireless, and is normally associated with a telecommunication network whose interconnections between nodes are implemented without the utilization wires. Wireless telecommunication networks are generally implemented with some type of remote information transmission system that uses electromagnetic waves, like radio waves, intended for the carrier and this implementation usually takes place at the physical level or levels of the network.
A Multi-hop Wireless Network consists of a set of mobile hosts that carry out basic networking functions like packet forwarding, routing, and service discovery without the help of an established infrastructure. Nodes of an ad hoc network relay on one another in forwarding a packet to its destination, because of the limited range of each mobile host’s wireless transmissions. The ad hoc network uses no centralized administration.
Figure 1.1.2 Multi-hop Wireless Network
This provides reliability that the network will not cease functioning just because one of the mobile nodes moves out of the range of the others. Different nodes be supposed to be able to enter and leave the network as they want. Due to this limited transmitter range of the nodes, various hops are generally needed to reach other nodes.
Every node in an ad hoc network must be willing to forward packets for other nodes. Figure1.1 shows the representation of MANET If node A want to send data to D then it is necessary A, B, C, D all are in radio range after that communication is possible among these nodes. Every node acts both as a host and as a router for the topology of ad hoc networks varies with time as nodes move, join or leave the network, with this topological insecurity requires a routing protocol to run on each node to create and maintain routes among the nodes. Mobile ad-hoc networks can be deployed in areas where a wired network infrastructure may be undesirable due to reasons such as cost or convenience. This can be quickly deployed to support emergency requirements, instant needs and coverage in emergent areas.
Therefore there is a excess of applications for wireless ad-hoc networks. Since a matter of fact, for any day-to-day application such as e-mail and file transfer can be considered to be simply deployable inside an ad hoc network environment. Also, we need not emphasize the wide range of military applications possible with ad hoc networks. Not to mention, the technology was initially developed keeping in mind the military applications, for a field in an unknown territory where an infrastructure network is almost impossible to have or keep up. Here in such condition, the ad hoc networks having self-organizing ability can be efficiently used where other technologies either fail or cannot be deployed successfully.
In the Ad hoc networks there is an exciting approach to network design, which is not relying on complex and expensive infrastructure, mainly it required by their counterparts, this ad hoc network can operate in scenarios where conventional networks fails, such as disaster relief and military applications. Ad hoc networks are also particularly well suited for sensor networks and small scale temporary solutions (e.g., Conferences). Much research is also taking place in an effort to extend ad hoc networks to more general purpose applications, such as wireless local area networks (WLANs).
1.1.3 Properties of MANET
Multi-hops network has several significant properties. Some of them present below:
• Mobility: Nodes are free to move arbitrarily. Hence, the network topology may change accidentally and rapidly at irregular times, and may consist of both bidirectional and unidirectional links.
• Bandwidth-constrained, variable capacity links: Wireless links resolve the significantly lower capacity than their hardwired counterparts. In accumulation, the realized throughput of wireless communications, after accounting for the effects of multiple access, fading, noise, and interference conditions, is often much less than a radio's maximum transmission rate.
• Energy-constrained operation: All nodes in a MANET may rely on batteries or other exhaustible means for their energy. For these nodes, the most important system design optimization criteria may be energy conservation [3]. Our work is on efficient energy consumption.
• Self-Configuration: Nodes have capability to reconfigure network topology and discover new path when path breaks or node moves due to dynamic nature of networks.
• Absence of Centralized Router: In ad-hoc networks, each node play role as router that process route discovery techniques because specific coordinator does not designated as router.
1.1.4 Importance of Secure Communication
During the last decade, a novel type of network has gained impetus. This mobile ad hoc network (MANET) is not dependent on an underlying architecture as its predecessor. This mobile nodes building up the network are dynamically and arbitrarily located in such a way that connections between nodes may change on a frequent basis [4]. Unlike traditional networks, the ad hoc network does not rely on preexisting infrastructure. As a substitute, every node in the network collaborates to transmit data between points in the network. Such networks are a necessity in environments such as a natural disaster area or a military operation, everyplace no assumptions can be made about any preexisting infrastructure. Although, ad hoc networks offer additional flexibility when compared with conventional networks, it has increased cost of operation that must be considered in designing any protocols that control on top of such topologies. It provides resources such as bandwidth and powers are extremely limited. Of primary importance is the need to keep the amount of resources used during any operation to a minimum.
The proliferation of mobile computing and communication devices (e.g., cell phones, laptops, handheld digital devices, personal digital assistants, or wearable computers) is driving a revolutionary change in our information society. They are moving from the Personal Computer age (i.e., a one computing device per person) to the Ubiquitous Computing age in which a user utilizes several electronic platforms at a single instance through which he can access all the required information whenever and wherever needed.
A final factor is the growth of the ad-hoc network applications. This system has enabled mobile devices to communicate with other devices. Open nature of communication makes it vulnerable for various security threats. Secure communication is pre-requisite to gain trust of user. More recently, algorithms have been proposed that make use of information to provide content discovery to users in the network.
A variety of secure communication protocols have been proposed in recent years. These can be categorized into two major groups – centralized and peer-to-peer systems. Centralized systems depend on a central directory server which will handle the content location on behalf of a requesting client. These approaches are easier to implement and generally more reliable than the strictly peer-to-peer protocols as the central server is considered to have universal knowledge of the content available on the network. Peer-to-peer (P2P) approaches do not depend on a central server. As an alternative, the nodes in the network collaborate to provide the desired content location service.
A common assumption made by the majority of both centralized and P2P protocols is the abundance of resources in the network, most notably bandwidth. This assumption fails in an ad hoc network and an entirely different approach is necessary. Several protocols have been proposed to solve the problem of content location in ad hoc networks. However these solutions do not take sufficient care to lower the protocol overhead as they either depend on broadcasting information throughout the network or do not take into account link expenses.
Each approach has its own advantages and disadvantages. Every node is aware of its own position and is notified of its neighbors’ positions through small packets broadcasted by the neighbors to announce their position. Moreover, a node is able to establish the location of the destination through any location management scheme (VHR, GLS) [6]. This additional information allows improving routing significantly, especially for large-scale mobile ad-hoc networks, anywhere the amount of nodes can potentially reach several thousand or even millions such as considered in the terminodes project. In this way, the periodical advertisement of each node’s position by sending small packets can be avoided.
A node does neither need to have knowledge of its neighbors’ positions nor even of their existence. If a node wishes to send a packet, it just broadcasts it and every neighboring node receives it. The protocol takes care that only one of those nodes relays the packet to any extent further. This is accomplished by introducing a small additional delay at each node depending on its position relative to the last node and the destination. The node located at the most “optimal” position introduces the fewest delay and, thus transmits the packet at first. The other nodes detect this subsequent relaying and cancel their scheduled transmission. On one hand side, the overall delay is increased, but on the other hand side, the use of battery power can be reduced significantly at the same time as well.
1.1.5 Problem Statement
In mobile ad hoc network, mobile nodes are free to move from one location to another location means that position of mobile nodes is frequently changed. Due to the mobility (rate of position change of mobile node with respect to time) of nodes and continuously changing network topologies pose several challenges. Due to this best route may no longer remain at same time instant. So location management task is slightly difficult in mobile ad hoc network.
Mobile ad hoc network uses asymmetric links, so that nodes are frequently changing their position within network. There are many problems with routing:
– Routing overhead: In mobile ad hoc network, nodes often change their location in network so that routing table is frequently changed. Due to this the problem is routing overhead.
– Interference: This is the major problem in mobile ad hoc network. Wireless links in MANET come and go depending on transmission characteristics. Interference occurs due to noise, weather etc.
– Asymmetric links: Most of the wired networks rely on the symmetric links which are always fixed. But this is not a case with ad-hoc networks as the nodes are mobile and constantly ever-changing their position among network. For example consider a MANET (Mobile Ad-hoc Network) where node B sends a signal to node A but this does not tell anything concerning the standard of the affiliation within the reverse direction
– Dynamic topology: Topology is not constant in MANET, So that routing tables are frequently changed. Routing tables must reflect changes in topology [9].
The complete work observes that Mobile ad-hoc networks require routing protocols to discover route from source to destination. AODV routing protocols are usually used to discover route from source to destination. AODV is reactive routing protocol having minimum routing overhead and hop count parameter for route selection. The major problem with AODV routing protocol is it does not have any security policy or security mechanism to maintain privacy during communication. The main problem with MANET is fear of safety violation during communication. The complete work concludes that, in secure and hostile communication is major problem with MANET. There is need to develop security mechanism to achieve secure communication.
Furthermore, Work also observed that Asymmetric Key cryptography based RSA is a good solution to achieve confidentiality but suffer with extra overhead of key distribution. Whereas Diffie Hellman key exchange is good approach to generate symmetric key with minimum overhead. Work also examine that transmission require more energy than computation.
The complete study generate a requirement to develop security policy to establish secure communication among mobile nodes by maintain minimum security overhead.
In short, major concern with AODV is:-
Insecure Routing
Packet Dropping
Security
Uphold Confidentiality
Security Challenges
Wireless sensor network becomes very popular and offers wide range of applications that can be implemented in real world. To implement these applications more efficient and secure protocols and algorithms can be used. To design new protocol or algorithm first we have to discuss the challenges of wireless sensor network, which are as follows:
1.1.1.1. Security
In WSN, one of the most challenging and important parameter is security. The network does not have any secure medium for establishing communication between nodes, the data travels openly from one node to another and thus the chances of violation of confidentiality increases very much. There are various security issues with wireless sensor networks. Some of them are as follows:
1. Data Confidentiality
Data confidentiality deals with protection of data in the network. Many cryptographic algorithms are used to protect data between intended recipient and actual sender and insure data confidentiality. It is one of the most essential issues of network security. Everyone wants that its data travel over the network will be secured and no third person can read or modify that data. This is achieved by using either symmetric or asymmetric cryptography algorithm.
2. Data Integrity
Data integrity deals with reliability of data, that is, it ensures that the data sent by the sender is same and not modified by any other node in between the network [11].
3. Data Authentication
Data authentication ensures that the data received is the original message sent and not the modified by any other person/node during transmission. It is also achieved by using symmetric or asymmetric cryptography [12].
4. Data Freshness
Data freshness ensures that the data received is fresh one and not the expired one. An attacker can send expire packet and waste network resources, thus freshness of data is important to avoid this.
5. Data Availability
Data availability ensures that the data is available to the user even after in presence of attack like Denial of Service (DoS) attack.
1.1.1.2. Fault tolerance
Wireless sensor network has a limited power backup. Thus if any node fails in the network then working protocol should handle all types failure to maintain communication.
1.1.1.3. Scalability
WSNs can be deployed in hundreds or in thousands depending on the application, thus adding of new node should be accommodated by the working protocol. Working protocol should be able to extend existing network and accommodate large number of nodes.
1.2. Organization of Thesis
This thesis report is organized in seven chapters. Chapter 1 presents the introduction of the thesis. This chapter contains the context of the research and the research objectives are presented. Rest of the chapters of the thesis are presented as follows.
Chapter 2 introduces literature review. This chapter presents areas which have been identified as related work and technical background for the thesis. The areas include wireless sensor networks, security based approaches and other techniques to secure protocols against attacks. This chapter also reviews the solutions proposed in the literature.
Chapter 3 presents the identification of problem. This chapter includes different kind of routing protocols used for wireless sensor networks and a brief discussion about AODV routing protocol. The routing strategy of AODV is also elaborated with security flaws of AODV which makes it vulnerable to attacks. It also describes the problem statement and procedure adopted during research.
A new approach for data transmission is explained in Chapter 4. This chapter contains a secure way to transmit data over the wireless network. It also discusses the proposed algorithm with its working diagram.
Chapter 5 discusses the study of simulation environment. Simulation tool, simulation model and network topology used. It also explains various simulation parameters and strategy used for simulation in detail.
Chapter 6 presents two different approaches of transmitting the data over the sensor network. It presents the study of simulation environment, various parameters to observe performance of the network in detail and then presents the results of both approaches, i.e. with normal AODV and with modify AODV to prevent data from being accessed by malicious node. Comparison of results for both the approaches is also presented.
Chapter 7 presents the overall discussions of the thesis report. It concludes the whole research work and possible future research which can be carried out, is highlighted in the future work section.