CHAPTER 1 INTRODUCTION

Transcription

1 1 CHAPTER 1 INTRODUCTION 1.1 OVERVIEW OF MANETS A Mobile Ad-Hoc NETwork (MANET) is a collection of geographically distributed wireless mobile nodes forming a temporary network without using centralized administration, infrastructure, or centralized access points 1. MANETs can be used in a wide range of applications as they have the capability to establish networks at anytime, anywhere without the aid of an established infrastructure. Such networks find useful in military and other strategic applications such as disaster rescue, where the presence of fixed infrastructure networks are unavailable. MANETs are suitable for creating commercial applications for providing ever-present communication services, where existing infrastructure is unavailable. Examples include rapid information exchange in a forum, networking smart electronic devices or sensors, etc. Table 1.1, depicts the differences between adhoc networks and infrastructure networks. MANETs are autonomous in nature as communication takes place among the nodes through wireless links in a multi-hop fashion, i.e two nodes that are remote of each other communicate by creating routes through one or more intermediate nodes in the network. MANETs exhibit dynamic network topology and varying network connectivity as a result of mobility of nodes 2. However, due to node mobility, such multi-hop links break frequently causing interrupted communication. Further, in a sparse network, high mobility may potentially lead to partition of network due to loss of connectivity between nodes.

2 2 Table 1.1 Adhoc networks Vs Infrastructure networks Infrastructure-based networks Ad hoc networks Requirements Well established infrastructure with network components such as routers, switches, servers and base stations. None Node properties Plays End User role Dual role as end user and network functions Connections Wired or wireless Usually wireless Topology Provided by the pre-deployed infrastructure Self-organized topology maintained by the nodes Network functions Provided by the infrastructure Distributed to all participating nodes 1.2 SELF ORGANIZING NETWORKS (MANETS) Self organizing networks are networks without a central unit, where members must organize themselves into a network 3. The main objectives of self organization are scalability and long life networks. Self organization requires all routing protocols to be collaborative and distributive in nature. Self organization is categorized in two dimensions: Horizontal and Vertical dimensions. Horizontal dimension is achieved according to the necessary state information whereas vertical dimension is based on network layer.

3 3 a. Horizontal dimension: Location information Self organization is achieved by considering the relative or absolute positions of nodes. It also considers the association to a cluster of nodes in a multi-hop communication. Location information is obtained with the help of information exchange among distant nodes using routing techniques, topology control and clustering methods. Neighborhood information Self organization is achieved with neighborhood information obtained from local communication among immediate neighbors within their transmission range for single hop networks whereas with local broadcasts for multi-hop communication. Table driven routing and medium access control provide the necessary neighborhood information. Local state Self organization is achieved with local system states and environmental factors. The results of communications with the environment or indirect communications with other nodes using environmental changes (stigmergy) are considered as local system states. Data centric routing and task allocation process provide the local system states and environmental factors respectively. Probabilistic algorithms Probabilistic techniques do not depend upon state information and it is a rather stochastic process, where randomness is exploited for preventing unwanted synchronization. Figure 1.1 explains the principles and properties of self organizing and conventional networks. Conventional networks consider explicit

4 4 coordination of self organizing techniques whereas self organizing network go with implicit coordination. Fig 1.1 Principles of self organizing and conventional networks b. Vertical dimension: MAC layer explores the accessing techniques for local interaction in a medium. Network layer focus on topology control, maintaining routing table and for data gathering and aggregation. Application layer focus on synchronization and control with application reliant requirements (coverage, lifetime). 1.3 APPLICATION SCENARIOS MANETs find various applications with their capability to establish networks at anytime, anywhere without the support of an established infrastructure. The ease of deployment feature of MANETs makes them suitable for a variety of applications in military, civilian, education and other environments. A MANET has several advantages over the traditional sensing methods, with greater accuracy, larger coverage area and extraction of localized

5 5 features. In addition to the peer-to-peer communication, MANETs have various other applications 4 : Collaborative and distributed computing. For example factory floor automation. Rapid communication with smallest configuration among a set of people. For example, a group of researchers willing to share their research findings during a conference, a lecturer distributing notes to a cluster of students on the dash etc. MANETs can be used for emergency communication operations. In a disaster area, one cannot expect an established working network infrastructure, but may still need to provide communications between rescue agents. A MANET can be constructed consisting of the set of wireless devices carried by the agents and obtain a power-efficient communication network in the absence of a fixed network infrastructure. Inter-vehicle communication network can be formed with MANETs, to provide vehicle operators with current road traffic conditions, adaptive vehicle control signals, knowledge of multi-route recommendation and vehicle position with GPS taking the position of others into consideration. One of the promising applications of MANETS is the formation of interairplane communication network 5. It provides an efficient process of achieving fuel efficiency by adopting communication between peer airplanes continuously instead of depending on commands from a central base station which is unreliable in certain geographic locations. Formation of short range Wireless Personal Area Network (WPAN) for linking personal electronic devices with each other or to Internet is another

6 6 potential MANET application 6 with an objective of providing seamless connectivity between devices. Commando operations in military networks formed between soldiers and tanks. (a) (b) Fig. 1.2 MANET applications (a) Industry floor automation (b) Rescue (c) Vehicle-to-vehicle communication The various MANET applications mentioned above are summarized in Table 1.2.

7 7 Table 1.2 Examples of MANET applications Application Emergency networks Agent based networks Vehicular Adhoc Networks (VAN) WPAN Objectives To provide connectivity between rescue nodes and control server where the network infrastructure is unavailable To obtain energy efficient communication in the absence of infrastructure network. To enable real-time vehicle monitoring and adaptive traffic control To provide flexible connectivity between personal electronic devices or home appliances 1.4 CRITICAL FACTORS INFLUENCING NETWORK PERFORMANCE IN MANETS The following inherent characteristics of MANETs raise different performance challenges for the operation of the network 7 : Dynamically changing network topology requires frequent route updation necessitating quick convergence of the routing protocol. High quality routes obtained by long time route discovery process may not be very useful, as routes may change by the time route discovery is complete. Thus, based on application, there exists interesting trade-offs between the quality of the route, time and overhead caused for route discovery. The life time of a node s battery becomes an issue since the MANET nodes are battery operated devices that use battery energy to prolong life within an

8 8 ad hoc network. Energy efficient routing protocols become important criteria that may need to be addressed. The distributed nature and rapid change in the topology of MANET makes it harder to determine the location information of network nodes in time. Different transmission powers of mobile nodes lead to asymmetric connection topology. Limited wireless transmission range and restricted bandwidth of wireless links ensures minimum routing overhead, so that only a small fraction of network bandwidth is spent on control packets as opposed to data packets. Shared communication medium e.g. air, with broadcast nature necessitates secured channel access with authentication. Wireless transmissions pave way for ease of snooping, resulting in high security hazards. 1.5 RESEARCH ISSUES IN MANETS ROUTING PROTOCOLS The conclusion from the above statements is that the key component of successful and improved communication performance in MANETs is to design efficient routing protocols. The several research issues 8 that should be taken into consideration while designing a routing protocol are: Energy conservation. Limited wireless transmission range. Packet losses due to mobility-induced route changes and subsequent network partitioning.. Broadcast nature of the wireless medium leading to security hazards

9 Power aware communication Power saving at network level is more important than power saving at node level. In this case, despite slight increase in the power consumption of individual nodes for saving additional power at other nodes, the network lifetime can be extended at the cost of more processing energy. Power saving at network level is divided into following categories: Physical and link layer mechanisms - include transmit power control to explore the nodes neighbor list thereby providing a topology control mechanism due to dynamic mobility characteristics of nodes in MANETs. Moreover MANET nodes have only limited battery supply and act as routers for transmission, the distance that needs to be bridged can be reduced by variable transmission power. However, the optimum transmit power depends on the size of network topology either with direct transmission or full routing approach. Nodes sending messages directly to all other nodes are called direct routing, whereas transmission only through designated neighbor nodes is called full routing. Use of direct transmission for small network size is highly energy efficient. Use of full routing with a limited number of relying nodes for smaller networks is beneficial whereas, for larger networks, the optimal choice is to use as many relaying nodes as possible. Hence, this mechanism typically uses adaptive transmit power. Battery and power aware routing 9 - All routing algorithms aim at low cost routing in the sense the cost can be number of hops, the link quality etc. This causes overload in some nodes, leading to premature disruptions in the network. For MANETs with limited battery and multihop communication, routing mechanisms take into account the remaining battery capacity of intermediate

10 10 nodes to avoid individual node failure as well as to enhance over all network lifetime. The power aware communication in MANETs is achieved by the following methodologies: o Optimal on-demand routing methods. o Energy conservative methods. o Topology Control methods o Mobility control Methods o Load balancing methods. o Agent and multipoint relay based communication o Broadcasting Algorithms Mobility and Topology Control Dynamic mobility of hosts in MANETs leads to unpredictable connection topology critically affecting the network performance. The performance of an ad hoc network protocol can vary significantly with different mobility models. It may also vary over same mobility model with different parameters. Hence, knowledge of the impact of mobility pattern and network topology on the network performance is important for designing the routing algorithms. This section examines the impact of node mobility and reviews topology control algorithms Node Mobility A MANET s network topology is a function of the location and movement of its nodes. Single hop or multihop links can be made or removed due to node availability and limitations in communication range.

11 11 A D Node D entering Node A s coverage region C Y E Node C moving out of Node A s coverage region (a) A D Y (b) Fig. 1.3 Example of topology change due to node movement: (a) route from A to D through B; and (b) route from A to D through C Figure 1.3(a) shows an example of a change in network topology due to node movement. When node A needs to send a message to node Y, node C can serve as a router to final destination Y. However, if node C moves, the route (A- C-Y) s constituent links are broken and become invalid route and when such a

12 12 topology change occurs, routing protocol has to discover new valid routing paths to destination such as A-D-Y, as shown in Figure 1.3(b). The mobility model dictates the movement of nodes and their connectivity. A lot of models have been proposed so far including Random Way Point mobility model (RWP), Gauss Markov (GM) mobility mode, Manhattan Grid model (MG), Reference Point Group Mobility model (RPGM) etc. The choice of mobility model affects the performance of routing protocols. This is especially true for ad-hoc networks that rely on intermediate nodes for forwarding data between hosts. The following are the three different components resulting as the choice of mobility models: The absolute value of a performance metric e.g., throughput, or delay, of a protocol can vary widely with the mobility model. The variation of a performance metric with changes in one of the parameters such as transmission range can change qualitatively. The relative performance of two routing protocols is also dependent on the mobility model. Hence, MANETs routing protocol ought to be adaptive to network changes. This slide can have a momentous force on the overall performance of the network. However, this is a difficult process due to constraints like limited wireless bandwidth and battery power of nodes. Route discovery in networks with reactive routing protocols is usually a power-consuming process and causes additional transmission delay. On the other hand, in networks with proactive routing protocols, once topology change

13 13 occurs, the nodes broadcast the information for routing table update. This process dissipates communication power and channel resources. On the whole, the performance of MANET routing protocols significantly depends on the chosen mobility model 10 : Routing in adhoc networks with movement of independent nodes is more challenging in defined mobility traces, but provides better throughput with restricted mobility pattern. Reactive protocols are more speed-sensitive and perform better than proactive protocols under group node movement scenarios. In this scenario, energy conservation and throughput are better in reactive protocols due to the presence of a group leader who is responsible for the distribution and mobility of group members Topology Management One of the key factors of network management in MANETs is topology management which takes into consideration the physical and logical relationships among nodes. The main goal of topology management 11 is to conserve energy while connected. The following constitute the sense of topology management with the objective of achieving the following goals: Permitting a active participation of a few sub-branch of nodes in the network by adjusting the transmitted power of the nodes. Clustering or grouping of nodes to reduce energy consumption. Selecting getaway nodes for setting relationships with neighboring clusters

14 14 Active control of MANET s topology is possible by adjusting the transmission power of the nodes. Hence, the transmission power management method in MANETs is often referred to as topology control mechanism. Transmit power control is a physical layer mechanism, where different transmitting powers are assigned to different routing sources and destinations. The objectives of topology control especially in MANETs include reduction of power consumption as MANETs rely on mutihop communication. It also aims at increased throughput and minimum delay. The radio part of the MANET is the major circuit that consumes more energy than any other computational part. Despite, MANETs relying on multihop communication increase in radio power consumption and interference between transceivers is undesirable 12. Conversely, when the transmission range is too short, the network connectivity can be lost with sparse topology and may lead to network partitioning.. On the other extreme, when the transmit power assigned to the nodes is too high, the nodes run out of energy quickly, which is not desirable either. Hence, in MANETs, neighbor based topology control mechanism as power control is closely related to neighbor selection. Therefore, the transmission range of the nodes should be appropriately assigned to enable minimum power consumption and signal interference while the network connectivity is maintained 13. Most topology control algorithms attempt to limit the nodes cardinality, i.e., maximum degree and reduce signal interference to achieve the objectives of power conservation, prevent frequent link breaks and improved communication performance 14. Most of the existing topology control algorithms are reactive algorithms that attempt the topology variations after occurrence of a connection change occurs. Hence, to remove this limitation, current research focus is on

15 15 developing a proactive topology control algorithm or predictive algorithm that adjusts the transmission powers of communicating nodes. 1.6 RESEARCH MOTIVATION The biggest challenge in this kind of networks is to find the most efficient routing due to the changing topology and battery drain rate based on the processing power of nodes. The routes should be established in the shortest possible time, to ensure reduction in the delay of data delivery and to achieve a faster convergence rate. The routing algorithm should guarantee a sub-optimal path. Hence, in particular, energy efficient routing may be the most important design criteria for MANETs to prolong the network life span. Power failure of a mobile node not only affects the node itself but also its ability to forward packets on behalf of others and thus the overall network lifetime. A mobile node consumes its battery energy not only when it actively sends or receives packets but also when it stays idle listening to the wireless medium for any possible communication requests from other nodes. Thus, energy efficient routing protocols minimize either the active communication energy required for transmission and receipt of data packets or the energy during inactive periods. On the whole, an optimal routing protocol for MANETs should be fully distributed, adaptive to frequent topology changes, loop free with localized control and should provide the desired Quality of Services (QoS). 1.7 OUTLINE OF RESEARCH PROBLEM Computer network technologies have been in use for the last few decades to store, exchange and process data within an organization. The Internet is widely used in all developed countries for file exchange, home banking, online shopping and exploring World Wide Web 15. Mobile phone usage is enveloping all parts of

16 16 the world. Wireless networks have drastic growth from the widespread use of the Internet and mobile phones 16. Recent developments in low cost, small smart hand held devices having high computation performance with access to the Internet have made pervasive and ubiquitous computing possible 17. The users of these devices need to pay a rather high Internet access fee than the smart device cost. Most of developed countries have come out with Wireless Fidelity (Wi-Fi) hotspots for free Internet access, where in the users with smart devices need to get connected to nearby open access points. However, seamless connectivity is the most serious limitation with these techniques. Connectivity is available only when open access points exist nearby, thereby necessitating development of efficient methodologies to provide seamless network connectivity. MANETs are autonomous wireless communication networks capable of establishing themselves with a self-organized infrastructure. They are multi-hop networks featured with dynamic topology, wherein inter-node communication is through multiple stations 18. Like cell-based networks, MANETs do not require base stations. They carry out data transmission without a network infrastructure but with sufficient intermediate nodes. One of the desirable features of MANETs is the possibility of ready establishment of communication links between devices without the support of network infrastructure. Thus, the MANET technology can provide seamless connectivity between nodes even in the absence of the nearest open access points. They also enable access to the Internet under sparse open access point s scenarios. Furthermore, as MANET nodes communicate only with nearby neighbors, they need only short communication range thereby enabling the facility of smaller power to the nodes than those with other wireless communication technologies.

17 17 The following problems need solutions for enabling efficient inter-host communication within MANET. As most mobile devices are battery-powered, power- efficient communication is a key problem. The users are mobile, and it is usually infeasible to track all user locations. Thus, the communication links should be adaptively managed in a distributed manner. The first research issue in MANETs is power efficient communication. MANET stations are powered with a limited battery, wherein the replacement of batteries is quite difficult. Since the topology is dynamic and stations are battery constrained, node coordination is essential for localization and hence MANETs routing protocols ought to be energy conservative. An optimal routing protocol for MANETs should be fully distributed, adaptive to frequent topology changes; loop free with localized control, and must provide desired QoS. Secondly, rapid changes in the topology of a MANET make determination of the information about location of network nodes in real time rather difficult. The high mobility of MANET nodes leads to the use of localization services for position determination 19. Localization services should be robust against node failures and should provide low error of local estimation. The beacon based localization needs a few nodes to know about their positions with the known position beacon obtained through Global Positioning System (GPS) or by manual configuration. For indoor networks, which are unreachable by GPS, the information on location determined using RSSI (Received Signal Strength Indicator),is relayed hop by hop from the source to the destination. Thirdly, a power failure of a node affects the node s ability to forward packets on behalf of others, thus reducing the network lifetime. The conventional MANET routing protocols such as Dynamic Source Routing (DSR) 20 and Adhoc

18 18 On demand Distance Vector (AODV) routing 21 use common transmission range for transfer of data without consideration of the energy status of nodes. In fact, transmission energy cost has a higher contribution in total energy expenditure. Hence, the adaptive transmission power is preferred to the fixed transmission power, which is sufficient to reach the receiver node. Limiting factors like small size, limited computation power and energy source affect the result and much more with the use of GPS 22 for identifying the distance between nodes. RSSI values of nodes are used for determining the relationship of power-distance between source and destination 23. A further major issue in MANETs is finding optimal routes with less congestion. This can be achieved by balancing the load through multipath 24, which process was proposed with several metrics, in which the energy aware multipath load balancing contributes to energy management of MANETs. Many engineering discrete optimization applications such as job scheduling and network routing have been proposed with Ant Colony Optimization. Hence routing in dynamic networks, using ACO, seems to be appropriate as routing is achieved by transmitting ants rather than routing tables flooding Light Switch Paths (LSP). Various reliable and power efficient multicast routing protocols, using Swarm Intelligence (SI), with the help of reliability metric, have been developed 25,26. Heterogeneous MANETs are characterized by quorum of nodes with diverse link capacities, variable network density (frequent inclusion and deletion of nodes), limited practical bandwidth of the shared wireless channel and the limited battery power availability. However, with the establishment of hybrid architectures, there are chances of the route failure occurring during the data transmission. This failure leads to a greater overload and an increased delay. The

19 19 routing protocol which is aware of power or energy efficient may not satisfy all the desired QoS parameters for such architectures. Hence, a cluster based routing protocol with Mobile Agent (MA) seems to be suitable for improving the network lifetime 27. All major research activities discussed above have explored various on - demand power aware routing protocols for improvement of the constrained lifespan of the network. However, these protocols try to increase the network life time but do not guarantee a network remaining operational forever. Therefore, the charging of dying nodes in the order of their expected lifetime is essential for improving the network connectivity and lifespan.. Various schemes such as energy conservation, harvesting and battery replacement have been proposed to meet this challenge 28, OBJECTIVES OF THE INVESTIGATION The purpose of the present study is to contribute to an understanding of energy management schemes for improved QoS and reduced network failure of MANETs. Among them, the focus of the researcher will be on the following major issues: Design of energy efficient routing protocols, node mobility and its impact on network topology, transmission power control, agent based communication and energy replenishment of mobile hosts. Figure 1.4 shows the various energy management schemes in MANETs 30 with concentration on research methods highlighted in green colour. Specific objectives are: Develop a reliable ACO based routing protocol with an even load distribution using multipaths for optimizing the energy consumption in MANETs.

20 20 Study and examine the performance of the proposed ACO based routing protocol under different mobility models based on specific application of MANETs. Battery Management Schemes Device dependent Network Layer Energy Management Schemes Transmission Power Management Schemes System Management Schemes Data Link Layer Network Layer Processor Power Management Schemes Device management Schemes Fig 1.4 Classification of energy management schemes in MANETs Investigate the importance of Mobile Agents in hybrid MANETs for efficient data delivery with optimized energy consumption, using Residual Energy based Dominator Algorithm. Develop an intelligent algorithm for energy replenishment of MANET nodes to ensure an ever operational network and compare its performance with different routing schemes and study the tradeoffs involved in such systems, using an extensive simulation study 31,32.

21 MAJOR CONTIBUTIONS This thesis has made the following contributions: Has proposed a reliable ACO based routing protocol called Autonomous Localization based Energy Efficient Path (ALEEP_with_ACO) routing protocol for optimizing the energy consumption in indoor MANETs. ALEEP_with_ACO aims to find the optimal energetic path which can reduce the energy consumption of the mobile nodes and increase the lifespan of the network. Has analyzed the performance of Autonomous Location Based Energy Efficient ACO routing protocol with dissimilar MANET mobility models. This work focuses on fulfilling the specific objective of thoroughly simulating ALEEP_with_ACO under two different mobility models; Disaster Area (DA) and STreet RAndom Waypoint (STRAW ) mobility model and examining it performance under these models with RWP model. Since our routing algorithm is location based, mobility characteristics such as geographic restrictions and temporal - spatial velocity can be very well easily, using these two specified mobility models. Has proposed a novel energy consumption model using Residual Energy based Mobile Agent selection scheme (REMA). Mobile agents dynamically choose the appropriate upper layer agents by sharing topology information among nodes for reliable data transmission. Mobility weightage within the zone group and across different zone groups and the congestion free traffic characteristics are analyzed through the use of this scheme and multi-mode gateway selection process. The energy of the nodes can be retained for the maximum time to increase the battery life while the gateway

22 22 is selected based on the maximum weight, which utilizes various route path data transfer mechanisms. Energy Management Schemes Transmission Power Management Schemes Battery Management Schemes Routing Based Techniques Autonomous Localization based Energy Efficient (ALEEP_with_A CO) Routing Protocol Cluster Based Techniques Residual Energy based Mobile Agent selection scheme (REMA) cluster routing protocol recharging schemes Dynamic and Secure Joint Routing and Charging Scheme with Mobile Power Back Ferry Nodes in Mobile Adhoc Networks Fig 1.5 Overview of proposed energy efficient transmission power control and battery management schemes Has proposed a co-routing cum charging mechanism for MANETs by introducing special Mobile Power Bank Ferry (MPBF) nodes called multihop ferry nodes, which move around MANET environment by shouldering the responsibility of on demand battery charging. They also act

23 23 as gateway nodes for transmission of network control packets. A co-routing and charging mechanism is implemented with Residual Energy based Mobile Agent (REMA) and MPBF s. Network proposed by the researcher has been assumed to be a heterogeneous one consisting of traditional MANET nodes with limited energy and a few MPBF nodes with relatively abundant energy sources. Once deployed, these MPBF s collaboratively monitor the environment and process the request of critical node charging. Consumption of energy from the MPBF nodes affords a most trustworthy energy supply than deriving energy from the surrounding environment. Fig 1.5 shows the area of research focus of this thesis PERFORMANCE METRICS In this work, various developed routing techniques are compared via the following traditional protocol dependent and protocol independent performance metrics and mobility metrics: 1. Conventional Metrics: Packet Delivery Ratio (PDR) denotes the fraction of successfully delivered packets to the total number of packets generated in the network. Throughput denotes the ratio of data packets received per second to data packets sent. End to end delay denotes the average amount of time that is taken by a packet to reach its final destination from source. It includes the route discovery wait time, which a node may experience in case a route is not available. Packet loss is the fraction of packets lost on their route to destination. The loss is usually due to congestion in the network and buffer overflows.

24 24 Packet loss = Number of lost packets / number of received packets Remaining Energy (Battery Capacity) is the battery capacity of a node after each successful transmission. This metric helps in extending network lifetime. Energy consumption is the total energy consumed by the network for a particular initiated transmission. Network lifetime denotes the time till the failure of the first node in the network due to energy depletion. Node density denotes the number of nodes deployed in the network. A wide range of densities is required for the different applications which test the scalability of the protocol. Cost value can be the number of hops, Euclidean distance, link metrics or the remaining energy of the nodes battery. 2. Mobility Metrics: Mobility model allows mathematical analysis and uses the following protocol independent mobility metrics 33. These metrics can be extracted directly from the traces resulting from the mobility model. Link based metrics and range based metrics are used with more realistic propagation models. Average node degree - It represents the number of nodes connected to a particular node under consideration on an average. It is a measure of the node density. Average time to link break is the frequency of failure of the links and the routes based on links obtained by varying the transmission range.

25 25 Metrics such as Node Degree Distribution (NDD) and Clustering Coefficient (CC) are of particular interest in MANETs for group mobility as the movement patterns of mobile nodes are not independent of each other. Node Degree Distribution (NDD) - denotes the number of potential Agent nodes for a mobile node. Clustering Coefficient (CC) - denotes the number of cluster heads present in the network. 3. Topology metrics Variable Transmission power is the rate of change in transceiver power w.r.t Euclidean distance or multi hop neighbours. Link duration for a pair of nodes - is the average time the link remains active once it becomes available. Path availability - is the fraction of time a path is available between a pair of nodes. Number of neighbors - is another indicator that can reveal the existence of groups in a mobility model ORGANIZATION OF THE THESIS The chapters of the thesis are organized as follows. Chapter 1: Provides the introduction to the research issues in the areas of MANETs and our major contribution. Chapter 2: Discusses the available literature on the proposed work.

26 26 Chapter 3: Describes the design of the proposed autonomous localization based energy efficient routing protocol for indoor MANETs. Chapter 4: Analyze the performance of proposed ALEEP_with_ACO algorithm under various mobility models. Chapter 5: Explains the methodology, algorithm, implementation, results and analysis of the proposed Residual Energy based Mobile Agent algorithm. Chapter 6: Explains the methodology, algorithm and implementation of the proposed on-demand charging and co- routing for energy replenishment in MANET nodes. Chapter 7: Summarizes the major contributions of the research presented in this thesis and scope for future work.