Author: Jamal-deen Abdulai
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Mobile wireless ad hoc networks (MANETs) have become of increasing interest in view of their promise to extend connectivity beyond traditional fixed infrastructure networks. In MANETs, the task of routing is distributed among network nodes which act as both end points and routers in a wireless multi-hop network environment. To discover a route to a specific destination node, existing on-demand routing protocols employ a broadcast scheme referred to as simple flooding whereby a route request packet (RREQ) originating from a source node is blindly disseminated to the rest of the network nodes. This can lead to excessive redundant retransmissions, causing high channel contention and packet collisions in the network, a phenomenon called a broadcast storm. To reduce the deleterious impact of flooding RREQ packets, a number of route discovery algorithms have been suggested over the past few years based on, for example, location, zoning or clustering. Most such approaches however involve considerably increased complexity requiring additional hardware or the maintenance of complex state information. This research argues that such requirements can be largely alleviated without sacrificing performance gains through the use of probabilistic broadcast methods, where an intermediate node rebroadcasts RREQ packets based on some suitable forwarding probability rather than in the traditional deterministic manner. Although several probabilistic broadcast algorithms have been suggested for MANETs in the past, most of these have focused on Ã'Â"pureÃ'Â" broadcast scenarios with relatively little investigation of the performance impact on specific applications such as route discovery. As a consequence, there has been so far very little study of the performance of probabilistic route discovery applied to the well-established MANET routing protocols. In an effort to fill this gap, the first part of this thesis evaluates the performance of the routing protocols Ad hoc On demand Distance Vector (AODV) and Dynamic Source Routing (DSR) augmented with probabilistic route discovery, taking into account parameters such as network density, traffic density and nodal mobility. The results reveal encouraging benefits in overall routing control overhead but also show that network operating conditions have a critical impact on the optimality of the forwarding probabilities. In most existing probabilistic broadcast algorithms, including the one used here for preliminary investigations, each forwarding node is allowed to rebroadcast a received packet with a fixed forwarding probability regardless of its relative location with respect to the locations of the source and destination pairs. However, in a route discovery operation, if the location of the destination node is known, the dissemination of the RREQ packets can be directed towards this location. Motivated by this, the second part of the research proposes a probabilistic route discovery approach that aims to reduce further the routing overhead by limiting the dissemination of the RREQ packets towards the anticipated location of the destination. This approach combines elements of the fixed probabilistic and flooding-based route discovery approaches. The results indicate that in a relatively dense network, these combined effects can reduce the routing overhead very significantly when compared with that of the fixed probabilistic route discovery. Typically in a MANET there are regions of varying node density. Under such conditions, fixed probabilistic route discovery can suffer from a degree of inflexibility, since every node is assigned the same forwarding probability regardless of local conditions. Ideally, the forwarding probability should be high for a node located in a sparse region of the network while relatively lower for a node located in a denser region of the network. As a result, it can be helpful to identify and categorise mobile nodes in the various regions of the network and appropriately adjust their forwarding probabilities. To this end the research examines probabilistic route discovery methods that dynamically adjust the forwarding probability at a node, based on local node density, which is estimated using number of neighbours as a parameter. Results from this study return significantly superior performance measures compared with fixed probabilistic variants. Although the probabilistic route discovery methods suggested above can significantly reduce the routing control overhead without degrading the overall network throughput, there remains the problem of how to select efficiently forwarding probabilities that will optimize the performance of a broadcast under any given conditions. In an attempt to address this issue, the final part of this thesis proposes and evaluates the feasibility of a node estimating its own forwarding probability dynamically based on locally collected information. The technique examined involves each node piggybacking a list of its 1-hop neighbours in its transmitted RREQ packets. Based on this list, relay nodes can determine the number of neighbours that have been already covered by a broadcast and thus compute the forwarding probabilities most suited to individual circumstances.
Author: Mustafa Bani Khalaf
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Mobile Ad-hoc Networks (MANETs) have lately come to be widely used in everyday applications. Their usability and capability have attracted the interest of both commercial organizations and research communities. Recently, the Vehicular Ad-hoc Network (VANET) is a promising application of MANETs. It has been designed to offer a high level of safety for the drivers in order to minimize a number of roads accidents. Broadcast communication in MANETs and VANETs, is essential for a wide range of important services such as propagating safety messages and Route REQuest (RREQ) packets. Routing is one of the most challenging issues in MANETs and VANETs, which requires high efficient broadcast schemes. The primitive and widely deployed method of implementing the broadcast is simple 'flooding'. In this approach, each node 'floods' the network, with the message that it has received, in order to guarantee that other nodes in the network have been successfully reached. Although flooding is simple and reliable, it consumes a great deal of network resources, since it swamps the network with many redundant packets, leading to collisions contention and huge competition, while accessing the same shared wireless medium. This phenomenon is well-known in MANETs, and is called the Broadcast Storm Problem. The first contribution of this thesis is to design and develop an efficient distributed route discovery scheme that is implemented based on the probabilistic concept, in order to suppress the broadcast storm problem. The proposed scheme is called a Probabilistic Disturbed Route Discovery scheme (PDRD), and it prioritizes the routing operation at each node with respect to different network parameters such as the number of duplicated packets, and local and global network density. The performance of the proposed scheme PDRD has been examined in MANETs, in terms of a number of important metrics such as RREQ rebroadcast number and RREQ collision number. Experimental results confirm the superiority of the proposed scheme over its counterparts, including the Hybrid Probabilistic-Based Counter (HPC) scheme and the Simple Flooding (SF) scheme. The second contribution of this thesis is to tackle the frequent link breakages problem in MANETs. High mobility nodes often have frequent link breakages; this potentially leads to re-discovery of the same routes. Although different probabilistic solutions have been suggested to optimize the routing in MANETs, to the best of our knowledge they have not focused on the problem of frequent link breakages and link stability. II Unlike other existing probabilistic solutions, this thesis proposes a new Velocity Aware-Probabilistic (VAP) route discovery scheme, which can exclude unstable nodes from constructing routes between source and destination. The main idea behind the proposed schemes is to use velocity vector information to determine the stable nodes and unstable nodes. A proper rebroadcast probability and timer are set dynamically according to the node stability. Simulation results confirm that the new proposed scheme has much better performance in terms of end-to-end delay, RREQ rebroadcast number and link stability. The routing in VANETs is very critical and challenging in terms of the number of broken links and packet overheads. This is mainly due to the fast vehicles' speed and different vehicles' movement directions. A large number of routing protocols such as Ad-hoc On-demand Distance Vector (AODV) and Dynamic Source Routing (DSR) have been proposed to deal with the routing in MANETs. However, these protocols are not efficient and cannot be applied directly to VANETs context due to its different characteristics. Finally toward this end, this thesis proposes new probabilistic and timer probabilistic routing schemes in order to improve the routing in VANETs. The main aim of the proposed schemes is to set up the most stable routes to avoid any possible link breakage. These schemes also enhance the overall network performance by suppressing the broadcast storm problem, which occurs during the route discovery process. The proposed schemes also make AODV protocol suitable and applicable for VANETs. Simulation results show the benefit of the new routing schemes in terms of a number of metrics such as RREQ rebroadcast number, link stability and end-to-end delay.
Author: Abdalla Musbah Omar Hanashi
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Broadcasting is an essential and effective data propagation mechanism with several important applications, such as route discovery, address resolution and many other network services. Though data broadcasting has many advantages, it can also cause a high degree of contention, collision and congestion, leading to what is known as 'broadcast storm problems'. Broadcasting has traditionally been based on the flooding protocol, which simply overflows the network with a high number of rebroadcast messages until these reach all the network nodes. A good probabilistic broadcast protocol can achieve high saved rebroadcast (SRB), low collision and a lower number of relays. When a node is in a sparse region of the network, rebroadcasting is relatively more important while the potential redundancy of rebroadcast is low because there are few neighbours which might rebroadcast the packet unnecessarily. Further, in such a situation, contention over the wireless medium resulting from Redundant broadcasts is not as serious as in scenarios with medium or high density node populations. This research proposes a dynamic probabilistic approach that dynamically fine-tunes the rebroadcast probability according to the number of neighbouring nodes distributed in the ad-hoc network for routing request packets (RREQs) without requiring the assistance of distance measurements or location-determination devices. The main goal of this approach is to reduce the number of rebroadcast packets and collisions in the network. The performance of the proposed approach is investigated and compared with simple AODV, fixed-probabilistic and adjusted-probabilistic flooding [1] schemes using the GloMoSim network simulator and a number of important MANET parameters, including node speed, traffic load and node density under a Random Waypoint (RWP) mobility model. Performance results reveal that the proposed approach is able to achieve higher SRB and less collision as well as a lower number of relays than fixed probabilistic, simple AODV and adjusted-probabilistic flooding. In this research, extensive simulation experiments have been conducted in order to study and analyse the proposed dynamic probabilistic approach under different mobility models. The mobility model is designed to describe the movement pattern of mobile customers, and how their position, velocity and acceleration change over time. In this study, a new enhanced dynamic probabilistic flooding scheme is presented. The rebroadcast probability p will be calculated dynamically and the rebroadcasting decision will be based on the average number of nodes in the ad-hoc networks. The performance of the new enhanced algorithm is evaluated and compared to the simple AODV, fixed-probabilistic, adjusted-probabilistic and dynamic-probabilistic flooding schemes. It is demonstrated that the new algorithm has superior performance characteristics in terms of collision, relays and SRB. Finally, the proposed schemes are tested and evaluated through a set of experiments under different mobility models to demonstrate the relative merits and capabilities of these schemes.
Author: M. Günes
Publisher: Springer
ISBN: 3319627406
Category : Computers
Languages : en
Pages : 91
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Book Description
This SpringerBrief presents the design and performance evaluation of communication protocols based on dissimilarity metrics for wireless multihop networks. Dissimilarity metrics are used to infer the network topology based solely on local information to efficiently disseminate packets throughout the network, reducing both redundancy and congestion which is covered in this brief. The performance evaluation of the proposed communication protocols has been conducted by both meticulous simulation and real experimentation in a wireless multi-hop testbed. The obtained results in this brief corroborate the hypothesis regarding the validity of dissimilarity metrics, which can be used to design efficient communication protocols. This SpringerBrief is a good starting point for advanced-level students studying computer science and electrical engineering, as well as researchers and professionals working in this field.
Author: Jun Zhi-zhong
Publisher: Springer Science & Business Media
ISBN: 3642179932
Category : Computers
Languages : en
Pages : 554
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Book Description
Ad hoc networks, which include a variety of autonomous networks for specific purposes, promise a broad range of civilian, commercial, and military applications. These networks were originally envisioned as collections of autonomous mobile or stationary nodes that dynamically auto-configure themselves into a wireless network without relying on any existing network infrastructure or centralized administration. With the significant advances in the last decade, the concept of ad hoc networks now covers an even broader scope, referring to the many types of autonomous wireless networks designed and deployed for a specific task or function, such as wireless sensor networks, vehicular networks, home networks, and so on. In contrast to the traditional wireless networking paradigm, such networks are all characterized by sporadic connections, highly error-prone communications, distributed autonomous operation, and fragile multi-hop relay paths. The new wireless networking paradigm necessitates reexamination of many established concepts and protocols, and calls for developing a new understanding of fundamental problems such as interference, mobility, connectivity, capacity, and security, among others. While it is essential to advance theoretical research on fundamental and practical research on efficient policies, algorithms and protocols, it is also critical to develop useful applications, experimental prototypes, and real-world deployments to achieve an immediate impact on society for the success of this wireless networking paradigm.
Author: Al-Bahadili, Hussein
Publisher: IGI Global
ISBN: 1466601922
Category : Computers
Languages : en
Pages : 582
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Book Description
"This book reviews methodologies in computer network simulation and modeling, illustrates the benefits of simulation in computer networks design, modeling, and analysis, and identifies the main issues that face efficient and effective computer network simulation"--Provided by publisher.
Author: G Ram Mohana Reddy
Publisher: CRC Press
ISBN: 1315351633
Category : Computers
Languages : en
Pages : 139
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Book Description
In recent years, a lot of work has been done in an effort to incorporate Swarm Intelligence (SI) techniques in building an adaptive routing protocol for Mobile Ad Hoc Networks (MANETs). Since centralized approach for routing in MANETs generally lacks in scalability and fault-tolerance, SI techniques provide a natural solution through a distributed approach for the adaptive routing for MANETs. In SI techniques, the captivating features of insects or mammals are correlated with the real world problems to find solutions. Recently, several applications of bio-inspired and nature-inspired algorithms in telecommunications and computer networks have achieved remarkable success. The main aims/objectives of this book, "Mobile Ad Hoc Networks: Bio-Inspired Quality of Service Aware Routing Protocols", are twofold; firstly it clearly distinguishes between principles of traditional routing protocols and SI based routing protocols, while explaining in detail the analogy between MANETs and SI principles. Secondly, it presents the readers with important Quality of Service (QoS) parameters and explains how SI based routing protocols achieves QoS demands of the applications. This book also gives quantitative and qualitative analysis of some of the SI based routing protocols for MANETs.
Author: Nitin Afzalpulkar
Publisher: Springer
ISBN: 8132226380
Category : Technology & Engineering
Languages : en
Pages : 964
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Book Description
This volume comprises the proceedings of the International Conference on Recent Cognizance in Wireless Communication & Image Processing. It brings together content from academicians, researchers, and industry experts in areas of Wireless Communication and Image Processing. The volume provides a snapshot of current progress in computational creativity and a glimpse of future possibilities. The proceedings include two kinds of paper submissions: (i) regular papers addressing foundation issues, describing original research on creative systems development and modeling; and (ii) position papers describing work-in-progress or research directions for computational creativity. This work will be useful to professionals and researchers working in the core areas of wireless communications and image processing.
Author:
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Languages : en
Pages :
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In mobile ad hoc networks (MANETs)[1], a mobile station (MS) can communicate with nodes outside of its transmission range by employing intermediate nodes as relays. To find a path to a specific destination node, the source node broadcasts route request packets that are forwarded to all other nodes. A simple flooding scheme is employed in AODV[2], where every node rebroadcasts these route request packets even if some of its neighbors have already broadcast the requests and thus the rebroadcasts may reach no additional nodes. In MANETs, broadcasting is extensively used in route discovery, address resolution, and many other network services. The efficiency of broadcasting protocol can dramatically affect the performance of the entire network. Appropriate use of a probabilistic method can reduce the number of rebroadcasting, therefore reduce the chance of contention and collision among neighboring nodes. A good probabilistic broadcast protocol can achieve higher throughput and lower energy consumption, without sacrificing reachability or having any significant degradation. In this research, we study the problem of using probabilistic approaches to improve broadcasting and route discovery performance in wireless ad hoc and sensor networks. Our contributions can be summarized as follows. First, we propose a selfish node based approach. In this approach, we categorize MSs into normal nodes and selfish nodes. Normal nodes forward packets for other nodes while selfish nodes do not. The advantage of using selfish nodes is that the total rebroadcast traffic can be reduced. The disadvantage is that we may miss the optimal route and suffer from a low delivery rate. In this approach, we use a probabilistic method to set up a proper number of selfish nodes. Using a combination of gossiping and dominating set, we can reduce the route discovery cost by minimizing the number of rebroadcasts, while achieving higher delivery rate due to the reduction of rebroadcast traffic, thereby reducing the number of collisions. Second, we propose a leveled probabilistic approach. In this approach, we use a pre-assigned probability model to avoid redundant packet relays. In our protocol, a MS probabilistically sends relay packets (rebroadcasts) according to its neighborhood information. Our approach categorizes MSs into four groups. For each group of nodes, we assign a specified value of rebroadcasting probability. The MSs with more neighbors are given higher rebroadcasting probability. Using this method, we can reduce routing cost by minimizing the number of rebroadcasts in route discovery phase without significantly affecting the network connectivity. Third, we propose a dynamic probabilistic approach. In this approach, we dynamically adjust the rebroadcasting probability as per the node distribution and node movement. This is conducted based on locally available information. In addition, our approach does not require any assistance from accurate distance measurements or exact location determination. This approach can further reduce routing cost by adapting its behavior according to the environment changes. Fourth, we compare MANETs and WSNs (wireless sensor networks). We realize the difference between MANETs and WSNs in terms of the node characteristics, energy consumption, mobility model and the traffic model. We also evaluate sensing coverage and communication coverage for different sensor range or communication range. Fifth, we propose a broadcasting scheme using connecting areas. We assign/select connecting areas during the network start up period. Only the connecting area head node located inside one of the connecting areas is responsible to rebroadcast the packet while the nodes outside the connecting areas do not rebroadcast. By choosing the size of the connecting area and the placement of the connecting areas, we can reduce the rebroadcasting cost while maintaining the reachability. Sixth, we propose a scheme that is based on redundant degree of each sensor. In this approach, we evaluate the redundant degree value of each sensor node and use this value to decide whether to rebroadcast packet or not. The rebroadcast from a node with high degree of redundancy has high possibility to be redundant. We set up a threshold to allow nodes with low enough degree connectivity to rebroadcast packets. In this work, we first describe the details of our protocols, comparing them with AODV and other protocols, and presenting evaluation results in MANETs. Analytical and simulation results show that our approaches outperform the AODV protocol on several metrics in most cases, including the average number of rebroadcasts, average number of packet collisions, end-to-end delay, and the throughput. We propose broadcasting protocols in wireless sensor networks, and explore other methods to further improve the performance of broadcasting and route discovery in MANETs and WSNs.
Author: Dhirendra Kumar Sharma
Publisher: Sankalp Publication
ISBN: 9391190731
Category : Education
Languages : en
Pages : 106
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Book Description
In this book, the focus is on the analysis and design of efficient, adaptive, and scalable routing protocols for Mobile Ad Hoc Networks. Next section presents the objective of the work performed in the context of this book. The main objective of this book is to develop routing protocols, which are appropriate for challenging environment of mobile ad-hoc networks. Given the inherent characteristics of these networks, the solutions must be adaptable to dynamic topologies, efficient with the bandwidth usage, scalable and energy efficient when various network parameters are concerned. Moreover, the focus is also on realistic approaches having relevance in real-life deployments. This means that the protocols should not be designed merely based on generic assumptions, which could lead to incorrect conclusions. Network Simulator (ns2.34) is the tools, which are used to determine that the developed algorithms are implementable in real networks. For validation in ad hoc networks, a specific scenario should also be mentioned for which the routing protocol has been designed. Meeting of these objectives includes providing the perception of the realities of ad-hoc networking. In addition, the proposed solutions should be compared against corresponding solutions found in the literature. New solutions must offer better performance with respect to others, to be able to contribute something to the research community. To summarize, the main goal of this book is to improve the knowledge in ad-hoc networking by providing solutions, which can help in developing new features for MANETs. This book will give the details of the methodology employed to achieve the goals.
