Analysis of the Expected Number of Hops in Mobile Ad Hoc Networks with Random Waypoint Mobility

AbstractThe number of hops between the source and destination nodes is a key parameter in studying multi-hop ad hoc networks analytically. To the best of our known, there is no analytical work that considers the hop count of paths in MANETs in a random mobility environment. This paper presents a theoretical study for the expected number of hops between any random source-destination pair in multi-hop ad hoc networks where nodes move according to the random waypoint mobility model. The effects of network parameters such as node density, size of the network area, and node transmission range are studied. Simulation experiments for different network parameters have been conducted to validate the proposed analytical approach

Thwarting Sybil Attackers in Reputation-based Scheme in Mobile Ad hoc Networks

Routing in mobile ad hoc networks is performed in a distributed fashion where each node acts as host and router, such that it forwards incoming packets for others without relying on a dedicated router. Nodes are mostly resource constraint and the users are usually inclined to conserve their resources and exhibit selfish behaviour by not contributing in the routing process. The trust and reputation models have been proposed to motivate selfish nodes for cooperation in the packet forwarding process. Nodes having bad trust or reputation are detected and secluded from the network, eventually. However, due to the lack of proper identity management and use of non-persistent identities in ad hoc networks, malicious nodes can pose various threats to these methods. For example, a malicious node can discard the bad reputed identity and enter into the system with another identity afresh, called whitewashing. Similarly, a malicious node may create more than one identity, called Sybil attack, for self-promotion, defame other nodes, and broadcast fake recommendations in the network. These identity-based attacks disrupt the overall detection of the reputation systems. In this paper, we propose a reputation-based scheme that detects selfish nodes and deters identity attacks. We address the issue in such a way that, for normal selfish nodes, it will become no longer advantageous to carry out a whitewash. Sybil attackers are also discouraged (i.e., on a single battery, they may create fewer identities). We design and analyse our rationale via game theory and evaluate our proposed reputation system using NS-2 simulator. The results obtained from the simulation demonstrate that our proposed technique considerably diminishes the throughput and utility of selfish nodes with a single identity and selfish nodes with multiple identities when compared to the benchmark scheme

Modelling and performance analysis of mobile ad hoc networks

PhD ThesisMobile Ad hoc Networks (MANETs) are becoming very attractive and useful in many kinds of communication and networking applications. This is due to their efficiency, relatively low cost, and flexibility provided by their dynamic infrastructure. Performance evaluation of mobile ad hoc networks is needed to compare various architectures of the network for their performance, study the effect of varying certain network parameters and study the interaction between various parameters that characterise the network. It can help in the design and implementation of MANETs. It is to be noted that most of the research that studies the performance of MANETs were evaluated using discrete event simulation (DES) utilising a broad band of network simulators. The principle drawback of DES models is the time and resources needed to run such models for large realistic systems, especially when results with a high accuracy are desired. In addition, studying typical problems such as the deadlock and concurrency in MANETs using DES is hard because network simulators implement the network at a low abstraction level and cannot support specifications at higher levels. Due to the advantage of quick construction and numerical analysis, analytical modelling techniques, such as stochastic Petri nets and process algebra, have been used for performance analysis of communication systems. In addition, analytical modelling is a less costly and more efficient method. It generally provides the best insight into the effects of various parameters and their interactions. Hence, analytical modelling is the method of choice for a fast and cost effective evaluation of mobile ad hoc networks. To the best of our knowledge, there is no analytical study that analyses the performance of multi-hop ad hoc networks, where mobile nodes move according to a random mobility model, in terms of the end-to-end delay and throughput. This work ii presents a novel analytical framework developed using stochastic reward nets and mathematical modelling techniques for modelling and analysis of multi-hop ad hoc networks, based on the IEEE 802.11 DCF MAC protocol, where mobile nodes move according to the random waypoint mobility model. The proposed framework is used to analysis the performance of multi-hop ad hoc networks as a function of network parameters such as the transmission range, carrier sensing range, interference range, number of nodes, network area size, packet size, and packet generation rate. The proposed framework is organized into several models to break up the complexity of modelling the complete network and make it easier to analyse each model as required. This is based on the idea of decomposition and fixed point iteration of stochastic reward nets. The proposed framework consists of a mathematical model and four stochastic reward nets models; the path analysis model, data link layer model, network layer model and transport layer model. These models are arranged in a way similar to the layers of the OSI protocol stack model. The mathematical model is used to compute the expected number of hops between any source-destination pair; and the average number of carrier sensing, hidden, and interfering nodes. The path analysis model analyses the dynamic of paths in the network due to the node mobility in terms of the path connection availability and rate of failure and repair. The data link layer model describes the behaviour of the IEEE 802.11 DCF MAC protocol. The actions in the network layer are modelled by the network layer model. The transport layer model represents the behaviour of the transport layer protocols. The proposed models are validated using extensive simulations

Link failure detection, network recovery, and network reliability in multi-hop wireless networks

In this thesis, we study Wireless Mesh Network (WMN) and Mobile Ad hoc NETwork (MANET), which are two kinds of wireless multi-hop communication networks. WMNs and MANETs are promising technologies that have the ability to provide effective solutions to many applications in the technological, social, military, disaster recovery, and economic fields. Some of these applications are the extension of the cellular network's coverage, broadband internet access, and community and neighborhood networks. The big challenge in these kinds of networks is the frequent link failures, which make them less reliable compared to other kinds of networks. Implementing a fast mechanism to detect link failures, effective and reliable routing protocols and metrics, and a powerful reconfiguration scheme to recover from the link failures greatly enhance the WMNs and MANETs performance, and increase their reliability and availability. Our research has three directions. In the first direction, we study link failure detection approaches and link failure recovery techniques. In this direction, we mathematically analyze Hello based link failure detection approach implemented in routing protocols that use two routes, one as a primary route, and the other one as a backup route that is immediately used upon link failures. The objectives behind the above analysis are to mathematically calculate the packet delivery ratio, and to find how much gain we could achieve by using two routes instead of one. Our results show that the packet delivery is increased by 1.5 times by using two routes instead of one. It also shows that applying two routes is essential to cover high link failure rate values, and the need using two routes instead of one is more urgent in WMNs and MANETs with higher link failure rate values, i.e. less reliable networks. In addition to that, we propose a novel framework that dynamically assigns the values of Hello based link failure detection scheme parameters based on the communication types and the QoS requirements. Besides that, we propose a novel protocol to enhance the Hello based link failure detection scheme performance. In the second direction, we study the reliable routing protocols and metrics. This thesis proposes a novel adaptive routing protocol to increase the network connectivity and reliability, while minimizing the hop count, reducing the network nodes' spatial distribution and memory, and simplifying the routing process. The network reliability and connectivity are investigated in the last direction. Based in our study, the only ways to provide reliable and stable communications, virtually decrease the packet loss to zero, and to support multimedia communications in MANETs and WMNs are by using multi-route instead of one, and letting the routing protocols select the most stable routes among the available routes. The network node density specifies the probability that a route exists between any randomly chosen source and destination pair. Thus, to ensure the existence of two routes between any source and destination pairs, the node density must be above a certain threshold. In this thesis, we propose a mathematical model to find the above threshold. Our results show that the probability to have two routes exponentially increases with the number of nodes until it reaches the saturation region where the increase of the number of nodes has negligible improvements in terms of network availability. In addition to that, we study the effects of nodes mobility on the network connectivity. Our work is evaluated by MATLAB