Dynamic ad hoc networks (DANETs) are similar to mobile ad hoc networks (MANETs), but the network density and mobility change significantly over time and space. Many researchers have proposed types of key management schemes for ad hoc networks. In this chapter, we provide a timely survey of the existing solutions and describe the state-of-the-art techniques for DANETs security key management, where we particularly consider those more suitable for DANET. Following a brief discussion on the limitations and challenges of key management in DANET, we introduce the main and desirable features and evaluation metrics of key management. Then a categorization of existing key management systems is presented. Finally, we conclude this chapter with a summary of further developments.

Wireless ad hoc networks consist of a collection of mobile nodes that dynamically form a network without the use of any existing network infrastructure. In such networks, each mobile node can serve as a router. Packet delivery is achieved through a single-hop transmission if the communicating nodes are neighbours, otherwise packets can be routed through multiple intermediate nodes. Energy efficiency is important issue in ad hoc networks, where mobile nodes are powered by batteries and it may not be possible to recharge them during a session. The limited battery lifetime can cause one or more links in the network to fail and affect the operation of the network. To maximize the network lifetime, traffic should be routed such that the energy consumption is minimized. We present a survey of energy-efficient routing approaches that have been proposed for various types of ad hoc networks, including mobile ad hoc networks (MANETs), ad hoc mesh networks, and cognitive radio networks. We discuss the main features of each approach and analyse their benefits and operation strategies.

In the last few years, Vehicular ad hoc Networks (VANETs) have attracted a lot of attention and have triggered the development of many new attractive applications. They have become a fundamental component of many intelligent transportation systems and VANETs are being used to improve road safety and enable a wide variety of value-added services. Nevertheless, VANET applications have stringent security requirements because they affect road traffic safety. Several security threats and different types of attacks against VANETs have emerged recently that attempt to compromise the security of such networks. These attacks can cause catastrophic results such as the loss of lives or the loss of revenue for those value-added services. Therefore, making VANETs secure has become a key objective for VANET designers. Since traditional security mechanisms are not always suitable to some unique features in VANETs (e.g., high mobility of nodes), industry and academia have been focusing on improving VANET security. We present threats and attacks that can be launched on VANETs and we identify the security solutions to mitigate them. We also highlight VANET security challenges that still need to be addressed to enable robust, scalable, cost-effective secure solutions for VANETs.

The applications where mobile ad hoc networks are connected to the Internet are gaining popularity. However, several technologies should be applied in order to guarantee a reliable connectivity. Particular cares should be applied to the gateway discovery process. The enhancements related to the gateway discovery process are mainly achieved by controlling the propagation of the gateway messages in the network. Two specific parameters need to be controlled in this process: the frequency of the messages and the area in which they are propagated. This chapter explains how these two parameters are tuned to adapt to the dynamic characteristics of the network. Although the techniques are proposed for the integration of a MANET into the Internet, its applicability could be extended to any other mechanism where broadcast messages are used in a multihop wireless communication.

The objective of this chapter is to provide a general and flexible analysis method for the capacity of a wireless ad hoc network. First of all, the total capacity of a typical ad hoc network is defined, characterized and formulated as a function of the cumulative distribution function (CDF) of the received SIR. Then, a closed form expression for the CDF of signal to interference power ratio (SIR) is approximated, which directly results in a closed form solution for the total network capacity. Among various capacity metrics, the focus of this chapter is on the total outage capacity as a practical example. The effect of the outage threshold, β, on the total capacity of the network is studied and the optimum β that maximizes the capacity is determined.

Routing plays important roles in dynamic VANET and becomes more critical than conventional mobile dynamic ad hoc networks. Thus, the design of new routing protocols for these networks requires actual research efforts associated within this chapter, since there is no considerable previous evaluation of routing for VANET. This chapter presents the state-of-art of routing for VANET, with a performance evaluation of some of the proposed protocols. It is identified that new research trends and some issues regarding this new technology are highlighted.

With the popularity of wireless devices and the increase of computing and storage resources, there are increasing interests in supporting mobile computing techniques. Particularly, ad hoc networks can potentially connect different wireless devices to enable more powerful wireless applications and mobile computing capabilities. To meet the ever-increasing communication need, it is important to improve the network throughput while guaranteeing transmission reliability. Multiple-input-multiple-output (MIMO) technology can provide significantly higher data rate in ad hoc networks where nodes are equipped with multi-antenna arrays. Although MIMO technique itself can support diversity transmission when channel condition degrades, the use of diversity transmission often compromises the multiplexing gain and is also not enough to deal with extremely weak channel. Instead, in this work, we exploit the use of cooperative relay transmission (which is often used in a single antenna environment to improve reliability) in a MIMO-based ad hoc network to cope with harsh channel condition. We design both centralized and distributed scheduling algorithms to support adaptive use of cooperative relay transmission when the direct transmission cannot be successfully performed. Our algorithm effectively exploits the cooperative multiplexing gain and cooperative diversity gain to achieve higher data rate and higher reliability under various channel conditions. Our scheduling scheme can efficiently invoke relay transmission without introducing significant signalling overhead as conventional relay schemes, and seamlessly integrate relay transmission with multiplexed MIMO transmission. We also design a MAC protocol to implement the distributed algorithm. Our performance results demonstrate that the use of cooperative relay in a MIMO framework could bring in a significant throughput improvement in all the scenarios studied, with the variation of node density, link failure ratio, packet arrival rate and retransmission threshold.

The provisioning of real-time applications such as voice and video over ad hoc networks have received a lot of attention among researchers mainly due to the increasing demand of this service among users. This is particularly challenging due to capacity requirements and stringent delay constraints. In general, wireless nodes have limited resources like capacity and battery power. In multi-hop wireless mobile networks, one of the key issues is how to route packets efficiently. Some of the important factors that need to be considered in designing a routing scheme for ad hoc networks are: minimum delivery latency, higher probability of packet delivery, energy efficiency and adaptability. Therefore, the design of an efficient and reliable routing scheme for such applications is a major challenge. This chapter provides background and describes related research efforts in single path and multipath routing in Mobile ad hoc Networks (MANETs). A brief outline of the operation as well as strengths and limitations of each scheme is presented. In addition, the open issues that must be addressed in the design of efficient routing algorithms are discussed.

Although ant-based routing protocols for MANETs have been widely explored but most of them are essentially single-path routing methods that have heavy burden on the hosts along the shortest path from source to destination. The robustness of these protocols is comparatively not good which is further weakened by the positive feedback mechanism of ant. Link-disjoint multipath routing is more robust and can support QoS better than single-path routing in MANETs. In this chapter, we present swarm intelligence and link disjoint multipath routing to solve the problem of dynamic routing issues of MANET. A novel approach named Ant Colony Inspired Routing for Mobile ad hoc Networks (QAMR) is discussed. In this approach, forward ants and backward ants are used to determine the paths with QoS properties satisfied. QAMR establishes and utilizes multiple routes of link-disjoint paths to send data packets concurrently and adopts pheromone to disperse communication traffic, thus it can adapt to the dynamic changes of the network and better support for QoS.

Due to mobility and frequent node failure, the topology of a mobile ad hoc network (MANET) is highly dynamic. Routing protocols should adapt to such dynamism, and continue to maintain connection between the source and the destination. A hybrid computational intelligence-based multipath routing algorithm is presented in this chapter. The proposed method employs Hopfield neural network (HNN) as a disjoint path set selection tool for choosing disjoint paths that maximise the network reliability. The parameters of Hopfield model are also optimised by particle swarm optimisation (PSO) algorithm. This method selects disjoint paths in such a way that the network reliability is maximised. For this purpose, each node in the network is equipped with an HNN. Simulation results show that the proposed PSO-optimised HNN-based routing algorithm has better performance as the reliability of multiple paths is increased while the number of algorithm iterations is reduced as compared with the non-optimised HNN multipath routing. In addition, the PSO-optimised HNN-based routing algorithm shows better performance in terms of reliability and number of paths when compared with the backup path set selection (BPS) algorithm.

A Mobile ad hoc Network (MANET) is a self-configuring, dynamic, multi-hop network composed of mobile nodes that operate without the need of any established infrastructure. The creation of stable, scalable and adaptive clusters with good performance, faster convergence rate and minimal overhead is a challenging task in MANET. This chapter proposes two clustering techniques for MANET, which are (k, r)-Dominating Set-based, weighted and adaptive to changes in the network topology. The set of dominating nodes functions as the clusterhead (CH) to relay the data and control packets. The proposed scenario-based clustering algorithm for MANETs (SCAMs) is a greedy approximation algorithm, whereas the Distributed SCAM (DSCAM) selects the (k, r)-dominating set through a distributed election mechanism. These algorithms achieve variable degree of CH redundancy through the parameter k, which contributes to reliability. Similarly, flexibility in creating variable diameter clusters is achieved with the parameter r. The performance of these algorithms are evaluated through simulation and the results show that these algorithms create stable, scalable and load-balanced clusters with relatively less control overhead in comparison with the existing popular algorithms.

Due to user's requirement of wireless connectivity irrespective of his geographical position the dynamic ad hoc networking (DANET) is gaining popularity to its peak today. In mobile ad hoc networks (MANETs), autonomous mobile devices connect with each other forming a temporary network without any centralized administration. The widely accepted ad hoc routing protocols do not address possible security threats at the network layer of MANETs. In this chapter, we investigate Blackhole and Grayhole attacks that cause denial-of-service and badly disrupt normal network functionalities. We present an algorithm that introduces security aspect in the route discovery process of ad hoc On-Demand Distance Vector (AODV) protocol to protect MANETs against these two attacks; a node identifies malicious node by detecting unusual routing information and alerts other nodes about the adversary using default routing packets. The proposed approach detects and isolates multiple malicious nodes during route discovery process to assure safe and secure communication among mobile nodes. We analyse our approach theoretically and evaluate its performance using Network Simulator-2 (NS-2).

This chapter covers the problem of negotiation mechanism in IEEE 802.11-based ad hoc networking whose functioning components, being user devices or relay nodes over the wireless or Internet, interchange data using the classic MAC-DCF. In order to overcome the existing bottleneck of negotiation procedure in wireless ad hoc networks, we propose a new channel reservation scheme which basically helps to reduce the negotiation overheads and reduce the transmission delays without any extra bandwidth consumption. Then, the extended multi-channel CRF scheme for new multi-channel applications are discussed for shared controllability and increased multi-channel applications, each on separate frequencies. In order to solve the problem of access identification, a recent distributed channel reservation scheme is explained and reviewed where critical persistent problems such as hidden terminals and coexistence of control and data traffic on different frequency channels have been discussed in detail.

Geographic routing (GR) algorithms are attractive in ad hoc wireless networks owing to their efficiency, scalability and, in particular, energy efficiency. In this chapter, based on the fundamental GR algorithms, two energy efficient local forwarding schemes are proposed in a two-dimensional ad hoc wireless network. In the optimal range forward (ORF) algorithm, the optimal transmission ranges are utilized to reduce the energy consumption of the network. Furthermore, an optimal forward with energy balance (OFEB) algorithm is proposed to balance the residual energy of each node and to prolong the network lifetime. The authors compare the proposed algorithms with the existing GR algorithms, such as the most forward within radius and the nearest forward progress algorithms. The network lifetime, the network throughput, the number of packets successfully received by the destination and the average energy cost of each successfully received packet, resulting from all the algorithms mentioned above, are compared based on different node densities. It is shown that the performance of the OFEB algorithm is significantly better than the others.

Spectrum sharing is an important technique to improve the spectrum efficiency of dynamic ad hoc networks. However, since the BUSY/IDLE state of the ad hoc traffic could vary quickly, it is difficult to reduce the traffic collisions between coexisting networks. This chapter investigates a spectrum-sharing scenario, where a cooperative relay network intends to access the spectral band of a dynamic ad hoc network without making too many collisions with the ad hoc traffic. Adopting a binary continuous-time Markov chain (CTMC) traffic model to characterise and predict the ad hoc traffic, the spectrum access design of the cooperative relay network is formulated as a non-convex optimisation problem. We simplify this spectrum access design problem as a convex optimisation problem, which allows us to obtain a low-complexity optimal spectrum access strategy. Moreover, owing to the dynamic nature of the ad hoc traffic, the optimal spectrum access strategy needs to be attained within a short time and under practical limitations. To this end, we generalise the spectrum access design to an ergodic setting and propose an online spectrum access strategy. This online spectrum access strategy is able to achieve the optimal ergodic performance with negligible control delay, moderate signalling overhead and little computational capability requirement for the user equipment.

Ad hoc network is a wireless network without having fixed equipment/components. Here, the mobile device functions as an endpoint as well as intermediate point. The intermediate points (devices) are used to forward the message if the two wireless mobile nodes are not within their transmission range. Current communication system is playing an important role to allocate the resources for the multimedia applications. This chapter discusses the various algorithms for the mobile wireless ad hoc networks, which is an efficient method to allocate the resources for the sensitive applications using the weighted fair queue system. This method is very important during the period of network congestion. This system allocates sufficient bandwidth and provides quality of service to the end-users. This chapter also talks about the quality of services at various layers of open system interconnection model. Adaptation schemes provide different levels of service to different classes of traffic. Some of the quality of service schemes propose that the class of traffic should be modified as a result of events occurring in the network. The quality of service driven resource management architecture is used to serve as a system-wide framework within which resource management decisions can be performed in a coordinated fashion. The resource allocation scheme for multimedia applications using mobile agent is used to allocate the resources in the mobile ad hoc network. In addition to that it allocates the resources for hand-off applications and new applications.

With a long history, traffic controllers have great impact in our lives. In this chapter, we review five critical components in controlling traffic. We show that how different elements of these components can affect the traffic systems. Also, we present a quick review on mobility models, from communication engineers' and traffic engineers' perspectives. We show how these views are different from each other's. Intelligent transportation system (ITS) and its presence in the traffic controllers are the next topic of this chapter. Architecture of macroscopic and microscopic traffic controllers is explained too. Finally, we review the current issues in collaboration between VANET and traffic controllers before the conclusion of the chapter. The reviewed issues are deploying VANET infrastructures and using VANET-based P2P networks in traffic information systems.

The problem of providing energy efficient trust-aware routing arises due to easy exposure to insecure conditions and highly constrained nature of wireless sensor networks (WSNs). The reputation system-based solutions reported in the literature require the nodes to be in promiscuous mode to monitor continuously its environment to detect misbehaviour events which is considered to be a costly operation for WSN nodes due to their limited resources. In this chapter, a reputation system-based technique using efficient monitoring approach called Efficient Monitoring Procedure In Reputation System (EMPIRE) for trust-aware routing in WSNs is presented. EMPIRE provides a probabilistic distributed monitoring methodology that reduces the nodal monitoring activities, while keeping the performance of the system, from the behaviour and trust awareness perspective, at a desirable level. Simulation results of the reputation system show that reducing monitoring activities with EMPIRE does not have a significant impact on system performance in terms of security.

Wireless sensor networks, a special type of wireless ad hoc networks, consist of large numbers of wireless sensor nodes. The idea of a wireless sensor network is to achieve the same sensing quality as a remote sensing system by utilizing a large number of wireless sensor nodes to perform close-range sensing. Wireless sensor nodes are compact communication devices that can virtually fit in anywhere. They are battery-powered devices that can greatly reduce deployment overheads due to wirings. To ensure a terrain of interest is fully covered, usually more than enough wireless sensor nodes are deployed to provide redundant sensing coverage. With a proper onoff scheduling scheme, the total energy consumption of a network can be reduced without introducing significant impacts to its target detection capabilities. In this chapter, two bio-inspired scheduling schemes are revisited. In both schemes, wireless sensor nodes can decide to operate in different operation modes dynamically. The decisions are made based on local information. Performances of a network can be fine-tuned by adjusting the behaviours of the nodes in their mode decisions.