Complexity of Increasing the Secure Connectivity in Wireless Ad Hoc Networks

Exploring the effects of directional antennas on the secure connectivity and hop count of secure multi-hop ad-hoc wireless networks

Connectivity of Wireless Ad hoc Networks (WANETs) has received considerable attention in the past several years. In WANETs, achieving a secure connectivity is more challenging since all the communications should operate on secure links. In this paper, we investigate the characterization of the critical density λ c for Poisson random geometric graphs which is the central problem of secure connectivity. By combining the continuum percolation theory with the clustering coefficient method, we derive a tighter lower bound on λ c which provides fundamental understanding on the secure connectivity of WANETs.KeywordsWireless Ad hoc NetworksConnectivitySecurityCritical Density

In this paper we study connectivity in wireless ad-hoc networks by modeling the network as an undirected geometric random graph. The novel aspect in our study is that for finding the link probability between nodes we use a radio model that takes into account statistical variations of the radio signal power around its mean value. We show that these variations, that are unavoidably caused by the obstructions and irregularities in the surroundings of the transmitting and the receiving antennas, have two distinct effects on the network. Firstly, they reduce the amount of correlation between links causing the geometric random graph tend to behave like a random graph with uncorrelated links. Secondly, these variations increase the probability of long links, which enhances the probability of connectivity for the network.Another new result in our paper is an equation found for the calculation of the giant component size in wireless ad-hoc networks, that takes into account the level of radio signal power variations. With simulations we show that for the planning and design of wireless ad-hoc networks or sensor networks the giant component size is a good measure for "connectivity".

The wireless ad hoc networks (WANETs) provide a flexible and adaptable infrastructure for transferring data in different environments. It supports multiple description (MD) video transfers, addressing error-prone WANETs, which are becoming increasingly critical as their usage grows. Previous approaches to multicasting MD video in WANETs had significant challenges. Ensuring multimedia streaming quality over WANETs while reducing buffering and traffic are crucial challenges. To overcome the problems, this work proposes a cluster-to-cluster source route cooperative data transmission (C2C-SRCDT) method for packet communication in WANETs. Initially, nodes in cluster formation will be created, and each node’s weights will be evaluated for cluster head (CH) selection. Then, Dijkstra’s transmission routing aware-multiple description video (DTRA-MDV) method estimates the cluster node to select the shortest distance routes between each cluster to send the multiple (image/videos) data. Finally, the time-slot multiple route selection (TSMRS) technique improves throughput and reduces breakage links. C2C-SRCDT reduces buffering and transfers data quality (image/videos) based on network lifetime, bandwidth and transmission time. The proposed simulation is evaluated using various parameters: data delivery ratio, loss, delay, throughput and energy consumption. The proposed system achieves a data delivery ratio of 92%, a delay of 40 sec and a throughput of 91%. These metrics analysed the improvement in video or image quality and traffic to avoid data transfer and transmit the wireless network better than previous approaches.

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In this paper, we present the set of factors in the physical layer that are relevant to the performance evaluation of the routing protocols. Such factors consist of signal reception, path loss, fading and interference considerations. Therefore it would be desirable for routing algorithms in wireless ad hoc networks, to be able to select paths that are more likely to be stable. With this in mind we adopt a numerical approach based on Finite State Markov Chain channel model to study the performance of an ad hoc routing protocol under various radio propagation models. Further this paper presents a new cross-layer algorithm for joint physical and routing layers in wireless ad hoc networks, applying this to the Optimized Link State Routing (OLSR), protocol. We address the problem of link and route stability, focusing particularly on multipoint relay (MPR) selection method, to find the most optimal routes between any pair of nodes. Our simulation results indicate that the network throughput is greatly improved and the delay is significantly decreased using this cross-layer mechanism, compared to the original OLSR.

Distributed wireless systems (DWSs) are emerging as the enabler for next-generation wireless applications. There is a consensus that DWS-based applications, such as pervasive computing, sensor networks, wireless information networks, and speech and data communication networks, will form the backbone of the next technological revolution. Simultaneously, with great economic, industrial, consumer, and scientific potential, DWSs pose numerous technical challenges. Among them, two are widely considered as crucial: autonomous localized operation and minimization of energy consumption. We address the fundamental problem of how to maximize the lifetime of the network using only local information, while preserving network connectivity. We start by introducing the care-free sleep (CS) Theorem that provides provably optimal conditions for a node to go into sleep mode while ensuring that global connectivity is not affected. The CS theorem is the basis for an efficient localized algorithm that decides which nodes will go to into sleep mode and for how long. We have also developed mechanisms for collecting neighborhood information and for the coordination of distributed energy minimization protocols. The effectiveness of the approach is demonstrated using a comprehensive study of the performance of the algorithm over a wide range of network parameters. Another important highlight is the first mathematical and Monte Carlo analysis that establishes the importance of considering nodes within a small number of hops in order to preserve energy.

Given a placement of wireless nodes in space and a traffic demand between pairs of nodes, can these traffic demands be supported by the resulting network? A key issue for answering this question is wireless interference between neighbouring nodes including self interference along multi-hop paths. This paper presents a generic model for sustainable network load in a multi-hop wireless network under interference constraints, and recasts this model into a multicommodity flow problem with interference constraints. Using Farkas' Lemma, we obtain a necessary and sufficient condition for feasibility of this multicommodity flow problem, leading to a tight upper bound on network throughput. Our results are illustrated by examples.

This paper study the secure optimal QoS routing (SOQR) in wireless ad hoc networks (WANETs) based on the physical layer security techniques. Specifically, we consider a multi-hop WANET with malicious eavesdroppers and cooperative jammers, and formulate the SOQR as an optimization problem. To deal with this problem, we first derive the closed-form expressions of connection outage probability (COP) and secrecy outage probability (SOP) for any given end-to-end path, which serve as the performance metrics of communication QoS and transmission security, respectively. Then, we explore the minimum COP conditioned on that SOP is below a pre- specified threshold and obtain the corresponding achievable power allocation strategy. With the help of analysis of a given path, we further propose the SOQR algorithm which selects the secure path between a pair of source and destination nodes in a distributed manner to achieve the optimal QoS performance. Finally, numerical simulations are conducted to validate the efficiency of our theoretical results, as well as to illustrate the QoS-security tradeoffs.

Wireless Ad hoc Networks (WANETs) enable communication between nodes without fixed infrastructure. Connectivity is an important metric in WANETs. Dropout of nodes considerably impacts connectivity. In this paper, we study the connectivity of one-dimensional (1D) ad hoc networks under varying node dropout levels. We consider different statistical distributions of inter-node distances, namely the exponential, shifted exponential, and the Gaussian distributions which accurately model distance distributions in 1D networks. We derive analytical models for the multi-hop network connectivity probability as a function of the node dropout level and validate our results through MATLAB-based Monte Carlo simulations. Our findings show that while some distributions maintain their topological structure despite random node dropout, others change considerably, providing valuable insights for designing reliable vehicular networks under real-world adoption scenarios.

One of the challenging issues for supporting emergency services in wireless ad hoc networks (WANETs) is coordinating the network under emergency situations. It may lead to inefficient use of the network resources by increasing congestion, as well as affect the network connectivity due to the non-cooperation behaviors of some selfish users. In this paper, we focus on promoting self-supported and congestion-aware networking for emergency services in WANETs based on the idea of Do-It-Yourself1. We model network congestion and non-cooperation behaviors according to the relations between nodes in the constructed dependency graph. Then we propose an energy-efficient and congestion-aware routing protocol for the emergency services of WANETs. Based on the proposed model and routing protocol, we design two novel movement schemes, called Direct Movement to potential selfish/busy Relays (DMR) scheme and Iterative Movement to potential selfish/busy Relays (IMR) scheme for urgent sources to support themselves and to avoid congestion and non-cooperation. Analysis and simulation results show that our approaches significantly achieve better network performance and typically satisfy the requirements for emergency services in WANETs.

Wireless ad hoc networks have become valuable assets to both the commercial and military communities with applications ranging from industrial control on a factory floor to reconnaissance of a hostile border. In most applications, nodes act as data sources and forward information to a central base station (BS) that may also perform network management tasks. The critical role of the BS makes it a target for an adversary's attack. Even if an ad hoc network employs conventional security primitives such as encryption and authentication, an adversary can apply traffic analysis techniques to find the BS. Therefore, the BS should be kept anonymous to protect its identity, role, and location. Previous work has demonstrated distributed beamforming to be an effective technique to boost BS anonymity in wireless ad hoc networks; however, the increased anonymity and corresponding energy consumption depend on the quality and quantity of selected helper relays. In this paper we present a novel, distributed approach for determining a set of relays per hop that boosts BS anonymity using evidence theory analysis while minimizing energy consumption. The identified relay set is further prioritized using local wireless channel statistics. The simulation results demonstrate the effectiveness our approach.

Using directional antennas to conserve bandwidth and energy consumption in ad hoc wireless networks has attracted much attention from the research community in recent years. However, very little research has focused on applying directional antennas to broadcasting. In this paper, we propose a virtual link reduction (VLR)-based broadcasting protocol for ad hoc wireless networks using directional antennas. Based on two-hop neighborhood information, VLR relies on no location nor angle-of-arrival (AOA) information. VLR is a localized or distributed protocol, and it achieves full delivery. VLR operates on top of any existing broadcast routing protocols. In VLR, no node rebroadcasts a given packet more than once. No physical link is actually reduced, but if a packet has already been forwarded to the end node of the current link, the packet is no longer forwarded, that is, this link is virtually reduced. To evaluate the performance of the proposed VLR-based protocol, we conduct extensive simulation, for simplicity, assuming that there is no packet collision, no channel contention, and no mobility. Simulation results show that VLR outperforms most existing omnidirectional and directional broadcasting schemes in the sense that its normalized transmission cost and redundancy are significantly reduced. Based on the results, we conclude that VLR is more bandwidth and energy efficient.

Given a placement of wireless multi-radio nodes in space and a traffic demand between pairs of nodes, can these traffic demands be supported by the resulting network? The key issue in this setting is the wireless interference between neighbouring nodes using the same channel, including self-interference along multi-hop paths. We extend previous work addressing this problem taking into consideration the availability of multiple channels. As such, this paper presents a generic model for sustainable network load in a multi-hop multichannel setting and recasts this model in a multicommodity flow problem with interference constraints. A theorem is stated which gives a necessary and sufficient condition for the feasibility of this multicommodity flow problem. From this theorem an upper bound is derived for the throughput that can be achieved by the network, which is illustrated by examples. We indicate how the results can be used as a basis for a channel allocating algorithm.

Ad hoc networks that do not depend on fixed infrastructure but instead use multi-hop wireless links to communicate are called WANETs. These networks are decentralized and self-configuring. Because of their adaptability, they play a crucial role in emergency response, defense operations, and disaster management. Nevertheless, WANET routing is extremely difficult because of the unpredictable link quality, limited energy resources, dynamic topology, and mobile nodes. Although the Ad hoc On-Demand Distance Vector (AODV) protocol's on-demand route discovery is extensively used, it has a few drawbacks, such as a high energy consumption rate, a high rate of route failures, and limited support for Quality of Service (QoS). By facilitating data exchange between the network, media access control (MAC), and physical levels, this study improves AODV. The three enhanced versions of AODV that are suggested here are ER-AODV, E-AODV, and R-AODV. These versions aim to optimize routing decisions by considering energy metrics, signal strength, and transmission circumstances. The cross-layer variations outperform typical AODV in terms of throughput, latency reduction, packet delivery ratio, and energy consumption, according to NS-2 simulation results. In wireless contexts that are both dynamic and energy-constrained, the results show that cross-layer awareness greatly improves routing efficiency, reliability, and network longevity.