Techniques for maintaining connectivity in wireless ad-hoc networks under energy constraints

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".

A wireless ad hoc network is composed of several tiny and inexpensive device such as wireless sensor networks (WSNs) which have limited energy. In this network energy, efficiency is one of the most crucial requirements. Data transmitting in minimum power level is one way of maximizing energy efficiency. Thus, transmission power level of nodes should be managed in a smart way to improve energy efficiency. Topology control is one of the main algorithms used in a wireless network to decrease transmission power level while preserving network connectivity. Topology control could improve energy efficiency by reasonably tuning the transmission power level while preserving network connectivity in order to increase network capacity and lifetime. In pursuit of energy efficiency and connectivity, nodes can be selfish and are conflicting with each other. Therefore to overcome the conflict, game theory is used to construct energy efficient topology, as well as minimizing energy consumption. In this paper, the main goal and most recent energy efficient topology control algorithms in WSNs and ad hoc network are classified and studied according to their specific goals.

Heterogeneous small cell networks (HSCN), as a promising paradigm to increase end-user data rates and improve the overall capacity, is expected to be a key cellular architecture in 5G wireless networks. However, energy consumed in HSCN is considerable due to the massive use of small cells. In this paper, we investigate the energy consumption issue which stems from the enormous number of running small cell base stations (SBSs) deploying in the HSCN. We first propose power consumption models so as to characterize the active state and the idle state of SBSs, respectively. Then two sleep modes for SBSs tier, i.e. random sleep mode and load-awareness dynamic sleep mode, are proposed. The random sleep is designed based on a binomial distribution of the SBS operation probability. Through the analysis on activeness of SBSs, we define the operation probability for the SBS applying the proposed dynamic sleep mode is associated to its traffic load level. The closed-form expressions of success probability for coverage, which is used to decide whether an active user can connect to a SBS successfully, are derived for the proposed sleep modes. Energy consumption minimizations are presented for the two proposed sleep modes under the success probability constraint. Simulation results prove the effectiveness of the proposed two sleep modes. Different energy saving gains can be achieved via using of the energy saving strategy. The superior of the dynamic sleep mode by comparing the random sleep is also verified in terms of energy consumption, success probability and power efficiency.

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.

We consider the problem of maximizing the secure connectivity in wireless ad hoc networks, and analyze complexity of the post-deployment key establishment process constrained by physical layer properties such as connectivity, energy consumption and interference. Two approaches, based on graph augmentation problems with nonlinear edge costs, are formulated. The first one is based on establishing a secret key using only the links that are already secured by shared keys. This problem is in NP-hard and does not accept polynomial time approximation scheme PTAS since minimum cutsets to be augmented do not admit constant costs. The second one extends the first problem by increasing the power level between a pair of nodes that has a secret key to enable them physically connect. This problem can be formulated as the optimal key establishment problem with interference constraints with bi-objectives: (i) maximizing the concurrent key establishment flow, (ii) minimizing the cost. We prove that both problems are NP-hard and MAX-SNP (i.e., it is NP-hard to approximate them within a factor of 1 + ε for ε > 0) with a reduction to MAX3SAT problem.KeywordsSensor NodeWireless Sensor NetworkBoolean FormulaInterference ConstraintAuxiliary GraphThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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

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

This paper describes a new digital wireless data acquisition system that cam be used to measure electro-magnetic interference (EMI) in power stations or other similar harsh environments. It comprises of a remote acquisition unit (RAU), a wireless data communication network (WDCN) and a PC-based control platform. Using digital technology, the system transmits a signal (transient or steady state) of short duration & wide band through a narrowband channel over a longer duration. The RAU captures and stores the EMI signals and sends the information to the control platform at a convenient time, using the wireless data communication network. The wireless data communication network acts as a bi-directional data communication link between the RAU & the control platform. It is based on Bluetooth technology and has a point-to-multipoint topology. The RAU serves as the acquisition function of a digital storage oscilloscope (DSO) while the control platform carries out the display & control function of a DSO. The whole system, as such, may be regarded as a 'computerised wireless oscilloscope'.

Wireless body area networks WBANs are an exciting technology that will revolutionize physiological monitoring in the coming years. However, the widespread deployment of WBANs is restricted by steep energy limitations. Furthermore, they require acute security measures to protect user medical data. We aim to measure the energy consumption of a cellphone as it transmits and encrypts data in a mock WBAN scenario. We evaluated the impact of various design parameters in an effort to discover the ideal WBAN operational protocols. In conclusion, we recommend an optimal file size strategy, data communication network, and encryption algorithm that minimize energy consumption and enhance WBAN operation. Copyright © 2015John Wiley & Sons, Ltd.

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Ad hoc network is an extensive research area in wireless communications nowadays, and is particularly studied under energy constraints, since energy consumption of the network should be minimized. The physical layer (power control), link layer (scheduling), and network layer (routing) are known to have great impact on network performance as well as on power consumption. In this paper, we present an optimization problem that there may exist a power vector that minimizes the overall transmission power of the network which at the same time supports a particular data rate on each link and satisfies the SINR and maximum transmission power constraints at each node. We also formulate an optimization problem where we use both the energy consumed of each node in the routing path and the delay associated on each link as link costs. We provide numerical examples for our schemes and relationships between the parameters. An overview of our intended routing algorithm for ad hoc networks is also given as a preliminary step towards our distributed joint scheduling, power control and routing algorithm for ad hoc networks using cross layer approach.

Wireless network technology enables computing devices to communicate with each other without any physical medium. Compared with wired networks, wireless communication provides better connectivity and mobility, which allows mobile devices to access other local area networks or the Internet at anytime and anywhere. The benefits of flexible routing, global connectivity and a highly adaptive potential make mobile ad-hoc networks (MANET) suitable for a wide range of applications in both military and commercial environments, such as battlefields, disaster relief operations, mobile device/ personal networking, mobile information sharing and vehicular networks (Kant et al., 2005); (Liu et al., 2007). However, maintaining security in wireless ad-hoc networks is quite challenging. First, unlike wired networks that at least have some degree of physical protection, wireless communication over radio waves lacks defined and restricted boundaries. Anyone can connect to the network as long as the transmitted signal strength is strong enough to cover the area (Chan et al., 2005), and therefore, security attacks on data communication, such as passive eavesdropping, packet injection or even violations of confidentiality are widespread. Second, the end-to-end communication in MANET cannot rely on any fixed infrastructure, such as a base station or access points (AP); thus, existing security protocols that are based on a centralized or infrastructure-based network environment will not work in this mobile environment (Hubaux et al., 2001). Third, in order to achieve better network throughput in such a highly dynamic environment, the default routing protocol does not implement any security protection during end-to-end communication. In addition, the trust relationships between each node are very low as a consequence of the frequently changing topology and membership. Because of this, many attacks can be launched against the routing protocol, giving hackers a major opportunity to insert themselves as one of the cooperative nodes in the network. Therefore, the security protection that is used to ensure the integrity of the mobile ad-hoc network should not only repel external attacks, but also prevent internal attacks launched against the network from any compromised node. Most security mechanisms rely on data encryption, which is a message combined with a secret key to generate a ciphertext that cannot be revived without the original key. This encryption mechanism can prevent any unauthorized user from gaining access to the secured communication. However, a fixed secret key is vulnerable to deciphering by

In the past few years wireless sensor networks have received a greater interest in application such as disaster management, border protection, combat field reconnaissance and security surveillance. Sensor nodes are expected to operate autonomously in unattended environments and potentially in large numbers. Failures are inevitable in wireless sensor networks due to inhospitable environment and unattended deployment. The data communication and various network operations cause energy depletion in sensor nodes and therefore, it is common for sensor nodes to exhaust its energy completely and stop operating. This may cause connectivity and data loss. Therefore, it is necessary that network failures are detected in advance and appropriate measures are taken to sustain network operation. In this paper we extend our cellular architecture and proposed a new mechanism to sustain network operation in the event of failure cause of energy-drained nodes. In our solution the network is partitioned into a virtual grid of cells to perform fault detection and recovery locally with minimum energy consumption. Specifically, the grid based architecture permits the implementation of fault detection and recovery in a distributed manner and allows the failure report to be forwarded across cells. The proposed failure detection and recovery algorithm has been compared with some existing related work and proven to be more energy efficient.

Wireless sensor networks (WSN) include numerous sensor nodes deployed to collect data efficiently. Energy constraints and unreliable communication remain critical challenges in WSNs. This research proposes a Fuzzy Trust‐based Hybrid Levy Snake Optimization model to improve energy efficiency, scalability, and reliability in WSNs. The Fuzzy Trust‐based Hybrid Levy Snake Optimization model includes cluster formation, optimal cluster head selection using combined levy flight and snake optimization, and a fuzzy trust mechanism to enhance data security and minimize energy consumption. The algorithm identifies secure and energy‐efficient routing paths by evaluating trust factors and optimizing cluster head selection based on parameters like energy and delay. Extensive experiments validate the Fuzzy Trust‐based Hybrid Levy Snake Optimization model, demonstrating superior performance compared to traditional approaches. The Fuzzy Trust‐based Hybrid Levy Snake Optimization model achieves a packet delivery ratio of 98.5%, throughput of 98.7%, and network lifetime of 9500 ms while reducing energy consumption to 83 J and end‐to‐end delay to 0.01 ms. These findings highlight the Fuzzy Trust‐based Hybrid Levy Snake Optimization model's effectiveness in addressing energy and trust challenges in WSNs, offering a robust solution for secure and efficient data transmission.

Grant management procedure for energy saving TDM-PONs