Earticle

Many synchronization algorithms for orthogonal frequency division multiplexing (OFDM) systems have been proposed. Among them, the time synchronization algorithm by correlating the training sequence with the local known sequence can obtain good performance with a sharp synchronization peak. Detection threshold is an important and necessary parameter in time synchronization. In this paper, based on this algorithm, we evaluate three different methods of setting threshold and point out one method which performs well when SNR is in large dynamic range. The simulation results are consonant with our theoretic analyses and show that this method is suitable for OFDM systems in multi-path fading channel.

The continuously increasing diffusion of application scenarios requiring pervasive data sensing has lead to the development of novel monitoring solutions leveraging on Heterogeneous Sensor Networks (HSNs). At the moment, only little attention has been dedicated to the design of multi-purposes applications devoted to process, filter and use data from HSNs and aimed at providing composite services to the final users. Most available networks are currently managed by custom stand-alone applications, where many low level details are handled at application level. Actually, this approach presents many drawbacks in terms of system flexibility and adaptability. In such a scenario, the main goal is to decouple application logic from low level implementation details including the HW/SW platform and the programming language. Moreover, the specific units of functionality should be organized into autonomous and connectable modules operating in a distributed computing environment. This paper presents a management framework for rapid and flexible deployment of HSN-based applications based on XMPP/Jabber, a well-known XML-based open-source Instant Messaging protocol. The proposed solution aims to speed up the integration of different software modules into a network of services. The main benefits of the proposed solution include an increase of code reusability, platform independency, system scalability and modularity. The advantages of the proposed approach are demonstrated by presenting three use-cases.

For many applications of sensor networks, it is essential to ensure that messages are transmitted to their destinations within delay bounds and the buffer size of each sensor node is as small as possible. In this paper, we firstly introduce the system model of a mesh sensor network. Based on this system model, the expressions for deriving the delay bound and buffer requirement bound are presented using network calculus theory. In order to balance traffic load and improve resource utilization, three traffic splitting mechanisms are proposed. And the two bounds are derived in these traffic splitting mechanisms. To show how our method applies to real applications, we conduct a case study on a fresh food tracking application, which monitors the food freshness status in real-time during transportation. The numerical results show that the delay bound and buffer requirement bound are reduced while applying traffic splitting mechanisms. Thus the performance of the whole sensor network is improved with less cost.

A black hole attack is a severe attack that can be easily employed against routing in mobile ad hoc networks. A black hole is a malicious node that falsely replies for any route requests without having active route to specified destination and drops all the receiving packets. If these malicious nodes work together as a group then the damage will be very serious. This type of attack is called cooperative black hole attack. In [9], we proposed a solution to identifying and preventing the cooperative black hole attack. Our solution discovers the secure route between source and destination by identifying and isolating cooperative black hole nodes. In this paper, via simulation, we evaluate the proposed solution and compare it with other existing solutions in terms of throughput, packet loss percentage, average end-to-end delay and route request overhead. The experiments show that (1) the AODV greatly suffers from cooperative black holes in terms of throughput and packet losses, and (2) our solution proposed in [9] presents good performance in terms of better throughput rate and minimum packet loss percentage over other solutions, and (3) our solution proposed in [9] can accurately prevent the cooperative black hole attacks.

In this paper, we develop a new beacon-less localization scheme for non-flat surfaces for wireless sensor networks. Simulations are conducted for a Gaussian distribution of nodes about the deployment points on the non-flat terrain, as well as a node deployment corresponding to the terrain surface characteristics. The localization errors for the proposed method, for a non-flat terrain with the Gaussian distribution of nodes and the terrain conforming distribution, are comparable to those in the case of the location discovery scheme in [1] for the flat surface. The localization errors, when the distribution of nodes corresponds to the terrain are slightly larger than when the nodes are normally distributed. The results are applicable to localization in real life wireless sensor networks deployed over non-flat terrains.

The principal focus of this survey is on how to maximize the useful lifetime of ad hoc wireless networks through energy-efficient routing. Most of the studies on energy-aware routing protocols do not provide clear-cut notions about a network’s lifetime and therefore there is a lack of clear objectives in the design of algorithms. Hence, first the operational lifetime of ad hoc networks is defined. Then, published works that give solutions to energy-based problems are analysed by placing emphasis on common characteristics and drawbacks. It is aimed to reveal the factors that influence the depletion of energy in ad hoc networks. This should aid the design of energy-efficient solutions. Load balancing routing protocols are also surveyed as a means for extending a network’s operational lifespan, which is a technique that is overlooked in the literature. The immediate implications that load balancing has for energy consumption are indicated. Subsequently, a classification of load balancing routing protocols is provided along with a summary of load balancing methods that may be useful for efficient energy consumption.

Small and medium enterprises (SMEs) is leaning more on their information technology (IT) infrastructure but they lack the means to secure it appropriately due to financial restrictions, limited resources, and adequate know-how. Many SME managers believe that IT security in their company is basically equivalent to having a firewall and updating the antivirus software regularly. Strategic policies, information theft, business continuity, access controls, and many other aspects are only dealt with in case of security incidents. To improve security in a company holistically, four levels (organizational level, workflow level, information level, and technical level) need to be addressed. Parts of existing standards are useful to address issues on the organizational level; Pipkin’s approach is especially useful for SMEs. Modeling of business processes and taking security/dependability into account can improve reliability and robustness of the workflow level. On the information level, role-based access control is state-of the art.

Information Security is very important in e-Business. Previous IT governance frameworks have not given the connection between IT governance and e-business security sufficient attention. This paper identifies various levels of governance followed by a focus in the roles of information technology (IT) governance with reference to information security for today’s electronic business (e-business) environment. The emergence of and dependence on new technologies, like the Internet, have increased exposure of businesses to technology-originated threats and have created new requirements for security management and governance. We proposed a model achieves the necessary integration through risk management in which the tensions between threat reduction and value generation activities have to be balanced.