Sharif Digital Repository

Lifetime is the mos important concern in Wireless Sensor Networks (WSNs) due to limited battery power of sensor nodes. Moreover, a WSN should be capable of timely fulfilling its mission without losing important information in event-critical applications. In this paper, we focus on designing an energy-efficient and energy-aware real-time routing algorithm aiming to explore the long lifetime routing schemes in which delay constraint is satisfied in the presence of lossy communication links. To achieve this goal, our energy-aware forwarding protocol utilizes an optimum distance real-time routing algorithm to minimize energy consumption in unreliable WSNs. Simulation results reveal that the... 

Data aggregation is an effective technique which is introduced to save energy by reducing packet transmissions in WSNs. However, it extends the delay at the intermediate nodes, so it can complicate the handling of delayconstrained data in event-critical applications. Besides, the structure-based aggregation as the dominant data gathering approach in WSNs suffers from high maintenance overhead in dynamic scenarios for event-based applications. In this paper, to make aggregation more efficient, we design a novel structure-free Real-time Data AGgregation protocol, RDAG, using a Real-time Data-aware Routing policy and a Judiciously Waiting policy for spatial and temporal convergence of packets.... 

Presently, the urgency of creating efficient system to tackle natural hazards such as tsunamis, earthquakes, landslides and floods to cite just a few, have originated that Wireless Sensor Networks (WSNs) play an increasingly important role in the natural hazards scenario as an efficient early warning system, sometimes in synergy with satellites-GMES (Global Monitoring Earth Systems) and also with mobile robotics. Their integration into the web scenario, giving rise to the sensor-web technology, provides even more power to the intrinsic strengths of WSNs. The WSNs application in post-disaster scenarios is also an emerging challenging issue. In this paper the fundamental technology concepts of... 

Routing methods and algorithms in "Wireless Sensor Networks" attract researchers' attention a lot recently. In order to find the optimal path in WSNs depending on their type and application, various algorithms are proposed. In this paper, an optimal path finding algorithm based on "Game Theory" is discussed and improved. This algorithm finds a path witch is optimizing network lifetime, load distribution, and path reliability simultaneously  

One of the arising issues in wireless sensor networks is running multiple applications to reduce deployment, administrative and management costs. In this paper we assume a sensor network in which nodes of a group have a set of same applications in their external flash memory that some of them are loaded and running. Occasionally, these applications should be updated for reasons that are manifold ranging from fixing software bugs to retasking. It is often that updates for a subset of applications happen at the same time, for example when a routing protocol shared among a subset of applications is changed. To bring the sensor nodes up to date with the new versions of the applications, existing... 

Mapping and Scheduling are two central and critical steps in design flow of the Networks on Chips (NoCs). They deal with implementation of the applications on NoCs. In this paper a novel energy aware algorithm, called EAMS, for mapping and scheduling of concurrent applications to NoC platforms is developed. It is considered that, the NoC architecture consists of a set of heterogeneous IP cores. The introduced algorithm finds a mapping of the tasks of the application to available IP cores so that the overall energy consumption, meeting task deadlines, is minimized  

In this paper we consider a cooperative communication systems over Rayleigh fading channels. The system utilizes a combination of incremental and selective decode-and-forward (ISDF) relaying protocols. The symbol error rate (SER) of M-PSK modulation for the ISDF protocol is derived. Using an approximation of the SER expression, the optimal power allocation is investigated. In order to reduce the complexity of the receiver, we used a modified version of the ISDF protocol which does not use the storage or retransmission of the first phase signal. We also derived optimal power allocation coefficient for modified ISDF. It has been noted that for the optimal power allocation in the ISDF protocol,... 

Wireless sensor networks include small nodes which have sensing ability; calculation and connection extend themselves everywhere soon. Such networks have source limitation on connection, calculation and energy consumption. So, since the nodes have limited energy in sensor networks, the optimized energy consumption in these networks is of more importance and has created many challenges. The previous works have shown that by organizing the network nodes in a number of clusters, the energy consumption could be reduced considerably. So the lifetime of the network would be increased. In this paper, we used the Queen-bee algorithm to create energy efficient clusters in wireless sensor networks.... 

Aggregation services play an important role in the domain of Wireless Sensor Networks (WSNs) because they significantly reduce the number of required data transmissions, and improve energy efficiency on those networks. In most of the existing aggregation methods that have been developed based on the mathematical models or functions, the user of the WSN has not access to the original observations. In this paper, we propose an algorithm which let the base station access the observations by introducing a distributed method for computing the Principal Component Analysis (PCA). The proposed algorithm is based on transmission workload of the intermediate nodes. By using PCA, we aggregate the... 

Localization of sensor nodes has become a fundamental requirement for many applications over Wireless Sensor Networks (WSNs). In this paper, we propose a range-free approach based on the Received Signal Strength (RSS) changes. A discrete and probabilistic localization method is offered to localize a moving beacon relative to sensor nodes. In this method we came to a more reliable and accurate result without increasing the number of sectors. We achieved a considerable improvement in localization reliability by defining the primary and secondary sectors and utilizing a Kalman approach for making decisions. The decision making process is based on the allocated probabilities given to each of... 

We study the estimation of a Gaussian source by a Gaussian wireless sensor network (WSN) where L distributed sensors transmit noisy observations of the source through a fading Gaussian multiple access channel to a fusion center. In a recent work Gastpar, [ "Uncoded transmission is exactly optimal for a Simple Gaussian Sensor Network", IEEE Trans. Inf. Theory, vol. 54, no. 11, pp. 52475251, Nov. 2008] showed that for a symmetric Gaussian WSN with no fading, uncoded (analog) transmission achieves the optimal performance theoretically attainable (OPTA). In this correspondence, we consider an asymmetric fading WSN in which the sensors have differing noise and transmission powers. We first... 

Wireless Nano-scale Sensor Networks (WNSNs) are very simple and energy restricted networks that operate over terahertz band ranging from 0.1-10 THz, which faces significant molecular absorption noise and attenuation. Given these challenges, reliability, energy efficiency, and simplicity constitute the main criteria in designing communication protocols for WNSNs. Due to its simplicity and energy efficiency, carrier-less pulse based modulation is considered the best candidate for WNSNs. In this paper, we compare the performance of four different carrier-less modulations, PAM, OOK, PPM, and BPSK, in the context of WNSNs operating within the terahertz band. Our study shows that although BPSK is... 

Wireless sensor networks (WSNs) usually consist of many tiny sensor nodes and a Sink. Problems like nodes' misbehavior due to malicious, compromised or selfishness intentions, and WSNs' security vulnerabilities against different attacks due to free and unprotected communications, untrusted and broadcasted transmissions, hostile environments and limited resources, degrade the security and overall performance of WSNs. In another direction, most of the traditional security mechanisms are unsuitable for WSNs. One significant security solution against these problems is Trust Management System (TMS); TMS enhances the security by detecting the nodes' abnormal behaviors; it improves the cooperation... 

Unstructured wireless networks such as mobile ad hoc networks and wireless sensor networks have been rapidly growing in the past decade. Security is known as a challenging issue in such networks, in which there is no fixed infrastructure or central trusted authority. Further, node limitations in processing power, storage, and energy consumption add further complexity to addressing security in such networks. While cryptography has proven to be an effective solution capable of satisfying most network security requirements, it requires the use of efficient key pre-distribution algorithms compatible with the limitation of unstructured wireless networks. Typically, a key pre-distribution... 

Underwater wireless optical communications are an emerging solution to the expanding demand for broadband links in oceans and seas. In this paper, a cellular underwater wireless optical code division multiple-access network is proposed to provide broadband links for commercial and military applications. The optical orthogonal codes are employed as signature codes of underwater mobile users. Fundamental key aspects of the network, such as its backhaul architecture, its potential applications, and its design challenges, are presented. In particular, a promising underwater localization and positioning scheme based on this cellular network is presented. Furthermore, the proposed network is used... 

Wireless sensor networks consist of a large number of nodes which are distributed sporadically in a geographic area. The energy of all nodes on the network is limited. For this reason, providing a method of communication between nodes and network administrator to manage energy consumption is crucial. For this purpose, one of the proposed methods with high performance, is clustering methods. The big challenge in clustering methods is dividing network into several clusters that each cluster is managed by a cluster head (CH). In this paper, a centralized genetic-based clustering (CGC) protocol using onion approach is proposed. The CGC protocol selects the appropriate nodes as CHs according to... 

The paper deals with a new reliable data transport protocol for wireless sensor networks, referred as RDTP. One of the most prominent challenges in wireless sensor networks is reliable transport of data from sensor nodes to sink node. For designing protocols for such networks hardware, some constraining factors associated with energy and processing power must be taken into consideration. There are two generic methods, ARQ and FEC to achieve reliable data transport. Here, a reliable data transport protocol for wireless sensor networks is proposed, in which an efficient moduli set in redundant residue number system has been employed. The modulus set is exploited as a means for adding... 

Key predistribution in sensor networks refers to the problem of distributing secret keys among sensor nodes prior to deployment. Recently, many key predistribution schemes have been proposed for wireless sensor networks. To further improve these techniques, researchers have also proposed to use sensors' expected location information to help predistribution of keying materials. In this paper we propose a lightweight and scalable key establishment scheme for GPS-enabled wireless sensor networks. This scheme has little communication overhead and memory usage. Since communications and computations of key establishment schemes are done only once and when the network is begin initiated, actually... 

SPEED routing algorithm is a service quality based algorithm in which data aggregation dose not happen. In this article, data aggregation has been added to the conventional technique in SPEED algorithm. The idea involves virtual configuration of sensors and specification of an individual ID to the created data by the sensors in each region, then data aggregation in relay node is done by this ID, resulting in less energy consumption, lower traffic and repeated data, an increase in network lifetime and better quality of service. © 2009 IEEE  

We consider the minimization of power consumption in target tracking wireless sensor networks (WSNs) using dynamic modification of tracking interval. In this context, we first analyze the performance of such networks, using a quantitative mathematical analysis. Then we calculate an upper bound for the achievable improvement in total power consumption, when using an adaptive time interval modification algorithm for tracking moving objects with acceleration. Towards this optimum functionality, we propose a novel adaptive algorithm (AHC) to adapt the tracking interval such that it minimizes power consumption while keeping an acceptable accuracy. Simulation results show that using the proposed...