Search

In mobile ad-hoc networks (MANET), nodes are randomly distributed and move freely, and hence the network may face rapid and unexpected topological changes. In this paper, an improved greedy perimeter stateless routing protocol, called “LDAB-GPSR”, is proposed. LDAB-GPSR mainly focuses on maximizing the packet delivery ratio while minimizing the control overhead. In order to accomplish this, two techniques are introduced, the first one is the location prediction technique in which the greedy forwarding strategy is improved by choosing more stable routes for data forwarding. The second one is the adaptive beaconing technique in which the slow start algorithm is employed to adapt the beacon packet interval time based on the mobility of nodes and the data traffic load instead of using the periodic beaconing strategy. These two strategies together improve the overall performance of the GPSR routing protocol. The performance of the new proposed protocol is evaluated by carrying out several NS-2.35 simulation experiments. The simulation results show that LDAB-GPSR protocol outperforms the GPSR+Predict protocol in terms of packet delivery ratio, control traffic overhead, end to end delay, and throughput. The ratios of enhancement approaches 40%.

In this paper, a backup protection scheme is presented. The proposed scheme uses the concept of a cognitive radio-based wireless sensor network to implement a protection scheme without the need for conventional electric wires and/or optical fiber between current and voltage transducers, control panels, and circuit breakers. The proposed scheme uses unlicensed spectrum channels by applying spectrum sensing and frequency allocation algorithms that are used in cognitive radio based systems. The importance of the proposed scheme comes from its cost effectiveness compared to the Ethernet communication both wired and wireless if the data transfer and message exchange is done using cognitive radio_based communication for relatively long distances. The proposed scheme utilizes cognitive radio-based communication network to convey analog and digital signals within a substation. In this way, it saves the cost of the copper wires and/or optical fiber that would be used to transmit digital and analog signals. Further, it does not require the expensive spectrum licenses that would have been purchased if Ethernet long-distance wireless communications are utilized. To assess the benefits/challenges related to the application of cognitive radio_based communication, a detailed and realistic modeling of both power systems and cognitive radio_based communication systems is performed simultaneously. The proposed scheme is simulated using MATLAB/Simulink and performance of the proposed scheme was investigated under different communication scenarios.

Quantum Computing hopefully is the future of computing systems. It still on its first steps. The development of some quantum algorithms gives the quantum computing a boost on its importance. These algorithms (such as Shor’s and Grover’s algorithms) proved to have superior performance over classical algorithms [1-4]. The recent findings, that quantum error correction can be used, showed that the decoherence problem can be solved and hence the quantum computers can be realized [5-7]. The quantum algorithms are based on the use of special gates applied on one, two or more qubits (quantum bits). The classical computer uses different gates (NOT, AND, NAND, OR and XOR). Quantum gates are in many aspects different from classical gates where all gates must be reversible. This makes the quantum gates act as 2x2 transformation operators, where we have n input qubits and n output qubits. To understand the quantum bits and gates we describe the group of amplitudes that describes the state of a quantum register as a vector. A qubit with state 0 , which is

The Threshold-based Low-energy Adaptive Clustering Hierarchy (T-LEACH) protocol declares that cluster heads do not have to turn over every round but rather every batch of rounds. In other words, nodes keep serving as cluster heads as long as their energy is higher than a threshold energy. This article imposes upon major drawbacks of T-LEACH protocol and presents a Modified Threshold-based Cluster Head Replacement (MT-CHR) protocol. In the MT-CHR protocol, a new probability of being a cluster head, for any node in any round, has been proposed which agrees fairly with the assumptions introduced in LEACH protocol. Moreover, a new expression for threshold energy is proposed in which delaying the first node death and avoiding any data loss are taken into consideration. The performance of MT-CHR is evaluated using alive nodes, network lifetime, as well as network utilization performance metrics. The results are further compared with those obtained importantly from LEACH and T-LEACH protocols and the contributions of MT-CHR protocol are extremely impressive. As far as the real sensor network is concerned, the MT-CHR protocol is highly applicable and very effective as long-lasting networks are ascertained.

Over the previous decades, a need has emerged to empower human-machine communication systems, which are essential to not only perform actions, but also obtain information especially in education applications. Moreover, any communication system has to introduce an efficient and easy way for interaction with a minimum possible error rate. The keyboard, mouse, trackball, touch-screen, and joystick are all examples of tools which were built to provide mechanical human-to-machine interaction. However, a system with the ability to use oral speech, which is the natural form of communication between humans instead of mechanical communication systems, can be more practical for normal students and even a necessity for arm-disabled students who cannot use their arms to handle traditional education tools like pens and notebooks. In this paper, we present a speech recognition system that allows arm-disabled students to control computers by voice as a helping tool in the educational process. When a student speaks through a microphone, the speech is divided into isolated words which are compared with a predefined database of huge number of spoken words to find a match. After that, each recognized word is translated into its related tasks which will be performed by the computer like opening a teaching application or renaming a file. The speech recognition process discussed in this paper involves two separate approaches; the first approach is based on double thresholds voice activity detection and improved Mel-frequency cepstral coefficients (MFCC), while the second approach is based on discrete wavelet transform along with modified MFCC algorithm. Utilizing the best values for all parameters in just mentioned techniques, our proposed system achieved a recognition rate of 98.7% using the first approach, and 98.86% using the second approach of which is better in ratio than the first one but slower in processing which is a critical point for a real time system. Both proposed approaches were compared with other relevant approaches and their recognition rates were noticeably higher.

Peer-to-Peer (P2P) networks face the challenge of frequent pollution attacks. In such attacks, malicious peers pollute the network by sharing mislabeled, corrupt or infected content in an attempt to disrupt the system and waste network resources. When faced by such phenomenon, regular peers get discouraged from participating in the P2P network as they find less value in the system. In this work, we investigate the amount of resources required to restrain pollution attacks by means of content validation. We introduce multiple adaptive techniques that can minimize the spread of polluted content, while at the same time reduce the cost of content validation for peers participating in the network. Furthermore, the proposed pollution-restraint techniques are resistant to collusion from malicious peers, and they do not contribute to excessive communication overhead in the P2P network.

Cognitive radio networks (CRNs) open up the underutilized parts of the licensed spectrum for secondary reuse, so long as this secondary access does not cause harmful interference to the licensed users. Being able to run CRNs in a completely decentralized manner, as opposed to centralized operation, can be quite advantageous, because it avoids the complexity and single point-of-failure issues that arise from the presence of a central controller, and also eliminates the difficult step of establishing and maintaining a common control channel, which can suffer from saturation and malicious attacks. To that end, we propose in this paper a novel decentralized spectrum allocation technique for CRNs that not only provides great performance in terms of high throughput, excellent fairness, and minimal interference between cognitive users but also provides very stable network operation, in which cognitive users do not have to switch their operating frequency quite regularly. This is achieved by systematically observing the history of the spectrum usage to determine the proper channel assignment in the CRN. Our proposed technique is intuitive, is completely decentralized, and allows for quick reaction to changes in the CRN, such as when the primary users licensed to use the spectrum are suddenly activated.

Cognitive radio is an emerging wireless technology that is envisaged as a solution to the spectrum scarcity issue. To improve spectrum utilization, cognitive (unlicensed) wireless users are assigned an opportunistic access to vacant channels on the condition they avoid interference with primary (licensed) users. In this paper we present an impressive design of a low complexity and high efficiency dynamic spectrum access technique for cognitive radio networks. This spectrum assignment algorithm does not require central controllers nor the pre-establishment and maintenance of common control channels. Yet, it can provide throughput and fairness levels that approach the performance of centralized systems. In addition, the proposed technique reacts extremely well to disturbances in the cognitive radio network configuration, including when primary users are activated, or when newcomer cognitive users join the network. Furthermore, we present in this work an analytical model that can be used to provide quick predictions of the performance of our proposed algorithm.

A novel approach to managing a fully distributed cognitive radio network (CRN) is presented. This approach builds on the concept of history-based spectrum access, in which cognitive base stations (BSs) independently estimate the system load using history records and adaptively swap their occupied spectrum bands to ensure allocation fairness and high overall throughput. In addition, cognitive BSs monitor primary user (PU) behavior in order to avoid interfering with active PUs. In this work, we address two issues that afflict history-based access: the first is the high cost of the sensing devices needed at each cognitive BS to be able to independently draw conclusions about the status of the CRN and the second is the unreliability inherent in practical sensing hardware (such as energy detectors). Simulation results show that the proposed technique manages to solve the two abovementioned issues without any noticeable drop in performance and without sacrificing the distributed nature of the protocol.

With the development of internet technologies and communication services, message transmissions over the internet still have to face all kinds of security problems. Hence, how to protect secret messages during transmission becomes a challenging issue for most of current researchers. It is worth mentioning that many applications in computer science and other related fields rely on steganography and watermarking techniques to ensure information safety during communication. Unlike cryptography that focuses on scrambling the secret message so that it cannot be understood, the main objective of steganography and watermarking is to communicate securely in such a way that the hidden data are not visible to the observer. In other words, it seeks for the imperceptibility of stego-images quality to an unintended party through embedding efficiently the secret message in a digital media such as image, video, or audio. In this paper, we propose a new steganographic method to embed the secret data inside a cover image based on least-significant-bit (LSB) replacement method. The embedding process predominantly concentrates on distributing the secret message inside one share of a color image to appear like a 3D geometric shape that is constructed according to well-analyzed geometric equations. The dimensions of the geometric shape are determined pursuant to the size of secret message. Data distribution process makes our method to be of a great interest as of being so difficult for the hackers or intruders to reconstruct the shape from stego-images, thereby the security is improved. Furthermore, we compare the performance of our approach with two other relevant approaches in terms of peak signal-to-noise ratio (PSNR) and payload. The contribution of our approach was immensely impressive.DOI: http://dx.doi.org/10.5755/j01.itc.44.3.8949

There are many existing clustering protocols that aim at making the sensor network stay functioning longer out of which Low-Energy Adaptive Clustering Hierarchy (LEACH) and Threshold-based LEACH (T-LEACH) protocols. T-LEACH protocol takes advantage of LEACH main deficiency, which is about having high control overhead. In other words, T-LEACH proposes that cluster heads do not have to turn over every round but rather every batch of rounds. Nodes will keep serving as cluster heads as long as their energy is higher than a threshold energy. This article imposes upon major drawbacks of T-LEACH and proposes a Modified Threshold-based Cluster Head Replacement (MT-CHR). In MT-CHR, a new probability of being a cluster head, for any node in any round, has been proposed which agrees fairly with the assumptions introduced in LEACH protocol.

Most of the schemes that were proposed to improve the performance of transmission control protocol (TCP) over mobile ad hoc networks (MANETs) are based on a feedback from the network, which can be expensive (require extra bandwidth) and unreliable. Moreover, most of these schemes consider only one cause of packet loss. They also resume operation based on the same stand-by parameters that might vary in the new route. Therefore, we propose two techniques for improving the performance of TCP over MANETs. The first one, called TCP with packet recycling (TCP-PR), allows the nodes to recycle the packets instead of dropping them after reaching the retransmission limit at the MAC layer. In the second technique, which is called TCP with adaptive delay window (TCP-ADW), the receiver delays sending TCP ACK for a certain time that is dynamically changed according to the congestion window and the trip time of the received packet. TCP-PR and TCP-ADW are simple, easy to implement, do not require network feedback, compatible with the standard TCP, and do not require distinguishing between the causes of packet loss. Our thorough simulations show that the integration of our two techniques improves the performance of TCP over MANETs.

Peer-to-peer (P2P) traffic has increased rapidly over the past few years, with file sharing providing the main drive behind such traffic. Therefore, modeling P2P systems and studying their impact on the performance of the underlying network is a vital research topic. In this work we describe a flexible, efficient and easily expandable P2P simulation framework developed for the OPNET simulation package. The framework can be used to study a wide variety of issues regarding the packet-level and/or the flow-level performance of P2P systems, including the impact of cooperation incentives on file dissemination; mobility and quality of service (QoS) support in P2P distribution; and the effects of free-riding, resource pollution, and malicious attacks on P2P networks.

In this work, a model order reduction (MOR) technique for a linear multivariable system is proposed using invasive weed optimization (IWO). This technique is applied with the combined advantages of retaining the dominant poles and the error minimization. The state space matrices of the reduced order system are chosen such that the dominant eigenvalues of the full order system are unchanged. The other system parameters are chosen using the invasive weed optimization with objective function to minimize the mean squared errors between the outputs of the full order system and the outputs of the reduced order model when the inputs are unit step. The proposed algorithm has been applied successfully, a 10th order Multiple-Input–Multiple-Output (MIMO) linear model for a practical power system was reduced to a 3rd order and compared with recently published work.

This paper introduces a novel variant of the A^@? path planning algorithm, which we call Light-assisted A^@? (or LA^@? for short). The LA^@? algorithm expands less nodes than A^@? during the search process, especially in scenarios where there are complex-shaped obstacles in the path between the start and goal nodes. This is achieved using the concept of (virtual) light which identifies and demotes dead-end paths blocked by obstacles, thus ensuring that the search stays focused on promising paths. Three path planning problems are used to test the performance of LA^@?. These include path finding in a grid cluttered by randomly placed obstacles, robot navigation in a map containing multiple solid walls, and finally mazes. The results of these experiments show that LA^@? can achieve orders of magnitude improvement in performance over A^@?. In addition, LA^@? results in near-optimal solutions that are very close to the optimal path obtained by the conventional A^@? algorithm.

A new cross-layer routing protocol, named Dynamic Packet Guidance (DPG), is introduced for Mobile Ad hoc Networks (MANETs). Simulation results show that DPG is quite useful for usage in dense networks of mobile nodes, with medium-to-high speeds, and low-to-medium load. In these scenarios, DPG provides a superior performance compared to several well-known ad hoc routing protocols. The low end-to-end delay and smaller overhead that DPG achieves in such scenarios positively impacts the scalability of MANETs and reduces the energy requirements of nodes in such networks. DPG also shows immunity to failing nodes, as it operates consistently almost independently of failing nodes up to a certain ratio.

Cooperation incentive mechanisms are an essential ingredient to the success of Peer-to-Peer (P2P) systems as they restraint the phenomenon of free-riding. We introduce an enhancement on reputation-based cooperation incentives used by the eDonkey2000 (ED2K) P2P file sharing network. This enhancement, called History-based Reputation System (HRS), can achieve better detection and control of free-riders, and by doing so enhances the scalability and fairness of the P2P system. HRS does not need the help of dedicated servers and/or central authorities, thus avoiding a single-point of failure. In addition, simulation results show that HRS achieves higher average download rate and smaller average download time for altruistic peers in a file sharing P2P system.

Peer-to-Peer (P2P) traffic has increased rapidly over the past few years, with file sharing providing the main drive behind such traffic. In this work we perform a measurement study of the content shared over the popular BitTorrent P2P file sharing network. We mathematically model the file size distributions of shared files after categorizing them into Audio, Video, Archive and CD image classes. For each of these categories we look into the most popular shared file formats and investigate their file size statistics. This provides an important milestone to building a realistic simulation framework for P2P systems, and for future analytical modeling of P2P networks.

A fully integrated CMOS wideband distributed variable delay line for time array beam-formers is presented. The delay line works over a full difierential mode, and the delay cell function is based on difierential ampliflers with active inductive peaking loads. A delay resolution of 15ps is obtained with a maximum delay capability of 150ps. The designed active delay line provides 3 scanning angles with 8:6 - of spatial resolution. This delay line is applicable for a 4 channel beam-former with an operational bandwidth of 500MHz centered at 5GHz. Our active delay line consumes up to 352mW of power from a 2.5V supply. The circuit is simulated in standard 0.25"m BiCMOS process and occupies 252"m £ 123"m of silicon area.

With the development of internet technologies and communication services, message transmissions over the internet still have to face all kinds of security problems. Hence, how to protect secret messages during transmission becomes a challenging issue for most of the researchers. It is worth mentioning that many applications in computer science and other related fields rely on steganography and watermarking techniques to ensure information safety during communication. In this paper, we propose a new steganographic method to embed the secret data inside a cover image based on least-significant-bit (LSB) replacement method. The embedding process predominantly concentrates on distributing the secret message inside one share of a color image to appear like a 3D geometric shape. The dimensions of the geometric shape are variable pursuant to the size of secret message. Data distribution process makes our method to be of a great interest as of being so difficult for the hackers or intruders to reconstruct the shape from stego-images, thereby the security is improved. Furthermore, we compare the performance of our approach with two other relevant approaches in terms of peak signal-to-noise ratio (PSNR). The contribution of our approach was immensely impressive.

Smart Grids employ wireless sensor networks for their control and monitoring. Sensors are characterized by limitations in the processing power, energy supply and memory spaces, which require a particular attention on the design of routing and data management algorithms. Since most routing algorithms for sensor networks, focus on finding energy efficient paths to prolong the lifetime of sensor networks, the power of sensors on efficient paths depletes quickly, and consequently sensor networks become incapable of monitoring events from some parts of their target areas. In consequence, the design of routing protocols should consider not only energy efficiency paths, but also energy efficient algorithms in general. In this paper we propose an energy efficient routing protocol for wireless sensor networks without the support of any location information system. The reliability and the efficiency of this protocol have been demonstrated by simulation studies where we compare them to the legacy protocols. Our simulation results show that these algorithms scale well with network size and density., {"references":["V.C. Gungor, \"Multimedia Wireless Sensor Networks for Smart Grid\nApplications,\" in IEEE COMSOC MMTC E-Letter, vol. 6, no. 12, pp.9-\n11, 2011.","Emilio Ancillotti, Raffaele Bruno, and Marco Conti, \"The Role of the\nRPL Routing Protocol for Smart Grid Communications,\" IEEE\nCommunications Magazine, Vol.51, no.1, January 2013, pp. 75-83.","S. Shenker, S. Ratnasamy, B. Karp, R. Govindan, and D. Estrin. \"Datacentric\nstorage in sensornets,\" Proc. ACM SIGCOMM Workshop on Hot\nTopics In Networks, 2002.","S. Ratnasamy, B. Karp, L. Yin, F. Yu, D. Estrin, R. Govindan, and S.\nShenker. \"GHT: a geographic hash table for data-centric storage,\"\nProceedings of the ACM Workshop on Sensor Networks and\nApplications, pp. 78--87, Atlanta, Georgia, USA:ACM, September 2002.","Rowstron and P. Druschel, \"Pastry: Scalable, distributed object location\nand routing for large-scale peer-to-peer systems,\" in Proceedings of the\nMiddleware, 2001.","Sylvia Ratnasamy, Paul Francis, Mark Handley, Richard Karp, Scott\nShenker. \"A Scalable Content-Addressable Network,\" In Proceedings of\nthe ACM SIGCOMM, 2001.","Stoica, R. Morris, D. Karger, M. F. Kaashoek, and H. Balakrishnan.\n\"Chord: A Scalable Peer-topeer Lookup Service for Internet\nApplications,\" ACM SIGCOMM 2001, San Diego, CA, August 2001.","Y. Zhao, L. Huang, J. Stribling, S. C. Rhea, A. D. Joseph, and J. D.\nKubiatowicz, \"Tapestry: A resilient global-scale overlay for service\ndeployment,\" IEEE Journal on Selected Areas in communications, vol.\n22, no. 1, pp. 41-53, January 2004.","Karp and H. T. Kung. \"GPSR: greedy perimeter stateless routing for\nwireless networks,\" Proceedings of the 6th annual international\nconference on Mobile computing and networking, Boston,\nMassachusetts, United States, 2000, pages 243-254.\n[10] Rao, S. Ratnasamy, C. Papadimitriou, S. Shenker, and I. Stoica,\n\"Geographic routing without location information,\" in ACM MobiCom,\n2003.\n[11] James Newsome and Dawn Song, \"Gem: graph embedding for routing\nand data-centric storage in sensor networks without geographic\ninformation,\" in SenSys -03: Proceedings of the 1st international\nconference on Embedded networked sensor systems, New York, NY,\nUSA, 2003, pp. 76-88, ACM Press.\n[12] \"FIPS 180-1, Secure Hash Standard.\" U.S. Department of\ncommerce/NIST, National Technical Information Service, Springfield,\nApr. 1995.\n[13] C. Perkins and E. Royer,\"Ad hoc on demand Distance Vector routing,\"\nin proceedings of the 2nd IEEE Workshop on Mobile Computing Systems\nand Applications: (WMCA-99), New Orleans, Louisiana, USA, February\n1999.\n[14] Network Simulator, http://www.isi.edu/nsnam/ns/.\n[15] N. Sarkar, and W. Lol, \"A study of MANET Routing Protocols: Joint\nNode Density, Packet Length and Mobility\", in Proceedings of ISCC '10\nThe IEEE symposium on Computers and Communications, Reccione,\nItaly, June 2010."]}

OBJECTIVE—Latent autoimmune diabetes in adults is type 1 diabetes presenting as non–insulin dependent diabetes. One feature of the selection criteria is time independent of insulin treatment. We examine the validity of this criterion. RESEARCH DESIGN AND METHODS—Patients were recruited in nine European centers, and clinicians reported on criteria for initiating insulin. All patients were tested for GAD antibodies (GADAs) in a central laboratory. We examined time to insulin treatment for GADA-positive patients in six participating centers. RESULTS—There was intercenter variation in the criteria used to initiate insulin. Median time to insulin was 16.15 months (interqartile range 6.7–25.5) in centers with GADA testing compared with 45.6 months (29.5–61.8) in centers without routine GADA testing (P < 0.002). CONCLUSION—Time to insulin should not be used to define patients with LADA because it is dependent on local clinical judgment and the use of laboratory tests for GADA.

Quantum computing promises a leap in performance over classical computing. Its computational power was revealed after the introduction of some quantum algorithms such as Grover's search algorithm. Many classical algorithms especially that deal with Error Correcting Codes are introduced to solve an exhaustive search problem. The quantum techniques promise an optimal search speed that is of special importance when the size of the searched domain is quite large. In this paper we devise the use of quantum search algorithm introduced by Grover to implement the viterbi algorithm (VA). Due to lack of resources and the nature of implementing quantum algorithms, only theoretical results are obtained. The use of quantum search algorithm showed that we can reduce the number of search computations exponentially. For example if the classical VA requires 262144 searching operations for a signalling length of 1024 intervals, the quantum algorithm will need only 512 searching operations when single search quantum viterbi algorithm (SSQVA) is used. And for the multi search quantum viterbi algorithm (MSQVA) it needs 16384 searching operations for the same signalling length.