REV Journal on Electronics and Communications
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A New High Performance Decoder for LDPC Codes
Get PDFThe article introduces a new decoder for LDPC codes based on the general check matrix and soft syndrome. Simulation result shows that the new decoder can improve the performance of LDPC codes. Compared with some other improvements, the new decoding algorithm is simpler, and it can detect errors and be applied to great length LDPC codes
On The Performance of Underlay Relay Cognitive Networks
Get PDFThe bit error rate (BER) performance of underlay relay cognitive networks in the presence of Rayleigh fading is thoroughly analyzed in this paper. New exact and asymptotic analytic expressions under consideration of both interference power constraint and maximum transmit power constraint are derived in closed-form and are extensively corroborated by Monte-Carlo simulations. These expressions facilitate in evaluating effectively the network performance behaviour in key operation parameters as well as in optimizing system parameters. A multitude of analytical results expose that underlay relay cognitive networks experience the performance saturation phenomena while their performance considerably depends on the number of hops for the linear network model. Additionally, optimum relay position is significantly dependent of maximum transmit power, maximum interference power, and licensee location. Moreover, the appropriate order of locating unlicensees with different maximum transmit power levels can dramatically improve the network performance
A New Approach and Tool in Verifying Asynchronous Circuits
Get PDFResearch in asynchronous circuit approach has been carried out recently when asynchronous circuits are presented more widely in electronic systems. As they are more important in human life, their correctness should be considered carefully. Although there are some EDA tools for design and synthesis of asynchronous circuits, they are lack of methods for verifying the correctness of the produced circuits. In this work, we are about to propose a verification method and apply it in making a new version of the PAiD tool that can enable engineers to design, synthesize and verify asynchronous circuits. Experiments in verifying circuits have been also provided in this work
Modified Tapered Slot-line Antennas for Special Applications
Get PDFTapered slot-line antenna (TSA) is a well known printed end-fire antenna with traveling-wave feature. In order to further improve its performances and extend its functions, several techniques with patents were developed in SEU, and summarized in this article. Here include: grating-loaded TSA for gain enhancement, CPW back-fed TSA for broadening impedance bandwidth, asymmetric TSA structure for beam shaping and optimization, coupled TSA with hybrid network for monopulse beam forming. Both conceptual illumination and simulated/measured results are described
A Comparative Survey on 3D Models Retrieval Methods
Get PDFIn computer vision many studies have been conducted in order to perform the matching and comparison of 3D models of objects. The main goal of matching is to group the models into different categories according to their similarity in order to allow their retrieval for recognition purposes and for further usage. So, in most of the cases, the comparison is run on a large dataset containing various models whether they belong to the same type of object or not and generally having similar or different shapes and poses. The objects’ nature and characteristics are important factors to be taken into consideration before performing the comparison step. We distinguish between two main categories of objects: rigid objects and deformable objects whose treatment and handling differ in the modeling as well as in the comparison phases. In this paper, we will be focusing on the comparison of deformable objects, and thus dealing with objects whose shapes might vary in different instances. For this purpose two main approaches used in the retrieval of 3D deformable models will be reviewed and implemented: the spectral approach and the bag-of-features approach. The deformation or variation in shape involves different aspects depending on the type of object. It could be a change in the posture of an articulated or bendable model, or it could result from a variation (loss or gain) in the total mass leading to a change in the surface and thus in the shape of the object. Even more complex situations occur when both cases are combined together
Improving Delay-Based Data Dissemination Protocol in VANETs with Network Coding
Get PDFIn vehicular ad hoc networks (VANETs), for a large number of applications, the destination of relevant information such as alerts, is the whole set of vehicles located inside a given area. Therefore dissemination with efficient broadcast is an essential communication primitive. One of the families of broadcast protocols suitable for such networks, is the family of delay-based broadcast protocols, where farthest receivers retransmit first and where transmissions also act as implicit acknowledgements. For lossless networks, such protocols may approach the optimum efficiency. However with realistic loss models of VANET wireless communication, their performance is noticeably degraded. This is because packet losses have a double effect: directly on the amount of successfully received packets and indirectly with implicit acknowledgement misses. In this article, in order to combat the effects of packet losses, we combine delay-based broadcast with network coding, through a new protocol: Delay-based Opportunistic Network Coding protocol (DONC). By design, DONC aims at cancelling the twofold effects of packet and implicit acknowledgement losses. We describe the details of the DONC protocol, and we study its behavior, with realistic models and simulations. Results illustrate the excellent performance of the protocol
Improved Time and Frequency Synchronization Algorithm for 802.11a Wireless Standard based on the SIGNAL Field
Get PDFTime and frequency synchronization in the IEEE 802.11a OFDM (Orthogonal Frequency Division Multiplexing) wireless communication system is addressed in this paper. Usually synchronization algorithms rely only on training sequences specified by the standard. To enhance the synchronization between stations, we propose to extract known information by both the transmitter and the receiver at the IEEE 802.11a physical layer to be then exploited by the receiver in addition to the training sequences. Indeed the parts of the identified SIGNAL field are either known or predictable from the RtS (Request to Send) control frame when the CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) mechanism is triggered jointly to bit-rate adaptation algorithms to the channel. Moreover the received RtS control frame allows the receiver to estimate the channel before time synchronization stage improving then the performance of the proposed synchronization algorithm. Simulation results show that the performance of the proposed synchronization algorithm is improved as compared to existing algorithms
Jamming Impact on the Performance of MIMO Space Time Block Coding Systems over Multi-path Fading Channel
Get PDFThe combined effect of broad/partial band jamming on the analysis performance of multi-input/multi-output (MIMO) space time block coding (STBC) systems over Rayleigh fading channel is often neglected in the literature. To this end, this paper investigates the impact of different kinds of jamming on the performance of MIMO STBC systems. Closed form expressions for the bit error probability (BEP) of the performance of binary phase shift keying (BPSK) STBC communication system over Rayleigh fading channel under the impact of both partial band and broad-band jamming for different number of transmitting and receiving antennas are presented. Computer simulations are provided to validate the theoretical developments. It has been found that the performance of such systems is severely deteriorated in the presence of strong jamming power (with a signal to jamming power ratio less than − 10dB) and the worst scenario occurs in the presence of broad-band jamming