Transactions on Computational Science XXIX

This paper analyzes the reasons of appearance of non - Byzantine and Byzantine fault types in redundant computer systems. The proposed approach is based on analysis of the relationship between the modes of intercomputer communications and fault types. This analysis allows the users to design the redundant computer systems in such a way that Byzantine faults cannot appear. Consequently, designing the redundant computer systems, in which Byzantine faults cannot appear, allows the designers to increase the degree of reliability by preventing the masking of any forms of appearance of faults and by decreasing the time period of checkpoints. In addition, this approach decreases the cost of software and hardware involved in the execution of fault-tolerant procedures.

In the midst of emerging technology, reversible computing is promising due to its application in the field of quantum computing. The computing hardware plays a significant role in digital signal processing (DSP) and multimedia application; one such major computing hardware is multiplier. It is a practice to choose multiplier to compute square of an operand. Multiplication hardware requires more elementary computations which leads to performance degradation in terms of reversible performance metrics like quantum cost, garbage outputs, and ancilla inputs. Ancilla inputs and garbage outputs are overhead bits in a reversible circuit. Reversible quantum computers of many qubits are extremely difficult to realize, thus we propose garbageless circuit design for reversible square computation. The proposed design methodology is based on recursion. Recursion technique is adapted from Karatsuba’s recursive method to compute square of an operand; we designed inverse computation units to retrieve the inputs and obtain garbageless circuit. On comparing proposed circuit design with existing reversible square designs and Karatsuba multiplier design, we observed that our work improves number of input lines which includes data lines and ancilla lines.

In wireless communication, sensing failure, reliability, and fading affects the radio signals. Adaptive threshold and multiple antennas are one of the solutions of such problems. In this paper, authors introduced a novel multiple antennas based centralized spectrum sensing (SS) technique for cognitive radio networks (CRNs). This paper is divided into two parts: part A uses multiple antennas based improved sensing detector (MA_ISD), and part B uses multiple antennas based centralized spectrum sensing (MA_CSS) technique. Now, in the part A: the presented scheme uses two detectors (TD) concept, first one is an energy detector with a single adaptive threshold (ED-SAT) and the second one is an energy detector with two adaptive thresholds (ED-TAT). Both detectors imply multiple antennas, following selection combination to select best signals. The proposed model enhances the detection performance and takes less sensing or detection time. The thresholds are adaptive as they are dependent on noise variance (\( \sigma_{\omega }^{2} \)), and the value of this noise variance changes according to the noise signal. Both the detectors work simultaneously and their output is then fed to a decision device which takes the decision using an OR rule. Results confirm that the presented multiple antennas based improved sensing detector (MA_ISD) technique improves the detection performance by 24.6%, 53.4%, 37.9%, and 49.6%, as compared to existing schemes (i.e. EDT-ASS-2015 scheme, ED and cyclo-2010, adaptive SS-2012, and conventional-ED) scheme at −12 dB signal-to-noise ratio (SNR), respectively, while the number of antennas (N _r ) = 2. Meanwhile, proposed technique also decreases sensing time in the order of 47.0 ms, 49.0 ms, and 53.2 ms as compared to existing schemes (EDT-ASS-2015, Adaptive SS-2012, and ED and Cyclo-2010) scheme at −20 dB SNR respectively. Further, in the part B: cooperative SS (CSS) is introduced in which the local decisions from each cognitive radio are transferred to a fusion center (FC) that decides the final decision and shares the decision to every cognitive radio. It is also found that the proposed detection technique with CSS when a number of cognitive radio (CR) users (k) = 10, and N _r  = 2, achieves detection performance as per IEEE 802.22 at very low SNR i.e. −20 dB.

We describe an innovative Web-based platform to remotely perform complex geometry processing on large triangle meshes. A graphical user interface allows combining available algorithms to build complex pipelines that may also include conditional tasks and loops. The execution is managed by a central engine that delegates the computation to a distributed network of servers and handles the data transmission. The overall amount of data that is flowed through the net is kept within reasonable bounds thanks to an innovative mesh transfer protocol. A novel distributed divide-and-conquer approach enables parallel processing by partitioning the dataset into subparts to be delivered and handled by dedicated servers. Our approach can be used to process an arbitrarily large mesh represented either as a single large file or as a collection of files possibly stored on geographically scattered servers. To prove its effectiveness, we exploited our platform to implement a distributed simplification algorithm which exhibits a significant flexibility, scalability and speed.