Efficient and practical resource block allocation for LTE-based D2D network via graph coloring

In this paper, we construct a practical framework for efficiently allocating long term evolution (LTE) resource blocks (RB) among the users in a device-to-device (D2D) network. For such network that presumably operates under the LTE cellular network, our aim is to improve the overall throughput of D2D connections using opportunistic or fairness-based approach. Taking the practical considerations into account, our proposed framework allows a number of connections to share a single RB whenever possible, thus utilizing the radio resources. To do so, our solution first identifies a superior set of the interference-free D2D reuse groups via graph modeling and graph coloring approach. In particular, we model a D2D network with a two-overlapping disk graph for which a suitable coloring algorithm is proposed and its performance bound is calculated. Once the reuse groups are known, our solution optimizes the RB allocation among these groups based on their reported channel condition as well as the scheduling criterion, whether it is fairness-based or opportunistic. Through numerical experiments, we show that our solution can significantly improve the throughput performance of a D2D network.     

Flexible Prime‐Field Genus 2 Hyperelliptic Curve Cryptography Processor with Low Power Consumption and Uniform Power Draw

This paper presents an energy‐efficient (low power) prime‐field hyperelliptic curve cryptography (HECC) processor with uniform power draw. The HECC processor performs divisor scalar multiplication on the Jacobian of genus 2 hyperelliptic curves defined over prime fields for arbitrary field and curve parameters. It supports the most frequent case of divisor doubling and addition. The optimized implementation, which is synthesized in a 0.13 μm standard CMOS technology, performs an 81‐bit divisor multiplication in 503 ms consuming only 6.55 μJ of energy (average power consumption is 12.76 μW). In addition, we present a technique to make the power consumption of the HECC processor more uniform and lower the peaks of its power consumption.     

Recognition of the Communication Signals Using Particle Swarm Optimization and Support Vector Machine Based on the Multi-Resolution Wavelet Analysis

Automatic recognition of the communication signals plays an important role for various applications. This paper presents a novel intelligent system for recognition of digital communication signals. This system includes three main modules: feature extraction module, classifier module and optimization module. In the feature extraction module, multi-resolution wavelet analysis is proposed for extraction the suitable features. In the classifier module, a multi-class support vector machine (SVM) based classifier is proposed as the multi-class classifier. For optimization module, a particle swarm optimization algorithm is proposed to improve the generalization performance of the recognizer. In this module, it is optimized the SVM classifier design by searching for the best value of the parameters that tune its discriminant function, and upstream by looking for the best subset of features that feed the classifier. Simulation results show that the proposed hybrid intelligent system has high performance even at very low signal to noise ratios (SNRs).     

On Time-Frequency Resource Leasing in Cognitive Radio Networks

In this work, we introduce a new spectrum leasing based cognitive radio for OFDM-based primary/secondary networks. More precisely, we propose a new leasing scheme both in time and frequency domains in a network composed of a primary transmission and some secondary (cognitive) users forming a cooperative relay network. In the proposed scheme, the primary user decides to lease a part of its available resources (time and frequency) to a selected set of relays, with the aim of increasing its link reliability. The selected relays use a part of the leased resources for relaying the primary signal, and in counterpart, they are allowed to exploit the rest of the frame for their own data transmission. By defining appropriate cost functions, the proposed algorithm decides whether it is of advantage for the primary user to cooperate with the relay network or not. Moreover, if cooperation is advantageous for the primary network, the algorithm selects the optimal amount of the time-frequency resources (number of OFDM symbols and subcarriers) that are involved in the cooperation process. Simulation results show that by using the proposed relaying scheme, both primary and secondary (relay) networks can take advantage in terms of achievable data rates compared to classical leasing systems.     

Optimum pumping configuration for L-band EDFA incorporating ASE pump source

L-band gain improvement through usage of secondary pumping sources in the form of amplified spontaneous emission (ASE) was conducted. A simulation of the three-level rate equation that precedes the experimental approach provides a limited overview of the behavior of various inputs into the active medium-the erbium-doped fiber. Gain improvement as high as 6 dB was attained while incurring minimal noise figure penalty; in this case as low as 1 dB. For an L-band amplifier system employing ASE to improve gain, pumping the system counterdirectionally with ASE while the 980- or 1480-nm pumps are being used in a copropagating configuration would yield the best overall performance in terms of gain.     

BN-C Hybrid Nanoribbons as Gas Sensors

The effects of carbon monoxide (CO) and ammonia (NH₃) molecules adsorption on the various composites of boron nitride and graphene BN-C hybrid nanoribbons are investigated using the non-equilibrium Green’s function (NEGF) technique based on density functional theory (DFT). The effects of adsorption with possible random configurations on the average of the density of states (DOS), transmission coefficient, and the current–voltage (I–V) characteristics are calculated. The results indicate that, by embedding armchair graphene nanoribbon (AGNR) with boron nitride nanoribbon (BNNR), the various electronic properties can be observed after gas molecule adsorption. The electronic structure and gap of hybrids system is modified due to gas adsorption, and the systems act like the n-type semiconductor by NH₃ molecule adsorption. The hybrid structures due to their tunable band gap are better candidates for gas detecting compared to the pristine BNNRs and AGNRs.     

A theoretical discussion on the foundation of Stone??s blind source separation

This paper discusses the theoretical foundation of Stone’s BSS (Stone in Neural Comput 13:1559–1574, 2001; Stone in Independent Component Analysis: A Tutorial Introduction, A Bradford Book, London, 2004), and it proposes a novel BSS approach based on second-order statistics of the responses of two different linear filters to source signals. The proposed approach which includes Stone’s BSS as a special case helps us to understand how generalized eigenvalue decomposition (GEVD) concludes separating vectors in Stone’s BSS. It obtains the separating vectors by simultaneous diagonalization of covariance matrices of two different linear filters responses to the mixtures. The two employed linear filters are selected dependent on source signals structures under the assumption that they have different responses to source signals. Here, two FIR filters with coefficients selected in an opposite probabilistic way have been suggested for the proposed BSS. The proposed BSS method has been compared with Stone’s BSS, SOBI and AMUSE over speech and image mixtures in different noise levels.     

Available and Waiting Times for Cognitive Radios

Cognitive radios (CRs) have been recently proposed for the problem of spectrum scarcity. The principle of CRs?? operation is based on the opportunistic access to the frequency spectrum mainly dedicated to primary users (PUs). The statistical time pattern of PUs?? channel usage and arrival can affect the usability of specific frequency bands for CRs. In this note, the effect of the arrival rate and channel holding time of PUs on the available times for CRs is analyzed. To this end, first, based on Poissonian arrivals, the available time for CRs is calculated. Then, assuming a gamma distribution for the inter-arrival times and a uniform distribution of channel holding time of PU in these intervals, the probability density function and moments of the available time for CRs are derived. Next, the effect of PUs statistical parameters on the average number of packets and the average symbol rate that a CR can transmit is analyzed. Also, taking that CR needs at least T seconds, the average waiting time is calculated.     

A Robust Analytical Model of Mobile IP Handoff with Multiple Traffic Profiles

Mobile IP has been developed to provide the continuous information network access to mobile users. The performance of Mobile IP mobility management scheme is dependent on traffic characteristics and user mobility. Consequently, it is important to assess this performance in-depth through these factors. This paper introduces a novel analytical model of handoff management in mobile IP networks. The proposed model focuses on the effect the traffic types and their frame error rates on the handoff latency. It is derived based on general distribution of both successful transmission attempts and the residence time to be applicable in all cases of traffic characteristics and user mobility. The impact of the behavior of wireless connection, cell residence time, probability distribution of transmission time and the handoff time is investigated. Numerical results are obtained and presented for both TCP and UDP traffics. As expected, the reliability of TCP leads to higher handoff latency than UDP traffic. It is shown that, higher values of FER increase the probability of erroneous packet transfer across the link layer. A short retransmission time leads to end the connection most likely in the existing FA; however a long retransmission time leads to a large delivery time. The proposed model is robust in the sense that it covers the impact of all the effective parameters and can be easily extended to any distribution.