Power Control for Cognitive Radio Networks: A Game Theoretic Approach

In communication industry one of the most rapidly growing area is wireless technology and its applications. The efficient access to radio spectrum is a requirement to make this communication feasible for the users that are running multimedia applications and establishing real-time connections on an already overcrowded spectrum. In recent times cognitive radios (CR) are becoming the prime candidates for improved utilization of available spectrum. The unlicensed secondary users share the spectrum with primary licensed user in such manners that the interference at the primary user does not increase from a predefined threshold. In this paper, we propose an algorithm to address the power control problem for CR networks. The proposed solution models the wireless system with a non-cooperative game, in which each player maximize its utility in a competitive environment. The simulation results shows that the proposed algorithm improves the performance of the network in terms of high SINR and low power consumption.

     

Auto-tuning of PID controller according to fractional-order reference model approximation for DC rotor control

This paper presents a stochastic, multi-parameters, divergence optimization method for the auto-tuning of proportional–integral–derivative (PID) controllers according to a fractional-order reference model. The study aimed to approximate the step response of the real closed-loop flight control system to the response of a theoretical reference model for a smoother and more precise flight control experience. The proposed heuristic optimization method can auto-tune a PID controller without a precise plant model. This is very advantageous when dealing with model and parameter uncertainties in real control application and practice. Experimental study confirms the reference model driven auto-tuning of the DC rotor prototype.     

Development of Optical Code Division Multiple Access Based System Using Spectral Amplitude Coding via Fiber Bragg Gratings (FBGs)

Wireless Personal Communications - The multiple user’s based transmission systems are developed in the past using various multiple access techniques for fibre optic communications. Among...     

Solution Processing Route to Multifunctional Titania Thin Films: Highly Conductive and Photcatalytically Active Nb:TiO2

This paper reports the synthesis of highly conductive niobium doped titanium dioxide (Nb:TiO₂) films from the decomposition of Ti(OEt)₄ with dopant quantities of Nb(OEt)₅ by aerosol‐assisted chemical vapor deposition (AACVD). Doping Nb into the Ti sites results in n‐type conductivity, as determined by Hall effect measurements. The doped films display significantly improved electrical properties compared to pristine TiO₂ films. For 5 at.% Nb in the films, the charge carrier concentration was 2 × 10²¹ cm^?3 with a mobility of 2 cm² V^–1 s^–1 . The corresponding sheet resistance is as low as 6.5 Ω sq^–1 making the films suitable candidates for transparent conducting oxide (TCO) materials. This is, to the best of our knowledge, the lowest reported sheet resistance for Nb:TiO₂ films synthesized by vapour deposition. The doped films are also blue in colour, with the intensity dependent on the Nb concentration in the films. A combination of synchrotron, laboratory and theoretical techniques confirmed niobium doping into the anatase TiO₂ lattice. Computational methods also confirmed experimental results of both delocalized (Ti⁴⁺) and localized polaronic states (Ti³⁺) states. Additionally, the doped films also functioned as photocatalysts. Thus, Nb:TiO₂ combines four functional properties (photocatalysis, electrical conductivity, optical transparency and blue colouration) within the same layer, making it a promising alternative to conventional TCO materials.     

An Energy Efficient Message Scheduling Algorithm Considering Node Failure in IoT Environment

Advancements in the area of computing and the networking gave birth to a new concept Internet of Things (IoT). This can be thought as “network of future” connecting diverse objects/things together. The focus is on scheduling the messages in an IoT environment where things/sensors are clustered into IoT subgroups, each subgroup has a message broker that delivers the messages originated from the group to the ultimate receiver of the sensed data. The message scheduler works at the broker level to decide which message to be transmitted first. This scheduling improves the overall IoT system efficiency. Furthermore to keep the flow of services provided by these things/sensors continuous and non-disruptive, the optimal tackling of the faulty or failed nodes has become the salient feature of the proposed scheduling algorithm. The faults or failures identified on time help to initiate recovery or replacement procedures. To find the right level of replacement nodes deployed for the sensor network, we consider the energy a scarce resource and the cost of deployment of the backup nodes as per failure of the node occurring in the underlying environment. In this work we propose an energy efficient recovery and backup node selection for IoT systems followed with energy efficient message scheduling. Simulation results show the effectiveness and efficiency of the proposed message scheduling considering the node failure with recovery and replacement technique.     

A Monolithic Phased Array Using 3-bit Distributed RF MEMS Phase Shifters

This paper presents a novel electronically scanning phased-array antenna with 128 switches monolithically implemented using RF microelectromechanical systems (MEMS) technology. The structure, which is designed at 15 GHz, consists of four linearly placed microstrip patch antennas, 3-bit distributed RF MEMS low-loss phase shifters, and a corporate feed network. MEMS switches and high-Q metal-air-metal capacitors are employed as loading elements in the phase shifter. The system is fabricated monolithically using an in-house surface micromachining process on a glass substrate and occupies an area of 6 cm times 5 cm. The measurement results show that the phase shifter can provide nearly 20deg/50deg/95deg phase shifts and their combinations at the expense of 1.5-dB average insertion loss at 15 GHz for eight combinations. It is also shown by measurements that the main beam can be steered to required directions by suitable settings of the RF MEMS phase shifters.     

Time-variant balanced routing strategy for underwater wireless sensor networks

In the past decade, researchers’ interest in Underwater Wireless Sensors Networks has rapidly increased. There are several challenges facing the lifetime of UWSNs due to the harsh characteristics of the underwater environment. Energy efficiency is one of the major challenges in UWSNs due to the limited battery budget of the sensor nodes. In this paper, we aim at tackling the energy sink-hole problem that especially hits nodes close to the sink when they run out of battery power before other sensors in the network. We prove that we can evenly distribute the transmission load among mobile sensor nodes by letting sensor nodes adjust their transmission ranges. In this paper, we suppose that sensor nodes may adjust their transmission power up to three levels. Consequently, we strive for deriving the optimal load weight for each possible transmission power level that leads to fair energy consumption among all underwater sensors while taking into account the underwater sensors mobility. Performance results show that energy sink-hole problem is overcame and hence the network lifetime is maximized.

     

A modified rain attenuation prediction model for tropical V‐band satellite earth link

Radio wave propagation plays a very important part in the design and eventually dictates performance of space communication systems. Over time, the requirements of satellite communication have grown extensively where higher capacity communications systems are needed. Escalating demands of microwave and millimetre wave communications are causing frequency spectrum congestion. Hence, existing and future satellite system operators are planning to employ frequency bands well above 10 GHz. The challenge in operating at such high frequencies for communication purposes is that there exists stronger electromagnetic interaction between the radio signals and atmospheric hydrometeors. Such instances will degrade the performance of such high frequency satellite communication systems. The development of a revised model for a better‐improved rain fade prediction of signal propagations in tropical region is considered very important. Researchers and engineers can employ the model to accurately plan the future high frequencies satellite services. Copyright © 2014 John Wiley & Sons, Ltd.     

Efficiency calculation of feed structures and optimum number of antenna elements in a subarray for highest G/T

For an antenna array, different feed structure topologies may yield the same radiation characteristics. However, different topologies may result in different efficiency and noise performance. In this paper, parallel arm antenna arrays are analyzed for efficiency and noise temperature using the noise equivalent line length method (NELL) with the number of antenna elements in a subarray as a parameter. It is shown that efficiency of an antenna array feed structure as well as its noise temperature can be calculated using the NELL method. The comparison of the two parameters, efficiency and noise temperature, yield the optimum number of antenna elements in a subarray of a parallel arm antenna array for the highest G/T ratio.     

Azeotrope formation in gasoline–ethanol blends. Part 1 – Impact of nonionic on E10 distillation curve

Blending 10?vol% of ethanol into hydrocarbon base gasoline (HBG) increases significantly the vapour pressure of the blend (E10), and exhibits near-azeotrope behaviour that severely affects the shape of E10 distillation curve. The distillation curves of HBG and E10 fuel blend, were constructed using ASTM D86 distillation data, and the areas under each distillation curve, were calculated through the numerical trapezoid rule (NTR) and calculus definite integration (CDI) methods. Consequently, the area due to azeotrope formation (ADAF), was estimated. In this paper, we present the impact of small concentration of nonionic surfactant on the area under distillation curve (AUDC) of E10 fuel blend and the area due to azeotrope formation (ADAF). Also, the influences of the added surfactant on the volatility criteria of the investigated E10 fuel blend were discussed.