Degradation of the MIMO channel capacity due to additional noises of amplifiers

It is theoretically well known that a multiple input multiple output (MIMO) system can offer higher channel capacity than a conventional wireless system. The MIMO capacity is increased as a function of signal‐to‐noise ratio (SNR) and a number of antenna elements at both the transmitter and receiver. To realize MIMO capability in practical use, the implementation of all electronic devices is necessary to be considered. Amplifiers become the most common devices assembled at the transmitter and receiver with the purpose of overcoming the power loss in the wireless channel. High power amplifier (HPA) and low noise amplifier (LNA) are the special types of amplifiers that are compulsory for the transmitter and receiver, respectively. Both devices have the same function to provide the reliable power gains while adding as little noise as possible. For a MIMO system, the channel capacity sensitively grows as a function of SNR. Therefore, the changes in SNR due to HPA and LNA definitely degrade the system capacity. In this paper, the degradation due to both devices is investigated by taking the gain and noise figure of these amplifiers into account. The new formula of MIMO channel capacity including amplifier characteristics is originally proposed. The results indicate the remarkable consideration on using amplifiers as they may degrade the capacity up to 26%. This can be the guideline for MIMO researchers to spare the capacity margin caused by the additional noises of amplifiers. Copyright © 2008 John Wiley & Sons, Ltd.     

Financing Strategy of Low-Carbon Supply Chain with Capital Constraint under Cap-and-Trade Regulation

Cap-and-trade regulation provides incentives for manufacturers to reduce carbon emissions, but manufacturers’ insufficient capital can disrupt the implementation of low-carbon emission reduction technologies. To alleviate capital constraints, manufacturers can adopt external financing for low-carbon emission reduction investments. This paper studies the independent financing and financing cooperation behavior in a supply chain in which the manufacturer and retailer first implement low-carbon emission reduction technologies and then organize production and sales in accordance with wholesale price contracts. Through comparing the optimal profits and low-carbon emission reduction levels under the independent financing and financing cooperation mode, we come to the following conclusions: (1) Although financing interest increases the cost of the supply chain, manufacturers prefer to invest in reducing carbon emissions rather than buying carbon quotas. (2) When financing independently, a decentralized decision-making mode (MD) is the best choice for manufacturers. (3) In cooperative financing, when the supply chain adopts a decentralized decision-making mode (SD) in which the retailer determines the financing cost-sharing ratio according to their optimal profit, the profits of the supply chain and its members are significantly improved. (4) When manufacturers and retailers adopt a centralized decision-making model (SC) in cooperative financing, they jointly determine the financing cost-sharing ratio and the level of low-carbon emission reduction. If the financing cost-sharing ratio meets a certain threshold range, the profits of manufacturers and retailers achieve Pareto improvement, indicating that this cooperative financing model is effective.     

Powering Mobile Networks with Optimal Green Energy for Sustainable Development

Green wireless networking is an emerging area for many societies, especially academia and industry, in light of economic and ecological perspectives. Empowering wireless infrastructures exploiting green power sources can enhance sustainability due to the adverse effects of conventional power sources and atmospheric circumstances. Moreover, the specific power supply requirements for a base station (BS), such as cost effectiveness, efficiency, sustainability, and reliability, can be met by utilizing technological advances in renewable energy. Numerous drivers and motivators are involved in the deployment of renewable energy technologies and the transition toward green energy. Renewable energy is free, clean, and abundant in most locations throughout the year. In this work, a sustainable optimal stand-alone solar-powered model envisioning green cellular BSs for urban locations in Oman is proposed. This model can extend 24 h uninterrupted power supply support to a cellular BS that fully utilizes an integrated storage device. The system analysis is conducted using a hybrid optimization model for electric renewables (HOMER) based on actual prevailing conditions of the regions and their technical feasibility. The results showed can be achieved operational expenditure savings up to 16%. These outcomes provide a huge benefit to the cellular operators of Oman economically, technically, and ecologically.     

Design of a Low-Cost Air Quality Monitoring System Using Arduino and ThingSpeak

The impact of daily emissions of gaseous and particulate pollutants of machines and industries on human health and the environment has attracted increasing concerns. This impact has significantly led to a notable increase in mortality in the highly industrialized zones. Therefore, monitoring air quality and creating public awareness are important for a safer future, which led the governments globally to invest multi-billion in policymaking and solution stratification to address the problem. This study aims to design a real-time Internet of Things low-cost air quality monitoring system. The system utilizes air quality and carbon monoxide sensors for monitoring gaseous pollutants. Moreover, the system utilizes an Arduino Nano development board equipped with a WiFi module to effectively send readings to a ThingSpeak online channel platform for instantaneous and real-time display of air quality. The ThingSpeak uses HTTP protocols to send emails in raising awareness of poor air quality. The level of concentration is monitored graphically through channels with the help of ThingSpeak to aid remote communication. A threshold value is set. Thus, when pollutants have become unhealthy and harmful, the system trips off an alarm, and e-mail notifications are sent to the officials. The results have shown that the work was successfully implemented a design of a low-cost air quality monitoring system using Arduino and ThingSpeak, showing that an air quality system can be implemented using a low-cost technology, Arduino and ThingSpeak.     

THE DYNAMIC BEHAVIOR OF A BAYONET-TYPE THERMAL DIODE

The time-dependent heat transfer and temperature variation of a bayonet-type thermal diode are theoretically investigated. A one-dimensional analytical model is developed to predict the dynamic behavior of the diode during heating, and a lumped-system approximation is employed for the cooling phase. Results of the analytical model and FLUENT are compared with experimental data of a bayonet thermal diode tested in Utah. Measured solar flux, ambient and room temperatures for a 24-hour period are used as the input data for the analytical model and the numerical calculation. The diode temperature variations predicted by the analytical model and FLUENT are in good agreement with experimental data. The simple analytical model is therefore capable of predicting the diode performance under real weather conditions.     

Hepta-Band Antenna for 5G Applications

Wireless Personal Communications - A hepta-band resonance antenna is proposed for fifth-generation (5G) and designed on Taconic TLY-3 substrate, resonate at various specified frequencies and offers...     

Feedline Separation for Independent Control of Simultaneously Different Tx/Rx Radiation Patterns

The shortcoming of Wi-Fi networks is that one user can access the router at a time. This drawback limits the system throughput and delay. This paper proposes a concept of Simultaneously Different Tx/Rx (SDTR) radiation patterns with only one antenna set at the router. Furthermore, these two patterns have to be simultaneously operated at the same time so that the system delay can be eased. An omni-directional pattern is employed at router for receiving mode so that the router can sense carrier signal from all directions. At the same time, the router launches a directional beam pointed to another user. A proposed circuit allows these two modes to be able to operate the same time. To evaluate the SDTR concept, a prototype is constructed for testing in real circumstance comparing to computer simulation. As a result, the SDTR concept can improve the system throughput while decreasing the system delay comparing to conventional system.     

Labor Productivity Drivers and Opportunities in the Construction Industry

The study of labor productivity in the construction industry is gaining increasing attention as the industry faces multiple problems related to its workforce. This paper presents the results of a survey instrument applied to determine the relative level of relevance of construction labor productivity drivers and opportunities. Owners, general contractors, electrical contractors, mechanical contractors, consultants, and others participated in this survey. Management skills and manpower issues were identified as the two areas with the greatest potential to affect productivity according to survey respondents. Surprisingly, external factors, which are often cited as a major cause for reduced productivity in the construction industry, were considered to be one of the least relevant productivity drivers. These results suggest that respondents consider the improvement of labor productivity within their reach and control rather than determined by external conditions.     

Liquid-phase alkali-doping of individual carbon nanotube field-effect transistors observed in real-time

The carbon nanotube (CNT) is known to be very sensitive to changes in its surrounding environment. Our study is on the effects of mild, liquid-phase alkali-doping on electronic transport in individual CNTs. We find clear and consistent reversal from p- to n-type behavior, with all seven investigated CNT field-effect transistors (FETs) retaining a similar ON/OFF ratio and subthreshold slope. We have also measured the realtime electronic response during liquid-phase doping, and demonstrate detection of alkali cations with a signal response that ranges over more than three orders of magnitude. The doping is fully reversible upon exposure to oxygen, and the doping cycle is repeatable. We also confirm an earlier finding that the redox chemistry involved can facilitate thermodynamically stable solutions of CNTs, and its potential for multi-purpose use in nanotechnology processing may be appealing for large-scale fabrication.     

An Improved Dictionary Cracking Scheme Based on Multiple GPUs for Wi-Fi Network

The Internet has penetrated all aspects of human society and has promoted social progress. Cyber-crimes in many forms are commonplace and are dangerous to society and national security. Cybersecurity has become a major concern for citizens and governments. The Internet functions and software applications play a vital role in cybersecurity research and practice. Most of the cyber-attacks are based on exploits in system or application software. It is of utmost urgency to investigate software security problems. The demand for Wi-Fi applications is proliferating but the security problem is growing, requiring an optimal solution from researchers. To overcome the shortcomings of the wired equivalent privacy (WEP) algorithm, the existing literature proposed security schemes for Wi-Fi protected access (WPA)/WPA2. However, in practical applications, the WPA/WPA2 scheme still has some weaknesses that attackers exploit. To destroy a WPA/WPA2 security, it is necessary to get a PSK pre-shared key in pre-shared key mode, or an MSK master session key in the authentication mode. Brute-force cracking attacks can get a phase-shift keying (PSK) or a minimum shift keying (MSK). In real-world applications, many wireless local area networks (LANs) use the pre-shared key mode. Therefore, brute-force cracking of WPA/WPA2-PSK is important in that context. This article proposes a new mechanism to crack the Wi-Fi password using a graphical processing unit (GPU) and enhances the efficiency through parallel computing of multiple GPU chips. Experimental results show that the proposed algorithm is effective and provides a procedure to enhance the security of Wi-Fi networks.