Performance of a TV white space database with different terrain resolutions and propagation models

Cognitive Radio has now become a realistic option for the solution of the spectrum scarcity problem in wireless communication. TV channels (the primary user) can be protected from secondary-user interference by accurate prediction of TV White Spaces (TVWS) by using appropriate propagation modelling. In this paper we address two related aspects of channel occupancy prediction for cognitive radio. Firstly we investigate the best combination of empirical propagation model and spatial resolution of terrain data for predicting TVWS by examining the performance of three propagation models (Extended-Hata, Davidson-Hata and Egli) in the TV band 470 to 790 MHz along with terrain data resolutions of 1000, 100 and 30 m, when compared with a comprehensive set of propagation measurements taken in randomly-selected locations around Hull, UK. Secondly we describe how such models can be integrated into a database-driven tool for cognitive radio channel selection within the TVWS environment

Comparison of spectrum occupancy measurements using software defined radio RTL-SDR with a conventional spectrum analyzer approach

In the present day Cognitive Radio has become a realistic option for solution of the spectrum scarcity problem in wireless communication. Recently, the TV band has attracted attention due to the considerable potential for exploitation of available TV white space which is not utilized based on time and location. In this paper, we investigate spectrum occupancy of the UHF TV band in the frequency range from 470 to 862MHz by using two different devices, the low cost device RTL-SDR and high cost spectrum analyzer. The spectrum occupancy measurements provide evidence of the utility of using the inexpensive RTL SDR and illustrate its effectiveness for detection of the percentage of spectrum utilization compared with results from the conventional high cost Agilent spectrum analyzer, both systems employing various antennas

A geographical analysis of industry in Libya, with special reference to industrial location

This study will, it is hoped, provide a contribution to the knowledge of the industrial geography of a small third world country, Libya, by shedding light on the location and development of its industries. Particular attention has been given to the role of the government in industrial development and industrial location, and the changes which have taken place in Libya's industrial structure and problems. The study proper begins in part one, chapter two, by examining industrial structure and location from the late Turkish period to the mid- nineteen fifties. In chapter three an attempt is made to analyse the characteristics, location and growth of the oil industry, while the main developments and changes in the industrial structure and spatial patterns from 1964 to 1971 are discussed in chapter four. The roles of the private industrialist and the government, including the latter's measures of encouragement and industrial finance, as well as its direct participation, are critically examined in chapter five. In part two, chapter six is a geographical analysis of the nature, location and regional distribution of industrial activities as they existed in Libya in 1971. Chapter seven deals primarily with the main factors which affect present industrial location as well as the relationship between industrial location in Libya and some theories of industrial location. The areal distribution and character of industry in the main cities (Tripoli and Benghazi) has been examined very closely in chapter eight. Finally, in part three, chapter nine deals with the main industrial problems, whilst some important indicators for the industrial future and concluding statements are presented in chapter ten

Experimental detection using cyclostationary feature detectors for cognitive radios

© 2014 IEEE. Signal detection is widely used in many applications. Some examples include Cognitive Radio (CR) and military intelligence. Without guaranteed signal detection, a CR cannot reliably perform its role. Spectrum sensing is currently one of the most challenging problems in cognitive radio design because of various factors such as multi-path fading and signal to noise ratio (SNR). In this paper, we particularly focus on the detection method based on cyclostationary feature detectors (CFD) estimation. The advantage of CFD is its relative robustness against noise uncertainty compared with energy detection methods. The experimental result present in this paper show that the cyclostationary feature-based detection can be robust compared to energy-based technique for low SNR levels

Spectrum occupancy measurements and lessons learned in the context of cognitive radio

Various measurement campaigns have shown that numerous spectrum bands are vacant even though licenses have been issued by the regulatory agencies. Dynamic spectrum access (DSA) based on Cognitive Radio (CR) has been regarded as a prospective solution to improve spectrum utilization for wireless communications. Empirical measurement of the radio environment to promote understanding of the current spectrum usage of the different wireless services is the first step towards deployment of future CR networks. In this paper we present our spectrum measurement setup and discuss lessons learned during our measurement activities. The main contribution of the paper is to introduce global spectrum occupancy measurements and address the major drawbacks of previous spectrum occupancy studies by providing a unifying methodological framework for future spectrum measurement campaigns

Cooperative wideband spectrum sensing with multi-bit hard decision in cognitive radio

Cognitive radio offers an increasingly attractive solution to overcome the underutilization problem. A sensor network based cooperative wideband spectrum sensing is proposed in this paper. The purpose of the sensor network is to determine the frequencies of the sources and reduced the total sensing time using a multi-resolution sensing technique. The final result is computed by data fusion of multi-bit decisions made by each cooperating secondary user. Simulation results show improved performance in energy efficiency

Quality measurements of an UWB reduced-size CPW-fed aperture antenna

The paper presents a characterization of a compact co-planar waveguide (CPW)-fed slot loaded low return loss planar printed antenna designed for wireless communication and ultra-wideband (UWB) applications. Following a review of the antenna design, which was implemented and simulated using Agilent's Advanced Design System (ADS), the paper presents laboratory measurements of relative gain and impulse response transformed from the frequency domain. An antenna quality metric based on time-domain S21 is discussed and related to antenna quality metrics such as the System Fidelity Factor (SFF)

Development of remineralizing, antibacterial dental materials

Light curable methacrylate dental monomers containing reactive calcium phosphate filler (monocalcium phosphate monohydrate (MCPM) with particle diameter of 29 or 90 mu m) and beta-tricalcium phosphate (beta-TCP) at 1: 1 weight ratio in a powder:liquid ratio (PLR) of 1:1 or 3:1 and chlorhexidine diacetate (0 or 5 wt.%), were investigated. Upon light exposure, approximately 90% monomer conversion was gained irrespective of the formulation. Increasing the PLR promoted water sorption by the set material, induced expansion and enhanced calcium, phosphate and chlorhexidine release. Concomitantly, a decline in compressive and biaxial flexural strengths occurred. With a reduction in MCPM particle diameter, however, calcium and phosphate release was reduced and less deterioration in strength observed. After 24 h, the remaining MCPM had reacted with water and beta-TCP, forming, within the set materials, brushite of lower solubility. This provided a novel means to control water sorption, component release and strength properties. Measurable chlorhexidine release was observed for 6 weeks. Both diffusion rate and total percentage of chlorhexidine release decreased with lowering PLR or by adding buffer to the storage solutions. Higher chlorhexidine release was associated with reduced bacterial growth on agar plates and in a biofilm, fermenter. In cell growth media, brushite and hydroxyapatite crystals precipitated on the composite material surfaces. Cells spread on both these crystals and the exposed polymer composite surfaces, indicating their cell compatibility. These formulations could be suitable antibacterial, biocompatible and remineralizing dental adhesives/liners. (C) 2009 Published by Elsevier Ltd. on behalf of Acta Materialia. Inc

Comparing historical and current spectrum occupancy measurements in the context of cognitive radio

Cognitive radio (CR) technology promises to be one possible solution to solve the problem of lack of frequency spectrum, by allowing access of unlicensed users in licensed bands, based on an opportunistic approach and without interfering with the licensed (primary) user. A fundamental key to the success of such an approach is knowledge of the statistical properties of the spectrum occupancy, which forms the basis of the current project. Numerous measurement campaigns have already been carried out in the USA and in other locations worldwide. These measurement campaigns have been performed at different locations in the context of cognitive radio. This paper collects together previous research work carried out worldwide and compares it with spectrum occupancy measurements recently undertaken at the University of Hull, UK

Survey: A comparison of spectrum sensing techniques in cognitive radio

In the present day Cognitive Radio has become a realistic option for solution of the spectrum scarcity problem in wireless communication. One of the most challenging issues in cognitive radio systems is spectrum sensing concepts, which is considered an extremely well researched topic. In this paper we compare three main classes of spectrum sensing techniques (Energy detection, matched filtering and cyclostationary) analysis in terms of time and spectrum resource consumed required prior knowledge and complexity. We then rank the three classes according to accuracy and performance