Resource Management in Multicarrier Based Cognitive Radio Systems

The ever-increasing growth of the wireless application and services affirms the importance of the effective usage of the limited radio spectrum. Existing spectrum management policies have led to significant spectrum under-utilization. Recent measurements showed that large range of the spectrum is sparsely used in both temporal and spatial manner. This conflict between the inefficient usage of the spectrum and the continuous evolution in the wireless communication calls upon the development of more flexible management policies. Cognitive radio (CR) with the dynamic spectrum access (DSA) is considered to be a key technology in making the best solution of this conflict by allowing a group of secondary users (SUs) to share the radio spectrum originally allocated to the primary user (PUs). The operation of CR should not negatively alter the performance of the PUs. Therefore, the interference control along with the highly dynamic nature of PUs activities open up new resource allocation problems in CR systems. The resource allocation algorithms should ensure an effective share of the temporarily available frequency bands and deliver the solutions in timely fashion to cope with quick changes in the network. In this dissertation, the resource management problem in multicarrier based CR systems is considered. The dissertation focuses on three main issues: 1) design of efficient resource allocation algorithms to allocate subcarriers and powers between SUs such that no harmful interference is introduced to PUs, 2) compare the spectral efficiency of using different multicarrier schemes in the CR physical layer, specifically, orthogonal frequency division multiplexing (OFDM) and filter bank multicarrier (FBMC) schemes, 3) investigate the impact of the different constraints values on the overall performance of the CR system. Three different scenarios are considered in this dissertation, namely downlink transmission, uplink transmission, and relayed transmission. For every scenario, the optimal solution is examined and efficient sub-optimal algorithms are proposed to reduce the computational burden of obtaining the optimal solution. The suboptimal algorithms are developed by separate the subcarrier and power allocation into two steps in downlink and uplink scenarios. In the relayed scenario, dual decomposition technique is used to obtain an asymptotically optimal solution, and a joint heuristic algorithm is proposed to find the suboptimal solution. Numerical simulations show that the proposed suboptimal algorithms achieve a near optimal performance and perform better than the existing algorithms designed for cognitive and non-cognitive systems. Eventually, the ability of FBMC to overcome the OFDM drawbacks and achieve more spectral efficiency is verified which recommends the consideration of FBMC in the future CR systems.El crecimiento continuo de las aplicaciones y servicios en sistemas inal´ambricos, indica la importancia y necesidad de una utilizaci´on eficaz del espectro radio. Las pol´ıticas actuales de gesti´on del espectro han conducido a una infrautilizaci´on del propio espectro radioel´ectrico. Recientes mediciones en diferentes entornos han mostrado que gran parte del espectro queda poco utilizado en sus ambas vertientes, la temporal, y la espacial. El permanente conflicto entre el uso ineficiente del espectro y la evoluci´on continua de los sistemas de comunicaci´on inal´ambrica, hace que sea urgente y necesario el desarrollo de esquemas de gesti´on del espectro m´as flexibles. Se considera el acceso din´amico (DSA) al espectro en los sistemas cognitivos como una tecnolog´ıa clave para resolver este conflicto al permitir que un grupo de usuarios secundarios (SUs) puedan compartir y acceder al espectro asignado inicialmente a uno o varios usuarios primarios (PUs). Las operaciones de comunicaci´on llevadas a cabo por los sistemas radio cognitivos no deben en ning´un caso alterar (interferir) los sistemas primarios. Por tanto, el control de la interferencia junto al gran dinamismo de los sistemas primarios implica nuevos retos en el control y asignaci´on de los recursos radio en los sistemas de comunicaci´on CR. Los algoritmos de gesti´on y asignaci´on de recursos (Radio Resource Management-RRM) deben garantizar una participaci´on efectiva de las bandas con frecuencias disponibles temporalmente, y ofrecer en cada momento oportunas soluciones para hacer frente a los distintos cambios r´apidos que influyen en la misma red. En esta tesis doctoral, se analiza el problema de la gesti´on de los recursos radio en sistemas multiportadoras CR, proponiendo varias soluciones para su uso eficaz y coexistencia con los PUs. La tesis en s´ı, se centra en tres l´ıneas principales: 1) el dise˜no de algoritmos eficientes de gesti´on de recursos para la asignaci´on de sub-portadoras y distribuci´on de la potencia en sistemas segundarios, evitando asi cualquier interferencia que pueda ser perjudicial para el funcionamiento normal de los usuarios de la red primaria, 2) analizar y comparar la eficiencia espectral alcanzada a la hora de utilizar diferentes esquema de transmisi´on multiportadora en la capa f´ısica del sistema CR, espec´ıficamente en sistemas basados en OFDM y los basados en banco de filtros multiportadoras (Filter bank Multicarrier-FBMC), 3) investigar el impacto de las diferentes limitaciones en el rendimiento total del sistema de CR. Los escenarios considerados en esta tesis son tres, es decir; modo de transmisi´on descendente (downlink), modo de transmisi´on ascendente (uplink), y el modo de transmisi´on ”Relay”. En cada escenario, la soluci´on ´optima es examinada y comparada con algoritmos sub- ´optimos que tienen como objetivo principal reducir la carga computacional. Los algoritmos sub-´optimos son llevados a cabo en dos fases mediante la separaci´on del propio proceso de distribuci´on de subportadoras y la asignaci´on de la potencia en los modos de comunicaci´on descendente (downlink), y ascendente (uplink). Para los entornos de tipo ”Relay”, se ha utilizado la t´ecnica de doble descomposici´on (dual decomposition) para obtener una soluci´on asint´oticamente ´optima. Adem´as, se ha desarrollado un algoritmo heur´ıstico para poder obtener la soluci´on ´optima con un reducido coste computacional. Los resultados obtenidos mediante simulaciones num´ericas muestran que los algoritmos sub-´optimos desarrollados logran acercarse a la soluci´on ´optima en cada uno de los entornos analizados, logrando as´ı un mayor rendimiento que los ya existentes y utilizados tanto en entornos cognitivos como no-cognitivos. Se puede comprobar en varios resultados obtenidos en la tesis la superioridad del esquema multiportadora FBMC sobre los sistemas basados en OFDM para los entornos cognitivos, causando una menor interferencia que el OFDM en los sistemas primarios, y logrando una mayor eficiencia espectral. Finalmente, en base a lo analizado en esta tesis, podemos recomendar al esquema multiportadora FBMC como una id´onea y potente forma de comunicaci´on para las futuras redes cognitivas

The lateral distribution of the electromagnetic component in extensive air showers of size 10(^4) to 10(^6) particles

A small air shower array of diameter 120 m is described. This array is used to study extensive air showers of sizes ranging from 10(^4) to 10(^6) and also to supply information required for the hadron studies carried out using a flash-tube chamber placed in the Cosmic Ray laboratory of the University of Durham. The array was also used to trigger the Magnetic Automated Research Spectrograph which had its location in that laboratory. Eight liquid scintillation counters have been added to the initial fourteen plastic detectors. The array detecting elements are located in a triangular geometry around the Physics Department. In the data handling procedures, the initial array data were assembled, digitised and then transferred to an on-line I.B.M. 1130 computer disc where the data were primarily stored before being transferred to the larger I.B.M. 370/168 computer in order to be analysed. The array could be triggered in different ways depending upon the mode chosen and upon other experiments present. Results arc presented showing the effect of the inclusion of the liquid counters on the accuracy with which the analysis programme determines the location of the shower core and on the shower size value resulting from the data analysis. The depth of the liquid in the liquid counters was 20 cm which means that these liquid detectors responded to the photons and nuclear active particles of the extensive air showers. The lateral distributions of the electron-photon component of EAS as measured by one of the liquid counters and one of the plastic detectors (5 cm thick) are deduced and compared with the results of other experiments. The present results show good agreement with those of other workers when the effect of the thickness of the used detectors is taken into account, except for the results of Hasagawa (1962). A comparison is made between the distributions of the number of flash-tubes discharged in the red-side top measuring tray of the spectrograph and the theoretically predicted distributions

Synthesis and characterization of white light emitting CaxSr1-xAl2O4:Tb3+,Eu3+ phosphor for solid state lighting

A white light emitting CaxSr1-xAl2O4:Tb3+;Eu3+ phosphor was synthesized by a combustion method using metal nitrates as precursors and urea as a fuel. The X-ray diffraction patterns from the samples showed phases associated with monoclinic structures of CaAl2O4 and SrAl2O4. White photoluminescence with the CIE coordinates (x = 0.343, y = 0.325) was observed when the phosphor was optically-excited at 227 nm using a monochromatized xenon lamp. The white photoluminescence was a result of the combination of blue and green line emissions from Tb3+, and red line emission from Eu3+. The structure and photoluminescence properties of this phosphor are reported.The authors would like to acknowledge the financial support from the cluster funds of the University of the Free State and the South African National Research Foundation.A white light emitting CaxSr1-xAl2O4:Tb3+;Eu3+ phosphor was synthesized by a combustion method using metal nitrates as precursors and urea as a fuel. The X-ray diffraction patterns from the samples showed phases associated with monoclinic structures of CaAl2O4 and SrAl2O4. White photoluminescence with the CIE coordinates (x = 0.343, y = 0.325) was observed when the phosphor was optically-excited at 227 nm using a monochromatized xenon lamp. The white photoluminescence was a result of the combination of blue and green line emissions from Tb3+, and red line emission from Eu3+. The structure and photoluminescence properties of this phosphor are reported

Urinary and serum neutrophil gelatinase-associated lipocalin as a biomarker in Egyptian systemic lupus erythematosus patients: Relation to lupus nephritis and disease activity

AbstractBackgroundNeutrophil gelatinase-associated lipocalin (NGAL) is an excellent structural biomarker for the early diagnosis of acute kidney injury, prognosis, dialysis requirement and mortality in several common clinical scenarios.Aim of the workThe aim of this work is to detect the levels of both urinary and serum NGAL in SLE patients with and without lupus nephritis (LN) and to correlate their levels with renal biopsy class and disease activity.Patients and methodsThe study included 35 SLE patients; 22 with LN and 13 without as well as 30 matched controls. The SLE Disease Activity Index (SLEDAI) was assessed and the renal biopsy class determined. Urinary and serum levels of NGAL were assessed by ELISA.ResultsThe 35 patients had a median age of 30years and disease duration of 4years. They were 31 females and 4 males. The SLE patients had an elevated urinary NGAL (UNGAL) (median 19ng/ml, IQR 8–87) as compared to controls (median 2ng/ml, IQR 1–18.3) (p<0.006). Levels of UNGAL were higher in patients with LN than those without (p<0.023). In patients with LN, serum levels of NGAL were not significantly different from controls (p=0.6). The UNGAL level significantly correlated with the renal score of SLEDAI (r=0.54, p=0.001) but serum NGAL level did not (r=0.25, p=0.15). UNGAL significantly correlated with grade III and IV of renal biopsy (r=0.67, p=0.009). The sensitivity of UNGAL levels for the diagnosis of LN was 85.7%, with a specificity of 80%.ConclusionUrinary NGAL is a sensitive marker of proliferative nephritis in SLE and disease activity

Does ultrasound-guided continuous suprascapular nerve block affect frozen shoulder rehabilitation programme outcome?

Background: Physical therapy (PT) is often recommended for patients with frozen shoulder. However, it could be painful for some patients, and this could hinder the rehabilitation programme. Some procedures like joint injection and suprascapular nerve block (SSNB) could alleviate pain during this setting. Objective: The purpose of this study was to compare the effectiveness of continuous SSNB plus PT compared to PT alone in managing frozen shoulder.Patients and methods: A total of 76 patients with frozen shoulder were included in this study. They were divided into two groups: 38 patients in the injection group (IG) received SSNB via catheter before PT, while the remaining 38 participants in the control group (CG) received no block prior to PT (CG). The functional state of the shoulder joint was assessed via the constant shoulder scale before and just after PT, then one month later.Results: General patient characteristics, including age, gender, BMI, comorbidities, and trauma history, were statistically comparable between the two groups. When we examined the constant scores of the two groups, we found that both had low scores before treatment, which increased immediately after treatment and then increased again one month later. Nonetheless, the injection group had a much greater increase than the control group.Conclusion: When used with PT for the treatment of adhesive capsulitis, continuous SSNB is an effective option that enhances the response to PT. It is associated with better improvement in shoulder function