Design and Performance Analysis of Efficient Cooperative Wireless Communication Systems

Cooperative communication has recently become a key technology for modern wireless networks such as 3GPP long-term evolution and WiMAX, because in such networks the transmission rate, the communication reliability, and coverage problems could be improved in a cost-effective manner. This, however, faces many design challenges. First, cooperative transmission typically involves a relaying phase which requires extra resources. This may cause a reduction in the spectral efficiency. Second, extra control signaling increases the complexity of operation, which may limit practical implementation. In addition, a wireless channel is time-varying, mainly due to the multipath propagation. As a result, a careful design of efficient cooperative communication systems is required, not only to enhance the spectral efficiency and maintain the quality-of-service (QoS), but also to be practical. In this dissertation, we aim to address the challenges imposed by cooperative communication and wireless transmission, and design the efficient and distributed systems which can be practically implemented in existing wireless systems. The research work is divided into two main topics: 1) adaptive cooperative wireless systems with variable-rate transmission, and 2) cooperative wireless systems with a power consumption constraint. The first topic investigates how the spectral efficiency of cooperative wireless communication systems can be improved while maintaining the QoS in terms of bit error rate and outage probability. The spectral efficiency enhancement is achieved by using three techniques: adaptivity over the relay node (i.e., relay node is active or not), adaptivity over the modulation mode, and relay selection. Based on that, we propose several adaptive cooperative schemes for both the decode-and-forward (DF) and amplify-and-forward (AF) protocols. To evaluate these schemes, we provide performance analysis in terms of average spectral efficiency, average bit error rate (ABER), and outage probability over Rayleigh fading channels. We start with the single-relay cooperative system using DF protocol, in which two adaptive cooperative schemes with variable-rate transmission are proposed. The first scheme, called the minimum error rate scheme (MERS), aims to exploit the transmit diversity to improve the bit error rate. By trading the multiplexing gain against the diversity gain, we propose the second scheme, called the maximum spectral efficiency scheme (MSES), in which cooperative transmission is avoided whenever it is not beneficial. The MERS improves the ABER significantly and achieves equal or better average spectral efficiency compared to the fixed (i.e., non-adaptive) relaying scheme. In contrast, the MSES provides the best average spectral efficiency due to its ability to not only adapt to the channel variation but also to switch between cooperative and non-cooperative transmissions. To further increase the spectral efficiency, we then propose the third scheme, called variable-rate based relay selection (VRRS) scheme, in which a relay node is selected from among the available relay nodes, based on a predefined criterion. Furthermore, we propose two AF adaptive cooperative schemes, mainly to enhance the spectral efficiency. In the first scheme, we introduce a generalized switching policy (GSP) for a single-relay cooperative wireless system that exploits the variable-rate transmission and useful cooperative regions. The second scheme, called the AF efficient relay selection (AFERS) scheme, extends the GSP to also consider the relay selection technique. Analytical and simulation results verify that the AFERS scheme not only outperforms conventional direct transmission in terms of the average spectral efficiency, but also the AF fixed relaying and the outage-based AF adaptive cooperative scheme. The second topic investigates the fair power consumption of the relay nodes for AF cooperative wireless communication systems. The fairness is defined as to achieve equal power consumption over the relay nodes. We focus on how the relay selection process can be controlled in a distributed manner so that the power consumption of the relay nodes can be included in relay selection. We first introduce a simple closed-form expression for the weight coefficient used in order to achieve the considered fairness that depends only on the local average channel conditions of the relay path. We then derive closed-form expressions of the weighted outage probability and ABER and show that our proposed strategy not only has less complexity than the conventional centralized one but also provides better accuracy in distributing the total consumed power equally among the relay nodes without affecting the performance

The Effect of a Training Program Based on Playing on Alleviating the Behavioral Disorders among the Educable Intellectually Disabled Students in the Kingdom of Saudi Arabia

This study aims at investigating the effect of a training program based on playing on alleviating some behavioral disorders among the educable intellectually disabled students in Rafha Province in the Kingdom of Saudi Arabia. The importance of this study lies in presenting a training program based on playing to reduce social withdrawal. According to the scientific research, social withdrawal can be treated using the behavior modification methods regardless of the reasons that cause this disorder. Social withdrawal is a common behavioral pattern among the majority or almost all the intellectually disabled people. This social withdrawal behavior is caused by different factors. If the child suffers from a damaged central nervous system, he will not be able to perform the activities needed for treatment. The scientific research state that social withdrawal can be reduced using the behavior modification methods. The current study aims at investigating the effect of a training program based on playing on reducing the social withdrawal among the intellectually disabled children. To achieve this goal a training program based on playing has been designed and applied to an experimental group made of (4) students for six weeks, a daily session for six days every week

Ketamina en dosis bajas con anestesia local reduce la morbilidad postoperatoria de la cirugía del tercer molar: Revisión sistemática y metanálisis.

Objective: This review addresses a clinical research question related to lower third molar surgery (L3MS): does the combination of pre-emptive low-dose ketamine with local anesthesia (KLA) reduce postoperative complications compared with local anesthesia (LA) alone? Material and methods: A systematic literature search was performed to identify eligible articles by electronic searches of PubMed, Cochrane Central Register of Controlled Trials, EBSCO Library, Web of Science and grey literature through June 2019 without data or language restrictions. We analyzed all randomized controlled clinical studies (RCTs) comparing use of KLA with use of LA in L3MS regarding pain, swelling, and trismus outcomes. The quality of evidence was rated according to Cochrane’s tool for assessing risk of bias. Results: Five RCTs encompassing 230 extraction sites (KLA = 115, LA = 115) were included in this study. The standardized mean difference (SMD) with the 95% confidence interval (CI) was used to synthesize the results. The data show that there were significant differences between the two groups in post-operative pain (SMD -1.464, 95% CI -1.683 to -0.949, p= 0.001) and swelling (SMD -0.450, 95% CI -0.758 to -0.142, p= 0.004, all low quality evidence). However, there was no significant difference in the trismus (SMD -0.754, CI -1.487 to -0.022, p = 0.043, very low quality evidence). Conclusion: The combination of pre-emptive low-dose ketamine with LA significantly decreased pain and swelling within the first 24 hours after L3MS compared with the control group.Objetivo: Esta revisión aborda una pregunta de investigación clínica relacionada con la cirugía del tercer molar inferior (L3MS): ¿la combinación de ketamina preventiva en dosis bajas con anestesia local (KLA) reduce las complicaciones postoperatorias en comparación con la anestesia local (AL) sola? Material y Métodos: Se realizó una búsqueda bibliográfica sistemática para identificar artículos elegibles mediante búsquedas electrónicas en PubMed, Registro Cochrane Central de Ensayos Controlados, Biblioteca EBSCO, Web of Science y literatura gris hasta junio de 2019 sin restricciones de datos ni de idioma. Se analizaron todos los estudios clínicos controlados aleatorios (ECA) que compararon el uso de KLA con el uso de LA en L3MS con respecto a los resultados de dolor, hinchazón y trismo. La calidad de la evidencia se clasificó de acuerdo con la herramienta Cochrane para evaluar el riesgo de sesgo. Resultados: Se incluyeron en este estudio cinco ECA que abarcan 230 sitios de extracción (KLA = 115, LA = 115). La diferencia de medias estandarizada (DME) con el intervalo de confianza (IC) del 95% se utilizó para sintetizar los resultados. Los datos muestran que hubo diferencias significativas entre los dos grupos en el dolor posoperatorio (DME -1,464; IC del 95%: -1,683 a -0,949; p= 0,001) e hinchazón (DME -0,450; IC del 95%: -0,758 a -0,142 , p= 0,004, todas las pruebas de baja calidad). Sin embargo, no hubo diferencias significativas en el trismo (DME -0,754; IC: -1,487 a -0,022; p= 0,043, evidencia de muy baja calidad). Conclusión: La combinación de ketamina preventiva en dosis bajas con LA disminuyó significativamente el dolor y la hinchazón dentro de las primeras 24 horas después de la L3MS en comparación con el grupo de control

Bilateral acute angle closure glaucoma after hyperopic LASIK correction

AbstractAcute angle closure glaucoma is unexpected complication following laser in situ keratomileusis (LASIK). We are reporting a 49-years-old lady that was presented to the emergency department with acute glaucoma in both eyes soon after LASIK correction. Diagnosis was made on detailed clinical history and examination, slit lamp examination, intraocular pressure measurement and gonioscopy. Laser iridotomy in both eyes succeeded in controlling the attack and normalizing the intraocular pressure (IOP) more than 6months of follow-up. Prophylactic laser iridotomy is essential for narrow angle patients before LASIK surgery if refractive laser surgery is indicated

Flash Fiction from North Africa

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IMPROVING ROOTING AND GROWTH OF CONOCARPUS ERECTUS STEM CUTTINGS USING INDOLE-3-BUTYRIC ACID (IBA) AND SOME BIOSTIMULANTS

The current study was conducted to evaluate the effects of indole-3-butyric acid (IBA) at 100 ppm with or without biostimulants (Agrobacterium rhizogenes, seaweed extract and coconut water) as either a spray or drench for 3 minutes or 1 hour on rooting and growth parameters of three cutting types (tip, middle and basal) of Conocarpus erectus L. The data showed that the rooting percentage, root and vegetative characteristics of rooted cuttings were significantly increased by all treatments of IBA and/or biostimulants compared to the untreated cuttings. The individual treatments of seaweed extract and coconut water were more effective than IBA or A. rhizogenes alone. Seaweed extract as drench with or without IBA surpassed those of seaweed extract treatments as spray. Besides, the response of cuttings treated with coconut water for 1 hour was better than coconut water for 3 min. Tip cuttings were significantly better than the middle and basal ones, especially in relation to rootability of cuttings. Maximum rooting percentage and shoot characteristicsof plants were obtained from tip cuttings treated with IBA + coconut water for 1 hour, followed by IBA + seaweed extract as drench. The highest rooting percentage was associated with high endogenous levels of phenols, indole acetic acid (IAA) and gibberellic acid (GA) as well as the lowest abscisic acid (ABA) level in cutting tissues and the anatomical structure of rooted cuttings. So, it can be recommended treating tip cuttings of C. erectus with either coconut water for 1 hour or seaweed extract as drench combined with IBA for enhancing the rooting percentage, root and shoot growth parameters as well as content of endogenous root promoting substances