992 resultados para TDD MIMO communication


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Acoustic signalling has been extensively studied in insect species, which has led to a better understanding of sexual communication, sexual selection and modes of speciation. The significance of acoustic signals for a blood-sucking insect was first reported in the XIX century by Christopher Johnston, studying the hearing organs of mosquitoes, but has received relatively little attention in other disease vectors until recently. Acoustic signals are often associated with mating behaviour and sexual selection and changes in signalling can lead to rapid evolutionary divergence and may ultimately contribute to the process of speciation. Songs can also have implications for the success of novel methods of disease control such as determining the mating competitiveness of modified insects used for mass-release control programs. Species-specific sound “signatures” may help identify incipient species within species complexes that may be of epidemiological significance, e.g. of higher vectorial capacity, thereby enabling the application of more focussed control measures to optimise the reduction of pathogen transmission. Although the study of acoustic communication in insect vectors has been relatively limited, this review of research demonstrates their value as models for understanding both the functional and evolutionary significance of acoustic communication in insects.

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BACKGROUND In the last decades the presence of social inequalities in diabetes care has been observed in multiple countries, including Spain. These inequalities have been at least partially attributed to differences in diabetes self-management behaviours. Communication problems during medical consultations occur more frequently to patients with a lower educational level. The purpose of this cluster randomized trial is to determine whether an intervention implemented in a General Surgery, based in improving patient-provider communication, results in a better diabetes self-management in patients with lower educational level. A secondary objective is to assess whether telephone reinforcement enhances the effect of such intervention. We report the design and implementation of this on-going study. METHODS/DESIGN The study is being conducted in a General Practice located in a deprived neighbourhood of Granada, Spain. Diabetic patients 18 years old or older with a low educational level and inadequate glycaemic control (HbA1c > 7%) were recruited. General Practitioners (GPs) were randomised to three groups: intervention A, intervention B and control group. GPs allocated to intervention groups A and B received training in communication skills and are providing graphic feedback about glycosylated haemoglobin levels. Patients whose GPs were allocated to group B are additionally receiving telephone reinforcement whereas patients from the control group are receiving usual care. The described interventions are being conducted during 7 consecutive medical visits which are scheduled every three months. The main outcome measure will be HbA1c; blood pressure, lipidemia, body mass index and waist circumference will be considered as secondary outcome measures. Statistical analysis to evaluate the effectiveness of the interventions will include multilevel regression analysis with three hierarchical levels: medical visit level, patient level and GP level. DISCUSSION The results of this study will provide new knowledge about possible strategies to promote a better diabetes self-management in a particularly vulnerable group. If effective, this low cost intervention will have the potential to be easily incorporated into routine clinical practice, contributing to decrease health inequalities in diabetic patients. TRIAL REGISTRATION Clinical Trials U.S. National Institutes of Health, NCT01849731.

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We study experimentally how the ability to communicate affects the frequency and effectiveness of flexible and inflexible contracts in a bilateral trade context where sellers can adjust trade quality after observing a post-contractual cost shock and a discretionary buyer transfer. In the absence of communication, we find that rigid contracts are more frequent and lead to higher earnings for both buyer and seller. By contrast, in the presence of communication, flexible contracts are much more frequent and considerably more productive, both for buyers and sellers. Also, both buyer and seller earn considerably more from flexible with communication than rigid without communication. Our results show quite strongly that communication, a normal feature in contracting, can remove the potential cost of flexibility (disagreements caused by conflicting perceptions). We offer an explanation based on social norms.

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This is an exploratory study that aims, on the one hand, to examine in more detail how children between 12 and 16 years of age use different audiovisual technologies, what they feel and think when using them, and whom they like to speak to about such experiences. On the other hand, we look more deeply into the interactions between adults and children, particularly between parents and their children, in relation to these technologies when children use them at home or in other places. We analysed responses to questionnaires with several common items, administered separately to parents and children. Children’s responses reflect an important level of dissatisfaction when talking with different adults about media activities. Our findings support the thesis that more and more children socialise through new information and communication technologies with little or no recourse to adult criteria, giving rise to the emergence of specific children’s cultures. Crossing of the responses of parents and those of their own children shows us which aspects of media reality adults overestimate or underestimate in comparison to children, and to what degree certain judgements coincide and differ between generations. The results can be applied to the improvement of relations between adults and adolescents, taking advantage of adolescents’ strong motivation to engage in activities using audiovisual media

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BACKGROUND: Communication in cancer care has become a major topic of interest. Since there is evidence that ineffective communication affects both patients and oncology clinicians (physicians and nurses), so-called communication skills trainings (CSTs) have been developed over the last decade. While these trainings have been demonstrated to be effective, there is an important heterogeneity with regard to implementation and with regard to evidence of different aspects of CST. METHODS: In order to review and discuss the scientific literature on CST in oncology and to formulate recommendations, the Swiss Cancer League has organised a consensus meeting with European opinion leaders and experts in the field of CST, as well as oncology clinicians, representatives of oncology societies and patient organisations. On the basis of a systematic review and a meta-analysis, recommendations have been developed and agreed upon. RESULTS: Recommendations address (i) the setting, objectives and participants of CST, (ii) its content and pedagogic tools, (iii) organisational aspects, (iv) outcome and (v) future directions and research. CONCLUSION: This consensus meeting, on the basis of European expert opinions and a systematic review and meta-analysis, defines key elements for the current provision and future development and evaluation of CST in oncology.

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This article originates from a panel with the above title, held at IEEE VTC Spring 2009, in which the authors took part. The enthusiastic response it received prompted us to discuss for a wider audience whether research at the physical layer (PHY) is still relevant to the field of wireless communications. Using cellular systems as the axis of our exposition, we exemplify areas where PHY research has indeed hit a performance wall and where any improvements are expected to be marginal. We then discuss whether the research directions taken in the past have always been the right choice and how lessons learned could influence future policy decisions. Several of the raised issues are subsequently discussed in greater details, e.g., the growing divergence between academia and industry. With this argumentation at hand, we identify areas that are either under-developed or likely to be of impact in coming years - hence corroborating the relevance and importance of PHY research.

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It is well known that multiple-input multiple-output (MIMO) techniques can bring numerous benefits, such as higher spectral efficiency, to point-to-point wireless links. More recently, there has been interest in extending MIMO concepts tomultiuser wireless systems. Our focus in this paper is on network MIMO, a family of techniques whereby each end user in a wireless access network is served through several access points within its range of influence. By tightly coordinating the transmission and reception of signals at multiple access points, network MIMO can transcend the limits on spectral efficiency imposed by cochannel interference. Taking prior information-theoretic analyses of networkMIMO to the next level, we quantify the spectral efficiency gains obtainable under realistic propagation and operational conditions in a typical indoor deployment. Our study relies on detailed simulations and, for specificity, is conducted largely within the physical-layer framework of the IEEE 802.16e Mobile WiMAX system. Furthermore,to facilitate the coordination between access points, we assume that a high-capacity local area network, such as Gigabit Ethernet,connects all the access points. Our results confirm that network MIMO stands to provide a multiple-fold increase in spectralefficiency under these conditions.

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Expressions relating spectral efficiency, power, and Doppler spectrum, are derived for Rayleigh-faded wireless channels with Gaussian signal transmission. No side information on the state of the channel is assumed at the receiver. Rather, periodic reference signals are postulated in accordance with the functioning of most wireless systems. The analysis relies on a well-established lower bound, generally tight and asymptotically exact at low SNR. In contrast with most previous studies, which relied on block-fading channel models, a continuous-fading model is adopted. This embeds the Doppler spectrum directly in the derived expressions, imbuing them with practical significance. Closed-form relationships are obtained for the popular Clarke-Jakes spectrum and informative expansions, valid for arbitrary spectra, are found for the low- and high-power regimes. While the paper focuses on scalar channels, the extension to multiantenna settings is also discussed.

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The analysis of the multiantenna capacity in the high-SNR regime has hitherto focused on the high-SNR slope (or maximum multiplexing gain), which quantifies the multiplicative increase as function of the number of antennas. This traditional characterization is unable to assess the impact of prominent channel features since, for a majority of channels, the slope equals the minimum of the number of transmit and receive antennas. Furthermore, a characterization based solely on the slope captures only the scaling but it has no notion of the power required for a certain capacity. This paper advocates a more refined characterization whereby, as function of SNRjdB, the high-SNR capacity is expanded as an affine function where the impact of channel features such as antenna correlation, unfaded components, etc, resides in the zero-order term or power offset. The power offset, for which we find insightful closed-form expressions, is shown to play a chief role for SNR levels of practical interest.