185 research outputs found
Achievable spectral efficiency of line-of-sight MIMO fixed links with compact planar antenna arrays and power amplifier limitations
No full textFixed Point-to-Point microwave wireless systems with high spectral efficiency are needed to meet the pervasive and increasing demand for capacity in back-haul networks of mobile radio systems. In this context, spatially multiplexed LoS-MIMO (Line-of-Sight Multiple Input Multiple Output) systems have been studied for about twenty years, particularly in the millimeter wave frequency bands (above 15 GHz). However, their deployment in real networks has been really limited, to the authors’ knowledge. This has been due to several factors, i.e. the practical possibility of using extremely high-level modulation formats (nowadays up to 8192-QAM), the joint use of co-channel dual polarization, and the availability of wider channel bands in the new high frequency ranges (e.g. E-Band). In addition, a crucial reason has been the difficulty of installing multiple antennas spaced apart in order to maximize the MIMO spatial multiplexing so providing the maximum capacity gain. This optimal antenna separation, even for the classical MIMO with M = 2 antennas at the receiver and N = 2 antennas at the transmitter, can be several meters, e.g. 5.71 m at 23 GHz on a 5 km link. In this article, we analyze the performance of LoS-MIMO systems where antenna separation is highly sub-optimal, for limiting the array size, and a satisfactory performance is made possible by the exploitation of specific bit loading and power allocation strategies and the setting of the working region of the RF transmitter power amplifiers to operate at a given Signal-to-Inter Modulation Distortion Ratio (SIMDR). The result is an overview of the advantages and drawbacks of compact LoS-MIMO from a wider perspective than in the existing literature, including fundamental aspects for the practical implementation of these systems. Performance is discussed in many cases of interest and compared with the state of the art SISO (Single Input Single Output) system
Performance Evaluation of LoS MIMO Microwave Radio Systems Over Frequency Selective Multipath Fading Channels
No full textAlthough spectrally efficient microwave LoS-MIMO (Line of Sight-Multiple Input Multiple Output) systems seem to be practically attractive mainly at higher frequency bands (above 15 GHz), also at lower frequency bands, where frequency selective multipath fading is the dominant impairment for the outage time, they could play a significant role. Under this perspective, the paper analyzes performance of LoS-MIMO systems affected by frequency selective fading, taking into account the necessary equalization for satisfying the outage objectives. For the purpose of the analysis, we adopted a frequency selective 2×2 LoS-MIMO channel model extrapolated from the 2-ray model historically used in SISO (Single Input Single Output) systems and, exploiting the full statistical behaviour of the propagation channel model, we described a methodology for the evaluation of frequency selective LoS-MIMO outage performance. Then the proposed methodology is used to investigate the effectiveness of equalization in the intersymbol and mutual interference reduction of two equalizer structures, linear MMSE and MMSE Partial Response, using as a practical reference the target outage probability predicted on the same link for a SISO system. Finally, it is discussed the opportunity of using the Condition Number of the LoS-MIMO channel matrix transfer function as an exhaustive indicator of the channel quality
Thermal Forces from a Microscopic Perspective
No full textThermal gradients lead to macroscopic fluid motion if a confining surface is present along the gradient. This fundamental nonequilibrium effect, known as thermo-osmosis, is held responsible for particle thermophoresis in colloidal suspensions. A unified approach for thermo-osmosis in liquids and in gases is still lacking. Linear response theory is generalized to inhomogeneous systems, leading to an exact microscopic theory for the thermo-osmotic flow, showing that the effect originates from two independent physical mechanisms, playing different roles in the gas and liquid phases, reducing to known expressions in the appropriate limits
Long-term endoscopic surveillance of patients with Barrett’S esophagus. A prospective study.
No full textMutation of p53 in the progression of Barrett's epithelium to invasive esophageal cancer: A prospective study
No full textPersonalized surgery for rectal tumours : the patient's opinion counts
No full textIn recent times there have been many important changes in the surgical management of rectal cancer. The general thrust of these changes has been towards a less invasive approach with preservation of intestinal continuity and avoidance of the psychological se quelae of a stoma, It is also becomming increasingly apparent that profound sexual and autonomic dysfunction can be associated with abdominoperineal resection. This paper highlights these issues and the conflict between performing an adequate oncological proceedure and reducing the incidence of postoperative psychological morbidity, It outlines the great changes there have been in surgical technique and their relevance to psychological problems after surgery for rectal cancer, The need for auditing psychological morbidity when assessing the outcome of surgical series is emphasised, as is the importance of involving the patient in the medical decision making
Mémoire des corps, entre héritage et transmission
No full text(conférence/rencontre avec les chorégraphes Germaine Acogny et Salia Sanou et l’écrivaine Nancy Huston, médiation d’Irène Filiberti)Troisième rencontre issue du cycle de conférences organisé par Irène Filiberti et Guillaume Sintès dans le cadre du partenariat Pôle-Sud CDCN avec l’Université de Strasbourg. Université de Strasbourg, 3 février 2020
Problems after hysterectomy. A comparative content analysis of 60 interviews with cancer and non-cancer hysterectomized women.
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