Fifth-Generation Technologies for the Connected Car:Capable Systems for Vehicle-to-Anything Communications

Two strong technology trends, one in the mobile communications industry and the other in the automotive industry, are becoming interwoven and will jointly provide new capabilities and functionality for upcoming intelligent transport systems (ITSs) and future driving. The automotive industry is on a path where vehicles are continuously becoming more aware of their environment due to the addition of various types of integrated sensors. At the same time, the amount of automation in vehicles increases, which, with some intermediate steps, will eventually culminate in fully automated driving without human intervention. Along this path, the amount of interactions rises, both in-between vehicles and between vehicles and other road users, and with an increasingly intelligent road infrastructure. As a consequence, the significance and reliance on capable communication systems for vehicleto-anything (V2X) communication is becoming a key asset that will enhance the performance of automated driving and increase further road traffic safety with combination of sensor-based technologies [1]

Einschränkungen in koordinierten zellularen Netzwerken : Analyse, Einfluss auf die Performanz und Milderung

Die Kooperation von Basisstationen wird als eine vielversprechende Technik für zukünftige drahtlose Kommunikationsnetze angesehen. Diese Technik betrachtet die Antennen von Basisstationen zusammen mit den Antennen mobiler Nutzer innerhalb von Zellen als ein räumlich verteiltes MIMO System und eröffnet dadurch die Möglichkeit, durch eine gemeinsame Signalverarbeitung die Inter-Zell-Interferenz zu beseitigen und die spektrale Effizienz zu erhöhen. Obwohl mittlerweile die theoretischen Grenzen solcher kooperativer Schemata bekannt und gut verstanden sind, besteht die größte Herausforderung noch immer in der Umsetzung und praktischer Realisierung und zwar in der Form, dass das theoretische Potential vollständig ausgeschöpft wird. Zum einen ist der vertretbare Mehraufwand für Pilotsymbole, Feedback und Backhaul begrenzt. Zum anderen ist die Performanz auf Grund von imperfekter Kanalkenntnis und Synchronisation limitiert, welche durch Kanalschätzung, Feedbackquantisierung, Alterung der Kanalinformation, sowie durch unterschiedliche Träger- und Abtastfrequenzen zwischen den Basisstationen entsteht. Diese Beeinträchtigungen haben zur Folge, dass die gemeinsame Vorkodierung der Daten in Bezug auf den tatsächlichen drahtlosen Übertragungskanal fehlangepasst ist und sich so die Kooperationsgewinne deutlich reduzieren. Um die Signalverzerrung und die Interferenz zwischen den Nutzern, die durch fehlangepasste Vorkodierung verursacht wird zu analysieren, müssen die Einflussfaktoren jeweils individuell untersucht werden. Dazu wird zunächst ein Signalmodell für die koordinierte OFDM-Übertragung entwickelt, welches die Effekte der imperfekten Kanalkenntnis und Synchronisation berücksichtigt und zudem erlaubt, analytische Ausdrücke für das Signal-zu-Interferenz Verhältnis (SIR) der mobilen Nutzer herzuleiten. Die analytischen Ergebnisse werden anschließend numerisch verifiziert und entsprechende Systemanforderungen werden spezifiziert. Unter der Verwendung geeigneter Kanalmodelle sowie realer Kanalmessdaten werden Schranken für den maximalen Abstand zwischen Basisstationen abgeleitet, welche eine interferenzfreie und zeitsynchrone Datenübertragung erlauben. Weiterhin wird die Synchronisation von verteilten Basisstationen diskutiert, welche auf der Nutzung kommerzieller Oszillatoren basiert, welche an externe Referenzen (z.B. GPS) angebunden sind. Es werden Methoden zur Abschwächung der Beeinträchtigungen entwickelt, wie etwa adaptive Feedbackkompression und Kanalprädiktion. Die adaptive Feedbackkompression ermöglicht es den mittleren quadratischen Kanalschätzfehler (MSE) unterhalb einer bestimmten Schranke zu halten und dabei gleichzeitig die Feedbackinformation um eine Größenordnung zu reduzieren. Dagegen ist eine auf Doppler-Verzögerungen basierende Kanalprädiktion in der Lage den MSE um 10 dB zu reduzieren. Zur Bewertung der Performanz werden das SCME Kanalmodell sowie reale Kanalmessdaten verwendet. Multi-zellulare Simulationen zeigen, daß das mittlere SIR pro Nutzer um 10 dB angehoben werden kann. Praktisch bedeutet dies, daß entgegen der bisherigen Meinung neben größeren Feedbackverzögerungen und einer höheren Mobilität auch eine größere Anzahl von Nutzern unterstützt werden kann.Base station cooperation is recognized as a key technology for future wireless cellular communication networks. Considering antennas of distributed base stations and those of multiple terminals within those cells as a distributed multiple-input multiple-output (MIMO) system, this technique has the potential to eliminate inter-cell interference by joint signal processing and to enhance spectral efficiency in this way. Although the theoretical gains are meanwhile well-understood, it still remains challenging to realize the full potential of such cooperative schemes in real-world systems. Among other factors, such as the limited overhead for pilot symbols and for the feedback and backhaul, these performance limitations are related to channel and synchronization impairments, such as channel estimation, feedback quantization and channel aging, as well as imperfect carrier and sampling synchronization among the base stations. Because of these impairments, joint data precoding results to be mismatched with respect to the actual radio channel and the gains of base station cooperation are limited. In order to analyze the signal distortion and the interference among the multiple users, which are caused by mismatched data precoding, it is required to model and investigate impairment effects isolatedly. Therefore, a signal model is provided for base-coordinated orthogonal frequency division multiplexing (OFDM) transmission with channel and synchronization impairments, and closed-form expressions are derived for the mobile users’ signal-to-interference ratio (SIR). Analytical results are numerically verified and lead to practical system requirements. Based on channel modeling and outdoor measurements, inter-site distance limitations for interference-free and time-synchronous transmission are also investigated. It is further discussed how to synchronize distributed base stations by using commercial oscillators locked to externally provided references, e.g. signals provided by Global Positioning System (GPS). Mitigation techniques including adaptive feedback compression and channel prediction are developed. Adaptive feedback compression keeps the channel mean square error (MSE) below a threshold and achieves more than order of magnitude overhead reduction. Doppler-delay base channel prediction reduces the delay-based MSE by 10 dB, approximately. For evaluating purposes, the spatial channel model extended (SCME) as well as channel data from outdoor measurements are used. Multi-cellular simulations reveal that the users’ SIR can be enhanced by 10 dB on average. Practically this means that larger feedback delays, higher mobilities and a larger number of users can be supported in coordinated multi-point (CoMP), compared to than previously believed

Analysis of Synchronization Impairments for Cooperative Base Stations Using OFDM

Base station cooperation is envisioned as a key technology for future cellular networks, as it has the potential to eliminate intercell interference and to enhance spectral efficiency. To date, there is still lack of understanding of how imperfect carrier and sampling frequency synchronization between transmitters and receivers limit the potential gains and what the actual system requirements are. In this paper, OFDM signal model is established for multiuser multicellular networks, describing the joint effect of multiple carrier and sampling frequency offsets. It is shown that the impact of sampling offsets is much smaller than the impact of carrier frequency offsets. The model is extended to the downlink of base-coordinated networks and closed-form expressions are derived for the mean power of users’ self-signal, interuser, and intercarrier interference, whereas it is shown that interuser interference is the main source of degradation. The SIR is inverse to the base stations’ carrier frequency variance and to the square of time since the last precoder update, whereas it grows with the number of base stations and drops with the number of users. Through user selection, the derived SIR upper bound can be approached. Finally, system design recommendations for meeting synchronization requirements are provided

Disability in Patients with Inflammatory Bowel Disease: Correlations with Quality of Life and Patient's Characteristics

Background. Inflammatory bowel diseases may cause significant disability. However, little is known regarding the life domains where patients encounter most limitations. Objectives. To assess patients' overall disability and determine the life domains where most restrictions were applied. Secondarily, we sought for possible relationships among disability, quality of life (HRQoL), and population characteristics. Method. The study lasted for two years (2013)(2014)(2015) and included 200 patients [52% ulcerative colitis (UC)] from a referral centre. Disability was evaluated using the 36-item version of WHODAS 2.0 questionnaire. The influence of population characteristics on overall disability was assessed with linear regression. Results. Crohn's disease (CD) patients showed greater overall disability compared to UC (19.22 versus 15.01, = 0.001), with higher scores in the domains of relationships, life activities, and participation. Disability was negatively associated with HRQoL ( < 0.001). Long activity, extensive disease, rural residence, and employment independently influenced the overall disability in both groups. Additionally, significant influence was recorded for lower education in the UC and for operation and celibacy in the CD group. Conclusions. CD patients were facing more limitations compared to those with UC, especially in the domains of relationships, activities, and participation. Other than clinical factors, sociodemographic characteristics were also associated with increased disability

Disability in Patients with Inflammatory Bowel Disease: Correlations with Quality of Life and Patient’s Characteristics

Background. Inflammatory bowel diseases may cause significant disability. However, little is known regarding the life domains where patients encounter most limitations. Objectives. To assess patients’ overall disability and determine the life domains where most restrictions were applied. Secondarily, we sought for possible relationships among disability, quality of life (HRQoL), and population characteristics. Method. The study lasted for two years (2013–2015) and included 200 patients [52%  ulcerative  colitis  (UC)] from a referral centre. Disability was evaluated using the 36-item version of WHODAS 2.0 questionnaire. The influence of population characteristics on overall disability was assessed with linear regression. Results. Crohn’s disease (CD) patients showed greater overall disability compared to UC (19.22 versus 15.01, p=0.001), with higher scores in the domains of relationships, life activities, and participation. Disability was negatively associated with HRQoL (p<0.001). Long activity, extensive disease, rural residence, and employment independently influenced the overall disability in both groups. Additionally, significant influence was recorded for lower education in the UC and for operation and celibacy in the CD group. Conclusions. CD patients were facing more limitations compared to those with UC, especially in the domains of relationships, activities, and participation. Other than clinical factors, sociodemographic characteristics were also associated with increased disability

The Rating Form of IBD Patient Concerns: Translation, Validation, and First Implementation of the Greek Version

Background. The rating form of IBD patients’ concerns (RFIPC) provides a unique assessment of the worries and concerns of inflammatory bowel disease (IBD) patients. Our aims were primarily to validate the Greek version of RFIPC and secondarily to describe the pattern of Greek patients’concerns. Methods. After translating RFIPC, the questionnaire was given to IBD patients at baseline and after 12 weeks. The questionnaire’s measuring properties were evaluated based on the consensus-based standards for the selection of health status measurement instruments (COSMIN) recommendations. Premediated factorial structures were tested for goodness of fit with confirmatory factor analysis (CFA). Results. At baseline, 200 patients (94 with Crohn’s disease) completed RFIPC. After 12 weeks, the first 100 patients recompleted the questionnaire. CFA results were consistent with a slightly modified than the original factorial structure. Cronbach’s α and intraclass correlation coefficients were high. RFIPC scores negatively affected the quality of life. RFIPC was sensitive to detect important changes in patients’ condition and was able to discriminate between remission and active disease. Disease activity, full time employment, celibacy, and low education were associated with higher scores. Conclusion. The Greek version of RFIPC is a reliable, valid, and responsive tool to assess Greek IBD patients’ concerns

The use of over-the-scope clip in the treatment of persistent staple line leak after re-sleeve gastrectomy: Review of the literature

Staple line leak after sleeve gastrectomy (SG) is a severe complication associated with increased mortality rates and the potential need for reoperation. We report the successful management of a re-SG staple line leak with the use of an endoscopic over-the-scope clip

Ulcerative Colitis in Hematological Malignancies: Paraneoplastic Manifestation or Coincidental Bystander?

Evidence of coexistence of diverse hematological malignancies—lymphoma, leukemia, multiple myeloma, and myelodysplastic syndromes—and either ulcerative colitis or Crohn’s disease can be found in the literature. However, a more “systemic” effort to reach further and examine the potential of either one as paraneoplastic manifestation has not been performed. Based on these, three cases of ulcerative colitis manifesting before, simultaneously, and after the onset of different hematological malignancies are presented and critically evaluated