Adaptive Bayesian estimation in indirect Gaussian sequence space models

In an indirect Gaussian sequence space model lower and upper bounds are derived for the concentration rate of the posterior distribution of the parameter of interest shrinking to the parameter value $\theta^\circ$ that generates the data. While this establishes posterior consistency, however, the concentration rate depends on both $\theta^\circ$ and a tuning parameter which enters the prior distribution. We first provide an oracle optimal choice of the tuning parameter, i.e., optimized for each $\theta^\circ$ separately. The optimal choice of the prior distribution allows us to derive an oracle optimal concentration rate of the associated posterior distribution. Moreover, for a given class of parameters and a suitable choice of the tuning parameter, we show that the resulting uniform concentration rate over the given class is optimal in a minimax sense. Finally, we construct a hierarchical prior that is adaptive. This means that, given a parameter $\theta^\circ$ or a class of parameters, respectively, the posterior distribution contracts at the oracle rate or at the minimax rate over the class. Notably, the hierarchical prior does not depend neither on $\theta^\circ$ nor on the given class. Moreover, convergence of the fully data-driven Bayes estimator at the oracle or at the minimax rate is established

Punctured Trellis-Coded Modulation

In classic trellis-coded modulation (TCM) signal constellations of twice the cardinality are applied when compared to an uncoded transmission enabling transmission of one bit of redundancy per PAM-symbol, i.e., rates of $\frac{K}{K+1}$ when $2^{K+1}$ denotes the cardinality of the signal constellation. In order to support different rates, multi-dimensional (i.e., $\mathcal{D}$-dimensional) constellations had been proposed by means of combining subsequent one- or two-dimensional modulation steps, resulting in TCM-schemes with $\frac{1}{\mathcal{D}}$ bit redundancy per real dimension. In contrast, in this paper we propose to perform rate adjustment for TCM by means of puncturing the convolutional code (CC) on which a TCM-scheme is based on. It is shown, that due to the nontrivial mapping of the output symbols of the CC to signal points in the case of puncturing, a modification of the corresponding Viterbi-decoder algorithm and an optimization of the CC and the puncturing scheme are necessary.Comment: 5 pages, 10 figures, submitted to IEEE International Symposium on Information Theory 2013 (ISIT

Innovative Concepts within Knowledge Management

In our increasingly knowledge-based society the need for innovative concepts within the discipline of Knowledge Management (KM) becomes clear. Therefore, this article aims to shed light on current and uprising innovative technologies and concepts within the discipline of KM. This study conveys recent and previous scientific literature on the relevance of uprising innovative concepts within the various dimensions of KM. We conducted a systematic literature review (SLR) on various literature sources to cover the whole spectrum of innovative KM approaches. All 37 reviewed articles originate from acknowledged sources and were written in English. The findings show, which innovative concepts show relevance within KM, how they are classified into the three innovation categories social, technological, and organizational, how they manifest within KM and what to expect from future KM innovations

Innovative Concepts within Knowledge Management

In our increasingly knowledge-based society the need for innovative concepts within the discipline of Knowledge Management (KM) becomes clear. Therefore, this article aims to shed light on current and uprising innovative technologies and concepts within the discipline of KM. This study conveys recent and previous scientific literature on the relevance of uprising innovative concepts within the various dimensions of KM. We conducted a systematic literature review (SLR) on various literature sources to cover the whole spectrum of innovative KM approaches. All 37 reviewed articles originate from acknowledged sources and were written in English. The findings show, which innovative concepts show relevance within KM, how they are classified into the three innovation categories social, technological, and organizational, how they manifest within KM and what to expect from future KM innovations

Adaptive estimation of linear functionals in functional linear models

We consider the estimation of the value of a linear functional of the slope parameter in functional linear regression, where scalar responses are modeled in dependence of random functions. In Johannes and Schenk [2010] it has been shown that a plug-in estimator based on dimension reduction and additional thresholding can attain minimax optimal rates of convergence up to a constant. However, this estimation procedure requires an optimal choice of a tuning parameter with regard to certain characteristics of the slope function and the covariance operator associated with the functional regressor. As these are unknown in practice, we investigate a fully data-driven choice of the tuning parameter based on a combination of model selection and Lepski's method, which is inspired by the recent work of Goldenshluger and Lepski [2011]. The tuning parameter is selected as the minimizer of a stochastic penalized contrast function imitating Lepski's method among a random collection of admissible values. We show that this adaptive procedure attains the lower bound for the minimax risk up to a logarithmic factor over a wide range of classes of slope functions and covariance operators. In particular, our theory covers point-wise estimation as well as the estimation of local averages of the slope parameter

Reduced Complexity Super-Trellis Decoding for Convolutionally Encoded Transmission Over ISI-Channels

In this paper we propose a matched encoding (ME) scheme for convolutionally encoded transmission over intersymbol interference (usually called ISI) channels. A novel trellis description enables to perform equalization and decoding jointly, i.e., enables efficient super-trellis decoding. By means of this matched non-linear trellis description we can significantly reduce the number of states needed for the receiver-side Viterbi algorithm to perform maximum-likelihood sequence estimation. Further complexity reduction is achieved using the concept of reduced-state sequence estimation.Comment: 6 pages, 8 figures, accepted for ICNC'13. (see also: arXiv:1205.7031

Community care coordination for stroke survivors: results of a complex intervention study

Background: Outpatient follow-up care for stroke survivors is often inadequate and mostly self-organized by the patients themselves. In the German health care system, there are no standard care programs for patients after they are discharged from the hospital to support them with their multifaceted and heterogeneous health care needs. The objective of this complex intervention study was to evaluate the effectiveness of a post-stroke care coordination program in comparison to standard care in the first year after a stroke. Methods: Patients aged 55 and older who had survived a stroke or a transient ischemic attack (TIA) within the last 6 months before enrollment were included. Participants received care coordination either by telephone or face-to-face for up to 1 year. Patients’ health insurance claims data were used to measure outcomes. The control group consisted of stroke survivors receiving standard care and was constructed by exact matching based on six criteria. Outcome measures were health services utilization, rate of recurrent events, readmissions and accompanying costs, and mortality. Outcomes were tested using different multiple models. Results: In total, N = 361 patients were included in the analyses. Intervention participants had seen an outpatient neurologist more often (OR = 4.75; 95% CI: 2.71–8.31) and were readmitted to a hospital less frequently (IRR = 0.42; 95% CI: 0.29–0.61), resulting in lower hospital costs (IQR = €0–1910 in the intervention group, IQR = €0–4375 in the control group). There were no substantial group differences in the rate of recurrent events and mortality. Conclusion: This study showed the beneficial potential of care coordination for a vulnerable patient population: the utilization rate of important health services was increased, and the rate of hospital readmissions decreased as a result. Future research should focus on the risk of recurrent strokes and the long-term effects of improved care. Trial registration: DRKS00017526 on DRKS – German Clinical Trials Register (retrospectively registered: 21 June 2019)