Stability of spatial wireless systems with random admissible-set scheduling

We examine the stability of wireless networks whose users are distributed over a compact space. Users arrive at spatially uniform locations with intensity \lambda and each user has a random number of packets to transmit with mean \beta. In each time slot, an admissible subset of users is selected uniformly at random to transmit one packet. A subset of users is called admissible when their simultaneous activity obeys the prevailing interference constraints. We consider a wide class of interference constraints, including the SINR model and the protocol model. Denote by \mu the maximum number of users in an admissible subset for the model under consideration. We will show that the necessary condition \lamba \beta <\mu is also sufficient for random admissible-set scheduling to achieve stability. Thus random admissible-set scheduling achieves stability, if feasible to do so at all, for a broad class of interference scenarios. The proof relies on a description of the system as a measure-valued process and the identi??cation of a Lyapunov function. Keywords: Wireless networks, stability, Foster-Lyapunov, Harris recurrent, measure-valued process, interference constraints, SINR requirements, protocol mode

Backlog-based random access in wireless networks : fluid limits and delay issues

We explore the spatio-temporal congestion dynamics of wireless networks with backlog-based random-access mechanisms. While relatively simple and inherently distributed in nature, suitably designed backlog-based access schemes provide the striking capability to match the optimal throughput performance of centralized scheduling algorithms in a wide range of scenarios. In the present paper, we show that the specific activity functions for which maximum stability has been established, may however yield excessive queue lengths and delays. The results reveal that more aggressive/persistent access schemes can improve the delay performance, while retaining the maximum stability guarantees in a rich set of scenarios. In order to gain qualitative insights and examine stability properties we will investigate fluid limits where the system dynamics are scaled in space and time. As it turns out, several distinct types of fluid limits can arise, exhibiting various degrees of randomness, depending on the structure of the network, in conjunction with the form of the activity functions. We further demonstrate that, counter to intuition, additional interference may improve the delay performance in certain cases. Simulation experiments are conducted to illustrate and validate the analytical findings

Fast secure comparison for medium-sized integers and its application in binarized neural networks

In 1994, Feige, Kilian, and Naor proposed a simple protocol for secure 3-way comparison of integers a and b from the range [0, 2]. Their observation is that for p=7, the Legendre symbol (x∣p) coincides with the sign of x for x=a−b∈[−2,2], thus reducing secure comparison to secure evaluation of the Legendre symbol. More recently, in 2011, Yu generalized this idea to handle secure comparisons for integers from substantially larger ranges [0, d], essentially by searching for primes for which the Legendre symbol coincides with the sign function on [−d,d]. In this paper, we present new comparison protocols based on the Legendre symbol that additionally employ some form of error correction. We relax the prime search by requiring that the Legendre symbol encodes the sign function in a noisy fashion only. Practically, we use the majority vote over a window of 2k+1 adjacent Legendre symbols, for small positive integers k. Our technique significantly increases the comparison range: e.g., for a modulus of 60 bits, d increases by a factor of 2.8 (for k=1) and 3.8 (for k=2) respectively. We give a practical method to find primes with suitable noisy encodings.We demonstrate the practical relevance of our comparison protocol by applying it in a secure neural network classifier for the MNIST dataset. Concretely, we discuss a secure multiparty computation based on the binarized multi-layer perceptron of Hubara et al., using our comparison for the second and third layers.</p

Multiscale Discriminant Saliency for Visual Attention

The bottom-up saliency, an early stage of humans' visual attention, can be considered as a binary classification problem between center and surround classes. Discriminant power of features for the classification is measured as mutual information between features and two classes distribution. The estimated discrepancy of two feature classes very much depends on considered scale levels; then, multi-scale structure and discriminant power are integrated by employing discrete wavelet features and Hidden markov tree (HMT). With wavelet coefficients and Hidden Markov Tree parameters, quad-tree like label structures are constructed and utilized in maximum a posterior probability (MAP) of hidden class variables at corresponding dyadic sub-squares. Then, saliency value for each dyadic square at each scale level is computed with discriminant power principle and the MAP. Finally, across multiple scales is integrated the final saliency map by an information maximization rule. Both standard quantitative tools such as NSS, LCC, AUC and qualitative assessments are used for evaluating the proposed multiscale discriminant saliency method (MDIS) against the well-know information-based saliency method AIM on its Bruce Database wity eye-tracking data. Simulation results are presented and analyzed to verify the validity of MDIS as well as point out its disadvantages for further research direction.Comment: 16 pages, ICCSA 2013 - BIOCA sessio

Delegation of GP-home visits to qualified practice assistants: assessment of economic effects in an ambulatory healthcare centre

<p>Abstract</p> <p>Background</p> <p>Against the background of a decreasing number of general practitioners (GPs) in rural regions in Germany, the AGnES-concept (AGnES = GP-supporting, community-based, e-health-assisted, systemic intervention) supports the delegation of regular GP-home visits to qualified practice assistants. The concept was implemented and evaluated in different model projects in Germany.</p> <p>To explore the economic effects of this concept, the development of the number of home visits in an ambulatory healthcare centre was analysed and compared with the number of home visits in the surrounding county.</p> <p>Methods</p> <p>Information about GP-home visits was derived from reimbursement data of the ambulatory healthcare centre and a statutory health insurance. Information about home visits conducted by AGnES-practice assistants was collected from the project documentation over a time period of 12 consecutive quarter years, four quarter years before the beginning of the project and 8 quarter years while the project was implemented, considering background temporal trends on the population level in the study region.</p> <p>Results</p> <p>Within the ambulatory healthcare centre, the home visits by the GPs significantly decreased, especially the number of medically urgent home visits. However, the overall rate of home visits (conducted by the GPs and the AGnES-practice assistants together) did not change significantly after implementation of the AGnES-concept. In the surrounding county, the home visit rates of the GPs were continuous; the temporal patterns were approximately equal for both usual and urgent home visits.</p> <p>Conclusion</p> <p>The results of the analyses show that the support by AGnES-practice assistants led to a decrease of GP-home visits rather than an induction of additional home visits by the AGnES-practice assistants. The most extended effect is related to the medically urgent home visits rather than to the usual home visits.</p

A Quantum-Proof Non-Malleable Extractor, With Application to Privacy Amplification against Active Quantum Adversaries

In privacy amplification, two mutually trusted parties aim to amplify the secrecy of an initial shared secret $X$ in order to establish a shared private key $K$ by exchanging messages over an insecure communication channel. If the channel is authenticated the task can be solved in a single round of communication using a strong randomness extractor; choosing a quantum-proof extractor allows one to establish security against quantum adversaries. In the case that the channel is not authenticated, Dodis and Wichs (STOC'09) showed that the problem can be solved in two rounds of communication using a non-malleable extractor, a stronger pseudo-random construction than a strong extractor. We give the first construction of a non-malleable extractor that is secure against quantum adversaries. The extractor is based on a construction by Li (FOCS'12), and is able to extract from source of min-entropy rates larger than $1/2$. Combining this construction with a quantum-proof variant of the reduction of Dodis and Wichs, shown by Cohen and Vidick (unpublished), we obtain the first privacy amplification protocol secure against active quantum adversaries

Predictors of women's sexual outcomes after implant-based breast reconstruction

Objective: Although breast reconstruction has become an important treatment modality following mastectomy, few studies assessed predictors of postoperative sexual outcomes after breast reconstruction. Therefore, we aimed to study three sexual outcomes following implant-based breast reconstruction (IBBR), and associate multiple biopsychosocial factors with these outcomes. Methods: Data collection was part of a multicenter prospective study on IBBR. A predictive model was tested including medical, background and psychological predictors, partner relationship factors and physical sexual function. Data collection included clinical and questionnaire data (preoperatively and 1 year following reconstruction) using the BREAST-Q Sexual well-being scale (BQ5), and questions regarding sexual dysfunction and sexual satisfaction questions (Female Sexual Function Index). Results: The study sample consisted of 88 women who underwent mastectomy and IBBR. Mean postoperative BQ5 scores were lower than before surgery (M = 58 [SD = 18] vs 65 [SD = 20]; P =.01, Wilks' Lamdba =.88). Sexual dysfunctions were related strongest to orgasm inability and vaginal lubrication issues. The tested models predicted 37%-46% of the sexual outcomes: sexual outcomes were mostly predicted by psychosocial well-being, physical sexual function and partner support. Preoperative sexual and psychosocial well-being were positively associated with postoperative sexual well-being (r = 0.45 and r = 0.47). Conclusions: Although moderately positive sexual outcomes were reported after IBBR, some women reported issues with vaginal lubrication, breast sensation and orgasm. Sexual dysfunctions were predicted by vaginal lubrication and medical treatments, while sexual well-being and satisfaction were more predicted by psychosocial well-being and partner support. We advocate supportive care that includes partners and psychosocial functioning to optimize sexual outcomes after IBBR