Scheduling with Rate Adaptation under Incomplete Knowledge of Channel/Estimator Statistics

In time-varying wireless networks, the states of the communication channels are subject to random variations, and hence need to be estimated for efficient rate adaptation and scheduling. The estimation mechanism possesses inaccuracies that need to be tackled in a probabilistic framework. In this work, we study scheduling with rate adaptation in single-hop queueing networks under two levels of channel uncertainty: when the channel estimates are inaccurate but complete knowledge of the channel/estimator joint statistics is available at the scheduler; and when the knowledge of the joint statistics is incomplete. In the former case, we characterize the network stability region and show that a maximum-weight type scheduling policy is throughput-optimal. In the latter case, we propose a joint channel statistics learning - scheduling policy. With an associated trade-off in average packet delay and convergence time, the proposed policy has a stability region arbitrarily close to the stability region of the network under full knowledge of channel/estimator joint statistics.Comment: 48th Allerton Conference on Communication, Control, and Computing, Monticello, IL, Sept. 201

Plasmonic Nanoslit Array Enhanced Metal-Semiconductor-Metal Optical Detectors

Cataloged from PDF version of article.Metallic nanoslit arrays integrated on germanium metal–semiconductor–metal photodetectors show many folds of absorption enhancement for transverse-magnetic polarization in the telecommunication C-band. Such high enhancement is attributed to resonant interference of surface plasmon modes at the metal–semiconductor interface. Horizontal surface plasmon modes were reported earlier to inhibit photodetector performance. We computationally show, however, that horizontal modes enhance the efficiency of surface devices despite reducing transmitted light in the far field

The myth of ‘Europeanization’ of Turkish foreign policy: the Cyprus debacle as a litmus test

This article examines Turkish–EU relations and the Cyprus issue within the Europeanization framework. It seeks to underline how and to what extent EU conditionality was performed in Turkey’s Cyprus policy in the post-Helsinki period. The exploration of the relationship between domestic political pressures and the foreign policy choices of the AKP government on the Cyprus issue suggests that EU’s potential in transforming the foreign policy of candidates is both context dependent and questionable. Alongside EU-related factors such as the credible membership perspective, what accounts for change is predominantly determined by how domestic actors perceive it, and how much domestic power struggles are affected by it. © 2014 Taylor & Francis

The diagnostic value of adenosine deaminase activity in sputum in pulmonary tuberculosis

AbstractThis study was carried out in Atatürk Chest Diseases and Surgery Center. It's aim to determine and compare sputum adenosine deaminase (ADA) activity in pulmonary tuberculosis (tb), lung cancer and chronic obstructive pulmonary disease (COPD) patients in order to assess its diagnostic value. Patients and method: Eighty-four patients (25 tb, 30 lung cancer and 29 COPD) were included in the study. ADA activity in sputum and serum was measured. Sputum ADA activities of tb patients were significantly higher than the other two groups (P<0.05). Sputum/serum ADA ratios were similar in all groups. Sputum ADA activities between 150 and 200 U/L were the measurements with the best test performance according to the ROC curve. Sensitivity, specificity, positive predictive value, and negative predictive value were 44.0, 86.4, 57.8, 78.4% for 150 U/L and 32.0, 96.6, 80.0, 77.0% for 200 U/L, respectively. Area under the curve was 0.663. Because of low sensitivity, routine determination of ADA activity in sputum for the diagnosis of pulmonary tb is not recommended. However, it can be helpful in the diagnosis of smear-negative cases who are strongly suspected of tb

Exploiting channel memory for joint estimation and scheduling in downlink networks

We address the problem of opportunistic multiuser scheduling in downlink networks with Markov-modeled outage channels. We consider the scenario in which the scheduler does not have full knowledge of the channel state information, but instead estimates the channel state information by exploiting the memory inherent in the Markov channels along with ARQ-styled feedback from the scheduled users. Opportunistic scheduling is optimized in two stages: (1) Channel estimation and rate adaptation to maximize the expected immediate rate of the scheduled user; (2) User scheduling, based on the optimized immediate rate, to maximize the overall long term sum-throughput of the downlink. The scheduling problem is a partially observable Markov decision process with the classic ‘exploitation vs exploration ’ trade-off that is difficult to quantify. We therefore study the problem in the framework of restless multi-armed bandit processes and perform a Whit-tle’s indexability analysis. Whittle’s indexability is traditionally known to be hard to establish and the index policy derived based on Whittle’s indexability is known to have optimality properties in various settings. We show that the problem of downlink scheduling under imperfect channel state information is Whittle indexable and derive the Whittle’s index policy in closed form. Via extensive numerical experiments, we show that the index policy has near-optimal performance. Our work reveals that, under incomplete channel state infor-mation, exploiting channel memory for opportunistic scheduling can result in significant performance gains and that almost all of these gains can be realized using an easy-to-implement index policy

Getting the basics right-staging in head and neck cancer

The cornerstone of oncology literature and therefore medical practice is the ability to compare outcomes of treatment modalities for different stages of cancer

On Critical Buckling Loads Of Euler Columns With Elastic End Restraints

I n recent years, a great number of analytical approximate solution techniques have been introduced to find a solution to the nonlinear problems that arised in applied sciences. One of these methods is the homotopy analysis method HAM . HAM has been successfully applied to various kinds of nonlinear differential equations. In this paper, HAM is applied to find buckling loads of Euler columns with elastic end restraints. The critical buckling loads obtained by using HAM are compared with the exact analytic solutions in the literature. Perfect match of the results veries that HAM can be used as an efficient, powerfull and accurate tool for buckling analysis of Euler columns with elastic end restraint